Sharp, affordable 1000mm for D300

[Ted Miller]

I own a Celestron C90 1000mm f11 mirror lens, but it is one of the early model (late 70s), and it is just plain soft, agreeing with comments from others about this lens.

I am trying to figure out what my options are to find a sharp 1000mm lens for my D300 for less than $1500. My #1 criteria is that it be capable of producing SHARP photos on the (rather demanding) D300 sensor, photos I can blow up to 100% magnification and not groan.

My other criteria:

• Used is OK
• 3rd party lenses OK
• MF OK (AF always preferred)
• 500mm + 2x TC (or similar combo) OK
• mirror lens is OK (glass is nicer)
• 3rd party lens OK (e.g. Sigma, Tamron, Tokina)

So far one of the few choices I have tracked down is Nikkor Reflex 1000mm f11, last version (with the rotating collar). I can't afford a Nikon 500mm f4, and don't know if any third party 500/600mm lenses are sharp enough to stand up to the torture of a 2x TC.

To help you see where I am coming from, my primary birding lens at this point is a Nikkor 300mm f4.5 AIS, which is capable of producing sharp photos (when I nail the focus). Maybe what I want is not out there, but I am interested in ideas on where to look. (Prospects of having $4000+ to get the setups many of you have are slim to none in my lifetime.)

[Roger Clark]

Ted,
In lenses, you will have problems with quality unless you spend lots of money (quality costs). If you are willing to do manual focus and use a mirror, a telescope will get you the sharpness you want, and you can
get fast f/ratios and real cheap. Look at 6-inch (diameter) f/8 Newtonian/Dobsonian telescopes, or 8-inch f/5, or 10-inch f/4. A 10-inch f/4 is 1000 mm f/4 and would need a "coma corrector" which is available commercially. You can probably get a 1000 mm f/4 system for under $1,000. The disadvantage is that the system is quite large and bulky to move around. For example, check out "Dobsonian" telescopes, which come with their own mount that is very stable. If your needs are to set up in one spot and image, this is a good option.

A little secret: mirror "lenses" are actually quite good, but for 35mm sized imaging, the mirrors need to be pretty large (6-inch apertures and larger) in order to work well (there are issues with fielding the light cone with smaller apertures). There is a reason why ALL modern astronomical observatory telescopes are mirror designs: they actually work better than lenses and once you get larger, and mirror systems not only perform better but are lighter. And astronomers have the highest standards: near diffraction limited optics over a wide field. Space telescopes require diffraction limited imaging over a large field Mirrors can deliver.

[Ted Miller]

After considerable research and price watching on eBay, I am planning to start looking for a Nikon manual focus 600mm f5.6 lens. This seems to be the one that best meets my criteria (including affordability). With extenders I will have 600mm/5.6, 840mm/f8, 1200 mm/f11.

The other possibility is a Nikon 800mm/f8 lens, but the price on those has been just out of reach.

Any comments on my choice?:confused:

[Dan Brown]

A comment on your choice. I have a Nikor 400mm f3.5 MF that does not focus properly with my D300. It focuses well behind the point of apparent sharp focus. I believe that there is a way to adjust this focus problem but I haven't tackled it yet.

[Ted Miller]

I have a Nikor 400mm f3.5 MF that does not focus properly with my D300. It focuses well behind the point of apparent sharp focus.

Are you trying to use the stock focus screen? I bought the KatzEye screen, and it makes a world of difference. It looks much like the one in my Nikormat, with the split prism center, the microprism ring, and ground glass ring around that. I use my 300mm f4.5 with it, and it works fine. The screen agrees with the focus light (lower left corner of viewfinder), and I get sharp results that way.

I should set up an experiment in my basement sometime and try the eyepiece focus on my Celestron versus using the live-view set up to magnify up to 1:1 pixels on the screen (or on an external HDTV screen via HDMI).

Ted Miller

[Dan Brown]

Hi Ted. I am using the stock focusing screen. I will have to look into this problem! I used this lens with my D200 with no problem though!

[Ted Miller]

I am using the stock focusing screen. ....I used this lens with my D200 with no problem though!

Remember that the D200 is a lot less picky about sharpness because of the lower number of PPI (pixels per inch) on that sensor. The D300 really is very picky about getting things sharp, sort of like shooting Kodachrome or Fujichrome. They showed defects in equipment and technique that 400 ASA print film didn't even notice.:)