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Re: Canon G9 Point and Shoot for Sun CN
From: Peter Monta
Date: 2015 Jun 26, 20:02 -0700
From: Peter Monta
Date: 2015 Jun 26, 20:02 -0700
Hi Greg,
The Canon G9 (2009 model) was selected because it is the first (best value) semi compact non DSLR camera which can be operated in manual raw mode.
Looks like CHDK, the third-party firmware with many added features, is available for it too:
http://chdk.wikia.com/wiki/G9
http://chdk.wikia.com/wiki/G9
Using CHDK's raw images might help a little with the fidelity of the Sun's limb---your image looks like it has a few minor JPEG artifacts.
I wonder how stable the plate scale is with these zoom lenses (across time and temperature). I think I might already have some data on that (using a similar camera, Canon's SX160). With star-field images, the astrometry software produces a distortion map, and the plate scale at the center could then be compared across multiple runs.
The extreme ends of the zoom may be more repeatably realized by the camera hardware than any intermediate setting. For the consumer market, a highly-reproducible focal length setting has no particular benefit that I can see, so unfortunately the manufacturers don't have a lot of incentive here. But performance may already be very good with no cause for concern.
The extreme ends of the zoom may be more repeatably realized by the camera hardware than any intermediate setting. For the consumer market, a highly-reproducible focal length setting has no particular benefit that I can see, so unfortunately the manufacturers don't have a lot of incentive here. But performance may already be very good with no cause for concern.
Always good to have lots of reference stars spread over the field, but that's not possible with just Sun and horizon or Sun and mirror-Sun.
Cheers,
Peter
