Wilcox Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wilcox Park clear sky chart from 2005-11-06 to 2024-11-04.

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	17% 8% 3 7% 5% 4 4 4 5% 7% 37%	101335
	Night	18% 9% 3 7% 4 4 4 3 5% 6% 37%	97679
Transparency	Day	45% 5% 12% 23% 13% 2	104867
	Night	46% 5% 12% 22% 13% 1	102236
Seeing	Day	23% 15% 30% 20% 9% 2	14906
	Night	22% 14% 31% 24% 8% 1	23968

By Month

Percentage Cloud Cover NE (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	14% 10% 3 6% 4 5% 4 3 5% 6% 40%	2517
	11th to 20th	Day	16% 10% 5% 11% 5% 5% 4 3 6% 4 31%	2520
	21st to end	Day	21% 13% 4 7% 5% 4 5% 3 4 5% 29%	2904
February	1st to 10th	Day	17% 10% 3 7% 6% 5% 4 4 6% 5% 31%	1710
	11th to 20th	Day	14% 10% 3 8% 6% 5% 4 4 4 6% 37%	1846
	21st to end	Day	19% 9% 2 7% 6% 4 4 3 4 6% 35%	1570
March	1st to 10th	Day	24% 13% 4 8% 4 3 3 3 3 4 31%	3116
	11th to 20th	Day	12% 11% 3 7% 5% 5% 5% 4 5% 6% 37%	3288
	21st to end	Day	21% 9% 3 7% 5% 4 4 3 4 5% 37%	4161
April	1st to 10th	Day	20% 10% 3 6% 4 3 5% 3 5% 5% 36%	2280
	11th to 20th	Day	17% 8% 2 6% 5% 4 4 3 5% 7% 39%	2254
	21st to end	Day	21% 7% 3 6% 4 5% 4 3 4 6% 38%	2350
May	1st to 10th	Day	25% 9% 2 6% 4 4 4 3 5% 6% 31%	4125
	11th to 20th	Day	20% 7% 3 8% 5% 4 4 3 5% 7% 33%	4398
	21st to end	Day	12% 5% 2 5% 4 4 4 4 6% 9% 44%	4837
June	1st to 10th	Day	16% 7% 2 6% 5% 5% 5% 5% 6% 10% 34%	2660
	11th to 20th	Day	16% 6% 2 6% 4 5% 5% 4 8% 10% 34%	2660
	21st to end	Day	14% 7% 2 7% 6% 4 4 4 7% 9% 36%	2660
July	1st to 10th	Day	11% 6% 3 7% 6% 5% 6% 4 6% 9% 38%	4440
	11th to 20th	Day	10% 5% 2 6% 5% 5% 5% 5% 7% 11% 38%	4440
	21st to end	Day	13% 8% 3 8% 5% 5% 5% 4 6% 8% 34%	4814
August	1st to 10th	Day	19% 6% 3 8% 5% 5% 5% 4 5% 8% 31%	4316
	11th to 20th	Day	13% 6% 2 6% 4 4 4 4 6% 10% 41%	3730
	21st to end	Day	12% 4 2 5% 5% 4 4 4 6% 9% 44%	4180
September	1st to 10th	Day	14% 7% 3 6% 4 4 4 4 6% 7% 42%	2280
	11th to 20th	Day	12% 5% 2 6% 3 3 4 4 5% 6% 50%	2187
	21st to end	Day	17% 6% 2 5% 4 4 5% 4 7% 7% 40%	2090
October	1st to 10th	Day	20% 7% 2 6% 4 4 4 3 5% 6% 40%	1995
	11th to 20th	Day	15% 7% 2 7% 3 4 4 3 5% 6% 43%	1900
	21st to end	Day	23% 8% 2 5% 4 4 5% 4 5% 6% 34%	1900
November	1st to 10th	Day	13% 7% 3 6% 4 3 3 3 4 7% 47%	1698
	11th to 20th	Day	17% 8% 2 6% 4 4 4 3 5% 6% 39%	1710
	21st to end	Day	18% 8% 3 5% 5% 4 4 4 4 7% 38%	1601
December	1st to 10th	Day	19% 10% 4 8% 5% 5% 5% 4 6% 5% 30%	1520
	11th to 20th	Day	23% 8% 2 6% 4 3 4 3 5% 7% 36%	1906
	21st to end	Day	21% 11% 4 10% 6% 4 5% 2 5% 6% 25%	2772
January	1st to 10th	Night	17% 8% 3 7% 4 4 4 3 5% 5% 40%	4429
	11th to 20th	Night	15% 10% 4 10% 6% 5% 5% 4 4 6% 31%	4440
	21st to end	Night	25% 12% 3 7% 5% 4 3 3 5% 5% 28%	4747
February	1st to 10th	Night	16% 11% 4 7% 5% 4 5% 4 5% 6% 34%	2470
	11th to 20th	Night	15% 11% 4 8% 5% 5% 4 4 6% 5% 33%	2218
	21st to end	Night	19% 10% 3 6% 5% 4 4 3 5% 5% 36%	1884
March	1st to 10th	Night	24% 10% 3 7% 5% 4 4 3 4 5% 31%	3724
	11th to 20th	Night	12% 11% 3 8% 5% 5% 4 4 5% 5% 36%	3655
	21st to end	Night	18% 10% 4 9% 5% 4 3 2 4 4 37%	3471
April	1st to 10th	Night	19% 10% 3 7% 5% 5% 5% 4 6% 7% 30%	1900
	11th to 20th	Night	20% 8% 3 6% 4 4 4 3 5% 7% 36%	1875
	21st to end	Night	22% 8% 3 6% 4 3 3 3 5% 6% 39%	1829
May	1st to 10th	Night	27% 9% 3 6% 4 4 4 3 4 6% 31%	2834
	11th to 20th	Night	19% 8% 4 8% 5% 5% 4 4 5% 6% 33%	2505
	21st to end	Night	14% 7% 3 7% 4 4 4 4 6% 8% 41%	2738
June	1st to 10th	Night	16% 6% 3 6% 4 3 5% 5% 7% 6% 40%	1520
	11th to 20th	Night	16% 7% 3 5% 5% 2 5% 4 7% 8% 39%	1520
	21st to end	Night	12% 5% 2 5% 4 5% 4 4 6% 10% 41%	1520
July	1st to 10th	Night	12% 6% 2 6% 5% 5% 5% 4 7% 8% 40%	2520
	11th to 20th	Night	13% 6% 2 7% 5% 4 5% 4 7% 10% 38%	2520
	21st to end	Night	16% 9% 2 7% 5% 4 4 4 4 6% 40%	2739
August	1st to 10th	Night	22% 6% 2 6% 4 6% 5% 4 6% 7% 32%	2580
	11th to 20th	Night	14% 8% 2 7% 4 4 4 4 5% 7% 40%	3097
	21st to end	Night	11% 4 2 5% 4 4 4 3 4 7% 51%	3476
September	1st to 10th	Night	15% 6% 2 6% 4 4 4 3 5% 6% 46%	1900
	11th to 20th	Night	12% 5% 2 4 3 3 3 2 5% 7% 53%	1991
	21st to end	Night	16% 7% 2 6% 3 4 4 3 5% 6% 44%	2090
October	1st to 10th	Night	20% 7% 2 6% 5% 4 4 3 4 5% 41%	2180
	11th to 20th	Night	15% 6% 2 6% 4 4 4 3 4 7% 44%	2280
	21st to end	Night	22% 9% 3 6% 4 4 4 3 4 7% 36%	2698
November	1st to 10th	Night	15% 8% 2 5% 3 3 4 4 4 6% 45%	2453
	11th to 20th	Night	19% 9% 2 6% 4 4 4 3 5% 6% 39%	2470
	21st to end	Night	15% 9% 3 6% 5% 4 5% 3 5% 7% 40%	2574
December	1st to 10th	Night	21% 11% 3 7% 4 4 3 3 5% 6% 33%	2660
	11th to 20th	Night	20% 10% 3 7% 5% 4 5% 4 5% 5% 33%	3288
	21st to end	Night	23% 13% 4 7% 4 4 4 3 4 6% 28%	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	44% 4 12% 31% 8% 1	2518
	11th to 20th	Day	53% 6% 10% 23% 7% 1	2520
	21st to end	Day	59% 4 9% 20% 8% 1	2904
February	1st to 10th	Day	53% 4 12% 19% 11% 1	1710
	11th to 20th	Day	49% 5% 8% 23% 13% 2	1855
	21st to end	Day	52% 3 11% 21% 12% 2	1570
March	1st to 10th	Day	57% 4 10% 18% 9% 2	3119
	11th to 20th	Day	43% 9% 13% 24% 9% 2	3288
	21st to end	Day	50% 4 5% 16% 21% 4	4161
April	1st to 10th	Day	50% 5% 8% 20% 14% 3	2280
	11th to 20th	Day	45% 4 10% 22% 17% 2	2254
	21st to end	Day	48% 4 9% 21% 15% 3	2350
May	1st to 10th	Day	54% 5% 12% 16% 11% 1	4139
	11th to 20th	Day	50% 4 15% 21% 9% 1	4402
	21st to end	Day	35% 6% 13% 29% 15% 2	4837
June	1st to 10th	Day	44% 6% 13% 23% 12% 1	2660
	11th to 20th	Day	43% 6% 14% 25% 11% 1	2660
	21st to end	Day	44% 7% 12% 24% 12% 1	2660
July	1st to 10th	Day	43% 6% 14% 21% 15% 1	4370
	11th to 20th	Day	38% 7% 17% 25% 13% 1	4365
	21st to end	Day	47% 5% 14% 18% 14% 1	4661
August	1st to 10th	Day	51% 5% 14% 22% 8% 1	4302
	11th to 20th	Day	39% 5% 17% 30% 8%	3766
	21st to end	Day	35% 5% 14% 33% 13% 1	4180
September	1st to 10th	Day	40% 5% 12% 25% 17% 2	2280
	11th to 20th	Day	35% 4 11% 26% 23% 2	2187
	21st to end	Day	42% 5% 11% 23% 16% 2	2090
October	1st to 10th	Day	40% 5% 9% 20% 25% 2	3320
	11th to 20th	Day	33% 3 9% 27% 24% 4	3140
	21st to end	Day	34% 5% 14% 27% 17% 3	3112
November	1st to 10th	Day	38% 4 13% 26% 16% 2	1698
	11th to 20th	Day	45% 5% 10% 22% 17% 2	1710
	21st to end	Day	46% 4 13% 25% 10% 2	1601
December	1st to 10th	Day	56% 3 13% 17% 11% 1	1520
	11th to 20th	Day	48% 5% 16% 21% 9% 1	1906
	21st to end	Day	59% 6% 9% 18% 8%	2772
January	1st to 10th	Night	46% 3 14% 25% 10% 2	4429
	11th to 20th	Night	52% 6% 11% 20% 9% 2	4440
	21st to end	Night	58% 3 9% 19% 9% 1	4747
February	1st to 10th	Night	51% 4 13% 20% 10% 2	2470
	11th to 20th	Night	50% 5% 10% 16% 16% 2	2220
	21st to end	Night	50% 3 9% 21% 12% 4	1884
March	1st to 10th	Night	55% 4 9% 19% 11% 1	3734
	11th to 20th	Night	47% 6% 13% 22% 10% 2	3656
	21st to end	Night	49% 6% 6% 14% 21% 4	3471
April	1st to 10th	Night	53% 4 10% 19% 12% 2	1900
	11th to 20th	Night	47% 5% 9% 20% 17% 1	1875
	21st to end	Night	47% 4 9% 22% 15% 3	1829
May	1st to 10th	Night	56% 4 12% 17% 9% 2	2840
	11th to 20th	Night	53% 4 14% 19% 9% 2	2506
	21st to end	Night	41% 6% 16% 22% 14% 2	2739
June	1st to 10th	Night	42% 6% 11% 26% 13% 1	1520
	11th to 20th	Night	40% 6% 17% 26% 10%	1520
	21st to end	Night	38% 6% 15% 27% 14%	1520
July	1st to 10th	Night	39% 7% 17% 21% 16% 1	2480
	11th to 20th	Night	41% 7% 16% 25% 12%	2472
	21st to end	Night	45% 4 14% 19% 16% 2	2651
August	1st to 10th	Night	50% 8% 14% 19% 9% 1	2570
	11th to 20th	Night	42% 5% 15% 30% 8%	3127
	21st to end	Night	32% 5% 14% 36% 13%	3476
September	1st to 10th	Night	40% 4 12% 27% 16% 1	1900
	11th to 20th	Night	31% 4 11% 28% 25% 1	1991
	21st to end	Night	40% 5% 10% 25% 20% 1	2090
October	1st to 10th	Night	44% 4 12% 22% 18% 1	3635
	11th to 20th	Night	31% 3 11% 28% 26% 1	3779
	21st to end	Night	36% 4 13% 30% 16% 1	4436
November	1st to 10th	Night	40% 5% 10% 24% 19% 3	2453
	11th to 20th	Night	46% 4 11% 21% 15% 3	2470
	21st to end	Night	44% 4 15% 27% 9% 1	2574
December	1st to 10th	Night	52% 5% 12% 20% 10% 1	2660
	11th to 20th	Night	52% 6% 13% 16% 12% 2	3288
	21st to end	Night	57% 4 11% 19% 9%	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	27% 27% 27% 12% 7%	180
	11th to 20th	Day	32% 25% 28% 12% 3	180
	21st to end	Day	24% 30% 32% 9% 4 1	236
February	1st to 10th	Day	34% 27% 30% 7% 1	270
	11th to 20th	Day	29% 28% 31% 12% 1	454
	21st to end	Day	31% 21% 34% 11% 3	382
March	1st to 10th	Day	28% 21% 32% 17% 2	460
	11th to 20th	Day	29% 24% 32% 11% 3 1	460
	21st to end	Day	35% 20% 28% 11% 6% 1	506
April	1st to 10th	Day	34% 21% 27% 12% 7%	460
	11th to 20th	Day	28% 26% 26% 14% 5% 1	452
	21st to end	Day	28% 17% 34% 14% 5% 2	460
May	1st to 10th	Day	33% 15% 27% 16% 7% 2	463
	11th to 20th	Day	25% 13% 35% 18% 7% 2	487
	21st to end	Day	20% 11% 30% 26% 11% 2	529
June	1st to 10th	Day	20% 10% 35% 23% 11% 1	490
	11th to 20th	Day	18% 12% 29% 29% 10% 2	490
	21st to end	Day	19% 10% 33% 23% 12% 3	490
July	1st to 10th	Day	14% 7% 33% 28% 14% 4	485
	11th to 20th	Day	14% 6% 30% 32% 17% 1	484
	21st to end	Day	12% 8% 36% 30% 13% 2	532
August	1st to 10th	Day	16% 5% 30% 33% 11% 5%	486
	11th to 20th	Day	17% 5% 28% 27% 16% 6%	479
	21st to end	Day	13% 7% 29% 28% 15% 7%	539
September	1st to 10th	Day	20% 9% 23% 28% 14% 7%	490
	11th to 20th	Day	16% 8% 27% 21% 16% 11%	490
	21st to end	Day	21% 9% 32% 24% 10% 4	490
October	1st to 10th	Day	25% 11% 24% 22% 13% 4	490
	11th to 20th	Day	21% 13% 35% 22% 8% 2	490
	21st to end	Day	26% 15% 30% 21% 7% 1	439
November	1st to 10th	Day	21% 17% 29% 22% 9% 2	374
	11th to 20th	Day	26% 22% 25% 19% 6% 1	370
	21st to end	Day	24% 22% 30% 20% 3 1	261
December	1st to 10th	Day	24% 27% 31% 13% 4	180
	11th to 20th	Day	33% 24% 30% 11% 2	180
	21st to end	Day	30% 22% 30% 13% 5%	198
January	1st to 10th	Night	22% 20% 39% 17% 2	760
	11th to 20th	Night	26% 21% 33% 17% 3	760
	21st to end	Night	21% 21% 37% 19% 2	836
February	1st to 10th	Night	23% 19% 35% 21% 1	760
	11th to 20th	Night	23% 23% 38% 15% 1	743
	21st to end	Night	29% 19% 35% 16% 2	628
March	1st to 10th	Night	24% 23% 34% 16% 3	760
	11th to 20th	Night	25% 22% 36% 14% 4	760
	21st to end	Night	25% 22% 30% 18% 4	836
April	1st to 10th	Night	26% 20% 32% 19% 3	760
	11th to 20th	Night	25% 18% 32% 18% 6%	751
	21st to end	Night	25% 16% 34% 19% 5% 1	689
May	1st to 10th	Night	26% 15% 31% 21% 6%	570
	11th to 20th	Night	21% 11% 36% 28% 4 1	384
	21st to end	Night	18% 7% 30% 33% 11%	411
June	1st to 10th	Night	18% 7% 31% 32% 12%	380
	11th to 20th	Night	16% 7% 32% 32% 12% 1	380
	21st to end	Night	14% 6% 28% 40% 12% 1	380
July	1st to 10th	Night	14% 3 23% 41% 18% 1	370
	11th to 20th	Night	15% 4 22% 42% 15% 1	368
	21st to end	Night	13% 3 25% 44% 14% 1	416
August	1st to 10th	Night	13% 2 24% 42% 18% 1	413
	11th to 20th	Night	14% 3 20% 41% 20% 2	750
	21st to end	Night	16% 3 24% 36% 19% 2	836
September	1st to 10th	Night	18% 5% 29% 31% 14% 2	760
	11th to 20th	Night	16% 5% 28% 27% 21% 4	760
	21st to end	Night	20% 7% 26% 33% 13% 2	760
October	1st to 10th	Night	24% 8% 26% 30% 11% 1	760
	11th to 20th	Night	19% 11% 33% 27% 9%	760
	21st to end	Night	27% 13% 31% 23% 6%	836
November	1st to 10th	Night	21% 14% 33% 24% 8%	755
	11th to 20th	Night	24% 15% 33% 21% 5% 1	760
	21st to end	Night	19% 18% 35% 21% 6% 1	760
December	1st to 10th	Night	28% 19% 31% 18% 5%	760
	11th to 20th	Night	25% 19% 31% 21% 3	760
	21st to end	Night	27% 16% 38% 16% 2	836

Page generated at 2024-11-01 22:47:47. Version ac07

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