Common Astro Equipment thread sizes

[Hagar (Doug)]

I have just purchased a small lathe and Milling machine to use to make some adapters for my gear and some modelling.
I have spent some time trying to find thread sizes and pitch for some common astro equipment to almost no avail.

It might be good to put together a table with some of the common thread sizes for items like, filter threads, SC rear cell threads, Standard Tak threads, Focuser threads and the list could go on and on.

If you know any thread sizes commonly used, please post them here and I will put them all together in a document and ask Mike to post it in the projects and articles section for everyones use.

Thanks in anticipation.

[wasyoungonce (Brendan)]

This is a most excellent idea.

Maybe with pics/drawings of the said items in question?

Edit:
Televue RFL-4087 focal reducer system threads is a M65 diameter (2.55") x 24 TPI (UNC).

Most finder illuminators are M8 x .75mm pitch thread.

Skywatcher reticule eyepiece illuminator is M8 x 1mm pitch thread.

Thumbscrews many many types here.

edit:

edited TV threads dimensions.

[Hagar (Doug)]

Thread sizes I have managed to find so far:

2" Filters 48mm x 0.6mm
1 1/4" Filter 28.4mm x 0.6mm

Meade Large SCT 3.25" 16TPI without adapter
2" 24TPI with adapter fitted

Celestron SCT 3.3" 16TPI without adapter
2" 24 TPI with adapter fitted

T Thread 42mm x 0.75mm

Takahashi 2.7" Focuser 72mm x 1.0mm
Takahashi Sky 90 55.9mm x 0.75mm

Atik 11002 Camera front 54mm x 0.75mm

QHY Filter wheel in and out 54mm x 0.75mm

Takahashi Finder scope light M8 x 0.75mm

Vixen VC200L Focuser rear thread 60mm x 0.75mm

GSO 8" RC rear cell 90mm x 1.0mm

Web Cam adapter M12 x 0.5mm

EQ6 Pro altitude adjusting screws M12

[[1ponders] (Paul)]

This sounds like a great idea Doug. Thanks for initiating it. I won't be much help except for another suggestion. Once you have the list together would it be possible to save it as an excel file so that it can be sorted. I see that as being very useful for working out which makes and models have the same threads so we know which ones are interchangeable.

[bert (Brett)]

Doug: I have owned 3 different vixen refractors of various vintages (ed80 f9, ed103s f7.7 and my current fl102) they all have the same drawtube thread as the VC200L (60 x .75).
Brett

[Astroman (Andrew Wall)]

Great work, will be very helpful in the future. Some I know of are the Centre bolt to attach an EQ6 to it's base are M12 also, the small pin that goes into the tripod either has an M8 or M10 thread, depending on how old it is. I believe that the newer models are M10.

If anyone can find out is is an M5 thread for a Skywatcher 8" f6 Primary Mirror Collimation? I'd like to change these to larger knobs to make it easier to collimate. PM if there is a commercial version out there... Sorry to hijack the thread Doug, I thought someone would know..

[peter_4059 (Peter)]

These might be worth adding to the list also...
http://www.scopestuff.com/ss_sizes.htm

http://www.scopestuff.com/ss_scops.htm

I also found:
T thread: M42x0.75
C thread: 1" 32 TPI
2" SCT: 2" 24 TPI
2" filter: M48x0.75

[Tandum (Robin)]

Pentax Thread = M42x1mm

What is the imperial thread they use on rings for camera attachments?

[JohnG (John)]

Takahashi threads on the FSQ-106ED:

Captains Wheel output thread M120 - 1mm

Focuser Moving Tube M96 - 1mm

End of Black Extension Tube M76 - 1mm

[David Fitz-Henr]

This is a fantastic post Doug - looking forward to getting hold of all the results. Unfortunately I have nothing to add yet as I haven't really done much with adapters / threads yet, but like you I have recently acquired a small lathe so should become very useful!

[Hagar (Doug)]

This is coming along nicely. If I don't get anymore in the next week or so I will put it all together in a spread sheet and post it here and ask Mike to make it a sticky.

Thanks Guys, Keep em coming.

[erick (Eric)]

My old Celestron C8 should have a 2" 24tpi thread. I have a GSO diagonal that fits, but two other GSO accessories (a straight-through 2" and a 2" Crayford focusser) that do not fit. All my reading suggests they are all nominally 2" 24tpi, but that thread tolerances were changed at some stage enough to cause this problem. My micrometer and thread gauge work suggests it is a thread depth problem. I am waiting to sit down with a machinist to work through all the threads, accuately measure them and see what we can adjust.

[peter_4059 (Peter)]

Originally Posted by erick

My old Celestron C8 should have a 2" 24tpi thread. I have a GSO diagonal that fits, but two other GSO accessories (a straight-through 2" and a 2" Crayford focusser) that do not fit. All my reading suggests they are all nominally 2" 24tpi, but that thread tolerances were changed at some stage enough to cause this problem. My micrometer and thread gauge work suggests it is a thread depth problem. I am waiting to sit down with a machinist to work through all the threads, accuately measure them and see what we can adjust.

I'm certain it is 2" 24tpi however I've found there are machining differences in these threads depending on who has made them (ie GSO vs Orion) I assume this is a quality control issue rather than a difference in thread design.

[[1ponders] (Paul)]

Another thread that would be useful to include but I don't know what it is, is the thread on the inside of a standard Orion/Skywatcher finderscope when you unscrew the eyepiece. Great for attaching a guidecamera

[EyeSpy (Mike)]

How about this one. It is a bit of a blast from the past but there is some suggestion that it may still be out there in some of the old brass telescopes.

RAS thread An obsolete standard for eyepiece barrels. It consisted of a screw thread 1¼ inches in diameter with a pitch of 1/16 inch, derived from a standard gas-pipe fitting. It was introduced by the Royal Astronomical Society (RAS), but was abandoned in the 1970s in favour of push-fit eyepieces.

I have to admit I still own a push-fit draw tube with this thread on the eyepiece end.

[Hagar (Doug)]

Here is a very basic spreadsheet of the thread list compiled from this thread.

[erick (Eric)]

Thanks Doug - filed away for future reference.

[wasyoungonce (Brendan)]

Digging up old thread.

I have some small additions maybe others might like to provide some known data or more threads to update this some more.

A work in progress.

edit:...forgot the file...now attached....I'd forget my head if it wasn't screwed on.

[MrB (Simon)]

I have just measured the threads on the new Baader MPCC mkIII Coma Corrector.

Front filter: M48 x 0.6
Stopper ring/collar: M48 x 0.6
Removable T2 nosepiece:
Front: M45* x 0.5, Back: M42 x 0.75
(*male measured 44.42mm OD, female 43.96mm ID)

Note on the filter thread, it is 48mm but my thread pitch gauges had a best fit for the 0.6mm pitch rather than the 0.75mm listed in the spreadsheet for 2" filters.
I also note Doug's post (#3) lists 2" filter thread as M48 x 0.6.
Google search is inconclusive, maybe there are two 2" filter threads around?
I saw a thread on CN where someone got an email reply from Orion that their filter threads are M48 x 0.6, so.....

[niko]

Brendan,

please provide thread size and pitch for head securing device!



niko