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Play in focuser.

wookie1965

By wookie1965
in DIY Astronomer

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wookie1965

wookie1965

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Bought a second hand Meade LXD55 127 F9. 3 Achromatic telescope, the focuser was ropey at best think it needs Teflon strips but there is a lot of play in it as you can see from the video anyone got any ideas please.

I've stripped it down and used lithium grease other than that I have no idea.

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wookie1965

wookie1965

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5 hours ago, Dr_Ju_ju said:

Are there any grub screws opposite or 120 degrees away from the rack, that could be adjusted ??

No nothing I looked online because the explorer scientific and the Bresser are very similar they showed grub screws this has none. It does need a new Teflon strip but where to get them, measuring the old one its 2mm thick so new would need to be at least 3mm I would think.

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Gina

Gina

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Looks like the focuser tube just runs in the scope with no bearings of any sort or PTFE strips or anything to reduce the friction.  Could you take photos of the inside of the telescope where the focuser fits and also the focuser itself from both sides?

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wookie1965

wookie1965

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The focuser fits over the OTA held in place with 3 screws, Inside the focuser tube you have the gap for the gear teeth to go down on the opposite side are two very small pieces of what I think is black teflon which look worn other than than that there is nothing inside the tube.

20180709_122630.jpg

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wookie1965

wookie1965

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27 minutes ago, Chriske said:

I'm puzzled : How is the focusing tube held in place in the focuser... iow exactly in optical axis...?

I am assuming its the brass plate behind where the 4 screws are, 33 seconds into the video  That is all I can think of not the best built focuser.

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Gina

Gina

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55 minutes ago, Chriske said:

I'm puzzled : How is the focusing tube held in place in the focuser... iow exactly in optical axis...?

I don't think it is.  It's total rubbish IMO.  If the scope is worth it, I would replace the whole focuser.  It might be possible to glue some thin PTFE sheet into the tube but it's never going to be very good - sorry.  If I had that problem I would either rebuild the focuser with small ball bearings at 120° to the pinion, 4 of them to provide the necessary rigidity or replace the whole focuser.  I have repaired focusers in the past but I had a much better one to start with.

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wookie1965

wookie1965

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5 minutes ago, Gina said:

I don't think it is.  It's total rubbish IMO.  If the scope is worth it, I would replace the whole focuser.  It might be possible to glue some thin PTFE sheet into the tube but it's never going to be very good - sorry.  If I had that problem I would either rebuild the focuser with small ball bearings at 120° to the pinion, 4 of them to provide the necessary rigidity or replace the whole focuser.  I have repaired focusers in the past but I had a much better one to start with.

Its terrible I know just from taking it apart but I have never done anything like this before so I am snookered, my friend has said he has a Skywatcher one if I am interested just dont know whether it would fit straight on or I would have to get some plate made either way I am up a creek without a paddle.

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Chriske

Chriske

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28 minutes ago, Gina said:

I don't think it is.  It's total rubbish IMO.  If the scope is worth it, I would replace the whole focuser.  It might be possible to glue some thin PTFE sheet into the tube but it's never going to be very good - sorry.  If I had that problem I would either rebuild the focuser with small ball bearings at 120° to the pinion, 4 of them to provide the necessary rigidity or replace the whole focuser.  I have repaired focusers in the past but I had a much better one to start with.

+1

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Gina

Gina

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It looks like it would be very difficult to fit another focuser to that scope.  And TBH if the focuser is that bad I don't have much hope for the scope.  I hope you didn't pay much for it.

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wookie1965

wookie1965

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17 minutes ago, Chriske said:

Someone could print a new focuser for that scope...?

:wink2:

Not sure I have sent for a sheet of Teflon 2mm thick and getting a diagonal with a helical focuser should help fingers crossed.

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