Trap Pond State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Trap Pond State Park clear sky chart from 2005-11-06 to 2025-10-19.

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	13% 6% 2 6% 4 4 4 4 6% 8% 42%	126465
	Night	14% 7% 2 6% 4 4 4 3 5% 7% 44%	123244
Transparency	Day	25% 40% 8% 15% 11% 2	130038
	Night	25% 39% 7% 15% 12% 3	127740
Seeing	Day	17% 12% 29% 25% 13% 4	16394
	Night	17% 10% 29% 30% 12% 1	25735

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	14% 5% 2 4 3 3 3 3 4 6% 53%	3597
	11th to 20th	Day	13% 8% 3 8% 4 3 3 2 3 5% 48%	3904
	21st to end	Day	15% 8% 2 7% 4 4 4 3 4 5% 42%	4466
February	1st to 10th	Day	14% 7% 2 7% 5% 4 5% 4 6% 8% 39%	1800
	11th to 20th	Day	18% 7% 2 4 3 4 4 3 5% 5% 44%	1928
	21st to end	Day	16% 9% 3 7% 4 4 3 3 4 7% 40%	1650
March	1st to 10th	Day	19% 7% 1 4 3 3 4 3 4 7% 44%	4561
	11th to 20th	Day	10% 6% 2 6% 3 4 3 3 5% 7% 51%	4980
	21st to end	Day	15% 8% 2 6% 4 4 4 3 5% 6% 44%	5757
April	1st to 10th	Day	14% 6% 3 5% 4 4 3 3 5% 6% 46%	2400
	11th to 20th	Day	12% 6% 2 5% 4 3 4 3 5% 7% 49%	2374
	21st to end	Day	14% 7% 2 5% 3 3 3 4 5% 10% 43%	2400
May	1st to 10th	Day	18% 8% 3 7% 4 4 4 4 6% 9% 33%	5531
	11th to 20th	Day	21% 8% 2 6% 4 4 5% 4 5% 8% 33%	6290
	21st to end	Day	16% 6% 2 6% 4 4 5% 4 6% 9% 39%	6934
June	1st to 10th	Day	11% 6% 3 6% 5% 5% 4 5% 7% 9% 40%	2800
	11th to 20th	Day	12% 5% 2 5% 4 4 4 5% 6% 10% 44%	2800
	21st to end	Day	9% 5% 2 4 4 4 5% 5% 7% 11% 44%	2800
July	1st to 10th	Day	7% 5% 2 6% 4 5% 5% 5% 8% 13% 41%	6360
	11th to 20th	Day	11% 6% 3 8% 6% 6% 6% 6% 8% 10% 31%	6360
	21st to end	Day	7% 5% 2 6% 6% 6% 6% 6% 8% 11% 38%	6564
August	1st to 10th	Day	15% 7% 2 6% 4 5% 6% 5% 8% 11% 32%	4180
	11th to 20th	Day	9% 6% 3 7% 6% 5% 6% 5% 7% 10% 38%	3850
	21st to end	Day	8% 5% 1 6% 5% 5% 4 4 6% 9% 47%	4312
September	1st to 10th	Day	14% 5% 2 6% 4 4 5% 4 6% 7% 43%	2400
	11th to 20th	Day	11% 7% 2 7% 4 5% 4 4 5% 7% 44%	2375
	21st to end	Day	19% 7% 3 6% 4 4 4 4 6% 5% 37%	2194
October	1st to 10th	Day	16% 5% 2 6% 4 4 4 4 5% 6% 44%	2000
	11th to 20th	Day	18% 6% 2 3 3 3 3 3 4 4 51%	1980
	21st to end	Day	14% 6% 3 5% 3 4 3 3 4 5% 50%	2077
November	1st to 10th	Day	13% 5% 1 5% 4 3 4 3 5% 6% 51%	1761
	11th to 20th	Day	12% 6% 2 5% 4 4 4 3 5% 6% 49%	1800
	21st to end	Day	15% 4 2 6% 3 4 3 3 4 6% 49%	1730
December	1st to 10th	Day	11% 5% 3 6% 4 3 4 3 4 7% 51%	2600
	11th to 20th	Day	18% 10% 3 6% 3 3 3 2 4 5% 45%	2990
	21st to end	Day	13% 6% 2 5% 3 4 4 4 5% 8% 46%	3960
January	1st to 10th	Night	12% 7% 2 5% 3 3 3 3 4 5% 51%	6349
	11th to 20th	Night	14% 7% 2 6% 3 3 3 2 3 4 53%	6038
	21st to end	Night	15% 8% 2 5% 3 3 4 3 4 5% 46%	6490
February	1st to 10th	Night	17% 7% 3 5% 3 4 4 4 5% 7% 42%	2600
	11th to 20th	Night	19% 8% 2 4 4 3 4 3 4 5% 42%	2356
	21st to end	Night	18% 7% 2 4 4 4 3 3 4 6% 45%	1980
March	1st to 10th	Night	17% 8% 2 5% 3 3 3 3 4 5% 46%	5287
	11th to 20th	Night	13% 8% 3 5% 3 4 3 3 5% 7% 46%	4980
	21st to end	Night	16% 8% 3 6% 4 4 3 3 4 6% 44%	5174
April	1st to 10th	Night	18% 7% 2 5% 4 4 4 4 6% 6% 41%	2000
	11th to 20th	Night	12% 6% 2 6% 4 4 4 3 5% 6% 47%	1975
	21st to end	Night	16% 5% 2 5% 4 5% 4 4 6% 7% 43%	2000
May	1st to 10th	Night	16% 8% 3 8% 5% 5% 5% 4 6% 9% 32%	4362
	11th to 20th	Night	20% 10% 2 7% 4 4 4 4 6% 8% 32%	3632
	21st to end	Night	17% 8% 2 7% 4 4 4 4 6% 8% 37%	3920
June	1st to 10th	Night	12% 7% 3 5% 4 5% 5% 5% 6% 7% 42%	1600
	11th to 20th	Night	11% 5% 3 6% 6% 5% 5% 4 5% 9% 41%	1600
	21st to end	Night	8% 5% 2 7% 5% 4 6% 4 8% 11% 41%	1600
July	1st to 10th	Night	9% 6% 3 8% 5% 5% 5% 5% 8% 11% 36%	3598
	11th to 20th	Night	9% 8% 3 8% 6% 6% 6% 5% 6% 11% 33%	3597
	21st to end	Night	9% 7% 3 7% 5% 5% 5% 4 7% 10% 39%	4283
August	1st to 10th	Night	17% 7% 4 8% 5% 4 4 4 5% 9% 34%	2936
	11th to 20th	Night	10% 7% 3 6% 5% 5% 5% 4 6% 10% 41%	3197
	21st to end	Night	8% 6% 2 5% 4 4 4 3 5% 8% 53%	3586
September	1st to 10th	Night	15% 7% 2 5% 4 4 3 3 5% 7% 46%	2000
	11th to 20th	Night	11% 5% 2 5% 4 4 4 3 5% 8% 49%	2023
	21st to end	Night	20% 8% 2 5% 5% 4 4 4 5% 7% 36%	2203
October	1st to 10th	Night	15% 7% 2 5% 4 3 3 3 4 6% 47%	2400
	11th to 20th	Night	17% 5% 2 5% 3 3 3 3 4 5% 51%	2377
	21st to end	Night	14% 7% 3 4 3 3 3 3 4 6% 49%	2518
November	1st to 10th	Night	11% 6% 3 6% 4 3 3 2 5% 6% 52%	2537
	11th to 20th	Night	14% 7% 2 6% 4 3 3 3 4 5% 48%	2600
	21st to end	Night	12% 6% 2 4 4 3 3 3 5% 6% 51%	2665
December	1st to 10th	Night	11% 6% 2 5% 3 3 3 3 5% 7% 52%	4580
	11th to 20th	Night	19% 8% 2 6% 5% 3 4 3 5% 6% 39%	5205
	21st to end	Night	14% 8% 3 6% 4 4 4 3 5% 7% 43%	6996

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	22% 27% 4 21% 23% 4	3598
	11th to 20th	Day	30% 27% 4 16% 16% 6%	3904
	21st to end	Day	32% 31% 7% 20% 9% 2	4466
February	1st to 10th	Day	18% 63% 7% 8% 4 1	1800
	11th to 20th	Day	19% 61% 3 8% 7% 2	1937
	21st to end	Day	18% 62% 5% 7% 7% 1	1650
March	1st to 10th	Day	31% 29% 5% 14% 14% 7%	4561
	11th to 20th	Day	23% 30% 7% 20% 15% 4	4980
	21st to end	Day	30% 29% 7% 10% 16% 7%	5757
April	1st to 10th	Day	17% 63% 4 8% 7% 1	2400
	11th to 20th	Day	14% 63% 5% 9% 7% 1	2374
	21st to end	Day	15% 62% 5% 10% 7% 1	2400
May	1st to 10th	Day	37% 33% 11% 12% 6% 1	5563
	11th to 20th	Day	37% 32% 8% 17% 6%	6294
	21st to end	Day	31% 32% 9% 15% 12% 1	6949
June	1st to 10th	Day	17% 63% 4 8% 7% 1	2800
	11th to 20th	Day	12% 64% 6% 9% 8% 1	2800
	21st to end	Day	11% 62% 8% 10% 9% 1	2800
July	1st to 10th	Day	25% 32% 17% 15% 10% 1	6290
	11th to 20th	Day	38% 31% 14% 14% 2	6285
	21st to end	Day	28% 29% 10% 17% 16%	6376
August	1st to 10th	Day	30% 39% 12% 15% 3	4167
	11th to 20th	Day	24% 39% 8% 23% 6%	3886
	21st to end	Day	20% 37% 8% 21% 14% 1	4312
September	1st to 10th	Day	16% 59% 8% 9% 7% 1	2400
	11th to 20th	Day	18% 59% 6% 8% 8% 1	2375
	21st to end	Day	25% 58% 4 9% 3 1	2194
October	1st to 10th	Day	20% 37% 5% 15% 19% 4	3260
	11th to 20th	Day	13% 36% 4 18% 21% 8%	3220
	21st to end	Day	10% 36% 7% 21% 17% 9%	3403
November	1st to 10th	Day	16% 56% 5% 12% 8% 3	1761
	11th to 20th	Day	15% 57% 4 9% 12% 3	1800
	21st to end	Day	15% 57% 3 15% 9% 1	1730
December	1st to 10th	Day	22% 36% 10% 17% 11% 4	2600
	11th to 20th	Day	31% 32% 8% 17% 9% 3	2986
	21st to end	Day	25% 30% 13% 17% 14% 1	3960
January	1st to 10th	Night	25% 27% 4 17% 21% 5%	6349
	11th to 20th	Night	24% 27% 5% 21% 18% 6%	6038
	21st to end	Night	30% 29% 6% 21% 12% 2	6490
February	1st to 10th	Night	16% 63% 7% 10% 4 1	2600
	11th to 20th	Night	19% 61% 2 7% 9% 2	2358
	21st to end	Night	16% 62% 3 10% 7% 3	1980
March	1st to 10th	Night	31% 30% 5% 14% 10% 8%	5287
	11th to 20th	Night	25% 31% 7% 17% 15% 5%	4980
	21st to end	Night	30% 30% 6% 13% 16% 4	5174
April	1st to 10th	Night	19% 62% 3 7% 7% 1	2000
	11th to 20th	Night	15% 64% 4 8% 7% 2	1975
	21st to end	Night	16% 63% 5% 8% 7% 1	2000
May	1st to 10th	Night	36% 33% 10% 15% 4 1	4392
	11th to 20th	Night	38% 32% 9% 15% 6%	3633
	21st to end	Night	34% 31% 9% 14% 9% 1	3927
June	1st to 10th	Night	17% 64% 3 8% 8% 1	1600
	11th to 20th	Night	14% 64% 4 10% 8%	1600
	21st to end	Night	13% 62% 6% 11% 8% 1	1600
July	1st to 10th	Night	31% 31% 14% 13% 9% 1	3560
	11th to 20th	Night	36% 31% 16% 14% 3	3552
	21st to end	Night	31% 29% 11% 15% 14%	4157
August	1st to 10th	Night	35% 38% 10% 13% 4	2925
	11th to 20th	Night	24% 39% 9% 21% 6%	3227
	21st to end	Night	17% 37% 6% 20% 20% 1	3586
September	1st to 10th	Night	15% 58% 9% 12% 5% 1	2000
	11th to 20th	Night	15% 58% 4 12% 9% 1	2023
	21st to end	Night	25% 58% 4 8% 4	2203
October	1st to 10th	Night	21% 36% 7% 17% 17% 2	3920
	11th to 20th	Night	11% 36% 8% 13% 26% 6%	3876
	21st to end	Night	9% 36% 8% 20% 20% 7%	4142
November	1st to 10th	Night	17% 57% 4 11% 8% 3	2537
	11th to 20th	Night	16% 57% 3 8% 12% 4	2600
	21st to end	Night	13% 57% 5% 12% 11% 1	2665
December	1st to 10th	Night	20% 36% 9% 18% 15% 3	4580
	11th to 20th	Night	33% 33% 8% 14% 9% 3	5208
	21st to end	Night	30% 29% 11% 16% 14% 1	6996

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% 25% 34% 15% 4 1	200
	11th to 20th	Day	24% 30% 29% 13% 4	267
	21st to end	Day	21% 22% 40% 14% 3	330
February	1st to 10th	Day	21% 26% 36% 12% 4	300
	11th to 20th	Day	29% 22% 36% 12% 2	476
	21st to end	Day	24% 19% 38% 15% 4	414
March	1st to 10th	Day	23% 23% 32% 18% 4	500
	11th to 20th	Day	22% 21% 34% 17% 4 2	500
	21st to end	Day	22% 21% 35% 17% 4	550
April	1st to 10th	Day	22% 21% 37% 14% 5% 2	500
	11th to 20th	Day	18% 16% 33% 25% 6% 2	492
	21st to end	Day	19% 14% 36% 21% 7% 2	500
May	1st to 10th	Day	21% 16% 34% 19% 8% 1	503
	11th to 20th	Day	20% 12% 32% 26% 8% 1	527
	21st to end	Day	18% 8% 22% 31% 16% 5%	573
June	1st to 10th	Day	13% 9% 28% 30% 17% 3	530
	11th to 20th	Day	13% 7% 27% 31% 17% 6%	530
	21st to end	Day	11% 4 24% 36% 20% 5%	530
July	1st to 10th	Day	11% 4 18% 35% 24% 9%	525
	11th to 20th	Day	4 2 18% 38% 27% 10%	524
	21st to end	Day	8% 3 21% 35% 26% 7%	576
August	1st to 10th	Day	12% 4 21% 30% 22% 10%	526
	11th to 20th	Day	11% 4 18% 30% 29% 8%	519
	21st to end	Day	8% 5% 21% 31% 24% 11%	583
September	1st to 10th	Day	15% 5% 22% 29% 15% 13%	530
	11th to 20th	Day	13% 5% 24% 30% 19% 9%	530
	21st to end	Day	23% 8% 28% 25% 11% 5%	530
October	1st to 10th	Day	18% 7% 26% 25% 14% 10%	530
	11th to 20th	Day	20% 12% 25% 22% 18% 3	522
	21st to end	Day	15% 12% 33% 26% 11% 3	532
November	1st to 10th	Day	16% 12% 29% 24% 15% 4	395
	11th to 20th	Day	16% 16% 36% 22% 10% 1	400
	21st to end	Day	18% 18% 28% 25% 9% 2	330
December	1st to 10th	Day	19% 21% 39% 14% 7% 1	200
	11th to 20th	Day	24% 21% 34% 16% 6%	200
	21st to end	Day	22% 20% 29% 21% 8%	220
January	1st to 10th	Night	19% 19% 36% 22% 5%	800
	11th to 20th	Night	19% 17% 34% 26% 4	800
	21st to end	Night	19% 14% 41% 23% 3	880
February	1st to 10th	Night	20% 14% 39% 25% 3	800
	11th to 20th	Night	25% 20% 35% 20% 1	783
	21st to end	Night	22% 16% 37% 21% 3	660
March	1st to 10th	Night	19% 17% 37% 23% 5%	800
	11th to 20th	Night	22% 14% 36% 21% 6% 1	800
	21st to end	Night	20% 14% 38% 23% 5%	880
April	1st to 10th	Night	21% 16% 38% 20% 5%	800
	11th to 20th	Night	15% 12% 34% 33% 6%	791
	21st to end	Night	19% 8% 35% 30% 8%	800
May	1st to 10th	Night	19% 10% 32% 31% 8% 1	750
	11th to 20th	Night	18% 7% 30% 34% 10%	425
	21st to end	Night	15% 4 23% 38% 18% 1	433
June	1st to 10th	Night	14% 4 24% 45% 13% 1	400
	11th to 20th	Night	11% 2 20% 45% 22%	400
	21st to end	Night	8% 3 21% 49% 19%	400
July	1st to 10th	Night	9% 2 18% 47% 22% 2	390
	11th to 20th	Night	5% 2 14% 44% 34% 1	388
	21st to end	Night	6% 1 15% 48% 28% 3	591
August	1st to 10th	Night	10% 2 12% 46% 28% 2	605
	11th to 20th	Night	11% 2 16% 39% 28% 4	790
	21st to end	Night	9% 3 16% 39% 28% 5%	880
September	1st to 10th	Night	18% 3 16% 34% 26% 3	800
	11th to 20th	Night	13% 4 16% 35% 29% 4	800
	21st to end	Night	23% 7% 19% 32% 18% 2	800
October	1st to 10th	Night	19% 5% 19% 32% 19% 5%	800
	11th to 20th	Night	19% 9% 25% 31% 15% 1	793
	21st to end	Night	17% 8% 32% 29% 12% 2	836
November	1st to 10th	Night	13% 9% 32% 31% 13% 2	780
	11th to 20th	Night	16% 13% 32% 30% 8% 1	800
	21st to end	Night	14% 13% 32% 29% 11% 1	800
December	1st to 10th	Night	22% 13% 34% 21% 8% 1	800
	11th to 20th	Night	20% 13% 37% 25% 6%	800
	21st to end	Night	17% 12% 36% 30% 5%	880

Page generated at 2025-10-16 01:50:27. Version ac07

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