Svbony provided me with a Svbony SV503 70F6 ED telescope for review. This is a small 70 mm refractor with a two-lens cell, and one of the lenses is made of S-FPL51 glass. The use of ED glass provides a significant reduction in color halo (longitudinal chromatic aberration) around bright objects compared to a classic achromatic refractor of the same focal length. I also received a native Svbony SV193 0.8x (0.8x for 70F6ED) field flattener for this refractor for review.
Svbony SV503 70F6 ED can also be used as a spotting scope. And if the 80 mm ED version of the telescope is too large for such purposes, then the 70 mm version is already quite compact and mobile. Of course, a dedicated spotting scope will be even lighter and more compact, but if you need a versatile device for astronomical and terrestrial observations, then the SV5o3 70 ED will be a good choice.
The manufacturer has declared the following characteristics:
|Product Name||SVBONY SV503 70F6 ED Astronomy Telescope|
|Aperture||70mm / 2.75-Inch|
|Type of Focuser||RAP (Rack and Pinion)|
|Gear Reduction||1:10 Fine movement|
|Light gathering capacity||100x|
|Max. Useful magnification||140x|
|Tube outer diameter||88mm|
|Back Focus Length||90mm|
|Dovetail & Ring||Yes|
The telescope comes in a double carton box. The foamed material reliably protects the tube from damage during transportation. The tube is additionally packed in a plastic bag.
The tube is very compact, especially compared to the classic “long” refractor, but at the same time massive. The length of the tube with the metal hood folded, caps and 1.25″ adapter is 320 mm, with the focuser extended – 410 mm. Almost the entire body is made of metal. Workmanship is good. There is no platform for the finder.
The kit includes a tube in mounting rings and with a Vixen-type mounting plate, a 2″-1.25″ adapter, a metal lens cap, a plastic focuser plug, and a plastic protective cap for the focuser handle. Mounting rings and lens cap are lined with soft material on the inside. Fluff from the lens cap may get on the front lens – the manufacturer may need to change the material.
The outer diameter of the hood is 90 mm.
The hood is shifted by 54 mm.
The lens cell has two lens. The measured aperture is 69.98 mm. One element is made of low dispersion glass S-FPL51 (information from the manufacturer). Objective lenses – without scratches, bubbles and damage to the coating. Coating – yellow and green shades. A small amount of dust and lint on the outside (probably from the lens cap). The front of the lens has the following inscriptions: “D=70MM F/6 ED SMC Dual Speed Foucs”. Judging by the image of other similar telescopes on the web, it was me who was “lucky” with a typo. Let it be a hallmark of this tube 🙂
There are a number of diaphragms inside the tube. There are no traces of peeled off paint or dust inside.
The lens cell is metal, it is screwed into the tube along the thread. There are adjustment screws on the frame for each lens. To access them, you need to unscrew the hood from the orange ring.
Focuser – 2 inches, RAP (Rack and Pinion). The focuser tube has a scale in millimeters. The focuser travel is 90 mm.
Focuser gear ratio: 1:8.5, although 1:10 is stated. That is, for one revolution of the large handle, there are eight and a half revolutions of the small handle.
The rotation of the focuser knob is smooth, focusing is comfortable even at high magnification. Handles are metal, ribbed. It is also possible to rotate the entire focuser around the optical axis of the telescope by loosening one knurled screw, turning the entire focuser to the required angle, and then tightening the screw. This can be useful if the focuser knobs interfere with the rotation of the mount in certain positions (eg Sky-Watcher AZ-GTi). But it is better for these purposes to rotate the pipe, loosening the rings.
The focuser tube is blackened inside, but there are stray reflections. A 1.25″ adapter is included with a thread for a 2″ filter.
The adapter is problematic – my 1.25″ accessories do not fit completely into it – about 1 cm.
For the Svbony SV503 70F6 ED telescope, Svbony also produces its own field flattener SV193 (article W9152A) with a reduction factor of 0.8x. It is necessary to eliminate field curvature in astrophotography of deep space objects. For visual observations or when shooting planets, it is not needed. The field flattener is not included in the delivery set – it must be purchased separately. The field flattener is supplied in a cardboard box with a protective material. The caps are rubber, one of them does not fit well.
The field flattener has concave front and rear lenses. The manufacturer claims 3 lenses in the design. Coating bright yellow and green. The front has a 2″ filter thread. No damage or scratches.
Weight with caps is 288 grams.
Inlet thread diameter – 53.7 mm (male).
Inlet lens light diameter – 42 mm.
Outlet thread diameter – 47.9 mm (male).
Outlet light diameter – 34 mm.
To install the field flattener, it is necessary to unscrew the ring with clamping screws at the end of the focuser counterclockwise and carefully screw in the field flattener.
During visual observations of the Moon with Meade HD-60 6.5 mm (65x) and Levenhuk LER 3 mm (140х) eyepieces, the telescope showed a slight but noticeable chromatic aberration (a faint blue-violet halo). At the same time, the sharpness and contrast of the image, even with a magnification of 140x, were good – for the Moon, you can confidently use a magnification of up to 180x. A chromatic halo was visible in the star Rigel. On closer examination of the images of the Moon, I found that the red and green channels are sharp and without spherical aberration, but there is chromatism in the blue channel. Of course, this chromatism is SIGNIFICANTLY less than with inexpensive achromatic refractors (70/400, 70/500 or even 70/700).
-Svbony SV503 70F6 telescope
-Sky-Watcher AZ-GTi mount
-ZWO IR-cut filter
–ZWO ASI 183MC camera
Stacking 100 frames from 1685 with Autostakkert, wavelets and deconvolution with Astrosurface.
-Svbony SV503 70F6 telescope
-Sky-Watcher AZ-GTi mount
-Barlow lens NPZ 2x
-ZWO IR-cut filter
–ZWO ASI 183MC camera
Stacking 100 frames from 1146 with Autostakkert, wavelets and deconvolution with Astrosurface.
In the images of the Moon, “blue” is noticeable in the image – just a manifestation of residual chromatism in the blue channel.
The Svbony SV503 70F6 ED telescope proved to be excellent in observing and photographing the Sun with the Herschel wedge in the green region of the spectrum. I think that it can also be used successfully with a Barlow lens, as well as in conjunction with Quark-type chromospheric filters.
CA correction of the Svbony SV503 70F6 ED is fundamentally different from Svbony SV503 80ED F7:
– The 70ED has a sharper red channel than the 80ED.
– The 80ED has a clearer blue channel than the 70ED
– The green channel of the 70ED and 80ED is comparable in sharpness.
Ideally, all color channels should be equally sharp, but due to different apertures, apertures, focal lengths and glass grades, we get a significant difference in chromatic correction. In my opinion, 70ED is preferable for narrow-band shooting in the H-alpha line (hydrogen nebulae, or chromospheric shooting of the Sun), or for shooting with light pollution filters such as CLS, UHC L-enhance, L-extreme, etc. However, for visual observations (including due to aperture), as well as for shooting galaxies and star clusters 80ED (in particular, with an L-Pro filter), 80ED is better suited. In addition, 70ED is lighter, more compact, faster aperture.
But when testing the field flattener, I got a problem – with a standard M48x0.75 Canon EF T-ring and a Canon 550Da camera (the blue filter in front of the matrix was removed, and the matrix was slightly moved to the bayonet), I found significant distortions of stars across the field. At the same time, there were no problems with the same T-ring and the same camera with the Svbony SV503 80ED F7. Definitely, it is necessary to select the optimal working length and achieve complete elimination of the curvature of the field. I have already informed Svbony company about this issue.
All test images can be downloaded here https://cloud.mail.ru/public/NAJt/Tm5aDXYv8
+ Good mechanics and optics.
+ Good chromatism correction for visual observations (much better than an achromat with the same parameters).
+ Low price
– No finder dovetail base – must be purchased separately.
– Significant residual chromatism in the blue channel (however, quite expected due to the use of S-FPL51 glass and forcing the aperture ratio).
– Field flattener “from the box” does not provide good field correction with a DSLR camera – selection of the backfocus distance or use of a third-party field flattener is necessary.
– 2″-1.25″ adapter with a defect – too small an internal diameter.
My impressions of the Svbony SV503 70F6 ED telescope turned out to be contradictory. On the one side, good image quality for visual observations and lunar and planetary capturing, excellent compactness and good mechanics. But on the other side, there is a noticeable residual chromatism, as well as a field flattener that does not work correctly with a SLR camera and a defective 2-1.25″ adapter. In my opinion, the “native” field flattener should work with a telescope and a DSLR camera “from the box” – without additional extension rings, back focus selection, etc. Nevertheless, this tube is quite suitable for a chromatic-friendly astrophotographer who needs a light and compact tube for a small mount, or for shooting nebulae with light pollution filters (UHC, CLS, L-enhance, L- extreme, H-alpha), but at the same time with the obligatory selection of the back focus, or the purchase of a third-party field flattener for this focal length. Nevertheless, for such a price (especially in Russia), especially against the backdrop of Sky-Watcher prices, this tube has practically no competitors in terms of price / quality ratio.