autofocuser advice/recommendation

[MishMich]

I need to get a motorised focuser. I have an 8" OO SPX, and getting the focus right is a problem, especially on planets, as no matter how careful I am, the image jiggers - especially when I am trying to look at the laptop wich is about 1.5m away, with me looking away from the focuser. I also have a Celestron Onyx 80 ED, which is not such an issue.

However, the knobs on the SPX focuser fit the Onyx & vice versa - so anything that fits the Onyx will fit the SPX. I understand that the Onyx and the Equinox are much the same, part from the Onyx having a single-speed rather than a dual-speed.

I don't want to spend £500 on a new unit. I don't mind replacing the SPX focuser if it means I can add dual-speed and autofocus, and use the autofocuser on the Onyx as well if I want.

The shaft on which the knobs sit is appx between 4 & 4.5mm diameter - not 8mm. The knobs attach using a hex nut embedded in the shaft of the knob, which tightens against the shaft itself, the knob shaft acting as a sleeve around the shaft which ends up flush against the nylon spacers that sit either side of where the optical tube runs through the focuser. That is, the knobs do not screw into the end of the focuser shaft.

From what I can make out, that means that the Orion and Skywatcher autofocusers won't work - but I find that suppliers seem a bit cagey about what will or won't work with what. Does anybody happen to know of an autofocuser that will work by attaching to the shaft of a crayford as just described? And who supplies them?

M.

[russ]

Out of the box, the Autofocuser will work with the R&P focusers and the basic single speed crayford as fitted to the new Explorer models. I suppose if you are handy with metal work, you could knock up some sort of adapter plate to make it fit. But out of the box, the two plates supplied will not work with the Onyx focuser.

Also, there is no clutch with the Autofocus, so manual focus is completely disabled. Again, i suppose you could replace the grubb screw with a thumb screw and disengage the electric focus when needed.

I went through the same thought process and in the end (because i'm rubbish making things) decided i really needed that electric focus more than anything. So ripped off the Orion Optics Crayford and fitted the basic single speed Synta crayford to my scope and the Autofocus. It was a great decision to be honest. The basic crayford has zero image shift, so nothing to be gained from a more pricey model and focus is dead smooth with the Autofocus. No jitters anymore.

Regards

[MishMich]

Hi, yes, I just looked at the installation manual for the Orion Accufocus, and fitting the plate would be a problem. I guess I need to replace the focuser. Shame, I just reconditioned it...

Did the Synta crayford fit OK? Or did you have to drill out new holes? Do you have a link to what you got / where you got it?

M.

[russ]

Fitting was a complete nightmare. If only it was just the mounting holes that needed redrilling. Had the recut the centre hole on the tube and redrill the mounting holes. And all with no adequate tools. Only thing i had was a junior hacksaw blade. Took forever!

This is the one i fitted:

Skywatcher - Skywatcher Newtonian Focuser 1.25/2 inch

There maybe a mounting kit available now but i don't think so.

[MishMich]

What a shame. I was on the point of placing the order. How did you deal with swarf & dust? Did you remove the mirrors first, or what? I take it the fuocuser tube on the Synta crayford is wider than the hole it needs to go through on the SPX? by how much, out of interest?

Presumably the original OO focuser wasn't a Synta - maybe it was GSO? Wondering if a GSO focuser would work, and if they have some type of autofocuser.

M.

[MishMich]

JMI do an autofocuser for the Onyx, I'm wondering if one of the two for GSO newtomian crayfords might work for the SPX. A more expensive solution - but I'm not keen to start gouging out a bigger hole in the SPX just yet.

M

[russ]

The OO Crayford footprint is more or less the same size as the Skywatcher R&P. But the Skywatcher Crayford design requires a centre hole on the tube to be made approx 10-15mm larger. A lot of people have done it and seemed to have absolutely no problems. As with any job, having the right tools is key. When your toolkit consists of a hammer, 2 screw drivers and a saw, your never going to have the right tool. I still have no idea what that right tool would be.

I know Ant and Jeppeto have done this job with no major fuss.

I did remove everything from the tube and then washed (hosed) the inside of tube afterwards to make sure there was no debris left.

Amazingly it does look a good job.