Inexpensive 10 x 50 Finder

[Polar Bear]

I decided to try building this after getting annoyed at having to keep moving between the eyepiece on my reflector and the eyepiece on my finder.

Whilst doing this I often 'moved' the scope by catching it with my body , this being exacerbated as I use an AZ4 mount

It seemed sensible to have a finder that had a diagonal so the eyepiece would be just to the right of the scopes viewing eyepiece.

Parts for this came from a Tasco Galaxsee 60mm / 700mm refractor that was a car boot find at £5.00 and a pair of Sirius 20 x 50 binoculars at £4.99

After disassembling the Tasco and taking the objective lens off the binos I did some quick tests to find the focal length and focussing distances to give me 10m to infinity.

After this I then cut down the tube / rack on the focuser and shortened the body at the eyepiece end. I also cut down the binocular objective.

The telescope was dissasembled at the objective end

A bit of luck followed next when I discovered the binocular objective was a push fit into the telescope lens retaining ring and was secured with a tiny bit of superglue.

Binocular objective now firmly in place in the retaining ring was screwed back into the telescope lens sleeve

Scope tube was cut down , retaining screw holes drilled and the parts assembled.

Dew shield simply slides over the lens sleeve .

The 1" eyepiece holder can be unscrewed from the focuser tube and the diagonal can be screwed in.

With the adapters that were with the scope I can use either 1" or 1.25" eyepieces with or without the diagonal.

Focal length is approx 200mm so with the 50mm objective it is F4.0

It works with all my eyepieces and my little 1" / 20mm Vixen Kellner gives 10X magnification which suits it

Focus is from about 10m to infinity.

Image is bright and sharp with no cromatic fringing whatsoever so the Sirius objective must be of reasonable quality.

The bino's were dire with the collimination way out and the prisms held in with mastic and bits of tin !

A trip to B&Q next for some pipe fittings to make the mounting rings from.

Paul

[michael.h.f.wilkinson]

Nice DIY project. Doing something similar shortly. My main issue is getting cross-hairs in the finder. Did you manage that? On a previous home-made 10x50 I used some human hair (my own), but that is very fiddly. Any better ideas?

[Abernus]

not sure how effective this would be but you could get some very fine thread and try that

[Bizibilder]

Nylon fishing line works well. Don't buy "ordinary" monofilament - the stuff you put onto the reel - but get pole fisherman's pre-stretched hooklength, it wont stretch or sag.

PS its costly!! Much cheaper to find a fisherman and borrow a few inches of the stuff!

[acey]

Very nice job, well done. In the past I tried mounting an 80mm scope with mirror diagonal as a finder on my newt but found it confusing to have an upright left-right reversed view in the "finder" and an inverted image in the scope. As long as you can cope with that then I reckon it's worth the convenience of having the finder and main scope eyepieces close together. Personally I prefer having the same view (with slight rotation) in finder and scope, and find it a lot easier to read star maps if I don't have to mentally mirror-reverse them, so I went back to the straight-through approach. Still means a sore neck at times, though.

[AndyH]

Excellent job Paul !!

I've done a similar thing recently to make 2 80mm finders out of an old pair of Russian Bincs. The eyelenses were awful and virtually unusable, but the main lenses are fantastic!

My bino barrels were threaded to the prism housing and so I got a couple of delrin adapters made up by Ray, of RaysRings&Things. The barrels screw on to the adapter/delrin block, add a diagonal and a Tal 25mm Plossl, then a Tal eyepiece recticle and boom bam bosh, one 80mm finder. Sorted.

Cheers,

Andy.

[AndyH]

Nice DIY project. Doing something similar shortly. My main issue is getting cross-hairs in the finder. Did you manage that? On a previous home-made 10x50 I used some human hair (my own), but that is very fiddly. Any better ideas?

See if anyone is selling a Tal eyepiece recticle. You never know, someone may have one gathering dust. They were always a standard accessory with Tal scopes. They work beautifully in a Tal 25mm Plossl.

Cheers,

Andy.

[michael.h.f.wilkinson]

See if anyone is selling a Tal eyepiece recticle. You never know, someone may have one gathering dust. They were always a standard accessory with Tal scopes. They work beautifully in a Tal 25mm Plossl.

Cheers,

Andy.

Interesting tip, could very well try to get on of those (perhaps even with the Tal Plossl). I actually snapped up a cheapo 70mm F/5 achro going for 50 euros, complete with a 45deg upright, non-reversed view diagonal. Hopeless EPs included (plastic wannabe Huygens). I unscrewed the 1.25" barrel from the "optics", and pitched the latter out. I have got a 28mm Kelner from an old 7x50 bino which I fitted into the barrel, so all I need is a reticle to fit into it, and of course, make suitable mounting brackets.

[michaelmorris]

Nicely done. A great project.

[haitch]

The hard bit with the reticle is getting it at the focal point of the EP. You'll need some sort of ring to mount it on (like a ring from a broken filter) if the focal point is inside the EP.

Fisherman's spider web is the finest thread I've found for reticles. It's what they use for tieing flies and it's much finer than any fishing line I've found (finer than hair too!)

I bought a reel when I did mine - if any of you guys above* pm me your address and I'll send you a foot of it.

* Haven't got enough stamps for the whole world so need to limit it to you lot.

[AndyH]

Very true regarding placement of the recticle. I noticed on the Tal plossl/recticle combo, that the recticle is right up at the top(close to lens) of the eyepiece barrel on my 25mm Plossl.

Andy.

[michael.h.f.wilkinson]

I actually solved my problem with the reticle in my old way. I have very thin hair in terms of the thickness of individual hairs (thinning in total quantity too, by now;)), and stuck them to a 1.25" barrel. I then fitted the old Kelner EP from the cannibalized binoculars into it, and twisted it down until the cross-hairs (quite literally) were in focus, and glued it in position. I have decide to just get a set of mounting rings going for 35 euros NEW.