Author Topic: Image Calibration Problem  (Read 591 times)

Offline Hank

  • Newcomer
  • Posts: 15
    • View Profile
Image Calibration Problem
« on: 2018 October 06 13:27:15 »
I finally have some images to work on and I'm working my way through a tutorial on using Pixinsight for the first time. Everything seemed to be going o.k. with Master Superbias, Master Dark, and Master Flat. When it came to do Image Calibration on my Lights, I got the Error message: Incompatible image geometry - No image could be calibrated.

I need help in correcting this problem. Is the error in the actual taking of the images or have I done something incorrectly in Pixinsight?

Any help would be appreciated.

Hank

Offline astroedo

  • PixInsight Addict
  • ***
  • Posts: 156
  • Io ne ho viste... cose che voi umani...
    • View Profile
    • L'arciere celeste
Re: Image Calibration Problem
« Reply #1 on: 2018 October 06 13:55:15 »
It happens when the image sizes are different.

In my case happaned only one time with a Canon Camera:
In that case the problem came because I took the light and the flat frames using Maxim DL (saving in FIT) and the dark frames (Light dark and flat dark) directly in camera (Format CR2).

The problem was the same and I haven't found a solution yet.

Is your problem similar?

Offline Hank

  • Newcomer
  • Posts: 15
    • View Profile
Re: Image Calibration Problem
« Reply #2 on: 2018 October 06 14:13:07 »
I took my lights, darks and bias frames all on the same night. The lights and darks were done at the same settings and the only change with the bias frames was to use a very short shutter speed. As for the flats, they were taken at a different time and it is possible that the settings were different.

I'm wondering if I didn't have the image scale set properly when I took the lights darks and bias frames. Perhaps someone can tell me if that could be the problem. The camera is a SBIG 8300C on a Celestron STC 11" with a 6.3 FR.

Offline RickS

  • PTeam Member
  • PixInsight Jedi
  • *****
  • Posts: 1295
    • View Profile
Re: Image Calibration Problem
« Reply #3 on: 2018 October 06 14:20:54 »
It's not related to image scale.  This error usually means that the images are a different size (width and/or height) or have a different number of planes (monochrome vs RGB colour.)  Open your master calibration frames and a light in PixInsight and check they're all matching...

Offline Hank

  • Newcomer
  • Posts: 15
    • View Profile
Re: Image Calibration Problem
« Reply #4 on: 2018 October 06 14:41:34 »
Thanks, Rick but I'm new to this so how do I check on the image size.

The header for the Light gives the object then 1x1, then the exposure etc.

The header on the Master Dark is Gray 1:2 Master Dark. There was also a thumbnail.  Is it the difference in the 1x1 and the 1:2 that's causing the problem. If so how do I fix it?

Hank

Offline RickS

  • PTeam Member
  • PixInsight Jedi
  • *****
  • Posts: 1295
    • View Profile
Re: Image Calibration Problem
« Reply #5 on: 2018 October 06 15:48:24 »
Hi Hank,

The details of the currently selected image are normally displayed in the bar at the bottom of the screen.  See the attached screen grab. The "w' number is the width of the image in pixels. "h" is height. "n" is the number of planes.  These will all need to match between your calibration files and lights.

Cheers,
Rick.

Offline Hank

  • Newcomer
  • Posts: 15
    • View Profile
Re: Image Calibration Problem
« Reply #6 on: 2018 October 07 06:45:42 »
Thanks, Rick.

You were right, the Masters and the Lights don't match in size. The Masters are all 1676x1266 whereas the Lights are all 3352x2532. That makes the Lights twice as big as my Masters.

1. How could this happen? Except for the Flats, they were all taken by the same camera on the same night?

2. Is there any way that I can reduce the size of the Lights so that they will match?

3. Most importantly, how can I avoid doing this again?

I really appreciate your help on this. I'm finding astrophotography both challenging and enjoyable.

Hank