Vivitar series 1 600mm 1.8 catadioptric nasa lens?

It has the same lens design as a beauty dish or like the lights the dentist uses to beam light into your mouth.

Anyway, I don't expect it to be very high quality. That being said: f/1.8 at 600mm is unreal...

Just a guess, probaly wrong though haha it says 1:8 which isnt that a ratio of magnification or something?

Or maybe f/8 I know all lenses have a one and then the aperature usally

yeah the only ones i found when i searched were all f8

Sweet baby jesus what is that.

if you watch/photograph birds in bright sunlight and dont care about a shitty quality image, then go ahead and get it. if not, you probably have no use for a 600mm (which is 900+ on a crop, which I'll go ahead and assume you have) mirror (shitty quality) max aperture f8 lens

Thats a mirror lens, they use mirrors to achieve longer ranges.

The aperture is shitty, often times they aren't sharp and suffer from a lot of issues with ghosting and haloing because they are using mirrors to bounce light around, rather than optical glass to change the light that enters the lens into the image that hits the sensor.

Also, a lot of those lenses will have vignetting, then a light ring, then the image will get darker again in the center. It's not always apparent, but it will be once you start doing any post.

They are the same design as a lot of consumer telescopes. I wouldn't spend your money on it!

its f/8
zoom in on the photo it says 1:8

Yeah he's got it right. And I'd be willing to bet the guy above me is right too. An f1.8 mirror lens would be obscenely large. Look at how wide the opening is for f8 on todays mirror lenses, and that one too. NASA probably needed one for something cool in space but they couldn't pack/handle a real 800mm or whatever focal length it is.