CT152 F-5.9 Acromatic Refractor from Canadian-Telescopes.com
By Warren Maguire
I have been into ameteur astronomy for several decades and I have always wanted a big refractor. In May 2011 I finally decided to take the plunge. I purchased a CT152 Achromatic Refractor (sold as an OTA) from Canadian Telescopes.com located in Vancouver, Canada. This scope has a 152mm (6 in.) aperature with a 900mm focal length, which makes it a very fast F-5.9. The scope is equiped with a 3 inch, dual speed (10 to 1), rotatable, Crayford Focuser and comes with a 2 inch star diagonal with 1.25 inch adapter. Brass compression rings are used to hold the diagonal and eyepiece in place. The scope also comes with a very nice cradle with Vixen style dove tail bar and a very sturdy carry handle, all finished in a very attractive matte black. The OTA is finished in a glossy white and comes with a retractable dew shield and is truely first class. The objective lens cell has adjustment screws that allow collimation of the scope should it ever be needed. The objective lens is fully multi coated. Looking down the front end of the tube the deep purple color of the coatings looks even and blimish free. I can also see three baffles down the length of the tube to help cut down on stray light. Even the front lens cap is impressive. It's made of metal and screws on. No cheap plastic here. A finder scope and carry case are not included.
The selling price was 859.00 Canadian dollars ($938.00 US dollars at the then current exchange rate). Canadian Telescopes.com is not able to handle payments in US dollars. This caused a problem that had to be solved. I'll explain more at the end of this review.
To give you some background on myself, I'm 64 years old. I got my first telescope when I was 10 years old and I've been hooked ever since. I currently own 6 telescopes. My old Meade 10 inch LX-5 S.C. (bought in 1986) has been my main scope for the last 25 years. I've made many upgrades on it, including computer controls, and it still performs well. I joined our local astronomy club, The Central Valley Astronomers in Fresno, Calif., 25 years ago and I am currently on the board of directors.
The CT152 is actually a clone of Astro Telescope's 152mm F-5.9 refractor sold by Hands On Optics in Damascus, Maryland. The only difference being it comes with a 2 inch Crayford Focuser and no star diagonal. (This is why I wanted to buy from Canadian Telescopes.com.) Both of these scopes are manufactured by Kunming United Optics in China. From my understanding Canadian Telescopes and Hands On Optics are both exclusive dealers for these scopes, the former in Canada and the latter in the U.S.
Before I get started with my viewing experience with the CT152 I would like to mention there is an excellent review of the AT152 versian of my scope (with the 2 in. focuser) by Larry Carlino on this web site. After reading many reviews, it was his review that finaly convinced me that this was the scope I should buy. He has more experience with different scopes than I do and he goes into a lot of detail on the AT152's performance. If your considering buying an achromatic refractor, then Larry's review is a must read.
The only mechanical problem Larry noted in his review of the AT152 was with the rotation feature of the 2 inch focuser. He said it was noisy and stiff and wondered if the 3 inch focuser might be better. Unfortunately, I found the exact same problem with my scope's 3 inch focuser. However, I found an easy fix that solved the problem. I loosened the hex screws holding the end of the focuser in place and removed it. What I found were 2 large thin nylon gaskets. Apparently they are supposed to rub against each other when rotating the focuser, but they are completely dry. There is no lubrication. I put a thin coating of Vasilene on the gaskets and reinstalled the end piece. This solved the problem. The focuser now rotates smoothly.
My telescope arrived in perfect condition. There were no scratches or blemishes anywhere. The scope was inside a clear plastic bag and packed in a heavy guage cardboard box with foam inserts to cradle it and keep it from moving. Lifting it out of the box for the first time, I was amazed by it's apperance. I have never seen a refracter this large in diameter and this short! The diameter of the tube is 7 inches and the dew shield is 8 inches but the length is only 30.5 inches! This is with the dew shield retracted and the focuser racked in, without the diagonal.
I bought the telescope without having a mount to put it on. I wanted to make sure the all up weight of the telescope system I wanted to put on the mount would not exceed its payload capacity. The CT152 with its supplied accessaries weighs 24.5 pounds on my scale. I have a Celestron 102mm F-5 refractor which I mounted piggy back on to the CT152, by removing the carry handle and installing an ADM mini dove tail bar ($59.00) in its place. The dove tail bar can double as a carry handle. By using 125mm ADM mounting rings ($99.00) I can slide the C 102mm on to the CT152. The all up weight of this set up with eyepieces and everything is slightly under 34 pounds.
I decided to buy the Celestron CG5-GT go to mount with its advertised 35 pound payload capacity ($615.00 from High Point Scientific). I new I would be pushing this mount to its limit. But, I wanted to keep costs and weight down so I went with it. A side note on this mount. The Vixen type saddle supplied with the CG5-GT mount is not suitable for payloads above 20 pounds, in my oppinion. It's only about 2.5 inches long and its vice like teeth will tear up your dove tail bar. To solve this problem ADM makes an upgrade for the CG5 mount ($99.00). Their saddle is 6 inches long and smoothly grips the dove tail bar (no vice like teeth) and will not tear it up. I have been using this telescope and mount set up for visual observations for about 6 weeks now and I have had no problems. Carefully balancing the telescope is important. Once this is done the mount slews from object to object seemingly with little effort. The go to pointing accuracy has been excellent.
For first light I set up the scope in my front yard under Fresno, Calif.'s light polluted sky. Limiting magnitude is about 3.5. For comparison none of the stars in the Little Dipper's handle are visable except Polaris. I decided on Saturn as my first target. I must confess I was a little apprehensive at this point because, I am well aware of the chromatic aberration problems assocciated with short focus achromatic refractors when viewing bright stars, the moon, or planets. My C 102mm F-5 at powers above 50 or so has a severe problem with c.a.
With my Meade 14mm UW in place at 64 power I brought Saturn into view along with the nearby double star Porrima. What a pretty sight they make together in the same field. I couldn't see any c.a. at this power. Next I put my Meade 8.8mm UW into the diagonal, giving 102 power. I centered saturn and brought it into focus. What a pleasure it is to use this focuser. With my Meade 10 inch S.C., with its inevitable mirror shift, I'm used to rocking the focuser back and forth to find best focus. Not so with this scope. I used the large knob to roughly focus Saturn and the small knob to fine tune it. Saturn just seemed to snap into focus with knife edge clarity. There is zero image shift with this focuser, even when I have used over 300 power. With Saturn focused at 102 power I still couldn't see any c.a. Fresno's sky glow may be helping to hide it. All Ican tell you is I couldn't see it. I decided to go to 191 power usuing my Explore Scientific 4.7mm UW. As I bring Saturn into focus I can now see the c.a. It's not very obvious. It appears as a faint purple glow around the planet. However, this does not seem to interfere with the sharp clear view I have of Saturn. In moments of good seeing I can see subtle detail on the planet and the rings. Titan plus 4 other moons are also visable. I have a Baader Fringe Killer filter I bought to help my C 102mm F-5 with its c.a. problem. I installed it onto the E.S. 4.7mm eyepiece to see what effect it would have. The Baader filter cuts out about 50% of the c.a., but at a cost. The image is slightly dimmer and Saturn has a faint yellowish cast to it. I think for Saturn the view is better without the filter. The Baader filter may be of more value on a brighter planet like Jupter or Venus, but they are in the early morning sky and I haven't had a chance to view them. For my final test on Saturn I installed my Antares 1.6x 2 inch barlow, bringing the 4.7mm eyepiece to 306 power. The view is not quite as sharp as it was at 191 power, but still very good. The c.a. around Saturn has grown in diameter but not in brightness and as before, it doesn't seem to interfere with my view of Saturn. Usuing the Baader filter again produced pretty much the same results. I liked the view better without the filter. To make a direct comparison I installed the E.S. 4.7mm eyepiece on to the piggy backed C 102 F-5 giving 106 power. In this scope, the c.a. is very pronounced around Saturn and it DOES interfere with the view. This is a far different result than I had with the CT152 at 102 power.
I'm very happy with the CT152's performance on Saturn. My early fears about chromatic aberration with this scope have been greatly reduced, at least for now. Jupiter and the, Moon will be tougher challanges, but neither is available right now.
Since Porrima is close to Saturn I decide to go there next. This tough to split double star has a separation of only about 1.1 arc seconds. I have tried to split it twice in the last month with my Meade 10 inch S.C. and I failed both times. I can see 2 stars but they are overlapping and I can't get black sky between them. With the CT152 and my Meade 40mm SW at 23 power I centered Porrima. This eyepeace produces a big 3 deg. field on this scope. The stars surrounding Porrima are tiny pinpoints all the way to the edge of the field and with Saturn nearby it's a striking view. I decided to go to the 191 power E.S. 4.7mm to try for the split. Usuing the fine focus I dialed in Porrima, suddenly 2 diamond like pinpoint stars appeared in sharp focus with black sky between them. Porrima is cleanly split! This scope doesn't even break a sweat doing it. In fact the space between the pair is large enough that I wanted to see if I could split them at a lower power. I popped in the Meade 8.8mm for 102 power. Again Porrima is split. Razor thin black sky shows between the tiny pinpoint stars.
I head for the Double Double (Epsilon Lyra) with my 14mm at 64 power next. This quadruple system has 2 pairs of stars separated by 2.1 and 2.4 arc seconds respectivley. It is fairly tough to split, but doable for many ameteur scopes. My Meade 10 inch can split them at 139 power. I brought them into focus thinking I would need to go to 102 power to split them. Wrong. They're already split at 64 power. After Porrima the Double Double seems like childs play.
It's going to take me a while to get used to the tiny star images this scope can produce. None of the scopes I have ever owned can match it.
Ten days later I had the CT152 at our astronomy club's dark sky site, Eastman Lake, about a one hour drive north of Fresno. Except for a little sky glow to the south from Fresno the sky is very dark. The Milky Way stretches from horizon to horizon and is a wonderful site. With twilight just about done, I zeroed in on the cresent Moon in the western sky. At 102 power and 191 power features on the Moon's surface are shown in strikingly sharp detail, but chromatic aberration is a factor. The c.a. manifests itself as a very thin blue line on the limb of the Moon. It's only moderately bright and no more than a mild distraction. There was no sign of any c.a. on the Moon's surface features. I was a little worried crater rims might show some c.a., but they didn't. The c.a. really doesn't seem like much of a problem to me when viewing the Moon with this scope. Viewing the bright stars Vega and Altair showed c.a. that was somewhat more prominent than it was on Saturn.
For many years now my main viewing interest has been deep sky objects. In this area the CT152 is outstanding. C.A. ceases to be a factor at about mag. 3.5. At 64 power M-13 is a swarm of tiny glittering stars. At 102 power I have the impression I can see deeper into it's core than my Meade 10 inch can reveal. At 64 and 102 power M-51, The Whirlpool Galaxy, faintly shows its connecting bridge and a hint of spiral structure. M-81 and M-82 are a lovely site with both galaxies easly contained in the 1.3 deg. wide field at 64 power. M-17, The Swan Nebula is bright and contrasty, an amazing view for a 6 inch scope. The Ring Nebula was a delight at 102 power. At this power its small but its donut shape was very obvious even without averted vision. The open cluster M-11, The Wild Duck, was a very nice sight appearing as a spray of tiny stars at 102 power. The last object I viewed that night at Eastman Lake, turned out to be the most impressive of all. The Double Cluster in Perseus. It just fits into the 1.3 deg. field at 64 power. The feeling of diamond like pin point stars floating in the blackness of space was a stunning sight. If you want to impress somebody with a telescope view, just show them the Double Cluster with this scope. It's a guaranteed winner.
Before closing let me clear up how I purchased this scope usuing U.S. dollars. Canadian Telescopes has a working agreement with Woodland Hills Telescopes in southern Calif. Canadian Telescopes set up a deal allowing me to call Woodland Hills and buy the scope usuing my credit card for $938.00 U.S.D. Woodland Hills then sent a payment of $859.00 CDN dollars to Canadian Telescopes. Canadian Telescopes then shipped the scope to me. The scope arrived 7 days after I made that call. It was a little more trouble and expense to buy the scope this way, but it was the only way I could get the scope with the 3 inch focuser, which I really wanted.
I had hoped to include views of Jupiter in this review, but I haven't been able to drag myself out of bed at 3:00 AM to do it. I will try to do an update at a later date.
If you have read this review you have probably guessed I have a very high regard for this telescope. At $938.00 this scope wasn't cheap. But given the fit, finish, quality of construction and razor sharp optics, I believe it is a bargain. Sure, a 6 inch apo will out perform this scope, but at 7 to 10 times the cost! Other than lubricating the rotatable focuser (a 10 minute job for me) I wouldn't ask the manufacturer to change anything. For me this scope is a keeper.
I hope this review has been of some help to you.
P.S. I have no affiliation with any of the companies mentioned in this review.