Observatoire de Saint-Camille
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire de Saint-Camille clear sky chart from 2005-11-06 to 2026-06-01.

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 10% 6% 5% 5% 4 5% 6% 25%	131479
	Night	17% 14% 5% 12% 6% 5% 4 3 4 5% 24%	131698
Transparency	Day	60% 3 10% 18% 7% 1	134947
	Night	63% 3 9% 17% 8% 1	136318
Seeing	Day	29% 16% 28% 18% 7% 2	16598
	Night	27% 13% 25% 25% 9% 1	25685

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% 18% 9% 18% 7% 8% 7% 3 3 3 11%	4661
	11th to 20th	Day	9% 16% 8% 25% 15% 5% 4 2 2 3 10%	4650
	21st to end	Day	7% 16% 8% 15% 9% 14% 7% 4 5% 4 13%	5124
February	1st to 10th	Day	13% 18% 6% 15% 9% 6% 5% 3 4 3 17%	1732
	11th to 20th	Day	13% 22% 7% 16% 7% 5% 3 3 3 4 17%	2048
	21st to end	Day	13% 17% 6% 13% 8% 6% 4 3 4 5% 20%	1730
March	1st to 10th	Day	18% 16% 6% 14% 7% 5% 5% 3 3 4 20%	4576
	11th to 20th	Day	15% 16% 5% 11% 5% 4 5% 3 4 6% 26%	4823
	21st to end	Day	20% 16% 5% 11% 4 4 3 3 3 4 26%	5997
April	1st to 10th	Day	22% 16% 4 10% 5% 4 4 3 3 4 24%	2520
	11th to 20th	Day	21% 13% 4 7% 4 4 4 2 4 5% 32%	2555
	21st to end	Day	23% 13% 4 7% 4 4 3 3 4 5% 28%	2730
May	1st to 10th	Day	28% 11% 4 9% 5% 5% 5% 3 5% 5% 21%	6105
	11th to 20th	Day	21% 8% 3 8% 5% 5% 5% 4 5% 7% 28%	6458
	21st to end	Day	20% 10% 3 8% 5% 5% 5% 4 6% 6% 28%	7103
June	1st to 10th	Day	26% 8% 3 7% 4 4 5% 4 6% 8% 27%	2800
	11th to 20th	Day	19% 6% 3 7% 4 5% 5% 5% 5% 9% 32%	2800
	21st to end	Day	24% 8% 3 8% 5% 5% 5% 4 6% 7% 26%	2800
July	1st to 10th	Day	16% 8% 3 8% 6% 6% 6% 6% 8% 8% 24%	6360
	11th to 20th	Day	15% 7% 2 7% 5% 5% 5% 5% 7% 9% 33%	6360
	21st to end	Day	15% 7% 2 5% 4 4 4 4 6% 9% 40%	6926
August	1st to 10th	Day	19% 6% 2 8% 5% 5% 6% 5% 7% 8% 28%	4513
	11th to 20th	Day	18% 7% 3 8% 5% 5% 6% 5% 8% 8% 26%	4175
	21st to end	Day	21% 7% 2 6% 4 4 4 4 5% 7% 35%	4381
September	1st to 10th	Day	17% 7% 2 6% 5% 4 4 3 6% 7% 39%	2400
	11th to 20th	Day	19% 6% 2 5% 3 3 4 3 5% 7% 42%	2232
	21st to end	Day	21% 8% 3 5% 3 4 4 3 7% 8% 34%	2200
October	1st to 10th	Day	23% 10% 2 6% 4 4 4 3 5% 6% 32%	2188
	11th to 20th	Day	21% 14% 4 7% 4 5% 5% 4 5% 5% 25%	1862
	21st to end	Day	27% 17% 4 9% 4 4 4 3 3 4 21%	1980
November	1st to 10th	Day	20% 20% 4 7% 4 4 3 3 4 5% 26%	1851
	11th to 20th	Day	18% 20% 8% 10% 5% 3 3 3 4 4 22%	1890
	21st to end	Day	20% 22% 8% 10% 5% 4 3 3 4 4 17%	1714
December	1st to 10th	Day	17% 22% 7% 16% 9% 4 4 3 3 3 11%	2388
	11th to 20th	Day	19% 16% 8% 13% 6% 3 4 3 4 4 20%	2799
	21st to end	Day	19% 19% 6% 13% 5% 4 4 2 3 5% 18%	4048
January	1st to 10th	Night	12% 19% 9% 19% 8% 5% 4 3 3 3 14%	8234
	11th to 20th	Night	10% 20% 10% 23% 10% 6% 4 3 3 2 9%	8235
	21st to end	Night	7% 15% 6% 15% 10% 11% 6% 5% 4 4 17%	9057
February	1st to 10th	Night	12% 18% 6% 15% 8% 6% 4 3 4 5% 20%	2882
	11th to 20th	Night	13% 19% 6% 14% 8% 6% 4 3 3 3 20%	2458
	21st to end	Night	14% 16% 6% 11% 6% 6% 4 3 4 5% 24%	2076
March	1st to 10th	Night	19% 16% 6% 13% 5% 5% 4 2 3 4 23%	5484
	11th to 20th	Night	16% 17% 6% 10% 6% 5% 5% 3 5% 5% 23%	5355
	21st to end	Night	16% 16% 6% 11% 8% 4 4 3 4 4 25%	5175
April	1st to 10th	Night	23% 15% 4 7% 4 4 3 3 5% 5% 27%	2100
	11th to 20th	Night	22% 13% 3 7% 4 4 4 3 4 5% 31%	2014
	21st to end	Night	22% 13% 3 8% 4 4 4 3 4 5% 31%	1890
May	1st to 10th	Night	27% 10% 3 9% 4 4 4 3 5% 5% 24%	4098
	11th to 20th	Night	24% 9% 3 6% 4 4 5% 4 5% 7% 29%	3655
	21st to end	Night	20% 9% 3 7% 4 4 4 4 5% 7% 33%	4014
June	1st to 10th	Night	26% 9% 2 7% 4 3 3 4 7% 7% 27%	1600
	11th to 20th	Night	21% 7% 2 6% 3 3 5% 5% 6% 9% 34%	1600
	21st to end	Night	21% 8% 2 8% 6% 5% 4 3 5% 7% 30%	1600
July	1st to 10th	Night	16% 9% 4 9% 6% 5% 6% 5% 6% 8% 28%	3600
	11th to 20th	Night	19% 7% 3 6% 5% 4 4 4 5% 7% 36%	3600
	21st to end	Night	13% 7% 2 6% 5% 5% 5% 4 7% 8% 38%	3926
August	1st to 10th	Night	23% 7% 2 7% 4 5% 4 3 6% 7% 31%	2604
	11th to 20th	Night	17% 9% 3 8% 6% 5% 5% 4 6% 7% 31%	2872
	21st to end	Night	18% 8% 3 7% 4 4 4 4 4 7% 37%	3514
September	1st to 10th	Night	19% 7% 3 7% 4 4 4 3 5% 5% 40%	2000
	11th to 20th	Night	17% 5% 2 5% 3 3 4 3 5% 6% 47%	2167
	21st to end	Night	20% 7% 2 6% 4 4 4 3 4 6% 41%	2200
October	1st to 10th	Night	20% 8% 3 6% 4 4 4 3 4 6% 37%	2210
	11th to 20th	Night	22% 12% 3 8% 5% 4 5% 3 4 5% 29%	2537
	21st to end	Night	26% 13% 3 7% 5% 4 4 4 5% 4 26%	2860
November	1st to 10th	Night	22% 16% 4 9% 4 4 3 3 5% 5% 26%	2667
	11th to 20th	Night	18% 17% 7% 10% 5% 3 4 3 4 4 26%	2730
	21st to end	Night	19% 19% 7% 12% 5% 4 3 3 4 4 20%	2903
December	1st to 10th	Night	16% 21% 11% 20% 7% 4 4 2 2 3 10%	5013
	11th to 20th	Night	19% 20% 6% 15% 6% 5% 4 3 3 3 17%	5618
	21st to end	Night	19% 20% 5% 11% 6% 4 4 2 3 6% 21%	7150

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	81% 1 6% 9% 2	4662
	11th to 20th	Day	83% 2 3 8% 4 1	4680
	21st to end	Day	76% 2 4 9% 9%	5124
February	1st to 10th	Day	73% 3 5% 12% 6% 1	1732
	11th to 20th	Day	74% 2 6% 11% 5% 1	2057
	21st to end	Day	68% 3 7% 14% 6% 2	1730
March	1st to 10th	Day	72% 2 5% 10% 9% 3	4579
	11th to 20th	Day	62% 2 12% 13% 9% 1	4823
	21st to end	Day	64% 2 4 15% 14% 1	5997
April	1st to 10th	Day	65% 3 7% 15% 8% 2	2520
	11th to 20th	Day	57% 2 7% 20% 13% 1	2555
	21st to end	Day	59% 2 8% 18% 11% 2	2730
May	1st to 10th	Day	66% 3 7% 17% 6% 1	6116
	11th to 20th	Day	56% 3 16% 17% 6% 2	6462
	21st to end	Day	55% 3 11% 19% 10%	7103
June	1st to 10th	Day	56% 5% 10% 21% 8% 1	2800
	11th to 20th	Day	49% 5% 12% 23% 10% 1	2800
	21st to end	Day	58% 4 11% 19% 8%	2800
July	1st to 10th	Day	56% 3 15% 21% 6%	6290
	11th to 20th	Day	47% 3 14% 29% 6%	6285
	21st to end	Day	42% 3 14% 34% 7%	6728
August	1st to 10th	Day	53% 4 17% 22% 4	4499
	11th to 20th	Day	54% 4 18% 19% 5%	4214
	21st to end	Day	49% 3 14% 20% 12% 1	4381
September	1st to 10th	Day	45% 5% 13% 27% 9% 1	2400
	11th to 20th	Day	42% 5% 11% 30% 12%	2232
	21st to end	Day	48% 4 12% 25% 10% 1	2200
October	1st to 10th	Day	52% 3 13% 25% 7%	3565
	11th to 20th	Day	56% 2 13% 25% 4	3013
	21st to end	Day	57% 3 14% 19% 7%	3180
November	1st to 10th	Day	62% 3 11% 17% 6%	1851
	11th to 20th	Day	67% 3 8% 13% 8% 1	1890
	21st to end	Day	71% 4 11% 11% 2	1714
December	1st to 10th	Day	80% 2 8% 7% 3	2388
	11th to 20th	Day	70% 3 6% 15% 6%	2799
	21st to end	Day	72% 2 5% 11% 9% 1	4048
January	1st to 10th	Night	78% 1 7% 9% 4	8234
	11th to 20th	Night	84% 2 5% 7% 3	8280
	21st to end	Night	72% 2 6% 11% 10%	9057
February	1st to 10th	Night	69% 3 7% 14% 6% 1	2882
	11th to 20th	Night	71% 3 7% 12% 7%	2460
	21st to end	Night	64% 3 7% 15% 10% 1	2076
March	1st to 10th	Night	68% 2 6% 13% 9% 2	5494
	11th to 20th	Night	65% 3 12% 13% 7% 1	5356
	21st to end	Night	66% 1 5% 16% 10% 1	5175
April	1st to 10th	Night	60% 3 7% 18% 11% 1	2100
	11th to 20th	Night	56% 3 6% 21% 11% 2	2014
	21st to end	Night	57% 3 8% 19% 11% 2	1890
May	1st to 10th	Night	64% 2 10% 16% 7% 1	4104
	11th to 20th	Night	56% 4 12% 21% 7% 1	3656
	21st to end	Night	52% 3 13% 18% 14%	4015
June	1st to 10th	Night	55% 4 11% 21% 9%	1600
	11th to 20th	Night	47% 4 11% 24% 12% 2	1600
	21st to end	Night	54% 4 12% 20% 10%	1600
July	1st to 10th	Night	54% 2 18% 19% 6%	3560
	11th to 20th	Night	48% 3 15% 27% 7%	3552
	21st to end	Night	45% 3 16% 28% 7%	3809
August	1st to 10th	Night	53% 4 14% 24% 4	2594
	11th to 20th	Night	54% 4 15% 19% 7%	2899
	21st to end	Night	48% 3 12% 23% 13% 1	3514
September	1st to 10th	Night	47% 5% 11% 26% 11% 1	2000
	11th to 20th	Night	39% 4 14% 32% 11% 1	2167
	21st to end	Night	45% 4 11% 27% 12% 1	2200
October	1st to 10th	Night	52% 2 9% 26% 10%	3613
	11th to 20th	Night	56% 3 10% 26% 6%	4125
	21st to end	Night	55% 3 13% 19% 9% 2	4610
November	1st to 10th	Night	62% 3 11% 18% 6% 1	2667
	11th to 20th	Night	64% 3 10% 15% 8% 1	2730
	21st to end	Night	69% 3 10% 13% 4	2903
December	1st to 10th	Night	83% 1 7% 7% 2	5013
	11th to 20th	Night	75% 2 5% 12% 6%	5619
	21st to end	Night	68% 2 8% 14% 8%	7150

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	29% 23% 33% 13% 2	220
	11th to 20th	Day	32% 25% 29% 11% 3	220
	21st to end	Day	31% 21% 30% 13% 4 1	242
February	1st to 10th	Day	35% 27% 26% 9% 3 1	252
	11th to 20th	Day	32% 24% 31% 11% 2 1	536
	21st to end	Day	31% 22% 29% 17% 2	446
March	1st to 10th	Day	31% 24% 26% 15% 4	540
	11th to 20th	Day	33% 24% 24% 15% 3 1	540
	21st to end	Day	36% 19% 25% 12% 7% 1	594
April	1st to 10th	Day	39% 17% 26% 12% 6% 1	540
	11th to 20th	Day	35% 20% 24% 14% 5% 2	532
	21st to end	Day	35% 17% 27% 14% 5% 2	540
May	1st to 10th	Day	34% 19% 28% 13% 6% 1	543
	11th to 20th	Day	28% 16% 27% 20% 7% 1	567
	21st to end	Day	26% 21% 29% 18% 5% 1	617
June	1st to 10th	Day	29% 15% 30% 18% 6% 1	530
	11th to 20th	Day	22% 17% 30% 22% 8% 1	530
	21st to end	Day	26% 16% 34% 16% 7% 2	530
July	1st to 10th	Day	20% 12% 33% 25% 9% 1	525
	11th to 20th	Day	19% 10% 39% 24% 8% 2	524
	21st to end	Day	21% 10% 34% 28% 5% 1	576
August	1st to 10th	Day	20% 11% 28% 25% 14% 2	526
	11th to 20th	Day	21% 7% 25% 26% 18% 3	519
	21st to end	Day	24% 13% 24% 22% 12% 6%	583
September	1st to 10th	Day	19% 9% 32% 22% 12% 5%	530
	11th to 20th	Day	20% 8% 22% 24% 17% 9%	530
	21st to end	Day	22% 13% 24% 24% 12% 5%	530
October	1st to 10th	Day	24% 15% 25% 18% 14% 4	530
	11th to 20th	Day	32% 14% 25% 17% 10% 2	453
	21st to end	Day	40% 15% 22% 17% 6%	462
November	1st to 10th	Day	37% 16% 27% 17% 4	425
	11th to 20th	Day	33% 17% 27% 17% 6% 1	430
	21st to end	Day	36% 20% 26% 15% 2	254
December	1st to 10th	Day	37% 15% 28% 15% 4 1	220
	11th to 20th	Day	37% 23% 29% 9% 2	220
	21st to end	Day	38% 20% 29% 9% 4 1	242
January	1st to 10th	Night	28% 20% 30% 19% 3	840
	11th to 20th	Night	29% 19% 29% 19% 5%	840
	21st to end	Night	22% 18% 31% 23% 6% 1	924
February	1st to 10th	Night	23% 19% 31% 21% 6%	840
	11th to 20th	Night	25% 19% 33% 19% 3	823
	21st to end	Night	26% 17% 31% 23% 3	692
March	1st to 10th	Night	29% 17% 30% 20% 3	840
	11th to 20th	Night	30% 17% 27% 21% 4	840
	21st to end	Night	27% 16% 26% 23% 7% 1	924
April	1st to 10th	Night	33% 15% 25% 22% 5%	840
	11th to 20th	Night	31% 14% 26% 22% 6%	770
	21st to end	Night	29% 18% 27% 19% 7%	630
May	1st to 10th	Night	30% 11% 29% 22% 8%	610
	11th to 20th	Night	24% 10% 28% 30% 7% 1	414
	21st to end	Night	25% 8% 27% 32% 8%	455
June	1st to 10th	Night	30% 7% 23% 32% 8% 1	400
	11th to 20th	Night	23% 8% 23% 33% 13%	400
	21st to end	Night	23% 6% 23% 37% 10% 1	400
July	1st to 10th	Night	17% 5% 27% 37% 13% 1	390
	11th to 20th	Night	16% 5% 21% 43% 13% 2	388
	21st to end	Night	17% 5% 19% 43% 16%	438
August	1st to 10th	Night	19% 4 15% 42% 20% 1	403
	11th to 20th	Night	18% 5% 18% 36% 21% 1	592
	21st to end	Night	21% 4 21% 33% 20% 2	834
September	1st to 10th	Night	21% 8% 21% 35% 14% 2	800
	11th to 20th	Night	19% 5% 20% 29% 24% 2	800
	21st to end	Night	24% 8% 23% 29% 15% 2	800
October	1st to 10th	Night	25% 11% 22% 28% 15% 1	800
	11th to 20th	Night	30% 11% 23% 26% 9% 2	800
	21st to end	Night	32% 14% 26% 24% 5%	880
November	1st to 10th	Night	33% 15% 23% 21% 8%	820
	11th to 20th	Night	28% 16% 27% 19% 9% 1	840
	21st to end	Night	32% 19% 23% 20% 5% 1	840
December	1st to 10th	Night	34% 17% 27% 16% 5%	934
	11th to 20th	Night	32% 21% 23% 19% 5%	920
	21st to end	Night	35% 18% 23% 19% 5%	924

Page generated at 2026-05-29 01:53:31. Version ac07

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