Focuser Backlash with Skymax 127 Mak

[Tony Connor]

Hi All,

Is their any way to adjust the backlash (5-6 turns) on the focus knob on the Skymax 127, it is a brand new scope so I’m on the brink of returning it unless there is an easy fix or I’m missing something. TIA.

[johninderby]

Try turning the focus knob all the way it can go in one direction then the other. Repeat a couple of times and it should sort it. The grease they use on the focusing mechanism isn’t always evenly ditributed and doing this will spread the grease out evenly. 

That’s assuming the focus knob isn’t loose of course.

Edited July 15, 2020 by johninderby

[Tony Connor]

14 minutes ago, johninderby said:

Try turning the focus knob all the way it can go in one direction then the other. Repeat a couple of times and it should sort it. The grease they use on the focusing mechanism isn’t always evenly ditributed and doing this will spread the grease out evenly. 

That’s assuming the focus knob isn’t loose of course.

Thanks for the reply John...I tried this but no change, it’s as though whatever moves the Focuser is not meshed correctly?

[johninderby]

I suppose the focuser shaft could have become detached.or partly detached. 🤔

Being a brand new scope would just return it. Probably a simple fix but I wouldn’t take the back of a new scope to find out.

 

Edited July 15, 2020 by johninderby

[Captain Scarlet]

5-6 full turns on the focus knob is huge. I'd expect backlash as such to be of the order of a quarter turn. It sounds to me as if the threaded rod which the focus-knob pulls up and down is not properly fixed at its other end to the buttress-plate behind the primary mirror. If that's the case, it may be the rod will become separated from it in due course, in which case the threaded rod will be flopping around inside the tube and potentially spreading the evil black grease with which it's covered. I'd definitely send it back I'm afraid.

For an idea of what's going on behind the focus-knob, take a look at this thread, which although about my Skymax 180, is more or less the same focus design. But as John said, definitely do not take it apart, you may well invalidate any warranty.

Edited July 15, 2020 by Captain Magenta

[Tony Connor]

6 minutes ago, Captain Magenta said:

5-6 full turns on the focus knob is huge. I'd expect backlash as such to be of the order of a quarter turn. It sounds to me as if the threaded rod which the focus-knob pulls up and down is not properly fixed at its other end to the buttress-plate behind the primary mirror. If that's the case, it may be the rod will become separated from it in due course, in which case the threaded rod will be flopping around inside the tube and potentially spreading the evil black grease with which it's covered. I'd definitely send it back I'm afraid.

Thanks for that Magnus, I’m definitely leaning that way. 👍🏻👍🏻

[johninderby]

This vid of the insides of the Orion 127 mak which is the same scope as the Skymax 127 might be interesting.

 

[Captain Scarlet]

Christ! How NOT to take apart a mak of that design. I wonder how many have done what he's done and seriously damaged their mirrors as a result. He's basically pulled out the inner baffle tube from the outer, on which the primary sits, leaving the primary to hang off the focus rod inside. As soon as he takes off the focus-knob assembly, the primary collapses on to the corrector plate. I think there's a similar one with the mak 150 where the primary gets chipped in the process.

[johninderby]

I think they call it cack-handed. 🙀

Synonyms for cack-handed

• awkward, 
• butterfingered, 
• clumsy, 
• graceless, 
• ham-fisted, 
• ham-handed, , 
• heavy-handed, 
• maladroit, 
• unhandy

[Louis D]

I've got two Synta 127 Maks, one Orion branded, one Celestron branded, and neither has any focus backlash and both were well used when I bought them.  I would return that scope straight away as that is not right to have focus backlash like you describe.

[jambouk]

Have you observed the primary and seen that it doesn’t move for the first 5 turns? If it really doesn’t move the primary, send it back or talk to them first.

[Tony Connor]

Thanks for all the replies chaps, I’ve sent it back and asked for a replacement 👍🏻👍🏻

[sputniksteve]

What is focuser backlash?

[Louis D]

27 minutes ago, sputniksteve said:

What is focuser backlash?

When focus doesn't immediately change when focus direction is reversed due to slop in the mechanism.

[sputniksteve]

Thanks.