Ngc 253

PKay (Peter) · #1 24-10-2017, 03:57 PM

A difficult target for my 3.5" refractor, but we have to try these things.

Last night. 3 hours of 30 sec subs.
First time for me to image across the meridian (YAY!!)

Everything just worked (aside from a rogue cloud).

Image is cropped bigtime.

I am happy with the result and advice is always welcome :-)

Mickoid (Michael) · #2 24-10-2017, 05:19 PM

Peter, that's a fine result with a 3.5" scope. Lovely detail coming through, you should be pleased with that. What is the make of the scope? I tried this a few weeks back with 30 X 1 min subs using a 4" refractor and a DSLR and got the picture below. Where has all your colour gone? Were you using a mono CCD?

PKay (Peter) · #3 24-10-2017, 07:06 PM

"Where has the colour gone"

No Idea.

Maybe over exposed??

I need help!!

Scope: Orion Eon
Camera: (ZWOAsi1600MC-C)

ChrisV (Chris) · #4 25-10-2017, 12:46 AM

I reckon you have it all there in your image, mine looked like yours until I found a way to help colour on HarrysAstroShed.

Near the end of processing I boost the target colour as follows - mask the background, then boost the target colour by using CurvesTransform on S (saturation) rather than the default RGB/K. It was a revelation to me! If you still need it, you can then use ColourSaturation to selectively enhance colour components - but I didn't use this on my NGC253.

Now I will get back to reading 'Inside Pixinsight', a jolly good read ...

PKay (Peter) · #5 25-10-2017, 09:18 AM

The plot thickens.
I did some testing this morning and found 2 problems.

Somehow the gain setting had changed in my Sharpcap profile.
It was set at 400 (should have been 200).
That led to a huge increase in noise.
I took some darks at both settings and at gain 400, the image is total crap.

Now this is weird:
I put a red filter on the scope and took a few images.
To see the image correctly (red) in the sharpcap preview, I use the GRBG debayer setting.

I have previously assumed that this same code is used in PI for the debayer process.

Guess what...it's different.
I had to use GRGB code to get a red image.

Someone has got it wrong (either PI or Sharpcap)

So that explains my lack of colour.