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Orion Expanse E.P. Review



 
 
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  #1  
Old July 21st 03, 09:08 PM
Bill Greer
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Default Orion Expanse E.P. Review

Review of Orion Expanse 20mm, 15mm, 9mm, and 6mm eyepieces:

Eyepieces arrived well packaged, looking new. The 20mm and 15mm had
clear, rubber, stretch-to-fit caps over both ends. The 9mm and 6mm
had more traditional, semi-flexible plastic caps -- black caps over
the eye ends and off-white caps over the barrel ends. I liked the
more traditional caps better. Time will tell whether my cold weather
concerns with the stretch-to-fit caps will be justified or not . . .

Day testing and impressions using ST-80 (72.5mm aperture, 400mm focal
length):

Wide apparent field. Not sharp near field edge. Comfortable eye
relief without eyeglasses. Eye relief a bit too short for comfortable
use with glasses on. Eye position was critical with the 9mm. Part of
the field would black out if the eye placement wasn't just right. The
other eyepieces in the set were more forgiving of eye placement. The
central area of the fields seemed sharp and well corrected.

Since the ST-80 is my "fastest" scope (meaning it's the scope that
provides the largest, easiest to measure exit pupils), I used it to
focus on a distant hill top in order to measure exit pupils. A
homemade dynamometer marked at 1/10 mm intervals was used. A dark
green filter was added to make it easier to measure the small disks of
light.

I took into account that my ST-80 has an effective aperture of about
72.5mm and a focal length of 400mm when I calculated magnification and
then 'reverse-calculated' the focal lengths of the eyepieces. The
calculated focal lengths were within 1mm of the stamped focal lengths
on all eyepieces except the 9mm. The 9mm eyepiece had a calculated
focal length of about 10.4mm, but errors in my measurements may have
contributed to that result. There were plenty of opportunities for
errors to creep into my measurements!

Night testing and impressions using a 5 inch f/6 apochromat:

Actually, I was out last night under a mostly cloudy sky making
transit timings in order to calculate true fields of view of all the
eyepieces with and without each of my two barlows. It wasn't until
this morning that I decided to write this review. The clouds were
such that extended observations of any single object were impossible
to make. Nevertheless, some things were noticed:

The field edges were judged to be adequate for providing a 'context'
or background for whatever was being studied in the field center; but
they were insufficiently sharp for any kind of critical work. The
field centers were sharp and well corrected.

Eye relief impressions were identical -- in every way -- to the
daytime eye relief (and eye placement) impressions.

The star I used for transit measurements was Theta Aquilae (magnitude
3.2). A ghost reflection of the star was obvious in the 6mm eyepiece.

I was able to observe Mars as clouds repeatedly passed over and
uncovered it. The situation was too chaotic for me to consider making
any sketches. Nevertheless I was able to gain at least a vague
comparison between a 6mm U.O. Orthoscopic and the 6mm Expanse. A TV
2x barlow was used with both eyepieces. The Expanse was *far* more
comfortable to use -- much better eye relief than the Orthoscopic.
The Expanse insisted on creating a prominent ghost image of the red
planet -- easy enough to ignore, but it did make for a cosmetic flaw
in the view. The Orthoscopic produced a 'cleaner' image. Both
eyepieces showed the most prominent Martian features. Unsteady seeing
and frequent dodging of clouds prevented me from making a more
critical comparison. The telescope was used straight through --
without a star diagonal.

Indoor calculations and observations:

From my magnification and true field of view determinations I was able
to calculate the apparent fields of the Expanse eyepieces. The
calculated apparent fields ranged from 61 to 66 degrees with an
average of 64 degrees. Considering all the opportunity for errors to
creep into my calculations, I believe it's fair to say that the
Expanse eyepieces meet the advertised, wide 66 degree apparent fields
of view.

A white light was used to check the optical coatings of the eyepieces
this morning. In general, each Expanse eyepiece had one green
reflection, a small number of blue reflections, and mostly white
reflections. In other words, the optical coatings weren't very good.
As discovered last night, the coatings were insufficient to prevent
ghost images of small, bright objects.

Final opinion (at this point in time):

For the price ($182.95 delivered) this set of four eyepieces is a good
deal. (I expected less than perfect edge-of-field quality. One
generally has to pay for perfection!)

I still need to make some critical comparisons on deep sky, the moon,
and planets before deciding if any of these eyepieces end up in my
regular observing arsenal.

The wide apparent fields, the comfortable eye relief, and the
relatively low price make these eyepieces attractive for use with
visitors and children. (I just couldn't bear thinking about showing
Mars to my wife's parents using a 6mm Orthoscopic eyepiece!)

Bill Greer
  #2  
Old July 22nd 03, 12:29 AM
Jon Isaacs
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Default Orion Expanse E.P. Review

The wide apparent fields, the comfortable eye relief, and the
relatively low price make these eyepieces attractive for use with
visitors and children. (I just couldn't bear thinking about showing
Mars to my wife's parents using a 6mm Orthoscopic eyepiece!)

Bill Greer


Bill:

Nice review. I have a set from Adorama and nearly all my experiences agree
nicely with yours. I also have some UO orthos but since these eyepieces
arrived, the orthos (and my Plossls as well) just sit.

I haven't noticed the positioning problem you did with the 9mm, wonder if
something is not quite right there. The 6 and the 9 mm both have a secondary
lens, a Smyth or Barlow lens or some such thing. Both these came loose after a
short while. I removed the 1.25inch section and tighted them up from the top,
since then, no problems.

I have been using mine for seveal months now, I think these eyepieces are a
great bargin and a definite upgrade from standard and even premium Plossls.

jon



  #3  
Old July 23rd 03, 12:48 AM
Pete Rasmussen
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Default Orion Expanse E.P. Review

On Mon, 21 Jul 2003 14:08:15 -0600, Bill Greer
wrote:

Review of Orion Expanse 20mm, 15mm, 9mm, and 6mm eyepieces:


snip very nicely done review

Hi Bill,

My Orion 9mm Expanse is the only one I have so far and I agree it is
just a little bit tricky to use. On coatings, if you screw the upper
housing off and opaque the lenses you will see with light source all 4
A-G surfaces are mulicoated. At least mine is. The negative achromat
in the barrel is fully coated presumably with mag fluoride. That
aspect is very light (nearly white) magenta colored and would
potentially explain your notation about "white" surfaces. IOW,
coatings on mine are excellent.

Also, I have done preliminary testing and this wide-angle model
appears extremely sharp with excellent contrast for moon and planets.
That is exceptional for the type and highly useful with undriven Dobs
for same viewing.

One problem I see is the internal mechanics need user modifications to
improve the contrast to full potential, and eliminate bright object
glare and ghosting. The inside of the upper housing can extremely
easily be flocked by auser simply unscrewing and removing the top and
bottom lens assemblies to access it. However, the nasty, shiny lens
spacer between the upper lens assembly is more difficult to get at,
but is not impossible to access to deaden. Upon completion the
eyepiece would be fantastic.

Clear skies,

Pete
  #4  
Old July 23rd 03, 10:07 PM
Pete Rasmussen
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Default Orion Expanse E.P. Review


I'd like to add as update that there seems no problem at all using the
9mm Expanse when an eye pupil is expanded somewhat. Deep sky viewing
with a pair is fantastic and very comfortable. Only when viewing a
brightly illuminated moon does this eyepiece design seem to get antsy.
Additionally, I was viewing Mars last night at 300x through a large
Dob with my pair of these attached and the views were truly excellent
with plenty of drift space to tag the planet. There were a couple of
minor floating ghosts outbound of field center but they were not
distractive to me.

Clear skies,

Pete

  #5  
Old July 24th 03, 12:09 AM
Rod Mollise
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Default Orion Expanse E.P. Review

I was viewing Mars last night at 300x through a large
Dob with my pair of these attached and the views were truly excellent
with plenty of drift space to tag the planet.


Hi:

I've got the 6mm, and it acquitted itself well on Mars last weekend at 300x.
Even close to 500x, it was doing fine, with the seeing being the main culprit
in any yuckiness. Very nice, reasonably priced eyepieces IMHO. I'll probably
buy a couple more.

Peace,
Rod Mollise
Author of _Choosing and Using a Schmidt Cassegrain Telescope_
Like SCTs and MCTs?
Check-out sct-user, the mailing list for CAT fanciers!
Goto http://members.aol.com/RMOLLISE/index.html
  #6  
Old July 24th 03, 12:19 AM
Rod Mollise
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Default Orion Expanse E.P. Review

Very nice, reasonably priced eyepieces IMHO. I'll probably
buy a couple more.


Oh...and let me add...Scopestuff and Adorama sell the very same eyepieces for
less $$$.

Peace,
Rod Mollise
Author of _Choosing and Using a Schmidt Cassegrain Telescope_
Like SCTs and MCTs?
Check-out sct-user, the mailing list for CAT fanciers!
Goto http://members.aol.com/RMOLLISE/index.html
  #7  
Old July 24th 03, 12:53 AM
Jon Isaacs
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Default Orion Expanse E.P. Review

I've got the 6mm, and it acquitted itself well on Mars last weekend at 300x.
Even close to 500x, it was doing fine, with the seeing being the main culprit
in any yuckiness. Very nice, reasonably priced eyepieces IMHO. I'll probably
buy a couple more.

Ron: Glad to hear you like, I like mine, not having any Naglers or Panoptics,
these are about all I use.

I have had good success with mine 6 at high powers but there are some internal
reflections when bright objects are not centered. Have you noticed this with
yours, maybe they had fixed this??

I have the 6, 9, and 15mm, the 9 is the best of the lot IMHO.

jon

jon
  #8  
Old July 24th 03, 09:53 PM
Rod Mollise
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Default Orion Expanse E.P. Review


I have had good success with mine 6 at high powers but there are some
internal
reflections when bright objects are not centered. Have you noticed this with
yours, maybe they had fixed this??


Hi:

Did not notice any.

Peace,
Rod Mollise
Author of _Choosing and Using a Schmidt Cassegrain Telescope_
Like SCTs and MCTs?
Check-out sct-user, the mailing list for CAT fanciers!
Goto http://members.aol.com/RMOLLISE/index.html
 




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