Altair 70EDT-F refractor and reducer
A highly portable triplet scope that delivers superbly at the eyepiece and on camera
The Altair 70EDT-F is a travel-friendly refractor with premium optics, offering the choice between grab-and-go visual observing and astrophotography. Our review telescope came as a package,
including a 0.8x reducer/flattener lens which corrects
for inherent coma and takes the 70mm diamater lens from an f/16 to an f/4.8 and a working focal length of 335mm. This means that when it’s combined with a DSLR or a dedicated astro camera, the 70EDT-F can
present images with a field of view that’s easily wide
enough for a large nebula such as the Orion Nebula, M42, or extended star clusters like the Pleiades, M45.
Making an impression
The telescope has a stylish appearance, combining classic white with red anodized trimmings, and it has the look and feel of a well-made instrument. Although its construction is solid, the OTA weighs just over 2kg.
Being around 30cm long with the dew shield retracted,
the scope should easily fit into your hand luggage or
a camera bag. Converting between the visual and photography modes is a simple matter of unscrewing the eyepiece clamp from the focuser drawtube, and
then fitting the reducer/flattener directly to the
drawtube, which eliminates any chance of introducing
flex or tilt into the imaging train.
At first, we used the supplied T-ring to attach our full-frame DSLR to the flattener, which has a built-in helical adjustment for fine-tuning the spacing. This proved to be asking too much of the flattening lens,
which is designed to work with APS-sized sensor DSLRs, so we swapped to a CCD camera with a smaller sensor and set about capturing images. The wide view on offer seemed perfect for the Horsehead Nebula region, and the nearby bright star Alnitak put the scope’s optics through their paces. It was reassuring to see the images coming in without a harsh-coloured halo around Alnitak
or reflection artefacts in the image. Although galaxies ▶
are presented as small objects
▶ at this focal length, our images of the Leo Triplet and The Whale and Hockey Stick galaxies demonstrated that the Altair 70EDT-F produces good, contrast-rich pictures with accurate star colours. The beauty of a refractor is that they offer hassle-free imaging, and this one was no exception, just an occasional tweak of focus was required, in line with temperature changes.
Take a sky tour
You can get great pleasure from taking a tour of the skies with a good small refractor. After removing the
flattener/reducer lens, and adding our own diagonal
and a 13mm eyepiece, we enjoyed an observing session
at 32x magnification. Starting with a quarter
illuminated Moon, the contrast-rich views allowed crisp observations of the terminator, the craters of Mare Crisium, and the ridges, mounds and hollows within Mare Fecunditatis, as well as some details lit dimly by earthshine. With a 4.5mm eyepiece, working at 93x, the details were tight and clear. We did notice the slightest hint of a green and yellow fringe on the brightest edge of the Moon, but it was nowhere near enough to distract from the enjoyment of the view.
Turning to the Pleiades, M45, at 33x, the main cluster stars were round and crisp while, as expected, those nearer the edges of the view tailed off a bit due to coma. The brightest parts of the Orion Nebula, M42, presented a glorious sight, snuggled around the Trapezium area. The view was clear and sharp with a decent amount of nebulosity visible in our suburban skies, no doubt assisted by the high-transmission coatings on the lenses. While navigating Orion we also took a peek at Betelgeuse, and it was good to see it presented with strong orange colouring. Although triplet refractors may be viewed as a luxury for observing, the good, true colour views present a strong argument in their favour, and the ability to travel easily to dark clear skies with the Altair 70EDT-F makes it even more attractive as an investment.
Overall, we found that the Altair 70 EDT-F with the reducer/flattener lens provides all round performance and great results from an eyepiece or a camera.