Vixen Deluxe or Tele Vue Barlow?

[Zeta Reticulan]

I have a lot of 2x Barlows, and a fair few 3x Barlows. The vast majority of my 2x Barlows are the short type. These are often considered more suitable for use in diagonals. This is undoubtedly true. However there are compromises with the light path that can produce aberrations in use. I only have two ‘full length’ 2x Barlows. A Tele Vue and a Vixen 73674 2x Deluxe.

Vixen claim that the Deluxe is intended to be used with fast focal ratio telescopes. I agree with this as it achieves focus in my f/6 Newtonian where the Tele Vue Barlow will not. Furthermore the Deluxe is fully multi-coated, has three elements and weighs 140g. The Tele Vue is multi-coated and apparently the lens cell consists of two elements of high index glass. It weighs approximately 136g according to Tele Vue. Regardless of these claims the Tele Vue feels slightly heavier to me. Although to be honest there isn’t much between them. 

I make the Tele Vue just over nine and a half centimetres tall, with the Vixen around two centimetres taller at about eleven and half centimetres. The seemingly overlong and detachable Vixen lens cell is around five centimetres. Making it three whole centimetres taller than the Tele Vue element. The Tele Vue features a brass compression ring complete with captive thumb screw. Its barrel has no undercut. This is in stark contrast to the Vixen’s plain thumb screw and undercut featured high on its lens cell. 

Generally I tend to use Barlow lenses with small and light eyepieces. This is possibly because I normally use short focal length Plossls and orthoscopics in combination with short tube refractors for lunar and planetary observing. I also regularly deploy several light, portable, grab and go set-ups. I pondered on what the lightest practical set-up might be with my f/6, 60mm ED doublet. One wide angle eyepiece giving about a three millimetre exit pupil would work. Then an eyepiece producing a one millimetre exit pupil, with finally a Barlow that could possibly work with both eyepieces.  

The wide angle eyepiece was a relatively easy decision and I went with a 19mm Tele Vue Panoptic. It is lightweight while producing nearly 19x for around a three and a half arc degree field of view. When used with a 2x Barlow it produces a one and a half millimetre exit pupil. These are a useful range of magnifications. Many spotting scope zooms vary from around a one and a half millimetre exit pupil to around a five to a seven millimetre one. The other eyepiece has been a less straightforward choice and can vary between a 6mm Vixen SLV, a 6mm TMB clone and a 6mm Orion Expanse inter alia. 

The Barlow selection was not obvious though. My first instinct was to use a high end ‘shorty’ as I imagined it would predominantly be used with the smaller eyepiece to give a half millimetre exit pupil. So less vibration at a 120x magnification. Furthermore there are weight and balance issues I have to take into consideration on a light portable set-up. Inevitably it came down to a selection between the Tele Vue and the Vixen. In a small Baader BBHS prism diagonal the Vixen protruded a full twenty millimetres further out than the Tele Vue. Although with the weight of the Vixen concentrated in the cell it had a lower centre of gravity. 

Visually there isn’t much difference between the Tele Vue and the Vixen Barlows. At first I leaned towards the Vixen. In my experience it has slightly better contrast, transmission and overall acuity. The brighter transmission is particularly noticeable to me, although unexpected considering it contained a triplet element compared to the doublet of the Tele Vue. This was the better choice for planetary viewing. The undercut was not a problem in the twistlock and I could live without a compression ring. The BBHS prism is much better at the red end of the spectrum than conventional prisms, as are all silver reflecting surfaces. Orange and orange-yellow stars benefitted from this particularly. The Vixen was basically used for splitting doubles and planetary observing.

So, everything sorted then. Except I had a brainwave. I could use the small and dumpy little Panoptic in the Vixen. Originally I didn’t envisage doing this often, if at all. Unfortunately the Panoptic displays some edge distortion when combined with the Vixen Deluxe. In fact, it seems to start after around 60° or so of field. I wondered if this would be the case with other Barlows. So I switched to the long Tele Vue. Lo and behold the edge astigmatism was cured! In fact the Panoptic and Barlow work so well together it’s basically like having a 9.5mm Panoptic. I suppose I can always switch back to the Vixen for occasional dedicated planetary viewing sessions. Both ‘long’ Barlows have their pros and cons. The Tele Vue was the best compromise. Possibly.