C.M. Crockett Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the C.M. Crockett Park clear sky chart from 2005-11-06 to 2024-01-16.

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	14% 5% 2 5% 5% 3 5% 5% 6% 8% 43%	74680
	Night	14% 6% 2 5% 5% 3 4 4 5% 7% 44%	75114
Transparency	Day	39% 6% 12% 23% 17% 3	74394
	Night	39% 6% 12% 23% 17% 4	74919
Seeing	Day	17% 9% 24% 26% 17% 7%	13863
	Night	17% 7% 28% 32% 14% 1	23565

By Month

Percentage Cloud Cover SE (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	15% 6% 3 5% 4 4 5% 5% 5% 6% 44%	1623
	11th to 20th	Day	16% 8% 3 6% 4 3 4 4 4 7% 42%	1665
	21st to end	Day	15% 7% 3 5% 6% 3 4 5% 4 7% 42%	1782
February	1st to 10th	Day	14% 7% 3 6% 6% 4 4 5% 5% 7% 38%	1620
	11th to 20th	Day	19% 7% 2 5% 5% 3 4 4 6% 6% 41%	1600
	21st to end	Day	18% 7% 3 6% 4 3 4 4 5% 7% 39%	1484
March	1st to 10th	Day	13% 5% 2 4 5% 3 4 3 5% 6% 49%	1980
	11th to 20th	Day	17% 6% 3 5% 5% 3 4 5% 5% 6% 42%	1980
	21st to end	Day	16% 7% 3 6% 6% 3 4 5% 5% 6% 38%	2186
April	1st to 10th	Day	12% 5% 3 5% 5% 3 4 4 5% 7% 46%	2160
	11th to 20th	Day	14% 5% 3 5% 4 3 4 4 5% 6% 48%	2134
	21st to end	Day	18% 6% 2 5% 5% 3 5% 4 6% 7% 40%	2160
May	1st to 10th	Day	16% 6% 2 5% 6% 3 5% 5% 6% 9% 38%	2324
	11th to 20th	Day	18% 6% 2 5% 5% 3 4 5% 6% 8% 38%	2350
	21st to end	Day	15% 6% 2 5% 4 3 4 5% 6% 9% 42%	2725
June	1st to 10th	Day	11% 4 2 5% 4 4 6% 6% 6% 9% 44%	2520
	11th to 20th	Day	11% 5% 2 5% 6% 3 5% 6% 7% 10% 40%	2520
	21st to end	Day	8% 3 2 4 6% 3 5% 5% 8% 10% 44%	2520
July	1st to 10th	Day	9% 6% 2 5% 5% 4 6% 6% 8% 9% 41%	2520
	11th to 20th	Day	5% 3 2 4 5% 4 6% 7% 8% 12% 43%	2370
	21st to end	Day	9% 5% 2 5% 6% 5% 6% 7% 8% 9% 37%	2547
August	1st to 10th	Day	9% 6% 2 7% 6% 4 6% 6% 8% 10% 36%	2327
	11th to 20th	Day	11% 5% 2 5% 6% 4 6% 6% 8% 10% 36%	2228
	21st to end	Day	10% 5% 2 5% 5% 4 5% 5% 6% 9% 44%	2376
September	1st to 10th	Day	14% 5% 3 5% 5% 3 4 5% 5% 7% 45%	2160
	11th to 20th	Day	11% 5% 3 4 4 2 5% 4 5% 8% 49%	2156
	21st to end	Day	20% 6% 3 5% 4 3 4 5% 5% 6% 40%	1881
October	1st to 10th	Day	17% 6% 2 4 4 3 4 3 5% 6% 47%	1800
	11th to 20th	Day	17% 4 2 4 4 3 4 4 5% 6% 48%	1800
	21st to end	Day	14% 5% 2 5% 4 2 3 5% 4 6% 49%	1980
November	1st to 10th	Day	12% 5% 2 4 4 3 3 3 4 7% 53%	1812
	11th to 20th	Day	14% 5% 2 3 3 3 5% 5% 4 7% 50%	1668
	21st to end	Day	16% 3 2 4 4 3 4 4 5% 5% 49%	1520
December	1st to 10th	Day	16% 6% 3 5% 5% 2 4 5% 7% 7% 42%	1520
	11th to 20th	Day	17% 6% 2 4 4 3 4 4 4 7% 46%	1910
	21st to end	Day	18% 6% 2 5% 5% 3 5% 5% 6% 8% 36%	2772
January	1st to 10th	Night	16% 6% 2 4 4 3 3 4 4 7% 47%	2540
	11th to 20th	Night	16% 7% 3 6% 5% 3 4 4 6% 6% 40%	2406
	21st to end	Night	15% 6% 3 5% 4 2 4 4 6% 5% 46%	2574
February	1st to 10th	Night	16% 7% 3 5% 5% 3 4 5% 5% 7% 40%	2340
	11th to 20th	Night	19% 6% 3 6% 4 2 3 3 4 6% 43%	2244
	21st to end	Night	17% 8% 3 5% 5% 3 4 4 4 5% 42%	1770
March	1st to 10th	Night	13% 4 2 4 4 3 4 5% 5% 6% 49%	1980
	11th to 20th	Night	18% 7% 2 4 4 3 5% 4 5% 6% 43%	1980
	21st to end	Night	15% 6% 2 6% 5% 3 4 4 5% 7% 42%	2170
April	1st to 10th	Night	14% 7% 3 6% 4 3 4 4 6% 6% 43%	1800
	11th to 20th	Night	12% 5% 2 5% 5% 3 3 4 5% 7% 49%	1775
	21st to end	Night	17% 5% 3 4 5% 3 4 5% 5% 8% 43%	1800
May	1st to 10th	Night	17% 6% 2 5% 5% 3 4 4 5% 9% 39%	1651
	11th to 20th	Night	18% 6% 2 5% 4 3 5% 5% 6% 7% 39%	1539
	21st to end	Night	13% 5% 2 6% 5% 3 5% 5% 5% 9% 42%	1550
June	1st to 10th	Night	11% 4 2 3 5% 3 5% 6% 7% 10% 44%	1440
	11th to 20th	Night	12% 6% 2 5% 5% 3 5% 6% 7% 7% 43%	1440
	21st to end	Night	10% 2 2 5% 6% 2 6% 6% 9% 8% 45%	1440
July	1st to 10th	Night	10% 4 3 6% 5% 4 5% 5% 7% 11% 40%	1440
	11th to 20th	Night	6% 4 1 4 6% 4 6% 6% 6% 11% 45%	1586
	21st to end	Night	8% 5% 2 6% 6% 3 6% 6% 7% 12% 39%	1771
August	1st to 10th	Night	8% 4 2 6% 8% 4 6% 7% 8% 8% 38%	1611
	11th to 20th	Night	10% 6% 2 7% 5% 4 6% 6% 6% 9% 38%	1652
	21st to end	Night	10% 6% 3 6% 6% 3 5% 6% 6% 10% 40%	1980
September	1st to 10th	Night	15% 6% 1 4 5% 2 5% 5% 6% 6% 44%	1800
	11th to 20th	Night	9% 6% 3 5% 5% 2 4 4 5% 6% 51%	1801
	21st to end	Night	18% 8% 2 5% 4 3 4 4 4 7% 41%	2078
October	1st to 10th	Night	18% 5% 3 4 4 3 4 4 4 6% 46%	2160
	11th to 20th	Night	16% 5% 2 5% 5% 2 3 3 4 6% 50%	2160
	21st to end	Night	14% 5% 2 4 4 2 4 4 5% 7% 48%	2376
November	1st to 10th	Night	12% 6% 2 5% 4 2 3 3 3 5% 54%	2263
	11th to 20th	Night	13% 6% 2 4 4 2 3 4 5% 7% 50%	2508
	21st to end	Night	13% 4 2 4 4 2 4 4 6% 7% 50%	2660
December	1st to 10th	Night	16% 7% 3 5% 4 3 4 4 4 6% 42%	2660
	11th to 20th	Night	17% 5% 2 4 4 3 4 3 5% 6% 45%	3285
	21st to end	Night	17% 6% 2 5% 5% 3 5% 5% 5% 7% 38%	4884

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	42% 5% 9% 23% 16% 5%	1624
	11th to 20th	Day	43% 4 11% 23% 16% 2	1665
	21st to end	Day	43% 4 9% 24% 17% 4	1782
February	1st to 10th	Day	45% 5% 11% 24% 13% 2	1620
	11th to 20th	Day	43% 4 9% 23% 17% 3	1609
	21st to end	Day	46% 3 13% 17% 17% 4	1484
March	1st to 10th	Day	37% 4 10% 24% 22% 4	1980
	11th to 20th	Day	43% 5% 10% 17% 18% 6%	1980
	21st to end	Day	45% 5% 9% 19% 16% 5%	2186
April	1st to 10th	Day	36% 6% 11% 21% 19% 7%	2160
	11th to 20th	Day	37% 5% 11% 21% 21% 6%	2134
	21st to end	Day	43% 6% 10% 22% 14% 4	2160
May	1st to 10th	Day	41% 8% 13% 20% 15% 2	2324
	11th to 20th	Day	44% 8% 13% 21% 13% 2	2354
	21st to end	Day	38% 7% 16% 26% 12% 1	2725
June	1st to 10th	Day	36% 7% 14% 26% 16% 1	2520
	11th to 20th	Day	38% 9% 14% 24% 14% 2	2520
	21st to end	Day	32% 8% 16% 26% 17% 1	2520
July	1st to 10th	Day	36% 10% 13% 22% 16% 2	2450
	11th to 20th	Day	30% 9% 18% 27% 14% 2	2299
	21st to end	Day	38% 9% 12% 22% 18% 1	2405
August	1st to 10th	Day	39% 9% 16% 25% 11%	2314
	11th to 20th	Day	39% 9% 14% 23% 14% 1	2228
	21st to end	Day	37% 6% 15% 24% 15% 3	2376
September	1st to 10th	Day	39% 6% 13% 19% 19% 4	2160
	11th to 20th	Day	33% 6% 9% 27% 21% 4	2156
	21st to end	Day	44% 6% 10% 20% 18% 2	1881
October	1st to 10th	Day	38% 5% 10% 26% 17% 4	1800
	11th to 20th	Day	37% 4 10% 24% 22% 3	1800
	21st to end	Day	36% 4 9% 25% 23% 4	1980
November	1st to 10th	Day	33% 3 10% 26% 23% 5%	1812
	11th to 20th	Day	35% 5% 10% 22% 21% 7%	1668
	21st to end	Day	37% 3 11% 26% 21% 3	1520
December	1st to 10th	Day	41% 5% 12% 26% 12% 4	1520
	11th to 20th	Day	39% 4 8% 31% 13% 4	1906
	21st to end	Day	44% 6% 13% 25% 12% 1	2772
January	1st to 10th	Night	38% 5% 9% 22% 19% 6%	2540
	11th to 20th	Night	44% 4 12% 21% 17% 3	2406
	21st to end	Night	39% 4 9% 24% 21% 2	2574
February	1st to 10th	Night	43% 6% 11% 22% 16% 2	2340
	11th to 20th	Night	43% 3 8% 22% 18% 6%	2246
	21st to end	Night	44% 4 9% 21% 16% 5%	1770
March	1st to 10th	Night	36% 4 11% 26% 20% 3	1980
	11th to 20th	Night	43% 5% 10% 20% 18% 4	1980
	21st to end	Night	41% 5% 10% 21% 16% 6%	2170
April	1st to 10th	Night	41% 5% 10% 19% 21% 5%	1800
	11th to 20th	Night	36% 5% 11% 21% 21% 6%	1775
	21st to end	Night	38% 7% 10% 26% 13% 6%	1800
May	1st to 10th	Night	42% 7% 12% 21% 14% 4	1651
	11th to 20th	Night	43% 7% 13% 21% 15% 3	1540
	21st to end	Night	38% 8% 16% 24% 13% 1	1551
June	1st to 10th	Night	33% 8% 14% 27% 16% 2	1440
	11th to 20th	Night	37% 9% 15% 22% 14% 2	1440
	21st to end	Night	33% 7% 18% 20% 19% 3	1440
July	1st to 10th	Night	37% 10% 16% 19% 14% 4	1400
	11th to 20th	Night	32% 9% 19% 23% 17% 2	1534
	21st to end	Night	33% 8% 18% 26% 14% 1	1672
August	1st to 10th	Night	38% 10% 16% 21% 13% 1	1600
	11th to 20th	Night	42% 8% 13% 23% 13% 2	1652
	21st to end	Night	38% 7% 16% 23% 13% 2	1980
September	1st to 10th	Night	38% 8% 11% 20% 17% 5%	1800
	11th to 20th	Night	33% 6% 10% 25% 23% 3	1801
	21st to end	Night	44% 6% 9% 20% 17% 3	2078
October	1st to 10th	Night	40% 4 10% 24% 18% 4	2160
	11th to 20th	Night	36% 4 9% 25% 22% 3	2160
	21st to end	Night	35% 5% 9% 23% 23% 5%	2376
November	1st to 10th	Night	34% 3 8% 26% 22% 7%	2263
	11th to 20th	Night	35% 4 8% 23% 23% 7%	2508
	21st to end	Night	34% 4 11% 26% 21% 4	2660
December	1st to 10th	Night	44% 4 11% 24% 15% 3	2660
	11th to 20th	Night	40% 4 10% 23% 18% 4	3288
	21st to end	Night	42% 6% 16% 21% 13% 1	4884

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	23% 18% 34% 19% 5%	231
	11th to 20th	Day	27% 21% 26% 23% 3	255
	21st to end	Day	23% 21% 35% 15% 6% 1	264
February	1st to 10th	Day	25% 18% 37% 15% 5%	240
	11th to 20th	Day	31% 19% 37% 11% 1	267
	21st to end	Day	24% 18% 32% 23% 3	346
March	1st to 10th	Day	18% 19% 34% 25% 4	420
	11th to 20th	Day	23% 17% 32% 21% 6% 1	420
	21st to end	Day	20% 16% 34% 21% 8% 2	462
April	1st to 10th	Day	20% 17% 28% 27% 7% 1	420
	11th to 20th	Day	15% 15% 24% 27% 15% 5%	412
	21st to end	Day	21% 12% 28% 24% 13% 1	420
May	1st to 10th	Day	21% 10% 29% 22% 13% 4	423
	11th to 20th	Day	19% 6% 27% 27% 14% 6%	447
	21st to end	Day	21% 1 19% 24% 24% 11%	485
June	1st to 10th	Day	10% 6% 19% 30% 25% 10%	450
	11th to 20th	Day	14% 6% 20% 30% 20% 10%	450
	21st to end	Day	9% 2 20% 37% 23% 10%	450
July	1st to 10th	Day	11% 4 11% 29% 29% 16%	445
	11th to 20th	Day	4 2 10% 31% 36% 17%	444
	21st to end	Day	11% 2 12% 30% 31% 14%	488
August	1st to 10th	Day	12% 3 13% 26% 32% 14%	446
	11th to 20th	Day	12% 3 11% 27% 30% 17%	439
	21st to end	Day	9% 2 14% 27% 27% 20%	495
September	1st to 10th	Day	15% 3 17% 26% 19% 20%	450
	11th to 20th	Day	13% 3 14% 28% 29% 14%	450
	21st to end	Day	23% 6% 18% 29% 17% 6%	450
October	1st to 10th	Day	21% 4 18% 27% 21% 9%	450
	11th to 20th	Day	15% 9% 24% 30% 18% 4	450
	21st to end	Day	16% 9% 31% 29% 11% 3	495
November	1st to 10th	Day	17% 9% 28% 27% 15% 4	433
	11th to 20th	Day	17% 10% 32% 27% 10% 3	328
	21st to end	Day	19% 12% 32% 26% 10% 2	180
December	1st to 10th	Day	18% 13% 40% 20% 7% 2	180
	11th to 20th	Day	23% 9% 34% 24% 10%	180
	21st to end	Day	25% 14% 30% 22% 9% 1	198
January	1st to 10th	Night	20% 12% 41% 24% 3	760
	11th to 20th	Night	20% 11% 35% 30% 4	741
	21st to end	Night	18% 12% 41% 27% 2	792
February	1st to 10th	Night	20% 10% 39% 27% 3	720
	11th to 20th	Night	24% 14% 40% 20% 1	703
	21st to end	Night	23% 13% 37% 25% 2	592
March	1st to 10th	Night	16% 14% 38% 28% 4	720
	11th to 20th	Night	23% 11% 36% 24% 5% 1	720
	21st to end	Night	17% 11% 39% 26% 6%	792
April	1st to 10th	Night	17% 11% 39% 27% 5%	720
	11th to 20th	Night	14% 9% 32% 34% 10% 1	711
	21st to end	Night	18% 6% 30% 36% 9%	720
May	1st to 10th	Night	20% 7% 28% 31% 13% 2	571
	11th to 20th	Night	20% 3 27% 36% 14% 1	478
	21st to end	Night	15% 2 15% 41% 25% 1	389
June	1st to 10th	Night	10% 2 19% 44% 23% 1	360
	11th to 20th	Night	13% 3 15% 43% 24% 2	360
	21st to end	Night	8% 3 14% 50% 23% 2	360
July	1st to 10th	Night	10% 3 14% 39% 29% 5%	350
	11th to 20th	Night	7% 1 8% 41% 38% 5%	490
	21st to end	Night	9% 2 12% 40% 32% 4	591
August	1st to 10th	Night	9% 1 8% 44% 35% 3	537
	11th to 20th	Night	12% 3 11% 39% 31% 4	588
	21st to end	Night	12% 1 10% 39% 32% 5%	792
September	1st to 10th	Night	19% 2 11% 30% 33% 5%	720
	11th to 20th	Night	12% 1 12% 37% 35% 3	720
	21st to end	Night	22% 3 19% 34% 22% 1	720
October	1st to 10th	Night	20% 3 18% 32% 23% 4	720
	11th to 20th	Night	18% 6% 25% 34% 17%	720
	21st to end	Night	18% 7% 31% 30% 14% 1	792
November	1st to 10th	Night	14% 6% 29% 37% 13% 1	740
	11th to 20th	Night	18% 7% 34% 31% 10% 1	760
	21st to end	Night	16% 8% 35% 32% 10% 1	760
December	1st to 10th	Night	21% 9% 35% 27% 8%	760
	11th to 20th	Night	17% 8% 38% 32% 5%	760
	21st to end	Night	21% 8% 32% 35% 4	836

Page generated at 2024-01-13 01:38:11. Version ac07

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