Updated: Mar 14, 2022
Everyone on Amazon who reviews Svbony’s 80mm ed refractor seems to love it. So I'm excited to try out the SV503 (thx Tyson) as it could be a a contender for the best beginners telescope for astrophotography.
Rosette Nebula shot in just 2.5 hours with the SV503 and matching 0.8 reducer by a ZWO ASI2600mm camera from my roof in London.
Here is a link to the Svbony 503: https://www.svbony.com/sv503-80ed-f7-doublet-telescope/
Build Quality: The SV503 is a nice light little scope. Its relative compactness has one drawback; with camera attached the telescopes centre of gravity is right about where the focuser knobs are. That means to balance it correctly you need to manoeuvre the dovetail so that is pokes out beneath the focuser. In my opinion the supplied dovetail is a bit too short to do this comfortably. Oh and another thing I can imagine visual nerds will complain that they need an extension tube to reach focus with their fancy eyepieces but that doesn’t bother me bc I’m an imager and I’ll take all the back focus I can get. Its very useful.
Talking of back focus the bespoke reducer that came with the scope (SV193) can work either with the normal 55mm distance between reducer and sensor or if you remove a ring you can get an extra 8mm – which is very exciting for us astrophotgraphy nerds because its gives us more space for filter wheels an OAGs. To sum up the telescope feels good and well suited to astrophotography.
Performance: Is she fast? I like fast scopes because they show all that lovely nebulosity without you having to spend days imaging. At F5.6 (with the 0.8 reducer) the sv503 isn’t super fast but she’s faster than the F6.4 skywatcher evostar 80ed (with its 0.85 reducer)… and as the shot of the Rosette was taken in just 2.5 hrs from my roof in London (albeit with the fancy zwo 2600mm camera) I’d say she’s fast enough.
How flat is the field? Pretty good. Very little aberration at the corner of my APC sized sensor. Full frame sensors do have slightly comet shaped stars at the edge but really nothing to write home about especially when compared to the aberrations you see on most dslr lenses.
(above: Quick test with a my canon 6d full frame sensor camera to test the SV503's field flatness)
Chromatic aberration: Yes she does have some colour fringing. As always its those pesky blues. If I were to take the shot of the Rosette Nebula again I’d probably use a stronger UV/IR cut filter like the ZWO IR cut filter which blocks most of the blue light below 400nm wavelength. *****UPDATE: I will be doing this test again as I've realised my blue filter lets through an unusually large amount of blue light below 400nm wavelength. I think using a 'regular' blue filter will represent this scope's chromatic aberration more accurately ******** and I’ve been spoilt with my refractors because my fancy pants rig boasts a Televue np101 which has almost no chromatic aberration at all. And my little Tak FS60cb has fluorite crystal front element which again boasts very little chromatic aberration. The SV503 definitely does have chromatic aberration. Its not as much as my 80mm achromat (Skywatcher ST80) but when you take photographs you’ll see it. I first noticed the fringing when I focused using the bhatinov mask.
Bhatinov mask channels revealing chromatic abberation (BTW I think this is a cool way of determining how much chromatic aberration a telescope has. If you are on my discord server then please send me your LRGB bhatinov mask images with your scopes so we can build up a data base that will compare the chromatic aberration of different telescopes).
On the left the above pic show the luminance channel (red, green and blue all together) in focus with a bhatinov mask covering the lens. You can tell its in focus because the vertical line cuts the diagonal lines exactly. On my newts the lines are flat but here the lines are a bit wavey due to the fact that the red, blue and green light doesn’t focus at exactly the same spot. I decided to see what the focus looked like for each of the channels individually. I discovered that the blue light wasn’t quite in focus. You can see what the blue light looks like on the right of the picture above. The blue channel’s pattern is much less crisp and the vertical line is not quite splitting the diagonals. This is apparently common in ed doublets although I expect the Skywatcher Evostar 80ed suffers slightly less from chromatic aberation because it’s easier to control chromatic aberration in slower scopes. Anyway I tweaked the focus to make the blue light a bit more in focus (despite the fact that this made the red and green slightly less in focus). Overall I hoped this little trick would give me a better image. And I think it did. The result is that while some of the brighter stars still have a blue halos there are a good few orange stars in there with no blue halo at all. TBH I think the shot looks really good. The nebulosity comes from shooting an hour of Ha(red) and an hour of Oiii (blue/green) with 3nm antilia filters. Narrowband is easy for refractors so I didn’t really expect any problems here and there weren’t.
Conclusion: The SVBony SV503 is a lovely compact and powerful scope. I haven’t tested it on the planets but I’m sure it would do well. Despite being so light I think it is just slightly too big to work on the dinky little Skywatcher AZ GTI mount in eq mode which is a shame but on a slightly larger mount (like the skywatcher eqm-35 which I was trying out here (review to come) this 80mm ed doublet is light enough to stay steady even during some challenging gusts. The SV503 has some chromatic aberration but then apparently all the other refractor scopes in this price range do as well (apart from the ones that are so slow you can’t really do astrophotography with them) and because I haven’t had much experience with the 503’s competitors I’m afraid I can’t say for sure whether this scope is the best scope in its class. Perhaps the best way to judge this scope is to see whether you think the pic that I took with it is any good (just 2.5 hrs remember!)