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IDProjectCategoryView StatusLast Update
0002420SkyChart1-Softwarepublic21-03-28 14:09
ReporterAlan Smith Assigned ToPatrick Chevalley  
Status assignedResolutionopen 
Target Version4.4 
Summary0002420: Show effect of airmass on apparent object magnitude
DescriptionThe airmass by zenith angle calculations shown both the Object Details > Visibility for your Observatory, and the bottom status bar of the chart, are very useful to determine object visibility.

Please could you add a new entry to show the adjusted apparent magnitude for that object at its current position on the chart, based on viewing it in that air mass (e.g. observing through 2x airmass will result in the linear object brightness of approximately half its catalogue value).

The new entry would be useful in both Object Details > Visibility for your Observatory, and the bottom status bar on the chart.

Many thanks
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Patrick Chevalley

21-03-28 14:09

administrator   ~0006973

I look a bit at the theory for the magnitude extinction.
This is not so simple because it depend a lot on the observing wavelength, site quality and the meteorological condition. To get it not too bad you need to do photometric observation for every specific night.
A standard mean value for visual band is 0.2 magnitude per air mass, but this can easily vary from 0.1 to 0.3.

I am a bit reluctant to show a value know to be false that unaware user can take as is.
Maybe it is not so hard to remember this value of 0.2 and apply mentally using the air mass value, simply 0.2 magnitude fainter at 2 air mass.
Anyway at most observing location the sky background brightening below 2 air mass is probably worst than extinction.

Issue History

Date Modified Username Field Change
21-03-28 09:36 Alan Smith New Issue
21-03-28 11:47 Patrick Chevalley Assigned To => Patrick Chevalley
21-03-28 11:47 Patrick Chevalley Status new => assigned
21-03-28 11:47 Patrick Chevalley Target Version => 4.4
21-03-28 14:09 Patrick Chevalley Note Added: 0006973