Wrong Image Scale in FITs Header

I take a single image with a QHY600M camera. The FIT file size is 119,484KB indicating it is binned 1X1. However in the FIT’s Header it reports the Image Scale as .79, which would be correct if it were binned 2x2.

The FITs Header indicates the Binning is 1x1.

The FITs Header indicates the pixel size is 3.76 by 3.76.

If you examine the FITs header alone it should become clear that there is a problem.

I will attempt to upload the image file to the forum.

If there is something you want me to test or verify please let me know.
Steve Hoffman

Link to Logs

Approx time of issue: 11:25 AM

Useful Info

OS: Microsoft Windows 11 Pro
Ver: 4.2.0.968 (64-bit)
.NET: 4.8
ASCOM: 6.6.1.3673

Well I tried to upload the FIT it won’t work. So here’s an image of the FIT header.

Here’s a link to the image file on google drive - Light_Target 1_30sec_1x1_V_30sec_frame1_2023-04-02_gain_0_offset_5_-10C.fit - Google Drive

steve hoffman

The pixel scale for 1x1 binning can be input in the Camera tab of the control panel. Are you sure that the correct value has been set?

Since you are using PixInsight: it is advisable to also input the value of telescope focal length in the Telescope tab of the control panel. SGP will then write the FITS keyword FOCALLEN to the FITS header. PixInsight’s ImageSolver script will read FITS keywords FOCALLEN and XPIXSZ and use them for computing the pixel scale. However, AFAIK PixInsight will not use the FITS keywords SCALE or PIXSCALE.

Bernd

1 Like

I was attempting to use SGP with Planewave’s PlateSolve2 and Astro-Physics Point Mapper (APPM). 1x1 binning was definitely set in the Camera tab of the ASCOM control panel (SEE ATTACHED). The OTA focal length was NOT set within the Telescope tab of SGP, this has been fixed.
Interestingly if Platesolve was evoked by right clicking on the image in SGP everything worked fine.
But Platesolve would not work if evoked from SGP->APPM. APPM always kept using the incorrect ImageScale as reported in the SGP FITs Header.

Steve

The above should have read…

But Platesolve would not work if evoked from SGP->APPM->Planewave’s PlateSolve2.
APPM always kept using the incorrect ImageScale as reported in the SGP FITs Header, no matter what I tried.

Double check your scale on the camera tab of SGP. We scale this value depending on the binning you’re using and pass it along to the solver. A blind solve would have likely corrected this. But guessing that the value entered for scale is incorrect.

image

Jared

I added the focal length to the telescope and it’s working now, thanks!!

Back in business.

Steve