*Review: Astrosystems 30mm WIDE SCAN III Eyepiece

Product Review
by David Knisely

30mm WIDE SCAN Type III Eyepiece

Available from Astrosystems
$225

The popularity of wide-field eyepieces has surged in recent years, and,
to a certain extent, so has their cost and complexity. Systems containing
more than the usual handful of elements are required to achieve good
correction of aberrations over wider fields especially in the shorter f/ratio
telescopes we see today. It was with some trepidation that I heard of the new
WIDE SCAN TYPE III eyepiece available from Astrosystems. I tried one and
decided that, for its cost, it might have a place in my eyepiece box.

The 30mm WIDE SCAN TYPE III is a 5-element 2 inch barrel diameter
eyepiece similar in size to a larger Erfle. The unit is 11 cm (4.33 inches)
long, about 5.7 cm (2.24) inches in diameter, and weighs in at around 455
grams (1 lb). The barrel is a chrome surface which is about 4 cm in length
and the standard 2 inches (5.08 cm) in diameter, with a safety groove for set
screws in its upper third. The 2 inch barrel is threaded for standard 2 inch
filter threads and the interior is grooved to reduced scattered light. The
main section of the eyepiece is a hard black surface with a rubberized knurled
base for better gripping in the hand with an eye lens end that has a standoff
or fixed "eyecup" to help position the eye.
Optically, the lenses are said to be multi-coated, and from the looks of
things, this is true. The coatings had no visible flaws and yielded an
overall greenish cast to light reflecting off the lenses. The eye lens is
about 3.7 cm across and was slightly concave on its outer surface. The field
stop on this eyepiece measures out to 43mm, and is slightly smaller than the
field lens itself, which appeared to be slightly convex. The nature of the
outer surfaces of this eyepiece might indicate that it could be a variation on
the Erfle design, which also has 5 elements. The apparent field of view is
stated to be 84 degrees, and an optical bench measurement showed this to be
accurate. The eye relief is difficult to measure (probably in the 11 to 13mm
range), but the fixed eyecup above the eye lens prevented me from seeing quite
the entire field of view with my glasses on.
I put the eyepiece to the test using my 10 inch f/5.6 Newtonian, my
100mm f/6 refractor, an 8 inch Celestron Schmidt-Cassegrain and a 14 inch
Celestron Schmidt-Cass. In larger focal ratios such as the f/10 SCTs, the
eyepiece performed fairly well, with fairly sharp star image over much of the
field of view. For a more stringent test, in the C14, I slewed Antares from
one edge of the field to the other and the eyepiece did start to show a little
astigmatism as the star got into the outer portions of the field. However, it
was nice to be able to fit the entire moon in the field of view with that
scope, even if the edges weren't perfectly sharp! The view was fairly high in
contrast, so the coatings looked to be doing their job. However, in shorter
f/ratios, the performance did decline in the outer third of the field. The
eyepiece yielded a whopping 4.1 degree true field in my 100mm f/6 refractor,
but at the cost of some noticable astigmatism. This became most apparent from
about 70% of the field radius out to the edge, where star images became short
arcs rather than points. It wasn't quite as bad as the astigmatism I had seen
in the 24mm Speers-Waler, but it was present. However, the views of the star
fields of the Milky Way were quite stunning even with the aberration present.
There is some pin-cushion distortion with this eyepiece which is
noticable if looking at straight lines near the edge of the field. However,
it isn't excessive, and in fact, is comparable to that found in some of my
Plossl eyepieces with their much smaller apparent fields of view. There was
little chromatic aberration present in this eyepiece (except perhaps towards
the edges when the eye is moved out of its normal centered observing
position), so it is fairly well corrected in that regard. Still, it looks
like this design could be a somewhat "pushed" Erfle, and that the design was
stretched perhaps a little too much really shows when used at focal ratios
below f/10. Use of a Barlow improved things somewhat, but did not eliminate
the astigmatism. I noted no severe kidney beaning or blackout, although you
do want to keep your eye well-centered on the eyepiece and right up to the
hard eyecup "guide" if you want to see the entire field. Compared to things
like the Meade 14mm Ultrawide or the TeleVue 31mm Nagler, this eyepiece's
performance wasn't exactly stellar, but it didn't cost nearly as much as those
two eyepieces either. If users want tack-sharp star images across an 80+
degree apparent field, they should be ready to pay the big bucks for a more
complex eyepiece design that delivers that kind of quality.

In summary, the Astrosystems 30mm WIDE SCAN III eyepiece is not in the
same league as the more expensive wide-field designs, but it does offer some
interesting wide-field performance which some people might find useful,
especially in an eyepiece that costs less than $250.

--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

**********************************************
* Attend the 10th Annual NEBRASKA STAR PARTY *
* July 27-Aug. 1st, 2003, Merritt Reservoir *
* http://www.NebraskaStarParty.org *
**********************************************

I have one also Ed...great eyepiece for the price...little coma
on the very edge working with an f4.5 system, but except for that,
which does not bother me, it is one great widefield eyepiece,
the 30 mm Type III Astrosystems WS. (Beats that 31 mm- $620 one, price
wise).
Clear skies,
Tom W.



Edward wrote:
"David Knisely" wrote in message
...

Product Review
by David Knisely

30mm WIDE SCAN Type III Eyepiece

Available from Astrosystems
$225

The popularity of wide-field eyepieces has surged in recent years,

and,

to a certain extent, so has their cost and complexity. Systems containing
more than the usual handful of elements are required to achieve good
correction of aberrations over wider fields especially in the shorter

f/ratio

telescopes we see today. It was with some trepidation that I heard of the

new

WIDE SCAN TYPE III eyepiece available from Astrosystems. I tried one and
decided that, for its cost, it might have a place in my eyepiece box.

SNIP
--
David W. Knisely


David,
Thanks for posting your experiences. I have a WS III in the box to and
really enjoy it. I have three scopes: two f8's and an f12. Last weekend I
had the opportunity to look through Tom T's BW Optik 30mm at a star party.
The WS III appeared to have a higher quality finish and coatings, but a
quick peek through the eyepieces revealed they are quite close in
performance. More time with better skies would be needed to offer much
more detail.

Ed

On Wed, 06 Aug 2003 23:29:17 GMT, "Edward" wrote:

Hi Ed,

You wrote:

Last weekend I
had the opportunity to look through Tom T's BW Optik 30mm at a star party.
The WS III appeared to have a higher quality finish and coatings, but a
quick peek through the eyepieces revealed they are quite close in
performance.

Curious if you denoted any difference with issue of blackout. It
seems to me from memory the Widescan was more prone to it than is the
new Chinese clone. This potentially having a lot to do with the
smaller, useable field stop acting as an eye guide. Did you by chance
get an indication one way or another?

Thanks in advance,

Pete

On Wed, 06 Aug 2003 14:59:44 -0500, David Knisely
wrote:

Product Review
by David Knisely

30mm WIDE SCAN Type III Eyepiece

snip

Hi David,

As usual a premier quality review. Was greatly enjoyed. This serves
well as example for others to follow.

Thanks!

Pete

Hi there. You posted:

Curious if you denoted any difference with issue of blackout. It
seems to me from memory the Widescan was more prone to it than is the
new Chinese clone. This potentially having a lot to do with the
smaller, useable field stop acting as an eye guide. Did you by chance
get an indication one way or another?

The exit pupil edge is fairly sharp and pronounced so you do need to keep your
eye fairly well centered when using the eyepiece, but the it wasn't showing
some of the horrid blackout or kidney beaning I have seen with some eyepieces.
The eyepiece overall acts a bit like an Erfle, and the unit has a somewhat
conical hard plastic eyecup at the end to act as the "guide". Clear skies to
you.
--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

**********************************************
* Attend the 10th Annual NEBRASKA STAR PARTY *
* July 27-Aug. 1st, 2003, Merritt Reservoir *
* http://www.NebraskaStarParty.org *
**********************************************

Yes, David, I agree...the 30 mm WS Type III acts similar, but not
as pronounced as my 2" 32 mm Erfle...but the curvature effects
are not nearly as pronounced...very good analogy. I noted that too.
Clear Skies,
Tom W.



David Knisely wrote:
Hi there. You posted:

Curious if you denoted any difference with issue of blackout. It
seems to me from memory the Widescan was more prone to it than is the
new Chinese clone. This potentially having a lot to do with the
smaller, useable field stop acting as an eye guide. Did you by chance
get an indication one way or another?


The exit pupil edge is fairly sharp and pronounced so you do need to
keep your eye fairly well centered when using the eyepiece, but the it
wasn't showing some of the horrid blackout or kidney beaning I have seen
with some eyepieces. The eyepiece overall acts a bit like an Erfle, and
the unit has a somewhat conical hard plastic eyecup at the end to act as
the "guide". Clear skies to you.

David

I have the 30mm widescan II and like it very much. Im using it in 8"
f6 newt and a 16" f 4.5 newt.. This eyepiece coupled with the
Universtiy optics 2" barlow is really nice..

Ive also just got in the 13 and 20mm widescans. There also nice for
the money.

Rich


On Wed, 06 Aug 2003 14:59:44 -0500, David Knisely
wrote:

Product Review
by David Knisely

30mm WIDE SCAN Type III Eyepiece

Available from Astrosystems
$225

The popularity of wide-field eyepieces has surged in recent years, and,
to a certain extent, so has their cost and complexity. Systems containing
more than the usual handful of elements are required to achieve good
correction of aberrations over wider fields especially in the shorter f/ratio
telescopes we see today. It was with some trepidation that I heard of the new
WIDE SCAN TYPE III eyepiece available from Astrosystems. I tried one and
decided that, for its cost, it might have a place in my eyepiece box.

The 30mm WIDE SCAN TYPE III is a 5-element 2 inch barrel diameter
eyepiece similar in size to a larger Erfle. The unit is 11 cm (4.33 inches)
long, about 5.7 cm (2.24) inches in diameter, and weighs in at around 455
grams (1 lb). The barrel is a chrome surface which is about 4 cm in length
and the standard 2 inches (5.08 cm) in diameter, with a safety groove for set
screws in its upper third. The 2 inch barrel is threaded for standard 2 inch
filter threads and the interior is grooved to reduced scattered light. The
main section of the eyepiece is a hard black surface with a rubberized knurled
base for better gripping in the hand with an eye lens end that has a standoff
or fixed "eyecup" to help position the eye.
Optically, the lenses are said to be multi-coated, and from the looks of
things, this is true. The coatings had no visible flaws and yielded an
overall greenish cast to light reflecting off the lenses. The eye lens is
about 3.7 cm across and was slightly concave on its outer surface. The field
stop on this eyepiece measures out to 43mm, and is slightly smaller than the
field lens itself, which appeared to be slightly convex. The nature of the
outer surfaces of this eyepiece might indicate that it could be a variation on
the Erfle design, which also has 5 elements. The apparent field of view is
stated to be 84 degrees, and an optical bench measurement showed this to be
accurate. The eye relief is difficult to measure (probably in the 11 to 13mm
range), but the fixed eyecup above the eye lens prevented me from seeing quite
the entire field of view with my glasses on.
I put the eyepiece to the test using my 10 inch f/5.6 Newtonian, my
100mm f/6 refractor, an 8 inch Celestron Schmidt-Cassegrain and a 14 inch
Celestron Schmidt-Cass. In larger focal ratios such as the f/10 SCTs, the
eyepiece performed fairly well, with fairly sharp star image over much of the
field of view. For a more stringent test, in the C14, I slewed Antares from
one edge of the field to the other and the eyepiece did start to show a little
astigmatism as the star got into the outer portions of the field. However, it
was nice to be able to fit the entire moon in the field of view with that
scope, even if the edges weren't perfectly sharp! The view was fairly high in
contrast, so the coatings looked to be doing their job. However, in shorter
f/ratios, the performance did decline in the outer third of the field. The
eyepiece yielded a whopping 4.1 degree true field in my 100mm f/6 refractor,
but at the cost of some noticable astigmatism. This became most apparent from
about 70% of the field radius out to the edge, where star images became short
arcs rather than points. It wasn't quite as bad as the astigmatism I had seen
in the 24mm Speers-Waler, but it was present. However, the views of the star
fields of the Milky Way were quite stunning even with the aberration present.
There is some pin-cushion distortion with this eyepiece which is
noticable if looking at straight lines near the edge of the field. However,
it isn't excessive, and in fact, is comparable to that found in some of my
Plossl eyepieces with their much smaller apparent fields of view. There was
little chromatic aberration present in this eyepiece (except perhaps towards
the edges when the eye is moved out of its normal centered observing
position), so it is fairly well corrected in that regard. Still, it looks
like this design could be a somewhat "pushed" Erfle, and that the design was
stretched perhaps a little too much really shows when used at focal ratios
below f/10. Use of a Barlow improved things somewhat, but did not eliminate
the astigmatism. I noted no severe kidney beaning or blackout, although you
do want to keep your eye well-centered on the eyepiece and right up to the
hard eyecup "guide" if you want to see the entire field. Compared to things
like the Meade 14mm Ultrawide or the TeleVue 31mm Nagler, this eyepiece's
performance wasn't exactly stellar, but it didn't cost nearly as much as those
two eyepieces either. If users want tack-sharp star images across an 80+
degree apparent field, they should be ready to pay the big bucks for a more
complex eyepiece design that delivers that kind of quality.

In summary, the Astrosystems 30mm WIDE SCAN III eyepiece is not in the
same league as the more expensive wide-field designs, but it does offer some
interesting wide-field performance which some people might find useful,
especially in an eyepiece that costs less than $250.