Skip to main content

VPHOT and APASS

Ed Wiley_WEY's picture
Ed Wiley_WEY
Offline
Joined: 2010-08-30

I was wondering if there is any easy way to bring APASS photometry into VPHOT? The variables in question are V718 Tau and V1235 Tau. My FOV is 20x30' and VPHOT only lists one comparison star far enough into the field to use (118). But there seems to be plenty of candidates in APASS withing 0.5 degrees of V718 Tau.

APASS
MZK's picture
MZK
Online
Joined: 2010-07-23

Hi Ed:

APASS may be made active on VPhot sometime after the next release. Geir and Arne will make the decision.

However, Geir had created this functionality many months ago and I know that it worked. The main issue that needs resolution is that too many comps are often present in a field! A way needs to be designed to select fewer comps on the basis of magnitude, color, or other parameter. 

I hope I don't get in trouble for mentioning this!? The current server issue has potentially put a crimp on this plan/schedule?

In the interim, I have used seqplot to identify APASS comps and created my own sequence for a few targets.

Ken

APASS
Ed Wiley_WEY's picture
Ed Wiley_WEY
Offline
Joined: 2010-08-30

Thanks for the reply, Ken. I can see the problem. I think I will try your method and see how it works. One way to extend the system might be to share use defined fields. I don't know enough about sharing to know if such a strategy would work. I can see problems with sharing was well.


Ed

APASS in Aladin
CMJA's picture
CMJA
Offline
Joined: 2010-10-01

 

Hi Ed,

I was wondering about the same thing (just 10 months later) and searched the AAVSO forums to find out. Guess not.

I use Aladin to display APASS stars (see attached). Didn't see alot of mention of Aladin in the forums either. Aladin is available here: http://aladin.u-strasbg.fr/aladin.gml

In Aladin, you can set up your own FOV and display a plethora of astronomic surveys including GCVS, VSX, all the big star (and non-stellar) surveys and, through file import, APASS stars.

Attached is a screenshot of Aladin centered on V0718 Tau with your 20'x30' FOV shown as a white rectangle, VSX stars indicated with red squares, and APASS stars indocated with green diamonds. While not integrated into VPhot, using Aladin this way makes it easier to assign comp and check stars from the APASS survey.

Steps to get this screenshot:

  1. Look up V0718 Tau in Aladin.
  2. Create and load your custom FOV.
  3. Load VSX stars from Virtual Observatory.
  4. Download APASS stars in CSV format.
  5. Open APASS csv file in Aladin.

Aladin has so much capability (documentation is on the web site). You may find others uses for it, so give it a try. If you need some help, just ask.

Michael

APASS in VPhot
MZK's picture
MZK
Online
Joined: 2010-07-23

I emailed Geir a few weeks ago and asked him about setting VPhot up to include APASS comps. With enough users asking (nicely) for this, he may be able to update his previous algorithm (1 year old) and get it working again. It was working for a few days at the beginning of last year. The major issue relates to filtering comps so that so many comps don't appear! That filter is what would take a lot of his programming time to accomplish.

So Geir, note that it is now on more than Ed's and my wishlist!!   ;)

Ken

APASS in VPhot
kge's picture
kge
Offline
Joined: 2010-07-19

Noted!

I'll talk to Arne about this again.

Geir

AAVSO 49 Bay State Rd. Cambridge, MA 02138 aavso@aavso.org 617-354-0484