Baum Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Baum Lake clear sky chart from 2005-11-06 to 2024-01-13.

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	5% 4 2 4 4 3 4 4 5% 7% 60%	74743
	Night	6% 5% 2 4 4 3 4 4 5% 7% 56%	74992
Transparency	Day	24% 7% 11% 21% 22% 16%	74452
	Night	26% 8% 12% 21% 20% 12%	74804
Seeing	Day	8% 12% 25% 29% 20% 7%	13844
	Night	7% 5% 19% 41% 25% 2	23142

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	7% 8% 3 5% 6% 4 7% 6% 7% 9% 38%	1519
	11th to 20th	Day	6% 5% 2 5% 7% 4 6% 6% 7% 8% 45%	1524
	21st to end	Day	6% 9% 3 5% 5% 3 6% 6% 6% 7% 44%	1782
February	1st to 10th	Day	6% 5% 3 5% 6% 4 5% 6% 6% 8% 47%	1620
	11th to 20th	Day	6% 7% 2 5% 6% 3 4 4 6% 8% 48%	1625
	21st to end	Day	4 6% 2 6% 6% 4 8% 6% 6% 7% 45%	1480
March	1st to 10th	Day	7% 7% 3 6% 6% 4 8% 7% 6% 9% 37%	1862
	11th to 20th	Day	7% 8% 2 4 5% 4 5% 7% 7% 9% 42%	1980
	21st to end	Day	6% 7% 3 6% 6% 5% 6% 5% 7% 9% 39%	2251
April	1st to 10th	Day	6% 6% 4 7% 6% 3 6% 5% 6% 8% 44%	2160
	11th to 20th	Day	7% 5% 2 4 5% 3 5% 5% 7% 8% 51%	2129
	21st to end	Day	5% 4 1 3 4 2 4 5% 4 8% 58%	2160
May	1st to 10th	Day	5% 3 1 3 5% 2 4 4 6% 7% 59%	2363
	11th to 20th	Day	7% 5% 1 4 3 2 3 5% 5% 7% 57%	2477
	21st to end	Day	7% 4 2 4 4 3 5% 4 6% 7% 54%	2723
June	1st to 10th	Day	5% 3 1 3 4 3 5% 4 5% 8% 60%	2520
	11th to 20th	Day	3 2 1 2 2 1 2 3 4 5% 75%	2520
	21st to end	Day	3 1 1 1 2 1 2 2 3 4 81%	2520
July	1st to 10th	Day	1 1 1 2 1 2 2 2 4 82%	2520
	11th to 20th	Day	1 1 1 1 1 1 2 2 3 87%	2520
	21st to end	Day	1 1 1 1 2 1 2 2 3 4 82%	2637
August	1st to 10th	Day	1 1 1 2 2 1 3 3 4 4 79%	2328
	11th to 20th	Day	1 1 1 1 1 2 2 3 3 86%	2229
	21st to end	Day	1 1 1 1 1 1 1 2 3 88%	2376
September	1st to 10th	Day	1 1 1 1 1 2 2 3 3 86%	2160
	11th to 20th	Day	3 1 1 2 2 2 2 3 4 7% 73%	2160
	21st to end	Day	3 2 1 2 2 1 2 3 3 5% 75%	1927
October	1st to 10th	Day	4 3 1 3 3 2 2 3 4 4 71%	1800
	11th to 20th	Day	3 2 1 3 4 3 4 4 4 7% 66%	1800
	21st to end	Day	6% 3 1 3 4 2 3 4 5% 7% 62%	1980
November	1st to 10th	Day	9% 5% 2 4 5% 3 5% 4 5% 8% 50%	1679
	11th to 20th	Day	6% 5% 2 5% 5% 4 6% 6% 7% 10% 44%	1650
	21st to end	Day	5% 5% 2 4 5% 3 5% 6% 6% 9% 51%	1520
December	1st to 10th	Day	8% 7% 2 4 5% 4 5% 5% 6% 8% 47%	1520
	11th to 20th	Day	10% 9% 4 8% 7% 4 7% 6% 7% 8% 29%	1928
	21st to end	Day	7% 7% 3 7% 9% 5% 6% 7% 8% 7% 34%	2794
January	1st to 10th	Night	7% 8% 3 5% 6% 4 6% 6% 7% 9% 40%	2646
	11th to 20th	Night	6% 6% 3 6% 5% 3 5% 5% 6% 7% 46%	2476
	21st to end	Night	8% 8% 3 6% 4 4 5% 5% 5% 6% 45%	2574
February	1st to 10th	Night	5% 6% 3 5% 5% 3 5% 5% 6% 9% 48%	2340
	11th to 20th	Night	6% 8% 2 4 5% 4 5% 5% 5% 9% 48%	2220
	21st to end	Night	5% 10% 3 4 5% 5% 5% 5% 7% 8% 44%	1776
March	1st to 10th	Night	8% 10% 4 6% 5% 3 6% 5% 6% 8% 39%	2096
	11th to 20th	Night	5% 8% 3 5% 4 3 5% 6% 7% 11% 43%	1980
	21st to end	Night	7% 7% 3 5% 5% 3 5% 6% 6% 9% 45%	2104
April	1st to 10th	Night	7% 6% 2 4 5% 4 6% 5% 6% 8% 47%	1800
	11th to 20th	Night	7% 5% 2 4 4 2 4 4 6% 8% 53%	1779
	21st to end	Night	8% 4 1 4 4 2 3 3 5% 8% 57%	1800
May	1st to 10th	Night	5% 3 1 4 4 3 4 4 4 6% 61%	1590
	11th to 20th	Night	7% 5% 2 3 4 3 4 5% 4 9% 54%	1416
	21st to end	Night	9% 5% 2 4 4 2 4 4 5% 6% 54%	1552
June	1st to 10th	Night	7% 4 2 3 3 2 4 4 5% 8% 58%	1440
	11th to 20th	Night	6% 2 1 2 2 2 2 3 4 6% 72%	1440
	21st to end	Night	2 1 1 2 3 1 3 2 4 5% 77%	1440
July	1st to 10th	Night	1 1 1 1 1 2 2 3 4 82%	1440
	11th to 20th	Night	1 1 1 2 1 1 1 2 2 4 85%	1440
	21st to end	Night	1 1 1 1 1 2 2 3 4 84%	1676
August	1st to 10th	Night	1 1 1 2 2 1 2 3 2 6% 80%	1611
	11th to 20th	Night	1 1 1 2 1 1 2 2 4 84%	1669
	21st to end	Night	1 1 1 1 1 1 2 3 3 86%	1980
September	1st to 10th	Night	2 1 1 1 1 1 1 2 2 4 86%	1800
	11th to 20th	Night	3 2 1 2 2 1 3 2 3 6% 76%	1800
	21st to end	Night	2 2 1 2 3 2 2 3 4 6% 73%	2028
October	1st to 10th	Night	5% 3 2 3 3 2 2 3 3 4 70%	2160
	11th to 20th	Night	3 2 1 3 3 2 4 3 4 6% 69%	2160
	21st to end	Night	6% 3 1 2 3 2 3 3 5% 7% 65%	2376
November	1st to 10th	Night	7% 6% 2 5% 4 4 5% 6% 6% 8% 47%	2398
	11th to 20th	Night	7% 6% 2 5% 5% 4 6% 5% 7% 9% 45%	2527
	21st to end	Night	5% 5% 2 4 4 3 5% 5% 6% 10% 52%	2660
December	1st to 10th	Night	9% 5% 2 5% 4 3 5% 5% 6% 9% 48%	2660
	11th to 20th	Night	12% 9% 4 7% 7% 4 5% 5% 7% 9% 31%	3276
	21st to end	Night	11% 10% 4 8% 7% 4 6% 5% 5% 9% 32%	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	39% 12% 17% 23% 8% 1	1519
	11th to 20th	Day	33% 11% 16% 20% 13% 7%	1524
	21st to end	Day	38% 7% 11% 24% 15% 4	1782
February	1st to 10th	Day	33% 8% 16% 22% 16% 4	1620
	11th to 20th	Day	34% 7% 14% 24% 18% 2	1634
	21st to end	Day	35% 10% 14% 26% 12% 4	1480
March	1st to 10th	Day	42% 10% 13% 20% 12% 3	1862
	11th to 20th	Day	35% 10% 15% 18% 19% 2	1980
	21st to end	Day	39% 12% 17% 21% 8% 3	2251
April	1st to 10th	Day	38% 9% 15% 21% 14% 3	2160
	11th to 20th	Day	31% 8% 13% 23% 18% 6%	2132
	21st to end	Day	25% 7% 17% 26% 22% 4	2160
May	1st to 10th	Day	24% 5% 13% 25% 26% 7%	2363
	11th to 20th	Day	27% 5% 13% 25% 23% 7%	2480
	21st to end	Day	29% 7% 15% 25% 19% 4	2724
June	1st to 10th	Day	24% 6% 11% 26% 24% 9%	2520
	11th to 20th	Day	13% 4 9% 23% 36% 16%	2520
	21st to end	Day	10% 3 5% 18% 34% 30%	2520
July	1st to 10th	Day	9% 2 4 14% 30% 41%	2451
	11th to 20th	Day	5% 2 4 14% 28% 47%	2445
	21st to end	Day	8% 3 3 11% 24% 50%	2490
August	1st to 10th	Day	10% 3 5% 17% 27% 39%	2312
	11th to 20th	Day	6% 2 3 14% 34% 41%	2229
	21st to end	Day	6% 1 3 14% 36% 40%	2376
September	1st to 10th	Day	5% 2 3 12% 30% 48%	2160
	11th to 20th	Day	13% 3 7% 21% 34% 22%	2160
	21st to end	Day	13% 3 7% 22% 30% 24%	1927
October	1st to 10th	Day	19% 4 7% 22% 28% 20%	1800
	11th to 20th	Day	17% 6% 11% 21% 30% 14%	1800
	21st to end	Day	21% 7% 14% 22% 21% 16%	1980
November	1st to 10th	Day	33% 7% 14% 21% 19% 6%	1679
	11th to 20th	Day	33% 9% 16% 23% 16% 3	1650
	21st to end	Day	28% 10% 13% 23% 20% 6%	1520
December	1st to 10th	Day	33% 11% 12% 22% 19% 3	1520
	11th to 20th	Day	46% 14% 12% 18% 9% 1	1928
	21st to end	Day	37% 16% 16% 22% 7% 1	2794
January	1st to 10th	Night	36% 12% 20% 20% 9% 2	2646
	11th to 20th	Night	33% 11% 17% 18% 13% 8%	2476
	21st to end	Night	38% 7% 11% 22% 18% 3	2574
February	1st to 10th	Night	32% 9% 13% 24% 16% 5%	2340
	11th to 20th	Night	32% 8% 16% 25% 17% 2	2222
	21st to end	Night	35% 9% 17% 22% 13% 4	1776
March	1st to 10th	Night	40% 12% 16% 18% 12% 3	2096
	11th to 20th	Night	33% 12% 16% 21% 16% 2	1980
	21st to end	Night	34% 13% 19% 22% 10% 2	2104
April	1st to 10th	Night	33% 10% 19% 24% 11% 3	1800
	11th to 20th	Night	27% 10% 19% 23% 16% 6%	1779
	21st to end	Night	26% 8% 18% 30% 16% 3	1800
May	1st to 10th	Night	24% 6% 12% 27% 25% 5%	1590
	11th to 20th	Night	27% 7% 15% 26% 17% 7%	1416
	21st to end	Night	29% 8% 17% 28% 16% 2	1552
June	1st to 10th	Night	25% 7% 14% 28% 21% 5%	1440
	11th to 20th	Night	15% 4 11% 23% 36% 11%	1440
	21st to end	Night	12% 3 6% 19% 34% 25%	1440
July	1st to 10th	Night	7% 3 5% 16% 32% 38%	1400
	11th to 20th	Night	6% 3 3 14% 28% 46%	1392
	21st to end	Night	8% 2 4 12% 27% 48%	1583
August	1st to 10th	Night	9% 3 6% 19% 30% 33%	1602
	11th to 20th	Night	8% 2 3 17% 34% 36%	1669
	21st to end	Night	5% 2 3 17% 37% 36%	1980
September	1st to 10th	Night	6% 3 4 11% 29% 48%	1800
	11th to 20th	Night	11% 4 7% 21% 35% 21%	1800
	21st to end	Night	13% 4 8% 22% 27% 26%	2028
October	1st to 10th	Night	20% 4 8% 21% 29% 18%	2160
	11th to 20th	Night	15% 7% 10% 23% 29% 15%	2160
	21st to end	Night	18% 6% 14% 26% 21% 15%	2376
November	1st to 10th	Night	32% 10% 14% 20% 16% 7%	2398
	11th to 20th	Night	32% 10% 15% 22% 17% 3	2527
	21st to end	Night	27% 8% 17% 23% 20% 6%	2660
December	1st to 10th	Night	31% 10% 13% 22% 20% 4	2660
	11th to 20th	Night	41% 15% 11% 19% 13% 1	3276
	21st to end	Night	41% 16% 13% 20% 9% 1	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	21% 13% 23% 31% 9% 2	180
	11th to 20th	Day	13% 17% 20% 32% 11% 7%	232
	21st to end	Day	12% 15% 21% 28% 15% 9%	374
February	1st to 10th	Day	11% 16% 20% 32% 19% 3	340
	11th to 20th	Day	12% 20% 25% 28% 15% 1	357
	21st to end	Day	10% 19% 28% 29% 13% 1	346
March	1st to 10th	Day	16% 24% 28% 20% 9% 2	420
	11th to 20th	Day	16% 16% 29% 25% 12% 2	420
	21st to end	Day	12% 23% 30% 23% 11% 2	462
April	1st to 10th	Day	13% 20% 31% 25% 9% 2	420
	11th to 20th	Day	15% 21% 26% 21% 13% 4	412
	21st to end	Day	7% 17% 29% 25% 18% 4	420
May	1st to 10th	Day	8% 17% 33% 25% 13% 4	423
	11th to 20th	Day	14% 13% 27% 23% 16% 7%	448
	21st to end	Day	9% 11% 21% 28% 22% 9%	485
June	1st to 10th	Day	5% 14% 29% 24% 19% 9%	450
	11th to 20th	Day	6% 12% 30% 29% 18% 5%	450
	21st to end	Day	1 8% 23% 34% 24% 9%	450
July	1st to 10th	Day	2 3 29% 32% 24% 9%	446
	11th to 20th	Day	3 27% 31% 26% 12%	444
	21st to end	Day	1 3 21% 35% 27% 13%	487
August	1st to 10th	Day	1 4 23% 34% 22% 15%	447
	11th to 20th	Day	1 4 21% 29% 29% 16%	437
	21st to end	Day	2 4 28% 31% 23% 13%	495
September	1st to 10th	Day	1 5% 23% 36% 29% 6%	450
	11th to 20th	Day	5% 7% 22% 33% 24% 9%	450
	21st to end	Day	4 9% 25% 34% 25% 4	450
October	1st to 10th	Day	5% 12% 24% 27% 23% 9%	450
	11th to 20th	Day	6% 10% 21% 28% 29% 7%	450
	21st to end	Day	8% 11% 21% 29% 22% 8%	495
November	1st to 10th	Day	12% 10% 17% 29% 25% 7%	275
	11th to 20th	Day	9% 5% 19% 35% 24% 7%	241
	21st to end	Day	7% 8% 18% 36% 25% 7%	180
December	1st to 10th	Day	17% 7% 21% 29% 18% 7%	180
	11th to 20th	Day	14% 7% 22% 31% 18% 7%	180
	21st to end	Day	13% 12% 21% 36% 16% 3	198
January	1st to 10th	Night	11% 8% 25% 38% 17% 1	760
	11th to 20th	Night	8% 8% 26% 41% 16% 1	728
	21st to end	Night	11% 4 24% 41% 18% 1	792
February	1st to 10th	Night	7% 7% 28% 40% 18% 1	720
	11th to 20th	Night	9% 7% 27% 41% 16% 1	704
	21st to end	Night	9% 10% 24% 43% 13%	592
March	1st to 10th	Night	12% 10% 26% 37% 14% 2	720
	11th to 20th	Night	9% 8% 25% 35% 22% 1	720
	21st to end	Night	9% 10% 29% 36% 16%	792
April	1st to 10th	Night	9% 7% 25% 43% 15% 1	720
	11th to 20th	Night	9% 7% 27% 38% 17% 3	711
	21st to end	Night	7% 8% 21% 42% 19% 2	720
May	1st to 10th	Night	5% 5% 28% 40% 20% 1	510
	11th to 20th	Night	10% 3 20% 38% 26% 3	354
	21st to end	Night	10% 4 15% 40% 30% 1	389
June	1st to 10th	Night	6% 2 16% 44% 31% 1	360
	11th to 20th	Night	5% 4 20% 45% 25% 2	360
	21st to end	Night	2 1 11% 46% 40% 1	360
July	1st to 10th	Night	1 1 3 49% 44% 2	350
	11th to 20th	Night	1 5% 50% 43% 1	348
	21st to end	Night	1 1 2 39% 54% 3	494
August	1st to 10th	Night	2 1 2 39% 51% 4	537
	11th to 20th	Night	2 1 5% 41% 47% 5%	601
	21st to end	Night	2 1 6% 45% 42% 4	792
September	1st to 10th	Night	2 1 9% 44% 41% 3	720
	11th to 20th	Night	3 2 10% 36% 43% 6%	720
	21st to end	Night	3 3 11% 42% 34% 7%	720
October	1st to 10th	Night	5% 3 17% 41% 30% 4	720
	11th to 20th	Night	4 4 15% 42% 33% 3	720
	21st to end	Night	8% 3 17% 40% 27% 5%	792
November	1st to 10th	Night	8% 7% 18% 40% 24% 3	740
	11th to 20th	Night	8% 6% 22% 44% 17% 3	760
	21st to end	Night	5% 6% 24% 39% 23% 2	760
December	1st to 10th	Night	11% 6% 23% 42% 17% 2	760
	11th to 20th	Night	12% 7% 22% 41% 16% 2	760
	21st to end	Night	14% 9% 28% 39% 10%	836

Page generated at 2024-01-09 22:25:01. Version ac07

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