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05-25-2011, 03:59 PM   #1
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I am interested to hear which Pentax lenses are best for astrophotography.

I have a dedicated astronomy camera which has a large chip (44mm square).

So it needs to be able to cover that without aberrations and have enough backfocus so I can use a digital focuser which is about 22mm thick.

I know 67 lenses work but what about the 645 series or others?


05-26-2011, 01:17 PM   #2
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The 6x7 lenses are designed to provide an image circle that will cover a film frame of 55mm x 70 mm - i.e. more in any dimension than your 44 mm X 44 mm sensor.

The frame of 645 film is 41.5 mm x 56 mm; thus there is a risk that you will get some vignetting with 645 lenses, (has to be small though?).

Lenses for smaller film formats: Youv'e got to have vigetting, I am sure.

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