Bubble Nebula LRGB

[Jannis]

Not much to show off, but it's still a progress, and also my first LRGB captured with the Polemaster and the Explorer 200 PDS.

It was very strong wind and clouds coming and going, causing around ~50% of the subs to be trashed. The remaining ~50% was rather washed out by the 99.5% illuminated moon, but gave it a go anyway...

I was struggling with the LRGB having different focus points though, and the stars in red and L were significantly larger even with optimal focus. I thought this was an issue only on refractors, but i guess this is caused by the MPCC. I tried to reduce the stars so they would be a better match, but didn't have much luck getting sharp stars though.

L 192x 30s
R 99x 30s
G 91x 30s
B 130x 30s

Flats added, but while they worked for L, they did not work so well for the color channels.

 

Also adding my previous attempt at this target, although I've only tried with narrowband before. Same frame and crop for direct comparison.

From December 28 2016:

And first attempt from February 1 2016:

[Guest]

That first image is pretty cool - such short exposures I thought you were using an ASI1600MM :-)

I've been lucky with focus on the ZWO LRGB filters as they appear to be pretty much parafocal 

Excellent results, I've only imaged this object once in a quite wide field - so your example is making me want to get a newtonian again :-)

David

[Jannis]

Thanks! The first pic is the one i took yesterday, the other two are only my previous attempts.

Exposures are indeed short. Full moon gave some limitations, but the main limit was the insane wind. I tried longer exposures but almost all got ruined.

I wish i could afford the ASI1600 / QHY163, but this years money is used up and i'll have to focus on smaller brighter targets for now. Like the ASI1600, the Polemaster have both low read noise and high QE, but it's limited to 120 sec exposure though.

The Baader filters i use are parafocal, but I think i just realized my mistake. I completely forgot about the backfocus distance... I will try to measure and adjust this and see if the problem goes away.

[Guest]

pretty cool images..