Cone Nebula redone

Benjamin (Ben) · #1 20-03-2018, 02:00 AM

Got an extra hour of colour data so have added that to the mix with some happier results. Details are: f7.5 ED80 on a recently belt modded HEQ5, ZWO ASI1600MM-Pro with EFW, Ha (5nm) 130 mins (28x 300s), RGB 49 mins each (49x 60s), captured in Sequence Generator Pro, calibrated and aligned/combined in Nebulosity and processed in StarTools. Really appreciate advice. My colours always tend to be a bit garish but I liked what naturally fell my way with this one (not so much by design).
Astrobin so you can see the noise! https://www.astrobin.com/full/338028/0/

PKay (Peter) · #2 20-03-2018, 08:19 AM

Hi Ben

It's getting a lot better and I think the colours are just fine.

Not for me to give advice, (since I am still a newbie) but I was once told my stars looked like donuts!

I notice a small circle in the stars. Is this a focus issue?

It has been interesting watch this one develop.

Onwards & upwards!

Benjamin (Ben) · #3 20-03-2018, 09:15 AM

Yeah, the donuts I think occur for two main reasons, the first being focus (some colour subs had noticeably better focus than others) and secondly I reckon it comes from combining the Ha layer, which has much smaller stars, with the RGB. Processing artefacts too maybe? That’s my guess anyway :-)

RickS (Rick) · #4 20-03-2018, 10:54 AM

Looks pretty good, Ben. You got all the brighter bits!

xelasnave · #5 20-03-2018, 11:01 AM

Looks rather good to me.
Alex

Benjamin (Ben) · #6 20-03-2018, 01:00 PM

Quote:

Originally Posted by RickS

Looks pretty good, Ben. You got all the brighter bits!

Yes! A few more hours and some dark skies needed for the rest I think :-)

Benjamin (Ben) · #7 20-03-2018, 01:02 PM

Quote:

Originally Posted by xelasnave

Looks rather good to me.
Alex

Thanks Alex :-)

Benjamin (Ben) · #8 20-03-2018, 04:30 PM

Quote:

Originally Posted by PKay

Not for me to give advice, (since I am still a newbie) but I was once told my stars looked like donuts!

I notice a small circle in the stars. Is this a focus issue?

Hi Peter,

I examined some of my processing files and found the donut issue arises only when Ha is combined with RGB when creating a synthetic luminance. The separate, combined RGB and Ha stacks don’t have this issue at all. So most likely about the tightness of the Ha data compared to the looser RGB data. Not sure of a solution other than blurring things out or maybe shrinking stars in the RGB data before making the synthetic luminance? Would love to hear fof possible solutions.

Until then I claim artistic license and suggest the stars be viewed like falling snow flakes on the darkened tree...

Benjamin (Ben) · #9 23-03-2018, 09:14 AM

The donut (or rather the 'halo') issue with stars seems actually not related to the combo of Ha and RGB or focus discrepancies - I can reproduce these halos on single RGB and Ha flies as well as the stacks. Somehow it’s on the raw image and reveals itself when it’s stretched a lot. A mild stretch seems fine but anything more extreme (as AutoDev does in SatrTools) then these halos reveal themselves. Where do they come from? The Skywatcher f7.5 ED80, the Astrodon filters, the ZWO ASI1600MM-Pro, or are these sort of natural artefacts (a glow)? I’m stumped?

Looking at past images with my DSLR they are also there to some degree so wonder if it is just the scope. The intensity of the central white dot is more pronounced in this ASI1600 image and the halos are more defined than in the noisier DSRL shots, so perhaps I'm just seeing these halos more clearly with the lower noise camera and the less noisy tighter Ha data?

N5SE (Sal) · #10 25-03-2018, 06:28 PM

great photo