Lake Shastina
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake Shastina clear sky chart from 2005-11-06 to 2024-02-20.

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 5% 4 3 4 4 5% 7% 52%	78436
	Night	7% 8% 3 5% 4 3 4 4 5% 7% 49%	80778
Transparency	Day	33% 7% 11% 20% 19% 10%	78147
	Night	36% 7% 12% 19% 17% 8%	80588
Seeing	Day	11% 15% 26% 28% 15% 5%	13955
	Night	10% 10% 23% 32% 20% 3	23232

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	9% 17% 6% 6% 5% 3 5% 5% 6% 8% 30%	2539
	11th to 20th	Day	17% 14% 3 6% 6% 2 5% 5% 4 8% 29%	2704
	21st to end	Day	11% 8% 3 6% 6% 3 6% 5% 7% 8% 36%	3146
February	1st to 10th	Day	3 9% 4 7% 6% 4 5% 7% 8% 8% 40%	1710
	11th to 20th	Day	7% 9% 4 6% 5% 3 6% 6% 6% 8% 41%	1657
	21st to end	Day	5% 14% 5% 6% 6% 3 6% 5% 6% 6% 37%	1478
March	1st to 10th	Day	6% 11% 4 8% 7% 4 8% 6% 8% 8% 31%	1908
	11th to 20th	Day	6% 9% 4 7% 6% 5% 5% 6% 7% 9% 37%	1980
	21st to end	Day	8% 11% 4 8% 6% 4 6% 6% 7% 9% 32%	2218
April	1st to 10th	Day	7% 10% 5% 8% 7% 4 5% 5% 6% 7% 36%	2160
	11th to 20th	Day	9% 11% 4 5% 5% 2 4 5% 6% 8% 41%	2129
	21st to end	Day	8% 10% 3 6% 5% 3 3 4 5% 9% 46%	2200
May	1st to 10th	Day	7% 7% 3 4 4 3 4 4 4 7% 53%	2369
	11th to 20th	Day	8% 8% 3 5% 4 2 4 4 6% 8% 48%	2477
	21st to end	Day	10% 9% 3 5% 4 2 5% 4 5% 7% 46%	2723
June	1st to 10th	Day	9% 6% 2 4 5% 3 5% 5% 5% 8% 49%	2520
	11th to 20th	Day	5% 4 2 3 3 2 4 4 4 6% 64%	2520
	21st to end	Day	2 2 1 3 2 2 3 3 3 6% 73%	2520
July	1st to 10th	Day	2 1 1 3 2 2 3 3 4 5% 74%	2520
	11th to 20th	Day	2 2 1 2 2 2 3 3 4 4 76%	2520
	21st to end	Day	2 1 1 2 1 3 4 5% 4 77%	2604
August	1st to 10th	Day	2 1 1 2 3 2 4 4 4 6% 71%	2328
	11th to 20th	Day	1 1 1 2 2 1 2 3 4 5% 78%	2282
	21st to end	Day	2 1 1 1 1 1 2 2 3 4 82%	2376
September	1st to 10th	Day	1 1 1 1 1 1 2 2 3 4 82%	2160
	11th to 20th	Day	3 3 1 2 3 2 4 4 5% 6% 68%	2160
	21st to end	Day	3 3 1 3 3 2 3 3 4 7% 68%	1901
October	1st to 10th	Day	5% 4 2 3 3 2 4 4 4 6% 62%	1800
	11th to 20th	Day	5% 5% 1 4 4 2 3 4 6% 7% 60%	1800
	21st to end	Day	5% 5% 2 5% 4 3 4 4 6% 8% 53%	1980
November	1st to 10th	Day	11% 9% 3 5% 5% 3 4 5% 6% 8% 40%	1710
	11th to 20th	Day	9% 9% 3 5% 6% 3 5% 7% 7% 11% 36%	1575
	21st to end	Day	6% 8% 4 6% 5% 3 5% 4 7% 8% 43%	1520
December	1st to 10th	Day	7% 7% 2 5% 6% 4 5% 6% 6% 8% 43%	1520
	11th to 20th	Day	8% 10% 4 6% 6% 5% 7% 7% 9% 10% 28%	1928
	21st to end	Day	10% 13% 4 6% 6% 4 5% 7% 8% 9% 29%	2794
January	1st to 10th	Night	9% 15% 6% 6% 6% 4 6% 6% 7% 8% 27%	4406
	11th to 20th	Night	13% 11% 5% 8% 5% 4 4 5% 5% 7% 33%	4257
	21st to end	Night	15% 14% 4 7% 6% 4 4 5% 5% 7% 29%	4521
February	1st to 10th	Night	6% 9% 4 6% 5% 3 5% 5% 7% 9% 40%	2470
	11th to 20th	Night	7% 10% 4 7% 5% 3 6% 5% 6% 8% 39%	2394
	21st to end	Night	6% 11% 5% 6% 5% 3 4 5% 6% 10% 39%	1776
March	1st to 10th	Night	8% 12% 4 8% 7% 4 6% 4 5% 8% 33%	2050
	11th to 20th	Night	7% 12% 3 6% 5% 5% 6% 5% 6% 9% 37%	1980
	21st to end	Night	7% 10% 4 8% 7% 4 6% 7% 7% 8% 33%	2138
April	1st to 10th	Night	8% 9% 5% 7% 5% 4 5% 6% 7% 7% 38%	1800
	11th to 20th	Night	7% 10% 4 5% 5% 2 5% 4 4 7% 46%	1779
	21st to end	Night	10% 10% 3 4 3 2 3 2 4 8% 51%	1756
May	1st to 10th	Night	6% 7% 2 5% 4 2 3 3 4 5% 59%	1589
	11th to 20th	Night	9% 7% 2 4 4 2 5% 5% 5% 9% 48%	1416
	21st to end	Night	8% 9% 3 5% 5% 2 4 5% 4 7% 50%	1552
June	1st to 10th	Night	9% 6% 2 4 4 2 5% 5% 6% 8% 49%	1440
	11th to 20th	Night	6% 5% 1 2 3 2 2 3 3 6% 68%	1440
	21st to end	Night	2 2 1 2 2 2 2 3 4 5% 76%	1440
July	1st to 10th	Night	2 1 1 2 1 1 2 3 3 5% 79%	1440
	11th to 20th	Night	2 2 1 2 3 1 2 2 2 4 80%	1440
	21st to end	Night	1 2 1 1 1 1 2 2 2 4 84%	1710
August	1st to 10th	Night	2 1 1 1 1 3 3 4 5% 78%	1611
	11th to 20th	Night	1 1 1 2 1 2 3 3 4 82%	1616
	21st to end	Night	2 2 1 1 1 1 1 3 3 84%	1980
September	1st to 10th	Night	2 1 1 1 1 1 1 2 5% 85%	1800
	11th to 20th	Night	4 3 1 1 2 2 2 3 3 6% 72%	1800
	21st to end	Night	4 4 1 2 3 1 2 3 4 6% 69%	2053
October	1st to 10th	Night	4 3 1 4 3 2 3 3 4 6% 67%	2160
	11th to 20th	Night	5% 4 2 3 4 2 3 4 4 8% 62%	2160
	21st to end	Night	6% 5% 1 4 3 3 3 4 5% 9% 57%	2376
November	1st to 10th	Night	8% 10% 3 5% 5% 3 5% 5% 5% 8% 42%	2367
	11th to 20th	Night	12% 8% 3 4 4 3 5% 4 7% 10% 39%	2603
	21st to end	Night	8% 9% 2 5% 4 3 6% 4 6% 8% 45%	2660
December	1st to 10th	Night	7% 7% 3 5% 5% 3 5% 4 6% 10% 44%	2660
	11th to 20th	Night	8% 11% 3 6% 5% 4 7% 6% 8% 9% 32%	3276
	21st to end	Night	11% 13% 4 6% 5% 4 5% 5% 6% 7% 34%	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	54% 9% 16% 16% 6% 1	2539
	11th to 20th	Day	55% 9% 12% 13% 7% 4	2704
	21st to end	Day	50% 7% 16% 17% 7% 3	3146
February	1st to 10th	Day	41% 10% 16% 18% 11% 4	1710
	11th to 20th	Day	42% 9% 14% 20% 13% 2	1666
	21st to end	Day	47% 9% 13% 18% 10% 4	1478
March	1st to 10th	Day	50% 9% 15% 15% 10% 1	1908
	11th to 20th	Day	46% 8% 13% 18% 13% 2	1980
	21st to end	Day	50% 10% 15% 16% 7% 2	2218
April	1st to 10th	Day	49% 8% 14% 16% 12% 2	2160
	11th to 20th	Day	42% 8% 15% 20% 12% 4	2132
	21st to end	Day	37% 8% 14% 25% 14% 2	2200
May	1st to 10th	Day	33% 5% 12% 28% 20% 2	2369
	11th to 20th	Day	36% 6% 13% 25% 16% 3	2480
	21st to end	Day	39% 7% 14% 25% 13% 1	2724
June	1st to 10th	Day	34% 7% 12% 28% 16% 2	2520
	11th to 20th	Day	22% 5% 9% 31% 26% 7%	2520
	21st to end	Day	15% 3 6% 25% 32% 18%	2520
July	1st to 10th	Day	13% 4 5% 20% 29% 29%	2451
	11th to 20th	Day	12% 4 4 18% 29% 33%	2445
	21st to end	Day	11% 4 5% 14% 31% 35%	2459
August	1st to 10th	Day	14% 6% 7% 19% 33% 22%	2312
	11th to 20th	Day	11% 4 4 17% 40% 23%	2282
	21st to end	Day	9% 2 4 18% 40% 26%	2376
September	1st to 10th	Day	8% 3 4 16% 32% 37%	2160
	11th to 20th	Day	18% 5% 8% 19% 35% 15%	2160
	21st to end	Day	18% 5% 9% 24% 27% 17%	1901
October	1st to 10th	Day	24% 4 12% 20% 24% 15%	1800
	11th to 20th	Day	26% 5% 11% 24% 25% 10%	1800
	21st to end	Day	30% 8% 12% 19% 19% 12%	1980
November	1st to 10th	Day	43% 6% 12% 20% 15% 4	1710
	11th to 20th	Day	42% 9% 15% 17% 12% 5%	1575
	21st to end	Day	39% 8% 14% 18% 15% 6%	1520
December	1st to 10th	Day	40% 9% 14% 17% 17% 3	1520
	11th to 20th	Day	54% 9% 15% 12% 9% 1	1928
	21st to end	Day	53% 10% 15% 14% 6% 1	2794
January	1st to 10th	Night	55% 9% 14% 14% 6% 2	4406
	11th to 20th	Night	51% 9% 14% 13% 8% 4	4257
	21st to end	Night	57% 7% 10% 13% 10% 3	4521
February	1st to 10th	Night	42% 8% 14% 17% 14% 5%	2470
	11th to 20th	Night	44% 9% 14% 19% 12% 3	2396
	21st to end	Night	43% 9% 16% 17% 13% 3	1776
March	1st to 10th	Night	50% 9% 14% 14% 11% 1	2050
	11th to 20th	Night	46% 8% 11% 19% 15% 2	1980
	21st to end	Night	47% 13% 17% 15% 7% 1	2138
April	1st to 10th	Night	45% 9% 16% 19% 9% 2	1800
	11th to 20th	Night	39% 7% 18% 18% 11% 5%	1779
	21st to end	Night	35% 6% 19% 28% 10% 2	1756
May	1st to 10th	Night	30% 5% 15% 31% 17% 2	1589
	11th to 20th	Night	33% 8% 18% 27% 11% 2	1416
	21st to end	Night	35% 8% 21% 27% 8%	1552
June	1st to 10th	Night	34% 6% 17% 33% 9% 1	1440
	11th to 20th	Night	20% 5% 13% 38% 20% 5%	1440
	21st to end	Night	13% 4 8% 33% 33% 8%	1440
July	1st to 10th	Night	10% 3 10% 25% 30% 23%	1400
	11th to 20th	Night	11% 4 5% 23% 33% 25%	1392
	21st to end	Night	8% 3 3 17% 41% 27%	1615
August	1st to 10th	Night	11% 4 7% 30% 31% 18%	1602
	11th to 20th	Night	9% 3 6% 24% 40% 18%	1616
	21st to end	Night	9% 3 6% 22% 36% 24%	1980
September	1st to 10th	Night	6% 3 5% 18% 32% 36%	1800
	11th to 20th	Night	15% 5% 8% 24% 34% 15%	1800
	21st to end	Night	19% 5% 11% 22% 24% 20%	2053
October	1st to 10th	Night	21% 7% 11% 19% 28% 15%	2160
	11th to 20th	Night	23% 5% 12% 23% 25% 12%	2160
	21st to end	Night	26% 8% 14% 21% 18% 12%	2376
November	1st to 10th	Night	43% 7% 13% 17% 14% 6%	2367
	11th to 20th	Night	41% 9% 14% 16% 14% 5%	2603
	21st to end	Night	38% 9% 13% 15% 17% 8%	2660
December	1st to 10th	Night	38% 9% 12% 19% 19% 3	2660
	11th to 20th	Night	53% 9% 9% 15% 13% 1	3276
	21st to end	Night	52% 8% 14% 14% 9% 2	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	17% 23% 33% 18% 6% 3	180
	11th to 20th	Day	21% 19% 23% 19% 14% 4	279
	21st to end	Day	17% 16% 26% 24% 13% 4	407
February	1st to 10th	Day	12% 20% 24% 32% 10% 2	370
	11th to 20th	Day	18% 24% 23% 23% 12% 1	363
	21st to end	Day	16% 20% 31% 24% 9% 1	346
March	1st to 10th	Day	17% 28% 30% 17% 7% 1	420
	11th to 20th	Day	18% 19% 28% 24% 10% 2	420
	21st to end	Day	18% 26% 29% 20% 7% 1	462
April	1st to 10th	Day	16% 26% 28% 20% 9% 1	420
	11th to 20th	Day	21% 20% 25% 21% 10% 2	412
	21st to end	Day	12% 21% 32% 20% 11% 4	420
May	1st to 10th	Day	13% 22% 31% 21% 10% 3	423
	11th to 20th	Day	17% 21% 25% 20% 13% 4	448
	21st to end	Day	15% 14% 26% 26% 13% 6%	485
June	1st to 10th	Day	10% 16% 24% 28% 16% 6%	450
	11th to 20th	Day	10% 19% 33% 24% 12% 3	450
	21st to end	Day	3 11% 32% 32% 18% 5%	450
July	1st to 10th	Day	3 9% 31% 35% 17% 5%	446
	11th to 20th	Day	1 6% 30% 39% 18% 7%	444
	21st to end	Day	1 5% 23% 41% 21% 8%	487
August	1st to 10th	Day	3 5% 26% 35% 22% 9%	447
	11th to 20th	Day	2 6% 24% 35% 22% 11%	437
	21st to end	Day	2 7% 25% 36% 21% 8%	495
September	1st to 10th	Day	2 8% 24% 40% 19% 7%	450
	11th to 20th	Day	6% 8% 26% 33% 22% 5%	450
	21st to end	Day	5% 16% 22% 31% 22% 3	450
October	1st to 10th	Day	8% 14% 24% 24% 23% 6%	450
	11th to 20th	Day	11% 11% 19% 30% 24% 5%	450
	21st to end	Day	9% 14% 26% 28% 16% 7%	495
November	1st to 10th	Day	14% 16% 24% 25% 16% 6%	306
	11th to 20th	Day	10% 10% 25% 26% 22% 6%	205
	21st to end	Day	11% 9% 27% 29% 19% 4	180
December	1st to 10th	Day	16% 13% 25% 25% 11% 11%	180
	11th to 20th	Day	22% 16% 19% 26% 8% 8%	180
	21st to end	Day	16% 15% 25% 27% 15% 3	198
January	1st to 10th	Night	14% 13% 30% 26% 13% 3	760
	11th to 20th	Night	13% 15% 27% 25% 16% 5%	760
	21st to end	Night	15% 11% 25% 29% 15% 5%	836
February	1st to 10th	Night	13% 13% 29% 32% 12% 2	760
	11th to 20th	Night	13% 13% 27% 29% 15% 2	742
	21st to end	Night	12% 14% 29% 33% 10% 1	592
March	1st to 10th	Night	15% 22% 28% 22% 11% 2	720
	11th to 20th	Night	13% 16% 23% 28% 17% 2	720
	21st to end	Night	13% 19% 32% 26% 10% 1	792
April	1st to 10th	Night	13% 18% 30% 26% 12% 1	720
	11th to 20th	Night	12% 14% 30% 26% 15% 3	711
	21st to end	Night	14% 11% 26% 28% 19% 2	676
May	1st to 10th	Night	10% 10% 31% 27% 21% 2	509
	11th to 20th	Night	12% 7% 24% 33% 22% 1	354
	21st to end	Night	12% 9% 24% 32% 22% 2	389
June	1st to 10th	Night	12% 7% 20% 37% 23% 1	360
	11th to 20th	Night	7% 8% 25% 44% 15% 1	360
	21st to end	Night	4 4 20% 47% 24%	360
July	1st to 10th	Night	2 1 15% 49% 32% 2	350
	11th to 20th	Night	2 12% 53% 32% 1	348
	21st to end	Night	1 1 8% 41% 44% 5%	528
August	1st to 10th	Night	2 1 8% 43% 40% 5%	537
	11th to 20th	Night	2 1 11% 43% 36% 7%	548
	21st to end	Night	2 2 17% 41% 34% 4	792
September	1st to 10th	Night	2 3 17% 40% 33% 5%	720
	11th to 20th	Night	4 3 18% 34% 35% 6%	720
	21st to end	Night	7% 5% 18% 34% 30% 7%	720
October	1st to 10th	Night	4 6% 23% 36% 27% 4	720
	11th to 20th	Night	7% 9% 18% 35% 26% 6%	720
	21st to end	Night	8% 10% 20% 34% 21% 8%	792
November	1st to 10th	Night	13% 10% 25% 33% 15% 5%	740
	11th to 20th	Night	16% 11% 26% 31% 12% 4	760
	21st to end	Night	12% 10% 24% 33% 18% 3	760
December	1st to 10th	Night	12% 14% 23% 30% 16% 4	760
	11th to 20th	Night	18% 14% 24% 28% 13% 3	760
	21st to end	Night	22% 17% 26% 24% 10% 2	836

Page generated at 2024-02-17 03:28:39. Version ac07

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