200 millimeters has long been one of my favorite focal lengths for deep sky astrophotography
the reason is is because some of my favorite images that i've ever taken have been done with my
canon 200 f 2.8 lens and 200 millimeters is wide enough that even with a micro four thirds sensor
you can fit in the very large supernova remnants like the spaghetti nebula that we're seeing here
but it also has enough reach that you can zoom in a bit and look at some really fine details on
these nebulae here we're seeing the north america and pelican nebulae in this video i'm going to be
comparing my old faithful the canon 200 millimeter f 2.8 l lens which retails for 749 us new
and this askar astro camera lens which is an f4 which retails for 729 us dollars and i'll start
my review with a series of star tests that i did before turning to their physical characteristics
because you see they're a bit different and i'll wrap up with their killer features and some of
my final thoughts and my recommendations my one big gripe with this canon lens is the chromatic
aberration which in this lens means red fringing around all the bright stars and you might think
like i did that the fringing should only be a problem with one shot color cameras like dslrs
or what we call one shot color osc astronomy cameras and the reason it would definitely be
a problem with one shot color cameras is because when the different uh wavelengths of light focus
at a different point if you're trying to focus all of the wavelengths at once you're going to get
some kind of uh haloing or or fringing or bloating or whatever you want to call it
but i found that it doesn't matter if i'm using one shot color or mono in any case the spot size
of the red stars would be different than they're supposed to be and you would still get red fringe
on blue stars it's quite annoying anyways this is all just preamble to say i was very excited to
receive this new alternative to the canon called the Askar ACL stands for Astro Camera Lens 200
f4 and Agena Astro which is an awesome online astronomy store i can't recommend them enough
has kindly lent this lens to me for this review so thank you so much Agena Astro i was excited to
compare this lens to my canon because some early reports indicated that this was a well corrected
and maybe better corrected lens which would mean cleaner stars and a better image overall so while
we're on the topic let's go ahead and start with comparing the chromatic aberration on these lenses
here's a crop from a single 30 second shot with the askar and a stock canon t7 dslr and here
is the same crop with the canon stopped down to f4 to make it a fair comparison
but i'll also put up here the canon at f 2.8 because i'm sure there are others out there who
might not like the diffraction spikes and want to see what it looks like wide open and i'd suggest
making your video full screen for the rest of this video to really get what's going on here because
the differences are small but important so you can clearly see the red fringing here on the canon
and really i don't see any chromatic aberration at all on the askar which is really quite impressive
and you can see on the canon it's not the chromatic aberration is not centered on the star
and that's because this crop was taken from the left part of the frame so the fringing
appears more on the right of the stars as that's towards the center of the frame it sort of always
goes in towards the center and you may think that this fringing is no big deal but believe
me once you stack it's more of a problem than in a single frame like you see here okay the next
star comparison i want to make is sharpness and the center of the frame at f4 and i'd say this is
basically a draw they're both sufficiently sharp and well corrected in the center
i really need to get one of those like lens testing targets that they use
indoors because even testing on the same night you'll get atmospheric disturbance
small focusing issues that make testing sort of absolute sharpness pretty difficult but
looking at a bunch of different test photos i took i really think they're in a similar league
in terms of center sharpness so now let's look at the corners for this i'm testing the corners
with a full frame camera i use the Canon EOS Ra because these lenses are advertised to be full
frame lenses and you'll likely get even better performance than this with a smaller sensor
but i think this is already pretty good really they're showing about the same amount of corner
distortion but the canon definitely looks worse throughout the range but that's more due to the
chromatic aberration that we already covered let me just pause to say that copy to copy variation
on any lens is a real thing so just because i'm seeing just a little bit of distortion on these
lenses doesn't mean someone else may get a copy of the lens and it may be not as good there's always
going to be some variability between each copy of the lens but the best i can do for these reviews
is base the comparisons on the lenses i have here at my disposal so now moving on to aperture it is
an advantage that the canon can shoot at f 2.8 which is a full stop brighter than the ascar's
maximum aperture of f4 but it's sort of a mixed bag because the canon stars really do tighten up
quite a bit between f 2.8 and f4 but if you stop down internally with the iris you're going to get
diffraction spikes and so speaking of diffraction spikes from stopping down internally let's compare
between the two because they both have an internal iris but they're somewhat different here's f 5.6
on deneb and personally i much prefer the askar at f 5.6 canon has a more distinct pattern with
sharper spikes while the askar is a little more soft and even and pleasing to me here's at f 4.5
on both and i looked it up and the canon uses eight aperture blades askar uses 10 and if you
count the number of spikes it correlates perfectly to the number of blades in the iris which of
course makes sense as the pattern is a result of the iris not being perfectly round so the number
of sides is reflected in the number of spikes in the pattern now i should mention if you aren't a
fan of these diffraction patterns on bright stars you can invest in pretty inexpensive filter step
down rings and then just use them without a filter to effectively change the aperture of the lens
without using the internal iris and you'll avoid having any sort of diffraction patterns going
this way but still get the benefit of stopping down and i've experimented with this in the
past it works pretty well it's a little bit less convenient but if you do want to go this route
you'd be stepping down from 72 millimeters with the cannon or 82 millimeters with the askar
okay now let's talk about these lenses physically and how well they work with accessories so the
askar is definitely a better value out of the box in terms of accessories as brand new right now
the askar is 20 cheaper but it already comes with this really nice rotating collar a vixen plate on
the bottom for easy mounting and a guide scope mounting shoe on the top and all of this stuff
is really solid well machined parts the lens also includes this metal lens hood and all this metal
makes it substantially heavier than the canon it's around two kilograms or four and a half pounds
while the canon is a lot lighter if you make it a fair comparison and add a third-party
lens collar like i did here and a vixen plate and a guide scope clamp like this um
that brings the cannon up to one and a half kilograms or three and a half pounds so still
quite a bit lighter than the askar but you have to add those things on and i should say that those
these three parts the collar the vixen plate and the clamp those could easily add a hundred
dollars to the cost of the lens so askar is definitely winning in the price comparison
another cool thing about the askar astro camera lens is that it has three rings on the barrel iris
coarse focusing and fine focusing and all three rings have locks so you can lock down after
you've found focus or after you've set your aperture and don't have to worry about them
shifting so that's a really great addition and makes a lot of sense for an astro camera lens
okay now let's move on to some of the biggest differentiators between these two lenses or their
killer features i'd say the askar's killer feature is that you can take off this back part here
and screw a two inch or 48 millimeter astro filter right into the imaging train and then
use it with any camera dslr astronomy camera doesn't matter with the canon if you you know
put this lens on a canon dslr the only way of getting a filter in would be a clip-in filter
or putting the two-inch filter in the front and using step-down rings but i don't recommend that
because it would add a lot of vignetting to this lens the askar is a completely manual lens it's a
manually controlled iris manually controlled focus it does have the you know the separate rings for
coarse and fine focus which i mentioned earlier but the canon's killer feature is autofocus
which might be important to people for a number of reasons so let me explain why
one the autofocus makes it a lot more useful as a daytime lens because then you can
do things like catch wildlife and all that kind of thing and take portraits and take advantage
of whatever the camera's autofocus system is including like eye autofocus and things like that
so for daytime this one wins and it might be worth that that extra cost of this over the askar
the second reason is if you're using this lens with a modern canon camera like my EOS Ra
i can actually just touch the screen with a bright star centered and it usually can
auto focus on the stars at a dark site when there's enough contrast this can be pretty handy
now of course if you do focus this way as soon as you get focused you'll want to switch
it back to manual focus so that the system doesn't try to keep auto focusing every shot
because that's going to waste a lot of time and will usually fail eventually
third reason for autofocus on a lens like this is i have this really cool accessory this is an ascom
compliant focus and iris controller for canon ef lenses by a company called astro mechanics and
it works with any canon lens with autofocus but you do have to get it for a particular dedicated
astronomy camera so you get the back focus right and the guy but the guy who makes these he makes a
bunch of different varieties for different camera systems so i have this one that works with my zwo
asi 1600 mm and i love this because i can use it with basically any ef uh autofocus lens that i own
and it can run the automated focus routine in software which is going to nail focus
much better and more consistently then i can do it by hand with just moving the focus ring
on the barrel here and i can also leave it for hours and let the software automatically check
focus every so often which is great on nights where the temperature is changing pretty rapidly
now even this advantage for the canon is only a limited advantage as deep sky dad already has a 3d
printed belt and pulley system for the askar 200 that comes in right around the same price as the
astro mechanics and also would give you autofocus it's not quite as versatile as the astromechanics
because it just works with this lens well this one would work with any canon ef lens but it's still
really great that it exists and it does level the playing field quite a bit between the two
so where does that leave us well if the wider brighter aperture of f 2.8 is important to you
or you like the focusing options you know the autofocus you want to use it as a normal
daytime canon lens with your canon camera then this one might be the better choice
but if you're mostly going to be using the lens for astronomy i'd really highly recommend the
ascar over the canon at least in my case it had much better star performance it has better
build quality and it's a better value because it includes you know this cool lens collar
the vixen plate the the guide scope shoe and it also is more versatile because one thing
i haven't mentioned yet is that it can be used with basically any camera system
because what it has is it's like a telescope on the back it just has 48 millimeter threads and
it has 55 millimeter back focus so just like any telescope you can adapt almost any dslr mirrorless
astronomy camera to this lens and as i mentioned now with the deep sky dad kit you can even have
automated focusing with this lens using a belt and pulley system and because i'm sure i'm going
to get comments about comparing the askar to the william optics redcat i don't have a red cat to
test there are differences of course the redcat is a fixed aperture it doesn't have an internal
iris and it's a 250 millimeter f 4.9 well this is a 200 millimeter f4 so they're somewhat different
but i understand that they're close enough that i could see them as competitors and maybe someone's
already compared them let me know in the comments if you've found a comparison like that i think
that's enough for this video i want to thank Agena astro again for loaning me the Askar lens
for review full disclosure i have now bought this copy from Agena because i want to keep it
mostly because even though i have the cannon um i was just really impressed by
the star performance and i want to shoot some broadband stuff like the witch's head again
uh with this and see if i can get much better stars than my previous attempts
well thanks for watching this has been Nico Carver nebulaphotos.com Clear Skies!
you