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AAVSO Batch Processing Outline

The general steps to go from collecting photons to generating a report are:

(Download Users Guide PDF with AAVSO Batch Processing tutorial)

1. Take images in at least one standard filter of the target during an entire session. If the color index of the target and comps are not known, then you should take images in a second standard filter that would form a common color index, e.g., V and R, B and V, etc.

1. If you have not determined the transforms for your system, you must take images in two standard filters of a Landolt (preferably) or Henden field. You would use these images to find the transforms using the methods in PhotoRed.

2. You do NOT have to find the nightly zero points and extinction every night. The AAVSO reduction method will use extinction, but it is a common value for all observations in a given filter and so it, along with the nightly zero point, drop out of the solution.

If you are observing in two or more standard filters, what is important is that you have first order extinction values that form reasonable differences for a given color index. For example, if using V and R, the extinction value should be such that k’v – k’r ~ 0.05. You should determine that this is a good value for your location and system but it will serve in most cases.

2. Assuming that you are intending to report transformed values and that you have used PhotoRed to determine the transforms for the one or more filters in which you observed, you would create a “Batch Reference File” (BRF). This process is required only once for a given target field unless you change the comparisons and/or the standard magnitudes for the comps and check stars and/or the color indices for the comps, check, and target.

In short, the batch reference file provides the RA/Dec and magnitudes for the comps, check, and target. PhotoRed will use AutoAstrometry and the data from the BRF to determine the location of the stars and target on each image and automatically measure them.

3. Once you create the Batch Reference File (BRF), make sure you have loaded the transforms for the system you are using and set the measuring apertures as needed. Those having only one scope/camera will not have to worry about recalling saved transforms. Those who observe using multiple setups must find transforms for each system, save those results, and recall them when measuring images.

4. Run the Batch Differential Photometry form. This form allows you to create a number of “batch definitions”, each with its own batch reference file and list of images. The entire set of batch definitions can be saved in a single file. So, for example, if you regularly observe 20 LPVs every week, you can create a single file that will process the images for all 20 stars and place the data in the data tables. With some planning, you never have to change the entries in the set and can use it for as long as nothing changes.