At the end of October 2022, Svbony announced the release of a mirror-lens telescope of the Maksutov-Cassegrain system with an aperture of 105 mm. This was quite unexpected, since before that among Svbony telescopes there were only lens telescopes (refractors). And so, Svbony kindly provided me with a MK105 telescope for testing.
The meniscus optical system was invented by the Soviet scientist and optician Dmitry Dmitrievich Maksutov in 1941. In the Maksutov-Cassegrain system, the primary mirror is a spherical high-aperture mirror. Spherical aberration of the primary and secondary mirrors is compensated for with a full aperture lens corrector (meniscus) at the front of the tube. In this case, a convex spherical secondary mirror can be deposited directly on the meniscus, but then the relative aperture of the telescope should be in the range of 1:12–1:15 to eliminate spherical aberration as much as possible. For the first time I looked into the meniscus telescope around 2007 and since then I have fallen in love with the “poppies” for their compactness, the complete absence of chromatism, the absence of rays in the image and unpretentious maintenance. However, despite the apparent simplicity (all optical surfaces can be spherical!), increased requirements are imposed on the mechanics, mirrors, and especially the meniscus, otherwise the telescope will not be able to provide alignment stability and diffraction image quality.
The manufacturer claims such features as 99% dielectric coating of the secondary mirror and two mounting pads for the finder.
Specifications from the manufacturer:
| Model | MK105 |
| Type | Maksutov-Cassegrain |
| Aperture | 105mm / 4.13 inch |
| Focal length | 1365mm / 53.74 inch |
| Focal Ratio | f/13 |
| Primary mirror | Multi-coated Precision Aluminum Coating |
| Secondary Mirror | 99% Reflectivity Dielectric Coatings and Multi Coating |
| Focuser | Internal |
| Mounting | Vixen Style |
| Mounting Base Number | 2PCS |
| Resolving power | 1.1arc seconds |
| Limiting magnitude | 12.1 |
| Light gathering power | 210x |
| Optical Tube Length | 377mm / 14.84inch |
| Optical Tube Diameter | 119mm / 4.68 inch |
| Optical Tube Net Weight | 2193g / 4.83lb |
| Adapter Thread | M42x0.75 For T-Ring |
The tube is delivered in a cardboard box, outside packed in a dense protective film. Inside the box there is a optical tube in protective foam, a bag and an additional film. The kit includes a tube with an installed mounting plate and a mounting platform for the finder, protective covers (2 pcs), screws for the finder. It is possible to complete with a finder, diagonal mirror, eyepieces and a filter.
The body of the tube, the frames of the primary mirror and the meniscus are metal. The body is long (with covers – about 380 mm). On the cell of the primary mirror there are two fasteners for the finder – screwed and built into the frame. The cell of the primary mirror is attached to the tube with three screws and slots in the tube body.
I did not find any chips, stains, scratches or cracks on the optics. However…
Hidden at the back of the tube behind three rubber plugs are three pairs of push-pull adjustment screws.
The primary mirror is held on a long tube – a special light-shielding hood. When the focuser knob is rotated through a special leash, the main mirror is shifted, followed by refocusing.
Some measurements
Optical tube diameter (rim): 119 mm
Entrance aperture: 105mm
Meniscus diameter from the inside of the pipe: 108 mm
Outlet diameter (visual adapter): 31.45 mm
Outlet thread: 41.88 mm
Outlet hole in the tube (after unscrewing the visual back): 35 mm
Focuser knob: 22mm ribbed, metal, length approx. 30mm.
Distance from flange to carrot hole: 36 mm
Tube length with caps: 380 mm
Mounting plate length: 180 mm
Rear frame diameter: 126mm
Secondary mirror diameter (approx): 34mm
Primary mirror diameter: 113.6 mm.
Working (reflecting) surface diameter: 113 mm.
Longitudinal travel of the main mirror: 21 mm.
Coating of the meniscus: green and lilac.
I checked the alignment of the tube with an artificial star, there is a small halo at the bottom right, which you can try to eliminate by alignment. The star was at a distance of about 5 meters.
When checking with a polarizing filter, slight stresses in the meniscus are noticeable, but I doubt that they will have a significant effect on the image.
Equipment:
-Svbony MK105 telescope
-Sky-Watcher AZ-GTi mount
-Barlow lens cell NPZ 2x
-ZWO ADC
-ZWO IR-cut filter
-ZWO 183MC camera
Stacking 1000 frames from 17834.
Source video.
Equipment:
-Svbony MK105 telescope
-Sky-Watcher AZ-GTi mount
-ZWO IR-cut filter
-Svbony SV705C camera
Processing: panorama from 4 frames, Autostakkert (100 frames from 2700), AstroSurface. Scale 50%.
Equipment:
-Svbony MK105 telescope
-Sky-Watcher AZ-GTi mount
-ZWO IR-cut filter
-ZWO ASI 183MC camera
Processing: Autostakkert (100 frames from 1000), AstroSurface, panorama from 2 with Microsoft ICE.
Summary
Svbony made quite a solid telescope with good optics and mechanics. The telescope is completely free from chromatic aberration, while being very compact and unpretentious in maintenance. The disadvantages include a small leakage of light protection at the edges of the working field of view, but I did not notice its effect on the image during visual observations with a 32 mm eyepiece and shooting with an astronomical camera.
Реклама: ООО “АЛИБАБА.КOМ (РУ)” ИНН 7703380158
