Orpington Astronomical Society

Astronomy => Astrophotography => Topic started by: The Thing on Mar 10, 2021, 09:44:04

Title: M106, NC4346, NGC4217 etc. etc.
Post by: The Thing on Mar 10, 2021, 09:44:04

240s x 75 = 4h, Gain 120 (Unity), Offset 4, Temp -5C

Image date, time and location:   2021-03-08, Manche, France
Telescope aperture and focal ratio:   TS1506UNC F4 TS GPU Coma Corrector
Camera and filters used:   ZWO ASI294MC Pro, Svbony 2" UV/IR
Processing applied:   DSS, StarTools

(http://gallery.orpington-astronomy.org.uk/albums/userpics/10050/normal_M106-DSS-4h_G120_O4_T-5_StarTools.jpg) (http://gallery.orpington-astronomy.org.uk/albums/userpics/10050/M106-DSS-4h_G120_O4_T-5_StarTools.jpg)
Title: Re: M106, NC4346, NGC4217 etc. etc.
Post by: Carole on Mar 10, 2021, 12:11:51
That's come out very nicely Duncan.

I found this target unexpectedly difficult due to the faintness of the outer disc of the galaxy and difficult to extract colour from the galaxy. 

Nice star colour.

Carole
Title: Re: M106, NC4346, NGC4217 etc. etc.
Post by: Roberto on Mar 10, 2021, 15:16:51
Duncan

There's a lot of detail in that image.  The colour of the stars is good and well saturated, yet the galaxies look green to me.  Can you colour balance the different channels for the galaxies to make the peaks coincide?  I am not familiar with the software you use but it may allow some other method of achieving this.

Roberto
Title: Re: M106, NC4346, NGC4217 etc. etc.
Post by: The Thing on Mar 10, 2021, 15:23:49
That'll be all that alien plant life...

In StarTools Colour module there are two ways of reducing green, Cap Green which is a bit like SNCR but make green brown or yellow (yep). And reducing the green contribution to overall correction. I was a little conservative with the first and the automatic setting didn't do enough of the second🙁
Title: Re: M106, NC4346, NGC4217 etc. etc.
Post by: NoelC on Mar 10, 2021, 16:26:30
Looks really good Duncan.
The stars really make it.

Noel
Title: Re: M106, NC4346, NGC4217 etc. etc.
Post by: Roberto on Mar 10, 2021, 16:41:24
Duncan

If you can upload/send me the colour FITS master file I may be able to do something in PixInsight to it.

Roberto
Title: Re: M106, NC4346, NGC4217 etc. etc.
Post by: RobertM on Mar 11, 2021, 22:35:01
Very nice Duncan.  The brighter stars have very good colour but I would agree with Roberto that there is something going on with colour in the less bright objects.

Robert
Title: Re: M106, NC4346, NGC4217 etc. etc.
Post by: The Thing on Mar 13, 2021, 09:10:50
I've tweaked the colour after re-calibrating my monitor. I tried Photometric Colour Calibration in PixInsight and it didn't make much difference to M106 so I've manually tweaked in StarTools with 95% Cap Green setting. Hope this is more pleasing to the eye :), there is certainly more detail revealed e.g. star forming areas. Click on it for a big version as usual.

(http://gallery.orpington-astronomy.org.uk/albums/userpics/10050/normal_M106-DSS-4h_G120_O4_T-5_StarTools_de-green.jpg) (http://gallery.orpington-astronomy.org.uk/albums/userpics/10050/M106-DSS-4h_G120_O4_T-5_StarTools_de-green.jpg)

Click here for a Hyperleda annotated version showing all the galaxies and other objects detected by ASTAP (http://gallery.orpington-astronomy.org.uk/albums/userpics/10050/M106-DSS-4h_G120_O4_T-5_StarTools_ASTAP-Anotation.jpg)
Title: Re: M106, NC4346, NGC4217 etc. etc.
Post by: RobertM on Mar 13, 2021, 10:49:20
There’s definitely more colour Duncan but the centre of M106 still has a green cast.

Did you colour calibrate it before stretching ?

Robert
Title: Re: M106, NC4346, NGC4217 etc. etc.
Post by: Carole on Mar 13, 2021, 11:11:31
I don't suppose you have an Ha filter?
The only images I have seen with much colour seems to be in Ha.  I had trouble with getting any colour from this target too.

Carole 
Title: Re: M106, NC4346, NGC4217 etc. etc.
Post by: Roberto on Mar 15, 2021, 13:13:48
Photometric CC will still leave a greenish tint but it will certainly rebalance your star colours correctly.  I tried doing that on the image you posted but since it is already stretched and the background is essentially flat, there was little effect.  Colour balancing has to be done before the image is stretched.  If you send me your master raw, I can have a go at it.

Roberto
Title: Re: M106, NC4346, NGC4217 etc. etc.
Post by: MarkS on Mar 16, 2021, 15:55:59
That's a great result Duncan!  Beautiful galaxies.

PhotometricCC can give results that are sometimes not quite right with small (i.e. undersampled) stars.  It seems to works well with larger stars though.

Mark