My student and I are beginners to variable star observing and photometry. We are currently planning first observations to gain practice in the technique, so for now we are sticking with known and well-studied variable stars with periods on the order of hours to a few days, and amplitudes of at least several tenths of a magnitude. We've chosen a handful of stars gleaned from the VSP, however in every case, the tool reports "no comp stars in this field". Does the AAVSO have any resource that can suggest a comp star for well-known variables, given the star's id and the size of the field? Alternatively, is there a link to such a resource?
For the record, the first stars we picked are:
Delta Cephei (of course)
u. Herculis
Eta Aquilae
Thanks in advance!
Elisabeth:
Del Cep has many comps in the VSP chart. What name did you use? Explain a little more carefully exactly what steps you have undertaken so far. What 'tool' reports "no comps in this field".
Have you actually taken some images yet?
What 'tool' are you using to open your image and conduct photometry? VPhot?
What filters did you use?
Are your images plate-solved?
Ken
We were using the AAVSO Observation Planner. We have just taken a few images of non-variable stars, and are in the process of preparing master calibration frames (darks and flats, already have master bias) for use with AIP4WIN. How does VPhot compare with AIP4WIN?
We are not using filters, but are planning to transform the DSLR Bayer channels to obtain magnitudes for V, B, and R.
The images we have taken so far do not require plate solving - we chose easily identifiable fixed-brightness stars close enough to fit inside our FOV. Of course we will need to do this when we begin imaging variables.
Eta Aquilei is known as HIP 97804, and VSX recognizes it. That said, I had to expand FOV to 180 min to find comps. But they are there!
U HER shows a bunch of comps within 60 min FOV.
Peter
What tool are you using that lets you control the chart FOV?
Elisabeth,
When you create a VSP chart from "pick a star" on the AAVSO home page, by default it will have a 1 degree FOV. If you then click on "plot another chart" you can customize that chart.
Scroll down through the options. You'll find the FOV option. Also, take note of all the other available options. If you go back to the top of the page you will find a small font link to the VSP Help Guide, a PDF document with lots of information on the chart plotting tool.
Phil