Long-focal-length refractors have always been a favourite among visual astronomers, not only for the exceptional lunar and planetary vistas, but also for the sharp, high-contrast deep-sky views that are possible.
Featuring a 101mm (4-inch) objective lens for increased light capture, Altair Astro has once again stepped into this market with its new offering, the Altair Planeta 101mm apo refractor.
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Unboxing and setting up
The Altair Planeta 101mm apo refractor is a 1,111mm-focal-length doublet.
With a two-glass optical system, its weight is well controlled and the telescope tube, with tube rings and mounting bar attached, comes in at a modest 4.8kg.
This allows this long refractor to be used on lighter, more portable mounts.
While it isn’t supplied with a carry case, the tube can be broken down into two segments – an 80cm main section and a 20cm focuser with extension section – allowing for easy transport to dark-sky sites.
Unpacking the single box that the Planeta arrived in, we uncovered a striking telescope of metal construction, with no plastic accessories to be seen.
Finished in bold blue and black, the refractor had the appearance and feel of a quality item.
Despite the tube length of 100cm, the low weight and ample Vixen bar allowed us to carry, mount and balance the telescope with ease.
How the Altair Planeta 101mm apo refractor performed
With a clear night ahead and a long list of targets to chase, we set about our three-star alignment.
Picking three of the brightest stars in the winter sky gave us an early opportunity to test out the Planeta’s optics.
Our initial impressions at low powers were very positive, with the alignment stars appearing crisp and sharp.
Alignment completed, we then slewed over to a bright Jupiter.
Despite being long past opposition, with its apparent size shrinking by the day, the planet and its four main Galilean moons appeared sharp, but small through our 25mm eyepiece.
Stepping up to a 15mm (74x magnification) and again to a 9mm eyepiece (123x magnification), the views consistently improved.
Through the 9mm, Jupiter’s equatorial bands were clear, with finer details and structures becoming discernible within them.
As we enjoyed our time with the planet, we realised that this was one of the most pleasing views we had seen through a relatively small-aperture telescope.
The seeing on this particular night was exceptional, so we took the opportunity to slew over to a 57%-illuminated Moon and, continuing with our 9mm eyepiece, we were rewarded with exceptional lunar detail.
Panning across the craters Ptolemaeus and Alphonsus, we could see crisp and beautifully high-contrast shadows cast by the crater walls.
Our views of the Moon were easily the clearest and sharpest we had seen, leaving us wowed.
Heading over to the Double Cluster, we were pleased to see both clusters in view using our 25mm eyepiece, with sharp stars across most of the field of view and only a hint of coma on the very outer edges.
Finishing our journey at Orion, we resolved four of the Trapezium stars, in addition to nebulous details.
Astrophotography
Not wanting to miss an imaging opportunity, we switched to our planetary camera.
Initially it took us some time to achieve focus, but several extension tubes later we gained the back focus required.
The need for extension tubes is not unusual for a refractor, but worth noting if you plan to use the Altair Planeta 101mm apo refractor for astrophotography.
Thanks to the excellent focuser, a sharp focus was easy to achieve and enabled us to capture a range of video clips for processing later.
Over the following weeks, we were pleased to affirm that the excellent views offered by the Planeta in our first tests were not a one-off, as we continued to enjoy lunar and planetary observations.
Viewing a 100%-lit Moon was also a pleasant surprise and showcased the Planeta’s high-contrast capabilities.
The Altair Planeta may have a modest price, but the quality of views it returns are anything but budget.
Even as experienced astronomers, we were left in awe at the excellent vistas provided.
Altair Planeta 101mm apo refractor optics examined
Offering 1,111mm of focal length and a 101mm aperture, the Altair Planeta 101mm apo refractor has a focal ratio of f/11.
While this is ‘slow’ for astrophotography, these features pack a real punch for visual observations due to the superior depth of field, in addition to reduced eyepiece aberrations.
As a doublet refractor, the telescope cools down rapidly compared with the thicker glass of triplet lenses.
Mounted upfront in a collimatable lens cell is a pair of S-FPL53 glass elements that are multi-coated.
These coatings work to reduce internal reflections and glare, and deliver improved colour correction.
While the Planeta delivered a flat field of view, we found that colour correction was exemplary, with no noticeable fringing even at the highest powers while honed in on some seriously bright stars.
Testing it on a 100%-illuminated Moon revealed a hint of green fringing at the very edge of the disc, but not enough to distract from the stunningly sharp, high-contrast views.
Altair Planeta 101mm apo refractor best features
Dual-speed geared focuser
The Planeta comes equipped with a 2.5-inch CNC-machined aluminium dual-speed focuser. This rack and pinion focuser feels solid, with a firm but smooth motion. This allows for very precise adjustments to be made with ease, while also securely supporting the heaviest eyepieces in our collection.
Vixen plate and tube rings
To hold the telescope securely, the Planeta comes with a pair of CNC-machined tube rings as standard, mounted to a 250mm Vixen-style dovetail plate. This narrower style of dovetail holds the 4.8kg telescope firmly, while allowing it to be mounted to virtually any telescope mount.
Dew shield
The Planeta’s retractable, solid metal dew shield ensures the refractor stays as compact as possible when not in use. Measuring 212mm in length, it protects the front elements from dew and stray light. During multiple damp evenings, we found that the lens stayed clear of dew for several hours without the help of dew heaters.
Bino viewer adaptor
To maximise its flexibility as a visual telescope, the Planeta has been designed with the use of binocular viewers in mind. Located in front of the focuser is a removable 100mm section of the main telescope tube that, once removed and with the focuser reattached, grants the user an additional 100mm of back focus.
Push-fit adaptors
To allow the use of both 2-inch and 1.25-inch eyepieces and accessories, the Planeta comes with a pair of machined adaptors. Both adaptors use brass compression rings to ensure that the barrel of your eyepiece is not scratched or damaged while in use.
Altair Planeta 101mm apo refractor vital stats
- Price: £849
- Optics: S-FPL53 doublet
- Aperture: 101mm
- Focal length: 1,111mm, f/11
- Focuser: Dual-speed geared
- Extras: Tube rings, dovetail bar
- Weight: 4.8kg
- Supplier: Altair Astro
- Tel: 01603 721946
- www.altairastro.com
This review appeared in the May 2024 issue of BBC Sky at Night Magazine
