Elentirmo Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Elentirmo Observatory clear sky chart from 2005-11-06 to 2024-02-20.

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	21% 9% 4 7% 6% 3 5% 5% 5% 7% 30%	78672
	Night	21% 9% 4 7% 6% 3 5% 5% 5% 7% 30%	80530
Transparency	Day	54% 3 11% 21% 11% 1	78380
	Night	56% 2 11% 21% 10% 1	80357
Seeing	Day	29% 19% 30% 16% 5% 1	16263
	Night	27% 16% 30% 20% 6%	23929

By Month

Percentage Cloud Cover NE (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	16% 11% 6% 8% 8% 4 5% 5% 6% 5% 26%	2526
	11th to 20th	Day	17% 13% 5% 14% 8% 5% 6% 4 5% 6% 17%	2654
	21st to end	Day	19% 9% 4 8% 7% 3 5% 5% 6% 7% 27%	3124
February	1st to 10th	Day	21% 12% 4 9% 8% 4 5% 5% 4 6% 21%	1710
	11th to 20th	Day	18% 10% 4 11% 8% 4 6% 5% 5% 6% 23%	1654
	21st to end	Day	12% 12% 5% 7% 7% 4 5% 3 6% 6% 32%	1356
March	1st to 10th	Day	18% 12% 5% 8% 9% 4 4 5% 4 6% 26%	1976
	11th to 20th	Day	17% 9% 5% 9% 6% 4 4 4 5% 6% 31%	1980
	21st to end	Day	17% 12% 5% 9% 6% 3 4 3 4 6% 31%	2178
April	1st to 10th	Day	26% 12% 5% 7% 6% 3 3 3 4 5% 26%	2145
	11th to 20th	Day	21% 9% 4 6% 5% 3 3 4 6% 6% 34%	2199
	21st to end	Day	24% 9% 3 6% 6% 3 4 4 4 7% 30%	2340
May	1st to 10th	Day	25% 10% 4 6% 5% 4 4 4 5% 6% 26%	2376
	11th to 20th	Day	22% 8% 4 7% 5% 3 4 4 5% 7% 32%	2478
	21st to end	Day	23% 8% 3 5% 5% 3 5% 5% 6% 8% 30%	2724
June	1st to 10th	Day	25% 9% 4 8% 5% 3 5% 4 5% 6% 26%	2520
	11th to 20th	Day	22% 8% 3 5% 5% 3 4 5% 4 6% 34%	2589
	21st to end	Day	26% 8% 4 7% 6% 3 5% 5% 4 7% 25%	2700
July	1st to 10th	Day	19% 7% 3 6% 5% 3 5% 5% 6% 8% 34%	2614
	11th to 20th	Day	19% 8% 3 6% 5% 3 4 6% 6% 9% 31%	2520
	21st to end	Day	22% 7% 3 6% 6% 4 5% 6% 6% 8% 28%	2645
August	1st to 10th	Day	17% 6% 3 6% 5% 4 5% 6% 6% 9% 35%	2327
	11th to 20th	Day	17% 8% 3 5% 6% 4 5% 6% 6% 9% 32%	2304
	21st to end	Day	16% 6% 2 5% 4 3 5% 4 6% 8% 41%	2477
September	1st to 10th	Day	16% 5% 3 5% 5% 3 4 5% 5% 8% 41%	2160
	11th to 20th	Day	19% 6% 2 6% 5% 3 4 4 5% 6% 42%	2083
	21st to end	Day	20% 6% 2 5% 5% 3 4 4 4 6% 42%	1927
October	1st to 10th	Day	19% 5% 3 5% 5% 3 4 4 5% 7% 38%	1800
	11th to 20th	Day	21% 7% 3 6% 5% 2 4 4 6% 8% 34%	1800
	21st to end	Day	22% 9% 3 6% 6% 3 5% 4 4 5% 32%	1980
November	1st to 10th	Day	22% 10% 4 7% 5% 4 5% 3 3 7% 31%	1557
	11th to 20th	Day	22% 9% 5% 7% 6% 3 5% 5% 5% 7% 27%	1520
	21st to end	Day	22% 9% 4 8% 7% 4 5% 4 4 6% 26%	1520
December	1st to 10th	Day	26% 12% 4 7% 6% 3 5% 5% 5% 5% 21%	1520
	11th to 20th	Day	32% 10% 3 6% 6% 3 5% 6% 5% 6% 18%	1906
	21st to end	Day	24% 10% 5% 8% 6% 3 4 5% 6% 7% 23%	2783
January	1st to 10th	Night	15% 10% 4 10% 9% 4 6% 6% 6% 6% 24%	4429
	11th to 20th	Night	20% 13% 5% 13% 8% 5% 4 5% 4 5% 18%	4308
	21st to end	Night	18% 11% 5% 9% 7% 4 5% 5% 6% 8% 22%	4532
February	1st to 10th	Night	20% 12% 5% 8% 6% 4 6% 6% 6% 6% 22%	2470
	11th to 20th	Night	18% 10% 4 8% 7% 4 6% 7% 6% 8% 24%	2397
	21st to end	Night	13% 10% 5% 9% 7% 4 6% 6% 6% 7% 29%	1898
March	1st to 10th	Night	17% 10% 4 8% 6% 4 6% 4 4 8% 28%	1971
	11th to 20th	Night	20% 8% 4 6% 6% 3 5% 6% 5% 7% 30%	1979
	21st to end	Night	17% 11% 4 7% 5% 3 5% 4 5% 5% 34%	2178
April	1st to 10th	Night	25% 11% 3 6% 4 3 5% 4 5% 4 29%	1814
	11th to 20th	Night	23% 8% 2 6% 5% 3 4 4 5% 6% 33%	1707
	21st to end	Night	26% 9% 3 6% 4 3 4 4 4 7% 30%	1620
May	1st to 10th	Night	25% 11% 3 5% 4 2 4 4 4 6% 30%	1583
	11th to 20th	Night	25% 7% 2 6% 5% 3 5% 4 5% 6% 33%	1416
	21st to end	Night	19% 11% 4 6% 6% 3 4 4 5% 7% 31%	1550
June	1st to 10th	Night	29% 9% 3 6% 4 3 5% 4 4 6% 28%	1440
	11th to 20th	Night	23% 9% 4 6% 5% 3 4 3 4 6% 33%	1381
	21st to end	Night	31% 9% 3 6% 5% 3 5% 3 4 5% 26%	1260
July	1st to 10th	Night	19% 8% 3 5% 4 3 4 4 6% 8% 35%	1322
	11th to 20th	Night	19% 10% 3 6% 7% 3 4 5% 6% 7% 28%	1440
	21st to end	Night	21% 8% 3 6% 5% 4 5% 4 5% 8% 32%	1671
August	1st to 10th	Night	16% 7% 3 5% 5% 3 3 5% 6% 7% 40%	1612
	11th to 20th	Night	19% 8% 3 5% 4 3 4 4 6% 8% 36%	1596
	21st to end	Night	16% 7% 2 6% 4 3 5% 4 4 7% 43%	1877
September	1st to 10th	Night	16% 6% 3 4 4 3 4 4 5% 7% 44%	1800
	11th to 20th	Night	20% 6% 3 3 4 2 4 3 5% 6% 44%	1875
	21st to end	Night	20% 9% 3 4 4 2 3 4 5% 7% 39%	2032
October	1st to 10th	Night	19% 6% 2 6% 4 2 3 4 5% 7% 42%	2160
	11th to 20th	Night	21% 6% 3 4 4 3 4 4 6% 7% 38%	2160
	21st to end	Night	25% 7% 2 4 4 2 5% 4 5% 7% 34%	2376
November	1st to 10th	Night	22% 8% 3 5% 6% 3 4 4 5% 6% 35%	2519
	11th to 20th	Night	22% 8% 4 6% 5% 4 4 5% 5% 7% 30%	2660
	21st to end	Night	20% 8% 4 7% 7% 3 5% 5% 5% 7% 29%	2660
December	1st to 10th	Night	25% 11% 4 8% 6% 4 5% 5% 5% 8% 20%	2660
	11th to 20th	Night	32% 10% 4 6% 6% 2 4 4 4 6% 22%	3293
	21st to end	Night	25% 9% 4 8% 5% 4 4 5% 5% 6% 25%	4884

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	59% 2 15% 17% 7% 1	2527
	11th to 20th	Day	66% 2 8% 18% 6%	2654
	21st to end	Day	57% 2 10% 20% 11%	3124
February	1st to 10th	Day	63% 3 10% 15% 9% 1	1710
	11th to 20th	Day	61% 3 10% 17% 7% 1	1662
	21st to end	Day	52% 3 11% 21% 11% 3	1356
March	1st to 10th	Day	60% 2 7% 18% 12% 2	1980
	11th to 20th	Day	52% 3 10% 18% 14% 2	1980
	21st to end	Day	54% 2 7% 21% 15% 2	2178
April	1st to 10th	Day	60% 2 7% 15% 13% 2	2145
	11th to 20th	Day	50% 3 9% 22% 14% 2	2199
	21st to end	Day	54% 2 10% 20% 12% 3	2340
May	1st to 10th	Day	59% 3 9% 17% 10% 2	2376
	11th to 20th	Day	52% 3 9% 22% 13% 1	2482
	21st to end	Day	52% 3 13% 21% 9% 1	2724
June	1st to 10th	Day	57% 3 10% 21% 8% 1	2520
	11th to 20th	Day	52% 3 12% 20% 13% 1	2589
	21st to end	Day	61% 3 10% 16% 10% 1	2700
July	1st to 10th	Day	48% 3 17% 20% 10% 1	2543
	11th to 20th	Day	52% 3 14% 23% 7% 1	2444
	21st to end	Day	53% 4 15% 22% 6% 1	2497
August	1st to 10th	Day	46% 4 14% 23% 11% 1	2314
	11th to 20th	Day	46% 3 17% 24% 9%	2304
	21st to end	Day	40% 4 12% 29% 14% 1	2477
September	1st to 10th	Day	40% 3 14% 26% 16% 2	2160
	11th to 20th	Day	43% 3 10% 26% 16% 2	2083
	21st to end	Day	43% 2 8% 27% 18% 1	1927
October	1st to 10th	Day	44% 2 11% 28% 14% 1	1800
	11th to 20th	Day	48% 3 12% 25% 11% 1	1800
	21st to end	Day	53% 3 10% 23% 10% 1	1980
November	1st to 10th	Day	55% 3 9% 22% 11% 1	1557
	11th to 20th	Day	57% 3 11% 19% 8% 1	1520
	21st to end	Day	58% 4 12% 18% 8%	1520
December	1st to 10th	Day	64% 3 10% 17% 6% 1	1520
	11th to 20th	Day	66% 2 8% 15% 8%	1905
	21st to end	Day	61% 2 17% 14% 5% 2	2783
January	1st to 10th	Night	61% 2 11% 22% 4	4429
	11th to 20th	Night	68% 2 10% 13% 7%	4308
	21st to end	Night	61% 2 10% 18% 7% 1	4532
February	1st to 10th	Night	63% 3 10% 15% 8% 1	2470
	11th to 20th	Night	59% 2 11% 18% 8% 1	2400
	21st to end	Night	55% 3 11% 21% 8% 2	1898
March	1st to 10th	Night	56% 2 10% 19% 11% 2	1980
	11th to 20th	Night	52% 3 11% 19% 12% 2	1980
	21st to end	Night	54% 2 9% 20% 13% 2	2178
April	1st to 10th	Night	58% 2 8% 15% 13% 3	1814
	11th to 20th	Night	53% 2 8% 21% 15% 2	1707
	21st to end	Night	56% 2 9% 20% 12% 2	1620
May	1st to 10th	Night	57% 2 9% 21% 10% 1	1583
	11th to 20th	Night	54% 3 8% 21% 13% 1	1417
	21st to end	Night	53% 3 14% 21% 8% 1	1551
June	1st to 10th	Night	59% 3 8% 22% 7%	1440
	11th to 20th	Night	56% 2 9% 21% 11% 1	1381
	21st to end	Night	64% 3 8% 15% 9% 1	1260
July	1st to 10th	Night	49% 4 15% 22% 10%	1284
	11th to 20th	Night	57% 3 10% 20% 9%	1392
	21st to end	Night	54% 3 14% 21% 7% 1	1579
August	1st to 10th	Night	46% 3 12% 27% 12%	1600
	11th to 20th	Night	48% 3 17% 22% 10%	1596
	21st to end	Night	43% 2 12% 27% 14% 1	1877
September	1st to 10th	Night	41% 3 11% 30% 14% 2	1800
	11th to 20th	Night	43% 2 7% 30% 17% 1	1875
	21st to end	Night	48% 3 6% 27% 15% 1	2032
October	1st to 10th	Night	43% 2 10% 27% 15% 1	2160
	11th to 20th	Night	46% 3 12% 30% 9%	2160
	21st to end	Night	51% 2 12% 21% 13% 1	2376
November	1st to 10th	Night	51% 3 13% 20% 12% 1	2519
	11th to 20th	Night	54% 3 11% 21% 10%	2660
	21st to end	Night	55% 4 15% 19% 7% 1	2660
December	1st to 10th	Night	64% 3 10% 18% 4	2660
	11th to 20th	Night	66% 3 7% 16% 7% 1	3295
	21st to end	Night	61% 2 11% 19% 6% 1	4884

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	33% 22% 30% 13% 2	370
	11th to 20th	Day	36% 22% 27% 12% 2	370
	21st to end	Day	24% 24% 36% 13% 3	407
February	1st to 10th	Day	33% 23% 27% 14% 2 1	370
	11th to 20th	Day	32% 29% 26% 12% 1	363
	21st to end	Day	26% 25% 32% 12% 4 1	282
March	1st to 10th	Day	28% 29% 31% 10% 2	420
	11th to 20th	Day	29% 30% 26% 10% 4	420
	21st to end	Day	29% 27% 29% 11% 3 1	462
April	1st to 10th	Day	42% 23% 26% 7% 2	420
	11th to 20th	Day	31% 28% 29% 9% 3	412
	21st to end	Day	32% 19% 31% 13% 4 1	420
May	1st to 10th	Day	34% 24% 28% 10% 2 1	459
	11th to 20th	Day	24% 21% 29% 20% 4 1	624
	21st to end	Day	32% 16% 31% 17% 3 1	680
June	1st to 10th	Day	30% 16% 31% 17% 6%	630
	11th to 20th	Day	26% 17% 31% 19% 6% 1	630
	21st to end	Day	33% 11% 29% 18% 7% 1	630
July	1st to 10th	Day	24% 9% 35% 23% 8% 1	620
	11th to 20th	Day	24% 8% 33% 24% 9% 1	618
	21st to end	Day	26% 12% 32% 22% 7% 1	585
August	1st to 10th	Day	20% 9% 37% 25% 8% 2	446
	11th to 20th	Day	23% 10% 33% 22% 10% 2	439
	21st to end	Day	21% 14% 28% 25% 8% 3	495
September	1st to 10th	Day	18% 13% 37% 24% 7% 1	450
	11th to 20th	Day	26% 18% 31% 13% 10% 2	450
	21st to end	Day	25% 14% 32% 19% 8% 2	423
October	1st to 10th	Day	24% 14% 34% 16% 10% 1	360
	11th to 20th	Day	26% 19% 31% 14% 8% 2	360
	21st to end	Day	28% 25% 29% 12% 4 2	396
November	1st to 10th	Day	28% 18% 30% 16% 7% 1	365
	11th to 20th	Day	32% 21% 28% 14% 5% 1	370
	21st to end	Day	33% 24% 29% 11% 2 1	370
December	1st to 10th	Day	36% 20% 30% 11% 2	370
	11th to 20th	Day	40% 25% 25% 8% 2	370
	21st to end	Day	34% 23% 30% 10% 3 1	407
January	1st to 10th	Night	29% 20% 34% 14% 2	850
	11th to 20th	Night	32% 19% 31% 15% 2	812
	21st to end	Night	25% 24% 31% 17% 2	836
February	1st to 10th	Night	29% 21% 31% 17% 2	760
	11th to 20th	Night	29% 26% 31% 12% 2	742
	21st to end	Night	21% 23% 33% 19% 4	592
March	1st to 10th	Night	25% 24% 34% 16% 2	720
	11th to 20th	Night	25% 21% 30% 19% 6%	720
	21st to end	Night	26% 21% 32% 16% 5%	792
April	1st to 10th	Night	34% 16% 30% 16% 4	554
	11th to 20th	Night	27% 19% 35% 15% 4	534
	21st to end	Night	31% 16% 30% 18% 4 1	540
May	1st to 10th	Night	32% 11% 34% 17% 5% 1	540
	11th to 20th	Night	29% 11% 30% 23% 6% 1	532
	21st to end	Night	23% 14% 35% 23% 5%	583
June	1st to 10th	Night	33% 8% 31% 24% 5%	540
	11th to 20th	Night	25% 11% 33% 25% 5%	481
	21st to end	Night	33% 4 24% 29% 10%	360
July	1st to 10th	Night	21% 8% 29% 33% 9%	409
	11th to 20th	Night	23% 7% 30% 31% 8%	522
	21st to end	Night	23% 5% 28% 33% 11%	590
August	1st to 10th	Night	19% 5% 26% 35% 14% 1	538
	11th to 20th	Night	22% 6% 26% 31% 13% 2	532
	21st to end	Night	20% 8% 26% 32% 14% 1	594
September	1st to 10th	Night	20% 7% 30% 31% 11% 1	540
	11th to 20th	Night	22% 10% 29% 25% 13% 1	615
	21st to end	Night	26% 11% 29% 23% 10% 2	720
October	1st to 10th	Night	23% 11% 30% 26% 10% 1	720
	11th to 20th	Night	23% 15% 31% 21% 9% 1	720
	21st to end	Night	31% 18% 28% 18% 4	792
November	1st to 10th	Night	28% 16% 29% 21% 5% 1	814
	11th to 20th	Night	28% 21% 27% 19% 5%	850
	21st to end	Night	28% 25% 26% 17% 4	850
December	1st to 10th	Night	32% 20% 31% 14% 3	850
	11th to 20th	Night	35% 23% 28% 11% 3	850
	21st to end	Night	32% 20% 30% 15% 2 1	935

Page generated at 2024-02-17 07:28:37. Version ac07

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