FIRST LIGHT
iOptron Photron RC6 6-inch Ritchey-Chrétien optical tube
Is this small, portable telescope equally capable of viewing and imaging?
VITAL STATS
• Price £399
• Optics Ritchey-Chrétien Cassegrain
• Aperture 150mm (6-inch)
• Focal length 1,370mm, f/9
• Focuser 2-inch dual-speed Crayford
• Length 490mm
• Weight 5.4kg
• Supplier Rother Valley Optics
• Tel 01909 774521
The Photron RC6 is the smallest telescope in iOptron’s Photron RC range, and this review looks at how it performs when used with eyepieces and a camera When the Photron RC6 arrived, we immediately inspected the alignment of the mirrors.
These are initially collimated at the factory, and then Rother Valley Optics (the supplier of the review model) re-checks each telescope on an optical test bench. Our initial check was conducted during the day with a Cheshire eyepiece, and then we re-tested the alignment using a suitable star once darkness had fallen. The tests confirmed the review model was in good condition and the collimation was near perfect. Any adjustments to the alignment of the primary and secondary mirrors can be made with an Allen key, but this shouldn’t need to be done too often.
It’s impossible to ignore the solid construction of the Photron RC6: the tube is steel with metal fittings at either end and there’s nothing flimsy about the design. The secondary mirror holder is held in place by sturdy 2mm steel struts, which show no sign of flopping or flexing in any orientation. Straight out of the box, the optical tube weighs nearly 5.5kg, but once it’s configured for use that weight increases, especially towards the rear of the telescope. The mount we used, like many, performs best when the telescope is nicely balanced, and to achieve this we attached additional weights at the front.
Steady focus
The Photron RC6 took around an hour to acclimatise, but once it had settled down we found that there was very little variation in focus over the course of a few hours’ use. Periodic checks during an imaging session revealed that only micro-adjustments were needed.
The Photron RC6 can be used for observing and imaging. Taking advantage of some clear moonless nights, we attached a colour camera and set about taking some pictures. Despite its petite dimensions, the Photron RC6 has a focal length of 1,370mm, which makes it capable of picking up smaller deep-space objects, such as galaxies, planetary
From there, we moved on to globular clusters, with M3 and M13 presenting nicely at the scale offered. We also managed to capture a few frames of Bode’s Galaxy, M81 and the Cigar Galaxy, M82. It struck us that the Photron RC6 would make a perfect setup option for imaging Messier objects, especially as it works so well with a colour camera and can be so easily transported to darker sky sites.
The Orion Nebula, M42, captured with the Photron RC6 and an Atik 460EX OSC camera, using 5’ exposures and 35 minutes of integration 
M13 is nicely presented with the same setup, using 10’ exposures and 2 hours and 10 minutes of integration 
The setup also brings out the colours in the Cigar Galaxy, M82, using 10’ exposures and 4 hours and 20 minutes of integration… 
…and Bode’s Galaxy, M81, using 10’ exposures and 2 hours and 30 minutes of integration
After proving its capabilities with a camera attached (the f/9 optics helped produce well contrasted images even with less-than-ideal suburban skies), we fitted a star diagonal and tried a selection of eyepieces. Starting with a 21mm wide-angle eyepiece, we found the view of a 75%-illuminated waning Moon was very pleasing at 65x magnification, with plenty of good natural colours and sharp detail on display, both around and within craters. Despite a fairly low elevation and moderate seeing conditions, the suggestions of craterlets within Plato held our attention for some time.
Our favourite view came with a 13mm eyepiece, which gave the lunar disc an almost threedimensional appearance at 105x magnification, while globular clusters M3 and M13 presented a rewarding spectacle that seemed to fill the view, even in the moonlight. A 10mm eyepiece working at 140x magnification pushed the seeing limits, but it was still able to present the glorious colours of a few red stars very nicely, particularly Betelgeuse (Alpha (α) Orionis) and Arcturus (Alpha (α) Boötis).
There’s no doubt that the Photron RC6 is a very capable telescope, suitable for both imaging and visual use. And at this price point it’ll appeal to both seasoned astronomers and newcomers alike.
Ritchey-Chrétien mirror design
First introduced over a century ago, Ritchey-Chrétien telescopes have become a design of choice for professional telescopes, including the European Southern Observatory’s Very Large Telescope and even the Hubble Space Telescope. The reason for its popularity is the combination of hyberbolic concave primary and convex secondary mirrors, which, unlike other designs, achieves an image free of distortions caused by spherical aberrations and coma.
Modern manufacturing processes have made it possible to produce these mirrors for amateur instruments and a Ritchey-Chrétien telescope might just present the optimal choice for an amateur. For example, a 6-inch (150mm) refractor with glass lenses that can produce comparable coma and chromatic aberration–free images would typically be much more expensive and much easier to transport.
Of course, any telescope style is a compromise to some extent but, pound for pound, the photographic and visual performance of the Photron RC6 ticks more boxes than its rivals. It warrants serious consideration, especially for first-time telescope buyers looking for an instrument nebulae and globular clusters. We took a few images of the Trapezium Cluster in Orion and the Photron RC6 produced good, round stars and nice, sharp edges on the nebulosity.
KIT TO ADD
1. iOptron 8×50 Finderscope and Bracket
2. iOptron Electronic Focuser for RC Series
3. iOptron 2-inch Dielectric Mirror Diagonal
