G49 Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the G49 Observatory clear sky chart from 2005-11-06 to 2026-06-16.

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	12% 9% 3 8% 5% 4 4 4 5% 7% 38%	138390
	Night	11% 9% 4 9% 5% 5% 5% 4 5% 6% 38%	133932
Transparency	Day	44% 6% 13% 25% 11% 1	141967
	Night	45% 5% 12% 24% 12% 1	138435
Seeing	Day	18% 15% 32% 24% 10% 2	18226
	Night	16% 13% 33% 28% 9% 1	28149

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	9% 14% 5% 19% 8% 6% 5% 3 4 6% 20%	4691
	11th to 20th	Day	5% 11% 6% 14% 7% 7% 8% 8% 8% 5% 21%	4788
	21st to end	Day	4 13% 6% 11% 5% 5% 6% 5% 6% 7% 32%	5812
February	1st to 10th	Day	8% 12% 5% 10% 8% 5% 5% 5% 6% 7% 29%	1890
	11th to 20th	Day	8% 12% 5% 10% 6% 6% 5% 3 6% 6% 34%	1844
	21st to end	Day	10% 12% 4 9% 6% 6% 4 4 5% 7% 33%	1614
March	1st to 10th	Day	12% 9% 3 6% 3 3 4 3 6% 7% 44%	4953
	11th to 20th	Day	9% 11% 3 8% 4 4 4 3 5% 7% 41%	5090
	21st to end	Day	21% 11% 4 9% 5% 5% 4 4 4 6% 26%	5627
April	1st to 10th	Day	16% 10% 4 8% 5% 4 4 4 5% 7% 34%	2520
	11th to 20th	Day	19% 12% 3 8% 5% 4 4 4 5% 5% 31%	2514
	21st to end	Day	21% 11% 3 7% 4 4 4 4 4 5% 31%	2730
May	1st to 10th	Day	11% 5% 2 6% 4 4 4 3 5% 6% 50%	7915
	11th to 20th	Day	16% 8% 2 5% 3 3 3 3 4 6% 45%	8222
	21st to end	Day	15% 8% 3 7% 5% 5% 4 4 5% 8% 38%	9047
June	1st to 10th	Day	11% 6% 2 5% 4 4 4 5% 7% 9% 44%	2940
	11th to 20th	Day	14% 7% 3 7% 5% 5% 4 4 7% 9% 35%	2871
	21st to end	Day	11% 5% 2 6% 5% 5% 5% 5% 7% 10% 39%	2918
July	1st to 10th	Day	9% 5% 2 6% 4 5% 5% 4 8% 10% 43%	6360
	11th to 20th	Day	9% 4 2 4 3 3 3 3 6% 8% 57%	6360
	21st to end	Day	7% 5% 2 6% 4 4 5% 4 7% 10% 45%	6819
August	1st to 10th	Day	12% 6% 2 6% 4 5% 5% 4 6% 8% 42%	4234
	11th to 20th	Day	12% 6% 2 6% 4 4 4 5% 6% 9% 42%	4171
	21st to end	Day	9% 7% 2 7% 4 4 4 3 6% 7% 46%	4481
September	1st to 10th	Day	11% 6% 2 6% 4 4 4 4 6% 8% 47%	2400
	11th to 20th	Day	12% 6% 2 5% 3 5% 5% 4 6% 8% 44%	2361
	21st to end	Day	14% 7% 2 6% 4 4 3 4 4 7% 46%	2110
October	1st to 10th	Day	16% 8% 2 6% 3 4 4 4 5% 6% 42%	2000
	11th to 20th	Day	15% 10% 3 7% 4 4 4 3 6% 6% 38%	2000
	21st to end	Day	17% 12% 4 7% 4 4 3 2 4 6% 37%	2183
November	1st to 10th	Day	12% 12% 4 8% 5% 4 4 4 5% 7% 36%	1717
	11th to 20th	Day	11% 13% 6% 12% 6% 5% 4 3 5% 5% 30%	1680
	21st to end	Day	13% 12% 4 9% 5% 4 4 4 5% 7% 33%	1680
December	1st to 10th	Day	7% 11% 4 14% 12% 7% 6% 4 5% 6% 23%	2690
	11th to 20th	Day	9% 17% 7% 11% 7% 4 5% 4 5% 5% 27%	3088
	21st to end	Day	20% 18% 9% 20% 5% 4 3 2 3 3 14%	4070
January	1st to 10th	Night	8% 13% 6% 14% 8% 6% 4 3 5% 6% 28%	8232
	11th to 20th	Night	5% 12% 6% 14% 7% 7% 10% 7% 6% 5% 20%	8188
	21st to end	Night	6% 14% 5% 9% 6% 5% 5% 3 5% 5% 35%	8402
February	1st to 10th	Night	7% 12% 5% 11% 6% 6% 6% 3 5% 5% 33%	2730
	11th to 20th	Night	7% 10% 3 9% 6% 6% 5% 4 5% 7% 39%	2663
	21st to end	Night	10% 10% 4 9% 6% 5% 4 3 5% 7% 37%	2191
March	1st to 10th	Night	10% 7% 3 7% 4 4 4 3 5% 7% 47%	5165
	11th to 20th	Night	10% 7% 2 8% 4 5% 5% 4 7% 9% 39%	5090
	21st to end	Night	23% 12% 4 10% 4 4 3 3 4 5% 28%	5543
April	1st to 10th	Night	15% 12% 3 7% 3 3 5% 4 5% 6% 37%	2100
	11th to 20th	Night	19% 10% 3 7% 4 3 4 3 5% 6% 35%	2051
	21st to end	Night	19% 10% 3 7% 3 4 4 3 4 6% 36%	1890
May	1st to 10th	Night	9% 6% 2 6% 4 4 4 3 5% 6% 51%	4968
	11th to 20th	Night	16% 6% 2 4 3 3 4 3 4 6% 49%	4670
	21st to end	Night	15% 9% 3 6% 4 4 5% 3 5% 7% 38%	5139
June	1st to 10th	Night	11% 5% 2 5% 3 3 5% 4 6% 8% 49%	1680
	11th to 20th	Night	8% 6% 2 5% 4 5% 5% 4 7% 8% 45%	1640
	21st to end	Night	9% 4 2 4 3 4 4 3 7% 9% 51%	1449
July	1st to 10th	Night	8% 4 1 5% 3 4 5% 5% 7% 9% 50%	3608
	11th to 20th	Night	6% 4 2 5% 3 3 4 3 6% 9% 55%	3617
	21st to end	Night	8% 5% 2 6% 4 4 4 4 6% 8% 49%	4036
August	1st to 10th	Night	12% 6% 2 5% 4 4 5% 4 5% 6% 48%	2926
	11th to 20th	Night	14% 4 1 4 3 3 4 3 6% 8% 50%	2888
	21st to end	Night	8% 6% 2 7% 4 4 4 4 6% 7% 48%	3421
September	1st to 10th	Night	8% 5% 2 5% 3 4 4 3 5% 8% 52%	2000
	11th to 20th	Night	10% 4 2 5% 4 4 4 3 6% 7% 53%	2035
	21st to end	Night	12% 6% 1 5% 3 3 4 3 5% 5% 53%	2270
October	1st to 10th	Night	13% 6% 2 5% 4 3 3 3 5% 5% 50%	2400
	11th to 20th	Night	16% 10% 2 6% 4 4 5% 3 5% 6% 41%	2400
	21st to end	Night	17% 11% 4 7% 4 3 4 3 5% 6% 38%	2655
November	1st to 10th	Night	13% 9% 3 7% 4 4 4 4 5% 6% 41%	2796
	11th to 20th	Night	13% 12% 4 11% 5% 4 4 3 4 5% 35%	2940
	21st to end	Night	13% 11% 3 9% 6% 5% 4 3 4 6% 35%	2940
December	1st to 10th	Night	6% 9% 5% 14% 8% 7% 6% 4 5% 7% 29%	4720
	11th to 20th	Night	9% 17% 7% 14% 7% 4 4 5% 4 5% 24%	5339
	21st to end	Night	21% 16% 8% 15% 5% 4 3 3 3 4 17%	7150

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	65% 5% 11% 14% 5%	4692
	11th to 20th	Day	60% 5% 9% 16% 9%	4788
	21st to end	Day	49% 6% 14% 22% 9%	5812
February	1st to 10th	Day	53% 5% 14% 19% 8% 1	1890
	11th to 20th	Day	49% 5% 11% 26% 8%	1853
	21st to end	Day	50% 5% 13% 20% 11%	1614
March	1st to 10th	Day	39% 4 18% 26% 11% 2	4953
	11th to 20th	Day	42% 5% 15% 28% 10% 1	5090
	21st to end	Day	58% 5% 10% 19% 7%	5629
April	1st to 10th	Day	49% 5% 12% 21% 12% 1	2520
	11th to 20th	Day	54% 5% 10% 18% 11% 1	2514
	21st to end	Day	54% 4 11% 21% 8% 1	2730
May	1st to 10th	Day	33% 5% 11% 29% 19% 2	7953
	11th to 20th	Day	40% 5% 8% 24% 19% 4	8226
	21st to end	Day	44% 6% 10% 29% 10% 1	9061
June	1st to 10th	Day	34% 7% 14% 31% 12% 1	2940
	11th to 20th	Day	43% 7% 13% 22% 13% 1	2871
	21st to end	Day	37% 8% 16% 27% 10% 2	2918
July	1st to 10th	Day	32% 9% 18% 31% 10%	6291
	11th to 20th	Day	26% 5% 16% 37% 15% 1	6285
	21st to end	Day	31% 8% 15% 29% 16% 1	6625
August	1st to 10th	Day	38% 7% 13% 28% 12% 2	4220
	11th to 20th	Day	36% 7% 14% 32% 10%	4210
	21st to end	Day	35% 7% 16% 28% 13% 1	4480
September	1st to 10th	Day	34% 7% 15% 32% 13%	2400
	11th to 20th	Day	36% 7% 17% 32% 8%	2361
	21st to end	Day	38% 5% 11% 34% 11% 1	2110
October	1st to 10th	Day	30% 3 9% 35% 22%	3260
	11th to 20th	Day	40% 5% 10% 27% 17% 1	3240
	21st to end	Day	44% 4 13% 29% 9%	3509
November	1st to 10th	Day	48% 5% 13% 19% 13% 2	1717
	11th to 20th	Day	56% 5% 13% 18% 9%	1680
	21st to end	Day	51% 5% 16% 21% 6% 1	1680
December	1st to 10th	Day	59% 8% 16% 12% 5% 1	2690
	11th to 20th	Day	58% 5% 15% 17% 5%	3085
	21st to end	Day	77% 4 8% 8% 4	4070
January	1st to 10th	Night	56% 5% 15% 17% 6%	8233
	11th to 20th	Night	62% 5% 10% 15% 9%	8188
	21st to end	Night	48% 5% 11% 25% 10%	8402
February	1st to 10th	Night	51% 5% 12% 21% 10% 1	2730
	11th to 20th	Night	44% 5% 14% 26% 9% 1	2664
	21st to end	Night	46% 5% 13% 22% 12% 1	2191
March	1st to 10th	Night	37% 4 14% 27% 16% 2	5165
	11th to 20th	Night	39% 6% 15% 26% 14% 1	5090
	21st to end	Night	60% 4 9% 18% 9% 1	5543
April	1st to 10th	Night	48% 4 9% 24% 14% 1	2100
	11th to 20th	Night	49% 4 8% 21% 15% 2	2051
	21st to end	Night	50% 5% 8% 22% 14% 2	1890
May	1st to 10th	Night	32% 6% 9% 31% 20% 2	4995
	11th to 20th	Night	35% 5% 9% 21% 23% 7%	4671
	21st to end	Night	44% 6% 9% 27% 13% 1	5149
June	1st to 10th	Night	32% 6% 14% 28% 18% 2	1680
	11th to 20th	Night	34% 8% 15% 23% 18% 3	1640
	21st to end	Night	28% 5% 16% 30% 17% 3	1449
July	1st to 10th	Night	28% 8% 18% 31% 14% 1	3570
	11th to 20th	Night	25% 6% 14% 39% 14% 2	3572
	21st to end	Night	33% 7% 15% 28% 15% 2	3920
August	1st to 10th	Night	35% 7% 11% 29% 14% 4	2916
	11th to 20th	Night	31% 6% 15% 32% 15% 1	2915
	21st to end	Night	34% 8% 17% 27% 13% 2	3421
September	1st to 10th	Night	31% 5% 13% 34% 17% 1	2000
	11th to 20th	Night	30% 6% 17% 30% 17%	2035
	21st to end	Night	33% 5% 12% 32% 17% 1	2270
October	1st to 10th	Night	24% 3 7% 35% 27% 4	3920
	11th to 20th	Night	33% 5% 12% 24% 22% 4	3899
	21st to end	Night	43% 4 12% 28% 13%	4279
November	1st to 10th	Night	43% 5% 12% 25% 13% 2	2796
	11th to 20th	Night	52% 5% 12% 20% 11% 1	2940
	21st to end	Night	51% 5% 15% 22% 7% 1	2940
December	1st to 10th	Night	53% 6% 17% 18% 5%	4720
	11th to 20th	Night	62% 5% 11% 17% 4 1	5341
	21st to end	Night	71% 4 9% 12% 3	7150

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	16% 12% 32% 29% 10% 2	330
	11th to 20th	Day	19% 15% 37% 25% 3 1	330
	21st to end	Day	17% 15% 38% 20% 8% 2	363
February	1st to 10th	Day	18% 17% 42% 18% 5% 1	330
	11th to 20th	Day	14% 22% 34% 25% 5% 1	330
	21st to end	Day	18% 18% 37% 23% 4	273
March	1st to 10th	Day	19% 17% 40% 17% 6%	330
	11th to 20th	Day	22% 15% 37% 19% 6% 1	330
	21st to end	Day	27% 21% 27% 17% 7% 2	382
April	1st to 10th	Day	26% 17% 34% 19% 4	540
	11th to 20th	Day	30% 19% 24% 20% 7% 1	552
	21st to end	Day	27% 19% 30% 17% 6% 1	750
May	1st to 10th	Day	20% 19% 32% 21% 7% 1	753
	11th to 20th	Day	22% 15% 30% 21% 10% 2	775
	21st to end	Day	18% 13% 30% 26% 11% 2	844
June	1st to 10th	Day	11% 11% 33% 30% 13% 2	780
	11th to 20th	Day	17% 14% 39% 21% 7% 1	756
	21st to end	Day	14% 14% 34% 24% 12% 2	730
July	1st to 10th	Day	9% 5% 29% 33% 17% 6%	721
	11th to 20th	Day	11% 10% 31% 29% 15% 3	718
	21st to end	Day	6% 10% 32% 33% 16% 4	794
August	1st to 10th	Day	11% 8% 30% 32% 17% 3	726
	11th to 20th	Day	15% 8% 24% 30% 18% 4	715
	21st to end	Day	11% 10% 30% 31% 15% 3	687
September	1st to 10th	Day	14% 13% 30% 25% 15% 2	530
	11th to 20th	Day	13% 10% 32% 29% 15% 2	491
	21st to end	Day	17% 16% 27% 22% 15% 2	330
October	1st to 10th	Day	18% 15% 30% 23% 11% 2	330
	11th to 20th	Day	20% 26% 36% 14% 3	330
	21st to end	Day	26% 19% 38% 13% 4	363
November	1st to 10th	Day	24% 20% 35% 16% 5% 1	330
	11th to 20th	Day	21% 22% 39% 15% 2	330
	21st to end	Day	25% 18% 42% 11% 3	330
December	1st to 10th	Day	15% 20% 36% 22% 7% 1	330
	11th to 20th	Day	22% 21% 34% 19% 3	330
	21st to end	Day	29% 15% 37% 17% 2 1	363
January	1st to 10th	Night	12% 15% 38% 27% 7% 1	1050
	11th to 20th	Night	17% 16% 36% 26% 5% 1	1050
	21st to end	Night	17% 15% 37% 26% 5%	1155
February	1st to 10th	Night	14% 16% 39% 24% 6%	1050
	11th to 20th	Night	12% 16% 42% 23% 6% 1	1029
	21st to end	Night	16% 16% 36% 24% 7% 1	807
March	1st to 10th	Night	17% 14% 36% 26% 7% 1	693
	11th to 20th	Night	20% 15% 35% 24% 6%	630
	21st to end	Night	22% 14% 31% 22% 9% 2	693
April	1st to 10th	Night	23% 15% 32% 25% 5%	630
	11th to 20th	Night	24% 13% 29% 26% 6%	623
	21st to end	Night	24% 13% 31% 23% 7% 1	630
May	1st to 10th	Night	18% 13% 33% 29% 5% 1	630
	11th to 20th	Night	17% 10% 36% 26% 10% 1	621
	21st to end	Night	16% 10% 29% 33% 12%	683
June	1st to 10th	Night	13% 6% 33% 38% 9%	630
	11th to 20th	Night	11% 8% 38% 36% 7%	615
	21st to end	Night	11% 6% 29% 38% 15% 1	600
July	1st to 10th	Night	6% 3 29% 36% 25% 1	585
	11th to 20th	Night	7% 7% 31% 40% 15% 1	582
	21st to end	Night	5% 5% 32% 39% 17% 2	657
August	1st to 10th	Night	7% 6% 23% 42% 20% 1	597
	11th to 20th	Night	13% 4 24% 37% 21% 2	594
	21st to end	Night	8% 6% 32% 33% 21% 1	660
September	1st to 10th	Night	10% 9% 29% 36% 14% 3	600
	11th to 20th	Night	11% 8% 37% 27% 15% 2	600
	21st to end	Night	13% 13% 31% 27% 15% 1	670
October	1st to 10th	Night	17% 13% 32% 26% 12%	800
	11th to 20th	Night	22% 15% 34% 22% 7% 1	800
	21st to end	Night	25% 14% 30% 24% 6%	880
November	1st to 10th	Night	19% 15% 34% 25% 7%	950
	11th to 20th	Night	20% 18% 33% 23% 6%	1050
	21st to end	Night	19% 20% 34% 22% 5%	1050
December	1st to 10th	Night	17% 13% 37% 26% 6% 1	1050
	11th to 20th	Night	20% 16% 34% 24% 5% 1	1050
	21st to end	Night	25% 15% 33% 23% 4 1	1155

Page generated at 2026-06-13 01:31:40. Version ac07

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