Burnt Chimney
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Burnt Chimney 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	14% 5% 2 6% 4 4 5% 4 6% 8% 42%	101021
	Night	15% 6% 2 5% 4 4 4 4 5% 7% 45%	98397
Transparency	Day	38% 7% 12% 22% 16% 4	104671
	Night	37% 6% 11% 23% 18% 5%	102886
Seeing	Day	18% 10% 22% 25% 18% 7%	15240
	Night	16% 8% 25% 31% 17% 2	25504

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	17% 5% 1 4 4 3 4 3 5% 6% 49%	2836
	11th to 20th	Day	14% 7% 2 5% 5% 5% 4 3 4 6% 45%	2840
	21st to end	Day	19% 8% 3 7% 5% 4 4 2 4 4 40%	3124
February	1st to 10th	Day	12% 7% 2 6% 5% 5% 5% 4 5% 7% 41%	1710
	11th to 20th	Day	18% 5% 2 5% 4 5% 4 3 5% 7% 41%	1691
	21st to end	Day	19% 8% 2 7% 4 4 4 3 5% 6% 39%	1659
March	1st to 10th	Day	22% 8% 2 5% 3 3 4 3 6% 7% 37%	3435
	11th to 20th	Day	11% 5% 2 4 3 3 4 3 5% 7% 54%	3480
	21st to end	Day	19% 7% 3 6% 3 4 4 4 5% 6% 39%	3815
April	1st to 10th	Day	11% 6% 2 4 4 3 4 4 6% 7% 50%	2170
	11th to 20th	Day	13% 6% 2 5% 4 3 4 4 5% 8% 46%	2254
	21st to end	Day	17% 6% 2 5% 5% 4 4 3 5% 6% 43%	2384
May	1st to 10th	Day	15% 6% 3 7% 5% 6% 6% 5% 7% 8% 32%	4082
	11th to 20th	Day	20% 7% 3 7% 5% 4 4 4 6% 7% 33%	4081
	21st to end	Day	9% 3 2 5% 5% 4 5% 5% 7% 10% 45%	4476
June	1st to 10th	Day	11% 4 2 5% 4 5% 5% 5% 8% 9% 43%	2470
	11th to 20th	Day	9% 5% 2 5% 4 6% 6% 5% 7% 10% 41%	2470
	21st to end	Day	9% 4 2 7% 5% 5% 6% 5% 8% 9% 40%	2470
July	1st to 10th	Day	6% 4 2 6% 5% 6% 6% 6% 9% 12% 38%	4120
	11th to 20th	Day	8% 5% 2 7% 5% 5% 7% 6% 8% 11% 36%	4120
	21st to end	Day	13% 8% 3 8% 6% 7% 7% 6% 8% 9% 26%	4466
August	1st to 10th	Day	15% 6% 2 7% 5% 5% 6% 5% 8% 12% 30%	4104
	11th to 20th	Day	8% 4 2 6% 5% 6% 6% 5% 8% 11% 40%	4044
	21st to end	Day	8% 4 2 5% 4 4 4 3 6% 10% 50%	4190
September	1st to 10th	Day	13% 5% 2 5% 4 3 4 4 5% 6% 49%	2264
	11th to 20th	Day	17% 6% 2 6% 4 4 4 3 5% 8% 41%	2090
	21st to end	Day	25% 5% 2 6% 4 3 4 3 4 6% 38%	2090
October	1st to 10th	Day	18% 5% 1 4 3 3 3 3 4 5% 52%	1902
	11th to 20th	Day	15% 4 2 3 3 3 3 3 5% 6% 53%	1900
	21st to end	Day	13% 5% 2 5% 3 3 3 3 4 6% 54%	2090
November	1st to 10th	Day	13% 4 2 4 3 3 3 3 4 6% 55%	1957
	11th to 20th	Day	15% 4 2 4 4 3 3 3 4 6% 51%	1865
	21st to end	Day	13% 4 1 5% 3 3 4 3 6% 8% 50%	1671
December	1st to 10th	Day	14% 7% 2 6% 4 5% 4 4 7% 7% 40%	1520
	11th to 20th	Day	15% 4 1 4 4 3 3 3 4 7% 54%	2057
	21st to end	Day	20% 5% 2 5% 3 4 5% 4 6% 7% 37%	3124
January	1st to 10th	Night	14% 6% 2 5% 3 3 4 3 4 5% 52%	4109
	11th to 20th	Night	15% 7% 2 5% 3 3 4 3 4 6% 49%	4120
	21st to end	Night	22% 7% 2 5% 3 3 3 3 5% 5% 42%	4532
February	1st to 10th	Night	15% 7% 2 5% 3 3 3 4 5% 6% 46%	2470
	11th to 20th	Night	19% 6% 2 6% 3 3 4 3 4 6% 43%	2370
	21st to end	Night	14% 7% 3 6% 4 4 5% 4 5% 7% 42%	1794
March	1st to 10th	Night	23% 8% 3 6% 4 3 4 3 6% 5% 35%	3418
	11th to 20th	Night	10% 4 2 4 3 3 4 4 6% 7% 54%	3480
	21st to end	Night	16% 6% 2 5% 3 3 4 3 5% 6% 48%	3817
April	1st to 10th	Night	14% 7% 2 5% 4 3 4 3 5% 7% 46%	2009
	11th to 20th	Night	14% 4 1 6% 4 2 4 3 5% 7% 50%	1875
	21st to end	Night	15% 4 2 4 3 3 4 3 5% 8% 47%	1812
May	1st to 10th	Night	16% 6% 3 6% 5% 5% 5% 4 5% 8% 37%	2813
	11th to 20th	Night	22% 9% 2 6% 4 4 3 3 4 6% 38%	2812
	21st to end	Night	10% 3 1 5% 4 4 5% 4 6% 11% 47%	3079
June	1st to 10th	Night	10% 3 1 4 4 5% 6% 5% 7% 12% 42%	1710
	11th to 20th	Night	10% 5% 2 5% 4 3 4 4 7% 11% 46%	1710
	21st to end	Night	8% 3 1 5% 5% 4 4 5% 8% 12% 45%	1710
July	1st to 10th	Night	6% 4 2 6% 5% 6% 5% 5% 8% 10% 42%	2840
	11th to 20th	Night	9% 5% 2 5% 5% 4 6% 5% 7% 11% 40%	2840
	21st to end	Night	10% 8% 3 8% 6% 6% 5% 5% 7% 11% 31%	3087
August	1st to 10th	Night	17% 6% 2 6% 4 5% 5% 5% 7% 11% 32%	2825
	11th to 20th	Night	8% 4 2 5% 4 5% 5% 6% 8% 11% 43%	2785
	21st to end	Night	8% 4 1 6% 4 4 4 4 6% 8% 51%	3434
September	1st to 10th	Night	12% 6% 3 6% 3 3 5% 4 6% 6% 47%	1912
	11th to 20th	Night	17% 5% 2 6% 4 4 4 3 5% 7% 42%	2090
	21st to end	Night	25% 6% 3 6% 4 4 3 3 4 5% 39%	2090
October	1st to 10th	Night	18% 5% 1 5% 3 3 4 3 4 6% 48%	2277
	11th to 20th	Night	15% 5% 2 4 3 3 4 3 4 5% 53%	2280
	21st to end	Night	14% 3 1 4 3 3 2 2 4 6% 57%	2508
November	1st to 10th	Night	14% 5% 2 5% 3 2 3 3 4 5% 53%	2341
	11th to 20th	Night	14% 4 2 4 4 3 3 3 5% 5% 53%	2532
	21st to end	Night	13% 5% 2 4 3 3 4 4 6% 6% 50%	2595
December	1st to 10th	Night	16% 7% 2 5% 5% 3 3 3 5% 6% 44%	2660
	11th to 20th	Night	15% 5% 2 5% 4 4 3 3 5% 6% 48%	3129
	21st to end	Night	18% 5% 2 5% 4 4 5% 4 6% 7% 38%	4532

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	36% 3 10% 27% 19% 5%	2837
	11th to 20th	Day	39% 4 7% 20% 25% 4	2840
	21st to end	Day	48% 3 6% 21% 19% 3	3124
February	1st to 10th	Day	40% 7% 11% 22% 17% 3	1710
	11th to 20th	Day	41% 5% 8% 24% 17% 5%	1700
	21st to end	Day	45% 5% 12% 15% 17% 5%	1659
March	1st to 10th	Day	45% 5% 9% 22% 13% 7%	3435
	11th to 20th	Day	30% 6% 8% 26% 20% 10%	3480
	21st to end	Day	46% 6% 9% 21% 16% 3	3815
April	1st to 10th	Day	32% 6% 12% 23% 20% 7%	2170
	11th to 20th	Day	36% 5% 12% 23% 19% 6%	2254
	21st to end	Day	42% 6% 12% 22% 14% 4	2384
May	1st to 10th	Day	47% 8% 14% 19% 11% 2	4120
	11th to 20th	Day	48% 7% 11% 23% 10% 1	4085
	21st to end	Day	31% 9% 17% 21% 17% 4	4489
June	1st to 10th	Day	35% 9% 16% 25% 14% 1	2470
	11th to 20th	Day	36% 11% 16% 20% 16% 2	2470
	21st to end	Day	36% 10% 16% 21% 15% 2	2470
July	1st to 10th	Day	35% 13% 21% 17% 10% 5%	4055
	11th to 20th	Day	37% 11% 19% 24% 9%	4051
	21st to end	Day	50% 10% 12% 18% 9%	4324
August	1st to 10th	Day	45% 9% 18% 22% 6% 1	4091
	11th to 20th	Day	35% 10% 17% 27% 10% 1	4083
	21st to end	Day	30% 7% 19% 29% 15% 2	4190
September	1st to 10th	Day	35% 8% 12% 21% 20% 4	2264
	11th to 20th	Day	40% 6% 10% 24% 18% 2	2090
	21st to end	Day	48% 6% 9% 18% 17% 2	2090
October	1st to 10th	Day	32% 4 8% 19% 29% 8%	3162
	11th to 20th	Day	24% 3 7% 24% 27% 15%	3140
	21st to end	Day	24% 3 11% 26% 24% 12%	3428
November	1st to 10th	Day	31% 4 10% 23% 26% 6%	1957
	11th to 20th	Day	35% 4 8% 23% 23% 8%	1865
	21st to end	Day	33% 5% 11% 24% 24% 3	1671
December	1st to 10th	Day	43% 6% 11% 18% 18% 4	1520
	11th to 20th	Day	33% 4 8% 24% 23% 8%	2054
	21st to end	Day	43% 6% 11% 24% 13% 2	3124
January	1st to 10th	Night	36% 3 9% 24% 23% 4	4109
	11th to 20th	Night	38% 5% 8% 19% 25% 5%	4120
	21st to end	Night	45% 4 7% 23% 15% 5%	4532
February	1st to 10th	Night	39% 5% 11% 24% 20% 2	2470
	11th to 20th	Night	43% 4 9% 20% 18% 6%	2372
	21st to end	Night	42% 6% 10% 23% 14% 5%	1794
March	1st to 10th	Night	49% 6% 9% 19% 14% 4	3418
	11th to 20th	Night	29% 5% 8% 22% 24% 12%	3480
	21st to end	Night	38% 5% 10% 23% 19% 5%	3817
April	1st to 10th	Night	38% 6% 11% 20% 21% 5%	2009
	11th to 20th	Night	34% 5% 11% 23% 21% 6%	1875
	21st to end	Night	35% 6% 12% 25% 18% 3	1812
May	1st to 10th	Night	44% 8% 14% 21% 11% 1	2840
	11th to 20th	Night	48% 6% 10% 23% 12% 1	2813
	21st to end	Night	29% 9% 18% 27% 12% 4	3087
June	1st to 10th	Night	33% 10% 17% 25% 15% 1	1710
	11th to 20th	Night	31% 10% 18% 23% 16% 2	1710
	21st to end	Night	30% 11% 17% 22% 16% 4	1710
July	1st to 10th	Night	35% 13% 19% 19% 12% 3	2795
	11th to 20th	Night	36% 10% 20% 24% 8% 1	2786
	21st to end	Night	45% 11% 15% 21% 8%	2988
August	1st to 10th	Night	46% 8% 18% 20% 7% 1	2814
	11th to 20th	Night	33% 9% 18% 28% 11% 1	2812
	21st to end	Night	31% 7% 13% 37% 10% 2	3434
September	1st to 10th	Night	37% 9% 12% 20% 16% 6%	1912
	11th to 20th	Night	41% 6% 10% 21% 20% 2	2090
	21st to end	Night	50% 5% 8% 18% 16% 3	2090
October	1st to 10th	Night	38% 4 8% 18% 25% 7%	3797
	11th to 20th	Night	25% 3 7% 22% 30% 12%	3779
	21st to end	Night	22% 3 7% 28% 27% 13%	4120
November	1st to 10th	Night	34% 4 9% 20% 25% 7%	2341
	11th to 20th	Night	33% 4 8% 22% 25% 8%	2532
	21st to end	Night	34% 5% 9% 25% 22% 6%	2595
December	1st to 10th	Night	42% 5% 8% 24% 17% 3	2660
	11th to 20th	Night	38% 5% 7% 23% 20% 7%	3131
	21st to end	Night	42% 5% 12% 21% 18% 2	4532

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	24% 25% 30% 16% 4 1	270
	11th to 20th	Day	27% 19% 36% 16% 1	270
	21st to end	Day	24% 24% 35% 13% 4	297
February	1st to 10th	Day	21% 21% 33% 19% 6%	270
	11th to 20th	Day	33% 23% 35% 6% 3 1	270
	21st to end	Day	26% 21% 30% 19% 3	314
March	1st to 10th	Day	21% 18% 30% 23% 7%	460
	11th to 20th	Day	21% 21% 30% 20% 6% 1	460
	21st to end	Day	24% 15% 32% 24% 5%	506
April	1st to 10th	Day	19% 20% 28% 23% 8% 1	460
	11th to 20th	Day	17% 15% 28% 23% 13% 4	452
	21st to end	Day	20% 12% 32% 22% 12% 2	460
May	1st to 10th	Day	19% 15% 30% 22% 11% 4	463
	11th to 20th	Day	19% 7% 23% 28% 16% 8%	487
	21st to end	Day	16% 4 18% 28% 24% 10%	529
June	1st to 10th	Day	10% 4 24% 34% 18% 9%	490
	11th to 20th	Day	9% 6% 15% 30% 26% 13%	490
	21st to end	Day	10% 4 21% 29% 28% 9%	490
July	1st to 10th	Day	10% 2 13% 27% 29% 18%	485
	11th to 20th	Day	7% 2 9% 29% 39% 15%	484
	21st to end	Day	11% 2 11% 31% 28% 17%	532
August	1st to 10th	Day	13% 4 17% 23% 30% 12%	486
	11th to 20th	Day	13% 2 11% 28% 27% 19%	479
	21st to end	Day	10% 3 9% 26% 31% 22%	539
September	1st to 10th	Day	16% 2 11% 24% 28% 19%	490
	11th to 20th	Day	20% 4 10% 23% 28% 15%	490
	21st to end	Day	28% 6% 17% 25% 19% 4	490
October	1st to 10th	Day	21% 4 16% 30% 22% 6%	490
	11th to 20th	Day	14% 12% 22% 25% 23% 4	490
	21st to end	Day	15% 10% 26% 28% 17% 4	539
November	1st to 10th	Day	17% 9% 23% 31% 17% 3	495
	11th to 20th	Day	19% 16% 27% 25% 11% 2	365
	21st to end	Day	17% 17% 26% 28% 9% 2	246
December	1st to 10th	Day	23% 20% 30% 21% 6% 1	180
	11th to 20th	Day	22% 16% 31% 23% 8% 2	225
	21st to end	Day	25% 15% 32% 18% 9% 1	297
January	1st to 10th	Night	20% 17% 35% 25% 4	760
	11th to 20th	Night	18% 15% 37% 28% 2	760
	21st to end	Night	20% 13% 40% 25% 2	836
February	1st to 10th	Night	17% 14% 38% 28% 3	760
	11th to 20th	Night	24% 16% 40% 19% 1	743
	21st to end	Night	20% 14% 41% 23% 3	628
March	1st to 10th	Night	16% 14% 37% 29% 4	760
	11th to 20th	Night	20% 14% 35% 23% 8% 1	760
	21st to end	Night	18% 11% 35% 31% 5%	836
April	1st to 10th	Night	18% 17% 30% 28% 6%	760
	11th to 20th	Night	15% 11% 34% 28% 13%	751
	21st to end	Night	17% 6% 31% 35% 11%	672
May	1st to 10th	Night	15% 8% 31% 31% 15%	570
	11th to 20th	Night	19% 5% 23% 32% 18% 2	561
	21st to end	Night	14% 3 14% 32% 33% 4	617
June	1st to 10th	Night	10% 2 15% 39% 31% 2	570
	11th to 20th	Night	11% 2 13% 33% 36% 5%	570
	21st to end	Night	8% 3 12% 42% 31% 4	570
July	1st to 10th	Night	10% 2 9% 32% 40% 7%	555
	11th to 20th	Night	7% 1 7% 34% 45% 6%	552
	21st to end	Night	7% 2 9% 40% 36% 5%	624
August	1st to 10th	Night	15% 2 8% 34% 37% 5%	567
	11th to 20th	Night	12% 2 8% 38% 36% 5%	564
	21st to end	Night	11% 1 9% 32% 39% 8%	807
September	1st to 10th	Night	13% 3 10% 29% 38% 7%	760
	11th to 20th	Night	19% 2 11% 30% 33% 5%	760
	21st to end	Night	27% 5% 16% 27% 23% 2	760
October	1st to 10th	Night	19% 5% 17% 29% 25% 5%	760
	11th to 20th	Night	17% 7% 24% 33% 18% 2	760
	21st to end	Night	16% 8% 24% 37% 13% 2	836
November	1st to 10th	Night	17% 7% 27% 34% 13% 2	780
	11th to 20th	Night	16% 11% 30% 32% 11% 1	800
	21st to end	Night	16% 12% 28% 32% 11% 1	779
December	1st to 10th	Night	22% 12% 34% 27% 5%	760
	11th to 20th	Night	17% 9% 40% 29% 5%	760
	21st to end	Night	21% 13% 32% 30% 4	836

Page generated at 2024-11-22 08:02:28. Version ac07

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