johnrt

Altair Astro 6” Ritchey Chretien review.

I have seen many people propose this scope as a possible purchase for either longer focal length DSO or planetary imaging, but I have yet to see anyone who has bought one post a detailed review. So, I thought I’d put my thoughts together after 9 months of owning this scope.

This same OTA is available under several different badges including GSO, Astro Tech and Altair Astro.

Altair Astro market this as a 1370mm f/9 astrograph priced very reasonably at £399. They claim it to be “ideal for imagers”. I’m told the large central obstruction for the secondary mirror makes it unsuitable for observing. I am purely a DSO imager so cannot offer my opinion on either observing or planetary imaging with this scope.

The dimensions are:

Tube length 390mm

Outside diameter 198mm

Weight 5.4kgs

Central obstruction of 77mm

Out of the box the first impressions I had was that the OTA was sturdy and well built with a nice finish. It came supplied with a variety of extension rings to attach the focuser so any combination of filter wheels, off axis guiders and camera can be brought to focus without difficulty. The OTA has vixen/skywatcher style dovetails mounted to the body on both the top and bottom, very handy to piggy back your guidescope with ease. I use an ST80/QHY5 combo on mine. It also has a standard skywatcher finder bracket fitted. I found the focuser a little cheap and plastic feeling and although the manufacturer says it is robust and will deal with a standard CCD & filter wheel, I find it is not quite up to the job and struggles to “wind in” working against gravity when the scope is pointing skyward. I plan to replace the focuser with a moonlight in due course. I also found the focuser draw tube to be very loose on delivery and required dismantling for adjustment to remove the play in the mechanism before it was fit for use.

As an astrograph out of the box for DSO imaging I find this scope unsuitable. The native f/9 is simply too slow to be effective (especially with the limited imaging time we get in the UK). A good reducer is required - I have used both a William Optics FF/FR II x0.8 reducer and an Astro Physics CCDT67 telecompressor with my Atik 314l+ with success. The Astro Physics x0.67 compressor being the most suitable, bringing the scope down to 900mm f/6, a reasonable spec for DSO imaging.

My second concern with this scope on delivery was the fact that the primary mirror was loose in it’s cell, causing it to tilt under gravity during use. The result was elongated stars and the image to always gradually drift across the field of view. Any sub exposures of over 2/3 minutes were unusable. This was infuriating, especially as it was the last place I looked after spending months tinkering with my balance, mount and guiding. Once I discovered the issue, it was a simple matter of tightening the compression ring which holds the primary in place and the problem was solved. *Warning you will invalidate your warranty removing the rear cell to make this repair*

Collimation at first is a little tricky, but once you know what to look for and how little adjustment is required it can be achieved in just a few minutes. A standard Cheshire collimating eyepiece is all that is required. Now the primary is secured in my OTA, it holds collimation well.

To conclude my overall impressions after 9 months of ownership are mixed. I only now feel after considerable trouble shooting I am ready to start serious imaging with my scope. The quality control in the manufacture of the instrument was poor causing it to be verging on unfit for purpose on delivery. However, now the issues have been resolved and I have matched the scope to a decent reducer I am looking forward to the results I anticipate it will deliver. I purchased this scope as an alternative to my ED80 triplet refractor, offering me the focal length the refractor could not give for smaller galaxy targets and planetary nebulae.

Would I recommend this scope to others?

If this is your first purchase of a scope for imaging then no, quality control is poor, and operation is certainly suited to a more experienced user. For someone willing to spend a little time and effort (and £’s) getting the scope up to scratch this will make a cracking little longer focal length imaging scope. Maybe I am expecting too much for £399 delivered, but I believe no scope should be delivered with the issues mine had on arrival. Hopefully this write-up will save you a little time if yours arrives in the same condition mine did.

Here are some sample images I have achieved so far with this scope. Please note they were taken before the primary mirror issue was fixed meaning sub exposure time was limited. They were also taken with the 0.8 reducer @ f7/2, slower than the f/6 I am now using the scope at with the APCCDT67 reducer.

How fitting that we have a lovely clear starry sky over us tonight. My scope is out and I'm enjoying it, but also thinking about the man who goy me interested in astronomy in the first place. RIP Patrick, you will be sorely missed.