Affiliation
American Association of Variable Star Observers (AAVSO)
Thu, 02/05/2015 - 00:51
I am reading the DSLR tutorial. Toward the end it gives the number of observations/day/s for different types of varibles. I assume an "observation" results in a clibrated light curve. All darks, flats, bias, lights, etc. that go into each light curve. Right?
That is many frames go into one observation?
Hello, I am not a really active CCD photometrist, but I can say that, basically all calibration frames that are required to reduce an image frame to a good observation, make up a single observation. And each such reduced image frame, be it a single exposure or a time series, is entered as an observation into WebObs.
The recommended number of obs/day for a variable type is based upon the rate of change of that type of variable. The idea is that you don't want to do too many observations (say on a daily basis) for a slowly changing variable such as a LPV (Mira).
Now, this cadence issue is a bit controversial, and its not really appropriate to go into the details of it here, given the scope of your question. Suffice it to say, this cadence for LPV's has come from the standpoint of visual observing, where undesired bias can creep into observing something so slightly changing, too frequently. For digital observations, reduced by software, there is no such bias. So, from a statistical point of view, such observations can be considered to be essentially "random" error, and then the more observations the better! (Really simplifying the matter).
Mike LMK
Hi Edwin,
an "observation" is the final magnitude estimate made from one or more light images that have been calibrated using master bias, dark and flat frames (each of which is made up of many individual images). Each observation constitues just one data point in a light curve which may have hundred or thousands of data points collected over a period of time - as short as a few hours to many decades depending on the target.
So yes, many frames go into one observation.
Cheers,
Mark