Baader Hyperion - questions about usage

[albedo0.39]

Hi there. I've just purchased a 2nd hand Baader Hyperion 8mm lens for a decent price. I'm dead chuffed and somewhat stunned because when it arrived, its huge next to the 9mm Ortho and 9mm Meade 5000 I have.

So, a few questions from those out there that have them already ?

Have you tried the lens without the built-in barlow? As you might know, by removing this small 2 element Barlow, you get an enormous FOV and double the focal length... but what of the image ?

Now a more technical question. I'd be really interested to see how the light from my scope travels through this lens compared with a "std" Plossl. I'd like to better understand the mechanism that gives rise to a wider FOV and why a lens with only 1mm focal length difference is just so massive next to the 2 others I have. Is there a software package out there that might allow you to "construct" an EP lens and work out the light path showing focus points ?

A quick look at the Baader website shows an elementary lightpath through this lens, but I'm looking for a whole lot more detail on lens and light paths

any ideas ?

Thanks

[Doc]

I have the 8mm Hyperion as well and it's a great eyepiece, very little coma compared to my 21mm. Awesome on the M13, you are just submerged into the middle of the cluster.

If you remove the barlow lens it then has a focal length of 21.8mm. I've only tried this once and cannot really say what the image was like but it was pretty good as far as I can remember.

If you mount a 2" filter between the body and front part of the eyepiece your 8mm becomes a 6.9mm.

[jgs001]

And if you get the extention rings, you can adjust the focal length of the eyepiece by up to half. I've used both on my 5mm to get it down to 2.5 mm... not easy to use mind... better to barlow it.

[albedo0.39]

that's good information, but when you add these extension rings, did you have any issues with focusing?

[Doc]

One issue I do have with my hyperions is if I use it in 2" form by removing the 2" to 1.25" adapter in my focuser I cannot reach focus. In 1.25" with the adapter reach focus easy.

If I remove the barlow lens and use in 2" format by removing the 2" to 1.25" adapter in the focuser it reaches focus fine.

I just hope the 30mm Pentax which is 2" will focus OK.

[Astro_Baby]

Doc I have the same problem with mine. I use an extension tube sometimes othertimes I just use the 1.25" to 2" adapter. I found the back focus isnt quite there for the Hyperions. Not quite sure why.

I have also heard that due to their complex lens design they dont work well with Barlows as a general rule. I cant say one way or the other as I havent had the chance yet to try them out with various Barlows under conditions which would be truly fair.

I think you'll be ok with the Pentax XW as my other 2" EPs work ok as did both a Pentax XW and an Ethos 13mm when I borrowed them.

[Doc]

Doc I have the same problem with mine. I use an extension tube sometimes othertimes I just use the 1.25" to 2" adapter. I found the back focus isnt quite there for the Hyperions. Not quite sure why.

I have also heard that due to their complex lens design they dont work well with Barlows as a general rule. I cant say one way or the other as I havent had the chance yet to try them out with various Barlows under conditions which would be truly fair.

I think you'll be ok with the Pentax XW as my other 2" EPs work ok as did both a Pentax XW and an Ethos 13mm when I borrowed them.

Thanks for that Mel.

I did try a 50mm extention but it went the other way and I couldn't focus with that either. I done some measurements and I only need an extra 15mm of travel. But it don't matter anyway as I just use it in 1.25" format.

[John]

Now a more technical question. I'd be really interested to see how the light from my scope travels through this lens compared with a "std" Plossl. I'd like to better understand the mechanism that gives rise to a wider FOV and why a lens with only 1mm focal length difference is just so massive next to the 2 others I have. Is there a software package out there that might allow you to "construct" an EP lens and work out the light path showing focus points ?

A quick look at the Baader website shows an elementary lightpath through this lens, but I'm looking for a whole lot more detail on lens and light paths

any ideas ?

Thanks

It's difficult to get hold of detailed information on the optical layouts of some of the more "bespoke" eyepiece designs because the companies that designed and market them want to protect that information of course.

Also it's not just the optical elements and their number and configuration; the type of glass used, the nature of the coatings used on the glass, the cement used for the cemented elements and the baffling used to supress stray light are all part of the mix which goes into eyepiece design.

It's a complex business !.

John