Stella Nova Observatory
Clear Sky Chart
History

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

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	15% 7% 2 6% 4 4 5% 4 6% 7% 40%	101372
	Night	16% 7% 2 6% 4 4 4 3 5% 7% 42%	97764
Transparency	Day	40% 7% 12% 23% 15% 3	105005
	Night	40% 7% 12% 23% 16% 3	102271
Seeing	Day	19% 10% 27% 24% 15% 6%	14964
	Night	18% 9% 29% 31% 12% 1	24321

By Month

Percentage Cloud Cover SE (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% 8% 2 6% 4 4 4 3 5% 5% 45%	2517
	11th to 20th	Day	14% 10% 3 10% 5% 5% 4 2 4 6% 34%	2721
	21st to end	Day	19% 10% 3 8% 4 5% 4 3 5% 5% 34%	3124
February	1st to 10th	Day	14% 10% 2 6% 5% 4 4 4 5% 8% 38%	1710
	11th to 20th	Day	16% 8% 2 5% 5% 4 4 3 6% 7% 40%	1745
	21st to end	Day	19% 11% 3 6% 4 4 4 2 4 4 38%	1570
March	1st to 10th	Day	24% 7% 2 5% 3 4 4 3 4 6% 38%	3264
	11th to 20th	Day	10% 6% 2 6% 4 5% 5% 4 5% 7% 45%	3480
	21st to end	Day	21% 8% 2 5% 4 4 3 3 4 5% 43%	3960
April	1st to 10th	Day	15% 8% 2 6% 5% 4 5% 4 5% 7% 39%	2280
	11th to 20th	Day	14% 7% 2 5% 5% 3 4 4 5% 7% 44%	2254
	21st to end	Day	17% 6% 1 5% 4 4 4 4 6% 7% 40%	2280
May	1st to 10th	Day	28% 7% 2 7% 4 4 3 3 6% 7% 30%	4036
	11th to 20th	Day	25% 7% 3 7% 5% 4 4 3 6% 7% 28%	4398
	21st to end	Day	11% 5% 2 5% 4 4 5% 4 6% 9% 45%	4823
June	1st to 10th	Day	13% 5% 2 5% 5% 5% 5% 4 7% 10% 40%	2660
	11th to 20th	Day	12% 6% 2 6% 5% 5% 6% 4 6% 9% 39%	2660
	21st to end	Day	10% 4 2 5% 5% 5% 5% 5% 7% 11% 42%	2660
July	1st to 10th	Day	6% 5% 2 6% 5% 6% 7% 6% 7% 12% 39%	4440
	11th to 20th	Day	9% 5% 2 6% 5% 5% 6% 5% 8% 11% 39%	4440
	21st to end	Day	10% 8% 3 7% 6% 6% 5% 5% 7% 8% 35%	4566
August	1st to 10th	Day	18% 5% 2 6% 5% 6% 6% 4 6% 8% 34%	4104
	11th to 20th	Day	11% 5% 3 6% 4 5% 5% 4 7% 9% 41%	3829
	21st to end	Day	11% 5% 2 5% 4 4 4 4 5% 7% 49%	4180
September	1st to 10th	Day	15% 6% 3 6% 4 4 4 2 4 7% 45%	2280
	11th to 20th	Day	13% 5% 2 4 3 4 4 2 5% 8% 50%	2280
	21st to end	Day	21% 7% 2 6% 4 4 4 4 5% 7% 37%	2025
October	1st to 10th	Day	18% 6% 2 4 4 3 3 4 5% 7% 44%	1900
	11th to 20th	Day	17% 5% 2 4 4 4 4 3 4 6% 47%	1900
	21st to end	Day	16% 6% 2 5% 3 3 4 4 6% 6% 46%	2090
November	1st to 10th	Day	12% 6% 2 5% 4 3 3 3 4 8% 51%	1766
	11th to 20th	Day	16% 6% 2 4 4 3 4 4 5% 6% 48%	1708
	21st to end	Day	16% 6% 2 6% 4 4 5% 3 5% 6% 44%	1520
December	1st to 10th	Day	17% 8% 3 6% 3 5% 4 4 5% 7% 38%	1520
	11th to 20th	Day	19% 8% 2 4 3 4 4 3 6% 7% 39%	1910
	21st to end	Day	16% 8% 3 8% 5% 5% 6% 4 6% 5% 35%	2772
January	1st to 10th	Night	15% 7% 2 7% 4 4 4 4 5% 7% 41%	4429
	11th to 20th	Night	18% 9% 2 5% 4 3 3 3 4 6% 42%	4235
	21st to end	Night	21% 9% 3 7% 4 3 3 3 4 5% 38%	4532
February	1st to 10th	Night	16% 8% 3 7% 5% 4 4 3 5% 6% 40%	2470
	11th to 20th	Night	17% 8% 3 7% 3 4 4 3 5% 5% 42%	2319
	21st to end	Night	16% 9% 3 6% 4 5% 4 4 5% 6% 40%	1884
March	1st to 10th	Night	22% 10% 2 6% 4 3 3 3 4 5% 39%	3588
	11th to 20th	Night	11% 6% 2 5% 3 4 4 3 4 6% 51%	3480
	21st to end	Night	15% 8% 2 7% 4 3 3 3 3 4 47%	3672
April	1st to 10th	Night	17% 7% 3 6% 4 4 4 3 6% 7% 38%	1900
	11th to 20th	Night	15% 6% 2 6% 4 4 4 3 5% 7% 43%	1875
	21st to end	Night	19% 6% 2 5% 4 2 3 4 4 7% 44%	1900
May	1st to 10th	Night	25% 8% 2 6% 4 4 4 3 5% 8% 31%	2887
	11th to 20th	Night	25% 10% 4 7% 5% 4 3 3 5% 7% 28%	2495
	21st to end	Night	12% 6% 1 5% 4 4 4 4 6% 10% 43%	2732
June	1st to 10th	Night	13% 4 2 4 4 4 3 6% 6% 8% 45%	1520
	11th to 20th	Night	12% 4 2 6% 5% 5% 5% 4 7% 10% 40%	1520
	21st to end	Night	10% 4 2 5% 5% 3 5% 5% 7% 10% 43%	1520
July	1st to 10th	Night	6% 5% 3 7% 6% 6% 6% 5% 8% 9% 40%	2520
	11th to 20th	Night	9% 5% 3 6% 5% 6% 6% 5% 8% 9% 38%	2520
	21st to end	Night	14% 7% 2 7% 4 4 5% 4 6% 8% 39%	2982
August	1st to 10th	Night	19% 5% 3 6% 5% 5% 4 4 6% 8% 36%	2825
	11th to 20th	Night	12% 8% 2 7% 4 4 5% 4 6% 7% 42%	2966
	21st to end	Night	12% 6% 2 5% 4 3 5% 3 6% 7% 47%	3476
September	1st to 10th	Night	13% 6% 3 6% 4 4 3 4 5% 6% 47%	1900
	11th to 20th	Night	12% 6% 2 5% 3 3 2 3 5% 7% 52%	1900
	21st to end	Night	21% 7% 2 5% 4 4 4 3 4 6% 40%	2151
October	1st to 10th	Night	20% 7% 3 6% 3 4 3 3 4 6% 43%	2280
	11th to 20th	Night	15% 5% 2 5% 3 3 4 3 4 6% 51%	2280
	21st to end	Night	18% 5% 2 4 3 3 4 3 5% 6% 48%	2508
November	1st to 10th	Night	10% 4 2 5% 4 3 4 4 4 5% 54%	2532
	11th to 20th	Night	15% 7% 2 5% 4 3 4 3 4 5% 47%	2477
	21st to end	Night	13% 5% 2 5% 5% 4 4 4 5% 7% 46%	2660
December	1st to 10th	Night	18% 7% 2 6% 5% 4 4 3 5% 7% 38%	2660
	11th to 20th	Night	17% 6% 2 6% 4 4 5% 3 6% 6% 41%	3285
	21st to end	Night	16% 8% 3 6% 5% 5% 5% 4 6% 8% 34%	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	39% 6% 14% 26% 12% 4	2518
	11th to 20th	Day	49% 6% 10% 18% 13% 3	2721
	21st to end	Day	50% 7% 10% 22% 9% 1	3124
February	1st to 10th	Day	44% 6% 13% 24% 11% 2	1710
	11th to 20th	Day	43% 5% 10% 25% 14% 3	1754
	21st to end	Day	49% 4 10% 20% 13% 4	1570
March	1st to 10th	Day	46% 5% 11% 26% 9% 2	3264
	11th to 20th	Day	34% 7% 12% 27% 17% 4	3480
	21st to end	Day	45% 5% 9% 20% 18% 3	3960
April	1st to 10th	Day	42% 7% 11% 19% 16% 4	2280
	11th to 20th	Day	38% 8% 11% 23% 16% 4	2254
	21st to end	Day	41% 6% 11% 21% 17% 4	2280
May	1st to 10th	Day	52% 7% 9% 20% 10% 2	4072
	11th to 20th	Day	52% 9% 13% 17% 7% 1	4402
	21st to end	Day	32% 9% 14% 25% 17% 2	4837
June	1st to 10th	Day	38% 9% 13% 23% 15% 1	2660
	11th to 20th	Day	39% 9% 14% 24% 12% 3	2660
	21st to end	Day	34% 10% 15% 25% 16% 1	2660
July	1st to 10th	Day	35% 11% 17% 21% 13% 3	4370
	11th to 20th	Day	36% 9% 16% 26% 12% 1	4365
	21st to end	Day	44% 9% 11% 19% 16% 1	4420
August	1st to 10th	Day	47% 8% 12% 24% 9%	4091
	11th to 20th	Day	37% 8% 12% 28% 14% 1	3868
	21st to end	Day	33% 7% 11% 28% 19% 2	4180
September	1st to 10th	Day	40% 6% 11% 19% 20% 4	2280
	11th to 20th	Day	34% 5% 10% 26% 21% 4	2280
	21st to end	Day	46% 7% 8% 18% 19% 2	2025
October	1st to 10th	Day	36% 5% 9% 18% 27% 5%	3160
	11th to 20th	Day	27% 5% 11% 26% 22% 9%	3140
	21st to end	Day	25% 4 12% 29% 28% 4	3428
November	1st to 10th	Day	33% 5% 13% 24% 21% 4	1766
	11th to 20th	Day	37% 6% 11% 24% 20% 3	1708
	21st to end	Day	40% 6% 11% 29% 11% 2	1520
December	1st to 10th	Day	46% 6% 16% 20% 11% 1	1520
	11th to 20th	Day	42% 5% 12% 30% 9% 1	1906
	21st to end	Day	47% 8% 15% 20% 10% 1	2772
January	1st to 10th	Night	41% 8% 12% 26% 11% 3	4429
	11th to 20th	Night	42% 5% 13% 24% 13% 2	4235
	21st to end	Night	47% 5% 9% 27% 10% 2	4532
February	1st to 10th	Night	45% 5% 13% 24% 12% 2	2470
	11th to 20th	Night	44% 4 10% 21% 18% 3	2321
	21st to end	Night	45% 6% 10% 20% 15% 5%	1884
March	1st to 10th	Night	47% 6% 10% 24% 13% 1	3588
	11th to 20th	Night	32% 7% 11% 31% 16% 2	3480
	21st to end	Night	40% 6% 7% 20% 22% 5%	3672
April	1st to 10th	Night	43% 6% 11% 19% 17% 4	1900
	11th to 20th	Night	38% 7% 11% 20% 20% 4	1875
	21st to end	Night	40% 7% 10% 21% 17% 5%	1900
May	1st to 10th	Night	51% 7% 9% 18% 13% 2	2917
	11th to 20th	Night	53% 9% 13% 13% 10% 1	2496
	21st to end	Night	35% 11% 14% 24% 13% 4	2739
June	1st to 10th	Night	36% 9% 12% 24% 18% 2	1520
	11th to 20th	Night	37% 10% 13% 23% 16% 1	1520
	21st to end	Night	34% 8% 14% 26% 15% 2	1520
July	1st to 10th	Night	37% 11% 17% 17% 12% 5%	2480
	11th to 20th	Night	38% 10% 15% 23% 12% 1	2472
	21st to end	Night	41% 9% 14% 18% 17% 1	2887
August	1st to 10th	Night	46% 8% 17% 21% 8% 1	2814
	11th to 20th	Night	40% 7% 11% 27% 14% 1	2993
	21st to end	Night	34% 8% 11% 29% 17% 2	3476
September	1st to 10th	Night	37% 7% 10% 21% 21% 4	1900
	11th to 20th	Night	32% 5% 10% 24% 25% 4	1900
	21st to end	Night	44% 6% 9% 19% 19% 3	2151
October	1st to 10th	Night	43% 6% 9% 19% 21% 2	3800
	11th to 20th	Night	25% 5% 10% 27% 27% 5%	3779
	21st to end	Night	25% 4 11% 32% 24% 4	4120
November	1st to 10th	Night	32% 5% 12% 25% 21% 5%	2532
	11th to 20th	Night	39% 4 10% 23% 19% 5%	2477
	21st to end	Night	36% 6% 12% 27% 16% 2	2660
December	1st to 10th	Night	46% 6% 12% 23% 13% 1	2660
	11th to 20th	Night	41% 7% 13% 22% 15% 3	3288
	21st to end	Night	43% 10% 15% 21% 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	26% 20% 35% 16% 3 1	180
	11th to 20th	Day	27% 24% 31% 16% 2	238
	21st to end	Day	22% 21% 36% 15% 6% 1	297
February	1st to 10th	Day	26% 17% 38% 14% 4 1	270
	11th to 20th	Day	24% 24% 39% 11% 2	352
	21st to end	Day	30% 15% 34% 19% 3	382
March	1st to 10th	Day	21% 20% 31% 22% 6%	460
	11th to 20th	Day	20% 21% 35% 18% 5% 1	460
	21st to end	Day	24% 16% 33% 21% 5% 2	506
April	1st to 10th	Day	22% 15% 35% 19% 7% 2	460
	11th to 20th	Day	17% 17% 28% 21% 12% 4	452
	21st to end	Day	25% 12% 30% 22% 9% 2	460
May	1st to 10th	Day	26% 14% 24% 21% 11% 3	463
	11th to 20th	Day	21% 10% 29% 22% 14% 5%	487
	21st to end	Day	18% 5% 21% 25% 22% 10%	529
June	1st to 10th	Day	15% 6% 30% 24% 18% 8%	490
	11th to 20th	Day	16% 6% 24% 29% 19% 6%	490
	21st to end	Day	14% 3 27% 30% 18% 8%	490
July	1st to 10th	Day	12% 4 14% 29% 26% 15%	485
	11th to 20th	Day	5% 3 15% 35% 30% 12%	484
	21st to end	Day	14% 3 21% 31% 24% 7%	532
August	1st to 10th	Day	13% 2 19% 28% 26% 11%	486
	11th to 20th	Day	11% 5% 18% 27% 26% 13%	479
	21st to end	Day	11% 4 18% 29% 24% 14%	539
September	1st to 10th	Day	19% 6% 18% 22% 22% 13%	490
	11th to 20th	Day	15% 3 20% 25% 24% 12%	490
	21st to end	Day	26% 8% 20% 25% 15% 6%	490
October	1st to 10th	Day	23% 6% 22% 23% 18% 8%	490
	11th to 20th	Day	18% 10% 26% 27% 16% 4	490
	21st to end	Day	18% 9% 34% 27% 10% 2	539
November	1st to 10th	Day	15% 10% 32% 27% 13% 3	398
	11th to 20th	Day	17% 16% 31% 24% 11% 1	368
	21st to end	Day	18% 18% 36% 19% 8% 1	180
December	1st to 10th	Day	24% 16% 34% 18% 4 2	180
	11th to 20th	Day	25% 19% 33% 14% 8% 1	180
	21st to end	Day	21% 17% 31% 22% 8%	198
January	1st to 10th	Night	18% 13% 42% 23% 4	760
	11th to 20th	Night	24% 13% 32% 27% 4	760
	21st to end	Night	18% 13% 42% 25% 2	836
February	1st to 10th	Night	20% 15% 36% 27% 2	760
	11th to 20th	Night	22% 18% 39% 20% 1	743
	21st to end	Night	22% 18% 38% 19% 3	628
March	1st to 10th	Night	18% 14% 38% 25% 5%	760
	11th to 20th	Night	19% 16% 36% 22% 6% 1	760
	21st to end	Night	21% 11% 38% 24% 6%	836
April	1st to 10th	Night	21% 13% 37% 24% 4	760
	11th to 20th	Night	18% 10% 33% 31% 8%	751
	21st to end	Night	22% 8% 32% 30% 8%	760
May	1st to 10th	Night	21% 7% 28% 34% 9%	621
	11th to 20th	Night	20% 5% 28% 36% 10%	374
	21st to end	Night	14% 2 19% 42% 20% 2	411
June	1st to 10th	Night	13% 3 23% 41% 20% 1	380
	11th to 20th	Night	14% 3 21% 44% 18% 1	380
	21st to end	Night	12% 3 16% 52% 16%	380
July	1st to 10th	Night	11% 3 16% 41% 27% 2	370
	11th to 20th	Night	8% 1 12% 45% 32% 3	368
	21st to end	Night	11% 1 16% 45% 25% 2	558
August	1st to 10th	Night	11% 2 10% 45% 30% 2	567
	11th to 20th	Night	13% 2 12% 39% 30% 3	667
	21st to end	Night	13% 3 13% 40% 28% 4	836
September	1st to 10th	Night	15% 3 19% 34% 25% 4	760
	11th to 20th	Night	13% 3 15% 36% 29% 4	760
	21st to end	Night	23% 3 18% 34% 20% 2	760
October	1st to 10th	Night	23% 4 21% 28% 20% 4	760
	11th to 20th	Night	17% 7% 27% 34% 14% 1	760
	21st to end	Night	19% 6% 33% 29% 13%	836
November	1st to 10th	Night	13% 6% 32% 36% 12% 1	780
	11th to 20th	Night	19% 11% 30% 31% 7% 1	763
	21st to end	Night	16% 12% 34% 30% 8%	760
December	1st to 10th	Night	23% 13% 33% 25% 6% 1	760
	11th to 20th	Night	18% 10% 40% 26% 5%	760
	21st to end	Night	20% 11% 38% 29% 2	836

Page generated at 2024-11-08 06:44:50. Version ac07

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