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 2024-01-15.

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	14% 6% 3 5% 5% 3 5% 5% 6% 8% 41%	75250
	Night	13% 6% 3 5% 5% 3 4 4 5% 7% 44%	74533
Transparency	Day	40% 7% 11% 21% 17% 4	74968
	Night	38% 6% 11% 21% 19% 5%	74335
Seeing	Day	15% 6% 20% 24% 22% 14%	13787
	Night	15% 5% 23% 32% 22% 4	23466

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	21% 8% 2 4 4 3 4 3 5% 5% 41%	1706
	11th to 20th	Day	23% 9% 3 6% 5% 2 3 3 4 5% 36%	1684
	21st to end	Day	18% 6% 3 4 4 3 3 3 5% 6% 46%	1980
February	1st to 10th	Day	21% 9% 3 5% 4 2 3 3 5% 5% 39%	1800
	11th to 20th	Day	22% 7% 4 6% 6% 3 4 3 4 5% 35%	1748
	21st to end	Day	23% 7% 3 6% 5% 2 4 4 4 5% 36%	1480
March	1st to 10th	Day	16% 7% 2 6% 5% 4 4 4 5% 5% 41%	1800
	11th to 20th	Day	20% 8% 3 5% 6% 2 4 5% 4 6% 36%	1890
	21st to end	Day	16% 6% 3 6% 6% 3 5% 5% 6% 7% 36%	2296
April	1st to 10th	Day	13% 6% 2 4 5% 3 4 4 6% 7% 45%	2160
	11th to 20th	Day	14% 6% 3 5% 5% 3 3 3 5% 7% 45%	2134
	21st to end	Day	12% 4 3 6% 5% 4 5% 5% 6% 8% 43%	2160
May	1st to 10th	Day	15% 5% 3 4 5% 3 5% 4 5% 6% 44%	2340
	11th to 20th	Day	12% 6% 2 6% 7% 3 5% 5% 5% 7% 41%	2301
	21st to end	Day	10% 5% 3 5% 6% 3 5% 6% 6% 10% 40%	2531
June	1st to 10th	Day	10% 5% 3 6% 6% 4 5% 6% 6% 9% 40%	2340
	11th to 20th	Day	5% 4 2 4 5% 4 5% 6% 8% 10% 46%	2379
	21st to end	Day	7% 4 2 6% 6% 3 6% 6% 8% 12% 40%	2520
July	1st to 10th	Day	8% 5% 3 7% 8% 5% 7% 7% 7% 12% 31%	2520
	11th to 20th	Day	10% 5% 2 6% 6% 4 8% 6% 8% 9% 36%	2345
	21st to end	Day	7% 5% 2 6% 7% 4 7% 7% 7% 11% 36%	2547
August	1st to 10th	Day	6% 5% 2 6% 7% 6% 7% 8% 8% 11% 32%	2157
	11th to 20th	Day	9% 5% 3 6% 7% 4 6% 8% 8% 9% 35%	2125
	21st to end	Day	12% 5% 3 7% 7% 4 6% 7% 6% 8% 35%	2376
September	1st to 10th	Day	11% 5% 3 5% 5% 3 5% 7% 7% 8% 40%	2129
	11th to 20th	Day	12% 5% 2 5% 6% 3 4 5% 6% 6% 45%	1980
	21st to end	Day	10% 4 2 4 4 3 5% 4 5% 7% 52%	1980
October	1st to 10th	Day	10% 4 2 5% 5% 2 4 4 3 5% 56%	1980
	11th to 20th	Day	11% 4 2 4 4 3 3 3 4 7% 53%	1962
	21st to end	Day	16% 5% 2 4 4 2 4 4 4 5% 50%	1821
November	1st to 10th	Day	12% 5% 2 4 4 2 3 3 4 5% 56%	1672
	11th to 20th	Day	14% 5% 3 5% 4 2 4 4 4 7% 49%	1710
	21st to end	Day	17% 6% 2 5% 4 3 3 6% 5% 7% 43%	1710
December	1st to 10th	Day	22% 8% 3 6% 5% 3 5% 5% 4 4 35%	1710
	11th to 20th	Day	18% 7% 3 6% 5% 3 4 4 4 5% 40%	2153
	21st to end	Day	18% 10% 4 7% 5% 3 4 4 5% 7% 33%	3124
January	1st to 10th	Night	19% 8% 3 5% 4 2 4 4 4 5% 43%	2459
	11th to 20th	Night	21% 9% 4 7% 6% 3 4 4 4 6% 34%	2380
	21st to end	Night	16% 8% 3 5% 5% 2 3 3 4 5% 45%	2376
February	1st to 10th	Night	20% 7% 3 5% 4 2 3 4 5% 6% 39%	2160
	11th to 20th	Night	22% 8% 3 6% 5% 2 3 4 4 4 39%	2098
	21st to end	Night	26% 7% 2 5% 4 3 5% 5% 5% 4 34%	1776
March	1st to 10th	Night	17% 6% 2 5% 4 3 4 3 5% 8% 42%	2160
	11th to 20th	Night	16% 7% 3 7% 5% 3 5% 5% 5% 7% 37%	2069
	21st to end	Night	14% 7% 2 6% 6% 3 4 4 6% 5% 43%	2073
April	1st to 10th	Night	11% 5% 3 5% 5% 2 4 5% 5% 8% 48%	1800
	11th to 20th	Night	15% 4 2 4 4 2 3 4 5% 8% 48%	1775
	21st to end	Night	11% 5% 2 4 4 2 4 5% 5% 7% 49%	1800
May	1st to 10th	Night	10% 5% 2 4 4 3 4 4 5% 8% 51%	1620
	11th to 20th	Night	11% 5% 2 5% 5% 4 5% 5% 6% 9% 43%	1592
	21st to end	Night	7% 5% 3 5% 5% 4 6% 5% 7% 10% 45%	1744
June	1st to 10th	Night	8% 5% 3 6% 5% 4 5% 5% 7% 10% 42%	1620
	11th to 20th	Night	3 2 1 4 3 2 6% 6% 7% 12% 54%	1572
	21st to end	Night	5% 4 3 4 4 3 5% 6% 6% 11% 49%	1440
July	1st to 10th	Night	9% 4 2 6% 6% 4 6% 7% 8% 8% 39%	1440
	11th to 20th	Night	7% 4 2 5% 6% 4 6% 6% 8% 11% 43%	1606
	21st to end	Night	7% 5% 2 5% 6% 4 6% 6% 8% 12% 40%	1771
August	1st to 10th	Night	5% 3 2 4 6% 3 6% 8% 9% 13% 42%	1777
	11th to 20th	Night	8% 4 3 4 6% 4 6% 5% 7% 11% 42%	1776
	21st to end	Night	8% 5% 2 6% 6% 3 5% 5% 6% 9% 44%	1980
September	1st to 10th	Night	8% 5% 3 5% 5% 3 4 4 6% 8% 49%	1813
	11th to 20th	Night	9% 5% 3 6% 6% 4 4 4 5% 8% 46%	1980
	21st to end	Night	9% 4 2 4 4 3 5% 3 4 7% 56%	1980
October	1st to 10th	Night	9% 3 2 4 4 2 3 3 4 6% 59%	1980
	11th to 20th	Night	12% 5% 3 5% 4 2 3 4 5% 5% 51%	1993
	21st to end	Night	14% 6% 2 4 4 2 3 4 5% 5% 51%	2533
November	1st to 10th	Night	12% 4 2 3 3 2 4 4 4 6% 54%	2406
	11th to 20th	Night	12% 5% 2 4 4 2 3 4 5% 6% 52%	2470
	21st to end	Night	16% 6% 3 5% 4 2 3 4 4 5% 46%	2470
December	1st to 10th	Night	20% 7% 3 5% 5% 3 5% 3 5% 6% 38%	2470
	11th to 20th	Night	18% 6% 3 5% 4 2 3 3 4 5% 47%	3042
	21st to end	Night	17% 9% 4 7% 7% 3 4 5% 5% 7% 30%	4532

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	45% 3 8% 21% 19% 4	1707
	11th to 20th	Day	51% 4 8% 17% 17% 2	1684
	21st to end	Day	41% 5% 8% 23% 21% 3	1980
February	1st to 10th	Day	48% 4 7% 20% 18% 3	1800
	11th to 20th	Day	52% 4 6% 20% 15% 4	1758
	21st to end	Day	50% 4 8% 15% 17% 6%	1480
March	1st to 10th	Day	45% 4 8% 15% 19% 8%	1800
	11th to 20th	Day	49% 7% 10% 15% 17% 3	1890
	21st to end	Day	44% 6% 12% 22% 14% 1	2296
April	1st to 10th	Day	37% 6% 10% 24% 17% 5%	2160
	11th to 20th	Day	39% 4 8% 20% 24% 5%	2134
	21st to end	Day	37% 5% 11% 28% 16% 3	2160
May	1st to 10th	Day	38% 7% 12% 24% 15% 4	2340
	11th to 20th	Day	41% 8% 13% 24% 14%	2305
	21st to end	Day	37% 9% 14% 24% 15% 2	2531
June	1st to 10th	Day	39% 9% 14% 20% 16% 2	2340
	11th to 20th	Day	30% 9% 16% 25% 17% 2	2379
	21st to end	Day	35% 10% 17% 19% 14% 4	2520
July	1st to 10th	Day	42% 11% 16% 19% 10% 2	2451
	11th to 20th	Day	38% 12% 21% 17% 9% 3	2275
	21st to end	Day	37% 12% 18% 23% 8% 1	2405
August	1st to 10th	Day	38% 13% 19% 19% 9% 2	2144
	11th to 20th	Day	40% 11% 15% 19% 13% 2	2125
	21st to end	Day	43% 10% 13% 20% 11% 3	2376
September	1st to 10th	Day	36% 10% 15% 18% 17% 4	2129
	11th to 20th	Day	37% 8% 12% 18% 21% 4	1980
	21st to end	Day	32% 5% 11% 24% 21% 7%	1980
October	1st to 10th	Day	31% 6% 7% 23% 27% 6%	1980
	11th to 20th	Day	31% 4 10% 21% 25% 9%	1962
	21st to end	Day	36% 4 6% 17% 28% 8%	1821
November	1st to 10th	Day	31% 4 8% 20% 29% 8%	1672
	11th to 20th	Day	36% 4 6% 21% 26% 7%	1710
	21st to end	Day	41% 5% 6% 20% 23% 6%	1710
December	1st to 10th	Day	50% 5% 7% 17% 18% 4	1710
	11th to 20th	Day	46% 4 8% 20% 19% 3	2150
	21st to end	Day	50% 6% 10% 20% 11% 3	3124
January	1st to 10th	Night	44% 3 9% 22% 18% 4	2459
	11th to 20th	Night	52% 4 7% 19% 15% 3	2380
	21st to end	Night	42% 3 7% 23% 21% 4	2376
February	1st to 10th	Night	45% 4 9% 20% 19% 4	2160
	11th to 20th	Night	49% 4 8% 17% 16% 6%	2099
	21st to end	Night	52% 4 6% 16% 15% 6%	1776
March	1st to 10th	Night	41% 4 8% 17% 20% 10%	2160
	11th to 20th	Night	45% 6% 10% 17% 17% 4	2069
	21st to end	Night	40% 6% 11% 22% 18% 3	2073
April	1st to 10th	Night	34% 5% 13% 22% 20% 4	1800
	11th to 20th	Night	34% 4 9% 20% 23% 11%	1775
	21st to end	Night	33% 5% 12% 26% 20% 3	1800
May	1st to 10th	Night	32% 7% 10% 24% 24% 4	1620
	11th to 20th	Night	36% 8% 17% 20% 17% 2	1593
	21st to end	Night	31% 10% 15% 25% 16% 3	1745
June	1st to 10th	Night	35% 10% 12% 22% 18% 3	1620
	11th to 20th	Night	22% 10% 18% 29% 18% 3	1572
	21st to end	Night	28% 10% 16% 25% 17% 4	1440
July	1st to 10th	Night	36% 13% 17% 20% 11% 3	1400
	11th to 20th	Night	31% 12% 21% 22% 12% 4	1553
	21st to end	Night	33% 13% 20% 22% 12% 1	1672
August	1st to 10th	Night	27% 12% 22% 25% 13% 1	1766
	11th to 20th	Night	34% 11% 21% 18% 13% 3	1776
	21st to end	Night	35% 11% 16% 22% 12% 5%	1980
September	1st to 10th	Night	31% 8% 17% 23% 16% 5%	1813
	11th to 20th	Night	36% 8% 13% 16% 24% 4	1980
	21st to end	Night	29% 5% 9% 24% 24% 9%	1980
October	1st to 10th	Night	27% 5% 8% 23% 28% 10%	1980
	11th to 20th	Night	35% 4 7% 22% 21% 11%	1993
	21st to end	Night	34% 4 5% 19% 28% 9%	2533
November	1st to 10th	Night	32% 4 7% 20% 25% 11%	2406
	11th to 20th	Night	33% 3 7% 19% 27% 10%	2470
	21st to end	Night	40% 3 6% 19% 25% 6%	2470
December	1st to 10th	Night	46% 5% 8% 19% 18% 3	2470
	11th to 20th	Night	40% 3 7% 20% 26% 5%	3044
	21st to end	Night	50% 6% 9% 19% 13% 2	4532

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	25% 15% 35% 16% 8%	270
	11th to 20th	Day	27% 12% 37% 16% 4 3	254
	21st to end	Day	16% 16% 44% 18% 5% 1	264
February	1st to 10th	Day	26% 13% 36% 18% 6%	240
	11th to 20th	Day	35% 13% 37% 13% 2	240
	21st to end	Day	35% 14% 29% 18% 5%	198
March	1st to 10th	Day	22% 12% 36% 25% 3 1	240
	11th to 20th	Day	22% 14% 33% 22% 8% 1	330
	21st to end	Day	21% 11% 32% 25% 11% 1	462
April	1st to 10th	Day	15% 11% 28% 27% 13% 5%	420
	11th to 20th	Day	16% 8% 27% 32% 14% 3	412
	21st to end	Day	17% 6% 26% 31% 16% 4	420
May	1st to 10th	Day	15% 7% 23% 29% 19% 7%	423
	11th to 20th	Day	11% 5% 18% 28% 24% 15%	447
	21st to end	Day	12% 4 13% 26% 23% 23%	485
June	1st to 10th	Day	12% 2 11% 25% 26% 23%	450
	11th to 20th	Day	7% 2 11% 21% 28% 31%	489
	21st to end	Day	8% 2 13% 25% 33% 19%	630
July	1st to 10th	Day	9% 2 8% 22% 30% 29%	621
	11th to 20th	Day	9% 1 5% 17% 27% 40%	448
	21st to end	Day	7% 1 7% 17% 33% 34%	488
August	1st to 10th	Day	9% 1 8% 20% 34% 28%	446
	11th to 20th	Day	9% 1 5% 22% 39% 23%	439
	21st to end	Day	14% 2 7% 16% 33% 29%	495
September	1st to 10th	Day	8% 2 8% 20% 39% 22%	450
	11th to 20th	Day	13% 1 10% 20% 32% 23%	450
	21st to end	Day	13% 2 12% 24% 36% 13%	450
October	1st to 10th	Day	11% 2 16% 32% 25% 14%	450
	11th to 20th	Day	10% 6% 27% 35% 19% 4	432
	21st to end	Day	23% 8% 20% 28% 17% 4	297
November	1st to 10th	Day	17% 4 26% 29% 20% 4	270
	11th to 20th	Day	13% 9% 34% 33% 9% 1	270
	21st to end	Day	17% 9% 32% 24% 14% 3	270
December	1st to 10th	Day	26% 14% 27% 22% 9% 1	270
	11th to 20th	Day	19% 13% 33% 20% 13% 1	270
	21st to end	Day	23% 12% 37% 22% 5% 1	297
January	1st to 10th	Night	22% 8% 38% 27% 5% 1	760
	11th to 20th	Night	23% 10% 35% 25% 7%	740
	21st to end	Night	18% 9% 41% 29% 3	792
February	1st to 10th	Night	22% 8% 36% 28% 6%	720
	11th to 20th	Night	26% 9% 34% 30% 2	703
	21st to end	Night	26% 12% 32% 27% 3	592
March	1st to 10th	Night	18% 8% 35% 33% 5%	720
	11th to 20th	Night	18% 7% 37% 30% 8% 1	720
	21st to end	Night	16% 7% 31% 33% 12%	687
April	1st to 10th	Night	12% 7% 33% 33% 15% 1	540
	11th to 20th	Night	15% 4 30% 36% 12% 2	533
	21st to end	Night	13% 6% 25% 38% 18% 1	540
May	1st to 10th	Night	12% 2 26% 37% 21% 3	540
	11th to 20th	Night	13% 1 16% 40% 25% 4	531
	21st to end	Night	9% 1 9% 36% 39% 6%	584
June	1st to 10th	Night	10% 2 10% 36% 38% 5%	540
	11th to 20th	Night	5% 1 7% 34% 43% 10%	540
	21st to end	Night	7% 1 6% 34% 43% 8%	540
July	1st to 10th	Night	9% 2 6% 27% 44% 13%	525
	11th to 20th	Night	7% 1 3 22% 50% 16%	522
	21st to end	Night	8% 1 6% 26% 46% 13%	591
August	1st to 10th	Night	5% 1 3 23% 55% 13%	537
	11th to 20th	Night	9% 1 7% 30% 44% 9%	534
	21st to end	Night	10% 1 5% 25% 49% 10%	594
September	1st to 10th	Night	9% 1 7% 31% 43% 8%	553
	11th to 20th	Night	10% 2 10% 32% 40% 7%	720
	21st to end	Night	10% 1 11% 34% 40% 4	720
October	1st to 10th	Night	10% 2 16% 35% 30% 8%	720
	11th to 20th	Night	15% 4 23% 37% 20% 2	720
	21st to end	Night	15% 5% 21% 37% 19% 3	792
November	1st to 10th	Night	14% 5% 20% 37% 21% 3	740
	11th to 20th	Night	14% 5% 32% 35% 13% 1	760
	21st to end	Night	18% 6% 27% 34% 14% 1	760
December	1st to 10th	Night	22% 7% 31% 31% 7% 1	760
	11th to 20th	Night	23% 6% 31% 31% 10%	760
	21st to end	Night	24% 7% 31% 32% 6%	836

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