Use subframe download for the auto focus crop feature


I noticed that when you have the Crop autofocus frames by X % set in the AF options, SGP will still download the whole frame from the camera. Changing this option to download only the cropped frame would give an additional place to optimize AF speed in addition to increasing binning.

Additionally I think that the crop value (%) is a bit misleading, the first time I tried this feature I wanted to halve the frame size and entered 50 as the value. But this crops the frame 50% from both directions, resulting in detection area of 0 pixels and me wondering why the AF doesn’t catch any stars :). If you’re not keen on changing the established setting, maybe cap it to 45% or so to make the error more obvious?


++ Jari

1 Like

While we probably will not actually crop the frame immediately, we can rework the % system to be a bit more intuitive.

A subframe might speed things up a bit though. My image download speeds are longer than the AF exposure itself at the moment.

Right. That said, the speed gain, in most cases, will likely not be substantive given that SGPro likes large sample sizes. The cropping is really only meant to get rid of edge junk on the edges of fields that aren’t properly flattened. Unless your fov is very large, any speed gains of measurable value from sub frames could be sharply detrimental to the quality of focus. There are, of course, exceptions to this… Like pointing at targets in the Milky Way. Any portion of that will likely have sufficient stars. I’m not saying it would be of 0 use… Just limited use. As such, it is not super high on the priority list (neither has it been archived away as “won’t implement”) .

Was taking a look at this tonight. This will be a temporary fix… 2.5 will make it obsolete as there is a feature in that will allow for direct selection (user drawn) of a particular region for AF frames. So… the change here “I think” is to alter the meaning of “crop”. I want to make sure before I do it so we don’t have the other half yelling at us when we switch…

Right now, crop is applied “per edge”. This means that possible values are between 0-50. A value of 25% would remove 25% of the total pixel from each edge. I think it is the desired behavior that this value can be between 0-100 (we won’t actually allow 100… this is just for illustration of point). Here, a value of 25% would mean 12.5% cropped from each side.

From a user experience perspective, is this what most folks want?

Sounds good!

Sounds very useful. When I’m trying to AF on a cluster, it gets confused - I can see isolated stars changing HFD in one direction yet the overall HFD goes in the other! Using a user-drawn crop will allow me to avoid things like that, which for many, will be in the center.

Minor changes to 2.4. Moving to the 2.5 queue for the larger FOV selection change.

Suggested solution sounds like much more sense for me too.

With ref to the issue of globular clusters causing issues…

How about a circular exclusion tool, mouse click at the center of the cluster in the frame,
on dragging the mouse the circle increases in size until the cluster is covered, let go and
hey presto Cluster is excluded. You could even allow multiple exclusion circles to be
drawn which will exclude the contents of a possible second problem object in the frame.

Just a thought