A Work Commenced April 27 2026
Product: Svbony MK 127
Country of Manufacture: China
Focal Length: 1500mm
Focal Ratio: F/11.8
Central Obstruction: 30%
Focuser: Dual Speed
Weight (OTA): 2.94kg
Accessories: 1.25 & 2-inch Adaptors, 0.65 Focal Reducer, lens cleaning cloth
Price: (UK); £409
In their now classic papers published back in the 1940’s, Dimitri Maksutov and Albert Bouwers independently published their designs for a meniscus camera, in which they suggested that the same camera could be modified into a new kind Cassegrain telescope. But it was not until 1957 that the American optical engineer, John Gregory, published his designs for a F/23 meniscus telescope. His prototype F/23 instrument had a spherical primary mirror matched to a spherical meniscus of the opposite power. Gregory added an aluminised spot on the inside surface of the meniscus but this design had too much residual chromatic aberration. A year later, Gregory published a revised design for a F/15 Maksutov Cassegrain with improved colour correction by aspherising either the secondary or primary mirror. The Gregory Maksutov characterised by a deeply curved meniscus with a central aluminised spot still suffers from significant coma and astigmatism moving off axis. The Dutch amateur astronomer and optical designer, Harrie Rutten, hit on the idea of introducing a separate convex mirror to the centre of the meniscus which added another degree of freedom to the Maksutov Cassegrain design, allowing for much improved off axis performance and a much flatter field. Moreover, adding a secondary operating independently of the meniscus and primary mirror allows shorter focal ratios to employed (F/8-12) compared with the typical F/13-15 adopted in many Gregory Maks.
His ‘Rumak’ design first appeared in the 1988 book, Telescope Optics, where on page 111, the authors compare spot diagrams of a conventional 8-inch F/15 Gregory Mak to a similar Rumak, clearly showing how much better the latter is moving off-axis:
The Rumak design quickly turned into reality when companies like Intes, Intes Micro, Santel, LOMO, Orion Optics UK and TEC began to offer Rumaks in apertures from 5 inches up to 8 or 10 inch monsters. But these were quite expensive. Things began to change a few years ago however, when Bosma marketed a 6-inch(150mm)F/12 Rumak which proved popular with lunar and planetary imagers and visual observers alike. The Maksutov Cassegrain is one of the most elegant optical designs, combining high optical performance with extreme portability.
In this review, I’ll be showcasing an exciting new Rumak telescope marketed by the Hong Kong-based company Svbony: enter the MK 127: a 5-inch F/11.8 optical tube assembly.
What’s in the Box?
The telescope arrived securely inside a snugly fitting box with foam cutouts. As well as the optical tube assembly, you get both 1.25 inch and 2-inch adaptors which are very nicely machined and screw directly onto the back of the telescope. Unlike cheaper adaptors that use a side screw that can scratch cameras or eyepieces, these have brass compression rings. You also get a dedicated 0.6x focal reducer that decreases the focal ratio to F/7.1. The reader will note that this cannot be used visually.
The optical tube is a handsome grey colour and has two brackets attached to attach a finder or guide scope. It’s reassuringly light, tipping the scales at under 3 kilos. The focuser is dual speed: an excellent feature that allows the user to coarse and fine focus. The meniscus cover is all metal and fits snugly in place protecting the optics from dust and damp. A Vixen-style dovetail plate allows it to be mounted on most any mount.
The glass meniscus is fully multicoated and is less curved than a Gregory Mak. Defocusing an artificial star provides the easiest way to measure the central obstruction which turned out to be about 30 per cent: a good result compared with some Gregory Maks and Schmidt Cassegrains I’ve owned and used in the past, which can be as large as 40 percent.
A telescope like this deserves a decent finder. But I hit a small snag when I tried to mount my 6 x 30 finder scope to the brackets on the MK 127. It was not wide enough to allow the foot to slide inside. I got round the problem by mounting a Skywatcher bracket instead.
Some reports online mentioned the stiffness of the cover on the secondary adjustment screws, but my unit had no such issues. It screwed off without any problems.
Looking inside the tube, I noted how clean and dust-free it was. All in all, I garnered the distinct impression that this was a robust, well-made telescope: certainly a step up from the Synta-branded 127mm Mak.
Daylight Tests
I elected to use a 2-inch Svbony dielectric diagonal to garner the best images from the telescope. I used a variety of 2-inch and 1.25 inch eyepieces to conduct my daytime tests.
I first checked collimation using an artificial star and was relieved to see it was perfectly aligned with nice concentric diffraction rings.
The MK 127 makes for an exceptionally powerful spotting scope. Its short length but robust design allows it to dampen out vibrations very quickly(less than a second) on my Vixen Porta II mount. Charged with an inexpensive GSO branded 30mm 2-inch eyepiece yielding 50x and a 1.36 degree true field, I was genuinely astonished how crisp and contrasty the daytime views were. The superior optical design and high focal ratio of the Rumak served up images that were sharp from centre to edge. Indeed, using the company’s SC001 imager, I took some photos of young leaves emerging from deciduous trees some 80 metres in the distance. For example, the image below was taken in bright Spring sunshine and the small CMOS sensor is roughly the equivalent of a 6mm eyepiece yielding an effective magnification of about 250x. I think the result speaks for itself!
I would actually go so far to say that the MK127 makes for a better spotting scope than a regular lens-based instrument with its low mass, small size, brighter images and complete lack of colour fringing, not to mention its ability to use different eyepieces. The image is upright but flipped left to right which is perfectly acceptable. Indeed, any IPhone can reverse the image with one click.
How close can the MK 127 focus? Well, with a 1.25 inch diagonal I could focus as close as 18 metres but when I switched to a 2-inch diagonal I could reduce this to just shy of 11 metres!
To Be Continued…….