15mm EP thread cleaning for filters

[Knighty2112]

I have  15mm Vixen LV EP which I bought off Astroboot a few months ago. It's a great EP for viewing with, and used it mostly for whole sun views of the Mercury transit yesterday. My issue with it is I have some coloured filters that I use for mostly planetary views (although I used them yesterday too on the sun to aid views etc), but some of the filters I have when I screw them in to the EP either won't go in correctly, or get tight halfway in when threaded in. I've checked the internal thread on the collar of the EP and that seems OK, with no obvious burrs, or signs of cross threading. I've also tested out the filters that has this issue with the 15mm EP in all my other EP's and don't get any issue when I thread them in to those EP's at all. I think the issue maybe the black paint/coating applied to the thread on the EP is making it tight for the EP's themselves, and due to manufacturing tolerances in sizes some filters will thread in OK, and others don't.

My question is is there a simple way to get rid of the black paint in the EP metal collar (only the first 3mm where the filter screws in). If I got some paint stripper and sat the collar in a dish containing some 3mm of solution will this dissolve the paint away OK? The only other issue with the EP is on most of my other EP's the metal collar that the filters screw into can actually be unscrewed from the EP itself. On the Vixen EP if I try to unscrew the collar it also starts to unscrew some of the lower lenses in the EP, and so don't want to unscrew the collar if this might damage the EP by dislodging any internal lenses or other components of the EP itself.

Anybody ever tried to clean away this black paint on their EP's before succesfully if they had similar issues? Any advise is welcome.  

[Mak the Night]

What make are the filters? Not all of them thread onto every adaptor thread. My Celestron, TV, Lumicon and Baader filters all fit this Celestron adaptor (below):

But my Lumicons and Celestrons won't thread entirely into my William Optics diagonal even though the Baaders do. My TeleVue Bandmate threads perfectly well onto TV eyepieces, some of my diagonals and the adaptor above, yet my Lumicon filters won't thread entirely onto any TV eyepieces but fit beautifully on my Omegon, Orion and TS Optics diagonals.

This filter thread discrepancy is a known problem.

 

[Knighty2112]

I have 4 Seben filters, and 4 Antares filters too which I just bought from a member on here. There are 2 from the Seben filters, and 2 from the Antares ones that have this issue, some just having tight spots, and a couple that won't screw in correctly after the first quarter turn or so. They are not a problem with any other EP which are a very assorted mix of EPs from Celestron Omni's, William Optics EP, Skywatcher plossl, and TMB planetary II EP (and numerous stock EPs too).

[Mak the Night]

23 minutes ago, Knighty2112 said:

I have 4 Seben filters, and 4 Antares filters too which I just bought from a member on here. There are 2 from the Seben filters, and 2 from the Antares ones that have this issue, some just having tight spots, and a couple that won't screw in correctly after the first quarter turn or so. They are not a problem with any other EP which are a very assorted mix of EPs from Celestron Omni's, William Optics EP, Skywatcher plossl, and TMB planetary II EP (and numerous stock EPs too).

Yeah, it's weird problem that I have difficulty getting my head around sometimes. At first I thought it was some problem with the filter thread either on the filter itself or the eyepiece/diagonal. I've since discovered that TeleVue and Lumicon filters have a reputation for not being totally universal. I just checked my Bandmate and it threads onto three of my diagonals including a WO and an Omegon. My Lumicon OIII fits the Omegon and TS Optics diagonals perfectly yet won't properly thread on the WO diagonal. I have no explanation for this. I have a feeling that there are three basic filter thread types but only two types are mutually compatible.

[ronin]

Unfortunately not all threads are the same so you will find that at times you get an eyepiece and filter that are incompatible.

Likely done so that you "had" to buy their filter for their eyepiece, but that rarely works and people did not buy the eyepiece again and neither the filter. I actually have the vague idea that at some stage (quite a few years ago now) one of the bigger manufacturers changed from their custom thread to the more universal one. It helped sales.

You may (just may) be able to buy a holder and swap the filter over, sure I have seen threaded filter holders somewhere - maybe TS (?). But I would not attempt to remove the paint from the threaded section, reflections and scatter would likely increase.

[Dave In Vermont]

If it threads (screws) in part way - leave it at that. As long as it's square, it only needs to be secure enough to not fall out. Other than that, you could get a machine-shop to cut new threads. Or you could buy a thread-chaser and cut your own.

Or just forget about using the combinations that don't work. A filter-wheel is another possibility.

I've had some that only would thread in part-ways. I don't think it has to do with the manufacturer. It seems to be a common problem when the thread-cutter being used at "X,Y,Z Filter Co. Ltd" hasn't been sharpened in awhile.

Good luck-

Dave

[Mak the Night]

8 minutes ago, Dave In Vermont said:

I've had some that only would thread in part-ways. I don't think it has to do with the manufacturer. It seems to be a common problem when the thread-cutter being used at "X,Y,Z Filter Co. Ltd" hasn't been sharpened in awhile.

 

I thought that this might explain some discrepancies, but the whole phenomenon doesn't make any logical sense in my experience, as there seems to be no continuity to the experience. I have filters which thread perfectly well into almost everything, yet the object they won't thread into accepts other filters perfectly fine. And I've never known a Baader filter not thread into anything! Weird.

[Dave In Vermont]

Must be a Poltergeist. Have you tried an exorcism? Or, maybe, the Gremlins who steal socks from the wash have run off with the missing threads.....

Cursed paranormal-phenomenology -

Dave

 

[Mak the Night]

I'm going with the filter thread gremlins!

[Knighty2112]

Thanks guys. Not a real big issue, but was just bugging me more than anything. Mostly the filters are used with the higher magnification EP's I use. It was only from yesterday when I tried using just a yellow filter to aid viewing of the transit that I really noticed this issue. Going to live with it rather than worry too much about it. A filter wheel is an option, but not something I'm planning to get for now. All my other EPs don't have an issue with all my filters, it just the Vixen one only. 

Cheers!  

[Knighty2112]

Just tried the wiggle test. On a filter that screws in OK on both the 15mm EP and a 6mm EP used as an example that has no issues with any filters, I've noticed that on the 6mm EP when the filter is screwed in, before it reaches its fully screwed in position there is a slight but pronounced wiggle that you can give to the filter when it is in the the screw thread. On the 15mm Vixen EP with the same filter, even though it screws in fully OK, there is hardly any wiggle at all (a fraction of what happens on the 6mm EP). The issue at least in my case seems to be that the 15mm Vixen EP has a slightly smaller and tighter screw thread in the collar than any of my other EP's. On further testing it also seemed to get tighter the deeper the filter is screwed in.

[Mak the Night]

Wiggling could do it lol.

[John]

Sometimes the action of fitting a filter to the eyepiece starts to remove the matt black coating on the inside of the lower part of the eyepiece barrel. One manufacturer (Pentax I think) actually mentions this in the eyepiece instructions and says that the initial threading of the filter will be tighter than subsequent ones and also warns you to watch out for small flakes of the black coating getting on to the lower lens surface of the eyepiece after using a filter.

 

 

 

[Mak the Night]

From what I can gather Baader utilise M28.5x0.6 threads for their 1.25“ filters. But there are adaptors for other sizes, so this may explain some of the discrepancies, or not. lol

http://www.amazon.com/M28-5x0-6-female-M49x0-75-adapter-filters/dp/B00OHXAMFO

All three of my Baader filters: ND 0.9, Neodynium & UHC-S fit every thread on every eyepiece and diagonal/adaptor I own.