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Explore Scientific AR 102

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Explore Scientific AR 102

By Paul Temple

As a guy with a robotic telescope that primarily does variable star photometry I actually miss looking through a telescope sometimes! Staring at a monitor from your warm house is a plus but as I get older I long to grab a scope let the photons roll into the Mark 1 eyeball! So a couple of months ago I began to think about a “grab and go” scope.

In my storage area was a 8” F/5 Astrograph that I no longer used. So I decided to sell it and use the proceeds to buy the “grab and go” scope. Luckily, I had a friend looking for this kind of scope and sold it to him. There is also a Celestron GT mount in the storage area that I have never used that would probably work as a mount for a light refractor.  The remaining question was what to buy?

As a life-long astronomy buff I have a lot of telescopes. My first real scope was a 60mm Sears refractor. I used this for years until it got broken while I was cleaning gunk off of the lens. In my current “stable” of scopes is “ The Bargain Bucket” a 8” homemade F/5 Dobsonian, “Little Eye” a Meade ETX 90mm, “The Beast” a Celestron 6” F/8 refractor, Temple 28 a Celestron 11” CPC roboscope and a Meade LX200 8” roboscope. One of my favorite scopes  is “ Dimestore,” my Meade 60mm, “junk” telescope. I got tired of listening to APO and ED Refractor users complaining about the venerable 60mm scopes so I bought one on EBay for 21 dollars delivered. I used it in it’s stock condition to view Mars at the last good opposition. I did a color sketch with watercolor pencils that got used in a montage of images from the Mars opposition and made one of the “image of the day” websites! After doing the sketch, I upgraded the focuser and use it for a “grab and go” scope. However, there’s just not enough aperture and though the Alt/Az mount is Ok, it could be better!

With $300 (US) to spend, my first thought was to buy the 72 mm ED from Astro Tech. All of the products that I have ever bought from them, including the 8” F/4 astrograph that was sold, have been great. The reviews on that scope were terrific, however, it just seemed to be a little on the small side. Though 72mm is way more scope than the 60 mm, I just wasn’t sure I wanted one that small, especially since it was over the budget by $75. Unfortunately, larger ED’s or APO’s were out of my price range. Just about everything else I looked at had some major flaw (bad focusers primarily) or was out of my price range. After perusing Astromart and seeing only one scope that I was interested in and it was over $450, I decided to check out slightly larger achromats. Better “bang” for the buck!

As mentioned earlier, “The Beast” is my 6” achromatic F/8 refractor that sits on a Sirius mount with a extension pier. Since it is over 100 pounds set up it is definitely not a “grab and go” scope! The optics are excellent though and the Chromatic Aberration is surprisingly well controlled for a scope like this. Plus, the Celestron Minus V filter (Same as the Baader Fringe Killer) does a good job on the CA and doesn’t change the color of the view much. With the experience of using “The Beast” I felt like a short Achromat would be a good telescope for me and even give me a bit more aperture for the money.

I looked at the High Point Scientific website to check out the AR series optical tube assembly from Explore Optics. These are nice looking scopes that come in 102mm, 127mm and 152mm diameter lenses and F/6.5 focal ratio. By the way I am not affiliated with HighPoint Scientific or Explore Scientific in any way! However,  Highpoint has been extremely helpful in all my dealings with them. The 127 caught my attention first but the price was over my budget. Plus the weight and size seemed to be going the wrong way for a “grab and go” scope. So I began to seriously consider the AR 102.

Email was sent to Highpoint and they responded quickly with links to reviews. Most of the reviews praised the build, optical quality and size of the scope. There was not a negative review that I could find on the internet or in their links. That is very unusual for just about any product. The only negative was the CA inherent in the short focal ratio but every review commented that it was not as bad as expected, nor did it hinder the quality of the views.  So I pulled the trigger and ordered the scope. Did I mention that it went on sale a day or so before I ordered it? Did I also mention that I got an open box unit for a 30 dollar discount under the already lowered price of $299 US.  It also came with a 25mm, 70 degree Bresser 2” eyepiece that wasn’t even mentioned in the ad!

Included in the purchase price is a 2” dielectric diagonal, finder scope and two speed focuser. After using “The Beast” for a while it became obvious that it needed a $200 dollar focuser upgrade just to make it usable for CCD imaging. Visual focusing was pretty rough as well. So when you add the $100 eyepiece, the $100 dollar 2” diagonal and a $200 dollar, 2 speed focuser with the AR 102, the telescope ended up being free! Over all the fit and finish is outstanding. Light weight, but well built. The focuser is very smooth and sensitive. This is important in short focal length telescopes since focusing is much harder to get right with the shorter focal length. The rings and dovetail are very sturdy and supply a handle to carry the scope with. The interior of the rings are covered with felt to keep the tube from being scratched. Clamps help to make sure the scope is oriented the way you want it.

The scope comes packaged in a double box with plenty of internal support. It arrived in good condition and quite fast. I also purchased a 5x Barlow lens and it was packed in a box and placed with the other accessories. Assembly  primarily was taking off the rings and stripping off the protective foam, then putting it back together. At 11 pounds it is easy to transport and as was mentioned earlier, the built in handle really helps to make it an easy carry.

I mounted the optical tube assembly on my old Celestron GT mount. This set up has flimsy tripod legs and lots of backlash but it is light and easy to use. With a 4,000 object database it will take you to most of the brighter optics a 4” scope can see. It also has a Baader dovetail clamp attached. This means anything with a vixen style dovetail can be mounted on it. Even with all the issues, it does track well and puts most objects near the field of view. Sometimes you have to use the finder but it is usually right on the edge of view in the eyepiece.

Now what about the optics? All of these fine features are of no avail if the optics are substandard. It has been a difficult task to test the optics this winter due to the bad weather. We live between two 10,000’ plus mountain ranges so the conditions are usually less than optimal, but this year has really been bad for astronomy. With a quick look at the ¾ moon in twilight (clouded up at dark!) I was impressed. There was a bit of purple fringing around the limb of the moon but not really any worse than “The Beast.” I used the 25mm, 70 degree, 2” eyepiece first just to check it out. This only gives you 26x but man what a field of view! The view was crisp and the face of the moon was very contrasty and showed rich detail. As expected, focusing was a bit more demanding but the 2 speed focuser made that chore much easier. The next time I got out the scope, I looked at Capella and did some basic star tests. At high power (165x) the diffraction rings looked good on both sides of focus. This test was a bit tricky since the conditions were so bad. There were high clouds and even stars overhead were twinkling. So the next time it was out, there were high cirrus clouds but a much steadier atmosphere. The moon was full so any CA would really show up. Using a 8.8 mm Meade 82 degree eyepiece and the Celestron Minus V filter there was only a hint of CA around the moon. When I switched to the 25mm, 2” eyepiece there was some purple fringing around the edge but I did not see it as being objectionable. It definitely did not affect the detail visible on the face. Before the sky was completely covered with a layer of thicker clouds I slewed to M 42 in Orion. Wow, even through clouds I could see the Trapezium clearly with the 8.8 mm and the 25 mm. It was much harder to differentiate the 4 stars at 26x with (25 mm) power but very easy at 75 (8.8 mm) and even easier at 188x (used at 2.5x Barlow with the 8.8 mm). When you add magnification, the views look very much like views with the 6” F/8, just a bit dimmer. So even with the short focal length, the scope takes magnification well and focusing is quite easy due to the 2 speed focuser. This was a concern with me since I did want to look at the planets from time to time. This scope is not maximized for planetary observing but still does it well.

The weak link to this set up is the Celestron GT mount, not the AR 102! Even with foam in the tripod legs, tightened up bolts, wooden blocks to force the legs out and bungie cords around the bottom of the tripod to help with vibrations it still jiggles a lot. Oh don’t forget the 11 pounds weight on the tripod tray. Even with all this it still has about a 5 second settle time and shakes with any breeze or touch. This scope on the Sirius mount would be amazing but again not very “grab and go.” So in the future will be a purchase of a manual Alt/Az mount. Still as jiggly as the mount is, it is still portable and gives acceptable views.

My overall impression is outstanding! It is a great deal for the money, even at the non-sale price of $399. At the current sale price of $299 it is almost a steal! The optics are very good, the fit and finish are outstanding and it is light and portable.  Overall, it is a real bargain. My only complaint is very minor. All the screws and fittings on this scope are metal except for 6 screws on the finder scope. Four out of the six screws on the finder rings are plastic and the two screws that hold the finder assembly on the optical tube are also plastic. It would seem to me that the dollar or so that is saved on the price of the screws isn’t worth it when compared to the total price and quality. However, they do work and hold the finder quite steady regardless of the nature of the screws, so I guess it is not really all that important. You could always replace them yourself if it bothers you that much.

Overall, I would highly recommend this scope as a low cost alternative to a more expensive ED or APO scope.  I can live with a bit of purple in an image as long as the image itself is still clear and color free. This the AR 102 admirably does!

Telescope Series Explore AR Air-Spaced Doublet
Telescope Optical Design Refractor
Refractor Design Achromat
Number of Refractor Elements 2
Telescope Aperture 4"
Telescope Focal Ratio f/6.5
Telescope Focal Length (mm) 663
Optical Coatings Explore EMD
Limiting Stellar Magnitude 12.5
Diagonal Included? Yes - 2" Star Diagonal
Telescope Eyepiece(s) Included? No, Sold Separately
Finder Included? Yes - 8 x 50 Finder Included
Focuser Style Crayford/Crayford Style
Focuser Size 2"
Focuser Speed Dual Speed
Telescope Mount Type No Mount - OTA Only
Telescope OTA Diameter (in.) 3.96 (100.7 mm)
Telescope OTA Length (in.) 25.5
Telescope OTA Weight (lb.) 11.3

  • CollinofAlabama, ArizonaScott, Talstarone and 20 others like this


Thank you for the review!

Since this was written I have done a couple of other things with the scope. The first change was to drill and tap the mounting plate for the Nextstar GT so it would fit on a Sirius Tripod. This has made this scope much more usable. These inch and a half tubular legs really make a difference in the steadiness of the setup. It still needs some work to eliminate most of the vibrations but a tap test that settles down in 3 seconds is usable. 


I also mounted the scope on my Sirius mount (This setup uses the Atlas Tripod with the two inch tubular legs). Wow, what an improvement. Accurate slews and rock steady views, even with a five mile per hour wind. I attached a flip viewer and ZWO 120MC (color) camera to the scope. With this setup I got a number of great images of M 42, Pleiades and Jupiter. The seeing was horrible when Jupiter was imaged! It was 25 degrees with a 5-8 mph wind, with lots of fireplaces going in the neighborhood. Jupiter was jumping all about in the scope due to the unsettled air. I was still able to image the two major bands on Jupiter.


After this further testing, the overall quality of the scope has become apparent. I plan on doing more planetary imaging in the future but primarily with "The Beast" and not the AR 102. However, it is good to know that you can get good results with this scope as an imaging scope. No, when the weather warms a bit I am really looking forward to just setting this scope up and looking at stuff!

Great article. And it is great to hear one does not have to spend a fortune to have fun at astronomy. A lesson for all of us. It is easy to become a APO snob and this shows that even a less expensive scope can work well.

    • Uldahl likes this

Very nice review Paul, the size of this scope is a A+ for grab n go, I have been looking real close at this scope and its larger brother the 127 but then were dealing with a 17-18 pound scope again and longer tube so the 11 pound AR102 is just the right size for an old CG5 with SS tripod. Your in depth observation of the CA the scope has also seems right on the money, 100MM scope F6.5 places it right in a good range with having tolerable CA, places it in around the same area as the 120XLT celestrons achro at F8.3. Good Job!


    • CollinofAlabama likes this

If I hadn't bought the Astro Tech AT 72 last year, this scope would be on my doorstep tomorrow. And at the 300 sale price, I can't see how you could go wrong.

Agree completely about just how great a deal this scope is.  Own it and love it.  About as close to the nonexistent "do all" grab'n go scope that I've ever found.

Why does ES put those comically large dew shields on their scopes?  I have the 80mm triplet and its a good scope, optically.  But it looks weird with that huge diameter dew shield.  Just my quibble for the day :)

    • Jon Isaacs, Curt B, Censustaker and 1 other like this
Hi Paul, I e mailed ES and they said that the 25mm 2" ep was part of a deal they had back in the fall so it looks like you get just the diagonal but hey that allot of scope for not allot of bucks. I have some HR stuff for sale and once sold I think I'll pick one up, have a C6 which I use for planets and stuff but would like to get a short FL frac for WF stuff and the next thing is one of those ZWO 120MC or the AstroVideo DSO, haven't decided but between the two scopes I will cover allot for a small investment. Sound like your having a blast.

Hello Paul. Thank you very much for the review.


I am looking for a, let say that, general purpose telescope on the internet and I saw your review about Explore Scientific AR 102.


I am a amateur photographer. I love astrophotography but I had no chance up to now to allocate the required time for my hobby because of my regular job. Now I want to do it. For this reason I have began to investigate possible telescopes I can buy.


My question is that : Is this cope will be a good choice for a starter? and Is this cope will be a good choice when I grow up within the time I develop my hobby?


Thank you very much for your comments.    



    • Jon Isaacs likes this

If ones goal is imaging then this scope will work' but for a newbie 80mm scopes that are faster like f5 are much better to start with. Now if visual is important also then this scope could serve both goals. Just remember the faster a scope is the quicker it takes to capture a good image. And the smaller a scope is the less important the mount is.  80mm are favorite for imagers. Their short' weight is light. Longer scopes are more prone to wind and vibration. Just some thoughts from someone who has been down this road.

    • dervish and richardsutor like this

After comparing the RFT views between my William Optics 102GT and the AR102 I really didn't see much of a difference. Since I already have a 90mm F-15.5 achro for planetary I sold the APO.

    • WMV likes this

If ones goal is imaging then this scope will work' but for a newbie 80mm scopes that are faster like f5 are much better to start with. Now if visual is important also then this scope could serve both goals. Just remember the faster a scope is the quicker it takes to capture a good image. And the smaller a scope is the less important the mount is.  80mm are favorite for imagers. Their short' weight is light. Longer scopes are more prone to wind and vibration. Just some thoughts from someone who has been down this road.

Hello starbob1, thank you very much for the reply. In my country I can find Celestron brand scopes. Could you please advise me some models? Which models of Celestron convey the facilities you have described? 


Thank you. 

    • Far-Out likes this

After comparing the RFT views between my William Optics 102GT and the AR102 I really didn't see much of a difference. Since I already have a 90mm F-15.5 achro for planetary I sold the APO.

My opinion is, good move.  My AR is nicest, most user friendly scope I've had in many years.  On my lighter/mid weight GOTO it does about everything visual I want more than well enough.  I am in my 60s with arthritis problems too so it just fits the bill, in terms of size, weight, and manageability, and especially at $299 ready to use.  And actual use is thoroughly enjoyableenjoyable, and I imagine would be for most anyone.


    • richardsutor likes this
Feb 12 2016 10:57 AM

There never seem to be any negative reviews on this site.

    • M57Guy likes this


Unless you find someone faulting a shipping damaged, or mishandled AR102 you're not likely to find a bad review.  Some simple arithmetic may help explain: $299 4" achromat, ready to use/complete; take away included 99% 2" diagonal ($99); take away dual speed focuser ($145); take away 8x50 finder scope and bracket ($49) for a total of $293 value. That means you get what's left,  a very nice OTA with excellent f6.5 collimatable optics, very nice hinged and knobbed rings set, dovetail bar with adjustable tilt axis, carry handle mounted to the rings for...now wait for it...$6.  And really, all of this comes pretty well put together already!  I think I was trolled here, but anyway not much to knock about this lil achro.


    • Mister T., Jim4321, Juan Rayo and 1 other like this

Well I must confess I got one of the AR 102 for Christmas .At first I thought another cheap scope, but after a night under the stars I hand to resend my first thoughts, It offered the best of everything you would look for in a scope. I must say its a great telescope . If your looking for grab and go this is well worth the money.

    • Mister T. likes this
Feb 13 2016 08:58 AM

Very nice review thank you !

WMV, Wayne, I am with you, even if you don't like the finder, sell it off for $40, already have a good diagonal, there is another $80 on the used market and you end up with a great little 4" achro that is F6.5, has about the same color correction as a 5" F9 but a hellovalot more portable ota which doesn't require a big mount.
Many years ago (in the nineties)when I got back into the hobby after my youth I went from a 4" C102HD to a Photon 127 F9 achro, now the photon scopes mechanics was a real PITA but the 5" lens was pretty good, yes some CA but it wasn't washing out the bright objects like the moon, Jupiter and Saturn, it just had some fine blueish around bright objects. For whatI would call a decent achro optics. Many in the refractor forum attest to the old meade AR5's 127mm F9 achro's as being very good optics with not the purple haze bothering the views so if this scope with a 102mm lens F6.5 optics has about the same CA as those old scopes you will be surprise. It not a 4" APO but for a scope that gives 90% of the views and cools down allot faster for the low price of admission its a no brainer. Just look how many guys in the refractor forum own this scope and they are very seasoned observers that really like it, use it more than there premium optics, that speaks volume.

BTW there are good reviews here on CN but when someone gets a lemon you also read about that and it must be a real PITA when manufacturers get a bad review here cause its not like Sky and Telescope were they don't want to reviews something bad when a company spends thousands a month in advertising in there magazine, you never see a bad review IN S&T today, years ago back in the nineties you did but not now. The old CN reviews you don't see as much, I feel many don't have the time so you have toady review articles like from many members which vary from all kinds of astronomy gear instead of one guy, I think its better than if the same ole guy does the same ole review. That gets long in the tooth after a while and now you have fresh new faces with some very good angles on what they are reviewing, its just great reading and again thanks to Paul for taking the time on a very good review covering many aspects of the scope without lots of fill.
    • MarkMittlesteadt and WMV like this

A lot of talk about this scope around here.

I don't mind the dew shield.

Love mine but thinking about a right angle finder though.

    • Mister T. and WMV like this

Jim, exactly!  Tony, RA finder was a must for my old inflexible neck although the straight thru original is well built.  Mines the Antares with the adjustable diopter eyepiece, very clear, bright and sharp.

    • Mister T. likes this
Feb 13 2016 02:38 PM

I had bought this scope when it was $399 or 499 I don't remember but its an excellent scope and manages imaging well too. Very good optics. At even $400 its a steal.

    • Mister T. likes this


Thanks for weighting the article, I very much enjoyed reading it.


I purchased the AR102 bundled with a Twilight 1 alt-azm mount almost 2 years ago for $600 and change.  It has been an awesome grab and go scope.  The CA or false color has not been at all objectionable and only really apparent when viewing very bright objects like the Moon, Jupiter or Sirius.  It's almost as if there is an minor electro-luminescent halo.  The scope delivers very crisp view and as others have said, the build quality is great.


I only have 2 minor complaints and they are not even with the scope but rather the stock finder.  The finder stock is not tall enough for my tastes, you have to contort your head so you can get eyes at the right level to see through.  ES does sell a longer finder stock for $59.  Also the crosshairs are hard to see when looking through the finder.  A good red-dot finder or an illuminated RACI finder will solve these issues.


At $299, this scope is an AWESOME value!



    • Mister T. likes this

Good review.

There are fewer scopes more likely to allow such easy observing under varied conditions than a small, short refractor with reasonable aperture.  It's been -15 C or worst the past few nights in the N.E. U.S. and using such a scope on a solid alt-az mount at least makes it more palatable to go outside since it is really "grab and go."  Also, I've got a couple of these medium-speed refractors (one a Celestron 4" and one a custom-made 4.7" f/8.0 using an Antares objective) and I am shocked at how good the diffraction patterns are.  There is colour, but no astimatism, out of roundness, very little spherical aberration, etc.  

I second every word of this fine review. I couldn´t resist at the price and pulled the trigger too. Even my wife didn´t rant too much...

    • Mister T. likes this
Alien Observatory
Feb 14 2016 09:22 PM

OK I went Crazy and ordered one from OPT.  Will report back on what I think in a few weeks...Thanks Patrick

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