full spectrum Archives - Infrared Conversions, IR Modifications & Photography Tutorials

IR Fireworks

What to do on the 4^th of July… Humm… Grill? Done. Catch up with family? Done. Relax? Done. Watch fireworks? Wait a second… How many of you have photographed fireworks? I’m guilty. But who’s photographed fireworks in IR? I’ve never done that, and probably few have. Let’s give it a try.

I climbed on the roof of my house to get a better vantage point and set-up my full spectrum 5D Mk II with a 720nm filter.

I use a Hoodman Loupe for focusing my 5D, since the filter blocks the visible light and makes the viewfinder useless. This technique works quite well for me and is what I’ve been using for more than 5 years. I wrote a blog on the topic.

I knew about where to look for the fireworks. So I installed my Pentax 67 55mm medium format lens and prefocused before it turned dark. It’s more difficult to focus once it is dark. I connected my shutter release and then waited…

At 9 o’clock on the dot, the fireworks began. I was shooting exposures from about 3-10 seconds at ISO 400 and f/5.6. This seemed to work well. Adjustments in framing, focusing and exposure need to be done quickly, as the fireworks continue. I continued to shoot until my memory card was full. It was close to 9:30, which is when the firework show typically ceases. A quick back of the camera indicated that I had captured some interesting shots.

So where were the trouble spots? First, I noticed that the 55mm lens had some significant internal reflections. I’m not sure if this was caused by the filter, or the basic lens design itself. My EF24-70mm f/2.8 has a similar issue with super-contrasting scenes. I’ll have to set-up an experiment to test my lenses under these conditions. I’ll share the results here. The three photos below, though still interesting show the effect of the internal reflection.

Releasing the shutter release mid explosion halts the motion of the firework and provides a truncated look. Note also a second shell climbing to altitude.

The other problem I encountered was the wind. I was standing on my roof and at times needed to grip the tripod to insure that it didn’t take a tumble. Interestingly, the wind also had an effect of blowing the fireworks. Many didn’t have the traditional firework shape, but rather a skewed , wind-swept look. This was also interesting.

Finally, as with any long exposures on digital cameras, there are some required management of hot pixels. Most modern DSLR’s have internal noise processing, But this requires an equal-length dark exposure for each light exposure. So I prefer to do this off-line using the technique outlined here . Since the exposures were fairly short, the hot pixels are manageable, even by manual removal methods.

I did very little post processing of these images. I set the camera with a custom white balance on a green subject. Most images were posted after a little cropping and re-sizing for the blog format, but not much more than that. I did process several in B&W, since that’s my favorite IR medium. Some photos have a bit of an abstract look to them.

By the time the fireworks show was over, the mosquitoes had found me. So I gathered up my tripod, camera bag, loupe and flashlight and headed off the roof. It all ended well and I enjoyed the experience. I hope you’ll give it a try next year.

Happy 4^th of July…

The Great Minor White and Infrared Photography

Born in 1908, Minor White was something different in terms of how and why he photographed. He incorporated as much of his own beliefs and philosophies into his work as he did photographic technique. His work is a mix of his mentality and the emotion he felt towards a scene or subject. He injected a part of himself into all the photographs he made. Bestowed by him are such words as “The photographer projects himself into everything he sees, identifying himself with everything in order to know it and to feel it better.” and one of my personal favorite quotes about us photographer’s mentality “…all photographs are self-portraits”.

Minor White-By Imogene Cunningham

It was with the existential mindset that White approached his photographs and perhaps there was none of his work as idealistically surreal as his adventures into the world of infrared. Not only was he a prolific photographer in the artistic and technical sense but he was one of the early practitioners of infrared photography who brought it’s incredible appeal to the masses. The IR images he made, just like his other works, projected a world blended with both the physical landscape and his own personal creativity.

By Minor White, 1958

By Minor White, 1955

By Minor White, 1955

Minor White and Infrared

How did Minor White make his IR photographs? With magic…. Well no, not exactly magic, but it certainly looked that way. Minor White used black and white infrared film, usually large format 4×5, to capture his dreamlike scenes. The infrared or more accurately “near-infrared” light spectrum falls around the 700-1200nm range and infrared film is manufactured to be sensitive to these wavelengths. However, seeing as IR film is also still sensitive to other wavelengths of light, IR filters must also be attached to the camera lens in order to filter out other types of unwanted light that falls in the more visible spectral range. It’s this filtration of the normally visible light and the inclusion of the near IR spectrum which we generally don’t see which gives IR photography their ghost-like quality. Development of the IR is surprising the same as many other conventional black and white films and requires basic darkroom techniques and chemicals.

IR Lens Filters

IR 35mm film

You may be wondering, “So why can’t I just use an IR filter on my digital camera to make IR photos?” And that’s good question. The answer lies in the very construction of most modern digital cameras themselves. IR wavelengths are generally unwanted and in conventional photography and therefore modern digital cameras have a built in IR filter that is placed in front of the image sensor to block out IR light. Even if an IR filter was placed on the lens the resulting transmitted IR light would in turn be filtered out by the camera’s own internal filter. So, how can you enable your digital camera to make IR photographs? Read on….

IR Photography in the Digital Age

As I mentioned earlier, the largest obstacle that stands in the way of making IR images with your currently digital camera is the built in IR sensor filter inside your camera. So if you want to venture into the world of IR photography this filter must be modified through an infrared camera conversion process.

New IR translucent filter being installed

This means that your camera’s sensor is now sensitive to incoming IR light. There are also many other possibilities to expand your infrared horizons with today’s digital camera bodies. Full spectrum, color IR, and a host of other tailored IR imaging effects can be produced depending on the type of conversion and IR lens filter combinations you happen to choose. The benefits to Find out more about infrared conversion possibilities here.

A Final Word About Minor White and Infrared Photography

The work of Minor White was profound, beautiful, innovative, provocative, and at times quite sad. His ventures into the world of IR photography showed us a the wonderment that is all around us, yet invisible all the same. His images speak volumes to the life he lived and to the way he approached the art of photography.

Today, we have so many ways to practice IR photowork whether it is with film and filters or with our digital cameras through a dedicated IR conversion. If you are considering the latter route, be sure to learn as much as possible about the possibilities and limits of digital IR conversions. Make sure whoever you trust your beloved camera to has the reputation for quality that you and your gear deserve. Read more about IR digital camera conversion here at LifePixel and be sure to check out what people just like you have to say about the level of service offered by the LifePixel team!

Bracketed Exposures for IR photography

What are bracketed exposures? If you’re familiar with this term, you know how useful they can be. There are multiple uses for bracketed exposures, but they are especially helpful in IR photography. Shooting bracketed exposures is where the camera is set-up to shoot the same scene, but at different exposures.

Nearly all stock cameras are meant to shoot in color. So when we get into the optics and start removing filters or adding other filters, the camera doesn’t work the same. The one area that really takes a beating is the metering. After a modification, the metering will still be fairly close. But shooting in IR or full spectrum will definitely change the way the camera’s metering system sees the world. I find that my full spectrum modified Canon 5D Mk II with a 740nm filter will usually meter a ½ to 1 stop (usually denoted by EV) brighter than a normal scene. Most of my other modified cameras were the same.

The shows a series of 3 bracketed exposures at -1, 0 +1 EV

When I shoot IR photos, I shoot bracketed exposures as a rule. I’ve had too many IR photos where I thought the metering was accurate only to find that there are highlights in the scene that are blown out (camera’s histogram is clipped on the RHS). Shooting bracketed exposures nearly always helps me recover these highlights or even allows me to process a different shot that is at the + or – end of the bracket.

How do you begin doing this? Well, most cameras these days will allow the use of bracketed exposures. This is where the camera will shoot 3 or more exposures for each image. Depending on how you set it up, the camera will typically shoot a normal exposure and one under exposed and another that is over exposed. Some cameras will shoot additional over/under frames and also allow you to skew how these different exposures are framed in the overall bracket. I like to set my camera to shoot the bracketed exposures in high speed mode, so I can get the 3 images in rapid succession with a single shutter button press.

This is the menu option for setting bracketed exposures on a Canon 7D. This one is set for -1, 0 +1 EV

My cameras (as to many) have several programmable settings where I can set f/stop, ISO, exposure mode, bracketed exposures, etc. So I have 2 custom settings that shoot only bracketed. On my camera, C1 is set up for 1 stop over and under. The camera will record 1 normally metered frame, one frame that is one stop under and one frame that is one stop over. C2 is the same operation except for 2 stops over/under. This makes it quick and easy for me to change the camera to different situations where 1 or 2 stops might be needed.

Many DSLR’s have the ability to set custom settings. This one is a Canon 5D MkII

So why else would I shoot bracketed exposures? One great feature is HDR. If you’re shooting a scene that has both bright and dark elements or the scene spans more dynamic range than a single shot can record, HDR or some other technique of exposure masking or blending is the way to do this. It’s also very helpful to have multiple exposures when shooting on the shadow side of the Sun, or toward the Sun. Many times you won’t see the need for HDR until after you return and are processing your images. It’s too late to do an HDR at that point. So by shooting bracketed exposures, you have the ability to do HDR or exposure blending on shots, after the fact.

This is an HDR of the 3 images shown above.

Isn’t shooting bracketed exposures going to wear out my camera? Won’t it take more memory? Yep, for both. Your shutter is now clicking 3 or more times for each scene. All of these shots have to be recorded on the memory card. Of the 7 modern DSLR’s I’ve owned, I’ve only replaced the shutter on one camera (my 30D), and that was at about 3700 clicks, for sure an anomaly. Most prosumer DSLR’s are good for 100k -150k shutter clicks. I’ve never shot 100k shots on any of my cameras. But I’m not a professional photographer. I venture to guess that most other casual shooters are the same. As for the memory consumption, memory cards are cheap.

Another example of scene that benefited from having more than a single exposure

There is a little good news. If you focus and shoot your IR like I described in my last blog, focusing through live-view, the mirror will stay locked up. So the wear associated with the mirror flipping up and down is removed from this operation. It also helps to use a tripod when shooting bracketed exposures, especially if you’re going to be using them for HDR. You can still align the images in post-processing. But it’s easier if the images begin with good alignment. I prefer to shoot all my IR with a tripod.

Scenes that are shot toward the Sun typically have a high dynamic range that benefit from having bracketed exposures

If you’re comfortable with shooting regular exposures with your IR photography, by all means proceed. I find that shooting bracketed exposures helps save many images that might have otherwise been unusable. Happy shooting.

Focusing a Full Spectrum Camera

If you’ve read any of my other blogs, you might know that I started IR photography as a spinoff of my astrophotography. Both of these types of photography have some similarities. First, most cameras need to be modified to shoot IR photos. For the exact same reason, you’ll need to modify your camera to shoot nebula-type astrophotography. This is needed because the internal UV/IR cut filter blocks the both the IR light for IR photography and the H-alpha light for shooting nebula (See my astrophotography series for more details).

When I first got started with astrophotography, I modified a canon 300D (Digital Rebel) with a full spectrum modification. I figured it would be the most flexible. Six years later, I still feel that way. I like the full spectrum modification as I can shoot astro, or any flavor of IR. by adding an original white balance filter allows me to use the camera for regular color photography.

The biggest drawback of a full spectrum modified camera is the need for external filters. These block the light that would normally pass through the viewfinder. Lifepixel calibrates their IR modified cameras for autofocus. But when shooting IR with a full spectrum mod, you loose the use of the viewfinder.

When shooting the 300D, I would compose, focus and prepare the shot with the filter removed. I’d then screw on the filter and set the lens to the higher f/numbers and shoot. It was sort a crap shoot whether or not I’d get what I wanted. It did work and I shot many photos like this. One of my all-time favorites was shot with the 300D, using this technique.

I was enjoying shooting IR and wanted a better way to compose and focus my images. So my second modified camera was a Canon 40D, also modified for full spectrum. It was one of the first DSLR’s that had a live-view option. I found that this was the key to effectively using a full spectrum camera. Since the camera is modified, it sees right through the externally mounted IR filter. So live-view works quite normally. I used this camera for several years before upgrading to a slightly higher resolution Canon 50D. This camera also had a better live-view LCD, which made focusing much easier. Then I finally bought and modified a full frame Canon 5D Mk II. All my cameras were modified with a full spectrum modification.

When you shoot IR with live-view, you can see the scene just as the camera sees it. After all, it’s the main sensor shooting this live-view image. I found that shooting with a green white balance gives the images in the live-view window a more appealing color. It is much easier to compose and focus. Having a custom white balance also makes the post-processing easier.

This is typical of what you’ll see on the camera’s LCD if you shoot without a CWB.

This is the same shot with a Green CWB frame and the camera set to use this frame for CWB.

The biggest problem for me was being able to see the LCD screen, while shooting in the bright daylight hours. I tried shading the camera with a black cloth draped over the camera. But this was pretty tedious and uncomfortable. So I bought a Hoodman loupe and never looked back. This allows you to see the LCD very clearly. On many cameras you can also zoom live view, which will further improve your focusing with the loupe.

Keep in mind that using the LCD for composing and focusing will consume more power than viewfinder methods. So be sure to carry an extra battery or two. Alternatively, if you use a battery grip you’ll have longer sessions before a battery change is needed. This comes at the expense of portability.

The camera & loupe can be a handful to manage if you’re doing hand-held shots. So I resolved myself long ago to shooting with a tripod. I made a custom tripod which is a little more compact and works perfectly for my IR set-up. But nearly any tripod will work, as long as it is stable.

Focusing an IR modified camera can be a challenge. So I thought it might be worth reviewing this topic again. With a little kit and a little practice, focusing becomes an after thought allowing you to concentrate on the other aspects of getting a great image. You don’t have to have a full spectrum modified camera to use this technique. But you should use this technique if you have a full spectrum modified camera. Practice, have fun and happy shooting.

If Your Eyes Could See… Part 2

In Part 1 of this series I presented a few color astro photos that represent what you’d see, if your eyes were super sensitive. In part 2, I’m presenting similar images, only these will be presented in one color, the color of H-alpha. Hydrogen alpha is likely the most important emission, for imaging the night sky. In my astrophotography blog series, I discuss the importance of H-alpha and how to image these nebula with a modified DSLR.

The Veil Nebula Complex

The Great Orion Nebula

The images in part 2 were all photographed in the H-alpha wavelength (656.28 nm). The exposures are long. The equipment is expensive. The tracking is critical. But the results are some of the most stunning images that I’ve ever photographed, all of which are invisible to the naked eye.

The California Nebula

All of these H-alpha images required a series of 30 minute long exposures. These are then stacked and processed to achieve the final result (again, see my astrophotgraphy series). Like their color counterparts, the subjects of these images are so dim that they are invisible to the naked eye. This makes locating the subjects somewhat tricky. The use of a computerized mount reduces the time needed to get the telescope pointed at the target. Then it’s just a matter of fine tuning and framing. The focus is set, , the guide camera is calibrated, the filter wheel rotated to the proper filter and the exposures begin. Thirty minutes later, I check the resulting image to see if I hit the target as intended. If so, the imaging continues until the object is too low in the sky to continue.

The Heart Nebula

The Jellyfish Nebula

Sometimes, I’ll look up an uncommon object and point the telescope in the general area and shoot a test exposure. Many times, this technique isn’t too fruitful, but once in a while, a gem is recorded. This is the case of the image below. I scoured the web looking for similar images, to no avail. So this particular area, rarely photographed, is one of my favorite subjects.

B30 and Friends

Probably one of my all-time favorites is my mosaic of the Orion area. This is an 8 frame 60 megapixel mosaic that required many nights to shoot and many more nights to assemble and process. Anyone that has processed very large images in Photoshop will sympathize on the amount of work required of the computer and it’s operator. Each frame was individually processed. When they were all complete, each one was registered in a special piece of software called Registar. Then all 8 were imported into Photoshop, assembled, blended and processed. more than 40 hour of post-processing was performed on this image alone.

The Orion Complex Mosaic

Imaging deep sky targets is not for everyone. It can get complicated quickly, with steep learning curves on both the imaging and post-processing sides. Imaging with a DSLR can be a superb entry into this field. If your interests lie in photographing H-alpha, like the images here, the DSLR will need to be modified, and an H-alpha filter purchased. An astro-modification or a full spectrum modification can be performed to allow the proper H-alpha wavelengths to pass. My preference is the latter for the maximum throughput and flexibility. It allows my DSLR to be used for astrophotography, IR photography or any other application I can dream up.

The Horsehead Nebula

I hope you’ve enjoyed this short series highlighting some of my favorite images. A modified DSLR is a great way to get started doing astrophotography. If you’re interested in giving this a try, take a look at an H-alpha modified DSLR or a full spectrum version.

If Your Eyes Could See… – Part 1

For those of us that shoot IR photos, we already have a glimpse into what the world looks like illuminated in the invisible light of infrared. It has fascinated me that photos photographed in this light can have such interest and depth. Similarly, I have seen things in the heavens that only those with the appropriate telescope and imaging equipment have seen. I say “seen”, but it in reality, our eyes are not sensitive enough to actually see these magnificent & hidden astroscapes.

In this series, I’ll be showing a few of my deep sky astrophotos. These were all shot with my widefield imaging equipment. First covered will be the nebula shot in “color”. The camera (a cooled, full frame CCD) is monochrome. So the color is assembled by shooting through a series of filters and assembling the color images in Photoshop. There are a couple RGB images that contain only red green and blue light and others shot through narrowband filters. You can also review my Astrophotography series, for more detail on some of this, including shooting with a DSLR.

M45 – The Pleiades

M45 is a beautiful open cluster that’s a little difficult to photograph. It’s a reflection nebula, which means the dust that is visible is being reflected from the nearby starlight. It needs to be imaged with RGB filters, instead of narrow band filters. So it is much more affected by light pollution. Even so, this image was shot from my backyard in a fairly heavily light polluted area. There is much more dust and nebulosity to be seen here when imaged from darker skies.

Tulip Nebula

If your eyes were much more sensitive, the night sky would look very different. Most of these images represent a field of view of about 4 x 8 full Moons. So the features are large and would be prominent in the night sky. Imagine looking out your window and seeing the Tulip Nebula rising from the East.

A telescope’s main function is to gather light. This is one of the purposes for larger and larger telescopes. Resolution is also improved, but let’s just look at the light gathering ability. Compare the diameter of a telescope’s aperture with the pupil in your eye. This large aperture gathers many times more photons than your eye alone. The larger the diameter, the better the light gathering and the easier it is to see faint objects.

M42 _The Great Orion Nebula

With the exception of the Orion nebula (shown above), most of the objects in photos shown here are not visible to the naked eye. The additional light gathering ability of the telescope helps to increase the visibility. Long exposures improve the image depth and visibility even more. This basically stacks more and more photons on the film or CCD until the image is visible. All of the images shown here contain at least several hours of integration time. As an example, the California Nebula was photographed with 6 filters, RGB and 3 narrow band filters over a period of 7 nights. This resulted in a total integration time of 18 hours. This may seem excessive, but image stacking helps significantly reduce the image noise. Even images from a modified DSLR produce fantastic results.

RGB Barnard 30 & Sh2-264

The image above was shot only with RGB filters and exposures of 5 and 10 minutes. The total integration time was 2.5 hours. I wanted to point out the difference of this image and the one directly below, which also includes data from 3 additional filters, Hydrogen Alpha (H-Alpha), Oxygen III and Sulphur II (narrowband filters). Each narrow band exposures were 30 minutes in length. Many were recorded over several nights bringing the total exposure integration time to nearly 20 hours. As you can see with longer the exposures, much more detail is visible.

HaRGB Barnard 30 + Sh226

Each of these images also requires a significant amount of processing time. The individual monochrome image stacks needed to be processed. Then the data from each filter color needed to be color mapped, aligned and overlayed. Some final processing is done and the image is complete. At least, that’s the way it’s supposed to work. I always found that I never seemed to actually finish any image. I’d continually tweak and adjust until I was happy, each time thinking it was done.

IC2177 – The Seagull Nebula

My imaging telescope is considered widefield (530mm f/5). It provides lower magnification, in favor of wider views of the night sky. Although slightly magnified, the images would still appear fairly large if you could see with super sensitivity.

SH2-129 – The Flying Bat Nebula

In the next part of this short series, we’re going to take a look at similar celestial views. However, these images were recorded using only a single filter. I’ll share some of my all-time favorites in my favorite formats. Stay tuned.

Aside: Did you know that Life Pixel does camera modifications for astrophotography? As I described in an earlier astrophotography blog , most stock cameras need to be modified to be able to see the all-important hydrogen-alpha emission. This emission is deep red and is blocked by most stock camera UV/IR cut filters. Replacing this filter with a modified version that passes the H-alpha emission is very important for the highest sensitivity and best results. Alternatively, the camera can be modified for full spectrum use and external filters added for astrophotography use. You can find details in the links below:

Full Spectrum Modifications

Hydrogen-Alpha Modification

Astrophotography Image Stacking – Astro Stacking

Hopefully you’ve been out shooting and applying what you’ve learned about astrophotography. For most there’s a fairly big learning curve with astrophotography. I was always pretty good with the computer, electronics, and the mechanical hardware, but learning to process the images was a huge challenge. Hopefully I can share what I’ve learned to help speed up your learning process.

There’s a lot to learn when it comes to taking the images from the camera to making a final image for display. You’ll find that 99% of the deep sky images that you shoot will require some form of post-processing. But before we even discuss doing any processing, let’s discuss how to best shoot the scene.

In the previous blogs, I’ve hinted about a technique that will let you get the most out of your astro images. Shooting very faint moving targets can be pretty challenging. It takes fairly decent equipment to get the really faint stuff, but beyond this, it’s important to properly photograph the subjects. There is one valuable technique that will help tremendously with processing and make the most of your data. This technique is stacking.

Let’s take a look at stacking in very basic terms. Shooting faint targets makes for generally noisy images. This is true for astrophotography as well as regular photography. This means that the photos look grainy and lack the silky smooth transition. In astrophotos, noise will disturb the transition from the target object to the dark regions. But if you shoot many photos of the same subject and stack them together, the result is far better than that of a single frame. The noise and graininess is filled in and the image will appear much smoother and complete. When I was going for the best quality images, I would generally shoot for between 10 and 20 hours of open shutter time. But again, these were for my very best deep sky images on professional level equipment. For me, that meant shooting over many nights and stacking all the data in the final image. I was shooting exposures that were ½ hour long,o I needed fewer frames. But the end result was a lot of data, that when assembled, resulted in very good data sets.

If you’re just starting out it’s not necessary for you to shoot this much. But generally the more you shoot the better. There’s a big difference that can be seen immediately in the final image. There is a point of diminishing returns, but most astrophotographers will never come close to this limit. So if you can start with shooting a couple hours you’ll end up with fairly decent data. But even shooting and stacking 10 images will be better than one single frame. The better the data, the easier it is to process into the final image.

How do we begin…? Once you have your mount aligned (see my previous blogs) the target framed and the lens or telescope focused, you can start shooting your images. Shoot the same subject, over and over. I generally use a computer or an intervalometer to take the work out of this. This allows me the ability to walk away and let the camera shoot until it’s done. Just be aware that you may need several batteries or an AC adapter for your camera. This is especially true in the cold. For your first outing, try to shoot for at least an hour of open shutter time. That means if you’re shooting 5 minute shots you’re going to want 12 of these to make an hour. It’s generally best to shoot with an exposure as long as possible, but not so long that the image becomes saturated with light fog or you begin to get star trails. I generally tried to shoot until I reached about 25-75% on the camera’s histogram. But this depends on the target and from where I’m shooting (and how much light pollution is present). Just keep in mind that 1 hour is not a magical number. Shoot more, if you have time and patience. This will make the post-processing after the stack easier and the final image even smoother.

Once you have the stack, what’s next? You need to process all these images into a single image. This is possible in Photoshop and there are some really great videos and information on the topic. So I’ll leave this learning process to those interested in doing the stacking in this manner.

The real benefit is doing the stacking in a program that is meant for processing astrophotos. There are many programs that are available to do this, some are even available for free. I used a program called MaximDL which is a high-end piece of professional astrophotography processing software. In addition to doing some processing, it also handles camera control, filter wheel control, focusing, guiding and many other aspects of shooting deep sky images. In a complex setup, it’s very beneficial to have control of everything in a single piece of software. However for those just starting out, look at getting Deep Sky Stacker (DSS). It is an excellent stacking program and is available at no cost. This allows you to practice shooting and processing images without investing a lot of additional money in software.

Be sure to take a look at the excellent instructions on the DSS website and online. It is fairly powerful and capable producing nice images. It will also allow the addition of calibration frames (discussed below), which is another very powerful feature for noise control. I generally found that I liked doing the stacking in DSS and then doing the remainder of the processing in Photoshop or similar image processing program. But that’s totally my preference. Each photographer should investigate the best workflow and combination of programs to use to produce the final image.

One really great feature of DSS is the comet stacking routine. Processing comets is even more complicated as the comet is typically in a different location in each frame. Some move slow enough not to have to worry about it. But others can move significant amounts in each frame. This typically takes some crafty processing to get a decent image. DSS takes a lot of the work out of it. This image was processed in DSS and Photoshop.

Coat hanger Asterism (CR399) and Comet Garradd

When beginning the stacking process, the images need to be quality sorted first and then aligned (or registered) first. The quality sorting can be done automatically in DSS, but I generally liked poking through the images and picking out the ones that were blurred from movement, or had clouds or planes. The registration or alignment will adjust the images up and down and also in rotation in order to bring all the frames in perfect alignment and then stack them together in one of several stacking methods. I generally prefer one of the median stacking methods.

Many of my astrophotos, including the comet photo above, were shot with professional level equipment. This equipment cost about half what my first house cost. To be fair I wanted to show what can be done with a DSR and Lens (or small telescope), so I re-processed some of my earliest images in DSS, knowing what I know now. These were shot with an Astro-modified, 6.3MP Canon 300D (Digital Rebel). This is one of the earliest DSLR’s. It was noisy and did not generally produce very clean astro images. But even with this old camera, the data was very usable and produced some fairly decent images. We’ll take a look at a few of these below:

My first modified DSLR for Astrophotography

Stacking Examples

Here are some examples of images right out of the camera and also some processed images. The first is a single frame that shows the Heart & Soul nebula (IC1805, IC1871, NGC 869 and NGC 884) as well as the double cluster. The top is out of the camera the next is after stacking and processing.

Unprocessed, right out of the camera

Stacked and post processed

The difference in these is drastic. In fairness, the single frame image was fogged by heavy light pollution. But this is a problem that will plague the majority of astrophotographers. The only way to combat this is to shoot from dark sites away from the city lights.

This next example is not as drastic. The top is out of the camera, the bottom is stacked and processed. Also included are crops of a single frame and stacked and processed images.

Single Frame and crop of the Rosette Nebula (NGC 2237)

Notice the missing details in the crop of this image.

Stack/post processed image and crop of the Rosette Nebula

The stacked image makes is much cleaner and much of the missing data has been filled in. Also note the better detail that is visible in the crop of the Rosette. This is the real benefit of the stacking method. One thing that you need to keep in mind with processing astrophotos is that it’s an incremental process. No single step is going to make a magical image from junk. Each step will add a tiny improvement, and with enough tiny steps you’ll end up with a very pleasing image. If you’re stacking many photos, most pieces of stacking software will take quite a while if you’re computer isn’t up to the task (like mine). So be patient and just let it run until it’s completed the registration and stacking processes.

Here’s another example of a single frame vs a stack. This one is of the Horsehead Nebula (B33) in Orion.

Single Frame and crop

Stack/post processed image and crop

It’s fairly easy to see the benefit of stacking when shooting astrophotos. One more advanced technique that will help reduce the noise in your stacks is called dithering. Basically this is moving the camera a couple pixels in a random direction after every frame. When using a median stacking method, objects in a different location on each frame will be eliminated. So using the stars as the alignment reference, the galaxies, nebulae or other subjects will remain in the same place. But hot pixels, satellites, planes, noise and other random effects will be in a different location, with respect to the stars, so these are eliminated when stacked. There are many guiding or tracking programs that will do dithering automatically. But even with a manual shutter release, it can help tremendously if you manually move the mount between exposures. It seems like a hassle, but dithering will add a fairly significant level of improvement. None of the images above (except the comet image) used dithering.

Another helpful addition is to add calibration frames. These will serve to help remove additional noise and other artifacts from the images. Dark frames will help remove hot pixels, Bias frames reduce read noise and flat frames will help clear up any dust spots or other specs that are caused by looking through the lens or telescope. There is a superb description of this in the FAQ section here. The newer more modern cameras tend to provide better noise and hot pixel control, so calibration might not be needed. But at the very least, flat frames should be used to ensure the removal of artifacts caused by a dirty lens or sensor. It will also help reduce any vignetting that occurs in the images. Remember: incremental improvements.

In the final installment of this Astrophotography series, we’ll discuss some of the details of going from a rough stacked image to the final image. This is where a lot of the magic happens so I hope you’ll stay tuned. In the meantime get out and shoot. See you soon.