Tularcitos Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tularcitos Observatory clear sky chart from 2005-11-06 to 2024-02-20.

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	6% 5% 2 4 4 2 4 4 5% 6% 59%	78556
	Night	6% 6% 2 5% 4 3 4 5% 5% 7% 53%	80667
Transparency	Day	23% 5% 9% 18% 24% 21%	78279
	Night	26% 6% 11% 17% 21% 20%	80466
Seeing	Day	9% 10% 25% 33% 19% 5%	14499
	Night	9% 5% 14% 30% 32% 10%	24073

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	11% 10% 4 7% 6% 3 5% 4 4 6% 42%	2763
	11th to 20th	Day	8% 8% 4 9% 8% 5% 6% 5% 5% 7% 36%	2860
	21st to end	Day	14% 11% 4 8% 6% 4 5% 5% 5% 8% 31%	3146
February	1st to 10th	Day	11% 9% 2 5% 5% 3 5% 4 4 6% 45%	1710
	11th to 20th	Day	9% 7% 3 6% 5% 3 5% 5% 5% 7% 45%	1798
	21st to end	Day	12% 9% 3 5% 5% 3 4 4 6% 5% 44%	1480
March	1st to 10th	Day	12% 9% 3 7% 7% 3 6% 6% 6% 8% 34%	1922
	11th to 20th	Day	11% 8% 2 6% 6% 4 6% 5% 7% 8% 37%	1980
	21st to end	Day	10% 7% 3 7% 4 3 5% 4 4 7% 45%	2226
April	1st to 10th	Day	10% 7% 5% 5% 4 3 4 5% 5% 8% 44%	2160
	11th to 20th	Day	7% 6% 2 4 5% 3 4 4 6% 7% 52%	2129
	21st to end	Day	6% 4 2 4 4 3 3 3 5% 7% 58%	2160
May	1st to 10th	Day	4 4 2 3 3 2 3 4 5% 8% 60%	2160
	11th to 20th	Day	4 3 2 3 3 2 4 4 5% 9% 63%	2298
	21st to end	Day	5% 4 2 4 4 2 4 4 5% 8% 58%	2723
June	1st to 10th	Day	3 3 1 3 3 2 4 3 5% 8% 64%	2520
	11th to 20th	Day	1 1 1 2 2 1 2 2 3 6% 79%	2520
	21st to end	Day	1 1 1 2 1 1 2 2 3 4 83%	2520
July	1st to 10th	Day	1 1 1 1 2 2 4 4 84%	2494
	11th to 20th	Day	1 1 2 1 1 2 3 4 5% 80%	2340
	21st to end	Day	1 1 1 1 2 3 4 6% 81%	2546
August	1st to 10th	Day	1 2 1 2 1 3 3 3 5% 80%	2328
	11th to 20th	Day	1 1 1 2 2 3 5% 84%	2127
	21st to end	Day	1 1 1 1 2 2 3 6% 83%	2376
September	1st to 10th	Day	1 1 1 1 1 2 2 2 3 86%	2160
	11th to 20th	Day	1 3 2 2 1 2 3 4 8% 73%	2160
	21st to end	Day	2 2 1 2 2 1 2 3 3 6% 77%	1931
October	1st to 10th	Day	3 3 1 3 3 2 3 3 5% 6% 69%	1800
	11th to 20th	Day	3 3 1 3 3 2 4 4 4 5% 68%	1800
	21st to end	Day	4 3 1 3 3 2 3 4 5% 6% 66%	1980
November	1st to 10th	Day	7% 4 2 4 5% 3 4 3 4 8% 56%	1834
	11th to 20th	Day	6% 4 2 5% 5% 3 4 4 6% 7% 55%	1710
	21st to end	Day	9% 5% 2 4 4 2 4 5% 5% 6% 55%	1653
December	1st to 10th	Day	6% 6% 2 6% 6% 3 5% 5% 6% 8% 45%	1520
	11th to 20th	Day	13% 11% 5% 9% 6% 3 5% 5% 7% 7% 31%	1928
	21st to end	Day	11% 9% 3 8% 6% 4 5% 6% 5% 7% 36%	2794
January	1st to 10th	Night	8% 13% 3 6% 6% 3 4 4 5% 6% 41%	4186
	11th to 20th	Night	9% 10% 3 8% 7% 5% 5% 6% 6% 8% 32%	4110
	21st to end	Night	12% 13% 4 8% 6% 4 5% 5% 5% 7% 31%	4521
February	1st to 10th	Night	10% 7% 3 6% 5% 3 5% 4 5% 7% 45%	2470
	11th to 20th	Night	9% 7% 3 6% 5% 3 5% 5% 6% 7% 43%	2251
	21st to end	Night	10% 8% 3 5% 6% 3 4 4 5% 7% 44%	1776
March	1st to 10th	Night	10% 9% 3 7% 6% 3 6% 6% 5% 6% 38%	2034
	11th to 20th	Night	8% 9% 3 6% 6% 3 5% 6% 6% 9% 40%	1980
	21st to end	Night	8% 6% 3 6% 6% 3 5% 6% 6% 7% 43%	2129
April	1st to 10th	Night	8% 6% 3 5% 6% 4 5% 5% 7% 8% 43%	1800
	11th to 20th	Night	7% 6% 3 5% 4 3 5% 4 4 6% 53%	1779
	21st to end	Night	4 5% 2 4 4 2 3 5% 7% 10% 53%	1800
May	1st to 10th	Night	2 5% 2 5% 5% 3 4 5% 5% 9% 57%	1800
	11th to 20th	Night	3 5% 2 3 5% 3 4 6% 6% 9% 54%	1586
	21st to end	Night	3 4 2 5% 3 3 5% 6% 7% 9% 53%	1552
June	1st to 10th	Night	2 3 2 4 3 3 4 5% 5% 9% 62%	1440
	11th to 20th	Night	2 1 3 2 2 3 3 4 7% 73%	1440
	21st to end	Night	1 1 1 2 2 3 3 6% 80%	1440
July	1st to 10th	Night	1 1 2 3 3 4 9% 78%	1461
	11th to 20th	Night	1 1 1 1 2 3 4 8% 78%	1620
	21st to end	Night	1 1 2 2 3 4 6% 9% 73%	1773
August	1st to 10th	Night	1 1 2 3 2 3 5% 5% 8% 70%	1611
	11th to 20th	Night	1 1 1 1 2 3 4 6% 80%	1775
	21st to end	Night	1 1 1 1 1 1 3 4 8% 78%	1980
September	1st to 10th	Night	1 2 2 1 3 2 2 5% 82%	1800
	11th to 20th	Night	2 2 1 2 2 2 2 4 5% 6% 72%	1800
	21st to end	Night	2 1 1 3 1 1 2 3 3 6% 76%	2024
October	1st to 10th	Night	3 3 1 2 3 2 4 4 4 6% 68%	2160
	11th to 20th	Night	3 4 2 4 4 3 3 3 4 6% 64%	2160
	21st to end	Night	4 2 1 3 3 2 4 3 4 8% 66%	2376
November	1st to 10th	Night	6% 5% 2 4 4 2 4 4 5% 8% 57%	2243
	11th to 20th	Night	6% 5% 3 4 4 3 4 4 6% 9% 53%	2470
	21st to end	Night	6% 5% 2 3 4 3 5% 4 5% 6% 56%	2522
December	1st to 10th	Night	8% 6% 3 5% 5% 3 4 5% 5% 7% 49%	2660
	11th to 20th	Night	12% 11% 4 8% 8% 4 5% 5% 5% 7% 31%	3276
	21st to end	Night	10% 8% 3 7% 8% 5% 7% 7% 7% 7% 32%	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	38% 8% 10% 28% 13% 3	2763
	11th to 20th	Day	42% 8% 12% 17% 12% 9%	2860
	21st to end	Day	47% 7% 10% 16% 14% 6%	3146
February	1st to 10th	Day	38% 4 8% 15% 21% 13%	1710
	11th to 20th	Day	36% 7% 8% 19% 21% 10%	1808
	21st to end	Day	40% 6% 8% 19% 19% 7%	1480
March	1st to 10th	Day	43% 7% 11% 17% 18% 5%	1922
	11th to 20th	Day	41% 6% 12% 17% 17% 6%	1980
	21st to end	Day	37% 7% 13% 21% 18% 5%	2226
April	1st to 10th	Day	37% 4 12% 22% 18% 7%	2160
	11th to 20th	Day	27% 6% 13% 25% 21% 8%	2132
	21st to end	Day	22% 6% 13% 29% 24% 6%	2160
May	1st to 10th	Day	19% 6% 13% 22% 31% 9%	2160
	11th to 20th	Day	16% 5% 12% 24% 31% 12%	2301
	21st to end	Day	19% 7% 17% 27% 24% 7%	2724
June	1st to 10th	Day	15% 6% 12% 23% 28% 15%	2520
	11th to 20th	Day	7% 3 10% 18% 33% 30%	2520
	21st to end	Day	7% 2 5% 12% 30% 44%	2520
July	1st to 10th	Day	3 2 5% 12% 25% 53%	2426
	11th to 20th	Day	7% 2 7% 10% 25% 48%	2271
	21st to end	Day	5% 2 5% 11% 29% 47%	2405
August	1st to 10th	Day	7% 2 6% 12% 25% 48%	2312
	11th to 20th	Day	4 2 4 11% 30% 48%	2127
	21st to end	Day	5% 1 4 12% 34% 44%	2376
September	1st to 10th	Day	5% 2 5% 7% 27% 53%	2160
	11th to 20th	Day	8% 3 7% 20% 34% 28%	2160
	21st to end	Day	11% 2 4 20% 39% 24%	1931
October	1st to 10th	Day	16% 4 8% 16% 28% 28%	1800
	11th to 20th	Day	17% 4 8% 21% 24% 26%	1800
	21st to end	Day	18% 3 10% 17% 27% 25%	1980
November	1st to 10th	Day	27% 3 10% 19% 24% 17%	1834
	11th to 20th	Day	25% 5% 12% 18% 25% 15%	1710
	21st to end	Day	30% 3 9% 16% 27% 16%	1653
December	1st to 10th	Day	34% 6% 12% 16% 18% 14%	1520
	11th to 20th	Day	53% 5% 8% 13% 15% 6%	1928
	21st to end	Day	45% 6% 11% 21% 12% 5%	2794
January	1st to 10th	Night	33% 9% 15% 24% 15% 4	4186
	11th to 20th	Night	43% 8% 13% 17% 10% 9%	4110
	21st to end	Night	45% 8% 12% 13% 14% 9%	4521
February	1st to 10th	Night	36% 5% 11% 14% 19% 15%	2470
	11th to 20th	Night	32% 6% 12% 18% 23% 9%	2252
	21st to end	Night	36% 5% 11% 22% 18% 8%	1776
March	1st to 10th	Night	42% 8% 14% 14% 16% 7%	2034
	11th to 20th	Night	36% 7% 11% 17% 19% 9%	1980
	21st to end	Night	31% 8% 16% 20% 17% 8%	2129
April	1st to 10th	Night	33% 6% 14% 22% 17% 9%	1800
	11th to 20th	Night	27% 5% 15% 23% 21% 10%	1779
	21st to end	Night	20% 7% 15% 26% 24% 8%	1800
May	1st to 10th	Night	17% 7% 14% 21% 27% 14%	1800
	11th to 20th	Night	18% 5% 16% 19% 29% 13%	1587
	21st to end	Night	17% 10% 18% 21% 25% 8%	1552
June	1st to 10th	Night	13% 6% 15% 23% 23% 20%	1440
	11th to 20th	Night	9% 5% 11% 15% 27% 34%	1440
	21st to end	Night	4 1 10% 12% 26% 48%	1440
July	1st to 10th	Night	2 2 7% 15% 23% 50%	1420
	11th to 20th	Night	5% 2 8% 13% 26% 47%	1566
	21st to end	Night	6% 2 8% 14% 25% 46%	1674
August	1st to 10th	Night	7% 2 8% 16% 22% 44%	1602
	11th to 20th	Night	5% 2 6% 11% 22% 55%	1775
	21st to end	Night	4 2 7% 13% 31% 42%	1980
September	1st to 10th	Night	5% 2 7% 8% 23% 55%	1800
	11th to 20th	Night	9% 2 7% 17% 28% 36%	1800
	21st to end	Night	9% 3 6% 15% 37% 29%	2024
October	1st to 10th	Night	15% 5% 8% 17% 23% 33%	2160
	11th to 20th	Night	19% 4 7% 17% 26% 27%	2160
	21st to end	Night	15% 4 8% 18% 27% 28%	2376
November	1st to 10th	Night	22% 4 11% 19% 24% 20%	2243
	11th to 20th	Night	25% 6% 12% 17% 24% 16%	2470
	21st to end	Night	26% 6% 10% 16% 25% 18%	2522
December	1st to 10th	Night	32% 6% 10% 17% 19% 16%	2660
	11th to 20th	Night	51% 5% 10% 14% 13% 7%	3276
	21st to end	Night	43% 9% 13% 17% 12% 5%	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	28% 16% 22% 20% 12% 2	313
	11th to 20th	Day	13% 15% 25% 29% 16% 2	370
	21st to end	Day	17% 13% 24% 26% 18% 2	407
February	1st to 10th	Day	19% 18% 22% 18% 18% 6%	370
	11th to 20th	Day	21% 13% 28% 26% 11% 1	431
	21st to end	Day	18% 15% 29% 26% 12% 1	346
March	1st to 10th	Day	23% 15% 29% 24% 8% 1	420
	11th to 20th	Day	21% 16% 26% 23% 11% 3	420
	21st to end	Day	19% 17% 33% 22% 8% 2	462
April	1st to 10th	Day	16% 15% 33% 22% 13% 1	420
	11th to 20th	Day	14% 18% 32% 26% 9% 1	412
	21st to end	Day	9% 16% 30% 28% 11% 5%	420
May	1st to 10th	Day	10% 11% 33% 30% 13% 3	423
	11th to 20th	Day	9% 14% 33% 27% 13% 4	448
	21st to end	Day	10% 11% 31% 28% 14% 6%	485
June	1st to 10th	Day	5% 7% 33% 31% 17% 7%	450
	11th to 20th	Day	3 9% 28% 38% 18% 5%	450
	21st to end	Day	1 4 25% 40% 24% 5%	450
July	1st to 10th	Day	1 22% 47% 22% 8%	446
	11th to 20th	Day	1 14% 47% 27% 10%	444
	21st to end	Day	15% 47% 25% 12%	487
August	1st to 10th	Day	1 2 25% 45% 19% 7%	447
	11th to 20th	Day	1 20% 44% 25% 10%	437
	21st to end	Day	1 17% 48% 25% 9%	495
September	1st to 10th	Day	1 4 18% 44% 26% 7%	450
	11th to 20th	Day	2 6% 27% 37% 21% 6%	450
	21st to end	Day	4 6% 17% 38% 28% 6%	450
October	1st to 10th	Day	3 7% 24% 36% 25% 5%	450
	11th to 20th	Day	4 8% 21% 30% 29% 8%	450
	21st to end	Day	7% 7% 23% 31% 25% 7%	495
November	1st to 10th	Day	9% 10% 19% 29% 28% 6%	430
	11th to 20th	Day	6% 9% 22% 31% 25% 8%	270
	21st to end	Day	11% 9% 21% 33% 22% 5%	243
December	1st to 10th	Day	12% 17% 21% 32% 14% 4	180
	11th to 20th	Day	14% 16% 19% 25% 19% 6%	180
	21st to end	Day	18% 20% 22% 23% 14% 5%	198
January	1st to 10th	Night	16% 6% 17% 31% 22% 8%	760
	11th to 20th	Night	13% 7% 15% 31% 27% 7%	760
	21st to end	Night	17% 7% 14% 34% 23% 5%	836
February	1st to 10th	Night	17% 8% 16% 30% 24% 6%	760
	11th to 20th	Night	15% 9% 15% 31% 23% 6%	742
	21st to end	Night	17% 8% 19% 33% 19% 3	592
March	1st to 10th	Night	18% 9% 18% 30% 21% 4	720
	11th to 20th	Night	13% 8% 18% 31% 23% 6%	720
	21st to end	Night	13% 9% 22% 31% 22% 4	792
April	1st to 10th	Night	12% 7% 21% 33% 24% 3	720
	11th to 20th	Night	11% 11% 21% 29% 22% 7%	711
	21st to end	Night	6% 8% 24% 29% 24% 9%	720
May	1st to 10th	Night	5% 8% 19% 35% 27% 7%	720
	11th to 20th	Night	6% 5% 18% 33% 30% 8%	524
	21st to end	Night	6% 5% 18% 30% 33% 8%	389
June	1st to 10th	Night	3 5% 18% 34% 32% 9%	360
	11th to 20th	Night	2 3 15% 36% 37% 7%	360
	21st to end	Night	3 8% 34% 45% 10%	360
July	1st to 10th	Night	7% 27% 51% 15%	370
	11th to 20th	Night	1 2 16% 56% 25%	522
	21st to end	Night	1 1 17% 57% 25%	591
August	1st to 10th	Night	1 1 6% 27% 51% 15%	537
	11th to 20th	Night	1 1 4 32% 48% 15%	707
	21st to end	Night	1 4 22% 56% 17%	792
September	1st to 10th	Night	1 1 5% 27% 51% 15%	720
	11th to 20th	Night	2 2 9% 33% 43% 11%	720
	21st to end	Night	4 2 8% 23% 48% 15%	720
October	1st to 10th	Night	5% 3 9% 33% 38% 12%	720
	11th to 20th	Night	5% 4 10% 31% 36% 14%	720
	21st to end	Night	5% 3 9% 33% 33% 16%	792
November	1st to 10th	Night	9% 4 13% 33% 30% 11%	740
	11th to 20th	Night	10% 4 14% 32% 32% 8%	760
	21st to end	Night	9% 4 16% 38% 25% 8%	760
December	1st to 10th	Night	13% 8% 17% 31% 25% 6%	760
	11th to 20th	Night	20% 6% 16% 30% 23% 5%	760
	21st to end	Night	19% 12% 17% 29% 19% 5%	836

Page generated at 2024-02-17 03:28:40. Version ac07

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