Talk About Low Profile Focuser!

[PRejto]

Anyone ever see/hear about this before? 1" thick with 3" of travel.

http://www.clementfocuser.com/

Peter

[MrB]

Yes, eventually I'm going to make one of these. Only thing holding me back is how to make a bellows to keep stray light out.

[Regulus]

Simon could you adapt a photographic Macro Bellows?

[rally]

Peter

PM'd you

Simon - Google is your friend on how to make your own bellows !

[MrB]

Rally, I had looked at pages about that years ago for another project and made a test one out of thick card, but I never thought to look up how to make a round one. Doesn't look that difficult.

I was looking at one of these focusers because my Feathertouch on my newt only has 20mm of travel, but the focal distance of my Wynne Reducer and the MPCC are so different I have to move the primary in the tube depending on which I want to use. The low profile and lack of drawtube make the Clement ideal :D

Trevor, I could probably use a square bellows, but a round one would be preferable. I have a Pentax bellows, but I can't bring myself to destroy such a nice piece of engineering.

[clive milne]

Don first published the design on the atm list around the year 2000 if memory serves me correctly. He quickly realised that it was commercially viable so removed the pics and engineering drawings from the public domain.

If you use 'way back then' you may be able to dig them up.

The atm community was probably at it's peak back then. There was a critical mass of very clever and knowledgeable people bouncing ideas off each other and actually building equipment. There was more than one idea lifted by commercial astronomical equipment manufacturers. I am sad to say that the collective technical curiosity and understanding apparent in forums seams to have been in ablation ever since.
The hostile treatment of one of the intellectual giants (Bratislav) by much lesser minds in the 'other' forum marked the end of an era for me. Anyway, I digress.

[PRejto]

I saw this mentioned yesterday in the Focus Max discussion group. It was new to me and didn't guess that this has been around for quite a while. Since one doesn't see it advertised I guess there may be others that might be curious about this design.

Clive, I appreciate your comments. I too notice a decided lack of civility on forums at times. It almost seems endemic to this age of computers, texting, tweeting, etc where people feel they can say "anything" and pretend it doesn't mean anything (or simply not care) when called on it. What a shame when the best minds decide not to participate. It's a real loss for the community and we should all think about how the words we use may be upsetting to others. But I digress too.

Peter

[coldlegs]

Tried to make one of them using tight hinges but there was too much slop
in them. Thought about trying to use some kind of very thin flexible
metal or spring steel sheet but that stuff is difficult to work with and
reliably drill accurate holes. Might be able to get away with a flexible
plastic or Teflon sheet. Ended up with with this focuser (see pic) which
has about a 110mm range.

Cheers
Stephen

[clive milne]

Here is one way to do it (that does work)
Get yourself a cheap tape measure, this is your hinge material.
Also acquire two pieces of steel approximately 5cm square and 6mm thick.
Drill a hole in each corner of both pieces. The holes are clearance size for whatever bolts you have on hand. Bolt them together then drill the desired hole pattern through both pieces.
Loosen the bolts enough so that you can get a section of tape measure between the two pieces under your holes. Tighten the bolts to clamp the hinge material in the metal sandwich you have just made. You should be able to drill through the jig quite easily with a little care.

[LightningNZ]

I started trying to build a focuser in this style before I moved to Australia. I was using stainless steel ball-bearing hinges. Sadly my not yet finished prototype was lost in the move (along with other stuff to a value of about $500 :( ). Even unfinished it would have been crazy heavy, I suspect it would have worked okay though.

I also bought a bag of 20 laptop hinges to try but they are very stiff and I no longer have access to a workshop. If anyone would like them to try I'll be happy to mail them for free.

Cheers,
Cam

[coldlegs]

Clive
Thanks for the technique. I'll have a shot at it for my next scope which will
probably be a year or so knowing the way I seem to keep collecting them.

Cheers
Stephen

[ericwbenson]

Hi,
I have a 3.5" version on the CDK20 in Ark, Mark has one also on his Tak106. The backfocus usage is more like 40mm (at least with the adapter for the CDK) and the travel is about 30mm. They are fairly hefty units and do work as advertised. However the interface for the camera is non-standard and needs a custom adapter, which is nothing new really in the imaging department. You need a robofocus to motorize it and the backlash is pretty invisible. Still some flex possible with heavier loads but I don't think it affects my imaging train at f/6.8. The robofocus attached in the standard way sticks out and can get in the way of rotating FWs/OAGs. I mounted mine backwards (robofocus motor pointing towards the scope) in a non-standard way and that solved that problem. There are a lot of screws in this thing (100+ IIRC) holding the hinges in a sort of interference fit, I am sure there is a lot of messing around to get the right recipe for the focuser to work properly (no play and doesn't jam), not for the faint at heart DIY.

EB