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 TV-60 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 TV-60); 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 stop reading 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 ...
At
A Glance
|
Telescope |
Celestron
Travel Scope 50 |
|
Aperture |
50mm |
|
Focal
Length |
360mm |
|
Focal
Ratio |
F7.2 |
|
Length |
310mm |
|
Weight |
200g |
Data from Me.
What’s
in the Box?
Whatever
else I end up saying about the Travel Scope, I can’t deny that 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 the Moon and nebulae and eagles in
close-up; all very attractive.
Design
and Build
So
you get loads of stuff, but what’s the scope like? External build quality looks
good, but as we will see the devil is in the design details.
Optics
The
objective appears to be a 50mm F7.2 achromatic doublet. A 50mm F7.2 falls well
outside the 1.22D rule for achromats – you could expect this scope to show
minimal chromatic aberration and foil-spacing is a good thing compared to a
cemented doublet.
Downsides
are that the lens has minimal, single-layer coatings on the outer surface only
(fully coated, Celestron??) and that the spacers look a bit skewed.
Coatings
are minimal, the objective too reflective.
Scope,
mount and diagonal weighing in at under half a kilo – now that’s portable!
Tube
On
the face of it the Travel Scope 50 looks quite good – a small (12” long) OTA
just wider than the lens, finished in nice metallic grey paint and with a
built-in tripod shoe with ¼-20 thread. The tube looks commendably blackened inside
and I think I can see a knife edge baffle in there.
Focuser
True
the focuser is plastic and 0.965”, but it’s 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.
However,
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).
Accessories
The
accessories are 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.
The
finder, as usual with cheap optical finders, is basically useless. You could
use the existing screw-holes and attach a red dot finder if you need one.
Included
backpack is good, with internal pockets and loops tailored for carrying scopes.
In
Use – Daytime
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.
In
Use – The Night Sky
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.
Fixing
the Travel Scope 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 good 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 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, though other types are a bit worse towards 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 sharp and has a good (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 now makes a
decent spotter, even with the existing accessories and can still focus to less
than 5m with a 25mm Plossl. 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.
3)
Drill the base of
a cheap red dot finder and attach it to the finder mount holes. You can safely
bin the original finder.
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 cynical marketing exercise – throw a few
cheap bits into a shiny box and flog it to kids and newbies. An ugly idea 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 decent little refractor that weighs less than any other
usable astro scope except the MiniBorg.
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 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 Travel Scope 50 is a super-light,
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 quite functional for the price of a cheap round of drinks.