A visit to
National Camera Exchange's used lenses page turned up a manual focus 200mm f/4 Olympus Zuiko OM lens. This should work with my ST-8300M, and old reviews suggest that it's got a chance of providing acceptable corner stars even when close to wide open. At a price of $40 it's worth a try. My impression is that the lens sells for $50-60 on the used market, which probably explains why it sat on NatCam's shelf for a long time at $90.
If you get the impression I've got a fixation with lenses, you're right. There have been too many objects that are a bit too large for my 422mm AT65EDQ, and I'm too impatient to make a mosaic for each of them. My telescopes currently give me a nice range of focal lengths:
- 2350mm (C925 @ f/10)
- 1480mm (C925 @ f/6.3)
- 700mm (TV 102 @ f/6.9)
- 422mm (AT65EDQ @ f/6.5)
These very roughly represent steps of two in scale. Extending these to shorter focal lengths with SLR lenses adds:
- 135mm (Tamron OM @ f/5.6)
- 70mm (Canon 17-70mm zoom @ f/5.6)
- 50mm (Zuiko OM lens @ f/1.8)
- 28mm (Tokina @ f/1.8)
The 200 mm lens fills the gap between scopes and lenses, taking the place of an old Tele-Astranar that won't reach focus with my CCD. Granted that these are a bunch of consumer-grade lenses I don't expect miracles from them.
The field of view of a 200mm lens used with an ST-8300 is huge: 5.1 x 3.9 degrees. Here are some objects that fit nicely into that field with a little room around the edges:
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IC 1396, which is more extensive than Sky Tools depicts |
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Lagoon and Trifid Nebulae and vicinity. |
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Rho Ophiuchi Nebula and vicinity |
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Orion Nebula and vicinity |
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M 31 et al. |
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IC 1318 et al. |
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Rosette nebula |
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North America and Pelican Nebulae |
The pictures represent the full field of a 200mm lens combined with an ST-8300 CCD camera as illustrated by
SkyTools3.
There are more objects than these suitable for the 200mm lens, but this will make a good start!
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