Finder

[jason24483]

I have a 9x50 finder scope which is straight through!

Can I buy an adaptor to make it a right angled finder!

Been looking but can't find what I'm looking for!

Many thanks

[michael.h.f.wilkinson]

Not really. You would need to shorten the tube to allow for the fairly long optical path of a 90 deg amici prism (like star diagonal but gives correct image) which is needed. Either try to get a secondhand RACI finder, or convert a defective pair of binoculars (your can sometimes get them for free), or convert a small achromat into a such a finder (these often come with a 45deg amici prism, which is also OK). I built my finder that way:

[JamesF]

Probably less pain to sell it and buy the type you want. Turning a straight through finder into an RA finder would involve all sorts of messing around to get the focal length right to match the extension to the optical path added by the diagonal.

James

[JamesF]

Errr, snap Even to the point where I built my own RA finder from a binocular objective, too

James

[laser_jock99]

Finders are strange things and largely based on personal preferences. I got a new refractor with a right angled scope and a new reflector came with a straight thru scope- first thing I did was swap them both over!

[Dreamweaver]

I bought a 10x50 90 degree finder scope for my 90mm Mak as I found the red spot telrad supplied to be inadequate when needing to star hop. The telred is great to start off your journey but then the 90 degree finder scope (east and west remember is reversed [unless you have the fully erecting prism which corrects east west too] I don‘t have the latter.) is very useful for star hopping, especially if you have 10x50 binoculars with the same field of view.

However please be aware that any patterns you are looking for may well look totally different in your finder scope compared to you binoculars once you start star hopping. This is because the orientation of the stars in your finder scope (depending on whether you have rotated your telescope through RA) will change accordingly! I did not know this at first and it caused me a lot of bewilderment.

For example if you wanted to navigate to NGC 889/869 (the double open cluster) from Cassiopeia using your 10x50 bins then the pattern of stars through your binoculars will be correctly orientated and you would learn, or try to picture in your head, the pattern of stars accordingly. However when you then look through your finder scope expecting to find the same pattern (although reversed east west) you may well find that the image is totally different and you will not recognise anything! You may well end up totally lost. This has happened to me several times when I first used my 90 degree finder until the penny finally dropped after several hours of considerable head scratching!!

I discovered this the hard way. I realised that the image in the finder scope changes with respect to movement in RA, thus rotating the image in the finder scope eith closkwise or anti-clockwise relative to the amount of rotation you need to go through to get to your target.

I now make sure the image in the finder scope is matched to the image in the binoculars before I commence star hopping. I wouldn't be without it now.

Hope this makes sense and is of help.

[jason24483]

Thanks for the advice guys, much appreciated!

I will prob sell and buy something else!

I have a 250px goto dob so the finder would only be for alignment!

Would a cheapish red dot be the way to go?