Lens advice

[TiffsAndAstro]

I need a decent lens for my 600d.

I'm looking hopefully less than £300 used uk.

There are some 150 and 180mm apo seem well regarded.

Also maybe up to 300mm focal length.

Canon l lens look nice but pricey for me.

[Elp]

I'd be cautious of some "apo" lenses, I had a sigma apo once and couldn't use it for astro as couldn't focus to infinity, and also it didn't seem that apochromatic. I've had a true apo lens and that was much more expensive.

Your best lens will be a Samyang 135mm F2, believe me, this is the lens to buy and they do crop up used less than your budget, a lot. You need to be patient. Also get the Canon EF version (well you are using a Canon after all but I've seen a lot of Sony ones for sale and suspect people buy them looking for a bargain not being aware that e mount has a much shorter backfocus than ef, even for using them with astro cameras it'll cause a slight issue).

Very budget look at M42 Asahi (Pentax) Takumars, particular the 50mm F1.4, 135mm F2.5 and 200mm F4. There's probably more but I have all three and have used them all for astro, very little distortion at the edges if at all, many modern lenses can't even do this simple thing, and these lenses are from the 1970s or later. Theyre not SY135 sharp (they're also not bad at all) mainly due to they were designed primarily to focus red light, then green and you'll see these colour fringes around your stars until you focus the red down before the green starts (you may need to adjust the infinity stop on the lens to get to the green halo state). Imaging mono narrowband you don't get this issue but you can't do this with your camera (well you sort of can but it's not worth it). Note using a lens from this era has a sort of "look" when doing astro, if you're expecting razer pixel pin sharp look elsewhere.

I know the Canon 200mm L2 USM is also a decent lens (think it's the f2.8) though haven't owned one.

Notice I've recommended fixed primes, I've yet to use a zoom which controls star abberations well that also works at a decent speed. Most lenses do need stopping down however to get your stars smaller and less distorted, some can handle it better than others (IE SY135, see a pattern here?).

 

Edited March 13 by Elp

[PhilB61]

A SW 72ed is just about within your budget, but also come up used quite often for around £200. This would be significantly better than most camera lenses, easier to focus and better colour correction. I have tried with a 400mm Sigma apo prime, Tamron 70-300 zoom  and an expensive Nikon 200-500 zoom. The cheap SW was easier to use and gave much better images than any of the others

[WolfieGlos]

15 minutes ago, PhilB61 said:

A SW 72ed is just about within your budget, but also come up used quite often for around £200. This would be significantly better than most camera lenses, easier to focus and better colour correction. I have tried with a 400mm Sigma apo prime, Tamron 70-300 zoom  and an expensive Nikon 200-500 zoom. The cheap SW was easier to use and gave much better images than any of the others

I would second this, but then I would definitely recommend.....

2 hours ago, Elp said:

Your best lens will be a Samyang 135mm F2, believe me

......this over the SW 72ED any day. Faster, wide field, and much more forgiving on your mount (which you haven't stated). Assuming a simple star tracker like the Star Adventurer, the SY135 at f/2 will be more than capable. The 72ED would, however, need a guided setup. And also suffers from tilt with bad copies.

[Elp]

Think theyve got a SAGTI. But you've said it, since I got my SYs I don't really image with my Z61 that much any more, it's just too slow in comparison even though the focal length of the scope allows for a bit more resolution.

[TiffsAndAstro]

20 hours ago, Elp said:

I'd be cautious of some "apo" lenses, I had a sigma apo once and couldn't use it for astro as couldn't focus to infinity, and also it didn't seem that apochromatic. I've had a true apo lens and that was much more expensive.

Your best lens will be a Samyang 135mm F2, believe me, this is the lens to buy and they do crop up used less than your budget, a lot. You need to be patient. Also get the Canon EF version (well you are using a Canon after all but I've seen a lot of Sony ones for sale and suspect people buy them looking for a bargain not being aware that e mount has a much shorter backfocus than ef, even for using them with astro cameras it'll cause a slight issue).

Very budget look at M42 Asahi (Pentax) Takumars, particular the 50mm F1.4, 135mm F2.5 and 200mm F4. There's probably more but I have all three and have used them all for astro, very little distortion at the edges if at all, many modern lenses can't even do this simple thing, and these lenses are from the 1970s or later. Theyre not SY135 sharp (they're also not bad at all) mainly due to they were designed primarily to focus red light, then green and you'll see these colour fringes around your stars until you focus the red down before the green starts (you may need to adjust the infinity stop on the lens to get to the green halo state). Imaging mono narrowband you don't get this issue but you can't do this with your camera (well you sort of can but it's not worth it). Note using a lens from this era has a sort of "look" when doing astro, if you're expecting razer pixel pin sharp look elsewhere.

I know the Canon 200mm L2 USM is also a decent lens (think it's the f2.8) though haven't owned one.

Notice I've recommended fixed primes, I've yet to use a zoom which controls star abberations well that also works at a decent speed. Most lenses do need stopping down however to get your stars smaller and less distorted, some can handle it better than others (IE SY135, see a pattern here?).

 

Wow ty for all this.

I'm avoiding variable zooms.

I already have a very nice seeming pentax 50mm f1.7.

Mounts are a pain. Which macro did you have that you didn't like?

200mm f2.8l would be super but maybe a tad too expensive and, as a noob, a little too much zoom?

Also, I like the idea of using whatever I do get as a guide scope if i ever get a proper telescope

[TiffsAndAstro]

20 hours ago, Elp said:

I'd be cautious of some "apo" lenses, I had a sigma apo once and couldn't use it for astro as couldn't focus to infinity, and also it didn't seem that apochromatic. I've had a true apo lens and that was much more expensive.

Your best lens will be a Samyang 135mm F2, believe me, this is the lens to buy and they do crop up used less than your budget, a lot. You need to be patient. Also get the Canon EF version (well you are using a Canon after all but I've seen a lot of Sony ones for sale and suspect people buy them looking for a bargain not being aware that e mount has a much shorter backfocus than ef, even for using them with astro cameras it'll cause a slight issue).

Very budget look at M42 Asahi (Pentax) Takumars, particular the 50mm F1.4, 135mm F2.5 and 200mm F4. There's probably more but I have all three and have used them all for astro, very little distortion at the edges if at all, many modern lenses can't even do this simple thing, and these lenses are from the 1970s or later. Theyre not SY135 sharp (they're also not bad at all) mainly due to they were designed primarily to focus red light, then green and you'll see these colour fringes around your stars until you focus the red down before the green starts (you may need to adjust the infinity stop on the lens to get to the green halo state). Imaging mono narrowband you don't get this issue but you can't do this with your camera (well you sort of can but it's not worth it). Note using a lens from this era has a sort of "look" when doing astro, if you're expecting razer pixel pin sharp look elsewhere.

I know the Canon 200mm L2 USM is also a decent lens (think it's the f2.8) though haven't owned one.

Notice I've recommended fixed primes, I've yet to use a zoom which controls star abberations well that also works at a decent speed. Most lenses do need stopping down however to get your stars smaller and less distorted, some can handle it better than others (IE SY135, see a pattern here?).

 

I have vintage 135 2.8 and 200 f3.5 and the stars show a lot of bird shapes. Less so if I stop down, but then it feels like what's point of a fast lens if I have stop it down? I'm guessing that's why we have proper telescopes.

As a noob, I'm keen to delay experiencing the fun of back spacing etc

[TiffsAndAstro]

18 hours ago, PhilB61 said:

A SW 72ed is just about within your budget, but also come up used quite often for around £200. This would be significantly better than most camera lenses, easier to focus and better colour correction. I have tried with a 400mm Sigma apo prime, Tamron 70-300 zoom  and an expensive Nikon 200-500 zoom. The cheap SW was easier to use and gave much better images than any of the others

SW 72ed is on my list but would need a flattener? 200 earth poinds on flo I think

I would like its colour coordination however. Possibly a tad heavy on my sw gti as I'm keen to mess with auto guiding.

[TiffsAndAstro]

17 hours ago, WolfieGlos said:

I would second this, but then I would definitely recommend.....

......this over the SW 72ED any day. Faster, wide field, and much more forgiving on your mount (which you haven't stated). Assuming a simple star tracker like the Star Adventurer, the SY135 at f/2 will be more than capable. The 72ED would, however, need a guided setup. And also suffers from tilt with bad copies.

Sy135 seems too much but will keep looking.

[Gfamily]

4 minutes ago, TiffsAndAstro said:

SW 72ed is on my list but would need a flattener? 200 earth poinds on flo I think

I would like its colour coordination however. Possibly a tad heavy on my sw gti as I'm keen to mess with auto guiding.

FLO have an OVL one for £89 

https://www.firstlightoptics.com/reducersflatteners/ovl-field-flattener.html

[PhilB61]

I used the Stella Mira adjustable flattener approx £100 from FLO with good success, round stars right to the edge of the frame on my D7500

Edited March 14 by PhilB61

[TiffsAndAstro]

100 seems much more do able ty

[Elp]

1 hour ago, TiffsAndAstro said:

I have vintage 135 2.8 and 200 f3.5 and the stars show a lot of bird shapes. Less so if I stop down, but then it feels like what's point of a fast lens if I have stop it down? I'm guessing that's why we have proper telescopes.

As a noob, I'm keen to delay experiencing the fun of back spacing etc

I suggest you read up on lens abberations, the main issue with your current lenses is coma. Common lens issue:

Chromatic abberation,

Coma,

Lateral CA (laca),

Longitudinal CA (loca).

If you look at the mtf graph of a SY135 you'll see why it's so good, even wide open at F2 there's little sharpness loss from centre to edge of frame. The main issue you'll get with the lens is tilt, but you can always crop that out.

To a lesser degree:

Decentred lens elements,

Astigmatism.

Edited March 14 by Elp

[Mr Spock]

I use a Sigma 150mm f2.8, but it is Nikon fit.

MPB have some Canon fit for £184 https://www.mpb.com/en-uk/product/sigma-150mm-f-2-8-ex-apo-dg-macro-hsm-canon-ef-fit

[TiffsAndAstro]

1 hour ago, Elp said:

I suggest you read up on lens abberations, the main issue with your current lenses is coma. Common lens issue:

Chromatic abberation,

Coma,

Lateral CA (laca),

Longitudinal CA (loca).

If you look at the mtf graph of a SY135 you'll see why it's so good, even wide open at F2 there's little sharpness loss from centre to edge of frame. The main issue you'll get with the lens is tilt, but you can always crop that out.

To a lesser degree:

Decentred lens elements,

Astigmatism.

Honestly, I bought a 135 2.8 200 f3.5 500mm f8 and tmount to ef adaptor for £60. I assumed they'd be a bit [removed word] compared to £500 scope  but wanted at least a couple of hours getting an idea of relative focal lengths before committing a bit more. I think they've been worthwhile for that. But I cant un see the birds

stopping them down does help. My dad's old mint 50mm pentax m f1.7 seems fantastic in comparison. 

[Elp]

If you want to see/frame FOV use the telescope simulator on Telescopius website.