Terrarouge Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Terrarouge Observatory clear sky chart from 2005-11-06 to 2024-11-10.

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	18% 12% 4 9% 5% 4 4 3 5% 6% 28%	102088
	Night	20% 12% 4 9% 5% 4 4 4 5% 6% 27%	97124
Transparency	Day	53% 7% 13% 18% 7% 1	105639
	Night	56% 7% 13% 16% 7% 1	101666
Seeing	Day	22% 11% 27% 27% 11% 2	17552
	Night	24% 11% 29% 27% 9% 1	24783

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	14% 14% 8% 24% 7% 4 4 3 4 4 14%	2526
	11th to 20th	Day	14% 17% 6% 14% 7% 5% 4 3 4 5% 20%	2530
	21st to end	Day	13% 11% 7% 15% 6% 4 5% 3 5% 5% 26%	3029
February	1st to 10th	Day	19% 14% 4 10% 4 5% 4 3 4 5% 26%	1710
	11th to 20th	Day	16% 16% 5% 11% 6% 4 4 3 4 5% 25%	1663
	21st to end	Day	11% 13% 6% 9% 7% 5% 4 3 5% 7% 29%	1476
March	1st to 10th	Day	22% 13% 4 7% 4 6% 4 3 4 5% 29%	3292
	11th to 20th	Day	13% 21% 9% 11% 6% 4 4 3 4 4 22%	3480
	21st to end	Day	24% 19% 6% 11% 5% 3 3 2 4 4 19%	3901
April	1st to 10th	Day	20% 14% 4 10% 5% 4 4 3 4 5% 27%	2280
	11th to 20th	Day	22% 12% 3 6% 5% 3 4 3 5% 6% 32%	2278
	21st to end	Day	21% 14% 4 7% 4 4 3 3 5% 7% 29%	2470
May	1st to 10th	Day	25% 19% 4 7% 4 3 4 3 3 5% 23%	4383
	11th to 20th	Day	17% 10% 3 7% 5% 4 4 3 5% 6% 37%	4398
	21st to end	Day	19% 11% 3 6% 5% 5% 5% 4 7% 7% 30%	4836
June	1st to 10th	Day	26% 12% 3 6% 5% 4 5% 3 5% 7% 24%	2660
	11th to 20th	Day	19% 10% 2 7% 5% 4 4 3 5% 7% 35%	2734
	21st to end	Day	24% 11% 3 7% 4 4 4 3 5% 6% 29%	2850
July	1st to 10th	Day	18% 9% 2 6% 5% 4 4 4 6% 8% 33%	4578
	11th to 20th	Day	16% 7% 3 7% 4 4 5% 4 6% 8% 35%	4440
	21st to end	Day	13% 8% 3 6% 5% 5% 5% 4 6% 8% 36%	4815
August	1st to 10th	Day	18% 9% 3 8% 6% 4 5% 5% 6% 8% 29%	4184
	11th to 20th	Day	14% 8% 2 7% 5% 5% 5% 4 6% 7% 37%	4045
	21st to end	Day	11% 6% 2 6% 4 4 4 4 6% 8% 44%	4290
September	1st to 10th	Day	16% 8% 1 7% 4 4 4 4 6% 8% 39%	2280
	11th to 20th	Day	17% 8% 3 7% 4 4 4 3 5% 6% 37%	2280
	21st to end	Day	17% 8% 3 6% 5% 4 4 4 5% 7% 37%	1987
October	1st to 10th	Day	18% 8% 3 8% 5% 4 5% 4 5% 7% 32%	1900
	11th to 20th	Day	20% 12% 4 8% 6% 5% 6% 4 5% 6% 25%	1900
	21st to end	Day	20% 16% 4 9% 6% 4 4 4 5% 6% 22%	2016
November	1st to 10th	Day	20% 14% 4 10% 4 5% 4 3 6% 5% 23%	1628
	11th to 20th	Day	20% 19% 5% 10% 5% 4 4 3 5% 6% 18%	1520
	21st to end	Day	19% 18% 8% 12% 5% 4 4 4 6% 6% 15%	1520
December	1st to 10th	Day	23% 19% 8% 12% 7% 5% 3 3 4 5% 12%	1520
	11th to 20th	Day	28% 17% 6% 13% 7% 5% 4 3 3 4 9%	1906
	21st to end	Day	20% 17% 8% 14% 6% 5% 4 3 3 4 16%	2783
January	1st to 10th	Night	13% 13% 6% 16% 6% 5% 5% 4 5% 6% 21%	4429
	11th to 20th	Night	20% 13% 5% 15% 6% 4 4 3 4 5% 21%	4440
	21st to end	Night	14% 12% 5% 15% 6% 5% 5% 4 6% 6% 24%	4628
February	1st to 10th	Night	20% 13% 4 9% 5% 5% 4 3 4 5% 26%	2470
	11th to 20th	Night	18% 16% 4 11% 6% 6% 5% 3 4 4 22%	2403
	21st to end	Night	13% 16% 5% 9% 7% 5% 4 4 4 4 30%	1976
March	1st to 10th	Night	20% 13% 4 11% 6% 4 4 4 4 5% 25%	3545
	11th to 20th	Night	21% 17% 8% 11% 6% 3 4 3 4 4 19%	3479
	21st to end	Night	25% 17% 6% 9% 5% 4 4 2 3 3 20%	3731
April	1st to 10th	Night	22% 12% 4 8% 6% 5% 3 3 5% 6% 26%	1900
	11th to 20th	Night	20% 13% 4 7% 4 4 4 3 4 6% 32%	1848
	21st to end	Night	24% 12% 4 6% 4 3 3 3 5% 5% 30%	1710
May	1st to 10th	Night	25% 16% 4 8% 4 5% 4 3 4 5% 22%	2566
	11th to 20th	Night	16% 9% 3 7% 5% 4 4 4 5% 8% 35%	2506
	21st to end	Night	19% 9% 3 8% 6% 5% 6% 5% 6% 7% 27%	2749
June	1st to 10th	Night	27% 10% 3 6% 6% 3 3 3 5% 7% 25%	1520
	11th to 20th	Night	22% 7% 2 4 4 3 4 3 5% 7% 38%	1457
	21st to end	Night	23% 10% 3 7% 6% 4 3 4 6% 5% 28%	1330
July	1st to 10th	Night	16% 10% 4 8% 4 5% 5% 5% 7% 9% 27%	2338
	11th to 20th	Night	17% 8% 2 6% 4 5% 5% 5% 7% 9% 32%	2530
	21st to end	Night	13% 8% 3 6% 4 4 4 4 6% 7% 41%	2750
August	1st to 10th	Night	19% 9% 2 7% 5% 5% 5% 4 6% 8% 29%	2732
	11th to 20th	Night	15% 6% 3 7% 5% 4 5% 4 5% 9% 38%	2782
	21st to end	Night	12% 6% 2 7% 4 5% 4 3 6% 9% 41%	3366
September	1st to 10th	Night	14% 7% 2 6% 4 4 4 4 5% 8% 41%	1900
	11th to 20th	Night	18% 7% 2 5% 4 3 4 4 4 6% 42%	1900
	21st to end	Night	18% 7% 2 6% 4 4 4 4 5% 7% 39%	2190
October	1st to 10th	Night	19% 7% 3 7% 4 4 4 3 5% 7% 37%	2280
	11th to 20th	Night	20% 9% 3 7% 4 4 5% 4 5% 7% 32%	2280
	21st to end	Night	25% 13% 3 9% 5% 4 4 3 4 5% 25%	2581
November	1st to 10th	Night	20% 14% 4 8% 6% 4 4 4 5% 6% 25%	2651
	11th to 20th	Night	23% 13% 4 8% 6% 5% 4 4 5% 7% 21%	2660
	21st to end	Night	23% 18% 6% 10% 5% 4 4 3 5% 6% 17%	2660
December	1st to 10th	Night	25% 17% 7% 11% 7% 4 5% 4 4 5% 13%	2660
	11th to 20th	Night	30% 14% 5% 11% 6% 4 4 3 3 4 16%	3293
	21st to end	Night	26% 16% 5% 14% 5% 4 3 2 4 4 18%	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	74% 8% 11% 4 3	2527
	11th to 20th	Day	60% 9% 11% 14% 6%	2530
	21st to end	Day	58% 7% 12% 13% 9% 1	3029
February	1st to 10th	Day	60% 5% 11% 15% 8%	1710
	11th to 20th	Day	61% 6% 9% 17% 6% 1	1671
	21st to end	Day	53% 5% 13% 16% 11% 2	1476
March	1st to 10th	Day	56% 5% 11% 19% 8%	3296
	11th to 20th	Day	62% 7% 10% 14% 6% 1	3480
	21st to end	Day	68% 4 9% 12% 6% 1	3901
April	1st to 10th	Day	57% 5% 10% 15% 10% 2	2280
	11th to 20th	Day	52% 5% 10% 20% 12% 1	2278
	21st to end	Day	53% 6% 13% 16% 11% 2	2470
May	1st to 10th	Day	60% 8% 11% 14% 6% 1	4398
	11th to 20th	Day	46% 8% 15% 23% 7%	4402
	21st to end	Day	48% 11% 15% 18% 7%	4836
June	1st to 10th	Day	57% 8% 13% 17% 5%	2660
	11th to 20th	Day	48% 6% 12% 23% 9% 1	2734
	21st to end	Day	55% 7% 12% 16% 9% 1	2850
July	1st to 10th	Day	47% 8% 16% 17% 11%	4508
	11th to 20th	Day	43% 8% 17% 24% 8%	4364
	21st to end	Day	42% 10% 19% 23% 6%	4662
August	1st to 10th	Day	51% 9% 14% 21% 5%	4170
	11th to 20th	Day	42% 9% 15% 25% 9%	4084
	21st to end	Day	34% 7% 15% 31% 12%	4290
September	1st to 10th	Day	41% 8% 14% 26% 10%	2280
	11th to 20th	Day	46% 7% 13% 22% 12%	2280
	21st to end	Day	44% 6% 12% 26% 11%	1987
October	1st to 10th	Day	49% 10% 14% 21% 7%	3160
	11th to 20th	Day	50% 7% 15% 20% 7%	3140
	21st to end	Day	54% 7% 17% 19% 3	3310
November	1st to 10th	Day	61% 7% 11% 15% 5%	1628
	11th to 20th	Day	68% 7% 12% 11% 3	1520
	21st to end	Day	68% 8% 13% 8% 3	1520
December	1st to 10th	Day	75% 7% 8% 7% 2	1520
	11th to 20th	Day	79% 7% 6% 6% 2 1	1905
	21st to end	Day	72% 5% 14% 6% 2	2783
January	1st to 10th	Night	62% 9% 17% 9% 2	4429
	11th to 20th	Night	59% 12% 11% 12% 5%	4440
	21st to end	Night	60% 9% 12% 14% 6%	4628
February	1st to 10th	Night	60% 4 9% 14% 11% 1	2470
	11th to 20th	Night	64% 5% 9% 13% 7% 1	2406
	21st to end	Night	55% 5% 11% 17% 10% 2	1976
March	1st to 10th	Night	60% 6% 7% 16% 9% 2	3554
	11th to 20th	Night	68% 5% 9% 12% 5% 1	3480
	21st to end	Night	69% 5% 7% 12% 6% 1	3731
April	1st to 10th	Night	59% 6% 11% 13% 9% 2	1900
	11th to 20th	Night	53% 6% 9% 19% 12% 1	1848
	21st to end	Night	56% 5% 9% 15% 13% 1	1710
May	1st to 10th	Night	64% 7% 9% 14% 6% 1	2571
	11th to 20th	Night	45% 9% 15% 21% 8% 1	2507
	21st to end	Night	51% 12% 17% 15% 5% 1	2750
June	1st to 10th	Night	58% 7% 12% 17% 7%	1520
	11th to 20th	Night	46% 6% 13% 22% 13%	1457
	21st to end	Night	55% 8% 14% 15% 8% 1	1330
July	1st to 10th	Night	51% 8% 16% 17% 5% 2	2299
	11th to 20th	Night	46% 9% 19% 19% 7%	2482
	21st to end	Night	40% 9% 17% 24% 9%	2663
August	1st to 10th	Night	51% 10% 15% 20% 4	2721
	11th to 20th	Night	42% 9% 17% 26% 6%	2809
	21st to end	Night	36% 10% 18% 25% 11%	3365
September	1st to 10th	Night	40% 9% 13% 27% 11%	1900
	11th to 20th	Night	43% 6% 12% 26% 12% 1	1900
	21st to end	Night	43% 7% 13% 26% 10%	2190
October	1st to 10th	Night	50% 7% 13% 22% 8%	3800
	11th to 20th	Night	43% 8% 16% 25% 9%	3779
	21st to end	Night	52% 6% 15% 20% 6%	4241
November	1st to 10th	Night	59% 8% 13% 15% 5%	2651
	11th to 20th	Night	63% 9% 12% 11% 5%	2660
	21st to end	Night	69% 8% 13% 8% 2	2660
December	1st to 10th	Night	73% 7% 10% 8% 2	2660
	11th to 20th	Night	74% 6% 7% 10% 3	3295
	21st to end	Night	72% 5% 11% 9% 2	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	24% 18% 39% 16% 3	370
	11th to 20th	Day	25% 21% 28% 18% 7% 1	370
	21st to end	Day	18% 13% 39% 26% 4	407
February	1st to 10th	Day	27% 18% 29% 19% 6% 1	370
	11th to 20th	Day	23% 17% 35% 19% 4 1	366
	21st to end	Day	15% 12% 36% 29% 7% 1	307
March	1st to 10th	Day	22% 14% 31% 26% 6% 1	418
	11th to 20th	Day	17% 16% 31% 27% 8% 1	460
	21st to end	Day	28% 14% 30% 19% 8% 1	506
April	1st to 10th	Day	28% 14% 33% 19% 5%	460
	11th to 20th	Day	23% 13% 34% 21% 8% 1	452
	21st to end	Day	23% 10% 26% 27% 12% 2	460
May	1st to 10th	Day	31% 9% 28% 23% 7% 2	624
	11th to 20th	Day	22% 6% 24% 30% 14% 4	674
	21st to end	Day	21% 6% 30% 33% 9% 1	735
June	1st to 10th	Day	29% 6% 24% 29% 10% 2	680
	11th to 20th	Day	20% 6% 26% 35% 12% 1	680
	21st to end	Day	28% 6% 19% 29% 15% 3	680
July	1st to 10th	Day	17% 3 22% 40% 17% 2	670
	11th to 20th	Day	16% 4 22% 36% 21% 2	668
	21st to end	Day	20% 3 20% 38% 17% 1	740
August	1st to 10th	Day	15% 3 19% 38% 21% 4	539
	11th to 20th	Day	20% 5% 20% 32% 17% 7%	479
	21st to end	Day	15% 6% 20% 32% 22% 4	539
September	1st to 10th	Day	16% 8% 28% 31% 15% 2	490
	11th to 20th	Day	18% 9% 27% 32% 13% 1	490
	21st to end	Day	19% 10% 25% 30% 13% 3	430
October	1st to 10th	Day	19% 9% 26% 29% 13% 3	390
	11th to 20th	Day	25% 12% 27% 23% 12% 2	390
	21st to end	Day	25% 15% 32% 20% 6% 2	429
November	1st to 10th	Day	23% 19% 32% 19% 6% 1	392
	11th to 20th	Day	26% 20% 31% 17% 5% 1	370
	21st to end	Day	27% 22% 28% 20% 3	370
December	1st to 10th	Day	29% 16% 31% 20% 3 1	370
	11th to 20th	Day	28% 28% 30% 13% 1	370
	21st to end	Day	24% 22% 34% 16% 3	407
January	1st to 10th	Night	26% 18% 33% 20% 3	850
	11th to 20th	Night	26% 16% 32% 22% 4	850
	21st to end	Night	20% 14% 35% 23% 7% 1	863
February	1st to 10th	Night	28% 13% 30% 24% 5%	760
	11th to 20th	Night	24% 15% 37% 21% 4	743
	21st to end	Night	19% 12% 33% 27% 9%	628
March	1st to 10th	Night	22% 10% 37% 26% 5%	760
	11th to 20th	Night	21% 10% 30% 29% 9% 1	760
	21st to end	Night	24% 12% 29% 24% 9% 1	789
April	1st to 10th	Night	29% 12% 28% 25% 6%	570
	11th to 20th	Night	24% 10% 32% 25% 8% 1	564
	21st to end	Night	27% 8% 28% 28% 8% 1	570
May	1st to 10th	Night	31% 7% 25% 24% 11% 2	570
	11th to 20th	Night	22% 6% 26% 32% 13% 2	562
	21st to end	Night	20% 6% 32% 34% 7%	616
June	1st to 10th	Night	29% 6% 22% 32% 9% 1	570
	11th to 20th	Night	23% 5% 23% 37% 10%	507
	21st to end	Night	24% 6% 22% 36% 11% 1	380
July	1st to 10th	Night	17% 3 21% 42% 17%	442
	11th to 20th	Night	16% 4 20% 43% 15% 1	552
	21st to end	Night	18% 3 21% 40% 17% 1	623
August	1st to 10th	Night	16% 3 17% 45% 18% 1	568
	11th to 20th	Night	17% 5% 22% 36% 19% 2	562
	21st to end	Night	15% 4 21% 38% 22% 1	627
September	1st to 10th	Night	16% 7% 26% 35% 15% 1	570
	11th to 20th	Night	20% 6% 24% 35% 14% 1	570
	21st to end	Night	21% 9% 28% 31% 8% 3	749
October	1st to 10th	Night	22% 7% 29% 28% 13% 1	760
	11th to 20th	Night	23% 13% 29% 25% 10% 1	760
	21st to end	Night	30% 15% 31% 20% 5%	875
November	1st to 10th	Night	24% 18% 31% 20% 5% 1	878
	11th to 20th	Night	27% 18% 29% 19% 5% 1	850
	21st to end	Night	32% 18% 29% 19% 3	850
December	1st to 10th	Night	31% 18% 32% 14% 5%	850
	11th to 20th	Night	28% 24% 31% 14% 3	850
	21st to end	Night	30% 19% 29% 18% 3 1	935

Page generated at 2024-11-07 07:55:43. Version ac07

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