Eclipsing binary star AD And

[Dave Smith]

Had a go at another eclipsing binary star last night. AD Andromeda. I was lucky to catch the minimum as the BAA website predicted it was around 11 pm. It actually occurred at 1.50am when luckily I was still taking images. I stopped earlier than I would have liked but with this game you don't see the results until they are processed. It was still clear when I stopped but I thought it was all over at that time. I will try to get the remainder of the curve another time. The orbital period is 0.986 days so the minimum will occur a little earlier each day. Note the time scale on the graph is UT (universal time = GMT)

Dave

[Stu]

Excellent stuff Dave, very interesting. I wonder why the BAA prediction was so far out?

[Dave Smith]

Thanks Stu. Sorry I should have corrected that.  The BAA prediction was around 11 pm GMT i.e. around midnight BST and the Krakow database said 1:50 BST and from my graph above it actually happened at around midnight UT (=GMT) or 1:00 BST. The period of this binary is apparently changing and the BAA were using an earlier period for the predictions. All very interesting and if weather permits I will try to capture other minimums

Dave.

[Stu]

Very interesting indeed. You may have covered this elsewhere, but how do you capture the light curve?

[Dave Smith]

Hi Stu

I use SGPro to capture the images, it is very good at getting the relevant star smack in the middle of the field of view and recognises the names such as AD And. On this occasion I did 30 sec exposures with 30 sec gaps between. You have to be ultra careful that the target star and any comparison stars are not near saturation. The data is then analysed using the free software Muniwin which can produce output files suitable for up loading to the BAA database or the aavso database. Those files can be opened in Excel to produce a graph. When Muniwin has analysed the results it does produce a graph but it is of the difference between the magnitudes of the variable and a comparison star which gives an indication of how it has gone.

There is loads of help on the BAA website, and the BAA does run a mentoring scheme to help those starting out. The finder charts with comparison stars can be downloaded from the aavso website.

Hope that helps.

Dave