Here's are my impressions of observing with the TMB 130 F6.  I'm not the type to keep notes, but certain memories stand out, and they're the ones to mention:

Bright stars: I don't look at stars much but of course I've looked at Vega, Spica and all the usuals to check out the optics. Racking the focus back and forth, there is no colour visible in the airy disk, which is perfect. See my notes about binoviewers later on though.

Deep sky sights:  Needle Galaxy - fantastic view at low powers, the central dust lane very obvious with direct vision. Really nice view putting the object in context with its surroundings.  M13 - stars visible right to the core with perhaps a little averted vision needed, fine very sprinkling against a nice dark background, just so with M3.  Dumbbell - very well formed "keyhole" visible with mottling inside, overall nebula well formed with indirect vision.  Ring Nebula - very well formed and very punchy especially with the IDAS Narrowband Nebula photo visual filter.  Pleiades - from "Deepest Darkest Devon" (thanks to Graham for allowing us to enjoy your wonderful farm). Incredible wide view with the dusty nebulosity around the brighter stars immediately obvious. You could stare for ages at this with the Pentax XL's.  Orion nebula - simply amazing for a 5" scope. I really couldn’t believe this was a 5" I think that the contrast in a refractor really brings out deepsky detail. Even with the Denkmeier binos which dim the view a bit, I actually saw more detail, with an illusion of artificial depth to the "cusp" and "batwing" shape of the nebula.

Saturn: - Much better contrast than any Cassegrain I've ever looked through. There is almost no “haze" around the object, as the tube is well baffled all the way through, so one can pick up moons easily. Saturn easily shows off several bands of varying gradations and I think I’ve seen 2 layers around the polar cap. A lot of subtle colour visible for a 5" aperture.  Very crisp ring shadows and Cassini division. Crepe ring is visible. Saturn's globe really looks 3D, and hangs in space against a very dark background. I have used this scope alongside an 18" Obsession which clearly showed the Encke division that morning and although I suspected a darkening, I could not see it with the 5" aperture.

Jupiter: - Faint features are much more visible, and are a lot more contrasty than in my previous scopes. Zones and belts (and the GRS) are immediately visible and very separate at low powers, with ragged edges turning into swirls and so-on as I increase the power. Circulation "curl" patterns in the Great Red Spot are visible and the outer gap between it and the South Tropical Zone is easy at lower powers. Festoons, barges and swirls are all easy to see, along with regular sets of ovals after the GRS (up to 6 in a row) caused by turbulence trailing the GRS. I've suspected white ovals North of the NTZ and the STB southwards once or twice with peripheral vision. Jupiter's moons are easily visible as discs in decent seeing. I have seen 2 moons next to each other, and I recall their different size and colour were clearly visible and quite striking. Satellite shadows are jet black like holes through the planet. I can follow most satellites across the disc but I have lost them sometimes in the middle. This so called widefield scope is brilliant on Jupiter and planets. Can't wait for Mars!

Power (and over use of it): The scope performs well at up to about 280x on bright objects like planets. You can push the power higher with little image breakdown, but  as the image becomes bigger, it also becomes much dimmer, so there is no real point in  exceeding 250x with this or any other 5" scope. I can't see any more detail simply because the image becomes dimmer the higher the power from here and it's practically at the resolution limit for this aperture in any case. The old 50-60x per inch rule seems valid, and this has nothing to do with optical quality, but aperture alone.

Optics: The optics on this scope are perfect. Star images are the same inside and outside focus as far as I can see with concentric diffraction rings and very little or no colour in the out of focus airy disc. The diffraction rings collapse perfectly into a star and remain concentric all the way until the star gets to its smallest point. Stars are tack-sharp.

Use with Binoviewers: Add binoviewers without the corrector, and they will come to focus, as this scope has plenty of in travel. For low/medium power use, don't bother with the binoviewer “correctors". For those who are obsessed with colour or absence of it, there is some red or blue colour if out of focus without the corrector lenses at high powers. This is perfectly normal at this fast F6 focal ratio with prisms, however as soon as you're in focus the colour disappears. It really is a testament to how will this scope is corrected that there is no in-focus colour with uncorrected "raw" use of a binoviewer. I use Denkmeier 2's with an  Astro Physics "BARCON" Barlow screwed into the front to increase the F ratio, and bring  me up to planetary powers, and one can see that this removes just about all colour inside  or outside focus. In the Denk II's, Jupiter and Saturn have to be seen to be believed, and are textbook, with high contrast details in Jupiter and Saturn very visible at about 250X.

How it handles poor seeing: According to many aficionados, small refractors are not as affected by bad seeing compared to centrally obstructed or large aperture scopes. I live in London, and while the seeing can be surprisingly good on occasion generally it's 6 out of 10. My best views have been in Devon and Kelling Heath in Norfolk. I think this scope handles average seeing much better than my 7" Mak did. I'm reasonably sure, though I admit it's not an objective thing. The real benefit is there are no visible tube currents, or currents formed by boundary layers on the optics. I suspect the oversize tube with walls further from the light path, plenty of baffles, plus the fast focal ratio, and lack of a light path all help to reduce thermal issues.

Focuser: The Starlight Feathertouch focuser is great, plenty travel (about 5 inches) very stable, very precise and I especially like the fact this it uses a self centering clamp for the 2" visual accessories. This has a knurled outer collar which is big and very easy to grip with gloves. No screws to come off in your hand or swinging diagonal problems you get with brass inserts and no de-centering of the optical train. By the way, I was interested to see the exact same focusers on the Greenwich Observatory 28" Refractor.

Dew control: The scope dewshield is black flocked (a nice touch to improve contrast).  It doesn't really stop dew if the humidity is high, so if you don't have a dew heater the next best thing is a decent flocked dew shield on top of the telescope one. No problems using the Kendrick 5" heater strip wrapped around the base of the telescope dew shield.  The lens cell and optics absorb the gentle heat without the need to turn the duty cycle over 50% on most nights. I've had the whole scope dripping wet but the optics completely dry in Devon when dewing was very high.

Mounting: I've had a Losmandy GM8 which was perfect for this  scope, recently upgraded to a G11 Gemini as I want to add another OTA, which  unsurprisingly also works great. I considered a Vixen Sphinx but it won't take the weight of the scope at around 25 pounds with binoviewers, eyepieces, finder, tube rings etc.

 

Criticisms:

Weight, it's a bit on the heavy side compared to the AP, OK they're hard to compare as the design philosophy is different. To be fair, overall the TMB just has a beefier aesthetic. To be unfair, it would be nice to see these optics in a light tube which also looks nice.

Baffling - there is plenty of baffling internally and it's all black edged, expect for one ring which has a shiny metallic inner edge. I'm not sure if this is an issue and the scope’s performance certainly isn't affected, but why leave a shiny edge on it when the rest is perfect?

Objective cap - the black paint is low quality, and comes off very easily, it would have been much better to anodise this or use paint which sticks better.

 

No serious issues, I really had to think about these and I'm nitpicking here!   Well that's about it. It's a great telescope, definitely the best quality instrument I've ever owned. It simply gives better images than a lot of scopes which are considerably larger and that's the quality you pay for.   Please APM, scale this design up and do us a 160mm F6 lightweight, they will outsell anything else!

 

Nick Witte-Vermeulen

September 2005

Flamsteed Astronomy Society

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TMB130 refractor continued...

TMB130 refractor — A user review