Trying AP again after over 20 years - first light and first hickups with 130/6.6 APO on CEM70 with ASI294MM - Crescent Nebula from London

[Daniel Karl]

Hey there ... 

So I did it - scrambled together a new kit and am trying myself again in AP.
I ended up with

130mm f/6.6 CF Triplet APO with TS-Optics 0.79 Photoline reducer/flattener
iOptron CEM70
ASI294MM + EFW + ZWO 7nm Ha OIII SII
ASI120MM mini on SW 8x50 finder/guider
ASIAir Pro

and against all odds I had a couple of clear nights on a trip to Wales and a clear night back in London to hit the ground running.
I was really impressed with how intuitive and easy it was to set up the system and get going.
Polar Alignment and guiding worked on the first attempt giving consistently under 0.6rms.

I'm not sure about the scope/field flattener yet - I definitely need to adjust backfocus and potentially have a tilt issue in the system,
but I didn't expect perfect stars on first assembly, so I'll have to see how far I can tweak the scope or if there is a bigger issue.

I also have an Skywatcher 120ED Apo with the SW reducer - plan is to compare the two and keep the one that works better

Definitely need to get an electronic focuser next because I feel even with Bahtinov mask, my focus is a bit of hit and miss. 
My processing 'skills' are also out of date by about 20 years, so there's a lot of room for development
 

First try was NGC6888 - only an hour integration out of Bortle 8 London, so it's noisy and not very deep. I also managed to miss the
focus on H alpha which doesn't help - haha.

Here's the OIII stack - four corners and middle. 
It seems I need to increase the back focus distance, but with the bottom left corner looking less elongated I assume there's also either some tilt in the system or the objective needs collimation?

 

If anyone has any thoughts, that'd be much appreciated

Cheers,

Daniel

 

Edited June 9, 2021 by Daniel Karl

[Tayson]

this region in SHO is awful. try to do HOO picture.

 

[Daniel Karl]

Thanks Tayson,

Just did a quick HOO comp and that's nice, too - although I quite like the palettes that hint to the different gas components.
There's just too many ways to combine HSO data
At the moment I'm really just focussing on getting all the optical issues sorted before I invest a few sleepless nights to end up with
wonky stars ... haha.

The lack of focus in Ha isn't helping unless one likes red halos.

 

[JeremyS]

Lovely shot @Daniel Karl 👍🏻

[AstroAndy]

Both are awesome pix...I'm partial yo the first one, it looks more "star trecky" (whatever that means).

[Daniel Karl]

Thanks @AstroAndy and @JeremyS