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 2024-11-08.

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 8% 5% 5% 4 4 6% 7% 31%	101483
	Night	17% 12% 4 9% 5% 4 4 3 5% 6% 30%	97617
Transparency	Day	52% 4 13% 20% 10% 1	105087
	Night	55% 4 11% 19% 10% 1	102102
Seeing	Day	23% 18% 28% 19% 9% 3	14541
	Night	23% 16% 28% 23% 9% 1	23911

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	17% 22% 8% 12% 6% 5% 5% 3 3 4 14%	2517
	11th to 20th	Day	12% 22% 8% 22% 11% 4 3 2 3 3 9%	2744
	21st to end	Day	22% 20% 8% 12% 7% 6% 5% 3 4 3 10%	3124
February	1st to 10th	Day	17% 20% 5% 14% 8% 6% 5% 3 4 4 14%	1710
	11th to 20th	Day	13% 17% 7% 17% 8% 6% 4 3 4 5% 16%	1663
	21st to end	Day	20% 16% 4 13% 7% 6% 5% 4 4 5% 17%	1480
March	1st to 10th	Day	19% 13% 5% 10% 5% 5% 4 3 3 5% 28%	3432
	11th to 20th	Day	10% 21% 4 8% 5% 6% 5% 3 5% 5% 27%	3480
	21st to end	Day	17% 12% 4 9% 5% 4 5% 3 5% 6% 30%	3815
April	1st to 10th	Day	18% 14% 4 8% 6% 4 4 3 4 5% 30%	2268
	11th to 20th	Day	19% 11% 3 8% 4 4 3 4 4 5% 34%	2263
	21st to end	Day	20% 11% 3 7% 4 4 4 3 4 6% 33%	2470
May	1st to 10th	Day	20% 9% 2 7% 5% 5% 4 4 5% 6% 32%	4108
	11th to 20th	Day	15% 10% 3 8% 6% 5% 5% 4 7% 8% 29%	4394
	21st to end	Day	12% 7% 2 5% 4 4 4 4 6% 8% 45%	4837
June	1st to 10th	Day	17% 6% 2 6% 5% 4 5% 4 7% 7% 37%	2660
	11th to 20th	Day	13% 5% 2 7% 5% 5% 5% 4 7% 9% 38%	2660
	21st to end	Day	15% 6% 1 6% 4 4 4 3 7% 9% 41%	2660
July	1st to 10th	Day	9% 5% 2 5% 5% 5% 5% 4 7% 9% 45%	4440
	11th to 20th	Day	12% 6% 2 6% 4 4 5% 4 8% 9% 39%	4440
	21st to end	Day	8% 5% 2 6% 5% 5% 5% 5% 8% 10% 41%	4529
August	1st to 10th	Day	18% 6% 2 6% 4 4 4 4 7% 9% 36%	4104
	11th to 20th	Day	14% 5% 3 7% 5% 6% 5% 5% 8% 9% 33%	4044
	21st to end	Day	13% 5% 2 5% 4 4 4 3 7% 9% 44%	4283
September	1st to 10th	Day	14% 7% 2 6% 4 4 4 4 6% 7% 41%	2280
	11th to 20th	Day	13% 4 2 5% 4 5% 5% 4 6% 8% 44%	2212
	21st to end	Day	16% 7% 3 8% 5% 5% 5% 4 7% 8% 32%	2024
October	1st to 10th	Day	21% 6% 3 7% 5% 4 5% 4 6% 7% 33%	1900
	11th to 20th	Day	20% 10% 4 9% 4 4 4 4 5% 6% 28%	1900
	21st to end	Day	26% 13% 4 10% 5% 5% 4 3 4 5% 22%	2090
November	1st to 10th	Day	15% 12% 3 10% 6% 5% 5% 3 5% 6% 31%	1714
	11th to 20th	Day	15% 15% 4 10% 5% 4 4 4 5% 6% 27%	1520
	21st to end	Day	19% 19% 5% 9% 7% 4 4 3 4 6% 20%	1520
December	1st to 10th	Day	19% 21% 6% 12% 5% 5% 5% 4 4 5% 14%	1520
	11th to 20th	Day	20% 20% 7% 13% 6% 4 4 3 4 5% 14%	1906
	21st to end	Day	27% 24% 6% 11% 5% 4 3 2 3 3 11%	2772
January	1st to 10th	Night	19% 21% 6% 11% 7% 5% 4 3 4 4 16%	4429
	11th to 20th	Night	14% 20% 8% 17% 10% 6% 4 3 4 4 10%	4212
	21st to end	Night	24% 21% 7% 14% 8% 5% 4 2 3 3 10%	4532
February	1st to 10th	Night	18% 19% 6% 12% 7% 5% 4 3 5% 5% 18%	2470
	11th to 20th	Night	15% 16% 6% 12% 7% 5% 6% 4 5% 5% 20%	2403
	21st to end	Night	18% 16% 5% 13% 6% 5% 5% 3 4 6% 19%	1970
March	1st to 10th	Night	21% 13% 4 9% 5% 4 4 3 3 4 31%	3408
	11th to 20th	Night	19% 17% 4 8% 5% 4 4 4 5% 6% 26%	3479
	21st to end	Night	16% 9% 3 6% 4 4 3 3 5% 6% 39%	3817
April	1st to 10th	Night	20% 13% 4 8% 5% 4 3 3 5% 5% 30%	1910
	11th to 20th	Night	18% 9% 2 8% 5% 4 4 3 5% 6% 34%	1875
	21st to end	Night	18% 9% 3 7% 5% 4 5% 4 5% 6% 35%	1715
May	1st to 10th	Night	23% 10% 3 7% 5% 4 3 3 5% 6% 32%	2833
	11th to 20th	Night	13% 8% 3 8% 5% 6% 6% 4 6% 8% 33%	2495
	21st to end	Night	13% 5% 2 6% 5% 3 4 4 6% 8% 44%	2738
June	1st to 10th	Night	12% 7% 3 6% 5% 6% 6% 5% 7% 7% 35%	1520
	11th to 20th	Night	11% 5% 2 6% 6% 5% 5% 4 6% 7% 42%	1520
	21st to end	Night	14% 6% 2 6% 5% 4 4 4 5% 8% 40%	1520
July	1st to 10th	Night	9% 6% 2 7% 5% 5% 4 4 6% 9% 43%	2520
	11th to 20th	Night	12% 5% 3 5% 4 4 4 4 5% 8% 45%	2520
	21st to end	Night	11% 4 2 6% 4 5% 5% 4 6% 7% 47%	3020
August	1st to 10th	Night	11% 7% 2 6% 5% 4 5% 3 6% 9% 41%	2825
	11th to 20th	Night	15% 7% 3 7% 4 4 5% 4 5% 8% 38%	2785
	21st to end	Night	9% 5% 2 6% 4 5% 5% 4 7% 9% 45%	3340
September	1st to 10th	Night	13% 7% 3 5% 4 4 4 3 5% 7% 45%	1900
	11th to 20th	Night	12% 5% 1 5% 3 4 3 3 5% 7% 50%	1966
	21st to end	Night	17% 7% 3 6% 4 4 5% 4 6% 8% 36%	2156
October	1st to 10th	Night	17% 7% 3 7% 5% 4 4 3 6% 6% 38%	2280
	11th to 20th	Night	21% 11% 3 8% 5% 4 4 3 4 6% 31%	2280
	21st to end	Night	27% 10% 3 7% 4 5% 4 4 5% 5% 26%	2508
November	1st to 10th	Night	16% 11% 3 8% 5% 3 3 3 5% 6% 37%	2519
	11th to 20th	Night	15% 12% 4 9% 6% 5% 5% 3 5% 7% 29%	2660
	21st to end	Night	18% 15% 5% 9% 5% 5% 5% 5% 6% 5% 22%	2660
December	1st to 10th	Night	21% 20% 6% 10% 6% 5% 4 4 4 5% 15%	2660
	11th to 20th	Night	17% 22% 6% 11% 6% 5% 4 3 4 4 18%	3288
	21st to end	Night	30% 17% 5% 10% 5% 5% 5% 3 4 5% 11%	4884

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	76% 4 7% 9% 3	2518
	11th to 20th	Day	83% 4 6% 5% 2	2744
	21st to end	Day	80% 3 12% 4 1	3124
February	1st to 10th	Day	74% 5% 9% 10% 1	1710
	11th to 20th	Day	72% 4 8% 13% 3	1672
	21st to end	Day	69% 5% 11% 10% 5%	1480
March	1st to 10th	Day	58% 4 11% 21% 6%	3435
	11th to 20th	Day	56% 4 19% 14% 6% 1	3480
	21st to end	Day	55% 6% 8% 23% 7% 1	3815
April	1st to 10th	Day	56% 4 11% 18% 9% 1	2268
	11th to 20th	Day	52% 4 10% 20% 13% 2	2263
	21st to end	Day	53% 4 9% 18% 12% 2	2470
May	1st to 10th	Day	52% 5% 11% 19% 12% 2	4120
	11th to 20th	Day	52% 5% 14% 20% 7% 1	4398
	21st to end	Day	37% 4 13% 27% 15% 3	4837
June	1st to 10th	Day	43% 6% 13% 20% 15% 2	2660
	11th to 20th	Day	41% 6% 15% 24% 14% 1	2660
	21st to end	Day	40% 5% 14% 25% 14% 1	2660
July	1st to 10th	Day	36% 4 13% 28% 18% 2	4370
	11th to 20th	Day	40% 4 13% 28% 14%	4365
	21st to end	Day	37% 5% 19% 22% 16% 1	4385
August	1st to 10th	Day	45% 5% 14% 23% 13% 1	4091
	11th to 20th	Day	45% 5% 16% 25% 9% 1	4083
	21st to end	Day	37% 4 12% 34% 12% 1	4283
September	1st to 10th	Day	41% 7% 13% 26% 12% 1	2280
	11th to 20th	Day	37% 5% 14% 29% 15% 1	2212
	21st to end	Day	49% 6% 14% 22% 9% 1	2024
October	1st to 10th	Day	42% 3 13% 27% 14% 1	3160
	11th to 20th	Day	47% 3 16% 21% 12% 1	3140
	21st to end	Day	53% 2 15% 23% 7%	3428
November	1st to 10th	Day	53% 6% 12% 19% 9% 1	1714
	11th to 20th	Day	57% 6% 16% 14% 6% 1	1520
	21st to end	Day	66% 5% 13% 12% 4	1520
December	1st to 10th	Day	72% 4 13% 9% 1	1520
	11th to 20th	Day	73% 5% 11% 9% 2	1906
	21st to end	Day	80% 3 10% 6% 1	2772
January	1st to 10th	Night	74% 4 11% 8% 3	4429
	11th to 20th	Night	79% 7% 7% 6% 2	4212
	21st to end	Night	81% 3 8% 6% 2	4532
February	1st to 10th	Night	71% 6% 8% 12% 3	2470
	11th to 20th	Night	66% 5% 11% 14% 4	2405
	21st to end	Night	67% 4 10% 13% 6%	1970
March	1st to 10th	Night	58% 3 11% 22% 6%	3418
	11th to 20th	Night	59% 4 13% 15% 7% 1	3480
	21st to end	Night	45% 5% 8% 25% 15% 1	3817
April	1st to 10th	Night	57% 5% 8% 19% 11% 1	1910
	11th to 20th	Night	50% 5% 10% 19% 14% 2	1875
	21st to end	Night	49% 5% 10% 19% 14% 2	1715
May	1st to 10th	Night	53% 5% 10% 18% 11% 3	2840
	11th to 20th	Night	48% 6% 16% 21% 8% 1	2496
	21st to end	Night	37% 5% 12% 24% 20% 2	2739
June	1st to 10th	Night	45% 7% 10% 22% 16% 1	1520
	11th to 20th	Night	39% 6% 12% 23% 19% 2	1520
	21st to end	Night	42% 6% 13% 23% 15% 2	1520
July	1st to 10th	Night	40% 4 11% 24% 19% 3	2480
	11th to 20th	Night	38% 3 14% 30% 13% 1	2472
	21st to end	Night	36% 5% 16% 24% 17% 2	2924
August	1st to 10th	Night	40% 4 15% 27% 13% 1	2814
	11th to 20th	Night	45% 4 14% 27% 10%	2812
	21st to end	Night	36% 4 12% 33% 14% 1	3340
September	1st to 10th	Night	38% 5% 14% 27% 15% 2	1900
	11th to 20th	Night	34% 4 12% 30% 19% 1	1966
	21st to end	Night	46% 6% 13% 22% 13% 1	2156
October	1st to 10th	Night	44% 3 8% 26% 18% 1	3800
	11th to 20th	Night	50% 3 13% 21% 13% 1	3779
	21st to end	Night	48% 3 16% 25% 8% 1	4120
November	1st to 10th	Night	48% 6% 10% 23% 11% 2	2519
	11th to 20th	Night	56% 5% 13% 17% 8% 1	2660
	21st to end	Night	62% 7% 14% 15% 3	2660
December	1st to 10th	Night	71% 5% 12% 10% 2	2660
	11th to 20th	Night	71% 5% 10% 11% 3	3288
	21st to end	Night	77% 3 11% 7% 1	4884

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	29% 32% 23% 10% 5% 1	180
	11th to 20th	Day	28% 32% 24% 13% 2 1	243
	21st to end	Day	25% 27% 29% 15% 3	297
February	1st to 10th	Day	32% 33% 27% 7% 1	270
	11th to 20th	Day	29% 37% 25% 7% 2	270
	21st to end	Day	39% 24% 27% 7% 2	285
March	1st to 10th	Day	27% 22% 32% 15% 4	460
	11th to 20th	Day	30% 20% 34% 13% 2 1	460
	21st to end	Day	30% 24% 25% 15% 4 2	506
April	1st to 10th	Day	26% 23% 32% 13% 5% 1	460
	11th to 20th	Day	31% 22% 23% 16% 6% 2	452
	21st to end	Day	28% 21% 30% 13% 7% 1	460
May	1st to 10th	Day	26% 17% 29% 17% 7% 4	463
	11th to 20th	Day	20% 14% 31% 22% 10% 3	487
	21st to end	Day	16% 16% 32% 22% 10% 4	529
June	1st to 10th	Day	20% 18% 34% 20% 6% 1	490
	11th to 20th	Day	15% 17% 30% 25% 11% 2	490
	21st to end	Day	20% 14% 33% 23% 8% 2	490
July	1st to 10th	Day	11% 9% 29% 29% 18% 3	485
	11th to 20th	Day	15% 10% 30% 25% 15% 4	484
	21st to end	Day	12% 10% 32% 30% 12% 4	532
August	1st to 10th	Day	16% 8% 25% 28% 15% 8%	486
	11th to 20th	Day	12% 8% 29% 27% 18% 7%	479
	21st to end	Day	14% 9% 29% 25% 14% 8%	539
September	1st to 10th	Day	15% 12% 26% 25% 15% 7%	490
	11th to 20th	Day	12% 9% 21% 24% 23% 11%	490
	21st to end	Day	19% 17% 27% 21% 11% 6%	490
October	1st to 10th	Day	23% 16% 26% 20% 12% 4	490
	11th to 20th	Day	25% 24% 27% 17% 5% 2	490
	21st to end	Day	36% 19% 26% 14% 5%	539
November	1st to 10th	Day	27% 23% 29% 14% 6% 1	337
	11th to 20th	Day	32% 28% 25% 9% 3 2	180
	21st to end	Day	32% 28% 29% 9% 1	180
December	1st to 10th	Day	29% 28% 30% 8% 4 1	180
	11th to 20th	Day	32% 30% 24% 12% 2	180
	21st to end	Day	33% 35% 24% 7% 1 1	198
January	1st to 10th	Night	31% 24% 29% 12% 4	760
	11th to 20th	Night	32% 25% 26% 15% 2	760
	21st to end	Night	25% 22% 32% 17% 4	836
February	1st to 10th	Night	28% 29% 28% 13% 2	760
	11th to 20th	Night	25% 27% 30% 16% 3	743
	21st to end	Night	29% 24% 29% 16% 2	628
March	1st to 10th	Night	25% 19% 34% 18% 5%	760
	11th to 20th	Night	27% 18% 31% 19% 4 1	760
	21st to end	Night	23% 16% 32% 22% 7% 1	836
April	1st to 10th	Night	26% 19% 31% 21% 3	760
	11th to 20th	Night	25% 16% 31% 19% 7% 1	751
	21st to end	Night	23% 11% 33% 25% 8%	575
May	1st to 10th	Night	21% 11% 25% 28% 12% 2	570
	11th to 20th	Night	15% 10% 32% 36% 6% 1	374
	21st to end	Night	13% 10% 27% 34% 15% 1	411
June	1st to 10th	Night	13% 8% 36% 32% 10%	380
	11th to 20th	Night	14% 8% 31% 34% 12%	380
	21st to end	Night	16% 8% 33% 36% 7%	380
July	1st to 10th	Night	11% 7% 26% 39% 17% 1	370
	11th to 20th	Night	11% 7% 29% 34% 17% 2	368
	21st to end	Night	13% 3 27% 38% 17% 2	583
August	1st to 10th	Night	10% 5% 21% 42% 20% 2	567
	11th to 20th	Night	10% 5% 23% 34% 25% 2	564
	21st to end	Night	13% 5% 25% 33% 22% 2	752
September	1st to 10th	Night	15% 8% 25% 33% 17% 2	760
	11th to 20th	Night	14% 6% 20% 30% 25% 4	760
	21st to end	Night	20% 11% 24% 27% 14% 4	760
October	1st to 10th	Night	18% 11% 30% 24% 15% 2	760
	11th to 20th	Night	27% 18% 25% 23% 7% 1	760
	21st to end	Night	34% 15% 28% 21% 3	836
November	1st to 10th	Night	24% 16% 30% 22% 9% 1	771
	11th to 20th	Night	23% 22% 31% 15% 8% 1	760
	21st to end	Night	28% 23% 29% 16% 5%	760
December	1st to 10th	Night	34% 24% 23% 14% 4 1	760
	11th to 20th	Night	27% 29% 27% 14% 3	760
	21st to end	Night	35% 21% 28% 14% 2	836

Page generated at 2024-11-05 08:15:48. Version ac07

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