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Old 19-10-2010, 10:12 AM
Martin Pugh
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Martin Pugh is offline
Join Date: Nov 2006
Location: Canberra, Australia
Posts: 1,314
Thanks again.

Gary - I think its Marco that uses a Pentax EDIF lens, which are hard to get I understand but absolute pristine for astrophotography. I also understand its impossible to get a Pentax lens to CCD camera adapter, but Pentax Lens to Canon adapters are readily available.

Humi - thanks for that tip - I hadnt realised you could alter focus from within the EOS utility. (I am very new to DSLRs!). That's a great tip - saves running out to the scope at every focus frame.

Doug - So, let me understand clearly. The 70-200 f4L IS USM lens is a much better performer than its f2.8L equivalent?
Questions: Why did you opt for the more expensive IS version - is IS really necessary when the lens is used for astrophotography?

Do DSLR astrophotographers use any sort of filter on the front of the lens, like a UV cut? Clearly, the more expensive ED lens might not need it but perhaps the cheaper ones do.

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