Santa Rosa
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Santa Rosa clear sky chart from 2005-11-06 to 2024-12-02.

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	9% 5% 2 4 3 3 3 2 4 6% 60%	105327
	Night	11% 6% 2 6% 3 3 3 3 4 5% 54%	103054
Transparency	Day	28% 3 7% 20% 23% 19%	105087
	Night	33% 4 8% 18% 21% 16%	102884
Seeing	Day	12% 9% 23% 30% 19% 6%	15448
	Night	13% 5% 13% 33% 30% 6%	24731

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	18% 9% 3 7% 4 3 3 3 5% 6% 41%	2705
	11th to 20th	Day	23% 10% 3 8% 4 4 4 3 4 5% 32%	2860
	21st to end	Day	23% 9% 3 7% 4 4 4 3 5% 6% 32%	3146
February	1st to 10th	Day	18% 6% 2 6% 4 3 4 2 3 4 47%	1710
	11th to 20th	Day	15% 7% 3 5% 5% 3 4 4 4 7% 43%	1701
	21st to end	Day	17% 7% 2 4 4 3 3 2 4 7% 47%	1570
March	1st to 10th	Day	21% 13% 4 7% 5% 4 4 3 4 5% 30%	3432
	11th to 20th	Day	12% 5% 2 4 3 3 4 3 5% 6% 54%	3490
	21st to end	Day	18% 9% 2 6% 4 4 5% 4 6% 7% 36%	3845
April	1st to 10th	Day	15% 7% 2 6% 4 4 4 4 6% 7% 42%	2280
	11th to 20th	Day	10% 5% 2 5% 4 4 4 3 4 7% 51%	2249
	21st to end	Day	8% 4 1 4 3 3 3 2 6% 9% 57%	2280
May	1st to 10th	Day	6% 3 1 3 2 2 2 2 3 5% 71%	4045
	11th to 20th	Day	4 3 1 3 2 2 2 2 4 6% 71%	4149
	21st to end	Day	4 4 1 2 2 2 2 2 3 5% 73%	4813
June	1st to 10th	Day	7% 6% 2 4 3 2 3 2 5% 8% 59%	2660
	11th to 20th	Day	2 3 1 2 2 2 2 2 4 7% 73%	2660
	21st to end	Day	3 3 1 3 2 2 2 2 3 5% 76%	2660
July	1st to 10th	Day	1 2 1 2 2 2 1 1 2 4 82%	4420
	11th to 20th	Day	1 2 2 3 2 2 2 2 4 5% 76%	4123
	21st to end	Day	1 2 1 3 2 2 2 2 3 4 78%	4455
August	1st to 10th	Day	1 2 2 5% 3 3 4 3 6% 7% 65%	4091
	11th to 20th	Day	1 2 1 2 2 2 1 2 3 5% 79%	3912
	21st to end	Day	2 4 2 5% 2 2 2 2 3 5% 72%	4180
September	1st to 10th	Day	1 3 1 3 1 2 2 2 4 6% 76%	2280
	11th to 20th	Day	4 4 2 4 2 2 3 2 4 7% 64%	2271
	21st to end	Day	4 2 1 3 2 2 2 2 3 6% 74%	2001
October	1st to 10th	Day	4 2 1 2 2 2 3 3 4 6% 72%	3180
	11th to 20th	Day	8% 4 1 4 2 2 2 2 3 5% 65%	3161
	21st to end	Day	8% 4 1 4 3 3 4 3 5% 7% 58%	3448
November	1st to 10th	Day	11% 4 1 5% 4 3 3 3 5% 7% 56%	1937
	11th to 20th	Day	13% 6% 2 6% 5% 3 3 2 4 6% 49%	1763
	21st to end	Day	12% 5% 1 4 3 3 5% 3 5% 6% 53%	1600
December	1st to 10th	Day	17% 8% 3 4 4 3 4 3 4 6% 44%	1528
	11th to 20th	Day	33% 9% 2 5% 3 2 4 2 4 5% 31%	1928
	21st to end	Day	22% 10% 2 6% 4 3 3 3 4 8% 35%	2794
January	1st to 10th	Night	17% 8% 2 5% 3 4 3 3 5% 8% 42%	4242
	11th to 20th	Night	23% 8% 3 7% 5% 4 5% 4 5% 5% 32%	4110
	21st to end	Night	25% 10% 3 8% 3 4 4 3 4 5% 31%	4521
February	1st to 10th	Night	18% 5% 2 5% 3 3 3 3 4 6% 48%	2470
	11th to 20th	Night	14% 9% 3 6% 3 3 3 3 5% 7% 44%	2364
	21st to end	Night	15% 6% 1 3 3 3 3 2 4 6% 53%	1884
March	1st to 10th	Night	21% 13% 3 6% 3 4 4 3 4 5% 35%	3438
	11th to 20th	Night	14% 5% 2 6% 3 3 2 3 4 5% 55%	3490
	21st to end	Night	16% 13% 3 7% 3 3 3 3 4 6% 39%	3808
April	1st to 10th	Night	12% 7% 3 5% 4 3 4 3 4 6% 50%	1900
	11th to 20th	Night	10% 6% 2 5% 4 4 3 2 3 6% 56%	1879
	21st to end	Night	7% 5% 2 4 2 3 3 3 4 6% 60%	1900
May	1st to 10th	Night	5% 3 1 4 3 2 2 2 3 4 71%	2910
	11th to 20th	Night	3 5% 2 8% 5% 4 2 2 3 5% 61%	2748
	21st to end	Night	3 3 1 3 2 2 2 2 3 4 76%	2762
June	1st to 10th	Night	5% 6% 2 3 3 3 3 4 5% 8% 58%	1520
	11th to 20th	Night	2 3 1 4 2 2 2 3 3 6% 72%	1520
	21st to end	Night	4 4 2 4 3 2 2 2 3 4 71%	1520
July	1st to 10th	Night	1 2 2 3 3 2 2 1 3 3 79%	2540
	11th to 20th	Night	1 3 5% 7% 3 3 2 2 3 4 69%	2843
	21st to end	Night	1 4 4 8% 4 4 4 3 4 7% 57%	3109
August	1st to 10th	Night	3 4 2 13% 6% 5% 5% 3 4 6% 49%	2848
	11th to 20th	Night	2 1 3 3 3 3 3 3 5% 72%	2930
	21st to end	Night	3 4 2 8% 4 3 2 2 3 4 66%	3498
September	1st to 10th	Night	1 2 1 3 3 3 2 2 4 6% 72%	1900
	11th to 20th	Night	5% 5% 2 6% 3 3 3 3 4 7% 59%	1905
	21st to end	Night	4 4 2 5% 2 2 2 2 4 4 70%	2178
October	1st to 10th	Night	3 4 1 3 2 2 2 2 3 4 73%	3800
	11th to 20th	Night	6% 7% 3 6% 3 3 3 2 3 4 59%	3777
	21st to end	Night	10% 3 2 3 3 3 3 3 4 6% 59%	4121
November	1st to 10th	Night	10% 6% 2 4 3 3 3 3 5% 7% 54%	2360
	11th to 20th	Night	13% 5% 2 6% 3 3 3 3 6% 7% 50%	2635
	21st to end	Night	12% 4 2 5% 3 3 3 3 4 6% 56%	2800
December	1st to 10th	Night	20% 6% 3 6% 3 3 4 3 4 6% 44%	2686
	11th to 20th	Night	32% 7% 2 4 4 3 3 3 5% 6% 31%	3276
	21st to end	Night	21% 8% 3 7% 4 4 4 3 4 5% 37%	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	45% 5% 11% 28% 8% 3	2705
	11th to 20th	Day	56% 4 10% 13% 10% 7%	2860
	21st to end	Day	54% 3 9% 18% 11% 4	3146
February	1st to 10th	Day	42% 4 7% 19% 20% 8%	1710
	11th to 20th	Day	42% 4 7% 20% 18% 7%	1710
	21st to end	Day	39% 4 10% 26% 15% 7%	1570
March	1st to 10th	Day	57% 4 9% 15% 12% 2	3432
	11th to 20th	Day	31% 4 11% 30% 13% 11%	3490
	21st to end	Day	46% 5% 14% 22% 11% 2	3845
April	1st to 10th	Day	42% 4 13% 21% 16% 4	2280
	11th to 20th	Day	33% 5% 14% 24% 20% 5%	2252
	21st to end	Day	25% 4 14% 31% 22% 4	2280
May	1st to 10th	Day	18% 2 12% 32% 21% 15%	4045
	11th to 20th	Day	17% 4 5% 32% 31% 12%	4152
	21st to end	Day	16% 4 11% 37% 29% 3	4814
June	1st to 10th	Day	25% 4 11% 29% 25% 6%	2660
	11th to 20th	Day	14% 3 10% 21% 37% 15%	2660
	21st to end	Day	14% 2 4 15% 36% 28%	2660
July	1st to 10th	Day	10% 2 2 7% 17% 63%	4351
	11th to 20th	Day	13% 3 3 7% 21% 54%	4053
	21st to end	Day	12% 2 1 8% 29% 47%	4315
August	1st to 10th	Day	19% 3 2 10% 27% 38%	4076
	11th to 20th	Day	11% 3 1 12% 43% 30%	3951
	21st to end	Day	18% 3 2 13% 37% 27%	4179
September	1st to 10th	Day	13% 2 3 11% 32% 40%	2280
	11th to 20th	Day	22% 3 5% 25% 33% 11%	2271
	21st to end	Day	15% 2 4 23% 32% 23%	2001
October	1st to 10th	Day	16% 2 3 12% 26% 41%	3180
	11th to 20th	Day	24% 2 6% 22% 26% 20%	3161
	21st to end	Day	27% 4 7% 24% 26% 12%	3448
November	1st to 10th	Day	29% 5% 7% 29% 19% 11%	1937
	11th to 20th	Day	37% 6% 10% 23% 17% 7%	1763
	21st to end	Day	34% 5% 10% 20% 19% 13%	1600
December	1st to 10th	Day	41% 5% 9% 18% 19% 9%	1528
	11th to 20th	Day	58% 3 7% 12% 15% 5%	1928
	21st to end	Day	50% 4 13% 20% 9% 4	2794
January	1st to 10th	Night	42% 6% 18% 23% 8% 3	4242
	11th to 20th	Night	55% 5% 11% 12% 10% 8%	4110
	21st to end	Night	55% 4 10% 12% 13% 6%	4521
February	1st to 10th	Night	39% 4 8% 20% 18% 11%	2470
	11th to 20th	Night	41% 4 9% 19% 19% 7%	2366
	21st to end	Night	33% 4 10% 27% 19% 6%	1884
March	1st to 10th	Night	53% 5% 12% 14% 14% 3	3438
	11th to 20th	Night	32% 4 9% 23% 22% 10%	3490
	21st to end	Night	47% 4 13% 24% 10% 3	3808
April	1st to 10th	Night	35% 5% 13% 21% 21% 4	1900
	11th to 20th	Night	31% 4 12% 26% 17% 9%	1879
	21st to end	Night	25% 4 10% 31% 25% 6%	1900
May	1st to 10th	Night	20% 2 5% 28% 28% 17%	2910
	11th to 20th	Night	25% 5% 5% 20% 26% 19%	2749
	21st to end	Night	15% 3 7% 39% 30% 6%	2762
June	1st to 10th	Night	25% 5% 9% 22% 31% 8%	1520
	11th to 20th	Night	15% 3 7% 21% 36% 18%	1520
	21st to end	Night	19% 3 4 12% 31% 30%	1520
July	1st to 10th	Night	14% 3 2 5% 20% 57%	2500
	11th to 20th	Night	22% 5% 3 5% 17% 49%	2790
	21st to end	Night	30% 4 2 4 21% 40%	3011
August	1st to 10th	Night	39% 3 2 11% 23% 23%	2839
	11th to 20th	Night	16% 5% 2 8% 38% 32%	2957
	21st to end	Night	25% 3 3 12% 33% 25%	3498
September	1st to 10th	Night	15% 4 2 9% 31% 39%	1900
	11th to 20th	Night	28% 3 4 18% 32% 14%	1905
	21st to end	Night	19% 3 3 21% 27% 27%	2178
October	1st to 10th	Night	17% 3 3 10% 22% 45%	3800
	11th to 20th	Night	31% 2 5% 20% 20% 21%	3777
	21st to end	Night	27% 3 5% 22% 26% 17%	4121
November	1st to 10th	Night	31% 4 10% 26% 18% 11%	2360
	11th to 20th	Night	33% 5% 11% 26% 17% 8%	2635
	21st to end	Night	32% 4 8% 20% 22% 14%	2800
December	1st to 10th	Night	42% 5% 8% 16% 19% 10%	2686
	11th to 20th	Night	54% 4 9% 14% 15% 4	3276
	21st to end	Night	50% 4 13% 18% 11% 3	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	31% 13% 24% 18% 11% 4	281
	11th to 20th	Day	24% 10% 23% 25% 15% 3	370
	21st to end	Day	18% 11% 22% 29% 17% 3	407
February	1st to 10th	Day	20% 13% 21% 22% 19% 5%	370
	11th to 20th	Day	20% 17% 26% 22% 13% 1	383
	21st to end	Day	18% 14% 25% 28% 14% 1	382
March	1st to 10th	Day	27% 15% 25% 21% 8% 2	460
	11th to 20th	Day	26% 13% 25% 21% 12% 4	460
	21st to end	Day	19% 17% 29% 25% 10%	506
April	1st to 10th	Day	18% 16% 26% 25% 10% 4	460
	11th to 20th	Day	17% 17% 28% 22% 12% 4	452
	21st to end	Day	10% 16% 29% 27% 13% 6%	460
May	1st to 10th	Day	13% 14% 31% 25% 13% 4	463
	11th to 20th	Day	11% 12% 28% 27% 16% 6%	488
	21st to end	Day	10% 10% 24% 31% 18% 7%	529
June	1st to 10th	Day	10% 11% 23% 33% 16% 7%	490
	11th to 20th	Day	4 11% 29% 37% 15% 3	490
	21st to end	Day	2 4 28% 36% 24% 6%	490
July	1st to 10th	Day	4 3 21% 45% 20% 6%	486
	11th to 20th	Day	1 1 18% 43% 27% 10%	484
	21st to end	Day	2 2 11% 49% 27% 9%	531
August	1st to 10th	Day	2 3 20% 42% 24% 9%	487
	11th to 20th	Day	3 4 22% 36% 27% 8%	477
	21st to end	Day	3 3 18% 39% 29% 8%	539
September	1st to 10th	Day	2 3 20% 39% 27% 9%	490
	11th to 20th	Day	7% 6% 22% 33% 23% 8%	490
	21st to end	Day	5% 7% 21% 34% 25% 8%	490
October	1st to 10th	Day	8% 6% 25% 26% 25% 10%	490
	11th to 20th	Day	9% 8% 18% 27% 26% 12%	490
	21st to end	Day	12% 8% 20% 30% 22% 7%	539
November	1st to 10th	Day	13% 9% 18% 26% 27% 8%	473
	11th to 20th	Day	13% 6% 19% 25% 25% 12%	281
	21st to end	Day	13% 9% 26% 25% 18% 10%	200
December	1st to 10th	Day	21% 13% 18% 20% 18% 11%	182
	11th to 20th	Day	26% 12% 21% 18% 17% 7%	180
	21st to end	Day	21% 11% 25% 23% 16% 5%	198
January	1st to 10th	Night	23% 6% 14% 31% 22% 5%	760
	11th to 20th	Night	21% 5% 15% 35% 20% 4	760
	21st to end	Night	21% 4 14% 33% 23% 4	836
February	1st to 10th	Night	19% 6% 14% 36% 22% 3	760
	11th to 20th	Night	17% 7% 17% 33% 21% 4	744
	21st to end	Night	18% 9% 17% 35% 19% 2	628
March	1st to 10th	Night	23% 8% 18% 27% 20% 3	760
	11th to 20th	Night	20% 7% 14% 31% 24% 3	760
	21st to end	Night	19% 7% 22% 32% 18% 2	836
April	1st to 10th	Night	15% 8% 20% 34% 20% 3	760
	11th to 20th	Night	12% 12% 19% 31% 22% 5%	751
	21st to end	Night	8% 10% 23% 27% 25% 6%	760
May	1st to 10th	Night	9% 5% 22% 32% 28% 4	607
	11th to 20th	Night	7% 3 16% 32% 36% 6%	515
	21st to end	Night	7% 7% 18% 29% 34% 6%	411
June	1st to 10th	Night	9% 4 19% 32% 33% 3	380
	11th to 20th	Night	4 5% 15% 44% 30% 3	380
	21st to end	Night	5% 2 13% 36% 41% 4	380
July	1st to 10th	Night	2 1 7% 35% 49% 6%	370
	11th to 20th	Night	3 1 3 30% 51% 13%	536
	21st to end	Night	3 1 2 31% 52% 11%	624
August	1st to 10th	Night	4 1 5% 32% 47% 11%	567
	11th to 20th	Night	2 7% 35% 46% 10%	630
	21st to end	Night	3 1 6% 32% 48% 9%	836
September	1st to 10th	Night	2 1 8% 31% 49% 9%	760
	11th to 20th	Night	7% 2 8% 34% 40% 9%	760
	21st to end	Night	5% 3 9% 34% 37% 12%	760
October	1st to 10th	Night	7% 3 13% 32% 35% 9%	760
	11th to 20th	Night	9% 3 11% 31% 37% 9%	760
	21st to end	Night	11% 3 10% 32% 33% 11%	836
November	1st to 10th	Night	13% 3 13% 31% 32% 9%	780
	11th to 20th	Night	14% 4 12% 36% 29% 6%	800
	21st to end	Night	14% 4 14% 37% 25% 6%	800
December	1st to 10th	Night	22% 6% 11% 32% 23% 5%	768
	11th to 20th	Night	27% 6% 14% 30% 19% 4	760
	21st to end	Night	24% 6% 19% 33% 17% 2	836

Page generated at 2024-11-29 07:43:09. Version ac07

Copyright © 2024 Attilla Danko.