Gold
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gold clear sky chart from 2005-11-06 to 2024-01-17.

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	15% 11% 5% 8% 7% 4 5% 5% 5% 7% 29%	74715
	Night	14% 12% 5% 9% 7% 4 5% 4 5% 6% 29%	75103
Transparency	Day	54% 6% 10% 18% 10% 1	74429
	Night	54% 7% 11% 18% 9% 1	74923
Seeing	Day	25% 19% 29% 17% 7% 3	13545
	Night	23% 20% 29% 20% 8% 1	23061

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	11% 14% 10% 15% 9% 4 5% 4 3 5% 20%	1517
	11th to 20th	Day	12% 17% 8% 15% 9% 5% 5% 3 4 4 18%	1614
	21st to end	Day	10% 14% 10% 16% 11% 3 5% 4 4 5% 17%	1782
February	1st to 10th	Day	14% 16% 8% 12% 10% 5% 5% 4 5% 4 17%	1620
	11th to 20th	Day	12% 13% 7% 14% 8% 4 5% 4 4 6% 21%	1573
	21st to end	Day	17% 14% 5% 11% 9% 3 3 4 4 5% 25%	1448
March	1st to 10th	Day	14% 13% 7% 11% 6% 3 4 4 4 6% 28%	1945
	11th to 20th	Day	13% 15% 6% 10% 8% 3 4 4 4 5% 27%	1980
	21st to end	Day	18% 12% 6% 8% 8% 3 4 4 5% 5% 28%	2199
April	1st to 10th	Day	13% 15% 6% 8% 6% 3 4 4 5% 6% 30%	2160
	11th to 20th	Day	16% 12% 4 7% 6% 3 5% 4 5% 5% 31%	2134
	21st to end	Day	20% 11% 3 7% 6% 3 4 4 4 5% 33%	2258
May	1st to 10th	Day	19% 13% 3 8% 7% 3 5% 4 5% 6% 28%	2349
	11th to 20th	Day	21% 9% 3 7% 6% 4 4 5% 4 7% 30%	2478
	21st to end	Day	14% 8% 3 6% 6% 3 5% 5% 6% 8% 37%	2725
June	1st to 10th	Day	16% 7% 3 7% 7% 3 5% 5% 5% 8% 34%	2520
	11th to 20th	Day	16% 7% 4 6% 6% 3 6% 6% 6% 8% 33%	2520
	21st to end	Day	14% 7% 3 6% 6% 4 6% 5% 6% 8% 35%	2520
July	1st to 10th	Day	11% 7% 4 7% 6% 4 6% 5% 7% 8% 35%	2520
	11th to 20th	Day	12% 7% 3 6% 7% 4 6% 6% 8% 9% 33%	2520
	21st to end	Day	12% 6% 3 7% 6% 5% 6% 7% 7% 7% 34%	2591
August	1st to 10th	Day	11% 6% 3 5% 8% 5% 7% 6% 7% 9% 33%	2327
	11th to 20th	Day	14% 8% 3 7% 7% 4 6% 6% 8% 9% 29%	2301
	21st to end	Day	14% 8% 3 6% 5% 5% 6% 6% 7% 8% 31%	2376
September	1st to 10th	Day	20% 7% 2 6% 5% 3 4 5% 5% 8% 36%	2160
	11th to 20th	Day	15% 7% 3 7% 5% 3 4 4 5% 6% 42%	2154
	21st to end	Day	19% 7% 4 7% 6% 3 5% 5% 5% 7% 32%	1882
October	1st to 10th	Day	17% 10% 3 7% 5% 4 5% 4 7% 6% 32%	1800
	11th to 20th	Day	20% 11% 4 7% 7% 3 4 4 6% 6% 29%	1800
	21st to end	Day	22% 15% 4 7% 5% 3 4 4 5% 5% 24%	1980
November	1st to 10th	Day	13% 13% 4 6% 6% 3 5% 4 5% 7% 35%	1709
	11th to 20th	Day	15% 17% 6% 9% 6% 3 4 5% 5% 7% 24%	1535
	21st to end	Day	16% 18% 7% 9% 6% 3 4 4 5% 6% 21%	1520
December	1st to 10th	Day	16% 18% 9% 14% 7% 3 4 4 4 4 15%	1520
	11th to 20th	Day	15% 18% 7% 13% 7% 3 4 5% 4 6% 18%	1906
	21st to end	Day	19% 22% 9% 11% 7% 3 4 3 3 4 14%	2772
January	1st to 10th	Night	12% 15% 9% 14% 9% 4 6% 5% 4 6% 17%	2649
	11th to 20th	Night	13% 15% 8% 12% 10% 4 6% 5% 5% 6% 18%	2487
	21st to end	Night	9% 15% 8% 14% 11% 5% 7% 5% 4 5% 17%	2574
February	1st to 10th	Night	13% 13% 8% 11% 11% 4 6% 4 5% 5% 20%	2340
	11th to 20th	Night	12% 12% 7% 12% 10% 5% 7% 4 6% 6% 21%	2273
	21st to end	Night	15% 12% 6% 12% 9% 4 5% 4 5% 5% 23%	1808
March	1st to 10th	Night	11% 11% 7% 13% 7% 4 5% 5% 5% 6% 26%	2001
	11th to 20th	Night	16% 14% 6% 9% 7% 3 4 4 4 5% 28%	1979
	21st to end	Night	12% 14% 6% 9% 7% 3 4 5% 5% 5% 30%	2156
April	1st to 10th	Night	16% 11% 6% 11% 5% 3 5% 5% 4 6% 28%	1800
	11th to 20th	Night	16% 12% 4 7% 6% 2 4 4 4 6% 35%	1775
	21st to end	Night	16% 11% 4 7% 5% 3 4 5% 5% 6% 34%	1717
May	1st to 10th	Night	18% 12% 3 6% 6% 2 5% 3 5% 6% 33%	1607
	11th to 20th	Night	15% 8% 4 6% 7% 4 6% 4 6% 7% 34%	1415
	21st to end	Night	12% 6% 2 7% 6% 4 4 5% 5% 7% 41%	1550
June	1st to 10th	Night	14% 7% 3 5% 5% 3 5% 5% 6% 10% 37%	1440
	11th to 20th	Night	13% 7% 2 6% 6% 3 5% 7% 6% 10% 37%	1440
	21st to end	Night	11% 6% 3 6% 5% 4 4 5% 5% 8% 43%	1440
July	1st to 10th	Night	8% 8% 2 6% 5% 3 5% 5% 5% 8% 44%	1440
	11th to 20th	Night	9% 5% 2 5% 5% 2 5% 5% 6% 9% 47%	1440
	21st to end	Night	12% 6% 2 5% 6% 4 5% 5% 6% 8% 41%	1724
August	1st to 10th	Night	8% 6% 3 5% 6% 4 5% 6% 6% 8% 43%	1611
	11th to 20th	Night	14% 7% 3 4 6% 3 4 5% 6% 9% 38%	1598
	21st to end	Night	12% 7% 3 5% 5% 3 5% 5% 6% 8% 41%	1963
September	1st to 10th	Night	16% 7% 2 6% 5% 2 4 4 4 6% 44%	1800
	11th to 20th	Night	12% 7% 3 6% 5% 2 4 4 5% 7% 46%	1803
	21st to end	Night	15% 9% 3 6% 5% 4 5% 4 5% 7% 37%	2078
October	1st to 10th	Night	16% 9% 3 6% 5% 3 4 4 4 8% 38%	2160
	11th to 20th	Night	17% 13% 3 7% 5% 3 3 4 6% 7% 32%	2160
	21st to end	Night	23% 14% 4 7% 6% 3 3 5% 4 6% 26%	2376
November	1st to 10th	Night	10% 12% 4 7% 6% 3 4 4 4 6% 39%	2366
	11th to 20th	Night	15% 14% 6% 9% 7% 4 5% 4 5% 6% 26%	2641
	21st to end	Night	14% 15% 7% 10% 7% 3 5% 4 5% 7% 22%	2660
December	1st to 10th	Night	14% 17% 10% 13% 7% 4 5% 5% 4 5% 16%	2660
	11th to 20th	Night	16% 15% 8% 13% 8% 4 5% 4 4 5% 18%	3288
	21st to end	Night	19% 16% 10% 12% 8% 4 4 4 5% 5% 13%	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	66% 7% 8% 13% 6% 1	1518
	11th to 20th	Day	69% 6% 9% 9% 7% 1	1614
	21st to end	Day	70% 5% 7% 10% 6% 1	1782
February	1st to 10th	Day	69% 6% 10% 10% 5% 1	1620
	11th to 20th	Day	64% 6% 6% 16% 8%	1582
	21st to end	Day	61% 5% 7% 18% 7% 2	1448
March	1st to 10th	Day	56% 6% 10% 19% 8% 1	1948
	11th to 20th	Day	59% 4 8% 17% 9% 3	1980
	21st to end	Day	58% 5% 6% 17% 11% 2	2199
April	1st to 10th	Day	55% 5% 10% 17% 11% 1	2160
	11th to 20th	Day	53% 7% 9% 16% 14% 1	2134
	21st to end	Day	53% 6% 6% 19% 13% 2	2258
May	1st to 10th	Day	57% 5% 9% 17% 9% 2	2349
	11th to 20th	Day	54% 6% 9% 18% 12% 1	2482
	21st to end	Day	45% 7% 15% 20% 11% 1	2725
June	1st to 10th	Day	47% 7% 12% 20% 13% 1	2520
	11th to 20th	Day	48% 7% 13% 19% 12% 1	2520
	21st to end	Day	45% 7% 12% 24% 11%	2520
July	1st to 10th	Day	45% 8% 11% 23% 12% 1	2450
	11th to 20th	Day	43% 8% 14% 22% 11%	2445
	21st to end	Day	44% 8% 13% 23% 10% 1	2446
August	1st to 10th	Day	45% 9% 13% 23% 10% 1	2314
	11th to 20th	Day	49% 9% 14% 20% 8% 1	2301
	21st to end	Day	47% 8% 10% 21% 12% 2	2376
September	1st to 10th	Day	47% 6% 10% 23% 13% 2	2160
	11th to 20th	Day	42% 6% 10% 24% 16% 1	2154
	21st to end	Day	50% 5% 10% 20% 14% 1	1882
October	1st to 10th	Day	51% 6% 11% 18% 12% 1	1800
	11th to 20th	Day	54% 6% 11% 20% 9%	1800
	21st to end	Day	61% 6% 10% 14% 8% 2	1980
November	1st to 10th	Day	48% 6% 10% 19% 13% 3	1709
	11th to 20th	Day	58% 6% 9% 18% 6% 2	1535
	21st to end	Day	64% 6% 10% 15% 5% 1	1520
December	1st to 10th	Day	72% 5% 9% 9% 5%	1520
	11th to 20th	Day	66% 6% 11% 12% 4	1906
	21st to end	Day	74% 5% 9% 10% 2	2772
January	1st to 10th	Night	65% 8% 8% 12% 6% 1	2649
	11th to 20th	Night	66% 7% 11% 11% 4 1	2487
	21st to end	Night	67% 7% 7% 11% 7% 1	2574
February	1st to 10th	Night	65% 7% 9% 12% 6%	2340
	11th to 20th	Night	62% 8% 9% 14% 6% 1	2275
	21st to end	Night	62% 6% 8% 14% 9% 2	1808
March	1st to 10th	Night	57% 7% 9% 20% 6% 1	2011
	11th to 20th	Night	57% 6% 10% 18% 9% 1	1980
	21st to end	Night	54% 7% 8% 15% 14% 3	2156
April	1st to 10th	Night	56% 6% 9% 16% 12% 1	1800
	11th to 20th	Night	51% 5% 11% 19% 13% 2	1775
	21st to end	Night	50% 6% 10% 20% 12% 2	1717
May	1st to 10th	Night	53% 6% 9% 20% 11% 2	1607
	11th to 20th	Night	49% 7% 10% 21% 13% 1	1416
	21st to end	Night	40% 9% 13% 24% 12% 3	1551
June	1st to 10th	Night	43% 7% 14% 23% 13% 1	1440
	11th to 20th	Night	41% 8% 15% 24% 11% 2	1440
	21st to end	Night	39% 8% 12% 27% 13% 1	1440
July	1st to 10th	Night	38% 7% 14% 24% 16% 1	1400
	11th to 20th	Night	32% 8% 16% 26% 17% 1	1392
	21st to end	Night	38% 8% 14% 22% 16% 1	1628
August	1st to 10th	Night	35% 10% 16% 28% 9% 1	1600
	11th to 20th	Night	40% 10% 14% 26% 10%	1598
	21st to end	Night	39% 7% 14% 25% 13% 2	1963
September	1st to 10th	Night	41% 5% 13% 25% 13% 3	1800
	11th to 20th	Night	37% 7% 13% 25% 17% 2	1803
	21st to end	Night	46% 6% 12% 22% 13% 1	2078
October	1st to 10th	Night	45% 7% 13% 20% 13% 1	2160
	11th to 20th	Night	50% 6% 13% 19% 10% 1	2160
	21st to end	Night	58% 6% 11% 16% 8% 1	2376
November	1st to 10th	Night	45% 8% 11% 19% 14% 3	2366
	11th to 20th	Night	57% 6% 10% 17% 8% 3	2641
	21st to end	Night	60% 7% 10% 17% 4 1	2660
December	1st to 10th	Night	70% 7% 8% 11% 3	2660
	11th to 20th	Night	67% 6% 8% 14% 4	3288
	21st to end	Night	72% 7% 9% 10% 2	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	36% 29% 23% 8% 4	180
	11th to 20th	Day	33% 34% 25% 6% 1	230
	21st to end	Day	30% 31% 30% 6% 2	264
February	1st to 10th	Day	40% 34% 23% 3	240
	11th to 20th	Day	37% 34% 28% 1	240
	21st to end	Day	42% 26% 26% 5% 1	314
March	1st to 10th	Day	34% 26% 29% 9% 2	420
	11th to 20th	Day	32% 26% 28% 10% 3 1	420
	21st to end	Day	31% 27% 27% 11% 3 1	462
April	1st to 10th	Day	33% 22% 29% 11% 3 1	420
	11th to 20th	Day	28% 25% 26% 13% 6% 3	412
	21st to end	Day	30% 21% 31% 14% 3 1	420
May	1st to 10th	Day	30% 23% 26% 13% 7% 2	423
	11th to 20th	Day	28% 19% 31% 15% 6% 2	447
	21st to end	Day	19% 13% 31% 20% 12% 4	485
June	1st to 10th	Day	19% 16% 34% 22% 7% 2	450
	11th to 20th	Day	20% 15% 27% 25% 10% 2	450
	21st to end	Day	17% 14% 37% 23% 7% 3	450
July	1st to 10th	Day	14% 9% 32% 25% 14% 5%	445
	11th to 20th	Day	10% 11% 32% 28% 14% 5%	444
	21st to end	Day	14% 11% 34% 26% 10% 4	488
August	1st to 10th	Day	12% 10% 26% 30% 16% 6%	446
	11th to 20th	Day	16% 8% 30% 27% 11% 8%	439
	21st to end	Day	16% 12% 31% 21% 13% 7%	495
September	1st to 10th	Day	22% 13% 22% 24% 13% 6%	450
	11th to 20th	Day	16% 9% 27% 24% 17% 7%	450
	21st to end	Day	22% 16% 25% 21% 12% 4	450
October	1st to 10th	Day	24% 13% 28% 18% 14% 3	450
	11th to 20th	Day	28% 22% 31% 14% 5% 1	450
	21st to end	Day	34% 23% 27% 14% 2	495
November	1st to 10th	Day	27% 19% 31% 15% 7% 2	383
	11th to 20th	Day	35% 26% 27% 10% 2	195
	21st to end	Day	32% 30% 31% 6% 1 1	180
December	1st to 10th	Day	42% 28% 21% 4 3 1	180
	11th to 20th	Day	36% 31% 27% 6% 1	180
	21st to end	Day	35% 31% 30% 3 1	198
January	1st to 10th	Night	25% 32% 31% 9% 2	760
	11th to 20th	Night	27% 29% 29% 13% 2	748
	21st to end	Night	23% 33% 31% 12% 1	792
February	1st to 10th	Night	27% 30% 32% 10%	720
	11th to 20th	Night	28% 33% 30% 8% 1	703
	21st to end	Night	32% 29% 28% 9% 1	592
March	1st to 10th	Night	23% 32% 33% 10% 2	720
	11th to 20th	Night	30% 25% 27% 15% 3	720
	21st to end	Night	22% 27% 33% 13% 4 1	792
April	1st to 10th	Night	26% 23% 32% 17% 3	720
	11th to 20th	Night	25% 20% 31% 16% 6% 1	711
	21st to end	Night	24% 16% 34% 23% 3	637
May	1st to 10th	Night	26% 13% 27% 26% 9%	527
	11th to 20th	Night	17% 14% 35% 24% 9%	354
	21st to end	Night	14% 11% 30% 30% 15% 1	389
June	1st to 10th	Night	16% 10% 29% 33% 11% 1	360
	11th to 20th	Night	15% 11% 27% 38% 9%	360
	21st to end	Night	10% 10% 35% 34% 11%	360
July	1st to 10th	Night	11% 5% 27% 37% 18% 2	350
	11th to 20th	Night	9% 5% 28% 36% 20% 1	348
	21st to end	Night	14% 6% 22% 38% 17% 2	544
August	1st to 10th	Night	11% 5% 23% 39% 21% 2	537
	11th to 20th	Night	15% 7% 19% 33% 23% 2	534
	21st to end	Night	13% 8% 23% 32% 21% 3	775
September	1st to 10th	Night	19% 7% 25% 30% 16% 3	720
	11th to 20th	Night	14% 9% 24% 27% 22% 4	720
	21st to end	Night	18% 13% 27% 23% 15% 3	720
October	1st to 10th	Night	22% 13% 27% 21% 15% 2	720
	11th to 20th	Night	25% 19% 31% 19% 5% 1	720
	21st to end	Night	31% 21% 31% 15% 3	792
November	1st to 10th	Night	19% 21% 34% 20% 6%	740
	11th to 20th	Night	27% 24% 29% 14% 4 1	760
	21st to end	Night	25% 24% 33% 14% 3 1	760
December	1st to 10th	Night	28% 30% 29% 9% 4	760
	11th to 20th	Night	28% 29% 29% 12% 2	760
	21st to end	Night	31% 27% 32% 10% 1	836

Page generated at 2024-01-14 09:55:00. Version ac07

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