4. Tips and Tricks¶
This is a collection of tips and tricks that can be useful for reducing different data, or to do it slightly differently from what is presented in the example.
4.1. Sky Subtraction¶
For sky subtraction, there are two input parameters to
users should be aware of:
offset_sky. Both serve to
match the sky frames to the target frame before the subtraction. The first,
scale_sky is multiplicative and is turned off by default for GSAOI, while
offset_sky is additive and is turned on by default for
The reason why
offset_sky is favored for GSAOI is that often the flux in
individual pixels can be very low and that is observed to make the
multiplicative scale less accurate. In any case, from experience, it was
offset_sky==True was more successful, more often, with GSAOI
data, which is why it was set as the default.
Depending on the data and the science objectives, those two input parameters might have to be experimented with. The only combination we would not recommend is setting both of them on. (The software will not let you either.)
When there are offset to sky, it is likely to be because the target fills the
field of view and there is no usable sky. In those cases, all sky scaling
and offsetting should be turned off (
skyCorrect:offset_sky=False). There is no sky to measure in the target
frame, any attempts at scaling or offsetting will result in an over subtraction
of the sky.