Can anyone recommend the cheapest option lens wise to shoot the moon.
It can be even manual lens for canon.
Always wanted to try but 70-200 too short even on 1.6 crop.
Here's a quick shot of a half moon in the daytime, not the best time for detail with the low contrast and blue hazing, taken with my Minolta 80-200mm (an old film era lens) @ 200mm on my 1.5 crop 24MP Sony A77, cropped down to just show the moon. For comparison I also shot it with my Tamron 16-300mm @ 300mm, a very wide range zoom which has sacrificed image quality for zoom range, and again with my Sony 500mm reflex lens. Night time shots in a good clear sky would supply better detail. However, you can see some crater detail at 200mm, a bit more at 300mm, and more again at 500mm. I was rather surprised to find this clear ordering, since the 80-200mm is a lens particularly revered for its sharpness and image quality, the 16-300mm is a very wide range general purpose zoom which has sacrificed image quality for a very wide zoom range, and the 500mm reflex lenses are "well known" to be much inferior in image quality to refracting prime lenses.
However, all these shots were taken at f8, since it was as usual a very bright sunny day on the moon. An f8 aperture reduces the differences in image quality between lenses. When cropping down as severely as is needed to fill the frame with the moon, which subtends about half a degree of arc, clearly focal length is the king. When shooting through such large distances of atmosphere the quality of the atmosphere, the "seeing" as astronomers refer to it, is the biggest killer of sharp detail. If you have a tracking telescope mount you can take long exposures to average out the atmospheric distortions. If on a fixed tripod you can stack multiple images to achieve the same effect.
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Based on this comparison I'm tempted to suggest that the cheapest option for good detailed moon shots will be the longest focal length you can get, with image quality a rather secondary consideration. You don't need a wide aperture since it's very brightly sunny on the moon - f8 is quite good enough. Good focus is however VERY critical, which ideally means manual focusing with the best focusing aids you can get.