adding erecting prism to Finderscope?

davewaldo · #1 22-07-2008, 03:52 PM

Hello all!

Today I received a GSO 8x50 straight through finderscope (this is all I could afford).

I'm sure this scope will suffice however I got to thinking about using some prisms to create a correct view finderscope.

I am considering using prisms available from surplus shed or possibly even part of a binocular.

Has anyone ever done this or could point me in the right direction before I waste money on prisms?

Here is an example of the bino part: http://www.surplusshed.com/pages/item/b1103.html

Not sure which type of prism to use??
http://www.surplusshed.com/pages/category/prisms_1.html

Any guidance would be great!

Cheers,

David.

Gama · #2 22-07-2008, 08:37 PM

If the eyepiece is fixed, then it makes everything 90 % harder.

Anything is possible, but first try and see how you go with it without anything.
If your still unhappy, then you can look at your options. But ive seen second hand finders with R.A views for under $50.00. Maybe just try your luck in the "Wanted" area of this site.
By the time you do all the work and time, etc, etc, is it worth it ?, or just grap a second hand one.

Theo

davewaldo · #3 23-07-2008, 08:33 AM

Thanks Theo, but I'm quite keen to have a straight through correct view. Sorry I didn't make that clear in my first post. I could have purchased an RA finder for little more but I prefer looking straight through a finder, especialy on a SCT.

I will give it a go for some time before I start this little project, but I'm keen to hear the thoughts of the wise.

Cheers,
Dave.

Gama · #4 23-07-2008, 06:29 PM

Your after an erecting prism, There should be some cheap ones somewhere as well.

Theo.

Roger Davis · #5 24-07-2008, 04:10 PM

Bending the light path means shortening your tube! Using a porro prism erecting system means cutting off around 50mm of the finderscope (or however much of a light path is bent through the porro prisms).

davewaldo · #6 24-07-2008, 04:28 PM

Thanks Roger, I'd not thought about that aspect. I might buy a couple of cheap prisms and experiment. I think I will use a cardboard tube until I have the design right, rather than chopping the existing tube.

cheers,

Dave