by Joe Stieber » Wed Aug 19, 2015 4:58 pm
DavidLeodis wrote:I would be grateful if someone could please inform me what the "2015 Aug 11.544" means on the image? I'm guessing that the .544 means 54.4% of the way through August 11 2015 and thus shortly after 12:30 p.m., but if so that would be daylight unless the decimal time is equivalent to such as Universal Time so Australia would then be dark under its local time. I'm
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Yes, that would be Universal Time as a fraction of the day, a common way of expressing the date/time in comet observing. Therefore, we have...
0.544 x 24 = 13.056 hours
0.056 x 60 = 3.36 minutes
0.360 x 60 = 22 seconds
So, it would be 2015 August 11, 13:03:22 UT. Indeed, it would be mid-day at the Prime Meridian, but half way around the globe in Australia, it would be the middle of the night.
Edit: Calculating the time to the second is probably overly precise, since this is likely a relatively long-duration exposure (unless it marks a specific start or finish time). There were no exposure details for this picture at the photographer's web site. The web site also indicates he lives in the UK, so I'm guessing he was using a remote telescope in Australia (a common technique these days). There were no details about the equipment used.
[quote="DavidLeodis"]I would be grateful if someone could please inform me what the "2015 Aug 11.544" means on the image? I'm guessing that the .544 means 54.4% of the way through August 11 2015 and thus shortly after 12:30 p.m., but if so that would be daylight unless the decimal time is equivalent to such as Universal Time so Australia would then be dark under its local time. I'm :?.[/quote]
Yes, that would be Universal Time as a fraction of the day, a common way of expressing the date/time in comet observing. Therefore, we have...
0.544 x 24 = 13.056 hours
0.056 x 60 = 3.36 minutes
0.360 x 60 = 22 seconds
So, it would be 2015 August 11, 13:03:22 UT. Indeed, it would be mid-day at the Prime Meridian, but half way around the globe in Australia, it would be the middle of the night.
Edit: Calculating the time to the second is probably overly precise, since this is likely a relatively long-duration exposure (unless it marks a specific start or finish time). There were no exposure details for this picture at the photographer's web site. The web site also indicates he lives in the UK, so I'm guessing he was using a remote telescope in Australia (a common technique these days). There were no details about the equipment used.