Archived posting to the Leica Users Group, 2017/06/22

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Subject: [Leica] IMG: Testing SL For Milky Way Imaging
From: rgacpa at gmail.com (Bob Adler)
Date: Thu, 22 Jun 2017 11:43:44 -0700
References: <CAAsXt4N016C4v79C=1K1pt2UB_GxeoLobq9OhS51FdOcWJskug@mail.gmail.com> <FAB2923F-0516-4CD8-B658-B6F92E0B11A0@twc.com> <74018A2A-00B0-4809-B3DB-38D0442B503C@gmail.com>

Hi Gene,
Thank you.
How do you prevent star trails with that long of an exposure? The normal 
rule to prevent trails and keep the stars sharp is 500/lens focal length ( I 
use 300 to 350 as the numerator). So using the SL 24-90 @ 24, I get a 
maximum exposure time of 15. I used mostly 20sec on most of these, though 
one was 15sec.
Are you using a star tracker of some sort?

Bob Adler
www.robertadlerphotography.com

> On Jun 22, 2017, at 10:53 AM, geneduprey2015 at gmail.com wrote:
> 
> I'm surprised you used such a high ISO. I have been using 3200 or 2400 
> with great results and between 25 & 30 seconds.  Great shot though.
> Gene
> 
> Sent from my iPhone
> 
>> On Jun 22, 2017, at 10:49 AM, Howard L Ritter Jr <hlritter at twc.com> 
>> wrote:
>> 
>> That?s a very nice capture of the region towards the center of the 
>> Galaxy, Bob. And even expanding the image on my screen, I don?t see any 
>> bothersome noise. There?s virtually none in the dark regions of the 
>> hills, and the mottling in the lake and the sky I think is primarily due 
>> to the innumerable stars. In any case, the SL?s performance at ISO 12500 
>> is impressive. That region is my favorite binocular target, and now that 
>> I?ve discovered how to nearly eliminate the effects of light pollution in 
>> my suburban sky, and begun to do sky imaging, it will be a target for 
>> that as well. 
>> 
>> I don?t recall whether you mentioned seeing them when I first posted 
>> them, but I took some similar shots of the Southern Hemisphere Milky Way 
>> from Australia in April. I took them with a Nikon D810A (the 
>> astrophotography model with the less IR-restrictive sensor cover plate) 
>> and the Nikon 14-24mm zoom at 14mm or the 24-85mm zoom at 50 or 85mm. The 
>> shots with the zoom were done with the camera on a tracking device to 
>> avoid star trailing. I used ISOs of 1600-6400.
>> 
>> http://gallery.leica-users.org/v/hlritter/Gallery_001/ 
>> <http://gallery.leica-users.org/v/hlritter/Gallery_001/>
>> 
>> I stretched the histogram of my images in PS by moving the white-point 
>> slider to brighten the stars and the black-point slider to darken the 
>> background sky, then fiddled with both, plus the grey-point slider, to 
>> get the effect I wanted. To get rid of vignetting, I also applied a 
>> flat-field correction frame that I took in daylight with a couple of 
>> layers of white T-shirt over the lens, and the camera aimed away from the 
>> sun at a sunlit scene, and then converted to greyscale. I think my images 
>> as posted are a bit hyper-real, but that?s a goal of photographing any 
>> celestial targets other than the bright moon and planets. In any case, 
>> they carry the flavor of the visual impact of seeing the Southern Milky 
>> Way and the Magellanic Clouds, for the first time, from the deep darkness 
>> of rural Australia. The left side of the region of the MW that I imaged 
>> adjoins on the right your region of the MW at the dense star cloud in the 
>> center of your first image. The very different orientation of the MW is 
>> what happens when your viewpoint is rotated 65 degrees clockwise!
>> 
>> Did you do any post-processing of these images? They have the look of raw 
>> images to me. If so, I?d be interested to see what the result of a 
>> histogram stretch might be. Would you mind sharing the raw file with me 
>> so I can play a little? I?ve added a couple of the raw images to my album 
>> so you can see the difference post-processing makes.
>> 
>> It?s possible to see very short star trails by enlarging your images. The 
>> rule of thumb is that they won?t be easily noticeable if the exposure 
>> time is not more than 300 sec divided by the FL in mm, so your 20-sec 
>> exposures at 24mm are pushing it. If you?re going to do much of this sort 
>> of thing, a camera tracker can be had for about the price of 2 or 3 SL 
>> batteries? ? Some of my images were exposed for longer than the rule of 
>> 300, which is possible when the region being imaged is well away from the 
>> celestial equator, where the stars move fastest.
>> 
>> (Pardon me if I?m telling you things you already know!)
>> 
>> ?howard
>> 
>> 
>>> On Jun 21, 2017, at 5:28 PM, Robert Adler <rgacpa at gmail.com> wrote:
>>> 
>>> Last night I went up to Silver Lake in the Sierras. It's at about 7,800'
>>> elevation. I went to see how the SL with the SL24-90mm would work with
>>> Milky Way photography. The two images were taken at 12,500 ISO @ 24mm,
>>> f/2.8 with a 20second exposure. I shot from 10:30pm until 3:00am...
>>> 
>>> Though there is a lot of noise, I don't find it distracting. The drama of
>>> the center of our galaxy seems to outweigh any noise issues. Please click
>>> on the image to make it larger to fit your screen:
>>> 
>>> http://www.robertadlerphotography.com/p133735760/h8e052599#h8e052599
>>> 
>>> I would appreciate others' opinions as to whether or not they find the
>>> noise distasteful or does it look more like film grain. The images were
>>> post processed in Capture 1.
>>> 
>>> Thanks for any opinions in advance,
>>> Bob
>>> 
>>> 
>>> Bob Adler
>>> www.robertadlerphotography.com
>>> *"Capturing Light One Frame At A Time"*
>>> 
>>> _______________________________________________
>>> Leica Users Group.
>>> See http://leica-users.org/mailman/listinfo/lug for more information
>> 
>> 
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Replies: Reply from geneduprey2015 at gmail.com (Gene Duprey) ([Leica] IMG: Testing SL For Milky Way Imaging)
In reply to: Message from rgacpa at gmail.com (Robert Adler) ([Leica] IMG: Testing SL For Milky Way Imaging)
Message from hlritter at twc.com (Howard L Ritter Jr) ([Leica] IMG: Testing SL For Milky Way Imaging)
Message from geneduprey2015 at gmail.com (geneduprey2015 at gmail.com) ([Leica] IMG: Testing SL For Milky Way Imaging)