Long focal length APO telescope from Altair released

The Altair 101 ED APO has a new long focal length ED doublet objective design with complete freedom from color aberrations. This is a telescope with premium optics for serious visual astronomy at a good price. it is very well suited for visual observation where sharpness and contrast are important.

A long focal length refractor is easy to focus due to the extended depth of field and gives extremely sharp images.  The long focal ratio minimises eyepiece aberrations, resulting an extremely flat field of view. An F11 telescope copes extremely well with turbulent air or "seeing", due to it's extended depth of field. Until now, however, there are no APO refractors with a focal ratio in the "portable" sweet spot at F11. 

Long focal length APO telescope from Altair released: Altair Planeta 101mm telescope, relaxed but powerful

Long-focus refractors have always been a favorite telescope for visual observation amongst planetary, lunar, and double-star enthusiasts, giving excellent contrast and "easy to reach" high powers - even with eyepiece designs that, while very sharp, often have uncomfortably short eye relief, and are quite intolerant of "fast" optics. One goal of this F11 planetary telescope is to allow the comfortable use of such eyepieces in their medium focal lengths, whilst controlling aberrations, especially at the field edge. Even "ultrawide" eyepieces perform better and contribute less color aberration at the field edge.

Technical specifications of the Altair 101 F11 ED APO:

• S-FPL53 ED Doublet F11 APO lens 1,111mm focal length, full multi-coatings on all surfaces in a collimatable lens cell with QC serial number. Guaranteed to arrive in perfect collimation.
• 2.5" Dual Speed Geared focuser with 1:10 ratio fine-focusing knob.
• Rear 2" pushfit adapter with 3x thumbscrews and inner compression ring.
• 2"-1.25" Push-Fit Adapter with non-marring brass compression ring.
• Finder bracket which can be mounted either side of the focuser body.
• Front push-fit metal dust cap, rear plastic plug style dust cap.
• CNC machined tube rings, fully adjustable for balance and rotation.
• 250mm Metal Vixen-format dovetail plate included with stainless steel screws, so you can use the scope with just about any telescope mount, including Celestron, iOptron, Skywatcher, etc.
• Retractable Metal dewshield of ~212mm length, 121mm diameter included. This can be unscrewed for objective lens removal or cleaning.
• The optical tube is 100cm length and weighs approx. 4.8kg including dovetail bar.
• The removable Binoviewer section is 100mm/10cm length therefore total tube length is 800mm/80cm when removed.
• Backfocus is 150mm from rear end of focuser to image plane. (250mm backfocus to the image plane if Binoviewer tube is removed).
• For transport, the focuser and extension can be removed as one part, resulting in two shorter parts of 80cm (the objective and main optical tube) and 20cm (focuser and extension tube). This overcomes space limitations. For airline transport or cleaning, the objective can be unscrewed after the dewshield is removed.

Perfect APO color correction for the demanding visual observer

No color aberration is visible in or out of focus. The contrast is great, and the tube baffles have been calculated to block extraneous light. Moreover, the doublet lens design has less glass elements for faster cooldown.

Ready for binoviewers

The optical tube has a removable rear section just in front of the focuser, which when removed, gives a generous additional 100mm of back-focus. This allows the use of binoviewers and some Hershel Wedges without resorting to a Barlow lens. Binoviewing is very easy - just detach the focuser and unscrew the mid-section, then screw the focuser back into the tube. No tools are required to break the scope down for travel.

Dual speed geared focuser and a light strong mechanics

A new 2023 design dual speed focuser offers tight, repeatable and precise control for observation at high powers, although ironically, finding sharpest focus is much easier with this long focal ratio design than with faster optics. CNC tube rings and a retractable dew shield make this a convenient instrument to use.

Not only for the moon and planets

The high contrast of eyepiece aberrations inherent to this design makes the 101mm APO a superb choice for double stars and deep-sky objects. Another area to benefit is of course solar observation with a Herschel wedge, or the use of a Daystar Quark, or other Hydrogen Alpha Etalon (with the appropriate ERF Altair Energy Rejection Filter). There are also new opportunities for the solar-modding community, where additional back-focus is often a requirement - afforded by the removable rear extension.

Will Gater, an astronomer and reviewer at Sky at Night Magazine, praised the Altair Planeta 101mm refractor for its optics and remarkable price. He highlighted its new long focal length ED doublet objective design, which offers freedom from color aberrations, and notes its suitability for serious visual astronomy due to its sharpness and contrast. Gater commends the telescope's performance in various observational contexts, from planetary to deep-sky objects, making it a versatile and valuable instrument for astronomers. "An Affordable Gem for Serious Astronomers," said Gater.