Am I correct that specifying a focus target and image target (a feature I have never used) WILL NOT cause the scope to go to that focus target when focus is being done as part of a sequence (as opposed to a manual focus command)? That seems to be the case with the V3 that I am using and, as such, it is pretty useless. I have V4 on a non-imaging machine and it does not appear to be different in this respect.
I know this request has been made more than once but I desperately need the ability to focus away from the imaging target. At longer focal lengths and galaxy season it can often be impossible to focus at all on the target itself due to lack of stars. FYI, I have been imaging for 35 years and have high quality equipment (Paramount, IDk, Nightcrawler) so neither experience or equipment is an issue.
I have no problem focusing with my refractors nor is there a problem focusing with the iDK in a FOV with more stars.
The odd thing is that there are often quite a few stars (just dimmer ones) in even the difficult small FOVs but SGP fails to “see” these and use them for focus (no HFD shown). I have tried different binning, minimum star size settings, exposure times, pretty much everything, to no avail for some targets.
I am getting to the point where I may have to consider switching to a software that allows either focus in a different location (as part of the sequence) or a single star focus ala FocusMax. Either that or I am locking myself out of imaging a lot of objects…
That is what I thought. Too bad. If we can’t get a better way to focus these targets, I may reluctantly have to find a software that will. Otherwise I am partly wasting some very expensive equipment.
A simple user-selected single star or subframe focus within the FOV capability would fix the problem. As would a single star Focusmax-like option. These have both often requested features.
Second related question is why SGP focus does not use all or most of the stars in the FOV that are easily visible in a normally stretched focus image. My target last night had maybe 10 easily visible stars in the image and yet only used three or so. I have to assume there is some internal and not user adjustable parameters that makes this choice? Making that more user adjustable would probably also help.
These are both way easier to implement and don’t have complexity, overhead and risk to sequence health that extra movement adds.
The parameter that has the most influence over this, but also the one that is most responsible for eliminating bad data is the minimum star size filter. Have you adjusted the value for this? You can do it in real time with a single image to find the spot that’s best for you. We had originally exposed the max size filter too, but that one is way easier to get in trouble with because it tends to change from target to target while the min star filter is pretty consistent across all targets.
I noted that although this was set to the minimum (2) there were still quite a few easily visible stars that were not being selected (at least they showed no HFD value). It looks like there is another variable not exposed that is preventing these stars from being used. Is that the reason?
Yes, there are several variables we chose to not expose for various reasons… mostly because it’s very hard to provide support for them. Which metric are you using? The onboard HFR? ASTAPs HFD?
Presently using the onboard HFR since I am still using V3 for actual imaging (although I own V4). Is there an advantage to using ASTAP HFD (especially in this situation)?