NGC 4631 Whale/Herring Galaxy

[jnelson]

Still tweaking the settings on the ASI533MC but thought I’d post a 2nd attempt at NGC4631, the Whale or Herring galaxy (I prefer herring), and it’s companion elliptical galaxy NGC 4627. Interesting target with central starburst region of active star formation per Wikipedia. Finally had a break in the relentless clouds last evening and grabbed 75 x 60s subs, 10 darks with the C8 at f/6.3, gain 150 (unity 100), offset 45, and stacked 20 frames. Hoped for better results as guiding was good but think I need to massage my collimation a bit to improve the focus and ideally get down to f/4 to get a better pixel match. Geez always something! Tried using Photopea along with GIMP which does have some nice features including a rather simple gradient tool (aka gradient reduction tool for dummies so a perfect match for me).

[Graeme1858]

Nice whale. It's an interesting shape, a bit different from the usual galaxy shape.

Your bloated stars look like a stacking artefact. Did you use DSS?

Regards

Graeme

[MariusD69]

Very nice! Well done!

[messier 111]

nice , thx

[jnelson]

Thanks. Yes I live stacked 75 subs and stacked 20 in DSS. I believe the other frames didn’t stack because of too few stars. I suppose the star bloat could be due to stacking artifact but also possibly due to over sampling since the image scale was 0.61 arcsec/pixel using Meade 0.63 reducer which I confirmed running it thru Astrometry. Just got some more spacers and was thinking about increasing the back focus to get to f/5 which would get me close to 1 arcsec/pixel. Worried a bit about vignetting but guess I could take care of that with flats. Also may try a UV/IR filter and see if that helps. Any other thoughts?