Canon 70-210mm f4 tele-lens for beginners?

[Bennet0602]

Ive seen these on ebay for really cheap and i was wondering if they are any good?

Around 200mm is in my opinion a really cool focal lenght and a aperature of f4 is pretty good compared to other cheap telephoto lenses (like my 75-300mm kit) with  f5.6 or 6.3 so i wanted to ask if some of you guys may have experience with these lenses? 

 

The setup i would run with a lens like this would be my unmodified Canon 450d along with a tripod and a tracker.

Edited December 21, 2021 by Bennet0602

[TerryMcK]

Zoom telephoto lenses are not a good idea as they have multiple elements within that can give strange artefacts to stars especially at the edge of the field. A prime lens is a better idea although you will still have to stop down even with those to minimise odd looking stars. A lot of people use the Samyang 135 F2 but that is expensive.

I have a Canon F/1.8 50mm prime lens that fits on my old 400D very well despite it being an EF lens. You can pick those up for under £100 brand new. However that produces ultra wide views of the sky so if you can get a prime in the ballpark of 130mm to 200mm all the better.