DSLR Deep Sky Astrophotography
For the Novice (or Novice at Heart!)
By Gary Colwell
Ok, you want to get started in the wonderful world of astrophotography, but you have more questions than answers…What do I need?, what do I do?...how do I do it?....
These are all questions I have asked myself…there are soooo many ways you can attack this hobby….and you can literally spend thousands…or a few hundred bucks…depending on what you want out of it…
I have been at this hobby for nearly 45 years now (ok…I am an old geek!)…and have just taken up astrophotography seriously for just over a year now….and I am amazed at just how daunting I thought it was at the beginning…only to find out that once you have a “plan of attack”…it is really quite simple and a whole lot of fun….nothing feels better (ok… maybe a week in the tropics might...lol.) than to gaze on your very first picture of some object in the heavens! It may not be of the Steve Barnes or Jack Newton type quality….but it is YOURS!
Alright…where do we start?…I will try to simplify things as much as I can without blasting you away with “Astro-jargon”….sometimes just some of the words are enough to scare anybody off!
Need #1 – DSLR Camera
You can have one of the fanciest telescope setups on earth, but if you don’t have a camera…well, astrophotography is not an option. Like the sands of the sea there are sooo many options here, but since we are getting started, lets talk basics.
There are two types that work great for the beginner…the Digital camera and the small astrophotography cameras you can buy like the Meade DSI, the Orion Starshoot etc.
If you have a digital SLR camera or DSLR as it is also known, this is the one we are going to use for the purposes of this exercise. You will need what is called a “T-ring” that allows you to further attach either a 1 ¼” or 2” photographic adapter sleeve that fits into the eyepiece holder of your telescope. Your telescope now becomes a super telephoto lens!
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go!
Make sure that the camera you are using has the ability to take time exposures (of at least 1 minute) or a bulb setting ( the best option) which allows you to take longer exposures.
NOTE:
You can also use dedicated astrocameras, which involve more work (and a computer to run) but the results are pretty good too. They either come in B&W (the cheapest price) and colour (considerably more.) You can pick up used cameras on sites like Canada Wide Astronomy Buy and Sell for between $150.00 and $250.00.
Need #2 – Telescope
Wow…here is the toughie!...what to use….but strangely enough almost any scope will do…
I have taken pics with Schmidt Cassegrains, Newtonians and refractors.... but the ones I like the most are refractors… the choice is up to you….but let me first dispel a common misconception…for the beginner…..Size DOESN’T Matter!....
What I mean by this is you can get just as good a picture with an 80mm aperture scope as you can with a behemoth 150mm. (albeit the 80mm image will be smaller in comparison). As a newcomer to astrophotography , use what you have.
Here are pics I have taken with an 80mm Skywatcher vs. my 110mm William Optics FLT Apo chromatic ( a difference of about $2500.00 in price)
M81&82
80mm.
M81&82
110mm.
So you see, you can get good results no matter what you use.
Need # 3 - Equatorial Mount
Another essential for deep sky astrophotography is that you have a mount that can guide the stars, otherwise you are severally limited in the exposure time you can achieve.
If you want to take respectable deep sky astrophotos, you will need a mount that can track equatorially, either using motors or hand controls. (Note: some scopes that come with motorized alt-azimuth mounts can be used for astrophotography but are limited to 1-2 minutes of tracking before the field begins to “rotate”….but more of that in a later article).
If you have an equatorial mount that is not motor driven, you can hand guide the mount, but your exposure time will be limited to the time you can accurately guide your mount before the lactic acid kicks in, and your hands and arms all cramp up!...lol.. Usually you can guide up to a 3 minute exposure once you get good at it…but not much more….
The three “P”’s with these hand guided methods and astrophotography .
For those who have equatorial mounts, the key is polar alignment. A very useful and FREE tool is a computer program called Polar finder. It can be found at: http://www.onealwebsite.com/AstroPage/software.htm
This program gives you a simple way to align your mount that is surprisingly accurate and easy! Just line up Polaris in your finder as pictured above for your time and latitude…and that’s it!
If you polar align your scope well, you can get up to 2-4 minutes tracking with good results. It ALSO depends on the “magnification” you are getting with your scope…by that I mean the resulting image size. Without getting into the math of it all, generally as a rule..
As you can see from my pictures of M81 &82, the 110mm (770mm focal length) image yields a greater “magnification” than did the 80mm…(495mm focal length). This means that any tracking errors will be magnified greater in the larger focal length scope than the smaller. This will mean less exposure time for the larger focal length than the smaller. This will have to be done by trial and error.
Other things that will affect the time you expose the image will be sky conditions….generally the darker the sky, the longer the exposure you can take. In Hamilton, anything longer than a few minutes will be washed out by background sky conditions…whereas, in Algonquin Park….well…the sky is the limit usually allowing 10 minute exposures or more….
Need#4 Processing Software?
Depending on how sophisticated you want to get with your processing (but as a beginner we will keep it simple ….KISS..) there are a number of freeware and commercial products available.
Since we are new to this type of astronomy, I am going to leave this to the end and discuss a few of the basics of taking a picture first.
In the digital age, unlike in the past when using film….exposure time is NOT as critical…ie. longer isn’t necessarily better. With a free program like REGISTAX, you can take a series of short exposure frames and “Stack” them on top of each other to create a more detailed image. More on this later…
Generally your exposure time will be dependant on the accuracy of your mounts tracking ability and sky conditions.
For the purposes of a newcomer to astrophotography, I suggest you start with taking
images of no longer than 2 to 3 minutes duration. This will allow you to get a decent picture that you will be happy with. Nothing is more frustrating than taking a bunch of 5 minute exposures only to have blurred results.
Ok, lets get into the nitty gritty and get taking some pictures!!!!! At this point I am assuming you have your scope and mount all polar aligned and ready to go!
Step 1. Set up your camera
Step 2. Select a good imaging target!!
As a beginner, don’t be trying to take pictures of some distant far away galaxy….start with something big and bright! This time of year, a few good objects are M42 the Great Nebula in Orion, M31 the Andromeda Galaxy, M44 the Beehive and the like…
For our purposes I would like to use M42…it always yields a ‘gasp’ the first time a new astrophotographer takes its picture!
Step 3 – Focus, Focus, FOCUS!
Assuming you have already set up your mount accurately and all is ready…it is time to focus…but NOT on M42….!! Focus your camera using a bright star or a few bright stars. This is going to be trial and error at first…but it is critical in obtaining a picture you are going to be happy with. The beauty of digital cameras is that you can take a whole bunch of pictures without wasting film…and that is what we are going to do…
Step 4 – Move scope to align your target
Move the scope so that the object you want to take is centered (using the guide scope as it is easy to pick out M42 with a guide scope. Once this is done you are ready to start taking pictures. At this stage we are only going to take jpeg images so that you can get used to the process. Once you get this stage down, we can discuss other methods in a later article.
Step 5- Take sample images to determine best exposure time!
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90
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120
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Step 5 - Save or Process the images
If you are like me, your first clear jpeg image of the heavens will thrill you to no end…sometimes all you want to do is keep the picture and be proud of your accomplishment…here is my vey first image of M42! It was a one minute exposure using a 300mm telephoto lens strapped to the back of my scope…..Not too shabby for a beginner!...
But if you are really like me you will want to push, process, highlight, stretch, adjust the death out of your picture….but remember the KISS process ( Keep It Simple Silly)…. The first thing is to get to the point where you get comfortable with the procedure. Once this is accomplished you can get a bit more fancy.
If you are adventurous and want to “push the envelope” you can try stacking multiple images. Like previously mentioned REGISTAX is a good program. ( this is why you have taken multiple pictures in step 4.) You can download this program at: http://www.astronomie.be/registax/ (But a bit of caution, take it slowly at the beginning…or else you run the risk of becoming frustrated. Try some other heavenly objects and get yourself accustomed to taking pictures first…)
Once you learn the basics of the program, you can stack your images to make them even more beautiful.
Well, that is about it for the “rudimentary” stuff….next month we will learn a bit more about how to take better and more detailed pictures….but in the meantime, practice these ideas and get familiar with the process…it is a huge learning curve as we go along, but like all things, get good at the basics and the rest will take care of itself!
Have fun with it…and DON’T EXPECT HUBBLE QUALITY IMAGES right away…that day will come. I am no expert in the field, just another fellow astronomer excited about the prospect of being able to enjoy pictures of the heavens that I took…and you will find out for yourself the same.
In less than a year…. I went from this….
To
this….
ToThis!!!
Good Luck!