Pageant Avenue Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pageant Avenue Observatory clear sky chart from 2005-11-06 to 2024-03-08.

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	7% 4 2 4 3 2 3 3 4 7% 61%	79168
	Night	9% 7% 3 4 4 2 3 3 4 7% 54%	80485
Transparency	Day	24% 5% 9% 18% 23% 22%	78903
	Night	30% 6% 10% 15% 19% 20%	80273
Seeing	Day	7% 5% 20% 38% 24% 6%	14816
	Night	9% 2 10% 31% 37% 11%	25248

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	10% 3 1 3 3 2 3 3 3 5% 64%	2858
	11th to 20th	Day	9% 5% 2 4 3 2 3 4 5% 7% 57%	3056
	21st to end	Day	13% 5% 2 4 4 2 4 4 5% 7% 49%	3498
February	1st to 10th	Day	11% 3 1 4 4 2 4 3 3 5% 59%	1900
	11th to 20th	Day	9% 5% 2 4 3 2 4 4 5% 8% 54%	1850
	21st to end	Day	11% 6% 2 5% 3 3 4 5% 4 7% 49%	1570
March	1st to 10th	Day	9% 5% 2 5% 3 2 4 5% 6% 12% 48%	1871
	11th to 20th	Day	9% 4 2 4 4 2 4 4 4 9% 54%	1880
	21st to end	Day	6% 4 2 4 3 2 3 4 5% 8% 59%	2299
April	1st to 10th	Day	8% 6% 2 3 4 2 3 5% 5% 8% 54%	2160
	11th to 20th	Day	5% 4 1 3 3 2 3 3 5% 6% 64%	2129
	21st to end	Day	8% 4 2 3 2 1 2 3 5% 7% 63%	2160
May	1st to 10th	Day	9% 4 2 5% 4 2 3 4 5% 7% 56%	2257
	11th to 20th	Day	6% 6% 2 5% 2 2 3 3 3 7% 61%	2301
	21st to end	Day	7% 6% 2 4 3 2 3 3 4 7% 59%	2530
June	1st to 10th	Day	6% 7% 3 4 3 2 3 2 3 7% 60%	2340
	11th to 20th	Day	4 5% 2 4 2 1 2 3 3 5% 69%	2340
	21st to end	Day	3 5% 3 4 3 1 2 3 4 5% 68%	2340
July	1st to 10th	Day	3 5% 2 4 3 2 3 3 4 7% 64%	2340
	11th to 20th	Day	2 4 2 4 3 1 3 4 5% 7% 65%	2340
	21st to end	Day	3 4 2 4 3 2 3 4 6% 8% 62%	2418
August	1st to 10th	Day	2 4 2 2 3 2 3 3 4 5% 72%	2149
	11th to 20th	Day	2 3 1 3 2 1 2 2 3 6% 73%	2122
	21st to end	Day	2 3 1 3 3 2 2 3 4 7% 70%	2376
September	1st to 10th	Day	4 3 1 3 3 2 3 3 4 6% 69%	2147
	11th to 20th	Day	3 4 1 2 1 1 2 3 3 6% 74%	1980
	21st to end	Day	4 3 1 2 2 2 2 2 3 5% 73%	1980
October	1st to 10th	Day	4 4 2 3 3 2 3 3 4 7% 64%	1980
	11th to 20th	Day	7% 4 1 3 3 1 2 3 4 5% 67%	1980
	21st to end	Day	5% 3 1 3 2 1 2 2 3 5% 73%	1898
November	1st to 10th	Day	5% 3 1 3 3 2 3 3 5% 6% 66%	1674
	11th to 20th	Day	6% 4 1 3 3 2 2 3 4 7% 66%	1710
	21st to end	Day	7% 4 2 3 3 3 3 5% 4 7% 60%	1710
December	1st to 10th	Day	7% 4 2 3 4 2 3 4 5% 8% 57%	1710
	11th to 20th	Day	13% 4 2 5% 4 3 5% 5% 5% 8% 45%	2169
	21st to end	Day	12% 5% 2 4 5% 4 5% 5% 5% 8% 43%	3146
January	1st to 10th	Night	9% 5% 1 3 3 2 3 2 4 5% 63%	4097
	11th to 20th	Night	10% 5% 2 5% 4 2 4 4 5% 7% 51%	3917
	21st to end	Night	16% 6% 2 4 3 2 3 3 5% 7% 48%	4180
February	1st to 10th	Night	10% 5% 3 4 3 2 2 3 5% 5% 58%	2280
	11th to 20th	Night	11% 6% 2 4 4 2 4 3 3 4 55%	2218
	21st to end	Night	13% 6% 2 5% 4 2 4 3 5% 6% 49%	1884
March	1st to 10th	Night	12% 7% 3 5% 4 2 5% 4 4 9% 45%	2249
	11th to 20th	Night	12% 8% 2 3 3 2 4 4 5% 8% 48%	2080
	21st to end	Night	9% 8% 2 4 3 3 4 5% 5% 7% 51%	2052
April	1st to 10th	Night	11% 7% 3 5% 4 2 3 3 5% 8% 49%	1800
	11th to 20th	Night	10% 10% 2 5% 4 2 2 2 4 5% 54%	1779
	21st to end	Night	10% 9% 2 5% 4 2 3 3 4 7% 52%	1800
May	1st to 10th	Night	9% 10% 4 5% 4 2 2 4 5% 9% 45%	1702
	11th to 20th	Night	9% 15% 5% 6% 4 3 3 3 3 9% 41%	1594
	21st to end	Night	14% 12% 3 4 3 2 3 3 3 6% 47%	1746
June	1st to 10th	Night	8% 13% 4 7% 4 2 3 3 5% 8% 42%	1620
	11th to 20th	Night	6% 10% 4 6% 4 2 2 3 5% 9% 50%	1620
	21st to end	Night	5% 9% 4 7% 4 2 3 3 5% 9% 51%	1620
July	1st to 10th	Night	3 9% 5% 5% 4 2 3 4 5% 8% 52%	1620
	11th to 20th	Night	2 6% 4 6% 4 2 3 5% 5% 8% 54%	1620
	21st to end	Night	3 7% 4 6% 5% 3 3 5% 4 10% 49%	1897
August	1st to 10th	Night	3 6% 3 5% 3 2 3 2 5% 8% 60%	1790
	11th to 20th	Night	3 8% 3 6% 4 2 2 3 4 8% 58%	1780
	21st to end	Night	4 5% 3 6% 4 2 3 2 4 7% 60%	1980
September	1st to 10th	Night	5% 6% 3 5% 4 2 3 3 4 6% 59%	1812
	11th to 20th	Night	6% 5% 1 2 2 1 2 2 4 7% 67%	1980
	21st to end	Night	5% 4 4 4 2 1 2 2 4 6% 66%	1980
October	1st to 10th	Night	5% 5% 2 3 4 2 3 3 5% 7% 60%	1980
	11th to 20th	Night	7% 8% 2 3 3 2 3 3 3 5% 62%	1980
	21st to end	Night	7% 6% 2 3 3 2 2 2 4 5% 65%	2451
November	1st to 10th	Night	6% 4 2 4 2 2 2 3 3 5% 64%	2405
	11th to 20th	Night	4 5% 2 4 4 2 3 3 4 5% 65%	2470
	21st to end	Night	7% 4 2 4 4 2 5% 4 4 8% 56%	2470
December	1st to 10th	Night	10% 5% 2 4 4 2 3 4 5% 7% 54%	2470
	11th to 20th	Night	14% 7% 2 5% 4 2 4 4 6% 7% 45%	3041
	21st to end	Night	13% 6% 2 5% 6% 3 4 5% 6% 6% 44%	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% 4 7% 23% 24% 20%	2859
	11th to 20th	Day	26% 7% 13% 24% 15% 15%	3056
	21st to end	Day	33% 6% 7% 15% 23% 16%	3498
February	1st to 10th	Day	28% 5% 7% 14% 20% 27%	1900
	11th to 20th	Day	27% 6% 9% 13% 25% 19%	1860
	21st to end	Day	33% 6% 10% 14% 21% 16%	1570
March	1st to 10th	Day	29% 6% 10% 19% 17% 19%	1871
	11th to 20th	Day	27% 6% 10% 18% 23% 15%	1880
	21st to end	Day	24% 6% 11% 25% 20% 14%	2299
April	1st to 10th	Day	29% 5% 11% 22% 23% 9%	2160
	11th to 20th	Day	21% 6% 10% 18% 27% 18%	2132
	21st to end	Day	21% 5% 11% 23% 28% 13%	2160
May	1st to 10th	Day	28% 6% 10% 18% 24% 14%	2257
	11th to 20th	Day	25% 5% 8% 23% 27% 11%	2304
	21st to end	Day	27% 5% 10% 23% 28% 7%	2530
June	1st to 10th	Day	26% 6% 10% 20% 24% 14%	2340
	11th to 20th	Day	19% 3 8% 14% 29% 27%	2340
	21st to end	Day	20% 3 7% 10% 22% 38%	2340
July	1st to 10th	Day	21% 3 11% 10% 22% 34%	2276
	11th to 20th	Day	18% 6% 12% 22% 23% 20%	2271
	21st to end	Day	19% 7% 15% 23% 26% 10%	2284
August	1st to 10th	Day	15% 4 9% 16% 28% 27%	2135
	11th to 20th	Day	14% 2 8% 20% 29% 26%	2122
	21st to end	Day	16% 3 9% 14% 31% 27%	2376
September	1st to 10th	Day	17% 4 7% 12% 30% 29%	2147
	11th to 20th	Day	15% 3 8% 10% 31% 33%	1980
	21st to end	Day	15% 4 6% 14% 31% 30%	1980
October	1st to 10th	Day	21% 4 6% 18% 22% 28%	1980
	11th to 20th	Day	21% 4 6% 13% 24% 33%	1980
	21st to end	Day	16% 4 5% 14% 22% 39%	1898
November	1st to 10th	Day	20% 4 7% 19% 17% 33%	1674
	11th to 20th	Day	20% 4 7% 15% 17% 36%	1710
	21st to end	Day	24% 4 9% 13% 19% 30%	1710
December	1st to 10th	Day	25% 5% 11% 17% 17% 25%	1710
	11th to 20th	Day	35% 8% 10% 13% 18% 16%	2168
	21st to end	Day	37% 8% 10% 21% 14% 11%	3146
January	1st to 10th	Night	23% 6% 7% 17% 29% 19%	4097
	11th to 20th	Night	31% 8% 11% 21% 13% 16%	3917
	21st to end	Night	36% 6% 9% 12% 19% 19%	4180
February	1st to 10th	Night	28% 4 9% 13% 19% 27%	2280
	11th to 20th	Night	33% 5% 7% 13% 20% 21%	2219
	21st to end	Night	35% 5% 7% 14% 22% 17%	1884
March	1st to 10th	Night	37% 6% 9% 16% 14% 18%	2249
	11th to 20th	Night	34% 6% 11% 15% 18% 16%	2080
	21st to end	Night	32% 7% 11% 20% 19% 11%	2052
April	1st to 10th	Night	34% 6% 11% 21% 17% 11%	1800
	11th to 20th	Night	33% 5% 9% 16% 21% 16%	1779
	21st to end	Night	35% 6% 12% 17% 19% 11%	1800
May	1st to 10th	Night	36% 7% 12% 16% 14% 14%	1702
	11th to 20th	Night	42% 9% 11% 14% 12% 12%	1595
	21st to end	Night	41% 5% 11% 18% 16% 7%	1746
June	1st to 10th	Night	40% 10% 14% 10% 16% 10%	1620
	11th to 20th	Night	32% 4 13% 11% 20% 20%	1620
	21st to end	Night	31% 4 12% 10% 16% 27%	1620
July	1st to 10th	Night	27% 5% 14% 11% 18% 24%	1575
	11th to 20th	Night	26% 6% 14% 18% 22% 14%	1566
	21st to end	Night	31% 7% 15% 20% 19% 7%	1792
August	1st to 10th	Night	23% 4 13% 18% 23% 19%	1780
	11th to 20th	Night	26% 4 12% 17% 24% 17%	1780
	21st to end	Night	22% 4 11% 14% 24% 24%	1980
September	1st to 10th	Night	27% 5% 8% 14% 20% 26%	1812
	11th to 20th	Night	20% 3 8% 10% 30% 29%	1980
	21st to end	Night	21% 3 8% 13% 32% 23%	1980
October	1st to 10th	Night	24% 5% 7% 18% 19% 27%	1980
	11th to 20th	Night	26% 4 9% 13% 18% 30%	1980
	21st to end	Night	23% 3 6% 12% 20% 36%	2451
November	1st to 10th	Night	22% 5% 9% 15% 16% 33%	2405
	11th to 20th	Night	23% 3 6% 13% 17% 38%	2470
	21st to end	Night	29% 5% 9% 15% 15% 28%	2470
December	1st to 10th	Night	30% 5% 8% 16% 15% 25%	2470
	11th to 20th	Night	36% 6% 9% 13% 20% 15%	3041
	21st to end	Night	36% 11% 13% 16% 11% 13%	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	16% 5% 14% 38% 25% 3	270
	11th to 20th	Day	12% 6% 19% 39% 19% 5%	388
	21st to end	Day	11% 8% 26% 33% 17% 5%	506
February	1st to 10th	Day	11% 8% 26% 33% 18% 4	460
	11th to 20th	Day	8% 8% 31% 35% 15% 2	455
	21st to end	Day	11% 10% 34% 32% 11% 1	382
March	1st to 10th	Day	12% 9% 33% 33% 11% 2	449
	11th to 20th	Day	13% 6% 28% 36% 14% 4	420
	21st to end	Day	6% 12% 33% 35% 12% 2	462
April	1st to 10th	Day	11% 5% 30% 33% 17% 4	420
	11th to 20th	Day	5% 9% 34% 35% 13% 4	412
	21st to end	Day	7% 9% 24% 36% 17% 7%	420
May	1st to 10th	Day	11% 7% 27% 34% 16% 6%	423
	11th to 20th	Day	8% 6% 25% 39% 19% 3	448
	21st to end	Day	7% 8% 26% 38% 17% 4	485
June	1st to 10th	Day	6% 4 20% 36% 29% 5%	450
	11th to 20th	Day	5% 3 16% 41% 28% 8%	450
	21st to end	Day	6% 1 12% 41% 32% 8%	450
July	1st to 10th	Day	6% 6% 40% 38% 10%	446
	11th to 20th	Day	4 3 36% 40% 17%	444
	21st to end	Day	3 1 3 38% 41% 14%	487
August	1st to 10th	Day	2 8% 41% 36% 13%	447
	11th to 20th	Day	4 5% 44% 34% 13%	437
	21st to end	Day	3 7% 42% 37% 10%	495
September	1st to 10th	Day	6% 10% 48% 30% 7%	450
	11th to 20th	Day	5% 2 16% 48% 23% 6%	450
	21st to end	Day	5% 3 20% 39% 27% 6%	450
October	1st to 10th	Day	4 6% 24% 40% 22% 5%	450
	11th to 20th	Day	7% 3 24% 40% 21% 5%	450
	21st to end	Day	5% 2 20% 38% 26% 8%	413
November	1st to 10th	Day	6% 5% 16% 38% 28% 7%	270
	11th to 20th	Day	7% 3 17% 37% 30% 6%	270
	21st to end	Day	7% 7% 19% 39% 23% 6%	270
December	1st to 10th	Day	10% 3 19% 37% 25% 6%	270
	11th to 20th	Day	6% 3 18% 37% 28% 7%	270
	21st to end	Day	12% 9% 20% 37% 16% 6%	297
January	1st to 10th	Night	9% 4 13% 38% 27% 9%	760
	11th to 20th	Night	8% 3 11% 41% 30% 8%	760
	21st to end	Night	12% 2 14% 41% 25% 5%	836
February	1st to 10th	Night	11% 3 12% 37% 30% 8%	760
	11th to 20th	Night	12% 4 14% 38% 26% 6%	744
	21st to end	Night	14% 4 14% 41% 23% 4	628
March	1st to 10th	Night	13% 4 13% 41% 25% 4	750
	11th to 20th	Night	15% 3 9% 34% 29% 9%	720
	21st to end	Night	10% 3 13% 38% 31% 5%	792
April	1st to 10th	Night	12% 3 10% 41% 28% 6%	720
	11th to 20th	Night	12% 4 13% 35% 30% 7%	711
	21st to end	Night	12% 4 10% 32% 33% 9%	720
May	1st to 10th	Night	10% 3 12% 34% 34% 6%	622
	11th to 20th	Night	12% 2 14% 28% 36% 7%	531
	21st to end	Night	15% 2 16% 27% 36% 4	584
June	1st to 10th	Night	11% 2 14% 30% 37% 7%	540
	11th to 20th	Night	8% 1 9% 28% 49% 6%	540
	21st to end	Night	6% 1 8% 27% 50% 8%	540
July	1st to 10th	Night	7% 1 6% 16% 55% 16%	525
	11th to 20th	Night	4 3 11% 60% 22%	522
	21st to end	Night	6% 4 11% 55% 24%	715
August	1st to 10th	Night	5% 1 4 15% 53% 23%	716
	11th to 20th	Night	6% 1 4 11% 51% 27%	712
	21st to end	Night	6% 3 9% 54% 28%	792
September	1st to 10th	Night	6% 1 5% 15% 55% 18%	720
	11th to 20th	Night	8% 1 5% 23% 51% 13%	720
	21st to end	Night	4 2 7% 29% 42% 16%	720
October	1st to 10th	Night	6% 1 8% 35% 42% 9%	720
	11th to 20th	Night	9% 2 9% 33% 37% 11%	720
	21st to end	Night	7% 2 10% 31% 34% 15%	792
November	1st to 10th	Night	7% 1 8% 36% 35% 12%	740
	11th to 20th	Night	5% 1 8% 37% 36% 13%	760
	21st to end	Night	7% 2 10% 41% 30% 10%	760
December	1st to 10th	Night	11% 2 11% 40% 28% 8%	760
	11th to 20th	Night	14% 3 14% 38% 25% 7%	760
	21st to end	Night	10% 4 15% 37% 25% 8%	836

Page generated at 2024-03-05 04:23:57. Version ac07

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