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Tele Vue Genesis Review

Fast, flat-field astrographs using the Petzval design have become common in recent years – think Takahashi FSQs, Vixen VSD and Tele Vue’s own NP-101 and NP-127 and Chinese copies marketed by various brands. But the Petzval is just an old-fashioned four-element camera lens design that Al Nagler of Tele Vue adopted for telescopes in the mid Eighties. One of those early Petzval designs was the Genesis.

The Genesis on test here was owned by a friend and taken by me in a part trade for a Takahashi FS-128. I didn’t know what to expect, but found a very interesting old ‘scope, as we will see.

At A Glance

Telescope

Tele Vue Genesis

Aperture

100mm

Focal Length

500mm

Focal Ratio

F5

Length

About 650mm

Weight

About 5 Kg

 Data from Me.

What’s in the Box?

Like most Tele Vue 4” refractors, the Genesis comes in a nice hard case.

Design and Build

The Genesis is deceptively similar to much more recent Tele Vues and shares most of their build characteristics. The overall appearance of this Genesis is subtly different from the later versions. I actually prefer the appearance of this one, but perhaps that’s just me.

Optics

I have written about Petzvals at length in the NP101 review. The Genesis is basically the same quadruplet design with an ordinary doublet up front and a second doublet reducer-flattener just in front of the focuser to make four elements in total. The front doublet is held in a slim and simple cell attached to the tube by rivets or blind-headed screws. The collimation is set at the factory by carefully nudging it into place on an optical bench and then fixing it (no adjustment is possible) – sounds crude but works out fine. Multi-coatings are good, but not quite up to modern standards.

The rear Petzval lens allows greater freedom to correct monochromatic aberrations, like field curvature and coma, than most other designs, but it doesn’t correct chromatic aberration. Instead, the ‘trick’ is that it reduces the focal length by about half (down to a very fast 500mm, F5 in this Genesis). That means the front doublet is actually about F10. Even though the front doublet is an ordinary achromat, a focal length of F10 substantially reduces false colour compared to F5, but doesn’t eliminate it (compare your typical Synta 102mm achromat, which is either F5 for a short tube model or F8 for the longer ones).

Now the Genesis is labelled “fluorite”, but here that is a little disingenuous. In a Takahashi, a fluorite element allows the doublet objective to be apochromatic. In the Genesis the magic mineral is in the Petzval element, but the doublet up front is an ordinary achromat (unlike the later NP-101 which has an ED-glass doublet up front, so it’s a proper apochromat).

Later Genesis models are similar, but have an aperture of 101mm and extend the focal ratio slightly to F5.4 (probably because adding an extra f-stop in the front achromatic doublet reduced false colour a bit).

The punch line to all this is tech-talk that the Genesis is an achromat, albeit one with a fast, flat field and the reduced false colour of a slower achromat.

Petzval lens of the near-identical (only brass) Renaissance model.

Painted dew shield and anodised lens cell.

Tube

Whereas the later (f5.4) Genesis models (like the NP-101 that replaced them) were finished in cream pebble-finish powder coat with a black anodised dew shield, these early models have a traditional gloss white tube and dew shield, though the latter slides over a black anodised lens cell. Otherwise the Genesis is similar to later Tele Vues – a short, slim OTA, simple, but all beautifully made for the long term, so very different from most mass-produced telescopes today.

Like most Tele Vues, the Genesis benefits from a screw-fit metal lens cap (‘screech, screech,’ as it’s unscrewed, ‘CLANG,’ as you fumble and drop it with freezing fingers).

Again, like other Tele Vues the tube has no baffles, it is just lined with what looks like (and may actually be) black painted sandpaper.

Focuser

The Genesis has the usual (for pre-imaging Tele Vues) heavy cast focuser body and chrome draw tube running by rack and pinion, with a 2” visual back and single lock knob. Oh, and you get solid chromed focuser knobs, like chromed versions of the brass knobs on a Renaissance, instead of the trademark later Tele Vue “Mag’ wheels”. Like all early Tele Vue focusers, it’s super smooth and easy.

Mounting

The Genesis has the trademark Tele Vue clamshell mounting ring. It has ¼-20 threads on the bottom so you can mount it on one of Tele Vue’s alt-az mounts (Panoramic or Gibraltar). Alternatively, you can get a short dovetail to fit which is CG5/Vixen compatible, but has matching ¼-20 threads on the bottom and a machined in lip so you can put it straight on a Tele Vue mount as well without removing the dovetail – neat.

That’s handy, because TV clamshells require some effort with an Allen key to open!

Accessories

It goes without saying that Tele Vue make loads of accessories, like eyepieces and barlows. The Genesis clamshell has a dovetail to fit a Tele Vue ‘Star Beam’ red-dot finder as shown in the photos.

The genesis comes in a hard case, not dissimilar to the one for a modern Tele Vue, except that it’s brown.

In Use – Daytime

Unlike many astro’ scope makers, Tele Vue has always advocated using its telescopes during the day for spotting and nature viewing. The Genesis gives a wonderful daytime view – pin sharp, bright and flat. Use a widefield eyepiece – Nagler, Panoptic or more recent Ethos or Delos – and you are treated to a real picture window view. Only at higher powers and on high contrast subjects does a bit of false colour creep in.

In Use – Astrophotography

Off axis aberrations are well controlled by the Petzval lens, though not to the same extent as an NP-101. Still, stars remain nicely pin-point to the edges of an APS-C frame.

Back in the day, as the manual says, TV intended the Genesis to be used as a telephoto lens for a 35mm camera, so coverage on APS-C is pretty good, with just a little drop-off in the corners.

There is a problem though and it is false colour. The Genesis’ achromatic nature shows up when imaging and every white or blue star is surrounded by a pretty blue halo. Fine for casual imaging, with a fast speed and flat field, the Genesis is not for the keen imager.

Below are unprocessed single APS-C frames of the Pleiades and the Moon taken through the Genesis. Note the false colour which is visible on the Lunar limb too.

In Use – The Night Sky

General Observing Notes

The Genesis may basically be an achromat, but otherwise optical quality is very high. People worry about collimation with Petzvals, but this one is certainly spot-on. Focus is snappy and the Genesis takes high magnifications well.

Cool Down

The doublet design of the Genesis means it cools quickly when you put it outside and is ready to use after just a short cool-down period. That makes it a handy quick-look scope.

Star Test

The star test looks excellent.

The Moon

According to the theory the Genesis should display chromatic aberration like a 4” F10 achromat. Now the rule about chromatic aberration in achromats is that to display “acceptable” CA levels, their focal length should be longer than about 1.22x their aperture in cm, which in this case would be about F12. So you might expect that the Genesis suffers from quite noticeable CA at higher powers; it does. At medium magnifications, the Moon is sharp and contrasty, but above about 70x it is surrounded by a pretty purple halo. At higher magnifications still, 100x and more, even crater shadows are washed in purple, though everything is otherwise very sharp and detailed. Repeat after me “it’s an achromat”! But whilst it’s not an NP101, the Genesis is not a Sky-Watcher StarTravel 102 either and it is quite usable for the Moon.

Jupiter

High power planetary viewing is a very colourful experience with the Genesis, though in other ways the optics hold up under high powers. Unfortunately, used as I am to APOs, I find a lot of CA rather hard to take and seeing Jupiter embedded in Imperial Purple isn’t the way I like it.

Deep Sky

I recall the time I first popped a Nagler into the Genesis and looked at the Orion Nebula. Given the large number of times, before and since, that I have looked at M42 that’s surprising. The view was just amazing – so flat and wide with such pinpoint diamond stars right to the field stop; at last that space walk they talk about. I was hooked. The Genesis is a telescope for sweeping star fields, for brighter DSOs and clusters. The Pleiades has never looked better and Andromeda is particularly detailed with that wide field.

Consider that very few 4” refractors have focal lengths of 500mm or less and even fewer combine it with a flat field. Takahashi’s FSQ matches it and the only scopes with less are the rare Pentax SDUF F4 and similar Vixen VSD100, but that is purely for imaging and very compromised for visual use. So 25 years on, the Genesis is still a rare visual instrument – supremely fast bright and wide. My guess is that sweeping for clusters is Al Nagler’s favourite thing and that is certainly what the Genesis is optimised for.

Summary

I loved the Genesis on deep sky, but the Genesis is less ideal for the Moon and planets due to significant false colour. All Tele Vue’s Petzvals give peerless deep sky views, but unlike the NP-101 the Genesis is pretty much a specialist visual deep sky scope. Someone recently said to me of the NP-101 (and I quote) “Oh the sharpness. Open clusters are mind blowing through those things.” Exactly the same could be said of the Genesis.

After perhaps a quarter of a century of, I would say, very regular use, the Genesis still performed flawlessly. The focuser was smooth and precise, the optics pin sharp with collimation spot on. And it still looked great. Tele Vues are solidly built. People talk about a “legacy telescope” and I suspect that Genesis will still be delivering lovely views long after both Al Nagler and I have gone. True, it’s not an APO and the NP-101 is vastly better in that respect, but for low to medium power wide-field viewing the Genesis is unequalled.

Confession time: on an emotional-attachment level, I think I liked the Genesis even better than the NP-101, for reasons that I find hard to explain. I preferred its looks and I think it was slightly shorter; perhaps it was even flatter and more stunning on deep sky. Its quirky single mindedness gave it character. Interestingly, the friend I bought it from still regrets selling it and reckons it gave him his finest views of extended DSOs like M31.

If you mainly like sweeping star fields, then Tele Vue’s classic Genesis is highly recommended, just remember it’s not an APO, so price accordingly.

Updated by Roger Vine 2018.

 

 

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