 200mm has long been one of my favorite focal lengths for deep sky astrophotography. The reason is because some of my favorite images that I've ever taken have been done with my Canon 200 f2.8 lens. And 200mm 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 200mm f2.8 L lens, which retails for $749 US new, and this Ascar 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 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 haloing 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 Ascar ACL stands for Astro Camera Lens 200 f4. And a Gina 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, Gina 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 Ascar 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 f2.8 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 Ascar, 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 the disfringing 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 in 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 ESRA 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 f2.8 which is a full stop brighter than the Ascars maximum aperture of f4. But it's sort of a mixed bag because the Canon stars really do tighten up quite a bit between f2.8 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 f5.6 on Dineb and personally I much prefer the Ascar at f5.6. Canon has a more distinct pattern with sharper spikes while the Ascar is a lot more soft and even and pleasing to me. Here's at f4.5 on both and I looked it up and the Canon uses 8 aperture blades, Ascar 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 72mm with the Canon or 82mm with the Ascar. Ok now let's talk about these lenses physically and how well they work with accessories. So the Ascar is definitely a better value out of the box in terms of accessories as brand new right now the Ascar is 20 dollars 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 of this metal makes it substantially heavier than the Canon. It's around 2 kilograms or 4 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 that brings the Canon up to one and a half kilograms or three and a half pounds. So still quite a bit lighter than the Ascar but you have to add those things on and I should say that 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 Ascar is definitely winning in the price comparison. Another cool thing about the Ascar 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 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 Ascar's killer feature is that you can take off this back part here and screw a 2 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 put this lens on a Canon DSLR the only way of getting a filter in would be a clip-in filter or putting the 2 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 Ascar is a completely manual lens. It's a manually controlled iris manually controlled focus. It does have 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. For daytime this one wins and it might be worth that extra cost of this over the Ascar. 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 autofocus 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 focus you'll want to switch it back to manual focus so that the system doesn't try to keep autofocusing 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 Astromechanics 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 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 1600mm and I love this because I can use it with basically any EF 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 than 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 Ascar 200 that comes in right around the same price as the Astromechanics 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 f2.8 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 Ascar to the William optics red cat I don't have a red cat to test there are differences of course the red cat is a fixed aperture it doesn't have an internal iris and it's a 250 millimeter f 4.9 while 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 a Gina Astro again for loaning me the Ascar lens for review full disclosure I have now bought this copy from a Gina because I want to keep it mostly because even though I have the Canon I was just really impressed by the star performance and I want to shoot some broadband stuff like the witch's head again 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