Wildcat Hills Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wildcat Hills Observatory 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	6% 5% 2 5% 4 4 4 4 6% 8% 54%	105593
	Night	6% 6% 2 5% 4 4 4 3 6% 7% 53%	103214
Transparency	Day	27% 6% 12% 26% 21% 8%	105334
	Night	29% 6% 14% 26% 19% 6%	103063
Seeing	Day	10% 9% 30% 30% 17% 5%	15909
	Night	9% 9% 39% 34% 8%	25965

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	2 5% 3 10% 5% 3 4 3 5% 7% 53%	2538
	11th to 20th	Day	3 9% 4 9% 6% 5% 5% 4 6% 6% 43%	2540
	21st to end	Day	2 5% 2 4 3 3 3 4 5% 8% 62%	2950
February	1st to 10th	Day	4 9% 4 9% 4 4 5% 3 6% 7% 44%	1721
	11th to 20th	Day	4 9% 3 7% 4 4 4 3 6% 7% 49%	1849
	21st to end	Day	4 8% 3 6% 5% 4 4 3 5% 6% 52%	1570
March	1st to 10th	Day	6% 10% 3 6% 4 3 3 3 5% 8% 50%	3130
	11th to 20th	Day	7% 6% 2 4 3 3 3 3 5% 6% 58%	3264
	21st to end	Day	8% 8% 3 7% 5% 5% 5% 4 6% 8% 41%	4165
April	1st to 10th	Day	8% 8% 2 5% 5% 4 5% 4 5% 8% 46%	2280
	11th to 20th	Day	13% 9% 2 6% 4 4 4 4 7% 7% 39%	2251
	21st to end	Day	11% 7% 2 5% 5% 5% 4 3 6% 8% 44%	2346
May	1st to 10th	Day	13% 7% 2 6% 3 3 4 3 5% 8% 45%	4120
	11th to 20th	Day	10% 5% 1 4 3 4 5% 4 6% 9% 47%	4347
	21st to end	Day	9% 5% 2 5% 4 4 5% 4 7% 8% 47%	4825
June	1st to 10th	Day	5% 4 1 4 4 3 4 4 7% 10% 52%	2660
	11th to 20th	Day	9% 3 1 3 3 4 4 4 6% 9% 52%	2660
	21st to end	Day	4 2 1 3 4 3 4 4 6% 10% 57%	2660
July	1st to 10th	Day	6% 4 2 4 3 3 4 3 5% 7% 59%	4430
	11th to 20th	Day	3 1 1 3 3 3 5% 4 8% 11% 59%	4430
	21st to end	Day	3 2 1 3 3 4 5% 4 7% 10% 58%	4802
August	1st to 10th	Day	9% 3 1 4 4 4 4 4 7% 10% 51%	4284
	11th to 20th	Day	3 3 2 4 3 5% 5% 4 6% 8% 58%	3726
	21st to end	Day	4 3 1 4 4 4 5% 3 6% 8% 58%	4180
September	1st to 10th	Day	6% 3 1 5% 3 3 3 3 4 6% 62%	2280
	11th to 20th	Day	7% 3 1 3 3 3 4 3 4 7% 64%	2201
	21st to end	Day	7% 4 1 3 2 2 3 3 4 6% 64%	2090
October	1st to 10th	Day	6% 3 2 2 1 2 2 3 4 75%	3331
	11th to 20th	Day	8% 3 1 5% 3 3 3 3 4 6% 61%	3150
	21st to end	Day	7% 7% 2 5% 3 3 3 3 5% 7% 56%	3123
November	1st to 10th	Day	4 5% 2 4 3 3 3 3 6% 8% 58%	1763
	11th to 20th	Day	4 5% 1 4 3 3 3 3 6% 6% 62%	1800
	21st to end	Day	4 7% 3 4 3 3 3 3 6% 7% 57%	1703
December	1st to 10th	Day	4 7% 2 7% 4 3 4 4 6% 7% 53%	1600
	11th to 20th	Day	4 5% 2 5% 3 3 3 4 6% 8% 57%	2006
	21st to end	Day	5% 9% 4 9% 5% 3 4 3 5% 6% 48%	2818
January	1st to 10th	Night	3 7% 2 7% 4 4 3 4 5% 7% 54%	4417
	11th to 20th	Night	2 7% 4 8% 5% 5% 5% 3 5% 7% 51%	4430
	21st to end	Night	3 6% 2 6% 4 4 4 3 5% 7% 57%	4745
February	1st to 10th	Night	3 10% 3 9% 5% 4 4 3 5% 7% 45%	2457
	11th to 20th	Night	5% 8% 3 6% 4 4 5% 4 7% 8% 45%	2218
	21st to end	Night	4 8% 3 8% 4 3 4 3 5% 6% 53%	1884
March	1st to 10th	Night	4 13% 3 6% 3 3 3 3 5% 6% 51%	3734
	11th to 20th	Night	7% 9% 3 6% 4 3 3 2 4 6% 53%	3694
	21st to end	Night	7% 9% 3 8% 4 4 4 4 6% 9% 43%	3477
April	1st to 10th	Night	10% 8% 2 6% 4 4 3 3 5% 7% 47%	1900
	11th to 20th	Night	11% 9% 2 6% 3 4 4 3 5% 5% 47%	1877
	21st to end	Night	13% 9% 3 6% 4 3 4 3 5% 6% 43%	1834
May	1st to 10th	Night	13% 9% 3 7% 4 5% 4 3 5% 8% 39%	2850
	11th to 20th	Night	11% 4 1 4 3 4 4 4 7% 10% 47%	2555
	21st to end	Night	12% 5% 1 5% 4 4 4 4 7% 8% 46%	2762
June	1st to 10th	Night	7% 4 2 5% 3 4 5% 5% 6% 10% 49%	1520
	11th to 20th	Night	8% 3 1 3 4 4 4 5% 8% 10% 51%	1520
	21st to end	Night	4 3 1 5% 4 4 5% 4 7% 11% 52%	1520
July	1st to 10th	Night	5% 5% 2 6% 4 5% 5% 4 6% 8% 50%	2540
	11th to 20th	Night	3 1 1 4 3 4 5% 5% 8% 11% 56%	2540
	21st to end	Night	3 3 1 5% 4 4 4 5% 8% 9% 53%	2761
August	1st to 10th	Night	13% 4 1 5% 4 5% 5% 5% 6% 10% 42%	2638
	11th to 20th	Night	4 4 1 5% 5% 4 5% 5% 7% 10% 50%	3113
	21st to end	Night	3 3 2 5% 4 5% 6% 5% 7% 8% 52%	3487
September	1st to 10th	Night	7% 4 1 4 3 4 4 3 5% 8% 57%	1900
	11th to 20th	Night	6% 4 2 4 3 2 3 4 5% 6% 61%	1978
	21st to end	Night	8% 4 1 3 4 3 4 2 5% 5% 61%	2090
October	1st to 10th	Night	6% 4 1 2 2 2 2 1 2 3 75%	3630
	11th to 20th	Night	8% 4 1 4 3 3 3 3 4 7% 60%	3778
	21st to end	Night	7% 6% 2 5% 3 3 3 3 5% 6% 58%	4402
November	1st to 10th	Night	5% 5% 2 5% 3 3 4 3 6% 8% 56%	2535
	11th to 20th	Night	5% 6% 2 5% 4 3 4 3 5% 8% 56%	2600
	21st to end	Night	5% 8% 2 4 4 3 3 3 4 6% 58%	2695
December	1st to 10th	Night	4 7% 2 6% 4 3 4 3 4 7% 55%	2800
	11th to 20th	Night	4 5% 2 5% 4 4 4 3 6% 8% 56%	3411
	21st to end	Night	6% 10% 3 7% 4 3 4 3 5% 7% 47%	4922

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	30% 5% 13% 28% 22% 1	2539
	11th to 20th	Day	37% 7% 17% 19% 17% 2	2540
	21st to end	Day	21% 5% 20% 34% 15% 4	2950
February	1st to 10th	Day	38% 6% 16% 23% 15% 3	1721
	11th to 20th	Day	34% 6% 11% 27% 18% 5%	1859
	21st to end	Day	32% 5% 13% 25% 19% 6%	1570
March	1st to 10th	Day	31% 4 9% 27% 25% 3	3130
	11th to 20th	Day	27% 5% 19% 31% 16% 3	3264
	21st to end	Day	37% 10% 14% 29% 9% 1	4165
April	1st to 10th	Day	35% 6% 14% 25% 14% 5%	2280
	11th to 20th	Day	40% 7% 13% 19% 16% 4	2254
	21st to end	Day	35% 7% 11% 28% 17% 2	2346
May	1st to 10th	Day	35% 8% 13% 25% 13% 6%	4120
	11th to 20th	Day	30% 8% 13% 30% 16% 2	4351
	21st to end	Day	30% 9% 16% 27% 15% 2	4825
June	1st to 10th	Day	24% 10% 17% 28% 16% 4	2660
	11th to 20th	Day	27% 7% 12% 27% 20% 7%	2660
	21st to end	Day	20% 7% 11% 26% 26% 9%	2660
July	1st to 10th	Day	23% 5% 9% 20% 28% 15%	4361
	11th to 20th	Day	16% 7% 12% 27% 24% 15%	4355
	21st to end	Day	19% 6% 11% 22% 23% 19%	4651
August	1st to 10th	Day	27% 7% 14% 26% 19% 7%	4269
	11th to 20th	Day	23% 7% 11% 22% 24% 13%	3762
	21st to end	Day	22% 6% 11% 20% 24% 18%	4179
September	1st to 10th	Day	23% 4 8% 21% 30% 15%	2280
	11th to 20th	Day	21% 4 9% 23% 30% 14%	2201
	21st to end	Day	22% 4 8% 23% 35% 8%	2090
October	1st to 10th	Day	16% 3 7% 18% 32% 24%	3331
	11th to 20th	Day	25% 4 10% 30% 24% 7%	3150
	21st to end	Day	28% 4 11% 27% 25% 5%	3123
November	1st to 10th	Day	24% 4 13% 27% 23% 9%	1763
	11th to 20th	Day	22% 4 12% 30% 26% 5%	1800
	21st to end	Day	26% 4 13% 28% 25% 5%	1703
December	1st to 10th	Day	29% 6% 14% 28% 20% 4	1600
	11th to 20th	Day	24% 5% 14% 34% 21% 1	2004
	21st to end	Day	35% 6% 11% 31% 15% 2	2818
January	1st to 10th	Night	29% 6% 12% 34% 17% 2	4417
	11th to 20th	Night	31% 6% 20% 21% 18% 4	4430
	21st to end	Night	26% 6% 20% 33% 13% 2	4745
February	1st to 10th	Night	38% 6% 15% 24% 14% 3	2457
	11th to 20th	Night	35% 7% 13% 25% 17% 4	2218
	21st to end	Night	32% 6% 11% 27% 19% 5%	1884
March	1st to 10th	Night	33% 5% 10% 21% 26% 5%	3734
	11th to 20th	Night	33% 5% 13% 27% 20% 2	3694
	21st to end	Night	35% 9% 21% 25% 8% 1	3477
April	1st to 10th	Night	35% 7% 13% 23% 17% 5%	1900
	11th to 20th	Night	37% 7% 12% 24% 16% 4	1877
	21st to end	Night	41% 6% 10% 27% 15% 1	1834
May	1st to 10th	Night	39% 8% 16% 20% 14% 3	2850
	11th to 20th	Night	27% 10% 20% 31% 8% 3	2556
	21st to end	Night	33% 10% 18% 26% 10% 3	2762
June	1st to 10th	Night	27% 9% 23% 26% 12% 3	1520
	11th to 20th	Night	26% 8% 17% 22% 19% 7%	1520
	21st to end	Night	23% 8% 13% 26% 23% 6%	1520
July	1st to 10th	Night	29% 8% 11% 21% 21% 10%	2500
	11th to 20th	Night	19% 7% 18% 23% 24% 9%	2492
	21st to end	Night	23% 7% 14% 23% 20% 12%	2674
August	1st to 10th	Night	35% 8% 15% 21% 17% 3	2630
	11th to 20th	Night	26% 9% 15% 22% 18% 9%	3143
	21st to end	Night	26% 7% 13% 18% 24% 12%	3487
September	1st to 10th	Night	25% 5% 8% 22% 26% 13%	1900
	11th to 20th	Night	23% 6% 9% 25% 24% 14%	1978
	21st to end	Night	24% 5% 8% 27% 25% 12%	2090
October	1st to 10th	Night	17% 3 7% 17% 28% 28%	3630
	11th to 20th	Night	24% 4 13% 27% 24% 7%	3778
	21st to end	Night	27% 4 10% 26% 23% 9%	4402
November	1st to 10th	Night	26% 5% 13% 25% 24% 7%	2535
	11th to 20th	Night	26% 4 11% 28% 24% 7%	2600
	21st to end	Night	28% 4 9% 30% 22% 6%	2695
December	1st to 10th	Night	29% 5% 15% 29% 19% 5%	2800
	11th to 20th	Night	25% 5% 13% 35% 19% 2	3412
	21st to end	Night	35% 5% 12% 31% 14% 2	4922

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	10% 8% 40% 28% 11% 3	270
	11th to 20th	Day	11% 20% 31% 33% 4	270
	21st to end	Day	7% 15% 48% 21% 7% 2	297
February	1st to 10th	Day	10% 16% 49% 21% 3	270
	11th to 20th	Day	9% 18% 44% 22% 5% 1	270
	21st to end	Day	12% 17% 47% 20% 3	225
March	1st to 10th	Day	9% 16% 38% 29% 8% 1	270
	11th to 20th	Day	12% 13% 34% 24% 14% 3	325
	21st to end	Day	14% 14% 37% 26% 7% 2	506
April	1st to 10th	Day	14% 16% 39% 22% 8% 1	460
	11th to 20th	Day	20% 17% 34% 21% 6% 3	452
	21st to end	Day	16% 13% 30% 25% 12% 3	526
May	1st to 10th	Day	17% 13% 26% 27% 13% 3	653
	11th to 20th	Day	18% 6% 27% 30% 14% 5%	675
	21st to end	Day	12% 10% 26% 29% 18% 4	734
June	1st to 10th	Day	5% 5% 26% 34% 20% 9%	680
	11th to 20th	Day	9% 7% 34% 32% 16% 3	680
	21st to end	Day	6% 4 29% 33% 24% 5%	680
July	1st to 10th	Day	8% 2 17% 39% 27% 7%	671
	11th to 20th	Day	5% 2 18% 41% 26% 7%	668
	21st to end	Day	5% 2 17% 37% 33% 6%	739
August	1st to 10th	Day	6% 2 19% 37% 31% 5%	635
	11th to 20th	Day	4 5% 22% 32% 26% 11%	477
	21st to end	Day	4 3 25% 33% 25% 9%	539
September	1st to 10th	Day	7% 5% 19% 35% 24% 10%	490
	11th to 20th	Day	6% 5% 22% 32% 25% 10%	411
	21st to end	Day	8% 7% 21% 34% 18% 11%	300
October	1st to 10th	Day	11% 8% 26% 23% 21% 11%	300
	11th to 20th	Day	7% 11% 37% 22% 17% 6%	300
	21st to end	Day	10% 12% 38% 28% 9% 3	330
November	1st to 10th	Day	8% 11% 40% 29% 9% 4	300
	11th to 20th	Day	7% 13% 42% 26% 11%	300
	21st to end	Day	11% 10% 41% 27% 9% 2	300
December	1st to 10th	Day	9% 16% 42% 24% 9% 1	300
	11th to 20th	Day	8% 14% 50% 22% 5%	300
	21st to end	Day	10% 16% 42% 23% 8% 1	306
January	1st to 10th	Night	7% 14% 43% 27% 8%	950
	11th to 20th	Night	7% 19% 42% 28% 3 1	950
	21st to end	Night	8% 12% 48% 27% 5%	969
February	1st to 10th	Night	7% 12% 53% 23% 4	760
	11th to 20th	Night	10% 12% 49% 26% 3	744
	21st to end	Night	8% 14% 50% 25% 3	628
March	1st to 10th	Night	9% 11% 46% 29% 5%	760
	11th to 20th	Night	11% 8% 42% 32% 6%	760
	21st to end	Night	13% 12% 42% 29% 4	627
April	1st to 10th	Night	14% 13% 39% 30% 5%	570
	11th to 20th	Night	14% 13% 40% 28% 3	563
	21st to end	Night	17% 11% 32% 33% 7%	570
May	1st to 10th	Night	20% 9% 31% 31% 9% 1	570
	11th to 20th	Night	19% 4 30% 37% 9% 1	561
	21st to end	Night	14% 8% 31% 36% 11%	617
June	1st to 10th	Night	9% 5% 30% 40% 14% 1	570
	11th to 20th	Night	8% 6% 39% 40% 7%	570
	21st to end	Night	5% 4 31% 48% 12%	570
July	1st to 10th	Night	6% 3 25% 47% 19%	555
	11th to 20th	Night	4 2 26% 53% 14% 1	552
	21st to end	Night	5% 1 21% 51% 21% 1	624
August	1st to 10th	Night	9% 2 22% 48% 19%	567
	11th to 20th	Night	5% 2 30% 49% 13% 1	564
	21st to end	Night	4 3 28% 48% 16% 1	627
September	1st to 10th	Night	8% 3 28% 48% 12% 1	570
	11th to 20th	Night	8% 4 29% 41% 16% 2	570
	21st to end	Night	9% 5% 31% 44% 12%	570
October	1st to 10th	Night	14% 5% 29% 37% 14% 1	655
	11th to 20th	Night	9% 7% 40% 34% 9%	760
	21st to end	Night	11% 8% 39% 35% 7%	1004
November	1st to 10th	Night	7% 7% 44% 34% 7% 1	975
	11th to 20th	Night	8% 13% 47% 28% 4	1000
	21st to end	Night	8% 10% 44% 32% 6%	1000
December	1st to 10th	Night	7% 14% 50% 25% 4	1000
	11th to 20th	Night	8% 10% 50% 28% 4	1000
	21st to end	Night	10% 14% 47% 24% 4	1063

Page generated at 2024-12-21 02:13:53. Version ac07

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