Chalk Bluff Staging Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Chalk Bluff Staging Area clear sky chart from 2005-11-06 to 2024-11-12.

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	9% 7% 1 3 2 2 2 2 3 4 63%	105224
	Night	11% 7% 2 3 2 2 3 2 4 5% 58%	102683
Transparency	Day	26% 3 6% 18% 25% 22%	104973
	Night	30% 3 7% 17% 23% 20%	102524
Seeing	Day	17% 15% 32% 24% 9% 3	15126
	Night	16% 8% 20% 32% 21% 4	24417

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	17% 18% 3 4 3 3 2 2 4 6% 38%	2539
	11th to 20th	Day	21% 13% 2 6% 4 4 3 3 4 4 35%	2700
	21st to end	Day	23% 13% 3 5% 3 3 3 3 4 5% 35%	3146
February	1st to 10th	Day	20% 10% 2 3 2 2 3 2 4 6% 45%	1710
	11th to 20th	Day	15% 15% 2 4 3 3 3 2 5% 5% 43%	1795
	21st to end	Day	17% 17% 2 4 2 2 2 2 4 4 43%	1570
March	1st to 10th	Day	20% 25% 5% 6% 3 3 2 2 3 6% 25%	3189
	11th to 20th	Day	13% 12% 2 2 2 2 2 2 3 4 56%	3490
	21st to end	Day	18% 23% 2 5% 3 4 3 3 5% 5% 29%	4004
April	1st to 10th	Day	16% 12% 2 4 3 3 4 3 4 6% 42%	2280
	11th to 20th	Day	14% 9% 2 4 3 3 3 3 4 5% 50%	2249
	21st to end	Day	12% 6% 1 4 3 2 3 2 5% 6% 55%	2280
May	1st to 10th	Day	9% 6% 1 3 2 2 2 2 3 4 67%	3945
	11th to 20th	Day	5% 3 1 2 2 1 2 2 3 4 75%	4377
	21st to end	Day	7% 3 1 3 2 2 2 2 3 5% 69%	4813
June	1st to 10th	Day	8% 5% 1 4 3 3 3 3 5% 6% 58%	2660
	11th to 20th	Day	4 2 2 1 2 2 2 3 5% 76%	2660
	21st to end	Day	3 1 1 2 2 1 1 2 2 3 82%	2660
July	1st to 10th	Day	1 1 1 1 1 1 1 2 92%	4420
	11th to 20th	Day	2 1 2 1 1 1 1 2 3 84%	4420
	21st to end	Day	1 1 1 1 1 1 1 2 2 87%	4564
August	1st to 10th	Day	3 1 1 2 2 2 2 2 3 4 78%	4091
	11th to 20th	Day	1 1 1 1 1 1 2 2 89%	3762
	21st to end	Day	2 1 1 1 1 1 1 2 2 88%	4180
September	1st to 10th	Day	2 1 1 1 1 1 1 2 3 86%	2280
	11th to 20th	Day	5% 2 1 2 2 2 2 2 4 5% 73%	2280
	21st to end	Day	5% 2 1 2 2 1 2 1 3 4 76%	2062
October	1st to 10th	Day	4 3 1 3 2 2 2 3 4 5% 72%	3180
	11th to 20th	Day	9% 2 1 2 2 2 2 2 3 5% 69%	3161
	21st to end	Day	7% 4 1 4 3 4 4 3 4 6% 60%	3448
November	1st to 10th	Day	13% 9% 2 3 3 3 3 3 4 6% 51%	1765
	11th to 20th	Day	15% 5% 1 4 4 3 3 3 6% 6% 50%	1719
	21st to end	Day	11% 9% 2 4 3 3 4 3 5% 5% 52%	1583
December	1st to 10th	Day	19% 7% 2 3 3 3 3 3 5% 7% 45%	1520
	11th to 20th	Day	28% 12% 2 5% 4 3 3 3 4 5% 31%	1928
	21st to end	Day	15% 9% 2 6% 3 4 4 4 6% 8% 39%	2794
January	1st to 10th	Night	14% 14% 3 5% 3 3 4 3 4 6% 41%	4406
	11th to 20th	Night	23% 10% 3 4 4 4 4 3 4 6% 36%	4261
	21st to end	Night	21% 15% 2 6% 4 4 4 3 5% 5% 31%	4521
February	1st to 10th	Night	18% 8% 3 4 3 2 3 2 4 6% 47%	2470
	11th to 20th	Night	14% 13% 2 4 3 4 4 3 5% 6% 44%	2270
	21st to end	Night	17% 12% 3 5% 2 2 3 2 3 6% 45%	1884
March	1st to 10th	Night	21% 23% 4 4 3 2 3 2 3 5% 30%	3682
	11th to 20th	Night	16% 9% 1 2 2 2 2 2 3 4 55%	3490
	21st to end	Night	19% 20% 3 4 3 3 4 3 5% 6% 31%	3648
April	1st to 10th	Night	15% 12% 2 5% 3 3 3 3 6% 5% 45%	1900
	11th to 20th	Night	14% 9% 2 3 3 2 4 2 5% 5% 51%	1879
	21st to end	Night	11% 6% 1 3 2 2 3 3 4 6% 59%	1900
May	1st to 10th	Night	6% 8% 1 3 3 2 2 2 3 5% 64%	3027
	11th to 20th	Night	5% 2 1 2 2 2 2 2 4 5% 73%	2516
	21st to end	Night	6% 3 1 3 2 2 2 2 3 5% 72%	2762
June	1st to 10th	Night	8% 5% 1 2 3 2 3 3 4 6% 63%	1520
	11th to 20th	Night	3 2 2 2 1 2 2 4 5% 77%	1520
	21st to end	Night	3 2 1 2 2 1 2 1 3 4 79%	1520
July	1st to 10th	Night	1 1 1 1 1 1 2 91%	2540
	11th to 20th	Night	3 2 1 2 1 2 2 1 2 2 81%	2540
	21st to end	Night	1 1 1 2 1 1 1 1 3 3 85%	2979
August	1st to 10th	Night	4 2 1 2 2 2 2 3 4 5% 73%	2848
	11th to 20th	Night	1 1 1 1 1 1 1 2 3 88%	3084
	21st to end	Night	3 1 1 1 1 1 1 1 2 87%	3498
September	1st to 10th	Night	2 1 1 1 1 1 2 2 3 85%	1900
	11th to 20th	Night	4 2 1 2 2 2 2 2 3 4 77%	1900
	21st to end	Night	3 2 1 2 1 2 2 2 4 5% 76%	2113
October	1st to 10th	Night	4 3 1 3 2 2 2 1 2 3 77%	3800
	11th to 20th	Night	5% 2 1 2 2 2 2 1 3 4 77%	3777
	21st to end	Night	11% 3 1 2 2 2 3 3 5% 6% 63%	4121
November	1st to 10th	Night	15% 7% 2 3 2 2 3 3 4 7% 53%	2533
	11th to 20th	Night	12% 4 1 4 3 3 3 3 6% 7% 53%	2483
	21st to end	Night	12% 8% 1 5% 3 3 3 3 4 5% 54%	2593
December	1st to 10th	Night	20% 7% 1 3 2 3 3 3 3 6% 50%	2660
	11th to 20th	Night	29% 10% 2 5% 3 2 3 3 4 7% 32%	3276
	21st to end	Night	18% 11% 3 6% 4 4 4 3 5% 6% 35%	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	49% 4 6% 21% 17% 3	2539
	11th to 20th	Day	54% 4 8% 14% 13% 7%	2700
	21st to end	Day	52% 4 8% 18% 13% 5%	3146
February	1st to 10th	Day	42% 3 9% 17% 19% 10%	1710
	11th to 20th	Day	43% 4 8% 18% 20% 7%	1805
	21st to end	Day	45% 2 9% 22% 15% 7%	1570
March	1st to 10th	Day	62% 5% 6% 11% 11% 5%	3189
	11th to 20th	Day	35% 3 7% 31% 19% 5%	3490
	21st to end	Day	57% 6% 10% 17% 8% 2	4004
April	1st to 10th	Day	44% 4 12% 21% 16% 2	2280
	11th to 20th	Day	37% 5% 12% 23% 17% 6%	2252
	21st to end	Day	30% 5% 13% 28% 21% 4	2280
May	1st to 10th	Day	23% 3 13% 26% 22% 13%	3945
	11th to 20th	Day	16% 3 8% 26% 39% 9%	4380
	21st to end	Day	19% 4 9% 41% 23% 3	4814
June	1st to 10th	Day	25% 5% 10% 22% 28% 9%	2660
	11th to 20th	Day	13% 3 8% 21% 36% 19%	2660
	21st to end	Day	10% 1 3 16% 37% 32%	2660
July	1st to 10th	Day	4 1 1 6% 16% 72%	4351
	11th to 20th	Day	9% 1 2 7% 18% 62%	4345
	21st to end	Day	7% 1 2 5% 29% 56%	4420
August	1st to 10th	Day	13% 1 1 8% 24% 53%	4076
	11th to 20th	Day	5% 1 2 6% 43% 43%	3798
	21st to end	Day	7% 1 1 11% 44% 35%	4179
September	1st to 10th	Day	7% 1 2 9% 34% 47%	2280
	11th to 20th	Day	15% 3 4 21% 38% 20%	2280
	21st to end	Day	15% 2 5% 19% 35% 25%	2062
October	1st to 10th	Day	17% 2 3 11% 33% 33%	3180
	11th to 20th	Day	20% 2 4 17% 40% 17%	3161
	21st to end	Day	27% 1 5% 23% 29% 15%	3448
November	1st to 10th	Day	35% 3 7% 19% 22% 14%	1765
	11th to 20th	Day	35% 3 10% 18% 23% 11%	1719
	21st to end	Day	34% 4 7% 19% 22% 13%	1583
December	1st to 10th	Day	39% 4 8% 19% 19% 11%	1520
	11th to 20th	Day	57% 3 6% 13% 14% 7%	1928
	21st to end	Day	43% 4 12% 21% 15% 5%	2794
January	1st to 10th	Night	44% 5% 10% 24% 13% 4	4406
	11th to 20th	Night	51% 4 10% 12% 15% 9%	4261
	21st to end	Night	55% 5% 7% 14% 13% 7%	4521
February	1st to 10th	Night	40% 3 7% 18% 20% 12%	2470
	11th to 20th	Night	42% 4 7% 19% 20% 9%	2271
	21st to end	Night	43% 3 7% 22% 19% 6%	1884
March	1st to 10th	Night	59% 4 9% 13% 10% 6%	3682
	11th to 20th	Night	34% 3 6% 23% 27% 6%	3490
	21st to end	Night	54% 6% 10% 18% 8% 2	3648
April	1st to 10th	Night	41% 4 12% 22% 17% 4	1900
	11th to 20th	Night	35% 5% 13% 23% 18% 6%	1879
	21st to end	Night	27% 4 13% 32% 20% 3	1900
May	1st to 10th	Night	23% 7% 11% 23% 26% 9%	3027
	11th to 20th	Night	15% 4 9% 20% 34% 18%	2516
	21st to end	Night	16% 5% 11% 38% 24% 6%	2762
June	1st to 10th	Night	22% 8% 10% 24% 25% 11%	1520
	11th to 20th	Night	11% 3 8% 23% 34% 21%	1520
	21st to end	Night	12% 1 4 14% 33% 36%	1520
July	1st to 10th	Night	4 2 1 5% 15% 73%	2500
	11th to 20th	Night	13% 1 2 7% 15% 63%	2492
	21st to end	Night	7% 1 2 5% 25% 60%	2886
August	1st to 10th	Night	15% 1 2 7% 23% 51%	2839
	11th to 20th	Night	5% 1 2 8% 39% 45%	3114
	21st to end	Night	8% 1 2 12% 36% 41%	3498
September	1st to 10th	Night	7% 1 3 8% 31% 51%	1900
	11th to 20th	Night	14% 2 5% 19% 39% 21%	1900
	21st to end	Night	13% 3 4 20% 33% 27%	2113
October	1st to 10th	Night	16% 2 3 10% 28% 41%	3800
	11th to 20th	Night	15% 1 4 23% 38% 18%	3777
	21st to end	Night	25% 2 4 22% 29% 18%	4121
November	1st to 10th	Night	34% 4 6% 20% 20% 16%	2533
	11th to 20th	Night	29% 5% 10% 20% 24% 12%	2483
	21st to end	Night	34% 3 6% 20% 22% 15%	2593
December	1st to 10th	Night	38% 5% 7% 17% 20% 13%	2660
	11th to 20th	Night	54% 3 6% 11% 19% 7%	3276
	21st to end	Night	50% 5% 8% 17% 15% 6%	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	44% 13% 19% 15% 7% 1	180
	11th to 20th	Day	31% 13% 24% 23% 8% 1	275
	21st to end	Day	29% 14% 21% 23% 11% 2	407
February	1st to 10th	Day	31% 15% 28% 18% 7% 1	370
	11th to 20th	Day	31% 19% 30% 16% 4	429
	21st to end	Day	29% 18% 34% 15% 5%	382
March	1st to 10th	Day	40% 22% 21% 12% 3 1	460
	11th to 20th	Day	34% 17% 24% 15% 8% 2	460
	21st to end	Day	33% 24% 28% 13% 3	506
April	1st to 10th	Day	25% 23% 29% 16% 5% 1	460
	11th to 20th	Day	29% 19% 28% 16% 6% 1	452
	21st to end	Day	17% 21% 31% 22% 8% 1	460
May	1st to 10th	Day	18% 26% 29% 18% 6% 2	463
	11th to 20th	Day	19% 19% 30% 20% 8% 4	488
	21st to end	Day	16% 14% 31% 25% 10% 4	529
June	1st to 10th	Day	11% 18% 31% 26% 10% 4	490
	11th to 20th	Day	11% 17% 39% 19% 9% 4	490
	21st to end	Day	3 15% 39% 27% 10% 6%	490
July	1st to 10th	Day	2 8% 48% 26% 12% 5%	486
	11th to 20th	Day	1 8% 44% 29% 12% 6%	484
	21st to end	Day	1 8% 42% 29% 13% 5%	531
August	1st to 10th	Day	5% 9% 39% 32% 11% 4	487
	11th to 20th	Day	3 11% 39% 31% 11% 4	477
	21st to end	Day	2 9% 42% 34% 11% 2	539
September	1st to 10th	Day	3 12% 43% 28% 12% 1	490
	11th to 20th	Day	9% 13% 36% 31% 9% 2	490
	21st to end	Day	6% 14% 38% 32% 8% 1	490
October	1st to 10th	Day	7% 19% 33% 29% 11% 2	490
	11th to 20th	Day	11% 12% 31% 31% 11% 3	490
	21st to end	Day	14% 16% 28% 29% 11% 2	539
November	1st to 10th	Day	22% 10% 23% 25% 17% 3	301
	11th to 20th	Day	17% 12% 25% 27% 17% 3	273
	21st to end	Day	20% 14% 21% 27% 16% 2	210
December	1st to 10th	Day	27% 13% 22% 19% 13% 5%	180
	11th to 20th	Day	28% 13% 22% 19% 15% 2	180
	21st to end	Day	28% 15% 21% 22% 12% 2	198
January	1st to 10th	Night	28% 9% 24% 23% 13% 5%	760
	11th to 20th	Night	22% 13% 26% 28% 10% 1	760
	21st to end	Night	26% 12% 21% 23% 16% 2	836
February	1st to 10th	Night	24% 12% 25% 26% 11% 1	760
	11th to 20th	Night	24% 11% 21% 27% 14% 3	744
	21st to end	Night	25% 13% 23% 29% 9% 2	628
March	1st to 10th	Night	31% 11% 20% 23% 12% 2	760
	11th to 20th	Night	27% 9% 19% 24% 20% 2	760
	21st to end	Night	29% 10% 23% 26% 12% 1	836
April	1st to 10th	Night	23% 7% 22% 31% 15% 2	760
	11th to 20th	Night	19% 11% 21% 31% 14% 3	751
	21st to end	Night	14% 8% 21% 34% 19% 4	760
May	1st to 10th	Night	12% 13% 22% 29% 21% 3	672
	11th to 20th	Night	10% 6% 17% 40% 23% 4	374
	21st to end	Night	12% 4 16% 34% 28% 6%	411
June	1st to 10th	Night	9% 4 16% 36% 30% 4	380
	11th to 20th	Night	4 6% 17% 38% 32% 3	380
	21st to end	Night	3 2 17% 42% 32% 4	380
July	1st to 10th	Night	1 1 14% 36% 44% 4	370
	11th to 20th	Night	1 1 13% 43% 36% 5%	368
	21st to end	Night	2 1 12% 32% 45% 8%	546
August	1st to 10th	Night	3 2 13% 40% 36% 6%	567
	11th to 20th	Night	2 2 15% 39% 34% 8%	722
	21st to end	Night	2 1 12% 46% 35% 5%	836
September	1st to 10th	Night	2 1 15% 43% 34% 5%	760
	11th to 20th	Night	4 2 16% 39% 30% 9%	760
	21st to end	Night	4 5% 24% 35% 23% 9%	760
October	1st to 10th	Night	8% 7% 18% 40% 24% 4	760
	11th to 20th	Night	10% 7% 20% 34% 24% 5%	760
	21st to end	Night	11% 9% 22% 30% 22% 6%	836
November	1st to 10th	Night	19% 7% 18% 30% 21% 5%	780
	11th to 20th	Night	14% 10% 24% 33% 16% 3	764
	21st to end	Night	17% 9% 27% 27% 17% 3	760
December	1st to 10th	Night	24% 13% 21% 28% 11% 2	760
	11th to 20th	Night	29% 10% 21% 27% 11% 2	760
	21st to end	Night	29% 14% 23% 24% 10%	836

Page generated at 2024-11-08 19:45:37. Version ac07

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