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Messier 4 Rasa 8" ZWO ASI071 MC Pro

Posted: Sun May 31, 2020 1:35 pm
by Topographic
This is my first effort with my RASA and the ASI 071.
Lights 100x$0s
Darks 100
Flats/DFlats 20
Bortle 3 (rural France)
Gain 95
Temp -5
APT

Ivo, I would be grateful if you could assess the data and processing (feel free to have a go yourself :) )

Anyone else want to play, feel free.


https://www.dropbox.com/sh/xz8y3wmw454s ... KuWLa?dl=0

https://www.astrobin.com/9hs564/

Re: Messier 4 Rasa 8" ZWO ASI071 MC Pro

Posted: Mon Jun 01, 2020 4:13 pm
by Topographic
Tried again.

This time I used the 'Sample' method for colour.

Which do people think is better or prefer?

David
M4 Sample.jpg
M4 Sample.jpg (414 KiB) Viewed 1605 times

Re: Messier 4 Rasa 8" ZWO ASI071 MC Pro

Posted: Tue Jun 02, 2020 4:42 am
by Burly
Sample image for me , very nice image indeed loads of colour, I will have a play with your data when I get a minute .

Re: Messier 4 Rasa 8" ZWO ASI071 MC Pro

Posted: Tue Jun 02, 2020 8:29 am
by Topographic
Burly

Thanks, I lean that way too. If you have a play if you post it I would be grateful if you could include a copy of thelog. It all helps with the learning process

Cheers

David

Re: Messier 4 Rasa 8" ZWO ASI071 MC Pro

Posted: Wed Jun 03, 2020 2:34 am
by admin
For accuracy, I'd say your initial image is more accurate.
M4 is old, meaning it has an overabundance of older stars yellow/red stars (indeed, it is home to many white dwarfs), given that any bright blue giants would have long expired. So, a yellower appearance of the cluster is to be expected.

As is the case with many OSCs., your ASI-071 shows an increased green response in the higher wavelength, which tends to make things more yellow. This is hard/impossible to balance out. The solution is to use a luminance filter (aka IR/UV filter) that cuts this response before it increases again.
I can't quite tell whether you used such a filter here, as the yellowing does not appear to be too bad compared to some other instruments having the same quirk/feature. However, the foreground (random) star field should exhibit a good random distribution of star colors, but is IMHO comparatively lacking in blue stars a little with an over-abundance of orange stars, providing some anecdotal (not conclusive) evidence that there a slight yellow bias. At the end of the day, just increasing the blue bias from the default color balance goes a long way I think, arriving at something in between the two images you posted.
Autosave001(3).jpg
Autosave001(3).jpg (494.89 KiB) Viewed 1551 times
Hope this helps at all!

Re: Messier 4 Rasa 8" ZWO ASI071 MC Pro

Posted: Fri Jun 05, 2020 6:49 pm
by Burly
Do you have the original fits file not the tiff

Re: Messier 4 Rasa 8" ZWO ASI071 MC Pro

Posted: Sun Jun 07, 2020 11:39 am
by alacant
Hi
Lovely shot.
I went low key; I have a thing with orange stars in globular clusters!
Cheers
m4

Re: Messier 4 Rasa 8" ZWO ASI071 MC Pro

Posted: Tue Jul 07, 2020 11:58 am
by Topographic
Burly wrote:Do you have the original fits file not the tiff
Burly

I just noticed this....or I don't remember responding :lol:

the autosave fit is in dropbox

David