The Bishop's Ranch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the The Bishop's Ranch clear sky chart from 2005-11-06 to 2024-11-02.

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	9% 4 2 4 3 3 3 3 4 6% 60%	101169
	Night	11% 5% 2 5% 3 3 3 3 4 6% 54%	97999
Transparency	Day	27% 4 8% 20% 23% 18%	100929
	Night	32% 4 9% 18% 21% 16%	97829
Seeing	Day	12% 10% 23% 30% 19% 6%	15367
	Night	13% 5% 14% 31% 30% 6%	24593

By Month

Percentage Cloud Cover SW (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	17% 7% 3 8% 4 3 3 3 5% 5% 41%	2713
	11th to 20th	Day	25% 9% 3 7% 5% 4 4 3 4 5% 32%	2860
	21st to end	Day	23% 8% 3 7% 4 4 3 3 5% 6% 34%	3146
February	1st to 10th	Day	18% 4 2 6% 5% 4 3 3 4 4 47%	1710
	11th to 20th	Day	14% 6% 3 6% 3 3 4 3 5% 7% 45%	1688
	21st to end	Day	16% 7% 2 5% 4 4 3 3 4 5% 48%	1570
March	1st to 10th	Day	22% 12% 3 7% 6% 3 4 3 4 5% 30%	3442
	11th to 20th	Day	11% 4 2 4 3 3 4 3 6% 7% 54%	3490
	21st to end	Day	21% 5% 2 6% 5% 5% 5% 4 6% 7% 36%	3838
April	1st to 10th	Day	14% 7% 2 6% 5% 4 4 3 5% 7% 43%	2280
	11th to 20th	Day	10% 5% 2 6% 3 4 4 4 4 7% 52%	2249
	21st to end	Day	6% 4 1 3 3 3 3 3 6% 8% 58%	2280
May	1st to 10th	Day	6% 3 1 3 2 2 2 2 3 5% 71%	4074
	11th to 20th	Day	4 3 1 3 2 2 2 2 4 5% 72%	4128
	21st to end	Day	3 3 1 2 2 2 2 2 3 5% 73%	4813
June	1st to 10th	Day	6% 5% 1 3 3 3 3 3 5% 8% 60%	2660
	11th to 20th	Day	2 3 1 2 2 2 3 2 4 6% 74%	2660
	21st to end	Day	3 2 1 3 2 2 2 2 3 4 77%	2660
July	1st to 10th	Day	1 2 1 3 2 2 1 1 2 3 81%	4420
	11th to 20th	Day	1 2 1 3 2 3 2 2 3 5% 76%	4113
	21st to end	Day	1 3 1 3 2 2 2 2 3 4 78%	4455
August	1st to 10th	Day	1 2 1 5% 3 3 4 3 4 7% 66%	4091
	11th to 20th	Day	1 2 1 2 1 2 2 2 3 5% 81%	3935
	21st to end	Day	1 3 2 4 3 2 2 2 4 5% 73%	4180
September	1st to 10th	Day	1 2 1 2 2 2 2 2 3 5% 77%	2280
	11th to 20th	Day	4 3 2 4 3 3 4 3 4 6% 66%	2257
	21st to end	Day	4 2 1 2 2 1 2 2 3 5% 75%	2009
October	1st to 10th	Day	7% 3 1 3 2 2 3 2 3 5% 70%	1900
	11th to 20th	Day	8% 3 1 4 2 2 3 3 3 6% 64%	1900
	21st to end	Day	11% 3 1 3 2 3 3 3 4 6% 61%	2090
November	1st to 10th	Day	10% 4 2 4 3 4 3 3 5% 6% 55%	1858
	11th to 20th	Day	12% 4 2 5% 4 4 3 4 4 6% 51%	1658
	21st to end	Day	10% 6% 1 4 3 4 4 3 4 5% 56%	1520
December	1st to 10th	Day	19% 5% 2 5% 4 4 3 3 4 7% 45%	1520
	11th to 20th	Day	33% 8% 3 5% 3 2 3 3 4 4 32%	1928
	21st to end	Day	24% 7% 2 6% 4 4 3 3 4 7% 36%	2794
January	1st to 10th	Night	16% 7% 2 5% 3 3 4 3 5% 7% 43%	4220
	11th to 20th	Night	23% 8% 2 6% 5% 5% 5% 3 4 5% 32%	4110
	21st to end	Night	25% 9% 3 7% 4 4 4 3 4 5% 33%	4521
February	1st to 10th	Night	17% 6% 2 5% 3 3 3 3 3 6% 49%	2470
	11th to 20th	Night	13% 8% 3 5% 3 3 5% 3 5% 7% 45%	2378
	21st to end	Night	14% 6% 2 3 3 3 3 3 3 6% 55%	1879
March	1st to 10th	Night	21% 11% 3 6% 4 4 4 3 4 5% 34%	3432
	11th to 20th	Night	13% 4 2 4 3 3 3 3 5% 5% 56%	3490
	21st to end	Night	16% 9% 3 8% 4 4 4 3 4 6% 39%	3813
April	1st to 10th	Night	10% 8% 2 6% 4 4 3 2 4 5% 52%	1900
	11th to 20th	Night	8% 6% 2 5% 3 4 4 3 4 7% 55%	1879
	21st to end	Night	6% 5% 1 4 3 3 3 3 4 7% 61%	1900
May	1st to 10th	Night	4 4 1 4 2 2 2 2 3 5% 71%	2892
	11th to 20th	Night	2 5% 2 8% 4 4 4 2 5% 5% 58%	2770
	21st to end	Night	3 2 1 3 2 2 1 2 3 5% 76%	2762
June	1st to 10th	Night	4 6% 2 4 3 3 3 3 5% 7% 60%	1520
	11th to 20th	Night	2 3 1 3 2 3 3 2 3 5% 74%	1520
	21st to end	Night	3 3 1 3 2 3 2 2 3 5% 72%	1520
July	1st to 10th	Night	1 2 2 2 2 2 2 2 3 4 79%	2540
	11th to 20th	Night	1 2 2 6% 3 3 2 2 4 4 71%	2851
	21st to end	Night	1 5% 5% 5% 3 3 3 2 6% 6% 63%	3109
August	1st to 10th	Night	2 4 2 13% 4 4 4 4 5% 6% 52%	2848
	11th to 20th	Night	2 1 3 2 2 2 2 4 5% 75%	2904
	21st to end	Night	1 4 2 7% 4 2 2 2 3 5% 67%	3498
September	1st to 10th	Night	1 2 2 3 2 2 3 2 4 6% 74%	1900
	11th to 20th	Night	5% 4 1 4 3 3 3 3 4 7% 62%	1918
	21st to end	Night	3 5% 1 4 2 2 2 2 4 4 71%	2171
October	1st to 10th	Night	5% 4 1 3 2 2 3 3 4 5% 67%	2280
	11th to 20th	Night	6% 4 2 4 3 4 3 3 5% 6% 60%	2280
	21st to end	Night	9% 3 1 4 3 3 4 2 4 6% 60%	2508
November	1st to 10th	Night	10% 5% 2 4 4 2 4 2 5% 7% 54%	2241
	11th to 20th	Night	12% 6% 2 4 3 3 3 3 5% 7% 51%	2517
	21st to end	Night	10% 4 2 5% 3 3 2 3 4 6% 57%	2660
December	1st to 10th	Night	20% 6% 2 4 3 3 4 3 4 5% 46%	2660
	11th to 20th	Night	33% 6% 1 4 3 3 3 3 4 6% 33%	3276
	21st to end	Night	24% 7% 2 6% 3 4 4 3 4 6% 37%	4862

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	44% 6% 12% 27% 7% 4	2713
	11th to 20th	Day	55% 6% 9% 13% 9% 8%	2860
	21st to end	Day	53% 5% 9% 17% 11% 5%	3146
February	1st to 10th	Day	43% 4 7% 19% 20% 8%	1710
	11th to 20th	Day	41% 5% 9% 19% 19% 6%	1697
	21st to end	Day	39% 5% 10% 25% 15% 7%	1570
March	1st to 10th	Day	55% 7% 8% 15% 12% 2	3442
	11th to 20th	Day	30% 6% 10% 29% 13% 11%	3490
	21st to end	Day	45% 8% 14% 20% 11% 2	3838
April	1st to 10th	Day	41% 5% 12% 22% 16% 4	2280
	11th to 20th	Day	33% 5% 14% 23% 19% 5%	2252
	21st to end	Day	24% 5% 14% 30% 23% 4	2280
May	1st to 10th	Day	17% 3 12% 30% 21% 16%	4074
	11th to 20th	Day	16% 3 7% 30% 31% 13%	4131
	21st to end	Day	15% 3 12% 38% 28% 3	4814
June	1st to 10th	Day	24% 4 11% 29% 25% 6%	2660
	11th to 20th	Day	14% 3 10% 20% 38% 15%	2660
	21st to end	Day	15% 2 4 15% 36% 28%	2660
July	1st to 10th	Day	11% 1 2 8% 16% 61%	4351
	11th to 20th	Day	12% 2 4 9% 22% 52%	4043
	21st to end	Day	13% 1 3 8% 30% 45%	4315
August	1st to 10th	Day	19% 2 5% 11% 26% 37%	4076
	11th to 20th	Day	9% 1 4 15% 42% 30%	3974
	21st to end	Day	17% 2 6% 15% 35% 26%	4179
September	1st to 10th	Day	12% 2 4 12% 31% 40%	2280
	11th to 20th	Day	21% 3 7% 25% 34% 11%	2257
	21st to end	Day	14% 3 6% 22% 32% 23%	2009
October	1st to 10th	Day	20% 3 6% 17% 30% 25%	1900
	11th to 20th	Day	25% 4 8% 20% 24% 21%	1900
	21st to end	Day	26% 4 8% 21% 25% 16%	2090
November	1st to 10th	Day	31% 5% 8% 28% 18% 11%	1858
	11th to 20th	Day	36% 5% 10% 24% 16% 8%	1658
	21st to end	Day	32% 4 11% 20% 20% 13%	1520
December	1st to 10th	Day	41% 5% 9% 16% 18% 9%	1520
	11th to 20th	Day	58% 4 6% 13% 14% 5%	1928
	21st to end	Day	49% 5% 12% 20% 10% 4	2794
January	1st to 10th	Night	41% 7% 18% 22% 8% 3	4220
	11th to 20th	Night	53% 8% 9% 12% 10% 8%	4110
	21st to end	Night	54% 6% 9% 12% 13% 6%	4521
February	1st to 10th	Night	38% 4 9% 20% 18% 11%	2470
	11th to 20th	Night	40% 5% 9% 19% 20% 7%	2380
	21st to end	Night	32% 4 12% 26% 20% 5%	1879
March	1st to 10th	Night	51% 9% 10% 13% 14% 2	3432
	11th to 20th	Night	31% 4 9% 22% 23% 10%	3490
	21st to end	Night	45% 8% 11% 23% 10% 3	3813
April	1st to 10th	Night	35% 6% 13% 22% 20% 4	1900
	11th to 20th	Night	31% 4 13% 26% 18% 9%	1879
	21st to end	Night	24% 4 10% 31% 25% 6%	1900
May	1st to 10th	Night	18% 3 6% 28% 28% 17%	2892
	11th to 20th	Night	24% 4 7% 21% 26% 19%	2771
	21st to end	Night	14% 3 7% 41% 30% 5%	2762
June	1st to 10th	Night	24% 4 9% 23% 30% 9%	1520
	11th to 20th	Night	15% 3 7% 22% 35% 19%	1520
	21st to end	Night	18% 1 5% 12% 31% 33%	1520
July	1st to 10th	Night	12% 1 3 6% 19% 59%	2500
	11th to 20th	Night	16% 2 5% 11% 18% 48%	2798
	21st to end	Night	23% 2 4 7% 24% 40%	3011
August	1st to 10th	Night	32% 2 6% 11% 24% 24%	2839
	11th to 20th	Night	13% 2 4 13% 37% 32%	2931
	21st to end	Night	22% 1 5% 14% 34% 23%	3498
September	1st to 10th	Night	14% 1 5% 11% 30% 39%	1900
	11th to 20th	Night	25% 3 7% 18% 34% 14%	1918
	21st to end	Night	19% 2 5% 20% 27% 26%	2171
October	1st to 10th	Night	20% 3 8% 16% 27% 26%	2280
	11th to 20th	Night	27% 3 6% 19% 22% 23%	2280
	21st to end	Night	27% 3 7% 19% 25% 19%	2508
November	1st to 10th	Night	31% 4 11% 25% 19% 10%	2241
	11th to 20th	Night	34% 4 13% 24% 17% 8%	2517
	21st to end	Night	30% 4 10% 21% 22% 13%	2660
December	1st to 10th	Night	42% 4 8% 17% 19% 10%	2660
	11th to 20th	Night	54% 4 9% 13% 15% 4	3276
	21st to end	Night	50% 7% 12% 17% 12% 3	4862

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	30% 13% 25% 17% 12% 3	289
	11th to 20th	Day	25% 9% 24% 24% 15% 3	370
	21st to end	Day	18% 11% 23% 27% 17% 3	407
February	1st to 10th	Day	21% 11% 21% 23% 20% 4	370
	11th to 20th	Day	22% 18% 24% 23% 12% 1	376
	21st to end	Day	19% 15% 24% 27% 13% 1	382
March	1st to 10th	Day	28% 17% 24% 22% 7% 2	460
	11th to 20th	Day	24% 15% 27% 20% 11% 3	460
	21st to end	Day	19% 17% 30% 23% 10%	506
April	1st to 10th	Day	19% 16% 27% 24% 10% 3	460
	11th to 20th	Day	17% 19% 28% 22% 11% 4	452
	21st to end	Day	11% 15% 30% 26% 12% 5%	460
May	1st to 10th	Day	14% 15% 31% 23% 13% 4	463
	11th to 20th	Day	13% 11% 30% 26% 15% 5%	488
	21st to end	Day	10% 11% 25% 30% 18% 6%	529
June	1st to 10th	Day	11% 11% 24% 32% 15% 6%	490
	11th to 20th	Day	6% 12% 30% 37% 12% 3	490
	21st to end	Day	3 4 27% 37% 23% 6%	490
July	1st to 10th	Day	6% 3 21% 43% 22% 6%	486
	11th to 20th	Day	1 1 18% 45% 27% 8%	484
	21st to end	Day	2 2 12% 47% 29% 8%	531
August	1st to 10th	Day	3 3 21% 42% 23% 8%	487
	11th to 20th	Day	3 3 23% 37% 26% 8%	477
	21st to end	Day	4 2 20% 38% 28% 9%	539
September	1st to 10th	Day	2 4 20% 39% 28% 9%	490
	11th to 20th	Day	7% 7% 23% 32% 23% 9%	490
	21st to end	Day	6% 6% 20% 34% 26% 8%	490
October	1st to 10th	Day	8% 7% 25% 24% 26% 11%	490
	11th to 20th	Day	9% 8% 19% 27% 27% 11%	490
	21st to end	Day	14% 7% 20% 28% 24% 6%	539
November	1st to 10th	Day	14% 10% 16% 28% 27% 6%	448
	11th to 20th	Day	12% 7% 17% 25% 26% 13%	246
	21st to end	Day	13% 8% 24% 26% 19% 11%	180
December	1st to 10th	Day	22% 14% 15% 22% 17% 10%	180
	11th to 20th	Day	28% 9% 22% 17% 14% 9%	180
	21st to end	Day	23% 10% 21% 25% 17% 4	198
January	1st to 10th	Night	23% 5% 16% 30% 22% 4	760
	11th to 20th	Night	23% 6% 15% 33% 20% 4	760
	21st to end	Night	21% 5% 15% 32% 24% 4	836
February	1st to 10th	Night	20% 6% 14% 35% 23% 3	760
	11th to 20th	Night	18% 7% 18% 32% 22% 4	744
	21st to end	Night	18% 10% 18% 32% 19% 3	628
March	1st to 10th	Night	23% 9% 18% 27% 20% 3	760
	11th to 20th	Night	19% 7% 16% 31% 22% 4	760
	21st to end	Night	19% 7% 22% 32% 17% 3	836
April	1st to 10th	Night	13% 9% 23% 31% 20% 4	760
	11th to 20th	Night	13% 11% 19% 30% 21% 5%	751
	21st to end	Night	9% 11% 25% 27% 24% 5%	760
May	1st to 10th	Night	10% 6% 21% 30% 29% 4	589
	11th to 20th	Night	7% 3 18% 33% 34% 6%	524
	21st to end	Night	7% 8% 18% 30% 33% 5%	411
June	1st to 10th	Night	7% 7% 20% 33% 31% 2	380
	11th to 20th	Night	4 6% 16% 44% 28% 2	380
	21st to end	Night	4 2 14% 36% 40% 4	380
July	1st to 10th	Night	2 1 10% 35% 46% 6%	370
	11th to 20th	Night	3 1 4 31% 48% 13%	544
	21st to end	Night	3 3 32% 51% 10%	624
August	1st to 10th	Night	5% 1 7% 31% 45% 11%	567
	11th to 20th	Night	2 6% 34% 49% 9%	617
	21st to end	Night	4 1 7% 29% 49% 10%	836
September	1st to 10th	Night	2 1 8% 28% 50% 10%	760
	11th to 20th	Night	6% 3 9% 33% 40% 9%	760
	21st to end	Night	5% 3 11% 33% 36% 12%	760
October	1st to 10th	Night	7% 4 13% 31% 35% 10%	760
	11th to 20th	Night	9% 3 12% 29% 38% 9%	760
	21st to end	Night	12% 2 12% 28% 35% 11%	836
November	1st to 10th	Night	12% 4 15% 27% 34% 8%	744
	11th to 20th	Night	15% 2 12% 35% 31% 5%	760
	21st to end	Night	12% 5% 15% 36% 27% 6%	760
December	1st to 10th	Night	24% 4 13% 29% 24% 5%	760
	11th to 20th	Night	29% 5% 14% 29% 20% 4	760
	21st to end	Night	24% 5% 19% 33% 17% 2	836

Page generated at 2024-10-29 22:22:58. Version ac07

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