The Dead Gekko Society Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the The Dead Gekko Society Observatory clear sky chart from 2005-11-06 to 2026-02-01.

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	11% 7% 2 6% 4 4 4 4 5% 7% 45%	126816
	Night	11% 7% 2 6% 4 3 3 3 5% 6% 49%	125401
Transparency	Day	37% 4 10% 25% 18% 4	130427
	Night	36% 4 10% 25% 20% 5%	129866
Seeing	Day	15% 11% 26% 26% 17% 4	17114
	Night	15% 10% 28% 30% 14% 1	27041

By Month

Percentage Cloud Cover SE (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	14% 13% 3 5% 5% 3 3 2 4 4 43%	4167
	11th to 20th	Day	7% 9% 4 7% 4 4 3 2 4 5% 52%	4170
	21st to end	Day	20% 8% 3 6% 3 2 3 3 3 4 45%	4587
February	1st to 10th	Day	17% 11% 3 7% 5% 3 3 3 4 5% 39%	1800
	11th to 20th	Day	14% 9% 3 7% 4 3 4 2 4 5% 43%	1764
	21st to end	Day	15% 9% 4 7% 4 3 4 3 5% 5% 42%	1778
March	1st to 10th	Day	13% 9% 2 5% 3 3 4 3 5% 5% 47%	4936
	11th to 20th	Day	9% 6% 2 5% 3 3 3 3 5% 7% 53%	4980
	21st to end	Day	12% 8% 3 8% 6% 5% 5% 3 6% 7% 37%	5462
April	1st to 10th	Day	13% 8% 2 6% 5% 4 4 4 5% 6% 45%	2337
	11th to 20th	Day	16% 8% 2 7% 4 4 4 4 5% 6% 40%	2374
	21st to end	Day	17% 9% 3 7% 5% 4 4 3 4 4 39%	2400
May	1st to 10th	Day	17% 8% 3 7% 5% 5% 5% 4 6% 7% 34%	5788
	11th to 20th	Day	10% 6% 3 7% 5% 5% 6% 5% 6% 7% 40%	5862
	21st to end	Day	19% 6% 2 7% 5% 5% 5% 4 5% 7% 36%	6434
June	1st to 10th	Day	8% 5% 2 6% 5% 4 5% 5% 6% 9% 44%	2634
	11th to 20th	Day	7% 4 2 6% 5% 5% 6% 5% 6% 9% 45%	2722
	21st to end	Day	3 3 2 5% 4 4 5% 5% 6% 9% 53%	2600
July	1st to 10th	Day	8% 4 2 6% 5% 5% 5% 5% 8% 10% 42%	5900
	11th to 20th	Day	5% 5% 2 6% 5% 4 5% 4 7% 10% 47%	5900
	21st to end	Day	5% 3 2 5% 4 5% 5% 5% 7% 11% 47%	6422
August	1st to 10th	Day	5% 3 2 4 4 3 4 4 6% 8% 57%	4234
	11th to 20th	Day	10% 5% 2 6% 5% 4 5% 4 6% 8% 47%	4078
	21st to end	Day	5% 4 1 4 4 4 5% 4 6% 8% 54%	4312
September	1st to 10th	Day	11% 5% 2 5% 4 4 4 3 5% 7% 51%	2400
	11th to 20th	Day	11% 6% 1 6% 5% 4 5% 3 6% 8% 45%	2282
	21st to end	Day	8% 4 2 5% 4 4 4 4 5% 7% 53%	2145
October	1st to 10th	Day	8% 5% 2 4 4 4 3 3 5% 7% 56%	2000
	11th to 20th	Day	12% 5% 2 5% 3 3 3 2 3 5% 58%	2000
	21st to end	Day	19% 7% 2 5% 3 3 3 2 3 4 50%	2200
November	1st to 10th	Day	12% 6% 2 4 3 2 3 3 4 6% 56%	2058
	11th to 20th	Day	11% 8% 2 5% 3 4 3 3 4 6% 51%	2069
	21st to end	Day	16% 8% 3 5% 4 2 2 3 4 5% 47%	1680
December	1st to 10th	Day	11% 8% 2 6% 4 2 3 2 4 5% 53%	2690
	11th to 20th	Day	11% 11% 2 6% 4 4 3 2 3 5% 49%	3088
	21st to end	Day	15% 19% 5% 7% 4 3 4 3 3 4 32%	4563
January	1st to 10th	Night	13% 9% 4 9% 6% 4 3 3 5% 5% 40%	6018
	11th to 20th	Night	9% 6% 2 8% 4 3 4 3 4 5% 51%	6030
	21st to end	Night	18% 10% 4 6% 3 3 2 2 3 4 45%	6633
February	1st to 10th	Night	15% 12% 2 6% 4 3 4 3 5% 7% 41%	2601
	11th to 20th	Night	16% 8% 3 8% 4 3 3 3 3 5% 45%	2521
	21st to end	Night	14% 8% 3 5% 3 3 3 3 5% 6% 45%	1870
March	1st to 10th	Night	15% 11% 2 6% 4 3 3 2 3 4 45%	4919
	11th to 20th	Night	9% 9% 2 4 3 3 3 3 5% 6% 52%	4980
	21st to end	Night	11% 9% 3 6% 4 4 4 3 5% 7% 43%	5467
April	1st to 10th	Night	12% 6% 2 4 3 4 4 3 4 7% 50%	2061
	11th to 20th	Night	14% 7% 2 5% 4 3 3 4 5% 7% 47%	1975
	21st to end	Night	18% 5% 2 6% 4 4 3 4 5% 7% 42%	2000
May	1st to 10th	Night	13% 9% 3 6% 4 3 3 3 5% 6% 43%	4107
	11th to 20th	Night	10% 7% 2 7% 3 5% 5% 4 7% 8% 42%	4053
	21st to end	Night	19% 8% 2 6% 4 4 4 3 5% 7% 39%	4443
June	1st to 10th	Night	7% 3 1 4 3 4 3 4 6% 9% 55%	1743
	11th to 20th	Night	4 4 1 3 3 4 5% 4 6% 11% 54%	1652
	21st to end	Night	2 2 1 3 3 4 4 4 7% 8% 63%	1800
July	1st to 10th	Night	7% 4 2 6% 5% 5% 4 4 7% 10% 47%	4078
	11th to 20th	Night	4 3 1 4 3 3 4 4 5% 9% 60%	4077
	21st to end	Night	4 4 2 5% 4 4 4 3 6% 9% 55%	4449
August	1st to 10th	Night	3 2 1 3 3 4 4 4 6% 10% 59%	2926
	11th to 20th	Night	7% 5% 2 5% 4 4 5% 4 5% 9% 50%	2975
	21st to end	Night	4 4 1 3 3 3 4 3 6% 9% 61%	3586
September	1st to 10th	Night	9% 4 1 3 3 3 4 3 6% 7% 56%	2000
	11th to 20th	Night	10% 4 2 5% 4 4 3 3 5% 7% 51%	2113
	21st to end	Night	7% 5% 2 5% 3 3 3 3 5% 6% 57%	2233
October	1st to 10th	Night	6% 4 2 3 3 3 3 3 5% 7% 62%	2400
	11th to 20th	Night	12% 5% 2 4 2 3 3 2 5% 5% 57%	2400
	21st to end	Night	17% 7% 2 5% 3 3 3 2 4 4 51%	2640
November	1st to 10th	Night	12% 5% 2 4 2 3 2 2 3 5% 60%	2460
	11th to 20th	Night	11% 6% 2 4 3 2 3 3 4 6% 56%	2541
	21st to end	Night	15% 8% 2 5% 4 2 3 2 4 5% 49%	2940
December	1st to 10th	Night	10% 10% 3 5% 3 2 3 2 4 5% 52%	4720
	11th to 20th	Night	15% 9% 3 6% 3 3 3 2 3 4 49%	5339
	21st to end	Night	18% 15% 5% 8% 4 4 3 3 3 4 33%	6651

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	46% 2 8% 24% 18% 2	4168
	11th to 20th	Day	36% 3 9% 25% 22% 5%	4170
	21st to end	Day	44% 2 6% 20% 21% 7%	4587
February	1st to 10th	Day	49% 4 9% 22% 13% 3	1800
	11th to 20th	Day	45% 4 8% 21% 17% 3	1773
	21st to end	Day	44% 4 7% 20% 17% 8%	1778
March	1st to 10th	Day	39% 3 6% 21% 16% 15%	4936
	11th to 20th	Day	31% 5% 7% 19% 25% 13%	4980
	21st to end	Day	47% 4 8% 30% 11% 1	5464
April	1st to 10th	Day	40% 5% 11% 23% 19% 3	2337
	11th to 20th	Day	44% 6% 10% 18% 18% 3	2374
	21st to end	Day	50% 4 9% 22% 14% 2	2400
May	1st to 10th	Day	48% 6% 10% 20% 15% 1	5826
	11th to 20th	Day	42% 7% 11% 23% 16% 2	5866
	21st to end	Day	46% 6% 11% 19% 17% 1	6447
June	1st to 10th	Day	34% 8% 15% 27% 15% 1	2634
	11th to 20th	Day	32% 8% 14% 28% 16% 2	2722
	21st to end	Day	25% 8% 17% 28% 17% 4	2600
July	1st to 10th	Day	36% 4 16% 28% 14% 2	5836
	11th to 20th	Day	32% 4 15% 33% 15% 1	5831
	21st to end	Day	30% 4 19% 33% 13%	6240
August	1st to 10th	Day	24% 6% 16% 29% 21% 4	4220
	11th to 20th	Day	36% 5% 16% 28% 14%	4117
	21st to end	Day	28% 5% 12% 37% 15% 3	4311
September	1st to 10th	Day	33% 5% 10% 26% 17% 9%	2400
	11th to 20th	Day	37% 5% 10% 23% 22% 3	2282
	21st to end	Day	30% 6% 9% 26% 26% 3	2145
October	1st to 10th	Day	17% 4 6% 17% 40% 16%	3260
	11th to 20th	Day	20% 2 5% 21% 38% 15%	3240
	21st to end	Day	30% 2 7% 32% 24% 5%	3538
November	1st to 10th	Day	31% 3 8% 27% 24% 7%	2058
	11th to 20th	Day	35% 3 7% 23% 22% 9%	2069
	21st to end	Day	41% 3 9% 21% 24% 3	1680
December	1st to 10th	Day	37% 3 7% 31% 22% 1	2690
	11th to 20th	Day	41% 2 5% 26% 24% 2	3085
	21st to end	Day	56% 4 6% 21% 12% 1	4563
January	1st to 10th	Night	47% 3 11% 21% 15% 4	6018
	11th to 20th	Night	37% 3 8% 20% 29% 3	6030
	21st to end	Night	45% 2 7% 19% 23% 4	6633
February	1st to 10th	Night	45% 4 10% 22% 14% 4	2601
	11th to 20th	Night	44% 3 8% 24% 18% 4	2522
	21st to end	Night	40% 4 8% 19% 23% 6%	1870
March	1st to 10th	Night	44% 4 5% 17% 20% 10%	4919
	11th to 20th	Night	33% 4 6% 25% 21% 11%	4980
	21st to end	Night	40% 5% 11% 28% 15% 2	5467
April	1st to 10th	Night	35% 4 11% 25% 20% 5%	2061
	11th to 20th	Night	35% 5% 8% 26% 21% 5%	1975
	21st to end	Night	43% 5% 11% 24% 15% 2	2000
May	1st to 10th	Night	41% 5% 11% 28% 12% 2	4134
	11th to 20th	Night	38% 8% 14% 24% 13% 4	4054
	21st to end	Night	44% 6% 13% 22% 12% 2	4452
June	1st to 10th	Night	24% 8% 15% 31% 17% 4	1743
	11th to 20th	Night	21% 7% 14% 34% 20% 3	1652
	21st to end	Night	19% 6% 16% 31% 22% 6%	1800
July	1st to 10th	Night	33% 5% 17% 27% 16% 3	4035
	11th to 20th	Night	22% 4 15% 39% 18% 1	4026
	21st to end	Night	26% 3 17% 36% 17% 1	4320
August	1st to 10th	Night	21% 5% 16% 36% 22% 1	2916
	11th to 20th	Night	32% 5% 17% 28% 17% 2	3002
	21st to end	Night	21% 4 13% 37% 22% 3	3586
September	1st to 10th	Night	27% 4 11% 30% 19% 9%	2000
	11th to 20th	Night	33% 5% 10% 23% 24% 5%	2113
	21st to end	Night	28% 4 9% 23% 30% 5%	2233
October	1st to 10th	Night	13% 3 6% 15% 40% 22%	3920
	11th to 20th	Night	21% 3 4 20% 32% 21%	3899
	21st to end	Night	30% 2 6% 32% 23% 7%	4252
November	1st to 10th	Night	29% 4 8% 25% 26% 8%	2460
	11th to 20th	Night	30% 4 7% 26% 25% 8%	2541
	21st to end	Night	39% 4 7% 23% 24% 4	2940
December	1st to 10th	Night	36% 2 8% 35% 16% 2	4720
	11th to 20th	Night	42% 2 5% 23% 23% 4	5341
	21st to end	Night	56% 3 7% 21% 9% 3	6651

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	23% 16% 38% 19% 4	330
	11th to 20th	Day	25% 23% 36% 14% 1	330
	21st to end	Day	20% 25% 37% 14% 4	363
February	1st to 10th	Day	26% 23% 36% 13% 2	300
	11th to 20th	Day	24% 29% 30% 15% 2	300
	21st to end	Day	29% 24% 33% 12% 2	249
March	1st to 10th	Day	22% 24% 34% 17% 3	300
	11th to 20th	Day	27% 21% 33% 17% 2	300
	21st to end	Day	27% 22% 41% 8% 3	330
April	1st to 10th	Day	22% 22% 33% 15% 7% 1	437
	11th to 20th	Day	22% 20% 34% 18% 5%	492
	21st to end	Day	23% 18% 29% 23% 6% 1	500
May	1st to 10th	Day	19% 16% 35% 22% 7%	668
	11th to 20th	Day	17% 11% 30% 26% 14% 2	725
	21st to end	Day	13% 8% 35% 25% 14% 5%	789
June	1st to 10th	Day	11% 4 19% 34% 26% 6%	730
	11th to 20th	Day	9% 3 19% 39% 24% 6%	730
	21st to end	Day	4 3 27% 38% 24% 4	730
July	1st to 10th	Day	8% 4 18% 29% 31% 10%	721
	11th to 20th	Day	5% 2 16% 37% 30% 10%	718
	21st to end	Day	8% 1 12% 34% 31% 13%	794
August	1st to 10th	Day	8% 3 14% 41% 29% 5%	726
	11th to 20th	Day	12% 1 11% 31% 37% 8%	661
	21st to end	Day	9% 2 13% 30% 34% 13%	583
September	1st to 10th	Day	9% 3 13% 34% 32% 9%	530
	11th to 20th	Day	9% 1 16% 39% 24% 10%	412
	21st to end	Day	10% 4 27% 27% 24% 7%	330
October	1st to 10th	Day	7% 7% 30% 30% 20% 6%	330
	11th to 20th	Day	13% 13% 35% 25% 12% 2	330
	21st to end	Day	29% 14% 29% 20% 6% 1	363
November	1st to 10th	Day	18% 14% 38% 23% 6% 2	330
	11th to 20th	Day	15% 20% 33% 21% 9% 2	330
	21st to end	Day	25% 18% 26% 24% 5% 2	330
December	1st to 10th	Day	21% 21% 32% 19% 5% 2	330
	11th to 20th	Day	24% 18% 35% 18% 5%	330
	21st to end	Day	23% 21% 38% 16% 2	363
January	1st to 10th	Night	19% 18% 34% 24% 5%	1050
	11th to 20th	Night	19% 22% 36% 19% 3	1050
	21st to end	Night	19% 18% 38% 23% 3	1155
February	1st to 10th	Night	22% 17% 37% 21% 3	1001
	11th to 20th	Night	21% 20% 39% 18% 2	967
	21st to end	Night	21% 19% 36% 22% 1	550
March	1st to 10th	Night	21% 15% 36% 26% 3	600
	11th to 20th	Night	24% 14% 33% 25% 4	600
	21st to end	Night	21% 13% 39% 21% 5%	660
April	1st to 10th	Night	17% 16% 37% 27% 4	600
	11th to 20th	Night	17% 14% 36% 26% 7%	593
	21st to end	Night	20% 12% 37% 24% 8%	600
May	1st to 10th	Night	14% 8% 32% 38% 9%	600
	11th to 20th	Night	15% 7% 25% 35% 16% 1	591
	21st to end	Night	14% 5% 25% 36% 17% 3	650
June	1st to 10th	Night	9% 3 15% 40% 32% 1	600
	11th to 20th	Night	5% 2 20% 44% 26% 2	600
	21st to end	Night	2 20% 49% 27% 2	600
July	1st to 10th	Night	5% 1 12% 36% 41% 5%	585
	11th to 20th	Night	5% 1 10% 41% 37% 6%	582
	21st to end	Night	5% 2 7% 41% 38% 7%	657
August	1st to 10th	Night	6% 1 10% 44% 37% 4	597
	11th to 20th	Night	8% 1 10% 42% 36% 4	594
	21st to end	Night	5% 1 12% 39% 38% 5%	660
September	1st to 10th	Night	11% 1 11% 38% 37% 2	600
	11th to 20th	Night	14% 2 10% 37% 33% 5%	600
	21st to end	Night	10% 3 20% 34% 29% 3	633
October	1st to 10th	Night	8% 3 22% 38% 26% 4	800
	11th to 20th	Night	14% 8% 33% 32% 14%	800
	21st to end	Night	21% 12% 29% 29% 9%	880
November	1st to 10th	Night	15% 9% 33% 31% 12%	820
	11th to 20th	Night	16% 12% 32% 32% 8%	861
	21st to end	Night	21% 15% 31% 26% 8%	1050
December	1st to 10th	Night	20% 14% 37% 24% 5%	1050
	11th to 20th	Night	23% 15% 33% 25% 4	1050
	21st to end	Night	21% 17% 37% 22% 4	1155

Page generated at 2026-01-29 00:21:46. Version ac07

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