Upstate Stars Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Upstate Stars Observatory clear sky chart from 2005-11-06 to 2025-09-19.

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	18% 10% 4 9% 5% 5% 4 4 5% 7% 30%	126501
	Night	18% 10% 4 9% 5% 4 4 3 5% 6% 31%	122541
Transparency	Day	50% 7% 12% 19% 11% 2	129990
	Night	50% 7% 13% 18% 11% 1	127126
Seeing	Day	27% 18% 27% 17% 8% 3	15949
	Night	25% 18% 25% 23% 9% 1	25064

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	10% 14% 9% 20% 10% 4 3 3 4 4 19%	3597
	11th to 20th	Day	14% 14% 7% 19% 9% 5% 4 3 4 4 16%	3570
	21st to end	Day	18% 13% 7% 9% 5% 4 4 3 4 5% 28%	4343
February	1st to 10th	Day	15% 15% 5% 11% 8% 5% 5% 4 5% 5% 23%	1800
	11th to 20th	Day	13% 11% 5% 11% 8% 5% 3 4 4 8% 28%	1878
	21st to end	Day	20% 11% 4 10% 7% 4 3 3 6% 5% 28%	1650
March	1st to 10th	Day	20% 14% 5% 9% 5% 4 3 3 4 5% 29%	4476
	11th to 20th	Day	13% 11% 5% 9% 5% 4 4 3 5% 6% 35%	4888
	21st to end	Day	19% 10% 3 9% 5% 4 4 3 5% 5% 31%	5832
April	1st to 10th	Day	19% 13% 4 8% 5% 4 4 3 5% 5% 30%	2400
	11th to 20th	Day	18% 11% 3 7% 5% 5% 4 4 5% 6% 33%	2374
	21st to end	Day	18% 11% 4 7% 5% 5% 4 3 5% 6% 33%	2405
May	1st to 10th	Day	30% 10% 3 7% 4 4 4 3 5% 6% 25%	6107
	11th to 20th	Day	20% 10% 3 8% 6% 5% 5% 4 5% 6% 28%	6318
	21st to end	Day	22% 8% 2 6% 5% 5% 6% 5% 7% 7% 28%	6949
June	1st to 10th	Day	18% 6% 3 7% 5% 5% 6% 4 7% 8% 31%	2800
	11th to 20th	Day	19% 8% 3 7% 5% 5% 5% 5% 6% 9% 29%	2800
	21st to end	Day	17% 8% 3 7% 5% 4 4 4 6% 9% 32%	2800
July	1st to 10th	Day	11% 7% 3 8% 6% 5% 5% 5% 7% 8% 34%	6360
	11th to 20th	Day	13% 6% 2 7% 5% 6% 6% 5% 7% 11% 31%	6360
	21st to end	Day	15% 6% 3 6% 4 5% 4 4 6% 9% 37%	6926
August	1st to 10th	Day	22% 7% 3 7% 4 5% 5% 4 6% 8% 30%	4345
	11th to 20th	Day	15% 7% 3 6% 5% 4 6% 5% 7% 9% 32%	3895
	21st to end	Day	18% 4 2 6% 4 5% 5% 4 7% 9% 37%	4312
September	1st to 10th	Day	18% 6% 3 6% 5% 4 4 3 5% 8% 38%	2400
	11th to 20th	Day	14% 6% 2 5% 3 5% 5% 4 6% 7% 43%	2333
	21st to end	Day	21% 7% 3 6% 4 4 4 4 6% 6% 35%	2090
October	1st to 10th	Day	21% 8% 3 7% 4 4 4 4 5% 6% 33%	1914
	11th to 20th	Day	18% 10% 3 6% 4 5% 5% 4 5% 6% 35%	1900
	21st to end	Day	23% 12% 3 7% 4 5% 4 3 5% 6% 27%	1962
November	1st to 10th	Day	15% 9% 4 6% 5% 4 4 3 5% 6% 40%	1761
	11th to 20th	Day	17% 13% 4 9% 5% 4 3 3 4 5% 33%	1800
	21st to end	Day	19% 14% 5% 8% 5% 4 4 3 5% 5% 27%	1610
December	1st to 10th	Day	17% 15% 5% 19% 6% 5% 4 3 3 4 18%	2600
	11th to 20th	Day	20% 15% 6% 10% 4 3 3 3 4 4 28%	2986
	21st to end	Day	19% 15% 7% 11% 6% 4 4 3 5% 5% 23%	3960
January	1st to 10th	Night	13% 10% 7% 20% 7% 4 4 3 5% 5% 22%	6349
	11th to 20th	Night	11% 14% 7% 19% 9% 5% 4 3 4 4 19%	6315
	21st to end	Night	16% 11% 5% 10% 8% 5% 5% 4 5% 6% 26%	6610
February	1st to 10th	Night	15% 13% 4 10% 6% 6% 5% 4 5% 6% 26%	2600
	11th to 20th	Night	14% 11% 4 12% 8% 6% 5% 3 6% 6% 25%	2407
	21st to end	Night	18% 11% 4 10% 5% 5% 4 3 5% 6% 28%	1980
March	1st to 10th	Night	19% 11% 3 9% 5% 4 4 3 5% 6% 30%	5364
	11th to 20th	Night	13% 10% 6% 9% 5% 4 3 3 5% 6% 35%	5053
	21st to end	Night	17% 13% 4 10% 5% 4 4 3 4 5% 32%	5086
April	1st to 10th	Night	19% 13% 4 9% 5% 4 5% 4 5% 6% 28%	2000
	11th to 20th	Night	18% 11% 4 7% 4 4 4 3 5% 6% 34%	1975
	21st to end	Night	19% 9% 4 7% 4 3 4 3 5% 6% 36%	1995
May	1st to 10th	Night	33% 10% 3 6% 3 3 3 3 4 6% 25%	3875
	11th to 20th	Night	21% 11% 3 7% 5% 4 4 4 5% 6% 31%	3575
	21st to end	Night	23% 11% 3 7% 4 4 3 4 5% 7% 30%	3926
June	1st to 10th	Night	17% 7% 2 7% 4 4 4 3 6% 8% 38%	1600
	11th to 20th	Night	18% 7% 2 5% 5% 3 4 4 5% 8% 40%	1600
	21st to end	Night	14% 5% 2 5% 4 5% 5% 4 7% 9% 42%	1600
July	1st to 10th	Night	13% 7% 3 7% 5% 4 4 4 5% 9% 39%	3600
	11th to 20th	Night	18% 9% 3 6% 5% 4 4 4 6% 8% 33%	3600
	21st to end	Night	14% 6% 2 6% 3 4 4 3 5% 7% 45%	3926
August	1st to 10th	Night	24% 8% 3 7% 5% 3 4 3 6% 6% 32%	2800
	11th to 20th	Night	17% 8% 3 7% 4 4 4 3 5% 6% 40%	3120
	21st to end	Night	14% 5% 1 5% 4 4 4 3 5% 8% 46%	3586
September	1st to 10th	Night	17% 6% 2 6% 3 3 4 3 5% 7% 44%	2000
	11th to 20th	Night	15% 5% 2 5% 3 4 3 3 5% 7% 49%	2024
	21st to end	Night	19% 7% 2 6% 4 4 4 3 5% 8% 38%	2090
October	1st to 10th	Night	21% 8% 3 7% 4 3 4 3 5% 5% 37%	2261
	11th to 20th	Night	19% 9% 2 7% 4 3 4 3 4 5% 39%	2280
	21st to end	Night	22% 11% 3 7% 5% 3 4 3 5% 6% 31%	2635
November	1st to 10th	Night	14% 9% 3 7% 4 4 5% 3 5% 6% 41%	2537
	11th to 20th	Night	21% 9% 3 8% 4 4 3 4 5% 6% 34%	2600
	21st to end	Night	16% 12% 4 8% 6% 4 4 4 6% 6% 30%	2788
December	1st to 10th	Night	15% 15% 6% 13% 6% 4 4 3 5% 6% 22%	4580
	11th to 20th	Night	25% 13% 4 9% 4 3 3 2 3 4 29%	5208
	21st to end	Night	21% 15% 6% 10% 6% 4 3 3 4 5% 23%	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	59% 10% 11% 15% 5% 1	3598
	11th to 20th	Day	66% 8% 8% 11% 5% 2	3600
	21st to end	Day	56% 5% 9% 19% 10% 1	4343
February	1st to 10th	Day	59% 7% 12% 14% 8%	1800
	11th to 20th	Day	54% 5% 10% 18% 11% 1	1887
	21st to end	Day	55% 6% 12% 17% 9% 1	1650
March	1st to 10th	Day	56% 5% 12% 13% 11% 3	4479
	11th to 20th	Day	46% 7% 15% 21% 6% 4	4888
	21st to end	Day	52% 6% 8% 12% 19% 4	5832
April	1st to 10th	Day	54% 6% 8% 20% 10% 3	2400
	11th to 20th	Day	50% 6% 11% 19% 12% 2	2374
	21st to end	Day	51% 5% 10% 18% 12% 3	2405
May	1st to 10th	Day	60% 6% 10% 14% 9% 2	6118
	11th to 20th	Day	54% 8% 8% 19% 10% 1	6322
	21st to end	Day	49% 9% 11% 19% 10% 1	6949
June	1st to 10th	Day	47% 8% 13% 19% 12%	2800
	11th to 20th	Day	49% 8% 14% 20% 8% 1	2800
	21st to end	Day	47% 7% 14% 23% 10%	2800
July	1st to 10th	Day	45% 9% 14% 21% 11% 1	6290
	11th to 20th	Day	43% 9% 14% 23% 10%	6285
	21st to end	Day	42% 7% 12% 24% 14% 1	6728
August	1st to 10th	Day	52% 6% 14% 19% 9% 1	4331
	11th to 20th	Day	44% 9% 16% 25% 6%	3932
	21st to end	Day	40% 7% 13% 30% 10% 1	4312
September	1st to 10th	Day	43% 6% 11% 24% 14% 1	2400
	11th to 20th	Day	38% 6% 11% 24% 20% 1	2333
	21st to end	Day	47% 6% 11% 19% 14% 2	2090
October	1st to 10th	Day	48% 7% 8% 20% 16% 2	3174
	11th to 20th	Day	41% 5% 9% 22% 15% 7%	3140
	21st to end	Day	38% 5% 16% 25% 13% 3	3213
November	1st to 10th	Day	42% 6% 16% 19% 15% 2	1761
	11th to 20th	Day	52% 5% 12% 17% 12% 3	1800
	21st to end	Day	55% 5% 15% 18% 5% 1	1610
December	1st to 10th	Day	65% 8% 10% 13% 4 1	2600
	11th to 20th	Day	59% 5% 12% 15% 9% 1	2986
	21st to end	Day	61% 6% 9% 12% 11% 2	3960
January	1st to 10th	Night	58% 7% 12% 13% 9% 1	6349
	11th to 20th	Night	61% 9% 12% 10% 7% 2	6360
	21st to end	Night	55% 7% 12% 12% 14% 2	6610
February	1st to 10th	Night	54% 7% 16% 15% 8% 1	2600
	11th to 20th	Night	54% 6% 14% 16% 9% 1	2409
	21st to end	Night	52% 6% 12% 19% 8% 2	1980
March	1st to 10th	Night	51% 6% 14% 15% 12% 2	5374
	11th to 20th	Night	46% 6% 20% 17% 7% 3	5054
	21st to end	Night	50% 6% 7% 16% 18% 2	5086
April	1st to 10th	Night	55% 6% 9% 18% 10% 2	2000
	11th to 20th	Night	49% 6% 11% 18% 15%	1975
	21st to end	Night	47% 7% 10% 19% 15% 3	1995
May	1st to 10th	Night	59% 7% 10% 14% 8% 3	3881
	11th to 20th	Night	52% 9% 11% 18% 9% 1	3576
	21st to end	Night	52% 8% 11% 20% 9% 1	3927
June	1st to 10th	Night	43% 6% 12% 23% 14% 1	1600
	11th to 20th	Night	41% 8% 16% 24% 11% 1	1600
	21st to end	Night	35% 10% 17% 24% 14% 1	1600
July	1st to 10th	Night	42% 7% 16% 19% 15% 1	3560
	11th to 20th	Night	48% 7% 12% 21% 11% 1	3552
	21st to end	Night	36% 6% 13% 29% 15% 1	3809
August	1st to 10th	Night	51% 7% 14% 20% 7% 1	2790
	11th to 20th	Night	42% 7% 16% 26% 9%	3149
	21st to end	Night	34% 7% 12% 34% 12%	3586
September	1st to 10th	Night	39% 7% 13% 25% 15% 1	2000
	11th to 20th	Night	36% 6% 10% 25% 22% 1	2024
	21st to end	Night	45% 5% 11% 21% 17% 1	2090
October	1st to 10th	Night	48% 7% 9% 21% 14% 1	3768
	11th to 20th	Night	38% 6% 12% 21% 17% 7%	3779
	21st to end	Night	39% 6% 16% 25% 12% 1	4334
November	1st to 10th	Night	42% 6% 12% 21% 17% 2	2537
	11th to 20th	Night	48% 6% 13% 18% 12% 3	2600
	21st to end	Night	48% 6% 18% 20% 7%	2788
December	1st to 10th	Night	58% 9% 12% 19% 3	4580
	11th to 20th	Night	57% 5% 13% 15% 11%	5208
	21st to end	Night	60% 6% 10% 10% 11% 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	36% 25% 27% 11% 1 1	200
	11th to 20th	Day	43% 25% 23% 7% 3	200
	21st to end	Day	31% 28% 30% 8% 3	302
February	1st to 10th	Day	36% 32% 26% 5% 1	300
	11th to 20th	Day	39% 31% 22% 7% 1	426
	21st to end	Day	37% 25% 26% 10% 2	414
March	1st to 10th	Day	33% 23% 28% 13% 3	500
	11th to 20th	Day	33% 26% 26% 12% 3 1	500
	21st to end	Day	35% 27% 24% 9% 5% 1	550
April	1st to 10th	Day	39% 23% 23% 10% 4 1	500
	11th to 20th	Day	34% 23% 23% 11% 6% 3	492
	21st to end	Day	31% 21% 31% 10% 5% 2	500
May	1st to 10th	Day	39% 18% 26% 11% 4 3	503
	11th to 20th	Day	23% 20% 31% 17% 5% 3	527
	21st to end	Day	24% 11% 29% 22% 11% 3	573
June	1st to 10th	Day	23% 14% 31% 20% 9% 3	530
	11th to 20th	Day	24% 15% 24% 24% 11% 2	530
	21st to end	Day	20% 15% 33% 21% 10% 1	530
July	1st to 10th	Day	13% 10% 30% 27% 15% 3	525
	11th to 20th	Day	15% 8% 31% 29% 14% 3	524
	21st to end	Day	17% 11% 35% 22% 12% 2	576
August	1st to 10th	Day	15% 12% 26% 25% 16% 6%	526
	11th to 20th	Day	18% 9% 25% 26% 17% 6%	519
	21st to end	Day	17% 10% 29% 22% 14% 7%	583
September	1st to 10th	Day	23% 11% 24% 22% 14% 7%	530
	11th to 20th	Day	14% 12% 24% 25% 14% 12%	522
	21st to end	Day	25% 12% 28% 19% 12% 4	490
October	1st to 10th	Day	29% 13% 24% 18% 13% 3	490
	11th to 20th	Day	25% 19% 26% 21% 8% 1	490
	21st to end	Day	32% 18% 26% 18% 6% 1	472
November	1st to 10th	Day	28% 20% 22% 19% 9% 2	395
	11th to 20th	Day	30% 24% 26% 16% 4 1	400
	21st to end	Day	32% 25% 29% 11% 2	210
December	1st to 10th	Day	34% 27% 25% 10% 5% 1	200
	11th to 20th	Day	42% 22% 27% 9% 2	200
	21st to end	Day	34% 27% 26% 10% 3	220
January	1st to 10th	Night	28% 28% 29% 14% 2	800
	11th to 20th	Night	31% 21% 27% 18% 3	800
	21st to end	Night	22% 26% 34% 15% 3	880
February	1st to 10th	Night	29% 23% 32% 15% 1	800
	11th to 20th	Night	29% 28% 30% 12% 1	783
	21st to end	Night	35% 23% 24% 15% 3	660
March	1st to 10th	Night	30% 22% 31% 14% 3	800
	11th to 20th	Night	26% 27% 27% 18% 3	800
	21st to end	Night	26% 24% 30% 15% 5%	880
April	1st to 10th	Night	30% 22% 29% 16% 4	800
	11th to 20th	Night	25% 21% 28% 19% 6%	791
	21st to end	Night	27% 20% 25% 21% 7%	795
May	1st to 10th	Night	32% 14% 23% 24% 6% 1	525
	11th to 20th	Night	22% 12% 28% 29% 8%	394
	21st to end	Night	20% 9% 22% 33% 15% 1	433
June	1st to 10th	Night	20% 9% 25% 31% 15% 1	400
	11th to 20th	Night	21% 8% 23% 33% 15% 1	400
	21st to end	Night	14% 5% 25% 41% 15%	400
July	1st to 10th	Night	16% 7% 19% 38% 18% 2	390
	11th to 20th	Night	16% 5% 20% 40% 18% 2	388
	21st to end	Night	16% 6% 21% 39% 16% 1	438
August	1st to 10th	Night	16% 4 21% 33% 23% 2	521
	11th to 20th	Night	16% 6% 16% 37% 20% 4	737
	21st to end	Night	19% 6% 18% 33% 23% 1	880
September	1st to 10th	Night	20% 7% 23% 28% 20% 2	800
	11th to 20th	Night	17% 7% 20% 28% 21% 7%	793
	21st to end	Night	22% 12% 21% 29% 14% 3	760
October	1st to 10th	Night	27% 13% 21% 21% 16% 2	760
	11th to 20th	Night	24% 14% 26% 27% 8%	760
	21st to end	Night	28% 19% 27% 20% 5%	836
November	1st to 10th	Night	19% 21% 27% 24% 8% 1	780
	11th to 20th	Night	28% 22% 22% 21% 6% 1	800
	21st to end	Night	25% 22% 28% 19% 5% 1	800
December	1st to 10th	Night	31% 26% 24% 16% 4	800
	11th to 20th	Night	32% 23% 26% 17% 3	800
	21st to end	Night	30% 25% 26% 16% 3	880

Page generated at 2025-09-16 01:49:09. Version ac07

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