Nikon ED50 parts (1 Viewer)

JBT,

Very interesting and can you post some pictures of your modified ED50 ? Heeeeeeee

I have owned a few Borgs, including the ED60. Nice compact and versatile system. Main issue is the drawtube focuser sags when used with a heavy diagonal and eyepiece. The result is some slight miscollimation. Probably not visable at low powers though.

JBT,

I don't have any experience with Borg scopes, but their system seems taylor-made for what you're trying to do.

I would have expected the Nikon objective to be corrected to compliment the chromatic and spherical characteristics of the Porro prism in the Fieldscope. Typically an objective like that shows spherical undercorrection and an increase on longitudinal chromatic aberration when the prism is removed from the light path. You might not notice that at the very low magnification. The yellow color you describe on the edge of the moon sounds like lateral color which should mostly be coming from the eyepiece. I can't understand why it would be worse in the Tak, unless perhaps the Tak's extra magnification is simply placing the lunar edge a little further off-axis. The Tak shouldn't show any longitudinal CA at such a low magnification.

Henry

Thanks for the info everyone! I'll try to get a few pic put up as soon as I can. Keep in mind it's not completely finished.

Henry, I only have 4 EPs as of right now and those are the fixed wide field Nikon that is 16x when used with the ED50, a 7mm Faworski(Bushnell), a University Optics 2" MK80 and a 30mm 88 degree Leitz. The 2 I used to view the moon when I saw the yellowish tint in the Tak were the Leitz and the MK80. Next time I veiw the moon I'll try the other two with the tak and see it I can still see the tint. If it were the EPs causing the tint wouldn't I see the same tint in the ED50? Maybe my Tak is out a whack?

Sorry I was only able to get one picture before my camera battery died. This pic is on my homemade scope next to the ED50. Body and prism only with both scopes. No objective or eyepiece. I put electrical tape at the end of the barrel on my homade scope to hold the ED50 objective on for testing. The parts that should allow me to thread the obective and the homemade scope tube together should be here by Saturday. Hopefully it will work.

As you can see the size of this scope is just about the same as the ED50. I don't have a proper scale to get the correct weight but according to my bathroom scale my homemade scope is 8-16 oz heavier. Depending on what EP I decide to use it could be quite a bit heavier.

As soon as my battery charges I'll post some more pics of it.

OK here's a few more pics with the scope put together. The 2 EPs in the pics are a UO MK80(black one) and a 30mm Lietz(silver one).

Very interesting, JBT.

I think, if you cam handle a 90 degree angle and reversed images, the image would be better with a diagonal prism or mirror. At best the William Optics Schmidt is a roof prism without phase correction and at worst (like in the Cloudy Nights review) it's a poorly made roof prism without phase correction. I would expect the Porro prism in the Fieldscope to be much better.

To minimize vignetting I think it would be better to place any necessary extension tubes between the objective and the prism rather than between the prism and eyepiece. The front aperture of the erecting system is likely to be the limiting factor for unvignetted FOV at such low magnifications and wide AFOV's, so the farther it's placed from the objective the better.

Thanks for the suggestion Henry. I've tried extension between the objective and the prism and it had no effect on the vignetting. The only thing that worked for me was moving the EPs further out from the prism. The extension tube has two functions one is to reduce vignetting and the other is it's the way I focus the scope.

I've tried mirror diaganols and I just can't get use to them. I did a side by side comparison between the WO 2" 45 degree diagonal and a 2" mirror diaganol used in 3 different scopes a TV76, a Vixen 80ss and the Tak fs60. Beside the vignetting caused by the WO prism I couldn't see much difference when mags were below 20x. Any advantage the mirror had was definitely not worth the discomfort of the 90 degree reverse image of the mirror.

If all goes according to plan I'm going to use only one EP in conjunction with a Mulit mag barlow to get mags between 10x and 30x depending on which multi mag barlow I choose to use. I did a side by side with the stock ED50 and my modified ED50 using the 16x Nikon EP. I felt the view through the modified could actually better then the stock. It was atleast just as good as the original. I won't know for sure until I do some more testing and digiscoping with it.

If I need higher power lets say anything above 30x I plan on using a TV 1.25 60degree diagonal or a high end 90 degree prism from Baader. If I use a multi mag barlow my high power EP of choice is going to be either the 7.5mm Tak, 12.5 Doctor or Nagler 3-6mm zoom. If I don't use the multi mag barlow then I'll go with the Nagler 3-6mm zoom.

No matter what I do it's going to be fun doing it.