Review – Explore Scientific 127 ED Air-Spaced Triplet Apochromatic Refractor

Explore Scientific 127 ED

Photo by Brian Hancock of Memphis Astronomical Society

August 2013 — It’s that time of year again for me to start thinking about what I want to purchase for my annual “Astro Splurge”. The previous year, 2012, I acquired a large Explore Scientific AR152 6″ f/6.5 doublet achromatic refractor and a CG-5 mount. You can read all about that here. If you read that article and the following comments, you know I really like that big achromat.

Orion Atlas Pro AZ/EQ

So during my musings on the 2013 “Astro Splurge”, I had completely convinced myself I was going to purchase a new mount for the AR152. The mount I picked out was the newly released Orion Atlas Pro AZ/EQ. The mount sounded great in theory, but after a little more thinking, and being honest with myself, I came to the realization that once the novelty wore off, I probably wouldn’t use that big heavy mount very much. Sometimes, especially on weeknights, I can barely get motivated enough to carry out the CG-5. At this point I decided to go an entirely different route and started looking into 5″ class ED apochromatic refractors.

I kept hearing about how much better the apochromats (apos) perform than their achromat (achro) bretheren (it’s a never ending debate over on the Cloudy Nights refractor forum), so I thought I’d see what all the hub-bub was about first hand. The two main contenders came down to the Sky-Watcher Pro 120 ED and the Explore Scientific 127 ED Triplet (ED127). The Sky-Watcher is a 120mm/4.7″ f/7.5 doublet with one lens element being crown premium Schott Glass and the other lens element being FPL-53 O’hara extra-low dispersion (ED) glass. The Explore Scientific is a 127mm/5″ f/7.5 triplet with the center ED lens element being the slightly less desireable FPL-51 Hoya glass. The Sky-Watcher Pro 120ED is known to be a great performer with wonderful color correction, especially for a doublet, and comes with some nice accessories such as a 2″ diagonal, 9×50 RACI finder, and a metal case. However, I eventually decided on the Explore Scientific scope because it’s a triplet instead of a doublet, it has 7mm more aperture, Explore Scientific has an amazing lifetime warranty and great customer service.

In October I finally ordered the Explorer Scientific ED127 Essential Edition along with a new Celestron AVX mount (the successor to the venerable CG-5). We all know, of course, that a new scope deserves a new mount. Right? The “Essential Edition” of the ES ED127 is a no frills package — it comes with a white aluminum tube with sliding dew shield, cradle with carry handle, Vixen style dovtail bar, dual speed rack and pinion focuser, and two extensions for the focuser tube. It does not come with a finder scope, diagonal, or carry case like the carbon fiber version of the scope.

I received the scope and mount from AgenaAstro just a few days after placing my order. The scope arrived in a single box dropped off at the front door by the brown truck guy. When I first picked up the box I immediately heard something rattling around inside. Not a good sign! Luckily, it only turned out to be one of the thumb screws used to adjust the focuser tension. One thing I noticed immediately when lifting the scope out of its box is how front heavy the scope is compared to a doublet. That extra lens makes a big difference in the weight up front, so care must be taken when lifting the scope to prevent the nose from taking a dive and crashing into something. After unboxing the telescope, the first thing I tried was the focuser, a nice looking rack and pinion dual speed job. The focuser racked out easily enough; however, when I tried to rack it back in, it would hang in spots and the smaller fine focusing knob would spin but wouldn’t move the focuer tube in or out. My AR152 also arrived with a bad focuser, so this made for 2 bad focusers in a row from Explore Scientific! I called up Explore Scientific and explained the issue.  They put me through to Lance who immediately knew what the problem was and walked me through adjusting some set screws on the focuser housing which solved the issue. After the fix, Explore Scientific offered to replace the entire scope if I still wasn’t happy with it. They really stand behind their products.

Overall, the scope seems pretty solid mechanically (once I got the focuser issue worked out). The focuser is a rotatable 2″ dual speed rack and pinion focuser  with 2 thumb screws for controlling the tension and one to lock the focuser in place. There is also a thumb screw to lock and unlock the rotating mechanism. The focuser isn’t great, but it’s not junk either. The scope came with two focuser draw tube extensions to get more in or out focus when needed. I have to have at least one of the draw tube extensions attached while observing or my eyepeices will not come to focus. One of the great things about having the draw tube extenders is that you can remove both of them and have enough in-focus to use a binoviewer.

The ES ED127 also has a sliding dew shield which is nice. It makes the scope much easier to transport and store with the dew shield retracted.

Dew Shield Retracted

127 ED Dew Shield Extended

Dew Shield Extended

Like the AR152, the scope has a nice solid cradle with a carrying handle on top making it really easy to lift the scope for mounting.

The Celestron Advanced VX mount has proven to be a very good match for the ED127 for both visual and planetary imaging. Only one 11 lb. counterweight is required to balance the scope in RA. The mount also carries the big AR152 better than the CG-5 even though the CG-5 is rated at a higher capacity. Everything about the AVX is more solid than the CG-5. A very impressive mount.

I have read a few complaints on the Cloudy Nights board about people receiving their ED127 and discovering an inordinate amount of dust and debris between the lens elements. Luckily I didn’t have that issue with mine. There was barely any dust on or between the lens elements. You can always expect a little dust on the lens with any new refractor, but the ED127 I received was unusually clean.

ED127 Lens Immediately After Unboxing

Optical Performance

Okay — enough of the mechanical stuff. Let’s get to where the rubber meets the road — optical performance!

First I’ll address what’s on everyone’s mind — chromatic aberration (CA).

As a quick review — chromatic abberation is an optical defect caused by different wavelengths of light not coming to focus at the same point. This happens with lenses because different wavelengths of light travel through glass at different speeds. This optical aberration manifests itself as a colorful halo around bright objects as well as reduced contrast caused by light not being concentrated at one focal point. Apochromatic lenses aim to dramatically or entirely eliminate this defect through the use of special extra-low dispersion (ED) glass. More economical apochromatic refracting telescopes such as the ED127 do a very good job elimating CA, but usually aren’t as good as the more premium branded telescopes. And it can vary from sample to sample with the cheaper scopes since the QC on them isn’t near as stringent.

The Explore Scientific ED127, or at least my sample, does indeed show a slight amount of CA on the brightest objects such as Venus, Jupiter, Sirius, and the limb of the Moon. If atmospheric conditions are good, it’s very difficult to detect the CA, but if the conditions are poor or the telescope isn’t thermally stable, it’s quite obvious. With that said, the CA is nothing compared to a standard doublet achromat.

I’m by no means an experienced star tester, but the ED127 star test looked very good. The collimation was spot on and the diffraction rings were, for the most part, the same on both sides of focus. My AR152 shows a fair amount of overcorrection when star tested, but I couldn’t detect much, if any, undercorrection or overcorrection in the ED127. Of course, Explore Scientific supposedly guarantees that all of their apochromatic refractors test at .25PV or better. I’m sure a more experienced star tester could find something I’m missing, but overall, the star test looks really good. A lot of other owners of the ES ED127 have reported similar results which tells me these scopes have fairly consistent optics.

Moon and Planets

I mainly got this telescope to use for lunar and planetary observation and imaging and it does not disappoint. The scope turned out to be a good deep sky performer too, but more on that later. The clarity the scope delivers is amazing! All it took was pointing it at the Moon once to make me a believer. Amazing contrast and no more purple crater shadows! Even at 1″ less aperture, the ED127 seems to resolve small details better than my 6″ achromat. Compared to the 6″ achro, finding perfect focus is much easier with the ED127 — sometimes I have to fiddle with the focuser a bit on the big achro to find perfect focus, but the ED127 snaps right into focus and there is no doubt when you are at best focus.

I’m still a newbie when it comes to planetary imaging, but I’ve managed to get some pretty good results (for a newbie) with the ED127 and a Celestron NexImage 5 camera. Pictures speak louder than words, so here’s a few of the images I’ve taken with the ED127.

ES 127 ED Jupiter

Jupiter at f/15

ES 127 ED Jupiter Double Shadow Transit

Jupiter Double Shadow Transit at f/15

ES 127 ED Jupiter

Jupiter at f/15

ES 127 ED Moon

Moon at f/7.5 2×2 binning

ES 127 ED Moon

Moon f/7.5 2×2 binning

ES 127 ED Moon Plato Crater

Theophilus, Cyrillus, and Catharina f/7.5

ES 127 ED Moon Plato Crater

Close Up of Plato Crater and Alpine Valley

ES 127 ED Saturn

Saturn at F/15

Deep Sky

A 5″ scope is typically not the scope you would turn to for deep sky observing; however, the ES ED127 has proven to be no slouch for a 5″ scope. I will throw out one caveat here — no matter how good the optics, this is still just a 5″ scope. If you like to chase down the faint fuzzies, you’d be better served by a larger scope — I would say this scope is on par with a 6″ reflecting type scope when it comes to the fuzzies.

Last autumn I set up the ED127 side by side with the AR152 for a deep sky shoot out and the results were not what I expected. I expected the big 6″ achro to provicde slightly better views on every object, but the reverse turned out to be true. Maybe one of these days I’ll post a detailed object by object recap of the shoot out, but that’s for another day.

ES 127 ED AR152

ED127 (foreground) and AR152 set up for a deep sky shoot out (Don’t worry, those blinds were closed before the shoot out.)

Like I said, the ED127 proved to be a little bit better than the AR152 on every object, except for diffuse objects which were about equal. Of particular note are objects that are stellar in nature such as open and globular star clusters. Stars focused tighter and had a lot more “punch” than in the achromat. A fringe killer filter does help tighten things up a bit in the achro, but it still doesn’t match the clarity of the apo. I feel like the apo is more capable of reaching its theoretical limiting magnitude than the big achro. I was quite surprised to see M13, the Great Globular Cluster in Hercules, slightly better resolved in the ED127. Common wisdom dictates that aperture always wins on globular star clusters.

I also compared a couple of galaxies, M31, The Andromeda Galaxy, and M33, The Triangulum Galaxy. I really didn’t see much difference between the apo and the achro when observing galaxies. M33 seemed a little bit easier to pick out in the apo because of the improved contrast, but the difference was very slight. M110, a darf satellite galaxy of Andromeda, was slightly brighter in the AR152 than the ED127. M110 fit in the same field of view as M31, in both scopes using a 38mm Q70 eyepiece.

Conclusion

I must say that I am very happy with the Explore Scientific ED127 and there is indeed some truth to the hype around ED and apochromatic refractors. Does the difference in performance justify the huge increase in price from an achro? It’s really hard to say, but for me, I would say yes. I think I’ve discovered my personal perfect telescope in the 5″ apo. For me it’s a perfect balance of portability, ease of maintenance, and performance. Have I stopped using my 6″ achromat? Nope. I find the AR152 to be the perfect outreach scope. I’ve also been using the AR152 during the spring to avoid pollen on the lens of the more expensive apo. Also, if you check out my review of the AR152, I’ve taken some pretty decent images with it. The image of Tycho in the blog header was taken with the AR152. Bottom line, if you don’t want to drop the coin for one of the premium apo refractors, but you want a little taste of that apo performance, the budget ED apos like the Explore Scientific ED127 or the Sky-watcher Pro 120 ED are a great choice. Clear skies!

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Book Review – The Greatest Comets in History: Broom Stars and Celestial Scimitars

With all of the talk about comets this year, I decided to pick up the book The Greatest Comets in History: Broom Stars and Celestial Scimitars by David Seargent – part of Springer Publishing’s Astronomers’ Universe series. The Greatest Comets in History chronicles the greatest of the great comets all the way back to ancient times starting with the great comet of 372 B.C., Aristotle’s comet. Before getting into specific comets, the book explains the method used for classifying comets as being one of the “greatest of the great” and then provides an introductory chapter about the nature of comets. The book also contains special chapters with in-depth coverage of Halley’s Comet, The Kreutz Sungrazers, and daylight comets. The book was a good read overall; however, the book can become a bit monotonous at times since some comets contain only easily forgettable technical data such as estimates of magnitude, tail length, and perihelion date and distance.

One of the things I really enjoyed about reading The Greatest Comets in History was how it illustrated the pace at which technology has advanced. Each chapter arranges comets in chronological order discussing the observations of each one. There are periods of hundreds or thousands of years where the observational techniques and general knowledge about comets barely increased at all. In contrast, we’ve progressed from photographing comets to intercepting them with space probes in less than 100 years! It was also interesting to note that the ancient civilizations of eastern Asia such as China and Korea recorded most of the earliest comet observations.

Chapter 2 is an in-depth look at Halley’s Comet and was my favorite chapter of the book. No other comet in history has had such a dramatic impact on civilization as Halley’s Comet. The chapter starts out discussing Halley’s Comet in general and then recounts the story of Edmond Halley’s calculation of the comet’s orbit and prediction of its return. The chapter then goes on to show how comet observations all the way back to 87 B.C. can be correlated to Halley’s Comet. A very fun read.

Chapters 3 – 5 chronologically cover the greatest comets from 372 B.C. all the way up to Comet C/2006 P1 (McNaught). Each chapter covers a specific date range with Chapter 3 covering 372 B.C. – A.D. 905, Chapter 4 covering 1000 – 1800, and Chapter 5 covering 1800 – Present (2007). With a few notable exceptions, reading about the comets up until the 18th century was kind of a snooze fest due to the lack of recorded information. Magnitude and tail length estimates and perihelion dates/distances for comet after comet quickly become a jumbled mess of facts and figures with nothing exceptional to anchor them in memory. Progressing through the book, and therefore time, we start to get much more interesting information about how each comet affected our scientific understanding as well as its impact on the general population. I especially enjoyed reading about the more recent comets starting with Comet C/1975 V1 (West). The author himself has observed most of these later comets.

The Greatest Comets in History is a fun and interesting read if comets interest you. It has a lot of good information about comets and the history of comet observation. Reading through the observational data for each comet can get a little monotonous at times, but overall the book is very engaging and I think the avid amateur or armchair astronomer will really enjoy reading it. The book certainly enhanced my understanding and appreciation of comets.

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Review – Explore Scientific AR152 Achromatic Refractor

I have wanted to own a large refractor for a long time, but I just never could justify purchasing one. I certainly can’t fit a large apo into my budget and reflectors seem to be an overall better value.  However, I eventually decided to do some research on 6″ achromats and took the plunge with an Explore Scientific AR152, a 6″ (152mm) f/6.5 achromatic refractor. The AR152 has received several good reviews since it came out, along with all of Explore Scientific’s products, and is offered at the unbelievable price of $750. I also considered purchasing the Celestron C6R or the Celestron Omni XLT 150R.  However, I was afraid the C6R, with its longer OTA at f/8,  would be too unwieldy for the CG-5 I planned to mount it on and the Omni XLT 150R was a little faster than I wanted at f/5. Also, the AR152 purportedly had a better build quality and better accessories than the Celestron offerings. I have now owned the Explore Scientific AR152 for 5 months, which is plenty of time to have experienced all of the good and bad things about this telescope. Let’s start from the beginning:

I ordered my AR152 from Astronomics, http://www.astronomics.com, in late September 2012 for $750. My order also included a Celestron CG-5 ASGT mount for the AR152 which was an additional $700. As usual, Astronomics was very quick in shipping my order.  I placed my order on Wednesday night and had the scope and mount by Saturday.

The telescope arrived in a single box which included the OTA, cradle with handle, dovetail mounting bar, 2″ dielectric diagonal, and an 8×50 straight through finder. There were no instructions of any kind included with the scope. All of the components have a solid high quality feel that exceeded my expectations given that this is a budget oriented achromat. I expected a few more cut corners for a large refractor at this price point.

Unboxed AR152

Instead of using the 8×50 straight through finder that came with the AR152 I decided to install a GSO 8×50 right angle correct image finder. I had to remove my GSO right angle finder from its stock bracket and install it in the finder rings that came with the AR152 since the GSO finder bracket has a Vixen style dovetail which isn’t compatible with the AR152. The AR152 finder rings have a spring loaded screw on the top of each ring and two nylon screws for adjusting the alignment of the finder. Once aligned, the finder holds alignment pretty well between observing sessions.

GSO 8×50 RACI in Stock AR152 Finder Rings

The AR152 is a large scope, but it wasn’t the beast I expected it to be.  I find the OTA to be quite easy to manage thanks to the included handle attached to the scope’s cradle — a very nice touch. The scope balances close to center on the CG-5 in declination, but one thing became clear very quickly — I should have ordered an extra 11lb. counterweight for the CG-5.  The CG-5 comes with one 11lb. counterweight, which isn’t near enough to balance the 23.5lb. AR152. Luckily, my CG-4 mount had a 7lb. counterweight that fit the CG-5 and was just enough to balance the AR152 in RA. I promptly ordered an extra 11lb. counterweight for the CG-5.  In practice the CG-5 has proven to easily handle the AR152 for visual use up to magnifications of about 250x with the tripod legs partially extended.

AR152 on CG-5 (left) – Celestron Omni XLT 102 on CG-4 (right)

 

AR152 (foreground) ES 127 ED Apo (background)

 

The front lens of the AR152 is gorgeous. The lens is a deep green color and has 3 sets of 2 push-pull type collimation screws for adjusting the collimation. The inside of the tube is nicely baffled and painted a very flat black and produces no reflection when shining a light down the tube.

AR152 Objective Lens (Black background is the inside of the dew shield.)

 

AR152 lens (left) – Omni XLT 102 lens (right)

 

The AR152 sports a large dew shield that is held on by friction provided by three strips of felt attached to the lens cell. To remove the dew shield you just simply pull it forward. The dew shield is also quite effective — I’ve never had the front lens dew up even in farily heavy dewing conditions.

The focuser on the AR152  is a 10:1 dual speed focuser with a  thumb screw for locking the focus and another thumb screw to adjust the tension. The focuser on the AR152 I received was pretty terrible. It would grab/jerk at certain points along the focuser’s travel.  After racking the focuser in and out a half dozen times hoping  it would smooth out, 2 lines/scratches began to appear on the focuser tube where the paint was being rubbed off. I called Explore Scientific and they promptly sent me a replacement focuser. The new focuser arrived about 3 days later with a prepaid shipping label for sending the original focuser back. The new focuser was very easy to install (there are only 2 set screws holding the focuser to the OTA) and was very smooth with no problems. The focuser holds the diagonal and all of my heavier 2″ eyepieces without any slippage near zenith.

Optical Performance

Collimation

My AR152 either arrived very slightly out of collimation or installing the new focuser caused a slight misalignment. I used a cheshire collimation eyepiece designed for collimating refractors to tweak the collimation which only took about 10 minutes. I just tweaked the push pull collimation screws one set at a time until I discovered the one that needed adjustment. The adjustment needed was very slight.

Chromatic Aberration

Chromatic Aberration (CA), the inability to bring all wavelengths of light to focus at the same point, is inherent in all achromatic refractors, especially ones with fast focal ratios like the f/6.5 AR152. This optical aberration manifests itself as a violet halo around the brightest objects and also causes a slight loss of contrast due to unfocused wavelengths of light. If you tend to be bothered by CA, or if you’ve never owned an achromat before, this is not the telescope for you. There is plenty of CA on objects of 2nd magnitude and brighter and it gets worse on nights with poor atmospheric conditions.  On nights of poor seeing, I’ve seen CA on objects as dim as 3.5 magnitude. On nights of good seeing, the CA is actually pretty well controlled and not all that distracting. The seeing conditions on my first night out with the AR152 were pretty bad. While trying to split E. Lyra (the double double)  I was able to get a dirty split; however, all 4 components exhibited a greenish color. A few nights later I tried E. Lyra again with better conditions and got a very clean split with all 4 components showing a normal white color. The only object that the CA has really bothered me on is the double star Alberio. At magnifications of less than 50x the blue and gold color of the stars is visible, but anything over that causes the striking colors to be lost to CA.

Chromatic Aberration on the Moon. (This is a low quality image taken by holding a cell phone camera to the eyepiece. Eyepiece is an 8.8mm Meade 5000 UWA giving 112x.)

 

I’ve tried using a 2″ Baader Semi-Apo filter to help reduce some of the chromatic aberration, but found that I actually preferred the unfiltered view. For me the filter dims the view too much and reduces contrast. Other reports have indicated that the Baader semi-apo increases contrast, but that was not my experience.

More recently I acquired  a 2″ Baader Fringe Killer filter which has a higher light throughput than the semi-apo filter. I’ve found the Fringe Killer to be a much better filter overall than the semi-apo. The Fringe Killer reduces some of the violet fringing around bright objects and increases contrast without dimming the view like the semi-apo filter.  The Fringe Killer does impart a slight yellowish tint to some objects, but I find this a lot less objectionable than the dimmer view provided by the semi-apo filter. I plan on leaving the Fringe Killer in the diagonal pretty much all the time.

Moon and Planets

To the apo only crowd, viewing the Moon and planets with a large fast achro is like committing an unpardonable sin. These folks will have you believing that an achromat will only show planets as a  fuzzy blob of false color and it might even turn your hair and face permanently purple if you look at Jupiter through one. However, even with the CA, I find that the AR152 gives nice sharp views of the Moon and planets.  The planetary views are definitely not as nice as you would get with an apo, but they’re not darned bad either. With that said, if the Moon and planets are your primary interest and you want every last possible detail, then you should be looking at other telescopes.  But don’t be fooled into thinking that an achromat cannot give a decent view of these objects with plenty of high contrast detail.

On nights of good seeing I’ve had very good views of Jupiter up to 300x and regularly use a 4.5mm Meade 5000 HD-60 on the giant planet giving 220x.  The GRS is an easy target for the AR152 as are larger barges and festoons.  The CA on Jupiter is obviously about as bad as it gets.  The planet exhibits a bluish halo around it that extends out from the planet about 1/2 the planet’s radius. The belts and zones on the planet also appear more of a grayish color instead of their natural reddish brown.  However, the belts and features on the planet are very crisp and sharp with loads of detail during moments of good seeing.

Open Clusters

Open clusters are definitely the AR152’s strong point. I would even go as far as to say that the AR152 has given me a new appreciation of these celestial wonders.

The double cluster in Perseus is especially beautiful in the AR152.  Using a 38mm Orion Q70 eyepiece both clusters are framed beautifully and show sharp pinpoint stars from field stop to field stop.  At a club observing event back in November 2012 the owner of a Meade 12″ SCT even commented that the double cluster looked much better in the AR152 than in his 12″ SCT.

The Wild Ducks cluster (M11), M46, M35, and M7 are all wonders to behold in the AR152. M46 looks like fine grains of sand scattered across a velvety black background with the small planetary nebula NGC 2438 easily visible; even from my light polluted backyard.

The bright stars in M45, the Pleiades, do show a slight amount of CA in the AR152, but it’s not objectionable.

Globular Clusters

The AR152 provides fairly good views of globular clusters. Six inches of aperture seems to be kind of the magic aperture where globular clusters really start to resolve.

M13 and M15 show many resolved stars in the AR152, whereas my 4″ achro shows these clusters as fuzzy patches with a few stars here and there.  My 10″ Dob; however, shows many more stars than the AR152. The dark propeller feature in M13 is detectable in the AR152 at around 140x, but it takes some work — this is normally an easy feature in my 10″ Dob.

Nebulae

M42 is spectacular in the AR152; as it is in just about any telescope. Six inches of clear aperture is enough to start showing actual structure in the nebula.  The E and F stars in the trapezium are fairly easy at around 90x on nights of good seeing.  Using an Orion 38mm Q70 or an ES 82 degree 24mm eyepiece gives a very beautiful high contrast low power view of the nebula.  The view has an amazing 3-D like effect.

M17, the Swan Nebula, is also a nice target in the AR152.  The “number 2” shape of the nebula is very prominent and stands out well in the AR152.

From a dark site NGC 2024, the Flame nebula, is an easy target for this scope showing the prominent dark lanes often referred to as the “tank tracks”.

M57, the Ring Nebula, easily shows its oblong ring shape with a few glimpses of structure visible. It doesn’t have quite the same “pop” as it does in my 10″ Dob, but it’s still nice.

Galaxies

To be honest I’m not that much of a galaxy hunter. If I plan on hunting down dim galaxies I typically pull out my 10″ Dob.  The only galaxies that I’ve viewed with the AR152 are M31 along with its companion galaxies and M33.  M31 honestly doesn’t look much different than it does in my 10″ Dob from my backyard.  M32 and M110 are both visible in the same field of view as M31 and nicely framed using a 38mm Q70 eyepiece. M33 was just a smudge of light and would have been difficult to detect had I not know what I was looking for.  One of the spiral arms of M33 is discernible from my backyard using my 10″ dob, but no such structure is visible with the AR152.

Update: 4/01/2013

I recently took a look at the M81/M82 galaxy pair with the AR152 from my backyard and must say the scope performed very well on these bright galaxies. Both galaxies fit nicely in the field of view of an ES 24mm 82 degree eyepiece.  The oblong round shape of M81 and the ragged cigar shape of  M82 were readily apparent. Increasing the magnification doesn’t really reveal much more detail on M81, but on M82 the ragged edges of the galaxy show some interesting detail. I was able to increase the magnification to 147x using an ES 6.7mm 82 degree eyepiece and still have plenty of light.

Conclusion

If you are looking for a well made large refractor but don’t want to take out a second mortgage on your house, then the AR152 may be the telescope for you. It’s certainly not a premium grade refractor, but at its price point I don’t think you’ll find a better built 6″ refractor. It really is an amazing package considering what you get for your money. For $750 you get a large refractor that is ready to go right out of the box without a lot of upgrades such as a better diagonal and focuser. The only component I felt the need to upgrade was the finder, but that’s personal preference — I’m not a fan of straight through finders.

With 6″ of clear aperture the AR152 is an excellent deep sky performer, especially on open clusters, and performs pretty well on planets too if CA doesn’t bother you too much. If CA is an issue for you, then you should steer well away from this telescope.

Overall I’m very happy with the AR152 — there’s just something magical about a large refractor.

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