hi this is Graham from Jenham's Astro if you watch my channel you'll know I'm a
big fan of this scope celestron c90 Maksutov you'd also have seen that recently I
picked up a bigger brother the sky watcher skymax 127 in this video I'm
gonna compare the two scopes firstly we're gonna look at my specifications so
you know what you get when you order each of these packages and secondly I'm
going to try to make a comparison of the optical performance okay so let's start
with aperture most important characteristic of a telescope so the
clues in the name skymax 127 127 millimeter 5 inch mirror
and the C 90 90 millimeters which is around about three and a half inches as
we've seen the skymax effective aperture is a bit lower than advertised
operates at around about 120 millimetres so a fair comparison is to say that this
is 120 millimeter scope and this is a 90 millimeter scope terms of focal length
there's 1500 millimeters there's a metre and a half a focal length inside the skyMax
and there were less 1250 for the C90 now the effect of that is that
the skymax design is operating at just under f12 and the celestron at
just under f-14 so this is closer to a classic mak focal ratio and we may
see the effect of that in some of the images when you buy either of these
scopes to come with a range of accessories so the skymax comes with
two eyepieces a 10 millimeter and a 25 millimeter and
I say they're actually not too bad and the c90 comes with a single thirty
two millimeter plossl which is quite a heavier construction than than these two
if that counts for anything is more glass in there. The scopes
both have finder scopes attached so the sky max has a red dot finder which is is
very effective and the c90 has an optical finder which is an eight by
twenty one which really I'd say it's pretty well useless you want to change
that so first thing you gonna want to do with the c90 is to put that in the bin
and put something like a red dot finder onto it or an optical finder of a
decent aperture. both of these scopes have some means of adjusting the angle
of viewing so the 127th comes with a 90 millimeter mirror diagonal pretty
lightweight ok to get you started whereas the c90 has 45 millimeter erecting prism now
these things but this probably reflects the fact that this scope is sold as a
spotting scope as well as an astronomical telescope and really I
wouldn't advise using this very much for astro targets because the prism
arrangements in one of these can introduce some strange artifacts and
generally they're not not usually popular for nighttime viewing so we look
around the back both of these scopes are supplied with the intention that you use
one and a quarter inch accessories not really much point using trying to fit
two inch accessories onto either of these scopes so they've got one point
two five inch visual back and it's basically the same unit but each of the
scopes has a tea thread on the back of the visual back so you could thread for
example digital SLR with a t-ring straight onto the back and get a very
solid fitting that's a good thing perhaps not so good is that both of them
have just got a couple of screws with which to grip your eyepiece
so that there may be an area to improve on if you look to spec up your scope a
little bit in terms of mountings sky max has a vixen dovetail bar nice green
paint finish these days and c90 has the same just a smaller unit a shorter unit
but perfectly adequate what else well as you've seen recently I think skywatcher
bundle a nice padded bag with the 127 which has some pockets
and some places to store your accessories and a nice carry handle you
see there
first c90 comes with a little rucksack
weight now this one tip scales at around 3 kilos
whereas c90 is about 2.2 so neither of these are heavy scopes the sky max feels
quite a lot bigger which is what you expect as it is but still both very grab
and go and then finally price so currently in
the UK the 127 skymax is retailing for around 250 pounds whereas the c90 is
around about 170 pounds so that's the comparison see the two scopes let's see
how they perform optically so how we're going to compare the two scopes
optically well because these are both max etaf scopes and because it doesn't
really get dark at this time of the year I've decided to do a back-to-back test
using planetary target so in this case I've got the C 90 and I put it on an
equatorial mount we're going to use an ASI 120 camera and a 2 x barlow and what
we're going to do is we're going to shoot some video of the planet and then
we're going to immediately swap out one optical tube for the other one so in
this case I'm then going to fit the sky max and we're going to do that a few
times and offline will process the images and we'll try to see if we can
compare the quality of the planetary image so in theory there's very little
changing between the conditions for one telescope to the other even though
obviously atmospheric scene can vary second to second but hopefully it's a
it's a fair test
okay so this is my first attempt of many so I took we've got the 127 video and
below we've got the output from the camera on the celestron c90 so first
thing to note I guess is that the planet is low in the sky from the UK we're not
using any dispersion correctors so this is a fairly fuzzy view but these two
videos taken a few minutes apart and you can get an idea of the sort of size
image scale and maybe some of the detail you can see for the two scopes so at
this point there we can't see the Great Red Spot I don't think that we can see
the equatorial bands one more prominent than the other and we'll process the
images and see if we can make a comparison
okay so I've put the two videos through registax and I've applied the same
stacking and wavelets to both so everything as far as I can control is
the same general comparisons well the image scale of course is is bigger the
detail as far as I'm concerned I've done a few videos on this first first evening
and processed each one and looked at the difference between the images and I say
there really isn't a huge amount of difference there's perhaps a little bit
more detail in the 127 image as perhaps you might expect but it's not hugely
different from that from the smaller Mak okay fast forward a few weeks in between
I've had several attempts to capture both of the planets and the weather and
some trees and my neighbor's house have got in the way so haven't you never get
a direct comparison so this has been the next opportunity and this time we can
see the Great Red Spot so we're seeing a different view of the planet and it's no
slight impart of the sky for me and the sky's a bit darker the backdrop
is a bit darker so perhaps the contrast is a little bit better but these two
videos taken just a few minutes apart I think you can see on the top the 127 is
showing perhaps slightly more detail on the video and we'll see how that
compares when we process both of these videos through registax
and here's the result so for my money I'd say that the 127 image is quite a
lot better than the C90's image here we got more detail in the
equatorial bands we've got better contrast for the Great Red Spot there
are three moons captured in both images I think they are Europa Ganymede and
then Io over on the right but overall this the 127 has captured a better image
than the C 90 but not by a huge amount
okay that's it hopefully the comparison has been useful if perhaps not quite as
conclusive as I was expecting think we've seen that both of the Maks can
produce good images of Jupiter although at the moment the conditions aren't
ideal I'll continue to compare these two scopes and I'll post some more
comparison videos moving on to other types of objects and we'll see how they
compare in the long term so thanks for watching hopefully it's been useful and
if you haven't already please subscribe to the Jenham's Astro channel for more
astro videos I wish you clear skies