Lack of observers.

Anthony - what software are you using to generate the curves? Is it AIP4Win?

HI Dave,

The actual photometry was accomplished using AIP4Win (V2) and the output saved as a text file. I then edited this file so as to keep three columns (julian date, differential magnitude change, error) so as to feed them into an online graphics program I accidently came across at ostrava.astronomy.cz/plotter.php .... one must be careful since the first two lines are ignored by the online program and, as such, it is easy to lose two data points (I add two blank lines up top to bypass this problem).

Also, how did you choose the comparison? And why only one?

I try and locate my two stars (comparison and check) so as to have a similar magnitude and spectral type as my variable. As for the one star, not really since I use two ... part of the analysis (within AIP4Win) includes a comparison between the comparison and check star during the whole session so that you can confirm there is no funny business going on.

Nice curves by the way

Glad you like 'em ... I was surprised how easy it is once you find the proper "ingredients" as far as binning, filter and exposure time are concerned.

I have additional results but they are partial due to the damn weather. My curve for DY Peg is REALLY impressive but I have a couple of small issues due to clouds and, hopefully, tomorrow I will be back at it for good this time.

PS. I also had to check the extent of the linear behaviour of my anti-blooming camera and which I confirmed to be linear up to 23,000 ADU. As a result, all of my exposures are such so as to never exceed this amount for any pixel.

PS. I also had to check the extent of the linear behaviour of my anti-blooming camera and which I confirmed to be linear up to 23,000 ADU. As a result, all of my exposures are such so as to never exceed this amount for any pixel.

That was going to be my next question

So, how's about this - how did you check linear behaviour? Was it easy?

PS. I also had to check the extent of the linear behaviour of my anti-blooming camera and which I confirmed to be linear up to 23,000 ADU. As a result, all of my exposures are such so as to never exceed this amount for any pixel.

That was going to be my next question

Hehehe, beat you to it ....

So, how's about this - how did you check linear behaviour? Was it easy?

Very easy and ten minutes worth of work .... just take one or two exposures at 1 sec of some bright star, follow up with another 1-2 exposures at 2 sec, again at 3 seconds and so on .... graph the results in Excel with exposure time on the x-axis and the ADU on the vertical axis and you will immediately see the behaviour of the camera and where the linearity breaks down.

If you wish, I can try and locate my Excel spreadsheet and graph ....

If you wish, I can try and locate my Excel spreadsheet and graph ....

Just found my spreadsheet .... I took three exposures each at 1", 3", 5", 7", 9", 11" ... 37", 39", and 41". I then proceeded to take the measurement of the mean ADU using a 100x100 pixel box around my star of interest and averaged this result for the three exposures (since I took three exposures at each time of 1", 3" etc). I plotted these averages on the Y-axis and the exposure time itself on the X-axis.

If it was possible to attach a (small) file with this message, I would have included the Excel spreadsheet with the figures for my 63 total exposures (21 triplicates) and the ensuing graph.

Hi Anthony,

Great to see you light curves!

Did you ever try using Photometric filters, or did you find them too dim for just period analysis.

Also what determined your exposure of 60s ?

I have just got a new (modest) CCD photometric setup with BVI filters.

John