Mont Ham-Nord
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mont Ham-Nord clear sky chart from 2005-11-06 to 2024-09-14.

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% 6% 5% 4 3 5% 6% 26%	100670
	Night	18% 14% 5% 10% 6% 5% 4 3 4 5% 27%	97196
Transparency	Day	58% 6% 11% 17% 7% 1	100428
	Night	60% 6% 11% 16% 7% 1	97059
Seeing	Day	27% 17% 29% 18% 7% 2	14637
	Night	26% 15% 27% 23% 8% 1	23464

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% 19% 9% 18% 11% 5% 4 4 3 3 11%	2517
	11th to 20th	Day	10% 16% 7% 23% 13% 5% 2 2 2 2 17%	2520
	21st to end	Day	11% 17% 10% 13% 7% 8% 5% 3 4 5% 17%	2772
February	1st to 10th	Day	13% 21% 6% 14% 9% 6% 5% 3 3 4 17%	1553
	11th to 20th	Day	14% 20% 9% 13% 9% 6% 4 3 3 4 16%	1848
	21st to end	Day	13% 20% 6% 12% 7% 6% 5% 3 4 5% 20%	1570
March	1st to 10th	Day	18% 16% 5% 12% 7% 4 3 3 4 5% 23%	3116
	11th to 20th	Day	15% 21% 7% 14% 5% 4 4 2 3 4 20%	3306
	21st to end	Day	17% 15% 5% 11% 4 4 3 2 3 4 32%	4088
April	1st to 10th	Day	22% 18% 4 10% 5% 4 3 2 4 3 25%	2280
	11th to 20th	Day	20% 14% 3 7% 5% 4 3 3 4 5% 32%	2314
	21st to end	Day	23% 14% 4 8% 5% 4 3 3 4 5% 27%	2470
May	1st to 10th	Day	24% 9% 3 8% 5% 5% 4 3 5% 6% 28%	4184
	11th to 20th	Day	19% 9% 3 7% 5% 4 6% 4 6% 8% 28%	4398
	21st to end	Day	17% 8% 3 8% 5% 6% 6% 4 7% 8% 29%	4837
June	1st to 10th	Day	25% 10% 2 7% 4 5% 5% 4 6% 8% 26%	2660
	11th to 20th	Day	19% 7% 2 6% 5% 5% 5% 4 7% 8% 32%	2820
	21st to end	Day	26% 9% 3 8% 5% 5% 4 3 6% 6% 25%	2660
July	1st to 10th	Day	16% 8% 3 8% 6% 6% 6% 5% 6% 7% 29%	4440
	11th to 20th	Day	17% 9% 3 7% 5% 6% 5% 5% 7% 7% 30%	4440
	21st to end	Day	17% 7% 2 6% 4 4 5% 4 6% 7% 38%	4814
August	1st to 10th	Day	19% 7% 2 8% 6% 5% 6% 5% 7% 8% 26%	4377
	11th to 20th	Day	20% 8% 2 8% 5% 6% 6% 5% 7% 8% 24%	4045
	21st to end	Day	21% 8% 2 6% 5% 5% 4 4 5% 6% 34%	4257
September	1st to 10th	Day	18% 7% 3 7% 4 5% 4 3 6% 6% 37%	2280
	11th to 20th	Day	21% 7% 2 5% 3 3 4 4 5% 7% 39%	2044
	21st to end	Day	20% 8% 2 6% 4 4 4 4 7% 8% 33%	1980
October	1st to 10th	Day	24% 11% 3 6% 4 4 5% 3 4 7% 29%	1971
	11th to 20th	Day	21% 15% 4 9% 5% 5% 5% 3 4 6% 22%	1671
	21st to end	Day	27% 19% 5% 8% 4 4 3 2 4 5% 19%	1782
November	1st to 10th	Day	19% 19% 4 8% 5% 3 4 3 4 4 28%	1671
	11th to 20th	Day	18% 18% 6% 11% 6% 3 3 3 4 6% 22%	1710
	21st to end	Day	18% 23% 7% 11% 5% 4 4 3 4 5% 18%	1522
December	1st to 10th	Day	22% 23% 8% 13% 5% 4 3 2 3 3 14%	1330
	11th to 20th	Day	20% 17% 7% 12% 6% 4 4 2 3 3 22%	1668
	21st to end	Day	22% 22% 7% 14% 5% 3 3 2 3 3 16%	2755
January	1st to 10th	Night	14% 20% 10% 16% 9% 5% 3 2 3 4 14%	4429
	11th to 20th	Night	11% 18% 6% 18% 12% 7% 5% 3 3 3 15%	4440
	21st to end	Night	10% 19% 8% 15% 7% 7% 5% 3 4 4 18%	4884
February	1st to 10th	Night	13% 16% 7% 14% 9% 5% 4 3 4 5% 20%	2623
	11th to 20th	Night	13% 17% 7% 15% 7% 6% 5% 3 4 4 19%	2218
	21st to end	Night	14% 15% 5% 12% 7% 5% 4 3 5% 3 26%	1884
March	1st to 10th	Night	21% 16% 4 7% 5% 3 5% 3 3 4 28%	3724
	11th to 20th	Night	15% 19% 7% 15% 6% 4 4 3 3 3 22%	3653
	21st to end	Night	15% 16% 5% 10% 7% 4 4 3 3 4 29%	3540
April	1st to 10th	Night	23% 13% 4 9% 4 3 4 3 4 4 29%	1900
	11th to 20th	Night	21% 11% 3 7% 5% 4 4 3 5% 5% 33%	1814
	21st to end	Night	23% 12% 4 7% 4 4 4 4 4 5% 29%	1710
May	1st to 10th	Night	24% 9% 3 7% 5% 5% 4 4 5% 6% 28%	2784
	11th to 20th	Night	22% 9% 3 6% 4 4 3 3 5% 7% 33%	2495
	21st to end	Night	18% 7% 2 6% 4 4 5% 4 6% 8% 35%	2738
June	1st to 10th	Night	23% 10% 3 5% 5% 4 4 3 7% 8% 27%	1517
	11th to 20th	Night	20% 6% 2 5% 5% 4 4 3 6% 8% 36%	1332
	21st to end	Night	21% 9% 3 7% 6% 5% 5% 3 5% 7% 30%	1520
July	1st to 10th	Night	12% 10% 3 9% 6% 6% 4 4 6% 8% 31%	2520
	11th to 20th	Night	19% 8% 3 6% 5% 5% 4 4 5% 7% 35%	2520
	21st to end	Night	16% 7% 2 6% 5% 4 5% 3 6% 7% 39%	2739
August	1st to 10th	Night	23% 8% 3 8% 4 4 4 4 5% 7% 30%	2520
	11th to 20th	Night	18% 10% 4 10% 5% 5% 5% 4 5% 7% 29%	2782
	21st to end	Night	18% 8% 2 8% 4 4 4 3 5% 6% 37%	3397
September	1st to 10th	Night	18% 8% 2 6% 4 4 5% 3 5% 6% 39%	1900
	11th to 20th	Night	18% 6% 2 5% 3 2 3 3 5% 6% 45%	1993
	21st to end	Night	19% 7% 2 6% 4 3 4 3 3 6% 42%	1980
October	1st to 10th	Night	19% 9% 3 7% 5% 3 4 3 5% 6% 35%	1988
	11th to 20th	Night	24% 11% 3 8% 5% 4 4 3 4 5% 28%	2288
	21st to end	Night	26% 14% 4 8% 4 4 4 3 4 5% 24%	2574
November	1st to 10th	Night	20% 15% 4 8% 5% 4 4 4 4 5% 27%	2407
	11th to 20th	Night	18% 14% 6% 11% 6% 4 4 2 4 4 26%	2470
	21st to end	Night	19% 18% 6% 12% 6% 4 3 3 3 4 22%	2649
December	1st to 10th	Night	20% 23% 8% 13% 6% 4 4 2 3 3 14%	2850
	11th to 20th	Night	19% 19% 7% 16% 6% 4 3 2 3 3 16%	3530
	21st to end	Night	22% 21% 5% 12% 5% 4 3 2 3 3 20%	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	78% 5% 8% 8% 2	2518
	11th to 20th	Day	76% 3 4 13% 3 1	2520
	21st to end	Day	70% 6% 8% 10% 6% 1	2772
February	1st to 10th	Day	73% 4 6% 11% 6% 1	1553
	11th to 20th	Day	73% 3 8% 10% 5% 1	1857
	21st to end	Day	67% 4 8% 14% 6% 2	1570
March	1st to 10th	Day	62% 7% 7% 12% 9% 2	3119
	11th to 20th	Day	67% 5% 9% 11% 7% 1	3306
	21st to end	Day	58% 4 7% 16% 14% 2	4088
April	1st to 10th	Day	64% 5% 9% 14% 8% 2	2280
	11th to 20th	Day	54% 5% 9% 19% 12% 1	2314
	21st to end	Day	59% 5% 8% 16% 10% 2	2470
May	1st to 10th	Day	54% 8% 11% 18% 8% 1	4198
	11th to 20th	Day	50% 10% 19% 14% 6% 1	4402
	21st to end	Day	48% 9% 12% 20% 11%	4837
June	1st to 10th	Day	54% 8% 11% 19% 7% 1	2660
	11th to 20th	Day	48% 7% 15% 21% 10% 1	2820
	21st to end	Day	58% 7% 10% 17% 7%	2660
July	1st to 10th	Day	50% 8% 14% 21% 7%	4370
	11th to 20th	Day	51% 6% 16% 24% 4	4365
	21st to end	Day	44% 7% 12% 29% 7%	4661
August	1st to 10th	Day	53% 7% 16% 20% 4	4363
	11th to 20th	Day	54% 9% 16% 16% 4	4084
	21st to end	Day	49% 6% 14% 18% 12% 2	4257
September	1st to 10th	Day	45% 7% 15% 23% 9% 1	2280
	11th to 20th	Day	43% 6% 13% 26% 11%	2044
	21st to end	Day	47% 7% 13% 23% 9%	1980
October	1st to 10th	Day	54% 6% 12% 20% 8%	1971
	11th to 20th	Day	62% 7% 13% 15% 3	1671
	21st to end	Day	68% 4 9% 13% 5% 1	1782
November	1st to 10th	Day	59% 6% 11% 17% 7%	1671
	11th to 20th	Day	65% 6% 9% 13% 7% 1	1710
	21st to end	Day	70% 5% 11% 11% 3	1522
December	1st to 10th	Day	77% 5% 7% 8% 3	1330
	11th to 20th	Day	70% 4 6% 14% 6%	1668
	21st to end	Day	76% 4 5% 9% 5% 1	2755
January	1st to 10th	Night	74% 6% 9% 8% 2	4429
	11th to 20th	Night	74% 6% 7% 9% 3	4440
	21st to end	Night	69% 7% 8% 10% 5% 1	4884
February	1st to 10th	Night	68% 4 9% 12% 6% 1	2623
	11th to 20th	Night	69% 5% 8% 11% 7%	2220
	21st to end	Night	62% 5% 8% 14% 10% 1	1884
March	1st to 10th	Night	60% 6% 10% 15% 8% 2	3734
	11th to 20th	Night	68% 5% 6% 12% 7% 1	3654
	21st to end	Night	61% 4 8% 17% 9% 2	3540
April	1st to 10th	Night	58% 5% 9% 15% 12% 1	1900
	11th to 20th	Night	52% 6% 9% 20% 11% 2	1814
	21st to end	Night	56% 7% 9% 16% 10% 2	1710
May	1st to 10th	Night	53% 9% 12% 17% 8% 1	2790
	11th to 20th	Night	48% 8% 14% 20% 8% 1	2496
	21st to end	Night	44% 8% 14% 17% 15% 1	2739
June	1st to 10th	Night	53% 8% 12% 18% 8%	1517
	11th to 20th	Night	44% 7% 12% 24% 11% 2	1332
	21st to end	Night	54% 7% 12% 18% 9%	1520
July	1st to 10th	Night	50% 7% 16% 18% 9%	2480
	11th to 20th	Night	48% 7% 18% 21% 6%	2472
	21st to end	Night	44% 7% 16% 26% 6%	2651
August	1st to 10th	Night	53% 6% 14% 22% 4	2510
	11th to 20th	Night	54% 9% 14% 18% 6%	2809
	21st to end	Night	47% 6% 12% 22% 12%	3397
September	1st to 10th	Night	45% 7% 13% 24% 10% 1	1900
	11th to 20th	Night	39% 6% 17% 30% 9% 1	1993
	21st to end	Night	44% 6% 12% 25% 12% 1	1980
October	1st to 10th	Night	49% 6% 11% 23% 11%	1988
	11th to 20th	Night	57% 7% 13% 19% 4	2288
	21st to end	Night	62% 6% 10% 14% 8% 1	2574
November	1st to 10th	Night	59% 6% 12% 17% 6% 1	2407
	11th to 20th	Night	62% 5% 12% 13% 7% 2	2470
	21st to end	Night	67% 5% 10% 13% 4	2649
December	1st to 10th	Night	77% 4 7% 9% 3	2850
	11th to 20th	Night	74% 5% 6% 10% 5%	3531
	21st to end	Night	71% 5% 6% 14% 4	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	28% 24% 35% 11% 1 1	180
	11th to 20th	Day	31% 24% 31% 12% 2	180
	21st to end	Day	22% 27% 30% 17% 4 1	198
February	1st to 10th	Day	34% 30% 27% 8% 1 1	198
	11th to 20th	Day	30% 28% 31% 9% 2	456
	21st to end	Day	30% 25% 26% 18% 2	382
March	1st to 10th	Day	27% 25% 28% 16% 4	460
	11th to 20th	Day	28% 26% 27% 13% 4 1	460
	21st to end	Day	31% 22% 27% 12% 8% 1	506
April	1st to 10th	Day	37% 18% 26% 13% 4 2	460
	11th to 20th	Day	32% 21% 23% 15% 7% 2	452
	21st to end	Day	34% 19% 28% 12% 4 2	460
May	1st to 10th	Day	31% 19% 27% 17% 5% 1	463
	11th to 20th	Day	24% 15% 31% 20% 8% 2	487
	21st to end	Day	23% 21% 32% 17% 6% 1	529
June	1st to 10th	Day	28% 18% 30% 16% 7% 1	490
	11th to 20th	Day	23% 13% 29% 23% 11%	650
	21st to end	Day	27% 14% 33% 17% 7% 2	490
July	1st to 10th	Day	20% 10% 34% 25% 9% 1	485
	11th to 20th	Day	20% 11% 39% 21% 7% 1	484
	21st to end	Day	22% 10% 33% 27% 6% 1	532
August	1st to 10th	Day	22% 12% 29% 24% 11% 2	486
	11th to 20th	Day	22% 8% 27% 25% 16% 1	479
	21st to end	Day	23% 13% 25% 21% 12% 6%	539
September	1st to 10th	Day	21% 12% 31% 21% 10% 5%	490
	11th to 20th	Day	23% 11% 22% 22% 15% 7%	463
	21st to end	Day	20% 14% 28% 23% 10% 4	450
October	1st to 10th	Day	26% 14% 26% 20% 11% 4	450
	11th to 20th	Day	31% 16% 28% 13% 11% 1	385
	21st to end	Day	39% 17% 24% 15% 5%	396
November	1st to 10th	Day	34% 15% 30% 18% 4	365
	11th to 20th	Day	32% 18% 28% 15% 6% 1	370
	21st to end	Day	30% 23% 31% 13% 3	204
December	1st to 10th	Day	36% 22% 25% 12% 4 1	180
	11th to 20th	Day	33% 27% 27% 11% 2 1	180
	21st to end	Day	38% 23% 26% 9% 3 1	198
January	1st to 10th	Night	26% 23% 31% 17% 3	760
	11th to 20th	Night	26% 22% 31% 17% 4	760
	21st to end	Night	20% 21% 32% 22% 5% 1	836
February	1st to 10th	Night	22% 22% 32% 20% 4	760
	11th to 20th	Night	24% 22% 33% 17% 3	743
	21st to end	Night	24% 21% 32% 19% 3	628
March	1st to 10th	Night	25% 18% 33% 21% 3	760
	11th to 20th	Night	27% 21% 27% 19% 5% 1	760
	21st to end	Night	25% 16% 28% 24% 6% 1	836
April	1st to 10th	Night	32% 15% 28% 21% 5%	760
	11th to 20th	Night	28% 16% 27% 22% 6%	690
	21st to end	Night	30% 15% 28% 20% 6% 1	570
May	1st to 10th	Night	28% 12% 29% 23% 7% 1	546
	11th to 20th	Night	21% 11% 31% 29% 6% 1	374
	21st to end	Night	24% 9% 31% 28% 8%	411
June	1st to 10th	Night	28% 9% 26% 28% 8% 1	380
	11th to 20th	Night	21% 7% 24% 36% 11%	380
	21st to end	Night	23% 7% 26% 33% 11% 1	380
July	1st to 10th	Night	16% 7% 28% 34% 14% 1	370
	11th to 20th	Night	17% 6% 25% 37% 14% 1	368
	21st to end	Night	17% 6% 23% 39% 15%	416
August	1st to 10th	Night	20% 5% 17% 38% 19% 1	379
	11th to 20th	Night	19% 6% 20% 36% 18% 1	562
	21st to end	Night	21% 5% 22% 31% 19% 2	783
September	1st to 10th	Night	23% 7% 24% 31% 13% 2	760
	11th to 20th	Night	21% 8% 21% 29% 19% 3	736
	21st to end	Night	23% 10% 26% 25% 15% 2	720
October	1st to 10th	Night	24% 12% 26% 24% 12% 1	720
	11th to 20th	Night	29% 14% 24% 22% 9% 2	720
	21st to end	Night	34% 16% 27% 20% 4	792
November	1st to 10th	Night	29% 16% 28% 20% 6%	740
	11th to 20th	Night	27% 18% 29% 16% 9% 1	760
	21st to end	Night	31% 21% 23% 20% 5%	769
December	1st to 10th	Night	35% 20% 24% 16% 5%	850
	11th to 20th	Night	28% 23% 26% 16% 5%	849
	21st to end	Night	35% 19% 27% 16% 4	836

Page generated at 2024-09-11 10:00:08. Version ac07

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