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 2026-06-16.

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	18% 12% 4 10% 6% 5% 5% 4 5% 6% 25%	137031
	Night	16% 14% 5% 12% 6% 5% 4 3 4 5% 25%	134963
Transparency	Day	59% 5% 11% 17% 7% 1	140488
	Night	61% 5% 10% 16% 7% 1	139596
Seeing	Day	28% 18% 29% 17% 7% 2	16810
	Night	26% 15% 27% 23% 8% 1	25743

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% 16% 8% 20% 9% 6% 7% 4 3 3 11%	4661
	11th to 20th	Day	7% 19% 8% 25% 15% 6% 3 2 2 3 11%	4650
	21st to end	Day	7% 13% 9% 15% 9% 11% 8% 4 6% 4 14%	5124
February	1st to 10th	Day	12% 19% 6% 15% 10% 6% 4 3 3 4 18%	1718
	11th to 20th	Day	14% 19% 9% 13% 9% 6% 4 3 3 4 17%	2048
	21st to end	Day	12% 19% 5% 13% 8% 6% 5% 3 3 4 21%	1730
March	1st to 10th	Day	17% 18% 6% 15% 7% 4 5% 3 4 4 20%	4576
	11th to 20th	Day	13% 17% 6% 12% 5% 4 5% 3 4 5% 26%	4826
	21st to end	Day	20% 16% 6% 10% 4 4 3 3 3 4 27%	5979
April	1st to 10th	Day	23% 17% 4 10% 5% 3 3 2 4 4 25%	2520
	11th to 20th	Day	21% 14% 4 7% 5% 4 3 3 4 5% 31%	2561
	21st to end	Day	23% 13% 4 8% 5% 3 4 3 5% 5% 27%	2730
May	1st to 10th	Day	27% 11% 4 9% 5% 5% 5% 3 4 6% 20%	7771
	11th to 20th	Day	18% 9% 3 9% 6% 5% 6% 4 6% 7% 27%	8221
	21st to end	Day	21% 10% 3 7% 5% 5% 5% 4 6% 7% 29%	9060
June	1st to 10th	Day	24% 9% 2 7% 4 5% 5% 4 6% 8% 27%	2940
	11th to 20th	Day	19% 8% 3 6% 5% 5% 5% 4 7% 8% 31%	3042
	21st to end	Day	25% 9% 3 8% 5% 5% 4 3 6% 6% 25%	2800
July	1st to 10th	Day	17% 9% 3 9% 6% 6% 7% 5% 7% 7% 23%	6360
	11th to 20th	Day	16% 8% 3 7% 5% 5% 5% 4 7% 8% 33%	6360
	21st to end	Day	15% 7% 2 5% 4 4 5% 4 6% 9% 39%	6926
August	1st to 10th	Day	19% 7% 2 8% 6% 5% 6% 5% 7% 8% 27%	4516
	11th to 20th	Day	20% 8% 2 8% 5% 6% 6% 5% 7% 8% 25%	4175
	21st to end	Day	21% 8% 2 6% 5% 5% 4 4 5% 6% 34%	4391
September	1st to 10th	Day	18% 7% 3 7% 4 5% 4 3 6% 6% 38%	2400
	11th to 20th	Day	19% 7% 2 5% 4 3 3 4 5% 7% 41%	2230
	21st to end	Day	20% 8% 3 6% 4 4 4 4 7% 8% 33%	2200
October	1st to 10th	Day	22% 11% 3 6% 4 4 5% 3 4 7% 32%	2189
	11th to 20th	Day	20% 15% 4 9% 5% 5% 4 3 4 6% 24%	1856
	21st to end	Day	26% 18% 5% 8% 4 4 3 2 4 5% 20%	1980
November	1st to 10th	Day	19% 20% 4 8% 5% 3 4 3 4 4 27%	1851
	11th to 20th	Day	17% 19% 7% 12% 6% 3 3 3 4 5% 22%	1890
	21st to end	Day	18% 24% 8% 12% 4 4 4 3 3 4 16%	1681
December	1st to 10th	Day	17% 19% 9% 15% 8% 6% 4 3 3 3 13%	2350
	11th to 20th	Day	18% 17% 8% 13% 6% 4 4 2 3 4 21%	2688
	21st to end	Day	18% 21% 7% 12% 6% 4 4 3 4 4 18%	4031
January	1st to 10th	Night	11% 17% 9% 20% 9% 7% 4 3 3 4 14%	8234
	11th to 20th	Night	9% 20% 9% 23% 12% 7% 4 3 2 2 9%	8235
	21st to end	Night	6% 13% 7% 15% 9% 11% 8% 5% 5% 4 17%	9057
February	1st to 10th	Night	12% 16% 7% 15% 9% 6% 4 3 4 5% 21%	2897
	11th to 20th	Night	12% 17% 6% 15% 8% 6% 5% 3 4 4 20%	2458
	21st to end	Night	13% 16% 6% 12% 7% 5% 4 3 5% 3 26%	2076
March	1st to 10th	Night	19% 15% 5% 13% 6% 5% 5% 3 3 4 22%	5484
	11th to 20th	Night	13% 16% 6% 14% 6% 5% 4 3 4 5% 23%	5353
	21st to end	Night	15% 17% 6% 10% 8% 5% 4 3 3 5% 25%	5177
April	1st to 10th	Night	23% 14% 4 9% 4 3 4 2 4 4 28%	2100
	11th to 20th	Night	21% 12% 4 7% 5% 4 4 3 5% 5% 31%	2007
	21st to end	Night	22% 12% 4 7% 4 4 4 4 4 5% 30%	1890
May	1st to 10th	Night	25% 11% 3 8% 5% 5% 4 4 5% 6% 25%	5182
	11th to 20th	Night	23% 9% 3 6% 5% 5% 4 3 5% 7% 30%	4639
	21st to end	Night	20% 10% 3 6% 4 4 4 4 5% 7% 32%	5114
June	1st to 10th	Night	23% 10% 3 5% 5% 4 4 4 7% 8% 29%	1677
	11th to 20th	Night	21% 6% 2 5% 5% 4 4 3 6% 8% 35%	1437
	21st to end	Night	21% 8% 3 7% 5% 5% 5% 3 5% 7% 30%	1600
July	1st to 10th	Night	15% 10% 3 9% 6% 5% 5% 4 7% 8% 29%	3600
	11th to 20th	Night	21% 8% 2 6% 4 4 3 4 5% 7% 36%	3600
	21st to end	Night	12% 7% 2 7% 5% 5% 6% 4 6% 7% 38%	3926
August	1st to 10th	Night	22% 7% 3 7% 4 4 4 4 5% 7% 31%	2600
	11th to 20th	Night	17% 9% 4 10% 5% 5% 5% 4 5% 6% 31%	2872
	21st to end	Night	18% 8% 3 7% 4 4 4 4 5% 6% 37%	3504
September	1st to 10th	Night	18% 8% 2 6% 4 4 5% 3 5% 6% 40%	2000
	11th to 20th	Night	16% 6% 2 6% 3 2 3 3 5% 6% 47%	2169
	21st to end	Night	19% 8% 2 6% 4 3 4 3 3 7% 42%	2200
October	1st to 10th	Night	18% 9% 3 7% 5% 3 4 3 5% 6% 37%	2210
	11th to 20th	Night	22% 11% 3 8% 5% 4 4 3 4 6% 29%	2543
	21st to end	Night	25% 14% 3 8% 4 4 4 3 4 5% 25%	2860
November	1st to 10th	Night	20% 16% 4 9% 5% 4 4 4 4 5% 26%	2667
	11th to 20th	Night	17% 14% 6% 12% 5% 4 4 2 4 4 26%	2730
	21st to end	Night	19% 19% 7% 13% 6% 4 3 3 3 4 20%	2929
December	1st to 10th	Night	15% 19% 10% 20% 10% 4 3 2 3 3 11%	5060
	11th to 20th	Night	20% 19% 6% 15% 6% 4 4 2 3 3 17%	5726
	21st to end	Night	18% 21% 5% 12% 5% 4 3 2 3 4 23%	7150

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% 4 6% 8% 2	4662
	11th to 20th	Day	82% 2 3 9% 3	4680
	21st to end	Day	73% 4 5% 9% 9% 1	5124
February	1st to 10th	Day	71% 4 5% 12% 6% 1	1718
	11th to 20th	Day	72% 3 7% 11% 5% 1	2057
	21st to end	Day	67% 4 7% 14% 6% 2	1730
March	1st to 10th	Day	68% 5% 6% 9% 8% 3	4579
	11th to 20th	Day	60% 5% 13% 12% 9% 1	4826
	21st to end	Day	62% 3 6% 15% 13% 1	5979
April	1st to 10th	Day	64% 4 8% 14% 8% 2	2520
	11th to 20th	Day	55% 5% 8% 18% 12% 1	2561
	21st to end	Day	59% 4 8% 17% 10% 2	2730
May	1st to 10th	Day	63% 6% 8% 17% 5% 1	7783
	11th to 20th	Day	54% 7% 15% 17% 6% 2	8225
	21st to end	Day	53% 6% 10% 21% 9% 1	9061
June	1st to 10th	Day	54% 8% 11% 19% 7% 1	2940
	11th to 20th	Day	48% 6% 14% 21% 10% 1	3042
	21st to end	Day	58% 7% 10% 17% 7%	2800
July	1st to 10th	Day	56% 7% 14% 18% 5%	6290
	11th to 20th	Day	47% 6% 15% 27% 6%	6285
	21st to end	Day	41% 7% 14% 31% 8%	6728
August	1st to 10th	Day	52% 7% 17% 20% 4	4502
	11th to 20th	Day	54% 8% 16% 17% 5%	4214
	21st to end	Day	49% 6% 14% 18% 12% 1	4391
September	1st to 10th	Day	45% 7% 14% 25% 8% 1	2400
	11th to 20th	Day	41% 6% 13% 29% 11%	2230
	21st to end	Day	47% 7% 13% 23% 10%	2200
October	1st to 10th	Day	52% 5% 14% 23% 7%	3566
	11th to 20th	Day	57% 5% 12% 24% 3	2994
	21st to end	Day	57% 3 16% 17% 6%	3180
November	1st to 10th	Day	61% 5% 11% 16% 6%	1851
	11th to 20th	Day	66% 5% 9% 13% 7% 1	1890
	21st to end	Day	73% 4 10% 10% 3	1681
December	1st to 10th	Day	77% 3 8% 8% 4	2350
	11th to 20th	Day	69% 3 5% 15% 7%	2688
	21st to end	Day	71% 3 6% 11% 9% 1	4031
January	1st to 10th	Night	76% 4 7% 9% 4	8234
	11th to 20th	Night	83% 4 5% 6% 3	8280
	21st to end	Night	69% 5% 6% 11% 10%	9057
February	1st to 10th	Night	67% 4 8% 13% 7% 1	2897
	11th to 20th	Night	68% 5% 7% 11% 7%	2460
	21st to end	Night	63% 5% 7% 15% 10% 1	2076
March	1st to 10th	Night	66% 5% 7% 12% 8% 2	5494
	11th to 20th	Night	63% 5% 11% 12% 7% 1	5354
	21st to end	Night	63% 3 6% 16% 10% 1	5177
April	1st to 10th	Night	59% 4 9% 15% 11% 1	2100
	11th to 20th	Night	54% 5% 9% 20% 11% 2	2007
	21st to end	Night	55% 6% 9% 18% 11% 2	1890
May	1st to 10th	Night	58% 6% 11% 16% 7% 1	5188
	11th to 20th	Night	53% 6% 12% 22% 6% 1	4640
	21st to end	Night	50% 6% 12% 18% 14%	5115
June	1st to 10th	Night	52% 8% 11% 20% 9%	1677
	11th to 20th	Night	45% 7% 12% 23% 11% 2	1437
	21st to end	Night	53% 7% 12% 18% 10%	1600
July	1st to 10th	Night	52% 6% 18% 18% 6%	3560
	11th to 20th	Night	47% 6% 17% 24% 7%	3552
	21st to end	Night	44% 6% 16% 27% 7%	3809
August	1st to 10th	Night	52% 6% 14% 23% 4	2590
	11th to 20th	Night	53% 8% 14% 19% 6%	2899
	21st to end	Night	48% 6% 12% 22% 12%	3504
September	1st to 10th	Night	44% 7% 13% 25% 10% 1	2000
	11th to 20th	Night	38% 5% 15% 31% 10% 1	2169
	21st to end	Night	44% 6% 12% 25% 12% 1	2200
October	1st to 10th	Night	50% 4 12% 25% 10%	3613
	11th to 20th	Night	54% 5% 11% 25% 5%	4144
	21st to end	Night	53% 4 14% 18% 8% 2	4610
November	1st to 10th	Night	60% 6% 12% 16% 5% 1	2667
	11th to 20th	Night	62% 5% 11% 13% 8% 1	2730
	21st to end	Night	69% 5% 10% 12% 4	2929
December	1st to 10th	Night	81% 3 7% 7% 2	5060
	11th to 20th	Night	73% 4 5% 12% 6%	5727
	21st to end	Night	67% 4 6% 14% 8%	7150

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% 26% 34% 10% 1	220
	11th to 20th	Day	31% 23% 33% 11% 2	220
	21st to end	Day	26% 26% 30% 16% 3	242
February	1st to 10th	Day	30% 29% 29% 10% 1 1	243
	11th to 20th	Day	29% 27% 32% 10% 2	536
	21st to end	Day	29% 25% 27% 17% 2	446
March	1st to 10th	Day	28% 26% 28% 15% 4	540
	11th to 20th	Day	30% 26% 27% 12% 4 1	540
	21st to end	Day	34% 21% 27% 11% 7% 1	594
April	1st to 10th	Day	38% 19% 25% 12% 4 2	540
	11th to 20th	Day	34% 21% 23% 15% 6% 1	532
	21st to end	Day	34% 19% 28% 13% 4 2	540
May	1st to 10th	Day	33% 18% 28% 15% 4 1	543
	11th to 20th	Day	27% 16% 30% 19% 7% 2	567
	21st to end	Day	25% 22% 32% 16% 5%	617
June	1st to 10th	Day	27% 18% 31% 17% 6% 1	570
	11th to 20th	Day	25% 14% 29% 22% 10%	722
	21st to end	Day	27% 15% 34% 16% 6% 2	530
July	1st to 10th	Day	21% 11% 34% 24% 9% 1	525
	11th to 20th	Day	19% 12% 39% 21% 7% 1	524
	21st to end	Day	22% 12% 34% 26% 6% 1	576
August	1st to 10th	Day	20% 11% 29% 26% 11% 2	526
	11th to 20th	Day	21% 8% 27% 26% 16% 2	519
	21st to end	Day	23% 13% 25% 21% 12% 5%	583
September	1st to 10th	Day	20% 12% 31% 22% 9% 5%	530
	11th to 20th	Day	21% 10% 23% 24% 15% 7%	530
	21st to end	Day	21% 13% 28% 24% 10% 4	530
October	1st to 10th	Day	24% 14% 27% 21% 10% 4	530
	11th to 20th	Day	30% 16% 28% 14% 11% 1	450
	21st to end	Day	39% 17% 25% 15% 4	462
November	1st to 10th	Day	36% 16% 29% 16% 3	425
	11th to 20th	Day	31% 18% 30% 14% 6% 1	430
	21st to end	Day	34% 22% 30% 11% 2	246
December	1st to 10th	Day	33% 20% 30% 13% 4	220
	11th to 20th	Day	33% 27% 27% 10% 2	220
	21st to end	Day	36% 21% 29% 10% 3 1	242
January	1st to 10th	Night	26% 23% 32% 17% 3	840
	11th to 20th	Night	27% 22% 31% 17% 4	840
	21st to end	Night	20% 21% 33% 21% 5% 1	924
February	1st to 10th	Night	21% 22% 32% 20% 5%	840
	11th to 20th	Night	25% 21% 34% 17% 2	823
	21st to end	Night	25% 20% 34% 19% 3	692
March	1st to 10th	Night	26% 19% 33% 20% 3	840
	11th to 20th	Night	28% 22% 26% 19% 4 1	840
	21st to end	Night	26% 16% 29% 23% 6% 1	924
April	1st to 10th	Night	33% 15% 27% 20% 5%	840
	11th to 20th	Night	29% 16% 28% 21% 6%	763
	21st to end	Night	30% 16% 29% 19% 6% 1	630
May	1st to 10th	Night	28% 12% 29% 23% 6% 1	604
	11th to 20th	Night	22% 10% 32% 29% 6% 1	414
	21st to end	Night	24% 10% 30% 28% 7%	455
June	1st to 10th	Night	28% 9% 26% 29% 9%	420
	11th to 20th	Night	22% 8% 24% 36% 11%	410
	21st to end	Night	22% 8% 26% 33% 11% 1	400
July	1st to 10th	Night	16% 6% 28% 34% 14% 1	390
	11th to 20th	Night	18% 5% 24% 37% 14% 1	388
	21st to end	Night	16% 7% 23% 39% 14%	438
August	1st to 10th	Night	19% 5% 17% 38% 20% 1	399
	11th to 20th	Night	18% 6% 19% 36% 19% 1	592
	21st to end	Night	21% 5% 22% 31% 18% 2	824
September	1st to 10th	Night	22% 7% 24% 32% 13% 2	800
	11th to 20th	Night	19% 7% 20% 29% 22% 2	800
	21st to end	Night	23% 10% 25% 26% 15% 2	800
October	1st to 10th	Night	24% 11% 27% 25% 13% 1	800
	11th to 20th	Night	28% 14% 25% 23% 9% 2	800
	21st to end	Night	33% 16% 28% 20% 5%	880
November	1st to 10th	Night	31% 17% 27% 20% 6%	820
	11th to 20th	Night	28% 19% 29% 16% 9% 1	840
	21st to end	Night	32% 22% 22% 19% 5%	851
December	1st to 10th	Night	33% 20% 26% 17% 5%	950
	11th to 20th	Night	29% 24% 26% 16% 5%	948
	21st to end	Night	35% 18% 27% 16% 4	924

Page generated at 2026-06-13 02:31:45. Version ac07

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