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Brandon Vernonscope 94mmF7 APO first impressions.


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Brandon Vernonscope 94mmF7 APO first impressions.

 

 

 

Hi all,

 

 

I recently took possession of a 94mmF7 APO refractor made by Brandon Vernonscope.

 

I had done a lot of research on these scopes before making the leap (more like a cram internet session while the scope was still available.) and I found various and sometimes conflicting opinions.

 

So, I thought I’d post some first impressions while they’re still recent.

 

The thing that sold me on this scope, despite its age (1980s) was the fact that its objective is a cemented triplet APO lens made by none other than Roland Christen of Astro-Physics fame. The rest of the scope is essentially Unitron, which is not a bad thing. Unitrons were the epitome of the long refractor age before Don Yeier of Vernonscope came along with this scope and turned accepted refractor doctrine on its head.

 

In fact, as Dave Trott explained in one of his videos, this scope marked the inflection point where the long F15 refractors (long F ratios to combat CA) gave way to much shorter and manageable ‘short tube’ refractors with equal to or superior CA correction. The Vernonscope 94mmF7 was the scope that started this APO revolution.

 

And only approx. 500 of these scope were ever made..

 

So what is it?

 

The Vernonscope 94mm is an F7 triplet APO refractor. And while it was revolutionary in its day, I have read many reports that criticize this scope because it can’t keep up with modern APOs.

 

Well, duh.

 

Multi/dielectric coatings and FPL-53/fluorite glass simply did not exist at the time, but despite that, Roland Cristen managed to design a triplet lens that came pretty close, even by today’s standards. And there is no substitute for the exceptional polishes and fine figures of Roland’s objectives. They go a long way to making up for the deficit that modern coatings and glass present. As I’m sure Roland would agree, it’s a lot easier and cheaper to deposit 99% di-electric coatings and claim the use of ED/Fluorite to flout your product than it is to put the time and effort into creating an exceptionally figured lens.

 

 

 

It uses an ‘old school’ (ie: not a Crayford) rack and pinion (my preference) Unitron super focuser with 2-1/4” of travel. This combined with a sliding drawtube which is itself capable of about 6.5” of outfocus means this scope can focus from infinity down to about 10ft.

 

The extension tailpiece will accept 2” accessories so it is fully compatible with today’s accessories. If you remove this tailpiece (why?) then the ID of the actual focuser body is 60mm (2.36”) which may have led to some of the comments read on-line criticizing the non-standard focuser dimensions. Bottom line is – don’t remove the focuser extension tube. If you bought one without the focuser tube, then you either have to find one, or make an adapter.  And without this focus extension tube, you will not be examining ants on your peonies… As an interesting aside, as Dave Trott also demonstrated, because this is a Unitron focuser, it will accept Unitron accessories – like the Unihex rotating EP holder. It just slides right in in place of the extension tube – I just have to find one.

 

And despite non-marring EP accessories being all the rage now, Unitron had this figured out 50 years ago. Their extension lock and diagonal lock are clever non-marring designs consisting of a bendable ‘tongue’ which bears against the extension tube or diagonal and whose tension can be adjusted with a thrumbscrew.

 

I admire the ‘old school’ design aesthetic. It is usually robust, well-made and precise. There is something to be said for handling something that was conceived and manufactured to high standards before CAD software, CNC machining, anodizing and 3D printing became the norm.

 

First impressions

 

  • It’s bigger than what the photos convey.
  • It’s very Unitron-like in its aesthetics. It should be as it’s basically a Unitron OTA (albeit a shorter one)
  • It’s hefty. I had forgotten what a 10lb telescope weighs…. I have found that the only true light refractors are Borg’s (I think they must fill their tubes with helium….)
  • I like the colour – sort of a gloss Robin’s egg blue which is nicely set off by the Unitron gloss black and bright metal hardware.
  • The lens is exquisite.

 

Early production runs were mistakenly labeled 92mmF7. They were all actually 94mm. This was corrected in later production runs. (mine is labeled 92mmF7)

 

The only plastic on the scope is the dust cap and the focuser & tube ring knobs.

 

Basic Specs

 

  • Optical: Cemented 94mmF7 triplet APO lens by Roland Cristen
  • Coatings: Magnesium Fluoride on both glass to air surfaces.
  • Lens cell: Unitron collimatable
  • OTA weight: 9lbs bare.
  • OTA OD: 110mm
  • Dew Shield OD: 123mm
  • Focuser: Rack and Pinion with 2-1/4” of travel with additional 6.5” of extension. (Unitron Super focuser)
  • Tube Rings: Unitron 1pc saddle/dual ring w. 2 x ¼-20 holes

 

But how does it perform?

 

The big joke about buying a new scope is that the minute you receive it, the clouds roll in and the heavens open up for at least a week. I sort of have the opposite problem. Gorgeous clear weather for 4 days……..but no mount to put the scope on. So my impressions are formed from looking out my office window with the scope ‘shimmed’ up on books, etc.….(a real poor-mans AZ mount..)

 

I’ve owned both Televue Rangers and their 60mm APO both of which shared the same focuser arrangement (sliding drawtube with helical focuser w. ¾” travel) which I never really liked. So, I was a bit hesitant about the similar arrangement on the 94mm. The thing that makes the difference is the 2-1/4” travel rack & pinion focuser. It is smooth and precise and because of its travel you don’t have to be accurate on the sliding extension. In practice, you really only have to do it once depending on whether you are using it for astro or terrestrial use. The extension tube slides easily and locks in place and the R&P focuser is smooth and backlash free with lots of focus travel.

 

Looking out my office window, the usual CA culprits of roof lines or branches against a bright sky show no CA in-focus, with a very subdued red or green on either side of focus. In my books, this is good enough to be called an APO. (Especially back in the day!) I would say it is equal to or better than a Televue Genesis SDF I owned years ago. That’s no mean feat considering the Genesis came along a decade later and used fluorite glass in its optical train.

 

The in-focus images are ‘hard’. By that I mean they are precise, no mush, no ambiguity. You know you have focus. Images are bright and tight.

 

I have not yet had the scope outdoors to see how it performs astronomically (no mount), but I will amend this review once I have done that.

 

In the meantime, I am fascinated by the scope. It is simple, elegant, well made and performs well (in limited testing) – and it has a history, which I always consider important. (will your Uber Chinese APO still be around in 50 years with a story to tell…?)

 

Hopefully, these observations and opinions will help anyone that is confronted with the pleasant torture of deciding whether to buy one of these scopes.


  • Bob Campbell, John rombi, Traveler and 25 others like this


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