Supernova Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Supernova Observatory clear sky chart from 2005-11-06 to 2024-01-12.

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	19% 11% 4 7% 6% 3 4 4 5% 7% 30%	74736
	Night	20% 12% 4 7% 6% 3 4 4 5% 6% 28%	74963
Transparency	Day	54% 6% 11% 19% 9% 1	74441
	Night	57% 6% 11% 17% 8% 1	74792
Seeing	Day	26% 15% 26% 20% 10% 3	13557
	Night	26% 13% 24% 27% 9% 1	22819

By Month

Percentage Cloud Cover NE (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	17% 21% 8% 10% 8% 4 6% 3 3 5% 15%	1517
	11th to 20th	Day	20% 20% 4 15% 5% 3 4 3 3 5% 16%	1448
	21st to end	Day	14% 18% 7% 10% 10% 5% 5% 4 4 6% 17%	1706
February	1st to 10th	Day	18% 16% 6% 14% 10% 5% 5% 4 3 4 14%	1620
	11th to 20th	Day	16% 16% 8% 13% 8% 4 3 3 3 6% 19%	1637
	21st to end	Day	21% 15% 7% 12% 8% 3 4 4 4 5% 17%	1480
March	1st to 10th	Day	17% 14% 6% 12% 6% 3 5% 3 5% 5% 23%	1797
	11th to 20th	Day	18% 16% 6% 9% 6% 3 3 4 4 5% 27%	1966
	21st to end	Day	23% 11% 3 6% 5% 2 3 4 4 6% 32%	2307
April	1st to 10th	Day	20% 13% 4 7% 5% 2 4 4 4 6% 31%	2160
	11th to 20th	Day	20% 9% 3 6% 5% 3 4 4 6% 5% 36%	2134
	21st to end	Day	23% 12% 3 6% 5% 3 4 4 4 5% 31%	2174
May	1st to 10th	Day	22% 10% 4 6% 5% 3 3 3 5% 6% 33%	2502
	11th to 20th	Day	19% 7% 3 5% 5% 3 5% 4 5% 7% 38%	2478
	21st to end	Day	16% 6% 2 6% 6% 3 5% 5% 6% 8% 38%	2725
June	1st to 10th	Day	20% 5% 3 6% 6% 3 5% 6% 6% 8% 32%	2520
	11th to 20th	Day	21% 5% 2 4 5% 3 5% 5% 6% 9% 34%	2520
	21st to end	Day	19% 6% 2 6% 5% 4 5% 6% 6% 8% 33%	2520
July	1st to 10th	Day	15% 5% 3 5% 6% 3 5% 5% 6% 8% 39%	2520
	11th to 20th	Day	14% 6% 3 5% 5% 3 6% 6% 7% 9% 36%	2520
	21st to end	Day	15% 6% 2 6% 6% 4 6% 6% 7% 8% 36%	2744
August	1st to 10th	Day	14% 5% 2 5% 6% 3 5% 6% 6% 9% 38%	2416
	11th to 20th	Day	15% 6% 2 6% 6% 4 5% 6% 7% 9% 33%	2211
	21st to end	Day	17% 7% 2 4 5% 3 5% 5% 6% 9% 38%	2376
September	1st to 10th	Day	16% 6% 1 5% 5% 3 5% 5% 5% 8% 40%	2160
	11th to 20th	Day	17% 6% 2 5% 4 2 3 4 4 7% 44%	2142
	21st to end	Day	18% 6% 3 5% 5% 4 5% 5% 5% 8% 37%	1958
October	1st to 10th	Day	23% 8% 3 7% 5% 4 4 4 4 6% 32%	1800
	11th to 20th	Day	23% 8% 3 5% 7% 4 3 5% 5% 7% 31%	1800
	21st to end	Day	29% 10% 3 7% 5% 3 5% 4 5% 5% 23%	1855
November	1st to 10th	Day	17% 13% 4 6% 6% 3 5% 5% 4 6% 31%	1671
	11th to 20th	Day	18% 15% 4 7% 7% 4 5% 4 5% 5% 26%	1634
	21st to end	Day	23% 16% 5% 9% 5% 2 4 5% 4 6% 20%	1520
December	1st to 10th	Day	22% 20% 7% 11% 6% 3 4 3 4 4 15%	1520
	11th to 20th	Day	22% 18% 10% 10% 6% 3 4 3 4 4 16%	1906
	21st to end	Day	27% 20% 8% 9% 6% 2 4 3 3 4 13%	2772
January	1st to 10th	Night	20% 20% 6% 11% 7% 4 4 4 4 5% 15%	2649
	11th to 20th	Night	20% 19% 6% 11% 7% 4 3 4 4 4 16%	2535
	21st to end	Night	14% 17% 7% 11% 10% 5% 5% 4 5% 5% 18%	2647
February	1st to 10th	Night	19% 15% 6% 14% 8% 4 5% 5% 4 5% 15%	2340
	11th to 20th	Night	16% 15% 6% 11% 9% 4 7% 4 5% 6% 18%	2207
	21st to end	Night	18% 15% 6% 12% 9% 3 4 4 3 6% 19%	1776
March	1st to 10th	Night	18% 13% 7% 10% 8% 3 4 4 3 5% 24%	2150
	11th to 20th	Night	20% 13% 5% 7% 7% 3 4 4 4 4 28%	1991
	21st to end	Night	21% 12% 4 6% 5% 2 4 4 4 5% 32%	2048
April	1st to 10th	Night	23% 12% 4 6% 5% 4 3 3 4 6% 29%	1800
	11th to 20th	Night	21% 9% 4 7% 5% 3 4 4 5% 5% 33%	1775
	21st to end	Night	21% 9% 3 5% 5% 3 5% 3 5% 7% 34%	1784
May	1st to 10th	Night	24% 8% 3 6% 5% 3 4 4 5% 5% 34%	1474
	11th to 20th	Night	15% 8% 4 5% 5% 3 3 5% 6% 8% 39%	1415
	21st to end	Night	15% 6% 2 5% 5% 3 5% 5% 5% 7% 42%	1550
June	1st to 10th	Night	20% 5% 3 5% 5% 3 4 5% 6% 8% 36%	1440
	11th to 20th	Night	19% 5% 2 4 4 3 4 5% 5% 8% 41%	1440
	21st to end	Night	16% 5% 3 6% 5% 4 5% 5% 6% 8% 38%	1440
July	1st to 10th	Night	13% 4 3 4 6% 3 5% 5% 6% 9% 42%	1440
	11th to 20th	Night	13% 4 2 5% 5% 3 5% 6% 7% 8% 45%	1440
	21st to end	Night	13% 5% 3 4 5% 4 5% 5% 6% 8% 43%	1574
August	1st to 10th	Night	15% 6% 2 4 5% 3 5% 5% 6% 7% 42%	1519
	11th to 20th	Night	15% 6% 3 5% 7% 4 5% 6% 6% 7% 36%	1670
	21st to end	Night	14% 5% 2 5% 4 3 5% 5% 6% 7% 43%	1980
September	1st to 10th	Night	16% 7% 2 5% 4 3 5% 5% 6% 7% 42%	1800
	11th to 20th	Night	19% 5% 2 4 4 3 3 4 4 5% 48%	1818
	21st to end	Night	19% 6% 2 4 4 3 5% 5% 6% 8% 40%	2000
October	1st to 10th	Night	25% 8% 3 7% 6% 4 4 4 4 6% 31%	2160
	11th to 20th	Night	24% 9% 3 6% 6% 3 5% 4 6% 6% 30%	2160
	21st to end	Night	30% 11% 3 7% 6% 3 4 3 4 5% 22%	2500
November	1st to 10th	Night	19% 11% 4 6% 6% 3 5% 4 4 6% 33%	2407
	11th to 20th	Night	21% 13% 4 6% 5% 3 4 5% 4 6% 28%	2542
	21st to end	Night	20% 17% 5% 7% 5% 3 4 4 5% 6% 23%	2660
December	1st to 10th	Night	24% 19% 7% 9% 6% 3 4 4 4 5% 15%	2660
	11th to 20th	Night	23% 18% 7% 11% 5% 3 4 4 4 5% 15%	3288
	21st to end	Night	30% 17% 8% 7% 5% 3 3 4 4 5% 15%	4884

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	71% 6% 8% 11% 4	1518
	11th to 20th	Day	72% 5% 8% 9% 4 2	1448
	21st to end	Day	69% 5% 11% 9% 5% 1	1706
February	1st to 10th	Day	75% 4 7% 9% 3 1	1620
	11th to 20th	Day	69% 5% 8% 14% 4 1	1646
	21st to end	Day	71% 4 9% 10% 6%	1480
March	1st to 10th	Day	64% 4 11% 15% 5% 1	1800
	11th to 20th	Day	61% 4 9% 13% 11% 1	1966
	21st to end	Day	55% 4 8% 15% 15% 2	2307
April	1st to 10th	Day	55% 5% 8% 21% 10% 2	2160
	11th to 20th	Day	50% 5% 11% 21% 12% 1	2134
	21st to end	Day	56% 5% 9% 17% 11% 3	2174
May	1st to 10th	Day	53% 5% 9% 18% 13% 2	2502
	11th to 20th	Day	46% 6% 11% 24% 12% 2	2482
	21st to end	Day	43% 9% 16% 20% 11% 1	2725
June	1st to 10th	Day	49% 8% 12% 20% 11% 1	2520
	11th to 20th	Day	46% 6% 13% 23% 10% 2	2520
	21st to end	Day	48% 7% 14% 20% 10% 1	2520
July	1st to 10th	Day	42% 8% 12% 25% 13% 1	2450
	11th to 20th	Day	42% 8% 16% 27% 6%	2445
	21st to end	Day	43% 9% 15% 22% 11%	2591
August	1st to 10th	Day	41% 9% 15% 23% 11%	2402
	11th to 20th	Day	45% 9% 16% 23% 7%	2211
	21st to end	Day	42% 9% 13% 26% 10% 1	2376
September	1st to 10th	Day	41% 7% 13% 27% 10% 1	2160
	11th to 20th	Day	40% 5% 11% 27% 16% 1	2142
	21st to end	Day	45% 7% 11% 25% 11% 1	1958
October	1st to 10th	Day	53% 7% 11% 19% 10% 1	1800
	11th to 20th	Day	53% 6% 15% 21% 6% 1	1800
	21st to end	Day	63% 7% 11% 11% 7% 1	1855
November	1st to 10th	Day	54% 6% 11% 19% 10% 1	1671
	11th to 20th	Day	60% 5% 10% 15% 8% 2	1634
	21st to end	Day	64% 6% 15% 12% 3	1520
December	1st to 10th	Day	73% 5% 9% 10% 2	1520
	11th to 20th	Day	71% 7% 11% 8% 3	1906
	21st to end	Day	75% 6% 5% 11% 3	2772
January	1st to 10th	Night	71% 6% 7% 11% 4	2649
	11th to 20th	Night	72% 6% 8% 9% 5%	2535
	21st to end	Night	70% 5% 9% 11% 5% 1	2647
February	1st to 10th	Night	71% 6% 9% 10% 4	2340
	11th to 20th	Night	67% 6% 9% 13% 5%	2209
	21st to end	Night	68% 5% 10% 11% 6%	1776
March	1st to 10th	Night	63% 4 10% 17% 5% 1	2160
	11th to 20th	Night	60% 5% 10% 17% 7% 1	1992
	21st to end	Night	56% 4 8% 18% 12% 3	2048
April	1st to 10th	Night	58% 4 11% 17% 8% 1	1800
	11th to 20th	Night	53% 6% 9% 19% 12% 1	1775
	21st to end	Night	50% 5% 11% 18% 12% 3	1784
May	1st to 10th	Night	53% 6% 9% 16% 13% 3	1474
	11th to 20th	Night	43% 6% 13% 23% 14% 2	1416
	21st to end	Night	40% 8% 16% 23% 11% 2	1551
June	1st to 10th	Night	46% 6% 13% 23% 12% 1	1440
	11th to 20th	Night	42% 6% 14% 23% 13% 1	1440
	21st to end	Night	41% 10% 11% 26% 12% 1	1440
July	1st to 10th	Night	37% 9% 13% 24% 15% 2	1400
	11th to 20th	Night	35% 8% 16% 28% 13%	1392
	21st to end	Night	39% 7% 14% 27% 12% 2	1486
August	1st to 10th	Night	38% 8% 15% 28% 10% 1	1509
	11th to 20th	Night	44% 8% 16% 22% 9%	1670
	21st to end	Night	38% 7% 14% 29% 12%	1980
September	1st to 10th	Night	40% 7% 13% 28% 11% 1	1800
	11th to 20th	Night	39% 5% 11% 27% 17%	1818
	21st to end	Night	42% 7% 13% 26% 11% 1	2000
October	1st to 10th	Night	53% 7% 11% 18% 10% 1	2160
	11th to 20th	Night	54% 7% 14% 17% 7% 1	2160
	21st to end	Night	65% 6% 10% 12% 7% 1	2500
November	1st to 10th	Night	54% 6% 12% 17% 11% 2	2407
	11th to 20th	Night	56% 6% 11% 18% 7% 2	2542
	21st to end	Night	63% 6% 14% 13% 3	2660
December	1st to 10th	Night	72% 6% 11% 10% 2	2660
	11th to 20th	Night	71% 7% 9% 9% 4	3288
	21st to end	Night	72% 7% 10% 10% 1	4884

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	38% 12% 26% 18% 6% 1	180
	11th to 20th	Day	40% 24% 28% 5% 2 1	162
	21st to end	Day	27% 25% 31% 13% 3	230
February	1st to 10th	Day	43% 25% 27% 5%	240
	11th to 20th	Day	33% 31% 28% 8%	304
	21st to end	Day	40% 18% 26% 14% 2	346
March	1st to 10th	Day	33% 19% 27% 19% 2	420
	11th to 20th	Day	31% 23% 28% 13% 4	420
	21st to end	Day	37% 19% 24% 15% 4 2	462
April	1st to 10th	Day	33% 21% 25% 15% 5% 1	420
	11th to 20th	Day	33% 19% 21% 14% 9% 3	412
	21st to end	Day	34% 19% 23% 16% 6% 2	420
May	1st to 10th	Day	30% 15% 29% 13% 8% 3	423
	11th to 20th	Day	24% 13% 32% 19% 10% 2	447
	21st to end	Day	18% 13% 28% 25% 13% 4	485
June	1st to 10th	Day	19% 16% 28% 26% 9% 2	450
	11th to 20th	Day	22% 12% 26% 24% 13% 3	450
	21st to end	Day	20% 12% 33% 22% 9% 3	450
July	1st to 10th	Day	18% 7% 26% 28% 16% 6%	445
	11th to 20th	Day	15% 6% 27% 30% 18% 4	444
	21st to end	Day	15% 7% 34% 28% 13% 3	488
August	1st to 10th	Day	14% 11% 20% 29% 19% 8%	446
	11th to 20th	Day	18% 8% 20% 29% 18% 7%	439
	21st to end	Day	17% 11% 24% 26% 16% 6%	495
September	1st to 10th	Day	18% 8% 23% 24% 17% 10%	450
	11th to 20th	Day	17% 9% 24% 20% 19% 10%	450
	21st to end	Day	19% 10% 27% 24% 14% 5%	450
October	1st to 10th	Day	27% 10% 26% 18% 14% 5%	450
	11th to 20th	Day	28% 16% 25% 20% 10% 1	450
	21st to end	Day	37% 13% 26% 18% 6%	432
November	1st to 10th	Day	29% 16% 19% 25% 10%	365
	11th to 20th	Day	33% 20% 24% 20% 3 1	294
	21st to end	Day	39% 14% 27% 16% 3	180
December	1st to 10th	Day	38% 17% 34% 8% 2 1	180
	11th to 20th	Day	35% 23% 28% 13% 1	180
	21st to end	Day	39% 22% 27% 12%	198
January	1st to 10th	Night	33% 21% 25% 18% 2	760
	11th to 20th	Night	33% 19% 27% 17% 4	725
	21st to end	Night	23% 21% 31% 22% 3	792
February	1st to 10th	Night	31% 19% 30% 19% 1	720
	11th to 20th	Night	28% 21% 33% 15% 3	703
	21st to end	Night	30% 19% 31% 18% 3	592
March	1st to 10th	Night	29% 17% 28% 24% 2	720
	11th to 20th	Night	31% 17% 28% 21% 3	720
	21st to end	Night	29% 16% 27% 21% 7% 1	792
April	1st to 10th	Night	29% 15% 29% 23% 3	720
	11th to 20th	Night	26% 16% 28% 22% 8%	711
	21st to end	Night	27% 14% 26% 26% 7%	704
May	1st to 10th	Night	29% 7% 24% 29% 10%	394
	11th to 20th	Night	20% 8% 29% 34% 8%	354
	21st to end	Night	17% 5% 23% 40% 15%	389
June	1st to 10th	Night	19% 6% 22% 42% 11% 1	360
	11th to 20th	Night	21% 4 20% 39% 16%	360
	21st to end	Night	15% 5% 23% 44% 12% 1	360
July	1st to 10th	Night	13% 3 17% 45% 20% 1	350
	11th to 20th	Night	14% 2 14% 49% 19% 2	348
	21st to end	Night	14% 4 16% 48% 17% 1	394
August	1st to 10th	Night	16% 5% 16% 38% 24% 1	445
	11th to 20th	Night	18% 4 14% 37% 24% 3	606
	21st to end	Night	17% 5% 16% 38% 23% 1	792
September	1st to 10th	Night	17% 6% 21% 35% 19% 2	720
	11th to 20th	Night	21% 6% 17% 30% 23% 4	720
	21st to end	Night	20% 7% 22% 33% 17% 2	720
October	1st to 10th	Night	28% 8% 21% 24% 18% 1	720
	11th to 20th	Night	28% 11% 23% 30% 7% 1	720
	21st to end	Night	35% 12% 25% 25% 3	792
November	1st to 10th	Night	26% 12% 25% 28% 9%	740
	11th to 20th	Night	31% 15% 25% 22% 7% 1	760
	21st to end	Night	32% 13% 28% 21% 6%	760
December	1st to 10th	Night	38% 17% 25% 18% 3	760
	11th to 20th	Night	35% 17% 27% 17% 4	760
	21st to end	Night	35% 21% 25% 17% 1	836

Page generated at 2024-01-08 22:31:27. Version ac07

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