hi this is Graham from Jenham's Astro if you're new to astronomy it won't be
long before you hear the term equatorial mount
and it's quite easy to get confused about what an equatorial mount is
sometimes they can look like this and other times they can look quite
different like this just depending on the
telescope you buy and the features that it has
so in this video i'm going to explain some of the basics of an equatorial
mounting including why it might be a good thing
to have for astronomy and how you basically set one up and use
it
so what are we going to do well let's take a trip a virtual trip
we're going to go to either the north pole or the south pole
now because i live in the northern hemisphere it's easier to go to the
north pole i'm going to take a telescope with me
i'm going to take this one which is a skywatcher star quest
102 which i recently reviewed and it's the
sort of telescope that a someone who's a beginner or new to
astronomy might choose now the reason i'm actually
taking it other than it being a relatively simple telescope is that it
comes with a mount that can be operated like this which is
an equatorial mount or it can also operate as another mount
which is called altitude and azimuth or "alt/az"
so firstly let's go to the north pole and let's sit down
actually on the north pole now during the night
what we're going to expect is that all of the night sky is going to rotate
about a point that is directly above us now that point
is the north celestial pole and in the northern hemisphere there happens to be
a fairly bright star polaris that's close to that
in this in the southern hemisphere ebony would rotate around
the south celestial pole so we're sat there
in the night time maybe we're having our sandwiches and we're just
watching the world rotate around the night sky rotate around that point
and if we wanted to um to follow a star with our telescope
to look at it we could set up our mount like
this which is really setting up in this
mode called alt as so it's very much like a camera tripod we could just
point the telescope at say the star that we're interested in and during the night
as the earth turned we just have to move the telescope
around because that star that object whether it's a cluster
a star is going to be tracking around an arc around that point directly above
us so so we can understand this because it
seems quite simple to be able to have a mount follow the
motion of an object in the night sky and it is a north pole it's simply
moving one axis of the map so if we go to the the
Jenham's prop department then let's label what's actually
happening here
so the north celestial pole remember is that point
directly above us
and the point about which uh the sky appears to rotate as the earth
rotates now that's all very well but we don't
really want to stay at the north pole very long
so once we've uh finished our our sandwiches
let's go home so let's try to visualize going from the north pole back to um
a latitude where we live so and let's try imagine
walking backwards so we're going to face
we're going to start walking away from the north pole and we're going to
face north so we're basically looking back at
the north pole as we walk backwards now this is just a virtual trip
because obviously it's not a good idea to walk backwards you're going to fall
in a hole but imagine doing it and then what you'd
actually see if you are trying to look at
the night sky as you walk backwards is that the point about which
the night sky is rotating is going to slowly move from being directly above
you it's going to reduce so that the angle
above the horizon of that point where everything is rotating follows the
value of your latitude and if we imagine trying to use the
telescope to in the same way that we were to
follow a star that's moving in the night sky
all we've got to do is re-establish that the telescope mount
points to that axis of rotation because now everything's rotating about a point
that's at some angle not a latitude of degrees above our horizon
so if you look at this mount again and we
imagine setting instead of having it horizontal
or instead of having this at a 90 degree angle we
set that angle to the latitude of where we are
so we can do that we've got a scale on the back of the mount here
which allows us to set our latitude and now
we set it so that it's doing two things it's pointing
to the north so this direction is north
and we've established that we set the angle correctly so that
this axis of rotation is now pointing at polaris
so polaris is now up there and then we find that star again
and all we need to do is move the equatorial mount
in that one dimension just like we did when we're on the north pole
and we'll follow that star so basically in a nutshell
an equatorial mount is simply an altitude azimuth mount
like this which i think we can probably all
like a camera tripod it is simply a mount that allows you to rotate
the axis of rotation so you can point that axis called the polar axis towards
that north or south celestial pole and it allows you to do that so that
it's very easy to follow the stars because you're just moving one control
whether it be a hand control like this slow motion or whether it be a motor
drive it's just much easier than making two adjustments
up and down and along constantly you simply make one
movement and then you follow the object in the night sky
so that should be pretty easy to figure out now i've been doing astronomy for a
long time and if i take my mount outside like this which is quite a sophisticated
mount i don't really need to think twice about
this why well one because i know
what to do i've done it many times but secondly because the design of the mount
tells me what to do it's got a telescope inside
that axis that we know we need to point to the north celestial pole so straight
away i know oh i've got to point that towards polaris and i can find polaris
in the night sky i look north and um and there it is
at around 50 degrees above the horizon so a telescope like this
in a way it's designed so you it's intuitive i can take it outside
it even has a north an "N" marked on the tripod
here so oh okay i'll just point that in the direction north
make sure that i've got the tripod level and then i find polaris in this
telescope once i've done that i turn on the motor
drive and off we go it will turn in right ascension and follow the object
i can even use a database to find objects um
with a few more steps but the issue is on a
simple mount you might not have all those features and it therefore to my
mind it isn't necessarily intuitively obvious how you set it up
so let's come back to this basic mount the star quest we've seen that you can
tilt it and use it in these two modes but there's nothing really if we come
outside we take away our our prop
which way do you point it to point it north you point itself there isn't any
obvious orientation in the same way that there
is when you've got a feature like a polar scope like a telescope there
inside the mount as we saw on the other
equatorial so a couple of things i'd do i would firstly
figure out that you need to have this axis here of the mount the mount the
angle rotates about this axis like that
so therefore to set the latitude you you do that as we've seen but you also
need to point the telescope to the north so
make your own north indicator or south if you're in the south
make it i've got it out of cardboard here you can obviously do a better job
of me put it on a leg of the mount
hopefully you can see that there just about put it on a leg of the mount
that is lined up with that axis that you're rotating about when you're
setting your latitude to carry outside point that direction
north after you've done that and you've levelled the tripod
you'll start to realize again you'll get this this visual
sight that even though you've got no polar telescope
to look through here there is no feature
on this mount for that but you will then realize that
north is or the north celestial pole rather
is going to be in that direction you've basically got to align it roughly you
should be able to see polaris in the northern hemisphere and
essentially you're going to be putting the mount down pointing it north
and then checking roughly that it is then
going to be this part of the mount pointing towards the north star
and after that it's basically going to work if you're not doing astro
photography if you're just doing visual observing that
is a good enough rough way of putting your mount outside and
aligning it just by eye to the north and then you should
basically find that if you put a low power eyepiece into
your telescope find the star or the object you're interested in
then only one axis of adjustment should be needed
to keep that target in the field of view if you find that it's drifting a little
bit you're having to start to apply corrections on the other axis it's
called the declination axis well fine you can just adjust that
second control up now and again or you can just make a slight adjustment
just turn the mount around a little bit and just
find the object again and just see whether it still drifts out the field of
view you can make those sort of adjustments
without any gadgets what i actually do is i take my phone outside of me i've
got a compass app on it probably you have two and as long as
when i'm first putting the telescope outside
it is level and i've adjusted the tripod legs so that it is level
and this end that i've put on here is pointing north
using the the compass app then basically everything is set up i don't need to do
anything smarter than that in order to use my equatorial
mount unless you move around location that angle is fixed you can set it
accurately to your latitude you can do it once and then basically
forget it so hopefully with this video you've seen
that all an equatorial mount is is an altazimuth mount
tilted so that you've maintained this axis of the mount pointing towards
the axis about which the sky will appear to rotate
and there's nothing smarter about it than that
and definitely if you're an a newbie to astronomy then
setting one of these things up does not need to be scary
you do not need to do clever alignment routines you just need to basically
understand that you have a level tripod point the mount north
set your latitude and off you go
so i hope this explanation of an equatorial map has been useful
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