Bonebrake Center of Nature and History
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bonebrake Center of Nature and History clear sky chart from 2005-11-06 to 2024-11-25.

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	12% 7% 3 6% 4 4 4 3 5% 7% 43%	101305
	Night	12% 8% 3 6% 4 3 4 3 5% 6% 45%	98239
Transparency	Day	38% 5% 11% 25% 17% 3	104940
	Night	38% 5% 10% 25% 19% 4	102744
Seeing	Day	18% 13% 28% 25% 13% 3	15629
	Night	18% 13% 32% 25% 11% 1	25443

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	12% 13% 4 8% 5% 3 4 3 4 5% 40%	2632
	11th to 20th	Day	12% 12% 3 8% 4 4 4 3 4 5% 42%	2850
	21st to end	Day	22% 10% 4 6% 3 3 3 3 4 4 38%	3135
February	1st to 10th	Day	15% 11% 4 8% 6% 4 4 2 5% 5% 36%	1710
	11th to 20th	Day	14% 10% 3 6% 4 4 4 3 5% 6% 40%	1784
	21st to end	Day	14% 12% 2 7% 4 5% 4 3 5% 6% 38%	1570
March	1st to 10th	Day	18% 12% 3 6% 4 4 3 2 3 4 41%	3330
	11th to 20th	Day	13% 8% 2 4 3 3 3 3 4 6% 51%	3480
	21st to end	Day	14% 9% 3 7% 5% 5% 5% 3 5% 6% 37%	3927
April	1st to 10th	Day	11% 7% 2 6% 5% 3 4 3 6% 8% 45%	2280
	11th to 20th	Day	16% 8% 2 7% 5% 4 4 3 5% 6% 40%	2254
	21st to end	Day	19% 9% 3 7% 4 4 4 3 5% 5% 36%	2280
May	1st to 10th	Day	15% 8% 2 8% 5% 5% 5% 5% 7% 8% 33%	3794
	11th to 20th	Day	18% 7% 2 6% 5% 4 4 3 5% 7% 39%	4266
	21st to end	Day	12% 7% 3 7% 5% 5% 4 4 5% 7% 41%	4824
June	1st to 10th	Day	9% 6% 2 6% 5% 5% 6% 5% 5% 9% 43%	2660
	11th to 20th	Day	6% 5% 2 4 5% 4 5% 5% 7% 10% 49%	2660
	21st to end	Day	5% 4 1 4 4 4 5% 4 8% 10% 50%	2660
July	1st to 10th	Day	13% 5% 2 7% 5% 4 5% 4 6% 9% 40%	4440
	11th to 20th	Day	4 4 2 6% 4 4 5% 4 8% 12% 48%	4258
	21st to end	Day	7% 5% 3 7% 6% 6% 6% 5% 8% 10% 35%	4465
August	1st to 10th	Day	5% 4 1 4 4 4 4 4 7% 10% 53%	4104
	11th to 20th	Day	11% 6% 2 6% 5% 5% 5% 3 6% 8% 44%	3772
	21st to end	Day	8% 4 2 5% 3 3 4 4 6% 9% 52%	4180
September	1st to 10th	Day	12% 5% 1 4 4 4 3 3 6% 8% 49%	2280
	11th to 20th	Day	11% 5% 2 6% 4 3 4 4 6% 7% 48%	2280
	21st to end	Day	10% 4 2 6% 4 4 4 3 4 7% 51%	2024
October	1st to 10th	Day	9% 4 2 5% 2 4 3 3 4 7% 56%	1900
	11th to 20th	Day	14% 7% 2 5% 3 2 2 2 4 5% 54%	1900
	21st to end	Day	18% 7% 2 5% 3 3 3 2 5% 5% 47%	2090
November	1st to 10th	Day	12% 6% 2 5% 4 3 3 3 4 5% 53%	1853
	11th to 20th	Day	13% 8% 3 6% 3 3 4 3 3 7% 48%	1800
	21st to end	Day	14% 9% 4 6% 4 3 3 3 3 5% 45%	1642
December	1st to 10th	Day	13% 11% 3 6% 5% 4 4 4 5% 6% 40%	1520
	11th to 20th	Day	13% 11% 5% 9% 5% 5% 4 3 3 5% 38%	1918
	21st to end	Day	13% 17% 5% 9% 4 4 4 2 4 6% 31%	2783
January	1st to 10th	Night	13% 10% 5% 10% 5% 4 4 3 4 5% 37%	4318
	11th to 20th	Night	12% 9% 4 11% 6% 5% 6% 4 4 5% 35%	4120
	21st to end	Night	21% 14% 5% 7% 4 3 3 3 4 5% 34%	4532
February	1st to 10th	Night	15% 11% 4 8% 4 3 3 3 5% 5% 38%	2470
	11th to 20th	Night	14% 8% 4 7% 4 4 3 2 5% 6% 44%	2281
	21st to end	Night	16% 9% 3 7% 5% 4 3 3 5% 5% 40%	1884
March	1st to 10th	Night	19% 11% 3 5% 3 2 3 2 4 4 43%	3551
	11th to 20th	Night	13% 7% 2 5% 3 3 3 3 4 6% 49%	3480
	21st to end	Night	14% 12% 4 7% 5% 4 5% 4 5% 6% 35%	3703
April	1st to 10th	Night	9% 5% 2 5% 4 3 3 3 6% 8% 50%	1900
	11th to 20th	Night	13% 9% 2 6% 4 3 3 3 5% 6% 46%	1875
	21st to end	Night	18% 8% 3 6% 4 3 4 2 5% 7% 40%	1900
May	1st to 10th	Night	17% 7% 2 5% 3 3 4 3 5% 7% 44%	3086
	11th to 20th	Night	14% 9% 3 6% 3 3 3 3 5% 8% 43%	2634
	21st to end	Night	13% 8% 3 8% 6% 4 4 4 6% 7% 38%	2743
June	1st to 10th	Night	8% 4 1 6% 4 4 4 3 7% 9% 50%	1520
	11th to 20th	Night	5% 4 1 3 4 3 4 3 7% 11% 56%	1520
	21st to end	Night	3 3 1 3 3 3 4 4 6% 11% 59%	1520
July	1st to 10th	Night	11% 5% 2 5% 3 4 5% 4 6% 10% 46%	2530
	11th to 20th	Night	5% 3 1 4 3 3 3 3 6% 8% 61%	2708
	21st to end	Night	7% 6% 2 7% 5% 5% 5% 5% 7% 8% 43%	3098
August	1st to 10th	Night	4 3 1 4 3 3 4 3 6% 9% 59%	2836
	11th to 20th	Night	9% 5% 2 7% 4 4 5% 4 6% 8% 47%	3058
	21st to end	Night	5% 4 1 4 3 3 4 3 5% 8% 59%	3476
September	1st to 10th	Night	11% 5% 2 3 4 3 4 3 5% 5% 54%	1900
	11th to 20th	Night	9% 5% 2 5% 4 3 4 4 5% 8% 51%	1900
	21st to end	Night	9% 5% 2 4 4 4 3 4 5% 7% 54%	2132
October	1st to 10th	Night	7% 4 1 4 3 2 3 3 4 7% 62%	2280
	11th to 20th	Night	14% 6% 2 4 3 3 3 2 3 5% 54%	2280
	21st to end	Night	18% 7% 2 5% 3 4 3 3 4 4 48%	2508
November	1st to 10th	Night	11% 5% 2 4 3 3 3 3 4 5% 56%	2445
	11th to 20th	Night	13% 7% 3 6% 3 3 4 2 5% 6% 49%	2600
	21st to end	Night	15% 10% 3 5% 3 3 3 3 4 5% 46%	2628
December	1st to 10th	Night	16% 10% 3 7% 4 4 3 3 6% 7% 38%	2660
	11th to 20th	Night	14% 11% 4 7% 5% 4 4 3 4 5% 40%	3279
	21st to end	Night	14% 18% 8% 10% 5% 4 4 3 4 5% 26%	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	47% 4 7% 27% 14% 2	2633
	11th to 20th	Day	44% 4 8% 25% 16% 2	2850
	21st to end	Day	50% 3 8% 17% 16% 6%	3135
February	1st to 10th	Day	50% 4 10% 22% 13% 1	1710
	11th to 20th	Day	45% 4 11% 21% 14% 4	1793
	21st to end	Day	47% 4 7% 23% 13% 6%	1570
March	1st to 10th	Day	48% 4 6% 20% 14% 8%	3330
	11th to 20th	Day	35% 5% 9% 28% 16% 7%	3480
	21st to end	Day	47% 6% 14% 21% 11% 1	3927
April	1st to 10th	Day	38% 4 12% 25% 20% 1	2280
	11th to 20th	Day	45% 5% 10% 21% 16% 3	2254
	21st to end	Day	48% 5% 10% 21% 14% 1	2280
May	1st to 10th	Day	45% 10% 12% 21% 12% 1	3829
	11th to 20th	Day	44% 6% 11% 25% 13% 1	4270
	21st to end	Day	41% 6% 9% 24% 19% 1	4837
June	1st to 10th	Day	37% 7% 14% 26% 15% 2	2660
	11th to 20th	Day	29% 6% 13% 30% 19% 3	2660
	21st to end	Day	27% 6% 19% 27% 16% 5%	2660
July	1st to 10th	Day	39% 6% 13% 28% 12% 2	4371
	11th to 20th	Day	28% 6% 14% 34% 17% 2	4184
	21st to end	Day	39% 9% 18% 26% 7% 1	4325
August	1st to 10th	Day	25% 6% 17% 33% 19%	4090
	11th to 20th	Day	38% 5% 13% 26% 16% 2	3808
	21st to end	Day	28% 6% 15% 36% 11% 3	4179
September	1st to 10th	Day	33% 4 12% 28% 17% 6%	2280
	11th to 20th	Day	35% 5% 8% 26% 24% 1	2280
	21st to end	Day	33% 5% 8% 27% 24% 3	2024
October	1st to 10th	Day	17% 2 6% 19% 42% 13%	3160
	11th to 20th	Day	23% 2 5% 21% 38% 10%	3140
	21st to end	Day	30% 3 7% 32% 25% 4	3428
November	1st to 10th	Day	35% 3 9% 23% 23% 7%	1853
	11th to 20th	Day	38% 4 7% 23% 22% 7%	1800
	21st to end	Day	43% 3 8% 26% 19% 2	1642
December	1st to 10th	Day	44% 4 9% 27% 14% 2	1520
	11th to 20th	Day	50% 4 5% 17% 22% 1	1915
	21st to end	Day	56% 5% 8% 16% 13% 2	2783
January	1st to 10th	Night	48% 6% 9% 21% 15% 1	4318
	11th to 20th	Night	48% 7% 7% 22% 12% 2	4120
	21st to end	Night	54% 5% 8% 20% 12% 1	4532
February	1st to 10th	Night	47% 4 10% 22% 15% 2	2470
	11th to 20th	Night	43% 3 11% 23% 17% 3	2282
	21st to end	Night	46% 4 7% 22% 16% 5%	1884
March	1st to 10th	Night	45% 4 7% 23% 15% 5%	3551
	11th to 20th	Night	36% 5% 10% 25% 19% 5%	3480
	21st to end	Night	47% 7% 13% 24% 9%	3703
April	1st to 10th	Night	32% 3 13% 28% 20% 3	1900
	11th to 20th	Night	40% 4 10% 25% 16% 5%	1875
	21st to end	Night	45% 4 9% 26% 15% 1	1900
May	1st to 10th	Night	39% 8% 15% 21% 14% 2	3116
	11th to 20th	Night	40% 6% 14% 24% 14% 1	2635
	21st to end	Night	43% 8% 11% 22% 14% 1	2751
June	1st to 10th	Night	30% 6% 17% 25% 19% 2	1520
	11th to 20th	Night	22% 6% 13% 34% 21% 4	1520
	21st to end	Night	19% 5% 19% 31% 19% 7%	1520
July	1st to 10th	Night	35% 6% 15% 25% 16% 3	2490
	11th to 20th	Night	21% 5% 12% 40% 20% 2	2659
	21st to end	Night	36% 8% 16% 27% 11% 1	2999
August	1st to 10th	Night	21% 6% 17% 33% 22% 1	2826
	11th to 20th	Night	35% 6% 16% 25% 15% 3	3088
	21st to end	Night	23% 5% 15% 38% 16% 3	3476
September	1st to 10th	Night	31% 4 10% 28% 22% 5%	1900
	11th to 20th	Night	31% 5% 9% 26% 26% 2	1900
	21st to end	Night	30% 4 9% 25% 28% 3	2132
October	1st to 10th	Night	14% 2 6% 17% 47% 13%	3800
	11th to 20th	Night	24% 2 5% 20% 32% 16%	3779
	21st to end	Night	31% 3 7% 27% 28% 4	4120
November	1st to 10th	Night	31% 3 10% 28% 22% 6%	2445
	11th to 20th	Night	37% 3 6% 24% 23% 7%	2600
	21st to end	Night	42% 3 7% 25% 20% 2	2628
December	1st to 10th	Night	45% 4 10% 23% 17% 2	2660
	11th to 20th	Night	47% 3 7% 23% 17% 2	3281
	21st to end	Night	60% 6% 8% 15% 9% 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	26% 25% 36% 11% 1	270
	11th to 20th	Day	33% 24% 35% 8%	270
	21st to end	Day	22% 34% 32% 11% 2	297
February	1st to 10th	Day	28% 25% 35% 11% 1	270
	11th to 20th	Day	33% 28% 30% 8% 1	270
	21st to end	Day	35% 26% 30% 8% 1	225
March	1st to 10th	Day	26% 23% 40% 10%	270
	11th to 20th	Day	36% 20% 31% 10% 2	270
	21st to end	Day	32% 23% 33% 11% 1	359
April	1st to 10th	Day	24% 20% 37% 14% 4	460
	11th to 20th	Day	27% 21% 30% 18% 4	452
	21st to end	Day	24% 22% 31% 18% 4 1	460
May	1st to 10th	Day	23% 20% 33% 20% 4 1	479
	11th to 20th	Day	19% 15% 31% 22% 11% 3	675
	21st to end	Day	14% 10% 36% 25% 11% 4	734
June	1st to 10th	Day	11% 5% 27% 31% 21% 5%	680
	11th to 20th	Day	8% 3 25% 42% 19% 4	680
	21st to end	Day	6% 7% 32% 35% 16% 3	680
July	1st to 10th	Day	12% 2 20% 30% 28% 8%	671
	11th to 20th	Day	4 4 21% 39% 25% 6%	668
	21st to end	Day	10% 5% 18% 34% 27% 6%	739
August	1st to 10th	Day	8% 4 17% 42% 24% 4	676
	11th to 20th	Day	12% 4 21% 32% 24% 6%	510
	21st to end	Day	13% 2 14% 34% 28% 9%	539
September	1st to 10th	Day	13% 5% 16% 34% 26% 6%	490
	11th to 20th	Day	10% 3 23% 33% 23% 7%	490
	21st to end	Day	11% 12% 28% 27% 18% 5%	396
October	1st to 10th	Day	13% 10% 34% 27% 11% 5%	300
	11th to 20th	Day	22% 15% 36% 21% 4 1	300
	21st to end	Day	29% 19% 33% 18% 2	330
November	1st to 10th	Day	17% 16% 40% 20% 4 2	300
	11th to 20th	Day	23% 21% 34% 16% 5%	300
	21st to end	Day	28% 15% 38% 14% 5%	282
December	1st to 10th	Day	21% 27% 31% 14% 5% 2	270
	11th to 20th	Day	27% 21% 34% 14% 3	270
	21st to end	Day	28% 27% 33% 9% 3	297
January	1st to 10th	Night	22% 23% 37% 15% 3	950
	11th to 20th	Night	24% 26% 34% 12% 4	950
	21st to end	Night	21% 23% 39% 17% 1	1045
February	1st to 10th	Night	24% 21% 38% 15% 1	950
	11th to 20th	Night	23% 21% 41% 14% 2	806
	21st to end	Night	27% 24% 33% 14% 2	628
March	1st to 10th	Night	24% 18% 39% 18% 1	656
	11th to 20th	Night	24% 16% 36% 20% 4	570
	21st to end	Night	28% 17% 34% 17% 4	627
April	1st to 10th	Night	15% 20% 42% 21% 2	570
	11th to 20th	Night	20% 17% 33% 25% 4	563
	21st to end	Night	22% 15% 37% 20% 6%	570
May	1st to 10th	Night	18% 10% 37% 28% 8%	570
	11th to 20th	Night	19% 7% 33% 26% 13% 1	561
	21st to end	Night	12% 7% 32% 29% 17% 2	617
June	1st to 10th	Night	8% 5% 22% 36% 26% 3	570
	11th to 20th	Night	6% 3 26% 41% 22% 2	570
	21st to end	Night	3 2 28% 45% 20% 2	570
July	1st to 10th	Night	11% 1 14% 37% 30% 7%	555
	11th to 20th	Night	6% 2 19% 39% 30% 4	552
	21st to end	Night	6% 2 17% 44% 28% 3	624
August	1st to 10th	Night	6% 2 17% 42% 31% 2	567
	11th to 20th	Night	7% 3 18% 41% 28% 4	564
	21st to end	Night	7% 3 16% 37% 32% 5%	627
September	1st to 10th	Night	13% 2 18% 36% 26% 5%	570
	11th to 20th	Night	12% 2 17% 39% 24% 5%	570
	21st to end	Night	12% 6% 26% 30% 21% 4	712
October	1st to 10th	Night	8% 7% 32% 28% 22% 3	760
	11th to 20th	Night	17% 13% 36% 26% 8%	760
	21st to end	Night	24% 14% 34% 22% 6%	836
November	1st to 10th	Night	15% 12% 42% 25% 7%	780
	11th to 20th	Night	21% 16% 34% 22% 6%	800
	21st to end	Night	23% 19% 35% 18% 6%	878
December	1st to 10th	Night	23% 18% 36% 19% 4	950
	11th to 20th	Night	25% 15% 38% 19% 4	950
	21st to end	Night	24% 24% 36% 15% 2	1045

Page generated at 2024-11-22 07:02:24. Version ac07

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