M45 with Orion ST80

[frostynixon]

Hello everyone,

i bought the Orion awesome autoguider package which also included the Orion ST80 as a guide scope. This refractor has an 80mm aperture and is fairly fast at f5. 

It costs roughly 100,- Euros on its own. My main scope is a 8" F5 Newton telescope and at times i`m wishing for a wider field of view.

I already read that CAs on the ST80 are quite pronounced and also that the field is only flat on a small image circle. 

To find out how bad the abberations really are, i targeted M45. The exposure parameters are 24 x 300s with a Nikon D5300 on Skywatcher EQ6.

To give you an idea about the abberations i first post the image after stacking with DSS:

And then after processing:

The processing involved level adjustment, reducing of the star diameter (Noel Carboni) and local contrast enhancement (Noel Carboni).

Both images clearly show the chromatic aberation and geometric aberations. The chromatic aberations lead to star bloat (especially visible on the bright stars). In general the whole frame is not centro symmetric which could be due to a tilted(?) objective. Also when inspecting closely the bright stars you can see a bowtie like structure. Do you have any idea what causes this?

So what do you guys think? Do you have any tips on how to get the image symmetric?

best regards