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 2024-11-05.

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 5% 7% 45%	101007
	Night	13% 7% 2 5% 3 3 4 3 5% 7% 48%	98090
Transparency	Day	37% 5% 11% 25% 18% 4	104652
	Night	35% 4 11% 25% 19% 4	102585
Seeing	Day	17% 11% 26% 25% 17% 4	15513
	Night	17% 10% 29% 29% 14% 1	25303

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% 3 4 3 3 3 4 47%	2824
	11th to 20th	Day	13% 9% 2 6% 4 4 3 3 4 5% 47%	2850
	21st to end	Day	25% 7% 3 5% 3 2 2 2 3 4 43%	3135
February	1st to 10th	Day	16% 10% 3 6% 5% 4 4 3 5% 5% 39%	1710
	11th to 20th	Day	15% 10% 3 6% 3 4 3 3 4 6% 43%	1758
	21st to end	Day	17% 10% 2 6% 5% 4 4 3 5% 5% 38%	1570
March	1st to 10th	Day	20% 10% 2 6% 4 3 3 2 4 4 43%	3436
	11th to 20th	Day	13% 7% 2 5% 3 3 3 3 4 7% 52%	3480
	21st to end	Day	16% 7% 2 7% 5% 5% 5% 4 5% 6% 37%	3845
April	1st to 10th	Day	13% 7% 2 6% 4 4 4 3 4 6% 46%	2280
	11th to 20th	Day	17% 7% 2 6% 4 4 4 4 5% 6% 41%	2254
	21st to end	Day	19% 8% 2 7% 5% 5% 4 4 5% 5% 36%	2280
May	1st to 10th	Day	16% 7% 2 7% 5% 5% 4 4 6% 7% 35%	3850
	11th to 20th	Day	15% 6% 3 7% 4 4 4 3 6% 8% 39%	4082
	21st to end	Day	15% 6% 3 6% 5% 4 5% 4 6% 8% 37%	4811
June	1st to 10th	Day	9% 5% 2 6% 5% 5% 5% 4 6% 9% 45%	2660
	11th to 20th	Day	6% 4 2 5% 4 4 6% 5% 7% 10% 48%	2660
	21st to end	Day	5% 3 1 4 5% 5% 5% 5% 8% 10% 50%	2660
July	1st to 10th	Day	10% 5% 2 6% 4 4 5% 4 7% 9% 44%	4319
	11th to 20th	Day	5% 4 2 5% 4 5% 4 5% 7% 12% 48%	4120
	21st to end	Day	8% 6% 2 7% 5% 5% 7% 6% 8% 10% 35%	4465
August	1st to 10th	Day	5% 3 1 4 3 3 5% 4 6% 9% 58%	4104
	11th to 20th	Day	11% 5% 2 5% 4 4 5% 4 6% 9% 44%	3820
	21st to end	Day	5% 4 2 4 4 5% 4 3 5% 8% 55%	4180
September	1st to 10th	Day	11% 5% 1 5% 4 5% 4 3 5% 7% 49%	2280
	11th to 20th	Day	12% 7% 2 6% 4 4 4 4 5% 7% 46%	2280
	21st to end	Day	8% 5% 2 4 4 3 4 3 6% 6% 55%	1993
October	1st to 10th	Day	9% 4 2 6% 4 3 3 3 4 5% 57%	1900
	11th to 20th	Day	15% 6% 2 4 2 3 2 2 3 5% 56%	1900
	21st to end	Day	19% 7% 2 5% 3 3 3 3 5% 6% 47%	2090
November	1st to 10th	Day	13% 6% 1 5% 2 2 3 3 4 5% 56%	1893
	11th to 20th	Day	14% 6% 2 5% 4 4 3 3 5% 5% 51%	1710
	21st to end	Day	20% 9% 2 4 3 2 3 2 4 5% 46%	1587
December	1st to 10th	Day	15% 8% 3 7% 3 3 4 3 5% 5% 44%	1520
	11th to 20th	Day	16% 10% 4 8% 4 4 3 2 4 4 42%	1918
	21st to end	Day	15% 17% 4 7% 4 4 4 3 4 6% 32%	2783
January	1st to 10th	Night	15% 8% 4 6% 4 4 4 3 4 6% 41%	4126
	11th to 20th	Night	15% 7% 2 7% 4 3 4 3 4 5% 46%	4120
	21st to end	Night	23% 11% 3 5% 3 2 2 2 4 4 41%	4532
February	1st to 10th	Night	16% 9% 3 7% 3 3 3 3 4 6% 43%	2470
	11th to 20th	Night	16% 8% 2 6% 4 3 3 2 5% 5% 46%	2309
	21st to end	Night	17% 8% 2 5% 3 3 3 3 6% 5% 45%	1884
March	1st to 10th	Night	22% 8% 2 5% 3 3 3 2 4 4 43%	3433
	11th to 20th	Night	14% 6% 2 5% 4 4 3 2 5% 5% 51%	3480
	21st to end	Night	15% 9% 3 7% 5% 4 4 3 5% 6% 39%	3771
April	1st to 10th	Night	11% 5% 1 5% 3 3 2 3 6% 7% 53%	1900
	11th to 20th	Night	14% 6% 2 6% 3 3 3 3 5% 8% 47%	1875
	21st to end	Night	18% 6% 3 6% 4 3 4 3 6% 7% 40%	1900
May	1st to 10th	Night	18% 6% 2 5% 4 3 3 3 5% 6% 46%	3045
	11th to 20th	Night	14% 6% 2 6% 4 4 4 3 6% 9% 42%	2823
	21st to end	Night	15% 6% 2 7% 5% 4 3 4 5% 7% 41%	2752
June	1st to 10th	Night	8% 4 1 4 3 4 4 4 6% 8% 53%	1520
	11th to 20th	Night	4 3 1 4 3 2 4 4 6% 11% 58%	1520
	21st to end	Night	3 2 1 3 3 3 3 4 5% 9% 61%	1520
July	1st to 10th	Night	8% 4 2 5% 4 4 5% 5% 7% 9% 47%	2646
	11th to 20th	Night	3 2 1 4 3 3 4 3 5% 9% 61%	2850
	21st to end	Night	7% 6% 3 7% 4 5% 5% 4 7% 9% 42%	3098
August	1st to 10th	Night	3 2 1 3 3 3 4 4 6% 9% 63%	2836
	11th to 20th	Night	9% 4 2 5% 5% 4 4 4 6% 8% 50%	3009
	21st to end	Night	4 3 2 4 3 3 3 3 6% 8% 61%	3476
September	1st to 10th	Night	10% 4 2 4 3 3 4 3 5% 8% 56%	1900
	11th to 20th	Night	10% 5% 2 5% 4 4 4 4 5% 7% 51%	1900
	21st to end	Night	8% 5% 1 5% 4 3 3 3 4 6% 58%	2162
October	1st to 10th	Night	7% 3 1 4 3 3 3 3 5% 7% 61%	2280
	11th to 20th	Night	14% 4 2 3 2 3 3 3 4 5% 57%	2280
	21st to end	Night	17% 7% 2 5% 3 3 2 2 4 4 50%	2508
November	1st to 10th	Night	13% 5% 2 4 3 3 3 2 4 5% 57%	2284
	11th to 20th	Night	14% 6% 2 4 3 3 3 3 4 6% 54%	2470
	21st to end	Night	17% 9% 2 5% 3 2 3 3 4 5% 47%	2588
December	1st to 10th	Night	17% 9% 2 5% 3 3 3 2 5% 6% 44%	2660
	11th to 20th	Night	18% 9% 3 7% 4 3 3 2 4 5% 42%	3279
	21st to end	Night	20% 14% 3 8% 4 4 4 3 4 5% 31%	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	2280
May	1st to 10th	Day	46% 7% 13% 21% 12% 1	3885
	11th to 20th	Day	44% 6% 14% 24% 12% 1	4086
	21st to end	Day	42% 8% 11% 23% 14% 1	4824
June	1st to 10th	Day	36% 6% 15% 25% 16% 1	2660
	11th to 20th	Day	29% 7% 15% 30% 17% 2	2660
	21st to end	Day	27% 8% 17% 27% 17% 4	2660
July	1st to 10th	Day	34% 8% 17% 27% 13% 2	4253
	11th to 20th	Day	26% 7% 14% 33% 18% 2	4051
	21st to end	Day	39% 10% 19% 23% 8% 1	4325
August	1st to 10th	Day	23% 6% 18% 30% 22% 1	4090
	11th to 20th	Day	36% 6% 14% 29% 14% 1	3858
	21st to end	Day	26% 7% 14% 35% 15% 4	4179
September	1st to 10th	Day	34% 6% 11% 25% 16% 8%	2280
	11th to 20th	Day	36% 6% 10% 23% 23% 2	2280
	21st to end	Day	30% 5% 8% 27% 27% 3	1993
October	1st to 10th	Day	18% 3 5% 17% 43% 15%	3160
	11th to 20th	Day	22% 2 5% 20% 39% 11%	3140
	21st to end	Day	29% 4 7% 32% 24% 4	3428
November	1st to 10th	Day	32% 4 9% 27% 23% 6%	1893
	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	1900
May	1st to 10th	Night	40% 5% 15% 23% 14% 2	3075
	11th to 20th	Night	38% 6% 15% 24% 14% 2	2824
	21st to end	Night	41% 6% 14% 26% 12% 1	2760
June	1st to 10th	Night	28% 4 15% 30% 20% 2	1520
	11th to 20th	Night	20% 5% 15% 36% 20% 5%	1520
	21st to end	Night	20% 6% 18% 29% 19% 8%	1520
July	1st to 10th	Night	31% 8% 18% 24% 17% 3	2603
	11th to 20th	Night	19% 7% 13% 39% 21% 2	2796
	21st to end	Night	35% 9% 16% 30% 10% 1	2999
August	1st to 10th	Night	17% 7% 18% 37% 21% 1	2826
	11th to 20th	Night	31% 7% 17% 28% 15% 2	3037
	21st to end	Night	20% 6% 15% 36% 19% 4	3476
September	1st to 10th	Night	27% 5% 10% 31% 20% 7%	1900
	11th to 20th	Night	32% 6% 10% 24% 24% 4	1900
	21st to end	Night	28% 5% 9% 23% 31% 4	2162
October	1st to 10th	Night	14% 3 7% 16% 42% 17%	3800
	11th to 20th	Night	21% 3 5% 19% 34% 18%	3779
	21st to end	Night	30% 3 7% 28% 28% 5%	4120
November	1st to 10th	Night	31% 3 9% 26% 24% 7%	2284
	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	23% 17% 36% 19% 5% 1	460
May	1st to 10th	Day	22% 15% 33% 21% 8% 1	509
	11th to 20th	Day	16% 12% 32% 23% 14% 3	675
	21st to end	Day	13% 8% 35% 25% 17% 3	734
June	1st to 10th	Day	11% 5% 23% 30% 25% 6%	680
	11th to 20th	Day	6% 4 19% 39% 28% 4	680
	21st to end	Day	5% 5% 27% 35% 22% 5%	680
July	1st to 10th	Day	10% 1 15% 33% 31% 9%	671
	11th to 20th	Day	7% 2 16% 36% 31% 9%	668
	21st to end	Day	9% 3 13% 31% 31% 12%	739
August	1st to 10th	Day	11% 2 13% 39% 28% 7%	676
	11th to 20th	Day	14% 3 18% 28% 29% 8%	534
	21st to end	Day	10% 1 13% 32% 30% 15%	539
September	1st to 10th	Day	10% 3 13% 37% 29% 8%	490
	11th to 20th	Day	10% 4 16% 33% 26% 11%	490
	21st to end	Day	13% 9% 25% 28% 22% 3	329
October	1st to 10th	Day	10% 10% 28% 33% 14% 5%	300
	11th to 20th	Day	20% 13% 35% 24% 6% 2	300
	21st to end	Day	28% 17% 29% 21% 4	330
November	1st to 10th	Day	21% 11% 31% 28% 7% 2	282
	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% 9% 40% 23% 7% 1	570
May	1st to 10th	Night	17% 7% 35% 32% 8%	570
	11th to 20th	Night	18% 7% 30% 27% 17% 1	561
	21st to end	Night	12% 5% 27% 35% 18% 3	617
June	1st to 10th	Night	9% 4 18% 35% 31% 2	570
	11th to 20th	Night	5% 2 20% 46% 25% 2	570
	21st to end	Night	4 2 20% 40% 32% 2	570
July	1st to 10th	Night	6% 2 15% 34% 38% 5%	555
	11th to 20th	Night	3 1 11% 41% 38% 6%	552
	21st to end	Night	7% 12% 40% 36% 5%	624
August	1st to 10th	Night	4 1 13% 43% 35% 5%	567
	11th to 20th	Night	8% 1 15% 40% 32% 4	564
	21st to end	Night	8% 1 10% 37% 37% 6%	627
September	1st to 10th	Night	11% 2 14% 39% 31% 4	570
	11th to 20th	Night	13% 1 14% 37% 30% 5%	570
	21st to end	Night	9% 6% 22% 35% 26% 3	675
October	1st to 10th	Night	9% 5% 24% 34% 24% 4	760
	11th to 20th	Night	15% 10% 32% 29% 13% 1	760
	21st to end	Night	22% 12% 30% 27% 9%	836
November	1st to 10th	Night	15% 10% 34% 30% 11% 1	760
	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 2024-11-03 01:11:17. Version ac07

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