Corona Borealis poor quality

[themos]

Hello, this is the poor result from three light frames and 10 dark frames, piggybacked Canon Powershot, ISO400 , 64 second subs. The RA motor of my EQ1 was not set correctly so I get noticeable trailing, I may have fluffed the polar alignment too. This is the DSS output (full size available from the astrometry link) and I see that the camera dark signal is not fully compensated. I'm also not convinced that ISO400 buys me more than ISO100 (you might find a Melotte111 of mine with the same technique at ISO100). I'm looking into learning the Isis software for eliminating the dark signal. Any comments welcome.

http://live.astrometry.net/status.php?job=alpha-200807-07548688

[Ant]

Thats a nice constellation shot. The glow in the top right is a shame.

But that's fairly easily fixed. In photoshop, duplicate the layer, on the copy do a gaussian blur so the stars disapear. Then subtract and most og the glow should go as well.

Not sure anout the trailing? Alphecca looks nice and round to me!

Ant

[themos]

I don't have Photoshop. :crybaby: There's a tutorial for Iris available here that I'm trying to absorb!

The trailing is not too bad on this one because I used only the best 3 subs out of 40. That'll learn me to be more careful next time!

[themos]

forgot to say: thanks!

[jgs001]

Themos, looks pretty good. You should be able to do what Ant suggested with the GIMP, it's free.

[themos]

I recall I reached about magnitude 11.6 on the ISO100 Melotte111 set of frames. There's no indication that ISO400 in this set produces any gain on that but I'd have to make the comparison on the same night, same target, I guess. This is a just a compact Canon, zoomed at 6x, piggybacked on the cheapest, motorised equatorial mount.

[themos]

John, yes, there is the GIMP and there is a Windows version. Isn't it strictly 8-bit though? Anyway, that's what cloudy nights are for: learning image processing!

[jgs001]

I think you might be right on the current version, but the next release, there's some info posted up now, looks like it's going to handle 16bit.

[Sam]

Yes Gimp 2.6 is supposed to be 16bit and have a whole different underlying structure - the current gimp is still pretty good though.