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 2024-11-05.

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 8% 5% 4 4 4 5% 7% 30%	101515
	Night	20% 13% 4 9% 5% 4 4 3 5% 6% 27%	97501
Transparency	Day	52% 7% 12% 20% 9% 1	105024
	Night	57% 7% 11% 17% 8% 1	102081
Seeing	Day	26% 15% 26% 20% 10% 3	14688
	Night	27% 13% 24% 27% 9% 1	23810

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	15% 24% 8% 15% 6% 5% 4 2 2 4 15%	2517
	11th to 20th	Day	16% 21% 9% 18% 7% 4 3 2 3 4 14%	2520
	21st to end	Day	19% 25% 7% 11% 10% 5% 4 3 3 4 11%	2978
February	1st to 10th	Day	17% 17% 5% 14% 9% 6% 5% 3 3 4 16%	1710
	11th to 20th	Day	16% 18% 6% 15% 7% 4 3 3 3 6% 19%	1730
	21st to end	Day	21% 16% 7% 13% 6% 4 4 3 4 5% 19%	1570
March	1st to 10th	Day	25% 15% 4 10% 4 3 4 2 4 4 24%	3116
	11th to 20th	Day	14% 20% 6% 9% 5% 3 4 3 4 5% 25%	3466
	21st to end	Day	19% 13% 4 9% 4 3 3 3 4 5% 33%	4055
April	1st to 10th	Day	20% 16% 3 8% 4 3 3 3 4 6% 30%	2280
	11th to 20th	Day	21% 10% 2 7% 4 4 4 3 5% 5% 35%	2254
	21st to end	Day	23% 12% 3 7% 4 4 4 3 4 5% 31%	2295
May	1st to 10th	Day	25% 9% 3 7% 4 4 4 3 4 6% 31%	4394
	11th to 20th	Day	19% 9% 3 6% 5% 5% 5% 4 6% 7% 32%	4398
	21st to end	Day	15% 6% 2 6% 4 4 5% 4 6% 8% 40%	4837
June	1st to 10th	Day	20% 6% 2 8% 5% 4 5% 5% 6% 8% 31%	2660
	11th to 20th	Day	20% 6% 2 4 5% 5% 5% 5% 6% 9% 34%	2660
	21st to end	Day	19% 7% 2 6% 5% 4 5% 5% 6% 8% 32%	2660
July	1st to 10th	Day	13% 6% 2 6% 5% 5% 5% 4 7% 11% 35%	4440
	11th to 20th	Day	12% 7% 3 6% 5% 5% 6% 5% 7% 10% 36%	4440
	21st to end	Day	14% 6% 2 7% 5% 5% 6% 5% 7% 8% 37%	4814
August	1st to 10th	Day	19% 6% 2 6% 4 4 5% 4 6% 8% 34%	4249
	11th to 20th	Day	19% 7% 2 7% 4 5% 6% 4 7% 9% 30%	3868
	21st to end	Day	20% 6% 2 5% 4 4 4 4 6% 9% 37%	4180
September	1st to 10th	Day	16% 6% 1 5% 4 4 5% 4 5% 8% 41%	2280
	11th to 20th	Day	16% 6% 2 6% 3 3 3 4 4 7% 45%	2260
	21st to end	Day	18% 6% 3 6% 5% 5% 4 4 5% 7% 36%	2066
October	1st to 10th	Day	22% 8% 2 8% 4 5% 4 3 4 6% 32%	1900
	11th to 20th	Day	23% 9% 2 6% 6% 4 3 3 5% 7% 32%	1900
	21st to end	Day	27% 10% 3 7% 4 4 4 3 5% 6% 25%	1958
November	1st to 10th	Day	17% 14% 4 7% 5% 5% 5% 4 5% 6% 30%	1708
	11th to 20th	Day	18% 16% 4 8% 6% 4 5% 3 5% 5% 26%	1634
	21st to end	Day	23% 17% 4 9% 5% 3 4 4 4 6% 20%	1520
December	1st to 10th	Day	22% 22% 6% 11% 5% 4 3 2 4 4 15%	1520
	11th to 20th	Day	22% 19% 9% 12% 5% 4 4 3 4 3 16%	1906
	21st to end	Day	27% 22% 7% 10% 5% 3 3 2 3 4 13%	2772
January	1st to 10th	Night	20% 23% 7% 14% 5% 4 3 3 4 5% 12%	4429
	11th to 20th	Night	15% 19% 8% 19% 9% 5% 4 3 4 3 11%	4440
	21st to end	Night	22% 20% 7% 15% 8% 5% 3 2 3 3 11%	4661
February	1st to 10th	Night	18% 17% 5% 14% 7% 5% 4 4 4 5% 16%	2470
	11th to 20th	Night	15% 17% 6% 13% 8% 5% 5% 3 5% 5% 18%	2334
	21st to end	Night	18% 15% 6% 13% 8% 4 3 4 4 6% 19%	1884
March	1st to 10th	Night	23% 12% 5% 11% 6% 4 4 3 3 5% 25%	3724
	11th to 20th	Night	20% 20% 5% 9% 5% 3 4 3 4 5% 22%	3491
	21st to end	Night	21% 12% 4 10% 4 4 4 3 4 4 30%	3576
April	1st to 10th	Night	23% 13% 3 7% 4 4 3 3 4 6% 29%	1900
	11th to 20th	Night	22% 10% 3 7% 5% 4 4 3 5% 5% 33%	1875
	21st to end	Night	20% 9% 2 6% 5% 4 4 3 5% 6% 34%	1883
May	1st to 10th	Night	29% 9% 3 6% 5% 3 4 3 5% 5% 28%	2562
	11th to 20th	Night	19% 11% 4 8% 4 4 3 4 5% 6% 33%	2495
	21st to end	Night	16% 7% 2 6% 5% 4 4 4 5% 7% 39%	2738
June	1st to 10th	Night	19% 7% 2 6% 5% 4 4 4 6% 8% 35%	1520
	11th to 20th	Night	18% 5% 1 5% 4 4 5% 4 6% 8% 41%	1520
	21st to end	Night	17% 5% 3 7% 4 5% 4 4 6% 8% 37%	1520
July	1st to 10th	Night	15% 6% 3 7% 6% 5% 5% 4 7% 8% 36%	2520
	11th to 20th	Night	15% 7% 2 6% 4 4 4 5% 6% 7% 41%	2520
	21st to end	Night	14% 7% 2 5% 3 4 4 4 6% 8% 43%	2739
August	1st to 10th	Night	21% 9% 2 6% 4 3 4 3 5% 6% 36%	2663
	11th to 20th	Night	20% 8% 3 7% 5% 4 4 3 5% 6% 36%	2927
	21st to end	Night	16% 5% 2 5% 4 4 5% 4 6% 8% 41%	3476
September	1st to 10th	Night	16% 8% 2 6% 3 3 5% 3 6% 7% 42%	1900
	11th to 20th	Night	17% 6% 1 5% 3 4 3 3 4 5% 49%	1919
	21st to end	Night	19% 7% 2 5% 3 5% 5% 4 6% 8% 38%	2112
October	1st to 10th	Night	25% 8% 3 8% 5% 5% 4 3 4 6% 31%	2280
	11th to 20th	Night	23% 9% 2 7% 5% 5% 4 3 5% 6% 31%	2280
	21st to end	Night	29% 11% 3 8% 5% 4 4 3 4 5% 23%	2639
November	1st to 10th	Night	19% 12% 3 7% 5% 5% 4 3 4 6% 32%	2470
	11th to 20th	Night	21% 14% 4 7% 4 4 4 4 4 6% 28%	2542
	21st to end	Night	20% 17% 5% 8% 5% 5% 4 3 5% 5% 23%	2660
December	1st to 10th	Night	24% 21% 5% 10% 5% 5% 4 3 4 5% 15%	2660
	11th to 20th	Night	22% 19% 6% 12% 5% 4 4 3 5% 4 15%	3288
	21st to end	Night	30% 18% 7% 8% 4 4 3 3 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	70% 9% 8% 10% 3	2518
	11th to 20th	Day	74% 7% 7% 8% 3 1	2520
	21st to end	Day	76% 6% 9% 5% 3 1	2978
February	1st to 10th	Day	74% 4 8% 10% 3 1	1710
	11th to 20th	Day	69% 5% 8% 14% 4 1	1739
	21st to end	Day	69% 4 10% 11% 6%	1570
March	1st to 10th	Day	63% 6% 10% 14% 6% 1	3119
	11th to 20th	Day	59% 7% 15% 10% 8% 1	3466
	21st to end	Day	54% 5% 8% 18% 14% 1	4055
April	1st to 10th	Day	56% 4 8% 21% 9% 2	2280
	11th to 20th	Day	51% 5% 11% 21% 11% 1	2254
	21st to end	Day	55% 5% 9% 17% 11% 3	2295
May	1st to 10th	Day	53% 6% 10% 19% 11% 1	4408
	11th to 20th	Day	49% 8% 12% 22% 7% 1	4402
	21st to end	Day	40% 8% 14% 26% 12% 1	4837
June	1st to 10th	Day	49% 8% 11% 20% 11% 1	2660
	11th to 20th	Day	46% 6% 14% 23% 10% 1	2660
	21st to end	Day	49% 7% 14% 21% 9% 1	2660
July	1st to 10th	Day	40% 8% 14% 25% 12%	4370
	11th to 20th	Day	40% 8% 15% 27% 9%	4365
	21st to end	Day	42% 9% 15% 24% 10%	4661
August	1st to 10th	Day	45% 8% 14% 20% 13%	4235
	11th to 20th	Day	47% 9% 17% 21% 6%	3907
	21st to end	Day	42% 8% 13% 30% 7% 1	4180
September	1st to 10th	Day	40% 7% 13% 28% 11% 1	2280
	11th to 20th	Day	39% 5% 11% 28% 16% 1	2260
	21st to end	Day	46% 6% 12% 24% 11% 1	2066
October	1st to 10th	Day	46% 7% 12% 26% 8% 1	3160
	11th to 20th	Day	46% 5% 15% 23% 11%	3140
	21st to end	Day	46% 7% 16% 23% 8%	3209
November	1st to 10th	Day	54% 6% 11% 19% 9% 1	1708
	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	73% 7% 9% 8% 3	4429
	11th to 20th	Night	73% 11% 7% 6% 3	4440
	21st to end	Night	78% 6% 7% 6% 3 1	4661
February	1st to 10th	Night	70% 6% 9% 11% 4	2470
	11th to 20th	Night	68% 6% 9% 14% 4	2336
	21st to end	Night	67% 5% 10% 12% 6%	1884
March	1st to 10th	Night	61% 7% 8% 17% 7%	3734
	11th to 20th	Night	62% 7% 11% 15% 4 1	3492
	21st to end	Night	58% 4 6% 20% 10% 2	3576
April	1st to 10th	Night	58% 5% 11% 17% 8% 1	1900
	11th to 20th	Night	54% 6% 9% 18% 12% 1	1875
	21st to end	Night	50% 5% 11% 18% 13% 3	1883
May	1st to 10th	Night	56% 7% 9% 15% 10% 2	2568
	11th to 20th	Night	50% 7% 14% 20% 8% 1	2496
	21st to end	Night	42% 9% 12% 21% 15% 2	2739
June	1st to 10th	Night	46% 6% 12% 23% 12% 1	1520
	11th to 20th	Night	42% 6% 14% 23% 13% 1	1520
	21st to end	Night	43% 10% 10% 25% 12% 1	1520
July	1st to 10th	Night	45% 8% 12% 20% 15% 1	2480
	11th to 20th	Night	40% 7% 14% 25% 13%	2472
	21st to end	Night	39% 6% 12% 30% 12% 1	2651
August	1st to 10th	Night	47% 8% 13% 24% 8%	2653
	11th to 20th	Night	47% 7% 14% 25% 7%	2954
	21st to end	Night	39% 7% 15% 30% 9%	3476
September	1st to 10th	Night	41% 7% 12% 28% 11% 1	1900
	11th to 20th	Night	38% 5% 11% 28% 17%	1919
	21st to end	Night	44% 7% 12% 25% 11% 1	2112
October	1st to 10th	Night	52% 7% 10% 21% 9%	3800
	11th to 20th	Night	45% 6% 15% 19% 13% 1	3779
	21st to end	Night	53% 6% 11% 23% 6%	4338
November	1st to 10th	Night	54% 6% 12% 17% 10% 2	2470
	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	39% 23% 30% 6% 2 1	180
	21st to end	Day	28% 24% 31% 14% 3	258
February	1st to 10th	Day	40% 23% 28% 7% 1	270
	11th to 20th	Day	34% 30% 27% 8% 1	337
	21st to end	Day	39% 17% 28% 13% 2	382
March	1st to 10th	Day	33% 18% 27% 18% 3	460
	11th to 20th	Day	32% 22% 28% 14% 3	460
	21st to end	Day	36% 20% 24% 14% 4 2	506
April	1st to 10th	Day	35% 21% 24% 15% 5% 1	460
	11th to 20th	Day	35% 20% 21% 13% 9% 3	452
	21st to end	Day	33% 18% 23% 17% 6% 2	460
May	1st to 10th	Day	31% 14% 30% 14% 8% 3	463
	11th to 20th	Day	24% 11% 31% 21% 11% 2	487
	21st to end	Day	17% 13% 28% 26% 12% 4	529
June	1st to 10th	Day	20% 16% 27% 25% 9% 2	490
	11th to 20th	Day	21% 12% 26% 26% 13% 3	490
	21st to end	Day	21% 13% 32% 21% 9% 3	490
July	1st to 10th	Day	16% 7% 27% 28% 16% 5%	485
	11th to 20th	Day	15% 7% 27% 30% 17% 4	484
	21st to end	Day	14% 8% 34% 28% 13% 3	532
August	1st to 10th	Day	16% 11% 20% 29% 18% 7%	486
	11th to 20th	Day	19% 8% 20% 28% 18% 7%	479
	21st to end	Day	18% 11% 23% 26% 16% 6%	539
September	1st to 10th	Day	19% 9% 22% 24% 16% 10%	490
	11th to 20th	Day	16% 8% 23% 20% 20% 12%	490
	21st to end	Day	20% 10% 27% 25% 14% 4	490
October	1st to 10th	Day	27% 10% 25% 20% 14% 4	490
	11th to 20th	Day	28% 16% 24% 20% 11% 1	490
	21st to end	Day	35% 13% 26% 19% 7%	469
November	1st to 10th	Day	29% 16% 20% 26% 9%	378
	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	34% 18% 27% 17% 4	760
	21st to end	Night	24% 20% 31% 21% 3	836
February	1st to 10th	Night	30% 19% 30% 20% 1	760
	11th to 20th	Night	29% 20% 33% 15% 3	743
	21st to end	Night	31% 18% 31% 17% 3	628
March	1st to 10th	Night	29% 17% 28% 24% 2	760
	11th to 20th	Night	32% 17% 28% 21% 3	760
	21st to end	Night	29% 16% 28% 21% 6% 1	836
April	1st to 10th	Night	29% 15% 30% 23% 3	760
	11th to 20th	Night	27% 16% 28% 21% 8%	751
	21st to end	Night	27% 14% 27% 26% 7%	743
May	1st to 10th	Night	30% 7% 24% 29% 10%	415
	11th to 20th	Night	20% 9% 29% 33% 9% 1	374
	21st to end	Night	17% 5% 23% 41% 14%	411
June	1st to 10th	Night	19% 6% 21% 43% 11% 1	380
	11th to 20th	Night	21% 4 20% 39% 16%	380
	21st to end	Night	17% 5% 22% 43% 12% 1	380
July	1st to 10th	Night	14% 3 16% 46% 19% 1	370
	11th to 20th	Night	14% 2 14% 49% 19% 2	368
	21st to end	Night	14% 4 16% 48% 18% 1	416
August	1st to 10th	Night	17% 6% 16% 38% 23% 1	470
	11th to 20th	Night	19% 4 14% 36% 24% 3	641
	21st to end	Night	17% 4 16% 38% 23% 1	836
September	1st to 10th	Night	18% 6% 20% 34% 19% 2	760
	11th to 20th	Night	20% 6% 16% 30% 25% 4	760
	21st to end	Night	20% 8% 22% 33% 16% 2	760
October	1st to 10th	Night	28% 8% 21% 24% 18% 1	760
	11th to 20th	Night	28% 10% 23% 30% 8% 1	760
	21st to end	Night	34% 12% 25% 25% 3	836
November	1st to 10th	Night	26% 12% 25% 28% 8%	760
	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 2024-11-03 02:11:24. Version ac07

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