APASS2 fields

Affiliation
American Association of Variable Star Observers (AAVSO)
Tue, 12/21/2021 - 22:45

Soon, a follow-on survey to APASS will begin.  The initial product will be BVgri photometry of all of the naked-eye stars.  There is a nice catalog - the Bright Star Catalog - that contains about 9104 targets, and will be the initial target list for the survey.  While most of these stars have good B,V magnitudes, I don't think any have Sloan calibration.

There are several possible telescope systems that will be used.  We could task the Bright Star Monitors, at least those in photometric locations.  We could use the original APASS telescopes after they are upgraded.  There is a prototype system using a 30cm f/4 corrected Newtonian at my place.

Let's assume that the original APASS ASA N8 (200mm f/3.6) systems are used.  With a QHY600, these yield 2.87x1.91 degree FOV with 1.077arcsec pixels.  You could use each star as the center and take 9104 images.  You could tile the entire night sky, taking ~7500 images with minimal overlap.  Or, you could perhaps take fewer images by looking at how many stars fall within a given field of view and perhaps optimize field centers to avoid blank areas.  You probably would want to keep stars to calibrate within, say, 1 degree of the sensor center so as to avoid vignetting and field distortion in the telescope.

So which approach to take?  Perhaps someone would be interested in studying the problem?  The Yale Bright Star Catalog itself can be downloaded from

http://tdc-www.harvard.edu/catalogs/bsc5.html

and that would be a good starting point.  I think the Vizier version uses J2000, which would be more convenient than the original B1950 coordinates.

Arne

Affiliation
American Association of Variable Star Observers (AAVSO)
Happy new year, Arne!Maybe…

Happy new year, Arne!

Maybe a HEALPix-like approach could be taken? Level 6 HEALPix in equatorial system on BSC5 (9110 stars) would give 8006 fields with density higher than 1 star per square degree and with HEALPix surface area of 0.8393 square degrees. The sky is kind of ... sparse. Below is the link for a visualization of those "pixels" in aitoff projection.

https://hermes.to.ee/~tonis/healpix_6_bsc5.png

Best wishes,
Tõnis