M33 (reprocess) + question on PhotometricColorCalibration

[lazjen (Chris)]

Late last year I had a go at M33. Today I did a reprocess of the limited data that I have got right now.

Both times I couldn't get the PI's PhotometricColorCalibration to work. Nothing I seemed to do to tweak the params could get the stars to match properly (I'm sure I had the focal length and pixel size close to correct). So, anyone got any tips? I'd like to make the colour on this closer to "correct" as I can.

Astrobin (details, better pic, etc): https://astrob.in/lwqtpr/B/

[multiweb (Marc)]

I did that one years ago and I have colors pretty close to what you've got.

[lazjen (Chris)]

That's neat - how did you colour calibrate?

[Bart]

Nice!


When using PCC, I find that it is better to use a raw fit file to grab the image info from and apply it to your colour image.



If you are drizzling your files, you need to change the focal length by the factor of your dizzle scale. For example, my native focal length is 930mm so if I 2x drizzle, it becomes 1860mm.


Other than that, I really leave everything else the same.



Hope the helps.

[lazjen (Chris)]

By using a Raw fit file - do you mean for the location/time information?

Yeah, I do the change for the drizzle scale - you can either alter the focal length or the pixel size (one or the other).

[Bart]

Yes, open a raw lum file from your set, and click on it in PI to make it active. Hit the box in PCC to get data from image and then drag the blue trinagle to your colour image to apply after setting pixel scale or focal length. As long as your image cropping is not to heavy and your image centre is close, this should work every time.



I always had trouble with PCC until I started doing this.

[lazjen (Chris)]

I managed to get PCC working for another galaxy I did recently, but this one it's definitely not happy on. I tried what you suggested, but no luck for me (I actually had the location details correct anyway - it didn't change). It's not cropped, so I haven't changed that part. It is drizzled, just like my other galaxy image.

I guess it will just have to remain a mystery for now.

[multiweb (Marc)]

Originally Posted by lazjen

That's neat - how did you colour calibrate?

TBH I don't really remember. It was a while a go. I think I did it in MBJ's goodlook at the time.

[etill (Elliot)]

I find the image solver script easier / more configureable, you can set the pixel scale directly if you have it. It usually sucessfully solves even when PCC doesn't, then PCC will use that solution when you hit aquire from image.

[lazjen (Chris)]

Originally Posted by multiweb

TBH I don't really remember. It was a while a go. I think I did it in MBJ's goodlook at the time.

Ok, no worries.

I find the image solver script easier / more configureable, you can set the pixel scale directly if you have it. It usually sucessfully solves even when PCC doesn't, then PCC will use that solution when you hit aquire from image.

I'll give this a try and see if it can work for me.