Ojai
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ojai clear sky chart from 2005-11-06 to 2024-12-24.

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	4 3 1 3 2 2 3 2 4 5% 71%	105196
	Night	5% 3 1 2 2 2 2 2 3 5% 72%	103684
Transparency	Day	17% 4 6% 18% 27% 28%	104953
	Night	17% 3 5% 18% 28% 29%	103516
Seeing	Day	6% 8% 27% 37% 17% 5%	15742
	Night	5% 2 15% 34% 34% 9%	25528

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	6% 2 1 3 2 2 3 2 3 5% 70%	2585
	11th to 20th	Day	9% 4 1 3 3 3 2 2 4 8% 60%	2860
	21st to end	Day	11% 4 1 4 3 3 4 4 6% 8% 52%	3223
February	1st to 10th	Day	9% 5% 2 3 2 3 2 2 4 5% 62%	1900
	11th to 20th	Day	8% 3 1 3 3 3 3 2 5% 8% 61%	1850
	21st to end	Day	8% 4 2 4 3 3 3 3 4 6% 59%	1570
March	1st to 10th	Day	12% 5% 2 5% 3 4 4 3 4 6% 52%	3138
	11th to 20th	Day	5% 2 1 3 2 3 3 3 4 6% 68%	3392
	21st to end	Day	7% 5% 2 4 4 4 4 4 7% 8% 51%	4119
April	1st to 10th	Day	6% 4 1 4 3 3 3 2 5% 8% 62%	2280
	11th to 20th	Day	4 4 1 4 3 3 3 3 4 7% 65%	2249
	21st to end	Day	3 4 1 2 3 2 2 3 4 6% 69%	2280
May	1st to 10th	Day	3 3 1 2 1 2 2 2 3 4 75%	3800
	11th to 20th	Day	1 7% 3 3 2 4 4 3 6% 7% 60%	4035
	21st to end	Day	2 8% 2 4 3 2 3 2 3 5% 66%	4494
June	1st to 10th	Day	3 4 2 3 3 3 3 3 4 7% 66%	2660
	11th to 20th	Day	2 2 1 3 2 2 2 2 4 7% 73%	2660
	21st to end	Day	2 1 1 2 2 2 2 3 4 82%	2660
July	1st to 10th	Day	1 1 1 1 1 1 2 3 87%	4420
	11th to 20th	Day	1 1 2 2 2 2 2 3 4 80%	4297
	21st to end	Day	1 1 1 1 2 1 2 2 4 85%	4314
August	1st to 10th	Day	1 1 1 2 1 2 2 2 3 4 83%	3783
	11th to 20th	Day	1 1 1 1 1 1 2 2 90%	3724
	21st to end	Day	1 1 1 1 1 1 2 3 89%	4180
September	1st to 10th	Day	1 1 1 1 2 2 2 4 5% 81%	2280
	11th to 20th	Day	1 1 1 2 2 2 2 2 2 4 81%	2200
	21st to end	Day	1 1 2 2 2 2 2 3 3 82%	2090
October	1st to 10th	Day	2 1 1 1 1 1 2 1 3 4 83%	3411
	11th to 20th	Day	2 1 1 2 3 3 3 4 4 5% 73%	3161
	21st to end	Day	2 3 1 3 3 3 3 2 4 4 72%	3448
November	1st to 10th	Day	2 2 1 2 2 2 3 2 4 4 76%	1797
	11th to 20th	Day	4 3 1 3 2 2 3 2 4 6% 71%	1800
	21st to end	Day	4 3 1 3 3 4 3 4 4 7% 64%	1800
December	1st to 10th	Day	6% 4 2 4 2 4 3 3 5% 7% 61%	1800
	11th to 20th	Day	18% 6% 2 4 3 2 3 3 6% 6% 47%	2118
	21st to end	Day	12% 5% 2 6% 4 3 4 3 5% 7% 49%	2818
January	1st to 10th	Night	7% 3 1 3 2 3 3 2 4 5% 67%	4346
	11th to 20th	Night	7% 4 3 5% 3 3 4 3 4 8% 57%	4110
	21st to end	Night	12% 5% 2 3 3 3 3 3 5% 7% 55%	4431
February	1st to 10th	Night	8% 5% 2 4 2 2 2 3 3 5% 64%	2280
	11th to 20th	Night	8% 3 1 3 2 2 3 2 4 5% 67%	2218
	21st to end	Night	10% 4 1 3 4 3 3 2 3 5% 62%	1884
March	1st to 10th	Night	9% 6% 1 4 3 3 4 3 6% 7% 54%	3736
	11th to 20th	Night	4 2 1 2 3 3 2 3 4 7% 69%	3583
	21st to end	Night	11% 3 1 2 2 3 3 2 4 5% 63%	3533
April	1st to 10th	Night	6% 3 1 3 3 2 3 2 5% 6% 66%	1900
	11th to 20th	Night	4 3 1 3 2 2 2 2 4 6% 71%	1879
	21st to end	Night	3 3 1 2 2 3 3 3 3 6% 72%	1900
May	1st to 10th	Night	2 2 1 2 2 2 2 1 3 3 80%	3180
	11th to 20th	Night	1 3 2 3 2 2 4 3 3 4 72%	2869
	21st to end	Night	1 3 1 2 2 2 3 2 3 3 78%	3088
June	1st to 10th	Night	1 3 1 2 1 3 3 2 4 6% 74%	1520
	11th to 20th	Night	1 2 1 1 2 2 2 2 3 4 80%	1520
	21st to end	Night	1 1 1 1 1 1 2 3 3 86%	1520
July	1st to 10th	Night	1 1 1 1 1 2 3 3 87%	2540
	11th to 20th	Night	1 1 1 1 2 2 2 3 4 84%	2661
	21st to end	Night	1 1 1 1 1 1 1 2 3 88%	3252
August	1st to 10th	Night	1 1 1 1 1 1 1 2 4 86%	3166
	11th to 20th	Night	1 1 1 1 1 1 2 2 90%	3126
	21st to end	Night	1 1 1 2 2 92%	3498
September	1st to 10th	Night	2 1 1 1 1 2 1 1 3 3 85%	1900
	11th to 20th	Night	1 1 1 2 1 1 2 1 2 3 85%	1978
	21st to end	Night	1 1 1 1 2 2 1 3 4 84%	2090
October	1st to 10th	Night	2 1 1 1 1 1 1 2 2 87%	3566
	11th to 20th	Night	1 2 1 2 2 1 3 8% 4 5% 71%	3777
	21st to end	Night	2 3 1 2 2 2 2 1 2 4 80%	4121
November	1st to 10th	Night	3 2 2 2 2 2 2 4 6% 74%	2499
	11th to 20th	Night	3 3 1 2 2 2 2 2 4 5% 74%	2600
	21st to end	Night	5% 4 1 4 3 2 3 4 4 6% 66%	2600
December	1st to 10th	Night	7% 4 1 3 2 2 3 3 4 6% 64%	2600
	11th to 20th	Night	19% 5% 1 3 3 3 3 3 6% 6% 47%	3303
	21st to end	Night	13% 5% 2 5% 4 4 4 3 5% 6% 49%	4910

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	18% 3 5% 26% 34% 13%	2585
	11th to 20th	Day	25% 4 15% 22% 19% 15%	2860
	21st to end	Day	30% 4 7% 23% 23% 14%	3223
February	1st to 10th	Day	26% 4 3 17% 25% 26%	1900
	11th to 20th	Day	23% 3 6% 18% 29% 21%	1860
	21st to end	Day	26% 5% 6% 21% 26% 16%	1570
March	1st to 10th	Day	32% 6% 9% 22% 17% 14%	3138
	11th to 20th	Day	17% 6% 14% 32% 16% 16%	3392
	21st to end	Day	27% 9% 11% 28% 19% 6%	4119
April	1st to 10th	Day	23% 5% 11% 24% 25% 12%	2280
	11th to 20th	Day	20% 4 8% 26% 29% 13%	2252
	21st to end	Day	18% 4 8% 27% 33% 11%	2280
May	1st to 10th	Day	14% 4 7% 22% 35% 18%	3800
	11th to 20th	Day	23% 4 11% 24% 28% 10%	4038
	21st to end	Day	20% 5% 9% 31% 28% 6%	4494
June	1st to 10th	Day	20% 4 9% 24% 30% 14%	2660
	11th to 20th	Day	13% 3 7% 16% 34% 26%	2660
	21st to end	Day	9% 3 3 11% 35% 39%	2660
July	1st to 10th	Day	5% 1 1 8% 15% 69%	4351
	11th to 20th	Day	9% 2 3 11% 24% 50%	4222
	21st to end	Day	7% 2 4 18% 28% 41%	4178
August	1st to 10th	Day	8% 2 2 11% 44% 34%	3770
	11th to 20th	Day	4 1 1 11% 30% 53%	3760
	21st to end	Day	5% 2 1 11% 30% 51%	4179
September	1st to 10th	Day	8% 3 4 10% 29% 46%	2280
	11th to 20th	Day	9% 3 3 14% 33% 38%	2200
	21st to end	Day	9% 2 3 13% 37% 36%	2090
October	1st to 10th	Day	8% 2 4 11% 20% 55%	3411
	11th to 20th	Day	11% 4 2 17% 39% 27%	3161
	21st to end	Day	17% 3 3 10% 34% 34%	3448
November	1st to 10th	Day	13% 3 3 18% 30% 32%	1797
	11th to 20th	Day	16% 2 6% 15% 26% 35%	1800
	21st to end	Day	21% 4 6% 14% 23% 32%	1800
December	1st to 10th	Day	24% 4 7% 14% 25% 26%	1800
	11th to 20th	Day	37% 5% 5% 17% 21% 15%	2117
	21st to end	Day	34% 5% 8% 24% 17% 11%	2818
January	1st to 10th	Night	22% 3 5% 14% 39% 16%	4346
	11th to 20th	Night	27% 5% 9% 25% 17% 16%	4110
	21st to end	Night	29% 5% 5% 18% 27% 16%	4431
February	1st to 10th	Night	25% 3 4 16% 26% 27%	2280
	11th to 20th	Night	21% 3 5% 19% 27% 25%	2219
	21st to end	Night	27% 3 6% 17% 26% 20%	1884
March	1st to 10th	Night	28% 7% 6% 22% 24% 12%	3736
	11th to 20th	Night	16% 6% 10% 29% 22% 17%	3583
	21st to end	Night	25% 4 10% 26% 26% 9%	3533
April	1st to 10th	Night	21% 5% 9% 25% 25% 15%	1900
	11th to 20th	Night	16% 5% 7% 23% 29% 19%	1879
	21st to end	Night	17% 3 6% 24% 36% 13%	1900
May	1st to 10th	Night	12% 5% 6% 18% 34% 25%	3180
	11th to 20th	Night	14% 2 11% 32% 23% 18%	2870
	21st to end	Night	10% 5% 9% 33% 36% 7%	3088
June	1st to 10th	Night	13% 3 11% 28% 29% 15%	1520
	11th to 20th	Night	8% 2 7% 20% 34% 28%	1520
	21st to end	Night	6% 2 3 14% 33% 43%	1520
July	1st to 10th	Night	5% 1 2 7% 13% 72%	2500
	11th to 20th	Night	6% 2 3 10% 27% 52%	2613
	21st to end	Night	5% 1 3 19% 27% 43%	3150
August	1st to 10th	Night	7% 1 2 13% 38% 39%	3156
	11th to 20th	Night	4 1 1 9% 30% 55%	3156
	21st to end	Night	3 1 1 10% 34% 51%	3498
September	1st to 10th	Night	8% 2 2 8% 29% 51%	1900
	11th to 20th	Night	8% 2 3 11% 37% 39%	1978
	21st to end	Night	7% 1 2 13% 35% 41%	2090
October	1st to 10th	Night	7% 2 2 9% 20% 60%	3566
	11th to 20th	Night	9% 4 2 18% 35% 32%	3777
	21st to end	Night	12% 2 2 7% 31% 45%	4121
November	1st to 10th	Night	13% 3 4 14% 31% 34%	2499
	11th to 20th	Night	15% 2 5% 13% 26% 39%	2600
	21st to end	Night	21% 3 6% 17% 21% 33%	2600
December	1st to 10th	Night	22% 3 5% 16% 22% 31%	2600
	11th to 20th	Night	37% 4 7% 14% 21% 17%	3303
	21st to end	Night	34% 5% 7% 24% 19% 11%	4910

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	16% 10% 34% 30% 8% 1	213
	11th to 20th	Day	14% 9% 32% 34% 10% 1	370
	21st to end	Day	10% 15% 35% 28% 9% 2	431
February	1st to 10th	Day	10% 13% 36% 29% 10% 3	460
	11th to 20th	Day	10% 13% 37% 30% 9% 1	455
	21st to end	Day	13% 15% 38% 26% 7% 1	382
March	1st to 10th	Day	15% 16% 39% 23% 8%	460
	11th to 20th	Day	12% 13% 39% 24% 10% 1	460
	21st to end	Day	11% 19% 34% 29% 7%	506
April	1st to 10th	Day	9% 13% 35% 29% 12% 3	460
	11th to 20th	Day	7% 14% 37% 31% 8% 4	452
	21st to end	Day	6% 11% 33% 31% 15% 5%	460
May	1st to 10th	Day	10% 10% 29% 38% 10% 4	463
	11th to 20th	Day	5% 11% 27% 35% 18% 3	488
	21st to end	Day	5% 10% 32% 33% 15% 4	529
June	1st to 10th	Day	4 7% 23% 37% 24% 6%	490
	11th to 20th	Day	2 4 26% 40% 21% 7%	490
	21st to end	Day	1 3 20% 46% 24% 7%	490
July	1st to 10th	Day	1 11% 49% 30% 9%	486
	11th to 20th	Day	2 7% 46% 31% 14%	484
	21st to end	Day	2 1 8% 47% 30% 13%	531
August	1st to 10th	Day	1 1 14% 47% 26% 11%	487
	11th to 20th	Day	2 1 9% 50% 25% 13%	477
	21st to end	Day	2 1 14% 48% 26% 9%	539
September	1st to 10th	Day	1 2 17% 47% 24% 8%	490
	11th to 20th	Day	2 5% 26% 46% 17% 4	490
	21st to end	Day	1 7% 21% 45% 23% 4	490
October	1st to 10th	Day	2 6% 27% 45% 18% 2	490
	11th to 20th	Day	1 5% 33% 41% 17% 3	490
	21st to end	Day	4 8% 27% 40% 18% 4	539
November	1st to 10th	Day	4 8% 26% 41% 20% 3	333
	11th to 20th	Day	4 7% 36% 34% 18% 3	300
	21st to end	Day	7% 11% 31% 34% 15% 3	300
December	1st to 10th	Day	7% 8% 31% 35% 18% 1	300
	11th to 20th	Day	7% 8% 32% 33% 16% 3	253
	21st to end	Day	15% 15% 32% 25% 11% 2	204
January	1st to 10th	Night	11% 4 21% 38% 19% 7%	760
	11th to 20th	Night	7% 4 22% 41% 22% 4	760
	21st to end	Night	11% 5% 26% 39% 15% 4	836
February	1st to 10th	Night	10% 6% 20% 37% 22% 6%	760
	11th to 20th	Night	9% 3 23% 39% 19% 7%	744
	21st to end	Night	11% 5% 24% 38% 18% 4	628
March	1st to 10th	Night	10% 3 24% 39% 21% 3	760
	11th to 20th	Night	8% 3 19% 40% 24% 6%	760
	21st to end	Night	8% 3 22% 41% 23% 3	836
April	1st to 10th	Night	6% 3 18% 44% 24% 5%	760
	11th to 20th	Night	5% 4 22% 36% 28% 4	751
	21st to end	Night	4 3 20% 40% 25% 8%	760
May	1st to 10th	Night	3 3 17% 39% 33% 5%	760
	11th to 20th	Night	3 3 16% 33% 39% 7%	583
	21st to end	Night	1 2 17% 38% 34% 7%	608
June	1st to 10th	Night	2 1 8% 31% 49% 9%	380
	11th to 20th	Night	1 1 8% 29% 53% 9%	380
	21st to end	Night	1 3 29% 54% 13%	380
July	1st to 10th	Night	1 1 1 15% 65% 18%	370
	11th to 20th	Night	1 2 8% 60% 28%	437
	21st to end	Night	2 2 13% 56% 28%	705
August	1st to 10th	Night	1 1 2 22% 57% 17%	756
	11th to 20th	Night	1 1 2 15% 61% 20%	752
	21st to end	Night	1 2 18% 57% 21%	836
September	1st to 10th	Night	3 1 4 25% 49% 19%	760
	11th to 20th	Night	2 2 6% 30% 47% 12%	760
	21st to end	Night	1 1 8% 33% 45% 12%	760
October	1st to 10th	Night	3 1 9% 42% 40% 6%	760
	11th to 20th	Night	3 1 14% 38% 36% 8%	760
	21st to end	Night	3 3 14% 38% 31% 11%	836
November	1st to 10th	Night	3 3 17% 40% 28% 9%	780
	11th to 20th	Night	5% 2 17% 38% 30% 8%	800
	21st to end	Night	7% 2 23% 39% 24% 5%	800
December	1st to 10th	Night	8% 4 20% 39% 25% 4	800
	11th to 20th	Night	12% 2 23% 41% 18% 4	800
	21st to end	Night	11% 4 22% 40% 17% 6%	850

Page generated at 2024-12-21 01:13:50. Version ac07

Copyright © 2024 Attilla Danko.