A Work Commenced December 9 2024.
Product: Svbony SA401 25x-75x 100 APO
Country of Manufacture: China
Clear Aperture: 100mm
Armouring: Forest Green Rubber
Magnification Range: 25x-75x
Field of View: 1.77 degrees @ 25x -0.92degrees @ 75x
Focal Length: 556.2mm
Focal Ratio: 5.6
Close Focus: 10m
Focuser: Single Speed, Helical
Coatings: Fully Multicoated
Objective Design: 4-Element Double ED APO
Prism Type: K9 Porro
Exit Pupil: 4mm@ 25x, 1.3mm@ 75x
Ability to use Interchangeable 1.25” Eyepieces:Yes
1.25” Eyepiece Adaptor: Yes
Waterproof: Yes IPX7
Nitrogen Purged: Yes
Weight: 2.9kg
Length: 458mm
Accessories: 1.25” eyepiece adaptor, SC001 imaging camera, scope protective jacket, IPhone adaptor, instruction manual, lens cleaning cloth
Price(UK): £750.00
Over the last few years I’ve watched spotting scopes grow in size. Just a few years back, birders and nature watchers routinely used 60-80mm scopes to study their targets at distance, but recently, a new breed of super big spotters have been released onto the sports optics market, with apertures of 95mm, 100mm and even a 115mm now being routinely employed by enthusiasts who can now enjoy greater light gathering power and higher resolution images. Big spotting scopes employing ordinary crown & flint glass suffer badly from chromatic aberration at higher powers, making them practically unusable at their highest magnification settings(60x or so), necessitating the need for extra low dispersion elements to reduce colour fringing, and increase image sharpness and contrast. But as the aperture increases whilst retaining the typical fast focal ratios(<F/6) required of spotting scopes, chromatic aberration becomes very aggressive indeed, requiring much more attention to detail. Many of these scopes have triplet objectives with one element employing fluorite crystal to stave off colour fringing around high-contrast targets. Fluorite is very expensive though, is very brittle and slightly water soluble, characteristics that reduce its durability in the long run. Another approach is to use two ED elements, similar to that employed by some fast refractor astrographs.
In this review, I wish to showcase a new 4-element, dual ED APO spotting scope by the Hong Kong-based company, Svbony, embodied in their new flagship line of premium spotting scopes, the SA401 series. Two models are available; the smaller 85mm and the 100mm showcased in this review. Furthermore, both retail for well under £1000.
First impressions:
Typical of Svbony, the SA401 100mm APO scope arrived in packaging I can only describe as immaculate. Double boxed, the instrument was sturdily positioned inside its white foam casing, together with various accessories, including a SV 402 1.25” eyepiece adapter, a 2 mega pixel SC001 imaging camera, and a black scope jacket to protect it from the elements. Let’s take a closer look at the instrument.
The magnesium alloy chassis of the SA401 100mm APO spotting scope is overlaid by a thick layer of forest green rubber armouring, with black extremities at the eyepiece and objective ends. The textured rubber single speed helical focuser is also finished in black. An attractive cherry-red ring positioned behind the retractable lens shade displays the essence of the SA401 design, employing two ED elements in its APO designation, and covering a magnification range of 25x to 75x.
The focused cone of light from the 4-element objective is reflected to the zoom eyepiece via a Porro prism using K9 optical glass(the optical equivalent of BK7) which is perfectly suitable for this F/5.6 instrument. In addition, K9 optical glass has a lower dispersion profile than BAK4, which helps a wider range of visible wavelengths to remain tightly focused before being magnified by the eyepiece.
Like their other spotting scopes, a large, round knob is located on the upper right of the chassis just ahead of the helical focuser. Once loosened, the built-in mounting bracket can be smoothly rotated through a full 360 degrees, which enables the user to achieve a comfortable viewing position irrespective of the location of the target.
The interior of the SA401 spotter is very clean and dust-free, as the photo below shows, with nicely machined baffles, and other blackened components to help reduce stray light and maximise image contrast.
Ergonomics:
The SA401 100mm APO 25x-75x tips the scales at 2.9kg, with the extra heft over other 100mm spotting scopes probably attributed to its 4-element objective. It feels really solid in the hand. Fit and finish are fantastic. The helical focuser moves smoothly and precisely allowing the user to bring any object beyond about 10m to a crystal clear focus.
The zoom eyepiece has plenty of eye relief. Testing with glasses on, I was able to access the entire field throughout the full magnification range of the instrument.
The zoom eyepiece can be removed from the instrument simply by unscrewing it. The user can then insert other eyepieces or the supplied SC001 imaging camera, by means of the SV406 adapter (also supplied), as shown in the photographs below:
For most of my initial testing, I mounted the SA401 on my trusty Vixen Porta II altazimuth mount via a small dovetail plate seen attached to the instrument in the second photo above. This mount has slow motion controls on both axes, allowing me to quickly centre a target or track it. For more portable work away from my home I elected to use the lighter weight SV402 mount with its fluid panning head. More on this later.
True Aperture Test:
A spotting scope costing this much ought to be operating at is full aperture. Researching other models in the same price range, such as the Celestron M2 Regal 100mm ED, revealed that it was not operating at 100mm but more like 90mm. I set up a simple flashlight test to measure the effective aperture of the SA401 and found it to be exactly 100mm.
That’s a reassuring result, as the whole point of using a large spotting scope like this is to avail of its additional light gathering power, especially in low light situations.
Bright Light Test: Not all people who buy and play around with spotting scopes will use them for nature studies. Some folk who live in high rise apartments like to get good views of the town or city in which they live, whether by day or by night. A spotting scope showing strong internal reflections from bright city lights would be off putting. To test this, I turned the SA401 on some bright street lights at various distances up to 100 yards away. I’m happy to report that there was very minimal reflections seen and only on the very brightest sources. This would be a good instrument to enjoy cityscapes after dark.
Optical Impressions:
Arriving late in the afternoon on a dull winter’s day, I aimed it at some trees about 100 yards in the distance. Racking the zoom eyepiece throughout its 25x to 75x range, I was able to get a very sharp, crisp and bright image with excellent contrast at all magnifications. Edge-to-edge sharpness appeared excellent in my test unit. Colours were natural: not too warm or cold. The apparent field of view(AFOV) became quite noticeably wider as I moved up in magnification though. Moving back to 25x I felt the field was a little narrower than I expected based on my experience with other zoom eyepieces. Looking closely at some branches against a grey sky showed that the instrument displayed very minimal colour fringing at the 75x setting. I could immediately tell this was a noticeable step up in colour correction from the SA405 85mm scope(an ED triplet) I reviewed a couple of years ago. Some of this residual CA was coming from the eyepiece for sure. Over the next few days, I took a series of images with my IPhone just handheld to the eyepiece set at 75x to give the reader an impression of the degree of colour correction evident in the scope in various lighting conditions, drawing on the excellent work of Roger Vine who reviewed the Zeiss Harpia 95mm spotting scope. Let’s take a closer look:
The above image zoomed in to look at the aerial:
And tree branches against a dull grey sky:
In the next two images, I present a view of a Rook perched high in a tree with the winter Sun behind me, followed by another Rook against a dull grey sky:
In one final test for chromatic aberration, I inserted the SC001 digital imaging camera into the optical train and pointed the properly acclimated scope at a waxing gibbous Moon. Here is a single shot I obtained:
Commentary on the Images
I hope the reader who carefully examines the images, which have not been processed in any significant way, will conclude, as I have, that colour fringing in the SA401 100mm spotting scope is extremely low or even insignificant. This residual secondary spectrum could easily be removed post processing of course. Reflecting on Mr Vine’s comments on Zeiss’ flagship spotting scope and his posted images, I would agree that even this very sophisticated (with a price tag to match!), shows significant lateral colour, even more I’d say, than the SA401 tested here. Vine also makes the point that observing a jet black Crow against a uniform grey background sky will show colour fringing even on a scope as sophisticated as the Zeiss Harpia. The reason is that high-end spotting scopes have far more complicated optical designs than regular ‘apochromatic’ astronomical refractors, and it shows when eliminating the last vestige of false colour in the image. What’s more, optical testing of high-end spotting scopes show they fall below that of high quality astronomical refractors, but work fine within the magnification range over which they were designed.
Vine likens the view through the Harpia to a Televue 85: a simple ED doublet, at the same magnification. I would add that this is very likely to be the case on any high end spotting scope advertised as ‘APO.’ If you want better apochromatic performance at powers beyond 60x, you’re going to have to move to a moderate focal length (>F/6) astronomical triplet ED refractor and put up with the world the wrong way round(read left-right reversed).
The reader will also take note of the edge performance of the SA401 spotting scope, as evidenced by the image of the trees, showing the sharpness right up to the field stops. That’s an impressive result, in my opinion, and quite in keeping with my initial visual report. The SA401 does not utilise a field flattener but its excellent edge sharpness is probably down to its smaller true field of view(1.77 degrees)
Under the Stars:
The collimation of the SA401 100mm spotting scope was perfect. I used the SC001 imager to get an image of the intra-focal Fraunhofer diffraction pattern of the bright star Capella, with limited results, as it’s not designed to take high resolution astronomical images. Nevertheless, you can see that the pattern is perfectly round, indicative of the proper squaring on of all the components in the optical train. A few of the outer diffraction rings are also in evidence:
With three outer planets on the sky at the time of writing I was keen to see how they appeared in the SA401. Saturn showed a beautiful yellow globe with the rings seen almost edge on at 75x. Mighty Jupiter, now exceptionally well positioned in the night sky at my northerly latitude, was magnificent at 75x. The creamy-white oblate sphere was tack sharp with no false colour, the planet crisscrossed by numerous belts and zones. I enjoyed several satellite eclipses over a period of weeks and I was impressed to be able to see the famous Great Red Spot at this relatively low power. Fiery Red Mars rising later in the constellation of Cancer, showed a tiny, crisp orange disk with no chromatic aberration that I could make out. The views I enjoyed at 75x inspired me to crank up the power to get a closer look.
As mentioned earlier, the SA401 is capable of accepting 1.25” eyepieces, but not all those I tested were able to come to focus at infinity. While simple short focal length Plossls and orthoscopics worked superbly, one of my absolute favourites, like the exceptional Svbony SV215 3-8mm planetary zoom, did not focus at infinity. By unscrewing the lenses from my 2x and 3x Barlow lenses and placing them ahead of these eyepieces, I could boost the magnification further(up to 200x). Another winning combination was inserting these amplifying lenses ahead of the SV191 7.2-21.6mm zoom to give a useful range of magnifications.
Taking advantage of exceptional seeing conditions during the second week of December, when a huge high-pressure bubble over Scotland brought calm but gloriously clear sub-zero temperatures, I turned the instrument on these planets once again. Saturn at 150x looked even more magnificent with its largest satellite, Titan, easy to see. Jupiter showed very nice details at 139x – swirls, spots and festoons, racing their way across the planet as it rotated. The instrument stubbornly refused to show any significant secondary spectrum. On one night, I watched as a Galilean satellite appear as a tiny ‘pimple’ on the limb of the planet, growing larger as it rounded mighty Jove, before ‘pinching off’ to join the other moons in orbit. Wonderful! In the wee small hours of a freezing December night, I cranked the magnification up to 180x to take a closer look at Mars. Though the ruddy Martian disk remained small, I was clearly able to make out the Syrtis Major and a prominent northern polar ice cap. A word of advice would come in handy here. The complex optical design of this spotting scope needs some time to acclimate. Taking it out on a whim from a warm indoor environment to observe the planets at these high powers will likely disappoint. I recommend a good hour of prior acclimation to get the best out of this telescope.
The SA401 100mm spotting scope shows stars as beautiful pinpoints with no chromatic halos around the brightest luminaries. While I’ve been blown away with the views served up by a high-quality 15 x 70 binocular, the view of the Pleiades through the SA401 on a dark, moonless night, was quite simply a show stopper! The beautiful asterism filled the low-power field at 25x, with its constituent blue- white stars shining gloriously. I could even make out some hints of the reflection nebula around Merope. And while my main telescopes are all optimised Newtonians, the view through the SA401 brought back fond memories from my small refractor days, with its crisp, high-contrast views.
As a double star specialist, I was keen to see how the SA401 fared on a variety of these targets. Choosing a power of about 150x, I managed excellent splits of Castor A & B, Epsilon 1 & 2 Lyrae, Polaris A & B, and the spectacular triple system, Beta Monocerotis. Rigel proved more elusive, but on a night of very good seeing, I managed a convincing sighting of its faint close-in companion. I could have visited many more but star hopping is a lot more challenging without a finder scope. Sighting along the side of the tube just has its limits!
All in all, the SA401 proved to be an impressive performer under the stars. It would really benefit from having a simple finder though. Come on Svbony! Stick a bracket on the side of the tube.
Field Craft:
A large, high-quality spotting scope like the SA401 deserves a decent mount for mobile terrestrial observations. I was looking for a tripod light enough to carry on foot, but strong enough to accommodate the sizeable weight of this big 100mm instrument. I took a punt on Svbony’s SA402 tripod which has a number of attractive features, including its light weight(2.2 kilos) a hydraulic gimbal and large pan handle for easy manoeuvres both in azimuth and altitude.
It comes with a quick-release bracket for rapid and easy mounting and dismounting of the spotting scope. The strong, extendable 30mm-diameter aluminium legs reach a height of about 65 inches: perfect for my standing observations and imaging applications. Fully retracted, it stands just 27 inches above the level ground.
The sturdy head can support weights up to 6 kilos. One other nice feature of the SA402 mount is the ability to lock the leg spreaders in place. The base of the legs also have decent rubber pads to add extra grip. Though I would not recommend the SA402 for astronomical observations, owing to its lack of slow motion, fine controls, it proved ideal for using the scope during the day.
The black neoprene jacket fits snugly around the telescope and provides extra protection of the optics against the elements.
To be Continued…….