SW 130PDS First Light - What Went Wrong?

[StevieO]

Hi all,

I gave my new SW130PDS first light last night. Seeing was good but not great. I collimated to the best of my ability (this is my first newt) and got 16 acceptable subs of the Western Veil at 200sec together with darks, flats and bias, using my unmodded Canon 700D. After stacking the resulting file had lost all detail from the right half of the image.

Here are basic stretches of the stacked image and one of the subs, which looks normal to me.

I also got some subs of the North American Nebula which also looked fine but the same thing happened after stacking.

I'd be really grateful for some advice on what might cause this effect in the stacked image.

Regards

StevieO

[Uranium235]

What software did you stack with? Your starfield looks good (very good actually), so youve probably slipped up somewhere in stacking.

Try a basic stack in DSS (average stacking, no calibration, no cosmetic hot pixel processing), and see what happens.

[Alien 13]

As above, also make sure your sofware is the correct vesion for your camera Canon RAW files are strange beasts

Alan

[StevieO]

What software did you stack with? Your starfield looks good (very good actually), so youve probably slipped up somewhere in stacking.

Try a basic stack in DSS (average stacking, no calibration, no cosmetic hot pixel processing), and see what happens.

Hi,

I stacked in DSS using default settings.

Since posting the images I've tried stacking again without flats and the result is below - much better. I don't know why the flats would have that effect, I used my usual method of placing my ipad, which has a white screen app, over the OTA aperture and setting the camera to AV. I'm posting one of the flats too in case that's useful. 

Regards

StevieO

[Uranium235]

Ahhh... looks a lot better now!

Its difficult to tell whether your flats are suitable becuase there doesnt seem to be any evidence of vignetting (there should be some). For my 130, I take flats using a large flatscreen monitor about 9-12 inches away from the telescope in a very dark room (cellar), the light is also diffused with a sheet of A3 paper. Reason for backing off the light source is that it stops stray light from bypassing the primary/secondary and just going straight up the drawtube.

Keep poking about with your calibration frames, and you will find the source of your troubles eventually.

[StevieO]

Will do, thanks for your input. The ipad flats solution has worked ok for me up to now, but obviously needs to be rethought.

I've now posted the results of last night's efforts in the 'Imaging with the 130PDS' thread in Getting Started with Imaging.

Cheers

StevieO