Photometric Color Calibration not working

M

MattF

Member
Hello

I purchased PixInsight last week (Version: 1.8.8-4 Ripley for Windows 7) and am trying to edit some of my color-images taken with a Nikon D850 and a 135mm Rokinon lens. Unfortunately the Photometric Color Calibration process fails on all of them. As an example, in one image I have Deneb pretty much in the center. I do this: First I press “Acquire from image” which returns the focal length, pixel size and date/time in UTC. Then I enter the RA and declination of Deneb as found in Stellarium for that day and time. I leave the defaults for everything else and execute the process.

It does try to find matching stars but fails. During the process I get these messages:
* Previous attempt failed - this is try #31
useScaleDifferences=false
* Target image: Limiting to 32000 brightest stars.
Matching stars: done
856 putative star pair matches.
Performing RANSAC: done
* Previous attempt failed - this is try #32
Etc. etc. etc.

and eventually:
*** Error: Unable to find an initial set of putative star pair matches.
*** Error: The image could not be aligned with the reference star field
Please check the following items:
The initial coordinates should be inside the image.
The initial resolution should be within a factor of 2 from the correct value.
Adjust the star detection sensitivity parameter, so that the script can detect most of the stars in the image without mistaking noise for stars.
The catalog should be matched to the image. Choose the appropriate catalog and magnitude filter, so that the number of stars extracted from the catalog can be similar to the number of stars detected in the image.
*** Error: Unable to plate solve the image: Alignment failed
This is usually because the initial parameters are too far from the real metadata of the image.
** Warning: Process finished with errors:
PCC_T_XVH6L66RNT1A.xisf: The image could not be plate solved

I also tried to look up via Internet and entered NGC7000 (and M42, M51 and M101 in previous tries) – all failed. I get these messages.
Reading swap files...
1977.879 MiB/s
<* failed *>
*** Error: File I/O Error: Unable to create file: Win32 error (3): The
: /tmp/simbad.txtsystem cannot find the path specified.
*** Error: File I/O Error: Unable to create file: Win32 error (3): The
: /tmp/simbad.txtsystem cannot find the path specified.

I do need to run this process I believe, I have a hard time to get good colors into my image if I skip it. And so the quality is impacted.
Any feedback appreciated.
thanks
Matt

NB - support@pixinsight.com seems to be totally unresponsive. Is that normal?
 
can you post one of these images you are having trouble with? it's very hard to figure out what's going on without taking a look. the images are large so you'll have to upload them to google drive or similar and then set them to publicly shared and post the link here in this thread.

rob
 
since PCC should be one of the first things you do, the integrated image in still-linear form with no processing at all.

rob
 
I get the following error message with the current PixInsight v1.8.8-7 when I try to load m3.fit:

C:/Users/Bulrich/Downloads/M3/m3.fit
** Warning: Deprecated format: FITS
773 FITS keywords extracted.
Reading FITS image: 32-bit floating point, 3 channel(s), 7104x4728 pixels: 40%
*** Error: PCL Legacy FITS Format Support: FITS file read error: C:/Users/Bulrich/Downloads/M3/m3.fit
CFITSIO error message stack:
01 : Error reading data buffer from file:
02 : C:\Users\Bulrich\Downloads\M3\m3.fit
03 : Error reading elements 1 thru 7104 from image (ffgcld).
*** Error: Unable to read image.
<* failed *>

Can you please save the file in XISF format and upload it?

Bernd
 
Hi Matt,

you used a full frame camera. The corners are heavily shadowed, it doen't look like normal vignetting. So the first step I performed was cropping, with these settings:
left -1360, top -370, right -800, bottom -800

(If you solve the image at first and then crop it, the astrometrical solution is deleted again.)

The image contains the globular cluster M 3 in the constellation Canes Venatici. So when you want to solve the image and don't know the center coordinates, apply 'Search' on the ImageSolver and input an object identifier of an object in the filed of view, in this case M 3 (and not Deneb, NGC 7000, M 42, M 51 or M 101 which are far away).

ImageSolver script successfully solved the cropped image (settings: Search M 3 -> initial coordinates RA: 13 42 11.620, DE: +28 22 38.20, Distortion Correction enabled):

Image Plate Solver script version 5.6.1
===============================================================================
Referentiation matrix (world[ra,dec] = matrix * image[x,y]):
+2.66909816e-06 +2.23369757e-03 -3.97950269e+00
-2.23313867e-03 +2.41570739e-06 +5.51953483e+00
WCS transformation ....... Thin plate spline
Control points ........... 3167
Spline lengths ........... l:1436 b:310 X:295 Y:1459
Projection ............... Gnomonic
Projection origin ........ [2473.572970 1778.620591] px -> [RA: 13 37 24.613 Dec: +28 02 09.76]
Resolution ............... 8.040 arcsec/px
Rotation ................. -90.072 deg
Reference system ......... ICRS
Observation start time ... 2021-05-19 02:18:01 UTC
Observation end time ..... 2021-05-19 03:23:16 UTC
Focal distance ........... 96.46 mm
Pixel size ............... 3.76 um
Field of view ............ 11d 2' 31.3" x 7d 56' 47.4"
Image center ............. RA: 13 37 24.611 Dec: +28 02 09.87 ex: +0.001206 px ey: +0.000276 px
Image bounds:
top-left .............. RA: 13 18 26.470 Dec: +33 26 50.71 ex: -0.002407 px ey: -0.003767 px
top-right ............. RA: 13 20 23.492 Dec: +22 29 28.03 ex: +0.001999 px ey: +0.002208 px
bottom-left ........... RA: 13 56 20.241 Dec: +33 27 40.11 ex: -0.000101 px ey: -0.001934 px
bottom-right .......... RA: 13 54 30.249 Dec: +22 29 38.51 ex: +0.001543 px ey: -0.000941 px

After having solved the cropped image, I applied ABE (function degree 1, subtraction) in order to remove a linear gradient. Then PhotometricCalibration was applied. The Image parameters were aquired from the image. For background Neutralization I created a preview (Left: 2972, Top: 1782, Width: 102, Height: 38), enabled Region of Interest and used the preview. I encountered no errors.

What is the cause of the severe shadowing?
Maybe stopping down the lens would help?

In any case you will have to apply flat field correction (that means: matching dark frames, flat frames and flat-darks will be needed) in order to be able to use a larger field of view.

I annotated your image, see appended JPG. Besides 56 galaxies (NGC and IC catalogs), the comet C2020 T2 (Palomar) is captured, near NGC 5251.


Bernd
 

Attachments

  • m3_cropped_solved_ABE_PCC_Annotated.jpg
    m3_cropped_solved_ABE_PCC_Annotated.jpg
    361.3 KB · Views: 80
thanks a lot for your effort Bernd. I did exactly the same thing on my end I believe

1) crop the image to the dimensions you indicated. M3 was then in the middle, slightly in the lower part.
2) Call ImageSolver, clicked Search and entered M3. It returned the same RA and DEC that you indicated.
3) Click OK in ImageSolver. I get these errors


*** Error: Unable to find an initial set of putative star pair matches.

<* failed *>

*** Error: The image could not be aligned with the reference star field

Please check the following items:

Probably the dark shadows are there because I didn't shoot any flats, knowing that the image would be cropped heavily. I took 80 light frames at 45 secs/ f3.2 / ISO3200. The lens max. aperture is f2, but normally I try not to use the widest aperture possible.

Any tips how to get this working would be much appreciated.
thanks again
Matt
 
You are using an outdated version of PixInsight (1.8.8-4) which came with an outdated version of ImageSolver (5.4.1?, I dont't know for shure). The current version of the ImageSolver script is 5.6.1, but this version is probably usable only in connection with the current PixInsight version (1.8.8-8).

Possibly you will have to use the option 'Distortion Correction'. Note that there are two modes for the 'Target Image': 'Active window' and 'List of files'. Please make sure that the image is the active window and the option 'Active window' is used in ImageSolver.

If this doesn't work, I am sorry that I cannot help you. You would have to update to Windows 10 (this is recommended anyway) and to the current PixInsight version (1.8.8-8).

Bernd
 
yeah Windows 7 is holding me back. So much stuff runs on my current machine, I'm kind of hesitant to upgrade. Thanks a lot for your help anyway.
Matt
 
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