£10 10x40 eBay monocular as finder scope? Any experiences?

[furrysocks]

Building an 8.5" f/7.6 newt and looking for a suitable (or semi-suitable) finder. For cheap.

Found several sellers on eBay offering 10x40 compact monoculars (HK/China, obviously) for <£10 delivered. Seems to be one of the largest aperture/lowest mag monoculars available. Blue primary coating.

Anyone dared to try one of these out?

I'm figuring aperture is good, mag/fov appropriate, and image clarity irrelevant... Am I missing anything? Lack of right-angle might be a pain...

[furrysocks]

Ordered one at £8.97 from HK. If it's no good, I'll give it to a kid for their birthday.

[Steve Ward]

Lack of cross-hairs will be a distinct problem I think . . .

[JamesF]

Might be possible to unscrew the eyepiece and manufacture some with a bit of fusewire?

James

[furrysocks]

Good point - had thought about that, then promptly forgot. Never looked through a finder. Assuming one can just eyeball something to the center of the FoV?

[Steve Ward]

You could but you wouldn't get very far.

The FOV of the finder is so big that you'd struggle to find anything I think.

Might be better looking for a cheap 'proper' finder or going for a Telrad . . . http://www.firstlightoptics.com/finders/telrad-finder-astronomy.html

[JamesF]

Depends how accurate you want to be, I guess. If you can see the field stop easily then I don't think it should be too hard.

James

[furrysocks]

For the big scope, I'll get about 0.9 deg TFOV with my 30mm Plossl, and maybe up to 1.6 deg with a SWA 38mm 2". I'll look at modifying this monocular when I get it but going from a 5-6 deg finder to 0.9-1.6 deg scope view might be ok.

[Steve Ward]

For the princely sum of £8.97 it's well worth a play , how do you intend to mount it is the other question of course . . .

[furrysocks]

How I intend on making the rest of the scope is also a good question...! Making it up as I go along.

Something like this...

http://www.geocities.jp/toshimi_taki/8inch/8inch.htm#finder

[Steve Ward]

Fair enough . . .

It might be worth casting your eye here . . . http://www.cloudynights.com/ubbthreads/postlist.php/Cat/0/Board/atm . . . there are a lot more amateur telescope makers over the pond who don't mind their brains being picked . . .

Wish you well with the project , look forward to seeing the results . . .

[furrysocks]

Nice little monocular for <£10. Significantly brighter terrestrial observation compared with my Zeiss 7x21. Nothing to see above but clouds tonight, though.

Marked as Bushnell 10x40 85M/1000M.

Disassembles easily suggesting the addition of cross hairs should be possible, but reassembly required some trial and error to restore the appropriate focal range. The fat-end shroud unscrews but does not come clean off. The part to which the lens is mounted then unscrews from a female-threaded friction-fit slider located in the end of the barrel. The field stop is at the other end of that sliding bit. Not a great description, but it comes apart - that's the main thing.

Focuser is very smooth. Feels very robust, a nice weight and rubber grip is comfortable (as far as it can be ). Eye relief is not great, though the eye cup does fold, but not readily - I have a feeling it would deteriorate quickly with repeated use. Comes with a lanyard and a case but I appear to have lost the lanyard somewhere, already.

Somehow mounted to one of those cheap flexible leg tripods, this would make an absolutely excellent purchase for kids - so often the little telescopes that you see kids run around with are rubbish, but they love them! They'd love of one these more!

As a cheap alternative to a 9x50 finder, it's perhaps not ideal. But it's £9 very well spent, in my opinion. I'd recommend this budget piece to anyone with a pocket.

[furrysocks]

I've finally mounted one of these to my scope - I had to build the scope first! It's mounted with a couple of stiff springs, two captive bolts and two wing nuts - and a zip tie.

It got me Panstarrs last weekend - right down low above a neighbours garage. I'd have never found it in the scope (0.9deg TFOV) and it was not visible to the naked eye. The finder found it and centered it in the scope no bother. I could take it apart again and add crosshairs but I don't feel the need yet.

There is at least one other variety of 10x40 monocular on eBay at the moment - completely rubber clad, knobbly body instead of the moulded grip on this one. They're about a pound cheaper but the build quality is not the same, field stop slightly smaller, eyecup poorer, etc. I've currently got that one with a solar filter on the front of it - there's also a 16x40, I think, which would be better for that.

If you're getting one, get one that looks like this one.

Anyway, just though I'd give this wee update - as a cheap finder scope, it's two thumbs up!