M83 with DSLR

[Cyberman]

Hello, here is my attempt at M83
EQ6R, quattro 250, stock canon 600D, DSS, Startools
Lights 437x1min
D, F, DF, B 40 each
Thanks for looking and comments/tips welcome.
Cheers, Rob

[Mickoid]

That's a pretty good image Rob, you've captured nice detail and colour. Just watch your black clipping in post processing, with over 7hrs of data on this object, I would have expected it to reveal the halo around this galaxy that's seen on many deep shots of M83. You do, however, have a strange halo that extends out in the background around the galaxy, not sure if this was done by work to enhance the galaxy or maybe your Flats didn't calibrate correctly. These are minor issues and don't take away from it being a really fine shot taken with a DSLR. Nice job!

[oska]

Nice one Rob, the colour is great. Well done.

[xelasnave]

You must be very happy with such a fine image..well done.
alex

[gb44]

Yes, very nice. Did you use a coma corrector? OAG? Scope is impressive.
Have a look at SIRIL as the background extraction is good.

GlennB

[Cyberman]

Thanks John, Michael, Alex and Glenn.
Michael , that background halo is present in my DSS stacked image. Not sure where it comes from ? optical train ? coma corrector not in correct position?
If anyone knows what causes this , please let me know. please see attached uncropped image that shows the halo better (also processed a bit differently).
There was also a fair bit of light gradient.
Tried to minimize the background halo but this reduced the star glow about the galaxy.
Glenn , I use the skywatcher quattro F4 coma corrector. I don't have an OAG but use a converted finder-guider with asi 120mm-s quide scope.
Thanks for the comments and tips, Rob

[xelasnave]

Maybe a hint of dew? I say that only because I have traced so many "issues" from time to time to dew...and yes dew heaters etc but somehow a big "surge" of moisture gets past stuff sometimes to leave a hint but goes away leaving a mystery...Anyways I would not be too worried as you may find next session there is no issue...take time to realise that you produced a great image ...seriously very well done.
Alex

[Startrek]

Looks to me like typical Vignetting caused by your image train as most coma correctors introduces varying degrees of Vignetting into your image train. My TS Optics GPU does with my 10” and 8” f5 Newts. The Skywatcher f4 coma corrector is based on similar design principles as the TS GPU , just not as many elements so I’m confident that’s your issue
Correctly Calibrated Flats should eliminate it.
I use Huion A2 and A3 dimmable led tracing panels , taped some black cardboard over the panel and cut out a circle 5mm wider than the diameter of my Newt so the light covers the whole OTA. I take my Flats at night after each session. Slew the scope so OTA is pointing up to the sky ( obviously not tracking ) Grab a white T shirt stretch it over the end of the Newt using a big elastic band. Sit the led panel on top of the Newt, run my Flats Aid on APT and adjust illumination until I hit my target and ADU values. I take 40 flats and 60 Bias frames, my 2600 camera doesn’t need darks as it’s dark current is almost zero. My flats calibrate out fine with Bias frames, nice flat field , no vignetting and no dust donuts. Each camera and scope requires different calibration requirements.
It does take time to nail it !!

Cheers
Martin

[xelasnave]

Martin my dew comment was driven by my recent failure to take what was to be my first attempt at decent flats...when I inspected my results there was a huge blob in the middle which changed size during the batch...it dawned on me that maybe I needed to turn on the cameras heater...sure enough it was condensation...if there is any virtue in learning by your mistakes I should get there.

AND Rob what Martin says is on the money. I never bothered with flat frames, I had met to and even bought a flat panel that Martin recommended ages ago...just could not fit it in the work flow...however in my very first successful attempt it seemed to make my colour problems much much less and for the first time I was not cropping half my image....

Alex

[Startrek]

If I didn’t use calibration frames ( Flats ) I would be cropping 40% of my images that’s how bad Vignetting affects my image train with my new rigs ( mainly due to the new TS GPU coma corrector)
When I used my old Baader Mk3 coma corrector during my DSLR days some years ago , Vignetting wasn’t too bad and I only needed to crop 10% due to Vignetting and some coma affected stars. I never used to take Flats with the DSLR , cropping was my answer and also the Baader Mk3 never completely eliminated coma to the edges. However , the new TS GPU coma corrector eliminates coma all the way to the edges, provides tight halo free stars , but unfortunately introduced huge Vignetting.Sometimes you can’t have the best of both worlds.
Flats are my friend in Astrophotography and I wouldn’t swap my TS GPU coma corrector for anything, it’s tremendous.
The Huion dimmable led panel is not the perfect solution for taking Flats , there are many excellent Astro Flats panels and Flats boxes on the market but my set up works for me and has done for the past 3 years or so

Alex, in the Ascom or ZWO camera driver , make sure you switch the dew heater “On” for both your 2600 cameras regardless of seasons, I queried this a few years ago on the ZWO forum and the overwhelming response was “Yes” leave it “On” all year.
Cheers
M

[Cyberman]

Thanks Alex and Martin for your suggestions
Alex it could be dew but I think it looks like the optical train/ coma corrector. as per Martin.
I use flats. I use a tracing pad and 1 layer of thin white cardboard and 2 layers of Tshirt . 0.5sec exposure gets 1/3 across the histogram but I don't have access to ADU. This gets rid of my dust dougnuts but not this vignetting. I have tried the vignetting tab in the wipe function of startools and it looked different but not better.
I also do dark flats and biases. maybe I don't need the dark flats.
I will also try Siril background extraction as suggested by Glenn. I wonder if I can use this with Startools.
Cheers, Rob.

[Startrek]

Startools is a different animal from most post processing software , it actively tracks your signal and noise during processing and keeps a history of before and after activities to mathematically provide the best outcome for each module / tool ( Active tracking signal processing)
If you interrupt the processing at any stage with another softwares traditional processing techniques , Startools has no record of what your did or tried to achieve. This is counter intuitive and not recommended
However, in saying that you can use another software processing tool after Startools is completed ( after final noise reduction and saved ) to re process an image. Some folk use PI or Photoshop to tweak colour after completion of Startools as they find Startools difficult to use the Colour module. ( personally I don’t have an issue with ST colour module )

Cheers
Martin