My original reason to study KIC 9832227 wasn’t to create a lightcurve, but to measure the timing of this star to see if I could detect changes in the period over time: are the stars spiraling toward each other?
Observing session 5 was a good session, although I started well after sunset because of another commitment that flowed into making dinner and other chores. So, session 5 was a little bit short. But all those earlier problems with horizon and blurry images have now been solved, so although I only had 2 or 3 hours of observing time with this session, the image quality is somewhat above average.
The new points (a dark red in this graph, from about 4 hours to about 7 hours in the orbital cycle ) overlap points from other sessions, which means that we should be able to extract a timing measurement.
My timing spreadsheet gives me an orbital cycle time of 0.45790008182729164 days. That is 10 hours, 59 minutes, 22.57 seconds. The American Association of Variable Star Observers lists its orbital cycle time as 0.4579485 days. My measured timing is 4.18 seconds faster than the AAVSO’s time. However, I don’t (yet) have much confidence in my timing. The associated timing spreadsheet graph is quite broad and the points show lots of scatter. More data and editing/removing some of the relatively wild data points might tighten things up.
We’ll see.
Meanwhile, I think it’s really cool to be able to measure the orbital cycle time down to the second, despite using 30-second-long exposures. Just goes to show that if you have enough data points and are careful with your clock (the computer clock used to attach time to each exposure is kept synchronized with Coordinated Universal Time (UTC) to a few milliseconds), you can make surprisingly precise statements about orbits. Oh, and I am adjusting for the speed of light, which is an important correction in this measurement. (But one that I’ll cover in some future blog post.)
Exploring the binar star KIC 9832227 