hi this is Graham from Jenham's Astro in the last few years we've seen the
introduction of camera tracking platforms for astrophotography such as
this one the iOptron sky tracker now the idea of these platforms is they
provide a way into Astro photography for people potentially you've got a camera
like this a digital SLR they want to take pictures of the night sky without
all the expense of getting into purchasing a telescope and a telescope
mount they're portable so you can take them to dark skies and you can get into
Astro photography a lower price level than perhaps in the past where you
needed to buy more kit so platforms like this with cameras combined with lenses
like this which is the samyang 14 millimeter lens a wide-angle lens they
can produce fantastic results but the idea of this video is to see whether we
can do it a little bit cheaper so this lens the the samyang is also saw ways to
Rokinon and it's a very good astrophotography lens but it costs
around 300 pounds which which isn't cheap okay it's probably cost you more
than the tracking platform which the camera is riding on top of so
this video is designed to see if we can make decent Astro photographs with
cheaper lenses so I've picked three lenses that you can buy used for very
little money starting with a well known lens this is the Canon 50 millimeter
lens called the nifty 50 and it's a well known astrophotography lens which you
can pick up used for maybe around 30 35 pounds moving up in focal length you'll
find that auction sites are full of old lenses prime lenses often that is to say
that single focal length lenses and perhaps
they've got mountings that don't fit modern cameras so this is an example of
the lens is a hundred and thirty-five millimeter focal length it is f 2.8 so
it's relatively fast but it had an M 42 thread so we've got
an adapter on here to allow me to attach it to my Canon EOS and that cost me
about 25 pounds and then finally moving up in focal length but further we've got
200 millimeter prime lens so fixed focal length lens this one is f 3.5 so it's
again relatively fast it's got a got an aperture of 50 something millimeters and
it's made by Hoya and picked this one up again it's got an adapter to allow me to
connect it to my eos and picked it up to 26 pounds so we've got the three lenses
50 135 and the 200 millimeter and it doesn't matter to me that we can't use
these in automatic mode because an astrophotography you focus the targets
manually so in theory we don't know much about the optical quality of these
lenses but we can give it a try and see what we can get for our money it's what
process we're gonna follow well first off and find some targets in
this case from though this astronomy magazine and we're gonna line up the
platform with Polaris and set it running now for each lens I've chosen to take a
series of 30-second exposures with the camera set ISO 800 now through trial and
error there seems to be a good balance in order to capture a good amount of
starlight but not to start to fog the lens so I'm gonna take a series of 30
second shots and then we're going to stack them on top of each other using a
program called deep sky stacker and that will then allow us to do any image
manipulation we want to try and get the final image
so other than that we've got the lenses we've got the camera in the platform
you'll notice on top of the camera here I've got a red dot finder now this is
really an optional extra it's a it's a red dot finder that's got hot shoe
adapter underneath now the idea is that that will save us a bit of time just
through experience of doing astro photography with a platform like this
sometimes especially when you get to the longer focal length lenses it can take
you a while to find your target and that's frustrating
it wastes time and really with the addition of a simple accessory like this
you can speed up the process of image location so we're going to use that to
try to get through a few more images in a given time other than that the only
other thing we're gonna use we've got I've got a series of these these are
step-down rings which we may use depending on results for each lens and
they will allow us to adjust the aperture of the lens but we'll we'll
come to those as we make some progress
okay so the first thing to find out is how much sky can we capture with these
three lenses so I'm using a canon 700d which is a camera fitted with a crop
sensor so cameras like this they've got a field of view that's around 1.5 times
smaller than a full-frame camera so when I'm using the camera with the 50
millimeter lens then this is what we can see we can capture all of Orion this is
an image taken 60 frames 30 seconds stacked on top of each other in deep sky
stacker and we can see that that's an area of sky around 25 degrees by 17
degrees it's quite a lot of sky if we move on to the hundred and thirty-five
millimeter lens then this is the region you can see around 9 degrees by 6
degrees and it's enough to capture the area of Orion's belt down to Orion's
sword and then finally for the 200 millimeter lens as you'd expect a
correspondingly smaller area again this time around 6 degrees by 4 degrees so
firstly let's have a look at some of the image captured using the
50 millimeter lens now this is known as the nifty 50 this lens it's largely
plastic construction and it's got a focal ratio of F 1.8 now there is a
faster lens at 1.4 that's available but that's more expensive and the one point
eight is fairly easy to pick up used and it's got a good reputation so let's see
some of the images that I've managed to capture with it so in the summer sky
this is the North American nebula in Cygnus and this frame is six of six
frames of facts fact on top of each other 30 seconds again with the lens
operating at F 2.8 so straight away after that you can see that you get
pretty good star images across the the frame quite happy
with that sort of result and when you've got a large field of view you can
capture in one frame it's quite tempting to build a mosaic so took maybe a dozen
shots here of the Cygnus region and resulted in this mosaic which I'm
pretty pleased with that for what is a very basic lens and you can capture this
sort of image quite quickly moving on to the hundred thirty-five millimeter lens
so this used to be a quite a classic focal length for prime lenses and this
one f 2.8 and it's fitted with an adapter so that the original screw
thread can be mounted onto a bayonet lens bayonet camera like the canon eos
so first off to assess the quality of the lens I have a look at a bright
star so capella and I took a series of images
with different exposures and different focal ratios on the lens now looking
over on the on the Left I'm a little bit dismayed the first time I looked at the
image I could see that it is sort of bloated and distorted so even though
capella is a multiple star system that's not what we're seeing here it's just not
really able to capture a good quality image when we're testing the lens if you
like it's wide open so a bit disappointed with that but as we move
stepping down the lens f4 and f5 point six we get a better star image as you
might expect but we see the introduction of some spikes so these are the
diffraction spikes that I mentioned before that are caused by the Rings the
aperture iris inside the lens so that's the sort of effect that we're going to
get when we use the lenses own internal aperture control so I tried putting a
step-down ring on the front of the lens on the filter ring in place of using the
aperture inside the lens instead of using the iris to to step it down and
there was some small improvement to the image quality but not a huge amount so
moved on took a few quick shots of the Orion Nebula and again you can see quite
a large field of view here gives you an idea of what sort of region we're
talking about and a cropped image from the same same stack frame it's
reasonable quality it's not really anything too special
okay lenses of this focal length are really quite helpful for
conjunctions between planets and deep sky objects or maybe between planets and
the moon and we have one of those recently between the Pleiades and Mars
so I took a few frames with the with the 135 and a reasonable result I guess the
the obvious thing is that Mars has got very prominent diffraction spikes so
moving on to the 200 millimeter lens this is made by Hoya and it's an F 3.5
lens and once again in order to fit it onto the Canon there's an adapter ring
to to convert the original thread to the bayonet of the the modern camera and
once again I went back to capella to see a reference for the star quality and
took a couple of images initially at F five point six on the left here
we can see the diffraction spikes that we saw previously but this time when I
fit a step-down ring on the front of the lens then it removes the spikes quite
effectively and even though I'd say neither image is perfect we still got
quite a lot of red fringing around the star images in either case but certainly
the removal of the diffraction spikes I think is preferable to to using the
Irish inside the lens so took a few frames of that Mars and pleiades
conjunction again you can see this this is without the step-down ring and you
can see that you've got quite a lot of spikes on Mars so that's not really
satisfactory to me maybe looks quite nice on a star cluster but not when
you've got a planet so for the remaining frames I adopted approach of using the
step-down ring instead so here's a couple of familiar galaxies m81 and m82
now this is the whole frame and gives you an idea of the field of view this is
23 frames stacked on top of each other and I think it's quite a pleasing result and
I think the image quality across the frame looks pretty decent
and then a crop from the same frame shows you the two galaxies now yeah
as with all astro images you could take a few more frames and get a
better quality but I think I'm quite happy without that that's that's a
usable image for from a 25-pound lens and they're moving on to another target
the Whirlpool this shows you I suppose how small deep sky objects can be and
perhaps shows the difference between a field of view of a lens like this and
that that you might expect commonly with telescopes but nonetheless the
full-frame captures I think just the left-of-center you can see there there
is a very small galaxy and if we crop that the region of the frame there you
go that's so that is Messier 51 now I think really for the investment in this
lens once we've removed the diffraction spikes I think that is a pretty
reasonable result okay so let's remind what the purpose of this video was you'd
like to get into Astro photography and you've got a digital SLR so we've been
looking at one option where you buy a tracking platform like this one like the
iOptron sky tracker or maybe the sky watcher star adventurer and use the
digital SLR with whatever lenses you've got in order to try getting some good
astro images I think we've seen that that approach is gonna achieve results
most of the time certainly gonna be a lot cheaper than buying a telescope buying
a mount and putting the camera onto the back of that it's also going to be more
forgiving of errors in setting up the telescope and the mount and tracking and
all those other things you have to learn in order to get good astro images so of
the three lenses we've looked at I think it's a two out of three success rate the
200 millimeter lens that cost member about 25 pounds and the 50 millimeter
the nifty 50 of both excellent choices budget choices that will get you quite a
long way into Astro imaging and they allow you to cover a range of targets so
this is quite wide field targets and whereas we've seen some of the deep sky
objects can be capped quite well with a 200 millimeter lens
the other purchase 135 well for me I probably won't use this lens a great
deal more the image quality really isn't up to much and I suppose that part of my
investment has been lost but it wasn't a great deal of money so what else well I
guess it's best to try to get as good a quality lens as you can it is buyers
market for these used lenses because technology moves on and there's lots of
old lenses available on the market and as long as you can try to get as much
information as you can about the lens before you buy it like a look through
the lens if you can see it in person or get some recent photographs published on
if you're buying it remotely on an auction website trying to get the seller
to publish some images that show you the camera working at infinity other than
that we've seen stop down rings can be a cheap solution to avoiding diffraction
spikes and well what else it's definitely gonna be worth giving it a
try there isn't much to lose when you already spending 20 30 40
pounds on a lens definitely it's an alternative if you don't want to make a
further investment which can be a case of several hundred pounds for a
high-quality new lens so hope it's been useful thanks for watching and see you
again