Eyepiece problem.

[Strangelet]

This may be a stupid question but I have a Baader hyperion 17mm eyepiece and no instructions, how do you make it fit a 2" focuser?

Regards

Graham

[Chris H]

It's a dual collar ep, the stainless bit is 1.25" and above that the black part is 2" it should just drop ito the focuser.

[Cornelius Varley]

The Hyperion eyepiece is a modular design, unscrew the chrome 1.25"" nosepiece and the eyepiece will then fit a 2" focuser. The eyepiece now has a different focal length without the 1.25" nosepiece of 21.8mm Baader Hyperion 17mm. There is a table at the bottom of the page giving the focal lengths of the Hyperion range with & without the lower lens group.

Peter

[Strangelet]

Thanks for the reply, so if you use it in a 2" focuser do you have to remove anything ?

[Strangelet]

Sorry Peter our messages must have crossed.

[Strangelet]

Thanks Guys, that is what I thought. When I fit it to my Skywatcher 200 pds I can focus it with the 1"1/4 adapter fitted but not when it is as a 2" eyepiece, I need around 5mm more travel on the focuser, is that to be expected?

[stev74]

Your 200PDS should have came with an extension tube as it has a low profile focuser which is optimised for astro photography. So if you put the extension tube in the focuser first you should be able to focus the EP as a 2".

[Strangelet]

Hi Steve. I am using that. The 28mm 2" eyepiece that came with the scope focuses fine. The baader focuses fine with the 2" to 1" 1/4 adapter fitted. Having looked at teleskop servicing website it looks like you dont remove the lower portion in a 2" focuser, it must be me being a muppet! I just expected that if you want a 2" eyepiece you remove the Stainless section. Will have to see next time if it focuses in the 2" adapter with the nosepiece fitted.

I think I need some sleep this is starting to look like a dumb question.

Graham

[stev74]

Ok have you tried it with the extension tube out maybe it needs more inward travel?

Sorry if you have already tried that, I'm just trying to cover all the bases for you.

[Astro_Baby]

The Hyperion can have either its bottom end removed (the chrome bit) which will change its focal length (cant remember what the 17mm becomes with the chrome bit removed OR you leave the chrome bit on and just drop the whole EP into a 2" focuser in which case it retains whatever focal length its supposed to be (ie in your case 17mm) BUT if you do that you may need a bit of extra outward travel.

I have a 200 with a Moonliote focuser and if I want to use the Hyperions in their 2" mode I have an extension tube which adds about an inch to the focuser tube. I never bother because the view is not restricted using the 1.25 chrome bit on the Baader.

I think the chrome bit from memory is something like a sort of Barlow built into the lens which is whay the magnification drops when you remove it.

[Strangelet]

At its maximum outward travel (Focuser) if I release the securing screws and lift the eyepiece out of the focuser slightly I can focus it. a quick measurement with a tape rule says that I need about 5mm more. I just thought that all 2" eyepieces should focus within the travel of the focuser, but maybe not.

Graham

[Strangelet]

Thanks Astro_baby, I think thats what I have now concluded talking to everyone. I guess thats why they sell the stop rings to stop that portion hitting the mirror in a diagonal etc. I will use it complete, as it is, and not remove anything.

Thanks Again for all the help.

[stev74]

Ok got you now, basically then you would need to buy an extra extension tube which would allow the extra travel. But only if you want to use it as a 21.8mm EP (1.25 barrel out) rather than a 17mm EP (1.25 barrel in).

[John]

.... I just thought that all 2" eyepieces should focus within the travel of the focuser, but maybe not.

Graham

I can see your logic but, unfortunately, it's not the way it is

Different brands of 2" eyepiece (and 1.25" ones for that matter) have different focus points - some varying quite widely, even within the same eyepiece ranges.

Different focussers also have varying amounts of travel from not a lot (eg 30mm or so) to loads (eg: 150mm or more).

So it can be a bit hit and miss. At least if it's more outward focuser travel you need, you can use extension tubes. If you don't have enough inward travel its much harder to do anything about it.

[Strangelet]

Spot on. I think the problem was thinking that I had to change the eyepiece when fitting it in a 2" focuser and that is not the case. You quickly learn in this hobby that eyerything is not as it seems, or equal.

Graham