Fixing Star color

[strivedi]

Hi,

I am a newbie and still getting used to PI. Attached is my first processed image of M104 (entirely in PI).

I am not sure how to fix the star colors. I see several orange stars, that seem unnatural.

I have gone through Harry's tutorials and the PI video tutorials to apply the various processes (ACDNR, DBE, HDR Multiscale etc.).

Any suggestions would help. Thanks.

Shailesh Trivedi

[Geoff]

Did you use the ColorCalibration module?

[strivedi]

Geoff,

Yes I did.

Shailesh

[dgbarar]

Hi Shailesh,

I have looked at your image and these are some of my observations.  1) It appears that stars in the red channel are not as well focused as the other channels.  The halo around the stars from the red channel (especially the brighter ones) are what is accounting for stars orange appearance. Also, it appears that the blue channel is shifted slightly to left on some of the stars.

What type of optics and camera do you have?

Cheers,

Don Barar

[strivedi]

Don,

I am using Baader 36mm LRGB filters on a ST-8300M on AT8RC scope.

Exposures: 45secx15 RGB, 90secx15 L

I did not do any special skewing of blue or reds. I have used the same setup in the past when processing with Photoshop, Nebulosity, CCDstack and have not had a red shift as this one.

This is however my first image entirely done in PI. I love the PI flow and capabilities, want to buy it after my 45 days.

But this is a quirk that is bothering me.


Shailesh Trivedi

[dgbarar]

Hi Shailesh,

It might be interesting if you determined the FWHM of your individual composite channels.  Use the Dynamic PSF to determine FWHM.  Maybe at the time you shot the reds, the seeing was different.  Or, maybe there was issue of focusing when capturing the red channel.

It would terrific if other on the Pixinsight forum can provide their insight.

Cheers,

Don

[Zocky]

Did you apply star mask, or any other mask when processing?
If so, maybe your mask wasn`t OK.

[strivedi]

Don

I will try using the Dynamic PSF (have not used it, sorry I am a newbie) to see if the R, G, Bs have different PSF/FWHMs.

Zocky - no I did not use any star masks when processing.


Shailesh

[Zocky]

Maybe a good way to resolve your problem, would be if you upload somewhere individual stacked RGB FITS.

[strivedi]

Hi Zocky,

I added the individual R, G, B and stacked RGB FITs file at the link below:

http://www.astrobin.com/rawdata/publicdatapools/10/

Let me know if you can access it.

Shailesh Trivedi

[Zocky]

It requires a log in. I don`t have an Astrobin account so I can`t download the files.

[strivedi]

Zocky

An astrobin account is free & takes few minutes to sign up. It will allow you to download the files. I don't know of any other service for large file sharing; if you know of any please let me know. For example Dropbox requires you to download a Dropbox client on your PC which could take longer.

Shailesh Trivedi

[Zocky]

OK, I will sign up.

[Zocky]

Shailesh, here is a quickly processed image, using basic functions.
Stars in your image looks OK to me, and there is no strange halos. So you probably did something wrong in processing steps.
I noticed you have problem with dust on CCD and filters, and you have a big gradient. In the file name you have stated that you where using flat calibration, but it doesn`t look so. Did you use flat calibration, if so did you use flat frames for each filter? Did you use dark calibration?

[Geoff]

Zocky
 I don't know of any other service for large file sharing; if you know of any please let me know.

Shailesh Trivedi

See this link
http://pixinsight.com/forum/index.php?topic=4039.0
Geoff