Mirror lens wont focus

[Biscuit761]

Some may remember that I bought a 500mm F8 mirror lens of Ebay recently, have identified a problem with it.

After trying several times to get a good shot of the moon I have concluded that it will not focus on infinity. Its OK on trees in the distance and stuff quite close but just can not get it to focus on the moon, every shot is OOF - is this a general problem with these lenses ?

Not sure of the make as it is out in the car but it is a cheapie for sure.

Bill

[allymac123]

The focus point of the moon is not neccesarily infinity. It varies depending on atmospehric conditions.

Did you try different positions? This would be an excellent use for liveview as otherwise to manual focus on the moon I think you'd really need to continually adjust focus and shoot untill you get it right.

[Biscuit761]

Tried several different settings, as you wind it up it seems to get nearly there then stops just as you think you that with another 2 or 3 degrees of movement you are going to get it, really annoying.

Its as though the focal plane is in the wrong place if you get my drift.

Bill

[Pirate!!]

I was under the impression that when you turned on your camera (with lens attached) it auto focussed to infinity.

Why not go manual for the moon? The only AF mirror lens I know of (for any make) is the Minolta AF Reflex 500 F8 . . all others I believe are MF.

[Biscuit761]

Ah - I wonder if I had turned the focus selector on the camera to MF, wonder if this would make a difference ?

Bill