Ensembles and Bias
I'm using VPhot for image analysis, and I really like its capabilities. That said, using it is not the same as using it properly. I like the flexibility of being able to fine tune the ensemble, but am concerned about introducing user bias.
My question is -- how do you select the comps to include in your ensemble? Do you only eliminate those that show up as darker red, indicating they are perhaps outliers in the ensemble? Do you choose an ensemble that brackets your target's magnitude, similar to visual estimating? Do you perform trial and error to find the ensemble that minimizes error values (I suspect not)? Or do you -- and this is what "feels" right to me -- select the ensemble that results in a value for the check star you've selected that is closest to the known value (in parentheses)?
I want to make sure that I am reporting values that are proper / most scientifically meaningful, and it seems there's a lot of room for introducing user bias into the numbers if a well thought out method is not followed.
Thanks -- Brian (PRV)