[Aavso-photometry] Determination and use of BVRI transformationcoefficients with Maxim DL

[Lionel Catalan]

Thanks for the tip about Canopus. I checked their website, and it
seems ideed like an interesting software. One thing that was not clear
is whether one can load charts from the AAVSO website into Canopus.
Also, does one enter the data for comparison/check stars manually, or
does the software read them (somehow) from the chart?

Lionel

On 1/12/08, Greg Crawford <gc at nelsonbay.com> wrote:
> >I am using Excel to do the transformations. I don't think that Maxim
> >can do these transformations. In fact, I don't know any software that
> >can apply colour transformation coefficients. Do they exist for
> >Windows?
>
> Yes, MPO Canopus will work out colour transformation coefficients and first
> order extinction and nightly zero points internally. For example, with colour
> transformation coefficients, one loads one's images and a star chart on which
> the standard stars are marked. The magnitudes of the standard stars are stored
> in the program and supplied to the chart. An "automatch" matches the stars in
> your image to the stars on the chart. You select which stars on your image you
> intend to measure, and measure them for the whole set. Then a single mouse-click
> will give you colour transformation coefficients, along with a plot showing how
> close to the line each star falls and the standard deviation, so you can get an
> idea of the quality of your measurements. The first order extinction routine is
> similar, but you require image sets from high and low altitude. There are also
> routines for calculating the CIs of comparisons where those are not known.
>
> In a field where the comparison values are known, such as a typical AAVSO
> target, the routine is even simpler. Having used the first routine above to
> determine your colour transformation coefficients a few times a year, they are
> stored in the program. You then use another routine to identify the stars in
> your image (comparisons, check and target), and then run them through an
> automated matching a measurement process. In this process, the known comparison
> values are applied by the program. There is a check box to apply your stored
> colour transformation coefficients in the processing. The end result is a table
> of transformed measurements in the new AAVSO format.
>
>
> Greg
>
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