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Deep Sky Astrophotography Step-by-Step Walkthrough

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In this post, I’ll break down everything you need for deep sky astrophotography with a telescope. I’ll cover each piece of gear I use, and explain how it can be used to capture beautiful deep-sky images of space from your backyard.

Deep-sky astrophotography is a rewarding and fulfilling hobby, especially once you’re able to achieve impressive results from your own home. This post aims to give beginners a better idea of what you need, and what you can expect to accomplish yourself.

I’ll be setting up from scratch, and talk about each piece of gear used, so you can replicate my process. I’ll warn you right now, my methods are by no means “the right” way to do this, it’s just the way that works for me.

Deep Sky Astrophotography Walkthrough

The following video takes you through my current deep sky astrophotography routine step-by-step. For a more detailed description of the process, keep reading!

First things first, if you’re brand new to deep sky astrophotography, here’s how it works. I use a tracking equatorial telescope mount to compensate for the rotation of the Earth. Because the night sky slowly rotates throughout the night, we need to “freeze” the sky in place in order to capture a long exposure image.

A long exposure photo of 1-minute or more will collect much more light on an object in space than you could ever see with your naked eye alone. This detail is collected onto the camera sensor, and can then be processed to pull out even more color and detail.

When it comes to deep-sky astrophotography, you can consider the telescope to act as the camera lens. The focal length and aperture offer you the power needed to get a close-up look of some incredible deep-sky objects in space. In general, the most important aspect of deep-sky astrophotography is to collect as much data as possible – good data.

It needs to be sharp, well exposed, and well framed. With good data, the image processing stage is a lot of fun. With enough overall exposure time, your image will benefit from a strong signal-to-noise ratio.

You can learn more about the basics of deep-sky astrophotography in the “get started” section of this website. For now, I’ll focus on what you need to start capturing quality data from home.

deep sky astrophotography walkthrough

Before Getting Started

The last thing you want to do is spend time carefully setting up all of your gear on a night when the weather forecast is not promising. I usually don’t set up my equipment unless I am confident the sky will be clear until dawn. I monitor a variety of weather forecasting apps to see if the sky will be clear during the night from my location.

clear outside

I have found that the most accurate tool to forecast a clear night sky is Clear Outside by First Light Optics. I use the Android app version on my smartphone. The app includes several useful metrics including visibility, wind direction, estimated sky quality and more. I like the low, med, high cloud format and have found it to be astronishly accurate.

The Clear Sky Chart is another great tool to use, but I find the forecast to be a little optimistic for the most part. Often times, the forecast looks better on the clear sky chart than it does on Clear Outside. This tool is an online webpage rather than an app, but it has an impressive amount of locations across the world listed. Just Google your location + clear sky chart.

Step 1: Powering the Gear

We need to power the equipment, so I usually run an extension cord (or two) out to my imaging location in the backyard. Many people use a portable battery pack to power their gear, and so do I when I don’t have access to electricity.

You can save some serious cash by building your own battery pack using a deep-cycle marine battery and an inverter. I bought one of those battery booster packs from the hardware store for convenience – but they don’t last long and are overpriced.

The model I use is a Motomaster Eliminator 600W (Similar to this style) and it has enough juice to power all of my equipment for 1 night. After that, it’ll need another full charge to reliably go another night. I’ve had batteries die on me in the past, and it’s a heartbreaking moment.

Step 2: Level the Tripod Mount

An astrophotography telescope mount must sit on a tripod, or in my case a tri-pier. A rock-solid base for the equatorial tracking head of the mount is essential. You’ll need to confirm that it is level and secure to avoid headaches later on.

Equatorial Mount

Many people build a custom concrete pier and fasten their tracking mount to it for the ultimate stable platform. This, of course, requires a permanent spot for your equipment. I’ve thought about constructing a small observatory in my yard, but I’ve decided to wait until I have a little more property to work with.

No matter what size of tripod or pier you use for astrophotography, you need to make sure that it won’t slip or move throughout the night.

Step 3: An Equatorial Mount

Many astrophotography mounts include a built-in bubble level, which comes in really handy if you often set up in new locations. For the current mount that I use, I simply adjust the length of the  tri-pier legs until the mount head is as level as possible.

The astrophotography mount I currently use is an iOptron CEM60, which was generously loaned to me from Ontario Telescope and Accessories. It’s a center-balanced equatorial mount that uses a magnetic gear system.

iOptron CEM60

The mount moves the telescope in 2 axis, right ascension (RA) and declination (Dec). It allows me to point at any deep sky object that isn’t obstructed by trees or houses in my backyard.

Once it’s centered on the object, it will track it and keep it completely still so I can photograph it. (Autoguiding improves this, but I’ll cover that momentarily) The iOptron CEM60 is a GoTo mount, which means that I can enter the target name into the keypad, and then the mount will slew the telescope to it for me.

Recommended Telescope Mount Options:


telescope mounts

Entry Level: Orion Sirius EQ-G Computerized Telescope Mount

Intermediate: iOptron CEM60 Center-Balanced Equatorial Telescope Mount

Professional: Software Bisque Paramount ME II

Step 4: Polar Alignment

An accurate polar alignment is crucial for a successful deep-sky astrophotography image. The process of polar-aligning a telescope mount for astrophotography may sound difficult to achieve at first, but it’s really not that complicated.

The reason I mention it at this stage, is because you’ll need to roughly have your telescope mount polar aligned when setting it up. Meaning, the counterweight shaft should be pointing directly north. Because I am in the northern hemisphere, I use Polaris, the north star, as a guide to accurately polar align the mount.

polar alignment

If you live in the southern hemisphere, or can’t see Polaris, there are alternative ways to polar align. Software assisted methods such as drift alignment can help. I’ve used a polar alignment routine in a program called Sharpcap. PHD2 guiding (which ill cover shortly), also has a useful drift alignment tool.

The way I do it, is to use a simple app on my phone (PolarFinder) to tell me exactly where Polaris needs to be in my polar finder scope to be polar aligned from my location. It uses my GPS coordinates and places the star in the correct position for my exact location and current time.

Then, it’s just a matter of matching up what the app tells me on the mount be adjusting the alt-az knobs. The entire process should only take about 2 minutes once you are used to it. If you’re really not interested in this manual process, or cant see polaris. You should probably check out the Polemaster.


Step 5: Balancing the Telescope

Now that we’re polar aligned, we can get to the fun part – mounting the astrophotography telescope. Along with being polar aligned, balance is a major factor to consider when setting up your rig.

All equatorial mounts include a counterweight, which I’ll need to use to balance this 20-pound refractor telescope. You need to balance the scope in both axis, so that the mount doesn’t have to work any harder than it needs to when slewing and tracking objects in the night sky.

astrophotography how to

The telescope I’ll be using tonight is a William Optics Fluorostar 132. It’s an apochromatic triplet refractor, which is one of the best telescope types to use for the purposes of astrophotography. It has a focal length of 925mm and an f-ratio of F/7.

A telescope like this has enough aperture to pull in some serious light and get an up-close look at some of the most impressive deep sky nebulae.

We need to attach the imaging payload (the camera) to the telescope, along with the autoguiding system for an accurate overall weight to balance. This is the payload that will need to be tracking smoothly while the photos are being taken. Even the distance the focuser is from the tube will make a difference in the balance, so there may be some trial and error here.

The closer your imaging payload is to the maximum capacity of your mount – the more balance comes into play. For reference, the CEM60’s 60-pound payload capacity is very forgiving with my relatively light 25 lb imaging gear.

In general, your mounts payload capacity should ideally be double the weight of your astrophotography gear. This may seem excessive, but long focal lengths and long exposures demand the greatest of tracking accuracy. If you haven’t taken the time to balance your telescope, even the slightest imbalance may come back to haunt you over time.

Step 6: The Imaging laptop

There have never been so many great options for controlling your camera or mount remotely for astrophotography than there are now.

Dedicated astrophotography computers, mini pcs, and good old-fashioned laptops. I’ve been using the same laptop since I started taking images of space back in 2011. It runs Windows 7, and all of the astrophotography software needed to run a successful imaging session.

laptop computer

The Astrophotography Software I Use:

The computer has software installed for controlling the camera, the mount and of course an internet connection. I can remote in to this laptop from in the house using Team Viewwe to check up on things from inside the house.

Step 7: Autoguiding Setup

Now, let’s talk about this smaller telescope riding atop the big one. This is called a “guide scope”, and its job is to help the mount track with even greater precision.

I’ll attach a small camera into this telescope, which will feed an image to my computer with a looping image of stars. Then, my computer will communicate with the mount to make small adjustments in periodic error for improved tracking accuracy.


It sends guide pulses to the mount to based on the tiny movements it read from the guide star. This is called autoguiding, and it can be the difference between the ability to capture a 30-second exposure and a 5-minute exposure.

For my upcoming task of star alignment, I’ll use an eyepiece in this little telescope before attaching the camera. It’s a 32mm eyepiece – that offers a 52-degree wide field of view. This is beneficial for the next step of my process.

Step 8: Star Alignment

With the mount leveled, polar aligned, and the telescope balanced. We can actually turn this sucker on. With this mount, I need to first set the “zero position“, with both axis in the home position.

After that, I’ll begin a simple star alignment routine that calibrates the mount to have precise pointing accuracy.

This means that when I punch in the deep sky object I want to image, I can be sure that the telescope will land on it and put it dead center in the frame.

Certain objects are extremely dim, so it would be impossible to know if I have the telescope pointed at it without taking a series of test exposures. This can take precious time away from imaging on a clear night – so take the time to properly star align your mount first.

star alignment routine

I personally don’t mind this stage of the process, because I honestly enjoy a little time actually looking through the telescope and getting some minor physical activity.

But I understand that there are those of you out there that are either tired of this process or have mobility issues. For these folks, I suggest using a plate solving software aid such as Astro Tortilla.

The manual process of star alignment involves slewing to 2 or 3 bright stars and centering them in first the guide scope, and then through the primary imaging telescope. Since I’ll be pointing at some of the brightest stars in the sky, I like to perform my focus routine at the same time.

Step 9: Focus and Camera Control

I like to use the live-view image from the camera during star alignment to help center the stars. Rather than centering the star in an eyepiece, I’ll jump into my camera capture software to make this process easier and more precise.

The software is called Astro Photography Tool (APT for short).

Astro Photography Tool

The Astro Photography Tool Camera Control Software Interface

A camera control software like this not only lets you automate the length of each image and number of shots to take, but they also include features to help with focus, framing, and much more.

A dedicated astronomy camera like the one I’ll use tonight does not include a display screen with an image the was a DSLR does. This means that running an additional software tool to run the camera is necessary.

To focus, I use a tool called a Bahtinov mask that creates a star diffraction spike pattern on stars that are close to being focused. During my 3-star alignment routine, I roughly center the star in the wide field guide scope visually, and then use the live-view loop with the Bahtinov mask to both center the star in the primary imaging scope, and set my focus.

how to focus

What you’re aiming for is a centralized spike between the X. Next, I’ll talk about the camera itself.

Once you’ve found the best focus possible using the Bahtinov star diffraction spike method, you can lock the telescope focuser in place using the thumbscrew in the underside of the tube. Don’t forget to take the Bahtinov mask off before capturing your light frames! (I’ve made this humbling mistake before)

To retain focus throughout the night, you may need to re-focus later on, especially if the temperature has dropped significantly. A motorized focuser such as the Pegasus Astro model I demoed over the winter makes this task much easier by allowing you to make micro-step adjustments via software on your computer.

Step 10: Setting an Imaging Sequence

With the star alignment and focus routine out of the way, we can now slew to our deep sky target for the night.

Certain targets are better choices than others depending on your imaging conditions, moon phase, camera sensor size, telescope, filters etc. Over time, you’ll learn what you particular gear is best at, and set your self up for success whenever possible.

The camera I am using tonight is known as a one-shot-color camera. It shoots images using in broadband true color, using a sensor that collects light in RGB simultaneously. A monochrome camera is capable of collecting more signal (light) at once, but a filter wheel is needed to conveniently capture each color channel needed to produce a full-color image.

This camera is called the ZWO ASI294MC-Pro. It includes a cooling feature that keeps the internal sensor cold during long exposures. This is important because a hot sensor means more noise. Noise is the little pixels and artifacts that can really make a mess of your image. With a cool sensor, you’ll be able to create images with a much better signal-to-noise ratio.

astronomy camera

The ZWO ASI294MC-Pro One-Shot-Color Camera

For those shooting with a DSLR camera:

If you’re shooting deep sky astrophotography with a DSLR, the process is slightly different than the way I have featured in the video. This is particularly evident when it comes to the focus, framing and imaging sequence setup.

With the DSLR attached to the telescope via a t-ring and adapter and/or field flattener (these adapters are usually 0.8X and both reduce the focal ratio of the telescope, and “flatten” the field of view), you’ll want to frame up your target just as you would with a dedicated astronomy camera.

The camera and telescope will need to be in focus before attempting to frame your target, and you have a few options here. One option is to focus on a star using live view on the camera itself before connecting to APT. A high ISO (1600+) is recommended while focusing and framing as it will produce the brightest stars for reference purposes.

You could also use the “live view” mode in APT. A short exposure of 4-5 seconds should be long enough to focus using a Bahtinov mask. Then, you can use a longer exposure loop to frame your deep sky object.

Set the exposure length to about 5-10 seconds, using an ISO of 1600 or more. (6400 works well for this step). This should pull in enough stars too orientate your subject, even with a strong filter in front of the sensor. (Such as a clip-in Ha filter)

Step 11: Recommended Filters

From my city backyard, filters are necessary to capture any sort of usable image. If I want to shoot a true-color image with this camera, a light pollution filter will help ignore many of the wavelengths of light associated with things like streetlights and porch lights.

Even then, extensive image processing must be done to separate the deep sky object from the bright sky. It’s the price we pay for being able to enjoy this incredible hobby from the comfort of our backyards.

Tonight, I’ll be shooting with a much stronger filter. It will ignore all wavelengths of visible light except for 2 very narrow bandpasses.

The STC Astro duo narrowband filter collects the light associated with Hydrogen-alpha and Oxygen only. For certain emission nebulae, it can produce jaw-dropping images in even the heaviest of urban light pollution.

The Eagle Nebula

The Eagle Nebula using the STC Astro Duo-Narrowband Filter

Step 12: Slewing to Target

With everything balanced, aligned and ready to go, we can now hop into the camera control software to set up an imaging sequence.

The target I have chosen to shoot is the Butterfly Nebula in Cygnus. It rises above my house by 10 pm and I ‘ll track it along the sky until morning. I’ll need to perform a meridian flip when the mount reaches the Zenith, which just means the telescope needs to switch sides and start tracking again.

deep sky target

For narrowband images like the one I’ll share in this post, you’ll want to use a longer exposure than you would when shooting in color.

I’ll tell the software to shoot 40 x 6-minute images. To make sure that each one of these 6-minute subs is sharp, I’ll turn on the autoguiding system.

Step 13: Autoguiding

For autoguiding, I use a free software called PHD2 guiding. This tool runs my little guide camera, the Altair Astro GPCAM2. It houses a small mono sensor with one job – to follow a single star all night.

The software will communicate with the mount to make the small adjustments needed for improved tracking accuracy. I can also leverage a feature called dithering, which reduces overall noise in your stacked image by slightly shifting the position between each frame before capturing.

A way to know if your guiding is “good” or not is to view the graph tool in PHD2 guiding. A smooth graph will have a total RMS error under 1 second, as seen in the screenshot below.

PHD2 Guiding Graph

Helpful resource: Analyzing PHD2 Guide Logs

Step 14: Capture Your Deep Sky Target

Here are the individual steps I take to set up a complete imaging sequence in APT with PHD2 guiding.

  1. Connect camera (ASI driver)
  2. Choose “unity gain” setting
  3. Connect mount (iOptron Commander)
  4. Use live-view with Bahtinov mask
  5. Center 3-star alignment stars
  6. Focus on alignment star using star diffraction spike pattern
  7. Remove bahtinov mask
  8. Slew to target
  9. Set cooling to -20 (Cooling-Aid)
  10. Slew to target
  11. Adjust target framing using 20-30 second live view loop
  12. Run and calibrate PHD2 guiding
  13. PHD2 guiding with smooth graph
  14. Ensure dithering is active
  15. Start imaging plan (eg. 30 x 300-second subs, Binned 2×2)
  16. Grab a beer and watch each image appear!

Here is the image I captured using this setup on the night I recorded the video. The image includes just over 6 hours worth of total integrated exposure time using 6-minute images. The images were stacked in DeepSkyStacker to improve the signal-to-noise ratio before being processed in Adobe Photoshop to pull out more color and detail.

IC 1318 - The Butterfly Nebula

The Butterfly Nebula is located in the Sadr Region of Cygnus, and it an excellent astrophotography target to capture in narrowband hydrogen-alpha.

Final Thoughts

If you’re brand new to astrophotography, I hope you now have a better understanding of the process involved in capturing deep sky objects through a telescope. It may seem like a lot to take in all at once – because it is!

The good news is, if you are dedicated and passionate about astrophotography, small victories and improvements along the way are all you will need to keep going.

I certainly didn’t get to where I am at today in a hurry. Why would I rush through something I absolutely love doing?

My final advice to you would be to be patient and remember to enjoy each small victory along the way. The night sky is not going anywhere, and you have the rest of your life to explore it.

astrophotography step-by-step guide

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Perseid Meteor shower 2016

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This year’s Perseid meteor shower could be the best in years!

Update: Perseid Meteor Shower Photo shot on August 11, 2016

Perseid meteor photo from my backyard

Perseid Meteor photographed from my backyard the Night of August 10th-11th

August 11, 2016

I captured a photo of a small meteor the night of August 10th-11th, 2016 from my backyard.  I piggybacked my Canon 7D DSLR camera on my astrophotography telescope and equatorial mount so that I could take advantage of auto guiding for longer exposures.  This is a manual stack of 6 x 1.5-minute exposures at ISO 1600.

The night of August 11th-12th 2016 is expected to produce an outburst of Perseid’s not seen in 10 years.  The Perseid meteor shower is considered to be the best showing of meteors in the night sky for the entire year.  The warm August nights make the event extra enjoyable, as you can comfortably sit in a lawn chair and watch the whole show.  The best time to catch a shooting star is after midnight when the moon sets, as this will result in a much darker sky.  Below you will find tips on viewing the Perseid meteor shower, where to look, and how to photograph the event.  I even provide a brief astrophotography tutorial about how to create a composite image of this meteor shower.

When to watch:

The night of Thursday, August 11th, 2016

Perseid meteor shower photo

Perseid meteor streaking across the Milky Way – Photo by Robert Lenz


What exactly is a meteor shower?

Every year in August, Earth passes through a stream of dust and debris left by the comet named Swift-Tuttle.  It is interesting to note that there has been some debate as to whether this comet will eventually pass dangerously close to earth in just over 100 years.  Further investigation into the possible catastrophe revealed that the comet’s orbit is more stable than originally thought.  Phew!

Meteor shower 2016

A composite photo of Perseid meteors – Stock image

As Earth passes through the debris and particles left by Swift-Tuttle, those particles (meteorites) smash into the Earth’s atmosphere and burn up.  This event produces bright streaks of light across the sky that we see here on Earth as meteors, or shooting stars!  Many of these meteors are quite bright, and can cause a “wow” reaction from onlookers.  Sharing the moment of a meteor streaking across the sky with someone is a feeling you won’t soon forget.

Why is 2016 a special year for the Perseids?


On a good year, the Perseid meteor shower will produce about 1 meteor per minute under dark, clear skies.  During peak hours, as many as 2 meteors per minute are possible.

This year, the rate of meteors could be up to 3 per minute!

Dark skies are a must if you want to see as many meteors as possible.  If you are lucky enough to own a cottage or camp somewhere with little to no light pollution, you will see even the faintest of shooting stars.  If you can take in a wide panoramic view of the Eastern horizon, consider yourself spoiled!  I haven’t decided whether I will travel for this meteor shower this year, or set up shop in the backyard.

The explanation for the outburst this year has to do with the orbits of Jupiter and Saturn.  The position of those planets in relation with the debris left by Comet Swift-Tuttle has Earth primed for an extra special show this year.

Tips for viewing this Meteor Shower

You can begin looking for shooting stars at around 10pm when the Perseids are at the official peak.  Although the moon will still be up, the Perseids are known for producing some very bright meteors that can be seen even when the sky is not completely dark.  At this time of the night, the constellation Perseus will appear low in the sky, and the meteors will enter the atmosphere at a shallow angle. These meteors can be quite the spectacle!  These are known as “grazing” meteors that can last multiple seconds, and travel a wide distance across the sky.   I remember seeing the brightest, longest lasting meteor of my life in this scenario years ago from a friends backyard.


When is the best time to watch?

This event will really start to take off after midnight.  By then, the 57% full waxing gibbous moon will have almost set, and the real show can begin.  The location of the night sky you will want to observe is towards the constellation Perseus.  After midnight, Perseus will be high in the sky.  Use the star map below to get a better idea of the area in the sky you will want to monitor:


Perseus constellation

The radiant point for the Perseid meteor shower is the constellation Perseus

Perseus is south of the constellation Cassiopeia, which looks like a big “W” of stars.  This constellation will stand out as soon as it starts to get dark out, even under light polluted skies from the city. If you can’t spot Perseus right away, just use Cassiopeia as a reference point in the sky.


Best telescope for beginners

How to Photograph the Event

If you own a DSLR camera and a tripod, you’re in luck.  You have everything needed to capture beautiful photos of this celestial event!  A copy of Adobe Photoshop will also help you create a composition photo of multiple meteors streaking across the sky at once.  A point-and-shoot digital camera, such as a Canon Powershot or Nikon Coolpix may also be capable of capturing this event, as long as it has a manual mode with long exposure capabilities.  The main idea behind this process is that you will leave your camera shutter open for an extended period of time, for a better chance at capturing a meteor streaking across the sky.  Taking a series of long exposures over the duration of the event gives you a solid chance at capturing the action!

By shooting continuous 30-second exposures, your camera will have a constant eye to the sky.


Automate your imaging session

Using photographic accessories can help automate your imaging session, and give you a better chance at catching a few meteor photos.  A simple intervalometer will allow you to program the camera to take continuous exposures for an extended period of time.  The Canon timer remote controller has many features including an interval timer and exposure count setting.  This would do a great job of setting your camera to record the Perseid’s.

A must for DSLR Astrophotographers: BackyardEOS

You can also use software on your computer to automate your imaging.  BackyardEOS is a fantastic program for astrophotographers, and I use it for my personal deep-sky astrophotography exclusively.  BackyardEOS can also be utilized in situations like meteor showers, as it works as an interval timer for your DSLR.  For example, you could set your camera to take 100 x 30-second shots at ISO 800.  The frames are then downloaded to your laptop with plenty of storage room.  For the best results, make sure your computer has lots of hard drive storage space, and your DSLR has an AC power adapter.  Running out of storage space or battery power can ruin your night in a hurry!

To see BackyardEOS in action, watch my YouTube Video:

A Night in the Backyard

To see how I connect my laptop to my DSLR Camera, see:

My DSLR Astrophotography Equipment Setup

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Creating a meteor shower composite photo

When shooting your series of images, it is important to not move your positioning. Choose your initial framing carefully, because you will be sticking with it for the rest of the night!  The process of combining your images taken during the meteor shower is rather simple, but it will make a big difference in the impact your shot makes.  The idea is to create a single image containing every meteor you captured throughout the night. If you captured enough Perseid meteors (that came streaking out of the radiant point), you will have the elements needed to produce an image that dynamically represents the events that took place that night!


Perseid Meteor shower composite image

A glorious example of a Meteor Shower composite image – Leo Lam


Look for shooting stars!

Start by reviewing your photos, and try to isolate the shots that contain a meteor streaking across the sky. This can be very exciting, especially if you caught a bright one! Ideally, you will have at least 3-4 shots that contain meteors, but the more the better.  Now, register, stack and process a “base image” of your night sky. A stack of about 10 x 30-second exposures should give you a nice smooth image containing a sky full of stars and constellations. You can process this image to pull out some fainter stars, balance the background sky, and reduce noise. This will be the underlying layer of stars for your meteor shower composite. If you were able to include an interesting foreground subject, bonus points to you!


SLR astrophotography images

Multiple exposures captured during last year’s Perseid meteor shower



Pulling it all together

Next, take your meteor frames you selected earlier and place them on top of your base image as layers. Set these layers to “lighten” blending mode in Photoshop, to reveal only the meteor, but not the noisy, unprocessed background sky. You can subtly process your meteor frames to brighten the meteor slightly, but don’t over do it.  Do this with all of your meteor frames, to create a master file with every meteor that occurred during your session. You can then flatten the image (or create a new adjustment layer) and do some overall image edits.

Follow me on Twitter or Facebook for my latest updates on the 2016 Perseid meteor shower!

Learn more about the DSLR camera settings used for Meteor Showers and other types of astrophotography: Astrophotography Tips and Camera Settings

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Selective Processing for More Detail

Staying Inside – Image Processing

The unseasonably cold weather and precipitation we have experienced here in Southern Ontario have given me the perfect opportunity to go through my old astrophotography images and reprocess the data.  I have been advancing my image-processing skills by studying current astronomy images taken by the pros.

Being a creative professional myself, I have always understood and appreciated the power of inspiration. I am always interested in new image-processing techniques, photoshop tutorials and new software that can enhance my work.  Through selective processing, I have been able to squeeze out the most amount of detail from my astro images.

Western Veil Nebula

The Western Veil Nebula – I reduced the stars to show more contrast in the nebula

My latest take on The Swan Nebula is my favourite version yet. Through selective processing, I was able to tame the background stars, while intensifying the gorgeous pinks and reds in the nebula itself.  I also recently reprocessed my wide-field image of the Western Veil Nebula, with a focus on reducing star size, and overall image contrast and color. The “witch’s broom nebula” is a tough process, especially if you have to deal with a severe gradient behind all of those stars. After assessing the gradient in photoshop, (mostly due to heavy light-pollution) I can easily even out the sky background using the Gradient Xterminator plugin.

I am quite pleased at my latest results of the Eagle Nebula as well.  I went through my astrophotography folders from the past 4 years (like I said, it’s been cloudy!)  and found a set of almost 2 hours of frames on M16 that I had not previously used!  I combined all of the data together from May 2012, and May 2013 in Deep Sky Stacker to create an image with over 3 hours of exposure time.  I decided to keep the extremely wide-field view captured by my 80mm telescope, rather than cropping the photo around the nebula. This image really benefitted from the selective processing technique. By reducing the stars on a separate layer, I was able to keep all of the detail found in the nebula.

Eagle Nebula - 80mm Telescope

Wide field image of the Eagle Nebula with my 80mm telescope

Image Processing Techniques

One of the processing techniques I have been implementing into my photos is to process different elements of the image separately. By this, I mean to process the background, the stars and the nebulosity on their own.  I am able to do this by selecting each element of the image and stretching the data without affecting the other areas. For example, I can boost the vibrance and saturation of the nebula or galaxy without adding additional noise to the background of space and stars.

As I have stated many times, I prefer to tame the stars in the image to be as small as possible.  Normally, I would run the “make stars smaller” action to the entire image in Photoshop. This actually starts to diminish the precious detail in your deep-sky object that you worked so hard to capture! Many other actions that are intended to correct issues with the background space and stars can take away from your subject as well.

You can also manually Remove the Stars Completely from your image using photoshop.

Swan Nebula - 8 Inch telescope

My latest version of the Swan Nebula

Selective Processing

There are several ways to accomplish the selective processing technique to your astronomy photos.  You can create multiple adjustment layers of your image in Photoshop, and apply the various actions to each element of the image on a separate layer.  Once you have applied your desired settings applied to each layer, you can use layer masks to combine all aspects of the photograph into one.  This means you will likely have layers for:

  • The Background Space – With a balanced black-point set

  • The Background Stars – Small, sharp and with lots of accurate colour

  • The Brighter Stars – Soft, or with Diffraction Spikes and Color

  • The Deep-Sky Object – Full of luminance, color and detail

  • The Core or Brightest Area of the DSO – reduced to show detail, not blown out


Selective Processing - Astrophotography

Processing the nebulosity separately from the background stars in Photoshop

You can also process the selected elements of your images as separate documents.  Sometime I prefer to do this to really focus on achieving the best possible result for my focus area, without the temptation to poke around at another feature.  Once you have processed each version of the image with your focus area maximized, you can then combine the images using layer masks.  The blending and layer masking is definitely the most delicate stage of the process.  You can really make a mess of an image by failing to inspect all areas of your image before flattening.

I find it helpful to use a reference image of your deep-sky target. This is the best way to make sure you have not overstretched your image data, and that your colors and details are an accurate portrayal of that particular deep sky wonder. I often look for inspiration on APOD!  To stay connected with me and my latest astrophotography images, please follow my Facebook Page.  I hope you are all excited about the wonderful deep-sky targets that will be gracing our night sky the coming months, I sure am!


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