Hyperion 8mm and 21mm - Updated with a f/4.7 scope test

[James]

I finally got a chance to use the 8mm and 21mm Hyperions I bought off Rus back in May. I was able to grab an hour or so this evening. Given the short time I just set up my Skywatcher refractor (120mm f8.3 Evostar). My brief thoughts on the eyepieces follow and when I get the chance to test them with my 10" f/4.7 Newt I'll update this with how they fared.

21mm - I spent a while looking at the Milky Way through Cygnus and down through Aquila with this one and stopped at the Coathanger to see how it fared. There was evidence of astigmatism at the very edges of the field (last 5% or so) but it wasn't pronounced. Otherwise stars stayed in focus across the whole field. There's a fair amount of pincushion distortion at the very edges but that again didn't bother me (not exactly a huge problem when stargazing). For me the only problem was a bit of difficulty getting the right eye position. Even with the rubber eyecups that fold out I kept getting blackouts. After about 10 minutees though I had it sussed and things improved.

I then removed the bottom lens which turns the 21mm into a 32mm eyepiece (I think...). Whilst this introduced more astigmatism (the last 20% of the field) it wasn't a great problem. The same area was affected by field curvature as well in that stars that were focused in the centre were not at the edges and vice versa. However the true field of view was correspondingly greater ( the whole Coathanger fit in the field of view! )and I was actually quote impressed with the view (and it appeals to the Scotsman in me to get two eyepieces for the price of one...).

I then compared the views with a 24mm Panoptic. I did my best to allow for the difference in focal length. The view in the Pan was better all round, tighter stars, no astigmatism that I could detect and a slightly wider apparent field of view. The 21mm Hyperion doesn't appear to be quite 68 degrees. Of course I'd expect the view in the Pan to be better but I have to admit that it wasn't exactly miles better. I've read before that the Hyperions offer 90% of the quality for less than half the price and I'd have to agree with this. Would I trade in my Pan for a Hyperion? Well, no, but were I starting out again and had I realised I'd want to upgrade my mount I would have been happy with a Hyperion instead of the Pan.

The 8mm was a similar experience, perhaps slightly better. Slightly less astigmatism, a definite 68 degree apparent field of view, much easier in terms of eye position (by this point I'd realised that I needed to move my eyes away a few millimetres and the blackouts would cease).

In short I'm quite impressed with these eyepieces but the real test will be my f/4.7 scope....

Caveats:

The above is subjective and is my opinion. Your mileage may vary as the saying goes and what was a problem for me may well not be a problem for others. I used my right eye which is pretty much 20/20 vision.

Also, whilst the 21mm appeared to have a slightly smaller apparent field of view I didn't test this in any way. Its quite possible that it doesn't and that my eyes were playing tricks but I have heard others say the same thing...

James

[anthony]

Nice review - cheers

[Whippy]

Good review James, I don't know about the 21mm but the 8mm should be fine in your 10" as I use one in my f5 8".

Tony..

[Macavity]

I think it is generally held, and is ostensibly TRUE that the 21mm has more like a 60 deg AFoV. BUt, t'be honest, for me, there isn't a lot of difference. Folk often do slightly negate the 21, preferring the 17mm (which does have a full 68 Deg), I sense that's a bit "near" the 13mm though. So I still think my trusty 21mm is a good thing... Good to hear of positive PRACTICAL review. As ever, and pending a move to a darker/convenient site, most of my rambling is "theoretical".

For us "addicts of the calculator", a PDF: http://www.baader-planetarium.com/pdf/hyperion_brief_description_e.pdf which shows the claimed specifications.

As someone who now worries of "pup buying", Nice work!

[GazOC]

Nice review James, I had problems with the eye position at first as I'd come from using mainly orthos where the idea is to jam your eye into the lens!

[lunator]

Nice review James, I had problems with the eye position at first as I'd come from using mainly orthos where the idea is to jam your eye into the lens!

Gaz I know what you mean orthos work best wheb they are 2mm from your retina

[GordonCopestake]

I loved my 24 pan. So much that when I sold it I brought another. When I sold that I brought another. When I sold that...... Well, my next Pan24 i will be prised out of my cold dead hand hehe

[James]

Last night gave me a chance to try the Hyperions in my f/4.7 Newt… I know what I expected compared to using them in my refractor; I expected a greater degree of astigmatism, more of the field of view affected by it and possibly more pronounced field curvature, but…

21mm: Popped it in, found the densest starfield I could in the somewhat washed out Milky Way ( the curse of full moon) and had a peek. OK, astigmatism. Yep, its there and it affects perhaps the last 10% of the field of view but its only slightly worse than in the refractor but considering the fast focal ratio of my scope I was expecting it to be a lot worse. To be honest, for me, this still isn’t enough to spoil the view which for the majority of the field was crisp and sharp.

I then unscrewed the bottom section to give me a 32mm focal length eyepiece. Somewhat nervously I took a peek (I wasn’t optimistic about the quality of view it would give). Sure enough, the astigmatism had crept further into the field of view, perhaps 20% of the field of view was affected.

{side note, by 20% of the view I mean 20% of the distance from the edge of the field to the centre, not 20% of the whole field!}

This astigmatism to some extent negated the point in having a wider true field of view but the centre of the field was clear and sharp. Looking straight into the field of view gave a nice sharp image, its only when I look around a little that I see the astigmatism. In both situations some pincushion distortion was visible but again this wasn’t a problem (especially as it only happened in the very edges of the field of view.

Field curvature in both the 21mm and the 32mm alternatives is not noticeable, whether this is masked by the astigmatism or whether its due to the different scope I don’t know.

The 8mm eyepiece followed on from the 21mm in that compared to my refractor there was a little more visible astigmatism but the difference wasn’t much, again field curvature wasn’t noticeable and again pincushion distortion was there but only slightly. Basically it appears that the pincushion effect only happens in those areas already affected by astigmatism rendering it irrelevant.

In comparison to my 24mm Pan, well… this is where the money spent on the Pan really shows. The Panoptic gave sharp views right to the edge (although there is some pincushion distortion visible) but in fairness the view is every bit as good for the majority of the field of view.

Overall I was surprised; pleasantly so. An f/4.7 reflector is an tough test for eyepieces and the Hyperions handled it pretty well. Some of the astigmatism visible may have actually been exacerbated by coma from my Newt.

I should point out that not everybody is affected (or cares about) astigmatism or other effects in the edge of a field of view. My neighbour Mark who was out with me last night while I tested was impressed by the Hyperions and didn’t really notice the astigmatism in the 21mm (although he was aware of it in the 32mm version). It is only the far edges that are affected and perhaps it would be fairer to describe these eyepieces as giving sharp clear views 90% of the way to the edge of the field of view…

James

[James]

Just looked back through my notes and realized that I haven't mentioned one aspect of the Baader Hyperions that I should have and that is comfort of viewing/eye relief. After I'd gotten used to pulling my eye back a little from the eyelens the Baaders are very comfortable to use!!

James