Support for FITS-Tag: ROWORDER


Active member
Oct 3, 2019
Hello Pi-Team,

please consider to add support for the Fits header keyword "ROWORDER" with its possible values

Ensure to make data acquired from different sources reliable stackable in (Weighted) Batchpreprocessing. There you have an option, which is impacting all sub in the jobs, but it is not possible to mix bottom-up or top-down subs without manual preparation of the raw data.

If the fits tag is available in the header use it for orientation given. If not keep the exiting behavior.

I had a lot of issues when trying to calibrate lights with darks and bias until I found out, that PI orientated the calibration files 180 flipped, because they were taken with vendor's native tool for creating the dark library, which used bottom-up but the lights were top-down.

Further information:

Supporting applications:
Many apps listed under the link above, I additionally requested support for this tag in INDIGO (implemented on 18.07.2020, and APT which will be also done. N.I.N.A and MaxImDL, supported also lately the tag.

Thank you!
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Active member
Oct 3, 2019
Hi Juan,

Sorry, I did not know that. I was searching for it in the forum in advance, but have not got a hit. Thanks a lot. Sometimes wishes get fullfilled much quicker than expected.👍

Is there any info how this tag will interface with the "bottom-up" function in batch pre-processing? Thanks in advance.

Juan Conejero

PTeam Member
Sep 2, 2004
Valencia, Spain
Support for the ROWORDER keyword is now fully implemented and tested. It is enabled by default but can be controlled in FITS Format Preferences:


ROWORDER keywords with appropriate values are now always generated by our FITS format support module in newly created FITS files.

There are also new read-only format hints to control this feature: 'use-roworder-keywords' and 'ignore-roworder-keywords'.

Please note that we are making an exception to our customary development rules here. The FITS format has been deprecated in PixInsight, so nobody should expect new features implemented in our FITS module, except as strictly necessary to support vital new elements defined by new versions of the FITS standard. We are making this exception in the hope that it will help fix most practical FITS orientation issues, which is an important interoperability problem.