Angelus Oaks Heliport
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Angelus Oaks Heliport clear sky chart from 2005-11-06 to 2024-04-03.

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 3 3 2 3 3 4 6% 64%	79579
	Night	4 5% 2 3 3 2 3 3 4 6% 64%	80585
Transparency	Day	20% 3 6% 15% 27% 28%	79309
	Night	20% 3 6% 15% 27% 30%	80377
Seeing	Day	7% 10% 30% 35% 13% 4	14820
	Night	6% 5% 19% 34% 28% 8%	25015

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	6% 6% 1 3 3 2 2 3 4 7% 63%	2858
	11th to 20th	Day	7% 6% 2 3 3 2 3 3 5% 9% 57%	2938
	21st to end	Day	9% 9% 2 4 3 3 4 4 5% 7% 49%	3498
February	1st to 10th	Day	8% 7% 3 4 2 2 3 4 4 6% 57%	1900
	11th to 20th	Day	6% 8% 2 4 4 2 3 4 5% 7% 55%	1850
	21st to end	Day	9% 10% 4 5% 4 2 3 2 2 7% 52%	1570
March	1st to 10th	Day	7% 10% 2 4 5% 2 4 5% 4 8% 48%	1900
	11th to 20th	Day	6% 7% 4 3 4 2 4 4 4 9% 54%	1990
	21st to end	Day	5% 6% 1 4 4 3 4 5% 4 6% 57%	2418
April	1st to 10th	Day	7% 6% 2 3 4 2 3 4 5% 7% 57%	2185
	11th to 20th	Day	4 4 2 3 3 2 3 3 4 7% 66%	2129
	21st to end	Day	4 4 2 3 3 2 2 3 5% 8% 65%	2160
May	1st to 10th	Day	3 4 1 3 4 3 3 3 6% 7% 64%	2307
	11th to 20th	Day	3 2 1 2 2 1 3 4 5% 9% 69%	2301
	21st to end	Day	3 3 1 3 3 2 3 3 5% 6% 69%	2530
June	1st to 10th	Day	2 2 2 2 2 2 3 2 5% 6% 72%	2340
	11th to 20th	Day	1 1 1 1 2 2 3 4 83%	2340
	21st to end	Day	1 3 1 2 2 1 2 1 2 3 81%	2432
July	1st to 10th	Day	2 1 1 2 2 2 2 3 3 6% 75%	2411
	11th to 20th	Day	2 2 1 2 2 2 3 3 5% 7% 69%	2340
	21st to end	Day	2 2 1 4 3 2 5% 5% 7% 9% 60%	2498
August	1st to 10th	Day	2 1 1 2 3 1 3 3 4 6% 75%	2149
	11th to 20th	Day	1 1 2 3 2 4 3 4 6% 75%	2122
	21st to end	Day	1 2 1 2 3 2 3 3 5% 5% 74%	2376
September	1st to 10th	Day	3 2 1 2 2 2 3 4 5% 6% 71%	2147
	11th to 20th	Day	1 1 1 2 1 2 2 3 4 83%	1980
	21st to end	Day	2 1 1 1 2 1 2 3 4 5% 77%	1980
October	1st to 10th	Day	3 4 2 3 3 2 3 3 4 5% 69%	1980
	11th to 20th	Day	2 2 1 2 2 1 2 2 4 4 77%	1967
	21st to end	Day	2 3 1 2 2 1 2 3 3 5% 75%	1864
November	1st to 10th	Day	3 5% 1 4 4 2 3 3 4 5% 68%	1674
	11th to 20th	Day	4 3 1 4 3 2 3 3 5% 5% 67%	1710
	21st to end	Day	6% 4 2 4 4 3 4 4 4 7% 58%	1710
December	1st to 10th	Day	6% 6% 2 5% 5% 3 5% 4 5% 7% 53%	1710
	11th to 20th	Day	11% 7% 3 5% 5% 3 5% 6% 5% 8% 42%	2169
	21st to end	Day	6% 10% 3 6% 6% 4 5% 5% 4 6% 45%	3146
January	1st to 10th	Night	5% 7% 2 3 4 2 4 3 5% 5% 61%	4097
	11th to 20th	Night	5% 6% 2 4 4 2 3 4 5% 9% 56%	4019
	21st to end	Night	9% 9% 2 4 3 2 4 4 5% 7% 51%	4180
February	1st to 10th	Night	8% 11% 2 3 3 1 3 3 4 6% 56%	2280
	11th to 20th	Night	5% 9% 1 3 4 2 3 4 5% 6% 58%	2218
	21st to end	Night	8% 10% 3 5% 4 2 4 4 5% 6% 49%	1884
March	1st to 10th	Night	6% 9% 3 4 5% 3 5% 4 6% 9% 45%	2280
	11th to 20th	Night	4 9% 3 3 4 3 4 4 5% 8% 53%	2189
	21st to end	Night	4 9% 3 5% 4 2 4 5% 4 7% 53%	2176
April	1st to 10th	Night	4 7% 2 3 5% 2 3 5% 5% 7% 57%	1820
	11th to 20th	Night	3 5% 1 2 2 2 4 3 4 7% 67%	1779
	21st to end	Night	2 4 1 3 3 2 4 4 5% 6% 65%	1800
May	1st to 10th	Night	2 4 1 2 3 3 3 3 5% 8% 67%	1652
	11th to 20th	Night	2 3 1 2 2 2 3 3 5% 6% 71%	1594
	21st to end	Night	1 2 1 2 2 1 3 3 5% 7% 72%	1746
June	1st to 10th	Night	1 1 2 2 1 1 2 2 5% 5% 78%	1620
	11th to 20th	Night	1 1 1 1 1 1 2 2 4 85%	1620
	21st to end	Night	1 1 1 1 2 1 2 2 2 3 85%	1506
July	1st to 10th	Night	1 1 1 2 1 2 2 3 4 84%	1530
	11th to 20th	Night	2 2 1 2 3 2 3 3 4 5% 73%	1620
	21st to end	Night	1 3 2 2 3 3 4 4 4 6% 68%	1816
August	1st to 10th	Night	1 1 1 2 2 1 2 3 2 4 80%	1790
	11th to 20th	Night	1 1 1 1 1 2 2 3 5% 82%	1780
	21st to end	Night	2 1 1 2 2 1 1 2 2 3 83%	1980
September	1st to 10th	Night	2 2 2 1 1 2 2 3 5% 79%	1811
	11th to 20th	Night	1 1 1 1 1 1 2 3 3 87%	1980
	21st to end	Night	1 1 1 1 1 2 2 2 4 85%	1980
October	1st to 10th	Night	3 2 1 3 3 1 3 4 3 4 72%	1980
	11th to 20th	Night	1 2 1 2 2 1 2 4 3 3 79%	1989
	21st to end	Night	1 2 1 2 3 2 2 3 2 5% 75%	2492
November	1st to 10th	Night	3 5% 2 3 3 2 3 2 3 6% 69%	2405
	11th to 20th	Night	2 4 2 4 3 2 3 4 4 6% 66%	2470
	21st to end	Night	4 7% 2 5% 4 3 4 4 4 7% 56%	2470
December	1st to 10th	Night	6% 6% 3 5% 4 3 3 3 5% 9% 53%	2470
	11th to 20th	Night	10% 9% 3 6% 5% 2 4 4 7% 9% 43%	3041
	21st to end	Night	5% 7% 2 6% 5% 4 5% 6% 5% 8% 48%	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	21% 2 5% 18% 36% 18%	2859
	11th to 20th	Day	23% 4 11% 19% 27% 15%	2938
	21st to end	Day	31% 4 6% 15% 29% 15%	3498
February	1st to 10th	Day	27% 4 4 15% 24% 26%	1900
	11th to 20th	Day	26% 3 6% 15% 27% 23%	1860
	21st to end	Day	31% 3 7% 16% 24% 19%	1570
March	1st to 10th	Day	32% 3 8% 15% 24% 19%	1900
	11th to 20th	Day	25% 4 7% 19% 27% 17%	1990
	21st to end	Day	25% 3 9% 22% 26% 14%	2418
April	1st to 10th	Day	26% 3 8% 21% 27% 15%	2185
	11th to 20th	Day	18% 2 7% 19% 31% 22%	2132
	21st to end	Day	16% 4 8% 20% 37% 14%	2160
May	1st to 10th	Day	18% 3 8% 20% 30% 21%	2307
	11th to 20th	Day	12% 2 6% 22% 38% 20%	2304
	21st to end	Day	16% 3 7% 24% 33% 17%	2530
June	1st to 10th	Day	14% 2 5% 15% 36% 29%	2340
	11th to 20th	Day	6% 2 5% 10% 25% 52%	2340
	21st to end	Day	11% 2 3 6% 20% 58%	2432
July	1st to 10th	Day	12% 3 4 8% 19% 54%	2347
	11th to 20th	Day	16% 5% 7% 17% 24% 31%	2271
	21st to end	Day	19% 8% 9% 19% 23% 23%	2359
August	1st to 10th	Day	12% 5% 5% 9% 24% 45%	2135
	11th to 20th	Day	11% 5% 6% 14% 24% 41%	2122
	21st to end	Day	14% 3 4 9% 34% 35%	2376
September	1st to 10th	Day	15% 5% 5% 6% 27% 42%	2147
	11th to 20th	Day	8% 2 2 8% 32% 49%	1980
	21st to end	Day	11% 3 4 14% 28% 41%	1980
October	1st to 10th	Day	17% 2 5% 14% 26% 36%	1980
	11th to 20th	Day	11% 2 5% 11% 31% 40%	1967
	21st to end	Day	12% 3 4 9% 30% 43%	1864
November	1st to 10th	Day	18% 2 4 14% 32% 30%	1674
	11th to 20th	Day	20% 2 5% 13% 23% 37%	1710
	21st to end	Day	25% 3 5% 13% 27% 27%	1710
December	1st to 10th	Day	30% 3 7% 14% 22% 24%	1710
	11th to 20th	Day	36% 4 9% 14% 22% 15%	2168
	21st to end	Day	36% 5% 7% 20% 20% 13%	3146
January	1st to 10th	Night	22% 4 5% 15% 27% 26%	4097
	11th to 20th	Night	23% 4 10% 21% 27% 16%	4019
	21st to end	Night	31% 3 9% 13% 27% 18%	4180
February	1st to 10th	Night	29% 4 5% 13% 21% 29%	2280
	11th to 20th	Night	27% 2 5% 13% 26% 27%	2219
	21st to end	Night	32% 3 7% 14% 21% 24%	1884
March	1st to 10th	Night	33% 3 9% 16% 21% 20%	2280
	11th to 20th	Night	26% 4 8% 17% 26% 19%	2189
	21st to end	Night	27% 3 8% 19% 28% 14%	2176
April	1st to 10th	Night	23% 4 9% 20% 27% 16%	1820
	11th to 20th	Night	17% 2 7% 19% 30% 24%	1779
	21st to end	Night	14% 4 8% 18% 39% 18%	1800
May	1st to 10th	Night	13% 4 8% 19% 32% 24%	1652
	11th to 20th	Night	13% 3 6% 20% 36% 22%	1595
	21st to end	Night	11% 2 9% 23% 37% 18%	1746
June	1st to 10th	Night	9% 1 5% 16% 33% 36%	1620
	11th to 20th	Night	6% 2 4 10% 26% 52%	1620
	21st to end	Night	7% 1 2 5% 22% 62%	1506
July	1st to 10th	Night	7% 2 3 8% 20% 59%	1485
	11th to 20th	Night	14% 4 5% 18% 22% 37%	1566
	21st to end	Night	15% 6% 8% 21% 26% 23%	1715
August	1st to 10th	Night	10% 3 6% 11% 24% 47%	1780
	11th to 20th	Night	6% 3 4 15% 29% 42%	1780
	21st to end	Night	10% 2 3 10% 33% 43%	1980
September	1st to 10th	Night	10% 2 5% 9% 25% 50%	1811
	11th to 20th	Night	5% 1 3 9% 30% 51%	1980
	21st to end	Night	6% 1 3 15% 30% 44%	1980
October	1st to 10th	Night	15% 1 4 14% 29% 37%	1980
	11th to 20th	Night	11% 2 4 12% 30% 42%	1989
	21st to end	Night	13% 2 4 8% 26% 47%	2492
November	1st to 10th	Night	19% 1 4 11% 32% 33%	2405
	11th to 20th	Night	19% 2 5% 11% 26% 37%	2470
	21st to end	Night	26% 4 6% 12% 23% 29%	2470
December	1st to 10th	Night	28% 3 6% 12% 24% 27%	2470
	11th to 20th	Night	33% 3 11% 14% 21% 18%	3041
	21st to end	Night	30% 4 8% 19% 23% 15%	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	20% 7% 33% 28% 11% 1	270
	11th to 20th	Day	16% 9% 27% 34% 12% 2	322
	21st to end	Day	13% 14% 33% 28% 10% 1	506
February	1st to 10th	Day	16% 16% 30% 25% 12% 2	460
	11th to 20th	Day	14% 15% 35% 28% 6% 1	455
	21st to end	Day	17% 18% 35% 25% 5%	382
March	1st to 10th	Day	20% 18% 32% 23% 7%	460
	11th to 20th	Day	15% 16% 35% 27% 7% 2	460
	21st to end	Day	13% 23% 37% 21% 5% 1	506
April	1st to 10th	Day	12% 17% 31% 29% 10% 2	429
	11th to 20th	Day	8% 23% 35% 25% 6% 2	412
	21st to end	Day	6% 20% 32% 28% 9% 5%	420
May	1st to 10th	Day	8% 16% 36% 28% 9% 4	423
	11th to 20th	Day	6% 15% 36% 29% 11% 4	448
	21st to end	Day	6% 12% 37% 29% 12% 4	485
June	1st to 10th	Day	3 10% 30% 34% 16% 7%	450
	11th to 20th	Day	1 6% 32% 41% 13% 7%	450
	21st to end	Day	2 6% 27% 43% 15% 7%	450
July	1st to 10th	Day	1 1 19% 54% 15% 9%	446
	11th to 20th	Day	2 14% 49% 22% 11%	444
	21st to end	Day	2 1 16% 49% 18% 14%	487
August	1st to 10th	Day	2 2 25% 46% 15% 10%	447
	11th to 20th	Day	2 1 19% 48% 18% 12%	437
	21st to end	Day	2 21% 49% 17% 11%	495
September	1st to 10th	Day	4 3 30% 43% 16% 5%	450
	11th to 20th	Day	2 4 33% 42% 16% 2	450
	21st to end	Day	2 10% 29% 38% 17% 4	450
October	1st to 10th	Day	4 11% 33% 36% 15% 1	450
	11th to 20th	Day	3 9% 34% 37% 16% 2	450
	21st to end	Day	4 9% 28% 38% 18% 3	379
November	1st to 10th	Day	6% 9% 30% 40% 14% 1	270
	11th to 20th	Day	5% 8% 30% 39% 14% 4	270
	21st to end	Day	8% 11% 30% 36% 13% 3	270
December	1st to 10th	Day	11% 7% 34% 33% 13% 2	270
	11th to 20th	Day	8% 9% 31% 36% 13% 2	270
	21st to end	Day	16% 14% 35% 22% 10% 2	297
January	1st to 10th	Night	13% 6% 26% 30% 18% 7%	760
	11th to 20th	Night	10% 5% 26% 34% 19% 6%	760
	21st to end	Night	12% 7% 29% 33% 16% 4	836
February	1st to 10th	Night	14% 6% 25% 33% 15% 6%	760
	11th to 20th	Night	9% 9% 27% 31% 18% 5%	744
	21st to end	Night	15% 9% 29% 29% 15% 4	628
March	1st to 10th	Night	13% 9% 29% 31% 15% 3	760
	11th to 20th	Night	11% 8% 22% 33% 19% 7%	760
	21st to end	Night	9% 11% 26% 35% 16% 3	836
April	1st to 10th	Night	7% 8% 26% 37% 18% 4	728
	11th to 20th	Night	5% 9% 30% 32% 21% 5%	711
	21st to end	Night	4 9% 25% 34% 20% 8%	720
May	1st to 10th	Night	6% 5% 23% 39% 22% 5%	572
	11th to 20th	Night	4 5% 19% 36% 31% 6%	531
	21st to end	Night	4 5% 20% 38% 28% 5%	584
June	1st to 10th	Night	1 4 13% 44% 33% 6%	540
	11th to 20th	Night	1 1 15% 43% 36% 4	540
	21st to end	Night	2 1 8% 42% 42% 5%	426
July	1st to 10th	Night	3 32% 52% 12%	435
	11th to 20th	Night	3 2 36% 52% 7%	522
	21st to end	Night	2 1 3 26% 57% 11%	634
August	1st to 10th	Night	1 1 5% 31% 49% 14%	716
	11th to 20th	Night	2 1 24% 55% 17%	712
	21st to end	Night	3 1 3 25% 51% 17%	792
September	1st to 10th	Night	2 1 4 30% 48% 15%	720
	11th to 20th	Night	1 1 7% 37% 39% 14%	720
	21st to end	Night	1 1 12% 36% 39% 11%	720
October	1st to 10th	Night	4 3 16% 42% 29% 6%	720
	11th to 20th	Night	2 3 17% 37% 30% 11%	720
	21st to end	Night	3 5% 21% 31% 26% 12%	792
November	1st to 10th	Night	6% 4 19% 37% 26% 9%	740
	11th to 20th	Night	4 3 22% 37% 25% 9%	760
	21st to end	Night	8% 6% 24% 33% 22% 7%	760
December	1st to 10th	Night	9% 5% 26% 34% 21% 5%	760
	11th to 20th	Night	14% 6% 26% 33% 17% 5%	760
	21st to end	Night	12% 9% 29% 29% 16% 5%	836

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