Starburst Meadows Observatory
Clear Sky Chart
History

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

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	18% 7% 2 6% 4 4 4 4 5% 7% 38%	100939
	Night	19% 8% 3 6% 4 4 4 3 5% 6% 37%	98154
Transparency	Day	25% 47% 7% 13% 8% 1	104477
	Night	26% 47% 6% 12% 8% 1	102706
Seeing	Day	21% 14% 33% 22% 8% 2	14998
	Night	22% 12% 31% 26% 9% 1	23923

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	16% 7% 3 6% 5% 4 4 3 4 6% 42%	2517
	11th to 20th	Day	18% 6% 2 6% 4 5% 4 4 4 6% 41%	2520
	21st to end	Day	18% 12% 2 6% 3 4 4 3 4 5% 38%	2772
February	1st to 10th	Day	18% 9% 3 6% 5% 3 4 4 5% 5% 37%	1686
	11th to 20th	Day	13% 9% 3 7% 5% 5% 5% 4 5% 5% 38%	1848
	21st to end	Day	16% 12% 3 6% 5% 4 4 4 5% 6% 36%	1570
March	1st to 10th	Day	26% 13% 2 6% 4 4 4 3 4 5% 30%	3116
	11th to 20th	Day	17% 8% 2 6% 4 4 4 4 5% 7% 39%	3416
	21st to end	Day	24% 8% 2 6% 4 3 4 3 5% 5% 35%	3900
April	1st to 10th	Day	20% 10% 3 6% 5% 3 4 4 5% 6% 35%	2280
	11th to 20th	Day	19% 6% 2 5% 4 4 4 4 5% 7% 39%	2354
	21st to end	Day	23% 8% 2 6% 5% 4 4 3 5% 6% 35%	2470
May	1st to 10th	Day	24% 10% 3 7% 5% 4 5% 4 5% 6% 28%	4106
	11th to 20th	Day	19% 9% 3 7% 5% 4 5% 3 6% 7% 33%	4129
	21st to end	Day	17% 6% 2 6% 4 4 5% 4 6% 8% 38%	4837
June	1st to 10th	Day	22% 7% 2 6% 5% 4 5% 4 5% 7% 33%	2660
	11th to 20th	Day	17% 7% 2 6% 5% 4 4 4 4 8% 40%	2660
	21st to end	Day	22% 7% 2 6% 5% 4 5% 4 5% 7% 32%	2660
July	1st to 10th	Day	15% 7% 2 6% 5% 5% 5% 4 7% 9% 35%	4440
	11th to 20th	Day	12% 6% 2 6% 4 4 5% 4 7% 10% 39%	4440
	21st to end	Day	21% 6% 2 5% 4 3 4 4 6% 8% 37%	4814
August	1st to 10th	Day	16% 6% 3 7% 5% 4 5% 3 6% 8% 37%	4112
	11th to 20th	Day	17% 7% 3 7% 4 4 4 4 6% 8% 35%	4045
	21st to end	Day	9% 4 1 5% 4 5% 5% 5% 7% 9% 47%	4350
September	1st to 10th	Day	13% 4 2 5% 4 4 4 3 5% 7% 49%	2231
	11th to 20th	Day	12% 6% 2 5% 3 3 2 3 4 6% 55%	2090
	21st to end	Day	17% 6% 2 5% 3 3 4 4 5% 7% 44%	2090
October	1st to 10th	Day	19% 7% 3 6% 4 4 4 2 5% 6% 40%	2090
	11th to 20th	Day	17% 6% 2 6% 4 4 4 2 3 6% 44%	1835
	21st to end	Day	22% 8% 2 5% 3 3 3 3 4 5% 41%	1881
November	1st to 10th	Day	17% 6% 3 4 3 3 3 3 4 6% 47%	1734
	11th to 20th	Day	21% 4 2 4 3 3 3 4 5% 6% 45%	1710
	21st to end	Day	22% 9% 2 5% 3 3 3 2 4 6% 43%	1702
December	1st to 10th	Day	23% 9% 3 5% 5% 4 4 3 3 4 38%	1368
	11th to 20th	Day	22% 9% 3 5% 3 3 3 2 4 5% 42%	1734
	21st to end	Day	26% 10% 3 6% 4 4 4 3 4 6% 30%	2772
January	1st to 10th	Night	16% 9% 3 6% 4 4 3 3 5% 5% 43%	4429
	11th to 20th	Night	14% 8% 3 9% 5% 5% 4 4 4 6% 38%	4440
	21st to end	Night	20% 10% 3 8% 4 4 4 3 4 5% 35%	4884
February	1st to 10th	Night	17% 9% 3 6% 5% 5% 4 3 5% 6% 36%	2492
	11th to 20th	Night	13% 10% 3 6% 6% 5% 4 3 5% 5% 40%	2218
	21st to end	Night	15% 10% 3 6% 4 4 3 3 5% 5% 41%	1884
March	1st to 10th	Night	28% 10% 3 5% 3 3 3 3 4 5% 32%	3724
	11th to 20th	Night	14% 8% 3 9% 6% 5% 5% 4 6% 7% 33%	3528
	21st to end	Night	25% 9% 3 5% 4 3 4 4 7% 5% 30%	3728
April	1st to 10th	Night	22% 10% 2 5% 4 4 5% 2 4 6% 36%	1900
	11th to 20th	Night	20% 6% 2 6% 5% 4 5% 5% 5% 6% 38%	1774
	21st to end	Night	23% 6% 2 6% 5% 4 4 3 4 6% 36%	1710
May	1st to 10th	Night	23% 8% 3 7% 3 4 4 4 7% 7% 28%	2834
	11th to 20th	Night	18% 9% 3 8% 5% 5% 5% 5% 7% 8% 27%	2794
	21st to end	Night	17% 8% 4 7% 5% 3 5% 4 5% 7% 36%	2738
June	1st to 10th	Night	22% 8% 2 8% 5% 4 4 5% 5% 7% 32%	1520
	11th to 20th	Night	17% 8% 3 5% 5% 3 4 3 6% 8% 39%	1520
	21st to end	Night	23% 8% 3 6% 4 4 5% 3 6% 7% 32%	1520
July	1st to 10th	Night	13% 8% 4 7% 6% 5% 6% 5% 6% 8% 32%	2520
	11th to 20th	Night	14% 7% 2 8% 5% 5% 5% 4 7% 9% 35%	2520
	21st to end	Night	16% 6% 2 6% 4 4 4 5% 6% 8% 38%	2739
August	1st to 10th	Night	21% 7% 2 8% 5% 4 5% 4 6% 6% 32%	2784
	11th to 20th	Night	17% 9% 3 7% 5% 4 4 4 7% 8% 32%	2782
	21st to end	Night	11% 6% 2 5% 5% 4 3 4 5% 8% 46%	3303
September	1st to 10th	Night	13% 7% 2 5% 3 4 4 3 5% 5% 49%	1948
	11th to 20th	Night	15% 7% 1 5% 2 3 3 2 4 6% 51%	2090
	21st to end	Night	15% 7% 2 5% 3 4 3 3 5% 6% 48%	2090
October	1st to 10th	Night	19% 6% 2 6% 3 4 5% 4 5% 6% 40%	2090
	11th to 20th	Night	18% 6% 2 6% 4 4 4 3 5% 7% 42%	2342
	21st to end	Night	24% 6% 2 6% 3 4 3 3 4 5% 38%	2717
November	1st to 10th	Night	17% 6% 2 5% 4 4 4 3 5% 6% 45%	2505
	11th to 20th	Night	19% 6% 1 4 4 4 4 3 5% 6% 43%	2470
	21st to end	Night	17% 7% 2 6% 4 4 3 3 5% 6% 43%	2471
December	1st to 10th	Night	22% 10% 2 6% 4 4 4 3 5% 5% 36%	2807
	11th to 20th	Night	22% 7% 2 4 3 4 3 4 5% 5% 41%	3455
	21st to end	Night	25% 10% 3 7% 4 4 3 2 4 4 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	27% 38% 9% 20% 6%	2518
	11th to 20th	Day	25% 39% 8% 18% 8% 1	2520
	21st to end	Day	32% 40% 8% 13% 7%	2772
February	1st to 10th	Day	17% 65% 5% 7% 5% 1	1686
	11th to 20th	Day	18% 64% 3 8% 7% 1	1857
	21st to end	Day	16% 65% 3 8% 6% 2	1570
March	1st to 10th	Day	39% 40% 4 6% 9% 1	3119
	11th to 20th	Day	26% 42% 7% 12% 10% 3	3416
	21st to end	Day	35% 39% 2 8% 12% 3	3900
April	1st to 10th	Day	19% 65% 2 6% 6% 2	2280
	11th to 20th	Day	16% 65% 4 9% 5% 1	2354
	21st to end	Day	19% 65% 2 7% 6%	2470
May	1st to 10th	Day	34% 47% 7% 9% 3	4120
	11th to 20th	Day	31% 43% 12% 11% 3	4133
	21st to end	Day	27% 42% 11% 12% 9%	4837
June	1st to 10th	Day	16% 65% 5% 10% 4	2660
	11th to 20th	Day	14% 65% 4 9% 7% 1	2660
	21st to end	Day	16% 64% 4 10% 5%	2660
July	1st to 10th	Day	28% 39% 6% 18% 8%	4370
	11th to 20th	Day	24% 38% 11% 18% 8%	4365
	21st to end	Day	32% 37% 8% 15% 8% 1	4661
August	1st to 10th	Day	30% 39% 10% 17% 4	4098
	11th to 20th	Day	32% 40% 11% 13% 4	4084
	21st to end	Day	17% 40% 11% 18% 14% 1	4350
September	1st to 10th	Day	11% 61% 6% 14% 8%	2231
	11th to 20th	Day	16% 60% 3 12% 8% 1	2090
	21st to end	Day	15% 60% 3 14% 7% 1	2090
October	1st to 10th	Day	30% 39% 6% 16% 8% 1	3480
	11th to 20th	Day	17% 37% 6% 21% 18%	3025
	21st to end	Day	20% 37% 8% 18% 14% 2	3081
November	1st to 10th	Day	18% 57% 7% 11% 6% 1	1734
	11th to 20th	Day	17% 59% 3 9% 9% 3	1710
	21st to end	Day	17% 59% 6% 9% 8% 1	1702
December	1st to 10th	Day	20% 59% 5% 10% 6%	1368
	11th to 20th	Day	25% 48% 4 11% 8% 4	1734
	21st to end	Day	37% 39% 5% 11% 6% 2	2772
January	1st to 10th	Night	27% 37% 8% 19% 7% 2	4429
	11th to 20th	Night	28% 37% 10% 14% 9% 2	4440
	21st to end	Night	36% 41% 5% 13% 5%	4884
February	1st to 10th	Night	18% 65% 5% 6% 5% 2	2492
	11th to 20th	Night	16% 64% 3 7% 9% 1	2220
	21st to end	Night	18% 64% 2 7% 6% 3	1884
March	1st to 10th	Night	37% 40% 6% 8% 5% 3	3734
	11th to 20th	Night	28% 43% 6% 13% 8% 2	3529
	21st to end	Night	38% 40% 3 7% 9% 4	3728
April	1st to 10th	Night	19% 65% 2 6% 7% 2	1900
	11th to 20th	Night	17% 66% 3 7% 7% 1	1774
	21st to end	Night	18% 65% 5% 6% 5% 2	1710
May	1st to 10th	Night	32% 46% 10% 9% 3	2840
	11th to 20th	Night	32% 44% 10% 10% 3	2795
	21st to end	Night	28% 43% 10% 11% 8% 1	2739
June	1st to 10th	Night	17% 66% 4 8% 5%	1520
	11th to 20th	Night	14% 65% 7% 8% 5% 1	1520
	21st to end	Night	18% 64% 5% 10% 4	1520
July	1st to 10th	Night	29% 39% 8% 13% 10%	2480
	11th to 20th	Night	30% 38% 7% 17% 8%	2472
	21st to end	Night	29% 38% 7% 18% 9%	2651
August	1st to 10th	Night	37% 39% 9% 11% 5%	2774
	11th to 20th	Night	33% 40% 9% 12% 5%	2809
	21st to end	Night	21% 40% 10% 17% 12%	3303
September	1st to 10th	Night	14% 61% 5% 13% 7% 1	1948
	11th to 20th	Night	18% 59% 3 11% 7% 1	2090
	21st to end	Night	15% 60% 4 15% 6% 1	2090
October	1st to 10th	Night	27% 39% 10% 14% 9% 1	3480
	11th to 20th	Night	16% 37% 6% 21% 20% 1	3891
	21st to end	Night	21% 37% 7% 19% 13% 2	4467
November	1st to 10th	Night	19% 56% 4 12% 7% 1	2505
	11th to 20th	Night	18% 59% 3 9% 9% 1	2470
	21st to end	Night	16% 60% 6% 9% 8% 1	2471
December	1st to 10th	Night	22% 59% 3 9% 7%	2807
	11th to 20th	Night	24% 49% 5% 10% 12% 1	3456
	21st to end	Night	35% 38% 6% 12% 8% 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	23% 26% 27% 19% 6%	180
	11th to 20th	Day	27% 21% 25% 22% 5% 1	180
	21st to end	Day	17% 19% 37% 20% 7%	198
February	1st to 10th	Day	26% 16% 36% 19% 3	346
	11th to 20th	Day	20% 23% 40% 15% 1	456
	21st to end	Day	23% 18% 36% 19% 4	382
March	1st to 10th	Day	23% 18% 38% 18% 3	460
	11th to 20th	Day	19% 24% 39% 15% 3 1	460
	21st to end	Day	24% 23% 31% 13% 6% 3	506
April	1st to 10th	Day	27% 21% 31% 16% 4 2	460
	11th to 20th	Day	23% 17% 34% 17% 6% 2	452
	21st to end	Day	28% 15% 35% 17% 4 2	460
May	1st to 10th	Day	27% 18% 32% 18% 5% 1	463
	11th to 20th	Day	19% 13% 42% 18% 7% 1	487
	21st to end	Day	21% 12% 35% 26% 5% 2	529
June	1st to 10th	Day	21% 12% 33% 24% 8% 2	490
	11th to 20th	Day	16% 12% 38% 23% 9% 2	490
	21st to end	Day	24% 10% 34% 23% 9% 1	490
July	1st to 10th	Day	20% 6% 34% 28% 11% 2	485
	11th to 20th	Day	15% 6% 33% 31% 12% 3	484
	21st to end	Day	16% 5% 33% 30% 13% 3	532
August	1st to 10th	Day	15% 6% 29% 32% 14% 3	486
	11th to 20th	Day	16% 6% 29% 30% 13% 6%	479
	21st to end	Day	12% 7% 31% 29% 16% 5%	539
September	1st to 10th	Day	16% 7% 31% 29% 15% 3	490
	11th to 20th	Day	16% 8% 31% 23% 14% 7%	490
	21st to end	Day	19% 9% 31% 24% 12% 5%	490
October	1st to 10th	Day	21% 13% 24% 25% 12% 4	490
	11th to 20th	Day	21% 15% 27% 23% 10% 3	393
	21st to end	Day	29% 13% 27% 22% 8% 1	429
November	1st to 10th	Day	19% 18% 28% 23% 9% 2	386
	11th to 20th	Day	24% 18% 31% 21% 6% 1	370
	21st to end	Day	25% 19% 27% 22% 6% 1	370
December	1st to 10th	Day	25% 15% 36% 16% 7%	218
	11th to 20th	Day	26% 26% 30% 15% 4	180
	21st to end	Day	26% 24% 28% 16% 6% 1	198
January	1st to 10th	Night	20% 20% 35% 21% 4	760
	11th to 20th	Night	24% 19% 34% 19% 4	760
	21st to end	Night	19% 20% 38% 20% 3	836
February	1st to 10th	Night	21% 19% 34% 23% 3	760
	11th to 20th	Night	21% 20% 38% 19% 2	743
	21st to end	Night	20% 17% 34% 23% 5%	628
March	1st to 10th	Night	23% 17% 38% 20% 2	760
	11th to 20th	Night	21% 15% 36% 20% 8%	760
	21st to end	Night	23% 15% 34% 22% 5% 1	836
April	1st to 10th	Night	27% 13% 34% 22% 4	760
	11th to 20th	Night	21% 12% 35% 26% 6%	650
	21st to end	Night	26% 10% 30% 27% 6% 1	570
May	1st to 10th	Night	24% 8% 31% 27% 8% 2	570
	11th to 20th	Night	24% 7% 32% 28% 8% 1	556
	21st to end	Night	26% 5% 24% 34% 11% 1	411
June	1st to 10th	Night	27% 6% 22% 32% 12% 2	380
	11th to 20th	Night	20% 3 26% 35% 15% 1	380
	21st to end	Night	26% 4 23% 35% 11% 1	380
July	1st to 10th	Night	19% 5% 17% 42% 15% 1	370
	11th to 20th	Night	18% 2 22% 37% 19% 2	368
	21st to end	Night	17% 3 17% 41% 21% 1	416
August	1st to 10th	Night	16% 3 20% 41% 18% 1	539
	11th to 20th	Night	16% 4 20% 39% 20% 2	562
	21st to end	Night	16% 4 22% 36% 21% 2	728
September	1st to 10th	Night	14% 3 29% 33% 20% 1	760
	11th to 20th	Night	18% 5% 28% 26% 19% 3	760
	21st to end	Night	18% 6% 25% 32% 17% 3	760
October	1st to 10th	Night	23% 8% 23% 28% 18% 1	760
	11th to 20th	Night	19% 11% 31% 26% 11% 2	760
	21st to end	Night	28% 12% 29% 24% 7%	836
November	1st to 10th	Night	19% 11% 33% 27% 7% 2	771
	11th to 20th	Night	22% 15% 34% 21% 7% 1	760
	21st to end	Night	21% 18% 33% 22% 5%	761
December	1st to 10th	Night	27% 14% 36% 17% 6%	850
	11th to 20th	Night	24% 19% 33% 21% 3	826
	21st to end	Night	27% 16% 35% 19% 3	836

Page generated at 2024-11-05 08:15:53. Version ac07

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