What controllers can integrate to a Meade Motorfocuser? SGP challenge connecting
At present I have a Celestron CF9.25 SCT mated to a Meade Motorfocuser controlled by a JMI PCFC connected via USB to my computer
As this gear doesn’t have absolute position I am unsure if SGP would even allow it attempt autofocus? (In fact it won't even allow it to connect - says it's not supported)!
I am thinking of upgrading and getting something that works flawlessly (like the Moonlight focuser and stepper motor on my WO 110FLT. Two questions:
Am I right - there is no controller for a Meade Motorfocuser on a Celestron scope that will allow SGP to run any advanced automatic focus routines? If I can just swap to a different ASCOM controller for the JMI PCFC that will work with SGP that would be very nice for the next few months!
Given that it isn’t just swap over the JMI PCFC to a different motor controller??? What focuser would people suggest - I am tempted to go MoonLight again as it works flawlessly with my WO refractor.
Someone asked a similar question regarding Meade focuser recently.
I think the answer is no it will not work for what you want.
Reason being the Meade focuser uses a DC motor that simply moves one way or the other with no reference points so you cannot goto a specific point. Yes many controllers can make the Meade focuser operate, (travel in and out), but the issue is how the focuser works.
Go the Moonlite or similar, they are built for the purpose you have. Stepper motors are the way to go.
I’d suspect “absolute” position with an SCT is a “relative” term
The reason is, your just slopping the mirror up and down the baffle tube. It might be precise enough, but depending on how gloopy your baffle tube lube is, I’d reckon it isn’t wildly repeatable.
Celestron sell a stepper-based motor focuser for their SCTs, connects via USB and includes an ASCOM driver. The same problem remains though.
I fear an additional focuser on the visual back is you’re salvation - although if you’re imaging, do your sums carefully when it comes to your back focus.
I pretty much never move the mirror using (an upgraded Starizona 10:1 fine focuser I swapped for the standard Celestron focuser) as per my post I already have a Meade motorfocuser mated to the back of the SCT.
The issue being SGP doesn't want to play at all with the JMI PCFC that controls the Meade motorfocuser via USB back to the PC. My question is can this motor focuser be controlled by any other focus control unit that SGP will play nice with?
I have a Celestron motor on my C925 and it seems to be repeatable position wise. In SGP you need to reverse the focuser direction and then use backlash compensation on what becomes the "Out" direction (Down the baffle) and use around 1000 steps (A full turn of the knob) of backlash compensation.
You have to reverse the direction in SGP as Celestron don't provide that functionality in the driver and they regard "out" as being away from the rear cell, which focal plane wise is equivalent to "IN" on just about every other telescope design. If you don't reverse them the focus routine in SGP will step it "Out" (Up the tube) and then every focuser move during the focus run will be "IN" toward the rear cell and have backlash compensation applied. It all amounts to extra focuser wear and extra time taken on every single focus run, of which there will need to be plenty to keep the temperature related drift under control.
Downside at least to the first series Celestron motor is they do not have a temperature sensor built in which I think is a bit of a dumb idea for such temperature sensitive scopes. In the summer I was trading extra subs for sharp subs and having it do a focus run about every 15 minutes as early in the night it could go from pin sharp to doughnuts in that time. If I was going again I would probably adapt a ZWO EAF on to it to have the temp sensor.
My Celestron - being carbon fibre - is pretty temperature immune to focus change. I never use the fine focuser for imaging - only rough focus if I ever do visual.
The Meade motor focuser alone is used when I do astro photography (so the primary mirror never moves if I am lucky) - but as said the Meade unit is not based upon a stepper motor - so no matter its precision or lack there off a ASCOM driver if it existed would have to simulate a focus position then up or down its count relative to the length of the change position pulse sent to it. It would not be anywhere near as accurate and repeatable as a stepper motor design, let alone a great one like the Moonlight with a temperature monitor for compensation built in to the package.
Really I just wanted to short term work around as I learn SGP before I upgrade the focuser. Would happily go Moonlight again so long as I can clearly distinguish two motorfocusers - which was associated with which scope and camera in SGP. Having 3 ZWO cameras - defined as 1, 2 and 3 - bit pot luck which camera gets which designation some days - is a real pain!
Differentiating between focusers is easy, you just need to create an equipment profile for each scope and load the one that matches the scope you are using at the time.
Be wary if you get a Moonlite if you mean by temperature compensation that you have it moving the focuser during a sub, or between subs based on a temperaur compensation model. Firstly it has to have more or less zero lateral movement for in sub moves to work, and I spent quite some time training temperature compensation once and used it in lieu of regular focus runs and found that it was hard to make it's reaction match the reaction of the scope, it would generally lead or lag the scopes focus drift. Add to that a cell of cool or warm air rolling through at the right time could trigger a compensation move when the change was transient and the scope essentially rode through it without reaction, instead of improving focus you would get an out of focus sub.
Thanks noted - haven't tried any automate focus routines yet - as focus seems to be help excellently - but that may be my inexperience.
Using a mono camera plus filter wheel I was pondering just focus on Luminance - and have offsets calculated for all other filters, so when I image a target start on Lum - focus, then do all imaging and only either on 1)_ next target or 2) 1-2 hours or 3) temp change > 4 degrees do another automated Lum focusing routine.
I don't do mono (Yet) but for instance SGP does do filter offsets, so you can focus on Lum with an offset applied (That you need to work out for yourself) for each other filter, though RGB filters should be easy to focus through, NB filters can be tougher.
Target change, elapsed time, and temp change are all good triggers, also possibly filter changes as well as otherwise you might find it changing filters then promptly going back to LUM to focus as it was nearly due on one of the other filters. How many degrees temperature change to trigger a focus run is something you need to work out on a scope by scope basis. My SCT just about needs it every half a degree but my SVX80 probably only needs it every couple of degrees. I do that one at sequence start, every two degrees, on pointing change, on meridian flip and once per hour.
I've been working on hacking my Meade Microfocuser to get it working with my ZWO EAF, so I could course focus the SCT, lock the mirror, then use the microfocuser to manage the fine focus during the imaging session.
I dismantled it, removed the existing DC Motor and bracket (cable still attached), removed the gear from the crayford shaft, and was able to mount the EAF directly to the shaft.
The shaft turns about 275 degrees (or so) for the full travel of 1/2inch.
With the EAF giving 5760 steps per rotation, that gives me a range of 4400 steps to work with, which is plenty, and didn't need any gearing.
Was able to get the ZWO bracket mounted by replacing one of the screws that holds the crayford carrier down (at the far end). Not sure the size of that - I happened to have a thumbscrew that was the right size and just needed a little spacer.
I had 3D printed a case (well the first half of the case) from a model someone uploaded on CloudyNights, but for now, I don't think I'm going to bother with a case.
I can't gauge performance yet, as I'm still waiting for an adapter to arrive so I can de-fork the SCT and mount it on the EQ6, but it looks like it's going to be a nice solution.
In a nutshell, for no money (I had already bought the EAF previously for use on my 80ED), I've managed to get a focuser for the SCT which can now by run up on an EQ mount.
And, the entire process is completely reversable - nothing was cut or damaged, and I can put it back how it was if I ever wanted to sell the scope and put it back on the forks.
I don't do mono (Yet) but for instance SGP does do filter offsets, so you can focus on Lum with an offset applied (That you need to work out for yourself) for each other filter, though RGB filters should be easy to focus through, NB filters can be tougher.
Target change, elapsed time, and temp change are all good triggers, also possibly filter changes as well as otherwise you might find it changing filters then promptly going back to LUM to focus as it was nearly due on one of the other filters. How many degrees temperature change to trigger a focus run is something you need to work out on a scope by scope basis. My SCT just about needs it every half a degree but my SVX80 probably only needs it every couple of degrees. I do that one at sequence start, every two degrees, on pointing change, on meridian flip and once per hour.
Only SGP flat out refuses to connect to JMI as it is not appearing as an absolute focuser - so SGP doesn't enable any wiggle room with this focuser
