SUNY Ulster
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the SUNY Ulster 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	16% 7% 2 6% 5% 4 5% 4 6% 7% 38%	101773
	Night	17% 7% 2 6% 4 4 4 3 5% 7% 40%	98350
Transparency	Day	42% 8% 14% 22% 13% 2	105292
	Night	42% 7% 13% 22% 14% 2	102920
Seeing	Day	20% 13% 28% 25% 11% 3	15006
	Night	19% 10% 29% 31% 10% 1	24184

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	13% 8% 3 5% 4 4 4 4 6% 6% 43%	2517
	11th to 20th	Day	13% 9% 4 10% 6% 5% 4 5% 6% 6% 31%	2520
	21st to end	Day	18% 11% 4 9% 6% 5% 4 3 5% 5% 31%	2946
February	1st to 10th	Day	14% 9% 3 9% 6% 5% 5% 4 5% 6% 34%	1710
	11th to 20th	Day	12% 7% 2 9% 5% 4 5% 4 6% 6% 41%	1824
	21st to end	Day	19% 9% 2 6% 4 4 4 4 5% 5% 37%	1570
March	1st to 10th	Day	24% 10% 3 8% 4 4 3 3 3 4 35%	3116
	11th to 20th	Day	10% 7% 2 7% 5% 4 5% 5% 6% 8% 42%	3341
	21st to end	Day	20% 8% 3 6% 4 4 4 3 4 6% 39%	4130
April	1st to 10th	Day	17% 9% 3 7% 4 5% 4 4 5% 6% 37%	2280
	11th to 20th	Day	16% 7% 2 6% 5% 5% 4 3 6% 6% 40%	2254
	21st to end	Day	20% 5% 3 5% 5% 4 4 3 5% 6% 39%	2326
May	1st to 10th	Day	25% 8% 3 6% 4 4 4 3 5% 7% 31%	4163
	11th to 20th	Day	19% 7% 2 6% 5% 4 5% 4 6% 7% 34%	4398
	21st to end	Day	12% 5% 2 5% 4 4 5% 5% 7% 10% 42%	4837
June	1st to 10th	Day	15% 5% 2 6% 5% 5% 5% 5% 7% 9% 36%	2660
	11th to 20th	Day	14% 5% 2 6% 5% 4 5% 4 8% 9% 37%	2660
	21st to end	Day	13% 5% 2 5% 5% 5% 5% 5% 7% 9% 37%	2660
July	1st to 10th	Day	10% 6% 2 8% 5% 6% 6% 5% 7% 8% 37%	4440
	11th to 20th	Day	9% 5% 2 6% 5% 5% 6% 5% 8% 12% 38%	4440
	21st to end	Day	13% 7% 2 7% 6% 5% 5% 5% 6% 7% 35%	4814
August	1st to 10th	Day	18% 6% 2 7% 4 5% 5% 4 6% 8% 34%	4287
	11th to 20th	Day	13% 6% 2 6% 4 4 5% 4 7% 8% 41%	3730
	21st to end	Day	12% 5% 2 5% 4 5% 5% 4 7% 9% 43%	4180
September	1st to 10th	Day	13% 6% 2 6% 5% 4 4 3 5% 6% 45%	2280
	11th to 20th	Day	14% 4 1 5% 3 4 4 3 5% 7% 51%	2204
	21st to end	Day	18% 5% 2 5% 4 4 4 4 5% 7% 41%	2090
October	1st to 10th	Day	19% 6% 2 5% 4 4 4 3 4 6% 42%	1969
	11th to 20th	Day	13% 6% 2 6% 4 3 5% 4 5% 7% 44%	1900
	21st to end	Day	22% 5% 2 6% 4 5% 4 4 5% 6% 37%	1923
November	1st to 10th	Day	12% 8% 2 5% 5% 3 3 3 4 6% 50%	1761
	11th to 20th	Day	16% 7% 2 5% 5% 3 4 3 5% 6% 44%	1800
	21st to end	Day	17% 9% 2 5% 5% 4 5% 4 5% 7% 39%	1661
December	1st to 10th	Day	17% 7% 4 8% 6% 6% 5% 4 5% 5% 33%	1600
	11th to 20th	Day	22% 7% 2 5% 3 4 4 3 5% 6% 41%	1986
	21st to end	Day	19% 10% 3 8% 6% 5% 4 4 5% 6% 30%	2796
January	1st to 10th	Night	16% 6% 3 6% 4 4 4 3 6% 7% 43%	4429
	11th to 20th	Night	14% 8% 5% 10% 5% 5% 4 3 5% 6% 35%	4440
	21st to end	Night	22% 13% 3 6% 5% 4 4 4 5% 5% 31%	4694
February	1st to 10th	Night	14% 10% 3 6% 4 4 4 4 6% 6% 38%	2470
	11th to 20th	Night	12% 8% 3 7% 5% 5% 5% 4 5% 6% 40%	2240
	21st to end	Night	16% 10% 2 7% 4 4 4 4 4 5% 41%	1884
March	1st to 10th	Night	24% 9% 2 6% 3 3 4 3 4 6% 36%	3724
	11th to 20th	Night	12% 8% 3 7% 4 4 5% 4 6% 8% 41%	3617
	21st to end	Night	14% 11% 3 7% 4 4 3 3 4 4 41%	3501
April	1st to 10th	Night	18% 8% 3 7% 4 6% 4 4 6% 7% 34%	1900
	11th to 20th	Night	18% 7% 2 6% 5% 4 3 4 5% 8% 38%	1875
	21st to end	Night	21% 7% 2 5% 4 3 4 3 4 5% 42%	1853
May	1st to 10th	Night	26% 7% 2 7% 3 4 3 3 5% 6% 32%	2806
	11th to 20th	Night	22% 9% 3 7% 4 3 4 3 4 7% 34%	2495
	21st to end	Night	13% 6% 2 6% 3 4 5% 4 6% 8% 42%	2738
June	1st to 10th	Night	16% 5% 2 6% 4 3 4 4 5% 9% 42%	1520
	11th to 20th	Night	14% 6% 3 5% 3 4 4 4 6% 10% 42%	1520
	21st to end	Night	13% 3 2 5% 3 4 4 4 6% 10% 45%	1520
July	1st to 10th	Night	10% 5% 2 6% 5% 5% 5% 4 7% 8% 42%	2520
	11th to 20th	Night	12% 6% 2 6% 5% 4 4 4 7% 10% 40%	2520
	21st to end	Night	16% 6% 3 6% 4 4 4 4 5% 6% 41%	2739
August	1st to 10th	Night	21% 6% 2 6% 4 4 5% 4 5% 8% 36%	2619
	11th to 20th	Night	15% 6% 2 6% 5% 4 5% 4 5% 6% 42%	3088
	21st to end	Night	13% 5% 2 5% 3 3 4 3 5% 6% 52%	3476
September	1st to 10th	Night	14% 5% 2 5% 5% 4 4 3 4 7% 47%	1900
	11th to 20th	Night	13% 5% 1 4 3 3 4 3 4 7% 54%	1976
	21st to end	Night	17% 6% 2 5% 4 4 3 3 5% 7% 45%	2090
October	1st to 10th	Night	20% 7% 3 6% 3 4 4 3 4 5% 41%	2209
	11th to 20th	Night	17% 6% 2 5% 3 3 4 3 5% 5% 48%	2280
	21st to end	Night	23% 6% 2 7% 3 3 3 3 4 7% 39%	2674
November	1st to 10th	Night	13% 6% 2 6% 4 4 4 3 5% 7% 47%	2537
	11th to 20th	Night	18% 7% 2 5% 3 3 4 4 5% 5% 43%	2600
	21st to end	Night	15% 7% 2 5% 5% 4 3 3 6% 6% 44%	2735
December	1st to 10th	Night	18% 8% 2 6% 5% 4 4 3 5% 7% 38%	2800
	11th to 20th	Night	22% 8% 2 6% 4 4 4 3 5% 6% 37%	3428
	21st to end	Night	20% 11% 3 7% 4 4 3 3 5% 6% 34%	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	39% 6% 15% 30% 8% 2	2518
	11th to 20th	Day	49% 8% 13% 20% 8% 2	2520
	21st to end	Day	54% 6% 11% 19% 8% 1	2946
February	1st to 10th	Day	49% 7% 13% 18% 12% 1	1710
	11th to 20th	Day	43% 7% 11% 22% 15% 3	1833
	21st to end	Day	48% 5% 11% 21% 12% 3	1570
March	1st to 10th	Day	53% 5% 12% 18% 10% 2	3119
	11th to 20th	Day	35% 9% 17% 27% 10% 2	3341
	21st to end	Day	46% 6% 7% 16% 21% 5%	4130
April	1st to 10th	Day	47% 7% 10% 20% 13% 4	2280
	11th to 20th	Day	43% 6% 11% 21% 15% 3	2254
	21st to end	Day	45% 6% 10% 20% 15% 4	2326
May	1st to 10th	Day	51% 9% 12% 15% 12% 2	4177
	11th to 20th	Day	47% 9% 15% 19% 8% 1	4402
	21st to end	Day	32% 9% 16% 26% 15% 2	4837
June	1st to 10th	Day	42% 9% 16% 19% 13% 1	2660
	11th to 20th	Day	41% 9% 16% 23% 10% 1	2660
	21st to end	Day	40% 11% 13% 23% 12% 1	2660
July	1st to 10th	Day	41% 10% 14% 19% 15% 1	4370
	11th to 20th	Day	35% 10% 18% 23% 13%	4365
	21st to end	Day	46% 8% 13% 17% 14% 1	4661
August	1st to 10th	Day	47% 9% 16% 19% 9% 1	4273
	11th to 20th	Day	37% 9% 18% 27% 9%	3766
	21st to end	Day	34% 8% 16% 28% 13% 1	4180
September	1st to 10th	Day	40% 7% 12% 22% 17% 2	2280
	11th to 20th	Day	33% 6% 11% 24% 23% 2	2204
	21st to end	Day	40% 7% 13% 21% 17% 3	2090
October	1st to 10th	Day	38% 7% 10% 19% 23% 3	3268
	11th to 20th	Day	31% 6% 10% 28% 23% 3	3140
	21st to end	Day	32% 6% 15% 25% 18% 4	3148
November	1st to 10th	Day	36% 5% 14% 26% 17% 2	1761
	11th to 20th	Day	40% 7% 11% 22% 18% 2	1800
	21st to end	Day	44% 6% 14% 26% 8% 2	1661
December	1st to 10th	Day	51% 7% 14% 17% 10% 1	1600
	11th to 20th	Day	44% 6% 16% 22% 10% 2	1986
	21st to end	Day	53% 7% 14% 18% 7%	2796
January	1st to 10th	Night	41% 6% 15% 25% 11% 3	4429
	11th to 20th	Night	47% 6% 14% 20% 10% 2	4440
	21st to end	Night	52% 7% 12% 19% 9% 1	4694
February	1st to 10th	Night	45% 7% 15% 21% 11% 1	2470
	11th to 20th	Night	44% 7% 12% 18% 16% 4	2242
	21st to end	Night	45% 5% 11% 22% 13% 4	1884
March	1st to 10th	Night	49% 7% 12% 20% 11% 2	3734
	11th to 20th	Night	39% 8% 16% 24% 11% 2	3618
	21st to end	Night	44% 6% 8% 15% 22% 5%	3501
April	1st to 10th	Night	48% 7% 11% 19% 13% 2	1900
	11th to 20th	Night	44% 7% 11% 18% 19% 1	1875
	21st to end	Night	44% 6% 10% 20% 16% 3	1853
May	1st to 10th	Night	51% 7% 12% 18% 11% 2	2812
	11th to 20th	Night	50% 9% 13% 18% 9% 2	2496
	21st to end	Night	37% 9% 17% 23% 12% 2	2739
June	1st to 10th	Night	40% 7% 12% 23% 17% 1	1520
	11th to 20th	Night	37% 9% 19% 25% 10% 1	1520
	21st to end	Night	33% 9% 16% 26% 14% 1	1520
July	1st to 10th	Night	37% 10% 17% 20% 14% 2	2480
	11th to 20th	Night	38% 8% 16% 24% 13% 1	2472
	21st to end	Night	42% 8% 14% 18% 16% 2	2651
August	1st to 10th	Night	47% 10% 16% 19% 9% 1	2609
	11th to 20th	Night	41% 8% 16% 26% 10%	3118
	21st to end	Night	32% 7% 13% 33% 15% 1	3476
September	1st to 10th	Night	38% 7% 12% 24% 17% 1	1900
	11th to 20th	Night	31% 6% 12% 25% 24% 2	1976
	21st to end	Night	39% 6% 11% 22% 21% 1	2090
October	1st to 10th	Night	42% 7% 11% 21% 18% 1	3690
	11th to 20th	Night	29% 4 10% 29% 26% 2	3779
	21st to end	Night	33% 6% 14% 30% 16% 2	4399
November	1st to 10th	Night	37% 6% 12% 23% 19% 3	2537
	11th to 20th	Night	43% 5% 12% 21% 17% 3	2600
	21st to end	Night	40% 6% 16% 27% 10% 1	2735
December	1st to 10th	Night	46% 7% 14% 23% 10% 1	2800
	11th to 20th	Night	47% 6% 15% 17% 13% 2	3428
	21st to end	Night	50% 6% 15% 19% 8%	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	23% 21% 27% 19% 9%	180
	11th to 20th	Day	27% 21% 36% 14% 3 1	180
	21st to end	Day	19% 18% 39% 19% 5%	249
February	1st to 10th	Day	28% 23% 31% 16% 2	270
	11th to 20th	Day	22% 23% 37% 16% 2	432
	21st to end	Day	28% 16% 34% 18% 4	382
March	1st to 10th	Day	22% 17% 33% 22% 6%	460
	11th to 20th	Day	22% 24% 31% 18% 4 1	460
	21st to end	Day	27% 17% 30% 19% 5% 2	506
April	1st to 10th	Day	28% 17% 29% 17% 7% 3	460
	11th to 20th	Day	23% 22% 29% 15% 8% 3	452
	21st to end	Day	28% 15% 29% 18% 7% 3	460
May	1st to 10th	Day	30% 15% 27% 19% 8% 2	463
	11th to 20th	Day	17% 12% 33% 25% 10% 2	487
	21st to end	Day	18% 8% 24% 31% 15% 4	529
June	1st to 10th	Day	17% 12% 26% 28% 14% 3	490
	11th to 20th	Day	15% 10% 27% 31% 14% 2	490
	21st to end	Day	17% 12% 26% 27% 16% 3	490
July	1st to 10th	Day	13% 4 26% 33% 19% 4	485
	11th to 20th	Day	11% 5% 26% 35% 17% 5%	484
	21st to end	Day	13% 8% 26% 34% 16% 4	532
August	1st to 10th	Day	13% 7% 22% 35% 17% 7%	486
	11th to 20th	Day	14% 6% 20% 31% 21% 7%	479
	21st to end	Day	10% 8% 23% 32% 19% 9%	539
September	1st to 10th	Day	18% 10% 19% 27% 17% 9%	490
	11th to 20th	Day	14% 7% 26% 22% 19% 13%	490
	21st to end	Day	21% 8% 24% 28% 14% 6%	490
October	1st to 10th	Day	26% 9% 21% 23% 17% 4	490
	11th to 20th	Day	15% 15% 28% 27% 12% 3	490
	21st to end	Day	24% 12% 28% 26% 9% 1	451
November	1st to 10th	Day	17% 11% 29% 29% 10% 3	395
	11th to 20th	Day	22% 16% 30% 24% 7% 1	400
	21st to end	Day	21% 14% 33% 26% 5% 1	261
December	1st to 10th	Day	20% 26% 30% 17% 9%	200
	11th to 20th	Day	28% 20% 29% 20% 4	200
	21st to end	Day	21% 13% 38% 24% 3 1	204
January	1st to 10th	Night	18% 13% 37% 28% 3	760
	11th to 20th	Night	22% 13% 33% 28% 4	760
	21st to end	Night	17% 12% 38% 30% 3	836
February	1st to 10th	Night	20% 13% 36% 29% 2	760
	11th to 20th	Night	19% 16% 39% 25% 1	743
	21st to end	Night	23% 14% 36% 23% 4	628
March	1st to 10th	Night	22% 12% 35% 27% 4	760
	11th to 20th	Night	20% 15% 36% 25% 5%	760
	21st to end	Night	19% 16% 36% 23% 6%	836
April	1st to 10th	Night	24% 15% 34% 23% 5%	760
	11th to 20th	Night	21% 12% 34% 26% 7%	751
	21st to end	Night	24% 13% 28% 28% 7%	713
May	1st to 10th	Night	24% 12% 28% 27% 8%	555
	11th to 20th	Night	19% 7% 31% 37% 6%	374
	21st to end	Night	15% 7% 19% 39% 18% 1	411
June	1st to 10th	Night	16% 5% 22% 41% 15% 1	380
	11th to 20th	Night	15% 4 22% 42% 16% 1	380
	21st to end	Night	13% 4 19% 47% 16% 1	380
July	1st to 10th	Night	14% 3 15% 46% 21% 1	370
	11th to 20th	Night	11% 4 16% 47% 20% 1	368
	21st to end	Night	12% 5% 15% 47% 19% 1	416
August	1st to 10th	Night	13% 3 12% 46% 23% 3	439
	11th to 20th	Night	13% 4 16% 38% 26% 3	741
	21st to end	Night	15% 4 15% 39% 25% 2	836
September	1st to 10th	Night	16% 3 21% 37% 20% 3	760
	11th to 20th	Night	15% 4 20% 32% 24% 5%	760
	21st to end	Night	18% 6% 21% 36% 18% 2	760
October	1st to 10th	Night	23% 8% 23% 28% 16% 2	760
	11th to 20th	Night	19% 8% 26% 37% 10% 1	760
	21st to end	Night	27% 8% 28% 30% 7%	836
November	1st to 10th	Night	15% 9% 31% 34% 10% 1	780
	11th to 20th	Night	22% 11% 32% 27% 7% 1	800
	21st to end	Night	20% 11% 33% 30% 6% 1	800
December	1st to 10th	Night	23% 13% 33% 25% 6%	800
	11th to 20th	Night	25% 10% 31% 30% 4	800
	21st to end	Night	23% 10% 35% 28% 3	851

Page generated at 2024-12-21 04:13:52. Version ac07

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