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GSO 2" Superview 42mm
Submitted: Thursday, 7th April 2005 by Mark Hodson

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The GSO 2" SuperView 42mm

Update 6th December 2004 - please see end of review for more updated information about performance in an f/5 scope.

Update 24th November 2004 - please see end of review for more updated information.

My name is Mark Hodson from South East Queensland and I don’t claim to be any sort of expert when it comes to telescope optics. My only claim to fame is having had several commercial, custom and home made scopes over my 40 or so years. I have owned, and viewed through many different eyepieces ranging from cheapish to Televiews which are regarded by many to be the panicle of eyepieces and I would have to agree on this.

The problem is that not every one can afford a Teleview and have to contend with finding a cheaper alternative.

I have had several people interested in a review on this eyepiece so will do this preliminary review and update it when I can.

Now I am not going to compare this eyepiece with a TV, Meade or Pentax, but am just going to give a simple run down on how it performs in a 12.5” f6 Newtonian and later on an update on a F5 Newtonian and an 80mm f7.5 ED refractor.

I will also be using a GSO 2” 2X Barlow and using it in a 2x and 1.5x format as well as using a Teleview 4x Powermate just to see how it goes in these items.



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The folding eyecup

This range of eyepieces has stirred up a lot of interest and a quick search on the Web will find many comments and reviews on these.

The 2” range of these eyepieces come in a 50mm 42mm and 30mm all 5 elements design and with a claimed AFOV of 54, 65, and 70 degs respectively but this depends on who is selling them and again there is some controversy as to the actual AFOV of these eyepieces. It seems the general consensus is the 42mm is more like 56-60degs.

Now as I am no expert on this field, I can only state that the fields stop is 41.5mm. I have tried to get a confirmation on this from GSO but have not had a reply as of yet.

What I have done is to compare it with a 42mm 2” Kellner I admit to owning, which is a 3 element known 50deg, eyepiece against the side of a building to see what the difference is.

The conclusion is the Superview has a definite and noticeable larger field of view, but as to weather it is 65degs I can’t say at the moment, but I intend to try to measure it in due course.

The main thing I noticed is that horizontal and vertical lines of the building sidings were noticeable straighter in the Superview as compared to the Kellner design and this is in the f6 Newtonian at a few hundred metres.



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Check the size

The green blue coatings on these eyepieces and the Barlow of the same brand are first rate and I will compare them to my Teleview Powermate in depth of color under the same light. There is also a fold down eye cap which I find just about the right height for spectacle wearers and the eye relief is about 20mm.

The 42mm is 330grams and the top element is 33mm. There is a nice recess for the retainer screw to locate in. You can judge the size of this eyepiece in the photo on the left.



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Taking out the barlow lens

A little trick you can do if you have this eyepiece and 2x Barlow is to remove the Barlow lens assemble from the bottom and screw it into the filter threads on the bottom of the eyepiece . This give about a 1.5x magnification instead of 2x. It also requires more focus travel out to come to focus, so Newtonian owners may have some issues with this.

Now down to some viewing results and remember these are all initially in an F6 Newtonian with a well corrected RF Royce Conical mirror.

I will be focusing on brightness and edge of field correction and wow factor.

Where I live in the Lockyer Valley South East Queensland the skies are nice and dark, and after our recent downpour quite clear at last.

Objects viewed include M32 and companions M33, Pleaides, M42, The Large and Small Magellanic Clouds, Opencluster CR132, Saturn and many others.



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Screwing the barlow into the GSO 42mm to get 1.5x magnification

The first thing noticed is the ease of eye placement whether you wear glasses or not.

I wear glass for a slight astigmatism in my right eye but some times view with my left eye without glasses, and found the eye cap to be just about right for either method.

I was able to see the whole field of view and did not experience any blacking out of the image. Also with the 42mm I would have a 7mm exit pupil and at my age could not see the central obstruction of my F6 newt. 

In moving the scope over open and globular clusters and star field I found the stars to remain pin points of light as they entered and left the field of view. There appeared to be no distortion of the star fields as I panned across them.

The background sky appeared black may be not as much as my UO orthoscopics.

Speaking of which I tried the 42mm with the 4X Powermate on Saturn at 180X and compared it to using 25mm Orthoscopic in my 4X Powermate and found the detail of Saturn easy to pick out. Not as good as the Ortho combo but there is a magnification difference.

On bright stars or Saturn I could not see any internal reflections - something I do get in the Orthoscopics.

I also tried the 2x Barlow at both 2x and with the Barlow lens assemble in the 42mm housing at 1.5x. The one draw back to using it in the later at 1.5x is you need a fair bit of outward travel of the focuser, so Newtonian owners might have an issue with this, as I only just came to focus. But it does work and found I used it like this quite often during the night.

The focus distance of the 42mm alone posed no problem in the Newtonian and was not far from my orthoscopics .

So with these two items I now have the equivalent of 3 or 4 eyepieces with either Barlow or Powermate. The GSO Barlow is no Powermate but found it a lot better than a far more expensive Barlow from one of the big companies.

In summing up the edge correction at f6 is very good and typical or better of what can be expected of a 5 element design. I found that I did not have to refocus to bring stars at the edge into focus they were still just little points of light.

As I stated in the beginning these are not 82deg Televiews but than they don’t cost hundreds of dollars either. If your on a budget and want a good quality bargain priced 2” wide field eyepiece then at AU$99.00 you can’t go wrong and in my opinion they're well worth the money even at twice the price. I may get another of the series myself.

Your comments and criticisms and corrections are welcome in the forum but remember this is my first review so be kind to me.

The price was from Andrews Communication and I don’t have any affiliation with them except for some past purchases.

Clear Skies Mark Hodson.



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Checking the AFOV

Update 24th November 2004

After some research on the web into the AFOV of this eyepiece I stumbled across this quote from an owner of a Superview. 

“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.”

Now it appears that every comment or review has had something to say about the quoted AFOV. Everybody including myself, and remember I did say I was not an expert in optics, has measured the field stop on the lens retainer half way up the Barrel.

With this info in head I set about confirming this idea of the barrel end as the field stop. What I did is while looking down the eyepiece I introduced an object from the side towards the light path.

What I found is the instant the object went past the Inside diameter of the barrel towards the optical centre axis of the eyepiece it became visible in the field of view. This I found interesting, and while still looking down the barrel proceeded to unscrew the chrome barrel from the bottom of the eyepiece.

I was actually able to see the barrel turning in the view.

Placing a small piece of blue tack on the 41.5mm lens retainer which everyone thought was the field stop failed to show up until after it protruded 1.0mm towards the optical centre.

So with the formula for working out the AFOV and it goes like this > AFOV = diameter of field stop / focal length of eyepiece x 57.3 < the AFOV works out to about 64.8 degrees. With the 41.5mm that was wrongly being used it comes out at about the 56 degrees. I have since sat down and checked my eyepiece collection as to weather they measure up and surprisingly most do.

So another lesson learnt.

Please, any comments or corrections on this subject directed towards the forum would be appreciated. For those who have requested, I should have the results with the refractor and f5 newt within a couple of weeks.

Also I will be doing a review on the Andrews 2” 30mm 80 degree 5 element and the 11/4” Superview 20mm 68degree 5 element eyepieces , and I checked there AFOV as well.

Update 6th December 2004

Finally got to finish the testing of the 42mm on Saturn%25 (Graeme's) 12” F5 GSO Dobsonian and on my new 80mm f7.5 ED refractor. The Dobsonian has been fully colliminated, including the focuser.

Objects viewed included 47 Tucanae, Orion Nebula, the Pleiades and Sirius.

As expected the view at the edge of the FOV on the F5 Dob was not quite as sharp as in the F6 Newtonian of mine, but both Graeme and I felt that it was more than usable at F5 to about 95% of the way out. It really depends on what you expect from a $99.00 eyepiece but we felt that even at twice the price it was a more than a competent eyepiece.

In the refractor it was simply sharp across the whole field with possibly the last 1-2% a little fuzzy, but I put this down to the barrel being used as a field stop and the blackening on the inside where a filter would go was gone and quite shiny.

This I found in my new 30mm 80 deg EP as well and gives a slight yellow coloring in that last bit of the view when used during the day. I have since reblackened the threads and it has reduced this effect quite a lot.

Overall I am very pleased with this eyepiece field of view and sharpness, ease of use and eye relief. It is a definite keeper, although the new 30mm to be reviewed has me not grabbing the 42mm first for those wide field views.

Review by Mark HodsonDiscuss this review at the IceInSpace Forums.
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