Gold Ridge observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gold Ridge observatory 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	12% 6% 3 5% 6% 4 5% 5% 6% 8% 41%	74881
	Night	12% 6% 2 5% 5% 3 4 5% 5% 8% 45%	74948
Transparency	Day	27% 38% 7% 12% 13% 3	74604
	Night	24% 38% 7% 13% 14% 4	74744
Seeing	Day	16% 10% 23% 24% 18% 9%	13631
	Night	15% 9% 23% 28% 21% 4	23709

By Month

Percentage Cloud Cover SE (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	19% 7% 3 4 3 2 4 4 4 6% 42%	1706
	11th to 20th	Day	16% 8% 4 5% 4 2 3 4 5% 5% 43%	1674
	21st to end	Day	16% 8% 3 5% 4 3 3 4 4 5% 45%	1953
February	1st to 10th	Day	17% 9% 3 5% 6% 3 5% 4 4 7% 38%	1800
	11th to 20th	Day	20% 9% 3 5% 4 3 3 3 4 5% 42%	1748
	21st to end	Day	20% 7% 2 5% 5% 3 4 4 4 6% 38%	1480
March	1st to 10th	Day	14% 7% 3 5% 5% 3 3 4 5% 6% 46%	1800
	11th to 20th	Day	19% 6% 4 6% 6% 3 3 4 4 7% 38%	1971
	21st to end	Day	16% 6% 3 6% 5% 3 4 5% 6% 7% 40%	2178
April	1st to 10th	Day	13% 6% 3 5% 5% 3 4 4 5% 7% 45%	2129
	11th to 20th	Day	12% 6% 2 5% 6% 3 5% 3 5% 6% 46%	2134
	21st to end	Day	9% 5% 2 4 4 4 4 4 6% 7% 51%	2218
May	1st to 10th	Day	10% 5% 2 5% 5% 2 4 5% 6% 9% 48%	2340
	11th to 20th	Day	9% 6% 3 5% 6% 4 7% 6% 5% 8% 42%	2301
	21st to end	Day	9% 5% 3 5% 6% 3 6% 6% 6% 8% 43%	2531
June	1st to 10th	Day	10% 7% 3 7% 7% 5% 7% 7% 7% 10% 31%	2340
	11th to 20th	Day	6% 3 2 4 7% 4 7% 7% 8% 11% 41%	2340
	21st to end	Day	6% 4 3 6% 8% 6% 7% 7% 9% 10% 35%	2340
July	1st to 10th	Day	8% 6% 3 7% 8% 5% 8% 8% 9% 11% 28%	2340
	11th to 20th	Day	7% 5% 3 7% 8% 5% 8% 7% 9% 11% 30%	2340
	21st to end	Day	7% 5% 3 7% 7% 5% 8% 8% 9% 12% 30%	2547
August	1st to 10th	Day	7% 5% 3 6% 7% 6% 8% 9% 9% 13% 28%	2233
	11th to 20th	Day	11% 6% 3 6% 7% 5% 7% 7% 6% 9% 32%	2125
	21st to end	Day	12% 6% 3 7% 6% 5% 7% 6% 6% 10% 32%	2376
September	1st to 10th	Day	10% 6% 3 7% 7% 5% 6% 6% 6% 7% 38%	2042
	11th to 20th	Day	14% 5% 2 5% 5% 4 5% 5% 6% 7% 42%	1980
	21st to end	Day	12% 6% 3 5% 5% 3 3 5% 3 6% 48%	1980
October	1st to 10th	Day	11% 5% 2 4 4 3 3 5% 4 6% 52%	1980
	11th to 20th	Day	12% 5% 1 4 4 2 3 3 4 7% 54%	1954
	21st to end	Day	13% 5% 1 5% 5% 3 3 4 4 5% 54%	1922
November	1st to 10th	Day	11% 6% 2 5% 4 3 3 3 4 5% 54%	1672
	11th to 20th	Day	13% 5% 2 4 4 2 3 4 5% 6% 52%	1710
	21st to end	Day	13% 7% 2 4 5% 2 4 4 6% 7% 46%	1710
December	1st to 10th	Day	19% 7% 3 4 5% 3 5% 4 5% 7% 38%	1710
	11th to 20th	Day	16% 8% 3 6% 5% 3 4 4 3 5% 43%	2153
	21st to end	Day	20% 8% 4 5% 5% 2 4 4 5% 7% 35%	3124
January	1st to 10th	Night	17% 8% 3 5% 3 2 4 4 4 6% 43%	2459
	11th to 20th	Night	17% 8% 3 5% 5% 3 4 4 5% 6% 40%	2430
	21st to end	Night	16% 7% 3 5% 4 2 4 4 4 5% 45%	2398
February	1st to 10th	Night	15% 7% 3 5% 5% 3 4 4 5% 6% 42%	2160
	11th to 20th	Night	19% 7% 3 5% 5% 2 3 3 4 5% 43%	2098
	21st to end	Night	19% 7% 3 5% 5% 3 4 4 5% 7% 38%	1776
March	1st to 10th	Night	14% 6% 3 5% 4 2 4 4 5% 7% 47%	2160
	11th to 20th	Night	14% 7% 2 4 5% 3 5% 4 6% 8% 40%	1985
	21st to end	Night	13% 5% 2 5% 5% 3 4 4 5% 7% 45%	2178
April	1st to 10th	Night	11% 5% 2 4 5% 3 5% 5% 6% 7% 46%	1845
	11th to 20th	Night	13% 6% 2 4 5% 2 3 3 5% 7% 50%	1775
	21st to end	Night	8% 5% 2 4 4 3 5% 4 5% 6% 54%	1739
May	1st to 10th	Night	9% 3 1 3 4 4 4 5% 5% 9% 52%	1620
	11th to 20th	Night	8% 6% 2 5% 6% 4 6% 7% 6% 8% 43%	1592
	21st to end	Night	8% 4 2 5% 4 3 4 6% 6% 8% 49%	1744
June	1st to 10th	Night	4 5% 3 5% 6% 4 7% 7% 9% 11% 37%	1620
	11th to 20th	Night	3 2 2 4 5% 3 5% 7% 8% 12% 49%	1620
	21st to end	Night	5% 5% 2 5% 6% 3 5% 5% 7% 11% 45%	1620
July	1st to 10th	Night	7% 5% 2 6% 6% 4 6% 8% 8% 11% 37%	1620
	11th to 20th	Night	5% 3 2 6% 7% 3 9% 7% 9% 13% 37%	1620
	21st to end	Night	5% 5% 2 6% 6% 4 7% 7% 9% 12% 37%	1771
August	1st to 10th	Night	5% 4 2 5% 6% 4 7% 6% 8% 13% 39%	1701
	11th to 20th	Night	7% 4 3 6% 6% 4 6% 7% 7% 9% 40%	1776
	21st to end	Night	13% 7% 3 6% 5% 3 5% 6% 7% 10% 37%	1980
September	1st to 10th	Night	7% 5% 2 5% 5% 3 5% 6% 7% 10% 44%	1898
	11th to 20th	Night	11% 6% 2 5% 6% 3 4 4 6% 7% 46%	1980
	21st to end	Night	10% 5% 2 5% 4 3 3 4 5% 7% 52%	1980
October	1st to 10th	Night	9% 4 2 4 3 2 3 3 3 6% 60%	1980
	11th to 20th	Night	10% 5% 2 4 4 3 3 4 4 6% 55%	2003
	21st to end	Night	12% 6% 2 4 4 2 3 3 4 4 56%	2430
November	1st to 10th	Night	11% 6% 2 4 4 2 3 3 4 5% 58%	2406
	11th to 20th	Night	12% 6% 2 4 3 2 4 3 3 6% 54%	2470
	21st to end	Night	12% 7% 2 5% 5% 3 4 4 4 6% 47%	2470
December	1st to 10th	Night	17% 8% 3 6% 4 2 5% 3 5% 6% 42%	2470
	11th to 20th	Night	16% 7% 3 5% 4 2 3 3 4 5% 47%	3042
	21st to end	Night	18% 9% 4 6% 5% 3 4 5% 5% 8% 33%	4532

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	26% 40% 5% 11% 16% 3	1707
	11th to 20th	Day	28% 40% 4 11% 15% 2	1674
	21st to end	Day	29% 36% 5% 11% 15% 3	1953
February	1st to 10th	Day	31% 36% 5% 10% 15% 3	1800
	11th to 20th	Day	30% 36% 3 11% 15% 5%	1758
	21st to end	Day	31% 36% 5% 8% 17% 4	1480
March	1st to 10th	Day	26% 36% 5% 10% 15% 7%	1800
	11th to 20th	Day	30% 37% 8% 9% 12% 4	1971
	21st to end	Day	29% 38% 7% 14% 11% 2	2178
April	1st to 10th	Day	26% 37% 7% 13% 12% 4	2129
	11th to 20th	Day	23% 35% 4 12% 19% 7%	2134
	21st to end	Day	21% 37% 7% 17% 17% 2	2218
May	1st to 10th	Day	26% 38% 9% 13% 11% 3	2340
	11th to 20th	Day	26% 39% 10% 14% 9% 2	2305
	21st to end	Day	23% 39% 9% 15% 12% 1	2531
June	1st to 10th	Day	29% 40% 9% 15% 7%	2340
	11th to 20th	Day	20% 40% 13% 16% 10% 2	2340
	21st to end	Day	25% 41% 10% 14% 7% 2	2340
July	1st to 10th	Day	31% 43% 12% 8% 5% 1	2275
	11th to 20th	Day	29% 42% 12% 9% 6% 1	2271
	21st to end	Day	29% 45% 12% 11% 4	2405
August	1st to 10th	Day	26% 42% 14% 16% 2	2220
	11th to 20th	Day	33% 40% 11% 10% 5% 1	2125
	21st to end	Day	35% 40% 9% 9% 7% 1	2376
September	1st to 10th	Day	31% 39% 8% 10% 8% 4	2042
	11th to 20th	Day	30% 38% 7% 10% 13% 2	1980
	21st to end	Day	26% 37% 5% 11% 17% 5%	1980
October	1st to 10th	Day	21% 37% 5% 9% 21% 7%	1980
	11th to 20th	Day	23% 35% 4 14% 18% 6%	1954
	21st to end	Day	21% 37% 3 11% 21% 6%	1922
November	1st to 10th	Day	17% 39% 4 10% 20% 9%	1672
	11th to 20th	Day	22% 39% 4 9% 18% 7%	1710
	21st to end	Day	26% 40% 4 10% 16% 4	1710
December	1st to 10th	Day	26% 40% 6% 10% 13% 4	1710
	11th to 20th	Day	32% 32% 4 12% 17% 3	2150
	21st to end	Day	33% 26% 7% 13% 18% 2	3124
January	1st to 10th	Night	26% 39% 5% 12% 16% 2	2459
	11th to 20th	Night	28% 40% 4 13% 13% 3	2430
	21st to end	Night	31% 37% 3 11% 14% 5%	2398
February	1st to 10th	Night	29% 36% 4 12% 14% 6%	2160
	11th to 20th	Night	28% 36% 3 11% 15% 7%	2099
	21st to end	Night	28% 37% 6% 10% 14% 5%	1776
March	1st to 10th	Night	23% 36% 6% 13% 14% 9%	2160
	11th to 20th	Night	26% 38% 8% 13% 12% 3	1985
	21st to end	Night	24% 37% 6% 17% 13% 3	2178
April	1st to 10th	Night	24% 38% 7% 13% 13% 5%	1845
	11th to 20th	Night	20% 36% 4 15% 18% 8%	1775
	21st to end	Night	20% 37% 8% 17% 15% 3	1739
May	1st to 10th	Night	21% 39% 10% 15% 13% 2	1620
	11th to 20th	Night	25% 41% 10% 12% 11%	1593
	21st to end	Night	19% 39% 10% 19% 12% 2	1745
June	1st to 10th	Night	22% 42% 12% 14% 10%	1620
	11th to 20th	Night	17% 40% 14% 18% 9% 2	1620
	21st to end	Night	21% 39% 11% 14% 12% 3	1620
July	1st to 10th	Night	27% 43% 12% 9% 7% 1	1575
	11th to 20th	Night	25% 46% 13% 7% 7% 2	1566
	21st to end	Night	24% 43% 18% 11% 4 1	1672
August	1st to 10th	Night	19% 42% 15% 20% 4	1690
	11th to 20th	Night	26% 40% 13% 12% 8% 2	1776
	21st to end	Night	32% 40% 10% 10% 7% 2	1980
September	1st to 10th	Night	23% 42% 12% 11% 8% 4	1898
	11th to 20th	Night	27% 38% 7% 12% 13% 3	1980
	21st to end	Night	23% 36% 6% 12% 16% 7%	1980
October	1st to 10th	Night	17% 35% 6% 13% 22% 8%	1980
	11th to 20th	Night	21% 36% 5% 12% 19% 7%	2003
	21st to end	Night	20% 37% 4 11% 20% 8%	2430
November	1st to 10th	Night	13% 40% 5% 12% 18% 12%	2406
	11th to 20th	Night	21% 39% 4 11% 17% 8%	2470
	21st to end	Night	25% 39% 5% 10% 15% 6%	2470
December	1st to 10th	Night	25% 39% 5% 12% 14% 4	2470
	11th to 20th	Night	28% 32% 5% 10% 22% 3	3044
	21st to end	Night	35% 25% 7% 15% 16% 2	4532

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% 23% 34% 11% 2	270
	11th to 20th	Day	24% 24% 32% 13% 6% 1	258
	21st to end	Day	25% 27% 33% 13% 2 1	264
February	1st to 10th	Day	25% 24% 35% 13% 2	240
	11th to 20th	Day	37% 22% 30% 10% 1	240
	21st to end	Day	30% 18% 42% 10% 1	198
March	1st to 10th	Day	26% 20% 35% 17% 1 2	240
	11th to 20th	Day	23% 19% 34% 15% 8% 1	411
	21st to end	Day	23% 17% 31% 22% 6% 1	462
April	1st to 10th	Day	20% 16% 31% 20% 11% 2	420
	11th to 20th	Day	17% 15% 31% 23% 12% 2	412
	21st to end	Day	15% 10% 31% 30% 12% 3	420
May	1st to 10th	Day	14% 13% 27% 25% 16% 5%	423
	11th to 20th	Day	11% 5% 23% 33% 17% 11%	447
	21st to end	Day	13% 5% 15% 32% 20% 15%	485
June	1st to 10th	Day	13% 3 16% 33% 22% 13%	450
	11th to 20th	Day	7% 4 13% 26% 26% 23%	450
	21st to end	Day	8% 3 17% 25% 30% 17%	450
July	1st to 10th	Day	7% 1 8% 29% 31% 23%	445
	11th to 20th	Day	6% 2 9% 23% 32% 28%	444
	21st to end	Day	7% 2 9% 22% 38% 23%	488
August	1st to 10th	Day	9% 2 11% 24% 33% 22%	446
	11th to 20th	Day	10% 2 8% 30% 31% 19%	439
	21st to end	Day	14% 3 9% 26% 31% 17%	495
September	1st to 10th	Day	9% 5% 8% 28% 33% 16%	450
	11th to 20th	Day	15% 3 12% 28% 32% 10%	450
	21st to end	Day	13% 3 19% 26% 30% 9%	450
October	1st to 10th	Day	14% 3 26% 31% 19% 7%	450
	11th to 20th	Day	14% 7% 24% 30% 19% 5%	450
	21st to end	Day	18% 10% 26% 25% 18% 3	437
November	1st to 10th	Day	19% 10% 26% 34% 8% 3	270
	11th to 20th	Day	15% 20% 37% 21% 6%	270
	21st to end	Day	13% 17% 43% 19% 8% 1	270
December	1st to 10th	Day	26% 20% 32% 18% 3 1	270
	11th to 20th	Day	21% 22% 33% 17% 5% 1	270
	21st to end	Day	30% 14% 34% 18% 5%	297
January	1st to 10th	Night	24% 18% 31% 23% 4	760
	11th to 20th	Night	22% 16% 30% 24% 7%	748
	21st to end	Night	21% 17% 36% 22% 4	792
February	1st to 10th	Night	22% 12% 33% 27% 5%	720
	11th to 20th	Night	24% 17% 32% 25% 2	703
	21st to end	Night	22% 17% 36% 21% 3	592
March	1st to 10th	Night	17% 16% 34% 28% 6%	720
	11th to 20th	Night	19% 13% 35% 22% 10% 1	720
	21st to end	Night	16% 15% 30% 29% 10% 1	792
April	1st to 10th	Night	15% 12% 33% 28% 11% 1	585
	11th to 20th	Night	17% 11% 30% 27% 14% 2	533
	21st to end	Night	9% 9% 24% 40% 16% 1	540
May	1st to 10th	Night	9% 7% 27% 31% 23% 2	540
	11th to 20th	Night	10% 5% 20% 34% 26% 5%	531
	21st to end	Night	12% 1 12% 33% 37% 5%	584
June	1st to 10th	Night	8% 2 11% 39% 35% 6%	540
	11th to 20th	Night	3 1 10% 28% 39% 18%	540
	21st to end	Night	7% 1 8% 33% 42% 9%	540
July	1st to 10th	Night	7% 2 8% 21% 47% 15%	525
	11th to 20th	Night	4 2 4 20% 50% 20%	522
	21st to end	Night	7% 2 7% 25% 44% 15%	591
August	1st to 10th	Night	5% 1 6% 25% 45% 19%	537
	11th to 20th	Night	10% 1 6% 26% 48% 9%	534
	21st to end	Night	14% 2 7% 26% 38% 12%	594
September	1st to 10th	Night	8% 1 11% 27% 42% 10%	638
	11th to 20th	Night	14% 3 12% 29% 37% 6%	720
	21st to end	Night	12% 3 14% 33% 34% 4	720
October	1st to 10th	Night	11% 3 21% 34% 25% 6%	720
	11th to 20th	Night	12% 8% 24% 31% 21% 4	720
	21st to end	Night	15% 9% 23% 32% 19% 3	792
November	1st to 10th	Night	15% 7% 22% 33% 22% 2	740
	11th to 20th	Night	16% 11% 31% 28% 13% 1	760
	21st to end	Night	17% 13% 27% 31% 12%	760
December	1st to 10th	Night	22% 13% 28% 27% 9% 1	760
	11th to 20th	Night	24% 9% 31% 27% 9% 1	760
	21st to end	Night	27% 13% 26% 28% 6%	836

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