Old Man on His Back Ranch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Old Man on His Back Ranch clear sky chart from 2005-11-06 to 2024-03-06.

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	7% 7% 3 6% 6% 3 5% 5% 6% 8% 42%	78073
	Night	6% 7% 3 7% 6% 3 5% 5% 6% 8% 43%	81464
Transparency	Day	38% 8% 16% 24% 12% 2	77758
	Night	37% 8% 17% 24% 12% 2	81301
Seeing	Day	11% 9% 28% 31% 17% 4	14635
	Night	10% 8% 31% 36% 14% 2	24224

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	4 11% 5% 9% 8% 4 6% 6% 7% 11% 30%	2219
	11th to 20th	Day	3 6% 4 10% 7% 5% 8% 9% 9% 10% 29%	2220
	21st to end	Day	3 9% 4 6% 6% 4 5% 5% 6% 8% 42%	2792
February	1st to 10th	Day	7% 12% 6% 9% 8% 5% 6% 6% 7% 6% 27%	1710
	11th to 20th	Day	5% 10% 5% 8% 8% 5% 7% 8% 8% 9% 28%	1665
	21st to end	Day	4 10% 5% 11% 10% 5% 6% 6% 6% 8% 29%	1413
March	1st to 10th	Day	4 7% 5% 8% 9% 5% 7% 7% 7% 8% 33%	1931
	11th to 20th	Day	6% 7% 4 7% 8% 5% 5% 5% 8% 9% 36%	1980
	21st to end	Day	8% 8% 5% 10% 7% 4 6% 6% 7% 9% 29%	2195
April	1st to 10th	Day	6% 9% 3 7% 7% 4 5% 6% 7% 9% 37%	2160
	11th to 20th	Day	11% 12% 5% 8% 6% 3 5% 5% 5% 7% 34%	2272
	21st to end	Day	11% 10% 3 7% 6% 3 5% 5% 6% 9% 36%	2344
May	1st to 10th	Day	12% 9% 3 7% 6% 4 6% 5% 6% 7% 36%	2520
	11th to 20th	Day	10% 7% 3 6% 5% 3 5% 5% 5% 9% 41%	2478
	21st to end	Day	20% 9% 3 6% 6% 3 4 4 5% 7% 32%	2841
June	1st to 10th	Day	14% 6% 2 7% 5% 4 5% 5% 7% 9% 37%	2700
	11th to 20th	Day	14% 6% 3 5% 6% 4 6% 6% 6% 8% 38%	2700
	21st to end	Day	6% 3 2 4 4 2 5% 6% 6% 10% 51%	2700
July	1st to 10th	Day	4 4 2 3 4 3 4 5% 6% 10% 56%	2700
	11th to 20th	Day	4 3 2 3 4 3 5% 5% 6% 8% 57%	2700
	21st to end	Day	4 2 1 2 3 2 3 4 5% 8% 65%	2858
August	1st to 10th	Day	5% 3 2 4 3 3 5% 5% 5% 8% 57%	2432
	11th to 20th	Day	7% 3 1 4 5% 3 5% 4 5% 8% 56%	2299
	21st to end	Day	6% 3 2 3 4 2 3 5% 5% 9% 58%	2557
September	1st to 10th	Day	9% 4 2 4 4 3 4 4 5% 7% 53%	2160
	11th to 20th	Day	11% 4 3 4 5% 3 5% 4 5% 7% 49%	2103
	21st to end	Day	10% 5% 2 4 4 3 3 4 5% 8% 52%	1932
October	1st to 10th	Day	10% 10% 4 6% 5% 2 3 4 6% 7% 42%	1800
	11th to 20th	Day	8% 7% 3 8% 6% 3 4 5% 6% 8% 44%	1800
	21st to end	Day	5% 10% 3 8% 5% 3 5% 4 6% 8% 42%	1812
November	1st to 10th	Day	9% 12% 4 7% 6% 4 6% 5% 6% 8% 35%	1488
	11th to 20th	Day	3 7% 4 7% 7% 4 6% 6% 7% 8% 41%	1520
	21st to end	Day	5% 10% 5% 7% 7% 3 6% 7% 6% 8% 37%	1520
December	1st to 10th	Day	4 11% 5% 12% 8% 4 7% 6% 5% 7% 32%	1425
	11th to 20th	Day	3 8% 5% 10% 7% 4 6% 5% 6% 7% 38%	1685
	21st to end	Day	4 9% 3 6% 6% 4 5% 5% 5% 7% 46%	2442
January	1st to 10th	Night	3 7% 4 8% 8% 5% 7% 7% 8% 10% 34%	4726
	11th to 20th	Night	3 6% 5% 11% 9% 5% 7% 6% 7% 8% 33%	4740
	21st to end	Night	3 6% 4 10% 7% 4 5% 5% 6% 10% 40%	4897
February	1st to 10th	Night	6% 8% 5% 10% 8% 4 6% 7% 6% 9% 32%	2470
	11th to 20th	Night	4 9% 4 7% 8% 5% 6% 5% 8% 9% 34%	2402
	21st to end	Night	4 8% 4 10% 8% 3 6% 5% 7% 9% 35%	2041
March	1st to 10th	Night	5% 9% 4 9% 8% 5% 7% 5% 7% 9% 35%	2139
	11th to 20th	Night	6% 7% 3 7% 5% 4 7% 7% 7% 10% 38%	1980
	21st to end	Night	7% 9% 5% 9% 7% 4 6% 6% 7% 9% 31%	2160
April	1st to 10th	Night	6% 9% 4 7% 7% 4 6% 7% 6% 8% 37%	1800
	11th to 20th	Night	11% 9% 4 6% 6% 3 6% 6% 6% 7% 36%	1634
	21st to end	Night	10% 7% 4 7% 6% 4 6% 6% 6% 8% 37%	1615
May	1st to 10th	Night	11% 7% 3 5% 5% 3 4 5% 6% 7% 43%	1440
	11th to 20th	Night	10% 5% 2 4 5% 3 5% 6% 5% 9% 46%	1417
	21st to end	Night	17% 8% 3 5% 5% 3 5% 5% 7% 8% 34%	1431
June	1st to 10th	Night	13% 7% 3 4 5% 3 4 4 5% 8% 43%	1260
	11th to 20th	Night	10% 5% 3 6% 3 2 6% 4 7% 9% 44%	1260
	21st to end	Night	5% 3 2 4 4 3 4 3 5% 9% 58%	1260
July	1st to 10th	Night	5% 3 1 3 4 2 4 4 6% 9% 58%	1260
	11th to 20th	Night	4 3 2 3 3 2 3 4 6% 9% 60%	1260
	21st to end	Night	4 2 1 3 3 2 4 4 6% 8% 64%	1459
August	1st to 10th	Night	7% 3 2 3 4 3 3 4 5% 9% 58%	1506
	11th to 20th	Night	7% 3 1 3 3 2 3 4 5% 9% 58%	1602
	21st to end	Night	9% 3 2 3 3 2 4 4 5% 8% 57%	1798
September	1st to 10th	Night	9% 4 2 5% 5% 2 3 4 4 6% 56%	1800
	11th to 20th	Night	9% 5% 2 4 4 3 4 5% 6% 8% 49%	1854
	21st to end	Night	7% 5% 2 4 4 3 4 5% 5% 8% 54%	2027
October	1st to 10th	Night	10% 6% 3 5% 5% 3 4 4 5% 8% 47%	2160
	11th to 20th	Night	6% 6% 3 5% 5% 3 4 5% 5% 10% 47%	2160
	21st to end	Night	7% 8% 3 7% 6% 4 5% 5% 6% 7% 43%	2523
November	1st to 10th	Night	8% 9% 3 7% 7% 4 5% 5% 7% 8% 38%	2590
	11th to 20th	Night	3 7% 3 7% 7% 3 6% 7% 7% 9% 42%	2660
	21st to end	Night	4 7% 5% 8% 7% 4 6% 5% 6% 8% 40%	2660
December	1st to 10th	Night	4 8% 4 10% 7% 4 6% 6% 7% 8% 36%	2753
	11th to 20th	Night	3 8% 5% 8% 7% 3 5% 5% 6% 9% 40%	3506
	21st to end	Night	4 6% 3 5% 5% 3 4 4 6% 8% 53%	5214

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	46% 11% 19% 20% 4	2219
	11th to 20th	Day	44% 11% 14% 19% 10% 1	2220
	21st to end	Day	36% 10% 25% 24% 4	2792
February	1st to 10th	Day	54% 8% 14% 17% 8%	1710
	11th to 20th	Day	48% 12% 16% 18% 7%	1674
	21st to end	Day	52% 6% 17% 16% 8% 1	1413
March	1st to 10th	Day	44% 12% 20% 18% 6%	1931
	11th to 20th	Day	42% 10% 19% 22% 6%	1980
	21st to end	Day	47% 11% 20% 16% 5%	2195
April	1st to 10th	Day	41% 10% 17% 24% 8%	2160
	11th to 20th	Day	48% 8% 14% 21% 8% 1	2275
	21st to end	Day	44% 8% 15% 27% 6% 1	2344
May	1st to 10th	Day	45% 7% 15% 21% 10%	2520
	11th to 20th	Day	39% 8% 16% 26% 10%	2482
	21st to end	Day	51% 8% 14% 20% 7%	2841
June	1st to 10th	Day	42% 9% 17% 22% 9%	2700
	11th to 20th	Day	41% 8% 15% 23% 11% 1	2700
	21st to end	Day	26% 9% 17% 34% 14% 1	2700
July	1st to 10th	Day	23% 7% 16% 30% 19% 4	2626
	11th to 20th	Day	22% 7% 14% 25% 26% 6%	2619
	21st to end	Day	15% 6% 12% 33% 27% 7%	2699
August	1st to 10th	Day	24% 6% 13% 30% 20% 6%	2416
	11th to 20th	Day	26% 7% 15% 30% 19% 3	2299
	21st to end	Day	23% 6% 12% 28% 25% 5%	2557
September	1st to 10th	Day	30% 6% 12% 27% 18% 7%	2160
	11th to 20th	Day	34% 7% 14% 28% 14% 3	2103
	21st to end	Day	30% 6% 13% 32% 16% 2	1932
October	1st to 10th	Day	39% 8% 17% 25% 11%	1800
	11th to 20th	Day	37% 7% 18% 25% 12% 2	1800
	21st to end	Day	38% 8% 19% 24% 11%	1812
November	1st to 10th	Day	45% 10% 15% 21% 8% 1	1488
	11th to 20th	Day	38% 9% 21% 23% 9%	1520
	21st to end	Day	42% 11% 18% 20% 8% 1	1520
December	1st to 10th	Day	51% 8% 17% 17% 7% 1	1425
	11th to 20th	Day	43% 10% 22% 21% 4	1684
	21st to end	Day	36% 6% 14% 23% 12% 7%	2442
January	1st to 10th	Night	39% 12% 22% 19% 6% 1	4726
	11th to 20th	Night	46% 8% 14% 17% 13% 1	4740
	21st to end	Night	38% 9% 21% 27% 5%	4897
February	1st to 10th	Night	47% 7% 16% 19% 9% 1	2470
	11th to 20th	Night	42% 10% 18% 20% 9% 1	2403
	21st to end	Night	43% 8% 15% 23% 11% 1	2041
March	1st to 10th	Night	44% 10% 17% 19% 10%	2139
	11th to 20th	Night	39% 9% 20% 22% 9% 1	1980
	21st to end	Night	45% 11% 18% 19% 7%	2160
April	1st to 10th	Night	41% 10% 16% 23% 10%	1800
	11th to 20th	Night	44% 9% 11% 23% 12% 2	1634
	21st to end	Night	43% 7% 15% 24% 10% 1	1615
May	1st to 10th	Night	38% 7% 14% 26% 13% 1	1440
	11th to 20th	Night	34% 7% 15% 26% 17% 1	1418
	21st to end	Night	46% 8% 14% 23% 8%	1431
June	1st to 10th	Night	39% 6% 19% 24% 11% 1	1260
	11th to 20th	Night	34% 8% 16% 24% 16% 2	1260
	21st to end	Night	25% 7% 14% 37% 16% 2	1260
July	1st to 10th	Night	20% 8% 13% 33% 21% 6%	1225
	11th to 20th	Night	20% 6% 15% 26% 23% 9%	1218
	21st to end	Night	17% 5% 12% 30% 30% 6%	1378
August	1st to 10th	Night	22% 7% 13% 31% 19% 9%	1498
	11th to 20th	Night	23% 6% 14% 31% 20% 6%	1602
	21st to end	Night	25% 6% 10% 25% 27% 7%	1798
September	1st to 10th	Night	28% 6% 12% 26% 19% 9%	1800
	11th to 20th	Night	31% 7% 13% 27% 16% 5%	1854
	21st to end	Night	28% 6% 14% 31% 18% 3	2027
October	1st to 10th	Night	35% 8% 16% 25% 16% 1	2160
	11th to 20th	Night	33% 6% 17% 28% 14% 2	2160
	21st to end	Night	39% 9% 15% 26% 11% 1	2523
November	1st to 10th	Night	43% 8% 16% 21% 10% 2	2590
	11th to 20th	Night	36% 9% 22% 24% 9%	2660
	21st to end	Night	39% 8% 25% 19% 8%	2660
December	1st to 10th	Night	44% 10% 18% 20% 8% 1	2753
	11th to 20th	Night	40% 9% 24% 23% 4 1	3507
	21st to end	Night	29% 6% 16% 26% 17% 6%	5214

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	7% 11% 27% 32% 15% 9%	180
	11th to 20th	Day	7% 6% 33% 31% 17% 7%	180
	21st to end	Day	7% 11% 33% 37% 12% 1	252
February	1st to 10th	Day	12% 12% 34% 29% 11% 2	270
	11th to 20th	Day	11% 5% 34% 33% 13% 3	270
	21st to end	Day	8% 6% 33% 34% 14% 5%	225
March	1st to 10th	Day	7% 9% 35% 32% 15% 2	365
	11th to 20th	Day	8% 10% 32% 29% 14% 7%	420
	21st to end	Day	10% 9% 30% 28% 19% 4	462
April	1st to 10th	Day	10% 12% 34% 31% 12% 1	420
	11th to 20th	Day	14% 13% 33% 29% 9% 2	412
	21st to end	Day	17% 12% 25% 29% 14% 3	424
May	1st to 10th	Day	15% 7% 21% 30% 22% 4	603
	11th to 20th	Day	14% 6% 26% 29% 20% 6%	625
	21st to end	Day	18% 9% 22% 24% 21% 7%	679
June	1st to 10th	Day	15% 10% 23% 28% 22% 3	630
	11th to 20th	Day	15% 13% 34% 24% 12% 2	630
	21st to end	Day	9% 6% 24% 32% 23% 6%	630
July	1st to 10th	Day	5% 5% 22% 38% 26% 5%	621
	11th to 20th	Day	6% 5% 27% 37% 21% 4	618
	21st to end	Day	4 4 25% 37% 24% 6%	684
August	1st to 10th	Day	6% 7% 22% 38% 21% 7%	551
	11th to 20th	Day	9% 6% 17% 38% 22% 8%	437
	21st to end	Day	5% 5% 28% 33% 20% 7%	495
September	1st to 10th	Day	12% 9% 32% 29% 16% 2	450
	11th to 20th	Day	13% 8% 24% 32% 18% 4	450
	21st to end	Day	16% 8% 29% 27% 14% 6%	402
October	1st to 10th	Day	20% 5% 25% 26% 19% 4	270
	11th to 20th	Day	11% 9% 32% 27% 17% 4	270
	21st to end	Day	12% 12% 39% 25% 10% 1	297
November	1st to 10th	Day	13% 16% 33% 27% 10% 1	270
	11th to 20th	Day	7% 14% 40% 27% 10% 1	270
	21st to end	Day	8% 10% 39% 27% 13% 3	270
December	1st to 10th	Day	10% 10% 40% 26% 12% 2	225
	11th to 20th	Day	9% 13% 37% 30% 9% 2	180
	21st to end	Day	11% 11% 25% 32% 18% 3	198
January	1st to 10th	Night	7% 10% 34% 33% 13% 2	950
	11th to 20th	Night	7% 11% 37% 32% 10% 2	950
	21st to end	Night	7% 11% 37% 31% 13% 1	969
February	1st to 10th	Night	9% 9% 27% 37% 15% 3	760
	11th to 20th	Night	8% 9% 36% 35% 11% 2	744
	21st to end	Night	7% 7% 29% 36% 18% 4	628
March	1st to 10th	Night	8% 9% 34% 35% 13% 2	742
	11th to 20th	Night	10% 6% 32% 36% 15% 2	720
	21st to end	Night	11% 7% 32% 32% 15% 3	774
April	1st to 10th	Night	11% 8% 32% 37% 11% 2	540
	11th to 20th	Night	17% 7% 30% 35% 11% 2	533
	21st to end	Night	13% 7% 31% 36% 13%	540
May	1st to 10th	Night	13% 7% 23% 38% 18% 1	540
	11th to 20th	Night	12% 6% 26% 33% 20% 2	531
	21st to end	Night	19% 6% 26% 29% 16% 5%	463
June	1st to 10th	Night	16% 9% 22% 30% 21% 2	360
	11th to 20th	Night	13% 11% 30% 34% 12%	360
	21st to end	Night	6% 5% 25% 40% 21% 3	360
July	1st to 10th	Night	4 5% 25% 46% 19% 1	350
	11th to 20th	Night	7% 5% 30% 45% 13% 1	348
	21st to end	Night	5% 3 22% 47% 22% 1	474
August	1st to 10th	Night	8% 3 25% 44% 19% 1	537
	11th to 20th	Night	9% 2 20% 44% 24% 1	534
	21st to end	Night	12% 4 21% 40% 22% 1	594
September	1st to 10th	Night	11% 4 26% 41% 16% 2	540
	11th to 20th	Night	11% 5% 26% 38% 19% 1	594
	21st to end	Night	9% 6% 28% 38% 16% 2	720
October	1st to 10th	Night	13% 5% 27% 34% 19% 1	720
	11th to 20th	Night	9% 8% 30% 36% 15% 2	720
	21st to end	Night	10% 12% 34% 34% 10% 1	859
November	1st to 10th	Night	14% 10% 35% 32% 9%	925
	11th to 20th	Night	7% 12% 40% 29% 10% 2	950
	21st to end	Night	8% 8% 38% 36% 10%	950
December	1st to 10th	Night	8% 9% 34% 33% 15% 2	950
	11th to 20th	Night	7% 10% 36% 33% 13% 2	950
	21st to end	Night	10% 7% 33% 36% 12% 2	1045

Page generated at 2024-03-03 05:28:57. Version ac07

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