500mm cat lenses

[chupathingie]

Anyone used one? 500mm f6.3 by various brands for under $200. The price sounds ridiculous, but I can understand them being cheaper due to the main elements being 1st surface mirrors.

My guess is that the focus might be a little soft (they’re fairly small for cats), but that’s just a guess… which would make it a no-go for me for astrophotography, but I wanted to see if anyone here has an opinion of their performance.

[caradoc]

I’ve got one. “Phoenix” brand. It’s crap. I picked it up for under $100 for a very specific project, and haven’t touched it since.

[fluffybunny]

Similar to caradoc, got one many moons ago during 35mm film days, could not make it work, thought it was me, tried it again in a digital body and it turns out it wasn’t me.

[lokisbong]

Well I learned 2 new things today. I had never heard of this type of camera lens before and It seems you all have had no luck with them So I won’t think to hard about getting one If the chance pops up.

[fluffybunny]

Well I learned 2 new things today. I had never heard of this type of camera lens before and It seems you all have had no luck with them So I won’t think to hard about getting one If the chance pops up.

Not saying that good ones don’t exist, they might. Never pursued it.
(I got me a Tokina 150-500mm f/5.6 AT-X adapted to Canon and never looked back).

[chupathingie]

Thanks for the input, it seems like the collective view is “poop”. 😆

As far as the lens goes, it’s basically a mini-Celestron or Meade telescope with a focal reducer (I’m only comparing the design). The reason why I was guessing the focus would be soft is because when you make one of these that small, the central obstruction formed by the secondary mirror is such a high percentage of the surface area of the primary that you lose a lot of contrast and increase the diffraction dramatically. All other things being equal, bigger is pretty much always better with optics… as you scale this design up, the % of obstruction by the secondary decreases. This thing’s only got a ~3″ primary. It’s not much of an issue at the 8″ scale, and even less so at 11″ or 16″.

[staplermofo]

I hear nice things about the 800mm.

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