Shaver Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Shaver Lake clear sky chart from 2005-11-06 to 2025-01-07.

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	7% 6% 1 3 2 2 3 2 4 5% 65%	108749
	Night	7% 5% 1 3 2 2 3 2 4 5% 63%	109031
Transparency	Day	23% 4 6% 20% 26% 21%	108497
	Night	23% 3 7% 22% 25% 19%	108873
Seeing	Day	11% 10% 30% 32% 12% 5%	15408
	Night	10% 4 17% 33% 27% 9%	25003

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	10% 13% 2 5% 3 2 3 3 4 8% 47%	2587
	11th to 20th	Day	13% 10% 3 8% 4 5% 4 4 5% 6% 38%	2697
	21st to end	Day	15% 9% 2 6% 4 4 4 4 6% 8% 37%	3146
February	1st to 10th	Day	14% 11% 2 4 3 2 3 3 4 6% 48%	1824
	11th to 20th	Day	10% 13% 2 5% 4 3 3 3 4 5% 47%	1850
	21st to end	Day	16% 12% 3 7% 3 3 3 2 4 4 41%	1570
March	1st to 10th	Day	12% 17% 4 7% 4 3 4 4 5% 7% 31%	3138
	11th to 20th	Day	8% 10% 2 5% 3 2 3 3 4 6% 54%	3383
	21st to end	Day	14% 19% 3 7% 3 3 4 3 4 5% 34%	4120
April	1st to 10th	Day	10% 10% 3 5% 3 3 3 4 4 6% 49%	2280
	11th to 20th	Day	11% 10% 2 5% 4 4 3 3 4 5% 50%	2249
	21st to end	Day	9% 8% 2 4 3 3 3 3 5% 7% 53%	2280
May	1st to 10th	Day	7% 4 2 2 2 2 2 2 4 5% 68%	3941
	11th to 20th	Day	4 3 1 2 2 2 2 3 4 5% 73%	4071
	21st to end	Day	5% 3 1 3 2 2 2 2 3 5% 73%	4783
June	1st to 10th	Day	4 3 1 3 3 3 3 3 6% 6% 64%	2660
	11th to 20th	Day	1 2 2 1 2 2 2 3 4 81%	2660
	21st to end	Day	2 2 1 2 2 1 1 2 2 3 83%	2660
July	1st to 10th	Day	1 1 1 1 1 1 1 2 91%	4420
	11th to 20th	Day	1 2 1 2 2 2 2 2 3 3 82%	4420
	21st to end	Day	1 1 1 2 1 1 2 1 3 4 84%	4589
August	1st to 10th	Day	1 2 1 1 1 1 1 1 2 2 86%	3854
	11th to 20th	Day	1 1 1 1 1 1 2 3 90%	3724
	21st to end	Day	2 1 1 1 1 1 1 2 2 88%	4180
September	1st to 10th	Day	2 1 1 1 1 1 1 2 3 85%	2280
	11th to 20th	Day	2 2 1 2 2 2 2 2 2 4 79%	2214
	21st to end	Day	3 2 2 1 2 2 2 3 4 78%	2090
October	1st to 10th	Day	3 3 1 2 2 2 2 3 4 4 74%	3345
	11th to 20th	Day	4 2 1 2 2 2 2 2 3 3 76%	3161
	21st to end	Day	5% 3 2 4 3 3 3 3 4 6% 63%	3386
November	1st to 10th	Day	7% 8% 2 4 3 3 3 3 5% 7% 56%	1764
	11th to 20th	Day	7% 4 1 3 2 3 3 4 5% 6% 61%	1800
	21st to end	Day	9% 6% 2 4 3 3 3 2 4 6% 57%	1800
December	1st to 10th	Day	7% 3 1 4 3 3 3 4 5% 6% 61%	2791
	11th to 20th	Day	18% 8% 2 5% 4 3 4 3 5% 6% 42%	3028
	21st to end	Day	14% 9% 3 5% 4 3 4 3 5% 8% 41%	4004
January	1st to 10th	Night	11% 8% 3 4 3 3 3 2 5% 8% 49%	4490
	11th to 20th	Night	15% 10% 3 5% 3 4 4 4 6% 7% 38%	4265
	21st to end	Night	15% 9% 2 5% 4 4 4 3 7% 8% 38%	4521
February	1st to 10th	Night	13% 10% 2 4 2 3 3 3 5% 6% 50%	2354
	11th to 20th	Night	11% 9% 2 4 3 3 3 2 5% 7% 52%	2218
	21st to end	Night	13% 10% 3 5% 3 3 2 3 4 5% 50%	1884
March	1st to 10th	Night	13% 14% 3 5% 4 3 5% 3 6% 7% 38%	3736
	11th to 20th	Night	7% 8% 2 4 3 3 3 2 4 6% 58%	3593
	21st to end	Night	16% 11% 2 5% 4 4 3 3 4 7% 43%	3533
April	1st to 10th	Night	11% 7% 1 3 3 3 2 3 5% 6% 55%	1900
	11th to 20th	Night	8% 6% 1 4 4 3 3 3 4 5% 60%	1879
	21st to end	Night	6% 5% 1 3 2 3 3 3 4 6% 63%	1900
May	1st to 10th	Night	5% 3 1 2 2 2 2 1 3 4 73%	3031
	11th to 20th	Night	3 2 1 1 2 2 2 3 5% 77%	2834
	21st to end	Night	3 2 1 2 1 1 1 2 2 4 81%	2776
June	1st to 10th	Night	4 3 1 3 2 1 3 2 3 6% 71%	1520
	11th to 20th	Night	1 1 2 1 1 2 2 3 3 84%	1520
	21st to end	Night	1 1 1 1 1 1 2 2 2 88%	1520
July	1st to 10th	Night	1 1 1 1 2 2 92%	2540
	11th to 20th	Night	2 2 1 3 2 2 1 2 3 3 79%	2540
	21st to end	Night	1 1 1 2 1 1 2 2 2 3 83%	2966
August	1st to 10th	Night	1 2 2 1 2 2 2 3 4 81%	3092
	11th to 20th	Night	1 1 1 1 1 1 1 1 2 91%	3126
	21st to end	Night	2 1 1 1 1 1 1 1 2 89%	3498
September	1st to 10th	Night	1 1 1 1 1 1 2 2 90%	1900
	11th to 20th	Night	2 2 1 2 1 1 1 2 3 3 82%	1966
	21st to end	Night	2 1 1 1 2 1 2 3 3 83%	2090
October	1st to 10th	Night	2 2 2 1 2 2 2 2 3 82%	3631
	11th to 20th	Night	3 1 1 2 2 2 2 2 3 4 80%	3777
	21st to end	Night	4 2 1 3 1 2 2 2 3 5% 75%	4178
November	1st to 10th	Night	8% 5% 1 3 2 2 2 2 4 6% 62%	2535
	11th to 20th	Night	7% 3 2 4 2 2 2 2 5% 8% 63%	2600
	21st to end	Night	9% 7% 2 3 3 3 3 3 4 6% 56%	2600
December	1st to 10th	Night	8% 4 1 4 2 3 3 2 4 6% 62%	4390
	11th to 20th	Night	18% 8% 2 4 3 3 4 3 6% 9% 40%	5176
	21st to end	Night	11% 8% 3 7% 5% 5% 5% 4 7% 8% 38%	6952

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% 4 10% 29% 17% 4	2587
	11th to 20th	Day	46% 5% 10% 16% 14% 8%	2697
	21st to end	Day	44% 4 13% 23% 11% 5%	3146
February	1st to 10th	Day	38% 4 6% 24% 19% 10%	1824
	11th to 20th	Day	38% 5% 6% 22% 22% 7%	1860
	21st to end	Day	47% 4 7% 24% 16% 2	1570
March	1st to 10th	Day	49% 6% 10% 17% 12% 5%	3138
	11th to 20th	Day	29% 6% 14% 30% 12% 9%	3383
	21st to end	Day	49% 8% 10% 20% 11% 2	4120
April	1st to 10th	Day	35% 6% 12% 26% 18% 3	2280
	11th to 20th	Day	36% 5% 10% 25% 21% 3	2252
	21st to end	Day	31% 5% 11% 33% 18% 2	2280
May	1st to 10th	Day	19% 5% 9% 33% 29% 6%	3941
	11th to 20th	Day	14% 5% 7% 37% 35% 4	4074
	21st to end	Day	16% 4 7% 43% 30% 1	4784
June	1st to 10th	Day	19% 5% 11% 25% 31% 9%	2660
	11th to 20th	Day	9% 3 7% 23% 41% 17%	2660
	21st to end	Day	10% 2 2 14% 41% 32%	2660
July	1st to 10th	Day	4 2 1 6% 18% 69%	4351
	11th to 20th	Day	9% 3 2 9% 22% 56%	4345
	21st to end	Day	7% 3 2 15% 27% 46%	4444
August	1st to 10th	Day	8% 2 2 9% 38% 42%	3839
	11th to 20th	Day	4 2 1 8% 31% 54%	3760
	21st to end	Day	6% 2 1 10% 37% 44%	4179
September	1st to 10th	Day	7% 3 2 9% 37% 42%	2280
	11th to 20th	Day	11% 3 3 23% 37% 24%	2214
	21st to end	Day	12% 3 3 19% 39% 24%	2090
October	1st to 10th	Day	15% 3 3 12% 27% 41%	3345
	11th to 20th	Day	15% 3 2 17% 41% 22%	3161
	21st to end	Day	21% 5% 4 17% 37% 16%	3386
November	1st to 10th	Day	28% 5% 7% 20% 24% 16%	1764
	11th to 20th	Day	23% 4 8% 23% 31% 11%	1800
	21st to end	Day	30% 4 6% 18% 28% 15%	1800
December	1st to 10th	Day	24% 4 6% 24% 29% 13%	2791
	11th to 20th	Day	43% 4 10% 16% 20% 7%	3028
	21st to end	Day	42% 3 12% 24% 13% 6%	4004
January	1st to 10th	Night	34% 3 13% 26% 20% 4	4490
	11th to 20th	Night	43% 5% 8% 23% 14% 6%	4265
	21st to end	Night	42% 5% 12% 21% 15% 6%	4521
February	1st to 10th	Night	36% 3 7% 25% 19% 10%	2354
	11th to 20th	Night	31% 5% 8% 24% 25% 8%	2219
	21st to end	Night	37% 4 11% 25% 18% 6%	1884
March	1st to 10th	Night	43% 5% 9% 21% 16% 5%	3736
	11th to 20th	Night	27% 4 11% 33% 14% 10%	3593
	21st to end	Night	41% 5% 15% 26% 11% 2	3533
April	1st to 10th	Night	29% 5% 15% 29% 17% 5%	1900
	11th to 20th	Night	27% 6% 12% 29% 20% 6%	1879
	21st to end	Night	21% 5% 13% 39% 19% 2	1900
May	1st to 10th	Night	16% 4 8% 39% 27% 5%	3031
	11th to 20th	Night	10% 4 7% 41% 33% 5%	2835
	21st to end	Night	10% 3 8% 46% 31% 2	2776
June	1st to 10th	Night	16% 3 12% 28% 34% 7%	1520
	11th to 20th	Night	7% 3 7% 26% 41% 17%	1520
	21st to end	Night	6% 2 3 14% 41% 34%	1520
July	1st to 10th	Night	3 1 1 6% 19% 70%	2500
	11th to 20th	Night	11% 3 3 8% 25% 49%	2492
	21st to end	Night	8% 3 2 15% 27% 46%	2873
August	1st to 10th	Night	9% 2 3 12% 32% 42%	3083
	11th to 20th	Night	4 2 1 8% 26% 59%	3156
	21st to end	Night	7% 1 1 8% 36% 47%	3498
September	1st to 10th	Night	5% 1 1 12% 35% 46%	1900
	11th to 20th	Night	9% 2 4 20% 44% 21%	1966
	21st to end	Night	8% 3 3 23% 39% 24%	2090
October	1st to 10th	Night	10% 2 4 11% 29% 43%	3631
	11th to 20th	Night	11% 2 3 18% 39% 27%	3777
	21st to end	Night	14% 3 2 21% 39% 21%	4178
November	1st to 10th	Night	24% 4 8% 22% 26% 18%	2535
	11th to 20th	Night	21% 4 7% 22% 33% 14%	2600
	21st to end	Night	29% 4 6% 19% 30% 13%	2600
December	1st to 10th	Night	25% 3 6% 22% 27% 17%	4390
	11th to 20th	Night	40% 5% 10% 19% 21% 6%	5176
	21st to end	Night	42% 4 11% 21% 16% 5%	6952

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	32% 9% 26% 20% 11% 2	192
	11th to 20th	Day	20% 10% 26% 26% 14% 6%	272
	21st to end	Day	21% 9% 25% 27% 14% 5%	407
February	1st to 10th	Day	24% 12% 23% 25% 13% 4	424
	11th to 20th	Day	18% 16% 33% 22% 9% 2	455
	21st to end	Day	19% 16% 38% 19% 7% 1	382
March	1st to 10th	Day	25% 15% 35% 18% 6% 1	460
	11th to 20th	Day	23% 15% 28% 22% 9% 3	460
	21st to end	Day	25% 15% 33% 21% 5%	506
April	1st to 10th	Day	18% 13% 33% 27% 7% 2	460
	11th to 20th	Day	21% 18% 28% 25% 6% 2	452
	21st to end	Day	15% 10% 32% 27% 11% 4	460
May	1st to 10th	Day	16% 16% 32% 24% 8% 4	463
	11th to 20th	Day	14% 12% 27% 29% 13% 5%	488
	21st to end	Day	16% 8% 26% 32% 11% 8%	529
June	1st to 10th	Day	5% 12% 27% 34% 15% 7%	490
	11th to 20th	Day	4 10% 30% 36% 12% 7%	490
	21st to end	Day	2 8% 33% 35% 14% 8%	490
July	1st to 10th	Day	1 3 28% 43% 14% 10%	486
	11th to 20th	Day	2 2 25% 43% 15% 13%	484
	21st to end	Day	2 4 24% 47% 11% 11%	531
August	1st to 10th	Day	2 6% 36% 34% 13% 8%	487
	11th to 20th	Day	2 7% 29% 41% 11% 9%	477
	21st to end	Day	2 5% 28% 45% 15% 6%	539
September	1st to 10th	Day	4 6% 34% 40% 13% 4	490
	11th to 20th	Day	6% 10% 36% 36% 11% 2	490
	21st to end	Day	6% 10% 32% 39% 12% 1	490
October	1st to 10th	Day	5% 12% 33% 38% 11% 1	490
	11th to 20th	Day	5% 11% 32% 38% 11% 2	490
	21st to end	Day	8% 10% 34% 33% 14% 2	501
November	1st to 10th	Day	10% 12% 31% 29% 16% 2	300
	11th to 20th	Day	8% 13% 32% 28% 15% 4	300
	21st to end	Day	12% 14% 29% 28% 14% 4	300
December	1st to 10th	Day	16% 6% 28% 29% 17% 4	253
	11th to 20th	Day	18% 8% 26% 29% 16% 4	200
	21st to end	Day	22% 10% 31% 21% 10% 5%	220
January	1st to 10th	Night	18% 7% 21% 26% 17% 11%	784
	11th to 20th	Night	13% 4 25% 31% 18% 8%	760
	21st to end	Night	19% 6% 21% 31% 17% 7%	836
February	1st to 10th	Night	20% 4 19% 33% 17% 7%	760
	11th to 20th	Night	15% 6% 22% 30% 20% 9%	744
	21st to end	Night	18% 5% 21% 37% 14% 5%	628
March	1st to 10th	Night	20% 8% 16% 35% 16% 6%	760
	11th to 20th	Night	15% 6% 18% 27% 24% 9%	760
	21st to end	Night	18% 5% 17% 35% 20% 4	836
April	1st to 10th	Night	15% 6% 17% 38% 19% 6%	760
	11th to 20th	Night	11% 5% 23% 31% 23% 7%	751
	21st to end	Night	9% 6% 20% 35% 22% 8%	760
May	1st to 10th	Night	8% 5% 19% 36% 26% 7%	676
	11th to 20th	Night	8% 2 17% 35% 32% 6%	561
	21st to end	Night	6% 3 19% 30% 31% 11%	425
June	1st to 10th	Night	5% 1 13% 37% 36% 8%	380
	11th to 20th	Night	1 3 14% 37% 37% 9%	380
	21st to end	Night	1 2 12% 36% 41% 8%	380
July	1st to 10th	Night	1 2 10% 27% 52% 8%	370
	11th to 20th	Night	3 1 9% 30% 45% 12%	368
	21st to end	Night	2 1 9% 24% 45% 19%	533
August	1st to 10th	Night	3 1 10% 31% 44% 11%	707
	11th to 20th	Night	1 9% 28% 49% 12%	752
	21st to end	Night	3 1 8% 28% 47% 13%	836
September	1st to 10th	Night	2 1 9% 31% 44% 14%	760
	11th to 20th	Night	3 2 10% 34% 37% 14%	760
	21st to end	Night	3 1 15% 34% 34% 14%	760
October	1st to 10th	Night	5% 2 12% 46% 24% 10%	760
	11th to 20th	Night	6% 2 18% 34% 28% 13%	760
	21st to end	Night	5% 3 18% 30% 27% 17%	836
November	1st to 10th	Night	11% 3 14% 33% 25% 13%	780
	11th to 20th	Night	9% 5% 21% 36% 21% 9%	800
	21st to end	Night	13% 6% 21% 32% 20% 8%	800
December	1st to 10th	Night	16% 5% 19% 37% 17% 7%	800
	11th to 20th	Night	21% 5% 22% 32% 15% 5%	800
	21st to end	Night	20% 9% 23% 29% 16% 4	880

Page generated at 2025-01-04 00:23:59. Version ac07

Copyright © 2025 Attilla Danko.