Observatoire de la Pourvoirie St-Zénon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire de la Pourvoirie St-Zénon clear sky chart from 2005-11-06 to 2024-01-13.

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% 11% 5% 8% 7% 4 5% 5% 5% 6% 28%	74758
	Night	16% 12% 5% 8% 7% 4 5% 4 5% 6% 29%	74976
Transparency	Day	54% 8% 11% 17% 9% 1	74463
	Night	52% 8% 12% 18% 9% 1	74805
Seeing	Day	24% 20% 31% 17% 6% 2	13384
	Night	22% 17% 31% 22% 7% 1	22445

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	12% 18% 7% 11% 10% 5% 5% 4 4 5% 19%	1517
	11th to 20th	Day	13% 16% 7% 10% 8% 4 4 5% 5% 6% 21%	1456
	21st to end	Day	10% 12% 7% 10% 9% 4 6% 6% 5% 7% 25%	1584
February	1st to 10th	Day	10% 16% 6% 11% 10% 5% 6% 4 4 7% 20%	1548
	11th to 20th	Day	11% 17% 6% 11% 6% 5% 5% 5% 5% 5% 24%	1649
	21st to end	Day	13% 18% 6% 11% 8% 4 4 4 5% 4 23%	1480
March	1st to 10th	Day	13% 13% 6% 12% 8% 5% 5% 4 5% 4 25%	1797
	11th to 20th	Day	13% 15% 7% 9% 7% 3 5% 4 4 6% 28%	1859
	21st to end	Day	17% 13% 5% 9% 6% 3 4 5% 4 6% 30%	2376
April	1st to 10th	Day	18% 16% 6% 8% 7% 3 3 4 4 5% 25%	2160
	11th to 20th	Day	21% 11% 4 7% 6% 3 4 3 4 4 33%	2134
	21st to end	Day	19% 13% 5% 7% 6% 3 4 5% 4 4 29%	2326
May	1st to 10th	Day	20% 11% 4 7% 6% 2 4 4 4 6% 31%	2515
	11th to 20th	Day	19% 9% 4 7% 5% 3 5% 5% 4 6% 32%	2478
	21st to end	Day	20% 9% 3 7% 6% 3 5% 5% 4 6% 32%	2725
June	1st to 10th	Day	24% 9% 3 7% 6% 4 5% 5% 5% 7% 27%	2520
	11th to 20th	Day	17% 7% 4 6% 6% 4 5% 6% 6% 8% 31%	2520
	21st to end	Day	24% 8% 3 7% 6% 4 6% 5% 4 7% 25%	2520
July	1st to 10th	Day	15% 6% 4 6% 7% 5% 6% 5% 6% 8% 31%	2520
	11th to 20th	Day	15% 7% 4 6% 6% 5% 6% 7% 7% 7% 30%	2520
	21st to end	Day	14% 7% 4 9% 6% 4 5% 6% 7% 8% 31%	2744
August	1st to 10th	Day	16% 8% 3 8% 7% 4 7% 6% 7% 9% 25%	2506
	11th to 20th	Day	15% 7% 4 6% 7% 4 6% 6% 6% 7% 32%	2337
	21st to end	Day	14% 8% 3 7% 5% 4 5% 6% 6% 8% 34%	2376
September	1st to 10th	Day	16% 6% 3 6% 6% 3 4 4 5% 8% 38%	2160
	11th to 20th	Day	15% 8% 4 6% 6% 3 4 5% 5% 6% 40%	2086
	21st to end	Day	20% 10% 3 5% 4 2 4 4 4 6% 37%	1980
October	1st to 10th	Day	23% 10% 3 6% 6% 4 4 5% 5% 6% 29%	1852
	11th to 20th	Day	22% 14% 4 8% 8% 3 5% 5% 4 4 23%	1746
	21st to end	Day	25% 14% 5% 8% 6% 4 4 4 3 4 23%	1782
November	1st to 10th	Day	16% 15% 5% 8% 7% 3 5% 4 5% 5% 29%	1671
	11th to 20th	Day	17% 16% 7% 10% 7% 3 5% 4 5% 6% 21%	1596
	21st to end	Day	16% 18% 8% 10% 7% 4 5% 4 4 5% 21%	1520
December	1st to 10th	Day	22% 16% 7% 10% 7% 3 5% 4 3 5% 18%	1520
	11th to 20th	Day	19% 15% 6% 12% 7% 3 4 4 4 6% 21%	1906
	21st to end	Day	18% 17% 8% 11% 8% 4 4 3 3 5% 19%	2772
January	1st to 10th	Night	14% 18% 7% 12% 9% 5% 6% 4 5% 5% 16%	2649
	11th to 20th	Night	12% 15% 6% 11% 9% 5% 5% 6% 5% 7% 19%	2560
	21st to end	Night	9% 10% 6% 10% 10% 5% 7% 5% 5% 6% 27%	2772
February	1st to 10th	Night	10% 14% 6% 12% 8% 5% 6% 5% 5% 6% 23%	2408
	11th to 20th	Night	10% 14% 5% 12% 8% 5% 6% 5% 6% 7% 23%	2197
	21st to end	Night	12% 13% 6% 10% 7% 3 6% 5% 5% 7% 27%	1776
March	1st to 10th	Night	14% 14% 5% 10% 7% 4 5% 5% 5% 5% 24%	2150
	11th to 20th	Night	14% 16% 5% 8% 8% 4 4 4 5% 6% 27%	2097
	21st to end	Night	13% 12% 4 8% 6% 3 6% 5% 4 5% 34%	1980
April	1st to 10th	Night	22% 12% 5% 8% 6% 3 5% 4 5% 5% 26%	1800
	11th to 20th	Night	16% 10% 3 5% 6% 4 4 4 5% 6% 37%	1775
	21st to end	Night	20% 10% 5% 8% 5% 3 4 4 5% 4 34%	1634
May	1st to 10th	Night	18% 10% 4 7% 6% 4 3 3 4 6% 36%	1459
	11th to 20th	Night	19% 9% 3 6% 4 3 4 4 5% 6% 37%	1415
	21st to end	Night	18% 8% 3 6% 5% 3 5% 4 5% 7% 37%	1550
June	1st to 10th	Night	20% 8% 3 5% 6% 3 5% 5% 6% 9% 31%	1440
	11th to 20th	Night	18% 7% 4 5% 5% 3 5% 5% 5% 8% 35%	1440
	21st to end	Night	19% 7% 3 5% 5% 4 5% 4 6% 7% 35%	1440
July	1st to 10th	Night	12% 7% 3 6% 6% 3 5% 5% 6% 8% 40%	1440
	11th to 20th	Night	12% 5% 3 6% 6% 3 4 5% 5% 8% 42%	1440
	21st to end	Night	11% 6% 4 5% 6% 3 5% 4 6% 8% 42%	1574
August	1st to 10th	Night	11% 6% 3 5% 6% 3 5% 6% 7% 9% 40%	1432
	11th to 20th	Night	13% 8% 2 6% 5% 2 5% 4 6% 7% 41%	1541
	21st to end	Night	15% 7% 3 5% 5% 3 4 4 5% 7% 41%	1980
September	1st to 10th	Night	14% 8% 2 5% 5% 3 4 4 5% 7% 43%	1800
	11th to 20th	Night	16% 5% 2 5% 5% 3 5% 4 5% 5% 45%	1873
	21st to end	Night	17% 9% 3 5% 4 3 4 4 4 7% 43%	1980
October	1st to 10th	Night	17% 10% 4 6% 6% 3 4 3 4 6% 38%	2106
	11th to 20th	Night	20% 14% 4 8% 6% 2 4 3 5% 6% 28%	2214
	21st to end	Night	23% 11% 5% 9% 7% 4 4 5% 5% 5% 23%	2574
November	1st to 10th	Night	15% 12% 5% 8% 7% 3 5% 4 5% 7% 28%	2407
	11th to 20th	Night	16% 12% 5% 11% 6% 4 6% 5% 4 6% 25%	2581
	21st to end	Night	18% 15% 6% 10% 7% 3 4 5% 4 5% 22%	2660
December	1st to 10th	Night	18% 16% 7% 13% 8% 4 5% 4 4 5% 15%	2660
	11th to 20th	Night	19% 15% 6% 11% 8% 4 4 4 5% 4 21%	3288
	21st to end	Night	19% 18% 7% 11% 9% 3 4 4 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	65% 8% 8% 12% 6%	1518
	11th to 20th	Day	61% 6% 9% 13% 9% 1	1456
	21st to end	Day	55% 7% 10% 15% 11% 2	1584
February	1st to 10th	Day	64% 5% 7% 15% 8% 2	1548
	11th to 20th	Day	59% 7% 11% 12% 11% 1	1658
	21st to end	Day	62% 6% 7% 15% 9% 3	1480
March	1st to 10th	Day	59% 6% 9% 14% 10% 3	1800
	11th to 20th	Day	56% 6% 10% 12% 14% 3	1859
	21st to end	Day	53% 6% 9% 16% 12% 4	2376
April	1st to 10th	Day	59% 5% 11% 14% 9% 3	2160
	11th to 20th	Day	53% 5% 9% 19% 11% 2	2134
	21st to end	Day	56% 7% 8% 14% 12% 3	2326
May	1st to 10th	Day	52% 6% 8% 18% 13% 2	2515
	11th to 20th	Day	50% 8% 9% 17% 14% 2	2482
	21st to end	Day	52% 7% 10% 17% 13% 1	2725
June	1st to 10th	Day	55% 8% 10% 16% 9% 1	2520
	11th to 20th	Day	48% 8% 12% 20% 10% 2	2520
	21st to end	Day	58% 8% 10% 15% 8%	2520
July	1st to 10th	Day	45% 10% 15% 21% 9%	2450
	11th to 20th	Day	46% 10% 15% 21% 8%	2445
	21st to end	Day	47% 11% 15% 19% 7%	2591
August	1st to 10th	Day	51% 11% 16% 18% 4	2492
	11th to 20th	Day	45% 11% 17% 19% 8%	2337
	21st to end	Day	43% 9% 14% 21% 11%	2376
September	1st to 10th	Day	42% 8% 15% 23% 11% 1	2160
	11th to 20th	Day	42% 8% 14% 25% 10% 1	2086
	21st to end	Day	47% 7% 12% 24% 10%	1980
October	1st to 10th	Day	53% 8% 12% 19% 8% 1	1852
	11th to 20th	Day	62% 7% 12% 15% 4	1746
	21st to end	Day	62% 8% 10% 12% 7% 1	1782
November	1st to 10th	Day	54% 7% 12% 16% 9% 1	1671
	11th to 20th	Day	60% 8% 11% 13% 8% 1	1596
	21st to end	Day	63% 8% 12% 11% 4 1	1520
December	1st to 10th	Day	67% 6% 10% 12% 6%	1520
	11th to 20th	Day	61% 7% 11% 14% 8%	1906
	21st to end	Day	64% 7% 8% 12% 8%	2772
January	1st to 10th	Night	64% 8% 10% 12% 5%	2649
	11th to 20th	Night	61% 8% 10% 12% 7% 2	2560
	21st to end	Night	53% 7% 11% 14% 14% 1	2772
February	1st to 10th	Night	57% 7% 11% 15% 7% 2	2408
	11th to 20th	Night	55% 8% 11% 15% 10% 1	2199
	21st to end	Night	53% 6% 11% 16% 12% 2	1776
March	1st to 10th	Night	58% 7% 10% 14% 10% 1	2160
	11th to 20th	Night	56% 7% 9% 14% 12% 2	2098
	21st to end	Night	50% 6% 9% 19% 13% 3	1980
April	1st to 10th	Night	57% 6% 10% 15% 11% 2	1800
	11th to 20th	Night	45% 8% 11% 21% 13% 2	1775
	21st to end	Night	50% 6% 9% 19% 13% 2	1634
May	1st to 10th	Night	50% 5% 10% 18% 14% 3	1459
	11th to 20th	Night	46% 7% 10% 20% 14% 3	1416
	21st to end	Night	47% 7% 13% 19% 13% 2	1551
June	1st to 10th	Night	47% 9% 13% 20% 10% 1	1440
	11th to 20th	Night	45% 10% 11% 21% 11% 3	1440
	21st to end	Night	47% 9% 15% 18% 11%	1440
July	1st to 10th	Night	39% 8% 19% 23% 9% 1	1400
	11th to 20th	Night	39% 9% 17% 26% 8% 1	1392
	21st to end	Night	38% 10% 19% 25% 8%	1486
August	1st to 10th	Night	37% 13% 19% 25% 6%	1422
	11th to 20th	Night	38% 10% 18% 23% 9%	1541
	21st to end	Night	39% 8% 18% 26% 9%	1980
September	1st to 10th	Night	38% 9% 16% 23% 13% 1	1800
	11th to 20th	Night	36% 8% 17% 29% 8% 1	1873
	21st to end	Night	40% 8% 13% 27% 12%	1980
October	1st to 10th	Night	48% 5% 11% 24% 11% 1	2106
	11th to 20th	Night	54% 9% 14% 18% 6%	2214
	21st to end	Night	58% 9% 11% 14% 7% 1	2574
November	1st to 10th	Night	52% 9% 14% 19% 6% 1	2407
	11th to 20th	Night	54% 10% 13% 14% 7% 1	2581
	21st to end	Night	59% 9% 12% 13% 5% 1	2660
December	1st to 10th	Night	66% 9% 11% 10% 4	2660
	11th to 20th	Night	62% 8% 9% 12% 8% 1	3288
	21st to end	Night	65% 7% 8% 13% 6% 1	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	26% 23% 36% 12% 3	180
	11th to 20th	Day	25% 18% 38% 14% 5%	164
	21st to end	Day	17% 24% 40% 14% 3 1	176
February	1st to 10th	Day	31% 31% 31% 6% 1	208
	11th to 20th	Day	26% 28% 36% 9%	316
	21st to end	Day	28% 28% 29% 12% 3	346
March	1st to 10th	Day	25% 24% 33% 15% 3	420
	11th to 20th	Day	27% 26% 31% 13% 3	420
	21st to end	Day	30% 24% 26% 12% 6% 2	462
April	1st to 10th	Day	30% 21% 31% 14% 5%	420
	11th to 20th	Day	34% 21% 22% 14% 8% 1	412
	21st to end	Day	31% 22% 32% 10% 5% 1	420
May	1st to 10th	Day	29% 20% 32% 14% 3 1	423
	11th to 20th	Day	24% 22% 31% 16% 5% 2	447
	21st to end	Day	24% 22% 34% 14% 4 1	485
June	1st to 10th	Day	27% 18% 37% 12% 6%	450
	11th to 20th	Day	22% 18% 32% 16% 10% 1	450
	21st to end	Day	28% 14% 31% 19% 6% 2	450
July	1st to 10th	Day	16% 12% 40% 24% 6% 2	445
	11th to 20th	Day	16% 13% 38% 27% 5% 1	444
	21st to end	Day	15% 11% 33% 30% 8% 2	488
August	1st to 10th	Day	17% 12% 33% 26% 9% 2	446
	11th to 20th	Day	17% 8% 33% 25% 12% 5%	439
	21st to end	Day	16% 18% 31% 18% 12% 5%	495
September	1st to 10th	Day	20% 16% 30% 20% 11% 4	450
	11th to 20th	Day	18% 14% 30% 21% 11% 5%	450
	21st to end	Day	21% 18% 28% 17% 11% 4	450
October	1st to 10th	Day	26% 18% 26% 18% 9% 3	450
	11th to 20th	Day	27% 24% 26% 14% 7% 2	423
	21st to end	Day	33% 18% 31% 15% 3	396
November	1st to 10th	Day	27% 24% 26% 18% 5% 1	365
	11th to 20th	Day	30% 21% 32% 13% 4	256
	21st to end	Day	28% 30% 30% 9% 3	180
December	1st to 10th	Day	33% 18% 29% 12% 7% 1	180
	11th to 20th	Day	29% 33% 24% 11% 3	180
	21st to end	Day	31% 26% 28% 11% 4 1	198
January	1st to 10th	Night	25% 20% 37% 15% 4	760
	11th to 20th	Night	20% 22% 35% 19% 5%	732
	21st to end	Night	14% 19% 40% 22% 4	792
February	1st to 10th	Night	17% 22% 39% 18% 4	720
	11th to 20th	Night	21% 21% 36% 18% 3	703
	21st to end	Night	21% 21% 34% 20% 3	592
March	1st to 10th	Night	25% 20% 33% 18% 3	720
	11th to 20th	Night	26% 25% 28% 15% 5% 1	720
	21st to end	Night	22% 18% 32% 22% 6% 1	792
April	1st to 10th	Night	29% 18% 27% 21% 5%	720
	11th to 20th	Night	23% 19% 31% 21% 7%	711
	21st to end	Night	27% 19% 29% 19% 6%	554
May	1st to 10th	Night	26% 15% 30% 20% 8% 1	379
	11th to 20th	Night	24% 12% 32% 25% 7%	354
	21st to end	Night	21% 13% 38% 21% 7%	389
June	1st to 10th	Night	21% 11% 36% 25% 6%	360
	11th to 20th	Night	21% 10% 28% 30% 11% 1	360
	21st to end	Night	21% 7% 26% 33% 11% 1	360
July	1st to 10th	Night	13% 7% 33% 36% 10% 1	350
	11th to 20th	Night	12% 6% 30% 36% 14% 1	348
	21st to end	Night	13% 7% 29% 38% 13% 1	394
August	1st to 10th	Night	11% 7% 20% 46% 16% 1	358
	11th to 20th	Night	14% 7% 24% 35% 18% 1	477
	21st to end	Night	16% 10% 30% 27% 14% 3	792
September	1st to 10th	Night	16% 10% 30% 33% 11% 1	720
	11th to 20th	Night	18% 10% 29% 27% 15% 1	720
	21st to end	Night	21% 12% 28% 23% 14% 1	720
October	1st to 10th	Night	22% 16% 28% 24% 10% 1	720
	11th to 20th	Night	28% 16% 28% 20% 7% 1	720
	21st to end	Night	28% 18% 29% 21% 4	792
November	1st to 10th	Night	24% 20% 29% 22% 6% 1	740
	11th to 20th	Night	25% 19% 30% 17% 8% 1	760
	21st to end	Night	27% 23% 26% 18% 5% 1	760
December	1st to 10th	Night	27% 19% 30% 19% 4	760
	11th to 20th	Night	27% 19% 33% 15% 6% 1	760
	21st to end	Night	31% 21% 29% 17% 3	836

Page generated at 2024-01-10 10:16:11. Version ac07

Copyright 2024 Attilla Danko