The Cocoon Nebula (C19) LRGB

[JohnH]

I am continuing my meander around the Caldwell Catalogue with C19.

This is an old fashioned LRGB image captured over two nights. Total capture time 2 hrs 38 mins with my Sharpstar 15028 HNT. Unfortunately, I think my neighbour's security light must have been going on and off leaving some strange colour data which I have done my best to remove.



I am hoping to get capture some Ha to enhance both the L and RGB.

Regards,

John

[Carole]

Looking good John.

Carole

[JohnH]

http://gallery.orpington-astronomy.org.uk/displayimage-2810-_Cocoon_Nebula_.html

I have uploaded a cropped version of this image to the gallery. Rather surprisingly it is not too bad. However, the background looks as though it is clipped 

John

[Carole]

Oooh, pretty, but those stars are still problematic. 
Presume it is still to do with the Collimation you have had a hard time with. 

Some-one I knew (and could probably get in touch with again, though he hasn;t posted for about 9 months by the look of things), he had a very neat gadget for collimating, It wasn;t a laser collimator and it wasn't a cheshire.  Would you like me to find out what it was?  I saw him use it once.

[JohnH]

My head hurts!

I was looking at some of the sub-frames with the FWHMEccentricity script in PI. I took the L frames on the 4th and the RGB frames (in that order) on the 5th.

The L frame I looked at had Mean FWHM 3.444px, Eccentricity .855
The R frame had Mean FWHM 2.189px, Eccentricity .56
The G frame had Mean FWHM 2.457px, Eccentricity .52
The B frame had Mean FWHM 2.75px, Eccentricity .61

The changing factors are filters/frequency of the light passed and observing conditions (eg humidity, temperature, transparency and seeing).

Collimation was not changed, guide settings were not changed and the telescope was not moved.

Has anyone got a view as to the most significant factors?

Regards,

John