GSO SuperView 42mm 68° 2" Eyepiece - A Feverish Indoor Review

Being at home sick with a cold today, I had the infectious "bug" to do
some indoor evaluation work with a newly available model Taiwanese
wide-angle eyepiece I found. I bought it because the offered
specifications made it seem a potential candidate as budget
replacement to my University Optics Konig MK-70 40mm.

To the best of my knowledge this new-to-market Guan Sheng Optical Co.
product has been advertised for only three weeks now beginning with
eBay seller adastra4ync. The bid price being set at $69.00 or $79.00
for "Buy-It-Now" with $8.00 U.S. domestic rate shipping. About a week
later eBay seller owl1 launched his sales campaign for it at bid price
$49.00 or $59.00 for "Buy-It-Now" with $6.00 domestic shipping. These
both are likely record breaking cheap prices for a commercially made
astronomical telescope eyepiece in this class.

The outward appearance is clean and speaks of good quality. The
lettering is white paint embossed reading: GSO SUPERVIEW 42mm 68° FIVE
ELEMENTS. It measures 112mm tall with eyecup extended and 55mm for
major body diameter. There is a 22mm wide diamond knurled rubber grip
ring midway on the black anodized upper housing. A fold-down rubber
eyecup is added on top. There is a nicely plated silver colored 2"
format barrel with safety undercut. It is threaded for standard
filters. The optics have a desirable dull reflection green lens
multicoating variation throughout, with 6 air-glass surfaces indicated
as shown from an external light source. The model comes with a lower
barrel slide on dust cap and is placed in a gloss black cover
cardboard box.

There is also a new very similar looking GSO 50mm model out as well.
It is sold at the same price point and is specified as having about a
54° AFOV.

To get some highly useful reference points against a well known model,
I faced the unknown eyepiece head-to-head with my late version
Japanese made University Optics Konig MK-70 40mm 2" eyepiece. The one
I own has the full 70° AFOV vs. 68° as was found in earlier units that
were sold. I also used other various eyepiece optics to more closely
gauge this new models effective AFOV.

Compared Specifications (GSO SV 42mm / University MK-70 40mm)

Weight: 320g / 525g

Entrance Apertu 40mm / 47.5mm

Exit Apertu 34mm / 40mm

Field Stop: 47mm / 46.5mm

Interestingly the visibly used field stop location for the GSO 42mm is
effectively the very bottom edge (entrance ID) of the eyepiece barrel
itself. For reference, that's where the filter threads are located.
Holding the eyepiece alone to the eye shows it is vague visually to
see its circle all at one time. My eye tended to quicky fall below
the approx. 15mm eye relief margin to then barrel distort the view.

Once gauged, the effective AFOV measured no more than 64° with the
eyepiece freestanding. When placed in my (common) 41.5mm seat
aperture 2" 90° mirror star diagonal, the measure then fell to 58°.
This is well below the advertised (and physically labelled)
specification of 68° AFOV.

Since "under the weather", I wasn't about to head outside to get other
measures of actual optic system performance. Instead, I opted for
some brief views out a window with a 100mm f/6 achromat refractor.
The image given was sharp for approx. 80% from center-to-edge. Not
bad for the given 58° apparent field angle of the design. There was a
slight bit of field curvature also noted.

At this point I needed to stop and take a rest. Because the
University MK-70 40mm gives such a vastly larger view, I think I will
just hang onto it and give the GSO 42mm away to a friend in need.

Clear skies,

Pete

Pete Rasmussen wrote in message . ..
Being at home sick with a cold today, I had the infectious "bug" to do
some indoor evaluation work with a newly available model Taiwanese
wide-angle eyepiece I found.



Hi Pete ,

Sure hope your feeling better soon. Thanks for this
thoughtful evaluation . You are quite an asset to SAA . Looking
forward to some warmer days .
Leonard

On 4 Mar 2004 13:29:40 -0800, (Leonard) wrote:

Hi Pete ,

Sure hope your feeling better soon. Thanks for this
thoughtful evaluation . You are quite an asset to SAA . Looking
forward to some warmer days .
Leonard

Thanks, Leonard for the well wishes and commendation. The new
eyepiece seems nice and does have good user eyerelief. Probably very
sharp with a barlow, too. Looks like we beat your weather it has been
to 72° here the other day.

Clear skies,

Pete

I want to thank Pete for pointing out this GSO eyepiece. As he
mentioned the original specification statement of 68 degrees is rather
optimistic. My measure of the barrel that serves as a field stop is
47.5 mm. This gives an AFOV of about 65 degrees for a 42 mm eyepiece.
In the current shipment of these eyepieces, GSO has removed the 68
degree label. In their wholesale literature, they quote the eyepiece
as 65 degrees which it is.

The Meade $300 40 mm SuperWide is listed as having an AFOV of 68
degrees. I have seen a published review of this eyepiece that
indicates a field stop of 43 mm. If this estimate of the field stop is
correct, the Meade also has an AFOV of about 65 degees if my math is
correct. In any case, as Pete points out, the GSO should be good value
at the price.

There also is a 30 mm in this series. This one has a 37 mm field stop.
Again if my math is correct, this comes out to about a 70 degree AFOV.

Clear Skies (or at least less snow),

TOM Roginski (owl1)

Pete Rasmussen wrote in message . ..
Being at home sick with a cold today, I had the infectious "bug" to do
some indoor evaluation work with a newly available model Taiwanese
wide-angle eyepiece I found. I bought it because the offered
specifications made it seem a potential candidate as budget
replacement to my University Optics Konig MK-70 40mm.

To the best of my knowledge this new-to-market Guan Sheng Optical Co.
product has been advertised for only three weeks now beginning with
eBay seller adastra4ync. The bid price being set at $69.00 or $79.00
for "Buy-It-Now" with $8.00 U.S. domestic rate shipping. About a week
later eBay seller owl1 launched his sales campaign for it at bid price
$49.00 or $59.00 for "Buy-It-Now" with $6.00 domestic shipping. These
both are likely record breaking cheap prices for a commercially made
astronomical telescope eyepiece in this class.

The outward appearance is clean and speaks of good quality. The
lettering is white paint embossed reading: GSO SUPERVIEW 42mm 68° FIVE
ELEMENTS. It measures 112mm tall with eyecup extended and 55mm for
major body diameter. There is a 22mm wide diamond knurled rubber grip
ring midway on the black anodized upper housing. A fold-down rubber
eyecup is added on top. There is a nicely plated silver colored 2"
format barrel with safety undercut. It is threaded for standard
filters. The optics have a desirable dull reflection green lens
multicoating variation throughout, with 6 air-glass surfaces indicated
as shown from an external light source. The model comes with a lower
barrel slide on dust cap and is placed in a gloss black cover
cardboard box.

There is also a new very similar looking GSO 50mm model out as well.
It is sold at the same price point and is specified as having about a
54° AFOV.

To get some highly useful reference points against a well known model,
I faced the unknown eyepiece head-to-head with my late version
Japanese made University Optics Konig MK-70 40mm 2" eyepiece. The one
I own has the full 70° AFOV vs. 68° as was found in earlier units that
were sold. I also used other various eyepiece optics to more closely
gauge this new models effective AFOV.

Compared Specifications (GSO SV 42mm / University MK-70 40mm)

Weight: 320g / 525g

Entrance Apertu 40mm / 47.5mm

Exit Apertu 34mm / 40mm

Field Stop: 47mm / 46.5mm

Interestingly the visibly used field stop location for the GSO 42mm is
effectively the very bottom edge (entrance ID) of the eyepiece barrel
itself. For reference, that's where the filter threads are located.
Holding the eyepiece alone to the eye shows it is vague visually to
see its circle all at one time. My eye tended to quicky fall below
the approx. 15mm eye relief margin to then barrel distort the view.

Once gauged, the effective AFOV measured no more than 64° with the
eyepiece freestanding. When placed in my (common) 41.5mm seat
aperture 2" 90° mirror star diagonal, the measure then fell to 58°.
This is well below the advertised (and physically labelled)
specification of 68° AFOV.

Since "under the weather", I wasn't about to head outside to get other
measures of actual optic system performance. Instead, I opted for
some brief views out a window with a 100mm f/6 achromat refractor.
The image given was sharp for approx. 80% from center-to-edge. Not
bad for the given 58° apparent field angle of the design. There was a
slight bit of field curvature also noted.

At this point I needed to stop and take a rest. Because the
University MK-70 40mm gives such a vastly larger view, I think I will
just hang onto it and give the GSO 42mm away to a friend in need.

Clear skies,

Pete

(Tom Roginski) wrote in message . com...
Pete Rasmussen wrote in message . ..


Interestingly the visibly used field stop location for the GSO 42mm is
effectively the very bottom edge (entrance ID) of the eyepiece barrel
itself. For reference, that's where the filter threads are located.

Pete

It's a bit difficult to see how the filter-thread end of the barrel
could be the field stop, as the cone of light is expanding as it
passes by the filter threads and maxes out where the the field lens
meets the focal plane of the inverted cone of light (where the clear
diameter of the field lens equals the diameter of the light cone).
That is the location of the field stop. Unless the field lens is at
the very end of the barrel, right at the filter threads, the field
stop cannot be at the filter threads.
Clear skies,
Shneor Sherman

On 8 Mar 2004 13:00:20 -0800, (Tom Roginski)
wrote:

I want to thank Pete for pointing out this GSO eyepiece. As he
mentioned the original specification statement of 68 degrees is rather
optimistic. My measure of the barrel that serves as a field stop is
47.5 mm. This gives an AFOV of about 65 degrees for a 42 mm eyepiece.
In the current shipment of these eyepieces, GSO has removed the 68
degree label. In their wholesale literature, they quote the eyepiece
as 65 degrees which it is.

The Meade $300 40 mm SuperWide is listed as having an AFOV of 68
degrees. I have seen a published review of this eyepiece that
indicates a field stop of 43 mm. If this estimate of the field stop is
correct, the Meade also has an AFOV of about 65 degees if my math is
correct. In any case, as Pete points out, the GSO should be good value
at the price.

There also is a 30 mm in this series. This one has a 37 mm field stop.
Again if my math is correct, this comes out to about a 70 degree AFOV.

Clear Skies (or at least less snow),

TOM Roginski (owl1)
Hi Tom,

You are certainly welcome and thank you too for adding further
information. Let me say it has always been a pleasure dealing with
you. I wish I had bought the 42mm from you a week later when I saw
your ad! Anyway, am definitely looking forward to the new 30mm 70°
just mentioned it sounds excellent.

Clear skies,

Pete

On 9 Mar 2004 08:07:39 -0800, (Shneor Sherman)
wrote:

(Tom Roginski) wrote in message . com...
Pete Rasmussen wrote in message . ..


Interestingly the visibly used field stop location for the GSO 42mm is
effectively the very bottom edge (entrance ID) of the eyepiece barrel
itself. For reference, that's where the filter threads are located.

Pete

It's a bit difficult to see how the filter-thread end of the barrel
could be the field stop, as the cone of light is expanding as it
passes by the filter threads and maxes out where the the field lens
meets the focal plane of the inverted cone of light (where the clear
diameter of the field lens equals the diameter of the light cone).
That is the location of the field stop. Unless the field lens is at
the very end of the barrel, right at the filter threads, the field
stop cannot be at the filter threads.
Clear skies,
Shneor Sherman


I see it you aren't speaking to me directly, Shneor, yet I will reply
to the impersonalization.

I don't have a ray trace to understand why but the *effective* field
stop, as I wrote, is "visably used" at bottom of barrel for the
design. The actual focal plane is slightly higher up but the light
cone, for whatever reason, is factually clipped at the entrance where
the filter threads are located. This of course gives a "fuzzy" field
stop impression in normal use. I then explained that once a user adds
a further restrictive stop (ie. smaller eyepiece holder seat aperture
in the case of star diagonals) at the same relative point in space,
the AFOV of the eyepiece is reduced even more. This is without
question the case with this new eyepiece. Buy one and see for
yourself. I certainly don't lie about anything I write in review.

You indicate thrice about the field lens in eyepiece design, "meeting
the focal plane" and, "That is the location of the field stop" and,
"Unless the field lens is at the very end of the barrel, right at the
filter threads, the field stop cannot be at the filter thread". Well,
the field lens should never be *at* the field stop location as all the
dust attracted to the outer lens surface will be magnified and in
focus. Virtually all common designs have the field stop spaced
*before* the R1 surface or, in between elements like in the Nagler to
prevent this.

So, not to change the subject, did you not receive my last private
email response to your inquiry the other day? I kindly provided you
workable solutions to your quest to have wider true field with 1.25"
binoviewer eyepieces. One was concept to add an eye element to a 35mm
Ultima to reduce FL and increase AFOV so it would be useable in your
f/4 scope. I never did hear back from you and hope you are one to be
in appreciation of my time.

Pete

Pete Rasmussen wrote in message . ..
On 9 Mar 2004 08:07:39 -0800, (Shneor Sherman)
wrote:

(Tom Roginski) wrote in message . com...
Pete Rasmussen wrote in message . ..


Interestingly the visibly used field stop location for the GSO 42mm is
effectively the very bottom edge (entrance ID) of the eyepiece barrel
itself. For reference, that's where the filter threads are located.

Pete

It's a bit difficult to see how the filter-thread end of the barrel
could be the field stop, as the cone of light is expanding as it
passes by the filter threads and maxes out where the the field lens
meets the focal plane of the inverted cone of light (where the clear
diameter of the field lens equals the diameter of the light cone).
That is the location of the field stop. Unless the field lens is at
the very end of the barrel, right at the filter threads, the field
stop cannot be at the filter threads.
Clear skies,
Shneor Sherman


I see it you aren't speaking to me directly, Shneor, yet I will reply
to the impersonalization.

I don't have a ray trace to understand why but the *effective* field
stop, as I wrote, is "visably used" at bottom of barrel for the
design. The actual focal plane is slightly higher up but the light
cone, for whatever reason, is factually clipped at the entrance where
the filter threads are located. This of course gives a "fuzzy" field
stop impression in normal use. I then explained that once a user adds
a further restrictive stop (ie. smaller eyepiece holder seat aperture
in the case of star diagonals) at the same relative point in space,
the AFOV of the eyepiece is reduced even more. This is without
question the case with this new eyepiece. Buy one and see for
yourself. I certainly don't lie about anything I write in review.

Hi Pete,
I was not implying anything of the sort, and I thought I _was_
replying to you. Of course, a field stop can exist between the barrel
end and the field lens. I know my description was lacking in
completeness, and this one of those times where a picture would be
worth a thousand words. In any case, eyepieces that try to maximize
the field of view do not have a field stop other than the barrel.


You indicate thrice about the field lens in eyepiece design, "meeting
the focal plane" and, "That is the location of the field stop" and,
"Unless the field lens is at the very end of the barrel, right at the
filter threads, the field stop cannot be at the filter thread". Well,
the field lens should never be *at* the field stop location as all the
dust attracted to the outer lens surface will be magnified and in
focus. Virtually all common designs have the field stop spaced
*before* the R1 surface or, in between elements like in the Nagler to
prevent this.

Im my experience, having eyepieces like this, I have not found dust to
be a problem at all.

So, not to change the subject, did you not receive my last private
email response to your inquiry the other day? I kindly provided you
workable solutions to your quest to have wider true field with 1.25"
binoviewer eyepieces. One was concept to add an eye element to a 35mm
Ultima to reduce FL and increase AFOV so it would be useable in your
f/4 scope. I never did hear back from you and hope you are one to be
in appreciation of my time.

Sorry I did not get back to you. I do appreciate the thought you put
into your reply. I don't have lenses that would allow me to take
advantge of your thoughtful suggestions, nor do I have means of
mounting them even if I did. I know you often modify eyepieces. I have
never done that. Again, thank you for your suggestions.

Shneor

Pete

On 11 Mar 2004 08:50:20 -0800, (Shneor Sherman)
wrote:

Hi Shneor,

I know what you mean about a picture being useful. And if I took this
42mm eyepiece apart it might become obvious why it behaves as it does.

BTW, have tried it on the night sky now and is a bit tricky to hold
the view. Still nice and sharp and contrasty though and the 80%
toward edge estimate made earlier with f/6 refractor was about right.

What eyepieces did you have that were stopped right at the field lens?
If were to be the case all the dust, scratches, etc. would be focused
and magnified in view. This because the field stop is normally set at
the focal plane. Kellners are famous for dust showing up since the
focal plane is so close to the R1 surface in that design.

You can send a 35mm Ultima to me if you want for experimenting. I
could see about modifying it with an achromat added at eyeside. Is
often straight forward ATM kinda stuff and done simply with PVC and
tape.

I have built a super nice 6-element 47mm 40° 1.25 eyepiece before
similar to the 35mm Ultima design but without the unfriendliness to
the eye. Was over 10% wider than any commercial eyepiece and, since
with longer FL, the field stop was sharp and perfectly placed at the
bottom of the barrel ID

Clear skies,

Pete

Pete Rasmussen wrote in message . ..
On 9 Mar 2004 08:07:39 -0800, (Shneor Sherman)
wrote:

(Tom Roginski) wrote in message . com...
Pete Rasmussen wrote in message . ..


Interestingly the visibly used field stop location for the GSO 42mm is
effectively the very bottom edge (entrance ID) of the eyepiece barrel
itself. For reference, that's where the filter threads are located.

Pete

It's a bit difficult to see how the filter-thread end of the barrel
could be the field stop, as the cone of light is expanding as it
passes by the filter threads and maxes out where the the field lens
meets the focal plane of the inverted cone of light (where the clear
diameter of the field lens equals the diameter of the light cone).
That is the location of the field stop. Unless the field lens is at
the very end of the barrel, right at the filter threads, the field
stop cannot be at the filter threads.
Clear skies,
Shneor Sherman


I see it you aren't speaking to me directly, Shneor, yet I will reply
to the impersonalization.

I don't have a ray trace to understand why but the *effective* field
stop, as I wrote, is "visably used" at bottom of barrel for the
design. The actual focal plane is slightly higher up but the light
cone, for whatever reason, is factually clipped at the entrance where
the filter threads are located. This of course gives a "fuzzy" field
stop impression in normal use. I then explained that once a user adds
a further restrictive stop (ie. smaller eyepiece holder seat aperture
in the case of star diagonals) at the same relative point in space,
the AFOV of the eyepiece is reduced even more. This is without
question the case with this new eyepiece. Buy one and see for
yourself. I certainly don't lie about anything I write in review.

Hi Pete,
I was not implying anything of the sort, and I thought I _was_
replying to you. Of course, a field stop can exist between the barrel
end and the field lens. I know my description was lacking in
completeness, and this one of those times where a picture would be
worth a thousand words. In any case, eyepieces that try to maximize
the field of view do not have a field stop other than the barrel.


You indicate thrice about the field lens in eyepiece design, "meeting
the focal plane" and, "That is the location of the field stop" and,
"Unless the field lens is at the very end of the barrel, right at the
filter threads, the field stop cannot be at the filter thread". Well,
the field lens should never be *at* the field stop location as all the
dust attracted to the outer lens surface will be magnified and in
focus. Virtually all common designs have the field stop spaced
*before* the R1 surface or, in between elements like in the Nagler to
prevent this.

Im my experience, having eyepieces like this, I have not found dust to
be a problem at all.

So, not to change the subject, did you not receive my last private
email response to your inquiry the other day? I kindly provided you
workable solutions to your quest to have wider true field with 1.25"
binoviewer eyepieces. One was concept to add an eye element to a 35mm
Ultima to reduce FL and increase AFOV so it would be useable in your
f/4 scope. I never did hear back from you and hope you are one to be
in appreciation of my time.

Sorry I did not get back to you. I do appreciate the thought you put
into your reply. I don't have lenses that would allow me to take
advantge of your thoughtful suggestions, nor do I have means of
mounting them even if I did. I know you often modify eyepieces. I have
never done that. Again, thank you for your suggestions.

Shneor

Pete