Page 90 - BBC Sky at Night - September 2017 UK

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FIRST LIGHT See an interactive 360° model of this scope at
www.skyatnightmagazine.com/airyapo65f

PrimaLuceLab Airy APO 65F

apochromatic refractor

A three-element FPL-53 scope that takes aberration avoidance seriously

WORDS: PETE LAWRENCE

any regard refractors SKY SAYS… The Airy APO 65F possesses a
VITAL STATS as the perfect design Biased towards permanent flattener made from
of telescope, giving ZLGH!"HOG#$ORZ! FPL-53 glass, fitted internally.
• Price £793 Mhigh-contrast views Testing during the summer gave
• Optics FPL-53 triplet thanks to the lack of the central SRZHU$YLHZV#$ us a good choice of star clouds and
objective with this is a scope
integrated FPL-53 obstruction found in mirror-based best suited to large, expansive nebulae to pick
field-flattener instruments. On the downside, large from. To a large format imaging
• Aperture 65mm refractors are expensive and can be stunning deep- sensor objects such as the North
(2.5 inches) unwieldy. PrimaLuceLab’s Airy APO sky vistas America Nebula in Cygnus,
• Focal length 420mm 65F is small enough at 2.5 inches to be NGC 7000, provide a tough test
(f/6.5) both affordable and manageable. subject, with a field of view covered with stars
• Focuser Hybrid drive One negative effect of using a lens is right across the frame. Using our Canon EOS
focuser (Crayford- chromatic aberration, where the main lens 6D DSLR, the Airy APO 65F delivered some
style plus lockable is unable to bring all visible wavelengths to a excellent results: stars at the centre of the frame
rack and pinion) with
60mm movement common focus, resulting in colour fringing. appeared pin sharp, with only the slightest hint
• Extras Tube rings, The Airy APO 65F uses a three-element of distortion creeping in towards the extreme
1.25-inch OnAxisLock FPL-53 glass objective to address this issue. corners. Our large sensor test produced only
slight vignetting in the corners of the image.
A fully colour-corrected telescope is termed
adaptor
WWW.THESECRETSTUDIO.NET X 6 • Supplier 365 length makes this a relatively fast (f/6.5) Easy grip, easy grasp
• Weight Tube 2.3kg,
apochomatic, APO for short. The 420mm focal
tube rings 0.5kg
The scope uses what’s called an OnAxisLock
instrument. Coupled to a Canon EOS 6D full-
Astronomy
mechanism to hold equipment into the focuser
frame DSLR, we produced images covering a
• www.365astronomy.
2.1x1.7° rectangle of sky, an ideal size for extended
drawtube. This is an alternative to the traditional
com
objects such as star clouds, open clusters, nebulae,
• Tel 020 3384 5187
works by having a large, easy-grip locking ring
and galaxies like M31 and M33. thumbscrew locking found on most focusers and
Fast instruments can suffer from coma, which that causes an internal collar to tighten around
leads to distorted stars towards the edge of frame the barrel of whatever has been inserted when
and is normally addressed by attaching your tightened. A 1.25-inch OnAxisLock adaptor, using
own field-flattener between scope and camera. the same principal, is supplied to complement the >
OBJECTIVE TRIPLET LENS
Refractors make superb deep-sky optical properties of fluorite, a material
imaging instruments because of their that is easily damaged, expensive
contrast performance. To get the best and not particularly environmentally
results the optics need to bring all friendly. Stronger, cheaper and greener
colours of light to focus at the same alternatives are now popular. The
point. The triplet objective lens at FPL-53 name indicates that the glass is
the heart of the Airy APO 65F is made from a fluorite-lead compound
designed to do just that. Using three (F = fluorite, P = lead) with a low
FPL-53 glass elements, all colours refractive index (L) and is the 53rd
are brought to a single focus leading member of the material’s development
to a clean image that is free from family. In use, we didn’t encounter any
unwanted colour fringing. colour fringing even around bright
FPL-53 is an optical material that extended objects, and found the optical
attempts to replicate the exemplary qualities of the scope to be excellent.

skyatnightmagazine.com 2017