Page 1 of 1

Is that decent?

Posted: Tue Jan 05, 2016 10:41 pm
by Chaos
Greetings!

Newbie in astrophotography here! I really like star tools and till now i watch and read the tutorials. This is my first image test with a skywatcher adventurer mount 60x30sec. I couldnt stretch the image too much cause i didnt have flats only darks so i have extreme banding and noise i think due to light pollution. But i tried and i would like to ask is any of these images decent?
thank you

Re: Is that decent?

Posted: Fri Jan 08, 2016 2:08 pm
by Chaos
i gave another try and made a dropbox account so i can upload big files. I got some weird stars inside the big stars as you can see. What is that?

https://www.dropbox.com/s/yprp15okrq8oz ... .tiff?dl=0

Re: Is that decent?

Posted: Sat Jan 09, 2016 1:53 am
by admin
Hi,

Can you tell us a little bit more about what camera you used and how you stacked the 60 frames?

You've definitely recorded some of the nebulosity, which isn't bad for 30 seconds and no flats!

I would definitely give your sensor a clean and then take some flats - it will make it so much easier to tease out more detail and faint nebulosity.

Re: Is that decent?

Posted: Sat Jan 09, 2016 8:58 pm
by Chaos
Greetings! Thanks for your time! Images taken with a sony a7s unmodded iso 250 and a jupiter 200mm f4 lense. I stack them in dss following the way that proposed somewhere here that is best for star tools.

Re: Is that decent?

Posted: Mon Jan 11, 2016 6:58 am
by admin
Chaos wrote:Greetings! Thanks for your time! Images taken with a sony a7s unmodded iso 250 and a jupiter 200mm f4 lense. I stack them in dss following the way that proposed somewhere here that is best for star tools.
You're definitely doing well here with a great performing camera (but take those flats next time!)
You should probably try going for a higher ISO, around 800 (EDIT: it appears to be a rather high 3200 ISO for the A7s!) - I'm not entirely sure what the native ISO and dynamic range is for Sony's Exmor sensor in the A7s but shooting at a rather low 250 may be unnecessarily hobbling signal transfer into the digital domain (using higher ISOs of course does not give you more signal vs noise, but may counter quantizing errors if the lower ISO 250 emulation is accomplished in the digital domain by scaling down a signal that was acquired at a higher native ISO, such as 320, 400 or 640).

If the chromatic aberration is taking over too much (you seem to have it under control), you can stop down the lens a little.

The chromatic aberration can be ameliorated in post-processing as well (see 'fringe killer' in the Filter module).

Re: Is that decent?

Posted: Mon Jan 11, 2016 7:21 am
by admin
Doing a bit more digging, I found this very useful article by Ian Norman on the A7s including a confirmation that ISO 3200 is the best setting for this camera;

http://petapixel.com/2014/07/30/sony-a7 ... hy-review/

Re: Is that decent?

Posted: Tue Jan 12, 2016 11:13 pm
by Chaos
Thank you! Your advice were followed! I shot this from a darker sky and also iso 3200 and i took flats. I didnt stretch it much but star tools was :thumbsup:
I have done 2-3 versions and i will keep diging with this great software. Here i the file unstretched if someone want to pull out more.

https://www.dropbox.com/sh/n1s2rliiph6l ... jtoea?dl=0


here is the photo

https://www.dropbox.com/s/26v0f7xwd3rtmz7/1c.tiff?dl=0

Re: Is that decent?

Posted: Thu Jan 14, 2016 1:31 am
by admin
Excellent! You're really getting quite a bit of nebulosity through now - even the surrounding fainter stuff. Quite remarkable for 30s!
pleiades clean.jpg
pleiades clean.jpg (475.09 KiB) Viewed 6971 times