Antares/Stellarvue/Celestron 8x50 Finder

[johninderby]

Antares/Stellarvue/Celestron 8x50 Finder

Having recently bought an Antares 8x50 RA finder I found that it was a bit awkward to use with the scope in some positions. A straight through finder wasn't the solution either. What I really needed was a 45 degree finder. Trouble was I couldn't find one so I decided to create my own.

I tried a Celestron 45 degree erecting prism but there wasn't enough in-focus so that didn't work. However I had a Stellarvue 50mm objective that was a bit longer focal length so I tried that and now the problem was not enough out-focus. Rummaging around my spare parts box I found a Celestron polarizing filter holder that was like a very short eyepiece extension and would fit into the back of the Antares finder body. This required shortening the barrel of the prism so that it would fit into the filter holder. An added benefit is that I now have a rotating back on the finder.

At last it all fitted together and works perfectly and can be used no matter what position the scope is in. The Stellarvue objective gives a much brighter and sharper image than the Antares one so I've got a better finder now, as well as one at the right angle. Makes me wonder why a 45 degree finder isn't readily available.

John

[The Warthog]

I don't know if most people would think of something like this. It is obviously practical for you. I got a 7x50 RA correct image finder for my Newt, because I thought it would be less confusing than the half-corrected RA finder, and I was right. I thought about getting the 7x50 RA finder for my refractor, but have used only a Red-dot finder with great success, and never bothered with an optical finder.

Why did you not find a regular RA finder, which has the same view as your refractor, suitable? I would have thought that if you have the ep of the finder at the same angle as the ep on hte scope, everything would work out fine.

Oh, BTW, that is a very creative solution!

[johninderby]

Because the scope is set up for stand up observing the maximum height of the eyepiece off the ground is at the maximum useable height. This often means that a RA finder is higher still and hard to use. In this situation a straight through finder would work, but then becomes awkward to use at other times.

Hence the 45 degree finder which is fine no matter what position the scope is in. What I'd like to see is someone come up with a finder that had an adjustable diagonal from 0 to 90 degrees so you could always have the perfect angle.

John

[John]

Thats an interesting idea John. It reminded me of a Skywatcher vari-angle diagonal that caught my eye a while ago - that might be very useful for this purpose. It's at the top of this page:

Skywatcher Diagonals and Binoviewers by OVL

It might need some extra light path travel though.

John

[johninderby]

I thought of the Skywatcher vari-angle diagonal, but wanted an erect image type. Pity the Skywatcher one isn't an erect image one as it would be the perfect solution, although a bit bulky.

I suppose you could use an erecting eyepiece with a screw in crosshair and the vari-angle diagonal but the diag+eyepiece combination would stick out an awfully long way, not to mention the extra length of the lightpath.

John