Posted by
karenacollins on
Feb 23, 2016; 10:29am
URL: http://astroimagej.170.s1.nabble.com/Multiplot-magnitude-issue-tp267p354.html
Hi Christophe,
If the comps stars are not the exact same "color" as the target, you may
see airmass trend. The amount of the trend will depend on the filter and
the difference in the color of the objects. The trend could range from
zero to several tens of mmag if the airmass change is extreme. However,
at the scale you are plotting, you not be able to see the trend
graphically. One thing I noticed is that detrended data generally have a
line drawn through the average of the data, so I am wondering if
something is going wrong with the fit since your plot does not show a
line. Could you check and make sure all of the rows of the airmass data
column in the measurements table have a valid number in them?
The comp star magnitudes are effectively weighted by the brightness of
the star. See equation C1 in the arXiv paper here:
http://arxiv.org/abs/1601.02622I'm not sure what is going on with the C4 plot and the odd character in
the "then shift" column. I assume you are not able to enter zero in the
"then shift" column?
If you are not able to make progress based on the above comments, use
the "File" menu of the Multi-plot Main panel to save the plot settings
into a "plot config file" and then send me both the measurements table
and the plot config file for me to look at. You can send those directly
to karenacollins $&* at outlook ddoott com, without to gibberish
characters used to try to foil email spammers.
Karen