Nikon 105 is out of focus at infinity.

[Gordon]

Over the past 2 nights I thought I would try the 105 on some astro photos. The old 55 MicroNikkor has always given me excellent results, so I thought a comparison was in order.
I had the D70 mounted on the side of my equatorially driven telescope to track the stars, but even on the LCD screen the mages looked soft, but the full horror was revealed on the laptop screen. I'm going to have to send the lens back for replacement or fixing so it will focus. Its not a problem when used for macro, but if its got an ∞ sign on it, it should damn well focus on infinity!

heres the whole image, reduced which hides the poor focus, of the Southern Cross and Coalsack






here is a crop at 100% from the centre... is so bad I can barely bring myself to look at it! Those doughnut blobs should be small points of light.





not happy Gordon

[tsanglabs]

Do you have a picture using the 55 to compare?

[Gordon]

looking for one now, but heres an 85mm for comparison inthe meantime

http://members.ozemail.com.au/~loomberah/machholz.htm

Gordon

[PiroStitch]

Gordon, how did you manage to take those shots without the noise coming up? I tried to take a few long shutter shots but a lot of noise came up, even at ISO200 :S

[Gordon]

Gordon, how did you manage to take those shots without the noise coming up? I tried to take a few long shutter shots but a lot of noise came up, even at ISO200 :S

I used ISO400 its a 252sec exposure @f/2.8 with noise reduction on.

The main influence is the temperature, the noise is greatly reduced at cooler temps. If the detector is anything like the CCDs we use in astronomy, the noise halves for each 5 or 6degC drop in temp, so photos taken in winter will generally be much less noisy. Other than that, I try to avoid using more than 500ISO.
Are you using NR?

cant find any recent 55mm shots tsanglabs, will try and grab one tonight

Gordon

[digitor]

Is this a newer style AF lens? I've noticed that the AF lenses I have all focus past infinity (as if there's any such thing!) by a considerable margin, I guess to make manufacturing cheaper. I think the "official" reason is to allow for temperature variations! All the Nikkor MF lenses I have are all spot on infinity focus at the end stop, and would have been manually set during manufacture to do so.

Cheers

[Gordon]

Is this a newer style AF lens? I've noticed that the AF lenses I have all focus past infinity (as if there's any such thing!) by a considerable margin, I guess to make manufacturing cheaper. I think the "official" reason is to allow for temperature variations!
Cheers

It is for temp variations, but mostly for longer focal length lenses. Both my old ED (180 f/2.8 and 300 f/4.5 IF have this "feature") The new 105 micro doesnt, so I suspect the infinity point was not set correctly in manufacture.

Gordon

[digitor]

Ah, fair enough - I thought that maybe you had cranked the lens to its end stop, and it had gone past "infinity", hence the fuzzy stars - but it sounds like it doesn't even get that far.

Cheers