I will be replaceing the 6x30 finderscope on my 8" eq mounted newt. I am wondering about Apogees new richest field refractor as a finderscope. 80mm aperature with a 18mm 1.25" kellner eyepiece. I don't know the focal length as that info is not in any of the advertisements I have seen for this scope.
Finder scope
Started by [email protected], 02/19/2005 01:40PM
Posted 02/19/2005 01:40PM
Opening Post
Posted 02/19/2005 05:25PM
| Edited 02/19/2005 05:27PM
#1
It has definite possibilities but in my view there are several problems:
1. This is an F5.9 scope as I remember so it will have a focal length of about 480mm.
Field of view: As configured, with the 18mm Kellner, the field of view will be about 1.7 degrees at 27X. If your 8 inch Newt is F5 and has a 2 inch focuser then it makes little sense to use a finder with a 1.7 degree FOV when you can just buy a inexpensive GSO 30mm Superview which will give you a 2+ degree FOV in the main scope.
2. Diagonal, those inexpensive correct image diagonals are most often not full aperture so if you move to a widefield eyepiece be losing some effective aperture.
3. MOunting the Finder. You will need some rings and a way to mount the finder so that you can align it. Probably use guide scope rings from www.scopestuff.com Probably about $50.
In my view, this could function as a finder with the addition of a 2 inch diagonal and a 2 inch widefield eyepiece such as the 80 degee 30mm eyepiece that Herb sells here. This will provide you with a 5 degree FOV at 16X, definitely a nice place for a finder.
But when you add it all up, its going to be something around $300. In this price range there are other options that are better IMHO. If you don't add go the widefield route, you are better off just buying a widefield eyepiece for the Newt.
I think a better overall choice would be a 50 mm Orion finder, either straight through or RA and add a Telrad. The 50 mm finder is a major step up from that 30mm, gathering almost 3 times the light while retaining a reasonable field of view.
jon isaacs
1. This is an F5.9 scope as I remember so it will have a focal length of about 480mm.
Field of view: As configured, with the 18mm Kellner, the field of view will be about 1.7 degrees at 27X. If your 8 inch Newt is F5 and has a 2 inch focuser then it makes little sense to use a finder with a 1.7 degree FOV when you can just buy a inexpensive GSO 30mm Superview which will give you a 2+ degree FOV in the main scope.
2. Diagonal, those inexpensive correct image diagonals are most often not full aperture so if you move to a widefield eyepiece be losing some effective aperture.
3. MOunting the Finder. You will need some rings and a way to mount the finder so that you can align it. Probably use guide scope rings from www.scopestuff.com Probably about $50.
In my view, this could function as a finder with the addition of a 2 inch diagonal and a 2 inch widefield eyepiece such as the 80 degee 30mm eyepiece that Herb sells here. This will provide you with a 5 degree FOV at 16X, definitely a nice place for a finder.
But when you add it all up, its going to be something around $300. In this price range there are other options that are better IMHO. If you don't add go the widefield route, you are better off just buying a widefield eyepiece for the Newt.
I think a better overall choice would be a 50 mm Orion finder, either straight through or RA and add a Telrad. The 50 mm finder is a major step up from that 30mm, gathering almost 3 times the light while retaining a reasonable field of view.
jon isaacs
Posted 02/19/2005 06:27PM
#2
Russell sells a 9x60mm for $65 that fits in a regular 50mm mount. It is light and has a large FOV. He sells a dove tail bracket for it for $22.
http://www.ctaz.com/~optics/pics/60mmFinderAd.jpg
He is not a sponsor though and you could possilbly find one through a sponsor.
http://www.ctaz.com/~optics/pics/60mmFinderAd.jpg
He is not a sponsor though and you could possilbly find one through a sponsor.
[SIZE="Large"][/SIZE][COLOR="Blue"][/COLOR] Floyd Blue
Amateur Imager
Posted 02/21/2005 02:35AM
#3
Gary, listen to what Jon Isaccs is saying about finder scopes. The Orion 6X30 RA and their 9X50 RA finders are all you will need until you purchase 12 1/2" or larger scope. Orions offerings are inexpensive, easily mounted and give a very generous field of view You can't go wrong!!!
Roger in Tampa
Roger in Tampa
Funding Member
