Courtright Reservoir
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Courtright Reservoir clear sky chart from 2005-11-06 to 2024-07-16.

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 7% 3 5% 3 3 3 3 4 6% 61%	89712
	Night	4 7% 2 5% 3 3 3 3 4 6% 62%	89919
Transparency	Day	24% 5% 9% 22% 25% 14%	89421
	Night	24% 4 9% 23% 26% 14%	89732
Seeing	Day	10% 14% 31% 29% 14% 3	14800
	Night	8% 6% 23% 35% 24% 4	24345

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	7% 8% 7% 8% 3 3 3 3 4 6% 49%	2539
	11th to 20th	Day	6% 13% 2 6% 6% 5% 5% 4 4 7% 42%	2650
	21st to end	Day	6% 12% 4 6% 3 4 4 3 6% 11% 41%	3146
February	1st to 10th	Day	7% 10% 4 8% 2 2 3 3 6% 5% 50%	1853
	11th to 20th	Day	4 10% 5% 7% 4 3 3 3 3 6% 52%	1850
	21st to end	Day	7% 13% 5% 10% 5% 3 3 3 3 4 45%	1570
March	1st to 10th	Day	3 14% 6% 13% 4 5% 5% 5% 5% 7% 34%	3138
	11th to 20th	Day	3 9% 3 6% 3 5% 4 2 4 8% 54%	3330
	21st to end	Day	5% 14% 8% 13% 4 3 4 2 4 5% 37%	4148
April	1st to 10th	Day	5% 9% 4 7% 3 4 4 3 4 6% 50%	2280
	11th to 20th	Day	6% 11% 4 5% 3 3 3 2 4 5% 52%	2249
	21st to end	Day	6% 10% 2 3 3 3 4 3 5% 8% 53%	2280
May	1st to 10th	Day	4 7% 2 3 2 2 2 2 3 5% 69%	3976
	11th to 20th	Day	2 5% 2 2 2 2 3 2 4 5% 71%	4071
	21st to end	Day	3 6% 2 3 2 2 2 2 3 5% 70%	4736
June	1st to 10th	Day	3 5% 1 4 3 3 3 3 5% 7% 63%	2660
	11th to 20th	Day	2 2 2 1 2 2 2 3 5% 78%	2660
	21st to end	Day	2 2 1 2 2 2 2 1 3 3 80%	2660
July	1st to 10th	Day	1 1 1 2 2 2 2 2 4 5% 78%	2660
	11th to 20th	Day	3 2 1 3 3 2 2 3 3 4 74%	2593
	21st to end	Day	2 3 1 3 3 3 4 3 5% 6% 67%	2656
August	1st to 10th	Day	2 2 1 2 2 2 3 2 3 4 77%	2167
	11th to 20th	Day	2 1 1 3 2 2 2 2 4 5% 76%	2122
	21st to end	Day	2 2 1 1 1 2 2 2 3 4 80%	2376
September	1st to 10th	Day	2 1 1 2 2 2 3 3 3 5% 76%	2160
	11th to 20th	Day	4 2 1 2 2 2 2 3 3 5% 76%	2081
	21st to end	Day	2 4 1 2 2 3 2 2 4 5% 74%	1980
October	1st to 10th	Day	4 6% 2 3 2 3 3 2 4 4 68%	1926
	11th to 20th	Day	4 3 2 3 2 3 2 3 3 5% 70%	1800
	21st to end	Day	5% 3 1 3 1 2 2 2 4 4 72%	1926
November	1st to 10th	Day	4 7% 3 6% 2 3 4 2 4 6% 58%	1674
	11th to 20th	Day	5% 5% 1 3 3 3 3 3 5% 6% 64%	1710
	21st to end	Day	4 7% 2 6% 3 2 3 3 4 6% 60%	1710
December	1st to 10th	Day	8% 8% 2 4 3 3 3 2 3 7% 55%	1653
	11th to 20th	Day	12% 14% 4 7% 4 4 4 3 4 5% 39%	1928
	21st to end	Day	5% 9% 5% 8% 4 4 4 4 5% 8% 44%	2794
January	1st to 10th	Night	5% 10% 3 6% 3 2 3 3 4 6% 56%	4406
	11th to 20th	Night	7% 13% 4 7% 4 4 4 4 5% 7% 41%	4298
	21st to end	Night	5% 12% 3 6% 3 4 5% 4 6% 9% 42%	4521
February	1st to 10th	Night	7% 10% 3 6% 3 3 3 3 5% 5% 53%	2324
	11th to 20th	Night	5% 9% 4 6% 3 2 3 2 4 8% 54%	2218
	21st to end	Night	6% 9% 3 8% 5% 3 3 2 5% 5% 51%	1884
March	1st to 10th	Night	4 14% 6% 9% 3 3 4 3 6% 7% 42%	3736
	11th to 20th	Night	2 7% 3 6% 3 3 3 3 4 7% 58%	3645
	21st to end	Night	4 17% 4 9% 3 4 4 3 4 6% 43%	3504
April	1st to 10th	Night	5% 9% 3 6% 4 2 3 4 4 7% 54%	1900
	11th to 20th	Night	4 9% 3 5% 3 2 2 3 5% 6% 58%	1879
	21st to end	Night	3 7% 1 4 2 2 3 3 5% 6% 62%	1900
May	1st to 10th	Night	1 5% 1 3 2 2 2 2 3 5% 73%	2997
	11th to 20th	Night	2 4 1 2 2 2 2 2 4 5% 74%	2834
	21st to end	Night	2 3 1 2 2 2 1 2 2 4 78%	2837
June	1st to 10th	Night	3 4 1 3 2 2 3 3 4 7% 70%	1520
	11th to 20th	Night	1 1 2 2 2 2 2 4 5% 81%	1520
	21st to end	Night	1 1 1 1 1 1 1 2 3 3 85%	1520
July	1st to 10th	Night	1 1 2 2 1 1 2 2 3 86%	1520
	11th to 20th	Night	2 3 1 2 2 2 2 2 3 4 77%	1488
	21st to end	Night	3 2 1 3 2 3 3 3 3 5% 72%	1657
August	1st to 10th	Night	1 2 1 2 1 1 1 2 2 4 82%	1770
	11th to 20th	Night	1 1 1 2 1 1 2 2 2 4 84%	1780
	21st to end	Night	2 1 1 1 1 2 2 1 1 2 86%	1980
September	1st to 10th	Night	1 1 1 1 1 1 2 1 2 3 87%	1800
	11th to 20th	Night	2 2 1 2 1 2 1 1 3 2 84%	1877
	21st to end	Night	2 2 1 2 2 1 2 3 3 4 80%	1980
October	1st to 10th	Night	3 3 2 2 1 2 3 2 3 5% 74%	2029
	11th to 20th	Night	3 3 1 1 2 2 3 2 4 5% 75%	2160
	21st to end	Night	4 2 1 2 2 1 2 2 3 4 77%	2430
November	1st to 10th	Night	3 6% 2 5% 2 2 3 3 4 6% 65%	2405
	11th to 20th	Night	5% 4 2 3 2 2 3 2 5% 8% 63%	2470
	21st to end	Night	4 7% 2 5% 3 4 3 3 4 6% 59%	2470
December	1st to 10th	Night	8% 9% 2 5% 3 3 3 3 4 6% 55%	2522
	11th to 20th	Night	10% 18% 3 6% 4 3 3 3 5% 6% 40%	3276
	21st to end	Night	5% 8% 3 7% 5% 5% 5% 4 7% 8% 42%	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	34% 4 13% 24% 20% 4	2539
	11th to 20th	Day	39% 9% 11% 21% 13% 8%	2650
	21st to end	Day	36% 7% 14% 24% 14% 5%	3146
February	1st to 10th	Day	35% 3 10% 21% 19% 12%	1853
	11th to 20th	Day	35% 5% 9% 21% 23% 8%	1860
	21st to end	Day	43% 4 9% 22% 17% 5%	1570
March	1st to 10th	Day	44% 8% 11% 17% 14% 6%	3138
	11th to 20th	Day	26% 7% 13% 34% 14% 7%	3330
	21st to end	Day	46% 8% 12% 18% 13% 2	4148
April	1st to 10th	Day	36% 5% 14% 24% 17% 5%	2280
	11th to 20th	Day	33% 6% 12% 25% 19% 5%	2252
	21st to end	Day	29% 7% 17% 29% 17% 2	2280
May	1st to 10th	Day	18% 4 11% 35% 28% 5%	3976
	11th to 20th	Day	15% 5% 10% 32% 34% 5%	4074
	21st to end	Day	17% 5% 9% 33% 34% 2	4736
June	1st to 10th	Day	20% 7% 13% 26% 27% 7%	2660
	11th to 20th	Day	10% 4 9% 26% 36% 16%	2660
	21st to end	Day	10% 3 4 17% 39% 28%	2660
July	1st to 10th	Day	9% 3 4 13% 29% 42%	2591
	11th to 20th	Day	13% 5% 6% 14% 33% 29%	2518
	21st to end	Day	15% 5% 11% 18% 23% 29%	2508
August	1st to 10th	Day	12% 4 5% 11% 31% 37%	2152
	11th to 20th	Day	9% 5% 5% 14% 35% 31%	2122
	21st to end	Day	9% 3 4 13% 38% 32%	2376
September	1st to 10th	Day	9% 4 8% 13% 31% 36%	2160
	11th to 20th	Day	11% 4 7% 21% 32% 25%	2081
	21st to end	Day	14% 3 6% 22% 37% 19%	1980
October	1st to 10th	Day	20% 3 8% 17% 30% 23%	1926
	11th to 20th	Day	17% 3 8% 22% 30% 21%	1800
	21st to end	Day	16% 3 6% 22% 35% 19%	1926
November	1st to 10th	Day	27% 4 9% 21% 27% 12%	1674
	11th to 20th	Day	21% 4 9% 24% 29% 13%	1710
	21st to end	Day	26% 3 8% 18% 29% 15%	1710
December	1st to 10th	Day	30% 3 8% 22% 22% 14%	1653
	11th to 20th	Day	46% 6% 8% 14% 16% 9%	1928
	21st to end	Day	35% 7% 11% 21% 18% 8%	2794
January	1st to 10th	Night	30% 4 11% 28% 21% 6%	4406
	11th to 20th	Night	41% 6% 10% 20% 15% 8%	4298
	21st to end	Night	36% 7% 12% 21% 17% 7%	4521
February	1st to 10th	Night	33% 3 6% 23% 22% 13%	2324
	11th to 20th	Night	30% 5% 8% 21% 25% 11%	2219
	21st to end	Night	36% 3 10% 21% 22% 8%	1884
March	1st to 10th	Night	39% 5% 10% 19% 19% 8%	3736
	11th to 20th	Night	24% 5% 12% 31% 19% 9%	3645
	21st to end	Night	40% 6% 14% 23% 15% 3	3504
April	1st to 10th	Night	30% 4 13% 27% 19% 7%	1900
	11th to 20th	Night	26% 5% 13% 27% 20% 8%	1879
	21st to end	Night	20% 6% 16% 35% 20% 2	1900
May	1st to 10th	Night	15% 3 10% 35% 33% 4	2997
	11th to 20th	Night	12% 5% 9% 36% 35% 3	2835
	21st to end	Night	12% 4 9% 35% 38% 2	2837
June	1st to 10th	Night	15% 5% 13% 28% 35% 5%	1520
	11th to 20th	Night	7% 5% 8% 27% 36% 17%	1520
	21st to end	Night	7% 2 4 16% 41% 30%	1520
July	1st to 10th	Night	6% 1 3 12% 33% 44%	1480
	11th to 20th	Night	11% 4 5% 16% 35% 28%	1440
	21st to end	Night	14% 5% 7% 18% 28% 28%	1565
August	1st to 10th	Night	9% 2 6% 15% 33% 35%	1761
	11th to 20th	Night	7% 2 3 21% 35% 31%	1780
	21st to end	Night	9% 1 2 14% 40% 33%	1980
September	1st to 10th	Night	6% 2 3 14% 38% 38%	1800
	11th to 20th	Night	9% 3 5% 23% 37% 23%	1877
	21st to end	Night	10% 3 6% 21% 40% 21%	1980
October	1st to 10th	Night	14% 4 7% 20% 31% 25%	2029
	11th to 20th	Night	13% 3 6% 21% 32% 24%	2160
	21st to end	Night	12% 3 5% 22% 38% 20%	2430
November	1st to 10th	Night	21% 4 9% 23% 27% 17%	2405
	11th to 20th	Night	20% 3 9% 22% 31% 16%	2470
	21st to end	Night	26% 3 8% 18% 28% 16%	2470
December	1st to 10th	Night	30% 4 10% 18% 24% 14%	2522
	11th to 20th	Night	44% 5% 9% 16% 18% 9%	3276
	21st to end	Night	34% 7% 11% 19% 21% 8%	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	27% 20% 24% 20% 6% 3	180
	11th to 20th	Day	16% 16% 27% 22% 16% 3	251
	21st to end	Day	15% 16% 28% 27% 12% 3	407
February	1st to 10th	Day	17% 20% 28% 21% 11% 3	438
	11th to 20th	Day	16% 20% 32% 19% 11% 1	455
	21st to end	Day	18% 23% 34% 18% 7%	382
March	1st to 10th	Day	21% 21% 34% 19% 5% 1	460
	11th to 20th	Day	19% 20% 31% 19% 10% 2	460
	21st to end	Day	22% 22% 36% 16% 4	506
April	1st to 10th	Day	15% 19% 31% 27% 7% 1	460
	11th to 20th	Day	18% 22% 31% 23% 7% 1	452
	21st to end	Day	10% 17% 32% 25% 14% 2	460
May	1st to 10th	Day	11% 18% 30% 27% 13% 2	463
	11th to 20th	Day	15% 13% 23% 29% 17% 3	488
	21st to end	Day	13% 11% 23% 28% 20% 4	529
June	1st to 10th	Day	6% 11% 25% 30% 24% 4	490
	11th to 20th	Day	4 10% 30% 33% 17% 6%	490
	21st to end	Day	2 9% 28% 38% 19% 4	490
July	1st to 10th	Day	2 5% 30% 38% 22% 4	486
	11th to 20th	Day	3 5% 26% 40% 20% 7%	465
	21st to end	Day	3 4 30% 40% 17% 6%	487
August	1st to 10th	Day	2 7% 39% 37% 11% 4	447
	11th to 20th	Day	3 7% 34% 35% 18% 4	437
	21st to end	Day	2 5% 35% 39% 16% 2	495
September	1st to 10th	Day	3 8% 39% 36% 14% 1	450
	11th to 20th	Day	7% 13% 34% 36% 10% 1	450
	21st to end	Day	6% 12% 35% 33% 13% 1	450
October	1st to 10th	Day	6% 17% 36% 28% 12% 1	450
	11th to 20th	Day	5% 13% 34% 34% 12% 1	450
	21st to end	Day	9% 13% 31% 33% 12% 2	441
November	1st to 10th	Day	7% 17% 27% 26% 18% 4	270
	11th to 20th	Day	9% 13% 27% 33% 15% 3	270
	21st to end	Day	9% 15% 30% 26% 17% 3	270
December	1st to 10th	Day	15% 12% 30% 26% 14% 2	243
	11th to 20th	Day	13% 13% 33% 24% 15% 2	180
	21st to end	Day	19% 17% 29% 19% 13% 4	198
January	1st to 10th	Night	15% 10% 29% 22% 18% 6%	760
	11th to 20th	Night	10% 10% 33% 31% 13% 5%	760
	21st to end	Night	14% 11% 31% 28% 14% 3	836
February	1st to 10th	Night	14% 8% 29% 30% 15% 3	760
	11th to 20th	Night	11% 12% 28% 30% 16% 4	744
	21st to end	Night	14% 9% 32% 33% 10% 2	628
March	1st to 10th	Night	14% 9% 31% 32% 12% 3	760
	11th to 20th	Night	9% 12% 26% 29% 22% 2	760
	21st to end	Night	12% 9% 30% 34% 14% 1	836
April	1st to 10th	Night	11% 7% 27% 40% 14% 2	760
	11th to 20th	Night	9% 8% 29% 33% 19% 3	751
	21st to end	Night	8% 7% 28% 35% 18% 4	760
May	1st to 10th	Night	5% 5% 26% 39% 21% 4	655
	11th to 20th	Night	7% 4 23% 39% 26% 2	561
	21st to end	Night	6% 4 21% 35% 30% 4	461
June	1st to 10th	Night	3 2 17% 41% 33% 4	380
	11th to 20th	Night	1 2 19% 42% 33% 4	380
	21st to end	Night	1 1 17% 38% 38% 5%	380
July	1st to 10th	Night	1 10% 41% 43% 5%	370
	11th to 20th	Night	2 1 8% 40% 44% 6%	360
	21st to end	Night	2 1 8% 30% 51% 7%	475
August	1st to 10th	Night	2 1 15% 37% 43% 3	696
	11th to 20th	Night	1 8% 40% 47% 4	712
	21st to end	Night	3 9% 39% 45% 5%	792
September	1st to 10th	Night	2 1 11% 39% 42% 6%	720
	11th to 20th	Night	2 2 14% 45% 31% 6%	720
	21st to end	Night	3 2 16% 40% 33% 6%	720
October	1st to 10th	Night	4 2 22% 44% 22% 6%	720
	11th to 20th	Night	5% 3 24% 37% 25% 6%	720
	21st to end	Night	5% 4 20% 36% 26% 9%	792
November	1st to 10th	Night	9% 4 19% 39% 24% 6%	740
	11th to 20th	Night	7% 5% 27% 38% 20% 3	760
	21st to end	Night	7% 6% 30% 36% 16% 4	760
December	1st to 10th	Night	13% 8% 28% 36% 13% 3	760
	11th to 20th	Night	17% 8% 29% 32% 12% 2	760
	21st to end	Night	14% 13% 31% 27% 13% 1	836

Page generated at 2024-07-13 07:19:55. Version ac07

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