Stargate Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stargate Observatory clear sky chart from 2005-11-06 to 2024-01-15.

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	4 4 2 5% 5% 3 5% 5% 5% 7% 56%	74511
	Night	3 4 2 4 4 3 4 5% 5% 7% 60%	75273
Transparency	Day	26% 6% 8% 17% 27% 17%	74236
	Night	21% 6% 9% 19% 28% 17%	75068
Seeing	Day	8% 17% 27% 26% 17% 5%	13335
	Night	5% 13% 27% 31% 21% 3	23943

By Month

Percentage Cloud Cover SW (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	1 5% 2 5% 3 3 3 4 5% 8% 60%	1708
	11th to 20th	Day	2 5% 2 4 4 2 3 4 4 5% 65%	1656
	21st to end	Day	3 6% 3 4 4 2 4 3 3 7% 59%	1782
February	1st to 10th	Day	1 6% 2 4 4 2 4 3 5% 8% 61%	1620
	11th to 20th	Day	2 5% 3 6% 4 4 5% 4 6% 7% 55%	1649
	21st to end	Day	3 6% 2 4 5% 4 5% 4 4 7% 57%	1559
March	1st to 10th	Day	2 4 2 4 5% 3 5% 6% 6% 8% 56%	1980
	11th to 20th	Day	3 6% 3 5% 5% 3 4 4 5% 6% 56%	1980
	21st to end	Day	3 4 3 4 4 3 5% 4 6% 8% 57%	2178
April	1st to 10th	Day	1 3 2 4 4 2 5% 4 4 7% 64%	2124
	11th to 20th	Day	2 4 2 4 4 3 5% 5% 5% 6% 61%	2131
	21st to end	Day	3 3 2 3 3 2 3 4 4 7% 64%	2160
May	1st to 10th	Day	3 2 1 3 4 3 3 4 5% 6% 65%	2200
	11th to 20th	Day	4 4 2 5% 5% 3 5% 5% 6% 6% 55%	2301
	21st to end	Day	3 3 2 3 4 3 4 4 4 5% 65%	2530
June	1st to 10th	Day	3 2 1 3 3 3 4 5% 5% 8% 63%	2340
	11th to 20th	Day	2 2 1 4 4 2 4 3 4 4 70%	2340
	21st to end	Day	3 4 2 4 4 4 6% 5% 6% 6% 54%	2340
July	1st to 10th	Day	6% 4 3 7% 7% 5% 7% 7% 8% 8% 40%	2340
	11th to 20th	Day	5% 5% 3 7% 7% 6% 8% 8% 7% 9% 34%	2340
	21st to end	Day	7% 7% 3 8% 8% 5% 9% 9% 8% 9% 27%	2545
August	1st to 10th	Day	7% 6% 3 8% 8% 5% 7% 7% 7% 8% 34%	2328
	11th to 20th	Day	6% 6% 3 6% 8% 5% 7% 7% 7% 8% 37%	2183
	21st to end	Day	7% 5% 2 6% 7% 4 6% 7% 6% 9% 42%	2376
September	1st to 10th	Day	7% 6% 2 7% 6% 5% 5% 6% 7% 6% 43%	2160
	11th to 20th	Day	6% 5% 2 5% 5% 2 4 4 6% 6% 54%	2102
	21st to end	Day	4 3 2 4 4 2 4 4 5% 6% 61%	1922
October	1st to 10th	Day	6% 4 2 4 4 2 4 4 4 4 60%	1800
	11th to 20th	Day	4 4 1 2 3 1 2 2 3 4 74%	1800
	21st to end	Day	2 2 1 4 3 2 2 3 4 5% 72%	1980
November	1st to 10th	Day	1 2 1 2 3 2 3 4 4 7% 71%	1859
	11th to 20th	Day	1 2 1 3 3 2 3 4 5% 6% 69%	1900
	21st to end	Day	2 5% 2 5% 4 3 4 3 4 6% 62%	1633
December	1st to 10th	Day	3 4 2 4 4 2 4 5% 5% 7% 60%	1520
	11th to 20th	Day	3 6% 3 6% 6% 3 5% 5% 5% 7% 51%	1999
	21st to end	Day	1 5% 2 4 4 3 5% 4 5% 6% 59%	3146
January	1st to 10th	Night	1 4 2 4 4 2 5% 5% 5% 8% 61%	2457
	11th to 20th	Night	3 4 2 3 3 3 3 3 5% 7% 64%	2392
	21st to end	Night	3 4 2 4 4 2 4 4 6% 8% 59%	2574
February	1st to 10th	Night	1 4 2 4 3 2 3 4 4 7% 66%	2340
	11th to 20th	Night	2 4 2 4 5% 3 4 4 5% 7% 59%	2196
	21st to end	Night	1 4 2 3 3 2 3 5% 5% 8% 65%	1695
March	1st to 10th	Night	1 2 2 4 4 3 3 4 5% 9% 64%	1980
	11th to 20th	Night	3 5% 1 3 3 2 3 4 4 6% 64%	1980
	21st to end	Night	2 4 2 3 4 3 4 5% 6% 6% 62%	2178
April	1st to 10th	Night	2 2 1 3 3 2 4 3 5% 7% 68%	1835
	11th to 20th	Night	3 3 1 3 4 2 4 5% 5% 6% 64%	1777
	21st to end	Night	1 3 1 3 3 2 3 3 4 7% 69%	1800
May	1st to 10th	Night	2 4 1 2 3 2 5% 4 5% 7% 65%	1756
	11th to 20th	Night	4 4 1 3 3 2 4 5% 5% 9% 60%	1594
	21st to end	Night	2 2 1 3 2 2 3 3 4 5% 72%	1746
June	1st to 10th	Night	3 2 2 3 4 2 4 5% 4 7% 64%	1620
	11th to 20th	Night	3 2 1 2 3 2 3 4 4 5% 71%	1620
	21st to end	Night	4 4 2 4 5% 4 5% 5% 6% 6% 54%	1620
July	1st to 10th	Night	4 5% 3 6% 6% 4 5% 6% 8% 9% 45%	1620
	11th to 20th	Night	3 4 2 6% 7% 4 7% 9% 11% 11% 37%	1620
	21st to end	Night	5% 6% 3 7% 7% 6% 8% 9% 10% 11% 28%	1773
August	1st to 10th	Night	4 4 2 5% 5% 4 6% 8% 8% 10% 44%	1611
	11th to 20th	Night	6% 5% 4 6% 7% 4 8% 8% 8% 9% 37%	1717
	21st to end	Night	5% 3 2 6% 5% 3 6% 7% 9% 9% 46%	1980
September	1st to 10th	Night	7% 5% 3 7% 5% 3 5% 6% 7% 8% 44%	1800
	11th to 20th	Night	4 4 2 4 4 4 4 5% 4 6% 58%	1854
	21st to end	Night	4 4 2 3 3 2 3 4 4 6% 66%	2037
October	1st to 10th	Night	5% 4 1 4 4 2 3 3 4 6% 64%	2160
	11th to 20th	Night	2 3 1 2 2 1 2 2 3 4 76%	2160
	21st to end	Night	2 2 1 3 3 2 2 3 3 5% 73%	2376
November	1st to 10th	Night	2 2 1 2 2 2 3 4 4 6% 73%	2220
	11th to 20th	Night	1 2 1 2 3 2 3 4 5% 6% 73%	2280
	21st to end	Night	3 5% 2 4 3 2 3 4 4 6% 63%	2516
December	1st to 10th	Night	3 4 1 3 4 3 3 4 5% 7% 64%	2660
	11th to 20th	Night	2 5% 2 6% 5% 3 4 4 6% 9% 53%	3208
	21st to end	Night	2 4 2 4 5% 3 3 5% 5% 7% 61%	4521

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	22% 5% 8% 24% 29% 12%	1709
	11th to 20th	Day	21% 3 8% 24% 34% 10%	1656
	21st to end	Day	25% 4 7% 19% 33% 12%	1782
February	1st to 10th	Day	23% 4 11% 20% 27% 16%	1620
	11th to 20th	Day	27% 4 7% 23% 25% 15%	1658
	21st to end	Day	26% 4 5% 18% 27% 20%	1559
March	1st to 10th	Day	22% 6% 7% 18% 32% 16%	1980
	11th to 20th	Day	27% 4 6% 17% 30% 16%	1980
	21st to end	Day	23% 5% 7% 19% 33% 12%	2178
April	1st to 10th	Day	20% 4 6% 19% 34% 17%	2124
	11th to 20th	Day	23% 4 6% 16% 33% 18%	2134
	21st to end	Day	20% 4 6% 19% 35% 15%	2160
May	1st to 10th	Day	19% 5% 5% 15% 36% 20%	2200
	11th to 20th	Day	27% 6% 7% 15% 28% 17%	2304
	21st to end	Day	20% 5% 6% 12% 32% 25%	2530
June	1st to 10th	Day	18% 5% 7% 13% 30% 28%	2340
	11th to 20th	Day	17% 3 4 9% 23% 44%	2340
	21st to end	Day	27% 5% 8% 12% 24% 24%	2340
July	1st to 10th	Day	35% 10% 11% 15% 13% 17%	2276
	11th to 20th	Day	40% 11% 16% 16% 10% 7%	2271
	21st to end	Day	44% 13% 19% 16% 6% 1	2404
August	1st to 10th	Day	45% 10% 13% 11% 13% 8%	2313
	11th to 20th	Day	41% 9% 11% 16% 15% 7%	2183
	21st to end	Day	35% 10% 11% 19% 21% 4	2376
September	1st to 10th	Day	37% 7% 9% 14% 18% 14%	2160
	11th to 20th	Day	29% 5% 8% 15% 24% 20%	2102
	21st to end	Day	23% 5% 7% 17% 28% 21%	1922
October	1st to 10th	Day	26% 5% 7% 17% 23% 21%	1800
	11th to 20th	Day	17% 3 3 11% 35% 31%	1800
	21st to end	Day	15% 3 7% 17% 41% 17%	1980
November	1st to 10th	Day	13% 3 7% 23% 34% 20%	1859
	11th to 20th	Day	15% 4 6% 20% 38% 17%	1900
	21st to end	Day	24% 4 6% 15% 34% 18%	1633
December	1st to 10th	Day	22% 6% 7% 26% 25% 13%	1520
	11th to 20th	Day	31% 6% 8% 18% 27% 10%	1997
	21st to end	Day	24% 6% 8% 20% 23% 19%	3146
January	1st to 10th	Night	20% 6% 9% 20% 32% 11%	2457
	11th to 20th	Night	20% 4 8% 25% 32% 12%	2392
	21st to end	Night	22% 5% 8% 20% 32% 13%	2574
February	1st to 10th	Night	19% 4 10% 23% 27% 18%	2340
	11th to 20th	Night	23% 5% 8% 23% 23% 18%	2197
	21st to end	Night	16% 6% 8% 18% 35% 17%	1695
March	1st to 10th	Night	17% 4 5% 24% 32% 17%	1980
	11th to 20th	Night	21% 4 7% 20% 34% 15%	1980
	21st to end	Night	20% 6% 7% 21% 34% 12%	2178
April	1st to 10th	Night	16% 3 5% 24% 34% 16%	1835
	11th to 20th	Night	17% 5% 5% 18% 34% 21%	1777
	21st to end	Night	15% 5% 7% 19% 37% 17%	1800
May	1st to 10th	Night	18% 5% 6% 14% 37% 20%	1756
	11th to 20th	Night	21% 8% 8% 19% 28% 16%	1595
	21st to end	Night	14% 4 7% 14% 36% 26%	1746
June	1st to 10th	Night	19% 5% 5% 14% 28% 28%	1620
	11th to 20th	Night	15% 3 5% 11% 22% 45%	1620
	21st to end	Night	27% 6% 11% 14% 16% 26%	1620
July	1st to 10th	Night	32% 9% 13% 15% 13% 18%	1575
	11th to 20th	Night	31% 14% 21% 17% 8% 9%	1566
	21st to end	Night	42% 15% 22% 14% 6% 2	1674
August	1st to 10th	Night	29% 12% 23% 13% 14% 9%	1602
	11th to 20th	Night	38% 11% 15% 16% 12% 9%	1717
	21st to end	Night	27% 11% 17% 23% 16% 6%	1980
September	1st to 10th	Night	34% 8% 12% 16% 16% 14%	1800
	11th to 20th	Night	25% 6% 9% 17% 23% 20%	1854
	21st to end	Night	19% 5% 8% 16% 30% 22%	2037
October	1st to 10th	Night	23% 5% 8% 19% 25% 21%	2160
	11th to 20th	Night	14% 3 3 14% 34% 32%	2160
	21st to end	Night	15% 4 5% 19% 39% 18%	2376
November	1st to 10th	Night	12% 3 5% 25% 37% 18%	2220
	11th to 20th	Night	12% 5% 6% 22% 36% 20%	2280
	21st to end	Night	22% 5% 5% 16% 35% 17%	2516
December	1st to 10th	Night	19% 5% 9% 27% 27% 13%	2660
	11th to 20th	Night	25% 6% 10% 18% 27% 13%	3208
	21st to end	Night	21% 6% 9% 19% 25% 21%	4521

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	6% 33% 29% 22% 10% 1	270
	11th to 20th	Day	12% 24% 28% 22% 13% 2	252
	21st to end	Day	3 20% 41% 24% 9% 4	264
February	1st to 10th	Day	5% 27% 30% 25% 12% 1	240
	11th to 20th	Day	8% 30% 37% 20% 6%	240
	21st to end	Day	13% 42% 21% 18% 6% 1	277
March	1st to 10th	Day	12% 29% 30% 22% 5% 1	420
	11th to 20th	Day	16% 24% 33% 16% 10% 1	420
	21st to end	Day	14% 34% 32% 14% 5% 1	462
April	1st to 10th	Day	9% 26% 36% 19% 7% 2	420
	11th to 20th	Day	13% 31% 31% 18% 5% 1	412
	21st to end	Day	12% 25% 37% 21% 5% 1	420
May	1st to 10th	Day	8% 21% 44% 20% 6% 2	423
	11th to 20th	Day	6% 16% 37% 25% 13% 3	448
	21st to end	Day	6% 21% 36% 25% 11% 1	485
June	1st to 10th	Day	5% 11% 31% 34% 17% 2	450
	11th to 20th	Day	5% 13% 29% 30% 18% 4	450
	21st to end	Day	6% 10% 26% 35% 18% 5%	450
July	1st to 10th	Day	4 3 17% 41% 26% 9%	446
	11th to 20th	Day	7% 7% 31% 39% 16%	444
	21st to end	Day	8% 2 6% 26% 41% 17%	487
August	1st to 10th	Day	9% 3 12% 30% 36% 10%	447
	11th to 20th	Day	7% 5% 12% 35% 28% 13%	437
	21st to end	Day	11% 3 13% 30% 30% 13%	495
September	1st to 10th	Day	10% 4 17% 35% 28% 7%	450
	11th to 20th	Day	7% 5% 24% 36% 23% 5%	450
	21st to end	Day	7% 9% 26% 32% 20% 7%	392
October	1st to 10th	Day	8% 14% 29% 22% 19% 9%	270
	11th to 20th	Day	12% 9% 27% 29% 16% 7%	270
	21st to end	Day	9% 13% 25% 30% 18% 6%	297
November	1st to 10th	Day	4 20% 36% 24% 14% 2	270
	11th to 20th	Day	4 13% 28% 34% 15% 6%	270
	21st to end	Day	6% 24% 30% 23% 14% 4	270
December	1st to 10th	Day	8% 20% 24% 33% 13% 2	270
	11th to 20th	Day	6% 30% 27% 25% 11% 1	270
	21st to end	Day	13% 28% 34% 14% 10% 1	297
January	1st to 10th	Night	4 19% 25% 32% 17% 3	760
	11th to 20th	Night	7% 17% 30% 29% 14% 3	736
	21st to end	Night	4 18% 30% 29% 16% 3	792
February	1st to 10th	Night	3 21% 34% 27% 13% 2	720
	11th to 20th	Night	5% 20% 39% 26% 9% 1	704
	21st to end	Night	6% 25% 36% 28% 5%	592
March	1st to 10th	Night	3 25% 33% 26% 12% 1	720
	11th to 20th	Night	6% 17% 30% 29% 17% 1	720
	21st to end	Night	5% 20% 36% 29% 10% 1	792
April	1st to 10th	Night	4 24% 35% 27% 9%	575
	11th to 20th	Night	5% 24% 35% 26% 9%	533
	21st to end	Night	3 24% 37% 25% 9% 1	540
May	1st to 10th	Night	5% 15% 41% 31% 8% 1	540
	11th to 20th	Night	3 13% 34% 33% 14% 2	531
	21st to end	Night	3 11% 40% 32% 14%	584
June	1st to 10th	Night	3 6% 35% 37% 16% 2	540
	11th to 20th	Night	4 8% 33% 39% 15% 1	540
	21st to end	Night	5% 4 26% 37% 25% 3	540
July	1st to 10th	Night	5% 2 15% 40% 35% 3	525
	11th to 20th	Night	5% 8% 34% 44% 10%	522
	21st to end	Night	8% 2 6% 21% 50% 13%	591
August	1st to 10th	Night	5% 2 8% 28% 45% 13%	537
	11th to 20th	Night	8% 2 9% 32% 42% 7%	534
	21st to end	Night	6% 1 9% 33% 46% 6%	594
September	1st to 10th	Night	9% 2 11% 36% 38% 4	540
	11th to 20th	Night	5% 3 14% 40% 34% 4	594
	21st to end	Night	5% 4 21% 35% 30% 5%	720
October	1st to 10th	Night	7% 8% 26% 36% 20% 3	720
	11th to 20th	Night	4 7% 23% 41% 21% 4	720
	21st to end	Night	5% 10% 24% 33% 22% 5%	792
November	1st to 10th	Night	3 9% 28% 33% 23% 4	740
	11th to 20th	Night	2 12% 28% 32% 22% 5%	760
	21st to end	Night	7% 18% 25% 25% 22% 3	897
December	1st to 10th	Night	6% 17% 26% 34% 16% 2	950
	11th to 20th	Night	5% 22% 31% 26% 15% 1	912
	21st to end	Night	6% 22% 31% 29% 11% 2	836

Page generated at 2024-01-11 20:33:49. Version ac07

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