[Aavso-photometry] Reporting CCD fainter-thans

[Aaron Price]

 Arne and I just had a discussion about how to report CCD fainter-than observations. In the 
past, the policy was the same as with visual fainter thans in that we asked CCD observers to 
report the faintest comparison star they can see in the field. However, we were thinking that 
with CCD you can of course extend the range of the sequence (if you are confident in the 
linearity of your chip). So we would like to amend the policy.

 If you would like to report a fainter-than based on a CCD observation, you can continue to 
report the faintest comparison star you see on the chart. That is a safe and effective method. 
However, if you think your CCD image goes much deeper than this then you can choose to instead 
report the magnitude and uncertainty of any star in the field (as measured with our comparison 
stars) as long as the star has an SNR>=10. If you do this, it is very important that you 
report an accurate uncertainty measurement. So please take care with it.  

-- 

Aaron Price
Technical Assistant, Technology
American Association of Variable Star Observers
www.aavso.org