It was suggested in my last workshop to have an area of interest in your SubframeSelector script, just to avoid to include the effects of possible miscollimation in the calculation of the FWHM value in each image of a given data set. This way, the user could then select only the center of the frame, avoiding the corners, which in those circumstances have always higher FWHM values are may not be representative of the actual seeing conditions in the image. Could this be possible?
Hi Vicent,
A subframe region may be specified in the current version of SubframeSelector via Star Detection and Fitting > Subframe region. Values are left, top, width, and height (see the tooltip). All statistics and generated maps will reflect only this region appropriately. This feature is useful to improve performance also (I think you suggested this earlier, i.e. measure a small area to speed things up).
The FWHMEccentricity script has no equivalent option. I want to keep the UI as simple as possible. Please use the Crop process and Image Container as a first step and then use the script on the results.
An one suggestion. Some cameras don't have the saturation point at the top of the digital counts. Could you add a parameter to specify where is the saturation point?
A saturation point can be specified in the current version FWHMEccentrity via the Upper Limit option. The default is 1.0 (no clipping). I like to use 0.7 on my frames to clip off the non-linear anti-bloom region. On wider-field, reasonably exposed frames with lots of stars this option usually has only a small if any impact on the results. The relatively few saturated stars are seen as outliers and are rejected by the robust statistics.
Unfortunately SubframeSelector has no equivalent option yet. I will release a new version hopefully soon.
One question. I'm using now the SubframeSelector and it detects between 100 - 250 stars/image. It always says "Warning: insufficient number of fitted stars". I think 100 stars should give good statistics...?
I have not had a chance to work on this yet. As I mentioned before, good maps require sufficient stars all across the frames. My current plan is to not generate maps when requested and not enough stars are present (and a warning), and remove the warning otherwise.
Also in this workshop we experimented with using SubframeSelector to evaluate calibration frames. Looking at the plot of the median proved useful (at least to me). Vicent thought there would be value in a dedicated CalibrationFrameSelector but in the interim maybe we could have a switch to turn off star detection and the calculation of associated variables to save time when using SubframeSelector on calibration frames.
Hi Josh,
I will look into this option also.
Thanks,
Mike
