0

Bug: Moon "Does not rise/set/transit" (even at mid latitudes)

Rickbrown2000

February 20, 2017 21:07

None

Follow

I'm using SkySafari 5 Plus, v 5.2.0.0 on iPad and iPhone.  Often when selecting the moon and, then tapping the "info" icon, I find that the Moon's Rise/Transit/Set time may say, "Does not rise", "Does not transit", or "Does not set."

I could understand "Does not Rise" or "Does not Set" if my location were at the Arctic circle or something, but this is in Nebraska. :-)

To duplicate "does not set" condition: set location to Omaha, NE, and set time to Feb. 13, 2016, 7:26:56 PM.

To duplicate "does not transit" condition: set location to Omaha, NE, and set time to Feb. 10, 2017, 7:45:11 PM.

I don't have a "does not rise" example off hand, but I'm sure I've seen that too.

• Facebook
• Twitter
• LinkedIn

4 comments

• 0
  
  wtxnitz February 20, 2017 22:30

  The "does not rise/set/transit" message occurs when the event happens after midnight of your current day. SkySafari works midnight to midnight. If you bump to the next day, you'll see the event.

  In your "does not set" example, 2/13/16 7:26 pm. if you bump one day to the 14th, you'll see it sets at 12:06:58 AM - technically, it didn't set on the 13th, but the 14th - by 7 minutes. Not a bug, just a consequence of having to define the day somehow.

  same with the transit from the 10th. It transits at 12:48:51 am on the 11th. i.e., it does not ever transit on the 10th.

  It seems wrong until you understand what is happening. It's another case of the disjoint between the "normal" world switching at midnight while we night owls blow right through. I've adopted names for astronomy "days" like Montue, Tuewed, etc. when talking with fellow owls.

  One suggestion I've put forward as a possible addition to the "Tonight" list is a rolling list of sun/moon events beginning at the current set time. It's list of sunset, dusk, dawn, sunrise, moonrise, moonset, etc. in chronological order for the next 24 hours. It wraps past midnight and overcomes the "does not -- whatever issue" This would be really handy on the Apple Watch.

   

   

• 0
  
  Bill Tschumy February 21, 2017 04:02

  wtxnitz is correct.  This is not a bug but the way SkySafari has worked since its inception.

• 0
  
  Rickbrown2000 February 21, 2017 05:19

  So, why does this...um..."feature"...rear its ugly head only for the moon, and not for any other celestial objects?  Jupiter, for example, seems to be able to cross the "midnight boundary" just fine, when reporting its rise, transit, and set times.  Example: Omaha, NE, 7:00 PM of Feb. 20, 2017:

  SkySafri reports:

  Jupiter rises: 10:08:30 PM

  Transits: 03:48:20 AM.       <-- the next day!

  Sets: 09:24:02 AM.    <-- ditto

  But no such respect for the moon?  This just doesn't make sense to me.

   

• 0
  
  wtxnitz February 21, 2017 08:37

  I believe it's because Jupiter's motion against the background is much slower than the moon's. So Jupiter's transit listed for the 20 occurred early that am. So if you're at 7 pm on the 20th realtime, that transit for that day has already happened. It's probably possible to skip an event for Jupiter, but it moves so slowly it would be rare.

  Jupiter transit

  2/19 3:51:31 am

  2/20 3:47:28 am

  2/21 3:43:20 am

  in the "does not set" for the moon case

  moon

  2/11 rise 9:12 am set 9:47:25 pm

  2/12 rise 9:48 am set 10:57:50 pm - moon set before midnight 2/12

  2/13 rise 10:26 am set does not set - moon set "skipped" into the next 24 hour slot within the day. Think of it as a technicality.

  2/14 rise 11:06 am set 12:06:58 am - moon set just after midnight of 2/13, so it is officially 2/14, not 2/13

  2/15 rise 11:49 am set 1:14:04 am

  or just looking at consecutive moon sets

  2/11 9:47 pm, 2/12 10:58 pm, 2/14 12:07 am, 2/15 1:14 am

  notice there is about 1 hour and 7 to 10 minutes between set times. So no magical skips, just how they line up within one 24 hour period.

  remember, the moon moves an average of about 13 degrees each night from its orbit around the earth . You can watch it move relative to the stars, about like watching the hour hand.