Webster Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Webster Park clear sky chart from 2005-11-06 to 2024-12-24.

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	15% 10% 4 8% 5% 5% 4 4 5% 7% 32%	101916
	Night	18% 13% 4 10% 5% 4 4 3 5% 6% 27%	98190
Transparency	Day	50% 7% 12% 20% 9% 1	105489
	Night	55% 7% 11% 18% 9% 1	102705
Seeing	Day	21% 14% 29% 22% 10% 3	14678
	Night	23% 14% 28% 24% 11% 1	24029

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	16% 22% 8% 14% 7% 5% 4 3 4 4 14%	2517
	11th to 20th	Day	13% 24% 9% 16% 9% 5% 4 4 4 4 8%	2586
	21st to end	Day	20% 20% 7% 16% 8% 6% 4 3 4 5% 8%	3124
February	1st to 10th	Day	15% 17% 6% 15% 7% 6% 4 4 5% 5% 17%	1710
	11th to 20th	Day	13% 16% 8% 16% 8% 6% 5% 4 4 4 15%	1663
	21st to end	Day	20% 13% 5% 15% 8% 4 5% 3 5% 5% 18%	1532
March	1st to 10th	Day	19% 12% 5% 10% 6% 4 4 3 5% 5% 29%	3308
	11th to 20th	Day	11% 15% 5% 9% 7% 5% 5% 3 4 6% 30%	3480
	21st to end	Day	14% 11% 4 10% 4 4 4 4 6% 7% 32%	3900
April	1st to 10th	Day	18% 11% 4 7% 5% 4 3 3 5% 6% 34%	2280
	11th to 20th	Day	19% 9% 3 6% 4 4 4 3 5% 6% 37%	2254
	21st to end	Day	20% 10% 3 7% 5% 4 4 3 5% 6% 34%	2399
May	1st to 10th	Day	18% 9% 3 7% 4 4 5% 3 5% 7% 34%	4262
	11th to 20th	Day	13% 9% 4 8% 6% 5% 4 4 6% 11% 31%	4398
	21st to end	Day	10% 6% 2 5% 4 5% 5% 4 6% 9% 43%	4837
June	1st to 10th	Day	15% 6% 2 7% 5% 4 4 4 6% 8% 39%	2660
	11th to 20th	Day	12% 5% 2 5% 4 4 5% 4 8% 11% 41%	2660
	21st to end	Day	11% 6% 3 6% 4 5% 4 4 7% 8% 43%	2660
July	1st to 10th	Day	10% 5% 2 6% 4 5% 5% 4 6% 10% 45%	4440
	11th to 20th	Day	10% 4 3 5% 4 4 5% 5% 7% 9% 45%	4440
	21st to end	Day	8% 4 2 7% 5% 5% 5% 5% 7% 9% 42%	4722
August	1st to 10th	Day	16% 6% 3 6% 4 4 5% 3 6% 8% 40%	4104
	11th to 20th	Day	13% 6% 3 7% 5% 4 5% 5% 6% 8% 38%	4044
	21st to end	Day	13% 6% 2 5% 4 4 4 4 5% 8% 45%	4185
September	1st to 10th	Day	13% 7% 2 6% 4 5% 4 4 6% 7% 44%	2280
	11th to 20th	Day	14% 5% 2 6% 3 4 4 4 5% 8% 44%	2280
	21st to end	Day	16% 6% 3 7% 5% 5% 4 5% 6% 7% 35%	1991
October	1st to 10th	Day	19% 9% 2 7% 4 4 3 4 6% 7% 35%	1900
	11th to 20th	Day	19% 12% 4 7% 5% 5% 4 3 5% 8% 29%	1900
	21st to end	Day	27% 12% 3 8% 5% 5% 3 4 4 5% 23%	2067
November	1st to 10th	Day	14% 13% 4 9% 5% 5% 5% 4 5% 6% 30%	1751
	11th to 20th	Day	15% 15% 4 11% 5% 6% 4 5% 5% 7% 23%	1600
	21st to end	Day	21% 17% 7% 10% 5% 4 5% 4 5% 7% 17%	1600
December	1st to 10th	Day	21% 22% 7% 12% 6% 5% 3 3 4 5% 12%	1600
	11th to 20th	Day	18% 20% 9% 15% 5% 4 4 4 4 4 14%	1986
	21st to end	Day	26% 22% 6% 13% 6% 4 4 3 3 4 9%	2796
January	1st to 10th	Night	19% 22% 6% 14% 7% 5% 5% 3 4 4 11%	4429
	11th to 20th	Night	12% 22% 7% 18% 7% 5% 4 3 4 6% 11%	4372
	21st to end	Night	23% 22% 6% 16% 8% 4 3 3 3 3 10%	4532
February	1st to 10th	Night	17% 18% 5% 15% 6% 4 4 3 5% 5% 17%	2470
	11th to 20th	Night	14% 16% 6% 16% 8% 6% 5% 4 5% 5% 16%	2403
	21st to end	Night	17% 15% 6% 15% 6% 4 4 3 5% 6% 19%	1921
March	1st to 10th	Night	19% 13% 4 10% 6% 5% 4 3 4 5% 28%	3516
	11th to 20th	Night	17% 19% 5% 10% 5% 4 4 3 5% 6% 24%	3479
	21st to end	Night	17% 10% 4 11% 5% 4 4 3 4 5% 33%	3732
April	1st to 10th	Night	20% 12% 4 8% 5% 4 4 4 5% 6% 29%	1900
	11th to 20th	Night	18% 8% 3 8% 5% 4 5% 3 5% 7% 33%	1875
	21st to end	Night	20% 9% 3 6% 5% 3 5% 3 5% 7% 35%	1796
May	1st to 10th	Night	24% 9% 3 8% 5% 4 4 4 5% 5% 30%	2678
	11th to 20th	Night	18% 7% 3 7% 4 4 4 4 7% 8% 33%	2495
	21st to end	Night	11% 5% 2 6% 4 4 4 4 6% 9% 44%	2738
June	1st to 10th	Night	13% 7% 3 8% 5% 5% 5% 5% 6% 8% 36%	1520
	11th to 20th	Night	12% 7% 2 6% 4 6% 5% 4 6% 8% 41%	1520
	21st to end	Night	11% 6% 3 8% 6% 4 5% 4 6% 7% 40%	1520
July	1st to 10th	Night	14% 5% 3 5% 5% 4 5% 4 6% 9% 41%	2520
	11th to 20th	Night	10% 6% 2 7% 5% 5% 5% 3 6% 9% 43%	2520
	21st to end	Night	10% 6% 2 7% 4 4 5% 4 7% 8% 44%	2827
August	1st to 10th	Night	12% 6% 2 6% 4 4 5% 3 7% 9% 41%	2825
	11th to 20th	Night	15% 6% 3 7% 4 4 5% 4 6% 9% 37%	2785
	21st to end	Night	10% 5% 2 6% 4 5% 5% 5% 7% 10% 42%	3437
September	1st to 10th	Night	14% 7% 2 6% 4 4 4 4 5% 7% 44%	1900
	11th to 20th	Night	16% 6% 2 5% 4 3 3 4 5% 8% 44%	1900
	21st to end	Night	17% 6% 3 7% 5% 4 5% 4 6% 8% 35%	2185
October	1st to 10th	Night	19% 8% 3 8% 6% 4 5% 3 5% 6% 33%	2280
	11th to 20th	Night	23% 10% 3 7% 5% 5% 5% 3 5% 7% 28%	2280
	21st to end	Night	29% 12% 4 8% 4 4 4 3 5% 5% 23%	2529
November	1st to 10th	Night	17% 12% 3 8% 5% 4 4 4 5% 6% 31%	2545
	11th to 20th	Night	17% 16% 4 9% 6% 4 5% 3 6% 6% 24%	2800
	21st to end	Night	22% 17% 5% 10% 5% 4 3 4 6% 7% 18%	2800
December	1st to 10th	Night	19% 24% 7% 10% 6% 5% 5% 4 4 5% 12%	2800
	11th to 20th	Night	20% 20% 8% 13% 5% 4 4 3 4 5% 14%	3428
	21st to end	Night	30% 21% 6% 10% 5% 4 3 3 4 5% 9%	4933

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	73% 7% 10% 8% 2	2518
	11th to 20th	Day	78% 7% 10% 4 1	2586
	21st to end	Day	79% 7% 9% 4 1	3124
February	1st to 10th	Day	70% 6% 10% 12% 2	1710
	11th to 20th	Day	72% 6% 7% 12% 3	1672
	21st to end	Day	69% 5% 11% 11% 5%	1532
March	1st to 10th	Day	58% 5% 11% 20% 6%	3311
	11th to 20th	Day	55% 6% 17% 13% 9% 1	3480
	21st to end	Day	49% 8% 11% 23% 8% 1	3900
April	1st to 10th	Day	53% 6% 12% 17% 11% 1	2280
	11th to 20th	Day	48% 6% 10% 20% 14% 2	2254
	21st to end	Day	52% 6% 9% 18% 14% 2	2399
May	1st to 10th	Day	50% 7% 10% 19% 12% 2	4274
	11th to 20th	Day	48% 10% 14% 19% 8% 1	4402
	21st to end	Day	35% 10% 13% 25% 15% 2	4837
June	1st to 10th	Day	44% 8% 12% 20% 16% 1	2660
	11th to 20th	Day	37% 8% 14% 25% 14% 1	2660
	21st to end	Day	40% 8% 13% 22% 16% 1	2660
July	1st to 10th	Day	36% 6% 13% 31% 14% 1	4370
	11th to 20th	Day	35% 7% 16% 29% 13% 1	4365
	21st to end	Day	38% 9% 16% 25% 13%	4571
August	1st to 10th	Day	43% 7% 14% 21% 14% 1	4091
	11th to 20th	Day	44% 7% 15% 26% 8%	4083
	21st to end	Day	38% 6% 13% 34% 8% 1	4185
September	1st to 10th	Day	38% 8% 13% 29% 11% 1	2280
	11th to 20th	Day	38% 8% 13% 26% 15%	2280
	21st to end	Day	48% 7% 12% 22% 10%	1991
October	1st to 10th	Day	43% 6% 15% 25% 11%	3160
	11th to 20th	Day	48% 4 16% 20% 12%	3140
	21st to end	Day	51% 6% 13% 23% 6% 1	3381
November	1st to 10th	Day	55% 6% 10% 18% 9% 1	1751
	11th to 20th	Day	59% 7% 13% 14% 7% 1	1600
	21st to end	Day	66% 7% 12% 13% 2	1600
December	1st to 10th	Day	74% 5% 11% 9% 1	1600
	11th to 20th	Day	73% 7% 10% 6% 4	1986
	21st to end	Day	79% 6% 6% 7% 1	2796
January	1st to 10th	Night	74% 8% 10% 5% 2	4429
	11th to 20th	Night	72% 8% 10% 7% 3	4372
	21st to end	Night	79% 5% 8% 5% 2	4532
February	1st to 10th	Night	68% 6% 9% 12% 5%	2470
	11th to 20th	Night	68% 6% 10% 12% 3	2405
	21st to end	Night	64% 7% 11% 12% 6%	1921
March	1st to 10th	Night	57% 6% 12% 19% 5%	3526
	11th to 20th	Night	59% 7% 13% 14% 7%	3480
	21st to end	Night	50% 7% 10% 21% 10% 1	3732
April	1st to 10th	Night	56% 6% 10% 19% 8% 2	1900
	11th to 20th	Night	50% 6% 11% 17% 14% 1	1875
	21st to end	Night	48% 6% 12% 18% 14% 2	1796
May	1st to 10th	Night	54% 7% 10% 16% 11% 2	2685
	11th to 20th	Night	45% 8% 16% 20% 9% 2	2496
	21st to end	Night	33% 9% 14% 22% 20% 2	2739
June	1st to 10th	Night	43% 7% 12% 21% 15% 1	1520
	11th to 20th	Night	40% 6% 12% 22% 18% 2	1520
	21st to end	Night	41% 9% 11% 22% 16% 1	1520
July	1st to 10th	Night	40% 6% 12% 22% 17% 2	2480
	11th to 20th	Night	38% 5% 13% 29% 14% 1	2472
	21st to end	Night	38% 6% 14% 25% 16% 1	2737
August	1st to 10th	Night	39% 6% 14% 27% 13% 1	2814
	11th to 20th	Night	42% 6% 16% 26% 8%	2812
	21st to end	Night	35% 6% 13% 33% 12% 1	3437
September	1st to 10th	Night	38% 8% 12% 27% 13% 2	1900
	11th to 20th	Night	37% 6% 12% 27% 17% 1	1900
	21st to end	Night	44% 8% 12% 24% 11% 1	2185
October	1st to 10th	Night	47% 6% 9% 26% 11% 1	3800
	11th to 20th	Night	51% 5% 12% 19% 13%	3779
	21st to end	Night	50% 5% 11% 26% 7% 1	4165
November	1st to 10th	Night	52% 6% 12% 18% 10% 2	2545
	11th to 20th	Night	57% 8% 13% 13% 8% 1	2800
	21st to end	Night	63% 7% 14% 13% 2	2800
December	1st to 10th	Night	71% 8% 11% 8% 2	2800
	11th to 20th	Night	69% 8% 10% 9% 3	3428
	21st to end	Night	77% 6% 9% 6% 1	4933

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% 29% 11% 6%	180
	11th to 20th	Day	29% 24% 34% 13% 1 1	200
	21st to end	Day	26% 21% 33% 16% 4	297
February	1st to 10th	Day	27% 26% 35% 11% 1	270
	11th to 20th	Day	26% 30% 36% 7% 1	270
	21st to end	Day	35% 20% 33% 12% 1	344
March	1st to 10th	Day	21% 25% 34% 15% 4 1	460
	11th to 20th	Day	28% 20% 33% 16% 3 1	460
	21st to end	Day	29% 21% 30% 14% 5% 1	506
April	1st to 10th	Day	25% 20% 31% 19% 4 1	460
	11th to 20th	Day	27% 21% 27% 16% 7% 2	452
	21st to end	Day	26% 17% 32% 18% 6% 1	460
May	1st to 10th	Day	23% 11% 34% 19% 10% 3	463
	11th to 20th	Day	17% 10% 30% 31% 10% 2	487
	21st to end	Day	16% 10% 29% 26% 15% 4	529
June	1st to 10th	Day	17% 14% 30% 29% 10% 1	490
	11th to 20th	Day	15% 10% 29% 30% 13% 3	490
	21st to end	Day	14% 10% 32% 31% 10% 2	490
July	1st to 10th	Day	11% 6% 25% 34% 20% 4	485
	11th to 20th	Day	14% 6% 28% 29% 19% 5%	484
	21st to end	Day	10% 7% 32% 35% 14% 2	532
August	1st to 10th	Day	13% 6% 26% 33% 17% 5%	486
	11th to 20th	Day	13% 7% 25% 31% 19% 5%	479
	21st to end	Day	13% 6% 28% 30% 16% 6%	539
September	1st to 10th	Day	14% 11% 23% 28% 17% 7%	490
	11th to 20th	Day	15% 9% 19% 25% 21% 12%	490
	21st to end	Day	17% 13% 25% 26% 15% 4	490
October	1st to 10th	Day	23% 11% 29% 18% 13% 5%	490
	11th to 20th	Day	27% 16% 31% 17% 8% 2	490
	21st to end	Day	34% 15% 28% 19% 4	526
November	1st to 10th	Day	25% 18% 29% 16% 10% 1	385
	11th to 20th	Day	27% 24% 32% 13% 5% 1	200
	21st to end	Day	37% 20% 28% 13% 2	200
December	1st to 10th	Day	34% 18% 33% 10% 5% 1	200
	11th to 20th	Day	34% 24% 29% 14% 1	200
	21st to end	Day	34% 24% 27% 14% 1	204
January	1st to 10th	Night	28% 24% 31% 14% 3	760
	11th to 20th	Night	27% 22% 30% 18% 3	760
	21st to end	Night	22% 22% 34% 18% 4	836
February	1st to 10th	Night	27% 22% 33% 17% 1	760
	11th to 20th	Night	25% 23% 34% 15% 3	743
	21st to end	Night	26% 20% 35% 17% 2	628
March	1st to 10th	Night	27% 17% 34% 19% 4	760
	11th to 20th	Night	25% 20% 30% 20% 4 1	760
	21st to end	Night	25% 14% 32% 22% 6% 1	836
April	1st to 10th	Night	24% 14% 33% 23% 5%	760
	11th to 20th	Night	23% 14% 29% 26% 7% 1	751
	21st to end	Night	24% 10% 28% 26% 12%	656
May	1st to 10th	Night	24% 8% 21% 31% 15% 1	480
	11th to 20th	Night	16% 5% 29% 39% 11% 1	374
	21st to end	Night	12% 5% 28% 32% 21% 1	411
June	1st to 10th	Night	17% 4 29% 29% 18% 2	380
	11th to 20th	Night	15% 7% 24% 32% 20% 2	380
	21st to end	Night	13% 5% 27% 39% 16% 1	380
July	1st to 10th	Night	10% 3 22% 39% 24% 3	370
	11th to 20th	Night	11% 2 26% 35% 24% 3	368
	21st to end	Night	12% 3 22% 38% 23% 2	468
August	1st to 10th	Night	10% 4 22% 39% 22% 4	567
	11th to 20th	Night	12% 4 20% 35% 25% 4	564
	21st to end	Night	10% 5% 22% 34% 26% 2	810
September	1st to 10th	Night	16% 6% 20% 29% 26% 3	760
	11th to 20th	Night	17% 6% 15% 30% 25% 7%	760
	21st to end	Night	18% 9% 21% 29% 18% 5%	760
October	1st to 10th	Night	22% 12% 24% 22% 17% 3	760
	11th to 20th	Night	26% 14% 29% 22% 8% 1	760
	21st to end	Night	36% 11% 29% 21% 3	836
November	1st to 10th	Night	26% 13% 30% 22% 8% 1	780
	11th to 20th	Night	25% 21% 30% 16% 7% 1	800
	21st to end	Night	31% 18% 29% 16% 5%	800
December	1st to 10th	Night	31% 25% 28% 13% 3	800
	11th to 20th	Night	29% 24% 28% 16% 3 1	800
	21st to end	Night	35% 20% 29% 14% 2	851

Page generated at 2024-12-21 04:13:53. Version ac07

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