Eye relief - Baader Hyperion, where is it?

[Owmuchonomy]

I've always 'made do' with my rather limited and basic EP collection. SGL has taught me that to get involved in EP scrutiny is like unravelling my own nervous system. On the advice of a retailer I purchased an 8mm Baader Hyperion and the 14mm and 28mm FTRs. I've used the EP since January in both my scopes. The BH approach appeals because it gives you various options of FL. The FTRs work very well particularly on planets. Even M42 appeared as though on my doorstep. However, remove the 1.25" element to make a 2" 21.2mm eyepiece and for me things go bad. In order to get any view at all I have to cement my cornea to the glass. Yes I've read about EPs until I fall asleep but I can't find an explanation for this phenomena other than the EP in this 2" mode really isn't an EP. Could you enlighten me?

[Macavity]

I think it anecdotal (true factually too!) that the performance of the upper elements of Hyperions *alone* leaves a "certain amount to be desired". <wink> But basically, the eyepieces are designed to function with the aid of the corrective "Smythe lens" in the nosepiece. Anything else is perhaps more fortuitous than a major design feature!

You might have more success with the top half of the 21mm, which appears to be more of a "Barlowed Erfle" design. But there many rumours! Best to enjoy the known virtues of the Hyperion... The possibility to get a *flavour* of other focal lengths with extension tubes, rather than perfection. I was never overly fond of opening up my eyepieces in the field. I would (indeed will!) be re-buying Hyperions (The Aspheric too) again. Still fine for my intended purpose - Visual observing through a slower (F12) MAK150.

[sbooder]

I have no problem using my 8mm BH with the front element removed, this is true with both my scopes.  I wonder what is going on here?

[alan potts]

I have used Hyperions in the past and they were not at all bad in my F10 scope but I was not so impressed as i went faster,

I am not a fan of messing about with eyepieces to achieve other focal lengths, but each to his or her own. I most certainly would not take Televue eyepieces apart and slip different rings into place no matter what was being promised for doing so.

Maybe I am just a stick in the mud.

Alan

[rwilkey]

It's the Barlow element in the 1.25" nosepiece that gives the BH its good eye relief.  It's quite common for ep's to have this Barlow element mainly to increase eye relief, common examples are found in William Optics SPL's and also the popular BST Explorers/StarGuiders etc.

[John]

I've used most of the Hyperions and found them very nice eyepieces down to around F/7. In faster scopes than that their astigmatism starts to become rather distracting for me. Without the lens set in the 1.25" barrel they all (apart from the 24mm which does not have the lower lens set) you get a very mediocre eyepiece of around 22mm in focal length. Not worth the bother in my opinion. 

I tend to agree with Alan regarding the operation to add or remove the fine tuning rings especially in the dark with gloved hands. An accident waiting to happen and every chance of getting dust / dirt onto the lower lens set. The rings are good for extending the barrels of my Ethos eyepieces though