Observatoire de Sainte-Sophie
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire de Sainte-Sophie 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	16% 9% 3 8% 5% 5% 5% 4 6% 7% 33%	101582
	Night	16% 10% 4 8% 5% 4 4 3 5% 6% 34%	97479
Transparency	Day	48% 7% 14% 20% 10% 1	105045
	Night	49% 6% 13% 20% 10% 1	102105
Seeing	Day	21% 16% 32% 21% 8% 2	14538
	Night	21% 11% 33% 26% 8% 1	23486

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	15% 15% 5% 13% 6% 5% 4 4 5% 4 24%	2517
	11th to 20th	Day	13% 13% 5% 12% 6% 4 4 4 5% 5% 27%	2520
	21st to end	Day	12% 17% 6% 10% 6% 5% 5% 4 6% 5% 24%	2772
February	1st to 10th	Day	13% 16% 4 10% 7% 6% 4 3 4 5% 27%	1671
	11th to 20th	Day	11% 13% 5% 11% 7% 5% 5% 4 5% 7% 27%	1743
	21st to end	Day	17% 15% 4 11% 6% 5% 5% 3 4 5% 27%	1570
March	1st to 10th	Day	19% 13% 4 10% 7% 5% 4 3 4 4 26%	3116
	11th to 20th	Day	11% 17% 5% 11% 5% 5% 4 3 4 6% 28%	3306
	21st to end	Day	14% 9% 3 7% 5% 5% 4 3 5% 5% 38%	4154
April	1st to 10th	Day	20% 13% 3 7% 4 5% 4 3 4 5% 32%	2280
	11th to 20th	Day	22% 8% 2 6% 5% 4 4 4 5% 6% 35%	2254
	21st to end	Day	20% 10% 4 8% 5% 4 4 3 5% 5% 33%	2428
May	1st to 10th	Day	20% 9% 3 8% 5% 4 5% 4 5% 7% 29%	4413
	11th to 20th	Day	18% 8% 3 8% 5% 4 5% 3 7% 8% 31%	4398
	21st to end	Day	16% 6% 2 7% 5% 5% 5% 4 6% 8% 36%	4837
June	1st to 10th	Day	21% 7% 3 6% 6% 5% 5% 4 7% 7% 30%	2660
	11th to 20th	Day	14% 7% 3 7% 5% 5% 5% 5% 7% 7% 35%	2660
	21st to end	Day	19% 9% 4 7% 5% 6% 5% 5% 6% 6% 28%	2660
July	1st to 10th	Day	12% 6% 2 7% 6% 6% 6% 5% 7% 8% 35%	4440
	11th to 20th	Day	14% 5% 2 6% 4 6% 7% 5% 8% 9% 35%	4440
	21st to end	Day	11% 5% 2 5% 4 4 5% 4 6% 7% 46%	4814
August	1st to 10th	Day	14% 5% 3 7% 6% 6% 6% 6% 7% 8% 33%	4423
	11th to 20th	Day	14% 6% 3 7% 5% 5% 5% 4 7% 8% 37%	4022
	21st to end	Day	16% 4 2 6% 5% 4 5% 4 6% 8% 40%	4180
September	1st to 10th	Day	13% 5% 2 5% 5% 4 4 4 6% 9% 42%	2280
	11th to 20th	Day	13% 5% 2 6% 4 3 4 3 6% 7% 49%	2210
	21st to end	Day	17% 7% 1 6% 4 3 4 4 6% 7% 42%	2090
October	1st to 10th	Day	20% 7% 2 6% 4 4 4 3 5% 7% 36%	1944
	11th to 20th	Day	19% 9% 3 8% 6% 5% 5% 3 6% 6% 30%	1864
	21st to end	Day	22% 11% 3 7% 5% 4 4 3 5% 5% 31%	1881
November	1st to 10th	Day	15% 10% 3 6% 5% 5% 5% 3 5% 8% 34%	1708
	11th to 20th	Day	18% 11% 3 8% 5% 5% 4 4 5% 7% 30%	1609
	21st to end	Day	20% 12% 3 7% 6% 5% 4 4 5% 7% 26%	1520
December	1st to 10th	Day	22% 16% 4 10% 7% 4 4 3 4 4 23%	1520
	11th to 20th	Day	19% 16% 4 8% 5% 4 3 3 4 5% 28%	1906
	21st to end	Day	26% 17% 5% 9% 4 4 3 3 3 4 22%	2772
January	1st to 10th	Night	15% 15% 5% 10% 6% 5% 4 4 5% 5% 25%	4429
	11th to 20th	Night	11% 12% 5% 12% 7% 6% 4 3 5% 6% 28%	4440
	21st to end	Night	12% 15% 5% 12% 6% 6% 5% 4 4 5% 25%	4884
February	1st to 10th	Night	12% 13% 4 12% 7% 4 6% 3 6% 6% 27%	2508
	11th to 20th	Night	12% 11% 4 10% 5% 5% 5% 4 5% 6% 32%	2322
	21st to end	Night	14% 13% 4 9% 6% 5% 5% 3 4 5% 32%	1884
March	1st to 10th	Night	19% 12% 4 8% 5% 4 4 3 4 5% 32%	3724
	11th to 20th	Night	13% 19% 5% 8% 5% 4 4 2 5% 5% 29%	3650
	21st to end	Night	13% 9% 3 9% 6% 5% 4 3 4 4 40%	3477
April	1st to 10th	Night	23% 8% 3 7% 5% 4 4 3 5% 6% 32%	1900
	11th to 20th	Night	20% 7% 2 7% 5% 4 3 4 5% 6% 37%	1875
	21st to end	Night	21% 9% 3 6% 3 4 5% 3 5% 6% 36%	1750
May	1st to 10th	Night	20% 9% 3 8% 5% 4 4 3 5% 6% 32%	2556
	11th to 20th	Night	21% 8% 3 6% 3 4 4 3 6% 6% 37%	2495
	21st to end	Night	16% 7% 2 7% 5% 4 5% 4 6% 7% 36%	2738
June	1st to 10th	Night	20% 6% 3 7% 5% 4 4 4 7% 8% 33%	1520
	11th to 20th	Night	17% 8% 2 7% 3 5% 4 4 5% 7% 39%	1520
	21st to end	Night	19% 7% 2 7% 5% 4 5% 4 5% 7% 36%	1520
July	1st to 10th	Night	11% 7% 3 8% 6% 5% 6% 5% 7% 7% 36%	2520
	11th to 20th	Night	13% 6% 2 5% 4 4 4 4 6% 7% 44%	2520
	21st to end	Night	10% 5% 3 6% 4 5% 5% 4 6% 7% 46%	2739
August	1st to 10th	Night	13% 6% 3 7% 5% 5% 5% 4 5% 7% 39%	2506
	11th to 20th	Night	16% 7% 2 6% 4 4 4 3 5% 7% 42%	2772
	21st to end	Night	18% 5% 2 5% 4 4 4 3 5% 7% 42%	3476
September	1st to 10th	Night	10% 4 2 6% 5% 5% 4 4 6% 7% 47%	1900
	11th to 20th	Night	13% 5% 2 5% 4 3 4 3 4 8% 51%	1969
	21st to end	Night	17% 5% 2 5% 3 4 3 3 6% 7% 46%	2090
October	1st to 10th	Night	18% 7% 3 6% 5% 4 4 3 4 5% 41%	2232
	11th to 20th	Night	19% 8% 3 6% 4 4 4 3 5% 6% 37%	2315
	21st to end	Night	21% 9% 3 8% 5% 4 4 3 5% 6% 32%	2717
November	1st to 10th	Night	17% 9% 3 7% 5% 5% 4 4 5% 7% 34%	2470
	11th to 20th	Night	18% 9% 3 8% 5% 4 5% 4 5% 5% 35%	2569
	21st to end	Night	20% 13% 4 8% 5% 4 3 3 4 6% 30%	2660
December	1st to 10th	Night	19% 14% 5% 9% 6% 5% 5% 3 6% 6% 23%	2660
	11th to 20th	Night	21% 14% 4 8% 5% 4 4 4 4 4 28%	3288
	21st to end	Night	25% 17% 5% 9% 4 3 3 2 4 4 23%	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	61% 7% 12% 14% 5% 1	2518
	11th to 20th	Day	55% 9% 12% 16% 7% 1	2520
	21st to end	Day	59% 7% 12% 14% 6% 1	2772
February	1st to 10th	Day	59% 5% 9% 18% 8% 2	1671
	11th to 20th	Day	57% 5% 13% 15% 10% 1	1752
	21st to end	Day	59% 4 9% 15% 9% 3	1570
March	1st to 10th	Day	60% 5% 9% 15% 9% 1	3119
	11th to 20th	Day	55% 6% 12% 13% 11% 2	3306
	21st to end	Day	44% 6% 10% 20% 17% 3	4154
April	1st to 10th	Day	55% 4 9% 18% 11% 3	2280
	11th to 20th	Day	48% 6% 9% 22% 13% 2	2254
	21st to end	Day	53% 6% 9% 17% 12% 3	2428
May	1st to 10th	Day	51% 7% 10% 21% 9% 2	4427
	11th to 20th	Day	48% 8% 18% 15% 9% 2	4402
	21st to end	Day	42% 8% 13% 21% 14% 1	4837
June	1st to 10th	Day	51% 7% 11% 18% 11% 2	2660
	11th to 20th	Day	44% 9% 12% 21% 12% 3	2660
	21st to end	Day	54% 8% 12% 17% 9% 1	2660
July	1st to 10th	Day	42% 8% 15% 25% 10%	4370
	11th to 20th	Day	41% 9% 17% 26% 8%	4365
	21st to end	Day	36% 7% 15% 31% 10%	4661
August	1st to 10th	Day	45% 8% 18% 21% 8%	4409
	11th to 20th	Day	42% 9% 18% 26% 6%	4064
	21st to end	Day	41% 7% 17% 21% 14% 1	4180
September	1st to 10th	Day	37% 8% 16% 27% 13%	2280
	11th to 20th	Day	34% 6% 15% 31% 13% 1	2210
	21st to end	Day	42% 6% 15% 25% 11%	2090
October	1st to 10th	Day	44% 7% 14% 25% 9%	3230
	11th to 20th	Day	44% 6% 16% 27% 7%	3080
	21st to end	Day	42% 6% 21% 20% 10% 1	3081
November	1st to 10th	Day	47% 8% 14% 21% 9% 1	1708
	11th to 20th	Day	52% 7% 13% 17% 10% 1	1609
	21st to end	Day	56% 8% 16% 14% 6% 1	1520
December	1st to 10th	Day	65% 6% 10% 13% 5%	1520
	11th to 20th	Day	59% 5% 11% 17% 8%	1906
	21st to end	Day	66% 6% 10% 13% 6%	2772
January	1st to 10th	Night	58% 8% 15% 14% 5%	4429
	11th to 20th	Night	55% 7% 16% 16% 5% 1	4440
	21st to end	Night	59% 9% 13% 12% 7% 1	4884
February	1st to 10th	Night	57% 5% 11% 18% 8% 1	2508
	11th to 20th	Night	52% 6% 11% 20% 10% 1	2324
	21st to end	Night	54% 5% 10% 17% 13% 2	1884
March	1st to 10th	Night	53% 7% 11% 16% 9% 3	3734
	11th to 20th	Night	55% 7% 10% 14% 12% 2	3651
	21st to end	Night	47% 6% 7% 22% 14% 4	3477
April	1st to 10th	Night	52% 5% 8% 19% 14% 2	1900
	11th to 20th	Night	48% 5% 9% 22% 14% 2	1875
	21st to end	Night	49% 5% 8% 20% 14% 4	1750
May	1st to 10th	Night	51% 7% 12% 19% 8% 3	2562
	11th to 20th	Night	45% 8% 16% 17% 12% 2	2496
	21st to end	Night	45% 8% 10% 19% 16% 2	2739
June	1st to 10th	Night	47% 7% 12% 20% 13% 1	1520
	11th to 20th	Night	44% 7% 11% 21% 14% 3	1520
	21st to end	Night	47% 8% 12% 19% 13% 1	1520
July	1st to 10th	Night	44% 7% 17% 20% 12% 1	2480
	11th to 20th	Night	38% 6% 19% 29% 7%	2472
	21st to end	Night	35% 6% 20% 26% 13%	2651
August	1st to 10th	Night	43% 8% 13% 27% 9%	2496
	11th to 20th	Night	42% 5% 19% 26% 8%	2796
	21st to end	Night	41% 7% 15% 22% 13% 1	3476
September	1st to 10th	Night	34% 8% 16% 26% 16% 1	1900
	11th to 20th	Night	34% 6% 15% 33% 12% 1	1969
	21st to end	Night	38% 6% 13% 29% 14%	2090
October	1st to 10th	Night	44% 5% 14% 25% 11% 1	3726
	11th to 20th	Night	41% 6% 13% 29% 11%	3838
	21st to end	Night	43% 5% 20% 18% 13% 2	4467
November	1st to 10th	Night	49% 7% 13% 22% 8% 1	2470
	11th to 20th	Night	50% 6% 14% 19% 10% 2	2569
	21st to end	Night	56% 5% 12% 18% 8% 1	2660
December	1st to 10th	Night	62% 6% 12% 15% 5%	2660
	11th to 20th	Night	58% 5% 10% 19% 7% 1	3288
	21st to end	Night	65% 5% 9% 16% 6%	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	17% 21% 36% 22% 4	180
	11th to 20th	Day	25% 18% 38% 14% 4 1	180
	21st to end	Day	18% 19% 38% 20% 4 1	198
February	1st to 10th	Day	27% 25% 37% 10% 1	252
	11th to 20th	Day	20% 23% 42% 13% 2	350
	21st to end	Day	27% 19% 32% 19% 2	382
March	1st to 10th	Day	26% 17% 33% 19% 4	460
	11th to 20th	Day	22% 24% 33% 17% 3 1	460
	21st to end	Day	27% 20% 30% 15% 7% 1	506
April	1st to 10th	Day	26% 18% 32% 17% 6% 1	460
	11th to 20th	Day	30% 20% 26% 15% 7% 1	452
	21st to end	Day	27% 21% 30% 17% 5% 1	460
May	1st to 10th	Day	24% 17% 37% 17% 5% 1	463
	11th to 20th	Day	20% 16% 34% 22% 7% 1	487
	21st to end	Day	19% 20% 32% 22% 6% 1	529
June	1st to 10th	Day	22% 17% 31% 22% 7% 1	490
	11th to 20th	Day	17% 16% 31% 25% 9% 2	490
	21st to end	Day	26% 11% 30% 22% 8% 2	490
July	1st to 10th	Day	12% 11% 34% 28% 12% 3	485
	11th to 20th	Day	15% 10% 34% 28% 12% 2	484
	21st to end	Day	14% 9% 32% 31% 13% 2	532
August	1st to 10th	Day	14% 9% 28% 33% 14% 2	486
	11th to 20th	Day	13% 7% 27% 31% 15% 8%	479
	21st to end	Day	16% 12% 26% 26% 13% 6%	539
September	1st to 10th	Day	16% 7% 36% 24% 12% 6%	490
	11th to 20th	Day	12% 10% 26% 28% 18% 7%	490
	21st to end	Day	20% 12% 26% 24% 12% 5%	490
October	1st to 10th	Day	24% 14% 29% 20% 12% 1	490
	11th to 20th	Day	21% 17% 33% 20% 8% 1	470
	21st to end	Day	28% 16% 31% 20% 5%	429
November	1st to 10th	Day	24% 20% 29% 20% 6% 1	378
	11th to 20th	Day	23% 20% 33% 17% 6%	269
	21st to end	Day	26% 21% 32% 17% 4 1	180
December	1st to 10th	Day	26% 18% 28% 22% 6% 1	180
	11th to 20th	Day	24% 23% 37% 13% 1 1	180
	21st to end	Day	31% 24% 26% 12% 6% 1	198
January	1st to 10th	Night	23% 14% 34% 23% 5%	760
	11th to 20th	Night	22% 15% 35% 24% 4	760
	21st to end	Night	15% 13% 41% 25% 6%	836
February	1st to 10th	Night	18% 13% 42% 23% 4 1	760
	11th to 20th	Night	19% 14% 42% 20% 4	743
	21st to end	Night	22% 14% 35% 26% 3	628
March	1st to 10th	Night	23% 15% 34% 24% 4	760
	11th to 20th	Night	22% 17% 35% 20% 6%	760
	21st to end	Night	20% 13% 36% 25% 6%	836
April	1st to 10th	Night	26% 13% 33% 23% 4	760
	11th to 20th	Night	24% 13% 34% 24% 5% 1	751
	21st to end	Night	27% 13% 33% 21% 6%	610
May	1st to 10th	Night	22% 12% 34% 25% 5% 2	409
	11th to 20th	Night	22% 10% 30% 30% 8%	374
	21st to end	Night	19% 7% 41% 24% 8%	411
June	1st to 10th	Night	23% 8% 31% 28% 8%	380
	11th to 20th	Night	22% 6% 31% 30% 11%	380
	21st to end	Night	22% 7% 26% 31% 14% 1	380
July	1st to 10th	Night	10% 6% 35% 35% 13% 1	370
	11th to 20th	Night	11% 5% 26% 43% 14%	368
	21st to end	Night	13% 4 27% 42% 13% 1	416
August	1st to 10th	Night	15% 4 19% 44% 16% 1	378
	11th to 20th	Night	14% 4 25% 32% 22% 2	548
	21st to end	Night	15% 5% 27% 33% 18% 2	836
September	1st to 10th	Night	13% 6% 28% 38% 13% 1	760
	11th to 20th	Night	16% 5% 24% 33% 20% 2	760
	21st to end	Night	19% 7% 27% 31% 15% 2	760
October	1st to 10th	Night	21% 10% 29% 29% 10% 1	760
	11th to 20th	Night	23% 9% 33% 26% 8% 1	760
	21st to end	Night	26% 11% 33% 25% 5%	836
November	1st to 10th	Night	22% 13% 33% 25% 7% 1	760
	11th to 20th	Night	23% 13% 34% 21% 9% 1	760
	21st to end	Night	27% 15% 32% 19% 6% 1	760
December	1st to 10th	Night	26% 13% 35% 20% 6%	760
	11th to 20th	Night	27% 16% 32% 21% 4 1	760
	21st to end	Night	32% 15% 32% 17% 4	836

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

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