Cordova
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cordova clear sky chart from 2005-11-06 to 2024-02-25.

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	11% 7% 3 6% 5% 3 4 4 5% 7% 46%	78720
	Night	10% 6% 3 5% 4 2 4 4 5% 7% 50%	80611
Transparency	Day	38% 4 13% 27% 16% 2	78444
	Night	35% 4 13% 28% 18% 3	80408
Seeing	Day	14% 7% 30% 30% 15% 3	14722
	Night	13% 8% 33% 34% 11% 1	24823

By Month

Percentage Cloud Cover SE (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	9% 11% 5% 10% 9% 4 6% 5% 5% 6% 31%	2847
	11th to 20th	Day	7% 12% 5% 7% 5% 3 5% 5% 4 6% 40%	2850
	21st to end	Day	8% 10% 6% 12% 6% 3 4 4 4 5% 39%	3135
February	1st to 10th	Day	10% 9% 5% 7% 6% 3 3 4 6% 9% 36%	1710
	11th to 20th	Day	8% 8% 3 7% 5% 3 4 4 4 8% 44%	1778
	21st to end	Day	9% 8% 3 7% 5% 3 4 4 4 7% 44%	1520
March	1st to 10th	Day	9% 6% 4 6% 5% 3 4 4 4 6% 49%	1898
	11th to 20th	Day	16% 8% 3 5% 5% 3 4 4 5% 6% 42%	1980
	21st to end	Day	16% 12% 4 6% 6% 3 4 4 4 6% 34%	2178
April	1st to 10th	Day	14% 6% 2 6% 4 3 4 4 4 6% 48%	1980
	11th to 20th	Day	15% 6% 3 6% 5% 3 5% 4 4 7% 43%	2302
	21st to end	Day	20% 7% 2 5% 5% 3 4 3 6% 6% 39%	2340
May	1st to 10th	Day	15% 7% 3 5% 5% 3 5% 4 6% 7% 40%	2340
	11th to 20th	Day	15% 6% 3 5% 4 3 4 4 6% 7% 43%	2302
	21st to end	Day	14% 6% 2 6% 7% 3 5% 5% 6% 9% 36%	2531
June	1st to 10th	Day	7% 3 2 4 5% 2 4 5% 6% 9% 54%	2340
	11th to 20th	Day	10% 4 2 5% 4 3 4 4 6% 9% 50%	2340
	21st to end	Day	6% 4 2 4 5% 3 5% 6% 6% 9% 50%	2520
July	1st to 10th	Day	8% 3 2 4 5% 2 4 5% 6% 10% 50%	2430
	11th to 20th	Day	6% 3 2 4 4 2 4 5% 6% 8% 58%	2340
	21st to end	Day	6% 3 2 5% 5% 3 5% 6% 6% 10% 48%	2546
August	1st to 10th	Day	9% 5% 3 4 5% 3 5% 6% 7% 10% 43%	2328
	11th to 20th	Day	8% 3 2 4 4 3 4 5% 6% 8% 54%	2301
	21st to end	Day	10% 5% 2 3 3 2 4 4 5% 7% 56%	2574
September	1st to 10th	Day	13% 4 2 4 4 2 3 4 5% 5% 55%	2003
	11th to 20th	Day	10% 4 2 4 4 2 4 4 3 8% 55%	1980
	21st to end	Day	9% 3 1 4 3 2 3 3 5% 7% 59%	1980
October	1st to 10th	Day	13% 6% 2 4 4 2 3 4 4 6% 52%	1899
	11th to 20th	Day	11% 5% 3 4 3 2 3 3 4 5% 59%	1800
	21st to end	Day	13% 7% 2 5% 4 3 2 3 3 6% 52%	1940
November	1st to 10th	Day	8% 5% 1 4 4 2 3 3 4 7% 57%	1673
	11th to 20th	Day	8% 6% 2 5% 5% 3 3 4 4 6% 54%	1710
	21st to end	Day	13% 9% 2 5% 4 2 4 3 4 7% 48%	1658
December	1st to 10th	Day	8% 6% 3 6% 4 2 4 6% 6% 8% 48%	1520
	11th to 20th	Day	8% 9% 3 6% 5% 3 4 4 5% 8% 44%	2012
	21st to end	Day	14% 11% 4 12% 7% 4 5% 5% 4 5% 30%	3135
January	1st to 10th	Night	7% 11% 5% 11% 7% 3 5% 5% 5% 6% 36%	4108
	11th to 20th	Night	7% 8% 3 5% 5% 3 8% 5% 5% 5% 45%	4120
	21st to end	Night	10% 11% 5% 10% 5% 2 3 4 4 6% 40%	4532
February	1st to 10th	Night	11% 9% 4 6% 5% 3 5% 5% 5% 5% 41%	2470
	11th to 20th	Night	8% 7% 3 6% 5% 4 5% 5% 7% 8% 43%	2306
	21st to end	Night	9% 8% 2 4 4 4 3 3 4 6% 52%	1830
March	1st to 10th	Night	9% 6% 3 5% 4 3 4 4 5% 6% 51%	2061
	11th to 20th	Night	15% 7% 3 4 4 2 3 4 4 6% 48%	1980
	21st to end	Night	16% 9% 3 6% 4 3 5% 5% 6% 7% 37%	2178
April	1st to 10th	Night	12% 6% 2 4 5% 2 5% 4 4 6% 49%	1980
	11th to 20th	Night	13% 6% 2 5% 4 2 3 4 6% 7% 47%	1605
	21st to end	Night	15% 6% 3 4 5% 3 3 4 4 7% 46%	1620
May	1st to 10th	Night	16% 7% 2 4 4 2 4 4 6% 8% 43%	1620
	11th to 20th	Night	13% 6% 2 5% 4 2 4 5% 5% 8% 46%	1593
	21st to end	Night	14% 5% 2 4 4 3 5% 4 6% 10% 43%	1745
June	1st to 10th	Night	5% 4 1 3 3 3 4 6% 5% 9% 57%	1620
	11th to 20th	Night	8% 4 2 4 4 2 3 4 5% 9% 55%	1610
	21st to end	Night	4 3 2 3 3 2 3 4 5% 9% 60%	1440
July	1st to 10th	Night	7% 4 3 4 4 2 4 3 5% 9% 54%	1520
	11th to 20th	Night	4 3 1 4 3 3 4 4 6% 10% 59%	1620
	21st to end	Night	3 2 1 3 4 3 4 5% 7% 11% 56%	1772
August	1st to 10th	Night	5% 4 2 4 4 3 5% 5% 6% 10% 53%	1611
	11th to 20th	Night	5% 3 2 3 4 2 4 5% 6% 8% 58%	1600
	21st to end	Night	7% 4 2 4 4 2 3 4 4 7% 61%	1782
September	1st to 10th	Night	9% 3 2 3 3 2 3 3 4 5% 63%	1952
	11th to 20th	Night	9% 3 2 3 3 2 4 3 4 8% 58%	1980
	21st to end	Night	8% 3 2 3 4 2 4 3 4 6% 60%	1980
October	1st to 10th	Night	14% 4 2 4 3 3 4 5% 5% 6% 51%	2042
	11th to 20th	Night	12% 4 1 4 4 1 3 3 3 4 59%	2160
	21st to end	Night	13% 6% 2 3 3 2 3 3 4 5% 55%	2412
November	1st to 10th	Night	5% 4 1 5% 3 2 3 3 5% 8% 61%	2405
	11th to 20th	Night	8% 5% 3 4 4 2 3 4 4 6% 56%	2470
	21st to end	Night	11% 6% 2 3 3 2 3 3 4 7% 55%	2515
December	1st to 10th	Night	7% 7% 2 5% 5% 3 4 3 5% 7% 52%	2660
	11th to 20th	Night	9% 6% 3 5% 3 2 3 3 4 7% 54%	3180
	21st to end	Night	17% 12% 4 9% 4 2 3 4 4 5% 36%	4532

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	54% 3 13% 20% 9% 1	2848
	11th to 20th	Day	46% 3 18% 20% 12% 2	2850
	21st to end	Day	49% 4 12% 21% 13% 1	3135
February	1st to 10th	Day	45% 4 15% 23% 10% 2	1710
	11th to 20th	Day	39% 4 13% 25% 15% 3	1787
	21st to end	Day	40% 4 13% 24% 16% 3	1520
March	1st to 10th	Day	37% 3 12% 28% 16% 3	1898
	11th to 20th	Day	44% 4 9% 25% 16% 2	1980
	21st to end	Day	52% 4 15% 19% 9% 1	2178
April	1st to 10th	Day	39% 3 14% 25% 17% 2	1980
	11th to 20th	Day	43% 3 12% 25% 14% 3	2302
	21st to end	Day	45% 5% 11% 26% 13% 1	2340
May	1st to 10th	Day	44% 5% 14% 22% 14% 1	2340
	11th to 20th	Day	40% 5% 17% 26% 13%	2306
	21st to end	Day	45% 6% 17% 22% 10% 2	2531
June	1st to 10th	Day	27% 6% 18% 34% 14% 2	2340
	11th to 20th	Day	32% 6% 13% 31% 17% 2	2340
	21st to end	Day	30% 5% 15% 30% 16% 4	2520
July	1st to 10th	Day	29% 4 15% 32% 18% 2	2366
	11th to 20th	Day	25% 5% 13% 32% 20% 5%	2271
	21st to end	Day	28% 6% 15% 33% 16% 1	2405
August	1st to 10th	Day	33% 6% 22% 26% 12% 2	2314
	11th to 20th	Day	27% 5% 14% 33% 19% 1	2301
	21st to end	Day	28% 4 13% 27% 22% 5%	2574
September	1st to 10th	Day	32% 3 11% 30% 18% 6%	2003
	11th to 20th	Day	30% 4 12% 30% 22% 2	1980
	21st to end	Day	26% 3 9% 34% 27% 1	1980
October	1st to 10th	Day	36% 3 10% 26% 24% 2	1899
	11th to 20th	Day	30% 2 8% 29% 23% 8%	1800
	21st to end	Day	36% 3 11% 23% 22% 5%	1940
November	1st to 10th	Day	28% 2 13% 31% 22% 3	1673
	11th to 20th	Day	32% 3 12% 27% 23% 2	1710
	21st to end	Day	38% 3 10% 29% 16% 3	1658
December	1st to 10th	Day	34% 4 15% 31% 14% 2	1520
	11th to 20th	Day	40% 3 14% 31% 11%	2010
	21st to end	Day	56% 4 10% 20% 10% 1	3135
January	1st to 10th	Night	48% 5% 12% 22% 13% 1	4108
	11th to 20th	Night	40% 4 13% 28% 14% 1	4120
	21st to end	Night	47% 4 12% 20% 16% 1	4532
February	1st to 10th	Night	44% 4 13% 22% 14% 3	2470
	11th to 20th	Night	38% 4 14% 26% 16% 3	2307
	21st to end	Night	35% 3 10% 24% 22% 6%	1830
March	1st to 10th	Night	35% 4 11% 29% 17% 4	2061
	11th to 20th	Night	39% 3 9% 26% 19% 4	1980
	21st to end	Night	46% 6% 15% 22% 9% 2	2178
April	1st to 10th	Night	37% 3 11% 27% 20% 2	1980
	11th to 20th	Night	37% 3 13% 29% 16% 2	1605
	21st to end	Night	39% 4 12% 26% 18% 1	1620
May	1st to 10th	Night	40% 4 15% 25% 15% 1	1620
	11th to 20th	Night	37% 4 14% 28% 16%	1594
	21st to end	Night	38% 7% 18% 23% 14% 2	1746
June	1st to 10th	Night	24% 6% 18% 32% 18% 2	1620
	11th to 20th	Night	27% 4 15% 30% 19% 5%	1610
	21st to end	Night	22% 4 16% 33% 21% 4	1440
July	1st to 10th	Night	28% 4 15% 30% 18% 5%	1476
	11th to 20th	Night	21% 5% 14% 30% 23% 6%	1566
	21st to end	Night	20% 5% 19% 36% 18% 3	1673
August	1st to 10th	Night	26% 6% 20% 30% 15% 2	1601
	11th to 20th	Night	23% 5% 15% 36% 19% 3	1600
	21st to end	Night	25% 4 12% 29% 22% 9%	1782
September	1st to 10th	Night	25% 3 11% 29% 23% 9%	1952
	11th to 20th	Night	26% 4 10% 32% 23% 5%	1980
	21st to end	Night	26% 3 8% 31% 29% 3	1980
October	1st to 10th	Night	33% 4 10% 26% 23% 3	2042
	11th to 20th	Night	30% 3 7% 27% 26% 7%	2160
	21st to end	Night	32% 2 10% 26% 24% 5%	2412
November	1st to 10th	Night	24% 3 13% 29% 26% 6%	2405
	11th to 20th	Night	30% 3 10% 30% 23% 4	2470
	21st to end	Night	31% 2 12% 29% 22% 3	2515
December	1st to 10th	Night	33% 4 14% 32% 16% 2	2660
	11th to 20th	Night	32% 3 12% 38% 14% 1	3181
	21st to end	Night	52% 4 10% 25% 9% 1	4532

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% 11% 34% 26% 10% 2	270
	11th to 20th	Day	20% 14% 32% 24% 9% 1	270
	21st to end	Day	14% 6% 46% 25% 8% 1	297
February	1st to 10th	Day	15% 16% 43% 23% 3	270
	11th to 20th	Day	15% 10% 40% 26% 7% 2	270
	21st to end	Day	12% 13% 49% 21% 4	210
March	1st to 10th	Day	15% 11% 45% 22% 7% 1	240
	11th to 20th	Day	24% 8% 40% 19% 8% 2	240
	21st to end	Day	28% 14% 38% 14% 5%	264
April	1st to 10th	Day	18% 13% 49% 19% 3	240
	11th to 20th	Day	19% 14% 37% 22% 8%	580
	21st to end	Day	24% 13% 32% 20% 9% 2	600
May	1st to 10th	Day	19% 7% 35% 28% 10% 1	603
	11th to 20th	Day	20% 7% 32% 26% 12% 4	625
	21st to end	Day	20% 4 30% 29% 14% 3	679
June	1st to 10th	Day	6% 5% 24% 34% 23% 7%	630
	11th to 20th	Day	9% 4 30% 36% 17% 4	630
	21st to end	Day	8% 5% 33% 34% 18% 3	630
July	1st to 10th	Day	10% 1 15% 37% 29% 8%	621
	11th to 20th	Day	7% 1 18% 41% 26% 6%	618
	21st to end	Day	8% 1 17% 39% 31% 4	684
August	1st to 10th	Day	10% 1 14% 41% 28% 5%	626
	11th to 20th	Day	10% 2 16% 43% 24% 5%	615
	21st to end	Day	12% 2 18% 36% 28% 5%	693
September	1st to 10th	Day	16% 1 23% 40% 16% 4	293
	11th to 20th	Day	8% 1 28% 44% 13% 6%	270
	21st to end	Day	17% 5% 31% 30% 14% 3	270
October	1st to 10th	Day	21% 4 23% 34% 12% 6%	270
	11th to 20th	Day	10% 16% 39% 24% 10% 1	270
	21st to end	Day	21% 11% 39% 20% 8% 2	297
November	1st to 10th	Day	16% 11% 37% 25% 9% 3	270
	11th to 20th	Day	13% 10% 47% 20% 9% 1	270
	21st to end	Day	23% 11% 32% 23% 9% 2	270
December	1st to 10th	Day	9% 10% 44% 28% 8% 2	270
	11th to 20th	Day	20% 8% 39% 25% 7% 1	270
	21st to end	Day	20% 13% 42% 23% 2	297
January	1st to 10th	Night	13% 11% 35% 32% 8% 1	950
	11th to 20th	Night	13% 11% 37% 30% 8% 1	950
	21st to end	Night	14% 8% 40% 31% 6% 1	1045
February	1st to 10th	Night	16% 9% 41% 28% 5%	950
	11th to 20th	Night	12% 9% 43% 32% 4	832
	21st to end	Night	14% 12% 41% 27% 6%	610
March	1st to 10th	Night	13% 12% 39% 29% 5% 1	621
	11th to 20th	Night	18% 9% 37% 29% 6% 1	540
	21st to end	Night	22% 8% 39% 25% 6%	594
April	1st to 10th	Night	16% 13% 41% 25% 5%	540
	11th to 20th	Night	17% 11% 40% 27% 5% 1	533
	21st to end	Night	20% 6% 38% 26% 9% 1	540
May	1st to 10th	Night	20% 6% 34% 31% 9%	540
	11th to 20th	Night	17% 7% 34% 31% 12%	531
	21st to end	Night	16% 6% 28% 36% 13% 1	584
June	1st to 10th	Night	8% 3 24% 48% 16% 1	540
	11th to 20th	Night	10% 2 31% 43% 14% 1	540
	21st to end	Night	4 3 32% 45% 15%	540
July	1st to 10th	Night	10% 1 15% 43% 30% 1	525
	11th to 20th	Night	6% 1 17% 52% 23% 1	522
	21st to end	Night	5% 1 14% 55% 25% 1	591
August	1st to 10th	Night	7% 1 16% 52% 24% 1	537
	11th to 20th	Night	8% 2 18% 49% 22% 1	534
	21st to end	Night	9% 2 22% 40% 26% 2	594
September	1st to 10th	Night	10% 1 26% 41% 20% 1	540
	11th to 20th	Night	11% 4 27% 41% 17% 1	540
	21st to end	Night	10% 4 36% 35% 15% 1	540
October	1st to 10th	Night	17% 6% 30% 32% 13% 2	602
	11th to 20th	Night	14% 9% 38% 30% 9%	720
	21st to end	Night	17% 10% 30% 33% 10%	828
November	1st to 10th	Night	9% 9% 35% 36% 10%	925
	11th to 20th	Night	12% 11% 39% 30% 7%	950
	21st to end	Night	14% 10% 34% 31% 9% 1	950
December	1st to 10th	Night	12% 11% 41% 29% 7%	950
	11th to 20th	Night	15% 9% 35% 33% 7%	950
	21st to end	Night	18% 11% 36% 30% 5%	1045

Page generated at 2024-02-22 05:05:46. Version ac07

Copyright 2024 Attilla Danko