How to check if focuser is broken??

[04Stefan07 (Stefan)]

When I focus my scope it seems that it goes out of focus on its own?? It's hard to explain.

Example: I targeted Saturn and focused it but it feels like once I focus it and let go it goes out of focus.

I think I will take the scope to Bintel and get it looked at. I got a feeling I did something when I took the knob off and pushed the focus in by accidently.

[AG Hybrid (Adrian)]

Not difficult to explain at all. My crayford focuser used to slip as well under heavy weights. Most focusers like a GSO or Synta scope has a set screw at underneith. Tightening the set screw raises the draw tube above the crayford style focuser knob reducing friction and resistance, which can cause focus slip. Loosening the set screw brings the draw tube closer to the focuser knob/axel thingy and increases friction.

This is of course only relevant to a crayford style focuser. You didn't mention what scope this is for? If its a Skywatcher/Orion I can guess almost immediately what the problem is. If its GSO. Not so much.

[04Stefan07 (Stefan)]

Originally Posted by AG Hybrid

Not difficult to explain at all. My crayford focuser used to slip as well under heavy weights. Most focusers like a GSO or Synta scope has a set screw at underneith. Tightening the set screw raises the draw tube above the crayford style focuser knob reducing friction and resistance, which can cause focus slip. Loosening the set screw brings the draw tube closer to the focuser knob/axel thingy and increases friction.

This is of course only relevant to a crayford style focuser. You didn't mention what scope this is for? If its a Skywatcher/Orion I can guess almost immediately what the problem is. If its GSO. Not so much.

Sorry it's a 127 SLT MAK.

[raymo]

Maybe you have mirror flop. Make sure when you do the final fine
focussing adjustment that you are pushing the mirror up against
gravity,[turning the knob anti-clockwise], assuming that you have the standard focuser. You can tell if you have flop by turning the knob
back and forth, and see how much turning is required to to reverse
the focuser's effect. If there is excessive slack, it needs fixing, or
you just live with it.
raymo

[04Stefan07 (Stefan)]

Thanks for the replies.

I took the OTA to Bintel on the weekend and they checked everything in the OTA and they said that there's nothing wrong with it which was good news to hear!