hi this is Graham from Jenham's Astro.
I've had a couple of questions about the Celestron c90 telescopes,
both the old and the new models, so I thought I'd do a short Q&A
to answer these points. Firstly Justin you asked me about one of the original C
nineties dating back to the 1980s and 1990s. I have the same model so I'll run
through what the parts that you've got what that one does in case you haven't
seen it you can find a video on my channel which compares the old model
this one and the current model so that might be useful if you want to take a
look at that in addition if you do a Google search you can find Celestron's
original instruction manual for the Celestron 90 which has some good
information about got the accessories and how they will fit together there
were three models of it yours is the telephoto version but in addition it's
clear that the original owner has bought some extra accessories which will work
which would try to explain to you okay so this is very similar to the one
you've picked up I like to say first that some of these telescopes were
pretty good performers and others were real does quantity controls pretty
variable and if you looked online a lot of people have stories about this old
model this celestron c90 saying that they had problems with it having said
that there are some decent units out there and you may as well give it a go
put it together and see if you've got a good one or not
so from your video I can see that you've got the scope and eyepiece a diagonal a
barlow and another thing labeled SR which will come back to you later so
won't go through use the basic setup for how to use the scope so the first thing
you do is to attach it to the tripod which see you've got on this plate at
the bottom of the scope you can see there is a thread which should accept a
bolt from a standard photo tripod so nice and easy
shoot better attach the telescope onto the onto the photo tripod in a
straightforward way make sure it's nice and sturdy
even though it's a lightweight scope obviously you don't explore over
okay once you've done that the next thing you do is to take this little item
which is the star diagonal the purpose of a star diagonal is to bend the light
from the back of the telescope through 90 degrees so what you do is you insert
it into the back of the telescope and the you tighten the bolt just so that
it's secure like that and then finally you insert
the eyepiece so it's the same eyepiece that you've
got which is an 18 millimeter Kellner so Calmar is the design of the eyepiece and
which particular eyepiece you'll get a magnification of about 55 times so what
you do is you set that into diagonal tighten out with the screw and you're
all set to go so the light will come into the telescope be reflected off the
mirror in inside the diagonal and you'll be able to view in a comfortable viewing
angle if you're looking up at the stars or a moon for example so say that the
moon is a great object to start with there's a first target obviously never
the Sun for obvious reasons I'd be very dangerous but the moon is perfect for
this Scopes is quite hoping multiplication and as a bright it's a
bright star be easy to find you'll find that focusing is a bit tricky and you do
it by turning this knob here which it's a bit of an unusual feature of this e90
but give it a go you can get used to the technique that you need in order to
achieve a good focus okay so what about the other bits I borrow for my original
C 19 but I've got a similar unit for the current model which similar to the US or
in your video so what you do for this Barlow is basically a magnifier it it
will magnify by two and a half times unit that you have and what you do is
you insert it you remove the diagonal and the eyepiece first and you insert it
into the back of the telescope and then after that's tightened down in place
then you attach the diagonal and the I thesis before to the
end of that of the end of that Barlow and then with that arrangement should
get the magnification that's around 140 which is probably close to the maximum
you might be able to use and get a clear edge with the telescope like this
looking at the other items I'm a bit unsure if you have another unit called
an extender or not if so then the instruction sheet I mentioned earlier
can explain a little bit about how you can use that and finally you asked about
connecting a camera to telescope now that might be tricky because it's an old
telescope and the size of the mounting at the back is is an old size it's a
smaller size than the current telescopes that you buy today we use nevertheless
you've shown that you've got a unit with an S are marked on on the side of it
which I believe may be the adapter from the original telephoto unit which would
then screw on to the back of the scope and then your camera body if you take
the lens off should screw onto to the end of that adapter so I guess you have
to sort play around a little bit to see if the threads match and whether it
looks like that is an adapter to allow you to put your camera onto the back of
the scope so what I suggest is users go visually first and then go on to trying
to use it with a camera later okay so the second question that had was about
the new model of this s1 c90 which has been in production for about six years
so Tommy you asked about using a replacement finder the finder scope that
comes with the test cope is probably one of its weakest points it's not really
big enough and can make did I make it difficult to locate objects so good news
is that the finder is removable just with this Oh take it off and the
important thing is that the the bracket that accepts the finder is fairly
standard size so this distance but this distance along the base of that bracket
is it's about 30 millimetres so for example
I've got a skywatchers scope and it comes with this finder which is a
straight-through finder with a 50 millimeter lens and has a magnification
of 9 and the bracket is the same size as the one that comes with the with the C
90 so pretty straightforward you can attach this founder to the C 90 and
tighten up and off you go so nice and easy you can get hold of
these forever quite a reasonable price okay so hope
this has been helpful thanks for watching
you