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 2024-12-06.

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% 6% 2 6% 4 4 4 4 6% 8% 42%	101423
	Night	15% 7% 2 6% 4 4 4 3 5% 7% 43%	98254
Transparency	Day	39% 6% 12% 24% 16% 3	105066
	Night	39% 5% 11% 23% 18% 4	102750
Seeing	Day	17% 9% 24% 26% 17% 7%	15082
	Night	17% 7% 28% 33% 14% 1	24705

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	18% 5% 2 4 3 4 4 3 5% 6% 47%	2688
	11th to 20th	Day	14% 10% 3 8% 4 4 4 3 4 5% 40%	2840
	21st to end	Day	18% 9% 3 7% 5% 3 4 3 4 6% 38%	3124
February	1st to 10th	Day	14% 7% 3 7% 5% 5% 4 4 5% 6% 40%	1710
	11th to 20th	Day	18% 8% 2 5% 4 4 3 3 6% 6% 41%	1691
	21st to end	Day	18% 8% 3 6% 4 4 4 3 5% 6% 39%	1575
March	1st to 10th	Day	21% 7% 3 6% 5% 4 4 3 5% 7% 36%	3435
	11th to 20th	Day	10% 5% 2 6% 4 4 4 4 5% 7% 50%	3480
	21st to end	Day	20% 7% 2 6% 4 3 4 3 5% 6% 38%	3836
April	1st to 10th	Day	12% 6% 3 5% 5% 4 4 4 6% 7% 45%	2280
	11th to 20th	Day	13% 6% 2 5% 4 4 3 3 5% 6% 48%	2254
	21st to end	Day	17% 6% 2 6% 4 5% 5% 3 6% 6% 40%	2280
May	1st to 10th	Day	20% 9% 2 6% 5% 5% 5% 4 6% 8% 30%	4066
	11th to 20th	Day	22% 7% 2 6% 5% 4 4 4 6% 9% 32%	4172
	21st to end	Day	11% 5% 2 5% 4 4 5% 4 7% 9% 44%	4823
June	1st to 10th	Day	11% 4 2 6% 4 4 5% 5% 7% 9% 43%	2660
	11th to 20th	Day	11% 5% 2 6% 5% 4 5% 5% 7% 10% 41%	2660
	21st to end	Day	8% 4 2 5% 5% 5% 6% 4 8% 10% 44%	2660
July	1st to 10th	Day	6% 5% 2 5% 4 6% 6% 5% 8% 11% 43%	4440
	11th to 20th	Day	8% 6% 2 5% 5% 5% 5% 6% 8% 13% 38%	4164
	21st to end	Day	11% 7% 2 7% 6% 6% 6% 5% 7% 9% 36%	4466
August	1st to 10th	Day	15% 6% 2 6% 5% 4 5% 5% 8% 10% 34%	4104
	11th to 20th	Day	9% 4 2 6% 5% 5% 6% 5% 8% 9% 40%	3899
	21st to end	Day	10% 4 2 5% 3 4 4 4 6% 8% 50%	4180
September	1st to 10th	Day	13% 5% 3 6% 4 4 4 4 5% 6% 46%	2280
	11th to 20th	Day	12% 6% 2 4 3 3 4 3 5% 8% 48%	2275
	21st to end	Day	22% 6% 3 5% 4 4 4 4 5% 6% 38%	1985
October	1st to 10th	Day	17% 6% 2 4 3 4 4 3 5% 6% 47%	1900
	11th to 20th	Day	16% 4 2 4 3 4 3 3 5% 6% 50%	1900
	21st to end	Day	14% 5% 2 5% 3 3 3 4 4 6% 51%	2090
November	1st to 10th	Day	12% 6% 2 4 3 4 3 3 4 7% 53%	1909
	11th to 20th	Day	14% 6% 2 4 3 4 5% 4 4 7% 49%	1755
	21st to end	Day	15% 4 2 5% 4 3 4 3 6% 5% 49%	1600
December	1st to 10th	Day	15% 6% 2 5% 4 3 4 4 7% 7% 42%	1560
	11th to 20th	Day	16% 6% 2 5% 4 4 4 3 4 7% 46%	1910
	21st to end	Day	18% 6% 2 6% 4 4 5% 4 6% 8% 36%	2772
January	1st to 10th	Night	14% 7% 2 5% 4 3 3 3 5% 6% 48%	4255
	11th to 20th	Night	17% 8% 2 5% 3 3 3 3 4 6% 47%	4120
	21st to end	Night	20% 9% 3 6% 3 3 3 2 5% 5% 42%	4532
February	1st to 10th	Night	15% 7% 2 6% 5% 4 4 4 5% 6% 40%	2470
	11th to 20th	Night	19% 7% 2 7% 3 3 3 2 4 6% 44%	2373
	21st to end	Night	16% 8% 3 5% 4 4 4 3 5% 5% 42%	1877
March	1st to 10th	Night	21% 6% 2 6% 4 4 4 4 5% 6% 37%	3418
	11th to 20th	Night	12% 6% 2 4 3 4 4 3 6% 7% 49%	3480
	21st to end	Night	13% 7% 2 6% 4 4 3 3 5% 6% 47%	3796
April	1st to 10th	Night	14% 8% 3 6% 4 4 4 3 6% 6% 43%	1900
	11th to 20th	Night	12% 5% 2 6% 5% 4 3 3 5% 7% 49%	1875
	21st to end	Night	16% 5% 2 5% 4 4 5% 3 6% 8% 43%	1900
May	1st to 10th	Night	22% 9% 3 7% 5% 4 4 3 5% 8% 30%	2858
	11th to 20th	Night	23% 9% 2 7% 4 4 4 4 5% 6% 32%	2717
	21st to end	Night	11% 4 2 5% 5% 4 5% 4 6% 10% 44%	2732
June	1st to 10th	Night	10% 5% 2 5% 4 5% 4 4 7% 10% 43%	1520
	11th to 20th	Night	11% 6% 2 6% 4 4 5% 4 7% 8% 42%	1520
	21st to end	Night	10% 3 1 6% 5% 4 5% 5% 9% 8% 45%	1520
July	1st to 10th	Night	7% 4 2 7% 4 6% 6% 5% 8% 11% 40%	2520
	11th to 20th	Night	8% 5% 2 7% 6% 5% 6% 5% 7% 11% 38%	2792
	21st to end	Night	10% 9% 3 8% 5% 5% 5% 5% 7% 9% 35%	3087
August	1st to 10th	Night	15% 5% 2 8% 6% 5% 6% 5% 7% 9% 32%	2825
	11th to 20th	Night	10% 7% 3 9% 5% 5% 5% 4 6% 8% 36%	2895
	21st to end	Night	11% 5% 2 5% 4 3 4 3 5% 8% 50%	3476
September	1st to 10th	Night	14% 6% 1 5% 4 4 5% 4 5% 6% 45%	1900
	11th to 20th	Night	10% 6% 2 6% 4 3 4 3 6% 7% 50%	1902
	21st to end	Night	20% 9% 2 6% 4 4 3 3 4 6% 39%	2194
October	1st to 10th	Night	19% 6% 2 5% 4 4 4 3 4 5% 46%	2280
	11th to 20th	Night	15% 5% 2 6% 4 2 3 2 5% 6% 51%	2280
	21st to end	Night	13% 5% 2 4 4 3 4 3 6% 7% 50%	2508
November	1st to 10th	Night	12% 6% 2 5% 4 3 3 3 4 5% 54%	2386
	11th to 20th	Night	14% 7% 2 4 4 3 3 3 5% 7% 49%	2640
	21st to end	Night	13% 5% 1 4 4 4 4 3 6% 7% 50%	2800
December	1st to 10th	Night	16% 8% 3 6% 4 4 3 3 4 6% 43%	2737
	11th to 20th	Night	17% 6% 2 5% 4 4 3 3 5% 6% 44%	3285
	21st to end	Night	17% 7% 2 6% 4 4 5% 4 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	38% 3 8% 30% 16% 5%	2689
	11th to 20th	Day	46% 4 9% 19% 15% 7%	2840
	21st to end	Day	47% 5% 9% 23% 14% 2	3124
February	1st to 10th	Day	43% 5% 12% 24% 14% 2	1710
	11th to 20th	Day	42% 4 9% 23% 18% 3	1700
	21st to end	Day	46% 4 13% 17% 17% 4	1575
March	1st to 10th	Day	48% 4 9% 21% 13% 5%	3435
	11th to 20th	Day	33% 4 9% 26% 24% 5%	3480
	21st to end	Day	45% 6% 11% 19% 15% 4	3836
April	1st to 10th	Day	37% 6% 12% 21% 19% 7%	2280
	11th to 20th	Day	37% 5% 11% 21% 20% 6%	2254
	21st to end	Day	43% 6% 10% 23% 14% 4	2280
May	1st to 10th	Day	50% 8% 11% 20% 10% 1	4104
	11th to 20th	Day	48% 8% 11% 24% 8% 1	4176
	21st to end	Day	33% 8% 16% 23% 18% 2	4837
June	1st to 10th	Day	36% 8% 14% 25% 16% 1	2660
	11th to 20th	Day	36% 8% 14% 26% 14% 2	2660
	21st to end	Day	32% 7% 16% 26% 17% 1	2660
July	1st to 10th	Day	33% 9% 20% 20% 12% 5%	4370
	11th to 20th	Day	35% 8% 18% 28% 10% 1	4093
	21st to end	Day	43% 7% 10% 22% 17% 1	4324
August	1st to 10th	Day	42% 7% 18% 25% 7%	4091
	11th to 20th	Day	37% 7% 14% 27% 15% 1	3938
	21st to end	Day	32% 5% 16% 27% 18% 2	4180
September	1st to 10th	Day	38% 6% 12% 18% 21% 4	2280
	11th to 20th	Day	34% 5% 9% 27% 21% 4	2275
	21st to end	Day	46% 6% 10% 19% 17% 2	1985
October	1st to 10th	Day	37% 4 7% 18% 29% 5%	3160
	11th to 20th	Day	26% 3 8% 27% 27% 10%	3140
	21st to end	Day	22% 2 10% 29% 26% 10%	3428
November	1st to 10th	Day	33% 3 10% 26% 23% 5%	1909
	11th to 20th	Day	35% 5% 10% 22% 21% 6%	1755
	21st to end	Day	37% 4 11% 26% 21% 2	1600
December	1st to 10th	Day	40% 5% 12% 27% 13% 4	1560
	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	37% 4 9% 26% 20% 4	4255
	11th to 20th	Night	40% 3 10% 23% 20% 5%	4120
	21st to end	Night	45% 4 8% 25% 17% 1	4532
February	1st to 10th	Night	43% 5% 11% 23% 16% 2	2470
	11th to 20th	Night	43% 3 8% 22% 18% 6%	2375
	21st to end	Night	43% 4 10% 21% 16% 5%	1877
March	1st to 10th	Night	46% 5% 9% 24% 14% 2	3418
	11th to 20th	Night	33% 4 9% 25% 24% 4	3480
	21st to end	Night	39% 5% 9% 23% 20% 5%	3796
April	1st to 10th	Night	41% 5% 10% 19% 22% 4	1900
	11th to 20th	Night	36% 5% 12% 22% 21% 6%	1875
	21st to end	Night	37% 7% 11% 26% 14% 5%	1900
May	1st to 10th	Night	52% 7% 10% 19% 10% 3	2885
	11th to 20th	Night	51% 7% 10% 21% 9% 1	2718
	21st to end	Night	34% 9% 16% 25% 13% 3	2739
June	1st to 10th	Night	34% 8% 13% 27% 16% 2	1520
	11th to 20th	Night	37% 9% 14% 23% 14% 2	1520
	21st to end	Night	34% 6% 17% 21% 19% 4	1520
July	1st to 10th	Night	36% 10% 22% 17% 13% 3	2480
	11th to 20th	Night	39% 8% 21% 21% 10% 1	2740
	21st to end	Night	43% 7% 16% 19% 14% 1	2988
August	1st to 10th	Night	46% 8% 16% 22% 7% 1	2814
	11th to 20th	Night	44% 7% 11% 23% 14% 1	2922
	21st to end	Night	33% 5% 13% 30% 17% 1	3476
September	1st to 10th	Night	39% 7% 11% 20% 18% 6%	1900
	11th to 20th	Night	33% 5% 10% 26% 22% 3	1902
	21st to end	Night	46% 6% 9% 20% 16% 3	2194
October	1st to 10th	Night	41% 4 9% 20% 20% 5%	3800
	11th to 20th	Night	24% 3 11% 21% 32% 9%	3779
	21st to end	Night	22% 3 8% 32% 26% 8%	4120
November	1st to 10th	Night	34% 3 8% 26% 23% 7%	2386
	11th to 20th	Night	35% 4 8% 23% 23% 7%	2640
	21st to end	Night	34% 4 11% 25% 22% 4	2800
December	1st to 10th	Night	43% 4 11% 24% 15% 4	2737
	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	28% 21% 26% 22% 3	270
	21st to end	Day	22% 20% 35% 16% 6% 1	297
February	1st to 10th	Day	23% 16% 39% 17% 4	270
	11th to 20th	Day	31% 20% 35% 11% 2	298
	21st to end	Day	24% 16% 32% 23% 3 1	382
March	1st to 10th	Day	20% 18% 34% 23% 5%	460
	11th to 20th	Day	22% 18% 32% 20% 6% 1	460
	21st to end	Day	21% 16% 34% 21% 8% 1	506
April	1st to 10th	Day	20% 17% 29% 26% 6% 1	460
	11th to 20th	Day	15% 15% 25% 26% 14% 5%	452
	21st to end	Day	21% 12% 28% 25% 13% 2	460
May	1st to 10th	Day	21% 10% 29% 22% 13% 5%	463
	11th to 20th	Day	20% 6% 26% 27% 14% 7%	487
	21st to end	Day	19% 2 19% 25% 24% 10%	529
June	1st to 10th	Day	10% 6% 20% 29% 24% 10%	490
	11th to 20th	Day	13% 5% 20% 30% 22% 10%	490
	21st to end	Day	9% 2 20% 37% 22% 10%	490
July	1st to 10th	Day	11% 4 11% 31% 29% 15%	485
	11th to 20th	Day	5% 2 10% 32% 35% 16%	484
	21st to end	Day	12% 2 12% 30% 31% 13%	532
August	1st to 10th	Day	13% 3 13% 27% 30% 14%	486
	11th to 20th	Day	11% 3 13% 29% 28% 16%	479
	21st to end	Day	9% 2 14% 28% 27% 19%	539
September	1st to 10th	Day	14% 3 17% 26% 20% 19%	490
	11th to 20th	Day	14% 3 14% 28% 28% 14%	490
	21st to end	Day	27% 6% 19% 28% 15% 6%	490
October	1st to 10th	Day	21% 4 19% 27% 21% 9%	490
	11th to 20th	Day	14% 9% 24% 30% 18% 4	490
	21st to end	Day	15% 9% 31% 30% 12% 4	539
November	1st to 10th	Day	16% 9% 29% 28% 15% 3	470
	11th to 20th	Day	17% 10% 34% 27% 10% 3	355
	21st to end	Day	20% 12% 35% 23% 10% 2	200
December	1st to 10th	Day	18% 13% 39% 22% 6% 2	190
	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	21% 11% 35% 29% 4	760
	21st to end	Night	19% 12% 40% 27% 2	836
February	1st to 10th	Night	19% 9% 39% 29% 3	760
	11th to 20th	Night	24% 14% 40% 20% 1	743
	21st to end	Night	22% 13% 37% 25% 3	628
March	1st to 10th	Night	17% 14% 38% 28% 4	760
	11th to 20th	Night	22% 13% 35% 24% 5% 1	760
	21st to end	Night	17% 11% 39% 27% 6%	836
April	1st to 10th	Night	17% 11% 40% 27% 5%	760
	11th to 20th	Night	14% 9% 33% 34% 10% 1	751
	21st to end	Night	18% 6% 31% 36% 9% 1	760
May	1st to 10th	Night	20% 7% 27% 31% 12% 2	602
	11th to 20th	Night	20% 3 27% 35% 15% 1	505
	21st to end	Night	14% 2 16% 41% 25% 1	411
June	1st to 10th	Night	9% 2 20% 45% 23% 1	380
	11th to 20th	Night	12% 3 16% 42% 24% 2	380
	21st to end	Night	9% 3 15% 50% 22% 2	380
July	1st to 10th	Night	10% 3 14% 41% 28% 4	370
	11th to 20th	Night	7% 1 8% 42% 37% 5%	519
	21st to end	Night	10% 2 12% 40% 31% 4	624
August	1st to 10th	Night	10% 2 9% 43% 34% 3	567
	11th to 20th	Night	11% 3 12% 40% 30% 4	622
	21st to end	Night	12% 1 10% 40% 31% 5%	836
September	1st to 10th	Night	18% 3 12% 31% 32% 5%	760
	11th to 20th	Night	12% 1 12% 36% 35% 3	760
	21st to end	Night	24% 3 18% 33% 21% 1	760
October	1st to 10th	Night	20% 4 18% 31% 23% 4	760
	11th to 20th	Night	18% 6% 25% 34% 17% 1	760
	21st to end	Night	17% 7% 30% 32% 14% 1	836
November	1st to 10th	Night	14% 6% 30% 37% 13% 1	780
	11th to 20th	Night	18% 7% 34% 32% 9% 1	800
	21st to end	Night	15% 8% 36% 31% 9% 1	800
December	1st to 10th	Night	20% 9% 35% 27% 8%	783
	11th to 20th	Night	17% 8% 38% 32% 5%	760
	21st to end	Night	21% 8% 32% 35% 4	836

Page generated at 2024-12-03 06:45:15. Version ac07

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