Celestron Travel Scope 50 Review

 

Many Travelscopes will be headed under the Christmas tree ...

 

Everyone likes a cheap scope. I sometimes get sick of expensive kit, not least because I fret over it and agonise whether to take it somewhere for fear of damaging it in transit. In reality my TV60 and Questar rarely leave my property. When I go on holiday I generally just take compact binos.

I visited the Antipodes several times for business a few years back, but in the end and despite good intentions, laptop and manuals and suits took precedence and the scopes stayed home. I now regret missing the chance to take a look at the southern skies, even with a small scope. Who knows when I’ll get the opportunity again? If I’d had a tiny, super light scope on a table tripod I might well have taken it with me ... and enjoyed the Southern Cross, Magellanic Clouds and upside-down Moon.

Would the Celestron Travelscope 50 have done the job? It’s certainly light (OTA 200g) and small (smaller than a TV60); cheap enough not to worry about too – I got mine for just £43 delivered.

If You Own One Already – Read this first!

If you read on you’ll discover I’m not very pleased with the Travelscope in standard form, so if you’re happy with yours forget my review and enjoy! Any scope you’re using and enjoying is a good one. If however you have sneaking doubts about your Travelscope, read on because I’ll tell you what’s wrong and how to fix it ...

Design and Build

Loads of stuff and a pretty box!

Whatever else I end up saying about the Travelscope, I can’t deny Celestron have thrown in the works: scope, tripod, backpack, erect-image diagonal, 3x barlow, planetarium software, 20mm and 8mm eyepieces, finder ... and more. All packaged in one of those shiny boxes with pics of celestrial objects and eagles in close-up; all very attractive. So you get loads of stuff, but what’s it like?

The answer is ‘a mixed bag’. The padded backpack is very nice, with compartments that would take most small scopes and tripods. The tripod is light and a bit flimsy and wobbly, but quite usable. The software is a cut-down version of the Sky X you get with a Paramount! The erect-image diagonal has a plastic body but is quite good optically. After that, though, it gets worse. The eyepieces are Huygenians and don’t look to be coated. The barlow is all-plastic and works, dimly. But what about the scope?

On the face of it the Travelscope 50 looks quite good – a small (12” long) OTA just wider than the 50mm F7.2 achromatic lens, finished in nice metallic grey paint and with a built-in tripod shoe with ¼-20 thread. True the focuser is plastic and 0.965, but it feels really smooth and has loads of travel (back to that in a mo’) and no play; what’s more, the diagonal is hybrid (it takes 1.25” EPs) and they throw in an adapter so you could use your own 1.25” diagonal if you have one.

Neat little OTA

 

The lens is interesting. A 50mm F7.2 falls well outside the 1.22D rule for achromats – you could expect this scope to show minimal chromatic aberration. Looking at it, all you can tell is that the lens has minimal, single-layer coatings on the outer layer only (fully coated, Celestron??) and that the spacers look a bit skewed. The tube behind looks commendably blackened though and I think I can see a knife edge baffle in there.

Talking of baffles, the other end looks like worse news. Not only is the inside of the black plastic drawtube mirror-shiny, but there is a very narrow (5mm?) baffle halfway up it. Worse still, the baffle aperture is marred by stringy bits of plastic from the mould.

The focuser baffle stops the scope down to ~20mm and is roughly moulded.

The drawtube is shiny inside (and that baffle again).

In Use

Oh dear! Dim is not the word – this scope would make a summer day look like mid-winter. I had my suspicions and a look at the exit pupil confirms them:  it’s too small to even measure. This scope is stopped down (vignetted) to maybe 20mm. Perhaps worse are the reflections from the drawtube – they are so bad that the view is washed out by them. The 20mm eyepiece doesn’t help – it has a lot of curvature after 60% field width, but the 8mm isn’t too bad.

Perhaps the only encouraging thing is that there is no visible chromatic aberration and the centre field looks pretty sharp. Overall, though, I should have been warned by the cryptic comment ‘may also be used for casual astronomical observing at night’.  On the night-sky, only the Moon is worth looking at and even so it’s too dim to take much magnification. Stars are barely visible.

So what we really have is a 20mm scope with terrible, internal reflections that destroy contrast (this scope is an interesting lesson in why good scopes spend so much effort on ridges and blackening). The Travelscope reminds me of an Edu-toys scope I once bought for my daughter (the clue is in the name).  It looks plausible, but is close to unusable if you’re accustomed to decent scopes.

It’s obvious why the reflections are there, but the vignetting is more complex. A quick diagram on a piece of graph paper and some measurements suggest that the focuser-tube baffle is the biggest problem, but the tube itself intrudes too far into the OTA in normal use and the knife-edge baffle itself would stop the aperture down to 30mm, even without the focuser problems.

 

How To Fix the Travelscope 50

The ancient Greeks had a word for it, hubris - arrogance and aggression - a good word for anyone who takes a hacksaw to a commercial telescope. I have a smattering of university Physics, some optical theory from books and quite a lot of experience with telescope and binoculars; you’re probably much the same. Does that make us into Al Nagler? No. I can comment on Al’s scopes as an informed user, but the idea that I could improve one is ludicrous.

Trouble is, whoever designed (perhaps cobbled together would be a better word) the Travelscope 50 wasn’t Al Nagler. Let’s be blunt: in its delivered state the Travelscope 50 is virtually useless for astronomy. The view is incredibly dim, the contrast-destroying reflections terrible. It might show you the gross features of the Moon, but that is it. The Travelscope, for all its fancy backpack and decent tripod, its shiny metallic paintwork, is basically a toy.

So that’s it, right? End of story - a department-store toy refractor labelled with a once-august brand to fool unsuspecting buyers? Absolutely not. You see, the Travelscope is completely fixable, given a fair degree of hubris, a hacksaw, some sandpaper and matte black paint. Here’s what I did (we’ll get on to how it worked out afterwards):

(Standard disclaimer: this worked for me, but don’t blame me if you try it and it goes wrong!! If you’re a child, please ask your parents before ‘fixing’ your scope!)

1)      I carefully measured the maximum drawtube travel I need for my eyepieces and diagonal.

2)      I then removed the focuser by undoing the three screws and pulled it out of the OTA. 

3)      After that I chopped 5cm off the objective end of the drawtube with a hacksaw and cleaned the cut up with sandpaper. You might chop off a bit more or a bit less, depending on your diagonal and EPs.

4)      First with a large drill bit, then a roll of sandpaper, I opened the baffle in the focuser tube up to <<almost>> the full width, leaving perhaps a half-millimetre ring as a baffle.

5)      I put radial scratches on the inside of the drawtube with coarse sandpaper, washed it out, dried it.

6)      I masked the drawtube up then carefully blew a fine layer of matte black spray paint into both ends of the focuser tube to cover all the shiny (well, now scratched) plastic.

7)      Turning my attention to the other end, I marked the position of the objective cell on the tube with a pencil and removed it by undoing the three screws.

8)      Laying the cell flat, I carefully removed the plastic screw-on lens ring, masked it up and blew matte black onto the inner surface (well away from the lens).

9)      I pushed the baffle out of the metal OTA body and binned it, then blew a fine coating of matte black into the tube to cover the marks made by removing the baffle and the shiny protruding nuts and bolts.

10)   I similarly masked and painted the inside of the push-fit dew shield.

11)   I carefully put it all back together once the paint had dried.

 

Sometimes less is more ... baffle and chopped off section of focuser tube.

So all this butchery completely screwed the poor little scope up, right? Unfortunately (in the sense that it puts the manufacturer in a pretty bad light) not. In fact it transformed the Travelscope into a highly usable small astro refractor and spotting scope. The effective aperture is still stopped down a bit, to perhaps 45mm. But the view is enormously brighter and the contrast-killing reflections are gone. As we’ll see, it’s now a very nice little scope.

So why was the scope like that in the first place? Had they stopped it down to reduce huge chromatic aberration? Not at all, in fact CA is at fast APO levels – just as you would expect from the 1.22D rule. Was the stopping down to prevent gross field curvature and edge distortions? Again, no: with a decent eyepiece, like a TV Plossl, the field is good almost to the edge. Had they reduced the effective aperture to mask very low optical quality in the lens? This is the funniest part – in fact the lens is super sharp and has a fine (really) star-test; focus is very snappy and the focuser quite precise. Have the mods turned it into an astro-only scope? Not a bit of it – it’s a much nicer spotter too and can still focus to less than 5m with a 25mm Plossl.

It now makes a decent spotter, even with the existing accessories:

However, if this were my only scope and I wanted it for astronomy, I would do the following:

1)      Sell the erect image diagonal and buy a mirror diagonal instead. I got a cheap hybrid one for a fiver from a shop clearance; it’s fine.

2)      Sell the eyepieces and barlow and Invest the proceeds in a single, decent Plossl. I have a Meade 4000 25mm (14x) that works very well and is perfect for spotting and star-fields. If you like the Moon and planets, buy a 15mm (24x) or even a 10mm (36x) instead.

 

In Use – Fixed

As a daytime spotter it’s hard to fault, delivering nice sharp views with very modest false colour. I watched a pair of Jackdaws messing about on my neighbour’s chimney in pin-sharp detail this afternoon. In many achromats and binos, the boundary between Jackdaw and sky shows false colour; not with the Travelscope.

At night it’s still only a 50mm, but goes comfortably up to about 40x to show good detail on the Moon, again with little or no false colour (any you see will be from the standard eyepieces – switch to a Plossl and the CA vanishes). Out of interest I tried it with a 3.5mm Type 6 Nagler giving over 100x and way over the scope’s intended limits. Though it showed no more detail, the view of the gibbous Moon was still acceptable.

Jupiter’s NEB and SEB are shown with ease, as are the Galilean moons and a hint of further detail on the disk. Star fields like the Pleiades are jewelled velvet with pinpoint stars the way a small refractor should be and the Orion Nebula shows some detail like it would in good binos. Mars surprised me with a perfect tiny disk, even far from Opposition at just 7” diameter – something binos (or prismatic spotters) won’t show.

All in all, the Travelscope50 is now just how you’d expect it to be (and how it should be) fresh from Celestron. Those nice pics on the box now look realistic:

 

Summary

 

As it comes, the Travelscope 50 is a marketing exercise – throw a few cheap bits into a shiny box and flog it to kids and newbies. An ugly idea and one that Celestron should be ashamed of (sue me if you like and we’ll talk to Trading Standards about whether it’s a 50mm scope!).

Weirdly, if you take a couple of hours, a hacksaw and a deep breath you can turn the Travelscope into a very fine little refractor that weighs less than any other usable astro scope except the MiniBorg.

Scope, mount and diagonal weighing in at under half a kilo – now that’s portable!

In truth I have no idea why the scope was that bad to start with, no idea why they put in a very decent 50mm lens and stop it down to 20mm, no idea why it needed so much focus travel (and so such terrible vignetting), no idea why the focuser tube baffle was so narrow, no idea why the OTA was carefully blackened, but the inside of the drawtube was like a mirror. My suspicion is that the answer lies in the provenance of the focuser. Having designed the objective end they needed a focuser and just grabbed one from the assembly line for the traditional long focus 50mm achromats: in the longer scope the long draw tube and narrow baffle would not have caused vignetting.

Whatever the reasons for its problems, once fixed the Travelscope 50’s only disadvantage in use compared to something like a Borg Mini-50 is the single-layer lens coating and the 0.965 focus tube. Otherwise it’s a super-light weight, very nice little refractor with minimal CA, sharp optics and a good focuser – a perfect travelscope in fact, just like it says on the box.

In standard form, strongly not recommended – it’s almost unusable for astronomy.

With a few mods as described, highly recommended – Sell off the accessories and you’ve got something functionally close to a MiniBorg for the price of a cheap round of drinks.