View Full Version : How to take astro photos?
7th of April 2009 (Tue), 16:22
I've been searching through these posts, but haven't really came across anything about how to start taking astro photos.
I just bought a used S3 IS, and after going through the manual, found out that I can set the exposure to a maximum of 15 seconds. Don't have a telescope or anything like that (don't think I would even be able to get a telescope adaptor for the S3). Have a fairly decent tripod.
There have been some terms used here that I don't fully understand either, such as 'subs'.
Any suggestions on how to get started would be greatly appreciated.
Thanks in advance...
7th of April 2009 (Tue), 22:26
What sort of astro photos are you wanting to take? Deep sky stuff like galaxies and nebulae? Star trails? Planets? Wide-field stuff off the whole Milky Way? They're all slightly different and the answers may vary. Another important question - what's your budget?
"Subs" refers to subframes IIUC. Because many deep sky objects are so faint, you take many subs of the one object and stack them together to bring out more detail and reduce noise. These are what others refer to as light frames, dark frames, bias and flat frames etc. Good explanation here on the Deep Sky Stacker site, a free application that does the above for you.
7th of April 2009 (Tue), 22:27
To get started 15 seconds will be plenty for tripod work. I'm not familiar with your camera but you'll want to use the camera's delay timer to begin the exposure if it has one. For star field shots I'd suggest some test shots to determine how high an ISO setting your camera will allow with out too much noise. If you can soot 800 great but 400 will be fine if the noise is too much set any higher. Some test will also give you an idea of how long to expose at any given zoom(focal length). If you see the stars begin to look stretched or oblong back down on the zoom or shorten exposure.
"Subs" refer to sub exposures when stacking multiple exposures. This is an advanced processing technique for improving detail and lowering the noise level using software designed just for astrophotography. I wouldn't worry about that right now, just have some fun experimenting to determine your camera's capabilities and limitations. A good sturdy tripod will help with results. Good luck, let us know if you have any other questions and please post your results.
8th of April 2009 (Wed), 02:15
Welcome to one of the most frustrating, potentially expensive and yet ultimately rewarding of hobbies. Taking pictures of object that are not visible to the naked eye and many light years away is a huge challenge . In the UK we also have the additional limitation of near constant cloud cover to contend with.
I'm familiar with your camera (my wife has one) and if you have a decent sturdy tripod and some darkish skies you will get some nice wide starfields at ISO 800 and 15 second exposures at a mid zoom range. Dont point straight up as thats where rotation is fastest leading to blurring but aim high enough to miss any skyglow.
If you want to be adventurous take 20 15 second shots (subs) and stick them in Deep Sky Stacker. The output will appear disasterous but if you have Photshop and quick play with levels will bring the life back.
8th of April 2009 (Wed), 02:40
My first astro shots were just my 400D and 18mm lens, on a fixed tripod, and taking frames* of anything from 3 or 4 seconds to 30s. Some individual subs* were good, sometimes I stacked lots together in Deep Sky Stacker to bring out hidden detail a bit. It's a great way to get started, and just about EVERY photographer can do it...you don't *have* to spend hundreds or thousands on scopes and mounts to give this hobby a crack, which is why I love it so much, (even though I *have* spent over a thousand on scopes and mounts and stuff!! ;) )
* - Frames or subs just mean photos really. I tend to use the word frames mostly for some reason. If you ever use something like Deep Sky Stacker you'll see it lets you load "light frames", "dark frames" and "flat frames". Light frames are your images. Dark frames are photos taken with the camera lens on. You might ask why anyone would do this, but it's all to do with removing hot pixels in images. When you take long exposures you sometimes get white or red pixels on every photo. It's something to do with faults on the camera sensor. If you take photos with the lens cap on these hot pixels still appear, and software like Deep Sky Stacker can eliminate these for you when you apply the dark frames on top of the light frames. Flat frames are a whole other matter, and help remove vignetting...more about that another time perhaps! ;)
8th of April 2009 (Wed), 06:49
Thanks everyone for your replies.
As for my budget, it is whatever my wife will let me spend! :D Seriously, she is the one who handles the bills and stuff, and if it were not for her, we would probably be seriously in debit.
As for what I would like to capture, there is my realistic side and my fantasy dreaming side. Fantasy dreaming would be some cool deep sky stuff, like galaxies, nebula, the far reaches of the universe. Realisticalyl, the moon, milky way, stuff like that.
My equipment consists of a tripod, camera, laptop and a whole lot of patience. I don't mind sitting out on a nice clear night and doing some photo work. My brother-in-law has a farm out in the country away from city lights with clear open skies, which would be good for this type of thing. We are also about an hours drive away from Lake Huron where my sister-in-law has a cottage overlooking the lake. Always thought this would be a great place to get some cool photos of a stars over the lake. Also, this area is known for some really beautiful sunsets.
I have had a couple of telescopes in the past, but were not what you would call high-end scopes. They were 4.5" reflecting scopes on not very sturdy mounts. The slightest breeze, and the scope would shake.
I am still going through the manual and learning about the camera and its controls and functions. Hope to get out in the next week or so and start playing around at night with the camera.
8th of April 2009 (Wed), 07:44
You're welcome. Right now you can still catch Orion setting over Huron. Don't wait too long, it'll be out of site soon. Dark skies will definitely help you at this stage, and are extremely beneficial at every skill level.
11th of April 2009 (Sat), 18:34
I have a question myself about this.
I've seen some really nice shots of the milky way but they were multiple exposures all stacked up, and what the images reveal was amazing compared to what you can see with the naked eye.
Thing is, the exposures were very very long (lots of minutes) each, but the image had no blur which I'd expect to see if you open the shutter for that ammount of time due to the earth spinning.
How do you go about creating an image like that taking into account the stars moving in the sky due to the earths rotation?
Do you need some gear to track the movement?
11th of April 2009 (Sat), 22:27
Yes, you need to be tracking in sidereal rate to shoot extended exposures. The higher focal length you shoot at the more precise the tracking needs to be. A quality German equatorial mount is the staple of long exposure work. Lesser quality mounts will suffice at lower focal lengths for wide field work like imaging large portions of the Milky Way. A barn door tracker can be made very inexpensively if you are the build-it-yourself type. It can get the job done at low focal lengths when using a camera and lens.
When using a German equatorial mount you'll need to learn how to polar align, balance/level the rig before imaging each night unless you have a permanent observatory in the plans. It's a little intimidating at first but once you've learned the process and practiced it a few times it'll become second nature.
If you enjoy challenging photography and have the patience to overcome those challenges, you won't find a more rewarding and satisfying form of imaging. Collecting ancient light that has been hurling through space is awesome and the beauty out there can only be adequately described by the images themselves.
Please don't hesitate to ask questions, glad to help.
11th of April 2009 (Sat), 22:39
Great topic, answered a lot of information I was wondering about thank you
17th of April 2009 (Fri), 16:08
yep thanks for the tips too guys! ive been missing for awhile here but i have gone out a couple times to try this astrophotography (widefield) with my telescope but have continued to fail...definitely a learning process hahahaha.
at least after all those times going out i know how to set up my scope efficiently now....now if i could only take pics...
19th of April 2009 (Sun), 19:24
I just bought a used Canon EOS Digital Rebel XTI with Tamron 75-300mm lens from the same pawn shop that I bought my S3. Again, this camera appears to be in excellent phsyical and working condition as my S3 was. So, now I will be playing around with doing some star and moon shots with the new camera.
20th of April 2009 (Mon), 08:38
I have penned a couple of pages that may help.
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