Hello all,
What Chris is suggesting sounds like a great Idea. One thing to bare in mind though, when SGP does an auto focus run and successfully finds best focus position for the focuser it could ‘LOG’ the focusers position along with current temperature when it ran. It could add to the log every time it finds a temp which is missing from the Log file thus building up a database of starting positions based on temp. This database will be unique to everyone’s individual setups.
I myself when finishing an imaging session always crank the focuser tube all the way in as im sure most people do so when setting up, my focuser tube always begins at position zero and have to go through the annoying process of finding focus first. At the press of a button, SGP could consult this ‘LOG File’ after establishing what the current temperature is and find a focuser position based on that temp from a previously successful focusing run at that temp and auto push the focuser tube out to that position to start. Theoretically this position will be very close to focus anyway. Either SGP could run auto focus from here or run a little sequence like Chris has suggested to do any fine tune before a sequence proceeds or autofocus is invoked.
Obviously this isn’t going to do a huge amount for people who don’t have an autofocusing system installed but it would enhance automation which is what SGP is all about. I know the documentation states that SGP’s purpose is to maintain focus throughout a session but a small feature like this could also automate the initial focus stage too.
Focus pt: Used to specify a starting point as well as to specify the offsets for adjusting focus on filter change when using an absolute focuser when Auto adjust focus per filter is enabled. Because of the way in which “focus on filter” works it is recommended that you set the focus position of your filters near the same ambient temperature.
I would really like to see the initial focus position adjusted for temperature. This can be easily incorporated by getting two numbers from the user: 1) slope of focus least square fit line 2) intercept of the line. These two numbers define precisely the best focus position as a function of temperature. This would allow the maintenance of an excellent focus position completely automated for a long period of time. Auto focusing would not even be required, except perhaps from time to time to confirm that the best fit line is optimum.
If additionally, a maximum deviation of the focus position from this calculated value could be given, then I would have no reservations about running the autofocus routine on some regular interval during each night’s session. The reason I do not do so now is that, although the new auto-focus routine works wonderfully well, most of the time, it sometimes fails. When it fails, it leaves my focus position badly out of focus and that whole stretch of imaging time is toast. There are various reasons why it might fail, perhaps a brief cloud or wind gusts come along. My RC12 is particularly prone to auto-focus failures, so I never ever run the auto-focus unless I am attending it. It works so much better to just let the temperature compensation just do its thing.
This would in no way change anything for those folks who are very happy with the way it is running now. It would just be a new optional feature that could be turned on.
Yes, quite so. That is my standard way of operating now, on all my scopes. But I have to initiate it to a good focus position when the evening starts. I can’t start an automated process at 10 in the morning or 6 pm and let it completely run the night’s imaging session. I don’t know what the temp will be at 9:45pm when it starts taking images to be able to set the correct focuser position. I have to be at my computer at 9:45pm and do this manually.
Hi Jared,
I have not got a filter wheel although I did try this with a manual filter wheel connected in the sequencer. I set a filter called ‘Focus’ and a position of ‘7450’ in the control panel. In the Filter wheel module I picked ‘Focus’ and hit the set button at which point a dialog box came up, choosing yes still left my focuser at position zero. Then, I set up a simulated sequence and chose ‘Focus’ in the ‘Filter’ box for the event hoping on sequence start it would send the focuser to that position but it still didn’t and autofocus failed due to the focuser being at position zero. Obviously I’m missing something here…HELP !
Is this what you are looking for?
(I read your post as wanting to start a sequence (or the night’s run) with your focuser at a particular point…)
In focuser control:
…The Other button brings up a special menu seen below:
Controls:
Set absolute focus position for first filter use: Checking this option will cause the focuser to move to the absolute focus position set for that filter. The filter change can be for anything (the first event, AF override filter, Plate Solve override filter, etc.). Whatever filter is set first will cause the absolute position of that filter to be set. This is most often used with the “adjust focus per filter” option and it is important to note that the first (and only first) filter change will not behave in the way that all subsequent filter changes will behave. Normally, the focuser only moves by an amount equal to the difference between the old and new filters focus positions (the delta). Checking this option will not use any delta, but set an absolute position. This is useful if your first filter change will be for AF override and it will move the focuser to a point (regardless of temperature) where AF can succeed.
Unsure if the above works when you are not using a filter wheel…but you may have got over that part already with how you appear to have set things up. It may be worth a try…that is…check the “Set absolute focus position for first filter use”
Got all my kit out last Sunday night cos the Met office AND Met check, for the first time, actually agreed it was going to be a clear night, by the time it was dark enough to get initial focus the clouds started forming and 2 hours later, full cloud cover…Time to give up and go to bed…GRRRrrrrrrrr
