what thread size(external) is this please with updated image

[iwols]

Hi trying to find an adapter but need to know how you measure this external thread,are the thread pitch same on all scopes,ita a ts optics telescope

 

Edited December 28, 2020 by iwols

[Tomatobro]

A set of metric thread gauges from Ebay for about a fiver will measure the thread pitch

If its 74 mm O.D. and from a Skywatcher draw tube than the pitch is most likely 1 mm

Edited December 27, 2020 by Tomatobro
extra data

[Davey-T]

A few astro' things with M72 and M68 threads, get yourself a digital micrometer, cheap one will do and always handy.

Dave

[iwols]

Got one somewhere but where is it measured cheers

[tooth_dr]

Hi

If it’s 68mm and made by TS then I think it’s probably similar to Sharpstar, and they use M68x1.

They sell a M68 to M48 adapter, for going from M68x1 to M48x0.75

[tooth_dr]

If it’s M74 it will be 1mm pitch as well.

[iwols]

Super info where does the 68mm measure from please

[tooth_dr]

39 minutes ago, iwols said:

Super info where does the 68mm measure from please

It is hard to see from your photo, but it you just measure the diameter of the threads, it will be close to an even number eg 68 72 74.  This will be the MXX size.  The pitch is harder to measure, but from my recent adventures in 3d printing threads, I've discovered that camera lens filters are all 0.75 even up to 77mm, and that astro stuff like M48 M42 etc is 0.75.  The heavier stuff for connecting bigger reducers etc directly onto telescopes is 1.0mm such as M68 and M74.  There is be variations to this, but you can sort of tell by looking at thread and how fine it is.

Is that measurement 74mm above?

[iwols]

updated photo,sorry for the confusion

[Davey-T]

Looks like 78mm probably 1.0mm pitch.

Didn't look that big with tape measure, are you sure the micrometer was zeroed ?

Dave

Edited December 28, 2020 by Davey-T

[tooth_dr]

6 hours ago, Davey-T said:

Looks like 78mm probably 1.0mm pitch.

Didn't look that big with tape measure, are you sure the micrometer was zeroed ?

Dave

I agree with Davey, M78x1.0

[iwols]

Yes it was zeroed confession time, the tape was on the other thread just realised now trying to find a 78mm male to 54mm male, not sure they exist

[iwols]

the 78mm doesnt seem to tie in with the specs ive found,now more cofused unless im not reading it right(again)

Focal length:	580 mm
Focal ratio:	f/5.8
Objective:	Air-spaced triplet objective
Field corrector:	Single lens field corrector system
Corrected and fully illuminated field:	49 mm
Back Focus from 2" connection:	125 mm with retracted drawtube
Back Focus from M82x1 male thread connection:	145 mm with retracted drawtube
Drawtube travel:	40 mm
Clear aperture:	90 mm with anti-reflex thread
Connections on the eyepiece site:	M82x1 female (draw tube) / male (gender changed by rotator) and 2" connection
Connections on tilter:	M82x1 female at telescope side, M82x1 male at eyepiece side
Fine focusing:	1/10 micro transmission
Maximum photographic load:	6 kg

Edited December 28, 2020 by iwols

[iwols]

well can find nothing with a 78mm thread all seem to be 77mm

 

[tooth_dr]

What’s on the other side of that adapter pictured above:  M78 male to M?? male. 

[iwols]

right guys different attack,found an adapterthat came with the scope these sizes might be more common it has an internal thread and external what do you think these sizes are ,think ive got more chance getting these to 54mm male 

 

[Davey-T]

Top one is standard 48mm filter thread, don't know about the bottom one.

Dave

[tooth_dr]

On 28/12/2020 at 15:25, iwols said:

right guys different attack,found an adapterthat came with the scope these sizes might be more common it has an internal thread and external what do you think these sizes are ,think ive got more chance getting these to 54mm male 

 

As Davey says it’s standard M48 thread. I have used these adapters: M48F to M54M: for attaching a filter wheel. Is that the plan here?

[iwols]

yes but rotator instead thanks