Orpington Astronomical Society

Astronomy => Astrophotography => Topic started by: JohnH on May 09, 2025, 13:04:44

Title: M94
Post by: JohnH on May 09, 2025, 13:04:44
M94 is known as The Cat's Eye Galaxy or The Crocodile's Eye Galaxy.

(https://i.imgur.com/FQI5gvl.png)

FOV - 28' x 28' (Cropped from approximately 160' x 100')

Total imaging time 13 hours 27 minutes.

Processing: Pixinsight, GraXpert and Affinity Photo 2

This time I varied my processing slightly, Luminance is *just* Dual Band (Ha Oiii) - 5 hours 20 minutes.
Chrominance:
R - 1 hour 28 minutes
G - 1 hour 28.5 minutes
B - 1 hour 30 minutes
Ha - 3 hours 40 minutes

(Any disparity in totals due to rejected subframes)

Telescope - Sharpstar 15028 HNT
Camera - ZWO ASI1600MM Pro (monochrome -cooled to -10C)
Mount - iOptron CEM25P
Assorted ZWO gubbins - Electronic Focus, Filterwheel, Guide camera and telescope and ASIAir Pro.
Location: Bromley (Bortle 7)

I posted this image with an explanation of why I use a Dual Band filter for Luminance and how I use it on Astrobin. The general consensus from experts (Carole dissenting  :D  ) seems to be that I am totally wrong and that I will miss too much detail and too much of the spectrum and that I should use very short UV/IR filter images and remove the gradient from each one before integrating. For the moment I am happy to continue with what I am doing. As far as I am concerned it is a hybrid Broadband/Narrowband image (akin to using a Dual Band filter with an OSC camera) and goes a long way to defeating light pollution.

One thing I could, I suppose, is to create a "pseudo Luminance" from RGB and use that to create the star layer. That could give me better star colour.

I look forward to trying it out on nice big nebulae when the nights begin to get darker.

Regards,

John
 
Title: Re: M94
Post by: Carole on May 09, 2025, 16:54:46
It is certainly experimental but gets you reasonable results of targets otherwise likely imossible with conventional LRGB. 

Carole