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 2026-04-17.

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%	140249
	Night	6% 6% 2 6% 4 4 4 4 5% 7% 52%	139381
Transparency	Day	27% 6% 12% 26% 22% 7%	135121
	Night	30% 6% 13% 26% 20% 6%	135530
Seeing	Day	10% 10% 30% 29% 16% 4	17664
	Night	9% 9% 39% 34% 8%	27784

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 6% 3 10% 4 4 4 3 5% 7% 52%	4720
	11th to 20th	Day	2 7% 3 8% 5% 5% 5% 4 6% 7% 48%	4740
	21st to end	Day	2 5% 3 7% 4 4 4 4 5% 7% 56%	5483
February	1st to 10th	Day	4 9% 4 8% 4 4 4 3 6% 8% 45%	1903
	11th to 20th	Day	4 9% 3 7% 4 4 4 3 6% 7% 48%	2049
	21st to end	Day	3 7% 3 5% 5% 4 4 3 5% 6% 55%	1730
March	1st to 10th	Day	7% 12% 3 6% 3 3 3 3 4 7% 50%	4600
	11th to 20th	Day	7% 6% 2 4 3 3 3 3 5% 7% 57%	4779
	21st to end	Day	7% 8% 3 6% 4 4 4 4 6% 9% 43%	6101
April	1st to 10th	Day	8% 8% 2 5% 5% 4 5% 4 6% 8% 47%	2520
	11th to 20th	Day	12% 8% 2 6% 4 4 4 4 6% 7% 41%	2444
	21st to end	Day	11% 8% 2 5% 4 5% 4 3 6% 8% 44%	2470
May	1st to 10th	Day	10% 5% 2 6% 3 3 4 3 5% 7% 52%	5900
	11th to 20th	Day	9% 5% 1 5% 4 4 5% 4 7% 10% 46%	6244
	21st to end	Day	12% 6% 2 5% 3 3 4 4 6% 8% 48%	6925
June	1st to 10th	Day	5% 4 1 5% 4 3 4 4 7% 9% 52%	2800
	11th to 20th	Day	9% 3 1 3 3 4 4 4 6% 9% 53%	2800
	21st to end	Day	4 3 1 3 3 4 4 4 6% 9% 57%	2800
July	1st to 10th	Day	4 3 1 4 3 4 4 4 5% 8% 59%	6339
	11th to 20th	Day	3 2 1 3 3 4 5% 4 7% 10% 57%	6340
	21st to end	Day	5% 3 1 5% 4 4 5% 4 7% 9% 52%	6903
August	1st to 10th	Day	7% 3 1 4 3 4 5% 4 7% 10% 52%	6054
	11th to 20th	Day	2 2 1 4 3 4 4 4 6% 8% 63%	5366
	21st to end	Day	8% 5% 2 6% 4 5% 5% 4 6% 8% 49%	5984
September	1st to 10th	Day	6% 3 1 5% 3 3 3 3 4 6% 63%	2400
	11th to 20th	Day	7% 3 1 3 3 3 4 3 4 7% 62%	2317
	21st to end	Day	7% 4 1 3 2 2 3 3 5% 6% 64%	2200
October	1st to 10th	Day	6% 3 2 2 2 2 2 3 4 74%	3436
	11th to 20th	Day	7% 3 1 5% 3 3 3 3 4 6% 60%	3250
	21st to end	Day	7% 6% 2 5% 3 3 3 3 5% 7% 57%	3223
November	1st to 10th	Day	4 5% 2 4 3 3 3 3 6% 8% 58%	1853
	11th to 20th	Day	4 4 1 4 3 3 3 4 6% 6% 61%	1890
	21st to end	Day	4 7% 3 5% 3 3 4 3 5% 7% 57%	1788
December	1st to 10th	Day	2 4 2 5% 3 3 3 3 5% 6% 64%	2700
	11th to 20th	Day	3 5% 2 4 3 3 3 4 5% 7% 63%	3106
	21st to end	Day	4 7% 3 8% 5% 3 4 3 6% 7% 49%	4092
January	1st to 10th	Night	4 9% 3 8% 4 4 4 3 5% 6% 50%	8201
	11th to 20th	Night	2 6% 3 7% 5% 5% 4 4 5% 7% 51%	8250
	21st to end	Night	2 5% 3 8% 5% 5% 5% 4 5% 5% 54%	8787
February	1st to 10th	Night	3 9% 3 9% 5% 5% 4 3 5% 7% 45%	2715
	11th to 20th	Night	4 9% 4 7% 5% 4 5% 4 7% 8% 44%	2458
	21st to end	Night	3 7% 3 8% 4 3 4 3 5% 6% 54%	2076
March	1st to 10th	Night	7% 12% 3 5% 3 3 3 3 4 5% 53%	5494
	11th to 20th	Night	6% 8% 2 5% 4 3 3 3 4 6% 55%	5412
	21st to end	Night	9% 9% 3 7% 4 5% 4 4 6% 8% 40%	5094
April	1st to 10th	Night	10% 8% 2 6% 5% 4 4 3 5% 7% 47%	2100
	11th to 20th	Night	11% 8% 2 6% 3 4 4 3 5% 5% 47%	2037
	21st to end	Night	13% 9% 3 7% 4 3 4 3 5% 6% 43%	1930
May	1st to 10th	Night	11% 7% 2 6% 4 4 4 3 5% 7% 46%	4080
	11th to 20th	Night	10% 4 1 4 3 4 4 4 6% 9% 50%	3668
	21st to end	Night	15% 6% 2 5% 4 4 4 4 6% 7% 45%	3972
June	1st to 10th	Night	7% 4 2 6% 3 4 5% 5% 6% 10% 50%	1600
	11th to 20th	Night	7% 3 1 3 4 4 4 5% 7% 10% 50%	1600
	21st to end	Night	5% 3 1 5% 4 4 5% 4 7% 11% 52%	1600
July	1st to 10th	Night	3 4 2 6% 5% 5% 6% 4 7% 8% 51%	3640
	11th to 20th	Night	5% 3 1 4 4 4 5% 5% 7% 11% 50%	3640
	21st to end	Night	5% 4 2 6% 4 5% 5% 5% 7% 9% 48%	3970
August	1st to 10th	Night	10% 3 1 6% 5% 5% 6% 5% 7% 10% 43%	3729
	11th to 20th	Night	3 3 1 5% 4 5% 5% 5% 7% 9% 54%	4483
	21st to end	Night	7% 5% 2 7% 5% 5% 6% 4 7% 8% 45%	4993
September	1st to 10th	Night	7% 4 1 4 3 3 4 3 5% 8% 58%	2000
	11th to 20th	Night	7% 4 2 5% 3 3 3 4 5% 6% 59%	2082
	21st to end	Night	8% 4 1 4 4 3 4 2 5% 5% 61%	2200
October	1st to 10th	Night	6% 4 1 2 2 2 2 1 2 4 74%	3745
	11th to 20th	Night	8% 4 1 4 3 3 4 3 4 7% 60%	3898
	21st to end	Night	7% 5% 1 4 3 3 3 3 5% 6% 58%	4543
November	1st to 10th	Night	5% 5% 2 5% 3 3 4 3 6% 8% 56%	2665
	11th to 20th	Night	5% 5% 2 4 4 3 4 3 5% 8% 56%	2730
	21st to end	Night	5% 8% 2 4 4 3 3 3 4 6% 57%	2830
December	1st to 10th	Night	2 4 2 4 3 3 3 3 4 6% 65%	4710
	11th to 20th	Night	2 4 2 5% 4 4 4 4 7% 8% 56%	5321
	21st to end	Night	5% 9% 3 8% 4 4 4 4 6% 7% 46%	7128

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	32% 5% 14% 27% 21% 1	4723
	11th to 20th	Day	33% 6% 14% 23% 19% 5%	4740
	21st to end	Day	27% 5% 14% 28% 22% 5%	5483
February	1st to 10th	Day	36% 6% 15% 23% 17% 3	1903
	11th to 20th	Day	36% 5% 11% 26% 17% 5%	2059
	21st to end	Day	30% 5% 12% 25% 21% 6%	1730
March	1st to 10th	Day	33% 4 7% 25% 28% 3	4600
	11th to 20th	Day	26% 4 14% 25% 28% 3	4779
	21st to end	Day	35% 8% 15% 29% 12% 1	6101
April	1st to 10th	Day	34% 6% 14% 26% 15% 5%	2520
	11th to 20th	Day	39% 7% 13% 19% 18% 4	2447
	21st to end	Day	36% 7% 11% 28% 16% 2	2470
May	1st to 10th	Day	30% 7% 12% 31% 16% 5%	5900
	11th to 20th	Day	30% 8% 12% 27% 21% 2	6248
	21st to end	Day	33% 8% 13% 27% 17% 2	6926
June	1st to 10th	Day	25% 10% 17% 28% 16% 4	2800
	11th to 20th	Day	26% 7% 12% 27% 20% 8%	2800
	21st to end	Day	21% 7% 10% 27% 26% 10%	2800
July	1st to 10th	Day	21% 6% 8% 22% 29% 14%	6271
	11th to 20th	Day	19% 7% 11% 30% 21% 11%	6265
	21st to end	Day	26% 7% 11% 19% 20% 17%	6705
August	1st to 10th	Day	27% 7% 14% 26% 19% 7%	4405
	11th to 20th	Day	23% 7% 10% 22% 24% 13%	3882
	21st to end	Day	23% 6% 11% 20% 23% 18%	4311
September	1st to 10th	Day	22% 4 8% 23% 29% 14%	2400
	11th to 20th	Day	22% 5% 9% 23% 29% 14%	2317
	21st to end	Day	21% 4 8% 23% 35% 8%	2200
October	1st to 10th	Day	17% 3 7% 18% 31% 24%	3436
	11th to 20th	Day	25% 4 10% 30% 24% 7%	3250
	21st to end	Day	27% 4 11% 27% 26% 5%	3223
November	1st to 10th	Day	23% 4 13% 27% 23% 9%	1853
	11th to 20th	Day	22% 4 12% 30% 26% 5%	1890
	21st to end	Day	26% 4 12% 28% 24% 5%	1788
December	1st to 10th	Day	21% 5% 11% 34% 26% 4	2700
	11th to 20th	Day	20% 4 14% 37% 21% 3	3104
	21st to end	Day	32% 5% 11% 35% 15% 2	4092
January	1st to 10th	Night	33% 5% 10% 31% 17% 3	8202
	11th to 20th	Night	31% 6% 15% 26% 17% 5%	8250
	21st to end	Night	31% 5% 13% 28% 19% 4	8787
February	1st to 10th	Night	37% 6% 15% 25% 15% 3	2715
	11th to 20th	Night	37% 7% 12% 23% 16% 4	2458
	21st to end	Night	30% 5% 10% 27% 22% 5%	2076
March	1st to 10th	Night	33% 4 7% 21% 27% 7%	5494
	11th to 20th	Night	30% 4 10% 22% 31% 3	5412
	21st to end	Night	39% 8% 18% 22% 12% 1	5094
April	1st to 10th	Night	35% 7% 13% 23% 17% 5%	2100
	11th to 20th	Night	36% 6% 12% 24% 17% 4	2037
	21st to end	Night	41% 6% 10% 27% 15% 1	1930
May	1st to 10th	Night	35% 7% 14% 27% 16% 2	4080
	11th to 20th	Night	27% 8% 18% 30% 13% 4	3669
	21st to end	Night	36% 9% 15% 28% 10% 2	3972
June	1st to 10th	Night	28% 9% 23% 25% 13% 3	1600
	11th to 20th	Night	27% 8% 17% 22% 19% 7%	1600
	21st to end	Night	24% 8% 13% 26% 23% 6%	1600
July	1st to 10th	Night	27% 8% 10% 22% 24% 9%	3600
	11th to 20th	Night	25% 7% 18% 26% 18% 6%	3592
	21st to end	Night	30% 7% 14% 20% 20% 9%	3856
August	1st to 10th	Night	35% 8% 15% 21% 18% 4	2713
	11th to 20th	Night	26% 9% 15% 23% 18% 9%	3243
	21st to end	Night	27% 7% 13% 18% 23% 12%	3597
September	1st to 10th	Night	24% 5% 9% 23% 26% 12%	2000
	11th to 20th	Night	25% 6% 9% 24% 24% 13%	2082
	21st to end	Night	25% 5% 8% 27% 25% 12%	2200
October	1st to 10th	Night	17% 3 7% 18% 28% 27%	3745
	11th to 20th	Night	24% 5% 13% 27% 25% 7%	3898
	21st to end	Night	27% 4 10% 27% 23% 9%	4543
November	1st to 10th	Night	25% 5% 13% 25% 25% 7%	2665
	11th to 20th	Night	26% 4 11% 29% 23% 7%	2730
	21st to end	Night	28% 4 10% 30% 21% 6%	2830
December	1st to 10th	Night	22% 4 13% 35% 23% 4	4710
	11th to 20th	Night	24% 5% 12% 39% 18% 3	5322
	21st to end	Night	35% 5% 11% 32% 16% 2	7128

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	11% 10% 40% 28% 9% 2	330
	11th to 20th	Day	12% 22% 32% 29% 4	330
	21st to end	Day	7% 16% 47% 21% 7% 2	363
February	1st to 10th	Day	10% 19% 45% 22% 3	330
	11th to 20th	Day	9% 17% 44% 24% 5% 1	330
	21st to end	Day	13% 18% 45% 20% 3	273
March	1st to 10th	Day	10% 17% 36% 28% 8% 1	330
	11th to 20th	Day	13% 16% 34% 23% 12% 2	391
	21st to end	Day	13% 16% 38% 25% 6% 2	594
April	1st to 10th	Day	14% 18% 37% 22% 8% 2	540
	11th to 20th	Day	18% 18% 35% 21% 6% 3	517
	21st to end	Day	16% 14% 30% 25% 12% 3	570
May	1st to 10th	Day	17% 13% 26% 27% 13% 4	703
	11th to 20th	Day	17% 7% 28% 29% 14% 5%	725
	21st to end	Day	13% 10% 27% 28% 18% 4	789
June	1st to 10th	Day	6% 5% 26% 33% 21% 8%	730
	11th to 20th	Day	9% 7% 33% 32% 17% 3	730
	21st to end	Day	6% 4 29% 32% 24% 4	730
July	1st to 10th	Day	7% 2 18% 40% 26% 7%	721
	11th to 20th	Day	5% 3 18% 41% 26% 7%	718
	21st to end	Day	6% 3 17% 37% 32% 5%	794
August	1st to 10th	Day	6% 3 20% 38% 30% 5%	683
	11th to 20th	Day	4 4 21% 34% 26% 11%	517
	21st to end	Day	5% 3 25% 33% 24% 9%	583
September	1st to 10th	Day	7% 5% 19% 36% 23% 10%	530
	11th to 20th	Day	6% 5% 22% 33% 24% 9%	447
	21st to end	Day	8% 7% 21% 33% 19% 12%	330
October	1st to 10th	Day	10% 8% 28% 22% 21% 10%	330
	11th to 20th	Day	9% 12% 36% 22% 16% 6%	330
	21st to end	Day	9% 12% 37% 28% 11% 4	363
November	1st to 10th	Day	8% 13% 39% 28% 9% 4	330
	11th to 20th	Day	7% 12% 42% 28% 11% 1	330
	21st to end	Day	11% 10% 38% 28% 11% 2	330
December	1st to 10th	Day	9% 18% 43% 22% 8% 1	330
	11th to 20th	Day	9% 16% 48% 22% 5%	330
	21st to end	Day	10% 17% 44% 22% 7% 1	363
January	1st to 10th	Night	8% 14% 43% 27% 7%	1050
	11th to 20th	Night	7% 19% 43% 27% 3	1050
	21st to end	Night	8% 13% 48% 27% 4	1071
February	1st to 10th	Night	7% 12% 54% 23% 3	840
	11th to 20th	Night	9% 13% 50% 25% 3	824
	21st to end	Night	8% 15% 51% 24% 3	692
March	1st to 10th	Night	9% 11% 45% 29% 5%	840
	11th to 20th	Night	11% 9% 42% 32% 5%	840
	21st to end	Night	13% 13% 42% 29% 3	693
April	1st to 10th	Night	13% 13% 39% 31% 4	630
	11th to 20th	Night	15% 13% 40% 29% 3	611
	21st to end	Night	17% 12% 33% 32% 6%	600
May	1st to 10th	Night	19% 9% 31% 32% 9% 1	600
	11th to 20th	Night	19% 4 32% 36% 9% 1	591
	21st to end	Night	14% 8% 31% 36% 10%	650
June	1st to 10th	Night	10% 5% 30% 41% 14% 1	600
	11th to 20th	Night	8% 6% 39% 40% 7%	600
	21st to end	Night	5% 4 32% 47% 12%	600
July	1st to 10th	Night	6% 2 25% 48% 18%	585
	11th to 20th	Night	5% 3 26% 52% 14% 1	582
	21st to end	Night	5% 1 22% 50% 21% 1	657
August	1st to 10th	Night	9% 2 23% 47% 18%	597
	11th to 20th	Night	5% 2 29% 50% 13% 1	594
	21st to end	Night	4 3 28% 49% 16% 1	660
September	1st to 10th	Night	7% 3 27% 49% 12% 1	600
	11th to 20th	Night	8% 5% 29% 41% 16% 2	600
	21st to end	Night	9% 5% 30% 44% 12%	600
October	1st to 10th	Night	14% 5% 30% 38% 13% 1	690
	11th to 20th	Night	10% 7% 41% 33% 9%	800
	21st to end	Night	11% 8% 39% 34% 7%	1057
November	1st to 10th	Night	7% 8% 45% 33% 6% 1	1025
	11th to 20th	Night	8% 12% 47% 29% 4	1050
	21st to end	Night	8% 10% 43% 32% 6%	1050
December	1st to 10th	Night	8% 14% 49% 25% 3	1050
	11th to 20th	Night	8% 11% 50% 28% 3	1050
	21st to end	Night	10% 15% 48% 24% 3	1155

Page generated at 2026-04-14 00:44:24. Version ac07

Copyright © 2026 Attilla Danko.