Mambourg Farm Historical Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mambourg Farm Historical Park clear sky chart from 2005-11-06 to 2025-03-12.

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	15% 10% 4 8% 5% 5% 5% 4 5% 7% 32%	109397
	Night	15% 11% 4 8% 5% 4 4 3 5% 6% 34%	109625
Transparency	Day	49% 6% 11% 21% 12% 1	113102
	Night	49% 5% 10% 21% 13% 2	114047
Seeing	Day	21% 14% 27% 21% 12% 5%	15280
	Night	19% 11% 27% 28% 14% 2	25465

By Month

Percentage Cloud Cover SE (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	15% 22% 8% 14% 9% 4 3 3 4 5% 15%	4056
	11th to 20th	Day	14% 21% 7% 13% 8% 7% 4 3 3 4 18%	4060
	21st to end	Day	21% 16% 7% 10% 8% 6% 5% 3 4 4 17%	4466
February	1st to 10th	Day	21% 14% 5% 9% 6% 4 4 3 4 5% 25%	1800
	11th to 20th	Day	17% 13% 6% 12% 5% 5% 4 3 4 6% 26%	1905
	21st to end	Day	18% 14% 6% 9% 4 4 3 3 4 5% 30%	1650
March	1st to 10th	Day	21% 15% 5% 8% 5% 4 5% 3 4 5% 25%	3408
	11th to 20th	Day	14% 8% 3 8% 5% 5% 5% 4 5% 6% 37%	3491
	21st to end	Day	19% 9% 3 8% 4 4 4 3 5% 6% 34%	3815
April	1st to 10th	Day	13% 13% 3 9% 5% 5% 4 3 5% 6% 33%	2099
	11th to 20th	Day	17% 9% 3 6% 4 4 4 4 6% 6% 37%	2413
	21st to end	Day	18% 8% 3 8% 5% 5% 5% 4 6% 6% 33%	2470
May	1st to 10th	Day	20% 10% 4 7% 5% 5% 4 4 6% 7% 28%	4082
	11th to 20th	Day	21% 9% 3 6% 5% 4 4 3 5% 7% 33%	4081
	21st to end	Day	10% 6% 2 7% 5% 6% 6% 5% 8% 10% 35%	4476
June	1st to 10th	Day	12% 6% 2 7% 5% 5% 5% 4 7% 10% 37%	2470
	11th to 20th	Day	10% 6% 3 7% 5% 5% 5% 5% 7% 10% 37%	2470
	21st to end	Day	10% 7% 2 7% 5% 5% 6% 5% 6% 10% 36%	2470
July	1st to 10th	Day	11% 6% 2 7% 6% 5% 5% 4 6% 9% 39%	4120
	11th to 20th	Day	8% 5% 2 5% 5% 5% 6% 4 7% 11% 42%	4120
	21st to end	Day	12% 7% 2 7% 5% 5% 6% 5% 8% 8% 34%	4466
August	1st to 10th	Day	10% 5% 3 7% 5% 5% 5% 4 7% 10% 38%	4104
	11th to 20th	Day	9% 7% 2 6% 5% 5% 6% 5% 8% 9% 38%	4044
	21st to end	Day	5% 5% 2 6% 4 5% 5% 4 7% 9% 47%	4475
September	1st to 10th	Day	13% 6% 2 5% 4 3 4 3 6% 7% 47%	2090
	11th to 20th	Day	10% 5% 2 6% 4 5% 4 4 5% 8% 48%	2090
	21st to end	Day	18% 8% 3 7% 4 3 3 3 4 6% 41%	2090
October	1st to 10th	Day	12% 7% 2 6% 4 3 4 3 6% 7% 44%	2019
	11th to 20th	Day	14% 7% 2 6% 5% 4 5% 3 5% 7% 42%	1900
	21st to end	Day	20% 8% 3 8% 5% 4 3 3 4 5% 36%	2066
November	1st to 10th	Day	11% 7% 2 6% 4 3 3 3 5% 7% 49%	1762
	11th to 20th	Day	16% 14% 4 7% 4 4 4 3 5% 6% 34%	1800
	21st to end	Day	18% 14% 4 8% 4 4 4 3 4 7% 30%	1800
December	1st to 10th	Day	20% 13% 5% 14% 5% 4 4 3 4 4 24%	2930
	11th to 20th	Day	23% 15% 6% 10% 5% 4 4 3 4 6% 21%	3373
	21st to end	Day	20% 21% 6% 11% 6% 4 5% 3 4 5% 15%	4466
January	1st to 10th	Night	14% 18% 8% 17% 6% 5% 4 3 4 4 18%	5889
	11th to 20th	Night	14% 17% 7% 15% 8% 7% 6% 3 4 4 16%	5900
	21st to end	Night	21% 13% 7% 10% 6% 4 3 2 3 4 26%	6490
February	1st to 10th	Night	20% 14% 3 9% 5% 4 4 3 5% 5% 28%	2600
	11th to 20th	Night	18% 13% 3 10% 7% 5% 4 3 4 6% 26%	2378
	21st to end	Night	19% 13% 6% 9% 5% 4 3 3 4 4 28%	1980
March	1st to 10th	Night	21% 12% 3 6% 5% 4 4 2 4 6% 33%	3663
	11th to 20th	Night	13% 9% 2 6% 5% 4 5% 4 5% 6% 40%	3498
	21st to end	Night	18% 9% 3 6% 4 3 4 3 4 6% 39%	3817
April	1st to 10th	Night	14% 11% 3 6% 4 4 4 4 5% 7% 38%	2090
	11th to 20th	Night	14% 8% 3 7% 4 5% 3 4 6% 9% 37%	1721
	21st to end	Night	14% 8% 3 7% 4 5% 4 4 6% 7% 38%	1710
May	1st to 10th	Night	25% 11% 3 7% 4 4 4 3 5% 6% 26%	2813
	11th to 20th	Night	19% 9% 3 6% 3 3 4 3 4 8% 40%	2812
	21st to end	Night	8% 6% 2 7% 4 3 4 5% 8% 10% 42%	3079
June	1st to 10th	Night	9% 5% 2 6% 5% 4 4 4 6% 8% 46%	1710
	11th to 20th	Night	9% 4 2 6% 5% 4 4 4 8% 10% 44%	1710
	21st to end	Night	10% 6% 2 5% 3 5% 4 5% 7% 9% 44%	1710
July	1st to 10th	Night	10% 6% 3 6% 4 4 4 4 5% 7% 46%	2840
	11th to 20th	Night	8% 5% 2 6% 5% 4 5% 4 7% 9% 45%	2840
	21st to end	Night	8% 6% 3 8% 6% 6% 6% 5% 8% 8% 38%	3087
August	1st to 10th	Night	7% 7% 3 8% 5% 5% 5% 4 8% 10% 38%	2825
	11th to 20th	Night	10% 6% 3 8% 5% 4 4 3 5% 7% 44%	2785
	21st to end	Night	5% 3 2 5% 4 4 5% 4 7% 10% 51%	3146
September	1st to 10th	Night	12% 4 2 5% 3 4 4 3 5% 7% 51%	2086
	11th to 20th	Night	9% 3 2 4 3 4 4 3 5% 8% 55%	2090
	21st to end	Night	14% 8% 2 6% 3 3 3 3 5% 6% 47%	2090
October	1st to 10th	Night	10% 5% 2 6% 4 4 4 3 6% 7% 50%	2161
	11th to 20th	Night	14% 7% 3 6% 4 3 4 3 5% 7% 44%	2280
	21st to end	Night	19% 8% 2 6% 4 3 4 3 5% 6% 39%	2527
November	1st to 10th	Night	14% 7% 2 5% 4 3 3 3 4 6% 48%	2536
	11th to 20th	Night	16% 10% 3 7% 5% 4 4 4 5% 6% 35%	2600
	21st to end	Night	19% 13% 4 8% 4 4 4 3 6% 6% 29%	2600
December	1st to 10th	Night	18% 13% 5% 10% 5% 4 4 3 5% 6% 27%	4250
	11th to 20th	Night	19% 17% 7% 10% 4 4 4 3 4 5% 24%	4822
	21st to end	Night	21% 19% 6% 10% 6% 5% 4 3 4 6% 16%	6490

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	73% 4 8% 11% 4	4057
	11th to 20th	Day	71% 5% 7% 9% 7% 1	4060
	21st to end	Day	71% 4 9% 9% 6% 1	4466
February	1st to 10th	Day	62% 4 11% 14% 9%	1800
	11th to 20th	Day	61% 5% 9% 16% 9%	1915
	21st to end	Day	58% 3 11% 18% 8% 2	1650
March	1st to 10th	Day	60% 5% 9% 20% 5% 1	3408
	11th to 20th	Day	45% 6% 10% 28% 10% 1	3491
	21st to end	Day	51% 6% 9% 24% 11%	3815
April	1st to 10th	Day	52% 5% 10% 20% 11% 2	2099
	11th to 20th	Day	46% 5% 11% 19% 14% 4	2413
	21st to end	Day	50% 6% 9% 22% 11% 2	2470
May	1st to 10th	Day	54% 6% 9% 23% 7% 1	4120
	11th to 20th	Day	50% 6% 11% 20% 13% 1	4085
	21st to end	Day	38% 11% 14% 19% 14% 3	4489
June	1st to 10th	Day	41% 8% 11% 24% 14% 2	2470
	11th to 20th	Day	40% 8% 13% 22% 15% 1	2470
	21st to end	Day	41% 8% 15% 20% 14% 2	2470
July	1st to 10th	Day	42% 6% 12% 22% 16% 2	4055
	11th to 20th	Day	34% 7% 11% 30% 17% 1	4051
	21st to end	Day	44% 7% 11% 17% 17% 3	4324
August	1st to 10th	Day	40% 8% 13% 28% 10% 1	4091
	11th to 20th	Day	38% 7% 11% 30% 13% 1	4083
	21st to end	Day	32% 7% 14% 30% 15% 3	4475
September	1st to 10th	Day	36% 7% 10% 21% 22% 4	2090
	11th to 20th	Day	33% 5% 12% 26% 21% 3	2090
	21st to end	Day	44% 4 9% 22% 19% 1	2090
October	1st to 10th	Day	26% 4 9% 32% 28% 1	3357
	11th to 20th	Day	34% 3 11% 26% 21% 3	3140
	21st to end	Day	38% 3 11% 27% 19% 2	3380
November	1st to 10th	Day	36% 5% 9% 29% 18% 3	1762
	11th to 20th	Day	51% 5% 9% 20% 13% 3	1800
	21st to end	Day	55% 5% 10% 19% 10% 1	1800
December	1st to 10th	Day	64% 3 11% 17% 4	2930
	11th to 20th	Day	66% 3 10% 15% 5%	3370
	21st to end	Day	71% 5% 9% 11% 4	4466
January	1st to 10th	Night	71% 3 8% 14% 3	5889
	11th to 20th	Night	71% 4 9% 10% 5% 1	5900
	21st to end	Night	64% 3 10% 15% 6% 2	6490
February	1st to 10th	Night	58% 5% 10% 19% 8% 1	2600
	11th to 20th	Night	60% 4 9% 17% 9% 1	2379
	21st to end	Night	60% 4 9% 17% 9% 2	1980
March	1st to 10th	Night	53% 4 7% 25% 10% 1	3663
	11th to 20th	Night	43% 6% 10% 30% 10% 1	3498
	21st to end	Night	46% 5% 7% 28% 13% 1	3817
April	1st to 10th	Night	45% 6% 12% 21% 15% 2	2090
	11th to 20th	Night	43% 6% 11% 18% 19% 4	1721
	21st to end	Night	44% 5% 11% 23% 15% 2	1710
May	1st to 10th	Night	57% 7% 9% 19% 7% 2	2840
	11th to 20th	Night	44% 7% 10% 27% 11% 2	2813
	21st to end	Night	33% 9% 14% 28% 13% 4	3087
June	1st to 10th	Night	35% 8% 11% 23% 20% 2	1710
	11th to 20th	Night	31% 9% 16% 25% 17% 2	1710
	21st to end	Night	33% 8% 14% 25% 17% 3	1710
July	1st to 10th	Night	37% 6% 11% 23% 18% 6%	2795
	11th to 20th	Night	34% 7% 12% 30% 15% 2	2786
	21st to end	Night	40% 8% 12% 21% 14% 5%	2988
August	1st to 10th	Night	39% 8% 15% 26% 11% 1	2814
	11th to 20th	Night	39% 6% 9% 24% 22%	2812
	21st to end	Night	27% 7% 14% 30% 19% 3	3146
September	1st to 10th	Night	33% 5% 11% 23% 21% 6%	2086
	11th to 20th	Night	28% 6% 11% 27% 25% 3	2090
	21st to end	Night	39% 5% 9% 21% 24% 1	2090
October	1st to 10th	Night	28% 4 7% 29% 30% 3	3603
	11th to 20th	Night	31% 3 10% 27% 23% 5%	3779
	21st to end	Night	33% 4 8% 26% 25% 4	4151
November	1st to 10th	Night	38% 4 11% 25% 19% 3	2536
	11th to 20th	Night	49% 5% 8% 20% 15% 3	2600
	21st to end	Night	56% 4 11% 19% 9% 1	2600
December	1st to 10th	Night	58% 4 12% 21% 5%	4250
	11th to 20th	Night	63% 4 11% 16% 5%	4824
	21st to end	Night	70% 4 9% 13% 4	6490

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	28% 27% 32% 9% 3	300
	11th to 20th	Day	31% 25% 34% 7% 1	300
	21st to end	Day	32% 26% 30% 9% 3	330
February	1st to 10th	Day	32% 26% 29% 11% 2	300
	11th to 20th	Day	36% 30% 24% 8% 1	300
	21st to end	Day	32% 27% 35% 6%	249
March	1st to 10th	Day	27% 24% 31% 15% 3	410
	11th to 20th	Day	29% 20% 32% 13% 6%	464
	21st to end	Day	32% 16% 32% 15% 4	506
April	1st to 10th	Day	25% 20% 32% 15% 7% 2	460
	11th to 20th	Day	27% 17% 29% 17% 7% 3	452
	21st to end	Day	23% 20% 32% 17% 6% 2	460
May	1st to 10th	Day	27% 20% 28% 15% 7% 3	463
	11th to 20th	Day	21% 13% 31% 22% 9% 5%	487
	21st to end	Day	11% 11% 27% 27% 19% 6%	529
June	1st to 10th	Day	13% 9% 29% 29% 14% 6%	490
	11th to 20th	Day	14% 9% 25% 30% 16% 7%	490
	21st to end	Day	13% 7% 29% 29% 15% 6%	490
July	1st to 10th	Day	15% 4 19% 25% 22% 16%	485
	11th to 20th	Day	10% 5% 24% 28% 23% 10%	484
	21st to end	Day	14% 4 20% 28% 22% 12%	532
August	1st to 10th	Day	11% 5% 19% 31% 23% 12%	486
	11th to 20th	Day	13% 6% 22% 30% 18% 10%	479
	21st to end	Day	9% 5% 18% 31% 27% 11%	539
September	1st to 10th	Day	13% 7% 19% 26% 24% 11%	490
	11th to 20th	Day	11% 3 16% 27% 32% 12%	490
	21st to end	Day	25% 8% 20% 26% 18% 4	490
October	1st to 10th	Day	12% 7% 30% 29% 17% 6%	490
	11th to 20th	Day	18% 15% 30% 21% 13% 3	490
	21st to end	Day	26% 16% 30% 19% 8% 1	515
November	1st to 10th	Day	17% 19% 35% 20% 7% 2	300
	11th to 20th	Day	31% 17% 28% 16% 6% 1	300
	21st to end	Day	26% 23% 33% 15% 2	300
December	1st to 10th	Day	29% 22% 32% 13% 3 1	300
	11th to 20th	Day	27% 26% 34% 10% 3	300
	21st to end	Day	32% 22% 32% 12% 2	330
January	1st to 10th	Night	25% 22% 31% 18% 4	800
	11th to 20th	Night	28% 21% 31% 19% 2	800
	21st to end	Night	27% 17% 33% 21% 2	880
February	1st to 10th	Night	27% 16% 31% 24% 2	800
	11th to 20th	Night	28% 20% 32% 18% 1	783
	21st to end	Night	28% 15% 36% 19% 2	660
March	1st to 10th	Night	24% 15% 33% 24% 4	800
	11th to 20th	Night	21% 19% 31% 22% 7% 1	767
	21st to end	Night	25% 15% 30% 22% 7% 1	836
April	1st to 10th	Night	20% 16% 36% 22% 6%	760
	11th to 20th	Night	18% 12% 36% 22% 11% 1	570
	21st to end	Night	19% 9% 41% 25% 6% 1	570
May	1st to 10th	Night	21% 10% 31% 25% 12% 1	570
	11th to 20th	Night	20% 5% 28% 30% 15% 1	561
	21st to end	Night	8% 6% 24% 35% 26% 2	617
June	1st to 10th	Night	11% 4 26% 38% 20% 1	570
	11th to 20th	Night	9% 3 23% 41% 22% 1	570
	21st to end	Night	11% 4 23% 38% 22% 2	570
July	1st to 10th	Night	10% 3 17% 37% 26% 7%	555
	11th to 20th	Night	7% 2 16% 39% 29% 6%	552
	21st to end	Night	10% 3 14% 36% 35% 2	624
August	1st to 10th	Night	7% 2 14% 39% 34% 3	567
	11th to 20th	Night	8% 2 14% 40% 31% 5%	564
	21st to end	Night	9% 2 17% 31% 35% 7%	627
September	1st to 10th	Night	13% 4 17% 35% 26% 4	756
	11th to 20th	Night	11% 3 13% 36% 33% 5%	760
	21st to end	Night	18% 7% 22% 31% 20% 3	760
October	1st to 10th	Night	12% 5% 25% 33% 22% 3	760
	11th to 20th	Night	18% 11% 28% 30% 12% 2	760
	21st to end	Night	24% 12% 27% 28% 10%	836
November	1st to 10th	Night	18% 12% 25% 29% 15% 1	780
	11th to 20th	Night	22% 16% 28% 25% 9% 1	800
	21st to end	Night	26% 14% 28% 26% 6% 1	800
December	1st to 10th	Night	30% 16% 27% 22% 5%	800
	11th to 20th	Night	26% 16% 30% 23% 4	800
	21st to end	Night	29% 16% 29% 23% 2	880

Page generated at 2025-03-09 08:08:41. Version ac07

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