Casual Astronomy, Spaceflight News and Lower California Weather

Geminid Meteors and Aurora

By: LowerCal, 8:08 AM GMT on November 27, 2006

***** Evening December 17 Update

In the words of SpaceWeather.com

THE STORM IS OVER: A coronal mass ejection hit Earth on Dec. 16th, but the glancing impact failed to re-energize geomagnetic activity. The severe magnetic storm of Dec. 14th is truly finished.

Don't set your heart on a bright Geminid meteor straggler either ... but you could get lucky.

***** Afternoon December 16 Update

Sorry, auroral activity had fallen to "Low" and I did not check the forecast. There is a 50% chance of auroral resurgence.

There was another solar flare but it's not possible to determine how much of it is headed toward earth. When the STEREO solar satellites are in place that won't be such a problem. I'll also note that the 14 December event was seen as far south as Arizona - well beyond the expected northern tier of the United States.

For more see SpaceWeather.com

Also there is still a chance of a few bright Geminid stragglers for the next few nights.

***** Morning December 16 Update

No aurora tonight but there is still a chance for a few bright Geminid stragglers for the next few nights.

***** Afternoon December 15 Update

Aurora sightings were reported in Michigan and Massachusetts last night. There is still a chance of sightings along the northern tier of the United States tonight (December 15/16).

Counts for the peak of the Geminid meteor shower were about 100 per hour under dark skies on the night of December 13/14. There is a chance of seeing bright stragglers for the week that follows the peak.

Details on both from Sky&Telescope.

***** Afternoon December 14 Update

If you go outside tonight looking for Geminid stragglers (worthwhile as they tend to be bright) you might get a bonus if you live in the northern US - the northern lights! Aurora Watch

***** Early Morning December 14 Update

I was outside watching from 8:15pm to 12:25am and counted 65 meteors including 2 "fireballs". I've posted details in a comment below.

Considering the clouds and "city glow" I had to deal with it must have been quite a show for those with cloudless dark country skies.

***** December 13 Update

The peak of the Geminid meteor shower is tonight. I wanted to observe last night in order to see how the actual number of Geminid meteors was building this year. Mostly cloudy conditions at sundown persuaded me not too. My mistake -- I see there was a window of clear skies for me from 8-10pm last night.

I won't be making the same mistake for the peak of the shower tonight. In spite of currently marginal conditions (lots of high thin clouds) I'll be setting up the reclining chairs and sleeping bags and checking the cloud cover frequently.

Anyone else who is considering an attempt is more than welcome to leave a comment describing their experience. I hope it's a good one.

***** Original Entry

(Updates in bold.)

The best meteor shower of this year, the Geminids, will put on their best show on the night of 13/14 December over the continental US. After starting two nights earlier their rate will double and then double again as they build to their maximum. The Geminids have the highest usual maximum rate of all the meteor showers.

The highest number of Geminids will be visible in the midnight to 1am time frame when the constellation Gemini is nearly overhead. However unlike most other meteor showers many Geminids will be visible earlier in the evening. Near the northern border of the US they should reach half their maximum rate by 9pm. As far south as Miami the half maximum rate will occur closer to 10pm. It's possible to see a few Geminids even earlier in the evening. Not many meteors will be visible immediately after Gemini clears your horizon but some of the few that do could be spectacular "earthgrazers". "Earthgrazer" is the term used for a meteor that leaves a trail from horizon to horizon. Gemini will rise for the northern US by 6pm and for Miami by 8pm.

Maximizing the number of meteors you see:

Other than the timing already mentioned and lack of clouds the darkness of your sky will be the biggest factor in how many meteors you see. The moon will not rise until after 1am on 14 December and fortunately it won't be a factor until then this year. Escaping the many artificial lights of the city will help you darken your sky the most. A long drive into the country may not be an option but even a short walk or drive to a nearby park or less lighted area will make a difference. Once you arrive at your chosen location face the darkest part of the sky. For many this will be directly overhead and a reclining chair and/or comfortable sleeping bag is mandatory. If you set up on the beach then towards the water will most likely be the darkest part of your sky.

BTW once you are settled in at your chosen location don't use your flashlight. The human eye takes 15 minutes to become well adapted to the dark and sensitivity actually improves for a full 1 1/2 hours in the dark. Good dark adaptation will allow you to see those faint zip zip meteors that will keep your eyes skyward while waiting for a spectacular "fireball" as described in saddlegait's comments. "Fireball" is the term used for a meteor that appears brighter than any of the stars or planets.

Based on actual counts from last year for ideal conditions -- under clear dark country skies with no moonlight and with Gemini nearly overhead (midnight-1am) you can expect to see 100-120 Geminid meteors per hour on the night of 13/14 December this year! I hope you have the opportunity.

Updated: 1:22 AM GMT on December 24, 2006

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Seeing Stars

By: LowerCal, 12:04 AM GMT on November 07, 2006


Snapshot from November 07, 2006

Note those humidities ... OK.

Now note those visibilities ... :)

Those two places get very dark too, when the sun is down and the moon isn't up. You can see a lot of stars from those places .. like someone spilled a bag of sugar on a black velvet table cloth.





Current links - continually updated


*** 5:13 PM PST on November 06, 2006 ***
Of course you can't have clouds and most of the time you don't. It would be nice if the clouds that moved in today were preceding some much needed rain. Those visibilities ... they get even better after a good hard rain!

*** 5:58 PM PST on November 08, 2006 ***
You may be wondering about those large numbers for visibility because you're not used to seeing anything over 10 miles. I asked Hurricane Hunter and WU blogger Randy Bynon about it and here is his excellent answer.

Posted By: LRandyB at 4:43 AM PST on November 07, 2006.
LowerCal.. generally there is no limit to how far a station can report visibility. The prevailing visibility is defined as the greatest distance one can visibily see (you have to have some measured landmarks for accuracy) for at least half the horizon circle. Most weather stations break the 360 degree circle around them into quarters or eighths and pick landmarks such as buildings, towers, tree lines, runways, mountains and so forth in each quarter and determine what the distance is to those markers, usually using maps or GPS. Then they observe the visibility in each direction. Let's say you have 2 miles to the north, 1/2 mile to the east, 1 mile to the south, and 15 miles to the west. The greatest visibility you could report is 2 miles since you have at least two miles over half the circle around you.

The difference between the civilian and military stations near you is most likely not that one is civilian and one is military but rather one has an automated observing station and one is manned. An automated station has sensors to determine most of the observation elements including visibility and they can only sense that visibility so far. You will never see more than 10 statute miles reported from an automated station. And since many, if not most, NWS stations are at airports and the information is used mainly for aviation, there is no need to report more than 10 miles. Anything over 3-5 miles is considered unrestricted for pilots.

Updated: 5:36 AM GMT on December 30, 2006

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