Crest Airpark Astro-Shack
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Crest Airpark Astro-Shack clear sky chart from 2005-11-06 to 2024-11-05.

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	21% 9% 3 7% 5% 4 4 3 5% 6% 32%	106086
	Night	24% 10% 3 7% 5% 4 4 3 5% 6% 30%	101551
Transparency	Day	53% 8% 11% 17% 9% 2	105846
	Night	56% 8% 11% 16% 8% 2	101437
Seeing	Day	27% 11% 20% 25% 15% 3	15009
	Night	31% 10% 15% 26% 17% 2	23335

By Month

Percentage Cloud Cover NW (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	38% 14% 4 9% 6% 4 4 2 4 4 11%	2539
	11th to 20th	Day	25% 11% 4 9% 5% 4 4 4 4 6% 24%	2516
	21st to end	Day	42% 12% 4 9% 4 3 3 3 4 4 12%	2869
February	1st to 10th	Day	32% 12% 4 8% 5% 4 4 3 5% 7% 17%	1710
	11th to 20th	Day	32% 13% 4 8% 5% 4 3 3 3 6% 18%	1665
	21st to end	Day	27% 15% 4 9% 6% 4 4 3 4 3 20%	1489
March	1st to 10th	Day	18% 14% 4 10% 6% 6% 6% 4 6% 6% 20%	3198
	11th to 20th	Day	22% 10% 3 7% 5% 4 4 4 4 5% 34%	3490
	21st to end	Day	24% 14% 4 10% 6% 6% 6% 4 5% 6% 15%	3965
April	1st to 10th	Day	26% 13% 3 10% 5% 5% 5% 5% 6% 5% 16%	2280
	11th to 20th	Day	22% 12% 4 8% 7% 5% 5% 4 5% 6% 24%	2257
	21st to end	Day	21% 12% 4 11% 7% 6% 4 4 5% 6% 21%	2513
May	1st to 10th	Day	20% 8% 2 6% 4 4 5% 4 4 7% 35%	4420
	11th to 20th	Day	18% 8% 2 6% 4 4 5% 4 6% 8% 36%	4377
	21st to end	Day	26% 12% 4 10% 5% 5% 5% 4 5% 6% 18%	4813
June	1st to 10th	Day	22% 10% 3 7% 6% 5% 5% 4 6% 7% 26%	2660
	11th to 20th	Day	22% 11% 4 9% 6% 6% 5% 4 6% 7% 21%	2835
	21st to end	Day	12% 7% 2 9% 6% 5% 5% 3 6% 7% 38%	2850
July	1st to 10th	Day	8% 4 1 4 3 3 3 3 3 4 62%	4740
	11th to 20th	Day	6% 4 2 3 3 3 3 2 3 5% 67%	4434
	21st to end	Day	12% 4 2 5% 3 3 3 3 4 5% 55%	4790
August	1st to 10th	Day	6% 4 1 4 2 4 3 3 5% 7% 60%	4323
	11th to 20th	Day	12% 6% 3 7% 5% 5% 5% 4 6% 8% 40%	4026
	21st to end	Day	18% 8% 2 7% 4 3 3 3 4 6% 41%	4312
September	1st to 10th	Day	10% 6% 2 6% 4 4 4 3 5% 6% 50%	2280
	11th to 20th	Day	15% 7% 3 8% 5% 4 4 4 6% 7% 37%	2280
	21st to end	Day	19% 7% 3 7% 4 4 4 3 5% 8% 37%	2012
October	1st to 10th	Day	18% 6% 2 7% 4 4 4 3 6% 10% 38%	3180
	11th to 20th	Day	29% 9% 3 7% 4 4 4 3 5% 6% 26%	3161
	21st to end	Day	29% 9% 3 9% 6% 5% 5% 3 5% 6% 21%	3241
November	1st to 10th	Day	33% 10% 4 7% 5% 5% 4 4 4 5% 18%	1582
	11th to 20th	Day	32% 11% 3 8% 4 4 3 3 4 5% 22%	1520
	21st to end	Day	32% 10% 3 8% 4 4 4 3 5% 5% 21%	1520
December	1st to 10th	Day	29% 11% 3 6% 5% 5% 4 3 5% 5% 24%	1520
	11th to 20th	Day	33% 12% 3 7% 6% 5% 4 4 6% 6% 15%	1925
	21st to end	Day	27% 13% 5% 11% 7% 6% 4 4 4 4 16%	2794
January	1st to 10th	Night	38% 15% 4 8% 5% 5% 4 3 4 4 11%	4406
	11th to 20th	Night	28% 12% 4 7% 4 3 3 3 5% 7% 24%	4382
	21st to end	Night	39% 11% 4 7% 5% 5% 4 3 4 5% 14%	4786
February	1st to 10th	Night	32% 12% 3 9% 5% 5% 4 3 3 6% 18%	2470
	11th to 20th	Night	28% 12% 3 8% 5% 4 4 4 4 4 23%	2402
	21st to end	Night	29% 12% 3 8% 5% 3 4 5% 5% 5% 21%	1965
March	1st to 10th	Night	19% 14% 4 9% 6% 6% 6% 4 7% 7% 19%	3674
	11th to 20th	Night	21% 8% 3 6% 4 4 4 3 5% 6% 36%	3489
	21st to end	Night	30% 15% 4 9% 5% 4 5% 4 5% 4 14%	3687
April	1st to 10th	Night	25% 11% 4 9% 6% 5% 6% 5% 5% 6% 19%	1900
	11th to 20th	Night	20% 11% 3 8% 5% 5% 5% 4 6% 6% 28%	1870
	21st to end	Night	22% 11% 3 9% 7% 6% 5% 4 5% 7% 22%	1665
May	1st to 10th	Night	20% 11% 3 7% 4 4 3 2 4 4 37%	2540
	11th to 20th	Night	15% 9% 3 8% 5% 4 5% 4 6% 8% 34%	2516
	21st to end	Night	21% 13% 3 11% 6% 5% 4 4 5% 5% 21%	2762
June	1st to 10th	Night	17% 10% 4 8% 7% 5% 5% 4 4 6% 31%	1520
	11th to 20th	Night	18% 10% 3 8% 6% 6% 5% 5% 6% 7% 26%	1340
	21st to end	Night	12% 6% 3 6% 5% 4 3 4 5% 6% 45%	1330
July	1st to 10th	Night	6% 5% 2 6% 3 3 4 2 4 3 63%	2220
	11th to 20th	Night	4 4 1 3 3 2 2 2 3 4 72%	2508
	21st to end	Night	13% 3 1 4 2 3 3 3 4 6% 59%	2762
August	1st to 10th	Night	5% 4 1 4 3 3 2 2 4 6% 67%	2608
	11th to 20th	Night	14% 5% 2 6% 4 3 3 3 4 7% 48%	2812
	21st to end	Night	18% 6% 2 5% 3 3 4 3 4 6% 47%	3361
September	1st to 10th	Night	11% 4 2 5% 3 4 4 4 4 7% 53%	1900
	11th to 20th	Night	16% 8% 3 6% 4 4 4 3 4 5% 42%	1900
	21st to end	Night	17% 7% 2 8% 4 4 4 3 4 6% 42%	2163
October	1st to 10th	Night	18% 6% 2 7% 4 3 4 4 5% 8% 41%	3800
	11th to 20th	Night	28% 8% 3 6% 3 5% 5% 3 5% 6% 29%	3777
	21st to end	Night	30% 10% 3 7% 4 4 4 3 5% 6% 24%	4320
November	1st to 10th	Night	34% 9% 3 8% 4 4 4 3 5% 6% 21%	2594
	11th to 20th	Night	31% 10% 3 7% 6% 5% 3 3 4 5% 23%	2660
	21st to end	Night	30% 11% 4 7% 5% 4 4 3 5% 6% 23%	2660
December	1st to 10th	Night	29% 11% 3 7% 5% 4 4 4 4 5% 24%	2660
	11th to 20th	Night	30% 12% 4 9% 6% 4 4 4 5% 4 18%	3280
	21st to end	Night	30% 13% 4 11% 7% 5% 4 3 4 5% 15%	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	76% 8% 5% 7% 3 1	2539
	11th to 20th	Day	61% 9% 9% 13% 6% 1	2540
	21st to end	Day	76% 6% 6% 8% 3 1	2869
February	1st to 10th	Day	69% 7% 10% 9% 4 1	1710
	11th to 20th	Day	68% 7% 8% 10% 6% 1	1674
	21st to end	Day	69% 7% 8% 11% 5%	1489
March	1st to 10th	Day	62% 10% 11% 12% 5%	3198
	11th to 20th	Day	52% 8% 10% 27% 2 1	3490
	21st to end	Day	69% 10% 10% 9% 1	3965
April	1st to 10th	Day	68% 11% 12% 8% 1	2280
	11th to 20th	Day	63% 8% 9% 13% 6% 1	2257
	21st to end	Day	67% 8% 9% 10% 4 1	2513
May	1st to 10th	Day	49% 12% 10% 19% 10%	4420
	11th to 20th	Day	44% 15% 20% 17% 3	4380
	21st to end	Day	66% 11% 14% 8% 1	4814
June	1st to 10th	Day	60% 9% 15% 12% 5%	2660
	11th to 20th	Day	65% 8% 13% 10% 3	2835
	21st to end	Day	46% 8% 18% 19% 8% 2	2850
July	1st to 10th	Day	27% 6% 7% 21% 21% 17%	4666
	11th to 20th	Day	23% 5% 6% 27% 34% 5%	4358
	21st to end	Day	32% 4 11% 35% 16% 2	4639
August	1st to 10th	Day	25% 5% 10% 38% 20% 2	4306
	11th to 20th	Day	45% 4 19% 22% 8% 1	4065
	21st to end	Day	45% 5% 11% 26% 12% 1	4311
September	1st to 10th	Day	34% 7% 15% 25% 14% 5%	2280
	11th to 20th	Day	46% 8% 12% 17% 13% 3	2280
	21st to end	Day	47% 7% 16% 17% 11% 2	2012
October	1st to 10th	Day	43% 5% 13% 31% 8%	3180
	11th to 20th	Day	59% 4 11% 16% 8% 1	3161
	21st to end	Day	66% 4 11% 10% 7% 2	3241
November	1st to 10th	Day	68% 7% 9% 11% 4	1582
	11th to 20th	Day	67% 8% 7% 9% 7% 2	1520
	21st to end	Day	66% 6% 6% 11% 9% 2	1520
December	1st to 10th	Day	63% 8% 8% 13% 8% 1	1520
	11th to 20th	Day	68% 7% 11% 10% 4 1	1928
	21st to end	Day	69% 9% 9% 10% 3	2794
January	1st to 10th	Night	77% 7% 6% 6% 2 1	4406
	11th to 20th	Night	60% 9% 7% 16% 8% 1	4420
	21st to end	Night	73% 7% 7% 7% 5% 1	4786
February	1st to 10th	Night	69% 7% 9% 9% 5% 1	2470
	11th to 20th	Night	63% 9% 10% 9% 6% 2	2404
	21st to end	Night	66% 9% 8% 11% 5%	1965
March	1st to 10th	Night	61% 10% 9% 14% 5%	3674
	11th to 20th	Night	47% 10% 14% 25% 4 1	3490
	21st to end	Night	70% 11% 10% 9% 1	3687
April	1st to 10th	Night	66% 10% 12% 10% 2	1900
	11th to 20th	Night	58% 8% 12% 14% 7% 1	1870
	21st to end	Night	65% 9% 9% 11% 5% 1	1665
May	1st to 10th	Night	50% 8% 11% 20% 10%	2540
	11th to 20th	Night	45% 14% 19% 18% 3 1	2516
	21st to end	Night	63% 15% 13% 8% 1	2762
June	1st to 10th	Night	57% 9% 15% 14% 5%	1520
	11th to 20th	Night	59% 9% 17% 14% 2	1340
	21st to end	Night	42% 8% 21% 20% 7% 2	1330
July	1st to 10th	Night	31% 6% 7% 20% 17% 19%	2185
	11th to 20th	Night	20% 4 7% 29% 39% 2	2461
	21st to end	Night	31% 5% 12% 31% 19% 3	2674
August	1st to 10th	Night	20% 4 11% 41% 22% 2	2600
	11th to 20th	Night	42% 5% 21% 22% 8% 3	2839
	21st to end	Night	42% 4 13% 29% 11% 1	3361
September	1st to 10th	Night	32% 7% 15% 26% 15% 5%	1900
	11th to 20th	Night	46% 8% 9% 18% 13% 5%	1900
	21st to end	Night	45% 9% 12% 20% 11% 3	2163
October	1st to 10th	Night	43% 4 15% 31% 6% 1	3800
	11th to 20th	Night	57% 3 11% 19% 8%	3777
	21st to end	Night	64% 5% 9% 14% 9%	4320
November	1st to 10th	Night	67% 8% 10% 11% 4 1	2594
	11th to 20th	Night	66% 7% 8% 10% 6% 3	2660
	21st to end	Night	65% 7% 7% 11% 9% 1	2660
December	1st to 10th	Night	63% 7% 9% 12% 8% 1	2660
	11th to 20th	Night	68% 7% 10% 10% 4	3276
	21st to end	Night	70% 12% 6% 9% 3	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	39% 17% 18% 13% 9% 4	180
	11th to 20th	Day	36% 16% 16% 19% 9% 3	180
	21st to end	Day	41% 14% 18% 16% 8% 3	247
February	1st to 10th	Day	43% 11% 19% 17% 8% 2	370
	11th to 20th	Day	46% 13% 18% 15% 7% 1	365
	21st to end	Day	38% 17% 19% 21% 5%	343
March	1st to 10th	Day	32% 19% 22% 19% 8% 1	460
	11th to 20th	Day	32% 16% 20% 20% 9% 3	460
	21st to end	Day	37% 16% 22% 17% 8%	506
April	1st to 10th	Day	34% 17% 21% 16% 11% 1	460
	11th to 20th	Day	28% 20% 25% 17% 7% 3	452
	21st to end	Day	27% 18% 24% 21% 8% 1	460
May	1st to 10th	Day	22% 11% 26% 28% 11% 2	463
	11th to 20th	Day	29% 10% 23% 21% 13% 3	488
	21st to end	Day	31% 11% 21% 23% 11% 3	529
June	1st to 10th	Day	28% 9% 20% 25% 15% 2	490
	11th to 20th	Day	26% 14% 23% 23% 11% 3	665
	21st to end	Day	17% 8% 18% 33% 20% 3	680
July	1st to 10th	Day	15% 6% 16% 36% 24% 2	671
	11th to 20th	Day	11% 7% 19% 37% 22% 4	497
	21st to end	Day	10% 3 18% 39% 25% 5%	531
August	1st to 10th	Day	14% 5% 12% 35% 26% 8%	487
	11th to 20th	Day	9% 4 13% 36% 30% 8%	477
	21st to end	Day	18% 7% 21% 32% 16% 6%	539
September	1st to 10th	Day	16% 6% 22% 37% 15% 4	490
	11th to 20th	Day	21% 7% 19% 28% 21% 4	490
	21st to end	Day	20% 9% 23% 27% 19% 3	490
October	1st to 10th	Day	26% 10% 18% 23% 19% 3	490
	11th to 20th	Day	32% 9% 18% 21% 15% 4	490
	21st to end	Day	35% 14% 19% 19% 10% 4	420
November	1st to 10th	Day	41% 13% 16% 18% 12%	221
	11th to 20th	Day	38% 17% 17% 9% 14% 4	180
	21st to end	Day	39% 11% 17% 15% 14% 4	180
December	1st to 10th	Day	46% 11% 16% 12% 10% 6%	180
	11th to 20th	Day	44% 11% 19% 18% 7% 2	180
	21st to end	Day	36% 15% 15% 21% 11% 2	198
January	1st to 10th	Night	45% 15% 18% 16% 6%	760
	11th to 20th	Night	39% 13% 17% 22% 9% 1	760
	21st to end	Night	38% 11% 18% 25% 7%	836
February	1st to 10th	Night	40% 11% 18% 23% 7% 1	760
	11th to 20th	Night	36% 12% 16% 27% 9% 1	744
	21st to end	Night	39% 13% 16% 22% 8% 1	628
March	1st to 10th	Night	33% 14% 18% 22% 11% 1	760
	11th to 20th	Night	34% 12% 18% 24% 11% 1	760
	21st to end	Night	37% 14% 15% 24% 8% 2	836
April	1st to 10th	Night	34% 12% 15% 25% 11% 2	760
	11th to 20th	Night	29% 10% 20% 27% 11% 2	742
	21st to end	Night	31% 16% 11% 30% 12% 1	525
May	1st to 10th	Night	24% 13% 13% 30% 19% 1	380
	11th to 20th	Night	23% 7% 12% 30% 26% 2	374
	21st to end	Night	25% 11% 12% 24% 25% 4	411
June	1st to 10th	Night	24% 10% 13% 29% 23% 2	380
	11th to 20th	Night	28% 10% 13% 26% 21% 1	380
	21st to end	Night	19% 4 11% 32% 31% 3	380
July	1st to 10th	Night	13% 7% 9% 32% 35% 4	370
	11th to 20th	Night	11% 5% 7% 35% 38% 4	368
	21st to end	Night	9% 5% 6% 30% 44% 6%	416
August	1st to 10th	Night	13% 2 6% 25% 45% 8%	418
	11th to 20th	Night	11% 2 7% 25% 43% 12%	564
	21st to end	Night	17% 5% 7% 27% 39% 5%	751
September	1st to 10th	Night	14% 5% 8% 36% 31% 5%	760
	11th to 20th	Night	21% 6% 10% 24% 34% 6%	760
	21st to end	Night	22% 6% 12% 32% 25% 3	760
October	1st to 10th	Night	25% 5% 13% 29% 24% 3	760
	11th to 20th	Night	30% 10% 12% 26% 18% 4	760
	21st to end	Night	34% 9% 16% 29% 10% 2	836
November	1st to 10th	Night	39% 11% 22% 21% 7%	760
	11th to 20th	Night	40% 11% 17% 24% 7% 1	760
	21st to end	Night	37% 11% 18% 25% 8%	760
December	1st to 10th	Night	32% 12% 21% 25% 9% 1	760
	11th to 20th	Night	43% 10% 20% 19% 7% 1	760
	21st to end	Night	48% 13% 16% 17% 4	836

Page generated at 2024-11-02 23:11:28. Version ac07

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