Motor Focuser fixing points on an Esprit 150?

[BlueAstra (Graham)]

Does anyone know the correct mounting points for a motor focuser on an Esprit 150? Looking at the bottom of the focuser there are four slotted screwheads that seem to be set in concrete. Are these the best place? Also how do you get the focuser knobs off. The x10 knob comes off easily by undoing a screw, but there are no obvious screws for the large knobs. Again they appear to be set in concrete if you pull them. The focuser is a Pegasus cube on an L bracket.

[Ukastronomer (Jeremy)]

There isn't any hence I assume you have read my post ???

http://www.iceinspace.com.au/forum/s...d.php?t=174808

For me othing worse than having a fixed focusser with no access to quick manual focus

Synta told me you have to remove the micro focus knob and the other one from the other side and dissemble the whole unit, sod that, the only other way is to remove the 4 screws and make a plate and use longer screws on the base

[Ukastronomer (Jeremy)]

I have since modded this which has a much better mount

[that_guy (Tony)]

You can also mount it to the top of the focuser as well. Borrowed the design from Mike (Spartacus). I had it originally mounted to the bottom of the focuser like you'd normally but I found that taking it off and on was a huge pain. When you undo the screws at the bottom, the whole focuser assembly sorta comes off and having to retighten it just right every time was a hassle. This was for the ED100 and ED120 esprits but I'm sure the ED150 would be the same. Just larger. If you don't plan on taking the autofocuser off, than the bottom of the focuser is more stable and rigid.

[Ukastronomer (Jeremy)]

Originally Posted by that_guy

You can also mount it to the top of the focuser as well. Borrowed the design from Mike (Spartacus). I had it originally mounted to the bottom of the focuser like you'd normally but I found that taking it off and on was a huge pain. When you undo the screws at the bottom, the whole focuser assembly sorta comes off and having to retighten it just right every time was a hassle. This was for the ED100 and ED120 esprits but I'm sure the ED150 would be the same. Just larger. If you don't plan on taking the autofocuser off, than the bottom of the focuser is more stable and rigid.

How do you access manual focus

[that_guy (Tony)]

with the motor turned off, you can freely rotate the focuser manually. The fine knob is on the otherside.

[BlueAstra (Graham)]

I have now managed to attach the Pegasus Motor Focuser to the Esprit 150. With the help of the focuser patent drawing I was able to identify some of the features on the bottom of the focuser:

A – Threaded hole for grub screw. Not sure what this is for other than to hold a spare screw for the knob fixing screws. If you screw it right in then it hits the spindle and locks it.
B – Access hole for knob locking screws. Rotate the knob until the screw is visible, loosen screw and pull off the knob.
C, D – Not sure what these are other than to hold the spindle assembly to the focuser barrel.
E – Screws to hold the bearings (12 on patent drawing) which grip the metal plate attached to the barrel.
F – Tension screw which controls the pressure of the spindle against the metal plate
G – Locking knob (221) which clamps the barrel plate and prevents any movement of the focuser.

I wanted to remove the coarse knob to attach the motor focuser. However, it was stuck and would not remove easily. I removed the x10 knob (easy), loosened the tension screw F and withdrew the spindle with the coarse knob attached. I put the spindle in a vice (taking care not to grip the plate contact area) and twisted the knob off. Once off it went on and off quite easily, so something must have been holding it. I then re-inserted it into the focuser, re-attached the x10 knob and re-tensioned screw F. I now had a bare end of the spindle to attach the focuser to.

I offered up the motor/L bracket and found the L bracket was too long. It interfered with the locking knob G. I removed some material to avoid the clash. I then set the motor position on the bracket and secured it. I removed two M3 screws at C and used two longer screws with washers to secure the L bracket. A locking cylinder connected the motor to the focuser (a selection is supplied with the motor).

I connected the temperature sensor, 12V power and USB cable, and I can now control the focuser through its own app, or via Ascom in other programs. The motor is too stiff to allow manual focus via the knobs. You can get a manual control box but it’s quite expensive. I am currently trying to take out backlash by adjusting F, although there is backlash control in the software. I’m not familiar with focuser construction, but I was surprised that it operates by pressure of a bare metal spindle on a flat metal plate. I thought there would be some friction material between them. It remains to be seen whether it can cope with large camera loads at high declination. If not I may have to upgrade to rack and pinion.