LENS vs. TELESCOPE for Photographing Deep Space
This is an inexpensive lens from TTArtisan. This is a medium priced refractor telescope from William Optics. And this is an Ultra Premium lens from Canon. All of these can be used for deep sky astrophotography, but what's really the difference? That's what we're going to find out tonight. I'll be pointing all three of these at the Flaming Star Nebula in the constellation Auriga in a single night shootout and sharing all my thoughts with you on what I find.
Hey, my name is Nico Carver and I'm a deep sky astrophotographer. This video was the result of a question that I often get which is: why get a small refractor telescope for astrophotography when there are so many telephoto lens choices in the same focal length range of around 200 to 500 mm? And it's a good question and with this video I'm going to try to answer that as best I can using these real world examples here. So to give a bit of a spoiler it's not just about the final image or image quality. There are a lot of practical reasons in terms of focusing, compatibility with other astro gear like mounts, and other astro accessories like filters that make the small refractor desirable if you're really getting serious about astrophotography especially deep sky astrophotography. But camera lenses have their place too and they offer a lot of versatility if you're not all in on Astro and they come in all kinds of different price points so I thought it would be interesting for this video uh with the two lenses to compare a lens on the low end of price the TTArtisan 500 f6.3 with a lens on the high end which is this Canon
100 to 300 RF 2.8 before I jump into the review let me share a couple quick disclosures this TTArtisan 500 f6.3 was sent to me by TTArtisan for review same thing with the William Optics SpaceCat 61. William Optics sent this to me for review. The Canon 100 to 300 f2.8 RF lens I rented from lensrentals.com and that was done with proceeds from my patreon campaign and then finally the Sky-watcher GTi Mount that I used for testing these is on loan from Sky-watcher USA so thank you to all these companies for the opportunity to review their products here on the channel. I really appreciate it and allows me to make cool videos like this. So the first thing I want to
talk about is what goes into an astrophotography kit that's going to work with optics like these 300 mm focal length um you know in the case of these two and 500 mm focal length in the case of the TTArtisan is a long enough focal length in all these cases that for deep sky work meaning taking pictures of nebula galaxies you're going to want a tracking mount you don't want to do this untracked and you're probably also actually going to want an autoguiding system with lower focal lengths like 135mm you could just use the tracking mount or maybe even go untracked but for 300 millimeter and up I would suggest the tracking mount and an autoguider and what is autoguiding? It's this thing right here it's this tiny little telescope a separate telescope from your main one and also a separate camera that goes with the tiny telescope and what this does is it makes the tracking Mount more accurate by looking at the stars and doing a fast refresh like every second it's taking a new picture and if those stars move out of place it sends a small correction to the tracking Mount so the autoguider and the tracking Mount work together to allow you to take long exposures several minutes long without star trailing you get those pinpoint stars and that's what's really needed in astrophotography to reveal these dim objects in deep space like the Flaming star nebula that we're going to be looking at tonight telescopes and Telescope mounts like this Sky-watcher Star Adventurer GTi or these zZWO harmonic drive mounts use different dovetails than is standard with regular photography and what I mean by dovetail it's like a the mounting plate like an Arca-Swiss plate in regular photography the version of that in astrophotography would be a Losmandy plate which is a wider plate or a vixen plate like I'm using here and these Vixen plates are dovetail plates are called that because they were popularized by a Japanese telescope manufacturer called Vixen still around makes mounts and telescopes but mostly for the Japanese market so step one to even get the lenses onto the tracking Mount is we need to buy a universal Vixen dovetail plate and some specialty machine screws called quarter inch cap head hex screws in the right length to attach the lens uh foot here to the dovetail and we have to do all of this just to get it attached to the Mount but we still haven't figured out how to mount the guide scope so my solution to mounting the guide scope with a camera lens is I get an extra long Vixen dovetail the dovetail has to again be long enough that I can underling the guide scope and camera in front of the mount like this so again with a refractor all of this stuff is already thought out for you um I should say an Imaging refractor like this SpaceCat 61 I can just take this out of the package put a few pieces together attach the whole thing to my Mount and it's all ready to go with any camera lens you're going to have to to do a fair amount of ordering other parts and rigging them all up in order to use the lens as a deep sky astro lens now once you get past that hurdle with a lens let's say you want to use a filter like a Duo narrow band filter those are very popular today because they block a lot of light pollution and they let through emission nebula with the refractor you can just screw off one piece here on the back install the 48 mm threaded filter in the spot designed for It screw the piece back on and then the filter is held securely inside the telescope really neat with the camera lens you're going to have to hope that your particular camera has some kind of clip-in filter that you want to use designed for it so if you're a Sony or Nikon shooter you may find there's very little available for your particular camera with the refractor again any kind of astronomical filter is open to you okay the next big thing is focusing and with the spacecat refractor this has a really nice focusing system it's an internal Focus system that William Optics has patented but then it has the traditional uh telescope focusing knob and the 10:1 reduction knob for fine focus control the SpaceCat also comes with a really cool clear Bahtinov mask built right into the lens cap this is an excellent tool for nailing Focus manually by using a defraction pattern that this mask creates with bright stars and if you want to automate your focus with an electronic third party focuser with a lens you need to find a belt and a s probably a 3D printed part that will work for that and it may not really be worth it because once you add a belt you can't rotate the lens easily well with the refractor um it's very easy to add a third party electronic focuser and then rotation for framing purposes is never an issue here because it's here in the back behind the focuser and this manual Rotator is great it even has the markings um so you can know exactly how far you're rotating so I've gone through many of the advantages of the telescope for astrophotography purposes but what about the advantages of the lenses these ones the TTArtisan and the William Optics are very hard to change Focus quickly for fast moving subjects so a big part of what you're paying for with the Canon is excellent Optics like top top-of-the-line Optics but Optics that can also autofocus very fast and reliably across a zoom range and this brings us to another point which is focal length the SpaceCat 61 telescope has a fixed focal length of 300 mm at F 4.9 and that's it there are no other options it's just that and but it does that incredibly well that's what it's designed to do the TTArtisan is a fixed focal length to of 500 mm focal length at f6.3 as the maximum aperture but you can stop down that aperture with an internal Iris to a minimum aperture of F32 that kind of very small aperture is not needed for astrophotography but it does give it more versatility for daytime shooting compared to the refractor which has no internal Iris the Canon has a zoom range of 100 to 300 mm and it can do a maximum aperture of f2.8 across that whole range and a minimum aperture of F22 so for regular daytime shooting that kind of Versatility is what you're really paying for to be able to shoot at you know various focal lengths in any kind of lighting condition bright Sun you know nighttime dusk whenever it it doesn't matter and with image stabilization in the lens means it's ready for anything this is a Swiss army knife of lenses in terms of the situations you could put it in the TTArtisan is less versatile you'd probably only use it on a tripod uh because there's no image stabilization it only has manual focus but you can stop it down so if it's a bright day you need to stop it down you can the refractor is the least versatile for daytime um but that's of course intentional because every design Choice with this telescope was made with astrophotography in mind it's not even designed for visual astronomy this is an astrophotography telescope an astrograph they sometimes call it and I should also mention the SpaceCat definitely has my favorite branding of the bunch um at least the most fun branding I mean look at the front lens cap there and it even came with a space cat toy with a moving tail that my kittens were really entertained by the last thing to talk about here is the actual glass inside these instruments the quality and configuration of the glass inside is important for controlling imperfections that will pop up in your image and a big one to pay attention to a big imperfection that's important for astrophotography is chromatic aberration because when chromatic aberration is well controlled due to high quality glass the stars are going to be all their true color with no color fringing around the bright stars when chromatic aberration isn't as well controlled the Stars will have magenta violet or even multicolored fringing around them and that can be very distracting to the final you know impression of the image if there's a a lot of really bright Violet Halos the TTArtisan uses eight glass elements and two extra low dispersion glass elements we don't know what type those are they don't State the William Optics uses four glass elements in a petal configuration and at least one is extra low dispersion of the FPL-53 synthetic fluorite variety and FPL-53 is considered one of the best if not the best and most expensive when it comes to Ed glass the Canon uses 23 glass elements four are claimed to be ultra low dispersion although they don't specify the glass type one element is a fluorite Crystal lens and they're using actual fluorite uh that's going to be the most difficult to manufacture the most expensive and the rarest way to control chromatic aberration and I believe Canon is the only big company who actually makes fluorite lenses uh so even if you get one in a high-end telescope like a Takahashi that fluorite lens element was probably sourced from Canon I'm interested in all this stuff like glass types and all that but I'm by no means an expert in it for me the proof is in the pudding and that's why with these shootout reviews I always get out under the stars and take pictures with each setup trying to keep the all other factors as similar as possible like same Mount same camera to really give you an idea of what to expect from these different Optics so let's jump onto the computer and review all the images taken okay here are the tech details for this shootout I won't read through these you can pause the video and take a look if interested but basically all the gear is the same I shoot these all in the same night with the object high in the sky trying to equalize things as much as possible I also uh changed the total exposure time for the stacks based on the focal ratio so I can try to sort of equalize the signal to noise ratio in the stacks we're going to first look look at some single exposures with just an auto stretch nothing done to them and really what I'm trying to show here is uh the field coverage and so you can see with actually all three of these uh the field coverage is excellent and that's something I've actually noticed with fullframe lenses is usually there's not too much vignetting with a telephoto lens and that's true of the TTArtisan here and the Canon here so we're not seeing much shadowing of of the corners which is good now with telescopes it's actually rarer to not have some vignetting in the corners but the SpaceCat 61 did a really nice job here with field illumination and I don't really see any vignetting okay next we're going to look at the corners and the center of each one just from a single exposure so here's the cannon you can see that it's quite sharp in the center and then we have some Distortion in the corners it looks like this side is a little bit worse than this side I think that means there's some kind of uh tilt going on perhaps probably with how the camera is connecting to uh the the lens I'm not really that's usually where the issue is um it's a little bit better here with the SpaceCat uh if you look at the worst corner on the Canon it's right it's this one right here and it looks pretty out of focus pretty blurry well we're getting a little bit better correction or actually quite a bit better with the Space Cat uh again probably the worst corner is up here so maybe that suggests that my Canon Ra has a little bit of a sensor tilt issue um but if we look at the other corners and the sides here they're just a lot cleaner a little a lot you know quite a bit less distorted here with the SpaceCat compared to the Canon zoom lens now the TTArtisan actually surprised me because while yes we can see the classic Chromaic Aberration Violet Halos which I expected with a $300 lens in terms of distortion it's really not that bad I mean this is pretty impressive for a $300 lens now you're seeing fewer stars but I want to explain that that's not because it's less sensitive that's because we are more zoomed in with this lens we we're changing the the sampling of the stars um because this is at 500 mm and this one is at three these two are at 300 mm but I think it's still okay to compare things at different uh focal lengths as long as you're aware of what you're looking at now let's move on to the stacks I tried to keep the processing very minimal and similar with each of these Stacks here's the cannon I got the rotation uh quite a bit better with the Space Cat because the rotation is so much easier when you have that little rotation in the back uh than it is you know when the lens is you the only way to rotate is with the ring and it's a little annoying so I didn't I didn't try too hard since I was doing all this testing fairly quickly of course okay and then here's the TTArtisan and you can see again yeah it's more zoomed in uh than these two these are both at 300 mm this one is at 500 mm and you can see with these there's a little bit of a color difference uh I'd say that the the Canon feels a little Bluer um the Space Cat feels very neutral to me and the TTArtisan look looks a little bit yellower Greener and so I I'm thinking this is just down to the glass types all of this kind of stuff though can be normalized you know changed with color correction especially if you have a program like Siril or PixInsight you can use a photometric color calibration I didn't do that here cuz I think the differences are sort of interesting to see and then this is the last comparison and this one I find very interesting because they are so similar in terms of detail and what I'm seeing here among these three it's like Fair really close with the Flaming star nebula now remember this one is the TTArtisan is at 500mm while these ones are at 300mm so it's it's not as sharp as these two lenses because we're we're looking at something that's much more zoomed in and these ones are basically matching it but at a lower focal length however though for a lot of deep Sky objects who cares right you're you're you're wanting that Zoom anyways so it's like why not go for the cheaper lens well why not there are reasons of course um many of them I've already addressed in sort of the advantages with the telescope you know if you're in a light polluted area and you want to use a filter boom right away you're running into an issue with the lenses while with the telescope it already has that place to put in the filter there's all kinds and then the you know place for the guide scope place to connect to the Mount there's all kinds of reasons why uh the telescope for practicality beats this $300 lens but in terms of optical performance there's not a huge difference here now if you are a pixel peeper and what I mean by that is someone who really likes to uh go in and look at the stars up close of course with a lens um that's you know $300 you're going to see some of this Violet fringing on the stars and the longer the integration actually the more time you put into it the worse that gets uh so that's sort of an annoyance and once you get really experienced with astrophotography these Violet Halos really might start to bug you but if you're a beginner I don't see any reason why you might not start with something like the TTArtisan before upgrading maybe later on to something like this refractor which is going to again not maybe blow you away with how much better the image is but when you really look at those details like the stars here like if I look at this star right here even zoomed out I can see this has a really nice natural blue Halo in this image and in this one it's sort of muted I don't really see much color um and the Canon I should say I haven't been talking about as much but it did very well too um and it and it should for a $10,000 lens uh but I guess the Canon I just am including here in case I have any Watchers who are already into like sports and Wildlife and have something like this and they're like well could I use that for astrophotography and of course the answer is a resounding yes it's it's a very impressive lens for astrophotography as well as those other things so to sum up I would say the Canon is your all rounder if you have this lens you can use it for astrophotography but you can also use it for any kinds of other things the space cat is going to be the one you want if you're a dedicated as photographer for all the practical reasons but also because um it actually will give you the best results if you really care about things like you know the star profiles in the corners of a full-frame sensor which if you're doing something like mosaics or something that can actually be pretty important and then the TTArtisan here is the value champ of course it's it's giving excellent results considering how inexpensive the lens is okay and then the last thing I want to show you here is as I was putting this video together and talking to William Optics they let me know that they want to offer a special discount code for viewers of this channel so if you're interested in getting a SpaceCat 61 after seeing this review of it you can head over to William optics.com order it and use the code nebula photos at checkout for $50 off that telescope um and so again that's nebula photos at checkout and I'll have links for all three of these products in the description so thank you very much for watching hope you learned something here and until next time. Clear skies!
2024-03-12 07:15
