Shepherd's Rest
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Shepherd's Rest clear sky chart from 2005-11-06 to 2024-04-25.

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	14% 7% 2 5% 5% 3 4 4 5% 7% 44%	83510
	Night	14% 6% 2 5% 4 2 4 4 5% 6% 48%	85629
Transparency	Day	39% 5% 11% 24% 17% 4	83231
	Night	38% 4 11% 25% 18% 4	85428
Seeing	Day	17% 11% 26% 25% 17% 4	14684
	Night	17% 10% 29% 28% 14% 1	24679

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% 10% 2 5% 4 3 4 3 3 5% 47%	2824
	11th to 20th	Day	13% 8% 3 5% 4 3 3 4 3 6% 47%	2850
	21st to end	Day	25% 7% 3 5% 4 1 3 3 3 4 43%	3135
February	1st to 10th	Day	16% 9% 3 6% 5% 3 4 4 4 5% 39%	1710
	11th to 20th	Day	15% 9% 3 5% 4 3 4 4 4 6% 43%	1758
	21st to end	Day	17% 10% 2 5% 5% 2 5% 4 5% 6% 39%	1570
March	1st to 10th	Day	20% 10% 2 5% 4 2 3 3 4 4 43%	3436
	11th to 20th	Day	13% 6% 2 4 4 2 3 3 4 7% 52%	3480
	21st to end	Day	17% 7% 2 6% 6% 4 4 5% 5% 6% 38%	3845
April	1st to 10th	Day	13% 6% 3 6% 4 3 4 4 4 6% 46%	2280
	11th to 20th	Day	17% 7% 2 6% 5% 3 5% 4 5% 6% 41%	2254
	21st to end	Day	19% 7% 3 5% 6% 4 5% 5% 5% 5% 37%	2209
May	1st to 10th	Day	19% 7% 3 6% 6% 3 4 4 5% 7% 37%	2203
	11th to 20th	Day	15% 5% 2 6% 5% 3 5% 4 5% 7% 41%	2302
	21st to end	Day	12% 6% 4 6% 6% 4 6% 6% 7% 9% 35%	2712
June	1st to 10th	Day	9% 5% 2 5% 6% 3 5% 5% 6% 8% 46%	2520
	11th to 20th	Day	6% 3 2 5% 4 3 6% 6% 7% 10% 48%	2520
	21st to end	Day	5% 3 2 3 5% 4 6% 6% 7% 10% 50%	2520
July	1st to 10th	Day	10% 4 2 5% 6% 4 5% 6% 8% 10% 40%	2455
	11th to 20th	Day	5% 3 2 4 5% 3 6% 6% 7% 11% 46%	2340
	21st to end	Day	8% 5% 2 5% 5% 3 6% 7% 7% 10% 42%	2546
August	1st to 10th	Day	9% 4 2 5% 6% 4 6% 6% 7% 11% 40%	2328
	11th to 20th	Day	9% 5% 3 4 5% 4 6% 6% 7% 10% 41%	2177
	21st to end	Day	8% 5% 2 4 5% 3 4 5% 5% 9% 50%	2376
September	1st to 10th	Day	11% 5% 2 5% 5% 4 5% 4 5% 7% 48%	2160
	11th to 20th	Day	12% 6% 2 5% 4 3 4 5% 5% 7% 47%	2160
	21st to end	Day	9% 4 2 4 3 2 4 4 5% 6% 57%	1889
October	1st to 10th	Day	9% 4 2 5% 5% 3 4 4 4 6% 55%	1800
	11th to 20th	Day	15% 6% 2 4 3 2 2 3 3 5% 54%	1800
	21st to end	Day	20% 7% 2 4 3 2 2 4 5% 6% 46%	1980
November	1st to 10th	Day	13% 5% 2 4 3 2 3 4 3 5% 57%	1853
	11th to 20th	Day	14% 5% 2 4 4 2 4 4 4 5% 51%	1710
	21st to end	Day	20% 8% 2 3 3 2 3 3 3 5% 47%	1587
December	1st to 10th	Day	15% 8% 3 7% 4 3 4 3 4 6% 44%	1520
	11th to 20th	Day	16% 9% 4 7% 5% 3 3 3 3 4 42%	1918
	21st to end	Day	15% 17% 4 6% 4 3 4 4 4 6% 33%	2783
January	1st to 10th	Night	15% 8% 4 5% 5% 3 4 5% 4 7% 41%	4126
	11th to 20th	Night	15% 6% 2 6% 5% 3 4 4 4 5% 46%	4120
	21st to end	Night	23% 11% 3 4 3 1 2 3 4 4 41%	4532
February	1st to 10th	Night	17% 9% 3 6% 4 2 4 4 4 6% 43%	2470
	11th to 20th	Night	16% 7% 3 6% 4 2 3 3 5% 6% 46%	2309
	21st to end	Night	17% 8% 2 5% 3 2 3 4 5% 6% 45%	1884
March	1st to 10th	Night	22% 8% 2 4 4 2 3 3 4 4 43%	3433
	11th to 20th	Night	14% 5% 2 5% 4 2 3 3 4 5% 51%	3480
	21st to end	Night	15% 8% 3 6% 5% 3 4 4 5% 6% 39%	3771
April	1st to 10th	Night	11% 5% 2 5% 3 2 3 4 5% 7% 53%	1900
	11th to 20th	Night	14% 6% 2 5% 4 2 3 4 4 8% 47%	1875
	21st to end	Night	18% 5% 3 6% 5% 2 4 4 5% 7% 40%	1850
May	1st to 10th	Night	15% 5% 2 4 5% 2 3 3 4 6% 49%	1754
	11th to 20th	Night	17% 5% 2 4 4 2 4 3 4 7% 49%	1593
	21st to end	Night	10% 6% 2 6% 6% 3 5% 5% 6% 8% 42%	1560
June	1st to 10th	Night	8% 4 1 4 3 3 4 5% 6% 9% 53%	1440
	11th to 20th	Night	4 3 1 3 3 2 4 4 6% 11% 59%	1440
	21st to end	Night	3 2 1 3 3 3 4 4 5% 10% 62%	1440
July	1st to 10th	Night	5% 3 2 5% 5% 3 6% 5% 7% 10% 48%	1500
	11th to 20th	Night	3 2 1 3 3 2 4 5% 5% 10% 60%	1620
	21st to end	Night	6% 3 2 3 4 3 5% 4 7% 9% 52%	1772
August	1st to 10th	Night	5% 3 1 4 5% 2 5% 6% 7% 9% 51%	1611
	11th to 20th	Night	7% 3 2 4 4 3 4 5% 6% 8% 54%	1721
	21st to end	Night	6% 4 2 4 4 2 4 4 7% 8% 55%	1980
September	1st to 10th	Night	10% 3 2 4 3 2 3 4 5% 8% 55%	1800
	11th to 20th	Night	9% 5% 1 5% 5% 3 4 5% 5% 7% 51%	1800
	21st to end	Night	8% 4 1 4 5% 2 3 4 4 6% 59%	2047
October	1st to 10th	Night	8% 3 1 4 4 2 3 3 5% 7% 60%	2160
	11th to 20th	Night	15% 4 2 3 3 3 4 3 4 5% 55%	2160
	21st to end	Night	18% 7% 2 5% 4 2 2 3 4 4 50%	2376
November	1st to 10th	Night	12% 5% 2 3 4 2 3 3 4 5% 58%	2224
	11th to 20th	Night	14% 5% 2 4 3 2 3 3 4 6% 55%	2470
	21st to end	Night	17% 8% 3 4 3 2 3 3 4 6% 47%	2588
December	1st to 10th	Night	17% 8% 2 4 4 3 4 3 5% 6% 44%	2660
	11th to 20th	Night	18% 9% 3 6% 5% 2 3 3 4 5% 43%	3279
	21st to end	Night	20% 14% 4 7% 5% 3 4 4 4 4 32%	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	43% 3 7% 28% 17% 2	2825
	11th to 20th	Day	40% 3 10% 29% 14% 4	2850
	21st to end	Day	48% 2 9% 17% 19% 5%	3135
February	1st to 10th	Day	48% 3 11% 23% 13% 2	1710
	11th to 20th	Day	44% 3 10% 22% 17% 4	1767
	21st to end	Day	47% 4 8% 21% 14% 7%	1570
March	1st to 10th	Day	45% 4 7% 21% 14% 9%	3436
	11th to 20th	Day	34% 4 9% 29% 19% 6%	3480
	21st to end	Day	46% 5% 13% 22% 12% 1	3845
April	1st to 10th	Day	39% 5% 11% 23% 20% 2	2280
	11th to 20th	Day	44% 5% 12% 19% 16% 4	2254
	21st to end	Day	48% 6% 10% 21% 14% 2	2209
May	1st to 10th	Day	47% 6% 12% 23% 11% 1	2203
	11th to 20th	Day	42% 6% 14% 24% 13% 2	2306
	21st to end	Day	43% 10% 14% 21% 12% 1	2712
June	1st to 10th	Day	36% 6% 15% 26% 16% 1	2520
	11th to 20th	Day	30% 7% 15% 29% 17% 2	2520
	21st to end	Day	27% 8% 16% 28% 17% 5%	2520
July	1st to 10th	Day	35% 9% 18% 23% 13% 3	2389
	11th to 20th	Day	29% 8% 15% 26% 19% 4	2271
	21st to end	Day	34% 9% 15% 31% 10% 1	2405
August	1st to 10th	Day	34% 9% 17% 25% 14% 1	2314
	11th to 20th	Day	36% 7% 15% 27% 13% 1	2177
	21st to end	Day	31% 7% 14% 23% 18% 6%	2376
September	1st to 10th	Day	35% 6% 11% 26% 15% 7%	2160
	11th to 20th	Day	35% 6% 9% 24% 24% 2	2160
	21st to end	Day	28% 5% 8% 28% 28% 3	1889
October	1st to 10th	Day	32% 5% 9% 24% 25% 5%	1800
	11th to 20th	Day	36% 3 6% 24% 24% 7%	1800
	21st to end	Day	40% 4 8% 25% 17% 6%	1980
November	1st to 10th	Day	31% 3 9% 27% 23% 6%	1853
	11th to 20th	Day	36% 3 7% 23% 24% 7%	1710
	21st to end	Day	43% 3 8% 22% 22% 2	1587
December	1st to 10th	Day	42% 4 10% 26% 16% 3	1520
	11th to 20th	Day	48% 3 6% 19% 23% 1	1915
	21st to end	Day	54% 3 10% 18% 12% 3	2783
January	1st to 10th	Night	44% 3 9% 25% 17% 2	4126
	11th to 20th	Night	41% 3 11% 29% 15% 2	4120
	21st to end	Night	49% 3 10% 21% 15% 2	4532
February	1st to 10th	Night	44% 4 9% 24% 17% 2	2470
	11th to 20th	Night	41% 3 10% 23% 20% 3	2310
	21st to end	Night	41% 3 10% 22% 17% 7%	1884
March	1st to 10th	Night	46% 3 8% 20% 15% 8%	3433
	11th to 20th	Night	36% 4 10% 26% 20% 4	3480
	21st to end	Night	45% 5% 11% 27% 12% 1	3771
April	1st to 10th	Night	32% 5% 11% 25% 23% 5%	1900
	11th to 20th	Night	37% 4 10% 25% 18% 6%	1875
	21st to end	Night	43% 6% 11% 23% 15% 2	1850
May	1st to 10th	Night	37% 5% 14% 24% 18% 2	1754
	11th to 20th	Night	37% 4 15% 24% 16% 3	1594
	21st to end	Night	39% 7% 18% 22% 13% 1	1561
June	1st to 10th	Night	27% 5% 16% 31% 20% 2	1440
	11th to 20th	Night	20% 5% 15% 36% 19% 5%	1440
	21st to end	Night	19% 6% 17% 30% 19% 8%	1440
July	1st to 10th	Night	28% 9% 18% 25% 18% 2	1457
	11th to 20th	Night	19% 8% 16% 32% 22% 4	1566
	21st to end	Night	27% 8% 13% 37% 14% 1	1673
August	1st to 10th	Night	26% 8% 17% 36% 13% 1	1601
	11th to 20th	Night	28% 7% 16% 31% 17% 2	1721
	21st to end	Night	25% 7% 16% 26% 20% 6%	1980
September	1st to 10th	Night	27% 5% 11% 32% 20% 6%	1800
	11th to 20th	Night	32% 6% 10% 24% 24% 4	1800
	21st to end	Night	27% 5% 9% 23% 33% 4	2047
October	1st to 10th	Night	24% 5% 12% 27% 26% 7%	2160
	11th to 20th	Night	32% 4 7% 24% 26% 7%	2160
	21st to end	Night	39% 3 7% 22% 21% 7%	2376
November	1st to 10th	Night	30% 3 9% 27% 24% 7%	2224
	11th to 20th	Night	33% 3 7% 25% 26% 6%	2470
	21st to end	Night	41% 3 7% 24% 22% 3	2588
December	1st to 10th	Night	42% 3 11% 24% 18% 2	2660
	11th to 20th	Night	46% 2 7% 23% 19% 2	3281
	21st to end	Night	57% 3 10% 18% 10% 2	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% 21% 36% 14% 3	270
	11th to 20th	Day	33% 23% 28% 14% 2	270
	21st to end	Day	23% 28% 30% 15% 4	297
February	1st to 10th	Day	27% 22% 37% 10% 3 1	270
	11th to 20th	Day	29% 26% 33% 9% 3 1	270
	21st to end	Day	35% 19% 37% 8% 2	225
March	1st to 10th	Day	26% 21% 36% 14% 3	270
	11th to 20th	Day	30% 22% 33% 13% 2	270
	21st to end	Day	28% 24% 37% 9% 2	316
April	1st to 10th	Day	25% 18% 33% 18% 6% 1	460
	11th to 20th	Day	24% 23% 32% 15% 6% 1	452
	21st to end	Day	22% 16% 37% 20% 5% 1	437
May	1st to 10th	Day	22% 15% 33% 21% 8% 1	466
	11th to 20th	Day	17% 12% 32% 23% 14% 3	625
	21st to end	Day	13% 7% 35% 25% 18% 3	679
June	1st to 10th	Day	10% 4 22% 30% 26% 7%	630
	11th to 20th	Day	7% 4 19% 39% 27% 4	630
	21st to end	Day	5% 4 27% 35% 22% 5%	630
July	1st to 10th	Day	11% 1 14% 32% 33% 10%	621
	11th to 20th	Day	7% 2 16% 36% 31% 9%	618
	21st to end	Day	9% 2 13% 31% 32% 13%	684
August	1st to 10th	Day	11% 3 11% 40% 28% 7%	626
	11th to 20th	Day	14% 3 16% 28% 31% 9%	491
	21st to end	Day	11% 1 13% 32% 30% 14%	495
September	1st to 10th	Day	11% 3 12% 36% 30% 8%	450
	11th to 20th	Day	9% 3 16% 33% 27% 12%	450
	21st to end	Day	12% 8% 23% 30% 23% 3	298
October	1st to 10th	Day	11% 11% 29% 33% 13% 4	270
	11th to 20th	Day	21% 13% 37% 22% 4 1	270
	21st to end	Day	30% 18% 27% 20% 4	297
November	1st to 10th	Day	20% 11% 31% 28% 8% 2	270
	11th to 20th	Day	22% 15% 37% 15% 10%	270
	21st to end	Day	31% 16% 29% 17% 6% 2	270
December	1st to 10th	Day	21% 25% 29% 17% 6% 2	270
	11th to 20th	Day	28% 21% 29% 16% 6%	270
	21st to end	Day	28% 24% 32% 14% 3	297
January	1st to 10th	Night	21% 17% 36% 23% 3	950
	11th to 20th	Night	23% 17% 37% 18% 4	950
	21st to end	Night	21% 17% 38% 22% 2	1045
February	1st to 10th	Night	23% 16% 37% 21% 2	950
	11th to 20th	Night	22% 17% 41% 19% 2	835
	21st to end	Night	23% 20% 37% 17% 2	628
March	1st to 10th	Night	23% 15% 35% 24% 3	584
	11th to 20th	Night	23% 15% 32% 25% 4	570
	21st to end	Night	26% 12% 37% 20% 5%	627
April	1st to 10th	Night	15% 15% 41% 25% 4	570
	11th to 20th	Night	18% 16% 33% 26% 7%	563
	21st to end	Night	20% 8% 40% 24% 7% 1	555
May	1st to 10th	Night	17% 7% 35% 31% 9%	540
	11th to 20th	Night	19% 7% 29% 26% 17% 2	531
	21st to end	Night	12% 4 27% 35% 19% 3	584
June	1st to 10th	Night	9% 4 17% 36% 32% 2	540
	11th to 20th	Night	5% 1 21% 45% 25% 2	540
	21st to end	Night	5% 1 21% 38% 33% 2	540
July	1st to 10th	Night	5% 2 14% 33% 40% 6%	525
	11th to 20th	Night	3 1 11% 40% 38% 7%	522
	21st to end	Night	7% 11% 40% 36% 6%	591
August	1st to 10th	Night	4 1 12% 44% 35% 5%	537
	11th to 20th	Night	7% 1 14% 40% 33% 4	534
	21st to end	Night	9% 1 10% 37% 38% 5%	594
September	1st to 10th	Night	11% 2 14% 38% 31% 4	540
	11th to 20th	Night	12% 1 15% 37% 30% 5%	540
	21st to end	Night	9% 5% 21% 35% 27% 3	639
October	1st to 10th	Night	9% 5% 25% 33% 24% 3	720
	11th to 20th	Night	16% 11% 32% 29% 12% 1	720
	21st to end	Night	23% 12% 30% 26% 9%	792
November	1st to 10th	Night	14% 10% 35% 30% 11% 1	740
	11th to 20th	Night	19% 10% 35% 28% 9%	760
	21st to end	Night	23% 13% 32% 23% 9%	878
December	1st to 10th	Night	23% 13% 33% 25% 5%	950
	11th to 20th	Night	25% 14% 29% 28% 4	950
	21st to end	Night	26% 17% 33% 20% 4	1045

Page generated at 2024-04-22 08:25:45. Version ac07

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