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: http://hea-www.harvard.edu/~fine/Astro/about_flybys.html
Дата изменения: Unknown Дата индексирования: Sun Apr 10 08:42:05 2016 Кодировка: Поисковые слова: п п п п п п п п п п п п |
Some table cells are marked with colors. Generally red cells are items which are the most interesting (for instance, brighter, faster, or newly added). Orange cells are also interesting, but not as much, and yellow cells are slightly interesting.
Here are the descriptions of what each field means:
Magnitude | What it means |
---|---|
4 or less | Naked-eye viewable, even in most urban locations (assuming no clouds of course). EXTREMELY RARE! |
4-6 | Naked-eye viewable, in ideal dark-sky conditions away from cities. EXTREMELY RARE! |
6-10 | Visible in binoculars and small telescopes, with adequate sky conditions. VERY RARE! |
10-14 | Visible in medium-sized (6") telescopes under good conditions. RARE! |
14-18 | Visible in large telescopes (12") with ideal conditions. |
18 and up | Huge telescope required (25" or more) |
That web page does not estimate visual brightness, angular speed, or positions in the sky. To obtain this information, I use the Minor Planet & Comet Ephemeris Service.
I request hourly data, starting the day before the close approach, for three days, and scan for the maximum speed and brightness and when they occur. At this point, I don't go any finer than hourly. If a close approacher has the same speed or brightness for several hours, I will list the first hour in which it is predicted to be at it's maximum speed or brightness.
I use Boston as the location for all these requests. For very close approachers, this can introduce errors relative to other positions on the planet but it should be close enought to get a general idea.
I also request the oribital elements from this service by selecting "MPC 8-line" in the formats for orbital elements section. From this, I obtain the absolute magnitude. I also determine whether or not this is a PHA based on output on this web page.
Note that if the information for a particular approach on MPCs Forthcoming Close Approaches web page has not changed, I do not check the Ephemeris Service for changes.
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