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Old 19-01-2013, 07:47 AM
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gregbradley
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Join Date: Feb 2006
Location: Sydney
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14mm widefield lens on a full frame goes about 30 seconds usually with no trouble. But you will find those stars further away from the suth celestial pole move faster (more angle to cover) than those closer to the celestial pole so you can get in a widefield image stars streaking in some parts of the image and tight in other parts.

The solution is use a widefield lens like 10mm on APS sensors or 14 on full frame, use your 30 seconds, use maxmium ISO before noise becomes too bad (probably around ISO3200) and long exposure noise reduction on. White balance may vary with cameras with Nikon being a little green/yellow and Canon being a little bluish but around 4200K should be close. Save as a RAW that way you can fiddle with the white balance mostly afterwards.

If you want longer than that you need a Vixen Polarie or similar product. Then you can get 2 or 4 minutes if you set it up just right and are within the weight contraints.

50mm in my experience is way too long a focal length to use without tracking then it is awesome. 24mm on full frame I would consider the cutoff point and is pushing it a bit.

The rule should really state - the longest focal length you can use at 30 seconds (anything less than 30 secs ISO3200 is going to be underexposed) is 24mm on full frame or 15 seconds on APS sensors without tracking.

I don't know why camera manufacturers of DSLRs have maximum time of 30 seconds before the stupid bulb setting has to be used. Its like they think noone in their right mind will need more than 30 seconds. Hey - we're being discriminated against!!

Greg.
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