6 replies to this topic

[simoncarlisle]

i am considering getting the 17mm 60fov baader hyperion for my orion xt8 plus. looking through the specifications on the eyepiece i see that they unscrew and become a shorter focal length. i can't for the life of me find what this focal length shortened focal length is. 

 

does anybody know what this shorter focal length is?

 

simon

Edited by simoncarlisle, 05 March 2021 - 06:37 AM.

[beggarly]

Last column (without first group of lenses).https://www.baader-p...on_examples.pdf

[elythomaslumber]

I´m not sure if you are looking for the attached file. It is in German but there is a table included showing the different focal lengh if you insert one of the additional rings or both or remove one lense group.

So with the 17mm eyepiece to will additionally get 13.1mm (14mm ring), 10.8mm (28mm ring), 9.2mm (both rings) or 21.8mm without rings and without the 1 1/4" front lense group.

 

I bought that eyepiece as well as both rings but I´m very new to astronomics and did use the eypiece only as delivered (17mm) so far. I have also the 13mm eyepiece.

 

There is also a complete download page available including English docs: https://www.baader-p...om/de/downloads (scroll down...)

 

 

Hmm, the file I attached is to big, so here is a screenshot.

 

 

Attached Thumbnails

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Edited by elythomaslumber, 05 March 2021 - 07:19 AM.

[SeattleScott]

Consider that it isn’t particularly practical to be swapping the rings in and out during an observing session. For one it is fairly tedious. Some don’t like having to plop a barlow in. Here you have to do all this screwing and unscrewing. Secondly those rings are black and could be hard to find if dropped at night. I’m sure you could find it with a flashlight, but then there goes your night vision for 20 minutes. Also the optical performance of the eyepiece will change with the rings installed, potentially for the better or worse. Generally the longer the extension the better the edge correction as you are increasing the power of the Smythe lens. But AFOV might shrink, idk, and the eyepiece can become long and unwieldy. Certainly interesting to experiment with, especially as you don’t seem to have a diagonal to kill. You might find the 17 with ring outperforms the 13. So you might simply find you prefer the performance of one or the other with a ring installed and leave it that way. But I wouldn’t view it as a cheap way to double or triple your eyepiece collection. Certainly there are those who have experimented with these, and those who have left them installed in certain eyepieces because they preferred the performance that way. But I don’t hear about people going out every night and swapping these things in and out all night long to hit different magnifications. Maybe a couple nights to experiment and see what works for them, but it isn’t really a long term solution.

Scott

[Sol Robbins]

In my experience these eyepieces do not perform very well with the nose piece removed to achieve a lower magnification.

[vdog]

In my experience these eyepieces do not perform very well with the nose piece removed to achieve a lower magnification.

In my experience that is an understatement.  I would go with "unusable" myself. 

 

That 17mm, however, is a good eyepiece, and the fine-tuning rings do work, but I wouldn't plan on installing one in the field.  When I used one, I would always do this ahead of time and keep the EP in that configuration throughout the observing session.
 

[PJBilotta]

One of the nice things about all Baader products is their exceptionally fine and accurate machining, so they thread on almost effortlessly. While I no longer have Hyperions, when I did I found that re-configuring them - removing the bottom element and adding the spacing rings - was very easy, even in the dark. Just be sure you do it over a table or chair so you don't drop and damage the pieces.

 

The 17mm is a great eyepiece and can serve as three with the added rings. However, don't bother using it or any Hyperion in the low-power configuration without the lower section. The upper elements alone are just a basic Erfle, and are a mess outside of the inner 40-50% in anything faster than f/8.