Diy finder

[phattanglo]

Having read one or two posts which suggest that a budget 70 or 80mm frac can be turned into a decent finder scope, I was wondering how you achieve the cross hairs for targeting.

[Steve Ward]

http://www.rothervalleyoptics.co.uk/antares-27mm-cross-hair-kellner-eyepiece-125.html

[John]

The cross hairs would need to be placed right on the focal plane of the eyepiece of the finder so you want an eyepiece where you can get easy access to the field stop. I guess then it's a case of gluing two very fine wires across the field stop aperture. I used fine fishing line to replace some cross hairs once and that worked OK. Some folks might use real hairs

[michael.h.f.wilkinson]

I used two hairs (dwindling natural resource ) stuck across the field stop of an Antares 25mm 70° EP. I am planning to replace that solution by a proper cross-hair reticle (should be 35mm in this case).

[Dave In Vermont]

One maker actually bought a spool of spider-web from Black-Widow Spiders. It has the tensile-strength of steel and is easy to set in place.

How they collect this stuff is beyond me. But my old pet Tarantula left it all over the place, and a bite from old Boris wouldn't kill you - unlike the Hollywood movies. Besides, Boris never bit anyone too large to be her dinner.

Dave

[michael.h.f.wilkinson]

I have just managed to find a suitable reticle on Surplus Shed. Most 1.25" EPs with reticle have a field stop of 21mm at most, which restricts the FOV to 3.44 deg in my 70mm F/5 finder scope. The 25mm I have now has a 27mm field stop, giving me a much more useful 4.42 deg. The current version of the finder scope is shown here:

http://stargazerslounge.com/topic/185558-modding-my-diy-16x70-raci-finder-to-a-14x70-raci-finder-with-diy-crosshair/

[phattanglo]

I'll most likely look on astroboot or buy sell as one's pennies don't stretch very far. it'll sit on top of a 150p on an EQ3-2 mount so I think it needs to be fairly small and light. Can anyone recommend a scope to look out for.

Or would it just be cheaper to get a 9x50 scope, I'm looking for RACI ideally.

[michael.h.f.wilkinson]

I built mine from a cheap (60 euro) 70mm F/5 scope from a department store (similar to a SkyWatcher Mercury 705). These often come with a 45 deg erecting prism, which is not perhaps as nice as a right angle one, but does the job well. I have later replaced it with a cheap 90 erecting prism.  On a 150P you may have balance issues with a full blown 70mm scope. A 50mm RACI might be better. You can also build a finder out of a defunct pair of binoculars. I did that in the past, and it works well.

[phattanglo]

I take your point re the weight with my setup. I use a RDF but it is useful to have a real finder and my current 6x30 straight finder isn't  easy to use thanks to a neck injury.