ZZ Psc not where it should be!

[Mr Ian David Sharp]

Hi all,

I’ve been doing photometry on ZZ Psc after the recent alert posted by Jeremy.

I took a series of 63 exposures last night and used information and a chart from the AAVSO to perform the photometry with my usual Python/AstroArt workflow.

The problem I have been dealing with is that ZZ Psc does not seem to be located at the position from the AAVSO chart nor from a SIMBAD query. The location should be: RA: 23:28:47.64 Dec: 05:14:54.2

But I have to tell my software it is at these co-ordinates: 23:28:46.94 +05:14:47.77

It’s quite a long way out! I also tried using TychoTracker software and it shows the same issue. See attached image from a screen shot where TychoTracker is showing where the star ‘should’ be but I believe the bright star up and left is ZZ Psc.

When I go ahead and do the photometry I get V mag values that are very close to the recent values that are in the AAVSO database. See second attached image.

Anyone else have this issues? I’ve come across small discrepancies before, but nothing like this.

Cheers
Ian.

Attachments:

1. 

   ZZ-Psc-issue.png
   

2. 

   20250730_ZZ-Psc_IRB_PixelSkies-C11_IDS_plot_points.png
   

[Andy Wilson]

Hi Ian,
Looking at SIMBAD, I see it has a very high proper motion, approximately 0.5 arcseconds per year. So for an EPOCH of J2000 it should have a very different position.
Over the 25 years since the J2000 coordinates, I work this out at roughly -0.6″ in RA and -6.75″ in Dec. So pretty close to what you are finding.
https://simbad.u-strasbg.fr/simbad/sim-basic?Ident=ZZ+psc&submit=SIMBAD+search
Cheers,
Andy

[Robin Leadbeater]

If you look at the image cutout at SIMBAD
https://simbad.cds.unistra.fr/simbad/sim-basic?Ident=ZZ+PSc&submit=SIMBAD+search
and blink between the DDS and SDSS images you can actually see the position move between the two survey dates. The J2000 position is between the two (Sometimes for high proper motions you even see a double image Red/Blue in the colour DSS images because of the difference in dates)

• This reply was modified 1 day, 9 hours ago by Robin Leadbeater.

[Mr Ian David Sharp]

Wow! Proper motion – who’d have thunk it!?

Thanks for the replies chaps.

Cheers
Ian.

[Andy Wilson]

It is a remarkably high proper motion.
I just noticed the Gaia DR3 parallax puts it at just 17.5pc distant (57 light years). So a celestial next door neighbour! That helps to explain the high proper motion.
A good spot on those images Robin.
Cheers,
Andy

[Robin Leadbeater]

Proper motion confuses the heck out of some of the bots auto reporting transients. They compare the sky with their library image, looking at the differences and once the proper motion moves the star out of the psf of the library image it suddenly triggers a bright transient ! There are quite a few examples in the Transient Name Server

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