Regina Caelorum Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Regina Caelorum Observatory clear sky chart from 2005-11-06 to 2024-11-04.

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% 6% 2 6% 4 4 4 4 5% 8% 45%	101088
	Night	12% 6% 2 5% 3 3 3 3 5% 7% 50%	98026
Transparency	Day	36% 5% 11% 22% 19% 7%	104818
	Night	33% 5% 11% 21% 20% 10%	102423
Seeing	Day	13% 6% 19% 27% 25% 11%	14946
	Night	14% 6% 25% 35% 18% 2	24797

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 4 3 3 4 3 5% 7% 46%	2847
	11th to 20th	Day	17% 6% 2 5% 3 3 3 2 4 6% 51%	2850
	21st to end	Day	22% 10% 3 6% 3 2 2 2 3 6% 41%	3135
February	1st to 10th	Day	22% 8% 3 6% 3 3 3 2 4 6% 40%	1850
	11th to 20th	Day	20% 8% 2 6% 4 3 4 3 4 5% 41%	1849
	21st to end	Day	20% 8% 2 5% 3 3 4 3 4 5% 45%	1655
March	1st to 10th	Day	15% 9% 3 7% 6% 5% 4 3 5% 6% 36%	3436
	11th to 20th	Day	19% 8% 2 8% 5% 4 5% 5% 6% 7% 32%	3480
	21st to end	Day	15% 9% 3 7% 4 4 3 3 5% 7% 39%	3814
April	1st to 10th	Day	14% 8% 3 7% 5% 4 4 3 5% 7% 39%	2090
	11th to 20th	Day	14% 8% 3 7% 5% 5% 4 4 5% 7% 39%	2163
	21st to end	Day	13% 7% 2 6% 4 5% 5% 3 4 6% 45%	2289
May	1st to 10th	Day	19% 9% 3 9% 5% 5% 5% 4 6% 7% 30%	4082
	11th to 20th	Day	13% 6% 2 6% 4 4 4 4 6% 7% 42%	4082
	21st to end	Day	9% 7% 3 7% 6% 6% 6% 6% 7% 11% 33%	4477
June	1st to 10th	Day	5% 4 2 6% 5% 5% 6% 5% 7% 10% 45%	2470
	11th to 20th	Day	6% 4 1 5% 5% 4 5% 5% 7% 10% 48%	2470
	21st to end	Day	5% 5% 2 6% 6% 5% 6% 6% 8% 10% 41%	2470
July	1st to 10th	Day	8% 4 1 5% 4 5% 5% 4 7% 10% 47%	4120
	11th to 20th	Day	5% 5% 2 5% 4 5% 5% 5% 7% 10% 47%	4120
	21st to end	Day	13% 6% 3 7% 6% 5% 6% 4 6% 9% 35%	4465
August	1st to 10th	Day	2 2 2 2 2 3 3 4 8% 71%	4104
	11th to 20th	Day	3 2 1 3 3 3 4 3 6% 12% 59%	4041
	21st to end	Day	5% 3 1 5% 4 5% 6% 5% 8% 11% 47%	3937
September	1st to 10th	Day	7% 5% 2 6% 5% 5% 5% 5% 5% 10% 45%	2090
	11th to 20th	Day	10% 6% 2 6% 4 5% 5% 5% 7% 7% 43%	2090
	21st to end	Day	6% 3 1 5% 4 5% 5% 4 6% 8% 52%	2090
October	1st to 10th	Day	6% 3 2 4 4 4 4 3 4 6% 60%	2028
	11th to 20th	Day	12% 4 2 5% 3 3 3 2 4 5% 57%	1900
	21st to end	Day	13% 4 1 4 3 3 3 3 3 5% 58%	2090
November	1st to 10th	Day	11% 8% 2 5% 4 3 4 4 5% 7% 49%	1888
	11th to 20th	Day	11% 6% 2 5% 4 4 3 3 4 6% 52%	1900
	21st to end	Day	17% 7% 3 7% 4 3 4 3 4 6% 41%	1710
December	1st to 10th	Day	14% 9% 3 5% 4 3 2 3 6% 6% 46%	1710
	11th to 20th	Day	17% 8% 3 5% 4 4 4 2 5% 5% 43%	2161
	21st to end	Day	15% 8% 3 6% 3 3 3 2 3 6% 47%	3135
January	1st to 10th	Night	17% 7% 2 4 2 2 2 2 3 5% 54%	4108
	11th to 20th	Night	17% 6% 1 3 2 2 2 2 3 4 57%	4120
	21st to end	Night	21% 8% 3 6% 4 3 3 2 4 5% 42%	4532
February	1st to 10th	Night	19% 8% 2 6% 4 3 3 3 3 4 45%	2346
	11th to 20th	Night	20% 8% 3 5% 3 3 3 2 3 5% 46%	2218
	21st to end	Night	20% 7% 2 5% 3 3 3 3 4 6% 45%	1797
March	1st to 10th	Night	19% 8% 3 7% 5% 4 4 3 5% 6% 36%	3419
	11th to 20th	Night	19% 8% 3 7% 5% 4 5% 3 5% 7% 34%	3480
	21st to end	Night	13% 7% 3 7% 4 4 4 3 5% 5% 45%	3817
April	1st to 10th	Night	12% 5% 2 5% 5% 4 4 3 6% 7% 48%	2090
	11th to 20th	Night	12% 6% 3 5% 4 4 3 3 5% 7% 47%	1965
	21st to end	Night	12% 7% 2 6% 3 3 4 3 5% 7% 48%	1886
May	1st to 10th	Night	17% 10% 3 7% 4 4 4 4 5% 8% 35%	2823
	11th to 20th	Night	11% 6% 2 6% 4 4 4 3 6% 7% 46%	2823
	21st to end	Night	8% 6% 2 6% 5% 5% 5% 5% 7% 10% 41%	3090
June	1st to 10th	Night	5% 4 1 3 3 3 4 4 6% 11% 56%	1710
	11th to 20th	Night	3 2 1 3 2 3 4 4 6% 10% 63%	1710
	21st to end	Night	4 4 2 5% 4 4 4 4 7% 9% 53%	1710
July	1st to 10th	Night	4 3 1 4 4 4 5% 4 7% 12% 51%	2850
	11th to 20th	Night	3 3 2 4 3 3 3 4 7% 12% 56%	2850
	21st to end	Night	9% 7% 2 6% 4 4 4 5% 7% 10% 41%	3098
August	1st to 10th	Night	1 1 1 1 1 2 2 2 3 10% 76%	2836
	11th to 20th	Night	3 2 1 4 2 3 3 3 6% 12% 61%	2798
	21st to end	Night	3 3 2 4 3 4 4 4 7% 12% 55%	3713
September	1st to 10th	Night	6% 6% 2 5% 4 4 4 3 6% 8% 51%	2090
	11th to 20th	Night	8% 5% 2 6% 5% 4 4 4 5% 7% 49%	2090
	21st to end	Night	5% 4 2 6% 3 3 4 3 4 8% 59%	2090
October	1st to 10th	Night	4 3 1 4 2 3 3 2 5% 6% 66%	2133
	11th to 20th	Night	10% 5% 1 4 2 3 2 3 4 5% 61%	2280
	21st to end	Night	12% 5% 2 4 2 3 3 2 3 4 61%	2508
November	1st to 10th	Night	11% 5% 1 4 3 3 4 3 4 7% 55%	2263
	11th to 20th	Night	9% 6% 2 5% 4 4 3 3 5% 7% 52%	2280
	21st to end	Night	16% 7% 2 5% 4 4 3 3 4 5% 47%	2465
December	1st to 10th	Night	16% 7% 3 4 4 4 3 3 5% 5% 47%	2470
	11th to 20th	Night	16% 8% 3 6% 4 3 3 3 4 5% 45%	3036
	21st to end	Night	16% 7% 2 5% 3 3 3 2 3 4 52%	4532

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	38% 3 6% 20% 25% 9%	2848
	11th to 20th	Day	37% 3 5% 22% 27% 6%	2850
	21st to end	Day	48% 2 4 15% 20% 11%	3135
February	1st to 10th	Day	47% 3 5% 14% 21% 10%	1850
	11th to 20th	Day	46% 3 7% 15% 19% 10%	1859
	21st to end	Day	43% 3 6% 17% 17% 14%	1655
March	1st to 10th	Day	48% 4 8% 14% 21% 5%	3436
	11th to 20th	Day	50% 6% 9% 13% 16% 6%	3480
	21st to end	Day	43% 6% 8% 17% 21% 5%	3814
April	1st to 10th	Day	45% 4 8% 19% 14% 11%	2090
	11th to 20th	Day	45% 4 9% 16% 17% 9%	2163
	21st to end	Day	39% 5% 8% 20% 22% 6%	2289
May	1st to 10th	Day	51% 7% 11% 16% 10% 4	4120
	11th to 20th	Day	40% 6% 9% 18% 24% 2	4086
	21st to end	Day	40% 9% 12% 26% 11% 1	4489
June	1st to 10th	Day	30% 8% 14% 30% 16% 2	2470
	11th to 20th	Day	28% 6% 14% 29% 17% 5%	2470
	21st to end	Day	34% 8% 15% 26% 15% 2	2470
July	1st to 10th	Day	30% 7% 25% 32% 6%	4056
	11th to 20th	Day	31% 7% 17% 29% 15%	4051
	21st to end	Day	43% 8% 17% 25% 7%	4325
August	1st to 10th	Day	13% 4 14% 40% 28% 1	4090
	11th to 20th	Day	18% 5% 27% 38% 11% 2	4080
	21st to end	Day	28% 12% 19% 26% 14% 1	3936
September	1st to 10th	Day	33% 7% 12% 22% 17% 8%	2090
	11th to 20th	Day	36% 8% 13% 19% 18% 6%	2090
	21st to end	Day	29% 5% 11% 22% 19% 14%	2090
October	1st to 10th	Day	16% 2 7% 12% 22% 41%	3366
	11th to 20th	Day	19% 3 6% 17% 34% 22%	3140
	21st to end	Day	25% 3 4 21% 33% 14%	3428
November	1st to 10th	Day	37% 4 7% 19% 23% 10%	1888
	11th to 20th	Day	34% 4 8% 20% 22% 13%	1900
	21st to end	Day	45% 3 6% 16% 19% 11%	1710
December	1st to 10th	Day	40% 3 10% 20% 19% 9%	1710
	11th to 20th	Day	44% 3 6% 15% 21% 11%	2159
	21st to end	Day	41% 3 5% 14% 27% 10%	3135
January	1st to 10th	Night	36% 3 4 19% 26% 13%	4108
	11th to 20th	Night	34% 2 5% 17% 29% 13%	4120
	21st to end	Night	46% 3 3 15% 22% 11%	4532
February	1st to 10th	Night	45% 3 5% 13% 19% 15%	2346
	11th to 20th	Night	42% 3 6% 15% 20% 14%	2218
	21st to end	Night	43% 3 8% 13% 17% 16%	1797
March	1st to 10th	Night	48% 5% 8% 13% 19% 8%	3419
	11th to 20th	Night	51% 5% 8% 16% 14% 6%	3480
	21st to end	Night	41% 5% 8% 15% 23% 8%	3817
April	1st to 10th	Night	36% 5% 10% 19% 17% 13%	2090
	11th to 20th	Night	37% 4 10% 18% 18% 14%	1965
	21st to end	Night	36% 4 9% 20% 24% 7%	1886
May	1st to 10th	Night	48% 6% 10% 20% 12% 4	2850
	11th to 20th	Night	35% 7% 11% 20% 23% 4	2824
	21st to end	Night	35% 9% 14% 27% 11% 3	3099
June	1st to 10th	Night	22% 6% 18% 31% 21% 2	1710
	11th to 20th	Night	18% 5% 17% 34% 20% 6%	1710
	21st to end	Night	27% 6% 16% 30% 19% 2	1710
July	1st to 10th	Night	25% 8% 26% 35% 6%	2805
	11th to 20th	Night	21% 8% 21% 36% 14% 1	2796
	21st to end	Night	37% 8% 21% 26% 8%	2999
August	1st to 10th	Night	8% 4 16% 39% 31% 3	2826
	11th to 20th	Night	17% 6% 26% 38% 11% 2	2825
	21st to end	Night	22% 11% 22% 29% 14% 2	3713
September	1st to 10th	Night	30% 7% 17% 22% 16% 9%	2090
	11th to 20th	Night	34% 6% 15% 20% 18% 7%	2090
	21st to end	Night	25% 4 12% 24% 21% 14%	2090
October	1st to 10th	Night	13% 2 7% 16% 19% 43%	3562
	11th to 20th	Night	17% 2 4 19% 33% 26%	3779
	21st to end	Night	22% 2 5% 22% 32% 17%	4120
November	1st to 10th	Night	30% 4 9% 21% 23% 13%	2263
	11th to 20th	Night	32% 4 8% 21% 21% 14%	2280
	21st to end	Night	41% 3 8% 16% 20% 13%	2465
December	1st to 10th	Night	40% 3 6% 21% 19% 11%	2470
	11th to 20th	Night	42% 3 6% 13% 22% 14%	3037
	21st to end	Night	38% 3 4 15% 29% 12%	4532

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% 8% 37% 22% 9% 2	270
	11th to 20th	Day	22% 10% 33% 24% 9% 1	270
	21st to end	Day	23% 10% 37% 21% 8%	297
February	1st to 10th	Day	28% 13% 31% 22% 7%	270
	11th to 20th	Day	25% 17% 33% 19% 5%	270
	21st to end	Day	28% 14% 42% 15% 1	225
March	1st to 10th	Day	21% 13% 34% 25% 7%	270
	11th to 20th	Day	19% 15% 37% 21% 7% 2	270
	21st to end	Day	15% 13% 40% 22% 8% 1	297
April	1st to 10th	Day	21% 14% 35% 22% 7%	270
	11th to 20th	Day	23% 10% 33% 21% 11% 2	361
	21st to end	Day	17% 8% 33% 30% 9% 3	469
May	1st to 10th	Day	16% 8% 37% 29% 9% 1	653
	11th to 20th	Day	17% 5% 23% 32% 19% 4	675
	21st to end	Day	12% 5% 23% 35% 20% 5%	734
June	1st to 10th	Day	7% 2 10% 36% 35% 11%	680
	11th to 20th	Day	7% 2 12% 41% 30% 8%	680
	21st to end	Day	7% 3 8% 30% 38% 15%	680
July	1st to 10th	Day	7% 2 5% 26% 39% 20%	671
	11th to 20th	Day	2 2 3 27% 43% 24%	668
	21st to end	Day	5% 2 3 25% 45% 20%	739
August	1st to 10th	Day	4 1 1 22% 49% 23%	676
	11th to 20th	Day	7% 1 2 23% 47% 20%	665
	21st to end	Day	9% 1 3 12% 40% 35%	400
September	1st to 10th	Day	4 1 4 22% 36% 33%	300
	11th to 20th	Day	7% 3 4 20% 37% 29%	300
	21st to end	Day	7% 2 8% 23% 37% 23%	300
October	1st to 10th	Day	3 1 11% 32% 39% 13%	300
	11th to 20th	Day	9% 2 21% 36% 23% 9%	300
	21st to end	Day	21% 8% 22% 23% 19% 8%	330
November	1st to 10th	Day	15% 5% 21% 32% 19% 6%	279
	11th to 20th	Day	20% 6% 26% 29% 17% 4	270
	21st to end	Day	21% 13% 30% 23% 10% 3	270
December	1st to 10th	Day	19% 6% 30% 24% 14% 7%	270
	11th to 20th	Day	27% 9% 31% 25% 7% 1	270
	21st to end	Day	22% 9% 35% 23% 9% 1	297
January	1st to 10th	Night	20% 9% 34% 30% 7%	950
	11th to 20th	Night	22% 11% 29% 29% 9%	950
	21st to end	Night	19% 9% 33% 32% 7%	1045
February	1st to 10th	Night	24% 11% 34% 26% 4	826
	11th to 20th	Night	26% 10% 34% 27% 3	744
	21st to end	Night	27% 11% 42% 18% 2	541
March	1st to 10th	Night	22% 9% 38% 24% 5%	570
	11th to 20th	Night	16% 10% 39% 29% 7%	570
	21st to end	Night	14% 10% 45% 26% 5%	627
April	1st to 10th	Night	14% 8% 45% 28% 5%	570
	11th to 20th	Night	15% 9% 39% 30% 6%	563
	21st to end	Night	13% 9% 41% 28% 9%	570
May	1st to 10th	Night	11% 9% 42% 31% 6% 1	570
	11th to 20th	Night	12% 6% 30% 37% 13% 1	561
	21st to end	Night	8% 3 30% 41% 16% 2	617
June	1st to 10th	Night	8% 1 15% 47% 28% 2	570
	11th to 20th	Night	4 1 21% 51% 20% 3	570
	21st to end	Night	4 1 11% 45% 34% 4	570
July	1st to 10th	Night	4 2 7% 44% 37% 6%	555
	11th to 20th	Night	3 1 6% 49% 39% 3	552
	21st to end	Night	5% 1 5% 48% 38% 4	624
August	1st to 10th	Night	2 1 4 49% 41% 4	567
	11th to 20th	Night	6% 3 49% 38% 4	564
	21st to end	Night	4 1 5% 36% 46% 8%	627
September	1st to 10th	Night	8% 2 7% 35% 42% 7%	570
	11th to 20th	Night	11% 2 5% 33% 43% 6%	570
	21st to end	Night	6% 2 9% 39% 38% 6%	570
October	1st to 10th	Night	6% 1 11% 48% 29% 6%	613
	11th to 20th	Night	11% 5% 20% 42% 20% 2	760
	21st to end	Night	13% 6% 27% 34% 18% 2	836
November	1st to 10th	Night	13% 3 24% 39% 19% 2	755
	11th to 20th	Night	12% 7% 26% 40% 15% 1	760
	21st to end	Night	20% 9% 28% 28% 14% 1	945
December	1st to 10th	Night	20% 6% 29% 33% 11%	950
	11th to 20th	Night	23% 9% 26% 34% 7%	950
	21st to end	Night	20% 8% 31% 33% 8%	1045

Page generated at 2024-11-01 21:47:46. Version ac07

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