Observatoire du Geai Bleu
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire du Geai Bleu clear sky chart from 2005-11-06 to 2024-01-12.

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% 8% 3 6% 6% 3 5% 5% 5% 7% 34%	74749
	Night	18% 9% 4 7% 6% 3 4 4 5% 6% 34%	74946
Transparency	Day	49% 6% 13% 20% 11% 1	74454
	Night	51% 6% 11% 20% 11% 1	74775
Seeing	Day	21% 10% 28% 25% 12% 3	13437
	Night	22% 8% 30% 30% 10% 1	22514

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	17% 14% 6% 10% 7% 3 4 4 4 5% 26%	1517
	11th to 20th	Day	16% 16% 5% 8% 5% 3 4 4 4 5% 29%	1448
	21st to end	Day	11% 13% 4 9% 7% 4 4 5% 5% 6% 31%	1584
February	1st to 10th	Day	14% 16% 4 8% 7% 3 5% 5% 5% 5% 28%	1567
	11th to 20th	Day	13% 12% 5% 10% 7% 4 6% 5% 4 6% 29%	1663
	21st to end	Day	17% 14% 5% 9% 7% 3 4 4 5% 4 28%	1480
March	1st to 10th	Day	15% 11% 4 8% 7% 5% 6% 4 5% 6% 30%	1797
	11th to 20th	Day	15% 11% 3 6% 6% 4 5% 4 5% 6% 34%	1858
	21st to end	Day	17% 9% 4 7% 6% 3 5% 4 4 6% 36%	2376
April	1st to 10th	Day	21% 9% 4 6% 6% 3 5% 4 4 5% 32%	2160
	11th to 20th	Day	21% 7% 2 5% 5% 3 5% 4 5% 6% 37%	2134
	21st to end	Day	21% 9% 4 7% 5% 3 5% 4 4 6% 32%	2312
May	1st to 10th	Day	20% 7% 4 6% 6% 4 4 5% 5% 6% 35%	2489
	11th to 20th	Day	19% 6% 3 6% 6% 3 5% 4 6% 7% 36%	2478
	21st to end	Day	18% 6% 3 6% 5% 4 5% 5% 6% 7% 36%	2725
June	1st to 10th	Day	21% 7% 3 5% 6% 4 5% 5% 5% 9% 30%	2520
	11th to 20th	Day	15% 6% 3 6% 5% 3 6% 5% 6% 8% 37%	2520
	21st to end	Day	19% 7% 3 6% 7% 3 6% 6% 5% 8% 29%	2520
July	1st to 10th	Day	12% 5% 2 5% 6% 4 7% 6% 6% 9% 39%	2520
	11th to 20th	Day	12% 5% 3 5% 5% 4 6% 7% 7% 10% 36%	2520
	21st to end	Day	11% 5% 3 5% 6% 4 5% 7% 7% 10% 37%	2744
August	1st to 10th	Day	12% 5% 2 5% 7% 4 6% 6% 7% 8% 36%	2506
	11th to 20th	Day	10% 4 2 6% 7% 4 6% 6% 8% 9% 39%	2301
	21st to end	Day	13% 5% 2 5% 4 3 4 4 6% 8% 45%	2376
September	1st to 10th	Day	13% 5% 2 4 5% 3 5% 6% 6% 8% 42%	2160
	11th to 20th	Day	14% 5% 3 3 4 2 4 4 6% 6% 50%	2084
	21st to end	Day	16% 6% 2 5% 5% 3 5% 3 4 7% 43%	1980
October	1st to 10th	Day	20% 7% 3 5% 5% 3 5% 4 5% 7% 37%	1860
	11th to 20th	Day	19% 7% 5% 6% 7% 5% 5% 5% 5% 6% 29%	1754
	21st to end	Day	24% 9% 4 6% 5% 3 4 4 5% 5% 31%	1782
November	1st to 10th	Day	15% 8% 4 6% 5% 3 4 5% 6% 7% 36%	1671
	11th to 20th	Day	18% 10% 4 6% 5% 3 5% 5% 6% 7% 32%	1625
	21st to end	Day	21% 10% 2 7% 6% 3 6% 5% 5% 7% 27%	1520
December	1st to 10th	Day	24% 12% 6% 8% 6% 3 5% 4 4 5% 24%	1520
	11th to 20th	Day	21% 14% 5% 7% 4 2 4 4 4 5% 29%	1906
	21st to end	Day	27% 16% 5% 9% 4 2 3 4 4 3 23%	2772
January	1st to 10th	Night	16% 16% 5% 9% 7% 4 4 5% 5% 6% 23%	2649
	11th to 20th	Night	16% 15% 6% 8% 7% 3 5% 4 5% 5% 26%	2535
	21st to end	Night	12% 11% 5% 8% 7% 4 5% 5% 5% 6% 33%	2772
February	1st to 10th	Night	14% 13% 6% 10% 8% 4 4 5% 5% 5% 26%	2390
	11th to 20th	Night	15% 9% 5% 9% 6% 4 5% 5% 5% 5% 32%	2182
	21st to end	Night	16% 12% 4 9% 6% 3 4 4 4 6% 32%	1776
March	1st to 10th	Night	18% 12% 5% 7% 5% 3 5% 5% 4 5% 31%	2150
	11th to 20th	Night	16% 13% 5% 7% 6% 3 4 5% 5% 6% 32%	2097
	21st to end	Night	17% 9% 4 6% 5% 3 4 4 3 4 39%	1980
April	1st to 10th	Night	23% 9% 3 6% 5% 3 4 5% 4 7% 31%	1800
	11th to 20th	Night	20% 7% 3 5% 5% 3 4 5% 5% 6% 38%	1775
	21st to end	Night	22% 9% 4 6% 5% 2 4 4 4 5% 36%	1646
May	1st to 10th	Night	22% 7% 4 5% 5% 3 4 4 4 5% 37%	1486
	11th to 20th	Night	19% 6% 3 6% 5% 2 4 5% 5% 7% 37%	1415
	21st to end	Night	18% 6% 3 5% 6% 3 4 4 5% 8% 39%	1550
June	1st to 10th	Night	21% 6% 3 6% 5% 3 5% 5% 5% 9% 34%	1440
	11th to 20th	Night	17% 6% 3 5% 5% 3 5% 5% 6% 7% 38%	1440
	21st to end	Night	18% 7% 2 5% 6% 3 5% 5% 6% 8% 35%	1440
July	1st to 10th	Night	10% 5% 2 5% 5% 3 5% 6% 7% 8% 44%	1440
	11th to 20th	Night	11% 5% 3 5% 5% 3 5% 6% 6% 10% 40%	1440
	21st to end	Night	12% 5% 3 6% 4 3 5% 5% 7% 9% 42%	1574
August	1st to 10th	Night	11% 5% 2 6% 5% 4 4 6% 6% 9% 42%	1432
	11th to 20th	Night	12% 5% 2 5% 4 4 5% 5% 6% 7% 43%	1578
	21st to end	Night	14% 6% 3 5% 4 3 4 4 6% 8% 44%	1980
September	1st to 10th	Night	11% 5% 2 6% 6% 4 4 5% 5% 7% 46%	1800
	11th to 20th	Night	14% 5% 2 4 4 2 3 4 5% 7% 50%	1876
	21st to end	Night	16% 5% 2 5% 5% 2 3 4 5% 7% 46%	1980
October	1st to 10th	Night	18% 6% 3 6% 5% 3 4 5% 4 5% 42%	2096
	11th to 20th	Night	19% 8% 3 6% 5% 3 5% 4 5% 6% 36%	2204
	21st to end	Night	23% 8% 3 7% 5% 3 4 4 4 6% 32%	2574
November	1st to 10th	Night	18% 8% 4 7% 5% 3 4 5% 5% 7% 34%	2407
	11th to 20th	Night	19% 9% 3 6% 5% 3 4 5% 4 6% 35%	2550
	21st to end	Night	22% 12% 3 7% 6% 3 4 3 3 5% 31%	2660
December	1st to 10th	Night	21% 12% 5% 9% 6% 3 4 5% 5% 6% 23%	2660
	11th to 20th	Night	23% 13% 5% 7% 6% 2 3 4 3 5% 29%	3288
	21st to end	Night	27% 16% 5% 8% 5% 3 3 3 3 4 24%	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	62% 6% 11% 15% 6%	1518
	11th to 20th	Day	60% 5% 10% 13% 12% 1	1448
	21st to end	Day	52% 6% 12% 17% 12% 1	1584
February	1st to 10th	Day	59% 4 10% 18% 7% 2	1567
	11th to 20th	Day	57% 6% 12% 14% 10% 1	1672
	21st to end	Day	60% 4 9% 17% 9% 2	1480
March	1st to 10th	Day	55% 5% 11% 16% 11% 2	1800
	11th to 20th	Day	51% 4 14% 15% 13% 2	1858
	21st to end	Day	51% 5% 11% 17% 13% 3	2376
April	1st to 10th	Day	56% 4 9% 17% 12% 2	2160
	11th to 20th	Day	49% 5% 8% 23% 14% 2	2134
	21st to end	Day	53% 6% 9% 16% 12% 3	2312
May	1st to 10th	Day	50% 4 9% 20% 14% 2	2489
	11th to 20th	Day	46% 5% 12% 18% 15% 3	2482
	21st to end	Day	46% 7% 13% 18% 15% 2	2725
June	1st to 10th	Day	50% 7% 12% 18% 11% 2	2520
	11th to 20th	Day	43% 8% 11% 22% 13% 3	2520
	21st to end	Day	52% 7% 13% 17% 10% 1	2520
July	1st to 10th	Day	39% 9% 14% 26% 12% 1	2450
	11th to 20th	Day	39% 9% 16% 25% 10%	2445
	21st to end	Day	39% 10% 17% 24% 9%	2591
August	1st to 10th	Day	43% 9% 18% 23% 8%	2492
	11th to 20th	Day	38% 9% 19% 24% 10%	2301
	21st to end	Day	37% 7% 16% 25% 14% 1	2376
September	1st to 10th	Day	37% 8% 15% 27% 12% 1	2160
	11th to 20th	Day	35% 7% 13% 31% 14% 1	2084
	21st to end	Day	43% 5% 15% 26% 11% 1	1980
October	1st to 10th	Day	47% 6% 12% 22% 12%	1860
	11th to 20th	Day	53% 7% 14% 19% 6%	1754
	21st to end	Day	55% 5% 13% 18% 8% 1	1782
November	1st to 10th	Day	46% 7% 15% 21% 10% 1	1671
	11th to 20th	Day	52% 6% 13% 18% 11% 1	1625
	21st to end	Day	56% 7% 15% 16% 6% 1	1520
December	1st to 10th	Day	64% 5% 11% 14% 5%	1520
	11th to 20th	Day	58% 6% 11% 18% 7%	1906
	21st to end	Day	66% 6% 11% 11% 6%	2772
January	1st to 10th	Night	63% 5% 10% 15% 5%	2649
	11th to 20th	Night	61% 7% 11% 12% 8% 2	2535
	21st to end	Night	52% 6% 12% 16% 12% 1	2772
February	1st to 10th	Night	61% 6% 9% 16% 8% 1	2390
	11th to 20th	Night	53% 6% 11% 20% 10% 1	2184
	21st to end	Night	55% 5% 9% 17% 14% 1	1776
March	1st to 10th	Night	55% 5% 10% 17% 11% 2	2160
	11th to 20th	Night	53% 5% 10% 16% 13% 3	2098
	21st to end	Night	49% 5% 8% 19% 15% 4	1980
April	1st to 10th	Night	54% 4 9% 18% 14% 2	1800
	11th to 20th	Night	49% 4 8% 22% 15% 2	1775
	21st to end	Night	50% 5% 9% 19% 13% 4	1646
May	1st to 10th	Night	49% 5% 8% 18% 15% 5%	1486
	11th to 20th	Night	46% 6% 10% 17% 17% 4	1416
	21st to end	Night	44% 6% 11% 20% 16% 2	1551
June	1st to 10th	Night	49% 6% 11% 20% 12% 1	1440
	11th to 20th	Night	43% 7% 12% 21% 13% 3	1440
	21st to end	Night	47% 9% 12% 18% 14%	1440
July	1st to 10th	Night	35% 9% 14% 26% 15% 1	1400
	11th to 20th	Night	38% 8% 16% 27% 11%	1392
	21st to end	Night	37% 9% 19% 23% 12%	1486
August	1st to 10th	Night	39% 8% 17% 24% 12%	1422
	11th to 20th	Night	37% 10% 16% 24% 12%	1578
	21st to end	Night	37% 9% 15% 27% 12%	1980
September	1st to 10th	Night	38% 7% 15% 25% 15% 1	1800
	11th to 20th	Night	35% 6% 14% 32% 12% 1	1876
	21st to end	Night	39% 7% 11% 29% 14%	1980
October	1st to 10th	Night	44% 7% 10% 25% 14% 1	2096
	11th to 20th	Night	50% 7% 12% 24% 8%	2204
	21st to end	Night	54% 6% 12% 18% 9% 1	2574
November	1st to 10th	Night	50% 6% 13% 21% 9% 1	2407
	11th to 20th	Night	51% 6% 13% 19% 10% 1	2550
	21st to end	Night	58% 6% 11% 18% 8%	2660
December	1st to 10th	Night	62% 6% 12% 15% 5%	2660
	11th to 20th	Night	59% 5% 10% 18% 7% 1	3288
	21st to end	Night	65% 5% 9% 15% 5%	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	23% 13% 31% 24% 9%	180
	11th to 20th	Day	24% 14% 32% 24% 4 1	162
	21st to end	Day	18% 11% 36% 26% 8% 2	176
February	1st to 10th	Day	30% 23% 34% 12% 1	217
	11th to 20th	Day	20% 12% 40% 23% 5%	330
	21st to end	Day	28% 10% 33% 25% 4	346
March	1st to 10th	Day	24% 9% 33% 25% 8%	420
	11th to 20th	Day	20% 14% 34% 26% 5% 1	420
	21st to end	Day	27% 11% 31% 21% 9% 1	462
April	1st to 10th	Day	26% 15% 27% 22% 9% 2	420
	11th to 20th	Day	27% 16% 22% 23% 9% 3	412
	21st to end	Day	28% 12% 30% 21% 8% 1	420
May	1st to 10th	Day	24% 11% 34% 22% 8% 2	423
	11th to 20th	Day	20% 10% 31% 23% 13% 2	447
	21st to end	Day	18% 12% 33% 25% 11% 2	485
June	1st to 10th	Day	24% 10% 28% 26% 10% 2	450
	11th to 20th	Day	16% 11% 26% 31% 14% 3	450
	21st to end	Day	21% 9% 23% 30% 14% 4	450
July	1st to 10th	Day	14% 5% 25% 32% 19% 5%	445
	11th to 20th	Day	15% 5% 26% 33% 17% 4	444
	21st to end	Day	13% 5% 25% 34% 18% 5%	488
August	1st to 10th	Day	15% 6% 22% 33% 20% 5%	446
	11th to 20th	Day	10% 4 21% 33% 20% 12%	439
	21st to end	Day	14% 8% 24% 24% 19% 9%	495
September	1st to 10th	Day	13% 7% 27% 28% 18% 8%	450
	11th to 20th	Day	13% 8% 23% 28% 17% 10%	450
	21st to end	Day	17% 9% 27% 22% 18% 6%	450
October	1st to 10th	Day	22% 11% 26% 23% 14% 4	450
	11th to 20th	Day	19% 13% 32% 22% 12% 2	426
	21st to end	Day	31% 10% 28% 23% 8% 1	396
November	1st to 10th	Day	24% 14% 27% 24% 9% 1	365
	11th to 20th	Day	26% 12% 32% 19% 10% 1	285
	21st to end	Day	27% 14% 30% 18% 11% 1	180
December	1st to 10th	Day	29% 11% 23% 24% 10% 2	180
	11th to 20th	Day	23% 14% 35% 23% 3 1	180
	21st to end	Day	33% 15% 29% 15% 7% 1	198
January	1st to 10th	Night	25% 11% 31% 27% 6%	760
	11th to 20th	Night	24% 10% 33% 26% 7%	725
	21st to end	Night	17% 8% 36% 31% 7% 1	792
February	1st to 10th	Night	21% 9% 37% 27% 5% 1	720
	11th to 20th	Night	20% 10% 37% 28% 5% 1	703
	21st to end	Night	22% 8% 34% 31% 4	592
March	1st to 10th	Night	25% 8% 33% 29% 5%	720
	11th to 20th	Night	24% 10% 32% 26% 7%	720
	21st to end	Night	22% 7% 32% 31% 7%	792
April	1st to 10th	Night	27% 10% 27% 28% 7%	720
	11th to 20th	Night	24% 10% 31% 28% 6%	711
	21st to end	Night	28% 8% 32% 25% 7%	566
May	1st to 10th	Night	24% 7% 31% 30% 7% 1	406
	11th to 20th	Night	22% 8% 31% 31% 8% 1	354
	21st to end	Night	19% 6% 36% 30% 8%	389
June	1st to 10th	Night	25% 4 26% 36% 9%	360
	11th to 20th	Night	19% 7% 28% 34% 12% 1	360
	21st to end	Night	21% 4 26% 35% 14%	360
July	1st to 10th	Night	11% 6% 27% 40% 16% 1	350
	11th to 20th	Night	12% 4 22% 45% 17%	348
	21st to end	Night	13% 3 21% 47% 15% 1	394
August	1st to 10th	Night	14% 4 14% 47% 20% 1	358
	11th to 20th	Night	14% 4 21% 37% 24% 2	514
	21st to end	Night	15% 4 23% 35% 21% 2	792
September	1st to 10th	Night	15% 3 24% 40% 17% 1	720
	11th to 20th	Night	17% 4 21% 36% 20% 2	720
	21st to end	Night	18% 5% 27% 32% 17% 2	720
October	1st to 10th	Night	22% 5% 28% 34% 10% 1	720
	11th to 20th	Night	23% 8% 27% 30% 11% 1	720
	21st to end	Night	27% 8% 31% 27% 7%	792
November	1st to 10th	Night	23% 10% 30% 28% 8% 1	740
	11th to 20th	Night	23% 10% 34% 23% 10% 1	760
	21st to end	Night	28% 10% 31% 22% 8% 1	760
December	1st to 10th	Night	29% 8% 32% 24% 7%	760
	11th to 20th	Night	28% 11% 31% 24% 5% 1	760
	21st to end	Night	33% 9% 32% 20% 6%	836

Page generated at 2024-01-08 22:31:28. Version ac07

Copyright 2024 Attilla Danko