Canton de Shefford
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Canton de Shefford clear sky chart from 2005-11-06 to 2025-02-21.

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	19% 12% 4 9% 5% 5% 4 3 5% 6% 27%	108581
	Night	18% 15% 5% 10% 5% 4 4 3 4 5% 26%	110010
Transparency	Day	56% 7% 11% 18% 7% 1	112084
	Night	59% 6% 10% 16% 8% 1	114671
Seeing	Day	27% 17% 28% 19% 8% 2	14907
	Night	27% 14% 27% 23% 9% 1	23972

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	16% 25% 8% 19% 6% 6% 2 2 2 3 12%	3597
	11th to 20th	Day	11% 16% 10% 24% 9% 5% 5% 3 4 3 10%	3570
	21st to end	Day	12% 19% 8% 12% 6% 9% 5% 3 4 5% 18%	3960
February	1st to 10th	Day	15% 19% 6% 13% 8% 6% 4 3 4 4 19%	1705
	11th to 20th	Day	15% 19% 7% 14% 7% 4 5% 4 4 5% 17%	1913
	21st to end	Day	16% 18% 5% 10% 6% 6% 3 4 4 6% 21%	1570
March	1st to 10th	Day	21% 15% 5% 10% 6% 4 4 3 4 5% 22%	3116
	11th to 20th	Day	15% 23% 5% 11% 5% 4 3 3 4 4 23%	3257
	21st to end	Day	17% 14% 6% 10% 4 3 3 2 4 4 33%	4166
April	1st to 10th	Day	24% 15% 4 7% 5% 4 4 3 4 5% 26%	2280
	11th to 20th	Day	21% 12% 3 7% 4 4 4 2 4 4 34%	2263
	21st to end	Day	25% 11% 3 7% 5% 4 3 3 4 5% 29%	2470
May	1st to 10th	Day	24% 10% 3 7% 4 4 4 4 6% 6% 27%	4251
	11th to 20th	Day	19% 8% 3 8% 5% 6% 5% 4 7% 7% 28%	4398
	21st to end	Day	15% 8% 3 7% 5% 5% 5% 4 6% 8% 33%	4837
June	1st to 10th	Day	26% 8% 2 6% 5% 4 4 4 6% 7% 28%	2660
	11th to 20th	Day	18% 6% 2 6% 5% 5% 4 4 7% 7% 36%	2660
	21st to end	Day	24% 8% 3 7% 4 5% 5% 4 5% 6% 29%	2660
July	1st to 10th	Day	15% 6% 2 6% 5% 5% 7% 5% 7% 9% 33%	4440
	11th to 20th	Day	16% 6% 2 7% 5% 5% 5% 5% 7% 8% 32%	4440
	21st to end	Day	15% 7% 2 5% 5% 4 4 4 6% 8% 40%	4814
August	1st to 10th	Day	18% 8% 3 7% 5% 6% 5% 4 7% 9% 27%	4423
	11th to 20th	Day	19% 6% 2 7% 5% 5% 5% 4 7% 8% 33%	4004
	21st to end	Day	19% 6% 3 5% 4 4 4 3 6% 8% 38%	4180
September	1st to 10th	Day	17% 6% 2 6% 4 4 5% 4 6% 6% 40%	2280
	11th to 20th	Day	18% 5% 2 5% 3 4 4 3 5% 7% 44%	2157
	21st to end	Day	20% 7% 2 6% 4 3 4 4 7% 7% 37%	2090
October	1st to 10th	Day	26% 8% 3 6% 4 4 4 4 6% 7% 29%	2027
	11th to 20th	Day	23% 10% 4 7% 5% 4 4 4 5% 6% 28%	1815
	21st to end	Day	27% 15% 3 8% 3 4 4 2 3 5% 25%	1881
November	1st to 10th	Day	21% 14% 3 6% 5% 4 5% 4 4 4 30%	1761
	11th to 20th	Day	18% 18% 5% 9% 5% 5% 3 3 4 5% 25%	1790
	21st to end	Day	22% 19% 6% 10% 4 4 4 3 5% 4 19%	1600
December	1st to 10th	Day	19% 25% 7% 15% 5% 4 3 2 3 4 12%	2600
	11th to 20th	Day	20% 18% 7% 13% 5% 4 4 2 4 5% 19%	2986
	21st to end	Day	20% 19% 5% 12% 5% 4 5% 3 4 5% 18%	3960
January	1st to 10th	Night	14% 24% 9% 17% 6% 4 3 2 3 3 15%	6349
	11th to 20th	Night	10% 21% 9% 21% 8% 6% 5% 3 4 3 12%	6315
	21st to end	Night	13% 18% 6% 14% 8% 5% 4 3 4 4 21%	6996
February	1st to 10th	Night	15% 20% 5% 14% 7% 5% 4 3 4 4 18%	2695
	11th to 20th	Night	14% 17% 6% 14% 7% 5% 4 3 4 4 21%	2372
	21st to end	Night	15% 18% 5% 10% 6% 5% 4 3 3 4 27%	1885
March	1st to 10th	Night	22% 13% 4 8% 4 4 3 3 4 4 31%	3724
	11th to 20th	Night	17% 22% 6% 9% 5% 3 3 2 3 4 25%	3696
	21st to end	Night	14% 17% 6% 10% 4 4 3 3 4 3 32%	3466
April	1st to 10th	Night	24% 13% 4 9% 3 4 5% 3 4 5% 27%	1900
	11th to 20th	Night	24% 10% 3 7% 5% 4 3 4 3 6% 32%	1866
	21st to end	Night	22% 11% 3 7% 3 4 4 3 4 6% 32%	1710
May	1st to 10th	Night	24% 10% 3 8% 4 4 4 3 5% 7% 26%	2719
	11th to 20th	Night	22% 8% 3 8% 4 4 4 4 5% 6% 32%	2495
	21st to end	Night	18% 7% 2 6% 5% 4 4 4 5% 8% 36%	2738
June	1st to 10th	Night	26% 8% 2 5% 4 4 4 4 6% 8% 29%	1520
	11th to 20th	Night	20% 5% 3 5% 4 3 5% 3 6% 8% 37%	1520
	21st to end	Night	20% 8% 3 6% 4 5% 5% 4 6% 7% 32%	1520
July	1st to 10th	Night	15% 8% 4 8% 6% 5% 5% 4 7% 7% 32%	2520
	11th to 20th	Night	17% 7% 2 5% 5% 5% 4 4 6% 7% 38%	2520
	21st to end	Night	16% 7% 3 7% 4 4 5% 5% 6% 6% 38%	2739
August	1st to 10th	Night	24% 8% 3 6% 4 5% 4 3 5% 7% 31%	2506
	11th to 20th	Night	17% 8% 2 8% 6% 5% 5% 4 6% 6% 33%	2790
	21st to end	Night	18% 7% 2 5% 4 4 5% 3 5% 6% 41%	3476
September	1st to 10th	Night	17% 6% 3 5% 5% 3 4 3 5% 6% 42%	1900
	11th to 20th	Night	15% 5% 2 5% 4 3 4 3 5% 6% 47%	2023
	21st to end	Night	21% 5% 2 5% 5% 4 3 3 4 7% 41%	2090
October	1st to 10th	Night	21% 8% 3 7% 5% 3 4 3 5% 6% 35%	2152
	11th to 20th	Night	23% 10% 4 8% 5% 4 4 3 5% 5% 30%	2365
	21st to end	Night	27% 11% 3 8% 4 4 4 3 4 5% 26%	2717
November	1st to 10th	Night	21% 14% 3 7% 4 5% 5% 3 4 5% 28%	2537
	11th to 20th	Night	21% 15% 4 9% 4 4 3 4 5% 5% 27%	2605
	21st to end	Night	22% 18% 5% 10% 5% 3 3 2 4 5% 23%	2800
December	1st to 10th	Night	18% 28% 9% 13% 5% 4 3 2 3 3 11%	4580
	11th to 20th	Night	22% 20% 5% 14% 6% 4 4 2 2 2 19%	5208
	21st to end	Night	21% 19% 5% 10% 5% 4 4 2 3 6% 21%	6996

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	79% 5% 7% 8% 1	3598
	11th to 20th	Day	75% 8% 6% 8% 2	3600
	21st to end	Day	68% 8% 7% 10% 6%	3960
February	1st to 10th	Day	70% 5% 7% 12% 5% 1	1705
	11th to 20th	Day	70% 6% 8% 10% 5% 1	1922
	21st to end	Day	65% 6% 8% 13% 6% 1	1570
March	1st to 10th	Day	63% 6% 8% 14% 8% 1	3119
	11th to 20th	Day	65% 6% 9% 10% 10% 1	3257
	21st to end	Day	55% 5% 7% 16% 15% 1	4166
April	1st to 10th	Day	62% 5% 7% 16% 8% 1	2280
	11th to 20th	Day	54% 6% 7% 20% 12% 1	2263
	21st to end	Day	57% 5% 9% 17% 10% 2	2470
May	1st to 10th	Day	55% 7% 10% 19% 8% 1	4265
	11th to 20th	Day	52% 8% 17% 15% 7% 1	4402
	21st to end	Day	45% 9% 13% 22% 11% 1	4837
June	1st to 10th	Day	53% 7% 11% 19% 9% 1	2660
	11th to 20th	Day	45% 7% 13% 23% 11% 2	2660
	21st to end	Day	56% 6% 10% 19% 9% 1	2660
July	1st to 10th	Day	44% 8% 14% 26% 7%	4370
	11th to 20th	Day	45% 8% 15% 28% 4	4365
	21st to end	Day	42% 8% 13% 30% 7%	4661
August	1st to 10th	Day	51% 8% 15% 20% 6%	4409
	11th to 20th	Day	47% 8% 19% 20% 6%	4043
	21st to end	Day	44% 7% 16% 19% 13% 1	4180
September	1st to 10th	Day	43% 7% 13% 27% 11% 1	2280
	11th to 20th	Day	40% 5% 11% 30% 13%	2157
	21st to end	Day	45% 6% 13% 26% 10% 1	2090
October	1st to 10th	Day	46% 7% 15% 26% 6%	3365
	11th to 20th	Day	52% 5% 15% 24% 5%	2992
	21st to end	Day	52% 5% 16% 19% 7% 1	3081
November	1st to 10th	Day	56% 7% 10% 19% 7%	1761
	11th to 20th	Day	63% 7% 8% 14% 8% 1	1790
	21st to end	Day	68% 6% 12% 10% 3	1600
December	1st to 10th	Day	77% 5% 8% 8% 2	2600
	11th to 20th	Day	69% 5% 6% 15% 5%	2986
	21st to end	Day	69% 5% 7% 11% 8%	3960
January	1st to 10th	Night	76% 6% 8% 8% 2	6349
	11th to 20th	Night	76% 7% 7% 7% 2	6360
	21st to end	Night	67% 5% 8% 9% 10%	6996
February	1st to 10th	Night	69% 5% 7% 13% 6%	2695
	11th to 20th	Night	66% 6% 8% 13% 6%	2374
	21st to end	Night	62% 5% 8% 13% 11% 1	1885
March	1st to 10th	Night	57% 5% 9% 17% 9% 2	3734
	11th to 20th	Night	64% 5% 7% 12% 10% 1	3697
	21st to end	Night	56% 7% 5% 18% 11% 2	3466
April	1st to 10th	Night	60% 5% 7% 16% 11% 1	1900
	11th to 20th	Night	54% 5% 7% 20% 12% 1	1866
	21st to end	Night	53% 6% 9% 18% 12% 2	1710
May	1st to 10th	Night	57% 6% 11% 17% 8% 2	2725
	11th to 20th	Night	51% 7% 13% 20% 8% 1	2496
	21st to end	Night	45% 6% 12% 20% 16% 1	2739
June	1st to 10th	Night	52% 7% 10% 22% 9% 1	1520
	11th to 20th	Night	44% 7% 12% 22% 12% 3	1520
	21st to end	Night	51% 7% 12% 20% 9% 1	1520
July	1st to 10th	Night	48% 7% 13% 20% 11%	2480
	11th to 20th	Night	43% 8% 15% 26% 7%	2472
	21st to end	Night	45% 8% 15% 23% 10%	2651
August	1st to 10th	Night	51% 7% 13% 23% 6%	2496
	11th to 20th	Night	49% 7% 18% 19% 7%	2817
	21st to end	Night	43% 6% 13% 23% 14% 1	3476
September	1st to 10th	Night	42% 6% 12% 25% 13% 1	1900
	11th to 20th	Night	38% 5% 15% 29% 12%	2023
	21st to end	Night	43% 6% 12% 25% 13% 1	2090
October	1st to 10th	Night	51% 6% 10% 23% 9%	3594
	11th to 20th	Night	51% 5% 10% 25% 8%	3927
	21st to end	Night	53% 5% 13% 18% 10% 1	4467
November	1st to 10th	Night	58% 6% 10% 18% 7% 1	2537
	11th to 20th	Night	59% 6% 9% 15% 9% 2	2605
	21st to end	Night	65% 6% 10% 14% 4	2800
December	1st to 10th	Night	80% 5% 7% 7% 2	4580
	11th to 20th	Night	73% 5% 4 11% 7%	5208
	21st to end	Night	67% 5% 7% 12% 8%	6996

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	32% 20% 30% 13% 5%	200
	11th to 20th	Day	27% 27% 32% 12% 3 1	200
	21st to end	Day	25% 23% 33% 14% 5%	220
February	1st to 10th	Day	32% 34% 25% 7% 2	253
	11th to 20th	Day	32% 25% 33% 8% 2	461
	21st to end	Day	29% 22% 32% 16% 2	382
March	1st to 10th	Day	31% 18% 31% 17% 3	460
	11th to 20th	Day	28% 22% 32% 13% 4 1	460
	21st to end	Day	31% 23% 25% 13% 7% 1	506
April	1st to 10th	Day	35% 17% 26% 15% 6% 1	460
	11th to 20th	Day	34% 19% 25% 14% 6% 2	452
	21st to end	Day	34% 16% 30% 12% 6% 2	460
May	1st to 10th	Day	33% 16% 26% 18% 5% 2	463
	11th to 20th	Day	23% 15% 30% 21% 8% 2	487
	21st to end	Day	20% 19% 33% 21% 6% 2	529
June	1st to 10th	Day	28% 15% 29% 19% 8% 2	490
	11th to 20th	Day	21% 13% 32% 22% 11% 1	490
	21st to end	Day	28% 12% 31% 19% 7% 3	490
July	1st to 10th	Day	17% 10% 32% 27% 12% 2	485
	11th to 20th	Day	18% 11% 34% 27% 8% 3	484
	21st to end	Day	20% 11% 30% 29% 8% 2	532
August	1st to 10th	Day	19% 11% 29% 27% 12% 2	486
	11th to 20th	Day	20% 8% 27% 27% 15% 3	479
	21st to end	Day	22% 11% 24% 24% 13% 6%	539
September	1st to 10th	Day	18% 13% 30% 22% 12% 5%	490
	11th to 20th	Day	19% 10% 22% 23% 18% 9%	490
	21st to end	Day	18% 14% 26% 25% 13% 4	490
October	1st to 10th	Day	25% 15% 25% 20% 12% 3	490
	11th to 20th	Day	30% 18% 24% 18% 9% 1	445
	21st to end	Day	39% 16% 23% 18% 4	429
November	1st to 10th	Day	33% 19% 27% 16% 4 1	395
	11th to 20th	Day	29% 24% 25% 15% 6% 1	390
	21st to end	Day	37% 22% 30% 9% 3	200
December	1st to 10th	Day	35% 20% 27% 13% 5% 1	200
	11th to 20th	Day	33% 28% 27% 10% 2 1	200
	21st to end	Day	37% 18% 27% 13% 4 1	220
January	1st to 10th	Night	31% 18% 31% 16% 3	800
	11th to 20th	Night	27% 21% 32% 15% 5%	800
	21st to end	Night	22% 17% 33% 22% 6%	880
February	1st to 10th	Night	27% 18% 34% 18% 4	800
	11th to 20th	Night	24% 22% 33% 18% 3 1	783
	21st to end	Night	27% 17% 33% 22% 1	629
March	1st to 10th	Night	29% 17% 28% 21% 4	760
	11th to 20th	Night	28% 18% 26% 22% 6%	760
	21st to end	Night	27% 16% 27% 21% 7% 1	836
April	1st to 10th	Night	31% 15% 28% 21% 5%	760
	11th to 20th	Night	30% 15% 27% 20% 8%	742
	21st to end	Night	29% 16% 26% 20% 8%	570
May	1st to 10th	Night	28% 12% 29% 23% 7% 1	507
	11th to 20th	Night	24% 10% 32% 25% 9% 1	374
	21st to end	Night	22% 8% 32% 30% 7%	411
June	1st to 10th	Night	29% 9% 23% 29% 9% 1	380
	11th to 20th	Night	21% 7% 25% 34% 13%	380
	21st to end	Night	21% 9% 25% 33% 12% 1	380
July	1st to 10th	Night	15% 6% 28% 37% 13% 1	370
	11th to 20th	Night	15% 5% 24% 38% 17% 1	368
	21st to end	Night	16% 6% 25% 39% 14%	416
August	1st to 10th	Night	21% 4 19% 35% 19% 1	378
	11th to 20th	Night	17% 8% 20% 32% 22% 2	556
	21st to end	Night	19% 7% 22% 32% 19% 2	836
September	1st to 10th	Night	19% 8% 25% 32% 15% 1	760
	11th to 20th	Night	19% 7% 20% 29% 23% 2	760
	21st to end	Night	22% 8% 27% 25% 16% 2	760
October	1st to 10th	Night	25% 11% 26% 24% 13% 1	760
	11th to 20th	Night	29% 13% 23% 23% 9% 2	760
	21st to end	Night	35% 14% 27% 20% 5%	836
November	1st to 10th	Night	31% 16% 27% 18% 6% 1	780
	11th to 20th	Night	28% 19% 26% 17% 10% 1	800
	21st to end	Night	33% 18% 26% 17% 5% 1	800
December	1st to 10th	Night	35% 19% 27% 15% 4	800
	11th to 20th	Night	32% 20% 28% 16% 5% 1	800
	21st to end	Night	35% 18% 27% 16% 4	880

Page generated at 2025-02-18 03:26:26. Version ac07

Copyright © 2025 Attilla Danko.