AperturePhotometry script

[Andres.Pozo]

In the last version of PixInsight (1.8RC5) there is available an new script: AperturePhotometry. It has been developed by Vicent Peris (OAUV) and me. It calculates automatically the flux intensity of known stars in an image set and outputs the flux data in CSV tables. In the near future we're going to develop new tools to analyze the photometric tables, as well as new tools for astrophotography based on photometric data.

Although there are several methods for measuring the flux, this script uses one based on what are called apertures: windows of a given size where the flux is integrated. For each star we want to measure, an aperture is centered on the star with dimensions chosen by the user. The flux is obtained by adding the value of each pixel contained in the aperture and subtracting the estimated background level.

More details about the algorithms used and how to use the script can be found in the documentation of the script. The documentation can be read by selecting the script on the Process Explorer or by clicking the help button on the configuration dialog of the script (the button is at the lower left corner).

As an example, this graph is the result of an analysis of the fluxes of QV Cephei (eclipsing binary star) and the surrounding stars. The excellent data is from Ramon Naves:


This other image shows the detected stars:


Another example: this is an analysis of an eclipse of the extrasolar planet WASP-48b. Tha data was taken using the 60cm telescope at Aras de los Olmos Observatory.


These analysis have been done processing the data tables generated by AperturePhotometry using other tools. We hope to be able to do the same (or better  ) using PixInsight in a short time.

[Josh Lake]

This is phenomenal! I'll be sharing this new tool during my talk at NEAIC, and I was wondering about getting some good data to show it off. Would the example data above be available for public analysis?

Also, can you recommend some good targets that show a nice variation over a reasonable period of time? I will try to collect the data myself.

Again, wonderful, I've been hoping for something like this in PI for some time!

[kkretzsch]

Hi,
this is really a very good script. I used it to measure the light curves of several eclipsing binaries and it worked right from the beginning without any problems, thanks for this great work. Below (attachment) you can find my measurement of the minimum of CO LAC.

But getting there was quite a lot of manual work. Im using a DSLR and I had to do several preprocessing steps like:

• conversion to fits format
• channel extraction to extract G & B channel
• frame preprocessing (dark/flat/bias) and stacking (3 images) for each measurement to improve SNR

Unfortunately some important FITS keywords (e.g. DATE-OBS)  got lost in some of the processing steps so that additional post-processing manual work was necessary as well.

So I am wondering whether you have used PI for these preprocessing steps in your measurements or a different tool set.

It seems that all necessary tools for the preprocessing steps are already there in PI, but they are not aligned  to the workflow of  the photometry use case  so e.g. some FITS keywords got lost. I think with a little effort it should be possible to fix that. What are your plans for future developments in the  photometry area?

Thanks again for this excellent script!

[Andres.Pozo]

Hi,

you should ask this question to Juan since I can not do anything about processes losing keywords. I think that in your workflow the processes that lose the keywords are ChannelExtraction and ImageIntegration. I think that the first should be quite easy to fix. However, ImageIntegration should be harder since the process can not simply copy the keyworks but it should interpret some of them. In the case of DATE-OBS, the behavior can be quite complex when you integrate images taken in several nights.