Aperture: 103mm (4 inches)
Focal Length: 825mm; f/8
Eyepieces: None supplied
Mount: Atlux Go-To with Star Book
Telephone: 01582 726522
The Vixen Atlux AX103S is a substantial, high-end product that comes with some rather interesting features.
The telescope has a richly finished white aluminium tube with a retractable dew shield and a dual-speed, 10:1 high-precision rack-and-pinion focuser.
However, what makes this scope special compared to most other refractors is that it has a rear field-correction lens as well as its extra-low dispersion, apochromatic, multicoated 4-inch triplet objective (main) lens.
The rear lens corrects a problem common to normal refractors, the views of which suffer from ‘field curvature’.
This is when light passing through the edge of the lens is brought to focus closer to the lens than light passing through the centre, so image quality drops off towards the edge of the field of view.
The beautifully engineered, heavy-duty, cream-finished Atlux mount has a 34kg load capacity, making it a very sturdy platform for both visual and imaging use.
The mount is a Go-To, but it’s no normal Go-To.
It’s matched up to Vixen’s Star Book controller that incorporates a complete full-colour 22,725-object planetarium as well as the Go-To system itself.
We wanted to test the system by using it for both observing and imaging.
First, we carried out an extensive observing session to get accustomed to the Star Book controls.
Opticron supplied us with 20mm and 5mm Lanthanum eyepieces, a flip mirror and a finderscope for this review since these accessories aren’t included.
Assembly of the components was straightforward and we found the well-designed polar alignment scope very simple to use.
Although we were surprised that the Star Book’s 10 control buttons weren’t illuminated, they were very intuitive in use and we quickly felt at one with the unit.
We carried out a two-star alignment, choosing Vega and Aldebaran so we could examine these two very different stars.
Bright blue Vega sparkled crisply and the out-of-focus views of the Airy discs (the patterns of diffraction) either side of the point of focus revealed a very well matched pair of concentric rings, confirming the excellence of the optics.
Vega remained beautifully formed right out to the edge of the field of view.
The Star Book hand controller packs a 22,725-object planetarium
With Vega as our first alignment star, we were pleased to see the obvious red hue of Aldebaran appear in our 20mm eyepiece when we slewed to it to complete the star alignment.
Subsequent slews confirmed the high accuracy of the Go-To system.
Our first hop was back to the region of Vega for a look at M57, the Ring Nebula, and we were rewarded with a lovely view of this celestial smoke ring.
Nearby, the Double-Double quadruple star (Epsilon Lyrae) was split with ease using the 5mm eyepiece, and the high contrast view was stunning.
Heading for closer prey, Jupiter was a small but glorious sight with obvious bands and beautifully bright, pin-prick moons.
The full Moon was framed well in the 20mm eyepiece and the lack of colour fringing was a testament to the excellent optics.
The Pleiades, too, was a memorable sight, although we couldn’t fit the whole cluster into the field of view of the 20mm eyepiece.
The built-in polarscope
Digital camera sensors really show the effects of field curvature, so we were keen to see how well this refractor coped with this problem.
We analysed an image of the sky to see how ‘flat’ it appeared and were very impressed with the result, with pin-point stars right to the edge of the frame.
Some of our two-minute unguided images showed star trailing, but long exposures can be autoguided via the standard autoguider port on the Star Book.
With its excellent build quality and rich feature set, we thoroughly recommend this system if you’re looking to upgrade from your current setup.
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This review first appeared in the February 2010 issue of Sky at Night Magazine