Currently, if I have LRGB events in my sequence with dithering setup, when I start the run sequence, it centres the target with the L filter event. Then when that event is done and has moved onto the next event (i.e. R), the prior dithering has offset the centre for the start of this new event.
I would appreciate the ability to be able to re centre the target after each event, as I believe this would lead to slightly less loss of frame/smaller area cropping in the final stacked image.
Many thanks and leave a +1 if you think this would be useful for you.
That’s the intent of dithering. Its goal is to offset each frame by a few pixels, specifically so things like hot pixels or banding patterns aren’t in the same place each frame, and thus may be more easily removed during integration.
If the dither is moving your frames too far for your liking, then you can adjust the amount of dither either in SGP, or PHD, or both.
If you want “pixel perfect” exact centering in each frame (all things being equal and ideal) then you’ll have to disable dithering.
As a side note : If you are shooting LRGB all on the same night, there is no need to dither each frame, since an L won’t be stacked with an R, and so on. Dithering every 4 frames in this case, so each L is different from the previous L, and so on, would do the job nicely.
Thanks for your reply, since only each event is stacked with itself, the dithering makes sense within that channel, but there is no need for the next event, say R, to begin offcentre. R (and all subsequent events for that matter) can be recentred and dithering initiated within their own event.
Later, when using LRGBcombination for example, each individual stack of L, R, G & B, would contain cleaner data that benefitted from dithering, but one could choose the first exposure in an event that was centred as the reference frame for alignment of all subsequent exposures in that event. This way, when each of the four channels are combined, it is more likely that less cropping would occur.
Since any fixed pattern noise would be removed from dithering each exposure within each of the four stacks, no additive FPN would be revealed when carrying out LRGBcombination from each channel if they were re-centred.
“As a side note : If you are shooting LRGB all on the same night, there is no need to dither each frame, since an L won’t be stacked with an R, and so on. Dithering every 4 frames in this case, so each L is different from the previous L, and so on, would do the job nicely.”
This is assuming you have selected rotate through events as opposed to finish entire event first. I tried this once, setting it to dither every 4 frames and found that it rotated through the events and it waited for the 4th frame of L to dither, then it switched to the 4th frame of R and dithered, G & B the same. This was not what I expected to happen, I thought it would take 1 frame of L, then R, then G, then B and upon returning to the 2nd frame of L (being frame no. 5 in total) it would dither. Perhaps I did something wrong with this. I also did not like the downtime caused by having to refocus every filter when rotating through events, I do not have auto adjust focus per filter (offset calculations) ticked to avoid this.
In light of this then my friend, I simply setup my LRGB sequence as I wish for the night with finish entire events first, have it dither each frame within each event and then it moves to the subsequent events, refocuses and carries on. What I would like, is for each subsequent event to have the option to recentre the first frame, so that the first frames in each of the events are plate solve matched.
This in my opinion, would minimise cropping in post-process.
I will have to recheck my rotate through events again, perhaps i did something wrong. Still, the downtime from refocusing each filter (unless i setup my offsets and i’m a bit iffy about that considering i use a doublet and focus is different for varying elevations (i.e. blue channel)), negates the gain from less dithering settling time.
Great suggestion, I actually tried this two nights ago and it worked like a charm, recentering for each filter! Just didn’t have the chance to report back here and update the post
Its goal is to offset each frame by a few pixels, specifically so things like hot pixels or banding patterns aren’t in the same place each frame, and thus may be more easily removed during integration.
