Galunlati 2 Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Galunlati 2 Observatory clear sky chart from 2005-11-06 to 2025-09-19.

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	13% 7% 2 7% 5% 4 5% 4 6% 8% 40%	126740
	Night	14% 7% 3 6% 4 4 4 3 5% 7% 43%	122337
Transparency	Day	40% 5% 11% 22% 17% 4	130473
	Night	39% 5% 10% 21% 19% 6%	126675
Seeing	Day	15% 6% 21% 24% 21% 13%	16074
	Night	15% 5% 23% 32% 22% 4	25579

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	17% 10% 4 9% 3 3 3 3 5% 4 40%	4056
	11th to 20th	Day	17% 6% 3 10% 4 3 2 2 3 5% 45%	4124
	21st to end	Day	20% 10% 4 6% 3 3 3 3 4 6% 38%	4972
February	1st to 10th	Day	21% 9% 3 6% 3 3 3 3 5% 5% 38%	2000
	11th to 20th	Day	22% 8% 4 7% 5% 4 4 3 4 5% 35%	1948
	21st to end	Day	22% 8% 3 6% 4 3 3 3 4 5% 38%	1650
March	1st to 10th	Day	18% 10% 3 8% 5% 5% 4 3 5% 5% 33%	4480
	11th to 20th	Day	13% 8% 2 6% 4 3 3 3 5% 7% 46%	4750
	21st to end	Day	13% 6% 3 7% 5% 4 4 4 5% 7% 42%	5775
April	1st to 10th	Day	14% 7% 2 5% 5% 4 4 3 6% 7% 44%	2400
	11th to 20th	Day	14% 6% 2 6% 4 4 3 3 5% 7% 45%	2374
	21st to end	Day	12% 6% 2 7% 5% 5% 4 4 6% 8% 42%	2400
May	1st to 10th	Day	18% 7% 3 6% 5% 5% 6% 4 6% 8% 32%	5862
	11th to 20th	Day	16% 9% 3 9% 6% 5% 5% 4 7% 7% 30%	5861
	21st to end	Day	17% 8% 3 6% 4 4 4 4 5% 8% 38%	6433
June	1st to 10th	Day	10% 6% 2 7% 5% 5% 5% 5% 6% 9% 39%	2600
	11th to 20th	Day	5% 5% 2 6% 5% 5% 6% 5% 8% 10% 44%	2644
	21st to end	Day	6% 5% 2 7% 6% 5% 6% 5% 8% 12% 39%	2800
July	1st to 10th	Day	5% 5% 2 7% 6% 6% 7% 6% 8% 12% 37%	6360
	11th to 20th	Day	7% 5% 2 6% 5% 6% 7% 6% 9% 12% 34%	5905
	21st to end	Day	11% 8% 3 8% 6% 6% 6% 6% 8% 11% 28%	6424
August	1st to 10th	Day	4 3 1 5% 4 5% 6% 5% 7% 11% 49%	3914
	11th to 20th	Day	6% 4 2 6% 6% 6% 6% 5% 7% 10% 43%	3849
	21st to end	Day	7% 4 2 6% 5% 4 5% 4 6% 7% 52%	4312
September	1st to 10th	Day	11% 6% 2 6% 4 5% 5% 5% 7% 8% 41%	2365
	11th to 20th	Day	12% 5% 2 5% 5% 4 4 4 6% 7% 45%	2178
	21st to end	Day	11% 4 2 5% 4 4 4 3 6% 8% 50%	2090
October	1st to 10th	Day	10% 4 2 5% 4 3 4 3 3 5% 56%	2090
	11th to 20th	Day	10% 4 2 5% 3 4 3 3 5% 7% 54%	2071
	21st to end	Day	15% 5% 2 5% 3 3 3 3 4 5% 52%	1922
November	1st to 10th	Day	12% 6% 2 5% 4 3 3 3 4 4 54%	1762
	11th to 20th	Day	14% 5% 2 6% 4 3 4 3 4 7% 49%	1800
	21st to end	Day	16% 7% 2 5% 4 4 4 4 5% 7% 43%	1800
December	1st to 10th	Day	16% 7% 2 7% 4 3 4 3 4 4 45%	2930
	11th to 20th	Day	21% 10% 3 7% 4 4 3 3 4 5% 36%	3373
	21st to end	Day	19% 10% 3 7% 4 4 4 3 6% 7% 33%	4466
January	1st to 10th	Night	16% 10% 3 9% 3 3 4 3 4 5% 41%	5889
	11th to 20th	Night	17% 8% 3 8% 4 3 2 2 3 4 45%	5834
	21st to end	Night	18% 11% 3 6% 3 3 3 3 5% 5% 41%	5984
February	1st to 10th	Night	19% 8% 4 6% 4 3 3 3 5% 6% 40%	2400
	11th to 20th	Night	22% 9% 3 7% 5% 3 3 3 4 4 38%	2338
	21st to end	Night	23% 8% 2 6% 4 4 4 3 5% 4 36%	1980
March	1st to 10th	Night	22% 8% 3 8% 5% 4 4 3 4 6% 33%	5373
	11th to 20th	Night	11% 7% 2 6% 3 4 4 4 5% 7% 47%	5195
	21st to end	Night	15% 7% 3 7% 5% 4 3 3 4 5% 42%	5195
April	1st to 10th	Night	11% 6% 3 6% 5% 3 4 4 6% 8% 46%	2000
	11th to 20th	Night	14% 5% 2 5% 3 3 3 4 6% 7% 48%	1975
	21st to end	Night	12% 6% 2 5% 4 4 4 4 6% 7% 48%	2000
May	1st to 10th	Night	14% 9% 3 8% 5% 5% 5% 4 6% 7% 35%	4033
	11th to 20th	Night	17% 10% 3 9% 5% 6% 4 4 5% 6% 31%	4032
	21st to end	Night	12% 8% 3 7% 4 4 5% 4 6% 9% 38%	4421
June	1st to 10th	Night	9% 6% 3 7% 5% 5% 5% 4 7% 9% 42%	1800
	11th to 20th	Night	4 3 2 4 3 3 5% 5% 7% 12% 52%	1746
	21st to end	Night	4 5% 2 5% 5% 5% 4 5% 7% 10% 49%	1600
July	1st to 10th	Night	6% 5% 2 8% 6% 6% 7% 5% 8% 9% 38%	3618
	11th to 20th	Night	6% 5% 2 6% 6% 5% 6% 5% 9% 14% 35%	4030
	21st to end	Night	8% 7% 3 8% 6% 5% 6% 5% 9% 12% 30%	4427
August	1st to 10th	Night	3 3 1 4 3 3 4 5% 8% 11% 56%	3231
	11th to 20th	Night	5% 3 2 4 4 4 5% 4 7% 11% 51%	3200
	21st to end	Night	5% 4 2 4 3 3 3 4 6% 8% 59%	3586
September	1st to 10th	Night	7% 5% 3 6% 4 4 5% 4 6% 8% 48%	2015
	11th to 20th	Night	10% 5% 2 7% 5% 5% 4 3 5% 8% 46%	2179
	21st to end	Night	10% 4 2 5% 4 4 4 2 5% 6% 55%	2090
October	1st to 10th	Night	9% 3 1 4 4 3 3 3 4 6% 60%	2090
	11th to 20th	Night	12% 5% 2 6% 3 3 3 3 5% 5% 53%	2104
	21st to end	Night	13% 6% 1 5% 3 3 3 3 5% 5% 52%	2674
November	1st to 10th	Night	12% 5% 2 4 3 3 5% 4 4 6% 52%	2536
	11th to 20th	Night	13% 5% 2 5% 3 3 3 3 5% 6% 51%	2600
	21st to end	Night	16% 7% 2 6% 4 3 3 3 4 6% 47%	2600
December	1st to 10th	Night	19% 8% 2 5% 3 3 4 2 4 5% 44%	4250
	11th to 20th	Night	23% 9% 3 6% 3 2 2 2 3 4 42%	4822
	21st to end	Night	19% 9% 4 8% 5% 4 4 3 5% 6% 33%	6490

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	47% 3 8% 21% 19% 2	4057
	11th to 20th	Day	43% 3 6% 22% 25% 1	4124
	21st to end	Day	49% 3 7% 20% 18% 3	4972
February	1st to 10th	Day	48% 4 7% 20% 18% 3	2000
	11th to 20th	Day	52% 4 6% 19% 15% 5%	1958
	21st to end	Day	48% 4 7% 16% 19% 6%	1650
March	1st to 10th	Day	52% 4 6% 13% 17% 8%	4480
	11th to 20th	Day	37% 5% 7% 20% 20% 11%	4750
	21st to end	Day	41% 5% 10% 25% 17% 2	5777
April	1st to 10th	Day	38% 5% 10% 24% 17% 5%	2400
	11th to 20th	Day	38% 4 8% 22% 23% 6%	2374
	21st to end	Day	38% 5% 11% 27% 16% 3	2400
May	1st to 10th	Day	47% 7% 14% 20% 10% 2	5897
	11th to 20th	Day	50% 7% 15% 20% 9%	5865
	21st to end	Day	44% 6% 9% 23% 16% 2	6447
June	1st to 10th	Day	39% 9% 14% 20% 16% 2	2600
	11th to 20th	Day	33% 9% 16% 24% 17% 2	2644
	21st to end	Day	35% 10% 17% 19% 15% 4	2800
July	1st to 10th	Day	38% 6% 18% 27% 10% 1	6291
	11th to 20th	Day	39% 7% 26% 24% 4 1	5835
	21st to end	Day	49% 6% 23% 18% 4	6240
August	1st to 10th	Day	27% 8% 12% 35% 17% 1	3901
	11th to 20th	Day	34% 7% 14% 27% 14% 3	3885
	21st to end	Day	31% 6% 12% 23% 26% 2	4311
September	1st to 10th	Day	36% 9% 15% 19% 17% 5%	2365
	11th to 20th	Day	37% 8% 11% 19% 21% 4	2178
	21st to end	Day	33% 5% 12% 23% 20% 7%	2090
October	1st to 10th	Day	21% 4 4 15% 38% 17%	3480
	11th to 20th	Day	21% 3 6% 18% 31% 21%	3427
	21st to end	Day	27% 3 6% 22% 33% 9%	3147
November	1st to 10th	Day	33% 4 8% 20% 28% 8%	1762
	11th to 20th	Day	36% 4 6% 21% 27% 7%	1800
	21st to end	Day	40% 4 6% 21% 23% 5%	1800
December	1st to 10th	Day	43% 3 5% 22% 23% 4	2930
	11th to 20th	Day	52% 3 6% 21% 14% 4	3370
	21st to end	Day	50% 5% 10% 23% 11% 2	4466
January	1st to 10th	Night	46% 3 7% 20% 20% 3	5889
	11th to 20th	Night	45% 3 6% 17% 24% 5%	5834
	21st to end	Night	46% 3 4 19% 21% 6%	5984
February	1st to 10th	Night	45% 4 9% 20% 19% 4	2400
	11th to 20th	Night	51% 4 7% 16% 16% 6%	2339
	21st to end	Night	50% 4 6% 16% 18% 7%	1980
March	1st to 10th	Night	52% 4 6% 15% 17% 5%	5373
	11th to 20th	Night	35% 5% 7% 17% 22% 14%	5195
	21st to end	Night	45% 4 8% 20% 20% 4	5195
April	1st to 10th	Night	36% 5% 13% 21% 20% 5%	2000
	11th to 20th	Night	34% 4 9% 20% 23% 10%	1975
	21st to end	Night	34% 5% 13% 25% 19% 3	2000
May	1st to 10th	Night	46% 7% 12% 20% 13% 1	4060
	11th to 20th	Night	53% 6% 13% 17% 10% 1	4033
	21st to end	Night	40% 8% 12% 23% 15% 1	4429
June	1st to 10th	Night	36% 10% 12% 22% 18% 2	1800
	11th to 20th	Night	24% 10% 18% 27% 19% 3	1746
	21st to end	Night	28% 10% 15% 26% 17% 4	1600
July	1st to 10th	Night	39% 7% 18% 24% 9% 2	3580
	11th to 20th	Night	37% 7% 28% 23% 5% 1	3980
	21st to end	Night	45% 8% 26% 16% 5%	4297
August	1st to 10th	Night	20% 7% 13% 37% 22% 1	3220
	11th to 20th	Night	27% 7% 21% 27% 17% 2	3230
	21st to end	Night	24% 6% 15% 25% 27% 3	3586
September	1st to 10th	Night	32% 7% 16% 22% 17% 6%	2015
	11th to 20th	Night	36% 7% 13% 18% 22% 3	2179
	21st to end	Night	30% 5% 10% 24% 22% 9%	2090
October	1st to 10th	Night	20% 4 5% 17% 35% 19%	3480
	11th to 20th	Night	21% 2 4 18% 32% 23%	3487
	21st to end	Night	23% 2 4 27% 27% 15%	4399
November	1st to 10th	Night	33% 4 7% 21% 24% 10%	2536
	11th to 20th	Night	33% 3 7% 19% 27% 10%	2600
	21st to end	Night	40% 3 6% 20% 25% 6%	2600
December	1st to 10th	Night	43% 3 5% 21% 26% 3	4250
	11th to 20th	Night	47% 2 4 19% 23% 3	4824
	21st to end	Night	50% 4 8% 24% 12% 2	6490

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	24% 16% 35% 17% 7%	300
	11th to 20th	Day	25% 14% 40% 16% 4 2	300
	21st to end	Day	17% 15% 45% 18% 5% 1	330
February	1st to 10th	Day	26% 11% 38% 18% 7%	300
	11th to 20th	Day	32% 16% 35% 14% 2 1	300
	21st to end	Day	32% 14% 32% 17% 5%	249
March	1st to 10th	Day	24% 12% 36% 23% 5% 1	300
	11th to 20th	Day	20% 15% 34% 23% 7% 1	400
	21st to end	Day	19% 12% 34% 24% 9% 1	550
April	1st to 10th	Day	17% 13% 29% 25% 12% 4	500
	11th to 20th	Day	15% 10% 29% 30% 13% 3	492
	21st to end	Day	18% 6% 25% 32% 16% 4	500
May	1st to 10th	Day	16% 8% 25% 28% 18% 6%	503
	11th to 20th	Day	11% 6% 21% 26% 23% 13%	527
	21st to end	Day	13% 4 16% 27% 20% 19%	573
June	1st to 10th	Day	11% 3 13% 27% 26% 21%	530
	11th to 20th	Day	9% 2 12% 21% 28% 28%	574
	21st to end	Day	7% 2 12% 25% 33% 21%	730
July	1st to 10th	Day	9% 2 8% 23% 32% 27%	721
	11th to 20th	Day	10% 1 5% 16% 28% 39%	528
	21st to end	Day	9% 2 6% 17% 34% 32%	576
August	1st to 10th	Day	9% 1 7% 19% 37% 26%	526
	11th to 20th	Day	10% 1 7% 22% 37% 24%	519
	21st to end	Day	13% 2 7% 17% 32% 29%	583
September	1st to 10th	Day	9% 2 9% 23% 37% 20%	530
	11th to 20th	Day	12% 1 10% 23% 32% 22%	522
	21st to end	Day	15% 2 12% 25% 33% 13%	490
October	1st to 10th	Day	10% 2 15% 33% 25% 14%	490
	11th to 20th	Day	9% 6% 27% 34% 21% 4	471
	21st to end	Day	21% 7% 20% 30% 18% 5%	330
November	1st to 10th	Day	18% 4 27% 27% 19% 4	300
	11th to 20th	Day	13% 9% 35% 33% 9% 1	300
	21st to end	Day	16% 10% 32% 24% 14% 3	300
December	1st to 10th	Day	24% 14% 31% 22% 8% 1	300
	11th to 20th	Day	21% 13% 33% 20% 12% 1	300
	21st to end	Day	23% 12% 36% 22% 6% 1	330
January	1st to 10th	Night	22% 9% 38% 27% 5% 1	800
	11th to 20th	Night	23% 10% 36% 25% 7%	800
	21st to end	Night	18% 9% 41% 29% 3	880
February	1st to 10th	Night	22% 8% 36% 29% 6%	800
	11th to 20th	Night	26% 10% 33% 30% 2	783
	21st to end	Night	25% 12% 33% 27% 2	660
March	1st to 10th	Night	20% 9% 34% 31% 6%	800
	11th to 20th	Night	17% 8% 37% 31% 8% 1	800
	21st to end	Night	17% 7% 33% 32% 11%	763
April	1st to 10th	Night	12% 9% 34% 31% 14% 1	600
	11th to 20th	Night	15% 5% 32% 36% 11% 2	593
	21st to end	Night	13% 6% 25% 37% 17% 1	600
May	1st to 10th	Night	13% 3 26% 36% 20% 3	600
	11th to 20th	Night	15% 2 17% 40% 23% 4	591
	21st to end	Night	10% 1 11% 38% 35% 6%	650
June	1st to 10th	Night	11% 2 10% 37% 36% 5%	600
	11th to 20th	Night	5% 1 8% 34% 43% 9%	600
	21st to end	Night	7% 1 5% 33% 45% 9%	600
July	1st to 10th	Night	9% 1 6% 28% 44% 12%	585
	11th to 20th	Night	8% 1 3 21% 50% 16%	582
	21st to end	Night	10% 1 5% 25% 45% 13%	657
August	1st to 10th	Night	5% 1 4 24% 54% 12%	597
	11th to 20th	Night	8% 1 7% 30% 44% 10%	594
	21st to end	Night	10% 1 5% 27% 48% 10%	660
September	1st to 10th	Night	9% 1 8% 33% 41% 8%	615
	11th to 20th	Night	11% 2 9% 31% 40% 7%	793
	21st to end	Night	11% 1 12% 33% 39% 4	760
October	1st to 10th	Night	9% 2 16% 36% 29% 7%	760
	11th to 20th	Night	14% 4 23% 38% 20% 2	760
	21st to end	Night	14% 5% 21% 38% 19% 3	836
November	1st to 10th	Night	14% 5% 21% 37% 21% 3	780
	11th to 20th	Night	15% 5% 32% 34% 13% 1	800
	21st to end	Night	18% 6% 28% 34% 14% 1	800
December	1st to 10th	Night	23% 7% 32% 31% 7% 1	800
	11th to 20th	Night	23% 6% 30% 30% 10%	800
	21st to end	Night	24% 7% 31% 32% 6%	880

Page generated at 2025-09-16 00:49:12. Version ac07

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