Economy
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Economy clear sky chart from 2005-11-06 to 2024-12-09.

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	20% 11% 4 8% 5% 4 4 4 5% 6% 29%	102506
	Night	21% 11% 4 8% 5% 4 4 3 5% 6% 28%	97345
Transparency	Day	30% 48% 7% 10% 5%	106098
	Night	30% 48% 7% 10% 4	101842
Seeing	Day	25% 18% 31% 20% 6% 1	17511
	Night	25% 17% 30% 22% 5%	24793

By Month

Percentage Cloud Cover NE (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	14% 15% 5% 11% 5% 5% 5% 3 4 4 27%	2526
	11th to 20th	Day	16% 17% 5% 14% 7% 5% 4 3 5% 6% 19%	2571
	21st to end	Day	15% 10% 4 11% 6% 5% 7% 5% 6% 8% 24%	3124
February	1st to 10th	Day	19% 14% 4 10% 7% 6% 4 3 5% 6% 21%	1710
	11th to 20th	Day	17% 14% 4 12% 7% 6% 5% 4 5% 4 23%	1663
	21st to end	Day	13% 13% 5% 9% 8% 4 4 2 5% 7% 31%	1435
March	1st to 10th	Day	22% 13% 4 9% 6% 5% 4 3 4 5% 24%	3400
	11th to 20th	Day	13% 19% 8% 10% 6% 5% 4 3 4 5% 23%	3480
	21st to end	Day	29% 15% 4 10% 5% 4 4 3 3 3 19%	3816
April	1st to 10th	Day	23% 13% 4 7% 6% 4 4 3 4 5% 26%	2277
	11th to 20th	Day	20% 9% 3 8% 5% 5% 4 3 5% 7% 31%	2329
	21st to end	Day	22% 10% 3 8% 5% 5% 4 4 4 7% 29%	2470
May	1st to 10th	Day	23% 12% 4 10% 6% 4 4 3 5% 6% 23%	4251
	11th to 20th	Day	17% 9% 3 9% 6% 4 4 4 5% 7% 32%	4398
	21st to end	Day	18% 9% 3 8% 5% 5% 6% 5% 7% 9% 26%	4836
June	1st to 10th	Day	24% 10% 4 8% 5% 4 5% 4 5% 7% 24%	2660
	11th to 20th	Day	21% 8% 2 7% 5% 4 5% 4 5% 7% 32%	2826
	21st to end	Day	28% 9% 3 7% 5% 4 5% 3 4 6% 27%	2850
July	1st to 10th	Day	22% 9% 2 6% 4 5% 4 4 5% 6% 31%	4738
	11th to 20th	Day	21% 8% 3 6% 5% 3 4 4 5% 8% 33%	4440
	21st to end	Day	16% 9% 3 8% 5% 5% 5% 4 6% 7% 33%	4727
August	1st to 10th	Day	20% 10% 4 8% 5% 4 5% 4 6% 6% 28%	4105
	11th to 20th	Day	15% 8% 3 8% 5% 5% 5% 4 6% 7% 34%	4045
	21st to end	Day	11% 5% 2 6% 4 4 4 4 6% 8% 47%	4354
September	1st to 10th	Day	17% 6% 2 6% 4 4 5% 4 5% 7% 41%	2280
	11th to 20th	Day	18% 7% 3 6% 4 4 4 2 5% 6% 41%	2214
	21st to end	Day	19% 7% 2 6% 4 4 3 3 5% 7% 41%	2024
October	1st to 10th	Day	17% 6% 3 8% 5% 4 4 3 6% 6% 38%	1900
	11th to 20th	Day	21% 9% 2 6% 4 5% 5% 4 6% 6% 32%	1900
	21st to end	Day	20% 10% 4 8% 5% 4 4 3 5% 6% 31%	2090
November	1st to 10th	Day	23% 13% 3 7% 5% 4 5% 3 4 5% 29%	1594
	11th to 20th	Day	22% 15% 4 6% 4 4 4 4 4 5% 28%	1600
	21st to end	Day	19% 14% 6% 9% 6% 5% 4 4 5% 5% 24%	1600
December	1st to 10th	Day	24% 16% 4 9% 5% 5% 3 2 4 5% 23%	1584
	11th to 20th	Day	29% 14% 5% 8% 5% 3 4 3 4 4 20%	1906
	21st to end	Day	22% 14% 5% 14% 5% 4 5% 3 4 5% 18%	2783
January	1st to 10th	Night	14% 14% 5% 9% 6% 4 5% 4 5% 7% 27%	4429
	11th to 20th	Night	21% 14% 6% 12% 5% 4 4 3 5% 7% 20%	4394
	21st to end	Night	16% 11% 5% 13% 6% 5% 5% 4 5% 7% 23%	4532
February	1st to 10th	Night	20% 14% 5% 10% 7% 5% 5% 3 6% 6% 20%	2470
	11th to 20th	Night	18% 13% 4 10% 6% 5% 4 4 6% 6% 24%	2403
	21st to end	Night	13% 13% 5% 9% 6% 5% 5% 3 4 5% 31%	2017
March	1st to 10th	Night	22% 12% 4 12% 7% 5% 5% 3 3 5% 23%	3426
	11th to 20th	Night	19% 15% 7% 10% 5% 5% 4 3 5% 6% 20%	3479
	21st to end	Night	30% 11% 6% 8% 5% 4 3 2 3 4 24%	3816
April	1st to 10th	Night	23% 14% 2 8% 4 4 4 4 4 5% 27%	1902
	11th to 20th	Night	21% 10% 3 7% 5% 3 4 3 5% 7% 31%	1797
	21st to end	Night	26% 9% 3 7% 4 3 3 3 4 6% 30%	1710
May	1st to 10th	Night	22% 14% 3 8% 6% 5% 4 4 5% 6% 23%	2693
	11th to 20th	Night	19% 8% 3 6% 4 4 5% 4 6% 8% 34%	2506
	21st to end	Night	21% 10% 4 9% 6% 5% 4 3 6% 6% 27%	2749
June	1st to 10th	Night	26% 10% 3 7% 4 4 4 3 5% 8% 27%	1520
	11th to 20th	Night	20% 8% 2 6% 4 4 4 4 5% 7% 35%	1366
	21st to end	Night	24% 10% 3 8% 5% 4 5% 5% 5% 6% 25%	1330
July	1st to 10th	Night	21% 11% 3 8% 4 5% 5% 4 6% 7% 24%	2210
	11th to 20th	Night	24% 8% 3 7% 4 4 4 4 6% 7% 30%	2516
	21st to end	Night	16% 8% 3 7% 4 5% 4 4 6% 7% 37%	2831
August	1st to 10th	Night	23% 9% 3 6% 4 4 4 4 6% 6% 30%	2825
	11th to 20th	Night	18% 8% 3 6% 5% 4 5% 4 7% 8% 34%	2782
	21st to end	Night	14% 6% 2 5% 4 4 4 4 5% 7% 46%	3301
September	1st to 10th	Night	16% 6% 2 6% 4 4 4 3 5% 7% 42%	1900
	11th to 20th	Night	18% 7% 2 5% 5% 3 3 3 5% 6% 43%	1962
	21st to end	Night	19% 6% 2 6% 3 4 5% 4 5% 7% 39%	2155
October	1st to 10th	Night	19% 7% 2 6% 4 4 5% 4 5% 7% 38%	2280
	11th to 20th	Night	20% 8% 3 6% 4 4 4 4 5% 6% 36%	2280
	21st to end	Night	26% 9% 2 7% 4 4 3 3 4 6% 31%	2508
November	1st to 10th	Night	23% 10% 3 6% 4 4 5% 3 5% 6% 31%	2700
	11th to 20th	Night	21% 11% 3 8% 6% 4 5% 4 5% 6% 25%	2800
	21st to end	Night	23% 13% 4 8% 5% 4 5% 3 5% 5% 24%	2800
December	1st to 10th	Night	25% 14% 4 8% 5% 4 4 3 5% 6% 22%	2779
	11th to 20th	Night	30% 15% 4 8% 5% 3 3 2 4 5% 23%	3293
	21st to end	Night	25% 13% 4 11% 5% 4 4 3 4 5% 22%	4884

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	34% 41% 10% 10% 4	2527
	11th to 20th	Day	39% 43% 7% 9% 2	2571
	21st to end	Day	34% 45% 10% 6% 5%	3124
February	1st to 10th	Day	23% 65% 3 5% 3 1	1710
	11th to 20th	Day	21% 66% 3 5% 4	1671
	21st to end	Day	19% 65% 3 7% 5% 1	1435
March	1st to 10th	Day	36% 43% 7% 10% 3	3404
	11th to 20th	Day	39% 45% 7% 6% 3	3480
	21st to end	Day	47% 40% 3 5% 3 1	3816
April	1st to 10th	Day	22% 66% 3 4 4 1	2277
	11th to 20th	Day	19% 67% 3 8% 2	2329
	21st to end	Day	21% 66% 3 5% 5%	2470
May	1st to 10th	Day	37% 45% 6% 9% 3	4265
	11th to 20th	Day	29% 45% 11% 12% 3	4402
	21st to end	Day	29% 47% 12% 8% 4	4836
June	1st to 10th	Day	20% 66% 5% 7% 3	2660
	11th to 20th	Day	17% 66% 5% 8% 3	2826
	21st to end	Day	21% 63% 4 6% 6%	2850
July	1st to 10th	Day	36% 37% 7% 11% 8% 1	4663
	11th to 20th	Day	34% 39% 8% 16% 4	4364
	21st to end	Day	30% 40% 10% 15% 5%	4576
August	1st to 10th	Day	38% 40% 6% 13% 4	4092
	11th to 20th	Day	29% 41% 7% 14% 8%	4084
	21st to end	Day	21% 41% 8% 19% 11%	4354
September	1st to 10th	Day	15% 61% 7% 10% 6%	2280
	11th to 20th	Day	20% 60% 6% 9% 4	2214
	21st to end	Day	15% 61% 5% 13% 5%	2024
October	1st to 10th	Day	30% 40% 7% 15% 8%	3160
	11th to 20th	Day	29% 38% 5% 20% 7%	3140
	21st to end	Day	27% 38% 11% 14% 10%	3428
November	1st to 10th	Day	28% 58% 5% 7% 2	1594
	11th to 20th	Day	28% 58% 5% 6% 3 1	1600
	21st to end	Day	27% 60% 5% 6% 2	1600
December	1st to 10th	Day	28% 57% 4 8% 3	1584
	11th to 20th	Day	38% 48% 4 7% 2	1905
	21st to end	Day	45% 40% 7% 5% 2	2783
January	1st to 10th	Night	29% 42% 12% 15% 2	4429
	11th to 20th	Night	39% 41% 8% 7% 4	4394
	21st to end	Night	40% 42% 6% 9% 3	4532
February	1st to 10th	Night	25% 65% 3 4 3	2470
	11th to 20th	Night	21% 65% 3 6% 4	2406
	21st to end	Night	18% 66% 3 7% 6% 1	2017
March	1st to 10th	Night	41% 42% 3 9% 5%	3435
	11th to 20th	Night	41% 43% 6% 5% 4	3480
	21st to end	Night	46% 40% 3 6% 4	3816
April	1st to 10th	Night	21% 66% 3 5% 3 2	1902
	11th to 20th	Night	19% 66% 3 8% 4 1	1797
	21st to end	Night	21% 65% 3 5% 5% 1	1710
May	1st to 10th	Night	39% 44% 8% 7% 2	2699
	11th to 20th	Night	27% 45% 12% 13% 3	2507
	21st to end	Night	34% 45% 11% 7% 2	2750
June	1st to 10th	Night	19% 67% 5% 7% 3	1520
	11th to 20th	Night	15% 65% 6% 10% 3 1	1366
	21st to end	Night	19% 65% 5% 7% 4	1330
July	1st to 10th	Night	39% 39% 7% 8% 5% 1	2175
	11th to 20th	Night	35% 39% 11% 9% 5%	2469
	21st to end	Night	27% 38% 10% 18% 7%	2742
August	1st to 10th	Night	36% 41% 9% 13% 2	2813
	11th to 20th	Night	27% 43% 10% 14% 6%	2809
	21st to end	Night	20% 40% 12% 17% 11%	3300
September	1st to 10th	Night	14% 62% 5% 13% 6% 1	1900
	11th to 20th	Night	18% 61% 5% 11% 5%	1962
	21st to end	Night	14% 61% 6% 13% 4 1	2155
October	1st to 10th	Night	32% 39% 7% 17% 5%	3800
	11th to 20th	Night	22% 38% 8% 21% 11%	3779
	21st to end	Night	24% 39% 11% 16% 10%	4120
November	1st to 10th	Night	24% 59% 6% 7% 3	2700
	11th to 20th	Night	26% 60% 5% 6% 3	2800
	21st to end	Night	27% 59% 6% 6% 3	2800
December	1st to 10th	Night	27% 59% 4 7% 3	2779
	11th to 20th	Night	35% 49% 4 7% 4	3295
	21st to end	Night	41% 40% 8% 8% 2	4884

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	27% 23% 31% 17% 1	370
	11th to 20th	Day	34% 23% 28% 12% 4	370
	21st to end	Day	22% 21% 38% 16% 3	407
February	1st to 10th	Day	29% 24% 30% 15% 3	370
	11th to 20th	Day	26% 31% 28% 13% 2	366
	21st to end	Day	21% 23% 34% 17% 3 1	307
March	1st to 10th	Day	21% 28% 35% 13% 3	451
	11th to 20th	Day	21% 27% 33% 13% 5%	460
	21st to end	Day	29% 25% 31% 11% 4	506
April	1st to 10th	Day	31% 30% 26% 11% 2	460
	11th to 20th	Day	23% 29% 30% 13% 4	452
	21st to end	Day	27% 19% 31% 17% 6%	460
May	1st to 10th	Day	33% 20% 30% 12% 5% 1	543
	11th to 20th	Day	22% 17% 31% 22% 8% 1	674
	21st to end	Day	26% 15% 33% 22% 3 1	735
June	1st to 10th	Day	30% 14% 31% 20% 5%	680
	11th to 20th	Day	23% 15% 32% 24% 5% 1	680
	21st to end	Day	32% 10% 27% 23% 7% 1	680
July	1st to 10th	Day	24% 7% 34% 28% 7% 1	670
	11th to 20th	Day	21% 8% 31% 29% 11%	668
	21st to end	Day	22% 8% 32% 28% 10%	688
August	1st to 10th	Day	16% 7% 32% 34% 9% 1	486
	11th to 20th	Day	19% 11% 29% 29% 11% 2	479
	21st to end	Day	17% 10% 31% 27% 13% 2	539
September	1st to 10th	Day	18% 12% 33% 28% 9% 1	490
	11th to 20th	Day	22% 12% 30% 26% 8% 2	490
	21st to end	Day	19% 14% 33% 18% 14% 2	455
October	1st to 10th	Day	21% 12% 30% 23% 12% 2	390
	11th to 20th	Day	24% 21% 27% 19% 8% 1	390
	21st to end	Day	24% 23% 30% 17% 6% 1	429
November	1st to 10th	Day	27% 21% 30% 15% 6% 1	395
	11th to 20th	Day	31% 26% 26% 13% 4 1	400
	21st to end	Day	30% 25% 31% 11% 3	400
December	1st to 10th	Day	32% 21% 30% 15% 2 1	394
	11th to 20th	Day	34% 28% 26% 11% 1	370
	21st to end	Day	27% 27% 29% 14% 3	407
January	1st to 10th	Night	27% 24% 31% 16% 3	850
	11th to 20th	Night	29% 22% 31% 15% 4	835
	21st to end	Night	21% 25% 33% 17% 4	836
February	1st to 10th	Night	25% 23% 32% 17% 3	760
	11th to 20th	Night	25% 28% 31% 14% 2	743
	21st to end	Night	19% 21% 36% 20% 4	628
March	1st to 10th	Night	23% 22% 35% 18% 2	760
	11th to 20th	Night	22% 19% 31% 21% 6%	760
	21st to end	Night	24% 20% 31% 20% 5%	836
April	1st to 10th	Night	29% 18% 31% 19% 3	572
	11th to 20th	Night	25% 17% 33% 19% 5%	564
	21st to end	Night	28% 15% 31% 19% 6% 1	570
May	1st to 10th	Night	30% 14% 31% 19% 6%	570
	11th to 20th	Night	25% 13% 28% 27% 6%	562
	21st to end	Night	21% 15% 39% 22% 2	616
June	1st to 10th	Night	30% 12% 32% 23% 4	570
	11th to 20th	Night	22% 10% 32% 29% 6%	416
	21st to end	Night	27% 6% 28% 31% 8%	380
July	1st to 10th	Night	24% 5% 30% 35% 6%	370
	11th to 20th	Night	18% 9% 29% 35% 8%	539
	21st to end	Night	21% 6% 28% 36% 9%	623
August	1st to 10th	Night	17% 7% 29% 37% 10% 1	568
	11th to 20th	Night	20% 6% 29% 34% 10% 1	562
	21st to end	Night	17% 7% 26% 37% 12% 1	627
September	1st to 10th	Night	17% 9% 33% 31% 9% 1	570
	11th to 20th	Night	20% 11% 26% 32% 10% 1	632
	21st to end	Night	23% 12% 31% 26% 8% 1	760
October	1st to 10th	Night	23% 12% 26% 30% 8% 1	760
	11th to 20th	Night	24% 14% 34% 17% 8% 1	760
	21st to end	Night	31% 19% 26% 19% 4	836
November	1st to 10th	Night	27% 19% 29% 19% 5% 1	880
	11th to 20th	Night	26% 23% 28% 18% 4 1	900
	21st to end	Night	31% 23% 25% 18% 3	900
December	1st to 10th	Night	33% 18% 30% 17% 2	893
	11th to 20th	Night	33% 25% 29% 11% 2	850
	21st to end	Night	28% 25% 28% 16% 3 1	935

Page generated at 2024-12-06 04:54:46. Version ac07

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