astro adapter Fieldscope DS eyepieces (1 Viewer)

hinnark said:

Looksharp,

I doubt that you can use Nikon EPs with this adapter on your Pentax scope. Problem is to get sharp focus because the adapter couldn't get deep enough into the EP slot of the scope.

Steve

Click to expand...

Thanks for the comment!
The eyepiece arrived today and it is really amazing on the ED50A. If I drop the 27x into the Pentax, it reaches focus at infinity.
But if I remove the inner tension bushing, it comes a wee bit closer so I can focus beyond infinity too.

But if the adapter won't let the eyepiece come that close, the scope will not reach focus.

My BST Explorer 12 mm still holds it own in terms of sharpness, freedom from CA and a flat field. The Nikon has a warmer color representation and a VERY wide field, but that's about it. There is some CA visible at the extreme edges in both, but nothing that disturbs when birding.

I'm no more that curious about the Nikon/astro adapter.

looksharp65 said:

But if the adapter won't let the eyepiece come that close, the scope will not reach focus.

Click to expand...

This is exactly the problem. The 1 1/4" nosepiece of this adapter has a length of 22mm. Behind that there is a ring with a diameter of 37 mm that stops the eyepiece at the rim of the EP-slot so that it cannot get closer to the scope's intermediate image. At the same time the screwed adapter works as a kind of spacer because the EP's opening (Nikon EP's nosepiece) is not at the same place than the end of the nosepiece of the adapter, but a couple of millimetres behind it. I tried this anyway at a Coronado PST which has a 1 1/4" slot as well and think it's hard to imagine that this is different at the Pentax.

Steve

These Nikon Eyepieces have a disk,below the threads,about 1/8 of an inch deep,that actually measures 1 1/4 in diam., so astronomy diagonals and focussers should be able to hold the eyepiece ,depending on design..It should be really easy to fit a plastic,or metal tube,of the right inner and outer diameters,to work in 1 1/4 compression rings...

When I used my pentax PF65ED with the older Swarovski astronomy style Zoom(rare!), I didnt reach infinity focus either,So I had to remove the compression ring too( I think i was the original "Remover" , because I posted about this 5 or 6 years ago,when I owned the scope)..What I did was to fit a rubber gasket,used originally for gas pipes i think, directly in the eyepiece and then slipped the eyepiece in the scope and tightened the holder ring..It worked very well,......I did this because It was the ONLY eyepiece I had!..This could be too much of a hassle and since You already own another similar quality eyepiece,I can understand not bothering with It...

Thanks guys,

I'll keep the Japs apart. But tonight I came across a new C90 Mak at a bargain price in my neighbourhood, and I will begin with some of the eyepieces I already have, like the BST Explorers 12mm and 18mm, the Vixen LV 9mm and the GSO Superview 20 mm.

If I feel the urge to try it with a real good eyepiece, I'll hold the Nikon to it, but I'd probably rather get an XW14 or XW10.
The 27x is so nice on the ED50A that I could as well glue them together .