Cameron Park Rotary Club Community Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cameron Park Rotary Club Community Observatory clear sky chart from 2005-11-06 to 2024-02-25.

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	11% 4 2 3 3 2 3 3 4 5% 61%	78536
	Night	13% 5% 2 3 3 2 3 3 4 5% 57%	80793
Transparency	Day	26% 4 8% 18% 23% 20%	78250
	Night	30% 5% 9% 18% 21% 18%	80600
Seeing	Day	11% 6% 21% 33% 22% 7%	14165
	Night	13% 2 10% 36% 31% 7%	23642

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	25% 10% 2 3 3 2 3 3 4 5% 40%	2539
	11th to 20th	Day	25% 9% 3 7% 5% 3 3 4 4 4 34%	2763
	21st to end	Day	25% 9% 3 5% 5% 3 3 4 5% 7% 32%	3146
February	1st to 10th	Day	22% 6% 2 3 4 2 4 3 4 5% 46%	1710
	11th to 20th	Day	18% 7% 2 5% 3 2 3 5% 4 7% 46%	1802
	21st to end	Day	21% 8% 3 3 3 3 2 3 4 4 47%	1521
March	1st to 10th	Day	21% 8% 3 5% 4 2 4 5% 5% 5% 36%	1837
	11th to 20th	Day	21% 7% 2 4 3 3 4 4 5% 7% 40%	1980
	21st to end	Day	18% 6% 2 5% 4 2 5% 5% 5% 6% 42%	2272
April	1st to 10th	Day	16% 6% 2 4 4 2 3 4 5% 7% 45%	2160
	11th to 20th	Day	14% 3 2 3 4 2 3 4 5% 6% 53%	2129
	21st to end	Day	11% 3 1 3 2 2 3 3 5% 7% 59%	2160
May	1st to 10th	Day	7% 4 2 4 3 1 3 3 4 6% 64%	2192
	11th to 20th	Day	6% 3 1 3 3 2 3 4 4 7% 64%	2477
	21st to end	Day	7% 4 1 3 4 2 3 3 5% 7% 62%	2723
June	1st to 10th	Day	6% 3 2 3 3 2 3 3 4 7% 65%	2520
	11th to 20th	Day	1 2 1 2 2 1 2 2 3 4 80%	2520
	21st to end	Day	2 2 1 2 1 1 1 1 2 4 84%	2520
July	1st to 10th	Day	1 1 1 1 1 3 3 87%	2520
	11th to 20th	Day	2 1 1 1 1 1 2 2 3 3 86%	2520
	21st to end	Day	1 1 2 2 1 2 2 3 3 82%	2575
August	1st to 10th	Day	2 2 1 1 1 1 1 2 3 3 82%	2328
	11th to 20th	Day	1 1 1 1 1 2 2 4 86%	2139
	21st to end	Day	1 1 1 1 1 1 1 2 2 1 90%	2376
September	1st to 10th	Day	2 1 1 1 1 1 2 3 3 88%	2160
	11th to 20th	Day	3 2 1 3 2 2 2 2 4 4 76%	2160
	21st to end	Day	3 2 1 2 1 1 2 2 2 5% 78%	1954
October	1st to 10th	Day	5% 2 1 3 2 2 3 4 4 6% 69%	1800
	11th to 20th	Day	6% 3 1 2 2 1 3 4 4 5% 68%	1800
	21st to end	Day	7% 3 2 3 3 2 3 3 3 5% 65%	1980
November	1st to 10th	Day	13% 4 2 3 3 3 4 3 5% 7% 54%	1697
	11th to 20th	Day	13% 3 2 3 4 2 4 5% 5% 7% 53%	1710
	21st to end	Day	13% 4 2 3 3 2 4 4 4 6% 55%	1604
December	1st to 10th	Day	17% 5% 2 4 4 2 4 5% 4 6% 48%	1520
	11th to 20th	Day	29% 8% 3 5% 4 2 3 3 4 6% 33%	1928
	21st to end	Day	15% 6% 3 5% 4 3 5% 6% 6% 9% 37%	2794
January	1st to 10th	Night	18% 9% 3 4 4 2 3 4 5% 7% 41%	4406
	11th to 20th	Night	23% 7% 3 6% 5% 3 4 5% 5% 6% 36%	4202
	21st to end	Night	25% 8% 3 6% 6% 3 4 4 5% 5% 33%	4521
February	1st to 10th	Night	20% 6% 2 3 3 2 3 2 4 6% 49%	2470
	11th to 20th	Night	16% 6% 2 5% 4 2 3 4 5% 7% 46%	2264
	21st to end	Night	19% 7% 2 3 3 2 3 3 4 5% 48%	1829
March	1st to 10th	Night	24% 8% 3 5% 3 3 4 3 3 4 40%	2120
	11th to 20th	Night	21% 6% 2 4 3 2 4 4 5% 6% 43%	1980
	21st to end	Night	20% 6% 2 4 4 3 4 4 4 5% 46%	2082
April	1st to 10th	Night	14% 6% 2 5% 5% 3 5% 4 4 6% 47%	1800
	11th to 20th	Night	13% 4 2 4 4 2 3 3 4 7% 54%	1779
	21st to end	Night	9% 4 2 2 3 2 3 3 5% 7% 61%	1800
May	1st to 10th	Night	8% 3 1 4 3 2 3 3 4 6% 63%	1761
	11th to 20th	Night	8% 3 1 2 2 1 3 3 4 8% 65%	1416
	21st to end	Night	7% 2 2 3 3 2 3 4 4 7% 64%	1552
June	1st to 10th	Night	6% 3 1 3 3 2 2 3 5% 5% 67%	1440
	11th to 20th	Night	1 1 1 2 2 1 3 2 3 4 80%	1440
	21st to end	Night	2 1 1 2 2 1 2 2 3 3 82%	1440
July	1st to 10th	Night	1 1 1 1 1 2 2 3 88%	1440
	11th to 20th	Night	1 1 1 1 1 1 1 3 2 3 85%	1440
	21st to end	Night	1 1 1 2 2 1 2 3 4 5% 78%	1739
August	1st to 10th	Night	2 2 1 2 2 2 2 3 3 4 79%	1611
	11th to 20th	Night	1 1 1 1 2 1 2 3 4 4 82%	1761
	21st to end	Night	1 1 1 2 1 1 1 1 2 2 87%	1980
September	1st to 10th	Night	2 1 1 1 1 1 1 2 3 88%	1800
	11th to 20th	Night	3 2 1 1 2 1 2 2 2 4 80%	1800
	21st to end	Night	3 1 1 1 2 1 2 2 3 5% 79%	2002
October	1st to 10th	Night	6% 2 1 3 3 2 2 3 4 4 71%	2160
	11th to 20th	Night	6% 3 1 2 2 1 2 3 4 5% 71%	2160
	21st to end	Night	7% 2 1 3 2 2 2 3 3 6% 70%	2376
November	1st to 10th	Night	14% 5% 2 3 2 2 2 3 4 6% 57%	2380
	11th to 20th	Night	12% 4 1 3 3 2 3 4 5% 7% 56%	2470
	21st to end	Night	13% 4 2 3 3 2 4 3 3 6% 57%	2574
December	1st to 10th	Night	19% 5% 2 3 3 2 4 3 3 6% 50%	2660
	11th to 20th	Night	30% 7% 2 5% 4 2 3 3 5% 6% 33%	3276
	21st to end	Night	20% 7% 3 5% 6% 3 4 5% 5% 6% 35%	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	47% 5% 9% 24% 13% 3	2539
	11th to 20th	Day	52% 7% 8% 13% 11% 8%	2763
	21st to end	Day	51% 7% 11% 16% 11% 5%	3146
February	1st to 10th	Day	42% 3 10% 18% 17% 10%	1710
	11th to 20th	Day	39% 5% 10% 19% 21% 7%	1812
	21st to end	Day	42% 3 9% 21% 18% 7%	1521
March	1st to 10th	Day	48% 7% 10% 16% 16% 4	1837
	11th to 20th	Day	44% 4 10% 22% 15% 4	1980
	21st to end	Day	42% 7% 15% 19% 14% 3	2272
April	1st to 10th	Day	38% 6% 13% 23% 15% 5%	2160
	11th to 20th	Day	30% 6% 13% 25% 19% 6%	2132
	21st to end	Day	25% 5% 14% 28% 24% 4	2160
May	1st to 10th	Day	22% 5% 12% 26% 29% 7%	2192
	11th to 20th	Day	21% 4 10% 30% 25% 9%	2480
	21st to end	Day	24% 5% 15% 28% 22% 6%	2724
June	1st to 10th	Day	20% 4 11% 25% 29% 11%	2520
	11th to 20th	Day	9% 3 8% 21% 34% 25%	2520
	21st to end	Day	9% 2 3 13% 35% 38%	2520
July	1st to 10th	Day	5% 2 2 9% 25% 56%	2451
	11th to 20th	Day	8% 1 3 12% 25% 51%	2445
	21st to end	Day	8% 2 4 7% 25% 54%	2432
August	1st to 10th	Day	9% 1 4 11% 27% 48%	2312
	11th to 20th	Day	5% 1 3 10% 34% 48%	2139
	21st to end	Day	5% 1 2 10% 36% 46%	2376
September	1st to 10th	Day	5% 1 3 8% 28% 55%	2160
	11th to 20th	Day	13% 3 6% 20% 35% 24%	2160
	21st to end	Day	12% 2 6% 19% 34% 28%	1954
October	1st to 10th	Day	17% 5% 6% 20% 26% 27%	1800
	11th to 20th	Day	18% 4 6% 20% 25% 26%	1800
	21st to end	Day	22% 5% 6% 19% 27% 22%	1980
November	1st to 10th	Day	31% 3 11% 20% 22% 14%	1697
	11th to 20th	Day	31% 5% 10% 20% 25% 10%	1710
	21st to end	Day	30% 5% 9% 21% 25% 11%	1604
December	1st to 10th	Day	38% 5% 8% 20% 19% 10%	1520
	11th to 20th	Day	54% 4 7% 15% 14% 6%	1928
	21st to end	Day	40% 9% 17% 19% 11% 4	2794
January	1st to 10th	Night	41% 7% 14% 23% 11% 4	4406
	11th to 20th	Night	49% 7% 12% 12% 11% 9%	4202
	21st to end	Night	52% 7% 10% 13% 13% 6%	4521
February	1st to 10th	Night	39% 4 8% 18% 20% 11%	2470
	11th to 20th	Night	38% 5% 8% 21% 20% 8%	2265
	21st to end	Night	39% 3 9% 24% 18% 7%	1829
March	1st to 10th	Night	49% 5% 9% 16% 16% 5%	2120
	11th to 20th	Night	40% 5% 10% 19% 19% 7%	1980
	21st to end	Night	41% 8% 10% 20% 15% 6%	2082
April	1st to 10th	Night	39% 6% 12% 18% 19% 6%	1800
	11th to 20th	Night	31% 6% 13% 25% 16% 10%	1779
	21st to end	Night	23% 6% 13% 32% 21% 6%	1800
May	1st to 10th	Night	22% 5% 13% 20% 28% 10%	1761
	11th to 20th	Night	19% 4 13% 30% 24% 10%	1416
	21st to end	Night	19% 7% 15% 30% 24% 6%	1552
June	1st to 10th	Night	19% 7% 11% 26% 26% 11%	1440
	11th to 20th	Night	10% 3 6% 22% 33% 25%	1440
	21st to end	Night	10% 2 4 12% 35% 37%	1440
July	1st to 10th	Night	4 2 3 11% 27% 53%	1400
	11th to 20th	Night	7% 2 3 12% 21% 54%	1392
	21st to end	Night	11% 2 3 9% 23% 53%	1642
August	1st to 10th	Night	11% 2 3 15% 24% 45%	1602
	11th to 20th	Night	7% 2 4 11% 29% 47%	1761
	21st to end	Night	7% 1 2 11% 30% 50%	1980
September	1st to 10th	Night	5% 1 2 8% 29% 53%	1800
	11th to 20th	Night	11% 3 6% 18% 40% 23%	1800
	21st to end	Night	11% 3 5% 18% 32% 31%	2002
October	1st to 10th	Night	18% 3 6% 18% 26% 29%	2160
	11th to 20th	Night	16% 4 6% 18% 27% 29%	2160
	21st to end	Night	18% 3 6% 20% 28% 25%	2376
November	1st to 10th	Night	29% 4 10% 21% 19% 17%	2380
	11th to 20th	Night	28% 4 10% 22% 25% 11%	2470
	21st to end	Night	31% 4 8% 20% 24% 14%	2574
December	1st to 10th	Night	37% 4 9% 19% 17% 14%	2660
	11th to 20th	Night	52% 3 7% 15% 16% 6%	3276
	21st to end	Night	46% 10% 12% 16% 11% 5%	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	37% 9% 16% 22% 14% 3	180
	11th to 20th	Day	25% 6% 18% 29% 17% 5%	312
	21st to end	Day	25% 5% 20% 25% 20% 5%	407
February	1st to 10th	Day	26% 8% 19% 23% 20% 4	370
	11th to 20th	Day	22% 11% 26% 25% 14% 2	432
	21st to end	Day	20% 12% 24% 30% 12% 2	363
March	1st to 10th	Day	27% 11% 26% 24% 10% 1	420
	11th to 20th	Day	24% 11% 26% 22% 13% 4	420
	21st to end	Day	21% 10% 31% 24% 13% 1	462
April	1st to 10th	Day	20% 12% 28% 25% 14% 3	420
	11th to 20th	Day	16% 13% 29% 25% 13% 3	412
	21st to end	Day	10% 9% 25% 29% 20% 6%	420
May	1st to 10th	Day	8% 10% 30% 29% 17% 5%	423
	11th to 20th	Day	10% 9% 24% 27% 22% 8%	448
	21st to end	Day	8% 8% 19% 29% 25% 10%	485
June	1st to 10th	Day	6% 7% 23% 32% 22% 10%	450
	11th to 20th	Day	3 7% 27% 36% 22% 6%	450
	21st to end	Day	1 3 20% 41% 24% 10%	450
July	1st to 10th	Day	1 13% 51% 26% 8%	446
	11th to 20th	Day	1 14% 43% 34% 8%	444
	21st to end	Day	1 1 13% 45% 29% 12%	487
August	1st to 10th	Day	4 2 16% 43% 26% 9%	447
	11th to 20th	Day	1 1 21% 38% 27% 12%	437
	21st to end	Day	1 1 14% 46% 28% 10%	495
September	1st to 10th	Day	3 2 16% 47% 26% 7%	450
	11th to 20th	Day	6% 2 21% 39% 26% 5%	450
	21st to end	Day	3 5% 22% 40% 27% 3	450
October	1st to 10th	Day	4 8% 24% 31% 28% 6%	450
	11th to 20th	Day	7% 4 16% 32% 32% 8%	450
	21st to end	Day	11% 6% 18% 31% 27% 7%	495
November	1st to 10th	Day	15% 7% 13% 28% 28% 8%	293
	11th to 20th	Day	12% 3 16% 33% 24% 11%	270
	21st to end	Day	12% 5% 18% 32% 26% 7%	219
December	1st to 10th	Day	21% 4 16% 28% 21% 10%	180
	11th to 20th	Day	19% 7% 21% 26% 18% 9%	180
	21st to end	Day	22% 6% 22% 23% 20% 7%	198
January	1st to 10th	Night	25% 3 12% 30% 21% 9%	760
	11th to 20th	Night	17% 4 12% 38% 22% 6%	760
	21st to end	Night	23% 3 12% 34% 20% 8%	836
February	1st to 10th	Night	22% 3 14% 33% 22% 5%	760
	11th to 20th	Night	20% 3 15% 35% 21% 6%	744
	21st to end	Night	22% 3 13% 41% 16% 4	610
March	1st to 10th	Night	28% 4 12% 32% 19% 5%	720
	11th to 20th	Night	23% 3 13% 32% 25% 5%	720
	21st to end	Night	22% 3 15% 37% 19% 4	792
April	1st to 10th	Night	16% 3 12% 41% 25% 3	720
	11th to 20th	Night	14% 4 14% 36% 26% 7%	711
	21st to end	Night	9% 4 11% 39% 30% 7%	720
May	1st to 10th	Night	10% 3 15% 39% 27% 6%	681
	11th to 20th	Night	9% 2 8% 36% 39% 6%	354
	21st to end	Night	6% 2 10% 37% 39% 6%	389
June	1st to 10th	Night	6% 2 10% 37% 38% 7%	360
	11th to 20th	Night	1 1 12% 39% 43% 4	360
	21st to end	Night	3 1 5% 40% 46% 5%	360
July	1st to 10th	Night	1 3 35% 55% 5%	350
	11th to 20th	Night	2 2 41% 50% 5%	348
	21st to end	Night	2 2 30% 55% 11%	557
August	1st to 10th	Night	3 4 33% 52% 7%	537
	11th to 20th	Night	1 1 3 41% 45% 10%	693
	21st to end	Night	2 3 34% 55% 6%	792
September	1st to 10th	Night	2 1 5% 34% 51% 8%	720
	11th to 20th	Night	3 1 6% 36% 44% 10%	720
	21st to end	Night	3 2 8% 39% 36% 12%	720
October	1st to 10th	Night	7% 1 8% 42% 32% 11%	720
	11th to 20th	Night	8% 1 8% 35% 39% 8%	720
	21st to end	Night	7% 3 11% 35% 29% 15%	792
November	1st to 10th	Night	15% 2 9% 35% 28% 11%	740
	11th to 20th	Night	13% 2 11% 41% 25% 9%	760
	21st to end	Night	14% 3 13% 38% 23% 8%	760
December	1st to 10th	Night	20% 3 11% 37% 21% 8%	760
	11th to 20th	Night	29% 2 10% 34% 21% 4	760
	21st to end	Night	26% 4 14% 34% 18% 4	836

Page generated at 2024-02-22 03:05:46. Version ac07

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