Serenity Hill Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Serenity Hill Observatory clear sky chart from 2005-11-06 to 2024-12-02.

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	13% 7% 2 6% 4 4 4 4 6% 8% 42%	101201
	Night	14% 7% 2 6% 4 4 4 3 5% 7% 44%	98460
Transparency	Day	38% 7% 11% 22% 18% 4	104919
	Night	37% 6% 10% 22% 19% 5%	102869
Seeing	Day	17% 11% 24% 24% 17% 7%	15328
	Night	18% 10% 25% 28% 17% 3	25094

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	14% 15% 4 8% 4 4 4 3 4 5% 35%	2527
	11th to 20th	Day	21% 8% 3 7% 4 3 4 2 4 5% 40%	2662
	21st to end	Day	24% 9% 3 6% 3 3 3 3 4 5% 37%	3351
February	1st to 10th	Day	19% 11% 3 7% 4 3 3 3 4 5% 38%	1900
	11th to 20th	Day	20% 10% 3 7% 4 3 2 3 4 5% 38%	1848
	21st to end	Day	23% 9% 3 6% 4 4 4 2 4 6% 35%	1570
March	1st to 10th	Day	20% 12% 3 8% 4 4 4 3 5% 5% 32%	3120
	11th to 20th	Day	14% 7% 2 6% 4 4 4 3 4 6% 46%	3270
	21st to end	Day	12% 7% 2 7% 5% 5% 4 4 6% 7% 41%	4165
April	1st to 10th	Day	15% 6% 2 6% 4 4 4 3 5% 6% 46%	2280
	11th to 20th	Day	16% 8% 2 6% 4 3 3 3 5% 7% 44%	2254
	21st to end	Day	14% 6% 2 6% 4 4 4 3 6% 8% 41%	2280
May	1st to 10th	Day	17% 7% 3 6% 5% 4 4 4 6% 8% 35%	3982
	11th to 20th	Day	16% 7% 2 7% 5% 4 5% 4 6% 7% 37%	4081
	21st to end	Day	12% 7% 2 7% 5% 5% 5% 4 6% 9% 38%	4476
June	1st to 10th	Day	9% 7% 3 7% 4 4 6% 4 7% 10% 39%	2597
	11th to 20th	Day	5% 3 2 6% 5% 4 5% 5% 8% 9% 47%	2660
	21st to end	Day	6% 4 1 6% 5% 6% 7% 6% 8% 11% 42%	2660
July	1st to 10th	Day	7% 5% 2 7% 5% 6% 6% 5% 8% 12% 38%	4440
	11th to 20th	Day	8% 6% 2 6% 5% 5% 6% 5% 8% 12% 37%	4440
	21st to end	Day	17% 9% 4 8% 5% 5% 5% 5% 6% 8% 28%	4443
August	1st to 10th	Day	4 3 1 4 4 5% 5% 4 7% 10% 54%	3785
	11th to 20th	Day	7% 5% 2 6% 4 5% 5% 4 7% 10% 45%	3729
	21st to end	Day	5% 4 2 5% 3 4 4 4 5% 8% 55%	4180
September	1st to 10th	Day	11% 5% 3 6% 5% 5% 5% 4 6% 8% 43%	2280
	11th to 20th	Day	13% 5% 2 6% 4 4 5% 3 5% 7% 44%	2122
	21st to end	Day	11% 6% 2 5% 3 3 4 3 5% 7% 50%	2090
October	1st to 10th	Day	10% 5% 2 4 2 3 3 4 5% 6% 56%	2090
	11th to 20th	Day	11% 6% 2 4 3 3 3 3 5% 6% 54%	1956
	21st to end	Day	17% 7% 2 5% 3 3 3 2 3 5% 50%	1983
November	1st to 10th	Day	13% 6% 2 5% 2 2 2 3 3 5% 55%	1762
	11th to 20th	Day	16% 7% 2 4 3 3 3 2 5% 5% 50%	1800
	21st to end	Day	17% 9% 2 5% 4 3 4 3 5% 7% 44%	1800
December	1st to 10th	Day	23% 8% 3 6% 4 3 4 3 4 6% 36%	1719
	11th to 20th	Day	17% 9% 3 7% 4 4 3 3 4 5% 41%	2116
	21st to end	Day	15% 12% 5% 7% 5% 4 5% 4 4 6% 33%	2783
January	1st to 10th	Night	20% 13% 3 4 3 3 3 3 4 6% 39%	4428
	11th to 20th	Night	19% 10% 4 9% 4 3 3 2 3 4 38%	4307
	21st to end	Night	25% 10% 3 5% 3 3 3 3 4 4 38%	4305
February	1st to 10th	Night	20% 13% 3 7% 5% 4 4 2 4 5% 35%	2280
	11th to 20th	Night	22% 10% 3 6% 4 3 3 3 4 4 38%	2218
	21st to end	Night	23% 9% 3 6% 4 3 3 3 4 5% 36%	1884
March	1st to 10th	Night	22% 10% 3 6% 4 3 4 3 4 5% 36%	3733
	11th to 20th	Night	14% 8% 2 6% 4 3 3 3 4 6% 47%	3719
	21st to end	Night	16% 7% 2 7% 5% 4 4 4 5% 6% 40%	3466
April	1st to 10th	Night	13% 6% 3 5% 4 4 4 4 5% 6% 47%	1900
	11th to 20th	Night	16% 7% 1 4 3 3 3 3 5% 6% 47%	1875
	21st to end	Night	12% 7% 2 6% 4 4 4 3 5% 8% 44%	1900
May	1st to 10th	Night	16% 8% 3 7% 4 5% 3 3 5% 6% 41%	2912
	11th to 20th	Night	13% 8% 2 7% 5% 4 4 4 5% 8% 41%	2812
	21st to end	Night	8% 6% 2 6% 5% 5% 6% 4 7% 9% 42%	3079
June	1st to 10th	Night	10% 6% 2 7% 4 4 4 4 7% 8% 43%	1577
	11th to 20th	Night	4 3 1 3 4 4 4 4 7% 10% 56%	1520
	21st to end	Night	3 3 2 4 4 4 5% 5% 6% 12% 52%	1520
July	1st to 10th	Night	8% 4 2 6% 5% 5% 6% 5% 9% 11% 39%	2530
	11th to 20th	Night	6% 4 2 4 4 4 4 4 7% 13% 47%	2530
	21st to end	Night	11% 8% 4 8% 5% 5% 5% 5% 6% 10% 33%	3106
August	1st to 10th	Night	3 2 1 3 3 4 4 3 5% 8% 63%	3144
	11th to 20th	Night	4 3 1 4 3 4 5% 5% 7% 11% 53%	3100
	21st to end	Night	5% 3 1 4 3 3 4 3 6% 8% 58%	3476
September	1st to 10th	Night	9% 5% 2 6% 4 4 4 4 7% 7% 49%	1900
	11th to 20th	Night	10% 6% 2 5% 4 4 4 3 5% 7% 49%	2038
	21st to end	Night	9% 5% 2 6% 3 4 4 3 5% 6% 53%	2090
October	1st to 10th	Night	10% 4 1 3 2 3 3 2 4 6% 62%	2090
	11th to 20th	Night	13% 5% 1 6% 3 3 4 2 5% 5% 54%	2220
	21st to end	Night	17% 7% 2 4 3 3 3 3 4 5% 50%	2612
November	1st to 10th	Night	13% 5% 2 4 3 4 3 3 4 5% 53%	2536
	11th to 20th	Night	12% 5% 2 4 3 3 3 3 6% 7% 50%	2600
	21st to end	Night	16% 8% 2 5% 3 3 3 3 4 5% 47%	2600
December	1st to 10th	Night	21% 10% 3 5% 4 3 4 3 4 5% 38%	2495
	11th to 20th	Night	17% 8% 2 5% 3 3 3 3 4 5% 47%	3074
	21st to end	Night	18% 12% 4 7% 5% 5% 5% 4 5% 6% 30%	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	49% 6% 8% 20% 15% 2	2528
	11th to 20th	Day	46% 5% 11% 19% 19% 1	2662
	21st to end	Day	48% 5% 8% 21% 16% 1	3351
February	1st to 10th	Day	49% 4 8% 20% 16% 3	1900
	11th to 20th	Day	50% 4 6% 20% 16% 4	1858
	21st to end	Day	51% 4 8% 15% 15% 7%	1570
March	1st to 10th	Day	53% 6% 7% 12% 14% 8%	3120
	11th to 20th	Day	37% 7% 8% 24% 17% 6%	3270
	21st to end	Day	40% 7% 12% 22% 18% 1	4165
April	1st to 10th	Day	39% 5% 9% 22% 21% 4	2280
	11th to 20th	Day	41% 5% 9% 20% 20% 6%	2254
	21st to end	Day	39% 7% 11% 24% 17% 2	2280
May	1st to 10th	Day	42% 10% 11% 22% 13% 1	4018
	11th to 20th	Day	42% 10% 13% 21% 13% 1	4085
	21st to end	Day	39% 10% 12% 21% 17% 1	4489
June	1st to 10th	Day	38% 9% 14% 20% 17% 2	2597
	11th to 20th	Day	29% 9% 18% 25% 18% 3	2660
	21st to end	Day	32% 11% 16% 22% 15% 4	2660
July	1st to 10th	Day	35% 10% 18% 27% 7% 2	4371
	11th to 20th	Day	36% 9% 16% 30% 8% 2	4365
	21st to end	Day	53% 9% 11% 20% 7%	4301
August	1st to 10th	Day	23% 8% 15% 31% 21% 2	3773
	11th to 20th	Day	33% 8% 15% 25% 17% 3	3765
	21st to end	Day	27% 6% 12% 29% 24% 2	4179
September	1st to 10th	Day	36% 9% 12% 22% 16% 5%	2280
	11th to 20th	Day	38% 7% 11% 20% 21% 3	2122
	21st to end	Day	33% 6% 10% 24% 21% 6%	2090
October	1st to 10th	Day	18% 4 6% 15% 43% 13%	3480
	11th to 20th	Day	21% 3 7% 24% 29% 16%	3222
	21st to end	Day	29% 3 5% 24% 32% 7%	3247
November	1st to 10th	Day	33% 4 7% 22% 28% 6%	1762
	11th to 20th	Day	36% 4 7% 21% 25% 8%	1800
	21st to end	Day	41% 3 8% 22% 22% 4	1800
December	1st to 10th	Day	50% 5% 7% 20% 16% 3	1719
	11th to 20th	Day	45% 5% 9% 21% 17% 3	2113
	21st to end	Day	49% 7% 11% 21% 11% 2	2783
January	1st to 10th	Night	46% 5% 8% 23% 17% 2	4428
	11th to 20th	Night	50% 5% 7% 18% 16% 4	4307
	21st to end	Night	48% 6% 8% 23% 14% 2	4305
February	1st to 10th	Night	53% 4 9% 15% 17% 2	2280
	11th to 20th	Night	51% 4 7% 17% 16% 5%	2219
	21st to end	Night	51% 4 8% 16% 16% 5%	1884
March	1st to 10th	Night	49% 6% 9% 12% 16% 8%	3733
	11th to 20th	Night	37% 7% 9% 21% 16% 10%	3719
	21st to end	Night	43% 7% 9% 19% 21% 1	3466
April	1st to 10th	Night	36% 6% 12% 22% 20% 4	1900
	11th to 20th	Night	37% 4 8% 19% 23% 8%	1875
	21st to end	Night	38% 6% 12% 23% 18% 2	1900
May	1st to 10th	Night	42% 9% 10% 22% 14% 2	2941
	11th to 20th	Night	38% 10% 15% 20% 15% 1	2813
	21st to end	Night	31% 12% 15% 25% 15% 2	3087
June	1st to 10th	Night	36% 8% 13% 22% 19% 2	1577
	11th to 20th	Night	21% 8% 15% 34% 18% 4	1520
	21st to end	Night	24% 9% 20% 25% 18% 4	1520
July	1st to 10th	Night	35% 9% 19% 27% 9% 2	2490
	11th to 20th	Night	26% 8% 17% 38% 7% 3	2482
	21st to end	Night	46% 9% 14% 22% 9%	3008
August	1st to 10th	Night	19% 7% 11% 37% 25% 1	3132
	11th to 20th	Night	23% 8% 21% 29% 17% 2	3130
	21st to end	Night	23% 6% 13% 28% 27% 3	3476
September	1st to 10th	Night	30% 9% 13% 25% 18% 6%	1900
	11th to 20th	Night	33% 6% 12% 20% 26% 3	2038
	21st to end	Night	30% 6% 9% 24% 24% 7%	2090
October	1st to 10th	Night	18% 4 6% 17% 41% 14%	3480
	11th to 20th	Night	20% 3 5% 18% 34% 20%	3680
	21st to end	Night	26% 4 6% 26% 26% 12%	4298
November	1st to 10th	Night	33% 5% 8% 21% 26% 8%	2536
	11th to 20th	Night	32% 5% 8% 20% 26% 8%	2600
	21st to end	Night	39% 4 7% 23% 22% 5%	2600
December	1st to 10th	Night	48% 5% 8% 18% 17% 3	2495
	11th to 20th	Night	40% 4 7% 23% 22% 4	3076
	21st to end	Night	50% 8% 11% 18% 10% 3	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% 26% 34% 11% 4	270
	11th to 20th	Day	34% 23% 34% 6% 2 1	270
	21st to end	Day	26% 29% 33% 10% 2	297
February	1st to 10th	Day	29% 23% 32% 12% 3 1	270
	11th to 20th	Day	37% 23% 30% 7% 2	270
	21st to end	Day	43% 24% 25% 7% 2	225
March	1st to 10th	Day	30% 21% 33% 12% 4	270
	11th to 20th	Day	29% 22% 32% 14% 2 1	303
	21st to end	Day	27% 17% 33% 17% 5%	506
April	1st to 10th	Day	25% 17% 30% 20% 7% 1	460
	11th to 20th	Day	25% 16% 31% 20% 7% 1	452
	21st to end	Day	22% 14% 32% 22% 8% 2	460
May	1st to 10th	Day	21% 15% 28% 22% 10% 4	463
	11th to 20th	Day	15% 9% 30% 26% 13% 6%	487
	21st to end	Day	10% 8% 26% 27% 19% 10%	529
June	1st to 10th	Day	13% 6% 20% 28% 22% 11%	617
	11th to 20th	Day	5% 3 19% 35% 26% 12%	680
	21st to end	Day	7% 4 22% 34% 23% 10%	680
July	1st to 10th	Day	7% 3 15% 32% 29% 13%	671
	11th to 20th	Day	8% 4 12% 31% 34% 12%	668
	21st to end	Day	9% 2 14% 30% 30% 15%	590
August	1st to 10th	Day	10% 2 14% 33% 30% 12%	486
	11th to 20th	Day	10% 3 16% 33% 32% 8%	479
	21st to end	Day	11% 3 12% 21% 36% 17%	539
September	1st to 10th	Day	12% 4 11% 34% 29% 9%	490
	11th to 20th	Day	12% 3 13% 29% 30% 13%	490
	21st to end	Day	16% 6% 19% 27% 23% 9%	490
October	1st to 10th	Day	12% 5% 22% 30% 24% 7%	490
	11th to 20th	Day	11% 13% 34% 26% 13% 3	356
	21st to end	Day	27% 11% 32% 22% 7% 1	330
November	1st to 10th	Day	22% 12% 31% 26% 9% 1	300
	11th to 20th	Day	18% 20% 34% 23% 4	300
	21st to end	Day	26% 17% 27% 17% 11% 2	300
December	1st to 10th	Day	31% 21% 28% 15% 4 1	273
	11th to 20th	Day	26% 20% 28% 19% 6%	270
	21st to end	Day	27% 24% 35% 12% 2	297
January	1st to 10th	Night	26% 18% 31% 22% 3	950
	11th to 20th	Night	29% 19% 30% 18% 3	950
	21st to end	Night	23% 16% 39% 20% 1	909
February	1st to 10th	Night	29% 14% 34% 20% 3	760
	11th to 20th	Night	28% 19% 31% 20% 2	743
	21st to end	Night	31% 19% 32% 16% 2	628
March	1st to 10th	Night	23% 15% 33% 26% 3	760
	11th to 20th	Night	23% 15% 36% 21% 4 1	751
	21st to end	Night	20% 15% 33% 24% 8%	627
April	1st to 10th	Night	18% 13% 36% 24% 8% 1	570
	11th to 20th	Night	21% 11% 32% 27% 9% 1	563
	21st to end	Night	15% 10% 36% 27% 10% 1	570
May	1st to 10th	Night	17% 7% 33% 28% 14% 2	570
	11th to 20th	Night	12% 6% 28% 32% 20% 2	561
	21st to end	Night	8% 2 22% 35% 26% 6%	617
June	1st to 10th	Night	11% 3 16% 35% 30% 5%	570
	11th to 20th	Night	5% 2 12% 38% 38% 5%	570
	21st to end	Night	5% 1 13% 38% 36% 6%	570
July	1st to 10th	Night	10% 2 10% 29% 37% 11%	555
	11th to 20th	Night	8% 2 10% 27% 43% 10%	552
	21st to end	Night	7% 2 8% 33% 41% 8%	624
August	1st to 10th	Night	7% 1 7% 29% 47% 10%	567
	11th to 20th	Night	7% 1 10% 41% 37% 4	564
	21st to end	Night	9% 2 8% 33% 39% 9%	627
September	1st to 10th	Night	9% 2 10% 36% 36% 5%	570
	11th to 20th	Night	13% 2 13% 30% 35% 6%	708
	21st to end	Night	12% 3 15% 35% 30% 4	760
October	1st to 10th	Night	11% 4 17% 33% 28% 6%	760
	11th to 20th	Night	16% 8% 24% 32% 18% 1	760
	21st to end	Night	20% 9% 26% 30% 15% 1	836
November	1st to 10th	Night	16% 9% 24% 34% 16% 2	780
	11th to 20th	Night	15% 12% 32% 30% 10% 1	800
	21st to end	Night	22% 11% 31% 25% 11% 1	800
December	1st to 10th	Night	26% 13% 30% 25% 6%	768
	11th to 20th	Night	24% 12% 30% 27% 7%	779
	21st to end	Night	27% 17% 29% 23% 4	1045

Page generated at 2024-11-29 09:43:04. Version ac07

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