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 2026-05-02.

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% 12% 4 10% 6% 5% 5% 4 5% 6% 28%	131984
	Night	14% 13% 5% 12% 6% 5% 4 3 5% 6% 27%	130485
Transparency	Day	54% 6% 10% 19% 10% 1	135576
	Night	56% 6% 10% 17% 9% 1	134979
Seeing	Day	26% 20% 28% 16% 7% 2	16502
	Night	23% 20% 29% 19% 8% 1	26012

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% 18% 7% 23% 10% 3 3 2 3 3 15%	4661
	11th to 20th	Day	7% 17% 9% 25% 10% 7% 4 3 3 3 12%	5063
	21st to end	Day	14% 11% 6% 13% 9% 8% 6% 5% 6% 6% 17%	5780
February	1st to 10th	Day	12% 17% 7% 14% 8% 6% 5% 3 5% 4 20%	1890
	11th to 20th	Day	12% 14% 7% 16% 8% 5% 5% 3 4 6% 20%	1843
	21st to end	Day	16% 15% 5% 12% 7% 3 4 2 4 6% 26%	1693
March	1st to 10th	Day	15% 14% 8% 10% 4 3 3 2 4 5% 31%	4968
	11th to 20th	Day	11% 15% 7% 10% 5% 4 3 3 4 5% 33%	5090
	21st to end	Day	13% 12% 5% 12% 7% 5% 4 3 5% 5% 28%	5649
April	1st to 10th	Day	15% 17% 5% 9% 5% 4 4 3 5% 6% 28%	2520
	11th to 20th	Day	15% 13% 4 8% 5% 5% 5% 3 5% 5% 30%	2494
	21st to end	Day	19% 12% 3 8% 5% 4 4 3 5% 4 34%	2635
May	1st to 10th	Day	25% 12% 3 8% 5% 4 4 3 4 6% 26%	5938
	11th to 20th	Day	23% 11% 3 8% 5% 5% 4 4 5% 6% 25%	6318
	21st to end	Day	19% 9% 3 8% 5% 5% 5% 4 6% 7% 30%	6949
June	1st to 10th	Day	16% 8% 3 8% 5% 5% 5% 3 6% 8% 34%	2800
	11th to 20th	Day	17% 8% 3 7% 5% 5% 6% 4 7% 7% 32%	2800
	21st to end	Day	13% 8% 3 7% 5% 6% 5% 4 6% 8% 35%	2800
July	1st to 10th	Day	8% 7% 3 7% 6% 6% 6% 4 7% 9% 37%	6360
	11th to 20th	Day	8% 8% 3 8% 6% 7% 6% 5% 8% 9% 32%	6360
	21st to end	Day	11% 6% 2 7% 5% 5% 5% 5% 6% 7% 41%	6524
August	1st to 10th	Day	19% 8% 3 6% 5% 5% 5% 4 7% 8% 30%	4234
	11th to 20th	Day	16% 8% 3 8% 6% 6% 6% 5% 8% 9% 26%	4158
	21st to end	Day	13% 8% 2 6% 4 5% 5% 4 7% 9% 37%	4312
September	1st to 10th	Day	18% 8% 2 6% 4 4 5% 3 5% 7% 39%	2400
	11th to 20th	Day	14% 7% 3 7% 4 4 4 3 6% 6% 43%	2392
	21st to end	Day	22% 8% 3 8% 5% 4 5% 3 5% 7% 30%	2090
October	1st to 10th	Day	16% 10% 3 7% 4 5% 5% 3 7% 6% 34%	2000
	11th to 20th	Day	18% 12% 3 8% 6% 4 4 3 6% 6% 30%	2000
	21st to end	Day	20% 15% 3 8% 5% 4 4 4 5% 5% 26%	2200
November	1st to 10th	Day	12% 14% 4 7% 5% 4 4 3 5% 6% 35%	1893
	11th to 20th	Day	13% 20% 5% 10% 5% 3 4 4 5% 6% 23%	1696
	21st to end	Day	15% 20% 8% 10% 6% 4 4 3 5% 6% 19%	1680
December	1st to 10th	Day	14% 20% 10% 22% 6% 3 3 3 3 4 11%	2680
	11th to 20th	Day	17% 18% 8% 12% 7% 4 4 3 3 5% 19%	3066
	21st to end	Day	16% 22% 8% 13% 6% 4 3 3 4 4 16%	4048
January	1st to 10th	Night	10% 16% 9% 21% 11% 5% 4 3 3 5% 12%	8234
	11th to 20th	Night	8% 16% 8% 22% 11% 7% 5% 4 4 4 11%	7819
	21st to end	Night	11% 14% 6% 14% 9% 9% 8% 4 4 4 16%	8401
February	1st to 10th	Night	11% 15% 6% 13% 10% 6% 5% 3 5% 4 21%	2730
	11th to 20th	Night	11% 13% 6% 15% 9% 6% 5% 3 6% 5% 19%	2663
	21st to end	Night	14% 13% 6% 15% 8% 5% 4 3 6% 4 23%	2113
March	1st to 10th	Night	13% 15% 5% 12% 8% 6% 4 3 4 5% 26%	5077
	11th to 20th	Night	12% 15% 6% 9% 5% 4 3 3 4 6% 32%	5089
	21st to end	Night	11% 14% 5% 11% 5% 4 4 4 5% 5% 32%	5524
April	1st to 10th	Night	17% 14% 5% 11% 5% 4 5% 3 4 6% 27%	2100
	11th to 20th	Night	16% 14% 3 8% 5% 4 3 3 4 6% 33%	2075
	21st to end	Night	15% 12% 4 7% 4 4 4 3 5% 6% 35%	2002
May	1st to 10th	Night	28% 14% 3 6% 4 3 3 2 4 5% 26%	4021
	11th to 20th	Night	22% 14% 3 6% 5% 4 4 3 4 6% 30%	3575
	21st to end	Night	18% 12% 3 9% 5% 5% 4 3 5% 6% 31%	3926
June	1st to 10th	Night	15% 8% 2 7% 5% 4 4 4 6% 9% 37%	1600
	11th to 20th	Night	13% 8% 2 7% 5% 4 5% 5% 7% 8% 37%	1600
	21st to end	Night	11% 7% 3 7% 5% 5% 5% 3 6% 7% 42%	1600
July	1st to 10th	Night	10% 10% 3 8% 5% 5% 4 4 5% 8% 39%	3600
	11th to 20th	Night	10% 9% 3 8% 4 4 5% 4 7% 10% 38%	3600
	21st to end	Night	11% 6% 2 6% 4 4 4 4 5% 7% 46%	4325
August	1st to 10th	Night	17% 9% 3 7% 4 4 5% 4 5% 7% 35%	2915
	11th to 20th	Night	18% 9% 2 5% 4 4 4 4 5% 7% 38%	2875
	21st to end	Night	11% 8% 2 6% 4 4 4 4 6% 8% 42%	3568
September	1st to 10th	Night	15% 7% 2 6% 5% 3 4 3 4 6% 46%	2000
	11th to 20th	Night	11% 7% 2 6% 4 3 4 3 5% 7% 47%	2004
	21st to end	Night	19% 9% 3 8% 4 5% 4 3 5% 6% 34%	2310
October	1st to 10th	Night	16% 9% 3 6% 4 4 4 3 4 7% 40%	2400
	11th to 20th	Night	17% 13% 3 8% 4 4 3 3 5% 7% 33%	2400
	21st to end	Night	21% 15% 3 8% 5% 3 4 4 4 6% 28%	2640
November	1st to 10th	Night	10% 13% 3 8% 5% 5% 4 3 5% 6% 38%	2622
	11th to 20th	Night	14% 15% 5% 10% 6% 5% 4 3 5% 6% 26%	2919
	21st to end	Night	14% 17% 7% 12% 6% 5% 4 3 5% 6% 20%	2940
December	1st to 10th	Night	11% 16% 8% 22% 7% 6% 5% 3 4 5% 12%	4720
	11th to 20th	Night	17% 15% 8% 15% 6% 4 4 3 4 4 20%	5348
	21st to end	Night	16% 18% 9% 14% 7% 5% 4 3 5% 4 16%	7150

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	75% 3 6% 11% 4 1	4662
	11th to 20th	Day	76% 4 5% 9% 4 1	5097
	21st to end	Day	65% 5% 10% 15% 5%	5780
February	1st to 10th	Day	66% 5% 9% 12% 7% 1	1890
	11th to 20th	Day	64% 6% 6% 16% 8%	1852
	21st to end	Day	60% 5% 8% 19% 7% 2	1693
March	1st to 10th	Day	55% 4 11% 19% 10% 1	4971
	11th to 20th	Day	52% 5% 15% 17% 7% 3	5090
	21st to end	Day	57% 5% 6% 18% 12% 2	5649
April	1st to 10th	Day	57% 4 10% 16% 11% 1	2520
	11th to 20th	Day	54% 7% 9% 16% 13% 1	2494
	21st to end	Day	52% 6% 6% 20% 13% 2	2635
May	1st to 10th	Day	60% 5% 8% 17% 9% 2	5947
	11th to 20th	Day	57% 7% 8% 18% 9%	6322
	21st to end	Day	51% 7% 11% 20% 10% 1	6949
June	1st to 10th	Day	47% 7% 11% 20% 13% 1	2800
	11th to 20th	Day	49% 7% 13% 19% 11% 1	2800
	21st to end	Day	45% 7% 13% 23% 12%	2800
July	1st to 10th	Day	41% 7% 13% 26% 12% 1	6290
	11th to 20th	Day	43% 9% 15% 22% 12%	6285
	21st to end	Day	39% 7% 11% 27% 15% 1	6337
August	1st to 10th	Day	50% 7% 13% 20% 9%	4221
	11th to 20th	Day	49% 9% 14% 22% 6%	4197
	21st to end	Day	41% 7% 11% 31% 9% 1	4312
September	1st to 10th	Day	44% 6% 10% 26% 14% 2	2400
	11th to 20th	Day	40% 6% 10% 26% 16% 1	2392
	21st to end	Day	53% 5% 10% 18% 13% 1	2090
October	1st to 10th	Day	43% 5% 11% 22% 17% 1	3260
	11th to 20th	Day	47% 4 11% 19% 15% 4	3240
	21st to end	Day	43% 5% 15% 25% 11% 1	3538
November	1st to 10th	Day	48% 6% 10% 20% 13% 3	1893
	11th to 20th	Day	59% 6% 9% 18% 6% 2	1696
	21st to end	Day	66% 6% 10% 14% 5% 1	1680
December	1st to 10th	Day	76% 4 7% 9% 3	2680
	11th to 20th	Day	66% 5% 10% 14% 5%	3066
	21st to end	Day	71% 4 9% 9% 6%	4048
January	1st to 10th	Night	73% 6% 7% 10% 4	8234
	11th to 20th	Night	72% 6% 8% 9% 4 1	7860
	21st to end	Night	69% 5% 7% 12% 7% 1	8401
February	1st to 10th	Night	64% 7% 9% 13% 7%	2730
	11th to 20th	Night	64% 7% 9% 14% 6% 1	2665
	21st to end	Night	62% 5% 9% 14% 8% 2	2113
March	1st to 10th	Night	61% 4 12% 14% 7% 1	5087
	11th to 20th	Night	50% 7% 15% 18% 6% 4	5090
	21st to end	Night	52% 6% 7% 17% 15% 2	5524
April	1st to 10th	Night	58% 6% 9% 15% 11% 1	2100
	11th to 20th	Night	52% 5% 11% 19% 12% 1	2075
	21st to end	Night	49% 5% 10% 22% 12% 2	2002
May	1st to 10th	Night	61% 4 7% 17% 8% 2	4028
	11th to 20th	Night	54% 7% 12% 17% 9%	3576
	21st to end	Night	51% 8% 10% 18% 11% 3	3927
June	1st to 10th	Night	43% 7% 13% 22% 14% 1	1600
	11th to 20th	Night	41% 8% 15% 24% 11% 2	1600
	21st to end	Night	40% 9% 12% 26% 13% 1	1600
July	1st to 10th	Night	42% 6% 13% 24% 14% 1	3560
	11th to 20th	Night	38% 9% 16% 25% 11% 1	3552
	21st to end	Night	36% 6% 12% 26% 20% 1	4197
August	1st to 10th	Night	46% 8% 14% 23% 7% 1	2904
	11th to 20th	Night	43% 8% 14% 27% 8%	2902
	21st to end	Night	37% 6% 14% 32% 10% 1	3568
September	1st to 10th	Night	39% 5% 13% 27% 14% 2	2000
	11th to 20th	Night	35% 6% 13% 27% 17% 1	2004
	21st to end	Night	49% 6% 12% 20% 12% 1	2310
October	1st to 10th	Night	45% 6% 9% 22% 17% 1	3920
	11th to 20th	Night	43% 5% 12% 20% 13% 7%	3899
	21st to end	Night	43% 5% 15% 24% 12% 2	4252
November	1st to 10th	Night	45% 7% 11% 20% 14% 2	2622
	11th to 20th	Night	58% 6% 10% 16% 8% 2	2919
	21st to end	Night	62% 7% 10% 16% 4 1	2940
December	1st to 10th	Night	71% 7% 9% 10% 3	4720
	11th to 20th	Night	66% 5% 9% 14% 6%	5348
	21st to end	Night	70% 5% 8% 10% 6%	7150

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	37% 31% 21% 7% 3	220
	11th to 20th	Day	37% 34% 23% 5% 1	296
	21st to end	Day	37% 28% 28% 6% 2	363
February	1st to 10th	Day	39% 30% 25% 6%	330
	11th to 20th	Day	38% 32% 27% 2	330
	21st to end	Day	40% 27% 27% 4	409
March	1st to 10th	Day	35% 26% 28% 9% 2 1	540
	11th to 20th	Day	36% 26% 25% 10% 2 1	540
	21st to end	Day	32% 28% 26% 10% 3 1	594
April	1st to 10th	Day	36% 24% 26% 10% 3 1	540
	11th to 20th	Day	31% 27% 25% 11% 5% 2	532
	21st to end	Day	29% 22% 32% 13% 3 1	540
May	1st to 10th	Day	31% 23% 26% 12% 6% 2	507
	11th to 20th	Day	28% 18% 30% 15% 6% 2	527
	21st to end	Day	21% 14% 31% 19% 10% 4	573
June	1st to 10th	Day	21% 17% 33% 20% 8% 2	530
	11th to 20th	Day	22% 15% 28% 24% 10% 2	530
	21st to end	Day	18% 15% 36% 23% 6% 3	530
July	1st to 10th	Day	13% 10% 35% 25% 13% 5%	525
	11th to 20th	Day	10% 12% 32% 27% 14% 4	524
	21st to end	Day	14% 11% 34% 27% 10% 4	576
August	1st to 10th	Day	14% 10% 26% 30% 14% 6%	526
	11th to 20th	Day	16% 9% 30% 26% 12% 7%	519
	21st to end	Day	15% 13% 32% 21% 13% 7%	583
September	1st to 10th	Day	22% 13% 21% 24% 14% 7%	530
	11th to 20th	Day	14% 8% 24% 27% 19% 8%	530
	21st to end	Day	27% 15% 25% 19% 11% 3	530
October	1st to 10th	Day	23% 14% 27% 20% 13% 3	530
	11th to 20th	Day	28% 22% 30% 14% 5% 1	530
	21st to end	Day	33% 22% 28% 15% 3	583
November	1st to 10th	Day	28% 21% 30% 13% 6% 2	447
	11th to 20th	Day	36% 24% 28% 10% 2	236
	21st to end	Day	37% 29% 29% 5%	220
December	1st to 10th	Day	41% 30% 21% 4 3 1	220
	11th to 20th	Day	36% 33% 25% 5%	220
	21st to end	Day	38% 28% 29% 4 1	242
January	1st to 10th	Night	26% 32% 31% 9% 2	840
	11th to 20th	Night	29% 29% 28% 12% 1	840
	21st to end	Night	27% 33% 28% 11% 1	924
February	1st to 10th	Night	27% 29% 33% 12%	840
	11th to 20th	Night	29% 33% 29% 9% 1	823
	21st to end	Night	33% 28% 29% 9% 1	692
March	1st to 10th	Night	25% 31% 32% 10% 2	840
	11th to 20th	Night	31% 26% 27% 14% 3	840
	21st to end	Night	24% 28% 31% 12% 3 1	924
April	1st to 10th	Night	28% 24% 31% 15% 2	840
	11th to 20th	Night	26% 20% 31% 16% 6%	831
	21st to end	Night	23% 16% 34% 23% 4	742
May	1st to 10th	Night	27% 14% 26% 25% 8%	588
	11th to 20th	Night	19% 14% 34% 24% 9% 1	394
	21st to end	Night	15% 11% 29% 31% 14% 1	433
June	1st to 10th	Night	18% 10% 28% 33% 11% 1	400
	11th to 20th	Night	16% 10% 27% 38% 8%	400
	21st to end	Night	11% 12% 33% 33% 12%	400
July	1st to 10th	Night	11% 6% 26% 37% 18% 2	390
	11th to 20th	Night	9% 6% 27% 36% 20% 2	388
	21st to end	Night	13% 6% 23% 38% 18% 1	606
August	1st to 10th	Night	12% 5% 22% 38% 22% 2	597
	11th to 20th	Night	15% 7% 19% 33% 23% 2	594
	21st to end	Night	14% 8% 23% 31% 21% 3	862
September	1st to 10th	Night	18% 7% 25% 29% 17% 3	800
	11th to 20th	Night	12% 9% 22% 28% 25% 4	800
	21st to end	Night	22% 13% 25% 22% 15% 3	800
October	1st to 10th	Night	22% 13% 27% 20% 16% 2	800
	11th to 20th	Night	24% 19% 31% 19% 6% 1	800
	21st to end	Night	29% 20% 31% 16% 3	880
November	1st to 10th	Night	21% 22% 33% 19% 5%	820
	11th to 20th	Night	29% 23% 28% 14% 4 1	840
	21st to end	Night	27% 25% 32% 13% 3	840
December	1st to 10th	Night	29% 30% 28% 9% 4	840
	11th to 20th	Night	29% 29% 28% 12% 2	840
	21st to end	Night	31% 26% 30% 10% 1	924

Page generated at 2026-04-29 02:21:42. Version ac07

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