This request formalizes an earlier discussion and a few threads this year. While I find the AF routine is much improved for a number of challenging circumstances, big galaxies, globulars and diffraction spikes off bright stars still confuse the HFR calculation.
Specifically, may I suggest that if the existing Focus target feature in SGP is populated with a legal coordinate value above the imaging horizon and say within 20 degrees of the imaging target (to minimize mirror flop), SGP slews to the target for AF routines, before returning to its imaging target position for the exposure?
regards
This sounds like an excellent proposal to add to SGP V4 Buzz. When I image PNs at 4m focal length there are times when there are only a few detectable (but faint) stars when in perfect focus, meaning that at the start and/or end of an autofocus run there are no detectable stars, resulting in AF failure. Most times there are a handful of stars throughout an autofocus run, so autofocus does succeed, but the low quantity of detectable stars is not enough for robust estimation of HFR, leading to poor focus. Currently I have to give up on such targets if acquisition occurs while I’m sleeping.
The ability to automatically focus on a nearby target via an enhanced Focus target feature would be of great benefit to me, and especially so if the option to use Focus targets could be selected on a per-target basis (rather than globally). My Meade 16 has quite a lot of mirror flop even with the so-called mirror locks engaged, so ideally focus should be conducted on the target itself, but in cases where the target has no or low star count the suggested autofocus on Focus target feature would be a life-saver.
But for this feature to be most useful the Focus target feature would ideally hold a list of targets that could be easily added to, e.g, via cut and paste of multiple RA, Dec pairs (assuming SGP didn’t automatically populate the list with suitable locations). I envisage writing an app that could search suitable autofocus targets across a grid based on the imaging train’s FOV, and cut/pasting dozens of RA/Dec pairs at a single time.
I’m sure there are many long focal length geeks like myself who would find such a feature beneficial.
I second this feature enhancement. I used the focus target feature back in my early days of using SGP before I got an autofocuser. But it saved a ton time and I always had good focus since I usually did not have to go far to get a good field for focusing (or back then, a bright enough star for the B-mask)
Agreed. While the present improvements are great and appreciated, there is really no better way to eliminate artifact induced errors than to remove the source of the artifact entirely and this is by far the best way to accomplish that goal!