Tooley Pond
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tooley Pond clear sky chart from 2005-11-06 to 2026-05-17.

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% 13% 5% 10% 6% 5% 4 3 5% 6% 26%	132130
	Night	17% 15% 6% 12% 6% 5% 4 3 4 5% 24%	130711
Transparency	Day	59% 5% 10% 18% 8% 1	135582
	Night	63% 4 9% 15% 7% 1	135346
Seeing	Day	28% 19% 29% 16% 7% 2	16485
	Night	27% 18% 29% 19% 7% 1	25656

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	11% 19% 8% 24% 11% 6% 4 2 3 3 9%	4661
	11th to 20th	Day	8% 20% 11% 23% 12% 6% 4 2 2 3 9%	4650
	21st to end	Day	10% 18% 9% 16% 8% 12% 7% 3 3 3 12%	5339
February	1st to 10th	Day	14% 19% 8% 17% 9% 6% 4 2 3 4 16%	1890
	11th to 20th	Day	13% 19% 8% 15% 9% 5% 4 2 4 4 17%	1919
	21st to end	Day	15% 21% 7% 15% 8% 5% 3 3 4 3 16%	1730
March	1st to 10th	Day	18% 17% 8% 15% 5% 3 4 2 3 4 22%	4576
	11th to 20th	Day	11% 21% 7% 10% 5% 5% 4 3 4 5% 26%	4985
	21st to end	Day	19% 14% 6% 11% 6% 4 4 2 3 4 29%	5979
April	1st to 10th	Day	20% 18% 5% 8% 3 3 3 2 4 4 28%	2520
	11th to 20th	Day	21% 15% 4 7% 4 4 3 3 3 4 31%	2494
	21st to end	Day	22% 15% 3 7% 4 4 4 3 4 5% 30%	2593
May	1st to 10th	Day	28% 14% 4 7% 5% 4 4 3 4 5% 21%	6475
	11th to 20th	Day	18% 12% 4 8% 6% 5% 5% 4 5% 6% 28%	6402
	21st to end	Day	24% 11% 3 6% 4 4 5% 4 5% 6% 28%	6949
June	1st to 10th	Day	24% 9% 3 6% 5% 5% 5% 4 6% 6% 28%	2800
	11th to 20th	Day	20% 7% 2 7% 5% 5% 5% 5% 6% 7% 31%	2800
	21st to end	Day	23% 7% 3 7% 5% 5% 5% 4 5% 6% 30%	2800
July	1st to 10th	Day	14% 7% 2 6% 5% 5% 5% 5% 7% 9% 33%	6360
	11th to 20th	Day	13% 8% 2 7% 5% 5% 6% 5% 7% 9% 34%	6360
	21st to end	Day	14% 7% 2 6% 4 4 5% 4 7% 8% 39%	6926
August	1st to 10th	Day	18% 9% 3 7% 4 4 5% 4 5% 8% 33%	4513
	11th to 20th	Day	18% 8% 3 7% 5% 5% 5% 4 6% 7% 33%	4010
	21st to end	Day	19% 7% 2 5% 4 4 4 3 6% 8% 36%	4312
September	1st to 10th	Day	17% 7% 2 6% 5% 4 4 3 6% 7% 39%	2400
	11th to 20th	Day	17% 6% 3 5% 3 3 4 3 5% 6% 44%	2361
	21st to end	Day	20% 6% 2 6% 4 5% 5% 4 6% 7% 34%	2197
October	1st to 10th	Day	24% 10% 3 8% 4 4 4 3 4 5% 31%	2000
	11th to 20th	Day	22% 13% 3 8% 5% 4 5% 3 5% 5% 28%	2000
	21st to end	Day	26% 18% 4 7% 4 3 4 3 4 5% 23%	2016
November	1st to 10th	Day	15% 20% 4 8% 5% 5% 5% 3 5% 5% 25%	1851
	11th to 20th	Day	15% 17% 6% 11% 6% 5% 5% 3 3 4 25%	1788
	21st to end	Day	18% 24% 7% 13% 5% 4 4 3 3 4 16%	1680
December	1st to 10th	Day	17% 25% 9% 18% 9% 4 3 2 3 3 8%	2680
	11th to 20th	Day	17% 20% 9% 17% 6% 4 3 3 3 3 15%	3066
	21st to end	Day	18% 20% 6% 14% 6% 4 3 4 3 4 18%	4048
January	1st to 10th	Night	11% 22% 8% 22% 10% 5% 3 2 2 3 12%	8234
	11th to 20th	Night	9% 19% 12% 26% 12% 6% 4 2 2 2 7%	8235
	21st to end	Night	11% 16% 8% 19% 10% 11% 6% 4 3 3 10%	8840
February	1st to 10th	Night	14% 20% 7% 17% 8% 5% 4 3 3 3 15%	2730
	11th to 20th	Night	12% 17% 8% 15% 9% 6% 4 3 4 4 18%	2586
	21st to end	Night	13% 19% 7% 14% 8% 5% 4 3 4 5% 19%	2076
March	1st to 10th	Night	18% 14% 5% 13% 7% 5% 3 3 4 4 25%	5484
	11th to 20th	Night	13% 17% 6% 9% 5% 4 4 3 5% 7% 27%	5190
	21st to end	Night	19% 18% 6% 11% 6% 3 3 2 3 4 25%	5195
April	1st to 10th	Night	20% 17% 4 9% 4 3 3 3 3 5% 28%	2100
	11th to 20th	Night	20% 16% 4 7% 5% 4 4 3 3 5% 29%	2075
	21st to end	Night	23% 12% 4 7% 4 3 3 3 4 5% 32%	2026
May	1st to 10th	Night	32% 14% 4 7% 4 4 4 3 4 5% 20%	3728
	11th to 20th	Night	19% 12% 3 8% 5% 4 5% 4 5% 8% 30%	3623
	21st to end	Night	22% 12% 3 7% 4 4 4 3 5% 5% 30%	3926
June	1st to 10th	Night	22% 8% 2 6% 5% 4 5% 5% 6% 7% 31%	1600
	11th to 20th	Night	21% 8% 2 6% 3 4 4 4 6% 7% 36%	1600
	21st to end	Night	20% 8% 3 7% 4 5% 4 3 5% 6% 33%	1600
July	1st to 10th	Night	14% 7% 3 6% 5% 5% 5% 4 6% 9% 36%	3600
	11th to 20th	Night	17% 7% 3 6% 4 4 4 4 5% 7% 40%	3600
	21st to end	Night	11% 8% 2 6% 4 3 5% 3 6% 7% 45%	3926
August	1st to 10th	Night	20% 9% 3 7% 4 3 3 3 5% 6% 38%	2632
	11th to 20th	Night	18% 9% 3 8% 4 4 4 3 5% 6% 35%	3004
	21st to end	Night	13% 8% 3 6% 4 5% 5% 4 6% 8% 39%	3586
September	1st to 10th	Night	16% 8% 3 6% 3 4 4 4 5% 6% 42%	2000
	11th to 20th	Night	15% 6% 2 5% 3 3 3 3 5% 6% 47%	2037
	21st to end	Night	19% 8% 2 5% 4 4 3 3 5% 7% 40%	2200
October	1st to 10th	Night	24% 9% 3 5% 4 4 4 4 5% 6% 32%	2400
	11th to 20th	Night	21% 12% 2 7% 5% 3 4 3 5% 6% 30%	2400
	21st to end	Night	26% 18% 3 8% 4 4 4 3 4 4 22%	2823
November	1st to 10th	Night	19% 17% 4 7% 4 4 4 3 5% 5% 28%	2667
	11th to 20th	Night	17% 18% 6% 10% 5% 4 3 3 4 5% 25%	2830
	21st to end	Night	19% 22% 6% 12% 5% 4 3 3 5% 4 17%	2940
December	1st to 10th	Night	16% 25% 11% 21% 6% 3 3 2 2 3 8%	4720
	11th to 20th	Night	18% 22% 8% 15% 6% 4 3 2 3 3 17%	5348
	21st to end	Night	19% 20% 6% 14% 5% 5% 4 3 3 4 17%	7150

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	82% 4 4 8% 2	4662
	11th to 20th	Day	84% 2 2 4 6% 2	4680
	21st to end	Day	79% 3 5% 7% 5% 1	5339
February	1st to 10th	Day	74% 4 5% 13% 3 1	1890
	11th to 20th	Day	71% 4 6% 11% 7% 1	1928
	21st to end	Day	73% 4 7% 9% 6% 1	1730
March	1st to 10th	Day	68% 4 7% 10% 8% 2	4579
	11th to 20th	Day	60% 6% 12% 12% 7% 2	4985
	21st to end	Day	60% 4 5% 13% 15% 2	5979
April	1st to 10th	Day	61% 4 7% 16% 10% 2	2520
	11th to 20th	Day	56% 5% 6% 18% 13% 2	2494
	21st to end	Day	58% 5% 8% 15% 11% 3	2593
May	1st to 10th	Day	65% 5% 8% 15% 6% 1	6486
	11th to 20th	Day	56% 7% 11% 17% 8% 1	6406
	21st to end	Day	55% 6% 9% 21% 7% 1	6949
June	1st to 10th	Day	55% 7% 11% 16% 11%	2800
	11th to 20th	Day	50% 7% 11% 22% 9% 1	2800
	21st to end	Day	53% 8% 11% 18% 9% 1	2800
July	1st to 10th	Day	47% 3 15% 26% 10%	6290
	11th to 20th	Day	45% 4 14% 26% 10%	6285
	21st to end	Day	42% 5% 12% 35% 7%	6728
August	1st to 10th	Day	50% 5% 14% 22% 9%	4499
	11th to 20th	Day	50% 6% 15% 23% 6%	4049
	21st to end	Day	46% 4 15% 26% 9%	4312
September	1st to 10th	Day	43% 6% 13% 26% 10% 1	2400
	11th to 20th	Day	40% 6% 12% 27% 14% 1	2361
	21st to end	Day	48% 7% 13% 22% 10% 1	2197
October	1st to 10th	Day	51% 3 10% 26% 10%	3260
	11th to 20th	Day	51% 4 13% 19% 12% 1	3240
	21st to end	Day	53% 3 14% 23% 5% 1	3228
November	1st to 10th	Day	60% 7% 10% 15% 7%	1851
	11th to 20th	Day	63% 5% 10% 12% 7% 3	1788
	21st to end	Day	73% 5% 10% 8% 4	1680
December	1st to 10th	Day	84% 3 6% 5% 2	2680
	11th to 20th	Day	76% 4 5% 11% 4	3066
	21st to end	Day	71% 4 5% 9% 10% 1	4048
January	1st to 10th	Night	81% 3 5% 8% 3	8234
	11th to 20th	Night	86% 3 3 4 3	8280
	21st to end	Night	82% 2 4 6% 5%	8840
February	1st to 10th	Night	75% 4 7% 8% 6%	2730
	11th to 20th	Night	70% 6% 7% 12% 6%	2588
	21st to end	Night	67% 6% 8% 13% 6%	2076
March	1st to 10th	Night	64% 5% 7% 13% 10% 1	5494
	11th to 20th	Night	56% 5% 15% 14% 6% 3	5191
	21st to end	Night	64% 4 4 16% 10% 1	5195
April	1st to 10th	Night	60% 3 8% 17% 10% 1	2100
	11th to 20th	Night	58% 6% 7% 16% 12% 1	2075
	21st to end	Night	55% 5% 9% 18% 12% 2	2026
May	1st to 10th	Night	66% 6% 7% 12% 8% 1	3734
	11th to 20th	Night	53% 7% 11% 20% 10% 1	3624
	21st to end	Night	56% 6% 9% 18% 11% 1	3927
June	1st to 10th	Night	50% 8% 14% 18% 9% 1	1600
	11th to 20th	Night	48% 6% 14% 19% 13% 1	1600
	21st to end	Night	50% 7% 13% 21% 9%	1600
July	1st to 10th	Night	45% 3 18% 22% 11% 1	3560
	11th to 20th	Night	45% 3 14% 27% 10% 1	3552
	21st to end	Night	40% 5% 12% 34% 9%	3809
August	1st to 10th	Night	48% 5% 16% 23% 8%	2622
	11th to 20th	Night	49% 5% 15% 22% 8%	3031
	21st to end	Night	43% 4 14% 29% 9% 1	3586
September	1st to 10th	Night	42% 7% 13% 28% 11% 1	2000
	11th to 20th	Night	37% 5% 13% 30% 13%	2037
	21st to end	Night	43% 7% 12% 25% 12% 1	2200
October	1st to 10th	Night	52% 4 10% 23% 10% 1	3920
	11th to 20th	Night	50% 4 13% 20% 11% 2	3899
	21st to end	Night	57% 4 14% 19% 6% 1	4561
November	1st to 10th	Night	59% 6% 12% 14% 8% 2	2667
	11th to 20th	Night	62% 6% 9% 13% 7% 3	2830
	21st to end	Night	71% 5% 8% 11% 4	2940
December	1st to 10th	Night	84% 3 5% 6% 2	4720
	11th to 20th	Night	75% 4 5% 10% 6%	5348
	21st to end	Night	73% 4 5% 9% 7% 2	7150

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	24% 28% 34% 10% 4	220
	11th to 20th	Day	33% 30% 30% 6% 1	220
	21st to end	Day	28% 27% 31% 12% 1	281
February	1st to 10th	Day	35% 31% 27% 6%	330
	11th to 20th	Day	33% 31% 31% 5%	406
	21st to end	Day	35% 25% 32% 7% 1	446
March	1st to 10th	Day	29% 27% 30% 11% 2	540
	11th to 20th	Day	34% 26% 29% 9% 2 1	540
	21st to end	Day	37% 26% 24% 10% 3 1	594
April	1st to 10th	Day	38% 24% 25% 10% 4	540
	11th to 20th	Day	39% 20% 22% 13% 5% 2	532
	21st to end	Day	36% 19% 29% 9% 5% 2	540
May	1st to 10th	Day	36% 18% 28% 12% 5% 2	543
	11th to 20th	Day	26% 16% 32% 19% 6% 1	551
	21st to end	Day	24% 15% 31% 21% 9% 1	573
June	1st to 10th	Day	30% 15% 32% 17% 5% 1	530
	11th to 20th	Day	24% 15% 29% 25% 5% 2	530
	21st to end	Day	25% 17% 33% 17% 6% 1	530
July	1st to 10th	Day	18% 10% 34% 24% 12% 2	525
	11th to 20th	Day	19% 13% 29% 29% 8% 2	524
	21st to end	Day	17% 13% 37% 25% 7% 1	576
August	1st to 10th	Day	16% 11% 28% 27% 14% 4	526
	11th to 20th	Day	19% 10% 29% 26% 12% 5%	519
	21st to end	Day	21% 12% 31% 21% 11% 4	583
September	1st to 10th	Day	21% 12% 29% 19% 12% 7%	530
	11th to 20th	Day	16% 11% 26% 19% 18% 11%	530
	21st to end	Day	20% 13% 30% 20% 13% 3	530
October	1st to 10th	Day	28% 15% 26% 16% 13% 3	530
	11th to 20th	Day	28% 23% 29% 13% 6% 1	530
	21st to end	Day	38% 16% 28% 15% 3	481
November	1st to 10th	Day	31% 22% 28% 12% 6%	425
	11th to 20th	Day	31% 22% 29% 12% 4 2	328
	21st to end	Day	36% 23% 32% 8%	220
December	1st to 10th	Day	40% 17% 32% 10% 2	220
	11th to 20th	Day	34% 30% 29% 5% 1	220
	21st to end	Day	35% 22% 32% 9% 2 1	242
January	1st to 10th	Night	28% 26% 33% 10% 2	840
	11th to 20th	Night	31% 26% 27% 13% 3	840
	21st to end	Night	22% 26% 33% 15% 4	924
February	1st to 10th	Night	27% 27% 31% 14% 1	840
	11th to 20th	Night	25% 28% 33% 11% 2	823
	21st to end	Night	28% 23% 34% 13% 2	692
March	1st to 10th	Night	29% 22% 33% 15% 2	840
	11th to 20th	Night	31% 22% 29% 14% 3	840
	21st to end	Night	30% 21% 28% 16% 4 1	924
April	1st to 10th	Night	31% 22% 29% 16% 2	840
	11th to 20th	Night	33% 19% 26% 17% 5%	831
	21st to end	Night	31% 17% 29% 17% 5%	766
May	1st to 10th	Night	32% 13% 28% 21% 5% 1	448
	11th to 20th	Night	20% 13% 33% 26% 6%	406
	21st to end	Night	17% 13% 33% 29% 7% 1	433
June	1st to 10th	Night	25% 9% 30% 27% 10%	400
	11th to 20th	Night	24% 7% 30% 28% 11%	400
	21st to end	Night	22% 10% 33% 26% 9%	400
July	1st to 10th	Night	11% 6% 32% 38% 13%	390
	11th to 20th	Night	13% 5% 28% 38% 14% 2	388
	21st to end	Night	15% 9% 31% 36% 9% 1	438
August	1st to 10th	Night	19% 5% 25% 37% 13%	418
	11th to 20th	Night	20% 6% 21% 31% 19% 2	671
	21st to end	Night	18% 7% 31% 32% 12% 1	880
September	1st to 10th	Night	20% 9% 30% 25% 15% 1	800
	11th to 20th	Night	18% 7% 23% 30% 20% 3	800
	21st to end	Night	23% 11% 27% 23% 15% 1	800
October	1st to 10th	Night	28% 13% 26% 19% 13% 1	800
	11th to 20th	Night	29% 16% 28% 21% 6% 1	800
	21st to end	Night	37% 17% 27% 18% 2	880
November	1st to 10th	Night	31% 19% 28% 17% 5%	820
	11th to 20th	Night	30% 22% 28% 13% 7% 1	840
	21st to end	Night	34% 23% 26% 13% 4	840
December	1st to 10th	Night	34% 25% 26% 13% 2	840
	11th to 20th	Night	31% 25% 30% 10% 3 1	840
	21st to end	Night	33% 26% 27% 10% 3	924

Page generated at 2026-05-14 01:58:59. Version ac07

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