Observatoire Laforge-1
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire Laforge-1 clear sky chart from 2005-11-06 to 2024-11-05.

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	17% 16% 6% 12% 7% 6% 5% 4 5% 5% 18%	102297
	Night	13% 16% 6% 13% 8% 7% 6% 4 5% 5% 15%	96891
Transparency	Day	66% 6% 10% 13% 4	105612
	Night	69% 6% 9% 12% 4	101668
Seeing	Day	23% 10% 24% 24% 13% 5%	16527
	Night	21% 8% 26% 28% 14% 3	24198

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	10% 15% 5% 14% 12% 11% 11% 5% 9% 6% 3	1898
	11th to 20th	Day	5% 15% 9% 21% 10% 8% 12% 6% 7% 4 4	1944
	21st to end	Day	3 13% 6% 16% 9% 7% 9% 6% 10% 5% 17%	2754
February	1st to 10th	Day	2 10% 5% 13% 12% 11% 13% 11% 11% 7% 5%	1520
	11th to 20th	Day	4 12% 4 16% 13% 11% 11% 8% 10% 6% 6%	1532
	21st to end	Day	4 13% 6% 15% 10% 10% 10% 9% 8% 8% 7%	1545
March	1st to 10th	Day	11% 14% 6% 12% 8% 10% 9% 8% 7% 4 10%	3116
	11th to 20th	Day	10% 22% 9% 17% 8% 6% 7% 4 5% 4 9%	3244
	21st to end	Day	9% 18% 7% 18% 8% 7% 7% 6% 7% 4 9%	4166
April	1st to 10th	Day	13% 19% 6% 14% 8% 7% 6% 3 5% 5% 15%	2280
	11th to 20th	Day	10% 13% 5% 15% 7% 6% 5% 3 5% 5% 26%	2413
	21st to end	Day	13% 18% 7% 13% 6% 4 4 3 4 4 22%	2650
May	1st to 10th	Day	16% 22% 7% 11% 5% 4 4 3 3 5% 20%	4448
	11th to 20th	Day	16% 18% 6% 12% 5% 4 4 4 5% 6% 19%	4715
	21st to end	Day	19% 19% 6% 10% 5% 4 4 3 4 5% 22%	5335
June	1st to 10th	Day	19% 13% 4 7% 6% 4 4 4 5% 6% 29%	3040
	11th to 20th	Day	20% 12% 3 8% 6% 5% 5% 4 5% 6% 27%	3040
	21st to end	Day	21% 12% 3 8% 5% 5% 4 3 6% 6% 26%	3040
July	1st to 10th	Day	20% 8% 3 8% 5% 5% 5% 4 5% 6% 30%	5080
	11th to 20th	Day	24% 10% 4 9% 6% 5% 5% 4 5% 6% 20%	5080
	21st to end	Day	21% 12% 4 11% 6% 6% 6% 4 5% 6% 20%	5112
August	1st to 10th	Day	24% 12% 4 9% 6% 5% 5% 4 6% 7% 19%	4423
	11th to 20th	Day	16% 10% 3 8% 5% 5% 5% 4 6% 9% 31%	4359
	21st to end	Day	18% 11% 4 9% 5% 5% 4 4 5% 7% 28%	4546
September	1st to 10th	Day	30% 16% 5% 10% 6% 4 3 3 4 4 15%	2280
	11th to 20th	Day	25% 17% 5% 10% 5% 5% 4 3 4 6% 16%	2194
	21st to end	Day	27% 18% 5% 9% 5% 4 3 3 5% 5% 16%	2090
October	1st to 10th	Day	23% 24% 6% 11% 5% 5% 3 3 4 3 13%	1939
	11th to 20th	Day	26% 24% 8% 9% 4 4 3 4 3 3 12%	1710
	21st to end	Day	25% 22% 8% 16% 6% 3 3 2 3 3 9%	1881
November	1st to 10th	Day	19% 27% 10% 17% 8% 4 3 2 3 3 6%	1489
	11th to 20th	Day	18% 26% 12% 20% 7% 5% 2 2 2 2 4	1330
	21st to end	Day	11% 26% 8% 18% 10% 7% 4 2 3 3 6%	1330
December	1st to 10th	Day	9% 20% 7% 21% 14% 7% 7% 4 4 3 4	1251
	11th to 20th	Day	8% 20% 9% 18% 12% 8% 7% 4 4 3 8%	1433
	21st to end	Day	12% 18% 7% 13% 15% 9% 8% 6% 6% 3 4	2090
January	1st to 10th	Night	6% 15% 6% 18% 12% 11% 10% 6% 7% 5% 3	5067
	11th to 20th	Night	8% 15% 7% 19% 13% 12% 10% 6% 5% 3 3	5034
	21st to end	Night	4 15% 7% 14% 9% 8% 10% 6% 7% 6% 14%	4902
February	1st to 10th	Night	4 12% 5% 13% 12% 11% 13% 9% 9% 6% 8%	2660
	11th to 20th	Night	4 14% 6% 15% 11% 7% 9% 8% 10% 6% 9%	2531
	21st to end	Night	4 12% 5% 13% 10% 10% 10% 7% 9% 8% 11%	1909
March	1st to 10th	Night	7% 12% 5% 11% 10% 10% 8% 7% 7% 6% 16%	3724
	11th to 20th	Night	11% 22% 9% 16% 10% 6% 5% 4 4 4 11%	3712
	21st to end	Night	8% 19% 8% 15% 8% 8% 7% 5% 5% 4 13%	3466
April	1st to 10th	Night	12% 17% 6% 12% 8% 7% 6% 4 5% 4 19%	1900
	11th to 20th	Night	11% 13% 6% 12% 6% 4 4 3 4 4 33%	1716
	21st to end	Night	14% 14% 5% 11% 7% 5% 4 2 5% 4 28%	1548
May	1st to 10th	Night	18% 22% 7% 9% 5% 3 4 2 3 4 21%	2493
	11th to 20th	Night	15% 13% 6% 10% 5% 5% 4 3 4 6% 28%	2188
	21st to end	Night	18% 18% 7% 11% 5% 4 4 3 5% 4 22%	2254
June	1st to 10th	Night	18% 11% 3 7% 5% 4 4 4 5% 5% 34%	1140
	11th to 20th	Night	21% 8% 2 6% 6% 3 3 4 5% 8% 32%	1140
	21st to end	Night	22% 11% 3 7% 4 4 3 4 4 7% 31%	1140
July	1st to 10th	Night	19% 9% 3 9% 5% 5% 5% 4 5% 7% 29%	1900
	11th to 20th	Night	20% 9% 3 8% 5% 5% 4 3 5% 7% 31%	1900
	21st to end	Night	20% 11% 4 10% 5% 6% 5% 4 6% 6% 24%	2448
August	1st to 10th	Night	19% 11% 4 10% 6% 5% 5% 4 5% 6% 25%	2506
	11th to 20th	Night	13% 9% 4 8% 4 4 4 4 7% 8% 36%	2470
	21st to end	Night	20% 9% 3 9% 5% 4 4 3 4 5% 34%	3075
September	1st to 10th	Night	27% 12% 4 11% 5% 4 4 3 4 5% 21%	1900
	11th to 20th	Night	21% 16% 4 10% 6% 5% 4 3 4 5% 22%	1985
	21st to end	Night	26% 15% 4 9% 5% 3 4 3 4 6% 21%	2090
October	1st to 10th	Night	24% 21% 4 8% 5% 4 3 3 4 6% 18%	2238
	11th to 20th	Night	25% 23% 6% 9% 6% 4 4 2 4 4 13%	2470
	21st to end	Night	23% 24% 7% 15% 6% 4 4 2 3 3 10%	2717
November	1st to 10th	Night	20% 24% 9% 17% 7% 5% 4 2 3 3 7%	2685
	11th to 20th	Night	19% 24% 10% 21% 9% 5% 3 1 2 2 4	2850
	21st to end	Night	12% 23% 9% 18% 11% 6% 5% 3 3 3 7%	2850
December	1st to 10th	Night	8% 20% 9% 20% 13% 9% 7% 4 3 2 5%	2926
	11th to 20th	Night	9% 18% 8% 18% 12% 8% 6% 5% 5% 3 7%	3769
	21st to end	Night	8% 17% 8% 15% 14% 10% 8% 5% 5% 3 5%	5588

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	75% 6% 7% 9% 2	1899
	11th to 20th	Day	79% 6% 6% 6% 2	1944
	21st to end	Day	62% 5% 6% 13% 12% 2	2754
February	1st to 10th	Day	66% 8% 8% 12% 6%	1520
	11th to 20th	Day	71% 7% 6% 11% 4	1540
	21st to end	Day	69% 6% 9% 9% 5% 1	1545
March	1st to 10th	Day	70% 7% 6% 12% 5%	3119
	11th to 20th	Day	76% 6% 6% 8% 4	3244
	21st to end	Day	74% 5% 6% 10% 5%	4166
April	1st to 10th	Day	70% 6% 7% 11% 5%	2280
	11th to 20th	Day	60% 6% 7% 19% 7%	2413
	21st to end	Day	66% 5% 9% 14% 6%	2650
May	1st to 10th	Day	66% 8% 9% 15% 3	4462
	11th to 20th	Day	63% 8% 11% 15% 3	4719
	21st to end	Day	64% 6% 8% 17% 6%	5335
June	1st to 10th	Day	54% 7% 11% 18% 8% 1	3040
	11th to 20th	Day	56% 7% 11% 17% 9%	3040
	21st to end	Day	57% 7% 11% 17% 7%	3040
July	1st to 10th	Day	53% 7% 12% 24% 4	5001
	11th to 20th	Day	62% 7% 11% 16% 3	4993
	21st to end	Day	63% 7% 13% 15% 1	4950
August	1st to 10th	Day	64% 8% 14% 13% 1	4409
	11th to 20th	Day	49% 6% 21% 21% 3	4401
	21st to end	Day	55% 7% 18% 15% 4	4546
September	1st to 10th	Day	73% 6% 10% 8% 3	2280
	11th to 20th	Day	70% 8% 10% 11% 2	2194
	21st to end	Day	71% 6% 11% 12% 1	2090
October	1st to 10th	Day	70% 5% 11% 14% 1	3212
	11th to 20th	Day	77% 4 9% 9% 1	2822
	21st to end	Day	83% 4 6% 5% 1 1	3081
November	1st to 10th	Day	86% 5% 5% 3 1	1489
	11th to 20th	Day	89% 5% 3 2 1	1330
	21st to end	Day	85% 4 5% 5% 1	1330
December	1st to 10th	Day	84% 7% 5% 3 1	1251
	11th to 20th	Day	81% 5% 7% 5% 3	1433
	21st to end	Day	80% 6% 6% 4 3	2090
January	1st to 10th	Night	78% 7% 8% 6% 1	5067
	11th to 20th	Night	83% 5% 4 6% 2	5034
	21st to end	Night	66% 5% 4 8% 15% 2	4902
February	1st to 10th	Night	69% 7% 5% 14% 5%	2660
	11th to 20th	Night	66% 8% 10% 11% 5%	2534
	21st to end	Night	64% 7% 9% 12% 8%	1909
March	1st to 10th	Night	62% 6% 9% 14% 8%	3734
	11th to 20th	Night	76% 6% 5% 9% 4	3713
	21st to end	Night	71% 8% 6% 10% 6%	3466
April	1st to 10th	Night	67% 6% 8% 13% 5% 1	1900
	11th to 20th	Night	54% 6% 8% 20% 12% 1	1716
	21st to end	Night	59% 5% 9% 17% 10% 1	1548
May	1st to 10th	Night	67% 4 7% 18% 5%	2499
	11th to 20th	Night	56% 7% 12% 19% 6%	2189
	21st to end	Night	62% 7% 9% 15% 6%	2255
June	1st to 10th	Night	50% 6% 11% 22% 9% 2	1140
	11th to 20th	Night	50% 7% 13% 20% 10%	1140
	21st to end	Night	53% 7% 10% 21% 9%	1140
July	1st to 10th	Night	54% 6% 12% 24% 3	1870
	11th to 20th	Night	53% 6% 13% 24% 4	1864
	21st to end	Night	59% 8% 16% 15% 3	2371
August	1st to 10th	Night	59% 9% 14% 18% 1	2496
	11th to 20th	Night	46% 6% 18% 27% 3	2494
	21st to end	Night	53% 6% 15% 21% 3	3075
September	1st to 10th	Night	66% 7% 11% 13% 3	1900
	11th to 20th	Night	64% 8% 12% 14% 2	1985
	21st to end	Night	65% 5% 14% 13% 3	2090
October	1st to 10th	Night	63% 6% 17% 14% 1	3745
	11th to 20th	Night	71% 8% 10% 10% 1	4097
	21st to end	Night	79% 6% 6% 7% 2	4467
November	1st to 10th	Night	84% 5% 6% 4 1	2685
	11th to 20th	Night	89% 5% 3 2 1	2850
	21st to end	Night	82% 7% 6% 4 1	2850
December	1st to 10th	Night	85% 6% 4 3 1	2926
	11th to 20th	Night	79% 7% 7% 6% 1	3769
	21st to end	Night	81% 6% 5% 6% 2	5588

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	12% 6% 30% 28% 21% 4	180
	11th to 20th	Day	11% 11% 31% 37% 7% 3	180
	21st to end	Day	7% 7% 28% 30% 21% 8%	198
February	1st to 10th	Day	4 8% 23% 41% 18% 5%	180
	11th to 20th	Day	3 5% 34% 29% 18% 10%	206
	21st to end	Day	6% 12% 31% 31% 17% 4	357
March	1st to 10th	Day	11% 8% 22% 31% 21% 8%	460
	11th to 20th	Day	12% 8% 29% 28% 18% 5%	460
	21st to end	Day	13% 11% 32% 27% 13% 4	506
April	1st to 10th	Day	17% 6% 28% 30% 15% 4	460
	11th to 20th	Day	14% 11% 29% 25% 14% 8%	452
	21st to end	Day	20% 11% 26% 25% 13% 4	460
May	1st to 10th	Day	20% 8% 24% 26% 13% 8%	472
	11th to 20th	Day	20% 9% 23% 26% 17% 6%	674
	21st to end	Day	25% 11% 27% 25% 10% 2	820
June	1st to 10th	Day	27% 5% 26% 23% 14% 5%	870
	11th to 20th	Day	26% 11% 19% 28% 11% 4	870
	21st to end	Day	25% 9% 24% 22% 16% 4	870
July	1st to 10th	Day	26% 7% 21% 26% 13% 7%	856
	11th to 20th	Day	30% 8% 20% 28% 12% 2	852
	21st to end	Day	30% 8% 17% 19% 17% 9%	713
August	1st to 10th	Day	30% 8% 15% 22% 16% 8%	486
	11th to 20th	Day	24% 7% 23% 19% 16% 11%	479
	21st to end	Day	27% 9% 21% 23% 12% 8%	539
September	1st to 10th	Day	40% 12% 21% 16% 8% 3	490
	11th to 20th	Day	28% 14% 24% 21% 10% 3	490
	21st to end	Day	31% 12% 25% 18% 9% 4	490
October	1st to 10th	Day	31% 14% 24% 20% 8% 2	486
	11th to 20th	Day	35% 13% 21% 20% 7% 4	390
	21st to end	Day	31% 13% 23% 19% 10% 4	429
November	1st to 10th	Day	32% 16% 29% 16% 5% 3	234
	11th to 20th	Day	24% 11% 33% 23% 8% 1	180
	21st to end	Day	12% 17% 30% 23% 15% 3	180
December	1st to 10th	Day	13% 12% 25% 18% 22% 9%	180
	11th to 20th	Day	18% 8% 35% 24% 12% 2	180
	21st to end	Day	13% 7% 31% 33% 11% 6%	198
January	1st to 10th	Night	15% 7% 26% 31% 18% 4	1040
	11th to 20th	Night	12% 8% 31% 29% 16% 4	1025
	21st to end	Night	10% 5% 24% 36% 20% 5%	841
February	1st to 10th	Night	7% 7% 26% 38% 17% 5%	760
	11th to 20th	Night	11% 3 26% 36% 20% 5%	743
	21st to end	Night	9% 4 28% 34% 20% 4	628
March	1st to 10th	Night	6% 7% 27% 33% 23% 4	760
	11th to 20th	Night	13% 9% 28% 29% 18% 3	760
	21st to end	Night	14% 8% 32% 32% 12% 3	836
April	1st to 10th	Night	20% 7% 31% 27% 13% 2	760
	11th to 20th	Night	16% 6% 26% 34% 16% 2	592
	21st to end	Night	16% 10% 29% 32% 12% 1	408
May	1st to 10th	Night	26% 9% 21% 30% 12% 2	380
	11th to 20th	Night	19% 8% 24% 32% 14% 2	374
	21st to end	Night	19% 10% 30% 32% 7%	411
June	1st to 10th	Night	23% 4 25% 33% 14% 1	380
	11th to 20th	Night	23% 10% 20% 35% 12% 1	380
	21st to end	Night	26% 7% 23% 28% 14% 1	380
July	1st to 10th	Night	25% 5% 22% 32% 14% 2	370
	11th to 20th	Night	24% 7% 22% 32% 14% 1	368
	21st to end	Night	21% 6% 19% 26% 23% 4	416
August	1st to 10th	Night	26% 4 18% 30% 19% 3	378
	11th to 20th	Night	24% 5% 20% 26% 23% 2	376
	21st to end	Night	26% 5% 20% 31% 15% 2	591
September	1st to 10th	Night	33% 9% 26% 22% 9% 1	760
	11th to 20th	Night	28% 11% 26% 26% 8%	760
	21st to end	Night	33% 11% 25% 21% 8% 2	760
October	1st to 10th	Night	35% 11% 28% 18% 7% 1	760
	11th to 20th	Night	36% 9% 22% 23% 8% 1	760
	21st to end	Night	34% 10% 26% 17% 11% 3	836
November	1st to 10th	Night	32% 12% 25% 21% 8% 2	795
	11th to 20th	Night	29% 13% 26% 19% 10% 3	850
	21st to end	Night	22% 10% 30% 25% 9% 4	850
December	1st to 10th	Night	16% 12% 28% 26% 15% 3	926
	11th to 20th	Night	15% 8% 30% 30% 15% 3	1040
	21st to end	Night	16% 7% 25% 32% 16% 3	1144

Page generated at 2024-11-03 02:11:14. Version ac07

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