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Photometry Transforms Generation Program - status and problem workaround

mgw's picture
mgw
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Joined: 2010-08-01

If you're trying the new Photometry Transforms Generation Program discussed at the AAVSO meeting (PTGP - at http://www.aavso.org/ptgp) a problem has been identified.  To use the program with your data, all input lines must end with a final delimiter - either a comma or semicolon.  For example (compare to Users Guide page 3):

Filter identification line -    Filt,b,v,r,     (note final comma added)

Date of observation line - Julian_Day;2456628.19110;   (note final semicolon added)

Star instrument magnitude measurement line -  112,-7.747,258,-9.436,411,-9.475,415,    (again note final comma added)

An updated version 4.1 of the program will be available soon.  Changes will include converting to standard AAVSO nomenclature for transforms, adding additional information for stars selected for removal/addition on the transform plots, adding the Tr_vi transform, providing an INI output format line which can be directly input to the TA program, and eliminating the need to have a delimiter at the end of each line.

Also, if someone can provide me a Maxim file for M67 or NGC7790, I'll try to add that input format in the 4.1 release.  If not, it will soon follow. Also, the standard deviation error for each transform will be added soon.

Gordon

   

     

 

Photometry Transforms Generation Program
Tonisee's picture
Tonisee
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Joined: 2011-06-23

Gordon, this is an impressive work and a really great news, too!

While it is possible to create transormations "manually" or using spreadsheets or even trying to tame IRAF photcal, definitely it's not neither easy nor convenient. I have used all three ways, and while I am very satsified with final results from IRAF, using many stars per frame ("cluster standards") has been always huge and painful manual work on intermediate text files...

After reading the user manual of PTGP, I have some questions as well:

  • is it planned to add uncertainties for computed coefficients?
  • what about extinction coefficients k' and k'' and also zero points - that would allow to use those solutions even for all-sky work (also for very wide-field photometry?)?
  • would it be possible to change transformation equation without changing big parts of the code, to use e.g. (B-V)^2 terms etc?
  • is PTGP planned to publish as open source?

Just my suggestion about standard areas, Landolt equatorial and +50 declination fields could be included with software as default or example ones. Nowadays they contain both bright and faint stars and OK color range as well. Maybe Stetson secondary cluster standards could be interesting as well?

Best wishes,

Tõnis

Question Response
mgw's picture
mgw
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Joined: 2010-08-01

Tõnis,

Plans for the future of PTGP are still in flux, but here are some initial answers - and follow on questions -

1.  If by uncertanties in the transform coefficients if you mean the standard deviation of the linear curve fit to the data, yes, this will be added shortly. (It will be in the next release - 4.1)  There could be another error measure that took into account the errors in both the submitted machine magnitudes and comp stars.  Not sure how to do that, but if am willing to look at this if that is what is wanted.

2. I had not thought about adding extinction coefficients, but if there is enough interest I will look at this.

3.  It would not be difficutl to modify the program to support changing the transform equation, but I'm not sure how to implement such a request or manage configuration control of the system.  Can you be more speicific about what you wouild like to see?

4. Open source is fine, and George and Gary mentioned this. I'm certainly willing to give away the source code - I just don't know enough about the full implications of opens soure, particularly if it means updates from multiple people need to be brought together into a new release periodically.  I'll be working to sort my way through the implications of full "open source" and provide a specific answer soon.  FYI, the source code is in the downloads in the .py file.

Gordon

Open Source
David Benn's picture
David Benn
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Joined: 2010-07-29

Hi Gordon

VStar is licenced under the GNU Public Licence (well, a "network oriented" variant called Affero GPL). Let me know if you want to chat about licences. It may be worth having a standard approach to licencing AAVSO software. Something for broader discussion I suppose. 

David

work on hold..
mgw's picture
mgw
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Joined: 2010-08-01

David,

My wife passed away a couple of days ago.

I'll get back to you in a couple of weeks.

Gordon

Gordon I'm so sorry to hear
David Benn's picture
David Benn
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Joined: 2010-07-29

Gordon

I'm so sorry to hear that. My sincere condolences.

David

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