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General Photography Technique Discussion on General Photography Technique

Astrophotography

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  #1  
Old 18-05-07, 07:36
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Default Astrophotography

Recently I posted a couple of Milky Way photos taken when on a trip to Australia. I have now just completed processing my images from that trip and have put them on my website.

If you are interested you can view them on http://www.graviton.demon.co.uk
and follow the link to Southern Skies

Dave
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Old 18-05-07, 07:55
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Superb, Dave, looks like you had a great trip.
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Old 18-05-07, 16:38
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As always, master pieces.
Very well done Dave and thanks for sharing.

Southern sky is so beautiful. Don't know why? Even McNaught when reaching to southern sky showed its best. May be they have the sky in their side (Minus the Northern star).

Dave when taking these wide angle picture at 5 minute time, you must have used the camera on a tracking device as no star tracing seen, am I right? Or did you use several short interval images with stocking in pp.
BTW just another dumb question, What could we expect from sky with wide angle lens in Northern hemisphere, in other words, when and were to point the lens next time, if sky was clear of pollution and stray light of city, if opportunity permits. Any suggestions?
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  #4  
Old 18-05-07, 17:38
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Quote:
Originally Posted by SharonW View Post
Superb, Dave, looks like you had a great trip.
Thanks Sharon, yes it was superb - we are already talking about next time. (Well you can dream!)

Quote from Sasson "Southern sky is so beautiful. Don't know why? Even McNaught when reaching to southern sky showed its best. May be they have the sky in their side (Minus the Northern star)."

Things always seem to happen where you are not. Interestingly on this trip we were introduced to Robert McNaught at Siding Springs Observatory. In spite of his name I hadn't realised that he was from Scotland.

Quote from Sassan "Dave when taking these wide angle picture at 5 minute time, you must have used the camera on a tracking device as no star tracing seen, am I right? Or did you use several short interval images with stocking in pp."

Yes you are right I did use a driven mount (the details are on my website) but it took me much of the time mastering how to polar align it. Most pictures were taken in the last two days. For some of the images (longer focal lengths) I did have to take some short exposures and then stack them but the Milky Way pictures were only one exposure.

Quote from Sassan
"BTW just another dumb question, What could we expect from sky with wide angle lens in Northern hemisphere, in other words, when and were to point the lens next time, if sky was clear of pollution and stray light of city, if opportunity permits. Any suggestions?"

The Milky Way is the best target. The centre of the Milky Way is easily the best part but we don't quite see it from the UK. If you are further south than us you may be able to see it late Summer. I think I did post a Milky Way shot from here earlier in the year when I was practicing for this trip.

A standard lens (e.g. 24mm) would be good for constellation shots even from a fixed tripod. Something like 20s using iso 400 should produce something interesting.
Whenever there is a comet around it is worth trying with a standard lens but there is no predicting when that may happen.

Dave
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Old 19-05-07, 00:07
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Thanks very much Dave for your extensive description. I wish my physics professor was as descriptive and knowledgeable as you.

Lucky you to see the original McNaugh.

Yes neighbor's grass is always greener...

Mount Wilson is located on top of LA, no wonder harboring giant TV radio stations transmitters. It also hold a ground for Astro camp (With a 60 inch telescope) that a photographer friend of mine has participated in it some long back. May be I need to check their summer activities for hopefully any participation chance or find a local astro club that can help. Mean while I will try the wide angle approach when sky permits. I have a tiny telescope with motor drive, Mead AT60 but anytime I tried to initialized it(So called Easy Two-star Alignment....), got so frustrated that went back to my fixed tripod. I guess I can learn things better with interaction rather than from manual.

Well thanks again for your info and hope you get to see crystal clear southern sky many many times and hopefully thread us with the result of your journeys.
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Last edited by sassan; 19-05-07 at 00:10.
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Old 19-05-07, 14:43
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Dave,

Great set of images. I had your site bookmarked. I found it from a cruise round Astro sites while studying this aspect of imaging in a bit more detail.

Perhaps you should fire up a Astro Photoraphy thread when you have time, to keep all this valuable info in one place.

Well done again for the inspiartion to broaden our photographic horizons.

Stevie was also well impressed. All I could hear as she looked though was .......... cor ..... wow .............. amazing.

Don
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Old 19-05-07, 16:55
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Dave,

Perhaps you should fire up a Astro Photography thread when you have time, to keep all this valuable info in one place.

Don
That sounds like an excellent idea Don.

Is it possible for a moderator to retitle this thread as simply "Astrophotography" and move it to the techniques forum, please?

Dave
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  #8  
Old 22-05-07, 14:18
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That sounds like an excellent idea Don.

Is it possible for a moderator to retitle this thread as simply "Astrophotography" and move it to the techniques forum, please?

Dave
I see that has now been done, thank you.

Dave
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  #9  
Old 22-05-07, 14:41
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Most people on this forum will not have access to a driven mount but may still want to have a go at some astrophotography. One of the easiest things to take is of the night sky using a fixed tripod and do a long time exposure. Attached is a 15 minute exposure with the camera pointing towards the pole star and you will immediately notice that sky glow can be a real problem. To some extent it can be improved in photoshop as in the second picture. However I have just come across (via an OU forum) a piece of free software that enable you to effectively take a long exposure without the sky glow. You instead take a large number of 30s exposures and stack them. The program will do that for you by just giving it a list of images. The sofware is available at http://www.startrails.de
As far as I can see any camera can be used but an advantage of a DSLR is that it can be set on multiple exposures and a remote lead set on continuous and the camera will keep on doing 30s (or whatever the longest automatic time is on the camera) until it is disabled. A two hour set would produce some interesting pictures. The trick then is to have an interesting forground.
It would be worth having the iso set high e.g. 800 iso if available but will work on lower.

By the way, the dust on my sensor has since been removed.

Dave
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File Type: jpg Star trails PS_2032.jpg (46.5 KB, 15 views)
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  #10  
Old 22-05-07, 18:30
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Dave's already started a good job here by the look of it so this seems as good a time to mention dark frames and the Nikon Noise Trick. The Nikon D70, which has serious noise problems (for astronomers anyway) above 200ISO, actually does some noise reduction even if you don't want it to, and with astro work, a small star could easily be misconstrued as noise.

If you set the D70 for, say, a 5 minute bulb exposure, with the noise reduction system OFF, BUT, then physically turn the whole camera OFF at 5 minutes, you will have a completely unmodified frame, no mistakenly removed stars....

The only other thing you have to do is take a "dark frame" for the same amount of time and subtract this from the original shot. Make a dark frame by taking the same time exposure, with the switch off method, but this time with the lens cap on. This, then, will only take a shot of the thermal noise. Take the thermal noise away from the original and bingo, a perfect no noise exposure.

Did that make sense ??
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