Re: Processing results not as I expected
Posted: Sun Sep 22, 2019 7:35 am
Hi David,
Most of these issues stem from anomalies in the dataset;
You will notice every workflow (including the one above) starts with inspecting the dataset and cropping away stacking artifacts.
Without doing so, you are effectively instructing Wipe to remove gradients from much-darker-than-real-background pixels. As a result Wipe will construct a gradient model that backs off in those areas, as Wipe (and StarTools as a whole) never clips your data unless explicitly allowed to. Wipe in general is extremely sensitive to dark anomalies like stacking arifacts, dust donuts, trees and anything else that might be darker than the true recorded background level. If you have such dark anomalies and you cannot (or don't want to) remove them, you can mask these out however.
If you are using data where overexposing stars have had their values modified to no longer be unity (e.g. full brightness), the second algorithm will - rightfully - no longer regard these pixels as overexposing stars, as they are not overexposing any more. E.g. StarTools treats pixels at unity as singularities with an unknowable value.
Out of all stackers I am aware of, DSS in is a bit "unique" in its treatment of singularities, in that it treats pixels at full unity as values at full unity, rather than unknowable quantities. This, for example, results in overexposing stars dimming during some of its calibration steps, compared to other over exposing stars in the same image, as well as colour discrepancies in highlights due to treating colour channels at unity as having their value at unity, rather than as an unknowable quantity.
Regardless, you can correct difficulties with mask generation by lowering the "Threshold" parameter from 100.00 to whatever percentage of unity the dimmest overexposing star in your image sits at.
Hope this helps!
Most of these issues stem from anomalies in the dataset;
It appears you have left stacking artefacts around the edges.perdrix wrote:When doing the wipe, I saw this
You will notice every workflow (including the one above) starts with inspecting the dataset and cropping away stacking artifacts.
Without doing so, you are effectively instructing Wipe to remove gradients from much-darker-than-real-background pixels. As a result Wipe will construct a gradient model that backs off in those areas, as Wipe (and StarTools as a whole) never clips your data unless explicitly allowed to. Wipe in general is extremely sensitive to dark anomalies like stacking arifacts, dust donuts, trees and anything else that might be darker than the true recorded background level. If you have such dark anomalies and you cannot (or don't want to) remove them, you can mask these out however.
Star mask generation uses two algorithms in tandem; one for "small" star detection of stars that do not over expose, and one for "big" stars that do overexpose.Star mask generation
If you are using data where overexposing stars have had their values modified to no longer be unity (e.g. full brightness), the second algorithm will - rightfully - no longer regard these pixels as overexposing stars, as they are not overexposing any more. E.g. StarTools treats pixels at unity as singularities with an unknowable value.
Out of all stackers I am aware of, DSS in is a bit "unique" in its treatment of singularities, in that it treats pixels at full unity as values at full unity, rather than unknowable quantities. This, for example, results in overexposing stars dimming during some of its calibration steps, compared to other over exposing stars in the same image, as well as colour discrepancies in highlights due to treating colour channels at unity as having their value at unity, rather than as an unknowable quantity.
Regardless, you can correct difficulties with mask generation by lowering the "Threshold" parameter from 100.00 to whatever percentage of unity the dimmest overexposing star in your image sits at.
Hope this helps!