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GSO 30mm: Wot No Seagulls?


Nightspore

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The GSO ‘StellaLyra’ 30mm SuperView weighs in at a respectably lightweight 285 grams. It has a claimed 68° FOV with 5 lens elements in 3 groups. The coatings seem like the usual GSO ‘green’.

 

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There is a purported 22mm of eye relief (which seems fairly accurate) and I make it 100mm tall (folded down rubber eye-guard) with a 30mm eye lens. I measured the field stop at 35mm.

 

vWzW7Ptm.jpg

 

The overall aesthetic is a straightforward ‘no-frills’ design with a smooth aluminium barrel. The upper housing features a rubber grip. My guess is that it is some form of Erfle. Mine cost £69.

 

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The SuperView series has been a huge seller for GSO and they can be purchased under various brand names. I have a pair of ‘Altair’ 15mm SuperViews for my binoviewer. However, the SuperView line has been criticised by some for displaying edge of field astigmatism, particularly in faster scopes. Although why anyone expects Panoptic or Nagler type performance at these prices is a bit of a mystery.

 

VUqqGJxm.jpg

 

The 30mm ‘StellaLyra’ seemed like an answer to a particular problem for me. I wanted a lightweight 2” eyepiece around 30mm for rich field viewing with short tube refractors. The weight is important to me as I have a physical disability. For a really fast deployment I want everything to fit into these two bags:

 

tnOcF4km.jpg

 

Heavy eyepieces can also affect balance on light mounts. My usual ‘go to’ eyepieces are 31mm and 36mm Baader Hyperion Aspherics, a 27mm TV Panoptic or a 28mm ES. The 31mm Baader has a larger FOV and a bigger field stop than the SuperView; but it can’t do this:

 

RgWcf9Zm.jpg

 

GSO threads are usually pretty compatible, but it was a bit of a ‘no-brainer’ that my 2” GSO Barlow element would be able to thread into it. Although this does add to the overall weight slightly it saves me carrying another 2” eyepiece. Depending on whether this diminishes the focal length by 1.6x or 1.5x (the jury’s still out) it makes it 18.75mm or 20mm. I tried the Barlow originally with a 32mm GSO RK (Reversed Kellner).

 

UhR3cLym.jpg

 

The RK (shown above in the diagonal) is lightweight, and I like its ergonomics, it produces a bright and well contrasted image. It can also produce the ‘floating in space’ effect often reported in other reversed Kellner designs. Unfortunately it suffers from seagulls the size of pterodactyls in anything faster than f/8. Adding the Barlow element shoots many of the avian dinosaurs down but the fastest scope I can actually use it in is my 80ED DS Pro Evostar (f/7.5). I originally tried the RK in my f/5.8 72ED DS Pro. The results were far from satisfactory. It kind of reminded me of the scene in Star Wars when the Millennium Falcon jumped into hyperspace and all of the stars stretched out into long white lines. I’m not joking.

 

vzz4IEcm.jpg

 

Last night I thought I was in with a chance as it was predicted to be clear for around an hour. Although my weather forecasting apps couldn’t all decide on which particular hour. So I ventured out with the ‘Night of Reckoning’ rapid deployment ST80 at 18:00. The transparency was below average with a few scudding clouds and the seeing was about Antoniadi II~III. The first target (without the Barlow element) was Cr 70 aka the ‘Serpent Cluster’ in Orion’s Belt at 13.3x. To my relief there were no seagulls and well over 70% of the field showed no discernible off-axis astigmatism, although to be honest I tend to predominantly observe on-axis. The Pleiades and Hyades (Melotte 25) were stunning. I spent some time in Cassiopeia, Perseus and Auriga. NGC 559, NGC663, The Owl Cluster and the Double Cluster all looked excellent with good colour separation and were well contrasted. I managed the Andromeda Galaxy and later even got a hint of the Crab Nebula through rapidly diminishing transparency. I added the Barlow element (20~21x) and revisited most of what I’d observed earlier and M42. I was pleased to discover that there was no really obvious vignetting, although it pushed the eye relief out a bit more. The 30mm GSO SuperView isn’t a 27mm Panoptic, 28mm ES or 31mm Baader Hyperion Aspheric, but I didn’t expect it to be. OK, maybe a few small seagulls. It can display a small amount of astigmatism near the edge of field. I thought it did well in a short tube achromat and a pretty good 2” eyepiece for under 70 quid. Definitely a keeper.

 

 

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ZN0e7uSl.jpg

 

It never fails to amaze me that most of the gear in the above picture is considered 'inexpensive'.

 

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The SuperView sits well in the diagonal with the Barlow element added.

 

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