Heaven's Plateau
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Heaven's Plateau clear sky chart from 2005-11-06 to 2024-10-25.

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	9% 5% 1 3 2 2 2 2 3 5% 65%	101089
	Night	11% 5% 1 3 2 2 3 2 4 5% 61%	97927
Transparency	Day	23% 3 7% 18% 24% 25%	100839
	Night	27% 4 7% 18% 22% 21%	97766
Seeing	Day	12% 12% 31% 30% 12% 4	15150
	Night	13% 4 15% 36% 26% 6%	24499

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	21% 11% 2 4 3 3 2 2 3 5% 45%	2539
	11th to 20th	Day	21% 8% 3 6% 4 5% 4 3 4 5% 36%	2736
	21st to end	Day	22% 10% 2 5% 4 4 4 2 5% 6% 36%	3146
February	1st to 10th	Day	20% 9% 2 4 2 3 3 2 4 5% 47%	1710
	11th to 20th	Day	14% 10% 2 4 3 3 3 3 3 7% 47%	1840
	21st to end	Day	20% 11% 2 4 3 3 3 2 4 4 44%	1570
March	1st to 10th	Day	17% 15% 3 7% 4 4 5% 4 6% 6% 28%	3160
	11th to 20th	Day	15% 7% 1 3 2 2 3 2 3 5% 56%	3490
	21st to end	Day	18% 12% 2 6% 4 4 4 3 5% 6% 35%	4028
April	1st to 10th	Day	15% 8% 1 4 3 3 4 3 4 7% 47%	2280
	11th to 20th	Day	13% 6% 2 5% 3 2 3 2 5% 5% 54%	2249
	21st to end	Day	11% 4 1 3 3 2 3 3 4 6% 60%	2280
May	1st to 10th	Day	8% 4 1 2 2 2 2 2 4 4 70%	3879
	11th to 20th	Day	4 3 1 2 1 2 2 2 2 5% 77%	4310
	21st to end	Day	6% 3 1 2 2 2 2 2 3 5% 73%	4813
June	1st to 10th	Day	6% 3 1 4 3 2 2 3 4 6% 66%	2660
	11th to 20th	Day	2 1 1 2 2 2 2 2 4 4 80%	2660
	21st to end	Day	2 2 1 2 1 2 2 2 3 2 83%	2660
July	1st to 10th	Day	1 1 1 1 1 2 93%	4420
	11th to 20th	Day	2 1 1 2 1 1 2 2 2 3 84%	4420
	21st to end	Day	1 1 1 1 1 1 1 1 2 3 88%	4528
August	1st to 10th	Day	2 1 1 2 2 1 2 2 3 4 81%	4061
	11th to 20th	Day	1 1 1 1 1 3 3 88%	3724
	21st to end	Day	2 1 2 1 1 1 1 2 2 88%	4180
September	1st to 10th	Day	2 1 1 1 1 1 2 3 88%	2280
	11th to 20th	Day	2 2 1 2 2 2 2 2 3 5% 76%	2271
	21st to end	Day	4 2 1 2 2 1 1 1 3 4 80%	2085
October	1st to 10th	Day	6% 2 1 3 2 2 2 2 3 6% 70%	1900
	11th to 20th	Day	6% 2 1 2 2 2 3 3 4 5% 70%	1900
	21st to end	Day	8% 2 1 3 2 2 2 3 4 4 68%	2025
November	1st to 10th	Day	12% 6% 1 4 3 3 3 3 5% 7% 52%	1680
	11th to 20th	Day	11% 4 1 4 3 3 4 3 4 7% 56%	1710
	21st to end	Day	12% 7% 1 4 3 3 2 3 4 6% 55%	1653
December	1st to 10th	Day	16% 6% 2 4 3 3 4 2 4 5% 52%	1520
	11th to 20th	Day	28% 9% 2 5% 3 4 4 2 4 5% 34%	1928
	21st to end	Day	14% 8% 3 6% 4 4 5% 4 7% 7% 39%	2794
January	1st to 10th	Night	16% 9% 2 5% 3 3 3 2 5% 6% 46%	4406
	11th to 20th	Night	23% 8% 2 6% 4 4 4 4 5% 5% 36%	4228
	21st to end	Night	22% 10% 2 6% 4 4 4 3 5% 6% 35%	4521
February	1st to 10th	Night	18% 8% 2 4 4 2 2 3 4 5% 48%	2470
	11th to 20th	Night	16% 8% 1 4 3 3 3 3 5% 7% 47%	2227
	21st to end	Night	17% 9% 2 4 2 3 3 2 4 5% 50%	1884
March	1st to 10th	Night	20% 16% 2 4 4 3 4 4 4 5% 35%	3710
	11th to 20th	Night	16% 6% 1 3 2 2 2 2 3 4 57%	3490
	21st to end	Night	23% 11% 2 4 4 3 4 3 4 6% 37%	3623
April	1st to 10th	Night	14% 6% 1 5% 4 3 3 3 4 6% 50%	1900
	11th to 20th	Night	12% 6% 1 4 3 3 4 3 4 6% 55%	1879
	21st to end	Night	10% 4 1 3 2 3 3 3 6% 7% 59%	1900
May	1st to 10th	Night	5% 6% 1 2 1 2 2 2 4 6% 71%	3095
	11th to 20th	Night	4 1 1 1 1 1 1 2 3 6% 77%	2580
	21st to end	Night	4 2 1 2 1 2 2 2 2 4 77%	2762
June	1st to 10th	Night	5% 3 1 3 2 2 2 3 4 6% 68%	1520
	11th to 20th	Night	1 1 2 1 1 2 1 4 3 83%	1520
	21st to end	Night	2 1 1 2 2 1 1 1 2 3 85%	1520
July	1st to 10th	Night	1 1 1 1 1 1 94%	2540
	11th to 20th	Night	3 2 1 2 2 2 3 2 3 4 78%	2540
	21st to end	Night	2 1 1 2 2 2 2 2 3 84%	3029
August	1st to 10th	Night	3 2 1 2 1 2 2 2 3 3 78%	2877
	11th to 20th	Night	1 1 1 1 1 2 1 3 2 87%	3126
	21st to end	Night	4 1 1 1 1 1 1 1 2 88%	3498
September	1st to 10th	Night	2 1 1 1 1 1 2 3 88%	1900
	11th to 20th	Night	4 2 1 2 1 2 2 1 3 3 80%	1907
	21st to end	Night	3 1 1 1 1 2 2 1 2 3 81%	2090
October	1st to 10th	Night	5% 2 1 3 2 2 3 2 3 4 73%	2280
	11th to 20th	Night	6% 2 1 2 2 2 2 2 3 5% 74%	2280
	21st to end	Night	7% 1 1 2 2 2 2 2 3 5% 72%	2436
November	1st to 10th	Night	13% 5% 1 3 3 2 2 2 4 6% 59%	2397
	11th to 20th	Night	11% 3 2 3 3 2 3 3 4 7% 58%	2470
	21st to end	Night	12% 5% 1 4 3 3 3 2 4 5% 57%	2524
December	1st to 10th	Night	18% 6% 1 4 2 3 3 2 4 6% 51%	2660
	11th to 20th	Night	29% 8% 2 4 3 3 3 3 5% 5% 35%	3276
	21st to end	Night	17% 8% 3 6% 4 5% 4 4 5% 6% 36%	4862

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	44% 4 8% 24% 17% 4	2539
	11th to 20th	Day	50% 6% 9% 13% 13% 9%	2736
	21st to end	Day	49% 6% 9% 19% 12% 5%	3146
February	1st to 10th	Day	41% 3 7% 21% 17% 10%	1710
	11th to 20th	Day	38% 4 8% 20% 24% 6%	1850
	21st to end	Day	44% 3 8% 22% 18% 5%	1570
March	1st to 10th	Day	52% 7% 14% 12% 11% 3	3160
	11th to 20th	Day	31% 5% 11% 31% 12% 10%	3490
	21st to end	Day	45% 8% 15% 20% 9% 2	4028
April	1st to 10th	Day	36% 5% 13% 23% 17% 6%	2280
	11th to 20th	Day	31% 4 14% 27% 18% 6%	2252
	21st to end	Day	25% 4 13% 31% 23% 4	2280
May	1st to 10th	Day	18% 4 10% 30% 25% 13%	3879
	11th to 20th	Day	13% 2 6% 26% 42% 10%	4313
	21st to end	Day	15% 3 9% 32% 35% 5%	4814
June	1st to 10th	Day	20% 4 10% 24% 30% 12%	2660
	11th to 20th	Day	10% 2 6% 23% 36% 23%	2660
	21st to end	Day	10% 2 2 12% 31% 43%	2660
July	1st to 10th	Day	3 1 5% 15% 75%	4351
	11th to 20th	Day	9% 1 2 6% 17% 65%	4345
	21st to end	Day	6% 1 1 5% 27% 59%	4385
August	1st to 10th	Day	10% 2 2 7% 24% 56%	4046
	11th to 20th	Day	5% 1 1 5% 35% 53%	3760
	21st to end	Day	7% 1 2 7% 40% 43%	4179
September	1st to 10th	Day	6% 1 2 8% 32% 51%	2280
	11th to 20th	Day	13% 2 5% 20% 38% 21%	2271
	21st to end	Day	12% 2 4 18% 37% 27%	2085
October	1st to 10th	Day	17% 3 6% 17% 26% 31%	1900
	11th to 20th	Day	17% 3 6% 19% 29% 26%	1900
	21st to end	Day	19% 3 6% 21% 29% 22%	2025
November	1st to 10th	Day	32% 3 8% 20% 21% 16%	1680
	11th to 20th	Day	28% 5% 8% 19% 27% 13%	1710
	21st to end	Day	30% 4 7% 19% 27% 13%	1653
December	1st to 10th	Day	35% 4 9% 19% 21% 12%	1520
	11th to 20th	Day	54% 4 5% 14% 14% 9%	1928
	21st to end	Day	39% 8% 14% 21% 12% 6%	2794
January	1st to 10th	Night	39% 5% 12% 24% 16% 4	4406
	11th to 20th	Night	48% 6% 9% 15% 12% 9%	4228
	21st to end	Night	49% 7% 9% 16% 12% 7%	4521
February	1st to 10th	Night	39% 3 6% 18% 20% 13%	2470
	11th to 20th	Night	36% 4 8% 23% 20% 9%	2228
	21st to end	Night	38% 3 9% 24% 19% 6%	1884
March	1st to 10th	Night	50% 6% 10% 17% 12% 5%	3710
	11th to 20th	Night	31% 4 8% 25% 20% 11%	3490
	21st to end	Night	47% 7% 12% 22% 9% 4	3623
April	1st to 10th	Night	35% 5% 15% 21% 19% 6%	1900
	11th to 20th	Night	31% 5% 12% 27% 16% 9%	1879
	21st to end	Night	24% 5% 11% 35% 18% 6%	1900
May	1st to 10th	Night	17% 3 12% 28% 24% 15%	3095
	11th to 20th	Night	11% 2 9% 26% 36% 16%	2580
	21st to end	Night	12% 3 8% 40% 30% 6%	2762
June	1st to 10th	Night	17% 5% 13% 23% 29% 13%	1520
	11th to 20th	Night	7% 3 6% 25% 34% 24%	1520
	21st to end	Night	9% 1 2 13% 33% 42%	1520
July	1st to 10th	Night	3 1 5% 15% 75%	2500
	11th to 20th	Night	13% 2 2 7% 13% 62%	2492
	21st to end	Night	9% 1 1 5% 23% 61%	2934
August	1st to 10th	Night	12% 1 1 7% 23% 55%	2868
	11th to 20th	Night	5% 2 1 6% 32% 53%	3156
	21st to end	Night	8% 1 1 10% 37% 44%	3498
September	1st to 10th	Night	5% 2 2 7% 34% 51%	1900
	11th to 20th	Night	12% 2 3 19% 40% 25%	1907
	21st to end	Night	11% 2 2 20% 36% 29%	2090
October	1st to 10th	Night	18% 3 5% 17% 28% 30%	2280
	11th to 20th	Night	15% 3 6% 18% 32% 27%	2280
	21st to end	Night	15% 3 5% 20% 31% 25%	2436
November	1st to 10th	Night	27% 4 8% 20% 21% 19%	2397
	11th to 20th	Night	26% 4 7% 22% 27% 14%	2470
	21st to end	Night	30% 4 6% 19% 25% 15%	2524
December	1st to 10th	Night	36% 3 8% 20% 18% 15%	2660
	11th to 20th	Night	50% 4 6% 14% 18% 7%	3276
	21st to end	Night	45% 8% 11% 17% 12% 7%	4862

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	33% 11% 23% 20% 9% 3	180
	11th to 20th	Day	23% 6% 24% 32% 11% 3	298
	21st to end	Day	22% 9% 27% 24% 15% 3	407
February	1st to 10th	Day	28% 12% 23% 23% 11% 3	370
	11th to 20th	Day	22% 15% 31% 22% 8% 1	450
	21st to end	Day	24% 15% 30% 22% 8% 1	382
March	1st to 10th	Day	29% 21% 25% 19% 5% 1	460
	11th to 20th	Day	27% 18% 23% 19% 10% 2	460
	21st to end	Day	23% 19% 32% 20% 5%	506
April	1st to 10th	Day	20% 17% 34% 20% 8% 1	460
	11th to 20th	Day	19% 23% 26% 24% 7% 1	452
	21st to end	Day	10% 18% 31% 25% 12% 3	460
May	1st to 10th	Day	12% 20% 33% 24% 8% 3	463
	11th to 20th	Day	13% 16% 30% 23% 13% 5%	488
	21st to end	Day	12% 14% 24% 32% 13% 5%	529
June	1st to 10th	Day	7% 12% 32% 30% 10% 8%	490
	11th to 20th	Day	5% 16% 34% 31% 9% 5%	490
	21st to end	Day	3 7% 38% 32% 12% 8%	490
July	1st to 10th	Day	1 5% 40% 35% 12% 7%	486
	11th to 20th	Day	2 3 33% 42% 12% 8%	484
	21st to end	Day	2 2 35% 39% 14% 8%	531
August	1st to 10th	Day	3 6% 38% 35% 13% 5%	487
	11th to 20th	Day	1 6% 39% 35% 13% 5%	477
	21st to end	Day	2 5% 35% 39% 15% 4	539
September	1st to 10th	Day	3 7% 40% 35% 13% 2	490
	11th to 20th	Day	5% 12% 34% 35% 13% 1	490
	21st to end	Day	4 10% 34% 39% 10% 2	490
October	1st to 10th	Day	5% 12% 32% 34% 14% 3	490
	11th to 20th	Day	7% 11% 28% 34% 16% 4	490
	21st to end	Day	10% 11% 27% 32% 16% 4	514
November	1st to 10th	Day	16% 9% 21% 27% 20% 7%	276
	11th to 20th	Day	12% 8% 19% 34% 19% 8%	270
	21st to end	Day	16% 9% 19% 31% 20% 5%	243
December	1st to 10th	Day	20% 7% 24% 24% 17% 8%	180
	11th to 20th	Day	19% 9% 28% 26% 11% 6%	180
	21st to end	Day	25% 13% 22% 21% 13% 6%	198
January	1st to 10th	Night	23% 5% 21% 26% 18% 7%	760
	11th to 20th	Night	18% 5% 19% 38% 15% 4	760
	21st to end	Night	22% 5% 20% 29% 19% 5%	836
February	1st to 10th	Night	21% 5% 20% 33% 18% 3	760
	11th to 20th	Night	20% 7% 19% 31% 18% 5%	744
	21st to end	Night	22% 8% 19% 34% 14% 3	628
March	1st to 10th	Night	26% 7% 18% 31% 15% 3	760
	11th to 20th	Night	22% 7% 16% 29% 20% 5%	760
	21st to end	Night	23% 8% 19% 29% 19% 2	836
April	1st to 10th	Night	18% 3 17% 41% 19% 3	760
	11th to 20th	Night	15% 7% 19% 37% 19% 4	751
	21st to end	Night	11% 3 18% 39% 23% 5%	760
May	1st to 10th	Night	10% 5% 20% 39% 22% 4	714
	11th to 20th	Night	8% 4 12% 39% 34% 3	412
	21st to end	Night	7% 2 13% 37% 36% 5%	411
June	1st to 10th	Night	6% 3 10% 37% 38% 6%	380
	11th to 20th	Night	1 1 12% 45% 36% 5%	380
	21st to end	Night	2 9% 44% 40% 5%	380
July	1st to 10th	Night	1 3 44% 46% 6%	370
	11th to 20th	Night	2 7% 38% 46% 7%	368
	21st to end	Night	3 1 5% 32% 46% 13%	570
August	1st to 10th	Night	3 1 5% 42% 41% 8%	583
	11th to 20th	Night	1 1 9% 45% 36% 8%	752
	21st to end	Night	1 6% 42% 46% 4	836
September	1st to 10th	Night	2 6% 47% 38% 6%	760
	11th to 20th	Night	4 2 10% 37% 37% 10%	760
	21st to end	Night	4 2 14% 40% 31% 9%	760
October	1st to 10th	Night	6% 4 13% 44% 25% 7%	760
	11th to 20th	Night	8% 3 13% 41% 30% 5%	760
	21st to end	Night	7% 3 17% 35% 25% 12%	812
November	1st to 10th	Night	14% 3 13% 36% 26% 8%	740
	11th to 20th	Night	12% 4 19% 38% 21% 6%	760
	21st to end	Night	15% 5% 21% 34% 19% 6%	760
December	1st to 10th	Night	22% 4 19% 34% 16% 5%	760
	11th to 20th	Night	27% 3 18% 31% 17% 4	760
	21st to end	Night	25% 7% 21% 29% 15% 3	836

Page generated at 2024-10-22 17:21:04. Version ac07

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