AAVSO Transform Campaign

American Association of Variable Star Observers (AAVSO)
Tue, 03/03/2015 - 05:14

Having multi-filter CCD observations transformed into the standard system is important: it makes our data cross-observer comparable and useful to the professional astronomers.

In 2014 we developed the tools to document and make this easier to do. Check out the documentation here.

And now M67, an excellent calibration target, is in the perfect position for evening observations.

What are you waiting for? Now is the time to move to the next level!

And there is help available: volunteers are listed below to help you learn each step of the process.

Goal of the campaign:
- Increase the number of observers who are submitting transformed data to WebObs.
    24 out of 134 observers submitted transformed observations in Jan-Feb 2015 
    Let's see if we can improve this metric!
- Use the tools developed this last year for transformation
   TG:  Transform Generator
   TA:  Transform Applier  version 2.30 or better  
--- Get those M67 images! Its a convenient evening target in the month of March.  Use best practice to get them BDF calibrated.
--- Extract the instrumental mags.
   VPHOT is the most convenient way to do this. It automatically identifies the standard stars in the field and TG is prepared to work with its output directly.
   Ken Menzies is available to help with questions: 
   If you use some other tool for extracting the mags then the issue will be using  the proper labels for the stars. AUID's are always preferred and are available
   with the photometry from VSP
--- Use TG to compute your transform coefficients
   Installation and process details are available here.   
   Gordon Myers is available to help with questions.  
   You can get your coefficients from TG in a format compatible with TA (INI file) when you save your results. 

--- Use TA to apply your transform your data
  - You prepare you WebObs submission as you already do. The only adjustments to that process:
      - Comp and Check stars should be identified by AUID. You may be able to use the  VSP labels, but AUID's are preferred.
      - The ChartID in your observation records needs to be a photometry page, not the picture chart.

  Installation and process details are avaiable at here.      
  - Get the latest version of TA here.           
  George Silvis is available to help with questions.  
  Before you start submitting TA transformed data, you should review the results. TA has a feature built in to help you. If you check "Test TC" the transform process will be applied to your Check Star data. Review the results in the Report tab. If your observations can reliably match the transformed standard magnitude of the Check star, then you can submit your variable star measurements with confidence.

--- Tell us how you're doing by posting comments to this thread. What needs to be changed to this process to make it easier? We'll fix it!






American Association of Variable Star Observers (AAVSO)
M11 Transform Coeffients

Here are my coeffients for M11 using the whole standard of comps (384) For BVI.

14" f/10 SCT and St-1001e Camera. Quite a load for VPHOT to process!

American Association of Variable Star Observers (AAVSO)
Newbie looking for feedback on transforms

As stated, I'm pretty new to photometry (but not to imaging).  I'm getting my feet wet by starting with generating my tranformations from images of NGC7790 from last summer, but the first number I'm getting for the color transform seems a bit high (don't really know if its reasonable):  T_bv = 1.308.  I've tried to follow the CCD manual as best as I can, and watched the CCD school video.  Details:

  • SBIG ST8XME on a C8 at f/10, with Chroma B and V filters
  • Stack of 3 images (averaged) in each filter (SNR(B)=88+/-2 (1sd), SNR(V)=132+/-1.5)
  • 35 stars in NGC7790 (uncrowded apertures), elimated outliers, R^2 for trendline = 0.996
  • Photometry using Muniwin, aperture diameter=11.8 pixels (aperture #7), inner annulus=15, outer=25 (average FWHM ~ 3.5 pixels or 3.3")
  • Transformed using a spreadsheet (for now)

Any feedback is appreciated, thanks.  I have more nights to analyze but don't expect a big difference since the plot looks pretty tight.