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DPChallenge Forums >> Tips, Tricks, and Q&A >> How to shoot complete circular star trails...
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12/15/2016 04:36:19 PM · #1
...which, I'm guessing, means an exposure of a few hours, some of which I need to spend sleeping, so I can't be out there watching and waiting...without your batteries crapping out on you, especially if you're trying to catch it in the cold?

Message edited by author 2016-12-15 16:38:45.
12/15/2016 04:48:31 PM · #2
Define what you mean by "complete."

You can't get a 360 deg full circle because you're going to encounter daylight at some point during that rotation of the earth. You can get a pretty long arc though, if you're patient, your camera has good batteries, and you have a certain set of skills and tools. In the digital age, most people don't do star trails by shooting a single exposure over several hours. Instead, they shoot multiple exposures of, say, 30 seconds each, and then use a software program to "stack" the resulting images. Google "star trail stacking" to find several such packages, as well as web sites offering to instruct you how to do it.
12/15/2016 04:52:43 PM · #3
John said it right. In my opinion with a very dark sky you can get a very good circle with 1h30m/2hours of shooting. Of course it's better to make single shots and stack them together. There are severak programs to create a single image. One of the them is Startrails,but there are a few of them.
12/15/2016 05:48:43 PM · #4
I want to do something like this: ' . substr('//images.dpchallenge.com/images_challenge/1000-1999/1266/120/Copyrighted_Image_Reuse_Prohibited_909228.jpg', strrpos('//images.dpchallenge.com/images_challenge/1000-1999/1266/120/Copyrighted_Image_Reuse_Prohibited_909228.jpg', '/') + 1) . ' and yes going by his notes, he used a single 79 min exposure...I don't think he used focus stacking, though yes I know how to do it. My preference though is to get it right in-camera, rather than have to rely on pp to put it all together for you.

I do still have my ol' Pentax K-1000 and accompanying 50mm, but no film and dang the image has to be shot with a digital camera.

Message edited by author 2016-12-15 17:52:31.
12/15/2016 05:56:36 PM · #5
As you can see in that image there is a DRAMATIC noise reduction and your camera is really under pressure doing that.

I've done it several times myself but I'm scared at taking so long a shot (even if my last Sony cameras have pixel remapping, so if some of the pixels die some others will do their job).
12/15/2016 08:37:04 PM · #6
The program Registax was created specifically for astrophotography.

Maybe it's obvious but you need to point your camera at Polaris (or the Southern Cross?) if you want near-circles.

You should be able to stack and merge a series of time-lapse exposures to achieve the same thing -- it was an area of contention in the "old rules" ... :-)
12/16/2016 08:07:33 AM · #7
Susan, for astro work you have to re-calibrate the "get it right in camera" mentality. You *do* still need to get it right in camera, meaning choosing the correct exposure time, ISO, lens aperture, yadda yadda, BUT - you will almost always be planning an exposure series, not a single exposure for best results, and an individual exposure will look much less like the end result. Your single exposure results must be geared to get the best end result after stacking. In this case what you want to do is to expose for the foreground, let that determine your exposure time. Then determine the number of exposures you need, gather your data and stack 'em up.
Stacking provides incredible noise reduction as a side benefit; random noise is reduced by the square root of the number of exposures averaged, so if you take only foiur exposures, your random noise is reduced by half! Note this does not affect fixed pattern noise, that's a different beast and there are also ways to deal with that by stacking, but we really don't have to these days with the sensor performance we have now.
12/16/2016 02:17:02 PM · #8
Originally posted by kirbic:

Susan, for astro work you have to re-calibrate the "get it right in camera" mentality. You *do* still need to get it right in camera, meaning choosing the correct exposure time, ISO, lens aperture, yadda yadda, BUT - you will almost always be planning an exposure series, not a single exposure for best results, and an individual exposure will look much less like the end result. Your single exposure results must be geared to get the best end result after stacking. In this case what you want to do is to expose for the foreground, let that determine your exposure time. Then determine the number of exposures you need, gather your data and stack 'em up.
Stacking provides incredible noise reduction as a side benefit; random noise is reduced by the square root of the number of exposures averaged, so if you take only foiur exposures, your random noise is reduced by half! Note this does not affect fixed pattern noise, that's a different beast and there are also ways to deal with that by stacking, but we really don't have to these days with the sensor performance we have now.


Ok...will give it a go your way...once the big ol winter storm headed our way has come and gone. Thanks all for the advice and pointers!
12/16/2016 10:04:02 PM · #9
This is what I took, are you asking something like this?

' . substr('//images.dpchallenge.com/images_portfolio/60000-64999/60581/120/Copyrighted_Image_Reuse_Prohibited_1192094.jpg', strrpos('//images.dpchallenge.com/images_portfolio/60000-64999/60581/120/Copyrighted_Image_Reuse_Prohibited_1192094.jpg', '/') + 1) . '
12/17/2016 06:03:17 PM · #10
Originally posted by pgirish007:

This is what I took, are you asking something like this?

' . substr('//images.dpchallenge.com/images_portfolio/60000-64999/60581/120/Copyrighted_Image_Reuse_Prohibited_1192094.jpg', strrpos('//images.dpchallenge.com/images_portfolio/60000-64999/60581/120/Copyrighted_Image_Reuse_Prohibited_1192094.jpg', '/') + 1) . '


Pretty much, yes. Did you use a super-wide or a fisheye, though? The beach at the bottom is quite curved, that looks like some lens distortion was going on. Focus stacking?

Message edited by author 2016-12-17 18:10:56.
12/18/2016 08:47:36 AM · #11
Originally posted by snaffles:

Originally posted by pgirish007:

This is what I took, are you asking something like this?

' . substr('//images.dpchallenge.com/images_portfolio/60000-64999/60581/120/Copyrighted_Image_Reuse_Prohibited_1192094.jpg', strrpos('//images.dpchallenge.com/images_portfolio/60000-64999/60581/120/Copyrighted_Image_Reuse_Prohibited_1192094.jpg', '/') + 1) . '


Pretty much, yes. Did you use a super-wide or a fisheye, though? The beach at the bottom is quite curved, that looks like some lens distortion was going on. Focus stacking?


In this case I used a fisheye because I was not carrying all my lenses when I was at Virginia beach, i had 24-70, 70-200 and fisheye. I wish I would have take 16-35 or 17-40 so that the circular feel would not have come :(

Anyway so this is what I had:

1. Setup in tripod to make sure it is study
2. used a remote wire to trigger the clicks
3. setup the 6d with 15mm fisheye with shutter speed of 30 seconds, aperture of 2.8 (I could have bumped this but), ISO was 320 (if I would have increased aperture so would have increased ISO to compensate the lighting.
4. took about 80 photographs
5. converted them all from RAW to JPg ( I really didn't need to do this)
6. Added them all in StarStaX application and click the button to merge them all and end result is what you are seeing and then did some final adjustment.

I am sure there are many other ways but since I was doing it for first time so what I did is what you see above :)
12/18/2016 08:50:24 AM · #12
Very cool final result and thanks very much for the tut, will have to check out StarStax. Just one question though...if this was about 80 captures and this was an entry...you'd be spending all day uploading originals for validation! ;-)

Message edited by author 2016-12-18 08:51:00.
12/18/2016 09:50:43 AM · #13
Originally posted by snaffles:

Very cool final result and thanks very much for the tut, will have to check out StarStax. Just one question though...if this was about 80 captures and this was an entry...you'd be spending all day uploading originals for validation! ;-)


Yes but again I dont think this would fall in any category because I believe somewhere there is another rule which says no more than 10 photographs used. If really want to keep the limit to 10 then need to go to bulb mode and adjust aperture and iso accordingly and also you would have to go far far away from the city light. Here in my case I face towards sea so there was no city light against the starts but there were some coming from behind.
12/18/2016 11:00:49 AM · #14
Originally posted by pgirish007:

Originally posted by snaffles:

Very cool final result and thanks very much for the tut, will have to check out StarStax. Just one question though...if this was about 80 captures and this was an entry...you'd be spending all day uploading originals for validation! ;-)


Yes but again I dont think this would fall in any category because I believe somewhere there is another rule which says no more than 10 photographs used. If really want to keep the limit to 10 then need to go to bulb mode and adjust aperture and iso accordingly and also you would have to go far far away from the city light. Here in my case I face towards sea so there was no city light against the starts but there were some coming from behind.


Yes you're right, the 10-photo limit does still apply to Standard...but in Extended anything goes. And you're right about bulb mode, which is usually how I shoot astro stuff. Fortunately I live out in the countryside and have access to a 100-acre property, so I can do a pretty good job of getting away from city lightwash.
12/18/2016 12:55:37 PM · #15
Originally posted by snaffles:

Yes you're right, the 10-photo limit does still apply to Standard...

I don't think so ... it just says "One or more captures ..."

And I think we've made some logical exceptions to the "submit every original" rule ... for example, if you combined 30 frames to make continuous star trails, I think you could send in every third frame or so -- successfully sneaking one old frame into the sequence would require such exceptional skill and planning as to be hardly worth the effort except as a challenge in itself.
12/18/2016 02:47:00 PM · #16
Oops I stand corrected on the 10-shot rule. Thanks Paul!
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