Canaan
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Canaan clear sky chart from 2005-11-06 to 2025-02-06.

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	16% 13% 5% 11% 6% 5% 5% 4 5% 6% 25%	108359
	Night	15% 14% 6% 13% 7% 5% 5% 3 4 5% 23%	109898
Transparency	Day	59% 6% 11% 16% 7% 1	111888
	Night	63% 5% 10% 14% 7% 1	114533
Seeing	Day	28% 20% 27% 16% 7% 2	14962
	Night	26% 18% 26% 22% 8% 1	23964

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	12% 15% 11% 22% 11% 9% 4 2 3 3 10%	3597
	11th to 20th	Day	7% 16% 7% 23% 17% 6% 4 2 4 3 11%	3570
	21st to end	Day	8% 15% 9% 16% 7% 8% 8% 3 4 4 18%	3960
February	1st to 10th	Day	13% 16% 7% 15% 10% 7% 5% 2 3 3 17%	1648
	11th to 20th	Day	9% 17% 10% 17% 10% 6% 5% 3 3 4 16%	1848
	21st to end	Day	11% 18% 5% 16% 8% 5% 5% 3 4 4 20%	1570
March	1st to 10th	Day	19% 18% 6% 12% 7% 5% 4 3 3 3 20%	3116
	11th to 20th	Day	14% 22% 8% 13% 6% 4 3 3 3 4 22%	3310
	21st to end	Day	16% 15% 5% 13% 5% 4 3 2 4 5% 27%	4065
April	1st to 10th	Day	19% 19% 4 11% 5% 3 3 2 3 5% 25%	2280
	11th to 20th	Day	16% 16% 4 9% 4 4 4 3 4 5% 31%	2304
	21st to end	Day	21% 16% 3 9% 4 4 4 3 4 5% 26%	2470
May	1st to 10th	Day	25% 13% 3 8% 5% 4 4 3 4 5% 25%	4106
	11th to 20th	Day	18% 10% 3 10% 6% 5% 5% 4 6% 7% 25%	4390
	21st to end	Day	14% 7% 3 8% 5% 5% 6% 5% 8% 10% 29%	4837
June	1st to 10th	Day	26% 10% 3 7% 5% 5% 5% 4 5% 7% 23%	2660
	11th to 20th	Day	18% 8% 3 7% 6% 4 5% 4 6% 7% 32%	2660
	21st to end	Day	22% 9% 3 8% 6% 5% 5% 4 7% 6% 25%	2660
July	1st to 10th	Day	15% 7% 3 8% 5% 5% 6% 6% 8% 10% 29%	4440
	11th to 20th	Day	13% 7% 3 9% 6% 6% 6% 5% 9% 9% 28%	4440
	21st to end	Day	17% 8% 3 7% 5% 5% 5% 3 6% 8% 34%	4814
August	1st to 10th	Day	17% 9% 4 10% 6% 6% 6% 4 6% 8% 24%	4330
	11th to 20th	Day	17% 9% 3 9% 6% 6% 6% 5% 7% 9% 22%	4045
	21st to end	Day	17% 8% 2 7% 5% 5% 4 4 5% 8% 35%	4226
September	1st to 10th	Day	17% 7% 2 6% 5% 4 4 4 5% 7% 38%	2280
	11th to 20th	Day	18% 8% 2 6% 4 3 5% 3 5% 7% 41%	2110
	21st to end	Day	17% 10% 2 7% 5% 4 4 5% 5% 8% 32%	2090
October	1st to 10th	Day	22% 13% 4 7% 4 5% 4 4 5% 5% 28%	2090
	11th to 20th	Day	16% 16% 4 9% 6% 4 4 4 6% 6% 26%	1780
	21st to end	Day	21% 23% 5% 7% 4 4 3 2 3 4 23%	1881
November	1st to 10th	Day	15% 19% 5% 9% 5% 5% 4 3 3 5% 27%	1761
	11th to 20th	Day	15% 19% 7% 12% 6% 4 4 3 4 4 22%	1800
	21st to end	Day	17% 17% 7% 14% 6% 4 6% 2 4 5% 19%	1675
December	1st to 10th	Day	10% 20% 8% 24% 12% 4 3 2 3 3 10%	2600
	11th to 20th	Day	14% 18% 9% 15% 6% 5% 5% 2 4 3 19%	2986
	21st to end	Day	16% 18% 6% 16% 6% 4 6% 2 3 4 18%	3960
January	1st to 10th	Night	9% 17% 11% 24% 12% 8% 4 3 2 2 9%	6349
	11th to 20th	Night	8% 17% 9% 21% 16% 6% 5% 3 3 2 8%	6315
	21st to end	Night	8% 15% 7% 15% 8% 9% 7% 4 4 4 17%	6996
February	1st to 10th	Night	11% 16% 6% 16% 11% 8% 5% 3 4 4 16%	2641
	11th to 20th	Night	8% 16% 8% 18% 10% 8% 6% 3 3 3 16%	2218
	21st to end	Night	12% 16% 6% 13% 8% 7% 5% 3 4 5% 23%	1884
March	1st to 10th	Night	19% 19% 5% 9% 5% 6% 4 3 4 4 23%	3724
	11th to 20th	Night	13% 21% 9% 13% 6% 5% 4 3 3 4 21%	3649
	21st to end	Night	17% 19% 6% 12% 6% 4 3 2 3 4 25%	3562
April	1st to 10th	Night	18% 15% 5% 10% 6% 4 3 4 5% 4 25%	1900
	11th to 20th	Night	17% 16% 3 9% 5% 4 4 3 5% 5% 30%	1825
	21st to end	Night	21% 15% 3 7% 6% 4 4 3 5% 4 28%	1710
May	1st to 10th	Night	24% 12% 3 8% 5% 4 4 3 4 6% 26%	2834
	11th to 20th	Night	19% 9% 3 9% 6% 5% 4 3 5% 8% 28%	2532
	21st to end	Night	17% 7% 2 6% 4 4 5% 4 5% 9% 36%	2738
June	1st to 10th	Night	27% 9% 3 7% 4 4 4 3 5% 6% 29%	1520
	11th to 20th	Night	18% 9% 2 6% 5% 5% 5% 3 6% 7% 35%	1520
	21st to end	Night	21% 8% 3 8% 6% 4 5% 5% 6% 6% 29%	1520
July	1st to 10th	Night	14% 7% 3 8% 6% 6% 7% 5% 6% 8% 31%	2520
	11th to 20th	Night	19% 7% 3 8% 4 4 4 4 6% 7% 34%	2520
	21st to end	Night	14% 8% 3 7% 5% 6% 5% 4 6% 6% 35%	2739
August	1st to 10th	Night	23% 9% 3 8% 5% 5% 5% 3 6% 6% 29%	2567
	11th to 20th	Night	15% 8% 4 10% 5% 6% 7% 4 6% 8% 27%	2782
	21st to end	Night	17% 9% 2 7% 4 4 4 3 4 6% 39%	3428
September	1st to 10th	Night	16% 8% 2 6% 3 5% 5% 3 5% 7% 41%	1900
	11th to 20th	Night	16% 7% 2 6% 4 3 4 4 4 6% 44%	2069
	21st to end	Night	19% 9% 2 5% 3 4 4 3 6% 7% 39%	2090
October	1st to 10th	Night	19% 11% 3 7% 5% 4 5% 4 4 6% 32%	2090
	11th to 20th	Night	18% 15% 3 8% 5% 5% 4 3 5% 5% 28%	2398
	21st to end	Night	22% 18% 4 8% 4 4 4 4 4 5% 23%	2717
November	1st to 10th	Night	17% 18% 6% 9% 5% 4 4 3 5% 5% 24%	2537
	11th to 20th	Night	15% 16% 7% 14% 5% 4 4 2 4 4 25%	2600
	21st to end	Night	16% 19% 7% 14% 8% 5% 4 2 3 4 18%	2720
December	1st to 10th	Night	13% 18% 9% 27% 11% 5% 4 3 3 2 8%	4580
	11th to 20th	Night	16% 20% 7% 18% 8% 5% 3 2 3 3 14%	5208
	21st to end	Night	16% 18% 7% 16% 6% 5% 5% 2 4 5% 17%	6996

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	81% 4 6% 8% 1	3598
	11th to 20th	Day	77% 4 6% 9% 3 1	3600
	21st to end	Day	71% 3 8% 9% 9% 1	3960
February	1st to 10th	Day	73% 4 6% 11% 5% 2	1648
	11th to 20th	Day	74% 4 8% 9% 5% 1	1857
	21st to end	Day	66% 6% 8% 11% 7% 2	1570
March	1st to 10th	Day	68% 7% 7% 8% 8% 2	3119
	11th to 20th	Day	67% 5% 8% 10% 8% 2	3310
	21st to end	Day	60% 5% 6% 14% 14% 1	4065
April	1st to 10th	Day	63% 5% 8% 14% 9% 2	2280
	11th to 20th	Day	55% 5% 9% 19% 10% 1	2304
	21st to end	Day	62% 5% 8% 14% 8% 3	2470
May	1st to 10th	Day	59% 8% 8% 17% 6% 1	4120
	11th to 20th	Day	53% 12% 15% 13% 6% 1	4394
	21st to end	Day	44% 12% 14% 21% 9%	4837
June	1st to 10th	Day	59% 8% 11% 17% 5% 1	2660
	11th to 20th	Day	49% 8% 12% 21% 9% 1	2660
	21st to end	Day	57% 8% 10% 17% 6%	2660
July	1st to 10th	Day	48% 5% 16% 22% 8%	4370
	11th to 20th	Day	48% 7% 16% 26% 3	4365
	21st to end	Day	49% 6% 10% 27% 7%	4661
August	1st to 10th	Day	56% 6% 15% 18% 5%	4316
	11th to 20th	Day	56% 7% 15% 18% 4	4084
	21st to end	Day	47% 5% 15% 19% 12% 2	4226
September	1st to 10th	Day	44% 8% 13% 24% 10%	2280
	11th to 20th	Day	43% 5% 12% 26% 13% 1	2110
	21st to end	Day	48% 8% 13% 20% 11% 1	2090
October	1st to 10th	Day	53% 4 11% 22% 10%	3480
	11th to 20th	Day	53% 4 12% 22% 8%	2931
	21st to end	Day	54% 4 13% 20% 9% 1	3081
November	1st to 10th	Day	60% 5% 10% 16% 8% 1	1761
	11th to 20th	Day	66% 6% 8% 9% 9% 2	1800
	21st to end	Day	68% 6% 12% 11% 3	1675
December	1st to 10th	Day	81% 3 8% 6% 3	2600
	11th to 20th	Day	67% 3 8% 12% 9% 1	2986
	21st to end	Day	71% 5% 4 9% 9% 2	3960
January	1st to 10th	Night	83% 4 7% 5% 1	6349
	11th to 20th	Night	82% 4 6% 6% 1 1	6360
	21st to end	Night	69% 3 8% 9% 9% 1	6996
February	1st to 10th	Night	71% 5% 8% 9% 5%	2641
	11th to 20th	Night	73% 5% 6% 10% 5% 1	2220
	21st to end	Night	65% 6% 7% 13% 8% 1	1884
March	1st to 10th	Night	64% 5% 9% 13% 7% 2	3734
	11th to 20th	Night	66% 8% 7% 10% 8% 1	3650
	21st to end	Night	66% 3 5% 13% 12% 1	3562
April	1st to 10th	Night	62% 5% 9% 15% 10% 1	1900
	11th to 20th	Night	55% 7% 9% 19% 10%	1825
	21st to end	Night	57% 7% 9% 14% 10% 2	1710
May	1st to 10th	Night	57% 8% 13% 14% 6% 1	2840
	11th to 20th	Night	50% 12% 15% 16% 6% 1	2533
	21st to end	Night	43% 11% 15% 18% 13%	2739
June	1st to 10th	Night	55% 8% 10% 19% 7%	1520
	11th to 20th	Night	47% 8% 13% 21% 9% 2	1520
	21st to end	Night	53% 11% 11% 18% 6% 1	1520
July	1st to 10th	Night	49% 7% 15% 21% 8%	2480
	11th to 20th	Night	49% 7% 13% 26% 6%	2472
	21st to end	Night	47% 7% 13% 23% 9%	2651
August	1st to 10th	Night	55% 6% 13% 21% 4	2557
	11th to 20th	Night	53% 7% 18% 15% 7%	2809
	21st to end	Night	47% 4 14% 22% 13% 1	3428
September	1st to 10th	Night	43% 8% 15% 25% 9%	1900
	11th to 20th	Night	41% 6% 15% 27% 11% 1	2069
	21st to end	Night	43% 7% 12% 25% 10% 2	2090
October	1st to 10th	Night	52% 4 13% 22% 9%	3480
	11th to 20th	Night	55% 4 11% 20% 10%	3986
	21st to end	Night	54% 4 15% 17% 9% 1	4467
November	1st to 10th	Night	62% 5% 12% 15% 6% 1	2537
	11th to 20th	Night	62% 4 9% 14% 8% 2	2600
	21st to end	Night	70% 6% 9% 11% 4	2720
December	1st to 10th	Night	83% 3 7% 5% 2	4580
	11th to 20th	Night	77% 3 4 8% 7%	5208
	21st to end	Night	71% 5% 6% 10% 7% 2	6996

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% 25% 36% 11% 2	200
	11th to 20th	Day	32% 27% 31% 7% 3 1	200
	21st to end	Day	25% 28% 30% 14% 4	220
February	1st to 10th	Day	39% 29% 24% 7% 1	251
	11th to 20th	Day	33% 29% 28% 8% 2	456
	21st to end	Day	33% 26% 25% 14% 2	382
March	1st to 10th	Day	32% 26% 28% 12% 3	460
	11th to 20th	Day	33% 27% 24% 13% 4	460
	21st to end	Day	35% 24% 21% 13% 6% 1	506
April	1st to 10th	Day	41% 20% 22% 12% 5%	460
	11th to 20th	Day	35% 24% 24% 10% 5% 2	452
	21st to end	Day	35% 22% 27% 11% 3 1	460
May	1st to 10th	Day	41% 18% 23% 12% 5% 1	463
	11th to 20th	Day	27% 20% 32% 16% 4 1	487
	21st to end	Day	22% 23% 30% 18% 5% 1	529
June	1st to 10th	Day	32% 18% 30% 12% 7%	490
	11th to 20th	Day	23% 19% 29% 20% 8% 1	490
	21st to end	Day	27% 19% 31% 15% 7% 2	490
July	1st to 10th	Day	19% 15% 34% 23% 7% 2	485
	11th to 20th	Day	16% 16% 37% 21% 8% 2	484
	21st to end	Day	20% 14% 34% 23% 7% 2	532
August	1st to 10th	Day	20% 15% 29% 21% 13% 2	486
	11th to 20th	Day	17% 12% 31% 23% 14% 3	479
	21st to end	Day	22% 16% 26% 21% 12% 4	539
September	1st to 10th	Day	23% 15% 25% 21% 11% 5%	490
	11th to 20th	Day	22% 12% 21% 20% 17% 8%	490
	21st to end	Day	20% 17% 23% 23% 11% 5%	490
October	1st to 10th	Day	27% 18% 23% 18% 12% 3	490
	11th to 20th	Day	29% 19% 27% 14% 9% 1	422
	21st to end	Day	35% 22% 23% 15% 5%	429
November	1st to 10th	Day	35% 20% 25% 16% 4	395
	11th to 20th	Day	30% 26% 27% 12% 5% 1	400
	21st to end	Day	38% 19% 28% 12% 3 1	275
December	1st to 10th	Day	34% 23% 27% 14% 3	200
	11th to 20th	Day	36% 28% 28% 7% 3	200
	21st to end	Day	37% 20% 30% 10% 3	220
January	1st to 10th	Night	26% 27% 32% 13% 2	800
	11th to 20th	Night	26% 24% 30% 16% 4	800
	21st to end	Night	21% 24% 32% 19% 3	880
February	1st to 10th	Night	24% 27% 31% 15% 2	781
	11th to 20th	Night	24% 28% 31% 15% 3	743
	21st to end	Night	26% 22% 32% 18% 1	628
March	1st to 10th	Night	27% 21% 31% 18% 3	760
	11th to 20th	Night	31% 20% 26% 17% 6%	760
	21st to end	Night	31% 20% 23% 17% 7% 1	836
April	1st to 10th	Night	33% 21% 25% 17% 4	760
	11th to 20th	Night	31% 18% 25% 19% 6%	701
	21st to end	Night	31% 19% 26% 18% 6%	570
May	1st to 10th	Night	28% 14% 30% 19% 7% 1	570
	11th to 20th	Night	22% 15% 30% 25% 7% 1	398
	21st to end	Night	22% 10% 27% 31% 9%	411
June	1st to 10th	Night	30% 9% 23% 28% 9%	380
	11th to 20th	Night	21% 9% 21% 33% 15%	380
	21st to end	Night	22% 9% 22% 35% 10% 1	380
July	1st to 10th	Night	18% 7% 25% 37% 12% 1	370
	11th to 20th	Night	17% 7% 23% 36% 16% 1	368
	21st to end	Night	15% 5% 23% 40% 16% 1	416
August	1st to 10th	Night	19% 4 19% 39% 19%	413
	11th to 20th	Night	18% 9% 22% 31% 19% 1	562
	21st to end	Night	20% 7% 20% 32% 18% 2	801
September	1st to 10th	Night	19% 10% 23% 32% 15% 1	760
	11th to 20th	Night	20% 9% 18% 26% 24% 2	760
	21st to end	Night	24% 11% 22% 24% 16% 2	760
October	1st to 10th	Night	27% 12% 21% 25% 14% 1	760
	11th to 20th	Night	28% 18% 22% 21% 10% 2	760
	21st to end	Night	33% 20% 25% 18% 4	836
November	1st to 10th	Night	31% 18% 24% 20% 7% 1	780
	11th to 20th	Night	27% 23% 25% 16% 8% 1	800
	21st to end	Night	31% 23% 25% 16% 5% 1	800
December	1st to 10th	Night	31% 24% 26% 15% 4	800
	11th to 20th	Night	31% 24% 26% 15% 4	800
	21st to end	Night	34% 20% 28% 16% 3	880

Page generated at 2025-02-03 03:05:49. Version ac07

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