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Home / GSO 30mm & 20mm Super-Views
by Peter Vercauteren 12/15/05 | Email Author

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GSO 30

GSO 30mm Superview


Since I recently bought a 14" Dob, it had become obvious that I started a quest to search for a good wide-field eyepiece around 30mm. From my former telescope (Nexstar 8) I had already inherited a GSO 20mm Super-View (67-deg FOV) and I will also review that eyepiece in this article. Unfortunately, the purchase of my new telescope had stretched the financial limits of my hobby so far (especially with my wife) that Pans or Naglers were completely out of the question. On top of that, my scope is an f/5 and all of the reviews tell you that for faster scopes there is no decent alternative among the cheaper eyepieces, not even in the 150-200$ range. After browsing through the Excelsis and Cloudynights websites over and over again, I decided to go for a GSO 30mm Super-View (70-deg FOV). In the articles and reviews on alternatives this eyepiece surprisingly came out as one of the best for faster scopes, even though it is maybe the cheapest of them all. I also had some very good experiences with the 20mm, which increased my confidence in GSO. So I guessed that spending 59$ on the eyepiece plus another 12$ for shipment to Europe would not break the bank and I wanted to take the risk. The 20mm only costs 34$ which almost sounds too good to be true. Really, these eyepieces are very very cheap.

I purchased both through Owl services and within a week the postman came to my door with a nice package containing the 30mm. Very good service! Inside, there was the beautiful and well-finished GSO eyepiece with nice greenish coatings, along with a decent plastic bolt case. The same goes for the 20mm which I bought half a year earlier, although here I had to wait for 3 weeks because of the slow Belgian customs. The 30mm is with its 316g certainly not the heaviest of eyepieces in its class, which is again an advantage when you have a critically balanced Dob. But still the quality of both eyepieces looks and feels superb and it is much better than you would expect from eyepieces at such a nearly ridiculously low price.

So here are some of my observing experiences. First with the 30mm. Just for the record, no coma corrector was used. First because I don't have one and second because I wanted to give a "pure" review for those people who do not have the money to buy one either. On my first clear night after receiving this eyepiece, I immediately turned my telescope in the direction of the Double Cluster. This was one of the main objects for which I intended to use this 30mm Super-View, and it would certainly give me a good idea about its qualities with all these stars scattered across the 70-degree FOV. The 30mm does take a bit of backward focusing in my telescope, but fortunately not past the limits of my HC-2 helical focuser. Anyway, it is absolutely not par-focal with the 20mm, which sits about half-way the focuser, in the vicinity of my 10mm Antares Speers-Whaler and Celestron 6mm and 4mm Pl?ssls. But since I only care about having a decent view, this difference doesn't bother me at all.

When I eventually got the focus right, I was filled with amazement. Stars were tack-sharp for about 70-80% of the FOV, and the rest was well within (my personal) tolerance limits. In the big sharp central area, stars really looked like the tiniest pinpoints you would only expect from the very high-end eyepieces. In the outer 20-30% stars became "a bit less pinpoints" and the especially brighter stars in the outer rim were a bit "stretched" into "eggs" with their points away from the centre. Only the very outer edge (last 2-3%) was a bit fuzzy. Astigmatism and false colour were only marginal to none. There was hardly any kidney-beaning and the 30mm easily makes you find a perfect and comfortable viewing position. This comment was shared by a friend of my astronomy club who also recently took a look through my new toy. He too thought that it is a wonderful eyepiece which can keep you gazing for hours without getting uncomfortable. The rubber guard of both eyepieces is a bit hard and can not be folded. But since you don't really touch it when looking, especially with the big lens of the 30mm, this is again not a disadvantage for me. Transparency is excellent by the way, just what you would expect from a high-quality product, and I've really started to love looking through it. When I then turned to the 20mm, the view was surprisingly similar, apart from the higher magnification. Here the Double Cluster only just fitted in the FOV and now you could see a bit better that the outer edges are not 100% sharp. But on that object I wouldn't use this eyepiece anyway.

Onto another nice open cluster, M37. In the 30mm, the cluster fills about half of the FOV and again stars were like the smallest of pinpoints you can imagine. Yet, stars show their (true) colours very well and the brighter orange star in front of the cluster really stood out. Again, the view in the 20mm was exactly the same, apart from the higher magnification. The cluster showed all of its details and perfectly fitted into the FOV of this eyepiece.

Next, I screwed on a Lumicon UHC on both eyepieces and I turned to M27. With the 30mm the Dumbell looked absolutely beautiful, although a bit too small. No question about it, this is a very good deep-sky scanning eyepiece! I actually rather preferred to try it on larger nebulas like the Veil or North-America, but the damp sky conditions and the first quarter moon didn't really allow it. In the 20mm, the Dumbell really shined and even under these bad skies the outer lobes and most of the finer details were stunning. I had the chance to try the 20mm under better conditions and what I saw was absolutely amazing. Details were superb and you could just keep on watching. Some might argue that this says more about the telescope than about the eyepiece itself. But I have to disagree on this. An eyepiece which shows a lot of coma and other errors just isn't fun to look through and will completely spoil your view. The GSO eyepieces will make you want to look more and more. I think that this says a lot about them. Anyway, I can't wait to try both eyepieces on M42.

Overall, the performance of the GSOs is very good to even excellent, even on a faster scope like mine and especially given its price. But let me be clear. These eyepieces are not and will never be a Panoptic or similar! But what do you expect from eyepieces at only 1/6th of the Pan's price? Then again, what is perfection? Does it even exist? A Pan will also show coma and it's a pity nobody in my club owns one so I could make a real head-to-head comparison. I have looked through a 35mm Pan once a couple of months ago, but of course this experience would be useless in this article. Yet, I believe that the so-called problems with faster scopes are a bit over-rated. Maybe the GSO's errors will become larger in an f/4.2? I don't know. All I can say is that they perform very well in my f/5.

So it all boils down to what you want. Are you a perfectionist and is money not an issue? Well, then a Panoptic or Nagler would be the best choice for you. The GSOs are definitely not "Pan-killers". But they are a darn good alternative!

Honesty obliges me to write one small post scriptum. The same friend in my club also has a 20mm Super-View. When I looked through it, the view was terrible with most of the FOV unsharp and even "seagulls" near the edges. At that time I didn't think of swapping his eyepiece with mine so we could not identify the problem as maybe being a quality difference from one GSO to the other. So for the moment I can only guess. Does the quality of the telescope mirrors play a part (mine's a Woden optics)? Is cool-down perhaps an issue? Therefore, again, I can only tell you what I observed through my GSO eyepieces in my telescope.

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