Baader SteelDrive Driver Discussion

[BlueAstra]

It was a digital vernier caliper. Oh, and I can't subtract, the errors in start position are 0.27, 0.18, 0.31mm, not 0.02. I suspected it might be backlash, but wasn't sure. It seems to be happening in one direction only though, and its variable. So I wonder, what do I enter as the backlash value? Does it matter its in one direction only?

I rather suspect its actually focus creep with the weight of the imaging rig (2.6kg), and the stepper motor is missing 'steps' on the inward leg where it is fighting gravity with the weight of the rig. Stepper motor not man enough for the job? There are some adjstment screws on the bottom of the focusser but I don't know what they do. Maybe they need to be tighter (or looser?). I initially tried the focus offsets for filters and it worked quite well, but if it doesn't go back to the same place its not usable.

Graham

[ianaiken]

Graham,

I did some tests with my SteelDrive here and I cant replicate your problem so I suspect it is weight related. I'm going to try tomorrow with the roof open and scopes pointing up to see if I can reproduce what your seeing. It is one way maybe due to slippage on the inward journey.

The scopes now in the OBS so I can't check which screws to tighten, I'm popping out shortly to do some measuring up for a bench so I will see if I can figure it out.

I know your using temp compensation and also filter offsets to skip having to focus, but would you still not run an auto focus routine anyway?

[ianaiken]

Graham,

I lack a digital vernier caliper so I can't measure the precise distances. If you keep going outward then inward 1000 steps do you ultimately end up being ~0.2mm further out each move cycle? I just put my focuser out and in more than several times and by eye it looks bang on each time, and my eyes have a decent tolerance. It looks like by your results that after 10 move cycles you would be a full mm out. I'm not seeing that but that's horizontal with only a reducer, extension tubes and QHY8L attached.

As for the screw under the focuser I think it's similar to a SW crayford so ultimately you want to tighten the big center one ever so slightly while loosining the outer ones or something along those lines. It's probably easier to reduce the weight on the end of the focuser and test again, then if it doesn't happen see about tightening up the drawtube to see if you can reduce the focuser backlash that may be present.

And it's raining but at least I'm playing with kit

[BlueAstra]

The focusser was pointing down about 45deg when I did the test, with the scope in its park position. From the previous measurements it would seem that it should gradually creep out by about 1mm with 5 iterations of 1000 steps, but I haven't verified this. It had moved 0.76mm in 4 steps. Will have a go at it. I'll also move the scope so the focusser is horizontal to try it without the 'gravity' effect, or maybe even take the whole camera rig off. I've been using the centre 'knob' on the bottom of the focusser as a locking knob, so it is quite tight at the moment. If I loosen it too much the focusser slowly defocusses.

I tried the autofocus routine in Maxim and it tried to produce a V curve, but failed (too many exposures, and a very wobbly curve). I'm fairly sure I've entered the correct numbers in the setup screen so maybe its the tension or the creep that confusing it. I'm a bit of a novice at this side of things, but I'm not sure you can set up a 'routine' to autofocus after each filter change in Maxim. I think CCD Commander can do that sort of thing.

BTW this is the vernier caliper I have. I think I got mine from Aldi for a similar price.

Graham

[ianaiken]

Hi Graham,

The centre knob that sticks out underneath is the locking knob, there should be a Allen key bolt beside that which is the one that needs tightening along with two black screws I think that also need adjusting. The knob that sticks out will not actually provide more pressure on the pinion it will just make it slip more. (Apologies if you meant the Allen key bolt just ignore me) I'm know for over tightening things so I would search for a guide on how to adjust a Crayford to stop slippage on the pinion by increasing the pressure.

Sequence Generator Pro can handle auto focus after each filter change, after a set amount of time, or after a certain temp change. Its very powerful. It can also do a meridian flip automatically and continue imaging.

[ianaiken]

Looks like the Baader website is now updated with the latest versions. So for SteelGo it is version 1.1.15 and it now comes with its own installer and install which installs to program files or wherever you choose. I've tested it out and it works fine without issue.

Although I am using ASCOM with Sequence Generator Pro I sometimes have to re sync the focuser, usually when the Steeldrive has been disconnected. Rather than zeroing it I just sync to absolute position using SteelGo. Pretty handy.

Overall, since the software issues have been resolved, I am very happy with the Steeldrive which I have now had chance to use for real in the OBS over the past clear nights we have had recently. It's work's very well with auto focusing routines and continues to work for the whole session. It's nice that I can use it with ASCOM for imaging, or with the hand controller when observing and manually if I wanted too. It's nice to do some manual focussing when observing and the SteelDrive allows for this.

I've not yet calibrated temp compensation yet but I will once I am able to sacrifice some clear sky and I get a decent enough temp change in one evening. This will save refocussing every x amount of temp change (which SG Pro supports very nicely) and ensure continual precise focus unless I really mess the calculations up

How is everyone else getting on?

[BlueAstra]

Hi Ian. Sorry not to get back to you earlier. I've not changed the software yet from my previous post. I find I have to connect Steelgo first to sync the absolute position (do you need to save to device?), close down Steego then open Maxim. I then have to select the com port in the Ascom chooser (everytime, why!!) then connect in Maxim. I can then nudge focus and even (once) autofocus. The problem now has moved to the 3" Baader focusser. Although the motor turns the knob, I think the focusser is slipping. Initially it would move out a distance, but moving back would not go back to the original zero (3kg load). I tightened the centre screw, which helped, but I'm not sure it's working properly. I tried autofocus, and it traced a V curve, but when it tried to go back to the minimum it missed, which I think is due to slippage. So working on that at the moment. Trying not to waste the few clear evenings fiddling with the focusser, since it sort of works. Will have a more detailed look on an indifferent night. I'll also try the new software out and let you know how I get on.

Graham