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I am planning to buy a 2X teleconverter for my Nikon 55–200 mm AF-S f/4–5.5 to capture the moon and other planets. (After connecting the 2X teleconverter the lens will become 110–400 mm and f/8–11)

Somewhere I read that after attaching the teleconverter the lens autofocus works only at f/2.8, and that autofocus will be slower.

  1. Would I able to take moon photos with the 2X teleconverter with manual focus with my Nikon 55–200 mm f/4–5.5 lens?

  2. How much will image quality be reduced by using a 2X teleconverter? Any samples would be appreciated.

  • What specific 2X TC are you considering? – Michael C Mar 21 '16 at 20:47
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    Unless the TC is a relatively capable one you maybe no better off than if you cropped the original image instead. AF speed (or AF itself) is not important in the stated application. You may be better off buying a used older good quality lens + adaptor and using it fully manually. – Russell McMahon Mar 22 '16 at 8:42
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Would I able to take moon photos with the 2X teleconverter with manual focus with my Nikon 55–200 mm f/4–5.5 lens?

Yes, you will be able to take moon photos. As you noted you, you will have to manually focus (which you would want to do anyways when shooting the moon). You will probably be somewhat underwhelmed, though. At 400 mm on a crop sensor body, the angle of view will be 2.3° (vertical) by 3.4° (horizontal). The moon is about 0.5° across. Therefore the image frame is about 4.6 times the moon diameter (vertical) by 7 times moon diamater (horizontal).

Just taking pictures of the moon itself, 400 mm will not be very impressive. However, if you shot the moon low on the horizon, with buildings or landscape features in frame to set it off, that 400 mm can make for some very impressive shots.

You also mentioned "other planets". Without a telescope and T-mount adapter to mount the camera on, planets will only appear as dots.

See also the following questions:

How much will image quality be reduced by using a 2X teleconverter?

It will be reduced quite a bit. Teleconverters work better with longer, fixed focal length lenses, than with shorter zoom lenses. Personally, I wouldn't consider using a teleconverter on anything less than 200 mm.

Compared to a fixed 400 mm lens, the 55—200 mm with 2X teleconverter (at full reach) will suffer primarily from some softness or loss of sharpness, and will be two stops darker. Regardless, you will still have a higher resolution image of the moon than you can currently take.

I would, however, recommend a sturdy tripod and head when shooting. Even though the moon is quite bright, you will want to shoot a shutter speed no slower than 1/400 second (using the inverse-focal-length rule of thumb).

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    "and of course will be a full stop darker. " - two stops, not one. – Euri Pinhollow Mar 21 '16 at 14:26
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    Don't discount cropping with such a combo for the larger planets. I've gotten discs of Jupiter resolved enough to distinguish the five major bands of its atmosphere with a 1.6x crop body + 200mm + 2X TC. Focus has to be perfect and the atmosphere has to be calmer than normal. – Michael C Mar 21 '16 at 20:40
  • Image quality reduction depends on both the particular lens and the particular TC. A very high quality lens with a very high quality TC will not demonstrate much image degradation at all. A crappy lens with a crappy TC will look horrible. Between the two extremes there is a lot of variation in between depending on the combination used. – Michael C Mar 21 '16 at 20:43
  • With stabilized lenses the moon can be comfortably shot handheld at speeds slower than 1/400, even with a 200mm + 2X TC combo with good results. But a tripod is always better than handheld for shooting anything in the night sky. – Michael C Mar 21 '16 at 20:46
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    Thus "... there is a lot of variation in between depending on the combination used." – Michael C Mar 21 '16 at 21:20
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What teleconverter are you planning to use with that lens? TCs can be quite picky about what lenses they work with, optically and even physically. I've got a Sigma 1.4TC which definitely isn't compatible with my other lenses bar the big telephoto I bought it for, other Sigmas included; elements would hit each other if they were mounted together.

That said, I don't think this would likely give the result you're looking for. You need a very long lens to get many pixels on the moon so 400 is still pushing it, and even if this combination physically works I don't reckon the resolution would be anything to write home about.

Is this a one-off or ongoing need? If you could I'd pick up something like Sigma's 120-400mm lens. Not that much more expensive than a TC for much the same reach but I suspect it'd give better results.

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