Completed Binocular Finder

[JamesF]

(well, all bar the painting at least).

A couple of photos of my completed 50mm binocular finder. Building this has been a bit of trial and error working out what sizes components needed to be, but daytime tests do seem to show that it works fairly well, so I'm hopeful of positive results when the cloud eventually lifts. I even managed to make some cross-hairs for the eyepiece using very fine wire. Total cost has worked out at less than £20 which is far better than the £90 to £100 it seems to cost to buy a "proper" one.

I'm going to build another as a finder-guider and I'll do a full write-up of the entire process for that now I have a better clue about what I'm doing

[Naemeth]

Wow, that looks impressive! How long did it take to build?

[JamesF]

In real terms, ages But that was mostly because I spent a lot of time working out dimensions, making mistakes and finding the right size parts and generally just working out how it all needed to go together based on the parts I had. I also had it sitting on my desk doing nothing for several weeks just to see if I had any other smart ideas about mountings. To build a second would probably take a matter of a few hours excluding hardening time for adhesives.

James

[pixelsaurus]

You bodgied half a binocular? Ooh! I have half of an 80mm bino and some spare bits. Nice one.

[Gina]

Very good I like it

[JamesF]

Actually, if anyone knows of a source for M3 or M4 knurled screws about 10mm to 15mm long in small numbers that won't cost a packet, I'd be pleased to hear about it. Best I can find at the moment are some 12mm ones with oval heads on ebay, but they're about 50p each in tens and they're more intrusive than I'd like. The normal eyepiece lockscrew style is much better. Astroboot has six finder adjustment screws described as "10-32" but I've no idea what that means so I don't know if I have an appropriate tap to cut the thread for them. And they're still nearly 50p each

James

[ObscuredbyClouds]

Hmm i like that, i started a post abit back regarding these but still havent got round to getting the parts yet Is that a bog standard 25mm EP on that dude?

Im on the hunt for some M10 lobe screw/nut things whatever there called lol, seem dear everywhere i look

[JamesF]

It's a standard 25mm ep, yes, except for the fact that I superglued a couple of wires across it inside to make cross-hairs. I'd already butchered my old Skywatcher 25mm ep to house my modded lifecam, so I picked up the ep and diagonal from Astroboot for a smidge over £10 IIRC. Actually I had a couple of each, plus another couple of 50mm binocular objectives because I was sure I'd build at least one more if the first worked out. As it is I'll probably build another RA finder and a straight through finder-guider.

These are the best I've managed to find for locking screws so far:

http://www.ebay.co.uk/itm/150651889666

I'm quite tempted just to use some Allen screws with knurled heads if I can find them in M3 or M4 sizes.

James

[Polar Bear]

Great stuff and good to see. I have a defunct Carl Zeiss 135mm lying around that may get the same treatment.

Paul

[ObscuredbyClouds]

look at them little screw things on this thread, will they do?

[JamesF]

It's hard to tell the size, but I suspect the heads are relatively large. I'd prefer something that was somewhere around 6mm to 8mm diameter.

I'm starting to think that as they're largely going to be "fire and forget" (I want them for alignment adjusters and diagonal retaining screws) I might just get standard stainless or BZP allen screws in the right size and use those.

James

[Gina]

I'm starting to think that as they're largely going to be "fire and forget" (I want them for alignment adjusters and diagonal retaining screws) I might just get standard stainless or BZP allen screws in the right size and use those.

James

Judging by the extortionate price of anything else I would agree!

[AndyH]

Super job James !!

If anyone was wondering about the small imperial threads........

The second number(ie:32 or 40) is the 'threads per inch'

4-40 UNC - thread o/d = 2.85mm(0.112")

6-32 UNC - thread o/d = 3.5mm(0.138")

8-32 UNC - thread o/d = 4.2mm(0.164")

10-32 UNF - thread o/d = 4.8mm(0.190")

Andy.

[JamesF]

Thanks for that Andy. I think it's highly unlikely I'll be able to find a suitable tap for that in the workshop so I'll leave them well alone and go with small metric screws instead.

James

[AndyH]

You see these threads sizes quite often, if you surf about some U.S. sites.

I've got a set of these Taps on my 'want' list.

[JamesF]

I've now built a second of these finders. Not quite identical to the first, but close enough. I've written it all up here: http://www.tanstaafl...e-finder-howto/

A few photos. First, a little jig I made up to measure the focal length of the objective lens:

The body of the finder and the adjustment ring. The pillar drill was playing up and I decided to make a second adjustment ring after I'd done this one and put it together because I wasn't happy with it:

The adjustment ring attached to the foot:

The body with the objective fitted, and my "substitute" O-ring:

And finally, the entire finder assembled, though it needs a bit of cleaning up and painting:

James

[Carbon]

Man, awesome job on that finder! Nicely done.

[Gina]

Very good