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Pentax PF-80ED, Straight & Angled

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#1 IDONTSEEIT

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Posted 15 June 2003 - 08:04 AM

:thewave:Hello again to all, I seem to have researched myself silly again, and once more I'm befuddled. I'm interested in the Pentax PF-80ED spotting scope based on several reviews I've read on Excelsis, and another site I don't recall. I like the fact that 1.25" eyepieces can be used on it, they specifically refer to the Pentax XL's. I plan to use it as a quick-look scope, and since it's nitrogen purged, and weather resistant, I'm thinking cool-down will be quick, dew-up shouldn't pose much of a problem, as well as it'll be quite durable, as it's designed for rugged field use. I like the idea of having something photo-tripod mountable, as conventional scope mounts are too bulky for me at this time, and my time for viewing is usually limited to about an hour.
My question is:
Does anyone have any ideas, suggestions, or information they can give me regarding sticking a diagonal into the end of the straight-through model, and essentially using it as a conventional scope? The reviews that I've read on it state that it showed very clear views without color, despite it's prismatic design, due to it's ED glass. I know a diagonal will fit, however will I be able to achieve focus? And would the combination of the diagonal and the prisms kill the contrast and make the views too dim?(obviously it will rob some light, but how much?)

Any thoughts, Ideas, suggestions, would be appreciated by this, still "green", newbie. :bow: :bow:

PS: I'm still waiting for all the optics books I've ordered to arrive, so my knowledge of optics is limited, Im have some ideas in my head,somewhere :foreheadslap:.

#2 Guest_**DONOTDELETE**_*

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Posted 15 June 2003 - 05:08 PM

Spotting scopes generally don't come to focus with a diagonal, but it's worth a try. Just use a cheap diagonal to start, or borrow one if you can.

You might be able to find a 45°-angle adaptor from Pentax, which should work with the scope. Better than nothing.


Jeff

#3 Patrik Iver

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Posted 29 July 2003 - 08:42 AM

I have an angled PF-80ED.

I expect the focus range is roughly the same for the both the angled and the straight model.

The scope works just fine with every eyepiece I own (mostly Pentax for the moment) except for a 35 mm Orion Ultrascopic (same as Celestron Ultima or Baader whatever-they-could-be-called). The focal point of the Ultrascopic is further back than for most EP:s due to the need to get a bigger field stop than would normally fit into the 1,25" barrel and thus get a wider field of view. This EP will not reach focus on anything more distant than some 10 or 20 metres.
In my opinion this tells us that a diagonal will not work.

The 45 deg. angled model is in my opinion otherwise a nice scope and is usable for some quick set-up astro work also. I do not own any EP:s shorter than 5 mm so I do not know how far you can push the magnification.

Best Regards,
Patrik Iver


#4 IDONTSEEIT

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Posted 30 July 2003 - 03:59 AM

Thanks Jeff and Patrik, I appreciate your responses. :bow:

Jeff, diagonals are not a problem, I have several, I didn't want to shell out about $800 for the scope to find out if it would work. :grin:

Patrik, I've done similar experiments with my Leica Televid 77 Apo, by simply laying eyepieces carefully into the socket. I had to remove the chrome barrels on some of them in order to achieve focus, some wouldn't focus regardless what I did.

I was wondering though, if a focal extender and/or reducer would be of any benefit for the Pentax and achieving focus with a diagonal??????

Thanks again to all, and dark skies to ya!

#5 Patrik Iver

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Posted 31 July 2003 - 12:33 AM

This is mostly guesswork, but here goes:

I would not expect a focal reducer to help matters because what it does is it bends the light even more thus in practice moving the focal point even more forward.

A barlow (tele-extender) could work in theory (moves the focal point back due to increased focal ratio), but I think that in practice the hardware which the barlow consists of usually pretty much negates this focal point movement. "Shorty"-type barlows are supposed to be able to reach focus on most scopes, but I think they will never be able to move the focal point the distance required to use a diagonal.

As I said, this is goesswork, so full disclaimers apply...

Is your Leica a straights or angled model?

Best regards,
Patrik Iver


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