Add PIERSIDE Keyword To FITS Header

Analysis/reduction software sometimes needs to know, for German Equatorial Mounts, whether images are taken looking to the East or to the West as that will have the effect of potentially inverting the image. The keyword that I need is PIERSIDE as documented by Diffraction Limited (and probably others). Maxim DL writes it to the header. Can you add it into the header in SGP?

On a related note, I see the FLIPPED keyword but it always seems to be false. How does that get set?

Thanks,
Kent

Seconded. Now that Pixinsight WBPP will accommodate groupings, it would be nice to have this written into the header so that WBPP can read it. I know we can modify our filenames with SGP to record side of pier, but this would make that unnecessary.

Kevin

Flipped is if the image is mirrored in Y.

Seems that PI handles this just fine during image registration. Just wondering how adding PIERSIDE would actually make any difference?

Jared

Hi Jared,

Thanks for getting back to me. Pierside is a keyword used by other software, such as Astrometrica, to align images that have gone through meridian flip. From what you say, FLIPPED would mean, essentially, a reversed image, not a rotated meridian flip. Good to know.

Thanks,
Kent

Why not use the angle vs the side of pier? Side of pier is generally pretty irrelevant … what if you don’t have a GEM? Or what if you have a gem and rotate 180 degrees after you flip to maintain the same field of view on the camera? I guess I’m just failing to understand how pierside is really useful for aligning images.

Jared

Hi Jared,

It’s not me. It’s used by Astrometrica, which I use. What I do now is run a sequence through PixInsight to align and flip, so all images are oriented similarly, then run that through Astrometrica to get astrometry on asteroids. Astrometrica is apparently not super-robust when it comes to alignment. This is a quote from Herbert Raab’s help file regarding the use of the pierside keyword:

PIERSIDE: For German Equatorial mounts, this keyword indicates on which side od the pier the telescope was during the exposure. When ‘PIERSIDE’ changes within an image sequence, Astrometrica will automatically flip the images accordingly.

I hope that helps, but it is a moot point for me right now as I’m running Win7 and SGP Version 4 won’t work on it. Some day I may get Win10 when your new features make it so I can’t stand it.

Kent

Some clarification of my request: WBPP2 in PixInsight has added a “grouping” capability. If, like me, you need separate flats for each side of the pier, WBPP will read the pierside keyword and apply the correct flats to the correct lights. From Adam Block’s videos on this, it sounds like some capture software (Adam uses ACP) already writes pierside into the FITS headers, so it would be helpful if SGP could add this capability. Thanks.

Kevin