Revenge of the Celestron Travel Scope 70

October 15, 2013


Update: This post seems to get a lot of traffic, especially around the holidays. If you’re looking for good gifts for amateur astronomers, including telescopes and binoculars that won’t break the bank, you may also be interested in myastronomical wish list for beginning stargazers.

– – – – – – – – – –

Last year I picked up a Celestron Travel Scope 70, mostly because it was cheap (~$65) and I was curious. Except for a couple of quick peeks with the scope, the only serious workouts it got were the transit of Venus and an all-nighter on Mount Baldy.

My feelings at the time–explained here–were that the scope was great a low-power scanning but useless at anything over 50x. Terry Nakazono suspected it was miscollimated, but I’d never collimated a refractor and I had plenty of other stuff to be getting on with, so I let the TS70 languish.

This fall, London has been showing more interest in astronomy and I let him have the TS70 as a hopefully more user-friendly alternative to the Astroscan, which is a cool scope but can be a real PITA to get on target with.

The first problem is that although the TS70 has an actual dovetail bar, it is so ludicrously short and so far forward on the tube that it is almost impossible to balance the scope. For reasons that escape me at the moment, I have several spare dovetail bars lying around, so I grabbed the next larger one to put on the TS70.


But there’s a problem: the bolts that hold the ludicrously short dovetail (LSD henceforth) on the scope are threaded into nuts inside the tube. You can see those nuts and bolts at the bottom of the tube in the middle distance in the above photo. But you can only see them because I had to remove the objective lens to get this picture.


Well, in for a penny, in for a pound: I disassembled the whole damn scope. Here are the bits. The hex wrench set and screwdriver are mine, the solar film inside the lens cap (described here) is one of my hacks, but the rest is as it came from the factory. Only, you know, taken apart. From 12:00, the bits are:

  • the tube with the finder still attached;
  • three screws for attaching the focuser to the tube;
  • said focuser;
  • the black plastic dust cap from the focuser;
  • the LSD, its two hex bolts, and their nuts;
  • the two pieces of glass that make up the objective lens;
  • the retaining ring for the objective lens;
  • the dust cap (with solar film) for the objective lens, with the dew shield inside.

The dew shield slides off, and the retaining ring for the objective lens simply unscrews. There’s nothing else holding the two components of the objective lens in; once the retaining ring is off you can simply tilt the tube down and let them fall out–onto something soft (so they don’t get scratched), that isn’t your hand (so they don’t get smudged with oils). The focuser is held into the tube with the three screws, and the LSD is held on with the two bolts and their nuts. So there are really only five fasteners holding the scope together, or six if you count the objective lens retaining ring.


So, about that objective lens. This is an achromatic doublet, meaning that it has two pieces of glass of different compositions (the ‘crown’ and the ‘flint’), to bring more than one color of light to focus at once.  In the above photo, the crown is on the left and the flint is on the right. They are different colors, but I’m not sure if that’s because of different light transmission or different coatings. Note the three little foil spacers on the flint, which keep the two lenses at the proper distance.

IF you ever disassemble a multi-element lens, it is extremely important that you keep the parts not only in the right order, but also facing the right way, or you are going to waste a lot of time trying different arrangements (and risking damage to the glass) until you discover how they go together. Better to just keep track of them as they come out.


Next item: unless their edges are blackened, lenses suffer from internal  reflections, which cause reduced contrast at the eyepiece. Lots of cheap scopes and eyepieces have un-blackened lens edges, so whenever I take something apart, I blacken the edges. I use a sharpie, two coats, but I’m sure there are other ways.

Aaanyway, the retaining ring for the objective lens is almost always too tight when the scope ships from the factory, and simply unscrewing the ring and gently shaking the tube to settle the lenses is often enough to improve collimation. And that’s all I did here.

So how’d it work out? Last summer, I wrote:

The scope starts to pant around 40x and anything north of 60x is just bad…. Trying to achieve focus on planets is maddening. Jupiter goes from a vertical fan of red light on one side of focus to a horizontal fan of blue light on the other, and only sort of flirts with being a clean disk in between those extremes, at an infinitesimally tiny point that the rack-and-pinion focuser tends to shoot right past.

But Saturday night out at the Salton Sea, the reassembled Travel Scope 70 was like a brand new scope. Images were still pretty crisp at 67x with a 6mm Orion Expanse, and going up to 133x with a Barlow did not just add empty magnification. Here are my observations on different objects.


At midnight, I split Polaris with the TS70 using the 6mm Expanse. I note this because In his review of the TeleVue 76 (an $1800 scope), Ed Ting wrote,

There was a time, not terribly long ago, when splitting Polaris was said to be a good test for a three inch scope. In today’s brave new apochromatic world, however, splitting Polaris is something of a joke.  Polaris is easy.  The double-double is easy.

That’s cool, but the TS70 is not an apochromat (a three-lens-element scope with better control of false color and therefore usually sharper optics than an achromat), nor is it a three-inch scope (2.75″ to be exact). So the fact that Polaris was cleanly split at relatively low magnification (67x) has to be a win.

Epsilon Lyrae

What about the double-double, aka Epsilon Lyrae? I Barlowed the 6mm Expanse to get 133x, which is where I run out of eyepieces and Barlows to increase the magnification on this scope. The northern member, ε1, was clearly elongated but not cleanly split, but ε2 was cleanly split. That’s a little nuts, because ε2 has a narrower separation (2.3 arc seconds) than ε1 (2.6 arc seconds), so it should be harder. I can think of several possible explanations, most having to do with the  fact that the ε1 pairs were lined up horizontally in the sky at 12:20 AM, whereas the ε2 pairs were lined up vertically:

  • the scope might have some astigmatism that is more pronounced horizontally than vertically;
  • my eyes might be more sensitive to vertical than to horizontal separations (I have no idea if this is true, but it’s possible. Maybe I should check some time.);
  • the separations were so seeing-dependent (even ε2 was not cleanly split all the time) that any unevenness in the atmospheric turbulence between me and the stars–say, the heat plume from a distant campfire–might have thrown things one way or another;
  • the more pronounced brightness difference between the ε1 components (magnitudes 4.7 and 6.2) compared to the ε2 components (5.1 and 5.5), although not normally a factor, might have made that one a tougher split since I was working at the hairy edge of what the scope and the conditions would support.

Anyway, since the closer pair of the double-double was cleanly split even under the less-than-perfect conditions Saturday night, I feel confident saying that this scope will split the double-double.


From my notebook:

1:50 AM. Jupiter in TS70 with 25mm Plossl (16x), just a bright spot. In 12mm Plossl (33x), a disk with two bands. In 6mm Expanse (67x), hints of more than 2 belts during moments of steady seeing, but bad seeing easily visible in image–Jupiter looks like it is on fire. Barlowed 6mm Expanse (133x): this is too much mag. No new detail, and previously seen belts and zones are harder to make out. No problem focusing using moons, though–I think problems are seeing, not scope.

3:57 AM. TS70 to Jupiter, in 6mm Expanse (67x, definitely more than 2 belts/zones showing now that Jupiter is higher in the sky. Planet is still visibly “burning” in the bad seeing. Three to four belts visible, meaning at least two different belts in addition to the bold equatorial belts, but hard to hold both extra belts at one.

Trapezium in Orion

Again from the notebook:

  • 25mm Plossl (16x) – 2 components (3 visible, but only 2 cleanly split)
  • 17mm Plossl (24x) – 3 components
  • 12mm Plossl (33x) – 4 components cleanly split

TS70 waxing gibbous moon 2013-10-12


Mars was a visible disk in 6mm Expanse, but swimming in the near-horizon murk near Regulus.

M81 and M82 easily visible in 25mm Plossl (16x), showing some detail in 12mm Plossl (33x).

M31, M32, and M110 visible in one field with 12mm Plossl (33x).

I spent some time on the moon, and snapped the photo above using a Canon S100 point-and-shoot and a 25mm Plossl. I flip-flopped it left-to-right and lightly sharpened it in GIMP, but didn’t mess with the brightness or color. It’s not an amazing image–a 90mm Mak will thoroughly spank this scope (proof)–but it’s not bad.


So, I have to revise my opinion of this scope. As supplied, I still have major reservations:

  • the tripod is wretched, and struggles to hold a small point-and-shoot digital camera stably, let alone a telescope;
  • the finder is a joke: too small to start with, then stopped down, and using plastic lenses to boot. But it makes a decent sight tube if you strip out the guts. London thinks the stripped version is the bee’s knees;
  • supplied backpack is okay, but no pockets inside or out, and only one partial divider inside (not that you’re buying this for the backpack, just sayin’);
  • eyepieces are nothing special and replacing them should be a top priority;
  • as supplied, my scope had two major problems: the LSD, which all TS70s ought to share, and badly miscollimated optics on this sample, which were easy enough to fix by completely disassembling the telescope and voiding the waranty. Also, focus is still a hairy procedure at high powers, and it is easy to overshoot best focus.

However, if you’re willing to buy or build a new mount and put in a little elbow grease, there is a surprisingly capable scope lurking inside this unassuming package–one that is capable of doing useful work on the observing field. Even with mostly plastic, jokey accessories, this scope is still a decent deal, although I shudder to think about the many unfortunate users who try to use the scope on the supplied tripod.

I note that according to the commonly-used “50x per inch of aperture” rule of thumb for max magnification, a 2.75-inch scope ought to be good up to 138x, which is pretty darned close to what I was working at (133x). So to be fair all I have established here is that the scope is adequate, according to one widely-used and fairly conservative guideline. But it’s so much better now than it was last summer–an actual observing tool, not just a toy. And that’s a win.



  1. Except for the 50mm Galileoscope, all my low-end refractors that I’ve purchased required collimation and alleviating pinched optics. And then you’ll need to check the collimation on the diagonal as well – many come miscollimated. .

    Although loosening of the objective retaining ring can improve collimation (along with alleviating pinched optics), you’ll want to get a Cheshire refractor collimation eyepiece to see how well your scope is actually collimated.

    The scope I have that comes closest to the TS70 is the F/5 Orion Short Tube 80A (ST80A), which I’ve probably spent more time taking apart and fiddling with than I actually have observing with.

    The Skywatcher 80mm F/11 that you had looked nice – given the choice, I would take that over the ST80A (better optical performance and more forgiving of less than perfect collimation with a longer focal length).

  2. This reminds me of the 70/300 refractor I have. But the TS70 is a quality product compared with my 70/300! I had to get rid of the 0.965″ focuser and mount a 2″ diagonal on it, so I could use the full aperture! (Now I can only focus by sliding the eyepiece up and down, but hey, it works – somehow…)

    Isn’t it fun to have to invest some work to get out the full potential of a scope? I always find it sad that the main optical element in these scopes aren’t that bad, but somehow they manage to badly mangle these scopes in the factory.

  3. You said it. The ones that pain me the most are the little Maks, which tend to be super-sharp optically but are almost always sold with crappy prism diagonals that severely decrease their usefulness. I’d ten times rather they increased the price by $20 and threw in even a low-end mirror diagonal.

    But, as you say, there is something very satisfying about hacking on a scope to get it work better. I just wish so many beginner scopes didn’t need to be hacked.

  4. I’ve used plenty of Chinese-made equipment over the years, and though it hasn’t all been of premium quality, it has almost always been OK. I’ve never seen anything like my Travel Scope 70. It seems to have been assembled in an opium den.

    My first look though a good eyepiece and a mirror diagonal showed the focus “sweet spot” (such as it was) noticeably off-center. The focuser’s tube wasn’t pointed at the center of the objective. I fixed that by tilting the entire focuser assembly, which required filing the plastic housing, elongating one of the mounting holes in the metal tube, and improvising some shims. After that the “sweet spot” was centered in the eyepiece, but it still wasn’t sweet enough.

    I checked alignment with a Cheshire collimator and found the objective also needed some tilting, so I first tried the easiest thing: rotating the objective’s cell in 120-degree increments, as dictated by the three mounting screws. One position was less miscollimated than the other two, and in that position sharpness was noticeably better, but I was convinced it could still be improved.

    So I bit the bullet and more carefully adjusted the tilt of the objective cell. Because the heads of the flat-head mounting screws are countersunk in the plastic cell, I had to painstakingly reshape the three holes. It didn’t help that all three screws had been installed at odd angles to the tube. More filing, more shims, more testing. At the end of this maddeningly repetitive procedure collimation was looking much better in the Cheshire, though still a little short of perfect.

    By now the image was looking more respectable, too, but Jupiter was bright blue on one side and bright red on the other–very pretty but not what we hope to see in a telescope. (Atmospheric dispersion wasn’t the problem; the planet was high in the sky.) On a hunch I removed the doublet objective and tried rotating the crown relative to the flint. After some trial and error Jupiter’s halo was less colorful and more symmetrical, and the Cheshire showed the collimation was spot on. My telescope was finally performing much like yours.

    I write all this to let you and others know that in the absence of meaningful quality control at the factory buying one of these things is a real roll of the dice. Although all you had to do to tune up your copy was take it apart and put it back together, my experience was something else entirely. This was the telescope to try men’s souls.

    The bruise on my forehead from banging my head on the wall is starting to fade. Was it worth the trouble? I won’t try to answer that question until the hair I tore out grows back.

    Thanks for your good blog.

  5. Thanks, David, for sharing your experience. Unfortunately I think that poor quality control is just a fact of life with inexpensive astro gear. Sometimes you still get a gem, but sometimes you still get a stinker, too. I have been mostly lucky, especially with my Orion gear, but I have heard from enough other people to know that it’s not all roses.

  6. […] marker. This might reduce any internal reflections in the lens. (That photo is actually from my Celestron TravelScope 70 overhaul, but the procedure would be the same for the […]

  7. Hi! I’ve just bought this telescope for having some fun with the kids. We were really surprised you can actually see saturn’s rings with it! Even without knowing the first thing about telescopes, I say the mount was not going to do at all so I changed that for a sturdier one. After reading your article I’ll try blackening the edges of the lenses as well (and loosening the bolts if I can figure out which ones they are!) but I would appreciate any recommendations with the lenses. The one you mention from Orion is as expensive as the telescope… Is there anything middleway that would improve the experience without expending so much money?
    Paola (Barcelona, Spain)

  8. Hi Paola,

    For better eyepieces, you probably want Plossls. A Plossl is an eyepiece type, not a brand. Many manufacturers make them, because they are simple, hard to screw up, but give good results in almost any type of telescope. New Plossls usually go for $40-50 depending on the manufacturer and outlet but sometimes you can find them a bit cheaper. Some places you might check are Agena Astro, Astronomics, and the Telescope Warehouse on eBay. You can also check classified ads on astronomy forums, that might help you find something geographically closer. Best of luck and clear skies!

  9. Thanks for you help! Will do so asap!
    Regards from Spain

  10. […] but can’t do wide fields. The TravelScope 70 can do wide fields but still has limitations, even after its tune-up. And the C102 is a wonderful scope but not exactly small, and although its chromatic aberration is […]

  11. Thanks for the great, very detailed review.
    One question: is the dovetail vixie-compatible?
    Thanks in advance for your answer.

  12. Yeah, it’s a Vixen dovetail, just a very, very short one. I haven’t measured it but it’s not over 2 inches (50mm) long.

  13. Matt, just read this great review. Kudos on having the chutzpah to take the scope apart. I used to do that to stuff when I was 10, but then, of course, it wasalready broken and being thrown out anyway, and I couldn’t ever get it back together. All thumbs, that’s me.

    You mention that there’s a short Vixen dovetail on it. Do you know any way to use that to mount the TS 70 onto a larger OTA for use as a super-duper finder/wide-field scope? Is there a matching dovetail receptacle that I can buy so I can, I dunno, sticky tape it onto my existing OTA , so that I can then just slide this sucker into place? It’s a NexStar 127SLT Mak, by the way, which I absolutely love.

    Amazon is selling the TS 70 for 50 bucks, which is cheaper than any 8×50 or 9×50 out there. I think this would make an awesome finder, and a halfway decent low-power widefield scope, kind of counteracting the “deficiency” of my Mak’s 1 degree field of view.

    What do you think? You seem pretty handy – handy enough to take this thing apart and put it back together – any suggestions on how to do this?

  14. Hi Jon,

    Many thanks for the kind words! I have the Orion Apex 127 Mak, which I think is a pretty close match for the NexStar 127, if not a clone. I love mine, and I love it even more since I mounted a wide-field scope in tandem with it. I thought for a while that wide-field/superfinder might be the Travelscope 70, but in the end I got rings for my SV50 instead (pictures in this post. It was a very worthwhile thing to do–the Mak is optically awesome but as you said, the FOV is limited, and it’s nice to have a capable, variable-magnification widefield scope mounted alongside, both for finder duty and just for nice wide views now and then.

    Honestly, your best bet for getting the TS70 mounted on the Mak is probably to spring for tube rings. I put off doing that for a long time because I was loathe to drop so much dough on something that was ‘just’ mounting equipment, but I was sure a lot happier once I’d done so. As far as when to buy, a lot of dealers are having sales right now, and Orion usually has a big after-Christmas astro accessory sale.

    If you’d rather not spend that kind of money without getting to test-drive the setup first, there is another, inexpensive mounting option: get a couple of shortish lengths of some fairly solid tubing, like 1- to 2-inch PVC plumbing pipe, cut holes for zip ties or maybe a velcro strap, and use the paired tubes to hold the smaller telescope OTA parallel to the larger one, like David DeLano did on a smaller scale with his solar finder from this post. It won’t look very refined, but the TS70 weighs next to nothing so it should be plenty stable if you tie everything down tightly.

    One more possibility: try http://www.scopestuff.com/. They have all kinds of weird adapters, and you could probably find the bits you need to cobble something together.

    Good luck with your quest!

  15. Thanks for the quick response. Yup, the two OTAs are identical. Now I have a passion for Maks that I didn’t even know existed. Your rig is exactly what I want to do, except with the TS 70. Any reason you chose the SV 50 over the TS 70? Is the SV optically superior, even with the smaller aperture?

    Someone else just pointed me to scopestuff as well, and they have adjustable rings that hold the scope and fit into the already existing little vixen dovetail mount that’s there, the one for finders. It’s actually absolutely perfect, except it costs much more than the entire scope at $84.



    I guess you can’t have both cheap and good-looking. Well, maybe you can rent it for about an hour or so, but that’s something else entirely. Thanks.

  16. The other option would simply be to take my Mak OTA off of the mount, and just use the Vixen dovetail on the TS 70 to attach it to my current setup directly, so I could use it that way. A lot of overkill for a $50 scope.

    And I would still have to buy myself a 9×50 RACI separately anyway for the Mak. But it would be nice to have both the widefield and highly magnified views.

    Well, no rush to do this, then. This can wait. RACI has to come first, because the red dot is killing my neck/back.

  17. […] the TS70 performs MUCH better after having been disassembled and reassembled (details in this post). It’s not hard, all it takes is a screwdriver. Blackening the lens edges with a Sharpie […]

  18. Any reason you chose the SV 50 over the TS 70? Is the SV optically superior, even with the smaller aperture?

    No, optically the TS70 smokes the SV50 in every way and did so even before I tuned it up. The SV50 is about as good as an f/4 50mm achromat can be, but that’s still not nearly as good as a 70mm f/5.7 achromat, even a miscollimated one. The SV50 starts to pant at anything over about 30x, but at that magnification, even the pre-overhaul TS70 delivered a much brighter, higher-contrast image.

    I mounted the SV50 as a super-finder instead of the TS70 mainly because it was cheaper and easier. I go some inexpensive tube rings for the SV50 that let me slot it into the existing dovetail foot on the Mak. Could have done the same with the TS70, but the rings would have been more. And after I tweaked it, the TS70 is a heck of a lot of fun to just cruise around the sky with as a standalone scope.

    It’s actually absolutely perfect, except it costs much more than the entire scope at $84.

    Yeah, that’s exactly why I didn’t take that step for a long time. Eventually I realized it was silly to keep blowing my disposable income on more telescopes instead of getting some decent accessories to let my existing telescopes work at their full potential. I have never regretted getting decent rings, better diagonals, and good wide-field eyepieces; observing is so much more enjoyable when everything Just Works.

    RACI has to come first, because the red dot is killing my neck/back.

    Absolutely. I was fortunate in that one of the first books I picked up when I was getting into this was Scope Hacks, by Robert and Barbara Thompson. They wrote that getting a 9×50 RACI finder was one of the simplest upgrades but that it would have one of the biggest impacts on one’s observing, so I pulled the trigger way back when, and I have always been glad that I did. I’ve seen almost all of the Messier objects in my 9×50, and even a few from the H400. Optically, it’s pretty much identical to the SV50, just without the option of switching eyepieces (at least if you get the Orion version like I did, or a clone).

  19. Ugh, I’m kinda torn now, because there is a way for me to do the SV 50 thing like you, except with the TS 50, not 70. It will cost about 60 bucks with the OTA and the mounting ring, which is actually the Orion 9×50 RACI ring – it has the mount that slips right into the finder dovetail that’s already there. The cost is about the same as a RACI – Agena sells an 8×50 RACI with ring for $65.

    But I would soooo much rather get the TS 70 and figure something out about mounting it properly.

  20. Um.. you aren’t supposed to blacken the edges on this telescope. I’ve got the same type of telescope, and it works fine. I have had no problems with internal reflections in this telescope. Actually, internal reflections refer to the reflections inside the tube due to an uncoated internal body, not the edges of the lenses. Look at the inside of it. It is black in there already, compared to other telescopes I have. Some of the ones I have are high-end, too. The telescope tube being black eliminates the problem already. The only time you need to do that is if the coating wears off inside. Plus, most of the time, you are not going to be seeing the tube at all, because the eyepieces magnify the image and eliminate the view of the inside of the tube.

  21. Thanks for commenting, Robert.

    you aren’t supposed to blacken the edges on this telescope.

    I’m curious why you think that is so. Is there something magical about this scope that makes light not bounce off the internal edges of the lenses? Because that is true for every other refractive element in the optical train. Which is why decent eyepieces and high-end refractors have blackened lens edges, and advertise that fact:

    AT-72ED: “The edges of the objective lens are blackened to eliminate contrast-reducing stray internal reflections.”

    TV-76: “The highly optimized anti-reflection coatings, precision-ground edge-blackened lenses will deliver the goods.”

    Orion EON 130 triplet: “Contrast is equally rich thanks to blackened lens edges and two internal knife-edge baffles that prevent off-axis reflections of incoming light.”

    Skylight 102/f7 ED: “hand figured, fully multi-coated doublet, with blackened lens edges”

    TeleVue eyepieces: “Blackened lens edges and internal anti-reflection threads tweak the last bit of contrast for maximum image detail.”

    I’m not even going to post any more links to eyepiece descriptions that include blackened lens edges – virtually every popular mass-produced eyepiece has blackened lens edges, for the same reason that all refractors above entry-level have blackened edges on their objective lenses: to improve contrast by cutting down on stray light.

    I’ve got the same type of telescope, and it works fine. I have had no problems with internal reflections in this telescope.

    If you haven’t blackened the lens edges or taken any other steps to improve the contrast, you have no factual basis for that statement. It may “work fine” for you and you may not have noticed that the contrast is not as good as it could be, but until you actually compare before and after, you don’t know what tuning up the scope could do for your views. I have compared before and after and found a noticeable difference.

    Look at the inside of it. It is black in there already

    Unless your scope came off a different production line than mine, it is not really that black. Look at my second photo in the post above. The reason that the inside of the scope looks grey instead of black is that a lot of light is getting bounced back to the camera from the inside of the OTA. If that much light can bounce back toward the camera, it can bounce the other way, straight into the eyepiece. Most high-end scopes include knife-edge baffles, or rough, very flat black flocking, or both, for that very reason.

    Plus, most of the time, you are not going to be seeing the tube at all, because the eyepieces magnify the image and eliminate the view of the inside of the tube.

    Sorry, that’s completely wrong. The whole point of all of these contrast improving steps is that light scatters. You don’t have to “see” the inside of the tube for light to bounce off of the inside of the tube into some other part of the optical train – like the inside of the eyepiece drawtube, the inside of the eyepiece barrel, or the eyepiece field lens – where it can be reflected or refracted into the visible light pencil that enters your eye, thereby cutting down contrast.

    That’s why there’s almost no upper limit to how fanatical one can be about blocking stray light: install knife-edge baffles, flock the tube, baffle and flock the eyepiece drawtube, flock the inner surface of the eyepiece barrel (not common, but it could be done), blacken the objective lens edges, blacken the eyepiece lens edges, go back and do any one of those steps over with a better technique, a less-reflective surface, a flatter black. I’m not saying that anyone has to do these things to enjoy the view through a telescope – remember, I was impressed with the bright, contrasty views in the Travelscope 70 even before I tuned it up – only that they can be done and most of them will yield small but noticeable improvements in contrast.

    I’m sorry if it seems like I’m being hard on you, but your ideas about the value of blackening lens edges are directly contradicted by basic optical theory, and by how TeleVue, Astro-Tech, Starlight, etc., build and market their high-end refractors. I don’t think that the Naglers are having the lens edges blackened on TV-85s and NP-101s because they have been misled by some myth. It’s because they understand that light scatters (to some degree) off any surface that it hits, including the inner edges of the objective lenses, and cutting down on that scatter improves contrast at the eyepiece.

  22. Yeah, if it means anything, I gotta jump in and agree wholeheartedly with Matt – and the entire rest of the astronomy world. Matt is definitely, completely right about not only the blackening of the edges, but about the flocking of the tube, etc., etc. It’s not the light from the object you’re looking at that you have to be concerned with so much; it’s the light that is entering the tube from different angles, most notably light from any light pollution source – including other things in the night sky.

    Ever notice how you can see the light from a planet before you actually see the planet in your field of view? That’s because the light is entering at an angle, bouncing off of who knows what – the edges of the objective, the inside walls of the tube, a bunch of different things. Blackening, baffling, flocking, all of that reduces this type of scattering of the light.

    After light gathering ability, the next most important thing about a telescope is contrast. All the things that Matt mentioned improves contrast, makes a black sky blacker, and that improves your ability to see fine detail.

  23. Oh, and by the way, Matt, as an update to my questions on this thread, I did eventually end up mounting a wide-field refractor to my NexStar 127 Mak. From your recommendation, I did call up ScopeStuff – thanks very much for pointing me in that direction. The owner was on the phone with me for a good 45 minutes or so. He really took some time with me to go through various mounting options.

    Instead of going with the Travelscope 70, I went for the Orion ST-80. I bought it used off of eBay, it came with half a dozen eyepieces, and was a really great deal. I’ve since sold off half of them as duplicative of what I already had, but the scope itself has worked out great.

    The ScopeStuff guy steered me to a mount that he didn’t have at the ScopeStuff site; it was on his eBay site instead:


    The bungee cords that strap the mount to the Mak and that strap the refractor to the mount aren’t worth anything – both gave out spectacularly in just three months or so. Unfortunately, one set of bungees gave out just as I was carrying the whole rig, the tripod with both scopes on it, over my shoulder on the way back from a night’s observations, and the ST-80 dropped over 5 feet to the carpeted floor of my apartment building’s hallway. Fortunately, there was no sickening crunch, and even the collimation of the scope held up. I guess they build the ST-80 pretty well.

    However, the metal part of the mount itself is good enough. It cradles the refractor on top of the Mak and is adjustable so that the two scopes can be aligned. Still worth the $39 for the mount to be able to use both scopes at the same time! I got two industrial strength bungees from the hardware store, so even if one fails, I’m still in good shape.

    Thanks for your advice!

  24. I have had a TS 70 for about 4 years….It does great job. I like to do comparisons of refractors of the same aperture. I recommend that if you try a high end EP with quality ED glass the TS 70 rocks….I had my Astro Tech 72ED and TS70 viewing Jupiter earlier this year, each with a Baader Planetarium click stop 24-8mm. Of course the Astro Tech is totally color free, but the TS 70 at focus, no color on Jupiter through the zoom range, the color in out of focus minimal compared to lesser quality EPs. A Televue 2.5x Powermate has been used to boost magnification with good results.

    I will be using the TS 70 as a finder scope on my new Hyperstar imaging setup.

    Aloha, Roel in Kona Hawaii….

  25. Thanks for the report, Roel. Sounds like you got an excellent sample. I had an occasion about three weeks ago to use mine for a couple of evenings up on Mount Baldy, and I was once again impressed by how bright and contrasty the images are for a 70mm scope.

  26. is there any plossls that fit in the TS 70 or can u recommand me some that will make the view or zooming more clear and better.
    (i have no idea about these things. i wrote it coz u mentioned it above and i am about to buy a TS 70)
    thank you!

  27. Yeah, pretty much ALL Plossls will fit the TravelScope 70 – it has the standard 1.25″ focuser that the vast majority of amateur telescopes use.

    If you’re looking for better eyepieces, there is a line of budget Plossls from Astro-Tech that look good, for about $23 per eyepiece. Link. Or Celestron’s 8-24mm zoom eyepiece – that is good enough to keep one busy for a long time.

  28. Jon – belatedly, that NexStar 127/ST80 combo sounds positively dreamy. I’ve been getting into low power, widefield scanning lately and small fast refractors do a great job with that.

  29. Heh, heh, what a coincidence! For some reason, I found myself re-reading these comments just last night!

    Dreamy is right! It is such a perfect combo that I practically wonder why they don’t sell the two scopes together. The ST-80 is amazing at low-power widefield scanning. I never knew just how gorgeous the Milky Way in Cygnus was until I took it out and just tooled around in that vicinity for a couple of hours.

    I’ve been involved in a discussion over at Cloudy Nights on achromatic refractors, like the ST-80, and there is a particular post where there is a chart showing that even an f/5 achromat has relatively little chromatic aberration, because CA is related to the ratio between the aperture and the focal ratio.


    The only problem I’ve encountered is that it is just a bit too much weight for the SLT mount. It made the mount lose altitude if pointed in the wrong way, and then the problem persisted after I had removed the ST-80. I was under warranty at Celestron and sent it back, but their “30-day turnaround” was a solid two months. I’d love to solve that “problem” by getting myself an iOptron Minitower (or Minitower II, or Minitower Pro) that allows you to mount two scopes at the same time.

    Anyway, it was while the mount was with them for all that time that I remounted the ST-80 on another alt-az mount I have, a defunct Meade DS-2130 AT mount that, ahem, used to be motorized. It was then that I discovered that long after I started observing with first a 6-inch Newt, then an 8-inch one in my teenage years, 30 years later, in fact, that I could still starhop. With Stellarium at my side, it was positively easy with the almost 4-degree field that the ST-80 gives you. And I “discovered” the Cygnus Star Cloud, which I would like to rename “The Spine of Cygnus”. (Patent pending.) It is glorious to just sweep the refractor up and down the Milky Way.

  30. Thanks for the link to that thread. I had seen it but not read it yet; I figured the OP’s question could safely be answered ‘yes’. [EDIT: Whoops, just realized that the OP was you, and that you were asking a more specific question!] But I know lots of interesting things pop up in discussion on CN. Did you see the graph that Alan French posted comparing focal length and maximum true field? It’s on the second page in this RFT thread:


    It is glorious to just sweep the refractor up and down the Milky Way.

    That is something I don’t do nearly often enough. Usually under dark skies I am bouncing around, usually splitting my time between checking in on the best-of-class objects and tracking down new ones. I should sit down with a widefield scope, a low power widefield eyepiece, and just go exploring more often. There is something very satisfying about ‘discovering’ objects by scanning and then looking them up later. I will always remember stumbling across M25 while looking at Jupiter one evening.

    And Cygus…man. Under dark skies I have spent whole evenings there and not run out of things to see. I like “The Spine of Cygnus”, it’s an apt description. Just for the sake of due diligence, though, I should probably go have another look at it…

  31. Yeah, I was just curious about larger refractors. After getting all the answers, it’s pretty much not a way I’d go, especially where I am now and with what I observe. But that could change if I move.

    As for that RFT thread, yeah, there are a bunch of options. But the ST-80 is pretty amazing for its price. If you set up an alert on eBay and get the Cloudy Night refractor classifieds delivered to your inbox, you’ll be able to find a used one for about $90-100.

    Sure, the ST-80 has some CA, but that’s only if you look at bright objects. To paraphrase the old doctor joke, “Don’t do that.” An f/5 80mm refractor is designed for low-powered viewing, and that’s it. Either that, or as someone mentioned in that thread, and as someone else at CN has recommended to me, there’s an f/6 80mm, the Antares, which comes standard with a 2-inch focuser for pretty much the same price new. With a low-powered 2-inch lens, that’ll give you about 5 degrees FOV, and with even less CA than the ST-80.


    That second link is even cheaper than the first, but they’re Canadian sellers, and you’ll have to call to see if they deliver to the US.

    Like I said, the CA on the ST-80 is there, but easily ignorable; the Antares would be that much better. But really, it doesn’t matter. If you’re just using the scope for scanning around, there won’t be any CA on objects dimmer than, say, 2nd magnitude. I had mine out an outreach last week and had it on the Pleiades, and they were all sparkling blue. People were oohing and aahing at 27x.

  32. I have been tempted by both the ST80 and that f/6 Antares. But the C80ED I picked up last year is short enough and sharp enough that I’m unlikely to get another refractor in that aperture range. I’ve been contemplating something in the 4-5″ range, preferably fast focal ratio for widefield deep sky. The Orion 120ST and Explore Scientific AR102 and AR127 are all contenders. I’m open to other suggestions if there are affordable scopes I’ve overlooked.

  33. Oh, well, if you’ve already got an 80mm apo, then yeah, there’s not much reason to get something else in that size. It looks like that’ll give you a 2 2/3 degrees FOV, which isn’t anything to sneeze at, unless you’ve got a 2″ focuser on it. So I would say you’re all set there.

    I’m not one much in the whole refractor end of things – and thus the apparent naivety of my 6-inch achro thread. So I can’t really make any other suggestions to you. As I mentioned in that thread, there are a large couple of Celestron fracs. I’ve had my eyes on the Explore Scientific AR series for a very long time. The ES fracs do seem cheap, well, inexpensive, anyway, and fully equipped. But if you’re going to go for a 5-inch refractor, why not just go all the way and get yourself a 6″ instead? There is a great review on the 152 here:


    which finds that although it’s really very good, the one they were comparing it to was just that much better, but also more than that much more expensive.

    As I see it, the whole idea with getting a larger refractor is, well, to get a larger refractor. That was one of the reasons I asked the question in the first place. Sure, a 120 or 127 represents a big step up from an 80, but it’s the same as the 127 Mak we both already have. Why not go big or go home! The 152 isn’t THAT much more expensive or heavy than the 127, and it gets you another half a magnitude deeper, which is significant. If you want to get as much richfield out of it as possible, go for the Celestron Omni 150 XLT at f/5. Unfortunately, it seems like you can’t buy the OTA separately; maybe if you follow the classifieds, you can find it.

  34. Matt – I just keep on coming back to these two TS 70 reviews! The subject came up in a Facebook astronomy group that I’m a member of, called Telescope Addicts. Anyway, not trying to tempt you or anything, I just wanted to mention that if you were still interested in the AR 102, the price has dropped to $299!


    Uncle Rod did a writeup on it where his jaw dropped over that price drop. Enjoy!


  35. After reading Terry’s…..Revenge of the Celestron travelscope 70,I decided to buy one and must say it really is a great little scope.I also have an ST80 and have a hard time telling the difference between them, both in star cluster brightness and image resolution.
    Have not even tinkered with it yet!I do see an inside reflection from the inside edge of the focuser assembly and looks like the metal edge was not blackened and is a bit shiny but a sharpie should take care of that.
    The mount that comes with it is as Terry says of poor quality but it all just tucks away nicely in the supplied backpack.

  36. Sorry for the confusion.I meant to say it was Matt’s review of the travelscope 70.

  37. This posting was a very useful read for me.

    Last year I got the idea for using a Celestron Travel Scope 70 (TS70) as a cheap imaging scope after watching a YouTube review of the Celestron NexGuide all in one autoguider. The reviewer revealed he was satisfactorally using a TS70 as the guide scope.

    Under the stars the looked pretty sharp on the NexGuide screen. It also helped that an Amazon reviewer of the TS70 posted some of his DSO images with his review and they looked pretty good.

    I recently acquired TS70 along with a Celestron piggyback mount. I live in New England and Maryland where clear skies and good seeing are a rarity. The day the scope arrived Greater Boston was having clear skies with poor seeing and gusty winds. Nonetheless I decided to image from my south facing patio where I can only get a rough polar alignment. Even with that I was able to bag a decent image of M42 using 25x8s exposures using a 0.5X focal reducer.

    I decided to check the collimation with Chesire and found it was slightly off. Following this blogger’s suggestion I loosened the front retainer ring and jiggled the lenses until the lenses slid into perfect collimation. It only took a minute.

    I have yet to try out the TS70 on the moon, Jupiter or double stars but look forward to comparing the supplied eyepieces to the better eyepieces.

  38. Hi Rick.Great to hear to like the TS70.The supplied 20mm eyepiece I would say,is just great.Yes I have more expensive eyepieces and one specifically,ES 24mm 68deg is better however the cheaper Celestron 20mm,is very sharp too but does have a smaller field of view.Definitely,a keeper eyepiece.
    The other supplied eyepiece was a 10mm but I didn’t care for it as images were kind of dull,lacking brightness compared to my other 10mm Luminos eyepiece.

  39. I took your advice, but being a nooo I buggered up the lenses a bit. They got quite dusty so I cleaned them with alcohol wipes as delicately as possible but I have some smudges. The image is clear and nice, but I don’t know if I should worry and clean them more? I’m completely new to this (so I chose a cheaper scope to start, and considering my complete clumsiness it was a good idea) and would massively appreciate advice. I managed to avoid touching the lens as far as I know but not for 100%…

  40. Hi,

    I wanted to take your advice but clumsy as I am, I managed to dirty the lens and I can see some smudges when I light it up with a torch. I tried cleaning it with alcohol wipes but I think I failed. The image is clear enough though. I don’t see an effect of those smudges on it. But I’m a noob so who knows. Should I worry about it and try to clean it up more? Or leave it as it is?

  41. A small smudge will not affect the image too much, especially one that you can only see by holding a flashlight to the lens. In fact, the advice is to never, ever look at a lens with a flashlight, because you will always see something you’ll want to clean – and that something won’t effect the image, as you’ve noticed. Out of sight, out of mind.

    You generally shouldn’t clean your objective unless it is truly dirty and the dirt is effecting your image, because every time you do, you have the possibility of scratching it up, and that’s much worse than a little dirt or a smudge. The only exception to this is if something like pollen gets on the lens, because that can really stick there, so that really does need to be removed quickly. So in your case, you should just leave it as it is.

  42. Thanks Jon! And sorry for double posting. I had a page refresh as soon as I wrote the first thing, and knowing my talent I thought it deleted the message. Anyhow.

    Thanks a lot for the advice! I will leave my lenses alone. I think I got them to the stage of usability in the first place (after being a disaster of a person with them). The image indeed seems to have better contrast with the blackened edges. But I still get the red and blue frames to the planets (also a bit better but not ideal).

  43. The red and blue frames to Mars and Saturn are not being caused by your telescope. It is an optical phenomenon called atmospheric dispersion. It is essentially the same as the chromatic aberration that the achromatic refractor itself creates.

    Mars and Saturn are fairly low in the sky, with the result that you’re looking through miles more dense atmosphere than you would if it were closer to overhead – like Jupiter is. That thicker atmosphere down low causes the bright light from the planets to split so that you see different colors. The phenomenon diminishes as the planet gets higher in the sky.

  44. I doubt very much that what Be is seeing is atmospheric dispersion. It’s the same thing I see in my Travel Scope, no matter where in the sky the planet is located. Through careful collimation I’ve been able to minimize this aberration, but not eliminate it. (See my comment, February 21, 2014.)

    Note that Be says he sees the problem when looking at “the planets,” not specifically Mars and Saturn. Obviously, if he sees the “red and blue frames” when he looks at Jupiter while it’s high in the sky–and I suspect he does–the cause can’t be atmospheric dispersion.

  45. Be – the lenses will have to be very dirty and smudged before they’ll noticeably degrade the views. If you’re seeing an improvement now over where the scope was when you started, count yourself lucky and just enjoy the scope.

    As for red and blue around the planets, that could be chromatic aberration from the objective lenses, or CA from the eyepiece, or atmospheric effects, or some combination of the above. I have seen bad CA with low-grade eyepieces even when using reflectors and catadioptrics that are supposed to be CA-free, although mostly with cheap wide-fields and zooms. I don’t know what you’re rolling with, but IME Plossls are pretty immune to eyepiece-induced CA and they’re cheap and rugged.

  46. Wow, thanks guys that is really helpful. I think David is right because I have the same situation with Jupiter as well. But to be honest it doesn’t bother me much – there are moments when it’s minimal. I can’t really try collimating it better because I don’t have the tools to do that (special eyepieces right?) All this was really helpful – I panicked a little with the lenses admittedly (silly wee me), but that’s what happens to any newbie I guess.

    I am using the eye pieces that came with the telescope – poor grad student that I am, I have to spread the spending over months… I was wondering if any of you would have any advice on that, for that particular telescope. I need to be mobile the next few years so if I ever get to a point when I settle I will get a better scope, I am sure, but till then I am stuck with the travel one, so I just wanted to boost it a bit (although it already makes me happy with the views of the sky, modest as they are).

    (ah also- I’m a girl, I totally didn’t think to make my nick gender specific)

  47. Ah – reread the comments! Never mind 😀

  48. Be,

    “There are moments when it’s minimal” sounds like your telescope is working just as well as mine. That’s just fine–no need to worry about collimation!

    Since you asked for advice about eyepieces I’ll offer you a little. I think the eyepieces that come with the Travel Scope are surprisingly good. In fact, I think you’d do better spending your limited funds on something else and letting new eyepieces wait. I have two things to recommend.

    First, I’d suggest replacing the 45-degree diagonal with a 90-degree diagonal, because it will make it much, much more comfortable to look at objects high in the sky–where, as you’ve surely noticed, many astronomical objects happen to reside. I don’t recommend a so-called “star diagonal,” which would give you an image that’s upright but reversed as in a mirror. Who wants to see a looking-glass universe? Instead, I’d recommend a 90-degree correct-image diagonal, so that everything will appear the right way around.

    A good place to buy a 90-degree correct image diagonal is from Agena AstroProducts. I use one of theirs with my Travel Scope, and it works wonderfully at the low-to-medium magnifications that suit that scope. Here’s a link:


    Of course, you should keep the 45-degree diagonal for when you want to use your Travel Scope to watch the birds.

    Second, I’d suggest getting your hands on a better tripod, if you haven’t already. Almost any reasonably sturdy photo tripod would be better than the flimsy one that came with your Travel Scope. You might be able to find something good used.

    My Travel Scope has grown on me since I got it properly adjusted. In fact, I’ll be taking it with me on vacation this summer. It’s a great little scope and I don’t feel “stuck with” it at all.

    Sorry for calling you a “he,” by the way!

  49. For a tripod, check out the Ravelli APGL4, which Doug Rennie put me onto. It’s about the same price as the AmazonBasics version (and may be the same model, just with original branding), but with Ravelli’s guarantee. Doug reports that his can hold his 20×80 binos without slipping, so it should be more than enough for the TravelScope 70.

  50. My dear friend is ill and I’m looking for get well gift. He’s 66, loves travel and stargazing (bare eyeballs) but has never owned a telescope, let alone altered one. Would the unaltered version be a good start for a beginner? And what is the the most economical and easiest to install “improvement” you would recommend? Something a couple of rank neophytes couldn’t screw up? Finally, would the scope easily attach to a good camera tripod –One that folds easily for travel? Any feedback you can offer will be much appreciated. I need to purchase in October.

  51. I wouldn’t get this scope. It’s too fiddly, and a better tripod is an absolute must. By the time you’ve gotten that, you could have gotten one of Orion’s tabletop scopes for no more money. The one I have the most experience with is the SkyScanner 100 (see this post), but the GoScope 80 also has gotten good reviews, in particular from Sky & Telescope magazine. Both of them include very smooth tabletop mounts that can also go on top of standard photo or survey tripods, they weigh about six pounds apiece with mounts, and they sell for a little over $100. Here are direct links for the SkyScanner 100 and GoScope 80.

  52. Matt’s mentioned a couple of nice scopes, but if you’re willing to spend a little more than the $120-30 these scopes cost, you can do a little better for yourself. Aperture is king in this hobby, and although 80mm and 100mm are certainly nice, 130mm is better. More aperture lets you see dimmer objects, and lets you see brighter objects better, and with more detail.

    At $200, you can get the Astronomers Without Borders One Sky scope. This is a very easily portable, collapsible little tabletop dobsonian scope with 130mm of aperture. Sky & Telescope has issued a glowing review of the scope, a link to which is at the AWB website. Click on the products link, and then the One Sky.

    By the way, if you change your mind away from portability, for that same $200 you can get a 4-inch (102 millimeter) refractor that’s not a tabletop scope, but comes on a full-fledged tripod that’s decent: the Meade Infinity 102.

    Also, with any of these four short-focal length telescopes that Matt and I have mentioned – the 80, 100, 102, and the 130 – you’re going to need something called a Barlow lens to double or triple the magnification you get with the one or two standard eyepieces that come included with the scope. All four of these scopes are capable of high magnifications – up to 150-200x or so – that you’ll want/need to see detail in the moon and planets. But you won’t be able to get there with the eyepieces included with these scopes alone. A good Barlow that will let you do this will cost between $30 and $50, so you’ll have to factor that purchase into your final price. The 102 comes with three eyepieces (not the usual two you get with other scopes) AND it comes with a nice Barlow that will let you get up to these high magnifications. (And yes, I wish I got a kickback every time I recommended these scopes, but I don’t.)

  53. Regarding what Matt Wedel wrote August 17, 2014 at 1:17 PM
    …”For better eyepieces, you probably want Plossls.”

    How do you know if a certain eyepiece fits the Travelscope 70 or any other telescope for that matter? Are all eyepieces uniformly the same size?

  54. For all practical purposes, yes. Some older telescopes and a handful of truly bargain-basement models use 0.965″ eyepieces, and some widefield refractors and big reflectors can take 2″ eyepieces, but the vast majority of amateur telescopes use eyepieces with a standard 1.25″ barrel size. Anything other than 1.25″ will be clearly labeled as such. And there are adapters for converting both 0.965″ and 2″ focusers to use 1.25″ eyepieces.

  55. Just chiming in here to both agree with Matt and add a smidge more info. Yes, absolutely, all EPs are completely standardized as to size. In today’s market, unless you’re really seeking them out, 0.965″ EPs are hard to stumble across. And any EP that is 2″ will certainly be noted as being such, precisely because they’re bigger, better, and more special than 1 1/4″ EPs. So if you come across any EP and its size isn’t designated, you can be very sure that it’s a 1 1/4″ EP.

    I also want to echo Matt’s advice about better EPs – Plossls. Plossls represent a terrific value in today’s EP market. Most new scopes above about $300 or so come with a couple of Plossls standard, and if you’ve bought a scope that didn’t come with them, a Plossl is a very good EP to upgrade to. Plossls do it all, and at a very nice price – they’re sharp from edge-to-edge in just about any scope you use them in, and they also give a decently wide field of view (52 degrees) while doing so.

    There’s one important exception to Plossls doing it all – short focal length Plossls, which you should not buy. The way Plossls are designed, as the focal length of a Plossl gets shorter, so does the eye relief. Eye relief is the distance you have to keep your eyeball from the top lens of the EP so that you can take in the entire field of view that that EP offers you.

    Plossls generally have eye relief that is 2/3 of their focal length. So a 9mm Plossl will have around 6mm of eye relief. But below that, the eye relief gets so tight that it’s hard to keep your head still enough to keep your eye close enough to observe through it for any length of time. The lowest focal length Plossl you should buy should therefore be around 9 or 8mm due to the limited eye relief below that level.

  56. […] It’s fun to take a telescope all the way apart and put it back together, especially if it works better after you’ve done so. Everyone should try […]

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: