Let me have it....

Questions and answers about processing in StarTools and how to accomplish certain tasks.

Let me have it....

Postby Directlinq » Mon Jun 18, 2018 2:39 pm

Hi All

I have only just started with astrophotography and just when I think i know enough to get started another 15 ton of information gets thrown my way to sift through.
Nether the less I obtained my first data set of M81 and its got to be the worst thing I've ever seen. :(
I've ashamedly uploaded it here for you all to laugh at and hopefully pick it apart and tell me where i'm going wrong.
Any advise would be appreciated.

Current setup
Celestron 6SE, Alt AZ mount, 6.3 focal reducer.
30 lights, 10 darks, no Flats, No Bias, No Dark Flat
30 second exposures with 2000 ISO (I think 30 seconds on an Alt AZ mount is pushing it)
Camera Canon 60D
Stacked in Deep Sky Stacker, with no modifications.

https://www.dropbox.com/s/hwhky4eqhj7dlg6/NGC3031%20M81.fts?dl=0

Things i know I need to do, Flats, Bias, Darkflats.

I have had a play with star tools to see what information i captured above but with bad results. Maybe you guys could do better. Or maybe its just too bad.
Please tear this apart so i know what not to do next time and not to waste a clear nights sky.

Many thanks everyone
Directlinq
 
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Re: Let me have it....

Postby almcl » Mon Jun 18, 2018 4:53 pm

I have had a little play with your data, and to speed the processing, cropped the frame quite heavily to get rid of the vignetting (flats will help with this when you are able to take them).

Attached image is what I got after a very quick 'n dirty run through Startools and if that's your first go, well done, you've got the target and some detail in the arms.

Bias frames may help too, and are quite easy to do.

If you are going to do darks (and there's a body of opinion that thinks they can do more harm than good with a DSLR) then probably a minimum of twenty are necessary.

A query, how are you focussing? Some of the stars look a little 'soft' and it may be possible to sharpen them up a bit.

It may be that more data (try shorter as well as longer exposures - may also help with field rotation) will help.
Attachments
M81.jpg
M81.jpg (59.04 KiB) Viewed 958 times
Skywatcher 200P with an astro modded Canon 700d, cls ccd filter, field flattener, guided by QHY 5Lm, PHD2
almcl
 
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Re: Let me have it....

Postby Directlinq » Mon Jun 18, 2018 5:13 pm

Hi, wow you brought out a lot more detail than I was expecting.
I focused on a nearby star but it was only by visual focus. Is there a better way? Focus is always an issue for me.

I tried an bahtinov mask but it just showed me the star as usual which was strange unless I'm doing something majorly wrong.

Many Thanks for taking the time to have a look at it.
Directlinq
 
Posts: 2
Joined: Mon Jun 18, 2018 8:45 am

Re: Let me have it....

Postby almcl » Mon Jun 18, 2018 9:07 pm

I use a Bahtinov mask, but if you don't see the cross when you put the mask in place, something's not right. The mask does have to be made for your specific imaging equipment (focal length, objective diameter) to work correctly. Alternatively there are aids in capture software (APT is free to download and use and has both a Bahtinov aid and a FWHM aid and works well with Canon cameras but there are several others.)

You may get more and better, responses to questions about capture, focus and so on on https://stargazerslounge.com/, but this is a good place to ask about Startools processing techniques.
Skywatcher 200P with an astro modded Canon 700d, cls ccd filter, field flattener, guided by QHY 5Lm, PHD2
almcl
 
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Location: Shropshire. UK

Re: Let me have it....

Postby Rkonrad » Tue Jun 19, 2018 7:09 pm

Good first try! I agree that you should have longer light frames. I'm also wondering how the light pollution was where you are - this has a major impact on the final product. Also you should stack with flats at the minimum. Darks and bias frames are good but the flats are really mandatory. There is no need to shoot as high as 2000 iso. Try between 400-1600. In deepsky imaging iso doesn't help you get better exposure but helps reduce some read noise (higher is better) but this effect is minimal. Lower iso's increase the dynamic range so stars and galaxy cores aren't blown out. Here is my try - spent a moderate amount of time getting as good as I could. No colour applied as there wasn't enough exposure. All the best. Richard.

NGC3031 M81.jpg
NGC3031 M81.jpg (71.47 KiB) Viewed 937 times
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Re: Let me have it....

Postby happy-kat » Wed Jun 20, 2018 9:02 pm

Great start
Using your mount I would be trying a shorter exposure and pushing upwards towards 100 of them. As already mentioned flats aren't really optional. I have found with my Canon that flats and darks flats work best and darks add noise. Being an AltAz mount that is adding an element of dithering naturally which is a good thing. StarTools is great at helping to fix many issues like star shapes but the less there is to twiddle with the better.
Try 20 seconds, more light frames (aim for 100 and weed out the bad ones check the FWHM in DSS)) and flats and dark flats (say 20+ each of those)
There are recommended DSS settings to use with StarTools this is on this forum in a post somewhere.

FWHM: Full Width Half Maximum value. (in pixel)
This is the average for all the detected stars

There are plenty things to check for to maximise imaging with an altaz mount. Like where you are imaging in the sky can effect field rotation. Don't exclude taking the 6SE off and just using the DSLR with a camera lens to vary maximising what you can get out of what you have. Quite a few DSO are huge.
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