[Leica] IMG: Testing SL For Milky Way Imaging

[Bob Adler]

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"*
>>> 
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>> 
>> 
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