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Simple filter size question.....

Skipper Billy

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Skipper Billy

Skipper Billy

Posted
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I have a nosepiece advertised as threaded for a 2" filter - I ordered a filter advertised as 2" - the filter has arrived and says 48mm on the side and is too small.

Is there some secret convention??  Am I being thick ???  The only two options to choose from were 2" or 52mm - by my reckoning 52mm is bigger than 2"

Maybe I been sent an option that isnt advertised ??

I have emailed the retailer but not heard back yet - not that I expect to on a Sat. night !!!

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steppenwolf

steppenwolf

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48mm is the standard thread of a '2 inch' filter  - the 2 inches refers to the outer diameter of the filter so, of necessity, the filter thread must be less than two inches as the filter's thread has to fit inside the eyepiece's nosepiece. You are most certainly not being thick! What is strange, though, is that it appears to be too small in diameter!

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Skipper Billy

Skipper Billy

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Thanks for the clarification Steppenwolf.

The filter is this one......  http://www.firstlightoptics.com/uv-ir-filters/idas-heuib-ii-uvir-blocking-filter.html

and its supposed to screw onto this ..........http://www.firstlightoptics.com/adaptors/flo-adapter-for-skywatcher-focal-reducers.html

But it 'dizz nae' !!!

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Thalestris24

Thalestris24

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Hi

I don't have either of these but it looks like the filter should screw into the rh opening as shown in FLO's pic. The baader mpcc similarly has a 2"/48mm filter thread and I have a 2" lp filter screwed into mine :) Um, does your filter have 48mm printed on its edge?

Louise

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Thalestris24

Thalestris24

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Hi

Well you only need to see if they (filter and adapter) are pretty much the same. If one is, say, 5mm smaller (or bigger!) then that will tell you where the problem lies :) For example, I just looked at a 2" nb filter with a ruler and it's clearly 48mm across on the thread side.

Louise

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Floater

Floater

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Billy, off thread (no pun intended!), I know, but I just loved 'dizz nae'!

Would, of course, personally opt for the traditionally accepted Scots 'disnae'. But, for our international audience, who knows what's best?

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Skipper Billy

Skipper Billy

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OK -

The outside of the male thread on the filter is 47.82mm

The inside of the female thread of the nosepiece is 48.02mm

So the two threads miss each other completely and give 0.2mm slop.

I would have expected the numbers to be the other way round as the threads should interlock.

Cheapo chinese digital calipers but somewhere between .25 and .5mm slop seems about right.

Any ideas which part (or both parts) is incorrect ????

It disnae fit!!!  (@Floater ;-)  )

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Charic

Charic

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That's going to be an expensive paperweight unless you get it sorted soonest, It  sounds like you have received a  manufacturing error, or as is sometimes  still possible, user error, but I'm sure  thats not the case?

The longer nights are back with us again, now that Summer has gone, did it really arrive! Oh Yeah, I remember now,  about three Weeks worth of Thrips? Just wish the weather would move over to France - nothing against France mind you, so long as it clears from Scotland for a while.

Hope you get sorted soon Skipper!

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steppenwolf

steppenwolf

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I'll send you some waxed hemp from my McCallums so you can make up the difference :grin:

I've just measured my Hutech IDAS LP filter threads using my cheap Chinese calipers  :grin:  and they come out at 47.74mm and for reference, I have used the same calipers to measure the inside thread of one of my frequently used focal reducers and it measures 47.26mm which is about what I might expect (i.e. smaller!). The difference in our two filters is just 0.08mm (smaller than yours) yet it is a good fit in the disparate range of components that I use it on.  IF our two calipers are to the same accuracy (mebbe yes, mebbe no) this would indicate that it is the reducer that is out of spec. but either way, it is a most unusual circumstance.

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Thalestris24

Thalestris24

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Hi

I recently bought a 2" filter wheel. Try as I might I couldn't get any of my filters to screw in - the carousel holes were just a bit too small. So had to send the fw back. When you think about it, you only need a small mismatch to create a problem.

Hope you get it sorted

Louise

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Earl

Earl

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Does it slop if you fully tighten it, there should be a little play with thread and filters so they dont thread lock but should tighten when fully threaded together as the slack is taken up.

Do you have the 2" eyepiece or diagonal that comes with the ED80 to try the filter in?

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Skipper Billy

Skipper Billy

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10 out of 10 to FLO - new nosepiece/adapter on its way - tested with a 2" filter.

Seems like its not an uncommon issue - http://stargazerslounge.com/topic/228992-2-filter-is-just-barely-too-small-for-2-diagonal/

Surely a M48 thread should be the same in Japan, Germany, China, UK etc etc ..................

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