Getzville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Getzville clear sky chart from 2005-11-06 to 2025-11-03.

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% 11% 4 9% 5% 5% 4 4 5% 7% 30%	126983
	Night	17% 12% 4 9% 6% 5% 4 3 5% 6% 29%	123031
Transparency	Day	54% 4 12% 19% 10% 1	130576
	Night	56% 4 11% 18% 10% 1	127525
Seeing	Day	23% 18% 29% 19% 9% 3	15804
	Night	23% 16% 28% 23% 9% 1	25150

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% 22% 8% 18% 9% 5% 4 3 3 4 11%	3597
	11th to 20th	Day	12% 22% 9% 21% 10% 5% 4 2 3 4 9%	3888
	21st to end	Day	19% 16% 7% 16% 8% 8% 6% 3 4 3 10%	4466
February	1st to 10th	Day	17% 19% 5% 14% 9% 6% 5% 3 4 4 13%	1800
	11th to 20th	Day	14% 17% 7% 17% 9% 6% 4 3 4 5% 15%	1753
	21st to end	Day	20% 16% 4 13% 7% 6% 5% 4 4 4 17%	1556
March	1st to 10th	Day	17% 14% 6% 11% 6% 5% 4 2 3 5% 27%	4932
	11th to 20th	Day	10% 17% 4 8% 5% 6% 5% 3 5% 6% 30%	4980
	21st to end	Day	20% 13% 4 9% 5% 4 4 3 4 5% 28%	5465
April	1st to 10th	Day	18% 14% 4 8% 6% 4 4 3 4 5% 29%	2388
	11th to 20th	Day	18% 12% 3 8% 4 4 3 3 4 6% 34%	2384
	21st to end	Day	20% 11% 3 7% 4 4 4 3 4 6% 34%	2600
May	1st to 10th	Day	23% 10% 3 8% 5% 5% 4 4 4 6% 29%	5888
	11th to 20th	Day	17% 10% 3 8% 5% 5% 5% 3 6% 7% 30%	6314
	21st to end	Day	20% 8% 2 6% 4 4 4 4 6% 7% 35%	6949
June	1st to 10th	Day	17% 6% 2 6% 5% 4 5% 4 7% 7% 38%	2800
	11th to 20th	Day	13% 6% 2 8% 5% 5% 5% 4 7% 9% 37%	2800
	21st to end	Day	14% 6% 1 6% 4 4 4 4 7% 9% 41%	2800
July	1st to 10th	Day	10% 5% 2 6% 5% 4 5% 4 7% 9% 44%	6360
	11th to 20th	Day	11% 6% 2 7% 5% 4 5% 4 7% 9% 39%	6360
	21st to end	Day	10% 5% 2 6% 4 5% 4 4 7% 9% 46%	6515
August	1st to 10th	Day	18% 6% 2 5% 4 4 4 4 7% 9% 37%	4234
	11th to 20th	Day	14% 5% 3 7% 5% 5% 5% 5% 8% 9% 33%	4174
	21st to end	Day	13% 5% 2 5% 4 4 4 4 7% 9% 44%	4418
September	1st to 10th	Day	14% 7% 2 6% 3 4 4 4 6% 7% 42%	2400
	11th to 20th	Day	12% 4 2 5% 4 5% 5% 4 6% 8% 45%	2328
	21st to end	Day	16% 7% 3 8% 5% 5% 5% 4 7% 8% 32%	2130
October	1st to 10th	Day	20% 6% 2 6% 5% 4 5% 4 5% 7% 35%	2000
	11th to 20th	Day	20% 10% 4 9% 4 4 5% 4 5% 7% 28%	2000
	21st to end	Day	26% 13% 4 10% 5% 5% 4 3 4 5% 23%	2200
November	1st to 10th	Day	15% 11% 3 10% 6% 5% 5% 4 5% 6% 31%	1758
	11th to 20th	Day	14% 15% 4 10% 6% 4 5% 4 5% 6% 27%	1600
	21st to end	Day	19% 19% 4 9% 7% 5% 4 3 4 6% 20%	1600
December	1st to 10th	Day	20% 20% 5% 12% 6% 5% 5% 4 5% 5% 12%	2600
	11th to 20th	Day	22% 19% 5% 10% 5% 4 4 3 4 4 19%	2986
	21st to end	Day	23% 21% 6% 12% 7% 5% 4 3 4 4 11%	3960
January	1st to 10th	Night	16% 18% 6% 16% 7% 6% 5% 3 4 4 15%	6349
	11th to 20th	Night	11% 19% 8% 20% 11% 7% 4 3 4 4 10%	5979
	21st to end	Night	19% 19% 7% 17% 7% 6% 5% 3 4 4 10%	6490
February	1st to 10th	Night	18% 19% 6% 12% 7% 5% 4 3 5% 5% 18%	2600
	11th to 20th	Night	15% 16% 6% 12% 7% 5% 6% 4 5% 5% 20%	2533
	21st to end	Night	17% 16% 5% 14% 6% 5% 5% 3 4 6% 18%	2070
March	1st to 10th	Night	18% 12% 5% 9% 7% 4 4 3 3 5% 28%	4908
	11th to 20th	Night	15% 13% 3 7% 4 4 4 4 5% 7% 33%	4979
	21st to end	Night	19% 10% 4 7% 5% 4 4 4 5% 5% 33%	5467
April	1st to 10th	Night	20% 12% 4 9% 5% 4 4 3 5% 5% 29%	2010
	11th to 20th	Night	18% 10% 2 7% 5% 4 4 4 5% 6% 34%	1975
	21st to end	Night	18% 9% 3 7% 5% 4 5% 4 5% 6% 35%	1805
May	1st to 10th	Night	26% 11% 3 7% 4 3 3 3 4 5% 29%	4053
	11th to 20th	Night	13% 8% 3 8% 5% 5% 6% 4 6% 8% 35%	3575
	21st to end	Night	19% 7% 3 7% 5% 3 4 4 5% 7% 36%	3926
June	1st to 10th	Night	12% 7% 3 7% 5% 6% 6% 5% 6% 7% 36%	1600
	11th to 20th	Night	12% 6% 2 6% 6% 5% 5% 4 6% 7% 41%	1600
	21st to end	Night	14% 6% 2 6% 5% 4 4 4 5% 9% 40%	1600
July	1st to 10th	Night	10% 6% 2 7% 5% 5% 4 4 6% 9% 43%	3600
	11th to 20th	Night	11% 5% 2 6% 5% 5% 4 4 5% 8% 44%	3600
	21st to end	Night	10% 5% 2 5% 4 4 5% 3 6% 7% 49%	4333
August	1st to 10th	Night	10% 7% 2 7% 5% 4 5% 3 7% 9% 41%	2915
	11th to 20th	Night	15% 7% 3 6% 4 5% 5% 4 5% 9% 38%	2875
	21st to end	Night	9% 5% 2 6% 4 5% 5% 4 7% 9% 45%	3446
September	1st to 10th	Night	12% 7% 2 5% 4 4 4 3 5% 8% 45%	2000
	11th to 20th	Night	12% 5% 1 5% 3 3 3 3 5% 7% 52%	2070
	21st to end	Night	17% 7% 3 6% 4 4 5% 4 6% 8% 36%	2270
October	1st to 10th	Night	17% 6% 3 7% 5% 4 4 3 6% 6% 40%	2400
	11th to 20th	Night	20% 11% 3 8% 5% 4 4 3 4 6% 31%	2400
	21st to end	Night	26% 10% 3 7% 4 5% 4 4 5% 5% 28%	2640
November	1st to 10th	Night	16% 11% 3 7% 5% 3 3 3 5% 6% 37%	2579
	11th to 20th	Night	16% 12% 4 9% 6% 5% 5% 3 5% 7% 28%	2800
	21st to end	Night	18% 16% 5% 9% 6% 5% 5% 5% 6% 5% 22%	2800
December	1st to 10th	Night	18% 21% 8% 12% 6% 6% 4 3 5% 5% 13%	4580
	11th to 20th	Night	20% 22% 5% 10% 6% 4 4 3 3 4 19%	5208
	21st to end	Night	25% 17% 6% 11% 6% 5% 4 3 4 4 13%	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	80% 3 6% 8% 3	3598
	11th to 20th	Day	82% 3 6% 5% 4 1	3922
	21st to end	Day	80% 2 11% 4 3	4466
February	1st to 10th	Day	74% 5% 9% 10% 2	1800
	11th to 20th	Day	73% 4 8% 13% 2	1762
	21st to end	Day	69% 4 11% 10% 5%	1556
March	1st to 10th	Day	61% 2 13% 16% 8%	4935
	11th to 20th	Day	53% 3 20% 16% 7% 1	4980
	21st to end	Day	59% 4 6% 22% 8% 1	5465
April	1st to 10th	Day	57% 4 11% 18% 9% 1	2388
	11th to 20th	Day	52% 4 10% 20% 13% 2	2384
	21st to end	Day	53% 4 10% 19% 13% 2	2600
May	1st to 10th	Day	57% 4 10% 16% 10% 4	5897
	11th to 20th	Day	53% 4 10% 19% 12% 1	6318
	21st to end	Day	49% 3 12% 23% 12% 2	6949
June	1st to 10th	Day	44% 6% 13% 20% 16% 2	2800
	11th to 20th	Day	42% 6% 15% 23% 13% 1	2800
	21st to end	Day	40% 5% 14% 25% 15% 1	2800
July	1st to 10th	Day	38% 3 13% 28% 17% 1	6290
	11th to 20th	Day	42% 3 13% 27% 15% 1	6285
	21st to end	Day	35% 4 16% 27% 18% 1	6329
August	1st to 10th	Day	44% 5% 14% 23% 13% 1	4221
	11th to 20th	Day	45% 5% 15% 25% 9% 1	4213
	21st to end	Day	37% 4 12% 35% 12% 1	4418
September	1st to 10th	Day	40% 6% 13% 27% 12% 1	2400
	11th to 20th	Day	36% 5% 14% 31% 14% 1	2328
	21st to end	Day	49% 5% 14% 22% 9% 1	2130
October	1st to 10th	Day	41% 3 13% 27% 15% 1	3260
	11th to 20th	Day	47% 3 16% 21% 12% 1	3240
	21st to end	Day	53% 2 14% 23% 8% 1	3538
November	1st to 10th	Day	53% 6% 11% 20% 9% 1	1758
	11th to 20th	Day	57% 6% 15% 15% 7% 1	1600
	21st to end	Day	66% 5% 13% 12% 4	1600
December	1st to 10th	Day	73% 3 16% 7% 1	2600
	11th to 20th	Day	70% 3 10% 10% 7%	2986
	21st to end	Day	79% 2 9% 7% 3	3960
January	1st to 10th	Night	73% 3 8% 12% 3	6349
	11th to 20th	Night	79% 5% 6% 6% 4	6020
	21st to end	Night	80% 2 8% 6% 4	6490
February	1st to 10th	Night	71% 5% 9% 12% 4	2600
	11th to 20th	Night	66% 5% 11% 14% 4	2535
	21st to end	Night	68% 4 10% 12% 6%	2070
March	1st to 10th	Night	61% 2 11% 17% 9% 1	4918
	11th to 20th	Night	51% 3 15% 20% 8% 2	4980
	21st to end	Night	53% 4 7% 21% 13% 1	5467
April	1st to 10th	Night	58% 4 8% 18% 10% 1	2010
	11th to 20th	Night	50% 5% 10% 19% 14% 2	1975
	21st to end	Night	49% 5% 10% 20% 14% 2	1805
May	1st to 10th	Night	59% 4 8% 14% 11% 5%	4060
	11th to 20th	Night	48% 5% 14% 21% 12% 1	3576
	21st to end	Night	48% 4 10% 21% 15% 2	3927
June	1st to 10th	Night	45% 6% 10% 22% 16% 2	1600
	11th to 20th	Night	40% 6% 13% 22% 18% 2	1600
	21st to end	Night	42% 5% 13% 22% 16% 2	1600
July	1st to 10th	Night	39% 3 12% 25% 19% 2	3560
	11th to 20th	Night	39% 3 13% 29% 15% 1	3552
	21st to end	Night	35% 3 14% 24% 22% 1	4205
August	1st to 10th	Night	40% 4 15% 27% 13% 2	2904
	11th to 20th	Night	45% 4 14% 27% 10%	2902
	21st to end	Night	36% 3 13% 33% 14% 1	3446
September	1st to 10th	Night	38% 5% 14% 28% 14% 1	2000
	11th to 20th	Night	33% 4 12% 33% 18% 1	2070
	21st to end	Night	46% 6% 13% 22% 13% 1	2270
October	1st to 10th	Night	44% 3 7% 26% 19% 1	3920
	11th to 20th	Night	50% 3 12% 21% 13% 1	3899
	21st to end	Night	48% 3 15% 25% 9% 1	4252
November	1st to 10th	Night	48% 6% 10% 23% 11% 2	2579
	11th to 20th	Night	57% 5% 13% 17% 8% 1	2800
	21st to end	Night	62% 6% 14% 15% 3	2800
December	1st to 10th	Night	74% 3 13% 8% 2	4580
	11th to 20th	Night	70% 3 7% 11% 8% 1	5208
	21st to end	Night	75% 3 10% 9% 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	30% 32% 24% 10% 5% 1	200
	11th to 20th	Day	28% 32% 26% 11% 1 1	270
	21st to end	Day	26% 28% 28% 14% 3	330
February	1st to 10th	Day	33% 32% 27% 6% 1	300
	11th to 20th	Day	32% 36% 24% 6% 2	300
	21st to end	Day	40% 23% 27% 8% 2	312
March	1st to 10th	Day	28% 23% 32% 14% 3	500
	11th to 20th	Day	31% 20% 33% 12% 3 1	500
	21st to end	Day	31% 23% 26% 15% 4 1	550
April	1st to 10th	Day	27% 24% 30% 13% 4 1	500
	11th to 20th	Day	33% 21% 23% 15% 6% 2	492
	21st to end	Day	27% 22% 30% 13% 7% 1	500
May	1st to 10th	Day	27% 17% 30% 16% 7% 4	503
	11th to 20th	Day	21% 14% 30% 22% 9% 3	527
	21st to end	Day	18% 15% 32% 21% 10% 4	573
June	1st to 10th	Day	20% 19% 35% 19% 6% 1	530
	11th to 20th	Day	14% 17% 32% 24% 11% 2	530
	21st to end	Day	20% 14% 33% 23% 8% 2	530
July	1st to 10th	Day	12% 8% 30% 31% 17% 3	525
	11th to 20th	Day	15% 10% 30% 25% 16% 4	524
	21st to end	Day	12% 10% 33% 30% 11% 4	576
August	1st to 10th	Day	15% 8% 25% 30% 15% 7%	526
	11th to 20th	Day	13% 7% 29% 27% 17% 7%	519
	21st to end	Day	14% 10% 30% 25% 14% 8%	583
September	1st to 10th	Day	15% 12% 25% 25% 16% 7%	530
	11th to 20th	Day	11% 8% 21% 26% 23% 11%	530
	21st to end	Day	18% 16% 28% 21% 12% 5%	530
October	1st to 10th	Day	22% 15% 26% 21% 12% 5%	530
	11th to 20th	Day	25% 23% 28% 17% 4 2	530
	21st to end	Day	35% 19% 27% 14% 5%	583
November	1st to 10th	Day	26% 23% 29% 15% 6% 1	351
	11th to 20th	Day	31% 28% 27% 9% 4 2	200
	21st to end	Day	32% 29% 30% 9% 1	200
December	1st to 10th	Day	30% 27% 31% 9% 4 1	200
	11th to 20th	Day	33% 29% 26% 12% 2	200
	21st to end	Day	32% 34% 22% 8% 2 1	220
January	1st to 10th	Night	31% 24% 30% 11% 4	800
	11th to 20th	Night	32% 25% 26% 14% 2	800
	21st to end	Night	25% 23% 32% 16% 4	880
February	1st to 10th	Night	29% 29% 27% 13% 2	800
	11th to 20th	Night	26% 27% 29% 16% 3	783
	21st to end	Night	29% 24% 30% 16% 2	660
March	1st to 10th	Night	25% 19% 33% 18% 4	800
	11th to 20th	Night	27% 19% 31% 19% 4 1	800
	21st to end	Night	24% 16% 31% 21% 7% 1	880
April	1st to 10th	Night	27% 19% 31% 20% 3	800
	11th to 20th	Night	26% 16% 31% 20% 7% 1	791
	21st to end	Night	23% 12% 33% 25% 8%	605
May	1st to 10th	Night	22% 11% 26% 28% 11% 2	600
	11th to 20th	Night	15% 10% 33% 35% 6% 1	394
	21st to end	Night	15% 10% 27% 33% 14% 1	433
June	1st to 10th	Night	13% 8% 36% 34% 10%	400
	11th to 20th	Night	14% 9% 32% 34% 12%	400
	21st to end	Night	15% 8% 33% 37% 7%	400
July	1st to 10th	Night	10% 6% 26% 40% 17% 1	390
	11th to 20th	Night	11% 7% 29% 34% 18% 2	388
	21st to end	Night	13% 3 27% 38% 17% 2	614
August	1st to 10th	Night	10% 5% 20% 43% 21% 2	597
	11th to 20th	Night	10% 5% 22% 35% 25% 2	594
	21st to end	Night	13% 5% 25% 34% 21% 2	792
September	1st to 10th	Night	15% 8% 25% 32% 18% 2	800
	11th to 20th	Night	14% 6% 19% 30% 26% 4	800
	21st to end	Night	20% 11% 24% 28% 14% 4	800
October	1st to 10th	Night	18% 10% 29% 25% 16% 2	800
	11th to 20th	Night	26% 17% 27% 22% 6% 1	800
	21st to end	Night	33% 14% 29% 21% 3	880
November	1st to 10th	Night	24% 16% 30% 22% 8% 1	789
	11th to 20th	Night	23% 21% 31% 16% 8% 1	800
	21st to end	Night	28% 24% 28% 16% 5%	800
December	1st to 10th	Night	34% 24% 24% 14% 4 1	800
	11th to 20th	Night	28% 29% 26% 14% 3	800
	21st to end	Night	35% 20% 28% 14% 3	880

Page generated at 2025-10-31 02:02:38. Version ac07

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