Sunflower Observatory
Clear Sky Chart
History

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

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	3 4 2 4 3 4 4 4 6% 8% 58%	100927
	Night	4 5% 2 5% 3 4 4 3 6% 7% 57%	98288
Transparency	Day	20% 7% 12% 22% 25% 14%	100685
	Night	23% 7% 12% 21% 24% 13%	98120
Seeing	Day	5% 10% 28% 32% 22% 5%	15137
	Night	5% 4 29% 43% 18% 1	25225

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	2 6% 3 5% 2 3 4 4 6% 7% 58%	2766
	11th to 20th	Day	3 6% 2 4 2 2 3 2 5% 6% 64%	2860
	21st to end	Day	4 7% 2 5% 4 4 4 4 6% 7% 53%	3146
February	1st to 10th	Day	2 7% 3 5% 4 2 3 3 4 6% 60%	1734
	11th to 20th	Day	4 6% 2 6% 3 2 4 3 6% 7% 57%	1849
	21st to end	Day	3 10% 2 4 3 3 3 3 4 6% 59%	1570
March	1st to 10th	Day	3 5% 2 3 3 3 3 3 5% 7% 63%	3280
	11th to 20th	Day	4 8% 3 6% 4 4 4 4 6% 9% 48%	3490
	21st to end	Day	3 7% 2 5% 4 4 4 3 6% 6% 57%	3965
April	1st to 10th	Day	3 4 1 4 3 4 4 3 5% 6% 61%	2280
	11th to 20th	Day	3 6% 2 4 3 4 4 3 5% 6% 60%	2251
	21st to end	Day	3 5% 1 4 3 3 3 3 6% 8% 62%	2280
May	1st to 10th	Day	2 2 1 3 2 3 3 3 4 6% 70%	3800
	11th to 20th	Day	4 4 1 4 3 4 5% 4 6% 8% 57%	3967
	21st to end	Day	2 2 1 2 3 2 3 3 4 6% 74%	4825
June	1st to 10th	Day	1 2 1 2 3 3 4 5% 7% 10% 62%	2660
	11th to 20th	Day	2 2 1 2 3 2 3 3 5% 6% 71%	2660
	21st to end	Day	5% 3 2 4 4 4 6% 3 6% 7% 56%	2660
July	1st to 10th	Day	2 3 1 4 3 4 6% 5% 7% 9% 55%	4412
	11th to 20th	Day	1 2 1 4 3 5% 7% 7% 11% 12% 47%	4110
	21st to end	Day	3 3 2 5% 5% 6% 8% 8% 11% 12% 39%	4454
August	1st to 10th	Day	3 3 1 5% 4 6% 7% 6% 11% 12% 40%	3980
	11th to 20th	Day	2 2 1 3 3 3 4 5% 8% 10% 59%	3726
	21st to end	Day	3 3 2 5% 5% 5% 7% 6% 9% 11% 42%	4180
September	1st to 10th	Day	5% 5% 1 4 4 5% 5% 5% 7% 8% 51%	2280
	11th to 20th	Day	5% 3 1 3 3 4 4 4 5% 7% 59%	2280
	21st to end	Day	3 2 1 3 2 3 3 2 5% 8% 68%	2070
October	1st to 10th	Day	7% 3 2 5% 4 4 3 3 4 6% 60%	1900
	11th to 20th	Day	4 3 1 3 2 2 2 1 3 5% 75%	1900
	21st to end	Day	4 3 1 3 2 2 2 1 3 4 72%	2090
November	1st to 10th	Day	2 3 1 3 2 2 3 2 4 8% 70%	1808
	11th to 20th	Day	3 3 1 3 2 2 3 3 5% 6% 70%	1710
	21st to end	Day	4 6% 2 4 2 3 3 2 3 6% 64%	1710
December	1st to 10th	Day	4 5% 2 3 3 3 4 2 4 7% 64%	1554
	11th to 20th	Day	4 4 3 5% 4 4 4 3 5% 8% 56%	1926
	21st to end	Day	4 6% 2 3 2 3 3 2 4 7% 64%	2794
January	1st to 10th	Night	1 7% 4 8% 4 4 3 3 5% 6% 55%	4219
	11th to 20th	Night	3 6% 1 4 3 3 4 2 4 6% 64%	4110
	21st to end	Night	4 8% 2 5% 3 3 4 4 5% 7% 54%	4521
February	1st to 10th	Night	3 8% 3 5% 2 2 3 2 4 6% 62%	2443
	11th to 20th	Night	6% 7% 2 4 3 3 3 2 5% 7% 57%	2218
	21st to end	Night	4 8% 2 5% 3 3 2 2 3 6% 63%	1884
March	1st to 10th	Night	3 7% 2 4 3 3 3 2 4 5% 64%	3585
	11th to 20th	Night	9% 9% 3 6% 4 4 3 3 4 6% 48%	3490
	21st to end	Night	5% 7% 2 5% 3 3 3 3 4 6% 58%	3682
April	1st to 10th	Night	4 4 1 4 3 3 3 3 6% 6% 63%	1900
	11th to 20th	Night	4 6% 2 4 3 3 4 4 4 6% 61%	1877
	21st to end	Night	4 5% 1 4 3 3 3 4 5% 5% 63%	1900
May	1st to 10th	Night	5% 5% 1 4 3 3 3 3 4 5% 63%	3170
	11th to 20th	Night	5% 5% 2 5% 4 5% 5% 4 7% 8% 49%	2930
	21st to end	Night	4 2 1 3 3 3 3 3 4 6% 70%	2762
June	1st to 10th	Night	2 2 1 4 4 4 5% 4 6% 9% 59%	1520
	11th to 20th	Night	2 2 1 3 2 4 2 3 5% 7% 67%	1520
	21st to end	Night	5% 4 1 5% 4 4 5% 4 8% 8% 52%	1520
July	1st to 10th	Night	3 3 1 5% 5% 5% 6% 5% 7% 7% 53%	2540
	11th to 20th	Night	3 3 2 6% 5% 5% 6% 7% 10% 14% 39%	2859
	21st to end	Night	7% 5% 2 5% 5% 5% 7% 6% 10% 11% 38%	3109
August	1st to 10th	Night	3 5% 2 7% 7% 7% 7% 6% 10% 13% 32%	2956
	11th to 20th	Night	3 3 2 6% 5% 6% 7% 5% 9% 12% 43%	3113
	21st to end	Night	3 4 2 8% 6% 6% 8% 8% 10% 11% 33%	3487
September	1st to 10th	Night	5% 3 1 5% 4 4 5% 5% 7% 9% 52%	1900
	11th to 20th	Night	5% 4 2 4 3 4 5% 3 7% 8% 57%	1900
	21st to end	Night	5% 4 1 3 2 3 3 3 5% 6% 66%	2104
October	1st to 10th	Night	6% 4 1 4 3 3 3 3 4 5% 62%	2280
	11th to 20th	Night	3 2 1 3 2 2 2 2 3 4 75%	2280
	21st to end	Night	4 3 1 3 2 2 3 3 4 5% 70%	2508
November	1st to 10th	Night	3 2 1 2 1 2 2 2 4 5% 75%	2295
	11th to 20th	Night	2 2 1 3 2 2 2 2 4 5% 74%	2470
	21st to end	Night	6% 6% 2 3 3 2 3 2 4 6% 63%	2470
December	1st to 10th	Night	5% 7% 2 4 2 2 3 2 5% 6% 63%	2622
	11th to 20th	Night	5% 5% 2 4 3 4 4 3 6% 7% 57%	3271
	21st to end	Night	4 8% 2 5% 3 3 3 2 4 5% 62%	4873

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	20% 7% 12% 31% 26% 4	2767
	11th to 20th	Day	15% 6% 16% 36% 23% 4	2860
	21st to end	Day	24% 8% 13% 23% 26% 5%	3146
February	1st to 10th	Day	25% 5% 13% 24% 24% 10%	1734
	11th to 20th	Day	24% 4 10% 26% 24% 12%	1859
	21st to end	Day	23% 4 7% 19% 32% 15%	1570
March	1st to 10th	Day	17% 4 7% 21% 35% 16%	3280
	11th to 20th	Day	22% 11% 16% 22% 23% 6%	3490
	21st to end	Day	21% 6% 11% 22% 30% 9%	3965
April	1st to 10th	Day	19% 5% 10% 20% 30% 16%	2280
	11th to 20th	Day	22% 5% 9% 17% 29% 18%	2254
	21st to end	Day	18% 5% 11% 23% 30% 13%	2280
May	1st to 10th	Day	12% 5% 10% 17% 34% 22%	3800
	11th to 20th	Day	19% 9% 11% 22% 26% 13%	3970
	21st to end	Day	10% 4 7% 15% 24% 40%	4825
June	1st to 10th	Day	14% 7% 13% 21% 25% 20%	2660
	11th to 20th	Day	13% 5% 7% 14% 24% 37%	2660
	21st to end	Day	24% 7% 11% 19% 21% 19%	2660
July	1st to 10th	Day	21% 10% 12% 16% 19% 21%	4343
	11th to 20th	Day	20% 11% 21% 32% 12% 4	4041
	21st to end	Day	29% 13% 20% 27% 8% 2	4314
August	1st to 10th	Day	27% 13% 24% 19% 12% 5%	3966
	11th to 20th	Day	17% 8% 15% 28% 20% 12%	3762
	21st to end	Day	29% 11% 19% 23% 15% 3	4179
September	1st to 10th	Day	25% 10% 15% 21% 20% 9%	2280
	11th to 20th	Day	22% 8% 12% 18% 26% 15%	2280
	21st to end	Day	15% 4 9% 23% 33% 16%	2070
October	1st to 10th	Day	24% 6% 7% 20% 25% 17%	1900
	11th to 20th	Day	15% 3 6% 15% 38% 25%	1900
	21st to end	Day	16% 3 8% 20% 36% 16%	2090
November	1st to 10th	Day	14% 2 8% 22% 39% 15%	1808
	11th to 20th	Day	14% 4 9% 26% 36% 10%	1710
	21st to end	Day	21% 5% 7% 22% 31% 15%	1710
December	1st to 10th	Day	19% 6% 11% 32% 23% 9%	1554
	11th to 20th	Day	26% 6% 11% 21% 28% 9%	1924
	21st to end	Day	19% 5% 11% 20% 32% 13%	2794
January	1st to 10th	Night	26% 7% 11% 25% 24% 7%	4219
	11th to 20th	Night	18% 5% 16% 33% 23% 5%	4110
	21st to end	Night	25% 7% 13% 24% 25% 6%	4521
February	1st to 10th	Night	23% 4 12% 24% 25% 12%	2443
	11th to 20th	Night	25% 5% 9% 26% 23% 12%	2218
	21st to end	Night	23% 3 6% 17% 33% 17%	1884
March	1st to 10th	Night	19% 5% 7% 17% 38% 14%	3585
	11th to 20th	Night	29% 10% 10% 22% 23% 7%	3490
	21st to end	Night	21% 7% 10% 26% 28% 8%	3682
April	1st to 10th	Night	20% 4 8% 21% 29% 17%	1900
	11th to 20th	Night	22% 4 10% 19% 25% 20%	1877
	21st to end	Night	20% 5% 13% 19% 33% 12%	1900
May	1st to 10th	Night	16% 8% 10% 14% 27% 24%	3170
	11th to 20th	Night	24% 11% 16% 21% 15% 14%	2931
	21st to end	Night	12% 5% 9% 13% 19% 41%	2762
June	1st to 10th	Night	19% 9% 15% 19% 18% 19%	1520
	11th to 20th	Night	15% 5% 8% 15% 21% 36%	1520
	21st to end	Night	26% 8% 14% 16% 18% 20%	1520
July	1st to 10th	Night	28% 9% 11% 13% 13% 25%	2500
	11th to 20th	Night	28% 12% 22% 28% 7% 4	2806
	21st to end	Night	33% 13% 20% 25% 9%	3011
August	1st to 10th	Night	37% 13% 19% 16% 11% 5%	2947
	11th to 20th	Night	28% 11% 18% 16% 17% 9%	3143
	21st to end	Night	37% 11% 17% 22% 10% 3	3487
September	1st to 10th	Night	24% 10% 17% 22% 18% 9%	1900
	11th to 20th	Night	23% 7% 14% 16% 24% 16%	1900
	21st to end	Night	18% 6% 10% 19% 32% 16%	2104
October	1st to 10th	Night	24% 5% 9% 19% 23% 20%	2280
	11th to 20th	Night	14% 3 5% 16% 35% 26%	2280
	21st to end	Night	15% 3 8% 22% 35% 17%	2508
November	1st to 10th	Night	12% 3 8% 24% 38% 16%	2295
	11th to 20th	Night	13% 3 9% 24% 39% 13%	2470
	21st to end	Night	23% 4 7% 20% 30% 16%	2470
December	1st to 10th	Night	22% 4 10% 31% 26% 7%	2622
	11th to 20th	Night	24% 6% 12% 21% 27% 9%	3272
	21st to end	Night	24% 5% 9% 21% 29% 11%	4873

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	5% 10% 46% 29% 10%	270
	11th to 20th	Day	11% 6% 44% 31% 7%	270
	21st to end	Day	2 8% 45% 28% 14% 3	297
February	1st to 10th	Day	4 13% 44% 31% 7%	270
	11th to 20th	Day	7% 13% 48% 24% 7%	270
	21st to end	Day	10% 18% 49% 18% 4	225
March	1st to 10th	Day	3 21% 35% 30% 10%	355
	11th to 20th	Day	8% 20% 34% 27% 9% 1	460
	21st to end	Day	9% 28% 34% 22% 7%	506
April	1st to 10th	Day	6% 20% 41% 26% 6% 1	460
	11th to 20th	Day	8% 24% 40% 21% 6%	452
	21st to end	Day	6% 22% 39% 27% 5% 1	460
May	1st to 10th	Day	5% 16% 44% 26% 8% 1	463
	11th to 20th	Day	5% 13% 31% 32% 16% 3	540
	21st to end	Day	3 13% 30% 37% 15% 1	734
June	1st to 10th	Day	2 5% 21% 39% 30% 3	680
	11th to 20th	Day	3 6% 24% 39% 26% 3	680
	21st to end	Day	6% 3 19% 37% 29% 6%	680
July	1st to 10th	Day	2 1 13% 35% 40% 8%	666
	11th to 20th	Day	2 1 6% 27% 44% 19%	484
	21st to end	Day	3 1 6% 27% 44% 19%	531
August	1st to 10th	Day	3 2 7% 29% 43% 16%	487
	11th to 20th	Day	4 2 12% 34% 38% 11%	477
	21st to end	Day	4 1 11% 36% 38% 10%	539
September	1st to 10th	Day	5% 2 12% 37% 36% 9%	490
	11th to 20th	Day	4 2 20% 39% 29% 5%	490
	21st to end	Day	5% 5% 20% 35% 29% 6%	318
October	1st to 10th	Day	6% 7% 23% 34% 26% 4	300
	11th to 20th	Day	6% 8% 29% 29% 24% 3	300
	21st to end	Day	8% 9% 27% 35% 18% 3	330
November	1st to 10th	Day	5% 12% 32% 38% 13%	276
	11th to 20th	Day	3 6% 33% 39% 19% 1	270
	21st to end	Day	7% 13% 40% 26% 14% 1	270
December	1st to 10th	Day	5% 8% 42% 33% 12% 1	270
	11th to 20th	Day	4 12% 41% 34% 8%	270
	21st to end	Day	9% 14% 44% 28% 5%	297
January	1st to 10th	Night	3 4 35% 44% 12%	830
	11th to 20th	Night	6% 2 42% 39% 10% 1	760
	21st to end	Night	7% 4 35% 42% 12% 1	836
February	1st to 10th	Night	6% 5% 38% 43% 8%	760
	11th to 20th	Night	8% 5% 43% 38% 6%	744
	21st to end	Night	7% 4 50% 36% 2	628
March	1st to 10th	Night	7% 5% 39% 42% 7%	760
	11th to 20th	Night	6% 8% 33% 42% 11%	760
	21st to end	Night	4 8% 38% 43% 7%	754
April	1st to 10th	Night	5% 8% 45% 36% 6%	570
	11th to 20th	Night	7% 11% 39% 36% 8%	563
	21st to end	Night	5% 7% 42% 38% 8%	570
May	1st to 10th	Night	4 7% 35% 42% 11%	570
	11th to 20th	Night	6% 6% 27% 44% 16% 1	561
	21st to end	Night	4 7% 33% 45% 12%	617
June	1st to 10th	Night	2 3 21% 51% 22% 1	570
	11th to 20th	Night	2 2 25% 53% 17%	570
	21st to end	Night	5% 2 15% 50% 28% 1	570
July	1st to 10th	Night	4 1 11% 44% 38% 2	555
	11th to 20th	Night	3 1 6% 38% 47% 5%	552
	21st to end	Night	5% 1 5% 32% 50% 7%	624
August	1st to 10th	Night	4 1 7% 30% 52% 7%	567
	11th to 20th	Night	4 4 7% 45% 38% 3	564
	21st to end	Night	2 2 8% 41% 44% 3	627
September	1st to 10th	Night	5% 1 9% 47% 36% 3	570
	11th to 20th	Night	6% 1 10% 52% 30% 2	570
	21st to end	Night	5% 2 19% 49% 24% 2	603
October	1st to 10th	Night	6% 3 23% 47% 21% 1	760
	11th to 20th	Night	4 3 23% 51% 18% 1	760
	21st to end	Night	5% 3 28% 42% 19% 3	836
November	1st to 10th	Night	3 3 27% 48% 18% 1	799
	11th to 20th	Night	3 3 28% 49% 15% 1	950
	21st to end	Night	8% 4 33% 37% 17% 1	950
December	1st to 10th	Night	6% 4 37% 42% 10% 1	950
	11th to 20th	Night	8% 5% 37% 41% 9%	950
	21st to end	Night	8% 6% 42% 38% 6%	1045

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