Rue de Renard Observatory
Clear Sky Chart
History

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

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	13% 8% 3 6% 5% 4 4 4 5% 7% 41%	100944
	Night	14% 8% 3 6% 4 4 4 3 5% 7% 43%	98029
Transparency	Day	42% 6% 10% 24% 16% 2	100740
	Night	41% 5% 10% 23% 17% 3	97904
Seeing	Day	17% 11% 24% 24% 17% 8%	15358
	Night	18% 9% 24% 29% 18% 2	25117

By Month

Percentage Cloud Cover SE (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	13% 13% 8% 9% 6% 5% 5% 4 4 4 31%	2527
	11th to 20th	Day	18% 10% 4 10% 7% 4 6% 2 3 4 31%	2530
	21st to end	Day	26% 13% 7% 5% 4 3 3 3 4 5% 27%	3246
February	1st to 10th	Day	17% 12% 4 8% 4 4 4 3 5% 5% 35%	1900
	11th to 20th	Day	19% 10% 4 8% 6% 4 3 3 4 5% 36%	1848
	21st to end	Day	17% 12% 4 8% 5% 4 4 4 5% 5% 34%	1570
March	1st to 10th	Day	24% 13% 4 6% 3 3 3 3 3 5% 33%	3120
	11th to 20th	Day	14% 7% 2 6% 4 3 3 3 4 7% 48%	3285
	21st to end	Day	12% 8% 3 8% 5% 4 4 4 5% 7% 41%	4096
April	1st to 10th	Day	14% 6% 2 7% 5% 4 4 4 5% 7% 43%	2280
	11th to 20th	Day	13% 8% 3 6% 6% 4 4 3 6% 6% 41%	2254
	21st to end	Day	16% 7% 2 5% 4 5% 4 3 5% 7% 41%	2321
May	1st to 10th	Day	17% 8% 2 8% 6% 5% 5% 4 6% 8% 32%	4082
	11th to 20th	Day	18% 7% 3 7% 4 4 4 4 5% 8% 37%	4081
	21st to end	Day	11% 6% 3 7% 5% 5% 5% 5% 6% 7% 41%	4476
June	1st to 10th	Day	9% 5% 2 6% 5% 4 4 4 7% 8% 45%	2627
	11th to 20th	Day	5% 4 1 5% 4 5% 6% 5% 7% 10% 47%	2660
	21st to end	Day	5% 5% 2 5% 5% 6% 6% 4 8% 11% 43%	2660
July	1st to 10th	Day	10% 6% 2 6% 5% 5% 6% 5% 6% 11% 38%	4440
	11th to 20th	Day	7% 5% 2 6% 5% 4 5% 5% 7% 11% 43%	4440
	21st to end	Day	13% 10% 4 9% 7% 6% 5% 5% 7% 8% 27%	4574
August	1st to 10th	Day	6% 4 2 4 4 4 4 3 6% 10% 53%	3923
	11th to 20th	Day	9% 6% 2 6% 5% 5% 5% 4 8% 10% 40%	3729
	21st to end	Day	5% 3 2 5% 4 4 4 4 6% 9% 54%	4180
September	1st to 10th	Day	10% 6% 2 7% 5% 4 4 5% 5% 9% 43%	2280
	11th to 20th	Day	12% 4 3 6% 5% 4 5% 4 5% 7% 46%	2090
	21st to end	Day	12% 6% 2 6% 3 4 4 3 5% 6% 49%	2090
October	1st to 10th	Day	10% 5% 2 4 3 3 4 3 5% 6% 56%	2090
	11th to 20th	Day	12% 5% 2 5% 4 4 3 3 3 6% 53%	1995
	21st to end	Day	19% 7% 2 5% 3 2 3 3 4 5% 46%	1900
November	1st to 10th	Day	11% 6% 2 6% 3 3 3 2 3 5% 56%	1681
	11th to 20th	Day	15% 7% 3 5% 4 4 3 2 5% 6% 47%	1710
	21st to end	Day	17% 9% 3 6% 3 3 4 3 5% 5% 44%	1710
December	1st to 10th	Day	19% 11% 2 6% 4 4 4 3 5% 6% 36%	1710
	11th to 20th	Day	16% 13% 4 7% 4 5% 4 4 4 5% 34%	2056
	21st to end	Day	17% 15% 4 7% 5% 4 5% 3 5% 7% 28%	2783
January	1st to 10th	Night	18% 11% 4 8% 4 3 4 3 4 6% 35%	4428
	11th to 20th	Night	17% 14% 5% 9% 6% 5% 4 3 3 4 32%	4440
	21st to end	Night	24% 14% 4 6% 4 3 3 3 4 6% 30%	4393
February	1st to 10th	Night	22% 11% 4 8% 4 4 3 3 4 4 32%	2280
	11th to 20th	Night	20% 8% 4 8% 5% 4 3 3 3 5% 36%	2218
	21st to end	Night	21% 10% 4 8% 4 3 3 3 4 5% 34%	1884
March	1st to 10th	Night	23% 12% 3 6% 3 3 3 3 5% 5% 34%	3733
	11th to 20th	Night	13% 7% 2 6% 4 2 3 3 5% 6% 49%	3673
	21st to end	Night	15% 8% 3 7% 5% 4 3 3 4 7% 41%	3562
April	1st to 10th	Night	13% 5% 2 6% 4 3 5% 4 5% 7% 46%	1900
	11th to 20th	Night	15% 7% 2 5% 3 3 4 3 5% 7% 45%	1875
	21st to end	Night	14% 7% 3 6% 5% 5% 4 4 5% 8% 39%	1857
May	1st to 10th	Night	17% 8% 3 7% 4 4 3 3 6% 7% 37%	2813
	11th to 20th	Night	13% 7% 2 6% 4 5% 4 4 6% 8% 41%	2812
	21st to end	Night	7% 5% 2 6% 5% 5% 5% 5% 7% 9% 44%	3079
June	1st to 10th	Night	10% 6% 2 5% 4 5% 4 4 6% 9% 46%	1548
	11th to 20th	Night	5% 3 2 4 4 4 4 5% 8% 10% 53%	1520
	21st to end	Night	3 3 1 4 3 4 5% 4 8% 14% 51%	1520
July	1st to 10th	Night	6% 5% 2 5% 4 5% 5% 4 7% 11% 46%	2530
	11th to 20th	Night	7% 4 2 4 3 4 3 4 6% 9% 54%	2530
	21st to end	Night	9% 8% 3 10% 6% 6% 7% 5% 7% 8% 30%	2965
August	1st to 10th	Night	6% 4 1 4 3 3 4 3 5% 7% 60%	3002
	11th to 20th	Night	4 3 2 6% 4 4 5% 4 8% 9% 49%	3100
	21st to end	Night	4 3 1 4 3 3 4 3 5% 8% 62%	3476
September	1st to 10th	Night	11% 5% 2 4 4 4 4 3 5% 6% 51%	1900
	11th to 20th	Night	10% 4 3 6% 3 4 4 4 5% 6% 50%	2071
	21st to end	Night	11% 5% 2 4 4 2 4 3 5% 7% 53%	2090
October	1st to 10th	Night	9% 4 2 4 3 3 2 3 4 6% 61%	2090
	11th to 20th	Night	16% 5% 2 5% 3 3 3 2 4 4 53%	2181
	21st to end	Night	17% 7% 2 5% 3 4 3 3 3 6% 47%	2698
November	1st to 10th	Night	12% 5% 2 5% 3 4 3 3 3 6% 54%	2431
	11th to 20th	Night	14% 6% 2 5% 4 3 3 2 5% 6% 50%	2470
	21st to end	Night	17% 7% 2 6% 3 3 3 3 4 6% 46%	2470
December	1st to 10th	Night	21% 12% 3 6% 3 3 4 3 5% 5% 35%	2470
	11th to 20th	Night	17% 10% 4 6% 4 4 4 3 5% 5% 38%	3136
	21st to end	Night	17% 14% 5% 9% 5% 6% 5% 4 4 5% 26%	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	56% 5% 8% 21% 9% 1	2528
	11th to 20th	Day	58% 3 8% 20% 10% 1	2530
	21st to end	Day	60% 4 7% 20% 8% 1	3246
February	1st to 10th	Day	51% 3 9% 22% 13% 2	1900
	11th to 20th	Day	52% 4 7% 21% 13% 4	1858
	21st to end	Day	51% 5% 9% 15% 15% 5%	1570
March	1st to 10th	Day	56% 4 5% 18% 13% 5%	3120
	11th to 20th	Day	38% 5% 8% 28% 17% 4	3285
	21st to end	Day	42% 5% 11% 23% 17% 1	4096
April	1st to 10th	Day	41% 5% 11% 23% 19% 2	2280
	11th to 20th	Day	43% 5% 9% 22% 19% 3	2254
	21st to end	Day	43% 6% 10% 26% 13% 2	2321
May	1st to 10th	Day	49% 8% 12% 20% 10% 1	4120
	11th to 20th	Day	45% 8% 10% 24% 13%	4085
	21st to end	Day	39% 9% 12% 19% 20% 2	4489
June	1st to 10th	Day	35% 7% 12% 23% 20% 3	2627
	11th to 20th	Day	30% 9% 14% 25% 20% 2	2660
	21st to end	Day	32% 9% 15% 24% 16% 5%	2660
July	1st to 10th	Day	38% 8% 14% 26% 12% 2	4371
	11th to 20th	Day	31% 9% 14% 33% 12% 2	4365
	21st to end	Day	52% 8% 12% 19% 7% 1	4429
August	1st to 10th	Day	25% 7% 15% 31% 21% 1	3910
	11th to 20th	Day	36% 8% 12% 25% 18% 1	3765
	21st to end	Day	26% 7% 10% 34% 21% 3	4179
September	1st to 10th	Day	37% 7% 11% 21% 19% 4	2280
	11th to 20th	Day	37% 7% 10% 23% 22% 2	2090
	21st to end	Day	35% 5% 8% 24% 22% 5%	2090
October	1st to 10th	Day	29% 5% 9% 23% 30% 5%	2090
	11th to 20th	Day	34% 5% 7% 23% 25% 7%	1995
	21st to end	Day	41% 4 7% 24% 20% 4	1900
November	1st to 10th	Day	32% 4 8% 25% 25% 5%	1681
	11th to 20th	Day	39% 3 8% 24% 21% 5%	1710
	21st to end	Day	43% 3 7% 26% 17% 4	1710
December	1st to 10th	Day	49% 4 10% 23% 12% 2	1710
	11th to 20th	Day	53% 4 9% 20% 12% 1	2053
	21st to end	Day	54% 6% 12% 17% 10%	2783
January	1st to 10th	Night	51% 4 9% 24% 12% 1	4428
	11th to 20th	Night	58% 3 6% 19% 11% 2	4440
	21st to end	Night	57% 3 8% 20% 11% 1	4393
February	1st to 10th	Night	57% 3 8% 19% 12% 1	2280
	11th to 20th	Night	51% 4 7% 20% 15% 3	2219
	21st to end	Night	54% 4 8% 15% 15% 4	1884
March	1st to 10th	Night	53% 5% 8% 14% 17% 3	3733
	11th to 20th	Night	37% 5% 11% 25% 13% 9%	3673
	21st to end	Night	44% 5% 10% 24% 17% 1	3562
April	1st to 10th	Night	36% 5% 12% 25% 19% 4	1900
	11th to 20th	Night	39% 5% 10% 18% 22% 6%	1875
	21st to end	Night	42% 7% 9% 23% 17% 2	1857
May	1st to 10th	Night	45% 8% 12% 23% 11% 1	2840
	11th to 20th	Night	40% 8% 12% 25% 14% 1	2813
	21st to end	Night	33% 11% 14% 22% 19% 2	3087
June	1st to 10th	Night	34% 6% 13% 24% 20% 3	1548
	11th to 20th	Night	23% 7% 17% 24% 25% 4	1520
	21st to end	Night	22% 10% 18% 25% 18% 6%	1520
July	1st to 10th	Night	31% 8% 13% 30% 16% 3	2490
	11th to 20th	Night	26% 7% 12% 35% 17% 3	2482
	21st to end	Night	49% 10% 12% 19% 9% 1	2870
August	1st to 10th	Night	23% 6% 12% 38% 21% 1	2991
	11th to 20th	Night	28% 8% 17% 29% 17% 1	3130
	21st to end	Night	21% 6% 10% 35% 25% 3	3476
September	1st to 10th	Night	32% 7% 10% 24% 23% 5%	1900
	11th to 20th	Night	33% 5% 9% 24% 24% 5%	2071
	21st to end	Night	31% 5% 8% 22% 26% 6%	2090
October	1st to 10th	Night	25% 5% 8% 23% 33% 7%	2090
	11th to 20th	Night	35% 3 8% 21% 26% 7%	2181
	21st to end	Night	40% 3 7% 22% 21% 6%	2698
November	1st to 10th	Night	34% 4 7% 24% 25% 6%	2431
	11th to 20th	Night	35% 4 8% 23% 22% 8%	2470
	21st to end	Night	41% 3 8% 25% 20% 3	2470
December	1st to 10th	Night	51% 5% 10% 21% 12% 2	2470
	11th to 20th	Night	49% 4 8% 20% 17% 2	3138
	21st to end	Night	59% 5% 10% 15% 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% 22% 31% 18% 4	270
	11th to 20th	Day	28% 27% 29% 12% 3	270
	21st to end	Day	25% 23% 38% 10% 3	297
February	1st to 10th	Day	25% 24% 31% 16% 2 1	270
	11th to 20th	Day	31% 26% 33% 8% 3	270
	21st to end	Day	33% 24% 28% 11% 3	225
March	1st to 10th	Day	31% 19% 35% 12% 3	270
	11th to 20th	Day	28% 22% 31% 13% 5% 1	343
	21st to end	Day	27% 19% 32% 15% 7%	506
April	1st to 10th	Day	20% 20% 26% 24% 9%	460
	11th to 20th	Day	22% 15% 28% 23% 11% 2	452
	21st to end	Day	22% 15% 33% 17% 10% 2	460
May	1st to 10th	Day	22% 14% 27% 25% 9% 3	463
	11th to 20th	Day	19% 10% 24% 29% 12% 7%	487
	21st to end	Day	12% 6% 22% 31% 18% 12%	529
June	1st to 10th	Day	12% 6% 21% 25% 25% 11%	647
	11th to 20th	Day	5% 5% 19% 33% 28% 11%	680
	21st to end	Day	6% 3 24% 31% 23% 12%	680
July	1st to 10th	Day	12% 2 14% 30% 24% 18%	671
	11th to 20th	Day	8% 3 16% 30% 28% 15%	668
	21st to end	Day	11% 3 14% 29% 27% 15%	601
August	1st to 10th	Day	13% 2 13% 31% 26% 15%	486
	11th to 20th	Day	13% 2 19% 32% 26% 9%	479
	21st to end	Day	10% 2 11% 24% 35% 18%	539
September	1st to 10th	Day	12% 2 16% 24% 34% 12%	490
	11th to 20th	Day	12% 2 13% 27% 32% 14%	490
	21st to end	Day	17% 8% 19% 22% 23% 10%	490
October	1st to 10th	Day	11% 4 21% 32% 24% 8%	490
	11th to 20th	Day	14% 14% 31% 24% 13% 5%	395
	21st to end	Day	28% 12% 30% 23% 6% 2	330
November	1st to 10th	Day	15% 11% 36% 22% 12% 3	273
	11th to 20th	Day	19% 19% 30% 24% 7% 1	270
	21st to end	Day	26% 13% 31% 21% 8% 2	270
December	1st to 10th	Day	25% 20% 28% 19% 6% 1	270
	11th to 20th	Day	24% 17% 32% 21% 6%	270
	21st to end	Day	28% 21% 33% 16% 3	297
January	1st to 10th	Night	25% 17% 29% 24% 4	950
	11th to 20th	Night	29% 16% 32% 18% 4	950
	21st to end	Night	24% 16% 36% 22% 2	915
February	1st to 10th	Night	28% 14% 32% 23% 3	760
	11th to 20th	Night	27% 16% 35% 20% 2	743
	21st to end	Night	27% 18% 36% 17% 2	628
March	1st to 10th	Night	24% 15% 30% 27% 4	760
	11th to 20th	Night	23% 14% 32% 25% 6%	760
	21st to end	Night	23% 12% 30% 28% 7%	684
April	1st to 10th	Night	17% 13% 31% 31% 7% 1	570
	11th to 20th	Night	20% 8% 32% 27% 12% 1	563
	21st to end	Night	17% 9% 31% 32% 10% 1	570
May	1st to 10th	Night	20% 7% 28% 28% 16% 1	570
	11th to 20th	Night	14% 5% 22% 34% 20% 3	561
	21st to end	Night	7% 3 20% 36% 30% 4	617
June	1st to 10th	Night	11% 4 17% 36% 29% 4	570
	11th to 20th	Night	6% 2 14% 42% 34% 2	570
	21st to end	Night	4 2 16% 40% 34% 5%	570
July	1st to 10th	Night	9% 1 11% 30% 39% 10%	555
	11th to 20th	Night	9% 2 10% 28% 45% 7%	552
	21st to end	Night	10% 2 12% 34% 36% 7%	624
August	1st to 10th	Night	8% 1 9% 32% 43% 7%	567
	11th to 20th	Night	7% 13% 37% 38% 5%	564
	21st to end	Night	8% 1 9% 30% 45% 7%	627
September	1st to 10th	Night	13% 2 11% 32% 36% 5%	570
	11th to 20th	Night	10% 3 10% 31% 38% 7%	741
	21st to end	Night	13% 4 20% 30% 29% 5%	760
October	1st to 10th	Night	12% 4 17% 32% 29% 5%	760
	11th to 20th	Night	19% 7% 25% 31% 18% 1	760
	21st to end	Night	21% 8% 29% 27% 14% 1	836
November	1st to 10th	Night	15% 8% 26% 33% 16% 1	748
	11th to 20th	Night	16% 12% 32% 28% 11%	760
	21st to end	Night	22% 13% 24% 28% 13% 1	760
December	1st to 10th	Night	28% 10% 27% 28% 6%	760
	11th to 20th	Night	24% 12% 29% 26% 8% 1	817
	21st to end	Night	28% 15% 30% 23% 4	1045

Page generated at 2024-10-30 12:19:23. Version ac07

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