Telescope Service 65mm f/6.5 Quadruplet Astrograph refractor
Telescope Service — — €649
Written: Winter 2013/4

This intriguing little instrument has been available for approximately three years at the time of writing and this review is based on an evaluation spanning the winter of 2013/14.

Aperture: 65mm
Focal length: 420mm
Focal ratio: f/6.5
Resolution: ~1.8 arcsec.
Mass: ~3 kg
(inc. tube rings & dovetail)
Focuser: 2-inch R&P,
8cm travel, 360° rotation,
2:15 reduction gearing.
Retracted length: 34cm
88mm (for solar filter)
First impressions & Specifications
The first impression one gets of the TSAPO65Q is a solidly built, almost over-engineered instrument, of a design that feels perfectly proportioned, exuding an air of quality and durability; closer inspection merely reinforces this initial impression.

The ‘scope is supplied with a 2-inch to 1.25-inch reduction adaptor with brass compression rings, two CNC tube rings and a robust finder shoe — that’s it. The first thing you’ll need is a dovetail (TS’s PSFoto10 is a wise choice for most Vixen-compatible mounts) and DSLR imagers will need a 40mm 2-inch to T2 extension tube (say, TSFA240) plus a T-ring appropriate to their camera body. For visual use, a high-transmission 1.25-inch dielectric diagonal would be a wise investment.

The 2-inch rack & pinion focuser is a joy to use. The precision-milled helical brass rack of the review instrument had zero backlash. One turn of the pinion equates to about 16mm of draw tube travel over an 80mm range, the fine focusing reduction gearing being of a 2:15 ratio (1 turn ~ 2.1mm). The draw tube is also marked with a millimetre scale which is a nice feature when remembering where the approximate focus lies with various setups.

The focuser may be locked by a single thumbscrew on the top of the rear of the barrel, while the entire rear of the unit may be turned through 360° for precise camera framing — all without moving focus. Rated for loads up to 3 kg, the TSAPO65Q therefore dealt with my Canon 1100D like nothing was attached to it; in fact, with this camera body I never bothered with the focuser lock since it never shifted in any of my images.

In order to produce an instrument that is compact when stored (just 34cm long), the TSAPO65Q's retractable dewshield is very short, so you’ll need to fabricate an extension (as I did) or invest in a dew heater if your location is damp. The review ‘scope’s gorgeous deep green optical multi-coatings were blemish-free throughout and I was pleasantly surprised to see that the front section of the tube is flocked while the interior of the drawtube is milled — all desirable features designed to reduce scattered light that was confirmed both visually and photographically.

Optical performance
The optical layout of the TSAPO65Q is reproduced below. The objective (left) is a triplet design employing FPL-53 glass, while a single-element ED meniscus lens convex to the objective acts as field flattener. Hence it’s the four elements in the optical train that give rise to the Quadruplet name.
It’s claimed that the design delivers pin-point stars over a 44mm diameter circle, which equates to 6° at the stated 420mm focal length. The magic figure of 44mm corresponds to the diagonal of a conventional full-frame 35mm sensor — something I was unfortunately unable to test, but many others have with very satisfactory results.

The photographs below were based on the 27mm diagonal (i.e. 3° 38’ field) of a typical APS-C sensor such as that found in my astromodified Canon 1100D. Clicking on any image links to a full-size version in JPEG format. The TSAPO65Q and 1100D were mounted on a Celestron CG5-GT German equatorial and each of the 1-minute subs were unguided.

The Andromeda Galaxy (M31) with M32 and M110 — 29th November 2013. This is a stack of 18 1-minute ISO3200 images. Notice the magnitude 4.52 blue star Nu Andromedae 1/5th of the way in from the lower left corner.

The North America & Pelican Nebulae in Cygnus — 29th November 2013. This is a stack of 18 1-minute ISO3200 images.

The Rosette Nebula & cluster in Monoceros — 6th December 2013. This is a stack of 20 1-minute ISO3200 images with an Astronomik CLS-CCD clip filter.

All three images above were generated from deeply processed stacks of grainy ISO3200 subs, so any blue or red star bloat that may be evident is overemphasised. Furthermore, the German equatorial mount was unguided and therefore some small tracking errors may be seen. When one takes these factors into consideration, the TSAPO65Q clearly turns in a creditable performance with such a basic DSLR and an EQ5-class mount. It delivers symmetrical pinpoint stars to the corners of APS-C sensors with a high degree of correction for chromatic aberration, field curvature and coma. The ‘scope’s 420mm focal length also rather conveniently yields a field of exactly 3° x 2° with APS-C chips. (Click here for my DSLR field of view calculator.)

Visual use
The TSAPO65Q delivers first rate lunar, prominent planet and double star images when used with well-corrected eyepieces that are designed to work at f/6. I used a William Optics 24mm DCL-28 eyepiece (17x, 3°) in addition to 7mm (60x, 0.9°) and 3.2mm (130x, 0.4°) TMB Planetary oculars. Given the ‘scope’s modest 65mm aperture it’s only suited to the brightest deep-sky objects, but it does show prominent open clusters particularly well. The superb colour correction meant that the Moon was an arresting sight with no unsightly purple fringe at the limb or, indeed, any image breakdown at the highest magnification available to me.

On December 22nd, 2013 I watched Jupiter’s innermost Galilean moon Io emerge from occultation at 130x, looking like a tiny bead detaching itself from its parent planet close to 11:25pm. Most recently, I used the TSAPO65Q at 130x to observe the double shadow transit of Io and Ganymede between scudding terrestrial clouds close to 11pm on March 16th, 2014. When seeing permitted, the two shadows were like an inky black colon punctuation mark. At other times star images were virtually textbook with a high degree of symmetry between the intra- and extra-focal diffraction patterns, while at focus tight Airy discs nestled in perfectly collimated diffraction rings.

First, let me dispel a persistent & web-based rumour that this telescope exhibits pinched optics when used at low temperatures. This was an issue with early production run instruments (~2011) due to contraction of the rear lens cell stressing the field flattening element, but it was a QC issue that has thankfully been rectified. While last winter was not the coldest in eastern England, I used the TSAPO65Q for imaging and visually inspected double stars at high magnification in temperatures down to -7°C without a dew heater; I never saw any sign of pinched optics whatsoever.

Having spent three months with a TSAPO65Q, I shall be particularly sad to see it go. While its f/6.5 focal ratio may not seem particularly fast, I’ve demonstrated that even a novice astroimager can still record extended emission nebulae in surprisingly short times. Objects like the Rosette Nebula, North America Nebula, Andromeda Galaxy, Heart & Soul nebulae, etc. are ideal targets for the sensitive APS-C sensors of contemporary DSLR cameras — particularly if you have an autoguided mount and an Astronomik CLS-CCD filter or similar.

There are a number of competing 70mm ED imaging refractors out there, but most require a separate field flattener/corrector with the potential for misalignment or flexure. The TSAPO65Q’s all-in-one system makes it a very attractive imaging solution, one that gives every impression of durability and optical repeatability. Combine these factors with its grab-and-go visual credentials, then one has a very versatile package for both terrestrial and celestial use. Highly recommended.

v1.4 — April 2014