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8237Stargazing this season - also moonlight hiking

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  • John Ladd
    Apr 1, 2010
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      Here are some suggested stargazing nights.  You might think of camping above treeline on at least some of these nights.  Obviously, cloud cover could change your plans.

      The Perseid Meteor Shower is on the night of Aug 12 this year - should be about one meteor visible every minute that night and substantial activity in the surrounding nights.  The moon will set about 9:15 pm so this may be your best night of the season.  Pray for no cloud cover that night, but try the nights before and after.

      The Perseids is one of the best meteor showers to observe, producing up to 60 meteors per hour at their peak. This year's shower should peak on the night of August 12 and the morning of the 13th, but you may be able to see some meteors any time from July 23 - August 22. The radiant point for this shower will be in the constellation Perseus. The thin, crescent moon will be out of the way early, setting the stage for a potentially spectacular show. For best viewing, look to the northeast after midnight.

      From http://www.seasky.org/astronomy/astronomy_calendar_2010.html

      [Re last year] This year, Earth passes through the middle of the debris swarm in the early morning hours of August 12, 2009.  That is when you see the most meteors.  However, since the Perseid Meteors are such an old meteor shower, the debris field is so spread out that activity starts to pick up a couple weeks before and lasts until a couple weeks after the peak.  In fact, you get really good meteor shower activity for a couple days, or so, before and after the peak.

      For more, see

      http://astroprofspage.com/archives/2000

      Your other good stargazing will come on nights with a late moonrise (i.e. the moon rises well after the sun sets - see civil twilight times listed below) or on new moons.

      Good moonrise/moonset conditions:

      Almost half the nights are dark because the moon will be up during the day and down for at least the early part of the night
          For example, on June 27 there is a brief stargazing opportunity before moonrise at 9:30 pm - and more stargazing each night
          (about 30 more minutes of stargazing each night) until the full night is dark on July 12

                 June 27 to July 12
      July 28 to Aug 10
      Aug 28 to Sep 10
      Sept 27 to Oct 8

      For a few days each month the Moon will be low in the sky as twilight passes, and it will set (and therefore darken) as the night progresses.  For example, on June 13th you should have a dark sky by 10 pm - on June 16 by midnight

      June 13 to 16
      July 14 to 18
      Aug 13 to Aug 17
      Sep 13 to Sep 16
      Oct 11 to Oct 14

      New moons on

      June 12
      July 11
      Aug 9
      Sept 8
      Oct 7

      So for a day or two before and after those dates, stargazing is good even when the moon is up

      Civil twilight ends at 9:04 pm on June 21st (the longest day of the year) so you can't see stars well until later than that time of the evening.  As the season advances, the night skies will be visible a bit earlier each night (assuming favorable moon conditions) but the effect is very gradual at first.

      June 30 9:04 pm (PDT)
      July 15 8:58 pm
      July 31 8:44 pm
      Aug 15 8:25 pm
      Aug 31 8:00 pm
      Sep 15 7:36 pm
      Sep 30 7:11 pm
      Oct 15 6:49 pm

      Civil twilight is the time when it becomes difficult to see things on the ground from the remaining sunlight.  One formal definition is: "The time after sunset and before sunrise when the Sun is below the horizon but not more than 6° below it. During civil twilight, the sky is still quite bright and only the very brightest stars and satellites can be seen."

      The group's files area has tables of all these times.

      http://groups.yahoo.com/group/johnmuirtrail/files/Planning/

      These tables may also help if you want to know if you'll have enough moonlight to walk above treeline by moonlight.  For example, in the last week of August and the first few days off September, the moon will be up in the hours before sunrise so (if there is no cloud cover) you could probably hike from Guitar Lake to Whitney by moonlight alone.  (Also true for Late July-early Aug and late Sept-early Oct). Might be nice to see sunrise from the top.

      John Curran Ladd
      1616 Castro Street
      San Francisco, CA  94114-3707
      415-648-9279
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