Bought an older Pentax 85-f1000-refractor. OEM is a .96" digonal, prism, which is good quality but I dont want to invest in new .96" eyepieces for a number of reasons. How can I tell if a new 1.25" diagonal will work with this scope regarding fit, also concerned with inability to achieve focus. Many thanks, colin
Can I use 1.25" diagonal in 0.96" scope?
Started by stubby, 07/22/2002 04:35PM
Posted 07/22/2002 04:35PM
Opening Post
Posted 07/22/2002 05:19PM
#1
Check out the PVC plumbing supply at your local Home Depot, Lowes, ACO, etc.... I found an adapter for an old .965 Tasco that would slip over the end of the draw tube with some duct tape wraped around it to make it tight, and my 1.25 diag slipped in the other end and held in place with a set screw for wich I drilled and tapped a hole for. After I was done, I painted the thing black and it looked quite good.
Roger
Roger
Posted 07/23/2002 02:30AM
#2
Hi Colin.
Here's a few questions:
Does the Pentax prism diagonal have a 1.5-inch inlet barrel? (Mine does.)
How much distance (about) between front of prism housing & the juncture of the o.t.a. & drawtube, when scope's focused at infinity (Moon's good). In other words, how much *available* inward travel do you have, when using the prism & your current eyepieces?
Do you have a 1.5-to-1.25-inch adapter?
That's enough ??s for now. I'll let you catch up.
Assuming my prism is like yours, I can confirm the following: I need another inch or so inward, over the Pentax prism, after replacing it with a 1.25-inch mirror diagonal & using typical/standard eyepieces (.96-inch 18mm Kellner to 1.25-inch 18mm Kellner, for example). Maybe ~1.25 inches more, in some cases.
I've never seen an 85 in person. You have a wonderful, rare, achromat. If I ever seen one in the field, I'll pop in & check to see if it's you. (Likewise, if you see a little Pentax 75 EDHF, it might be me).
There's a shot of the 85 (& mount) on the APM website. Is that your layout? Check it out, if you haven't (might need to cut/paste the URL):
http://www.apm-telescopes.de/magazine/images/
PentaxRefraktor.jpg
Best wishes & plenty of available focus travel!
-Dan
Here's a few questions:
Does the Pentax prism diagonal have a 1.5-inch inlet barrel? (Mine does.)
How much distance (about) between front of prism housing & the juncture of the o.t.a. & drawtube, when scope's focused at infinity (Moon's good). In other words, how much *available* inward travel do you have, when using the prism & your current eyepieces?
Do you have a 1.5-to-1.25-inch adapter?
That's enough ??s for now. I'll let you catch up.
Assuming my prism is like yours, I can confirm the following: I need another inch or so inward, over the Pentax prism, after replacing it with a 1.25-inch mirror diagonal & using typical/standard eyepieces (.96-inch 18mm Kellner to 1.25-inch 18mm Kellner, for example). Maybe ~1.25 inches more, in some cases.
I've never seen an 85 in person. You have a wonderful, rare, achromat. If I ever seen one in the field, I'll pop in & check to see if it's you. (Likewise, if you see a little Pentax 75 EDHF, it might be me).
There's a shot of the 85 (& mount) on the APM website. Is that your layout? Check it out, if you haven't (might need to cut/paste the URL):
http://www.apm-telescopes.de/magazine/images/
PentaxRefraktor.jpg
Best wishes & plenty of available focus travel!
-Dan
Funding Member
