Rev. Superview 30/68 & Baader Hyp. Aspheric 31/72 Compared

[cloudsweeper]

I recently got the got the Baader Aspheric to add to the Hyperion stable (see pic) and to improve on the Rev Astro Superview.  The Rev costs more now than I paid, but is still a lot cheaper.  So was it worth it?

I used the two EPs in the 8SE Cat (with focal reducer), and targeted the Summer Beehive Cluster IC4665 for the exercise.

Both showed stars quite sharp to the edge of the FOV, with just a little field curvature and perhaps also a little astigmatism.  

The main difference however was that the Aspheric gave a nicer view - a bit wider, and with less (if any) blackout.  This is due to the Aspheric having 17mm of eye relief, compared with the Rev at 22mm.  

The Aspheric is a similar size to the Rev, and 50g heavier - not much, and it is still certainly not bulky.  And it has a better look and feel - not that those features are hugely important!  The adaptor that comes with it allows for use with a 1.25" diagonal - at the expense of some FOV (>56deg).

All in all, I am pleased with the small (I didn't expect anything more!) improvements offered by the Aspheric, but would still recommend the Rev as a low-cost 2" widefield EP.

Doug.

 

[Louis D]

Just curious why you chose the 31mm BHA over the 30mm APM UFF.  Was it simply to complete your Hyperion set?

[cloudsweeper]

28 minutes ago, Louis D said:

Just curious why you chose the 31mm BHA over the 30mm APM UFF.  Was it simply to complete your Hyperion set?

Yes Louis - I fancied an additional Hyperion.  I have especially liked the 36mm Asph., and often start sessions with it.  

I had considered the 30mm APM, but it's bulkier and costlier.  

(I did have an ES 30/82, but found it way too heavy (1kg), causing balancing issues.  And I didn't much like the Ring of Fire phenomenon!)

Doug.

[Don Pensack]

Whatever you do, don't use the conical 1.25" adapter with the 31mm or the 36mm.

The adapter severely limits the apparent field and causes all kinds of exit pupil aberrations.

[Louis D]

2 hours ago, Don Pensack said:

The adapter severely limits the apparent field and causes all kinds of exit pupil aberrations.

I would have thought it would just cause severe vignetting of the field.  How could it induce optical aberrations if it has no optical elements?

[Don Pensack]

It affects the exit pupil.  Normally, the exit pupil is solidly positioned behind the eyepiece.

With the adapter, the exit pupil seems to float as first the field of view is on the right side of the eyepiece's actual field, then on the left side, then top or bottom.

The exit pupil becomes a "floating" pupil and makes the eyepiece incredibly annoying to use.

I really don't know why they made or included that adapter.

OK, it's not an aberration per se, but it does render the exit pupil "difficult".

Edited October 5, 2022 by Don Pensack

[Louis D]

Bizarre.  It would be interesting to understand how this happens through ray tracing.  Perhaps it's related to SAEP.

[Don Pensack]

I think it is like a moving field stop where first one side of the field is illuminated, then the other as your head moves.

I seriously contemplated pulling those adapters out of the packages when I started selling the eyepieces many many years ago,

but there are people who use the eyepieces that way.