ASTRO: M31

Another "victim" of my newfound large field of view with the QHY8 camera was
M31. Previously I have only done some rather unsuccessful mosaics of M31
(and one or two DSLR shots).
I did not have the Skywatcher reducer/flattener at that time (August), so I
used the William Type II 0.8 reducer. I used it at the same spacing on the
ED80 as I had done on the ED120, but the ED80 apparently has less field
curvature, so the reducer was "overcorrecting" the image, which leads to
stars that look like image rotation (which definately was not the cause for
the prolonged stars). There were some nasty gradients (especially in the
green channel), which forced me to use two different kinds of artificial
flatfields in addition to the "real" flat.
Conditions were good by city standards, SQM-L reading near zenith was 18.9
in the first of two nights (a bit less next night).

Taken from the middle of Berlin with a Skywatcher ED80, William 0.8 reducer,
UV/IR-block filter on a G11 mount, QHY8 camera, 62x5 minutes.
http://ccd-astronomy.de/temp3/M31-62x5newsmallgut.jpg

Stefan

Stefan Lilge wrote:
Another "victim" of my newfound large field of view with the QHY8 camera was
M31. Previously I have only done some rather unsuccessful mosaics of M31
(and one or two DSLR shots).
I did not have the Skywatcher reducer/flattener at that time (August), so I
used the William Type II 0.8 reducer. I used it at the same spacing on the
ED80 as I had done on the ED120, but the ED80 apparently has less field
curvature, so the reducer was "overcorrecting" the image, which leads to
stars that look like image rotation (which definately was not the cause for
the prolonged stars). There were some nasty gradients (especially in the
green channel), which forced me to use two different kinds of artificial
flatfields in addition to the "real" flat.
Conditions were good by city standards, SQM-L reading near zenith was 18.9
in the first of two nights (a bit less next night).

Taken from the middle of Berlin with a Skywatcher ED80, William 0.8 reducer,
UV/IR-block filter on a G11 mount, QHY8 camera, 62x5 minutes.
http://ccd-astronomy.de/temp3/M31-62x5newsmallgut.jpg

Stefan

That came out well for all the light pollution you deal with. Wider the
field the worse the gradient problem. I keep seeing shots of this
galaxy with the colors apparently forced to golden and blue yet I see it
mostly as you got. Little real color except around OB associations that
do look blue.

Bet you didn't realize you picked up Arp 168. If you thought Arp 29 was
pretty normal to make his catalog M32 would seem the same to me yet it
is included under diffuse counter tails. I can't say I even see one for
sure.

I tried to image it this fall but weather was so bad I only got bits and
pieces. No where near the time I wanted. Not sure if it is processable
or not. Haven't tried as I'm still back in June for my processing.

Rick


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