Cygnus Supernova Remnant

[RobertM]

Again from Salcombe, quite amazing camera this !  Not much effort went into processing so there is a bit of a green background cast and too much NR. 3 x 30s unguided this time.  Unfortunately I had to crop quite a bit because one of the frames was way out.



Full size:
https://farm9.staticflickr.com/8759/18210620101_3e674b7e4c_o.jpg

[JohnP]

tad bright & like you say a bit heavy on the NR but for 3 subs truly amazing.... guess your liking the new camera?  John

[RobertM]

Thanks and yes it's an interesting camera, posing it's own unique problems.

[julian]

Very nice Robert

[Fay]

very nice Robert, looking forward to seeing  a full on image, all bells, lights  and whistles

[MarkS]

Was that on the RH scope?

It's a very impressive result for 3x30sec 

A lot of upcoming fun this Autumn - weather permitting!

Mark

[RobertM]

Fay, that might be a few months of considering the short nights.

Mark, yes on the RH.  I'll be posting some more with various subs when time allows.  Calibration has been deferred till I work out how to do it with this camera - its defeating PixInsight/me at the moment.

[MarkS]

I regularly bring this up but the initial big stretch of luminance must be done in a manner that preserves the RGB balance of each pixel.   The usual Photoshop "curves" method pushes the brighter parts of the images towards being white and therefore desaturates their colour i.e. actually alters the ratio of RGB in those pixels. IRIS can do this correctly (Hyperbolic Arcsine), so can Startools (Psychovisual colour constancy) but there is no standard way of doing it in PixInsight (though a hyperbolic arcsine function can be written).  In Photoshop it is impossible but can be partially compensated for by performing iterative stretching combined with iterative saturation increases.

This issue with colour is one reason why the Tony Hallas method of processing is becoming quite popular (certainly in the US).  The only good thing about the method (in my opinion) is that the initial stretch is done inside Adobe Camera Raw which also preserves colour constancy - it must do so, otherwise conventional photographers would be up in arms!  This provides a simple way to get fairly accurate colour rendition and is why people love the approach. But there are things about ACR that you don't want done to your images.  The Hallas method also cannot allow for flats and darks which is its major failing.

Do you remember this test image of mine?
http://www.markshelley.co.uk/webdisk/star_colour_test_image.tif   (right click and do "Save As" to download a copy)

It should come out looking like this after proper calibration:


Ivo Jager (author of Startools) did a test with my image using Startools which I reckon gives a slightly better result than IRIS to the human eye.

Mark

[RobertM]

Thanks Mark, I'll give Startools a go...