Hauppauge
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hauppauge clear sky chart from 2005-11-06 to 2025-09-04.

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% 7% 2 6% 4 4 4 4 5% 7% 41%	125955
	Night	17% 8% 2 6% 4 4 4 3 5% 6% 42%	122756
Transparency	Day	40% 7% 13% 22% 16% 2	129483
	Night	42% 6% 12% 22% 16% 3	127315
Seeing	Day	18% 9% 26% 29% 15% 3	16127
	Night	20% 8% 30% 30% 11% 1	25162

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% 6% 2 5% 3 3 3 3 5% 6% 51%	3597
	11th to 20th	Day	14% 8% 3 5% 4 4 4 3 5% 6% 45%	3570
	21st to end	Day	18% 10% 4 7% 4 4 4 2 3 5% 39%	4172
February	1st to 10th	Day	17% 7% 3 6% 4 4 4 4 5% 6% 40%	1868
	11th to 20th	Day	15% 7% 2 6% 4 3 4 3 5% 5% 45%	1948
	21st to end	Day	18% 9% 3 6% 5% 4 3 3 5% 6% 39%	1650
March	1st to 10th	Day	21% 9% 2 5% 2 3 3 3 4 5% 43%	4476
	11th to 20th	Day	11% 8% 2 6% 4 3 5% 4 7% 8% 43%	4674
	21st to end	Day	18% 9% 2 5% 4 3 4 3 5% 7% 40%	5970
April	1st to 10th	Day	18% 9% 3 5% 4 4 4 4 5% 7% 37%	2400
	11th to 20th	Day	17% 7% 2 5% 4 3 4 3 5% 6% 42%	2374
	21st to end	Day	19% 6% 2 5% 3 4 4 3 6% 6% 42%	2475
May	1st to 10th	Day	28% 9% 2 4 3 3 3 4 5% 8% 30%	5886
	11th to 20th	Day	23% 9% 2 6% 3 3 4 3 5% 6% 36%	6122
	21st to end	Day	21% 7% 2 5% 3 3 4 4 6% 8% 36%	6949
June	1st to 10th	Day	17% 5% 2 5% 5% 4 4 4 6% 9% 40%	2800
	11th to 20th	Day	16% 6% 2 5% 4 4 5% 4 6% 9% 39%	2800
	21st to end	Day	11% 6% 2 5% 5% 4 5% 4 7% 9% 42%	2800
July	1st to 10th	Day	12% 7% 2 6% 5% 5% 5% 4 7% 11% 36%	6360
	11th to 20th	Day	12% 7% 2 6% 4 5% 6% 5% 7% 11% 35%	6360
	21st to end	Day	14% 6% 2 6% 4 4 5% 4 6% 8% 41%	6926
August	1st to 10th	Day	18% 7% 2 7% 4 4 5% 4 7% 9% 34%	4320
	11th to 20th	Day	12% 5% 2 6% 4 4 4 4 6% 8% 43%	3850
	21st to end	Day	9% 4 2 5% 4 4 4 4 7% 10% 47%	4312
September	1st to 10th	Day	14% 6% 2 5% 4 3 4 3 5% 7% 47%	2316
	11th to 20th	Day	13% 5% 2 4 3 3 4 4 5% 7% 50%	2160
	21st to end	Day	20% 6% 2 6% 4 4 3 3 5% 6% 40%	2090
October	1st to 10th	Day	20% 6% 2 5% 3 4 4 2 4 8% 42%	2047
	11th to 20th	Day	15% 5% 2 5% 3 4 3 4 5% 7% 48%	1900
	21st to end	Day	19% 5% 2 5% 4 4 4 4 4 7% 43%	1893
November	1st to 10th	Day	14% 5% 2 6% 4 3 3 2 4 6% 51%	1761
	11th to 20th	Day	16% 7% 2 5% 3 3 3 2 4 7% 48%	1800
	21st to end	Day	15% 7% 2 5% 3 4 4 3 5% 6% 44%	1783
December	1st to 10th	Day	16% 6% 2 6% 4 3 3 4 6% 7% 44%	2600
	11th to 20th	Day	24% 8% 2 4 2 2 2 2 3 5% 46%	2986
	21st to end	Day	17% 9% 3 7% 4 4 4 3 5% 6% 39%	3960
January	1st to 10th	Night	14% 6% 2 5% 3 3 3 3 4 5% 52%	6349
	11th to 20th	Night	15% 7% 3 7% 4 3 3 3 4 5% 47%	6315
	21st to end	Night	17% 9% 3 7% 4 4 4 3 5% 6% 38%	6766
February	1st to 10th	Night	16% 9% 3 6% 4 4 4 3 5% 6% 41%	2530
	11th to 20th	Night	19% 7% 3 5% 4 4 4 3 6% 6% 40%	2338
	21st to end	Night	19% 8% 2 5% 4 4 4 3 5% 6% 42%	1980
March	1st to 10th	Night	20% 10% 2 5% 3 3 3 2 4 5% 43%	5364
	11th to 20th	Night	16% 9% 3 6% 4 3 3 3 4 5% 42%	5269
	21st to end	Night	20% 9% 2 7% 4 3 4 4 4 5% 38%	4962
April	1st to 10th	Night	20% 7% 2 6% 5% 5% 4 3 4 7% 37%	2000
	11th to 20th	Night	19% 8% 2 6% 4 3 4 3 5% 6% 40%	1975
	21st to end	Night	17% 9% 3 6% 3 3 3 4 4 6% 42%	1925
May	1st to 10th	Night	25% 10% 4 8% 4 4 4 3 5% 7% 27%	4054
	11th to 20th	Night	23% 10% 3 6% 4 3 4 3 5% 6% 33%	3814
	21st to end	Night	22% 9% 3 7% 4 3 3 3 5% 7% 34%	3926
June	1st to 10th	Night	18% 8% 2 5% 3 4 4 4 5% 8% 40%	1600
	11th to 20th	Night	17% 7% 2 5% 4 4 3 4 5% 10% 39%	1600
	21st to end	Night	11% 6% 3 6% 5% 4 5% 4 6% 9% 39%	1600
July	1st to 10th	Night	13% 10% 3 8% 5% 5% 5% 4 6% 8% 33%	3600
	11th to 20th	Night	18% 11% 3 7% 4 4 4 4 6% 8% 31%	3600
	21st to end	Night	14% 7% 3 6% 4 4 4 4 6% 8% 41%	3926
August	1st to 10th	Night	23% 7% 2 5% 4 4 5% 4 7% 7% 31%	2791
	11th to 20th	Night	13% 7% 3 6% 4 5% 5% 4 6% 8% 40%	3197
	21st to end	Night	9% 5% 2 5% 3 4 4 4 5% 8% 53%	3586
September	1st to 10th	Night	14% 5% 2 5% 4 5% 5% 3 6% 6% 45%	1931
	11th to 20th	Night	14% 5% 1 6% 3 3 3 3 4 6% 52%	2019
	21st to end	Night	19% 5% 2 7% 4 4 3 3 5% 7% 41%	2090
October	1st to 10th	Night	20% 8% 3 6% 4 3 3 3 4 6% 40%	2130
	11th to 20th	Night	14% 5% 2 5% 3 4 4 2 5% 5% 50%	2280
	21st to end	Night	20% 6% 2 6% 4 3 3 3 5% 6% 42%	2703
November	1st to 10th	Night	13% 5% 2 6% 4 3 3 3 5% 6% 50%	2537
	11th to 20th	Night	18% 7% 2 4 3 3 3 3 5% 4 48%	2600
	21st to end	Night	15% 6% 2 5% 4 4 3 4 6% 6% 47%	2615
December	1st to 10th	Night	16% 8% 2 4 4 3 3 2 3 5% 49%	4580
	11th to 20th	Night	26% 7% 2 4 3 3 2 2 4 4 43%	5208
	21st to end	Night	18% 8% 3 6% 3 3 3 3 5% 5% 42%	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	33% 5% 10% 31% 20% 2	3598
	11th to 20th	Day	38% 6% 12% 23% 16% 6%	3600
	21st to end	Day	47% 6% 10% 22% 14% 1	4172
February	1st to 10th	Day	44% 5% 14% 23% 13% 1	1868
	11th to 20th	Day	41% 5% 11% 25% 17% 2	1957
	21st to end	Day	45% 6% 11% 21% 14% 3	1650
March	1st to 10th	Day	41% 6% 13% 17% 14% 9%	4479
	11th to 20th	Day	35% 9% 15% 27% 12% 2	4674
	21st to end	Day	43% 6% 10% 14% 22% 5%	5970
April	1st to 10th	Day	44% 6% 11% 20% 15% 4	2400
	11th to 20th	Day	41% 5% 13% 21% 17% 3	2374
	21st to end	Day	40% 7% 11% 22% 17% 4	2475
May	1st to 10th	Day	51% 8% 17% 14% 9% 1	5897
	11th to 20th	Day	46% 8% 12% 19% 13% 2	6126
	21st to end	Day	42% 8% 14% 22% 13% 1	6949
June	1st to 10th	Day	39% 9% 14% 22% 15% 1	2800
	11th to 20th	Day	40% 8% 14% 24% 13% 2	2800
	21st to end	Day	36% 9% 16% 22% 15% 1	2800
July	1st to 10th	Day	42% 10% 13% 20% 14% 1	6290
	11th to 20th	Day	41% 9% 20% 21% 9% 1	6285
	21st to end	Day	39% 7% 12% 21% 19% 2	6728
August	1st to 10th	Day	45% 8% 15% 22% 9% 1	4306
	11th to 20th	Day	36% 7% 15% 32% 9% 1	3886
	21st to end	Day	30% 7% 14% 27% 20% 2	4312
September	1st to 10th	Day	37% 7% 14% 21% 19% 2	2316
	11th to 20th	Day	33% 6% 12% 24% 24% 2	2160
	21st to end	Day	45% 6% 11% 18% 19% 2	2090
October	1st to 10th	Day	34% 6% 12% 20% 22% 5%	3398
	11th to 20th	Day	25% 5% 11% 23% 32% 4	3140
	21st to end	Day	29% 5% 15% 26% 22% 2	3093
November	1st to 10th	Day	36% 6% 13% 22% 21% 2	1761
	11th to 20th	Day	38% 4 10% 23% 22% 3	1800
	21st to end	Day	39% 6% 15% 27% 11% 2	1783
December	1st to 10th	Day	39% 5% 17% 27% 12% 1	2600
	11th to 20th	Day	42% 3 14% 21% 17% 3	2986
	21st to end	Day	45% 8% 10% 20% 14% 3	3960
January	1st to 10th	Night	34% 5% 9% 25% 23% 3	6349
	11th to 20th	Night	40% 5% 13% 22% 16% 5%	6360
	21st to end	Night	46% 5% 10% 20% 16% 4	6766
February	1st to 10th	Night	44% 6% 13% 23% 12% 2	2530
	11th to 20th	Night	44% 5% 11% 20% 16% 4	2340
	21st to end	Night	44% 4 9% 22% 16% 4	1980
March	1st to 10th	Night	44% 4 11% 19% 13% 8%	5374
	11th to 20th	Night	42% 6% 13% 24% 11% 4	5270
	21st to end	Night	46% 5% 7% 13% 23% 5%	4962
April	1st to 10th	Night	46% 6% 11% 17% 16% 3	2000
	11th to 20th	Night	44% 6% 10% 18% 20% 2	1975
	21st to end	Night	43% 6% 10% 20% 17% 5%	1925
May	1st to 10th	Night	56% 8% 13% 13% 9% 1	4060
	11th to 20th	Night	51% 7% 13% 14% 13% 2	3815
	21st to end	Night	48% 7% 14% 20% 10% 1	3927
June	1st to 10th	Night	43% 7% 10% 20% 19% 1	1600
	11th to 20th	Night	39% 9% 13% 25% 12% 1	1600
	21st to end	Night	39% 9% 14% 24% 13% 2	1600
July	1st to 10th	Night	47% 9% 12% 21% 11% 1	3560
	11th to 20th	Night	48% 8% 14% 20% 9% 1	3552
	21st to end	Night	40% 7% 14% 24% 14% 1	3809
August	1st to 10th	Night	48% 9% 16% 17% 9% 1	2781
	11th to 20th	Night	39% 7% 15% 29% 9% 1	3227
	21st to end	Night	28% 7% 12% 33% 18% 1	3586
September	1st to 10th	Night	39% 8% 10% 25% 18% 1	1931
	11th to 20th	Night	33% 6% 11% 24% 22% 3	2019
	21st to end	Night	43% 7% 9% 20% 19% 3	2090
October	1st to 10th	Night	39% 6% 11% 23% 19% 2	3559
	11th to 20th	Night	24% 4 11% 26% 31% 4	3779
	21st to end	Night	31% 5% 13% 28% 21% 2	4453
November	1st to 10th	Night	35% 6% 13% 22% 20% 3	2537
	11th to 20th	Night	40% 4 10% 23% 19% 4	2600
	21st to end	Night	37% 6% 14% 29% 13% 2	2615
December	1st to 10th	Night	40% 3 13% 29% 12% 2	4580
	11th to 20th	Night	47% 4 9% 24% 14% 2	5208
	21st to end	Night	44% 5% 12% 20% 16% 3	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% 17% 32% 22% 6% 1	200
	11th to 20th	Day	17% 23% 39% 18% 4 1	200
	21st to end	Day	21% 11% 39% 22% 7% 1	267
February	1st to 10th	Day	24% 12% 38% 24% 3	368
	11th to 20th	Day	21% 15% 38% 24% 2	496
	21st to end	Day	23% 17% 33% 21% 6%	414
March	1st to 10th	Day	18% 14% 37% 26% 5%	500
	11th to 20th	Day	17% 11% 40% 26% 5% 1	500
	21st to end	Day	23% 12% 35% 22% 7% 1	550
April	1st to 10th	Day	23% 13% 33% 21% 10%	500
	11th to 20th	Day	22% 9% 30% 28% 11% 1	492
	21st to end	Day	24% 9% 30% 29% 8% 1	500
May	1st to 10th	Day	28% 8% 28% 27% 8% 1	503
	11th to 20th	Day	20% 6% 26% 35% 13% 1	527
	21st to end	Day	20% 3 17% 32% 25% 3	573
June	1st to 10th	Day	18% 4 19% 36% 21% 3	530
	11th to 20th	Day	17% 5% 23% 35% 18% 2	530
	21st to end	Day	12% 6% 22% 34% 23% 3	530
July	1st to 10th	Day	12% 4 16% 36% 26% 6%	525
	11th to 20th	Day	9% 6% 15% 35% 29% 7%	524
	21st to end	Day	13% 5% 18% 39% 22% 3	576
August	1st to 10th	Day	12% 3 17% 36% 26% 6%	526
	11th to 20th	Day	13% 3 16% 37% 26% 5%	519
	21st to end	Day	10% 5% 21% 36% 20% 9%	583
September	1st to 10th	Day	17% 5% 19% 28% 23% 9%	502
	11th to 20th	Day	14% 3 18% 33% 22% 10%	490
	21st to end	Day	22% 4 24% 28% 18% 3	490
October	1st to 10th	Day	24% 6% 19% 24% 19% 7%	490
	11th to 20th	Day	13% 8% 30% 30% 16% 3	490
	21st to end	Day	21% 9% 31% 25% 12% 2	434
November	1st to 10th	Day	14% 12% 24% 33% 14% 3	395
	11th to 20th	Day	18% 18% 31% 26% 8%	400
	21st to end	Day	19% 13% 30% 27% 10% 1	383
December	1st to 10th	Day	21% 11% 39% 22% 8% 1	200
	11th to 20th	Day	28% 18% 26% 23% 6%	200
	21st to end	Day	21% 14% 38% 17% 10%	220
January	1st to 10th	Night	20% 14% 41% 21% 4	800
	11th to 20th	Night	25% 12% 35% 25% 3	800
	21st to end	Night	20% 13% 42% 23% 3	880
February	1st to 10th	Night	20% 13% 38% 26% 2	800
	11th to 20th	Night	24% 12% 43% 20% 2	783
	21st to end	Night	23% 13% 38% 22% 4	660
March	1st to 10th	Night	21% 12% 38% 25% 5%	800
	11th to 20th	Night	19% 10% 40% 25% 6% 1	800
	21st to end	Night	21% 9% 38% 25% 5%	880
April	1st to 10th	Night	23% 9% 35% 28% 6%	800
	11th to 20th	Night	22% 8% 32% 30% 8%	791
	21st to end	Night	21% 6% 31% 35% 7% 1	725
May	1st to 10th	Night	24% 7% 28% 31% 9% 2	600
	11th to 20th	Night	22% 5% 32% 32% 9%	503
	21st to end	Night	22% 4 15% 37% 21% 1	433
June	1st to 10th	Night	21% 3 21% 38% 16% 1	400
	11th to 20th	Night	20% 2 15% 44% 19% 1	400
	21st to end	Night	11% 4 19% 48% 18% 1	400
July	1st to 10th	Night	12% 4 19% 40% 23% 2	390
	11th to 20th	Night	14% 4 14% 43% 24% 2	388
	21st to end	Night	15% 3 16% 47% 19% 1	438
August	1st to 10th	Night	10% 1 16% 46% 26% 1	512
	11th to 20th	Night	14% 3 16% 35% 29% 3	790
	21st to end	Night	13% 4 15% 37% 26% 5%	880
September	1st to 10th	Night	16% 2 21% 35% 21% 4	773
	11th to 20th	Night	17% 3 18% 35% 22% 6%	760
	21st to end	Night	21% 3 22% 33% 17% 3	760
October	1st to 10th	Night	24% 6% 25% 25% 16% 4	760
	11th to 20th	Night	18% 8% 29% 30% 14% 1	760
	21st to end	Night	23% 8% 33% 27% 9%	836
November	1st to 10th	Night	14% 9% 33% 29% 13% 2	780
	11th to 20th	Night	20% 12% 36% 24% 8% 1	800
	21st to end	Night	18% 13% 34% 27% 8% 1	800
December	1st to 10th	Night	24% 14% 34% 22% 6% 1	800
	11th to 20th	Night	23% 12% 38% 24% 4	800
	21st to end	Night	22% 12% 38% 23% 5%	880

Page generated at 2025-09-01 01:51:02. Version ac07

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