hi this is Graham from Jenham's Astro this video aims to see if you can take decent
astrophotos of deep sky objects using a small scope like this
the celestron c90 now if you watch my channel you'll know that I'm a big fan
of this scope, it's small lightweight and well-made and it's fantastic for
observing the moon and the planets now people often ask me if they can use
scopes like this for deep sky observing as well as for the planets in the moon
my usual answer is sometimes. small maks are fine for viewing deep sky objects if
they're small and bright but large fuzzy targets like distant galaxies or emission
nebulae either won't fit into its field of view or they're just too dim to see
still it got me thinking about whether I could get any decent photos of these
brighter deep sky objects using this scope and a relatively low-tech mount.
ok so this is the setup we've got the c90 I've added a different finder this
is a red dot finder replacing the stock finder which is really too small
alternatives to this might be something like a Telrad finder or a larger
optical finder scope. so for a digital SLR this is a Canon 700d and we're going
to capture the images from this using the free EOS utility software running on
a laptop. the scope is on an equatorial mount with a motor in one axis just in
the right ascension axis now this is a rather nice Vixen mount but in terms of
its size and its payload capacity a cheaper EQ3 that sort of thing you
might have with a decent first telescope is broadly speaking a similar kind of
mount and also there are alternatives now for tracker mounts that are capable
of carrying light weight imaging setups but the idea really is that it's a
relatively basic imaging setup. So what does that mean well it means we're not
going to use goto so we're going to be star hopping to the targets we haven't
got a guidescope attached so simple use of a red dot finder so we're not gonna
have a guidescope we're not gonna have a guide camera and we're not going to use
any guiding apps so it's a pretty simple approach
okay a quick word on object selection so I use the astronomy tools website which
includes a field of view calculator so you can see if an object will fit into
the frame that you have. so Astronomy tools, what you do is you select that
you're gonna do imaging mode in this case and then you can choose both the
telescope and the camera that you're gonna use so for the telescope in this
case the celestron c90 is already in the list of scopes if yours isn't
in here you can type in as a custom scope by putting its focal length and
aperture and then also you see a camera again common DSLRs like the
700d are in the list then you choose your deep sky object so in this case if
we were to choose something like Messier 45 the Pleiades then and we click to
add to the field of view we can see that really it doesn't fit the rectangle is
showing is the field of view we're going to get from the camera with this
particular object so and just to prove it here we go here's the first frame I
took with the C 90 and it pretty well matches that that you get from the
astronomy tool so this sort of large object isn't going to fit well probably
no real surprise if we choose something a little bit smaller here's the dumbbell
then this looks a much better candidate so clearly fits inside the field of view
and in fact if we zoom in so that we can get a closer view this is the predicted
size of the object in the frame and then here you go this is one uncropped frame
from the c90 of Messier 27 and pretty happy with that if we zoom in a little
bit crop the image then all all we've really done here is improve the
brightness and the contrast it's a little bit grainy but overall I'm quite
happy with the quality of this so clearly apparently nebulae like this one
are good targets especially if they're bright and relatively large
here's a globular. Globular's are great visually in
small Maks and Messier 13's come out really well nice tight ball of stars
nice and bright image really good target for this sort of scope
now something a little bit different this is one half of the double cluster
so this just shows you the idea of an open cluster I think probably this
particular image it needs a little bit more time to bring out the colors and
some more of the fainter stars but it gives you an idea of a large extended
object and then back to a planetary Messier 57 this is the uncropped frame
and what a fantastic object this is one frame 60 seconds and if we look a little
bit closer we just crop the frame really happy with that it's caught the central
star really well and nice view of the color as well, so the c90 I
think it's done really well just you can obviously take multiple frames and stack
get a better result but for the simple approach I'm happy with that and then I
mentioned the mission nebula Messier 42 can't really take a bad picture of it
but here you go this is a single frame for 60 seconds and it shows you it does
fit into the field of view obviously a larger top or objects like the
California Nebula won't fit
So how did this work out? Welll it proved that 90 millimeters is enough to take
decent deep sky object images for brighter targets there's no real
surprise that I suppose my normal imaging scope has a smaller aperture. But that scope operates at f5 and costs close toa thousand pounds whereas this one is
close to f-14 and costs under £200. so definitely possible to get some good
results but before you run outside with your small Mak or starter scope
please remember the downsides. long exposure astrophotography will only work
with accurate tracking and that's really where the real effort of Astro
photography comes in finding targets with a high magnification small field of
view scope like this is also quite difficult if you don't have a go to
setup can be frustrating certainly only possible as we've seen but it's it's not
straightforward to go go outside and get some good results without practice still
I think if you've got this kind of kit it's worth giving it a try and maybe if
you're already an imager why not challenge yourself to go back to that
discarded old scope you haven't used for a while and see if you can get some good
frames. okay I hope this video has been useful please hit the red subscribe
button if you'd like to see more Astro videos on my channel thanks for watching