AAVSO Batch Processing
The above screen shot was created in Canopus after analyzing images
in PhotoRed using the new AAVSO batch processing and reduction methods. The two sessions
matched perfectly and did not require any zero-point changes.
"I am VERY impressed! This AAVSO routine is just the ticket
for fast reduction of the eclipsing binary work and will be a great boon to all variable
observers." E.W., KS
In January 2008, the AAVSO implemented a new reporting format for CCD
observations. PhotoRed has been modified to meet the requirements of the new method and to
better conform to the approach used by most AAVSO observers. However, the new format does
introduce some new ways of looking at old concepts, particularly when talking about
ensemble photometry, so you need to keep an open mind and not assume what has been is what
In the simplest approach, it is not required that you get transforms
or determine nightly extinction values. In this case, the data would be reported as NOT
TRANSFORMED. If, however, you determine or know the color index values of the comps and
targets and have found the basic transforms for your system, then you can include these
corrections in the data and would report the data as TRANSFORMED. With only a little time
and care, reporting transformed values can significantly improve the accuracy of your
work, so you should consider finding the transforms for your system.
The QuickMags routines and
data table formerly used for AAVSO observations are no longer used. At this time, there is
no routine to convert the QuickMags data to the new AAVSO tables and probably wont
be. The data storage requirements to comply with the new AAVSO standards are substantially
different. The old QuickMag tables do not include a significant portion of the required
Users Guide PDF with AAVSO Batch Processing tutorial for a detailed look at the procedures
The full AAVSO format document is available on the AAVSO web site. In
short, here are some highlights and how PhotoRed works within the new guidelines.
photometry is allowed. To do so requires that
there be a check star whose magnitude is presumably known. The definition of a
check star for this purpose differs from the old one for a check star.
Before, and under the new format when not
claiming ENSEMBLE photometry, the check star magnitude was subtracted from the comparison
star magnitude for each observation. The trend of those values should have been a straight
line, indicating that neither star was variable.
The definition of a check star when doing
ensemble photometry is that it is second target but of known and constant
magnitude. It is treated like the target in that the one or more comparison stars are used
to find a reduced magnitude for the check star for each observation. This reduced
magnitude is reported along with the reduced magnitude of the target.
In a perfect world, the values for the
check star would be identical for each observation and would exactly match the true
magnitude of the star. Since this will not likely be true, the difference between the
reduced magnitude for the check star and its accepted (catalog magnitude) can be computed
and that difference applied to the targets reduced magnitude to get its
PhotoRed always uses
ENSEMBLE photometry, even if using one comparison and one check star. This is
not a user-settable option. Therefore, you must always have at least one comp, one and
only one check star, and one and only one target in each Batch Reference File (see below).
The AAVSO format is a character-delimited file, i.e., each
line in the simple text file is an observation with the fields being separated
by one of three characters. PhotoRed always uses the comma as the delimiter. This
is not a user-settable option.
The application of transforms is allowed. This is a
user-settable option available at the time you measure the images.
- The format allows
for DIFFERENTIAL (offsets from the comp magnitude) or ABSOLUTE (reduced to
"true" magnitude). The AAVSO strongly encourages ABSOLUTE. PhotoRed forces that
method. This is not a user-settable option.