Rosebud
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rosebud clear sky chart from 2005-11-06 to 2026-08-15.

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	12% 8% 3 7% 4 4 4 4 5% 7% 42%	143754
	Night	13% 8% 3 7% 4 4 4 3 5% 6% 44%	138436
Transparency	Day	39% 6% 12% 24% 17% 3	147350
	Night	40% 5% 11% 24% 17% 3	142919
Seeing	Day	17% 13% 29% 25% 13% 3	18079
	Night	18% 13% 30% 27% 11% 1	27813

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	11% 12% 5% 12% 4 4 4 3 4 5% 36%	4747
	11th to 20th	Day	7% 10% 3 8% 5% 5% 4 3 5% 6% 44%	5310
	21st to end	Day	15% 11% 4 8% 4 4 4 3 4 5% 38%	5812
February	1st to 10th	Day	14% 13% 4 8% 5% 4 4 3 5% 5% 34%	1890
	11th to 20th	Day	15% 10% 3 7% 5% 4 5% 3 4 5% 39%	1969
	21st to end	Day	13% 10% 3 8% 4 4 4 4 4 6% 40%	1730
March	1st to 10th	Day	15% 11% 3 5% 3 3 3 2 3 4 48%	4847
	11th to 20th	Day	9% 6% 2 5% 4 3 4 3 4 7% 52%	5090
	21st to end	Day	13% 9% 3 7% 5% 5% 5% 4 5% 8% 35%	5765
April	1st to 10th	Day	13% 7% 3 6% 5% 4 4 4 5% 7% 42%	2520
	11th to 20th	Day	17% 8% 2 6% 4 4 4 3 5% 5% 41%	2494
	21st to end	Day	18% 8% 3 7% 5% 4 4 3 6% 7% 35%	2520
May	1st to 10th	Day	15% 8% 3 7% 5% 5% 5% 4 6% 8% 34%	7140
	11th to 20th	Day	15% 8% 2 8% 4 4 4 4 6% 7% 38%	8122
	21st to end	Day	17% 8% 3 8% 5% 5% 5% 4 5% 6% 34%	9047
June	1st to 10th	Day	10% 5% 2 5% 4 5% 4 5% 8% 8% 44%	2940
	11th to 20th	Day	9% 4 1 5% 4 4 4 4 6% 10% 48%	2940
	21st to end	Day	6% 4 2 5% 5% 4 5% 4 7% 10% 48%	2940
July	1st to 10th	Day	9% 5% 2 6% 4 5% 5% 4 7% 10% 45%	8280
	11th to 20th	Day	6% 5% 2 6% 4 5% 5% 5% 7% 10% 45%	8145
	21st to end	Day	8% 5% 2 6% 5% 5% 5% 5% 7% 12% 42%	8337
August	1st to 10th	Day	6% 3 1 4 4 4 4 5% 8% 9% 51%	4364
	11th to 20th	Day	12% 5% 2 5% 4 4 5% 4 6% 7% 44%	3968
	21st to end	Day	7% 4 2 5% 4 4 5% 3 6% 8% 52%	4312
September	1st to 10th	Day	12% 5% 1 4 4 4 4 4 5% 8% 50%	2400
	11th to 20th	Day	10% 5% 2 5% 4 3 4 4 6% 8% 50%	2400
	21st to end	Day	9% 5% 2 5% 4 4 4 3 5% 7% 52%	2131
October	1st to 10th	Day	10% 4 2 6% 4 3 3 3 4 6% 56%	2000
	11th to 20th	Day	14% 6% 2 4 3 3 3 2 4 5% 53%	2000
	21st to end	Day	17% 9% 2 5% 3 3 3 2 4 6% 46%	2200
November	1st to 10th	Day	12% 6% 2 4 3 3 3 3 4 6% 53%	1908
	11th to 20th	Day	13% 7% 2 6% 4 3 3 4 5% 6% 47%	1890
	21st to end	Day	16% 11% 3 6% 3 3 3 3 4 5% 43%	1748
December	1st to 10th	Day	10% 10% 3 7% 4 3 3 3 4 5% 50%	2690
	11th to 20th	Day	12% 10% 4 7% 4 4 4 3 4 6% 42%	3088
	21st to end	Day	19% 19% 5% 10% 4 4 4 2 4 5% 24%	4070
January	1st to 10th	Night	13% 10% 6% 12% 5% 4 4 3 3 4 37%	8172
	11th to 20th	Night	9% 8% 4 12% 6% 5% 5% 3 3 4 41%	7680
	21st to end	Night	16% 12% 4 7% 5% 4 4 3 3 5% 38%	8402
February	1st to 10th	Night	15% 11% 4 8% 4 4 4 3 5% 5% 36%	2730
	11th to 20th	Night	15% 9% 4 8% 5% 3 3 3 5% 5% 40%	2536
	21st to end	Night	14% 10% 3 7% 4 4 3 2 5% 5% 41%	2076
March	1st to 10th	Night	18% 12% 3 5% 4 3 3 2 3 5% 42%	5269
	11th to 20th	Night	12% 9% 2 5% 3 3 3 3 4 6% 49%	5090
	21st to end	Night	16% 10% 4 7% 5% 5% 5% 4 5% 6% 34%	5404
April	1st to 10th	Night	12% 6% 3 6% 4 4 3 3 5% 6% 47%	2100
	11th to 20th	Night	14% 8% 3 5% 3 3 3 3 5% 7% 45%	2075
	21st to end	Night	18% 8% 3 6% 4 4 3 3 5% 6% 40%	2100
May	1st to 10th	Night	16% 8% 3 7% 4 4 4 4 6% 8% 36%	5702
	11th to 20th	Night	12% 6% 3 6% 4 4 4 3 6% 8% 44%	4752
	21st to end	Night	16% 9% 3 8% 5% 5% 5% 4 6% 7% 32%	5139
June	1st to 10th	Night	9% 5% 2 6% 5% 3 4 4 5% 8% 49%	1680
	11th to 20th	Night	7% 4 1 5% 4 4 4 4 5% 12% 51%	1680
	21st to end	Night	4 3 1 5% 4 3 3 4 6% 10% 57%	1680
July	1st to 10th	Night	9% 5% 2 6% 5% 4 4 4 6% 9% 47%	4708
	11th to 20th	Night	5% 4 2 5% 4 4 5% 4 7% 10% 50%	4824
	21st to end	Night	5% 4 2 5% 4 4 6% 4 7% 10% 47%	5770
August	1st to 10th	Night	5% 3 1 4 3 3 4 3 6% 8% 60%	3016
	11th to 20th	Night	11% 5% 2 5% 4 3 4 3 6% 8% 50%	3169
	21st to end	Night	6% 3 1 4 3 3 4 3 6% 8% 59%	3586
September	1st to 10th	Night	12% 6% 2 5% 3 3 3 2 5% 6% 54%	2000
	11th to 20th	Night	9% 5% 2 6% 4 4 4 3 4 8% 52%	2000
	21st to end	Night	9% 5% 2 5% 4 4 3 3 5% 5% 56%	2242
October	1st to 10th	Night	8% 4 1 4 3 2 3 2 4 7% 61%	2400
	11th to 20th	Night	13% 5% 1 5% 2 3 3 2 5% 6% 53%	2400
	21st to end	Night	19% 7% 1 4 3 3 3 2 4 5% 49%	2640
November	1st to 10th	Night	10% 7% 2 5% 3 3 3 2 5% 5% 55%	2608
	11th to 20th	Night	13% 7% 2 5% 4 3 4 2 4 6% 50%	2730
	21st to end	Night	17% 10% 3 6% 4 3 3 2 4 5% 44%	2867
December	1st to 10th	Night	11% 9% 3 8% 4 3 3 3 5% 5% 47%	4720
	11th to 20th	Night	15% 9% 4 6% 4 4 4 3 4 6% 42%	5339
	21st to end	Night	22% 17% 5% 9% 5% 4 4 3 3 4 24%	7150

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	51% 4 11% 22% 10% 2	4748
	11th to 20th	Day	40% 4 9% 26% 17% 4	5310
	21st to end	Day	48% 3 10% 17% 16% 5%	5812
February	1st to 10th	Day	52% 4 11% 22% 11% 1	1890
	11th to 20th	Day	48% 4 10% 19% 14% 4	1978
	21st to end	Day	44% 5% 7% 24% 15% 5%	1730
March	1st to 10th	Day	42% 3 6% 21% 21% 7%	4847
	11th to 20th	Day	33% 4 8% 24% 24% 7%	5090
	21st to end	Day	45% 8% 13% 26% 8%	5767
April	1st to 10th	Day	40% 6% 12% 23% 18% 1	2520
	11th to 20th	Day	44% 4 11% 22% 16% 3	2494
	21st to end	Day	48% 6% 12% 21% 12% 1	2520
May	1st to 10th	Day	45% 7% 12% 22% 13%	7175
	11th to 20th	Day	43% 7% 9% 22% 17% 2	8126
	21st to end	Day	49% 7% 9% 19% 15% 1	9061
June	1st to 10th	Day	34% 9% 14% 26% 15% 2	2940
	11th to 20th	Day	30% 7% 13% 28% 19% 3	2940
	21st to end	Day	29% 8% 17% 26% 15% 5%	2940
July	1st to 10th	Day	34% 6% 14% 27% 17% 2	8211
	11th to 20th	Day	32% 9% 16% 26% 16% 2	8070
	21st to end	Day	34% 7% 20% 31% 8% 1	8155
August	1st to 10th	Day	26% 8% 17% 34% 15%	4350
	11th to 20th	Day	37% 7% 14% 24% 17% 2	4005
	21st to end	Day	28% 7% 16% 32% 14% 3	4311
September	1st to 10th	Day	32% 7% 11% 26% 20% 4	2400
	11th to 20th	Day	33% 5% 9% 27% 24% 2	2400
	21st to end	Day	32% 6% 9% 26% 24% 3	2131
October	1st to 10th	Day	18% 3 6% 19% 45% 9%	3260
	11th to 20th	Day	23% 3 6% 22% 37% 10%	3240
	21st to end	Day	33% 3 7% 28% 26% 3	3538
November	1st to 10th	Day	33% 4 12% 25% 22% 5%	1908
	11th to 20th	Day	38% 4 9% 23% 21% 5%	1890
	21st to end	Day	45% 5% 8% 26% 16% 1	1748
December	1st to 10th	Day	37% 4 10% 33% 15% 1	2690
	11th to 20th	Day	44% 4 12% 22% 17% 1	3085
	21st to end	Day	63% 5% 11% 12% 7% 1	4070
January	1st to 10th	Night	52% 4 11% 23% 9% 1	8173
	11th to 20th	Night	47% 4 6% 25% 16% 3	7680
	21st to end	Night	51% 3 11% 19% 14% 2	8402
February	1st to 10th	Night	49% 5% 11% 20% 13% 2	2730
	11th to 20th	Night	46% 4 10% 22% 15% 3	2537
	21st to end	Night	44% 3 10% 23% 16% 4	2076
March	1st to 10th	Night	45% 4 6% 21% 20% 3	5269
	11th to 20th	Night	36% 4 9% 23% 21% 7%	5090
	21st to end	Night	48% 7% 10% 23% 10% 1	5404
April	1st to 10th	Night	36% 5% 13% 25% 18% 3	2100
	11th to 20th	Night	39% 6% 11% 23% 16% 5%	2075
	21st to end	Night	44% 5% 10% 23% 16% 1	2100
May	1st to 10th	Night	45% 7% 14% 21% 12% 1	5732
	11th to 20th	Night	37% 7% 12% 25% 17% 3	4753
	21st to end	Night	49% 8% 12% 18% 12% 1	5149
June	1st to 10th	Night	32% 8% 14% 26% 17% 3	1680
	11th to 20th	Night	26% 8% 14% 27% 23% 3	1680
	21st to end	Night	21% 8% 16% 30% 18% 7%	1680
July	1st to 10th	Night	33% 6% 14% 26% 19% 2	4670
	11th to 20th	Night	28% 8% 16% 29% 18% 2	4779
	21st to end	Night	30% 7% 21% 31% 10% 1	5641
August	1st to 10th	Night	21% 7% 19% 31% 20% 1	3006
	11th to 20th	Night	33% 6% 16% 26% 16% 3	3198
	21st to end	Night	22% 6% 17% 34% 17% 3	3586
September	1st to 10th	Night	32% 5% 10% 25% 23% 5%	2000
	11th to 20th	Night	31% 6% 10% 25% 26% 3	2000
	21st to end	Night	30% 6% 9% 24% 28% 4	2242
October	1st to 10th	Night	15% 3 7% 18% 48% 9%	3920
	11th to 20th	Night	22% 3 7% 22% 33% 12%	3899
	21st to end	Night	32% 4 8% 26% 27% 3	4252
November	1st to 10th	Night	32% 5% 11% 26% 21% 6%	2608
	11th to 20th	Night	36% 4 9% 24% 23% 4	2730
	21st to end	Night	44% 3 10% 25% 16% 2	2867
December	1st to 10th	Night	39% 4 9% 32% 14% 1	4720
	11th to 20th	Night	44% 4 12% 22% 18% 1	5341
	21st to end	Night	63% 5% 11% 14% 5% 1	7150

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	27% 25% 32% 13% 3	330
	11th to 20th	Day	30% 26% 36% 8%	330
	21st to end	Day	18% 30% 39% 10% 2	363
February	1st to 10th	Day	26% 25% 36% 13% 1	330
	11th to 20th	Day	30% 27% 31% 9% 2 1	330
	21st to end	Day	30% 23% 37% 9% 1	273
March	1st to 10th	Day	25% 28% 39% 8% 1	330
	11th to 20th	Day	34% 21% 33% 10% 1 1	330
	21st to end	Day	33% 23% 30% 12% 1	442
April	1st to 10th	Day	24% 18% 38% 15% 4 1	540
	11th to 20th	Day	29% 19% 31% 16% 5%	532
	21st to end	Day	24% 19% 35% 17% 5% 1	540
May	1st to 10th	Day	21% 17% 36% 20% 5% 1	585
	11th to 20th	Day	18% 17% 29% 25% 10% 2	775
	21st to end	Day	15% 10% 34% 25% 12% 4	844
June	1st to 10th	Day	10% 7% 27% 32% 18% 5%	780
	11th to 20th	Day	10% 6% 28% 36% 18% 2	780
	21st to end	Day	6% 8% 32% 37% 14% 3	780
July	1st to 10th	Day	11% 3 17% 32% 28% 8%	771
	11th to 20th	Day	7% 4 24% 36% 23% 5%	768
	21st to end	Day	9% 4 19% 36% 27% 6%	849
August	1st to 10th	Day	9% 3 20% 40% 23% 5%	776
	11th to 20th	Day	11% 4 20% 34% 25% 6%	582
	21st to end	Day	10% 3 19% 32% 30% 7%	583
September	1st to 10th	Day	11% 4 20% 34% 24% 6%	530
	11th to 20th	Day	9% 3 19% 32% 25% 12%	530
	21st to end	Day	12% 9% 22% 33% 17% 7%	440
October	1st to 10th	Day	12% 11% 31% 30% 13% 3	330
	11th to 20th	Day	20% 19% 30% 23% 7% 1	330
	21st to end	Day	31% 24% 27% 16% 2	363
November	1st to 10th	Day	18% 16% 41% 17% 7% 2	330
	11th to 20th	Day	23% 22% 31% 17% 6% 1	330
	21st to end	Day	28% 20% 29% 19% 4 1	330
December	1st to 10th	Day	20% 26% 32% 15% 5% 2	330
	11th to 20th	Day	24% 22% 37% 14% 4	330
	21st to end	Day	27% 25% 36% 10% 3	363
January	1st to 10th	Night	21% 21% 35% 19% 4	1050
	11th to 20th	Night	23% 25% 32% 17% 2	1050
	21st to end	Night	20% 21% 39% 19% 1	1155
February	1st to 10th	Night	23% 18% 39% 18% 2	1050
	11th to 20th	Night	23% 20% 37% 18% 2	901
	21st to end	Night	24% 21% 37% 17% 1	692
March	1st to 10th	Night	24% 18% 37% 19% 2	746
	11th to 20th	Night	24% 15% 36% 20% 4	630
	21st to end	Night	25% 19% 35% 18% 3	693
April	1st to 10th	Night	16% 20% 38% 22% 3	630
	11th to 20th	Night	21% 15% 36% 24% 4	623
	21st to end	Night	22% 15% 36% 22% 5%	630
May	1st to 10th	Night	18% 12% 34% 28% 8%	630
	11th to 20th	Night	18% 10% 28% 31% 12% 1	621
	21st to end	Night	13% 7% 29% 33% 17% 2	683
June	1st to 10th	Night	10% 4 23% 40% 22% 2	630
	11th to 20th	Night	8% 3 27% 42% 19% 1	630
	21st to end	Night	6% 3 25% 46% 17% 2	630
July	1st to 10th	Night	10% 2 11% 40% 31% 5%	615
	11th to 20th	Night	3 3 19% 41% 30% 3	612
	21st to end	Night	7% 1 17% 45% 27% 2	690
August	1st to 10th	Night	7% 2 16% 44% 30% 1	627
	11th to 20th	Night	7% 2 17% 41% 30% 3	606
	21st to end	Night	7% 2 15% 41% 32% 3	660
September	1st to 10th	Night	14% 3 16% 37% 26% 4	600
	11th to 20th	Night	11% 4 14% 37% 29% 5%	600
	21st to end	Night	10% 6% 24% 33% 23% 4	757
October	1st to 10th	Night	10% 5% 28% 32% 22% 3	800
	11th to 20th	Night	16% 13% 33% 27% 11% 1	800
	21st to end	Night	24% 14% 34% 22% 6%	880
November	1st to 10th	Night	14% 13% 38% 26% 9%	820
	11th to 20th	Night	18% 17% 34% 24% 7%	840
	21st to end	Night	24% 17% 34% 20% 5%	977
December	1st to 10th	Night	22% 18% 35% 20% 4 1	1050
	11th to 20th	Night	25% 15% 34% 23% 3	1050
	21st to end	Night	27% 19% 34% 18% 2	1155

Page generated at 2026-08-12 02:37:17. Version ac07

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