Big Springs
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Big Springs clear sky chart from 2005-11-06 to 2024-01-13.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	7% 5% 2 4 4 2 4 4 5% 8% 55%	74842
	Night	7% 6% 2 4 4 3 4 4 5% 7% 53%	74904
Transparency	Day	28% 5% 13% 28% 20% 5%	74546
	Night	30% 6% 13% 27% 19% 5%	74722
Seeing	Day	9% 7% 28% 32% 19% 5%	14571
	Night	10% 7% 35% 38% 10%	24661

By Month

Percentage Cloud Cover SW (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	4 6% 3 5% 3 2 4 4 4 7% 58%	1518
	11th to 20th	Day	5% 5% 2 5% 5% 3 4 4 5% 9% 53%	1456
	21st to end	Day	5% 7% 3 5% 4 3 5% 4 5% 8% 51%	1598
February	1st to 10th	Day	6% 7% 4 6% 6% 4 4 5% 5% 7% 46%	1749
	11th to 20th	Day	5% 7% 3 6% 6% 3 5% 5% 5% 6% 50%	1749
	21st to end	Day	5% 8% 3 5% 4 2 4 4 5% 7% 54%	1480
March	1st to 10th	Day	6% 5% 2 4 4 3 3 3 5% 6% 58%	1800
	11th to 20th	Day	8% 6% 3 5% 4 3 4 3 5% 7% 53%	1867
	21st to end	Day	9% 9% 4 6% 5% 2 4 4 6% 7% 44%	2322
April	1st to 10th	Day	10% 6% 2 4 4 3 3 4 5% 7% 53%	2160
	11th to 20th	Day	14% 6% 2 4 4 3 4 5% 5% 8% 46%	2131
	21st to end	Day	11% 5% 3 5% 5% 3 4 5% 5% 8% 47%	2291
May	1st to 10th	Day	13% 5% 2 5% 4 3 4 5% 5% 8% 46%	2340
	11th to 20th	Day	13% 5% 2 5% 5% 3 4 5% 5% 7% 47%	2307
	21st to end	Day	10% 5% 2 5% 5% 3 5% 4 6% 8% 47%	2724
June	1st to 10th	Day	7% 3 1 3 3 2 4 5% 6% 10% 57%	2520
	11th to 20th	Day	6% 3 2 4 4 2 4 5% 5% 8% 57%	2520
	21st to end	Day	3 3 2 2 3 2 4 5% 6% 8% 62%	2520
July	1st to 10th	Day	6% 3 2 3 3 2 4 5% 6% 9% 56%	2520
	11th to 20th	Day	4 2 1 3 3 3 4 5% 6% 9% 61%	2520
	21st to end	Day	5% 3 1 3 4 3 5% 6% 7% 10% 53%	2742
August	1st to 10th	Day	6% 4 2 4 5% 3 5% 6% 8% 10% 49%	2369
	11th to 20th	Day	4 2 1 4 5% 2 4 4 5% 8% 60%	2177
	21st to end	Day	4 4 2 3 3 2 3 4 5% 7% 62%	2376
September	1st to 10th	Day	7% 4 2 2 4 3 3 3 5% 7% 61%	2160
	11th to 20th	Day	7% 3 1 3 2 2 3 3 5% 7% 63%	2016
	21st to end	Day	8% 3 1 3 3 2 2 4 3 7% 63%	1980
October	1st to 10th	Day	12% 5% 1 3 3 2 3 4 4 6% 57%	1980
	11th to 20th	Day	8% 5% 2 4 2 2 3 3 3 6% 63%	1782
	21st to end	Day	9% 6% 2 3 2 2 4 3 4 6% 60%	1782
November	1st to 10th	Day	4 4 2 4 4 2 4 3 6% 7% 60%	1673
	11th to 20th	Day	6% 4 2 4 3 3 3 3 4 5% 64%	1710
	21st to end	Day	6% 6% 3 4 3 2 3 4 5% 7% 58%	1710
December	1st to 10th	Day	4 6% 4 6% 5% 2 3 3 5% 8% 55%	1573
	11th to 20th	Day	5% 4 2 4 5% 3 3 4 6% 8% 57%	1926
	21st to end	Day	9% 11% 3 7% 4 3 3 3 4 6% 47%	2794
January	1st to 10th	Night	4 6% 3 5% 5% 3 4 4 5% 8% 54%	2647
	11th to 20th	Night	5% 5% 2 4 4 3 4 4 5% 7% 56%	2549
	21st to end	Night	5% 8% 4 6% 4 2 4 5% 5% 7% 51%	2772
February	1st to 10th	Night	7% 8% 4 7% 5% 3 4 5% 6% 7% 46%	2210
	11th to 20th	Night	5% 7% 3 7% 6% 3 4 4 6% 8% 47%	2098
	21st to end	Night	5% 7% 2 6% 5% 3 4 5% 4 6% 52%	1776
March	1st to 10th	Night	6% 6% 2 5% 4 3 4 4 4 6% 55%	2160
	11th to 20th	Night	9% 7% 3 4 4 2 4 3 4 6% 55%	2092
	21st to end	Night	9% 9% 3 6% 5% 4 4 5% 6% 7% 42%	2030
April	1st to 10th	Night	11% 7% 3 5% 4 3 4 5% 5% 7% 47%	1800
	11th to 20th	Night	12% 7% 2 5% 5% 2 4 4 5% 7% 47%	1777
	21st to end	Night	13% 6% 3 5% 5% 3 5% 4 6% 7% 44%	1666
May	1st to 10th	Night	11% 6% 3 5% 6% 4 5% 6% 5% 8% 41%	1620
	11th to 20th	Night	15% 6% 2 5% 5% 3 3 4 4 8% 45%	1585
	21st to end	Night	15% 6% 2 5% 5% 3 5% 5% 6% 9% 39%	1552
June	1st to 10th	Night	8% 3 2 4 5% 3 3 6% 6% 9% 51%	1440
	11th to 20th	Night	9% 2 2 5% 4 2 5% 5% 7% 9% 50%	1440
	21st to end	Night	4 3 2 4 6% 4 7% 7% 8% 11% 46%	1440
July	1st to 10th	Night	9% 4 2 3 4 4 5% 6% 7% 10% 45%	1440
	11th to 20th	Night	4 2 2 4 4 3 6% 6% 7% 8% 54%	1440
	21st to end	Night	4 4 2 4 4 3 5% 7% 7% 11% 48%	1576
August	1st to 10th	Night	5% 3 2 5% 6% 3 5% 5% 7% 10% 48%	1567
	11th to 20th	Night	4 3 2 4 4 3 5% 5% 7% 7% 55%	1720
	21st to end	Night	4 3 2 4 3 2 3 4 6% 8% 61%	1980
September	1st to 10th	Night	8% 4 1 3 3 2 4 4 6% 8% 59%	1800
	11th to 20th	Night	7% 3 1 3 3 2 4 5% 6% 8% 58%	1944
	21st to end	Night	7% 4 1 4 4 2 3 3 4 6% 63%	1980
October	1st to 10th	Night	12% 5% 1 4 3 2 3 4 4 7% 56%	1980
	11th to 20th	Night	7% 4 1 3 3 2 2 3 4 6% 64%	2157
	21st to end	Night	9% 5% 2 3 3 2 3 3 4 6% 59%	2574
November	1st to 10th	Night	4 4 2 4 3 2 3 4 5% 7% 62%	2405
	11th to 20th	Night	5% 5% 2 3 4 3 4 4 5% 7% 58%	2470
	21st to end	Night	6% 5% 2 4 5% 3 3 3 4 7% 57%	2470
December	1st to 10th	Night	5% 7% 3 6% 4 2 3 4 4 7% 55%	2603
	11th to 20th	Night	4 5% 2 4 4 3 4 4 5% 7% 57%	3271
	21st to end	Night	12% 10% 3 4 3 2 3 4 5% 7% 48%	4873

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	28% 4 14% 32% 20% 1	1519
	11th to 20th	Day	29% 6% 15% 30% 17% 3	1456
	21st to end	Day	31% 5% 15% 31% 14% 3	1598
February	1st to 10th	Day	38% 5% 16% 23% 14% 4	1749
	11th to 20th	Day	35% 6% 12% 26% 17% 4	1759
	21st to end	Day	30% 5% 13% 27% 19% 5%	1480
March	1st to 10th	Day	27% 5% 13% 28% 22% 5%	1800
	11th to 20th	Day	32% 4 13% 24% 21% 5%	1867
	21st to end	Day	39% 7% 16% 24% 12% 2	2322
April	1st to 10th	Day	31% 5% 14% 30% 16% 4	2160
	11th to 20th	Day	36% 7% 15% 22% 17% 4	2134
	21st to end	Day	35% 5% 13% 27% 18% 2	2291
May	1st to 10th	Day	36% 5% 14% 29% 14% 1	2340
	11th to 20th	Day	36% 6% 18% 27% 11% 1	2311
	21st to end	Day	34% 8% 18% 24% 13% 3	2724
June	1st to 10th	Day	22% 6% 20% 33% 16% 3	2520
	11th to 20th	Day	24% 7% 13% 28% 21% 8%	2520
	21st to end	Day	19% 5% 13% 30% 27% 6%	2520
July	1st to 10th	Day	23% 6% 14% 29% 23% 5%	2451
	11th to 20th	Day	19% 6% 12% 28% 27% 9%	2445
	21st to end	Day	22% 9% 16% 29% 21% 3	2590
August	1st to 10th	Day	26% 10% 18% 27% 14% 6%	2353
	11th to 20th	Day	23% 6% 13% 29% 23% 6%	2177
	21st to end	Day	22% 5% 10% 26% 25% 12%	2376
September	1st to 10th	Day	24% 3 9% 26% 24% 14%	2160
	11th to 20th	Day	21% 5% 10% 26% 30% 9%	2016
	21st to end	Day	23% 4 7% 28% 31% 7%	1980
October	1st to 10th	Day	29% 4 10% 25% 26% 6%	1980
	11th to 20th	Day	25% 4 8% 30% 22% 10%	1782
	21st to end	Day	26% 4 12% 30% 21% 7%	1782
November	1st to 10th	Day	23% 4 15% 29% 23% 7%	1673
	11th to 20th	Day	23% 3 10% 33% 25% 5%	1710
	21st to end	Day	26% 4 11% 29% 24% 5%	1710
December	1st to 10th	Day	30% 4 13% 31% 19% 3	1573
	11th to 20th	Day	25% 4 14% 37% 18% 2	1924
	21st to end	Day	40% 5% 9% 30% 13% 2	2794
January	1st to 10th	Night	29% 6% 15% 30% 19% 2	2647
	11th to 20th	Night	26% 5% 14% 30% 20% 4	2549
	21st to end	Night	32% 5% 15% 30% 16% 2	2772
February	1st to 10th	Night	37% 5% 15% 24% 16% 3	2210
	11th to 20th	Night	35% 6% 14% 29% 14% 3	2098
	21st to end	Night	32% 5% 11% 27% 20% 5%	1776
March	1st to 10th	Night	31% 4 11% 27% 22% 6%	2160
	11th to 20th	Night	32% 5% 12% 23% 24% 5%	2092
	21st to end	Night	39% 7% 14% 24% 13% 2	2030
April	1st to 10th	Night	37% 6% 13% 23% 16% 6%	1800
	11th to 20th	Night	37% 5% 15% 24% 16% 3	1777
	21st to end	Night	39% 6% 12% 26% 15% 2	1666
May	1st to 10th	Night	39% 8% 16% 23% 13% 1	1620
	11th to 20th	Night	38% 7% 17% 26% 10% 1	1586
	21st to end	Night	42% 10% 16% 19% 10% 3	1552
June	1st to 10th	Night	28% 8% 24% 25% 12% 3	1440
	11th to 20th	Night	28% 8% 17% 25% 14% 7%	1440
	21st to end	Night	28% 10% 13% 24% 22% 2	1440
July	1st to 10th	Night	31% 9% 14% 26% 16% 4	1400
	11th to 20th	Night	24% 8% 14% 27% 21% 6%	1392
	21st to end	Night	25% 8% 20% 25% 18% 3	1488
August	1st to 10th	Night	29% 10% 20% 24% 12% 4	1559
	11th to 20th	Night	25% 8% 14% 28% 19% 5%	1720
	21st to end	Night	21% 7% 12% 27% 24% 10%	1980
September	1st to 10th	Night	23% 6% 11% 23% 26% 11%	1800
	11th to 20th	Night	23% 6% 12% 26% 23% 11%	1944
	21st to end	Night	25% 4 7% 28% 28% 8%	1980
October	1st to 10th	Night	30% 4 9% 25% 26% 6%	1980
	11th to 20th	Night	23% 4 9% 30% 24% 11%	2157
	21st to end	Night	27% 5% 13% 23% 24% 9%	2574
November	1st to 10th	Night	22% 5% 12% 29% 24% 8%	2405
	11th to 20th	Night	25% 5% 11% 29% 23% 7%	2470
	21st to end	Night	29% 4 10% 28% 24% 6%	2470
December	1st to 10th	Night	30% 4 13% 30% 19% 4	2603
	11th to 20th	Night	25% 4 12% 36% 20% 2	3272
	21st to end	Night	36% 5% 11% 33% 13% 2	4873

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	7% 6% 37% 32% 13% 4	270
	11th to 20th	Day	12% 9% 36% 37% 5% 1	246
	21st to end	Day	9% 9% 52% 22% 6% 1	264
February	1st to 10th	Day	11% 8% 50% 28% 4	240
	11th to 20th	Day	8% 12% 44% 26% 8% 2	240
	21st to end	Day	11% 14% 42% 26% 7% 1	198
March	1st to 10th	Day	10% 9% 36% 29% 14% 3	240
	11th to 20th	Day	10% 8% 34% 31% 15% 2	240
	21st to end	Day	16% 11% 35% 27% 9% 2	408
April	1st to 10th	Day	10% 15% 35% 29% 10% 1	420
	11th to 20th	Day	17% 17% 33% 23% 9% 1	412
	21st to end	Day	14% 11% 30% 27% 15% 2	551
May	1st to 10th	Day	15% 7% 29% 29% 16% 3	603
	11th to 20th	Day	17% 6% 28% 30% 17% 3	625
	21st to end	Day	14% 8% 29% 27% 17% 5%	679
June	1st to 10th	Day	6% 4 23% 30% 27% 10%	630
	11th to 20th	Day	5% 7% 30% 37% 19% 3	630
	21st to end	Day	5% 4 24% 39% 22% 6%	630
July	1st to 10th	Day	7% 3 16% 42% 25% 6%	621
	11th to 20th	Day	4 2 17% 39% 33% 5%	618
	21st to end	Day	6% 2 15% 38% 31% 8%	684
August	1st to 10th	Day	6% 3 14% 40% 31% 7%	626
	11th to 20th	Day	5% 3 22% 35% 28% 7%	491
	21st to end	Day	4 2 21% 36% 26% 11%	495
September	1st to 10th	Day	7% 4 20% 37% 23% 10%	450
	11th to 20th	Day	4 2 14% 38% 31% 12%	306
	21st to end	Day	12% 4 21% 27% 26% 9%	270
October	1st to 10th	Day	16% 7% 20% 24% 23% 10%	270
	11th to 20th	Day	9% 9% 31% 29% 16% 6%	270
	21st to end	Day	12% 11% 30% 29% 16% 2	297
November	1st to 10th	Day	6% 9% 36% 30% 17% 4	270
	11th to 20th	Day	8% 10% 31% 37% 12% 3	270
	21st to end	Day	10% 6% 36% 31% 14% 3	270
December	1st to 10th	Day	7% 7% 41% 34% 9% 1	270
	11th to 20th	Day	10% 9% 43% 28% 9% 1	270
	21st to end	Day	16% 11% 39% 28% 6% 1	297
January	1st to 10th	Night	7% 9% 42% 32% 10%	950
	11th to 20th	Night	8% 11% 39% 35% 7% 1	911
	21st to end	Night	8% 9% 45% 32% 6%	990
February	1st to 10th	Night	10% 9% 46% 29% 6%	720
	11th to 20th	Night	8% 8% 48% 31% 5%	704
	21st to end	Night	10% 8% 46% 32% 4	592
March	1st to 10th	Night	9% 9% 40% 36% 6%	720
	11th to 20th	Night	11% 7% 42% 32% 8%	652
	21st to end	Night	13% 7% 40% 34% 6%	594
April	1st to 10th	Night	15% 12% 35% 35% 3	540
	11th to 20th	Night	15% 11% 41% 30% 3	533
	21st to end	Night	17% 11% 32% 31% 8%	540
May	1st to 10th	Night	13% 9% 32% 36% 9%	540
	11th to 20th	Night	18% 5% 29% 36% 11%	531
	21st to end	Night	17% 7% 33% 32% 11%	584
June	1st to 10th	Night	9% 5% 30% 40% 16% 1	540
	11th to 20th	Night	11% 6% 37% 36% 9%	540
	21st to end	Night	6% 2 28% 50% 14%	540
July	1st to 10th	Night	9% 2 26% 48% 15%	525
	11th to 20th	Night	4 1 23% 56% 15% 1	522
	21st to end	Night	5% 2 20% 54% 18% 1	591
August	1st to 10th	Night	6% 2 19% 55% 18% 2	537
	11th to 20th	Night	4 2 25% 54% 15%	534
	21st to end	Night	4 2 27% 51% 16%	594
September	1st to 10th	Night	8% 3 30% 46% 13%	540
	11th to 20th	Night	8% 4 27% 44% 16% 1	540
	21st to end	Night	9% 6% 29% 41% 14% 1	540
October	1st to 10th	Night	15% 6% 25% 39% 14% 1	540
	11th to 20th	Night	9% 8% 31% 38% 13% 1	717
	21st to end	Night	12% 8% 32% 37% 10% 1	990
November	1st to 10th	Night	6% 6% 37% 41% 9% 1	925
	11th to 20th	Night	8% 8% 39% 37% 8%	950
	21st to end	Night	8% 7% 33% 41% 10% 1	950
December	1st to 10th	Night	8% 9% 43% 33% 6%	950
	11th to 20th	Night	8% 8% 39% 37% 7%	950
	21st to end	Night	12% 12% 37% 35% 4	1045

Page generated at 2024-01-09 23:25:02. Version ac07

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