Spodue Lookout
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Spodue Lookout clear sky chart from 2005-11-06 to 2024-03-06.

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	10% 9% 3 5% 4 2 3 3 4 6% 49%	78538
	Night	12% 10% 3 5% 4 2 4 4 5% 6% 46%	81005
Transparency	Day	36% 5% 10% 19% 19% 10%	78242
	Night	38% 6% 12% 19% 17% 8%	80822
Seeing	Day	14% 12% 23% 26% 18% 7%	13843
	Night	14% 7% 19% 35% 21% 3	23127

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	16% 18% 7% 9% 5% 3 4 4 3 6% 26%	2539
	11th to 20th	Day	25% 19% 7% 5% 4 2 3 2 4 4 25%	2540
	21st to end	Day	21% 16% 4 7% 5% 3 3 4 3 5% 28%	3114
February	1st to 10th	Day	12% 15% 4 6% 5% 2 4 3 5% 8% 36%	1710
	11th to 20th	Day	12% 16% 5% 6% 4 3 4 3 4 6% 36%	1701
	21st to end	Day	12% 16% 7% 7% 6% 3 4 3 4 6% 32%	1570
March	1st to 10th	Day	14% 17% 6% 7% 7% 3 4 3 4 6% 27%	1880
	11th to 20th	Day	15% 15% 5% 6% 4 3 3 4 5% 7% 33%	1980
	21st to end	Day	14% 17% 3 6% 6% 4 5% 5% 5% 6% 29%	2269
April	1st to 10th	Day	14% 15% 4 8% 6% 3 4 3 4 7% 32%	2160
	11th to 20th	Day	12% 13% 4 7% 5% 3 4 5% 4 6% 37%	2129
	21st to end	Day	8% 11% 2 6% 5% 3 4 3 5% 7% 47%	2163
May	1st to 10th	Day	8% 8% 4 5% 5% 3 3 5% 5% 6% 51%	2470
	11th to 20th	Day	10% 9% 3 5% 5% 2 5% 4 5% 7% 46%	2477
	21st to end	Day	11% 10% 3 6% 6% 3 5% 4 4 6% 40%	2723
June	1st to 10th	Day	11% 6% 3 4 5% 3 5% 5% 5% 8% 47%	2520
	11th to 20th	Day	5% 5% 2 4 4 2 3 3 4 6% 62%	2520
	21st to end	Day	5% 3 1 2 3 2 3 3 3 5% 71%	2520
July	1st to 10th	Day	2 2 1 2 2 1 2 3 4 4 77%	2520
	11th to 20th	Day	2 1 1 2 2 1 2 3 3 5% 80%	2520
	21st to end	Day	2 2 1 2 1 1 2 3 4 79%	2738
August	1st to 10th	Day	2 2 1 3 3 2 3 4 4 5% 70%	2328
	11th to 20th	Day	3 1 1 2 2 1 2 2 3 4 79%	2252
	21st to end	Day	3 2 1 1 1 1 2 1 3 4 82%	2376
September	1st to 10th	Day	2 2 1 2 2 2 2 2 3 4 78%	2160
	11th to 20th	Day	4 4 1 4 4 2 3 4 4 5% 65%	2160
	21st to end	Day	5% 5% 1 4 4 2 3 3 4 5% 65%	1931
October	1st to 10th	Day	9% 6% 2 5% 4 1 3 3 4 6% 59%	1800
	11th to 20th	Day	10% 6% 2 4 3 3 3 4 5% 8% 53%	1800
	21st to end	Day	13% 7% 2 5% 4 2 2 3 4 7% 51%	1931
November	1st to 10th	Day	16% 11% 3 6% 4 2 2 3 5% 7% 41%	1674
	11th to 20th	Day	17% 10% 3 5% 4 2 4 6% 6% 8% 34%	1601
	21st to end	Day	11% 13% 5% 7% 3 4 3 4 5% 8% 37%	1520
December	1st to 10th	Day	14% 12% 3 5% 5% 3 3 3 5% 7% 40%	1520
	11th to 20th	Day	22% 15% 3 6% 4 3 3 4 6% 8% 27%	1928
	21st to end	Day	15% 16% 5% 9% 7% 4 4 4 4 6% 26%	2794
January	1st to 10th	Night	14% 19% 4 7% 6% 3 5% 4 6% 7% 24%	4406
	11th to 20th	Night	20% 19% 4 8% 4 2 3 3 4 6% 28%	4420
	21st to end	Night	22% 17% 3 6% 4 3 4 4 4 6% 28%	4548
February	1st to 10th	Night	13% 12% 4 6% 4 3 4 4 5% 7% 38%	2470
	11th to 20th	Night	13% 14% 3 6% 4 3 3 4 4 6% 39%	2365
	21st to end	Night	11% 13% 6% 6% 5% 4 3 5% 4 8% 35%	1884
March	1st to 10th	Night	15% 14% 5% 6% 5% 3 4 5% 5% 6% 32%	2194
	11th to 20th	Night	14% 12% 4 5% 4 3 4 4 5% 7% 36%	1980
	21st to end	Night	13% 14% 5% 7% 5% 3 4 4 5% 8% 31%	2086
April	1st to 10th	Night	15% 11% 3 7% 5% 3 4 4 4 6% 37%	1800
	11th to 20th	Night	10% 10% 4 6% 5% 3 4 4 5% 6% 43%	1779
	21st to end	Night	10% 9% 2 4 4 2 4 4 6% 8% 48%	1795
May	1st to 10th	Night	9% 6% 2 3 3 2 4 4 5% 7% 55%	1489
	11th to 20th	Night	8% 7% 2 5% 4 3 4 5% 6% 8% 49%	1416
	21st to end	Night	8% 6% 3 5% 4 3 4 4 5% 8% 48%	1552
June	1st to 10th	Night	11% 5% 2 4 4 3 4 4 6% 9% 49%	1440
	11th to 20th	Night	6% 5% 2 3 4 3 3 2 4 6% 64%	1440
	21st to end	Night	4 2 1 3 2 2 3 2 3 4 73%	1440
July	1st to 10th	Night	2 1 2 2 1 3 3 4 6% 75%	1440
	11th to 20th	Night	1 2 1 2 2 1 2 3 3 3 80%	1440
	21st to end	Night	2 2 1 2 2 1 2 2 3 4 80%	1576
August	1st to 10th	Night	2 2 1 2 2 2 3 4 6% 6% 70%	1611
	11th to 20th	Night	2 1 1 1 2 1 3 3 4 4 79%	1646
	21st to end	Night	2 2 1 1 2 1 2 2 3 4 80%	1980
September	1st to 10th	Night	1 1 1 1 1 1 2 2 4 5% 80%	1800
	11th to 20th	Night	4 2 1 3 2 2 3 3 6% 6% 68%	1800
	21st to end	Night	6% 4 1 2 3 2 2 2 4 5% 68%	2026
October	1st to 10th	Night	5% 4 1 3 3 2 3 4 4 6% 63%	2160
	11th to 20th	Night	10% 5% 2 4 4 2 3 3 4 5% 58%	2160
	21st to end	Night	10% 6% 3 4 4 3 4 4 5% 7% 51%	2425
November	1st to 10th	Night	15% 10% 3 5% 5% 3 4 4 4 7% 39%	2405
	11th to 20th	Night	18% 10% 3 4 4 3 4 5% 5% 9% 35%	2574
	21st to end	Night	12% 11% 3 5% 4 3 4 4 4 8% 42%	2660
December	1st to 10th	Night	16% 10% 3 6% 4 3 3 3 4 8% 40%	2660
	11th to 20th	Night	20% 15% 4 5% 5% 3 4 5% 4 7% 28%	3276
	21st to end	Night	16% 16% 4 7% 5% 3 4 4 4 6% 30%	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	59% 8% 12% 15% 5%	2539
	11th to 20th	Day	64% 4 8% 13% 6% 4	2540
	21st to end	Day	57% 7% 12% 15% 7% 2	3114
February	1st to 10th	Day	47% 7% 15% 19% 11% 1	1710
	11th to 20th	Day	47% 7% 13% 17% 14% 3	1710
	21st to end	Day	51% 6% 14% 14% 11% 3	1570
March	1st to 10th	Day	56% 6% 13% 16% 8% 1	1880
	11th to 20th	Day	50% 6% 13% 17% 13% 1	1980
	21st to end	Day	54% 8% 15% 14% 8% 2	2269
April	1st to 10th	Day	53% 7% 10% 16% 11% 3	2160
	11th to 20th	Day	47% 5% 13% 20% 12% 4	2132
	21st to end	Day	36% 7% 15% 24% 16% 3	2163
May	1st to 10th	Day	33% 6% 10% 27% 20% 3	2470
	11th to 20th	Day	39% 5% 11% 24% 17% 4	2480
	21st to end	Day	43% 6% 13% 21% 15% 2	2724
June	1st to 10th	Day	35% 7% 12% 25% 19% 1	2520
	11th to 20th	Day	23% 5% 9% 29% 27% 7%	2520
	21st to end	Day	17% 3 7% 23% 33% 17%	2520
July	1st to 10th	Day	12% 2 7% 19% 29% 31%	2451
	11th to 20th	Day	9% 3 5% 17% 27% 38%	2445
	21st to end	Day	11% 2 4 13% 31% 39%	2586
August	1st to 10th	Day	15% 3 7% 19% 32% 24%	2312
	11th to 20th	Day	11% 2 5% 16% 39% 26%	2252
	21st to end	Day	9% 1 5% 17% 41% 26%	2376
September	1st to 10th	Day	11% 3 4 15% 32% 35%	2160
	11th to 20th	Day	19% 5% 9% 17% 32% 18%	2160
	21st to end	Day	21% 5% 10% 22% 24% 18%	1931
October	1st to 10th	Day	27% 5% 10% 18% 26% 14%	1800
	11th to 20th	Day	29% 5% 12% 22% 21% 10%	1800
	21st to end	Day	34% 6% 11% 20% 21% 8%	1931
November	1st to 10th	Day	42% 6% 12% 19% 18% 3	1674
	11th to 20th	Day	46% 8% 18% 14% 12% 3	1601
	21st to end	Day	44% 7% 12% 16% 16% 5%	1520
December	1st to 10th	Day	44% 6% 12% 22% 13% 3	1520
	11th to 20th	Day	55% 7% 14% 14% 10% 1	1928
	21st to end	Day	58% 8% 11% 15% 7% 1	2794
January	1st to 10th	Night	56% 10% 14% 14% 5% 1	4406
	11th to 20th	Night	57% 7% 10% 14% 8% 4	4420
	21st to end	Night	58% 7% 10% 14% 9% 2	4548
February	1st to 10th	Night	45% 7% 15% 18% 12% 3	2470
	11th to 20th	Night	45% 7% 14% 19% 13% 3	2367
	21st to end	Night	46% 9% 15% 17% 10% 3	1884
March	1st to 10th	Night	52% 7% 13% 16% 10% 2	2194
	11th to 20th	Night	46% 6% 14% 19% 15%	1980
	21st to end	Night	50% 8% 16% 17% 7% 2	2086
April	1st to 10th	Night	47% 7% 15% 18% 12% 2	1800
	11th to 20th	Night	41% 6% 16% 20% 13% 4	1779
	21st to end	Night	34% 7% 19% 25% 13% 3	1795
May	1st to 10th	Night	27% 6% 14% 33% 17% 3	1489
	11th to 20th	Night	33% 7% 15% 28% 14% 3	1416
	21st to end	Night	33% 7% 19% 27% 13% 1	1552
June	1st to 10th	Night	33% 7% 15% 28% 17% 1	1440
	11th to 20th	Night	22% 6% 10% 35% 22% 6%	1440
	21st to end	Night	16% 3 8% 30% 32% 11%	1440
July	1st to 10th	Night	11% 3 8% 23% 29% 27%	1400
	11th to 20th	Night	10% 3 6% 17% 33% 32%	1392
	21st to end	Night	10% 2 5% 13% 32% 38%	1488
August	1st to 10th	Night	13% 4 9% 23% 31% 18%	1602
	11th to 20th	Night	10% 3 6% 22% 35% 24%	1646
	21st to end	Night	11% 2 5% 21% 34% 28%	1980
September	1st to 10th	Night	8% 2 5% 19% 31% 35%	1800
	11th to 20th	Night	17% 4 9% 20% 31% 19%	1800
	21st to end	Night	20% 3 9% 24% 24% 20%	2026
October	1st to 10th	Night	21% 6% 12% 21% 26% 15%	2160
	11th to 20th	Night	28% 4 11% 24% 23% 10%	2160
	21st to end	Night	31% 7% 14% 20% 18% 11%	2425
November	1st to 10th	Night	44% 6% 11% 18% 16% 4	2405
	11th to 20th	Night	45% 8% 13% 18% 13% 3	2574
	21st to end	Night	41% 7% 13% 16% 16% 7%	2660
December	1st to 10th	Night	43% 7% 13% 19% 15% 3	2660
	11th to 20th	Night	55% 7% 10% 16% 12% 1	3276
	21st to end	Night	53% 9% 12% 14% 11% 2	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	30% 19% 24% 12% 9% 5%	180
	11th to 20th	Day	33% 13% 18% 19% 14% 3	180
	21st to end	Day	20% 13% 23% 22% 18% 5%	388
February	1st to 10th	Day	19% 16% 24% 23% 14% 3	370
	11th to 20th	Day	23% 17% 24% 20% 13% 3	383
	21st to end	Day	19% 18% 26% 27% 8% 1	382
March	1st to 10th	Day	25% 19% 28% 19% 8% 1	441
	11th to 20th	Day	22% 15% 24% 23% 13% 3	420
	21st to end	Day	23% 20% 24% 25% 7% 1	462
April	1st to 10th	Day	23% 18% 23% 24% 9% 3	420
	11th to 20th	Day	22% 20% 25% 18% 10% 4	412
	21st to end	Day	15% 20% 25% 21% 14% 5%	420
May	1st to 10th	Day	12% 17% 26% 26% 15% 4	423
	11th to 20th	Day	21% 16% 23% 20% 14% 6%	448
	21st to end	Day	17% 10% 21% 25% 18% 9%	485
June	1st to 10th	Day	10% 13% 25% 23% 20% 9%	450
	11th to 20th	Day	9% 17% 26% 26% 18% 4	450
	21st to end	Day	4 7% 20% 33% 25% 12%	450
July	1st to 10th	Day	3 4 24% 38% 24% 7%	446
	11th to 20th	Day	3 2 24% 36% 28% 7%	444
	21st to end	Day	2 3 19% 37% 27% 11%	487
August	1st to 10th	Day	2 2 23% 33% 27% 13%	447
	11th to 20th	Day	3 6% 16% 30% 28% 17%	437
	21st to end	Day	4 5% 19% 33% 28% 11%	495
September	1st to 10th	Day	3 5% 21% 36% 23% 12%	450
	11th to 20th	Day	6% 7% 21% 32% 24% 10%	450
	21st to end	Day	6% 13% 23% 27% 25% 6%	450
October	1st to 10th	Day	12% 10% 25% 24% 21% 9%	450
	11th to 20th	Day	15% 10% 21% 22% 25% 7%	450
	21st to end	Day	15% 12% 26% 21% 18% 8%	446
November	1st to 10th	Day	21% 11% 22% 28% 12% 6%	270
	11th to 20th	Day	19% 8% 21% 28% 16% 8%	219
	21st to end	Day	21% 11% 19% 26% 19% 5%	180
December	1st to 10th	Day	25% 9% 19% 23% 11% 12%	180
	11th to 20th	Day	28% 13% 23% 17% 15% 4	180
	21st to end	Day	22% 15% 22% 24% 16% 2	198
January	1st to 10th	Night	22% 10% 25% 25% 14% 4	760
	11th to 20th	Night	22% 11% 20% 24% 19% 5%	760
	21st to end	Night	19% 9% 18% 31% 17% 5%	836
February	1st to 10th	Night	19% 7% 23% 33% 16% 3	760
	11th to 20th	Night	19% 10% 22% 33% 14% 2	744
	21st to end	Night	17% 11% 22% 36% 14% 1	628
March	1st to 10th	Night	22% 12% 24% 27% 13% 2	742
	11th to 20th	Night	18% 10% 20% 30% 19% 2	720
	21st to end	Night	21% 12% 25% 29% 12% 1	792
April	1st to 10th	Night	19% 9% 24% 31% 14% 2	720
	11th to 20th	Night	14% 11% 29% 27% 15% 4	711
	21st to end	Night	13% 11% 23% 31% 20% 2	715
May	1st to 10th	Night	11% 3 29% 35% 20% 1	409
	11th to 20th	Night	10% 7% 17% 39% 24% 3	354
	21st to end	Night	11% 6% 23% 35% 23% 3	389
June	1st to 10th	Night	11% 5% 18% 41% 24% 1	360
	11th to 20th	Night	6% 5% 26% 44% 17% 1	360
	21st to end	Night	5% 1 14% 52% 28% 1	360
July	1st to 10th	Night	3 13% 53% 30% 1	350
	11th to 20th	Night	1 1 15% 57% 25%	348
	21st to end	Night	2 1 9% 56% 32% 1	394
August	1st to 10th	Night	2 1 7% 47% 40% 3	537
	11th to 20th	Night	2 1 9% 42% 41% 5%	578
	21st to end	Night	3 2 13% 46% 34% 2	792
September	1st to 10th	Night	1 1 16% 42% 36% 4	720
	11th to 20th	Night	4 3 13% 35% 37% 7%	720
	21st to end	Night	8% 4 15% 36% 29% 8%	720
October	1st to 10th	Night	5% 4 21% 37% 28% 5%	720
	11th to 20th	Night	11% 8% 13% 35% 28% 5%	720
	21st to end	Night	13% 7% 17% 33% 22% 7%	792
November	1st to 10th	Night	20% 7% 19% 34% 15% 4	740
	11th to 20th	Night	22% 8% 19% 33% 14% 3	760
	21st to end	Night	16% 9% 19% 32% 20% 4	760
December	1st to 10th	Night	22% 8% 16% 33% 17% 5%	760
	11th to 20th	Night	25% 7% 18% 32% 15% 3	760
	21st to end	Night	25% 15% 21% 28% 9% 2	836

Page generated at 2024-03-03 03:29:00. Version ac07

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