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Why You Should Start with a Refractor Telescope

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If you’re getting started in deep-sky astrophotography, I believe that a compact apochromatic (APO) refractor telescope is the best possible choice.

A compact APO refractor is portable and lightweight, making it a smoother transition from the camera lenses you may be used to. In fact, in many ways, a high-quality apochromat is very much like a telephoto lens. 

If you’re interested in photographing nebulae and large galaxies in the night sky through a telescope, this article should shed some light on the decision-making process ahead of you. 

astrophotography with a refractor telescope

My first refractor telescope was an 80mm Explore Scientific apochromatic triplet. 

Introduction

Throughout the past 8 years of deep-sky astrophotography, I’ve made lots of mistakes. In the beginning stages, I made critical errors in selecting and setting up equipment. 

From the beginning, my goal was to capture deep-sky images of nebulae and galaxies. This type of astrophotography requires the most advanced equipment and demands a careful setup routine. 

The type of telescope you choose early on can have a dramatic impact on the complexity of your deep-sky astrophotography setup. In my experience, a compact, wide-field refractor offers an improved user experience over the other telescope types during the acquisition stages of astrophotography.

For example, I began taking my first deep-space images with a reflector telescope. If I could go back and I do it all over again, I would have chosen a compact, wide-field refractor to start astrophotography with. 

setting up telescope

These days, I use a refractor telescope for 90% of my astrophotography. 

I am not saying that there is anything wrong with starting your astrophotography journey with a Schmidt-Cassegrain Telescope (SCT) or Newtonian Reflector, but I believe you will have some additional challenges to overcome early on. 

No matter what type of photography experience you have going in, deep-sky astrophotography through a telescope will have a number of challenges to overcome early on.

This includes understanding how to polar align an equatorial mount, how to focus your camera on a faint deep-sky object, and how to attach your camera to the telescope. two out of the three challenges become more difficult if you’re not using a wide-field refractor to start.

The statement above is not theoretical, I personally experienced these frustrating moments in my backyard years ago. I should have started with a compact refractor telescope. 

deep-sky astrophotography

A recent photo of NGC 7822 captured using a color camera and a 100mm refractor.

I Should Have Started with a Refractor

I often see newcomers to deep-sky astrophotography starting with a telescope that will make an already-challenging hobby even more difficult. I went through this experience personally, and this is what happened. 

My first astrophotography telescope was a Meade LXD55 6″ Schmidt-Newtonian. I purchased this reflector telescope from a local camera store second-hand, for a great price. 

At the time, I had very little knowledge of telescope-types, optical designs, or astronomy in general. I took the advice of the salesman at the store, and he assured me that “this telescope can be used for astrophotography”.

comparing a reflector to a refractor

The telescope I started taking pictures of space with.

First off, he was right. It could certainly be used for astrophotography, and I even found astrophotography images online taken by others using this particular model.

The problem was, this type of telescope presented some pretty daunting challenges to overcome. My long term love for astrophotography was at stake, as a poor experience could potentially sour me on this new adventure. 

Thankfully, I kept a positive mindset throughout the process despite having limited knowledge (and limited funds). 

This was my First Astrophotography Telescope

astrophotography telescope setup

My first telescope for Astrophotography was NOT a refractor, and it presented some challenges.

I mounted the Meade LXD55 SN6 to a Celestron CG-5 (Advanced Series GT) computerized telescope mount. The GoTo tracking mount was my biggest investment in the hobby early on, and looking back the mount was performed surprisingly well. 

A Schmidt-Newtonian is a promising instrument for astro-imagers. The corrector plate helps you collect images with less coma than a traditional reflector design.

Essentially it’s a catadioptric telescope that combines elements from both the Schmidt camera and the Newtonian reflector. A spherical primary mirror is combined with a Schmidt corrector plate to correct the image. 

It looks capable enough in the picture, so what’s wrong with starting your astrophotography adventure with a Newtonian Reflector, Schmidt-Cassegrain, or a Ritchey–Chrétien? 

Some would argue that there is nothing wrong with any of these choices, but here’s why it wasn’t a good fit for me:

It was Heavy and Difficult to Balance

It wasn’t a bad telescope, and I even managed to collect my first-ever deep-sky image with it. I really had no idea what I was doing at this point, and was absolutely thrilled to finally captured a tracked deep-sky object in the night sky. 

The problem with this old Meade telescope was that it was not a great type of telescope to start with. Looking back, a compact refractor telescope would have made my life a lot easier at the time. 

For starters, it was rather heavy and difficult to balance. It was at the maximum payload capacity of my equatorial mount (Celestron CG-5), and I even had to use some “custom” counterweights to achieve balance.

In the astrophotography world, you never want to have your telescope rig reach the weight limits of your telescope mount. This puts extra stress on the equatorial drive system and often results in poor tracking. 

first picture of Andromeda

My first picture of M31 (Andromeda) using the Meade reflector telescope (July 2011).

It Had Too Much Magnification

In my opinion, the telescope had a little too much focal-length as well. Extra magnification can be great for pulling in small targets, but it’s also more demanding on aspects such as pointing accuracy, tracking, and focus. 

Prime-focus astrophotography involves attaching your camera directly to the focuser of the telescope, with no additional eyepieces or lenses between them. That means that the native focal length of the telescope decides the field-of-view (FOV) and scale of the objects you shoot. 

The SC6 had a focal length of approximately 762mm, which could be considered to be a “mid-range” focal length. For comparison, my William Optics Zenithstar 73 refractor has a focal length of 430mm. 

I really shouldn’t complain about the 762mm focal length (FL) of the 6″ Meade, some amateur astrophotographers start out with an 8″ SCT with a demanding 2000mm+ FL. (I think I would have given up!)

The Focuser was Loose and Difficult to Secure

As newcomers will tell you, achieving a tight focus on your deep-sky subject can be challenging early on (Here are some tips).  It’s hard enough to find the optimal focus distance without worrying about the focuser “slipping” out of position on its own. 

Like a traditional Newtonian telescope, the focuser is placed near the front of the optical tube to collect light from the secondary mirror. This creates a challenging situation in terms of balance, especially when using a heavy, full-frame DSLR camera. 

The weight of my camera would put stress on the objective end of the optical tube. Despite using the locking screw, the DSLR would eventually fall downwards into the focuser as the night progressed. I constantly had to re-adjust focus after 4-5 images.

In general, I find reflector telescopes to be more challenging to focus than a refractor, and that was certainly the case with this F/5 Schmidt-Newt.

Start with a Compact, Wide-field Refractor

I’m not saying that a refractor telescope is the only way to go, but I think you’ll find that the astrophotography community generally agrees with me on this one. To be more specific, an apochromatic refractor is best. 

Refracting telescopes use lenses, not a mirror, to deliver crisp views through the eyepiece, and high contrast, well-corrected color images with your camera. 

In late 2011, early 2012, I invested in an Explore Scientific ED80 Triplet APO refractor. The reason I call this an “investment” is that not only did this telescope reward with me with my best images to date, but quality glass hold their value quite well.

ED80

Below, is an old photo of my 80mm refractor telescope on a Celestron CG-5 equatorial telescope mount. The difference between the images I was collecting with the Schmidt-Newt and the APO refractor was night and day. 

The stars were small and well-corrected (all of the colors came to a focus at once), and I no longer dealt with coma, reflections, and dramatic vignetting. 

Explore Scientific ED80

My first refractor telescope was an Explore Scientific ED80. 

Another advantage this telescope had was the field of view. Being a beginner, I had my heart set on capturing some of the most iconic deep-sky objects like the Orion Nebula, Andromeda Galaxy, and the Pleiades star cluster. 

The focal length of this telescope (480mm) was a perfect fit for all of these targets. I didn’t need to worry about creating a mosaic to fit the entire object in the frame. Images like this were the reason I got into astrophotography in the first place.

Finding targets in the night sky became a lot easier thanks to the forgivingly wide field of view. Even if the pointing accuracy of my computerized equatorial telescope mount was off, I could usually find my intended deep-sky target within the field-of-view of my first slew.

best telescopes for astrophotography

See my list of recommended refractors for astrophotography.

The first summer (2012) with my Explore Scientific 80mm refractor telescope was an exciting one. I captured several amazing photos of deep-sky objects with my Canon EOS Rebel Xsi DSLR. 

The most exhilarating photo came in July of 2012 when I attempted to photograph the Andromeda Galaxy with my 80mm refractor and stock Canon DSLR. The image was a monumental improvement over my attempt the previous summer. I was especially thrilled at the clarity of the image and natural star colors recorded. 

astrobackyard first andromeda

My first successful image of the Andromeda Galaxy (July, 2012). 

The Perfect Astrophotography Telescope

A high-quality doublet or triplet apochromatic refractor is capable of producing sharp, flat, well-corrected images. Almost all types of telescopes are capable of impressive astrophotography images, but some make you work a lot harder for it. 

For example, a Newtonian Reflector presents an advantageous light-gathering ability and an affordable price-per-aperture. However, Newtonians require regular collimation and adjustments to avoid coma and perform at their best.

An apochromatic refractor will perform much better in terms of photography than its less expensive achromat counterpart. 

The objective lens (consisting of 2 or more pieces of glass) of an apochromatic refractor is designed to focus light to the same point, and correct chromatic aberration. As you can see in the diagram below, an apochromatic objective focuses different wavelengths of light closer to the same point than an achromat does.

apochromatic vs achromatic

“The strict definition of apochromatism is having three wavelengths of light focusing to the same point.  This normally requires a third lens element in the objective.  The normal configuration is a positive, low-dispersion crown, combined with two high-dispersion flints, one negative and one positive.  The lenses can be cemented, air-spaced, or a combination thereof.” Starizona.

For a technical description of how a refractor telescope works, and the refractive index of certain mediums, check out this informative article

Pros and Cons of a Compact APO Refractor Telescope

There are some pros and cons to using a compact refractor telescope for astrophotography, and here they are:

Pros:

  • You can mount them to modest, entry-level equatorial mounts
  • Refractors are compact and lightweight compared to other telescope designs
  • The focusers are solid and easy to focus
  • They offer a similar experience to a high-end telephoto camera lens
  • The image quality potential for astrophotography is exceptional
  • Refractors do not require regular collimation or optical adjustments
  • They offer a forgiving, wide field-of-view

Sky-Watcher Star Adventurer Pro Review

You can mount a small refractor on a portable tracking mount like the Sky-Watcher Star Adventurer.

Minus:

  • They are the most expensive telescope type (price per aperture)
  • They are not well-suited for high-magnification planetary imaging
  • The apertures are often too small to observe faint deep sky objects
  • Galaxies and smaller DSO’s need 1000mm+ for an up-close view

My favorite astrophotos of all time were all taken using a refractor telescope. From my first experiences with the Explore Scientific ED80 to the massive Sky-Watcher Esprit 150 Super APO, refractors are my number one choice for astrophotography. 

The image below shows a William Optics Zenithstar 73 refractor mounted to a modest Sky-Watcher HEQ5 GoTo telescope mount. My DSLR camera is attached to the focuser of the telescope for deep-sky imaging at 430mm.

This entire ensemble can be lifted up and moved around the yard on a moment’s notice, so I usually keep the entire imaging system ready to go in the garage.

A setup like this is also refreshingly easy to travel with. It does not take up very much space in my vehicle and can be re-assembled quickly. 

telescope equipment

A portable deep-sky imaging setup with a 73mm refractor telescope. 

This versatile and reliable rig does not come at the expense of performance either. A small setup like this is capable of producing incredible astrophotography images using a DSLR/Mirrorless camera or a dedicated astronomy camera.

The photo below shows the image captured using the telescope setup pictured above in my video titled “Taking a Picture of the Andromeda Galaxy“.

This image includes 67 x 120-second exposures using a Canon EOS 60Da. 

Andromeda Galaxy

My latest version of the Andromeda Galaxy using a DSLR and a small refractor telescope. 

My Newtonian Reflector Collects Dust

In 2014, I decided to purchase an 8″ Newtonian Reflection, the Orion 8″ F/3.9 Astrograph Reflector. The idea was to add some light gathering power and a little more focal length at an affordable price. 

However, I had become used to the quick and setup time of my 80mm refractor, and balancing the big optical tube on my Sky-Watcher HEQ5 mount was time-consuming.

Also, I had to regularly collimate the tube before each and every imaging session. Perhaps the telescope was perfectly collimated before I attached my camera, but I always had to make sure before spending a night collecting images. 

I did manage to capture some impressive images with this setup, but surprisingly, the added aperture did not add the extra “punch” to my images I was looking for. In the end, this telescope was a lot more effort, for very little (if any) benefit to my astrophotography.

reflector vs. refractor for astrophotography

I do not use my 8″ Newtonian Reflector very much these days.

What Size and Brand Should You Buy?

I’ve used refractor telescopes with an aperture of 51mm, all the way up to 150mm. Smaller, compact APO’s are much more practical and affordable, yet do not sacrifice as much performance as you may think.

For example, the image of the Lagoon Nebula and Trifid Nebula region of Sagittarius was captured with a miniature (51mm aperture) William Optics RedCat APO and a DSLR camera. This quadruplet refractor weighs just 3.2 pounds and can fit in your carry-on bag

wide field deep sky astrophotography

Nebulae in Sagittarius using a William Optics RedCat 51 APO. 

Nearly every telescope manufacturer builds refractor telescopes, and I’ve had the opportunity to try many of them. I’ve had wonderful experiences using apochromatic refractors from Explore Scientific, William Optics, Meade, and Sky-Watcher.

William Optics compact doublets are very popular and rather affordable considering the optics used in their designs. The Zenithstar 73 APO is one such example, and a telescope I have personally taken a lot of beautiful images with.

The Sky-Watcher Esprit line of refractors is a step up, with the Esprit 100 Super APO (Triplet) being my most used refractor of all time. These telescopes are expensive and quickly grow in price as aperture is added. 

sky-watcher telescope

Setting up the Sky-Watcher Esprit 100 refractor telescope in the backyard. 

When choosing a refractor telescope for astrophotography, ensure that it is an apochromatic optical design, not an achromat. Also, ensure that the optical tube includes a robust, 10-1 speed focuser that can lock into position when needed. 

You’ll also need to confirm that the mounting hardware will allow you to mount the telescope to your equatorial mount, and add additional accessories such as a guide scope and camera for autoguiding. 

Make sure you invest in the appropriate field flattener for your refractor, as this extra glass lens will help flatten the field of view to the very edges of your picture.

Final Thoughts

If your astrophotography interests lie in taking images of nebulae and large galaxies, an apochromatic refractor should be your number one choice of telescope.

This category of deep-sky objects includes some of the most iconic wonders in space, and you could spend a lifetime capturing them.

Not only is an APO refractor a perfect fit in terms of focal length (native magnification), but the images with your DSLR/Mirrorless or dedicated astronomy camera will be extremely sharp and well-corrected.

If your looking to photograph the planets, a compact refractor is not for you. Smaller targets such as planets and many galaxies are not a good fit for a wide-field refractor.

But if you’re a fan of quick set up time, consistent results, and wide-field nebulae like the ones below, you simply cannot beat an APO refractor.

soul nebula

The Soul Nebula in Cassiopeia using a William Optics Zenithstar 73 APO. 

Pleiades

The Soul Nebula in Cassiopeia using a William Optics RedCat 51 APO. 

Recommended Refractors for Astrophotography

The following list of apochromatic refractor telescopes have all produced exceptional results for me personally, so I feel comfortable recommending them. They are all compact, wide-field instruments capable of producing images like the ones shared in this post. 

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Astrophotography with a DSLR Camera and Small Telescope

|Telescopes|18 Comments

This week, I returned to my roots and enjoyed some deep sky astrophotography using a DSLR camera and small telescope. Don’t get me wrong, dedicated astronomy cameras and heavy duty mounts are great, but my latest imaging session in the backyard was a breath of fresh air.

In this post, I’ll share my early results with a new compact refractor telescope, the William Optics Zenithstar 73 APO.  I’ve managed to collect some exposure time on a number of deep sky objects using a crop-sensor (modified) DSLR.

My experiences with the Z73 have reminded me how much I enjoy deep sky imaging through a wide field refractor with a DSLR. This is where my astrophotography journey began, and it has not lost its appeal over time. Not one bit.

AstroBackyard

Returning to my roots…

The cooler nights of fall have allowed me to begin using my DSLR camera again for astrophotography. The overnight low has dropped to about 8-10 degrees C, a welcome relief from the scorching, humid nights of summer.


These conditions not only make the longer nights more pleasant outside, but they offer up better conditions for photography as well. There is less moisture in the air and the electronics in my DSLR are able to function properly without becoming dangerously hot.

The temperature of the sensor in my Canon EOS Rebel T3i has been hovering around 25 degrees C during my imaging sessions, which is still warm enough to produce a quite a bit of noise. A 5-minute exposure at ISO 1600 is a lot to ask of a camera designed for daytime photography.

But enough about my old DSLR for now, let’s get to the fun part. (My new telescope). To stay up to date with my latest endeavours in deep sky astrophotography, please subscribe to my email newsletter.

DSLR camera and telescope

The William Optics Zenithstar 73 APO

The William Optics Zenithstar 73 is a compact doublet APO refractor designed specifically for astrophotography. Owners of full frame DSLR cameras will appreciate its 45mm diameter illumination circle for edge-to-edge images.

After picking up the Z73 from the William Optics booth at NEAF, I am finally using this premium refractor for astrophotography at home in the backyard. A series of rained out camping trips and even a clouded-out star party put a lid on my summer plans to use this portable APO under dark skies.

This compact and lightweight apochromatic doublet refractor has a lot going for it, including an ultra-wide field of view and high-end Ohara FPL-53 objective lens construction. I was fortunate enough to receive a complete package that includes the dedicated Flat73 field flattener, 50mm Guide Scope and more.

When asked which color I prefer, I had to keep the tradition of white and gold alive to match the Z61 APO and FLT 132 refractors. This “big brother” to the Z61 uses a new mounting ring and guide ring design, that match the gold Vixen-style dovetail bar.

Z73 Guide Scope Rings

After taking the Zenithstar 73 out of the neatly packaged soft carry case, the first thing I did was separate the guide scope rings a notch to provide a more balanced hold of the 50mm guide scope. I removed the Rotolock (which is an added accessory from the standard package) to thread the dedicated field flattener in for astrophotography.

A great place to thread a 48mm filter (such as the Baader Moon and Skyglow filter pictured below), is on the Flat73. Then, you can attach the field flattener to the telescope with the filter inside.

Flat73

I must say, I was spoiled with a totally complete package that included all accessories. These are additional items to consider when calculating the overall price of the package. The accessories for the Zenithstar 73 include:

Optional accessories:

  • Soft carry case
  • Flat73 1:1 Full frame flattener
  • 2” Rotolock with M63 threads
  • 50mm F/4 Rotolock Guiding scope
  • 48mm T mount for Nikon or Canon

What’s nice is, William Optics outlines everything you’ll need for a deep sky astrophotography system – and you can order it all together. You don’t need to go searching for field flatteners or guide scope rings that will fit your telescope. Astrophotography is the number one priority behind everything William Optics makes.

FPL-53 flourite glass

William Optics Zenithstar 73 APO Specs

Glass Type:FPL-53
Focal Length:430mm
F-Ratio:F/5.9
Weight:5.5 Lbs
Retracted Length:310mm
Focuser:2.5" Rack and Pinion
Dew Shield:Integrated
Mount:Vixen-Style Dovetail

 

The Zenithstar 73 APO is available at Ontario Telescope

 

Deep Sky Images from a City Backyard

The timing of the full moon and ever-present glow of my urban sky meant narrowband filters were the obvious choice. Even with a color DSLR camera, astrophotography can be enjoyed a great deal more with a simple clip-in ha filter.

The primary DSLR I use for deep sky astrophotography is an old Canon EOS Rebel T3i that has had the full spectrum modification performed. To compare it with a dedicated astronomy camera or CCD, you could consider it to be an un-cooled one-shot-color camera.

DSLR Ha filter

An Astronomik 12nm ha filter was snapped into the body of my APS-C sensor Canon T3i for the following images. With the Flat73 field flattener in place, it should come as no surprise that the stars in my image were recorded as pinpoints top the very edges of the image.

Sadr Region in Cygnus (Butterfly Nebula)

The Butterfly Nebula (IC 1318) is a rich emission nebula region in the constellation Cygnus. It is part of a much larger complex of gas and dust residing in the Sadr region. The photo below shows off the wide field of view and crisp stars you can expect when using an entry-level DSLR with the Z73.

Butterfly Nebula in Ha

I captured roughly 2 hours worth of exposure time in Ha using my Canon T3i through the Z73. The images are free of star-trailing and elongated stars thanks to the accurate tracking of my Sky-Watcher HEQ Pro Synscan mount.

This mount is a twin to the Orion Sirius EQ-G GoTo, which I often recommend to beginners as a robust, astrophotography-worthy mount for a setup like the one shown on this post. With a sound polar alignment routine, this equatorial mount can consistently provide sharp images of 5-minutes or much more. (The longest I’ve shot was 10)

The iOptron CEM60 center-balanced mount I used for the past 12 months has been returned to its rightful owner after a generous extended loan from Ontario Telescope. Luckily, the 5.5-pound William Optics Zenithstar 73 is nowhere near the limits of the HEQ5’s payload capacity.

GoTo Telescope Mount

The Heart Nebula in Cassiopeia

Next up is a rather dynamic looking nebula in Cassiopeia known as the Heart Nebula. As you can see, this massive target fits within a single field of view using the Zenithstar 73 with a crop-sensor DSLR camera. The F/5.9 aperture of the Z73 provides a healthy balance between light gathering ability and sharpness.

Heart Nebula in Ha

Both the Butterfly Nebula and Heart nebula images were produced using 5-minute image exposures at ISO 1600. Astro Photography Tool was used to automate the image captures, with PHD2 guiding helping to accurately guide my HEQ5 mount during each sub.

Dithering between each image and stacking multiple light frames helped to improve the overall signal to noise ratio in the images. The individual light frames were very noisy, but using dark frames in the stacking process (DeepSkyStacker) can really help to correct this.

Why I love a DSLR Camera and Telescope Setup Like This

For the type of astrophotography I’m most interested in these days, it’s hard to beat the photography opportunities available at the 400-500mm focal length. At 430mm and F/5.9, the Zenithstar 73 fits the profile of the ultimate wide field APO for deep sky.

I’ve repeatedly mentioned how much I love to use APO refractor telescopes, and I believe that they offer a better user experience and more consistent astrophotography results than any other telescope type.

Sky Watcher HEQ GoTo Mount

Telescopes that offer a longer focal length (of 1000mm or more) are great for small DSO’s and galaxies, but deep sky objects that cover a large area of sky such as the Heart Nebula are impossible to photograph with a DSLR without creating a mosaic.

One of the advantages of having a wide field of view is the ability to capture multiple deep sky objects in a single shot. It allows you to get creative with the framing of your target next to a star cluster or some interesting nearby nebulosity.

The photo opportunities are endless, and I you may find a lifetime of ideas before feeling the need for a telescope with an increased focal length.

Image Processing Narrowband Images from a DSLR

Here is a look at the individual light frames using the Canon T3i through the Zenithstar 73. The images have a red cast because of the strong narrowband filter that was used (h-alpha). I have registered and stacked the images just as I would with a color image in DeepSkyStacker.

light frames

Reviewing my RAW images in Adobe Bridge

DeepSkyStacker

For the Heart Nebula, I’ve got about 5 hours of total integrated exposure time. This is two nights worth of shots that I’ve separated into their own tabs in DSS. I captured matching dark frames of the same temperature, and also bias and flat frames to help produce the highest quality stacked image possible.

Extracting the Red Channel from an RGB image

The trick after that is – to extract the red channel with the strongest signal in Photoshop. Have a look at the difference in the image quality of the red channel alone vs. the full RGB image with weak Green and Blue channels.

channels in Photoshop

Notice the difference in signal from the red channel to blue when using a 12nm h-alpha filter

I copied the red channel channel out to a new image canvas, and processed it using many of the same techniques as a traditional deep sky image such as minimizing stars, a curves stretch and a bit of noise reduction. This greyscale image can then be added to existing color data, or become a part of a complete narrowband project that include SII and OIII.

For now, I’ll just enjoy the black and white image in good old Hydrogen Alpha.

Final Thoughts

It felt great to use my DSLR camera for some astrophotography again. I began my journey many years ago with a camera and telescope like this. If you are a beginner thats thinking about taking the plunge into deep sky astrophotography – I think you should go for it – and a setup like this is likely the best way to get started.

Next, I’ll shoot some broadband color images using a full frame DSLR with the Zenithstar 73 to really take advantage of the fully illuminated image circle. The Sky-Watcher HEQ5 has proven to be a reliabe GoTo mount over the years and continues to deliver incredible results for me. I look forward to more sessions like this in the coming weeks as the longer, cooler nights usher in the new deep sky targets of Fall.

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The ultimate astrophotography target for your DSLR and telescope

|Nebulae|7 Comments

It’s very exciting to know that the night sky is full of galaxies, nebulae and star clusters to observe and photograph.  The great Andromeda Galaxy, the glimmering Pleiades, and the vibrant red California Nebula are all jaw-dropping astrophotography subjects.

Astrophotography with a DSLR and telescopeBut what is the best way to capture these amazing deep-sky objects?

The followers of this blog know that I am all about astrophotography with a DSLR and telescope.  This is a popular deep-sky imaging setup and is capable of some incredible results using affordable equipment that can often be purchased used.

A DSLR camera is a perfect option for beginners as they are much more user-friendly than a dedicated CCD astronomy camera.  In the post below, I’ll give you the ultimate astrophotography target for your DSLR and telescope.

I use a Canon 600D DSLR and an Explore Scientific ED102 CF telescope. View my complete setup.

An amazing year of Astrophotography

As we approach the end of 2016, I would like to thank everyone who has connected with AstroBackyard this year. Whether it was a YouTube comment, retweet, or Facebook like, I really appreciate the support.  I’ve connected with beginners, seasoned veterans, and everyone in between this year. I hope you were able to get outside and partake in some astrophotography with your DSLR and telescope this year.

AstroBackyard - DSLR Astrophotography


As you learn more about astrophotography, it’s almost certain that you will want to revisit previous imaging projects.  The lessons learned during each and every night out with your DSLR and telescope make you a more efficient and organized astrophotographer. As a beginner, my goal was to photograph as many galaxies and nebulae as possible.  Equipped with more tools and knowledge, I am now taking a second look at some of best deep-sky objects the Universe has to offer.

Orion constellation

The Orion constellation from my backyard

As for my latest astrophotography project, I’ve moved on from my Horsehead nebula photo for the year.  Not that it couldn’t benefit from more time and processing, it’s just that I shared the photo so much that I thought it would be best to shelve the project for now and complete it next winter.  This project helped me hone my skills of combining narrowband data with color images, as seen in my latest video tutorial.

I have now started pointing my telescope towards the alluring diffuse nebula known as Messier 42. The glowing Orion Nebula is in prime position for imaging over the next month or two.  I have photographed M42 many times over the years, but since then I have made many advancements I made in terms of both equipment and technique.

With my telescope’s relatively wide focal length (714mm), I can include the Running man nebula (NGC 1973, NGC 1975 and NGC 1977) in the same frame. I added a modest amount of data using my old DSLR and telescope (Canon Xsi and ED80) to an earlier version of Orion last year, but not nearly enough to do it justice.

Why I’m photographing the Orion Nebula all over again

My previous version of the Orion nebula was shot with an 80mm telescope (Explore Scientific ED80) and a Canon Rebel Xsi (stock).  The image I produced consisted of RGB data only (No H-Alpha), and was lacking the rich color that astro-modified DSLR cameras can produce.

Orion nebula using a DSLR through and telescope

My 2015 version of the Orion Nebula

Ways to improve my Orion Nebula image:

  • The Canon T3i has a higher resolution than the Xsi
  • The Canon T3i camera is modified (IR cut filter removed)
  • I can add narrowband h-alpha data and combine it with RGB
  • The ED102 telescope has an increased focal length and light gathering ability

A new astrophotography project begins




On Thursday, December 22nd, I began my latest astrophotography project with my DSLR and telescope.  I have a new favorite spot in the backyard that offers the widest possible window to the sky when aiming at M42. Stellarium was helpful in planning this position for this particular time of year.

From my location, clear nights are few and far between in the winter months.  Obtaining enough data (5 hours+) to process the image to its full potential will be a challenge.  The final image will likely have much more Ha data than RGB.  The nights leading up to, and during the full moon are more commonly clear.

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M42 – A rewarding astrophotography target for beginners

New to using a DSLR and telescope? Try Orion!

Beginners are drawn towards the Orion nebula as an astrophotography target, and for good reason.  The bright color and intense details of this object can be captured even in very short exposures.  When shooting with a DSLR and telescope for the first time, focus and proper tracking are some of the biggest hurdles to overcome.  Fortunately, M42 is very forgiving in terms of both focus and tracking.

Focus

The bright stars that populate the area in and around the Orion nebula are perfect for adjusting focus and framing.  Many deep-sky objects are very dim, with no bright stars within the same field of view.  This can make focusing and framing the target a nightmare.  I like to use the stars in the Trapezium to achieve the best possible focus while using my Cameras live-view mode, or on BackyardEOS.

Framing

The stars in the Sword of Orion are a great help when it comes to aligning your image.  Even better than that is the fact that the overall size and shape of the nebula is revealed in short exposures (5 seconds).  This makes capturing test frames and making adjustments much easier.  This is not the case when shooting a faint reflection nebula such as the Witch Head nebula!

Tracking/Guiding

Beginners usually need time to fully utilize their telescope mount’s tracking and autoguiding abilities.  The longer the exposures, the more evident poor tracking becomes.  Luckily for beginners, an impressive photograph of M42 is possible using multiple exposures of 1 minute or less!  This target is just begging you to capture it!

Multiple exposures for more detail

The bright core of the Orion Nebula requires very short exposures to properly document the area.  To capture the Trapezium without over-exposing the image, I shot several 5-second subs at ISO 800.  I also set BackyardEOS to shoot a series of 30-second subs to capture the mid-tones and slightly less-bright areas surrounding the core.

Here are the totals from each series of shots at lengths of 5, 30, and 180 seconds at ISO 800.

  • 180″ – ISO 800 – 1 hour 9 minutes (23 frames)
  • 5″ – ISO 800 – 1 min 40 sec. (20 frames)
  • 30″ – ISO 800 – 5 min. (10 frames)

I registered and stacked each of the image sets in Deep Sky Stacker, and processed each of the files separately.  Once each image file was processed to maximize the intended level of detail, I blended the images together in Adobe Photoshop using layer masks.  This can be a difficult process, as this can sometimes lead to unnatural looking and/or flat looking deep-sky objects.

Here is the current state of my Orion Nebula image, using the short exposures in the core:

Orion Nebula with a DSLR and Telescope

The Orion Nebula – Early version using layer masks

As you can see, some of the faint outer nebulosity has been captured, yet the core of nebula is still well exposed without clipping any of the data.  In comparison, have a look at the stack of 5-second exposures at the exact same scale from the same imaging session:

Orion short exposures

A stack of 5-second exposures on the Orion Nebula

Using layer-masking in Adobe Photoshop, we can merge the data from all 3 image sets to reveal all of the details of the Orion Nebula in a single image. As I said earlier, this process can be difficult to master and takes time and patience to utilize properly.  If done properly, the nebula will look natural and full of detail.  I’ll provide updates along the way as I tackle this winter astrophotography project from the backyard.

Cold, long nights with my DSLR and telescope

Despite what the frigid winter temperatures do to our bodies, your DSLR will produce images with less noise in the cold!  The nights are also extra long, which means the potential of longer imaging sessions.  So fill your thermos will a hot drink, it’s going to be a long night. If you need me, I’ll be in the backyard.

Cheers, and all the best in 2017!

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Astrophotography in the City

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Saturday Night Under the Stars

Astrophotography in the City

Last weekend I posted a new video to my YouTube channel titled DSLR Astrophotography – A Night in the Backyard with my Camera. It is now Early-April, and we are in what amateur astrophotographers call “Galaxy Season”, as we transition from the Winter Constellations like Orion and Taurus, to the Summer Milky Way objects.  In between, there are some fantastic deep-sky objects to observe in the Spring Constellations Leo, Coma Berenices, and Bootes.

The forecast called for clear skies on that crisp, cold Saturday night in Southern Ontario, and I was ready to image some deep-sky objects with my camera and telescope.  After a late dinner, it was a race against the clock to photograph my first subject of the evening, the Waxing Crescent Moon. If you want to jump straight to the video, you can find it at the bottom of this post.

Live-View DSLR Through a Telescope

Using the Canon 70D’s live view screen for telescope observing

Crescent Moon Astrophotography

 

I barely had time to get the beautiful Waxing Crescent moon into my telescope’s eyepiece before it became obscured by the surrounding trees in my neighborhood!  I shot a live-view video of the moon (with Earthshine visible) with my Canon EOS 70D DSLR through the telescope.  This may be of interest to anyone wondering what the view is like through an 80mm refractor telescope.  You need an adapter to attach the camera to the telescope, which you can buy online here.

After I focused the Moon and experimented with different ISO settings and exposure lengths, I snapped a couple of shots before moving on with the rest of my night.  You can have a look at the equipment I use for astrophotography here.

 

Earthshine Moon

The sky from my backyard

Next, I wanted to provide some examples of the dark-sky quality from my backyard.  Living in the central part of town has its advantages, but dark skies are not one of them!  I experience heavy light pollution from all directions.  This makes using a light-pollution filter on my camera necessary for long exposures.  Currently, I use the IDAS LPS clip-in filter on my Canon Rebel Xsi DSLR.  This allows me to capture exposures of up to 5 minutes from my backyard.

 

Astrophotography in the City

The night sky from my backyard on April 9, 2016

 

The Big Dipper Asterism

Looking towards the Big Dipper in Ursa Major

Deep-Sky Target: Edge-On Spiral Galaxy in Coma Berenices

NGC 4565 – The Needle Galaxy

Once the moon had set, I promptly prepared my deep-sky astrophotography rig for a night’s worth of photons on my photography subject.  I settled on NGC 4565 – The Needle Galaxy because of it’s size, magnitude, and current location in our night sky.  The Needle Galaxy is an edge-on spiral galaxy that resides about 30-50 million lights years from Earth.  This handsome galaxy is the current photo in my 2016 RASC Observer’s Calendar hanging in my office at work, perhaps that is what gave me the idea!

Astrophotography in the City - Needle Galaxy from my backyard

NGC 4565 – The Needle Galaxy

Photographed on: April 9/10, 2016

Total Exposure Time: 54 Minutes (18 x 3 Min. Subs @ ISO 1600)
Mount: Sky-Watcher HEQ-5 Pro
Camera: Canon 450D (modified)
Telescope: Explore Scientific ED80 Triplet Apo

Guided with PHD Guiding
Stacked in Deep Sky Stacker
Processed in Adobe Photoshop CC

This interesting NGC object shows up rather small in my 80mm telescope, as many galaxies do.  A larger telescope with a focal length of 1000mm or more would be a better choice for this DSO.  I also had a bit of a challenging evening out the background colour of this image.  Flat frames would have made this issue much easier to deal with in post-processing.  With just under an hour of exposure time, it is safe to say that I will need to add more time to this image to bring out the colour and detail.


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I am completely blown away with the response to my YouTube Channel has received.  Thank you to everyone who has subscribed, I look forward to many new astrophotography videos in the future!

Beginner Advice:

What’s the best telescope for astrophotography?

Which camera do you recommend for beginners?

Astrophotography Settings and Tips

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Collimating a Newtonian Telescope

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Collimating a Newtonian telescope is something every backyard astronomer should experience.  In this post, I align my 8″ Orion Astrograph Newtonian for a night of astrophotography in the backyard.  My deep sky target is M101 – The Pinwheel Galaxy – in the constellation Ura Major.  With a proper alignment of the mirrors in this reflector, I should be able to capture a new portrait of the galaxy with my DSLR camera.

Spoiler – things do not go well.

My Newtonian Reflector is Ready for Spring

Collimating a newtonian reflector telescope

 

The clouds finally broke (to a certain degree) last Saturday night, and being the die-hard night-sky photographer that I am, I skipped out on all of the fun social activities taking place that night in exchange for a lonely time by myself under the stars.

Don’t get me wrong, there is nowhere I would rather be, but when things go horribly wrong, you begin to question your decision to stay home. On a positive note, I learned a little more about my equipment, and how to deal with the challenging and sometimes frustrating scenarios that come with deep-sky astrophotography.

Example photo using my Newtonian Reflector for Astrophotography:

Collimating a Newtonian Reflector

M51 – The Whirlpool Galaxy

Collimating a Newtonian Reflector

Orion 8″ f/4 Astrograph Reflector

While the sun was still up, I carefully collimated my Orion Astrograph to the best of my abilities.  The process of constantly collimating a Newtonian reflector is a big reason I generally prefer to use my apochromatic refractor.  That being said, once tuned-in, the light-soaking power of that fast 8″ mirror is hard to ignore.  Not to mention that this telescope has a focal length of 800mm compared to the wider 480mm in my Explore Scientific ED80.

The process of collimation is actually quite a simple process, once you know what you’re doing.  The hardest part is learning exactly what you are looking at when you position your eye over that open focuser tube.  Thankfully Sky and Telescope has an extremely helpful tutorial on their website, with the necessary diagrams for my brain to fully comprehend the ordeal.  (I am a visual learner – go figure!)  The diagram below was an integral part of my collimation success:

Collimation Diagram

The 3 Step Process outlined by Sky and Telescope‘s Nils Olof Carlin really helped simplify the process.  Like I mentioned earlier, these steps are a lot easier to take once you understand each part of the telescope from the diagram above.

Step 1: Center the secondary mirror on the axis of the focuser drawtube

Step 2: Aim the eyepiece at the center of the primary mirror

Step 3: Center your primary mirror’s sweet spot in the eyepiece’s field of view.

It’s Galaxy Season!

Thanks to some suggestions on my Facebook page, I narrowed down my imaging choice to Bode’s Galaxy and the Cigar Galaxy in Ursa Major (M81, M82).  The reason for this choice is that they are in a great position in the Northern sky from my latitude right now.

The lack of interesting nebulae and galaxies in the Southeast also swayed my decision.  I have imaged these two galaxies before with the Newtonian, but that was before modifying my Canon Xsi that can now pick up more of the pink nebulosity.

Top 8 Deep-Sky Targets for Galaxy Season

Markarian's Chain in Virgo Cluster

Markarian’s Chain

Where it all went wrong

A thick cloud cover put a lid on my imaging until about midnight on Saturday.  I studied the weather forecast and satellite animations carefully, and sure enough, the early spring constellations began to appear.  I napped for two hours beforehand, to make sure I had enough energy to image late into the night.  While carrying out the alignment process of my Sky-watcher mount, I noticed that the guide stars appeared sharp and crisp.  They even had the reassuring, round donut shape when unfocused. Clearly, my collimation session earlier had paid off!

Once I was polar and star aligned, I directed the tracking mount towards M81 – Bode’s Galaxy in Ursa Major.  There it was in the eyepiece, along with its close companion M82.  A rewarding view, even in the heart of the city.  I so rarely view these objects visually, I spent almost 5 minutes allowing my eyes to adjust and get a deeper view.

Okay, so far so good.  Time to get focused, and start imaging.  I framed the objects perfectly within my field of view and achieved sharp focus by using the handy frame and focus tab within BackyardEOS.  The last piece of the puzzle was to get PHD calibrated, and guiding on my object.

Orion Newtonian Reflector

My 8″ Orion Newtonian set up in the backyard

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PHD Guiding Issues When Imaging Near Polaris

“Star Did Not Move Enough” Error

I have heard from fellow astrophotographers about PHD guiding not calibrating when imaging close to the North Star, Polaris.  I have experienced this first hand a number of times myself, including on Saturday night.  The West calibration step continued to fail, displaying the “Star Did Not Move Enough” error message.

I fiddled with multiple settings within the PHD Guiding “Brain” button, including the much-debated calibration-steps parameter.  I also closed down PHD, and unplugged the autoguiding connection cable, to rule that out.  I have lost countless hours under moonless, clear skies to this scenario over the last 4 years.  I desperately need to come up with a permanent solution for this problem.  I had no choice but to switch targets, and hope that PHD would began doing what it was designed to do.  Autoguiding.  Luckily, I moved to a target in the same region of the sky that would also lend itself well to my current configuration.

I desperately need to come up with a permanent solution for this problem.  I had no choice but to switch targets, and hope that PHD would began doing what it was designed to do.  Autoguiding.  Luckily, I moved to a target in the same region of the sky that would also lend itself well to my current configuration.

M101 – The Pinwheel Galaxy

Sure enough, PHD calibrated itself, and began guiding on my subject.  It was now 2:00am, and I took my first 3 minute sub at 2:09am.  That’s 2 hours of frustration and wasted clear skies!  Patience and a positive attitude is certainly needed for this hobby, but taking action to not repeat past mistakes is even more important.  I will have to research alternatives to PHD guiding, or at least narrow down exactly what is going wrong when trying to calibrate PHD close to Polaris.  Once the graph looked steady, I set BackyardEOS to take 30, 210 second exposures on M101 and went to bed.

I will have to research alternatives to PHD guiding, or at least narrow down exactly what is going wrong when trying to calibrate PHD close to Polaris.  Once the graph looked steady, I set BackyardEOS to take 30, 210-second exposures on M101 and went to bed.

 

PHD Guiding Calibration

East Calibration – Finally! And a Steady Graph

 

Here’s the kicker.  Something wasn’t right with my guiding on M101 either.  I am not sure if it was because of the settings I had changed when trying to calibrate earlier, a conflict with the dithering I enabled within BackyardEOS, or a third unknown factor.  Either way, I captured 30 jerky frames of M101 while I slept.

I didn’t inspect the frames until I woke up again at 4:00am to review my results. It was at this point that I realized that this blog post would not be a success story.

 

Autoguiding Issues

 

Conclusion – I had a Rough Night!

I came up empty-handed, even after having such a well-planned out night with all my bases covered.  However, I went through the process of collimating a Newtonian telescope again, and now feel comfortable using this telescope more often for astrophotography.

I also came to the conclusion that I need to seriously address the on-going issues I have been having with PHD guiding to avoid more wasted nights in the future.  Thank you for your continued support of my astrophotography journey, and if you have any solutions for me, I would love to hear them!

Update: I now use PHD2 Guiding – and My Issues have been sorted

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