Lookout Ranch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lookout Ranch clear sky chart from 2005-11-06 to 2024-02-15.

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% 6% 2 4 3 2 3 3 4 7% 52%	78481
	Night	14% 7% 2 4 4 2 4 4 4 6% 47%	80636
Transparency	Day	32% 4 7% 20% 22% 14%	78204
	Night	37% 5% 8% 18% 20% 14%	80436
Seeing	Day	15% 12% 27% 26% 15% 4	14352
	Night	16% 8% 16% 29% 24% 7%	23687

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	24% 12% 3 6% 4 2 3 4 4 5% 32%	2772
	11th to 20th	Day	29% 12% 4 6% 5% 3 3 3 3 5% 27%	2860
	21st to end	Day	27% 11% 3 6% 5% 3 4 4 4 6% 27%	3146
February	1st to 10th	Day	20% 9% 3 5% 5% 2 4 3 4 5% 40%	1710
	11th to 20th	Day	17% 8% 3 5% 4 2 4 6% 5% 7% 38%	1612
	21st to end	Day	21% 9% 3 5% 4 1 3 3 4 7% 39%	1499
March	1st to 10th	Day	23% 12% 3 6% 5% 3 4 5% 3 6% 31%	1980
	11th to 20th	Day	23% 8% 4 5% 5% 3 5% 4 5% 7% 33%	1980
	21st to end	Day	18% 8% 3 5% 4 3 5% 4 5% 7% 36%	2178
April	1st to 10th	Day	18% 9% 4 5% 5% 3 5% 4 5% 7% 35%	2132
	11th to 20th	Day	14% 7% 3 5% 5% 2 3 3 5% 7% 44%	2129
	21st to end	Day	10% 6% 3 4 3 2 4 5% 5% 10% 49%	2202
May	1st to 10th	Day	9% 5% 2 3 3 3 2 4 5% 8% 56%	2340
	11th to 20th	Day	10% 5% 2 4 3 2 4 4 5% 8% 54%	2300
	21st to end	Day	9% 6% 2 5% 4 2 3 3 4 8% 54%	2715
June	1st to 10th	Day	8% 5% 3 4 4 2 3 5% 4 8% 53%	2520
	11th to 20th	Day	3 3 1 2 3 1 2 3 3 8% 71%	2520
	21st to end	Day	4 2 1 2 2 1 2 2 3 6% 75%	2520
July	1st to 10th	Day	2 2 1 2 2 1 2 2 3 5% 78%	2481
	11th to 20th	Day	1 1 1 2 2 2 2 2 3 6% 78%	2340
	21st to end	Day	1 1 1 2 2 2 3 3 2 6% 79%	2546
August	1st to 10th	Day	2 2 1 2 2 2 2 3 4 5% 75%	2328
	11th to 20th	Day	1 1 1 2 1 2 2 2 3 6% 80%	2290
	21st to end	Day	1 2 1 3 2 1 2 3 3 7% 75%	2376
September	1st to 10th	Day	1 2 1 2 1 2 2 3 6% 79%	2160
	11th to 20th	Day	5% 3 2 3 3 1 3 3 5% 8% 66%	2087
	21st to end	Day	4 3 1 2 2 1 2 3 4 7% 73%	1933
October	1st to 10th	Day	8% 3 1 2 3 2 2 3 3 6% 66%	1800
	11th to 20th	Day	10% 5% 1 4 3 3 3 3 4 6% 59%	1800
	21st to end	Day	11% 5% 2 3 3 2 3 3 5% 8% 54%	1980
November	1st to 10th	Day	13% 6% 2 5% 4 3 4 4 5% 8% 45%	1859
	11th to 20th	Day	16% 7% 2 6% 4 2 4 4 5% 7% 42%	1624
	21st to end	Day	12% 5% 2 5% 5% 3 5% 5% 4 7% 46%	1520
December	1st to 10th	Day	20% 9% 2 4 4 3 4 4 4 7% 39%	1520
	11th to 20th	Day	33% 8% 4 6% 5% 3 4 4 4 5% 24%	1928
	21st to end	Day	27% 10% 4 6% 5% 3 3 4 5% 7% 27%	2794
January	1st to 10th	Night	21% 10% 3 5% 5% 3 5% 5% 5% 7% 31%	4176
	11th to 20th	Night	25% 15% 4 8% 6% 3 4 3 4 5% 25%	4110
	21st to end	Night	30% 15% 4 5% 5% 3 4 3 4 5% 24%	4521
February	1st to 10th	Night	19% 8% 2 5% 4 3 4 4 5% 6% 41%	2470
	11th to 20th	Night	17% 9% 3 6% 5% 3 5% 5% 6% 6% 35%	2329
	21st to end	Night	17% 8% 2 4 5% 2 3 4 4 7% 43%	1754
March	1st to 10th	Night	22% 12% 4 6% 4 3 5% 3 5% 5% 31%	1980
	11th to 20th	Night	22% 8% 3 6% 4 3 4 3 4 7% 36%	1980
	21st to end	Night	18% 9% 3 5% 3 3 4 4 4 6% 41%	2178
April	1st to 10th	Night	14% 10% 4 7% 5% 3 5% 4 5% 8% 37%	1828
	11th to 20th	Night	12% 8% 3 5% 4 2 4 3 5% 8% 45%	1779
	21st to end	Night	8% 6% 1 4 3 3 4 3 5% 8% 54%	1756
May	1st to 10th	Night	7% 6% 2 4 2 2 3 4 5% 9% 57%	1620
	11th to 20th	Night	5% 6% 4 6% 5% 3 4 5% 5% 9% 50%	1593
	21st to end	Night	6% 7% 2 5% 5% 3 5% 5% 5% 8% 51%	1556
June	1st to 10th	Night	6% 7% 2 5% 5% 3 4 4 6% 8% 52%	1440
	11th to 20th	Night	3 2 1 2 2 1 2 2 5% 6% 72%	1440
	21st to end	Night	3 2 2 2 3 1 2 3 4 5% 73%	1440
July	1st to 10th	Night	1 2 1 2 1 2 3 4 6% 77%	1475
	11th to 20th	Night	1 1 2 2 1 3 3 2 5% 80%	1620
	21st to end	Night	1 1 1 2 2 2 3 3 4 7% 75%	1773
August	1st to 10th	Night	1 2 2 2 3 2 3 3 4 6% 72%	1611
	11th to 20th	Night	1 1 1 2 2 1 3 3 3 6% 76%	1608
	21st to end	Night	1 4 1 2 3 1 2 2 3 5% 76%	1980
September	1st to 10th	Night	1 2 1 1 2 1 1 2 3 6% 78%	1800
	11th to 20th	Night	5% 4 1 3 3 2 4 4 5% 8% 61%	1870
	21st to end	Night	4 3 1 3 3 2 3 3 3 6% 70%	2025
October	1st to 10th	Night	6% 5% 1 3 3 2 3 3 3 4 68%	2160
	11th to 20th	Night	8% 5% 2 3 3 2 4 4 5% 6% 58%	2160
	21st to end	Night	11% 4 2 3 3 2 3 4 6% 7% 54%	2376
November	1st to 10th	Night	14% 6% 3 5% 4 3 5% 5% 7% 7% 43%	2220
	11th to 20th	Night	15% 7% 3 5% 5% 4 5% 6% 5% 7% 38%	2550
	21st to end	Night	14% 6% 2 5% 4 3 3 4 5% 6% 48%	2660
December	1st to 10th	Night	21% 8% 3 4 5% 2 3 4 5% 7% 39%	2660
	11th to 20th	Night	32% 10% 3 6% 5% 2 4 3 4 7% 26%	3276
	21st to end	Night	26% 11% 4 6% 5% 3 3 4 4 5% 30%	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	53% 6% 13% 18% 7% 3	2772
	11th to 20th	Day	63% 3 9% 9% 9% 8%	2860
	21st to end	Day	57% 5% 7% 14% 12% 5%	3146
February	1st to 10th	Day	48% 3 7% 16% 18% 8%	1710
	11th to 20th	Day	44% 4 8% 20% 19% 5%	1621
	21st to end	Day	46% 5% 10% 21% 14% 4	1499
March	1st to 10th	Day	55% 4 10% 14% 15% 2	1980
	11th to 20th	Day	51% 5% 8% 18% 15% 4	1980
	21st to end	Day	47% 6% 10% 19% 15% 3	2178
April	1st to 10th	Day	46% 6% 11% 23% 11% 2	2132
	11th to 20th	Day	39% 5% 13% 22% 16% 4	2132
	21st to end	Day	31% 5% 13% 28% 19% 4	2202
May	1st to 10th	Day	26% 4 10% 31% 22% 6%	2340
	11th to 20th	Day	28% 5% 9% 30% 21% 7%	2303
	21st to end	Day	29% 5% 10% 37% 17% 2	2716
June	1st to 10th	Day	29% 5% 9% 27% 25% 5%	2520
	11th to 20th	Day	13% 4 8% 23% 37% 14%	2520
	21st to end	Day	13% 3 3 18% 37% 26%	2520
July	1st to 10th	Day	10% 4 2 13% 35% 35%	2414
	11th to 20th	Day	10% 2 4 14% 31% 39%	2271
	21st to end	Day	9% 3 1 10% 34% 43%	2405
August	1st to 10th	Day	11% 4 3 21% 32% 29%	2312
	11th to 20th	Day	8% 3 2 17% 38% 32%	2290
	21st to end	Day	10% 4 4 18% 38% 27%	2376
September	1st to 10th	Day	9% 3 2 14% 32% 41%	2160
	11th to 20th	Day	18% 3 5% 28% 34% 12%	2087
	21st to end	Day	14% 3 5% 24% 31% 24%	1933
October	1st to 10th	Day	22% 3 3 25% 27% 21%	1800
	11th to 20th	Day	27% 4 6% 20% 26% 18%	1800
	21st to end	Day	29% 4 8% 22% 20% 16%	1980
November	1st to 10th	Day	36% 5% 7% 26% 16% 10%	1859
	11th to 20th	Day	41% 4 11% 20% 15% 8%	1624
	21st to end	Day	37% 6% 10% 17% 20% 10%	1520
December	1st to 10th	Day	45% 5% 7% 17% 16% 11%	1520
	11th to 20th	Day	62% 4 6% 13% 12% 4	1928
	21st to end	Day	55% 6% 8% 18% 9% 3	2794
January	1st to 10th	Night	51% 7% 18% 12% 9% 3	4176
	11th to 20th	Night	63% 4 7% 11% 7% 8%	4110
	21st to end	Night	63% 4 6% 10% 11% 6%	4521
February	1st to 10th	Night	43% 5% 8% 18% 18% 9%	2470
	11th to 20th	Night	47% 6% 5% 19% 18% 5%	2331
	21st to end	Night	41% 5% 11% 22% 17% 4	1754
March	1st to 10th	Night	54% 6% 8% 13% 16% 2	1980
	11th to 20th	Night	49% 4 8% 19% 16% 4	1980
	21st to end	Night	43% 6% 13% 20% 14% 3	2178
April	1st to 10th	Night	45% 6% 12% 21% 13% 3	1828
	11th to 20th	Night	36% 6% 12% 24% 17% 5%	1779
	21st to end	Night	29% 4 12% 31% 19% 5%	1756
May	1st to 10th	Night	25% 6% 7% 27% 29% 7%	1620
	11th to 20th	Night	28% 7% 8% 29% 20% 8%	1594
	21st to end	Night	29% 7% 11% 32% 19% 3	1556
June	1st to 10th	Night	29% 6% 8% 25% 24% 8%	1440
	11th to 20th	Night	13% 4 9% 22% 38% 14%	1440
	21st to end	Night	14% 4 4 14% 33% 31%	1440
July	1st to 10th	Night	8% 4 1 10% 36% 40%	1434
	11th to 20th	Night	8% 3 3 11% 30% 44%	1566
	21st to end	Night	9% 4 1 8% 29% 49%	1674
August	1st to 10th	Night	11% 5% 2 15% 34% 32%	1602
	11th to 20th	Night	10% 4 2 14% 31% 39%	1608
	21st to end	Night	13% 3 3 14% 33% 35%	1980
September	1st to 10th	Night	8% 3 1 13% 31% 44%	1800
	11th to 20th	Night	18% 6% 5% 18% 37% 15%	1870
	21st to end	Night	17% 4 4 20% 26% 30%	2025
October	1st to 10th	Night	21% 3 5% 20% 25% 25%	2160
	11th to 20th	Night	25% 5% 4 19% 28% 20%	2160
	21st to end	Night	28% 4 6% 22% 22% 18%	2376
November	1st to 10th	Night	38% 7% 10% 18% 17% 11%	2220
	11th to 20th	Night	42% 7% 10% 18% 15% 7%	2550
	21st to end	Night	36% 4 9% 19% 20% 11%	2660
December	1st to 10th	Night	45% 4 8% 18% 16% 10%	2660
	11th to 20th	Night	59% 4 6% 14% 13% 4	3276
	21st to end	Night	57% 5% 9% 18% 9% 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	40% 15% 19% 15% 10% 1	322
	11th to 20th	Day	30% 13% 25% 18% 13% 3	370
	21st to end	Day	25% 13% 23% 22% 14% 3	407
February	1st to 10th	Day	26% 14% 24% 21% 12% 3	370
	11th to 20th	Day	24% 20% 23% 20% 11% 1	348
	21st to end	Day	26% 20% 24% 18% 10% 2	337
March	1st to 10th	Day	34% 18% 22% 19% 6% 1	420
	11th to 20th	Day	32% 14% 27% 18% 8% 1	420
	21st to end	Day	23% 24% 29% 16% 7% 2	462
April	1st to 10th	Day	25% 16% 33% 17% 7% 2	420
	11th to 20th	Day	23% 20% 29% 19% 8% 2	412
	21st to end	Day	15% 24% 34% 16% 9% 3	420
May	1st to 10th	Day	15% 16% 35% 21% 11% 3	423
	11th to 20th	Day	21% 14% 33% 21% 9% 2	448
	21st to end	Day	14% 15% 31% 26% 10% 3	485
June	1st to 10th	Day	10% 15% 35% 28% 10% 2	450
	11th to 20th	Day	9% 16% 35% 28% 10% 2	450
	21st to end	Day	2 8% 34% 36% 16% 4	450
July	1st to 10th	Day	4 6% 33% 39% 15% 3	446
	11th to 20th	Day	1 3 35% 36% 20% 5%	444
	21st to end	Day	2 23% 47% 21% 6%	487
August	1st to 10th	Day	4 3 35% 36% 17% 4	447
	11th to 20th	Day	2 4 29% 36% 24% 5%	437
	21st to end	Day	4 5% 25% 37% 23% 6%	495
September	1st to 10th	Day	4 6% 29% 35% 20% 6%	450
	11th to 20th	Day	6% 9% 25% 37% 19% 4	450
	21st to end	Day	5% 11% 28% 26% 22% 7%	450
October	1st to 10th	Day	7% 11% 25% 29% 20% 7%	450
	11th to 20th	Day	12% 9% 19% 27% 25% 8%	450
	21st to end	Day	15% 9% 23% 28% 19% 6%	495
November	1st to 10th	Day	16% 13% 21% 24% 22% 4	455
	11th to 20th	Day	17% 9% 17% 26% 24% 8%	244
	21st to end	Day	15% 12% 24% 23% 18% 8%	180
December	1st to 10th	Day	31% 10% 23% 14% 13% 9%	180
	11th to 20th	Day	30% 13% 21% 17% 12% 7%	180
	21st to end	Day	31% 14% 19% 20% 13% 4	198
January	1st to 10th	Night	29% 9% 13% 27% 18% 5%	760
	11th to 20th	Night	25% 7% 17% 28% 17% 6%	760
	21st to end	Night	25% 9% 10% 28% 22% 5%	836
February	1st to 10th	Night	24% 9% 15% 29% 20% 3	760
	11th to 20th	Night	23% 12% 17% 25% 18% 6%	722
	21st to end	Night	23% 13% 19% 28% 15% 3	592
March	1st to 10th	Night	29% 11% 15% 26% 15% 4	720
	11th to 20th	Night	28% 8% 15% 28% 19% 3	720
	21st to end	Night	25% 10% 21% 27% 14% 3	792
April	1st to 10th	Night	20% 15% 21% 24% 16% 4	720
	11th to 20th	Night	16% 15% 23% 24% 16% 6%	711
	21st to end	Night	15% 15% 25% 23% 18% 4	676
May	1st to 10th	Night	13% 9% 24% 29% 19% 6%	540
	11th to 20th	Night	10% 8% 25% 31% 21% 6%	531
	21st to end	Night	12% 15% 22% 30% 17% 4	393
June	1st to 10th	Night	10% 11% 26% 31% 19% 3	360
	11th to 20th	Night	6% 11% 27% 38% 17% 2	360
	21st to end	Night	3 2 24% 42% 26% 2	360
July	1st to 10th	Night	4 4 21% 34% 29% 8%	384
	11th to 20th	Night	2 1 19% 34% 34% 10%	522
	21st to end	Night	3 1 15% 30% 38% 14%	591
August	1st to 10th	Night	2 1 17% 36% 35% 9%	537
	11th to 20th	Night	3 2 13% 32% 39% 11%	540
	21st to end	Night	5% 2 13% 32% 38% 10%	792
September	1st to 10th	Night	3 4 13% 33% 35% 13%	720
	11th to 20th	Night	8% 6% 13% 32% 32% 9%	720
	21st to end	Night	7% 6% 15% 27% 32% 12%	720
October	1st to 10th	Night	8% 8% 12% 33% 30% 9%	720
	11th to 20th	Night	12% 4 10% 30% 33% 11%	720
	21st to end	Night	14% 6% 12% 28% 29% 11%	792
November	1st to 10th	Night	16% 9% 11% 27% 28% 8%	740
	11th to 20th	Night	19% 8% 13% 32% 24% 5%	760
	21st to end	Night	15% 11% 13% 31% 23% 6%	760
December	1st to 10th	Night	25% 8% 13% 28% 19% 7%	760
	11th to 20th	Night	30% 9% 15% 27% 15% 5%	760
	21st to end	Night	31% 11% 15% 24% 15% 4	836

Page generated at 2024-02-12 03:35:31. Version ac07

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