Mount Pinos
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mount Pinos clear sky chart from 2005-11-06 to 2024-11-06.

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	2 4 1 3 3 3 3 3 4 6% 69%	104837
	Night	2 4 2 4 3 3 3 3 4 5% 66%	102997
Transparency	Day	15% 3 5% 16% 28% 32%	104594
	Night	16% 3 6% 16% 28% 30%	102830
Seeing	Day	8% 11% 28% 33% 15% 5%	15546
	Night	6% 7% 18% 34% 29% 7%	25248

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	3 6% 3 5% 4 4 4 3 5% 7% 56%	2541
	11th to 20th	Day	4 6% 2 7% 4 4 4 4 6% 11% 49%	2860
	21st to end	Day	5% 9% 3 9% 5% 3 4 5% 6% 8% 43%	3215
February	1st to 10th	Day	4 8% 2 5% 4 3 4 4 5% 6% 54%	1900
	11th to 20th	Day	4 7% 3 6% 4 4 3 3 6% 8% 52%	1850
	21st to end	Day	4 7% 3 7% 5% 4 4 3 4 6% 53%	1570
March	1st to 10th	Day	3 9% 2 7% 6% 5% 6% 4 5% 7% 46%	3138
	11th to 20th	Day	2 6% 2 5% 3 3 4 3 5% 8% 59%	3380
	21st to end	Day	3 9% 2 5% 5% 5% 5% 5% 8% 8% 44%	4124
April	1st to 10th	Day	4 8% 2 5% 4 3 4 3 5% 7% 54%	2280
	11th to 20th	Day	3 4 2 5% 3 3 3 3 5% 6% 64%	2249
	21st to end	Day	3 3 1 3 3 2 3 3 5% 7% 66%	2280
May	1st to 10th	Day	2 2 1 2 2 2 2 2 4 4 76%	3817
	11th to 20th	Day	1 2 1 2 2 2 2 3 4 6% 76%	4071
	21st to end	Day	2 2 1 2 2 1 2 2 2 4 80%	4507
June	1st to 10th	Day	1 2 1 3 2 2 3 3 5% 7% 71%	2660
	11th to 20th	Day	1 1 1 1 1 2 3 4 85%	2660
	21st to end	Day	1 1 1 1 1 1 3 5% 84%	2660
July	1st to 10th	Day	1 1 1 1 1 1 2 3 88%	4420
	11th to 20th	Day	2 1 1 3 2 2 3 2 4 6% 75%	4360
	21st to end	Day	1 1 1 1 1 2 2 4 5% 80%	4334
August	1st to 10th	Day	1 1 2 1 1 2 2 3 5% 82%	3783
	11th to 20th	Day	1 1 1 1 1 1 2 3 90%	3724
	21st to end	Day	1 1 1 1 1 1 2 3 88%	4180
September	1st to 10th	Day	1 1 1 2 2 2 2 2 3 5% 81%	2280
	11th to 20th	Day	1 1 2 1 2 1 2 4 85%	2195
	21st to end	Day	1 1 1 2 2 2 2 3 4 81%	2090
October	1st to 10th	Day	1 2 1 2 2 2 3 2 3 4 77%	3428
	11th to 20th	Day	1 1 2 2 2 3 2 3 4 80%	3161
	21st to end	Day	1 2 2 5% 3 3 4 3 4 6% 70%	3448
November	1st to 10th	Day	2 4 1 4 4 3 3 3 5% 6% 66%	1733
	11th to 20th	Day	2 4 1 4 3 3 4 4 6% 6% 65%	1710
	21st to end	Day	3 6% 3 5% 4 5% 4 3 5% 6% 57%	1710
December	1st to 10th	Day	3 5% 2 6% 5% 4 5% 5% 5% 5% 55%	1710
	11th to 20th	Day	5% 7% 3 7% 6% 5% 6% 4 8% 7% 42%	2015
	21st to end	Day	5% 10% 4 7% 5% 6% 5% 5% 5% 6% 41%	2794
January	1st to 10th	Night	3 7% 3 8% 5% 4 4 3 5% 6% 51%	4401
	11th to 20th	Night	2 6% 2 7% 6% 5% 5% 5% 7% 8% 48%	4110
	21st to end	Night	5% 11% 3 7% 5% 4 4 4 6% 7% 44%	4450
February	1st to 10th	Night	3 9% 3 7% 5% 4 3 3 5% 7% 52%	2280
	11th to 20th	Night	4 7% 2 5% 4 3 4 3 5% 7% 56%	2218
	21st to end	Night	3 7% 2 7% 5% 4 5% 4 5% 6% 52%	1884
March	1st to 10th	Night	2 8% 2 8% 5% 5% 5% 5% 7% 10% 43%	3736
	11th to 20th	Night	2 5% 1 7% 5% 4 4 4 4 7% 57%	3597
	21st to end	Night	3 9% 3 10% 5% 5% 5% 4 5% 6% 43%	3528
April	1st to 10th	Night	3 7% 3 5% 5% 3 4 3 6% 7% 53%	1900
	11th to 20th	Night	3 6% 2 4 4 3 3 3 4 7% 63%	1879
	21st to end	Night	2 5% 1 4 3 2 3 3 4 7% 65%	1900
May	1st to 10th	Night	2 2 1 2 3 2 2 2 3 4 77%	3162
	11th to 20th	Night	1 2 1 2 1 1 2 2 3 4 80%	2834
	21st to end	Night	1 2 1 2 1 1 1 2 2 3 84%	3060
June	1st to 10th	Night	1 2 1 2 2 2 3 3 5% 5% 74%	1520
	11th to 20th	Night	1 1 1 1 1 1 3 4 87%	1520
	21st to end	Night	1 1 1 1 1 2 3 89%	1520
July	1st to 10th	Night	1 1 1 1 1 2 2 90%	2540
	11th to 20th	Night	1 1 1 1 1 2 1 3 3 86%	2597
	21st to end	Night	1 1 1 1 1 1 1 2 3 88%	3229
August	1st to 10th	Night	1 1 1 1 1 1 2 1 3 4 85%	3166
	11th to 20th	Night	1 1 1 1 1 1 2 92%	3126
	21st to end	Night	1 1 1 1 1 1 1 2 92%	3498
September	1st to 10th	Night	1 1 1 2 1 1 1 1 2 3 87%	1900
	11th to 20th	Night	1 1 1 2 1 3 3 86%	1983
	21st to end	Night	1 1 2 2 2 2 3 4 83%	2090
October	1st to 10th	Night	1 1 1 1 2 2 2 2 3 84%	3547
	11th to 20th	Night	1 1 1 2 1 2 2 3 5% 5% 77%	3777
	21st to end	Night	1 2 3 5% 2 2 2 2 3 5% 73%	4121
November	1st to 10th	Night	1 5% 2 4 3 3 3 4 6% 7% 63%	2467
	11th to 20th	Night	3 4 1 5% 2 4 4 3 5% 7% 63%	2470
	21st to end	Night	3 6% 2 5% 5% 4 4 4 6% 7% 55%	2470
December	1st to 10th	Night	3 6% 2 6% 4 4 4 4 5% 8% 54%	2470
	11th to 20th	Night	5% 7% 2 7% 7% 6% 6% 6% 7% 8% 39%	3185
	21st to end	Night	5% 8% 3 8% 6% 6% 6% 4 6% 7% 40%	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	20% 5% 6% 28% 32% 9%	2541
	11th to 20th	Day	24% 7% 15% 17% 26% 11%	2860
	21st to end	Day	32% 5% 10% 21% 22% 10%	3215
February	1st to 10th	Day	28% 3 5% 18% 25% 20%	1900
	11th to 20th	Day	25% 4 6% 21% 28% 17%	1860
	21st to end	Day	29% 5% 6% 21% 27% 12%	1570
March	1st to 10th	Day	30% 7% 8% 22% 21% 12%	3138
	11th to 20th	Day	20% 5% 11% 31% 21% 13%	3380
	21st to end	Day	27% 9% 11% 26% 22% 6%	4124
April	1st to 10th	Day	24% 5% 9% 24% 26% 12%	2280
	11th to 20th	Day	19% 4 9% 24% 30% 14%	2252
	21st to end	Day	14% 5% 9% 26% 36% 10%	2280
May	1st to 10th	Day	11% 3 6% 18% 38% 23%	3817
	11th to 20th	Day	9% 3 5% 19% 38% 26%	4074
	21st to end	Day	10% 2 4 21% 39% 23%	4507
June	1st to 10th	Day	13% 3 6% 20% 33% 25%	2660
	11th to 20th	Day	5% 2 5% 14% 33% 41%	2660
	21st to end	Day	6% 2 3 7% 29% 54%	2660
July	1st to 10th	Day	4 1 2 4 13% 77%	4351
	11th to 20th	Day	11% 3 3 10% 20% 53%	4285
	21st to end	Day	7% 2 5% 17% 25% 43%	4198
August	1st to 10th	Day	7% 2 3 9% 30% 49%	3770
	11th to 20th	Day	4 1 1 6% 24% 65%	3760
	21st to end	Day	6% 1 1 4 26% 62%	4179
September	1st to 10th	Day	7% 3 4 8% 30% 49%	2280
	11th to 20th	Day	5% 2 2 10% 35% 45%	2195
	21st to end	Day	8% 2 2 10% 39% 38%	2090
October	1st to 10th	Day	10% 3 3 9% 24% 52%	3428
	11th to 20th	Day	9% 1 3 9% 41% 36%	3161
	21st to end	Day	15% 3 3 10% 35% 35%	3448
November	1st to 10th	Day	16% 3 4 20% 32% 25%	1733
	11th to 20th	Day	17% 3 7% 17% 28% 27%	1710
	21st to end	Day	25% 4 7% 14% 24% 26%	1710
December	1st to 10th	Day	26% 5% 6% 17% 26% 20%	1710
	11th to 20th	Day	36% 6% 8% 19% 18% 12%	2014
	21st to end	Day	37% 5% 6% 17% 22% 12%	2794
January	1st to 10th	Night	23% 4 6% 22% 34% 12%	4401
	11th to 20th	Night	25% 7% 10% 20% 28% 11%	4110
	21st to end	Night	31% 4 9% 20% 23% 13%	4450
February	1st to 10th	Night	27% 5% 6% 15% 23% 22%	2280
	11th to 20th	Night	24% 4 7% 19% 29% 18%	2219
	21st to end	Night	27% 6% 7% 19% 26% 15%	1884
March	1st to 10th	Night	25% 7% 11% 22% 23% 12%	3736
	11th to 20th	Night	18% 4 10% 34% 21% 13%	3597
	21st to end	Night	23% 5% 14% 26% 27% 5%	3528
April	1st to 10th	Night	24% 3 12% 24% 24% 13%	1900
	11th to 20th	Night	17% 3 9% 23% 31% 16%	1879
	21st to end	Night	13% 3 9% 28% 36% 11%	1900
May	1st to 10th	Night	9% 2 8% 17% 35% 29%	3162
	11th to 20th	Night	9% 2 4 18% 42% 26%	2835
	21st to end	Night	7% 2 6% 21% 43% 22%	3060
June	1st to 10th	Night	10% 2 8% 21% 35% 23%	1520
	11th to 20th	Night	5% 1 5% 15% 32% 42%	1520
	21st to end	Night	4 1 2 7% 29% 57%	1520
July	1st to 10th	Night	4 1 2 4 14% 76%	2500
	11th to 20th	Night	6% 2 2 9% 18% 63%	2549
	21st to end	Night	5% 2 3 17% 26% 47%	3128
August	1st to 10th	Night	6% 2 1 10% 35% 46%	3156
	11th to 20th	Night	3 1 1 6% 28% 62%	3156
	21st to end	Night	4 1 1 6% 29% 60%	3498
September	1st to 10th	Night	6% 2 2 8% 29% 53%	1900
	11th to 20th	Night	4 2 3 10% 37% 43%	1983
	21st to end	Night	6% 2 2 13% 38% 40%	2090
October	1st to 10th	Night	7% 1 2 10% 21% 59%	3547
	11th to 20th	Night	8% 1 2 11% 32% 45%	3777
	21st to end	Night	11% 5% 3 8% 33% 41%	4121
November	1st to 10th	Night	16% 3 5% 18% 33% 25%	2467
	11th to 20th	Night	17% 4 7% 14% 28% 31%	2470
	21st to end	Night	23% 4 7% 15% 24% 27%	2470
December	1st to 10th	Night	25% 5% 6% 14% 26% 23%	2470
	11th to 20th	Night	40% 5% 8% 15% 19% 14%	3185
	21st to end	Night	33% 7% 5% 18% 23% 13%	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	19% 19% 30% 22% 8% 1	182
	11th to 20th	Day	18% 18% 30% 26% 7% 1	370
	21st to end	Day	17% 22% 32% 18% 8% 2	428
February	1st to 10th	Day	15% 17% 35% 23% 8% 3	460
	11th to 20th	Day	19% 18% 31% 23% 8% 2	455
	21st to end	Day	17% 20% 34% 23% 6% 1	382
March	1st to 10th	Day	16% 23% 33% 22% 5% 1	460
	11th to 20th	Day	16% 20% 31% 25% 7% 1	460
	21st to end	Day	16% 22% 33% 23% 6%	506
April	1st to 10th	Day	15% 14% 33% 25% 12% 1	460
	11th to 20th	Day	14% 16% 32% 26% 10% 1	452
	21st to end	Day	8% 15% 30% 27% 14% 5%	460
May	1st to 10th	Day	12% 14% 33% 26% 13% 2	463
	11th to 20th	Day	7% 11% 31% 31% 14% 5%	488
	21st to end	Day	10% 9% 27% 33% 15% 6%	529
June	1st to 10th	Day	4 8% 26% 33% 22% 7%	490
	11th to 20th	Day	2 7% 26% 38% 20% 7%	490
	21st to end	Day	2 5% 27% 37% 19% 10%	490
July	1st to 10th	Day	2 1 16% 45% 25% 12%	486
	11th to 20th	Day	4 1 12% 42% 26% 16%	484
	21st to end	Day	2 2 12% 42% 27% 14%	531
August	1st to 10th	Day	2 1 21% 43% 22% 12%	487
	11th to 20th	Day	2 3 17% 41% 29% 8%	477
	21st to end	Day	2 2 16% 49% 22% 9%	539
September	1st to 10th	Day	1 4 24% 43% 21% 6%	490
	11th to 20th	Day	1 8% 31% 43% 16% 2	490
	21st to end	Day	1 9% 29% 41% 17% 4	490
October	1st to 10th	Day	4 9% 31% 37% 18% 2	490
	11th to 20th	Day	4 9% 36% 34% 14% 3	490
	21st to end	Day	6% 12% 30% 35% 14% 3	539
November	1st to 10th	Day	8% 11% 29% 30% 19% 3	299
	11th to 20th	Day	8% 11% 29% 34% 15% 4	270
	21st to end	Day	10% 14% 32% 27% 13% 3	270
December	1st to 10th	Day	8% 13% 34% 30% 13% 1	270
	11th to 20th	Day	12% 17% 24% 28% 15% 4	221
	21st to end	Day	18% 25% 24% 21% 10% 3	198
January	1st to 10th	Night	12% 9% 24% 30% 17% 7%	760
	11th to 20th	Night	8% 8% 29% 34% 16% 5%	760
	21st to end	Night	12% 12% 28% 29% 14% 5%	836
February	1st to 10th	Night	12% 10% 25% 31% 17% 5%	760
	11th to 20th	Night	10% 9% 26% 31% 16% 8%	744
	21st to end	Night	10% 13% 24% 33% 16% 3	628
March	1st to 10th	Night	10% 13% 24% 33% 18% 2	760
	11th to 20th	Night	8% 10% 23% 33% 22% 4	760
	21st to end	Night	9% 13% 22% 34% 20% 3	836
April	1st to 10th	Night	7% 10% 28% 34% 18% 4	760
	11th to 20th	Night	6% 9% 24% 34% 24% 3	751
	21st to end	Night	5% 8% 25% 32% 23% 7%	760
May	1st to 10th	Night	5% 6% 25% 34% 26% 5%	755
	11th to 20th	Night	4 7% 17% 36% 33% 3	561
	21st to end	Night	5% 6% 22% 32% 32% 5%	593
June	1st to 10th	Night	2 4 14% 39% 35% 5%	380
	11th to 20th	Night	2 12% 43% 37% 7%	380
	21st to end	Night	1 1 9% 41% 42% 7%	380
July	1st to 10th	Night	1 1 2 31% 56% 10%	370
	11th to 20th	Night	2 1 29% 55% 13%	399
	21st to end	Night	2 1 2 23% 55% 17%	695
August	1st to 10th	Night	2 4 32% 51% 10%	756
	11th to 20th	Night	3 30% 55% 13%	752
	21st to end	Night	2 2 29% 53% 13%	836
September	1st to 10th	Night	1 1 6% 30% 49% 13%	760
	11th to 20th	Night	1 1 9% 44% 36% 9%	760
	21st to end	Night	1 2 13% 37% 39% 8%	760
October	1st to 10th	Night	2 2 15% 45% 31% 5%	760
	11th to 20th	Night	3 5% 18% 37% 30% 8%	760
	21st to end	Night	3 6% 18% 33% 30% 10%	836
November	1st to 10th	Night	3 9% 17% 38% 24% 9%	764
	11th to 20th	Night	5% 4 21% 38% 24% 8%	760
	21st to end	Night	6% 8% 26% 31% 23% 6%	760
December	1st to 10th	Night	8% 9% 25% 33% 21% 4	760
	11th to 20th	Night	12% 10% 20% 38% 15% 5%	760
	21st to end	Night	12% 11% 23% 33% 15% 6%	836

Page generated at 2024-11-03 10:19:00. Version ac07

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