Running Chicken IC2944

[TrevorW]

IC 2944 Nebula
Also known as the Running Chicken Nebula or the λ(Lambda) Centauri Nebula, is an open cluster with an associated emission nebula found in the constellation Centaurus, near the star λ Centauri. It features Bok globules, which are frequently a site of active star formation.
Distance to Earth: 6,523 light years
Magnitude: 4.5
Radius: 70.999 light years
Constellation: Centaurus
Apparent magnitude (V): 4.5
Notable features: open cluster with nebulosity, Bok globules
Scope Orion Eon110ED
Camera QHY 268c
Mount Losmandy G11
1hr 33 min in 3 minute subs no darks
date 21/02/2021 between 8 and 11pm seeing average

[gregbradley]

Overall not bad. The main critique here is about 2 things. The stars look harsh and lack colour. That to me means the stars are slightly overexposed which seems to be a whole lot easier to do with these CMOS sensors.

Secondly the Ha areas did not come out very well. To keep it in perspective 1:33 hours is a very short exposure time even for CMOS.

What settings are you using with your QHY268C? I have a couple of QHY cameras. The QHY600 is basically the same sensor just larger.

Try mode 2 extended full well mode, gain 0 offset 10. That works with preserving the stars because it makes the full well capacity (how many electrons each pixel can carry) much much larger. Its the full well capacity that affects the star colours more than a lot of other things. Too small and too long an exposure especially with high gain will give you white stars with no colour pretty quickly.

To get the most out of Ha objects perhaps one of those L extreme filters is the go.

Greg.

[TrevorW]

the gain setting was 12 offset 27 will try lower gain offset values- thanks

[gregbradley]

Originally Posted by TrevorW

the gain setting was 12 offset 27 will try lower gain offset values- thanks

Its more the mode.

Try gain 0 and offset 10.

Mode 2 is extended full well mode. That means you get really deep wells (to protect star colour and highlights) but still low noise.

That's the one I started using. It seemed to also reduce the horizontal lines these cameras seem to have in the background.

You gain about 50% more full well depth using the above. That is more important in my opinion than the read noise everyone seems to talk about.

One of my CCDs runs at 6 electrons read noise and you are hard pressed to notice much noise in the image. So perhaps an exaggerated importance is being placed on that.

I do see lots of CMOS images with all white stars which is lack of well depth and too high gain errors as well as too long exposure time.

I am finding 300 seconds pretty workable but look for highlights being blown out to show you need shorter exposure times. It could vary with the brightness of the target object. With my 183 I used 600 seconds and a different setting for narrowband than for regular colour imaging (higher gain to reduce the read noise which is more apparent in narrowband imaging, somewhat contrary to what I said above). Read noise is only important with narrowband imaging not colour imaging.

Greg.





Greg.