Burns
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Burns clear sky chart from 2005-11-06 to 2024-02-10.

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	6% 7% 3 6% 6% 3 5% 4 5% 7% 48%	78211
	Night	7% 7% 3 6% 6% 3 5% 5% 6% 7% 45%	80781
Transparency	Day	36% 5% 10% 20% 18% 11%	77915
	Night	38% 5% 12% 20% 16% 8%	80598
Seeing	Day	9% 7% 20% 28% 24% 12%	13542
	Night	10% 4 22% 39% 22% 3	22890

By Month

Percentage Cloud Cover SW (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	8% 12% 5% 12% 9% 5% 6% 7% 6% 7% 23%	2539
	11th to 20th	Day	12% 13% 6% 11% 8% 5% 6% 5% 6% 8% 23%	2540
	21st to end	Day	13% 14% 4 10% 9% 4 6% 5% 6% 7% 22%	2830
February	1st to 10th	Day	6% 9% 3 8% 9% 5% 7% 6% 7% 8% 32%	1702
	11th to 20th	Day	7% 9% 4 7% 6% 4 6% 6% 6% 8% 36%	1695
	21st to end	Day	6% 7% 5% 8% 6% 5% 6% 7% 8% 8% 34%	1480
March	1st to 10th	Day	7% 9% 4 9% 8% 4 6% 6% 6% 9% 32%	1800
	11th to 20th	Day	8% 10% 4 8% 7% 4 5% 5% 7% 8% 35%	1872
	21st to end	Day	8% 10% 4 9% 8% 4 7% 6% 6% 7% 32%	2362
April	1st to 10th	Day	8% 9% 4 7% 6% 4 5% 5% 5% 7% 38%	2160
	11th to 20th	Day	9% 8% 3 5% 5% 4 5% 5% 6% 7% 43%	2129
	21st to end	Day	6% 7% 3 6% 5% 3 4 4 5% 7% 49%	2250
May	1st to 10th	Day	5% 5% 2 5% 6% 3 4 5% 5% 8% 53%	2416
	11th to 20th	Day	9% 7% 3 5% 5% 3 5% 4 6% 8% 44%	2477
	21st to end	Day	7% 8% 3 7% 6% 4 5% 6% 5% 9% 39%	2723
June	1st to 10th	Day	8% 6% 3 5% 5% 4 5% 4 6% 8% 46%	2520
	11th to 20th	Day	5% 3 2 5% 5% 2 4 4 5% 7% 57%	2520
	21st to end	Day	3 3 1 3 3 2 3 3 4 5% 70%	2520
July	1st to 10th	Day	2 2 1 2 3 1 3 3 4 5% 75%	2520
	11th to 20th	Day	1 1 1 2 2 1 2 2 3 4 81%	2520
	21st to end	Day	2 1 1 2 3 2 2 3 3 4 77%	2741
August	1st to 10th	Day	3 2 1 2 3 2 3 4 5% 6% 68%	2507
	11th to 20th	Day	2 2 1 2 2 1 2 3 3 6% 77%	2177
	21st to end	Day	2 2 1 2 2 1 2 2 3 5% 78%	2376
September	1st to 10th	Day	2 2 1 2 3 2 3 2 3 5% 75%	2160
	11th to 20th	Day	4 3 1 3 4 3 3 4 4 6% 65%	2106
	21st to end	Day	5% 5% 1 4 5% 3 3 4 4 5% 62%	1980
October	1st to 10th	Day	7% 6% 3 5% 4 2 3 3 4 6% 57%	1854
	11th to 20th	Day	6% 5% 2 5% 5% 2 4 5% 5% 7% 55%	1800
	21st to end	Day	8% 7% 2 4 5% 3 4 5% 5% 6% 51%	1804
November	1st to 10th	Day	11% 8% 3 5% 6% 3 6% 4 6% 8% 40%	1674
	11th to 20th	Day	10% 8% 3 8% 6% 4 6% 5% 7% 10% 34%	1695
	21st to end	Day	7% 8% 3 6% 6% 5% 6% 6% 6% 9% 38%	1520
December	1st to 10th	Day	8% 9% 4 8% 8% 4 6% 5% 7% 9% 32%	1520
	11th to 20th	Day	12% 11% 5% 10% 9% 4 7% 6% 6% 8% 23%	1928
	21st to end	Day	9% 12% 6% 14% 10% 5% 6% 6% 5% 7% 21%	2794
January	1st to 10th	Night	9% 12% 5% 10% 9% 4 6% 6% 6% 9% 24%	4406
	11th to 20th	Night	15% 14% 4 7% 7% 5% 5% 5% 5% 7% 25%	4420
	21st to end	Night	14% 12% 5% 9% 9% 4 5% 5% 5% 8% 25%	4822
February	1st to 10th	Night	7% 9% 4 8% 6% 3 6% 6% 6% 9% 36%	2462
	11th to 20th	Night	8% 9% 4 6% 5% 3 6% 5% 6% 8% 41%	2152
	21st to end	Night	6% 8% 5% 7% 7% 3 6% 6% 7% 8% 37%	1776
March	1st to 10th	Night	9% 9% 5% 7% 7% 4 6% 5% 7% 8% 34%	2160
	11th to 20th	Night	9% 8% 3 6% 6% 5% 6% 6% 7% 9% 38%	2087
	21st to end	Night	7% 9% 3 7% 6% 4 6% 5% 6% 9% 39%	1994
April	1st to 10th	Night	9% 9% 2 6% 5% 3 4 5% 7% 9% 41%	1800
	11th to 20th	Night	6% 7% 3 6% 6% 4 5% 5% 6% 6% 47%	1779
	21st to end	Night	6% 6% 3 5% 4 2 4 5% 7% 8% 50%	1709
May	1st to 10th	Night	4 4 3 3 5% 3 5% 5% 6% 7% 54%	1540
	11th to 20th	Night	6% 6% 3 4 5% 3 6% 6% 7% 9% 46%	1416
	21st to end	Night	7% 6% 2 6% 6% 3 5% 5% 6% 8% 47%	1552
June	1st to 10th	Night	7% 5% 3 6% 5% 3 5% 4 6% 7% 49%	1440
	11th to 20th	Night	7% 4 2 3 3 1 4 3 5% 7% 60%	1440
	21st to end	Night	3 3 1 4 3 3 4 3 4 6% 68%	1440
July	1st to 10th	Night	2 2 1 3 3 2 2 3 5% 6% 71%	1440
	11th to 20th	Night	1 1 1 2 1 1 2 4 5% 82%	1440
	21st to end	Night	2 1 1 2 2 1 3 3 4 5% 75%	1576
August	1st to 10th	Night	4 1 1 4 4 2 3 5% 5% 8% 63%	1432
	11th to 20th	Night	1 1 1 2 2 1 2 3 5% 6% 77%	1723
	21st to end	Night	1 2 1 2 2 1 3 2 4 5% 76%	1980
September	1st to 10th	Night	2 2 1 2 3 1 2 2 3 4 80%	1800
	11th to 20th	Night	3 2 1 2 3 2 2 3 5% 6% 70%	1854
	21st to end	Night	4 4 1 3 4 2 3 4 4 5% 66%	1980
October	1st to 10th	Night	6% 4 2 3 4 2 3 4 5% 6% 62%	2104
	11th to 20th	Night	5% 3 1 3 4 2 4 5% 5% 7% 60%	2160
	21st to end	Night	6% 5% 2 5% 5% 3 4 6% 6% 7% 51%	2551
November	1st to 10th	Night	11% 8% 3 5% 5% 3 4 5% 6% 7% 42%	2405
	11th to 20th	Night	10% 7% 3 6% 6% 4 5% 5% 7% 9% 38%	2483
	21st to end	Night	8% 9% 3 5% 4 3 5% 4 5% 9% 44%	2660
December	1st to 10th	Night	10% 9% 4 7% 7% 4 4 5% 6% 8% 36%	2660
	11th to 20th	Night	11% 11% 4 8% 8% 4 7% 6% 7% 8% 26%	3276
	21st to end	Night	9% 10% 4 11% 9% 5% 6% 6% 7% 8% 26%	4862

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	58% 7% 13% 16% 5%	2539
	11th to 20th	Day	62% 7% 15% 11% 4 1	2540
	21st to end	Day	61% 8% 14% 12% 4 1	2830
February	1st to 10th	Day	48% 8% 20% 18% 6%	1702
	11th to 20th	Day	45% 7% 16% 22% 10% 1	1705
	21st to end	Day	45% 6% 17% 21% 10% 1	1480
March	1st to 10th	Day	48% 6% 14% 22% 9% 1	1800
	11th to 20th	Day	46% 6% 13% 23% 11%	1872
	21st to end	Day	51% 7% 14% 20% 7% 1	2362
April	1st to 10th	Day	44% 5% 13% 20% 14% 3	2160
	11th to 20th	Day	40% 3 11% 23% 19% 4	2132
	21st to end	Day	35% 6% 11% 27% 18% 3	2250
May	1st to 10th	Day	29% 5% 10% 32% 20% 4	2416
	11th to 20th	Day	37% 5% 8% 30% 16% 4	2480
	21st to end	Day	40% 6% 13% 23% 16% 2	2724
June	1st to 10th	Day	36% 5% 9% 27% 21% 2	2520
	11th to 20th	Day	27% 4 7% 26% 28% 9%	2520
	21st to end	Day	17% 3 6% 22% 32% 20%	2520
July	1st to 10th	Day	14% 2 3 17% 30% 34%	2451
	11th to 20th	Day	9% 2 3 12% 29% 45%	2445
	21st to end	Day	13% 2 2 9% 28% 47%	2589
August	1st to 10th	Day	17% 3 4 18% 32% 27%	2490
	11th to 20th	Day	11% 2 3 18% 33% 33%	2177
	21st to end	Day	11% 2 3 18% 38% 28%	2376
September	1st to 10th	Day	13% 2 2 20% 30% 32%	2160
	11th to 20th	Day	20% 3 6% 20% 29% 22%	2106
	21st to end	Day	25% 2 8% 24% 25% 15%	1980
October	1st to 10th	Day	29% 4 10% 21% 25% 11%	1854
	11th to 20th	Day	29% 4 11% 27% 22% 6%	1800
	21st to end	Day	34% 5% 14% 26% 19% 2	1804
November	1st to 10th	Day	41% 6% 13% 25% 15% 1	1674
	11th to 20th	Day	46% 6% 18% 22% 8% 1	1695
	21st to end	Day	42% 6% 18% 21% 12% 2	1520
December	1st to 10th	Day	50% 8% 16% 20% 5% 1	1520
	11th to 20th	Day	59% 8% 12% 17% 4	1928
	21st to end	Day	63% 7% 11% 15% 4	2794
January	1st to 10th	Night	56% 8% 18% 14% 4	4406
	11th to 20th	Night	61% 6% 13% 14% 5% 1	4420
	21st to end	Night	59% 8% 14% 14% 4 1	4822
February	1st to 10th	Night	45% 7% 18% 19% 9% 1	2462
	11th to 20th	Night	42% 7% 17% 22% 11% 2	2153
	21st to end	Night	44% 7% 17% 20% 11% 2	1776
March	1st to 10th	Night	48% 4 13% 21% 11% 3	2160
	11th to 20th	Night	42% 6% 15% 27% 10% 1	2087
	21st to end	Night	43% 7% 16% 25% 9% 1	1994
April	1st to 10th	Night	40% 5% 16% 23% 14% 2	1800
	11th to 20th	Night	37% 6% 13% 26% 16% 3	1779
	21st to end	Night	31% 5% 16% 29% 17% 2	1709
May	1st to 10th	Night	28% 5% 10% 32% 23% 1	1540
	11th to 20th	Night	33% 5% 12% 29% 18% 3	1416
	21st to end	Night	36% 6% 16% 27% 13% 2	1552
June	1st to 10th	Night	35% 5% 14% 27% 17% 2	1440
	11th to 20th	Night	25% 5% 9% 28% 26% 8%	1440
	21st to end	Night	18% 4 6% 25% 33% 15%	1440
July	1st to 10th	Night	15% 3 3 20% 28% 30%	1400
	11th to 20th	Night	7% 2 4 17% 29% 42%	1392
	21st to end	Night	12% 2 3 9% 30% 44%	1488
August	1st to 10th	Night	18% 4 4 20% 27% 26%	1424
	11th to 20th	Night	10% 2 5% 19% 31% 33%	1723
	21st to end	Night	13% 2 2 18% 36% 29%	1980
September	1st to 10th	Night	12% 2 3 17% 32% 34%	1800
	11th to 20th	Night	15% 3 7% 20% 31% 23%	1854
	21st to end	Night	20% 3 5% 23% 29% 19%	1980
October	1st to 10th	Night	24% 4 10% 22% 29% 11%	2104
	11th to 20th	Night	24% 4 10% 27% 27% 6%	2160
	21st to end	Night	31% 5% 16% 22% 21% 6%	2551
November	1st to 10th	Night	40% 5% 13% 22% 18% 2	2405
	11th to 20th	Night	43% 5% 17% 23% 11%	2483
	21st to end	Night	40% 5% 16% 21% 15% 2	2660
December	1st to 10th	Night	47% 8% 16% 19% 9% 1	2660
	11th to 20th	Night	57% 7% 14% 17% 5%	3276
	21st to end	Night	57% 7% 13% 14% 8%	4862

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	22% 4 24% 24% 21% 5%	180
	11th to 20th	Day	18% 8% 20% 28% 20% 7%	180
	21st to end	Day	11% 3 22% 36% 23% 6%	221
February	1st to 10th	Day	10% 10% 31% 29% 15% 5%	368
	11th to 20th	Day	13% 11% 29% 27% 16% 3	391
	21st to end	Day	12% 11% 30% 29% 16% 2	346
March	1st to 10th	Day	12% 12% 33% 27% 14% 1	420
	11th to 20th	Day	13% 12% 26% 29% 16% 4	420
	21st to end	Day	15% 14% 23% 31% 15% 2	462
April	1st to 10th	Day	15% 15% 25% 20% 20% 5%	420
	11th to 20th	Day	13% 16% 28% 23% 15% 7%	412
	21st to end	Day	10% 12% 25% 29% 19% 5%	420
May	1st to 10th	Day	8% 10% 23% 30% 21% 9%	423
	11th to 20th	Day	16% 9% 21% 23% 21% 10%	448
	21st to end	Day	10% 6% 17% 27% 25% 16%	485
June	1st to 10th	Day	9% 8% 20% 24% 21% 19%	450
	11th to 20th	Day	8% 11% 21% 28% 23% 10%	450
	21st to end	Day	3 4 18% 30% 26% 20%	450
July	1st to 10th	Day	5% 2 15% 31% 33% 14%	446
	11th to 20th	Day	2 1 18% 29% 35% 16%	444
	21st to end	Day	2 2 14% 27% 34% 21%	487
August	1st to 10th	Day	4 2 15% 28% 30% 21%	447
	11th to 20th	Day	2 3 11% 23% 33% 28%	437
	21st to end	Day	3 3 14% 27% 32% 20%	495
September	1st to 10th	Day	2 3 14% 27% 32% 22%	450
	11th to 20th	Day	8% 4 14% 25% 31% 18%	450
	21st to end	Day	7% 6% 16% 25% 33% 14%	450
October	1st to 10th	Day	10% 9% 17% 26% 22% 17%	450
	11th to 20th	Day	10% 6% 21% 25% 25% 13%	450
	21st to end	Day	11% 7% 19% 32% 20% 10%	319
November	1st to 10th	Day	14% 7% 20% 32% 21% 5%	270
	11th to 20th	Day	12% 5% 19% 33% 24% 7%	263
	21st to end	Day	11% 8% 16% 31% 26% 8%	180
December	1st to 10th	Day	13% 7% 17% 30% 19% 14%	180
	11th to 20th	Day	22% 7% 18% 35% 16% 2	180
	21st to end	Day	14% 8% 21% 32% 21% 4	198
January	1st to 10th	Night	14% 6% 24% 34% 19% 3	760
	11th to 20th	Night	16% 6% 19% 33% 22% 3	760
	21st to end	Night	14% 3 18% 40% 22% 3	836
February	1st to 10th	Night	12% 4 30% 36% 17% 1	758
	11th to 20th	Night	13% 4 25% 37% 19% 2	704
	21st to end	Night	12% 6% 29% 38% 14% 1	592
March	1st to 10th	Night	15% 4 26% 36% 17% 2	720
	11th to 20th	Night	12% 5% 22% 39% 20% 2	720
	21st to end	Night	12% 7% 29% 35% 15% 1	792
April	1st to 10th	Night	14% 6% 23% 38% 18% 2	720
	11th to 20th	Night	9% 7% 29% 34% 18% 3	711
	21st to end	Night	10% 5% 28% 39% 18% 1	629
May	1st to 10th	Night	6% 7% 30% 35% 21% 1	460
	11th to 20th	Night	9% 4 20% 40% 23% 4	354
	21st to end	Night	7% 4 23% 38% 24% 4	389
June	1st to 10th	Night	9% 5% 21% 41% 23% 1	360
	11th to 20th	Night	8% 4 27% 41% 19% 1	360
	21st to end	Night	4 2 21% 47% 25% 1	360
July	1st to 10th	Night	3 2 17% 54% 22% 1	350
	11th to 20th	Night	1 1 23% 57% 18% 1	348
	21st to end	Night	2 2 19% 52% 25% 1	394
August	1st to 10th	Night	3 2 16% 49% 26% 3	358
	11th to 20th	Night	1 1 10% 45% 38% 4	655
	21st to end	Night	2 2 13% 49% 31% 3	792
September	1st to 10th	Night	2 1 12% 45% 35% 4	720
	11th to 20th	Night	4 1 14% 37% 36% 8%	720
	21st to end	Night	6% 3 16% 39% 28% 7%	720
October	1st to 10th	Night	8% 2 21% 37% 29% 4	720
	11th to 20th	Night	7% 4 20% 38% 27% 5%	720
	21st to end	Night	8% 3 20% 42% 22% 5%	792
November	1st to 10th	Night	15% 3 19% 40% 21% 2	740
	11th to 20th	Night	14% 5% 21% 38% 19% 3	760
	21st to end	Night	13% 4 21% 36% 21% 4	760
December	1st to 10th	Night	15% 4 22% 38% 18% 4	760
	11th to 20th	Night	17% 5% 22% 35% 19% 2	760
	21st to end	Night	19% 6% 25% 37% 12% 2	836

Page generated at 2024-02-07 03:11:53. Version ac07

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