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Compass and Target issues

MNIA
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Joined: 2011-01-23

Hi,

I am currently trying to run a time series analysis on the star U Gem and I am experiencing two problems.

1. My images appear to be calibrated, however, the compass in the bottom right corner is wrong. The program still identifies the stars correctly, but I'm wondering if this could be messing up the sequence.

2. Once I identify my target star, comparison star, and check star, their locations do not stay constant from image to image. For some reason the bulls eye moves off the stars no matter how many different settings I try to change. It will be constant for a few images, then one of my identified stars will suddenly move out of the inner circle. When I try to run the time series no graph is made for my comparison stars, and the light curve for my target and check stars are identical.

- Nicole

Compass and Target issues
kge
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Joined: 2010-07-19

Hi Nicole, 

1. The compass is in no way connected to other calculations in VPHOT, so if there is a bug in the display of the arrows it will not affect results in any way.

2. Not sure what you mean with the apertures moving off? There is no display of the image while doing time series. I guess I'm missing something here. Note that on the time series result page, if you click on one of the target links, you will get to the details page containing a table with result from each image pr row, along with a thumbnail image of the target star. This should allow you to easily spot centroid problems.

Also note that there will be no graph for the comp star when only ONE comp star is used. The reason for that is that each comp stars light curve is determined using the remaining comp stars as reference. So if there are no other comp stars, no light curve can be made. These light curves are mainly used for identifying problems with the comps, such as variabililty.

I doubt that the light curves of your target and check stars are identical. They might be similar, especially when the target is not varying, but there will be small variations, and the average magnitude and its standard deviation should also differ.

Geir

Thanks for the help. When I
MNIA
MNIA's picture
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Joined: 2011-01-23

Thanks for the help. When I was talking about the circles moving off the selected stars, I meant in the sequence. After setting up the sequence - when I go through to check the correct stars are selected-some images are off. The centroid will be on the star in one image and misplaced a little in the next. Is there a way to correct this?

Compass and Target issues
kge
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Joined: 2010-07-19

OK, I see. Yes, there seem to be a problem when moving from image to image, for instance when using the arrows to the upper left on the image view page. The sequence does not get updated properly. I will see if I can fix it.

Just for the records: this is an display issue and not related to time series or time series results.

Geir

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