Lunt 60 help please on blocking filter

[sheri_barri]

Just discovered today that the blocking filter cap on the Lunt 60 seems to have unscrewed whilst using the double stack over time. Now the threads are not screwing back together to keep the blocking filter screwed into the body of the scope. There is no visible damage to the threads on either the filter cap nor the interior of the scope body but the two will not screw together. All recommendations and suggestions appreciated. I am afraid the scope cannot be used until this is resolved:(

Many thanks.

Sheri

[Merlin66]

I'd love to be able to help, but I've no first hand experience with the Lunts. Could you post a photo of the parts giving you the problem....if the threads look ok it maybe a simple fix.

[brianb]

Sorry to hear about your problem.

Lunt's customer service has a good reputation - have you tried e-mailing them?

[sheri_barri]

This is the area of fault. The threads when trying to screw the blocking filter on (which incidentally unscrews as the double stack is unscrewed from it to remove) never 'bites' and screws securely. It just keeps screwing round and round.

I've sent the photos off to Lunt as well and awaiting a reply. Hopefully positive.

All advice appreciated. Great weather today in Aberdeen... of course!

[Merlin66]

Hmmm

That's a very large diameter with a very fine thread..always a problematic combination. Could be that the threads are on top/ bottom tolerance and some slight wear has taken them out of spec.

IMHO I'd try and get it fixed via Lunt, but in the meantime either a couple of wraps of fine cotton in the threads of the filter holder section or a wrap of teflon tape might just provide enough grip to safely hold the parts together.

ken

[ollypenrice]

Yes, the old thread fix was always PTFE tape avaiable from plumbng supplies places. It does sound like a stripped thread.

Olly

[sheri_barri]

Hi Guys,

Useful suggestions, thank you. Hopefully Lunt come back today with something sensible or DIY it shall be!

Kind regards,

Sheri

[durr]

Sheri, I have just checked mine and the threads look pretty good and solid so not too sure what has happened there it sounds like you may have stripped the threads or some of them. When you unscrew the double stack make sure you hold the black part of the lens mount that is smooth, this prevents the screw unthreading every time you take off the DS. How bad are the threads and is there any grip at all?. If there is some grip then like the other guys mentioned PTFE tape will fix it. Steve

[ollypenrice]

A bit 'stable door after the horse has bolted' but a good trick when threading is to go backwards first, till you feel the start of the thread, then turn the right way.

Olly

[sheri_barri]

Hi Olly,

Cheers for the tip. I did try this as well and there is nothing... no start. It is really peculiar. No visible damage I can detect and no apparent thread start. It now behaves effectively like a push fit. There was no undue tightening during use, simply re-tightening the length of thread that had unscrewed while removing the double stack. Usually only one rotation, perhaps two. Odd. All suggestions welcome. So far PTFE and a rubber band are working in the meantime.

Cheers,

Sheri

[johninderby]

I've just taken a look at my Lunt 60. I can't detect any thread start myself, however it screws back in and locks really solid. No chance of it coming loose.

I would guess that the screwthread inside the tube may be a little over-sized, and while it may have been good enough when brand new it's only taken a bit of un-threading and re-threading to damage the thread enough to cause your problem. I have come across a couple of other scopes (not Lunt) that have had issues with a large diameter screwthread in the OTA not being cut properly.

John

[sheri_barri]

Hi John,

That certainly summarises the problem. What seemed fine for awhile suddenly... went. No indication of the problem developing. All smooth threading to that point.

Thanks for having a look at yours for comparison.

Cheers,

Sheri