VStar gets a workout

I presented a seminar on Dec. 3rd for a group of teachers from the local public schools at the Ladd Observatory. It was a hands-on workshop that involved the participants in visual and CCD observing of variable stars. There is a general description in the  Outreach Activities forum. In the past couple of weeks I've been using VStar extensively for planning observations, analyzing data and teaching. I'd like to report here on my use of VStar in preparation for and during the program.

Attached are a few plots showing data that I collected on Nov. 29th of RZ Cas. (An Algol type eclipsing binary system in the constellation Cassiopeia.) The first two plots show my CCD observations from about midnight to 5am. There is a bit of scatter due to the bright moon, urban light pollution and sky conditions. The third file is a phase plot showing the same data along with recent V and Visual observations from the AAVSO database. There is a slight offset between the V and B values due to the color of RZ Cas. (B-V is between 0.1 to 0.3) This data was collected to use as a comparison to the observations during the workshop, and also to have some data to work on in case the weather was overcast.

The sky was partly cloudy during the day but conveniently cleared just before the workshop started. We began with an intro to variable stars using VStar generated plots of Algol and my prior observations of RZ Cas. We then showed the group how to find and observe Algol in the night sky. At that point Algol was at normal brightness and we asked them to observe again later in the night to see the minimum. The next part of the workshop was learning to use a CCD camera which was used to take more images of RZ Cas. The size of the group was larger than I expected (about 20 people) so by the time that everyone had a chance to operate the CCD we didn't have time to analyze the images.

I had been prepared to use VStar more during the program as a backup in case the weather was uncooperative. Given the clear sky we spent most of the evening observing and didn't have time to look at plots of delta Cephei and my prior observations of SU Cas.

The night was a great success and they were excited about meeting again in January for the next session. After we finished for the night the clouds rolled in so I doubt that anyone would have been able to see Algol near minimum. Hopefully they will be able to use the materials that we handed out to try again in the next few weeks.

I've found VStar to be a very useful tool for planning observations, analyzing data and explaining star variability. As an example compare the two phase plots that are attached. The first uses the period from VSX of 1.195247 and the second uses 1.195254 which seems to be a better fit. I'll post more about using VStar for understanding changes in variable stars in another post as I plan my next workshop. For the curious who can't wait, take a look at this O-C diagram for a clue.