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Ha filter

Use a DSLR Ha Filter for Astrophotography

|H-Alpha|17 Comments

After almost a decade of taking pictures of space with a DSLR camera, I have come to the realization that a DSLR Ha filter is the quite possibly the most important astrophotography filter in your kit. Traditional light pollution filters designed to help you photograph deep sky objects in broadband (true-color) are useful, but a hydrogen-alpha filter makes the single greatest impact on your astrophotography overall.

Beginners often ask me which narrowband filter (line filter) I recommend to buy first, and it’s always an Ha (or “Hα”) filter. H-alpha is a specific deep-red visible spectral line with a wavelength of 656nm. Many nebulae in the night sky (and even some galaxies)  emit a strong signal of light in this wavelength and a hydrogen alpha filter helps to isolate and record this signal with your DSLR camera.

Astronomik 12nm Ha filter Canon EOS

In this post, I’ll explain why a clip-in DSLR h-alpha filter is not only the most powerful filter in your kit, but the one you’ll probably use the most. The DSLR Ha filter I use and recommend is the Astronomik 12nm Ha filter (Canon EOS). There are several versions of this clip-in DSLR filter available, including models for Canon full frame bodies like the popular Canon EOS 6D and 6D Mark II.

hydrogen alpha astrophotography

All of these images were captured with a Canon DSLR and an Astronomik 12nm Ha filter.

Not a fan of black and white images? No problem, use the data you collect in Ha as a powerful luminance layer to your color images. As with other narrowband filters, such as O III and S II, capturing data from a precise bandpass offers many creative opportunities to improve your existing images.

I’ve previously covered narrowband filters that collect multiple wavelengths (dual bandpass, quad bandpass etc.). This time, I’m focusing on the most important emission line of them all, hydrogen alpha.

The Effectiveness of a DSLR Ha Filter

Before I share my 7 reasons why I think everyone who shoots with a DSLR camera should have an h-alpha filter, I want to highlight what I believe is the most important feature of all. You can use a clip-in hydrogen alpha filter with a camera lens, and images collected in h-alpha through a short focal length are absolutely breathtaking. 

I’ve reviewed many astrophotography filters in the past, including broadband (or “broad spectrum”) filters that help to achieve a natural looking image from a light polluted sky. With so many incredible types of filters out there, how can one filter possibly be of any more useful than the rest?

Here are 7 compelling reasons:

benefits of ha filter

    1. You can capture images during any moon phase
    2. You can add dynamic details to existing color images
    3. Stars are recorded smaller and sharper
    4. Fast f-ratios (F/2.8) can be used without star bloat
    5. A clip-in Ha filter can be used with a camera lens 
    6. You can use an h-alpha filter on a stock DSLR (signal is much weaker)
    7. Single bandpass filters are usually more affordable than a multi-bandpass version

Have you ever seen your backyard sky through an h-alpha filter? It’s a pretty astonishing.  You can finally see the hidden structure of the Milky Way behind the veil of light pollution in the city. Here is a photo of the constellation Cygnus from my Bortle Scale Class 8 backyard using a 17mm camera lens. 

wide angle photography

Although the 48mm (2″) filter format can be utilized in more imaging configurations (such as a dedicated astronomy camera) a DSLR clip-in filter fits underneath your camera lens.

Taking wide field astrophotography images using a camera lens in place of a telescope is one of the most rewarding experiences in this hobby. For example, I captured this image of the North America Nebula under a nearly full moon using the Rokinon 135mm F/2.0 ED UMC lens. 

135mm lens

The North America Nebula (& Pelican Nebula) captured using an h-alpha filter and 135mm camera lens.

You can use a clip-in DSLR filter with a telescope as well, making it a practical solution for amateur astrophotographers looking to collect narrowband data. The key to the image acquisition stage, is to expose the images long enough so that the histogram shows that the data is separated from “the wall”. 

Optical systems with faster f-ratios, whether it’s a telescope or a camera lens, are better suited for narrowband astrophotography with a DSLR. The slower the focal ratio of your lens, the longer the exposure will need to be to adequately expose the image in h-alpha.

For reference, here is a look at a single, unstretched (linear) sub-exposure of the a DSLR image captured in Ha. The data observed in the red channel is the most important, as this is where all of the useful image data lies. 

red channel

A single 3-minute exposure from a DSLR camera using an H-Alpha filter.

Notice how the entire image has a red cast over it? If you look at the histogram, you’ll see that the majority of the signal (light) has been captured in the red channel. The signal in the blue and green channels is almost non-existent.

Narrowband H-alpha with a DSLR

You may be asking yourself, is it worth it to use an h-alpha filter with a DSLR?After all, the experts in the astrophotography forums will tell you that you can’t use a narrowband filter with a color camera and if you do, you’re crazy. 

Perhaps I am crazy, but I have personally enjoyed shooting narrowband images with a color camera for many years and I’ve been thrilled with the results (…maybe my standards are too low?)

The truth is, you can capture and stack narrowband images taken with your one-shot-color DSLR, RGB bayer filter and all, in DeepSkyStacker. Once the images have been registered and stacked using calibration frames, you should end up with an intermediate file that looks a little something like this:

Ha filter with a DSLR camera

The stacked result of 51 exposures using a DSLR camera and h-alpha filter.

From here, you can bring the stacked TIF file into Adobe Photoshop to extract the red channel and process in the monochrome image. 

Use a Clip-In Filter with a Camera Lens

One of the most understated benefits of a clip-in Ha filter is the ability to capture h-alpha images with a camera lens attached. This opens the door to impressive, wide field projects revealing the hidden H II gases in the night sky. Combining the Astronomik 12nm Ha filter with a 135mm lens is an incredibly effective combination. 

ha filter with camera lens

A clip-in filter is a convenient solution when using a camera lens for astrophotography.

Some telescopes, like the William Optics RedCat 51, include an internal threaded slot for a 48mm filter in the imaging train. However, the only possible spot for an h-alpha filter with a camera lens attached to your DSLR is inside the camera body.

Narrowband filters designed to thread externally to the large lens objective are not common, are a filter of that size (77mm) would be very costly. The Astronomik clip-in filters snap into the body of the DSLR securely, and most lenses will fit on top (be sure to check the compatibility of the lens you intend to use). 

I’ve used the Astronomik 12nm clip-in Ha filter with several cameras lenses including the “nifty fifty” (Canon EF 50mm F/1.8), and the ultra wide-angle Rokinon 14mm F/2.8. Here is a look at Barnard’s Loop captured using the clip-in Ha filter in my Canon EOS Rebel T3i.

Barnard’s Loop in Orion. Canon EF 50mm F/1.8 with the clip-in Ha filter beneath the lens. 

How To Process the Images

Capturing images using a clip-in hydrogen alpha filter with your DLSR is a lot of fun. No matter how light polluted your skies are, and how bright the moon is, you should see the distinct features of your deep sky object that are emitting light at the 656nm bandpass. Since DSLR cameras collect light through a Bayer filter, the signal is divided up into RGB channels that would normally build a full color image.

However, the h-alpha emission line is very specific, and will only record useful data in the red channel of your images (the other channels will be almost 100% noise). Knowing this, we need to extract the data from the red channel only, and process that channel as a monochrome image of its own.

Stack, Register and Calibrate the Image

The first step is to stack, register, and calibrate your raw images the way you normally would with a color images taken with your DSLR camera. This includes using darks, flats and bias frames to help produce a calibrated image with a healthy signal to noise ratio.

The sub exposures will look extremely red as shown in the example above, and so will the intermediate file that DeepSkyStacker spits out.

Extract the Red Channel in Adobe Photoshop 

After opening your stacked TIF file in Adobe Photoshop, open up the Channels Tab (If you do not see this tab, click on Window > Channels from the main menu), and have a look at the data. You should see that almost all of the pixel information resides in the red channel. 

Photoshop channels

Simply select the red channel from the “Channels” tab, and copy the information (On a Windows computer, CTRL-A (select all), CTRL-C (Copy). Then, select File > New, and Paste (CTRL-V) the information saved on the clipboard (the red channel layer). 

Process the Grayscale Image

The image pasted should default to grayscale mode, with only one channel (gray) in the Channels Tab. You can process this image the same way you would a color image, including adjusting the levels, curves, and even using dedicated astronomy actions.

From here, you can either save and share the image as a black and white hydrogen-alpha photo (which are beautiful, by the way), or you can apply this image to an existing color image to give it a dramatic punch. (See my HaRGB Tutorial). 

The Difference H-Alpha Makes

Some of the most incredible DSLR deep-sky images ever produced, were created using narrowband filters to isolate specific emission lines in the visible spectrum. You can use the same signal isolating techniques to enhance your existing RGB data.

A narrowband filter lets the h-alpha light of emission nebulae pass through to the camera sensor, and blocks almost all of the other wavelengths of light in the visible spectrum.

To be more specific, the Astronomik 12nm Ha filter allows 97%+ transmission of the H-Alpha line, and blocks nearly the entire remainder of the visible spectrum. This includes blocking unwanted wavelegnths in IR (infrared).

For objects like the Bubble Nebula (shown below), you an collect impactful signal that can be applied to your broadband images. 

adding ha with a DSLR

What does this mean?

It means that city light pollution and moonlight are largely ignored. This opens up the doors to imaging during the full moon, and from a city backyard. You no longer have to wait for the full moon/nearly full moon phases to pass to capture deep sky astrophotography images.

Adding Ha to RGB

Emission Nebulae and Hydrogen-Alpha

Emission nebulae are clouds of glowing H II gas, and they emit light at a very specific wavelength. This information is beneficial to astrophotographers, as we are able to isolate this wavelength for photography. The light from an emission nebula is created when the atoms in the gas are ionized by the formation of hot young stars.

The dominant wavelength in a hydrogen nebula is the deep red portion of the spectrum known as the hydrogen-alpha line (656nm to be exact).

visible spectrum - wavelengths in nm

The Visible Spectrum – Wavelengths in Nanometers

Why this is important for DSLR astrophotography

By using a Ha filter in your DSLR, it is possible to increase the contrast between objects in the h-alpha emission line and the skyglow background. The filter completely suppresses the emission lines of artificial lighting such as mercury (Hg) and sodium (Na).

The particulars of the Astronomik ha filter can be understood in the transmission graph below. The chart shows that the Astronomik filter allows 97% transmission of the h-alpha wavelength

Ha Filter Wavelengths

Images captured using a narrowband Ha filter have some pleasing characteristics.

At the top of the list is reduced star size. This further emphasizes the detail and contrast of a deep-sky image by allowing it to stand out from the surrounding sea of stars.

Filtering out skyglow and light pollution means that longer exposure times of 5 minutes and beyond from the city are possible from the city. You will likely capture more detail in your emission nebula targets than ever before. 

Soul Nebula in Ha

Challenges and Best Practices in the Field

Earlier in the post, I mentioned that you’ll want to shoot exposures that capture enough signal to produce a quality image. Specifically, you’ll need to make sure that the red channel data is not being clipped in shadows portion (left-hand side) of the histogram. 

Slower optical systems will demand longer exposures to reach this value, and that puts added importance on tracking accuracy and the need for autoguiding. If your telescope is in the F/6-F/7 range or slower, expect to collect images that are at least 3-minutes or more to create a useful sub exposure.

This is one of the many reasons I recommend using a DSLR Ha filter with a camera lens like the Rokinon 135mm F/2.0. A fast aperture lens will collect more light in a single shot, and suddenly only a 2-minute exposure is enough to collect a healthy SNR.

Ha filter for Canon

Framing and Focusing Targets

The light blocking qualities of narrowband filters means that you will no longer see faint stars through the viewfinder of your DSLR, or when using the live-view function. This can make finding targets and focusing your camera lens or telescope difficult.

In the image below, you’ll see an example of what a single test exposure of about 30-seconds may look like at ISO 1600. There is really only one bright star, and a very faint indication of nebulosity in a 30-second image.

can't see anything through camera

To frame up my image of the North America Nebula, I used a bright star (Deneb) as a reference. 

I find that the most practical solution to this challenge is to find the closest, bright star to your intended deep sky object as a point of reference. Even using a 7nm Ha filter (which is stronger and more targeted than the 12nm version), the brightest stars in the night sky will still show up in live-view.

The camera settings must be set to expose as bright an image as possible, which is typical of any framing and focusing routine with a DSLR. Use ISO 6400 or greater, with the maximum aperture of the camera lens. Make sure the camera is set to bulb exposure mode, so let it is letting as much light as possible.

Once you have located a bright star (you can use the Moon, too), take your time focusing the star using the 10X zoom in live-view. If you are using a camera lens, you may want to use tape to secure the focus adjustment ring to avoid knocking it out of position in the next step. 

Use a planetarium mobile app or a physical star map to locate the rough position of your target. If you’re lucky, there will be a bright star near your nebula to use as a reference like my example of NGC 7000 above. If not, you may need to take as many as 10+ test shots before you are happy with the framing of your target. 

A 30-second exposure at ISO 6400 should be more than enough time to indicate where the areas of hydrogen gas are concentrated. 

Choices – 12nm or 6nm versions

The 6nm version of the Astronomik Ha filter has an extremely narrow emission-line filter. This version targets an even narrower portion of the visible spectrum, blocking nearly the whole remainder of the spectrum. So wouldn’t the 6nm version the obvious choice?

6nm vs. 12nm

Despite the increase in contrast and more light-blocking power of the 6nm version, there were a few reasons I went with the 12nm. For starters, the 6nm version is more expensive, and that was a big reason why I decided to invest in the 12nm filter.

A major step in my pre-imaging routine includes framing my deep-sky target to include as much of the object and surrounding elements as possible. BackyardEOS or Astro Photography Tool can streamline this task with the frame and focus feature.

It’s not the end of the world, but it does take longer to get up and running that it would using a broadband filter that allows more light to reach the sensor. The 6nm would double these impacts, and increase this setup time.

Many backyard astrophotographers would disagree, wishing they had gone with the 6nm instead. I’ve shot images using a 7nm Ha filter (Optolong 7nm Ha), and the results are not drastically different. There is more contrast in the images that used a 6nm filter, but the exposures also need to be longer.

DSLR camera bodies

List of Compatible Canon EOS Cameras:

Here is the official camera compatibility list for the Astronomik clip-in Canon EOS Ha filter directly from the High Point Scientific website. I have personally used this Hα filter on a number of Canon camera bodies including full spectrum modified Canon EOS Rebel Xsi and T3i’s, and a stock Canon EOS 7D.

  • 7D
  • 7D Mark II
  • 20D
  • 20Da
  • 30D
  • 40D
  • 50D
  • 60D
  • 60Da
  • 70D
  • 77D
  • 80D
  • 300D (Rebel)
  • 350D (Rebel XT)
  • 400D (Rebel XTi)
  • 450D (Rebel XSi)
  • 500D (Rebel T1i)
  • 600D (Rebel T3i)
  • 700D (Rebel T5i)
  • 750D (Rebel T6i)
  • 760D (Rebel T7i)
  • 1000D (Rebel XS)
  • 1100D (Rebel T3)
  • 1200D
  • 1300D
  • 100D
  • 200D

Lens Compatibility

The Astronomik clip-in hydrogen alpha filter is not compatible with Canon EF-S mount lenses. The EF-S series of Canon lenses were designed to be used solely with Canon APS-C (crop) sensor DSLR’s, and have a smaller image circle. 

They fit deeper inside of the camera body, which means that they’ll run into the height of the filter if you try to attach the lens. In the photo below, you can see how the base of the lens mount is protruding too far to be compatible with a clip-in DSLR ha filter.

EF-S lens compatibility

Stick to full frame lenses on your crop sensor DSLR. The EF-S lens mount wont work with a clip-in filter!

On the other hand, Canon EF series lenses were designed to be used with both full frame camera bodies and crop sensor models. I’d recommend sticking with EF lenses for astrophotography in general, from a quality perspective.

I enjoy Canon’s L-series lenses, which is why several years ago I began purchasing used l-series lenses to cover every possible photography situation. Third party full frame lenses with the EF mount design such as the Rokinon 135mm F/2.0 ED UMC I mentioned earlier are compatible with DSLR clip filters like this. 

 

Canon EF lens mount

Clip-in filters like the Astronomik 12nm Ha (and similar clip filters) are compatible with Canon EF lenses.

Stick to full frame lenses such as the Canon EF line up and the many thir party lenses that mount to Canon cameras from Rokinon, Samyang, Sigma etc. One way to tell if your lens is a suitable design for Canon clip-in DSLR filters, is the small red indicator at the base of the lens. 

Does my camera need to be modified for astrophotography?

No. The same benefits of an H-alpha filter can be realized with a stock DSLR. However, the amount of red light your camera will be able to record will be reduced.  

If you are serious about your astrophotography, it is worth thinking about modifying your camera either yourself or by a professional. Here is a shot of the Eagle nebula using the Astronomik Ha filter and a stock Canon EOS 7D.

Using a ha filter with a stock DSLR

Example of using a Ha filter with a stock (unmodified) DSLR camera (Canon EOS 7D).

This is typically what a frame looks like taken using a Ha filter through an unmodified DSLR. This emission nebula could have been captured in greater detail using a modified camera, but the skyglow and wavelength suppression capabilities of the filter are still present.

I am a huge promoter of DSLR astro-mods. If your camera is used for astrophotography exclusively, why not modify your camera yourself? That’s exactly what I did to my Canon EOS 450D (Rebel Xsi) camera in 2014.

Modified camera for astrophotography

I carefully removed the IR cut filter on my Canon Rebel 450D by watching this video from Gary Honis. If you have either a light pollution or h-alpha filter covering your DSLR sensor at all times, you are not required to install any extra replacement filters. 

This is known as a full spectrum “naked sensor” mod, and it made a huge impact on my astrophotography images.

The Bottom Line

If you own a DSLR camera that has been modified for astrophotography, a clip-in Ha filter should be on your shopping list. I waited far too long before making this decision.

Combining H-alpha exposures to your existing RGB data can greatly increase the amount of detail and contrast in your nebula images, and even add dramatic details to certain galaxies. 

The ability to image during the full moon and surrounding week results in much more time under the stars. No more wasted moonlit clear nights.

If you live in the city, a Ha filter cuts through even the most severe light pollution. My Astronomik 12nm Ha filter cuts through my red-zone (Bortle Class 8) skies to reveal beautiful structures of hydrogen gas in the emission nebulae I photograph.

Narrowband filters allow you to collect impressive deep sky images from a light polluted backyard, and that’s a beautiful thing.

The clip-in versions offered by Astronomik are a perfect fit for several Canon and Sony cameras.

Heart and Soul Nebula

 

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Astrophotography with a 12nm ha filter

|Camera|7 Comments

With the aid of an Astronomik 12nm Ha filter, I can capture deep-sky images more often than ever before. With both the Canon EOS clip-in version for my DSLR and the 2″ CCD round mounted version for the my dedicated astronomy camera, I collect photons in every moon phase.

Despite the bright 80% illuminated moon this past Saturday night, I was able to capture some incredible deep sky photos of 2 deep sky emission nebula targets from my backyard in the city. Using my 102mm refractor telescopes, I collected isolated wavelengths of light on the Wizard Nebula in the constellation Cepheus, and Bubble Nebula in neighboring Cassiopeia.

Ha filter for Canon

The Astronomik 12nm H-Alpha Clip-in filter for Canon EOS DSLR cameras (See Video)

A narrowband Hydrogen-alpha filter (Ha) has the power to cancel out nearly all of the surrounding city glow and moonlight in the sky. In seemingly magical fashion, it reveals the faint nebulae in the night sky that are impossible to see through an eyepiece with the naked eye.

In the photo below, you’ll see my Explore Scientific ED102 refractor telescope, with an imaging payload that includes a 48mm (2-inch) Astronomik round mounted 12nm Ha filter. This filter is threaded to the nosepiece of my field flattener/reducer and fits securely into the focuser of the telescope.

Deep sky astrophotography telescope

In this post, I’ll discuss the advantages that a 12nm Ha filter can provide to your deep sky imaging experience. Whether you use a dedicated astronomy camera (mono or color), or a modified DSLR, a narrowband h-alpha filter will likely be the most useful filter you’ll ever use for astrophotography.

I personally had no idea what I was missing out on before I dove head first into narrowband astrophotography with my DSLR. You’ll need an astro-modified DSLR or dedicated astronomy camera to see the true benefits of this technique, which I will discuss in detail shortly.

Related Video: Results using a duo-narrowband filter with a color camera

Astrophotography with a 12nm ha filter

My current one-shot color CMOS camera performs exceptionally well with narrowband filters. Sure, a camera with a monochrome CMOS or CCD sensor with TEC (cooling) would outperform it, but I have a strange love of pushing my current gear to its limits.

The Altair Hypercam 183C includes internal fan cooling which keeps the sensor much cooler than a traditional DSLR. This comes in handy when shooting with a narrowband Ha filter, as you generally will want to shoot even longer exposures than you would in color. (This depends on your camera and the settings used)

After a very warm start to fall, the reality of a Canadian October night set in as the temperature plummeted to 4 degrees Celcius on Saturday. Who needs internal cooling when it’s freezing outside? It really is a great time of year for DSLR astrophotography – as the sensor can return to a more suitable temperature for long exposure imaging.

In the video below, you’ll get a behind the scenes look at my process of capturing the Bubble Nebula using an Astronomik 12nm Ha filter.

For an idea of what to expect when using a color camera, have a look at the following image of the Wizard Nebula captured in the Hydrogen Alpha wavelength. The individual image frames were captured using a gain setting of 60% on the 183C astronomy camera with a 12nm Ha Filter in front of the sensor.

The photo includes over 5 hours worth of 210-second exposures:

Wizard Nebula using a 12nm Ha Filter

The Wizard Nebula in Ha – Altair Hypercam 183C Color CMOS Camera

Total Exposure: 4 Hours, 54 Minutes (84 frames)

The reason the photo is black and white is that it was created by extracting the red channel from the original data collected from the color CMOS sensor. This process is easy to complete using Adobe Photoshop, by copying the data from the red channel to a new image.

You can then process the Ha data separately, as you would with luminance data from a monochrome camera. Again, the signal is not nearly as impressive as it would be using a dedicated monochrome camera, but it can certainly improve your existing color images.

To illustrate this point, I have added the additional light in captured Ha to existing some existing RGB (color) data on the Wizard Nebula. The HaRGB composition method continues to produce incredible results from my light polluted backyard.

Wizard Nebula in HaRGB

Using an H-Alpha Filter with a DSLR Camera

A DSLR camera is a fantastic way to start enjoying narrowband astrophotography with an H-Alpha filter, but there’s a catch. You must be willing to modify your existing stock DSLR camera (I modded my Canon 450 using this video as a reference) or purchase a pre-modified camera from a vendor that specializes in this service.

One point of confusion amateur DSLR astrophotographers may face is the description of the filter, and whether or not it is a good fit for your camera. For example, the Astronomik website lists the filter as a “narrow band filter for CCD photography”. So will this filter be effective with the color CMOS sensor in your DSLR?

DSLR Ha filter

The 12nm Astronomik Ha Filter – Clip-in version for Canon EOS DSLR’s

The answer is yes, but you’ll need to have a modified camera to reap the full benefits of a Ha filter. By modified, I mean that the internal stock IR cut filter has been removed from the camera sensor. There are professional astrophotography camera modification services available to perform this upgrade if you are not up to the task yourself.

The stock IR (Infrared) filter inside regular DSLR cameras is there to produce natural looking photos for daytime photography, yet blocks out certain wavelengths of hydrogen-alpha light emitted by emission nebulae in the night sky.

For my Canon Rebel T3i, no additional IR cut filter replaced the stock one that was removed, and this is called a “full spectrum modification”, or “naked sensor mod”. Because I have not installed a replacement UV/IR filter inside the camera, I need to make sure that I always use an external UV/IR filter to properly focus my broadband (color) images.

An example is the SkyTech CLS-CCD filter that I use to collect color images from my light polluted backyard. The “CCD” portion of the name is referencing the added bandpass filters a modfied DSLR camera requires to focus.

A 12nm Ha narrowband filter can dramatically increase the contrast between your deep sky object and a bright city sky. It suppresses the emission lines of artificial lighting such as Mercury and Sodium, leaving only the intense details of the h-alpha light wavelength in your image.

Using a DSLR camera with an h-alpha filter means that all of the “good” signal (not noise) will reside in the red channel. To showcase this trait, have a look at the comparison of blue signal vs. red in this narrowband image of the Heart Nebula.

channels in Photoshop

In September 2018, I captured images of two emission nebulae using my modified DSLR camera and a 12nm Astronomik Ha filter. The camera was attached to a wide field refractor telescope, the William Optics Zenithstar 73 APO.

If you currently shoot color deep sky images with a DSLR camera, I urge you to consider the idea of modifying it for astrophotography. You can then begin to tap into the amazing benefits of narrowband imaging using an h-alpha filter such as the Astronomik 12nm clip-in version.

The fact that you’ll be able to capture powerful images during a full-moon alone is worth the effort. Some of my most memorable astrophotography projects are HaRGB composite images that combine broadband RGB color images with added luminance signal of hydrogen-alpha.

A great feature of the clip-in variation of the Astronomik Ha filter is the ability to use it when a camera lens is connected. This means that you can capture wide field images of the night sky that isolate the interesting regions of emission nebulosity. Below, is an image created using a ha filter in conjunction with a 50mm camera lens on an iOptron SkyTracker mount:

Barnard's Loop in Orion

The Orion Constellation in H-Alpha using a 50mm Camera Lens

Creating an HaRGB Composite

Then, I combined the images shot in Ha with my color version of the image – shot through an Explore Scientific UHC filter. This creates a composite version of the NGC 7380 that uses the grayscale H-Alpha image as a luminance layer.

Next up is NGC 7635 – the Bubble Nebula. This is just the beginning of a full narrowband project that will include OIII and SII. This project will likely carry on through the month of October – as I will need to wait for New Moon to capture the broadband color images.

With Saturdays imaging season, I the project is off to a great start.

The Bubble Nebula in Ha

Bubble Nebula with a 12nm Ha Filter

NGC 7635 – The Bubble Nebula in Ha

Photo Details:

  • Exposure Time: 3 Hours, 33 Minutes (61 frames)
  • Camera: Altair Hypercam 183C (Gain 60%, Bin 2 x 2)
  • Filter: Astronomik 12nm Ha Filter

At this point, I have also collected images using the Astronomik 12nm OIII filter as well.  Another cold clear night in the backyard yeilded over 4 hours worth of total exposure time on my project.  The details of the Bubble Nebula in OIII are less dramatic than the h-alpha, but a necessary stage in my narrowband project.

The Bubble Nebula in OIII

Bubble Nebula using an Astronomik 12nm OIII filter

The Bubble Nebula in OIII

Photo Details:

  • Exposure Time: 4 Hours, 43 Minutes (81 frames)
  • Camera: Altair Hypercam 183C (Gain 60%, Bin 2 x 2)
  • Filter: Astronomik 12nm OIII Filter

Final Thoughts

I hope that you have enjoyed seeing my progress into narrowband deep sky astrophotography with the use of filters. The color CMOS sensor camera I am using is not ideal for this type of photography, but it certainly gets the job done with a little patience.

Ha Filter Astrophotography

I look forward to completing my narrowband project on the Bubble Nebula this month and will be sure to share my results.

With that being said, I am happy to announce the arrival of a Mono Camera as early as late October.  This is a brand new astrophotography camera at an entry-level price point.  Until next time, clear skies!

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