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 2024-01-31.

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	20% 12% 5% 8% 6% 3 4 4 5% 6% 26%	74609
	Night	19% 13% 5% 9% 7% 3 4 4 4 5% 27%	75466
Transparency	Day	58% 6% 11% 17% 8% 1	74314
	Night	59% 6% 10% 16% 8% 1	75296
Seeing	Day	27% 17% 29% 18% 7% 2	13741
	Night	26% 15% 27% 23% 8% 1	22776

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	18% 19% 9% 13% 11% 4 4 5% 4 3 10%	1517
	11th to 20th	Day	16% 18% 7% 14% 11% 3 4 3 3 3 18%	1520
	21st to end	Day	10% 14% 9% 11% 11% 4 6% 5% 4 5% 21%	1664
February	1st to 10th	Day	13% 20% 7% 13% 10% 4 6% 4 3 4 16%	1472
	11th to 20th	Day	15% 18% 10% 12% 9% 4 5% 4 3 4 16%	1748
	21st to end	Day	14% 18% 7% 11% 8% 5% 5% 4 4 4 20%	1480
March	1st to 10th	Day	15% 15% 6% 11% 9% 4 4 4 5% 5% 23%	1797
	11th to 20th	Day	17% 14% 6% 8% 8% 3 4 4 4 5% 26%	1876
	21st to end	Day	16% 16% 6% 9% 7% 3 4 4 4 4 27%	2326
April	1st to 10th	Day	23% 16% 5% 9% 7% 3 3 3 4 4 24%	2160
	11th to 20th	Day	21% 13% 3 6% 5% 3 4 4 4 5% 33%	2190
	21st to end	Day	23% 13% 4 7% 6% 3 4 4 4 5% 27%	2340
May	1st to 10th	Day	24% 9% 4 6% 6% 4 4 4 4 5% 31%	2376
	11th to 20th	Day	20% 10% 3 6% 6% 4 4 4 5% 7% 32%	2478
	21st to end	Day	22% 8% 3 6% 6% 4 5% 5% 6% 7% 28%	2725
June	1st to 10th	Day	27% 9% 3 6% 4 3 5% 4 5% 8% 26%	2520
	11th to 20th	Day	20% 7% 3 5% 5% 3 5% 5% 6% 8% 32%	2672
	21st to end	Day	25% 8% 4 7% 6% 3 5% 4 6% 6% 26%	2520
July	1st to 10th	Day	19% 6% 3 6% 6% 3 6% 6% 5% 8% 33%	2520
	11th to 20th	Day	18% 7% 3 6% 5% 4 5% 5% 6% 9% 31%	2520
	21st to end	Day	21% 7% 3 6% 6% 3 6% 5% 6% 8% 29%	2744
August	1st to 10th	Day	21% 7% 3 6% 6% 4 6% 5% 6% 8% 28%	2487
	11th to 20th	Day	19% 8% 3 6% 5% 3 5% 6% 6% 7% 32%	2304
	21st to end	Day	20% 6% 3 5% 6% 4 5% 5% 5% 7% 34%	2425
September	1st to 10th	Day	19% 7% 3 6% 5% 3 4 4 6% 6% 36%	2160
	11th to 20th	Day	21% 7% 2 4 4 2 4 5% 5% 7% 39%	2008
	21st to end	Day	20% 8% 3 5% 4 3 4 5% 7% 8% 33%	1980
October	1st to 10th	Day	24% 10% 3 5% 5% 3 5% 4 4 7% 29%	1971
	11th to 20th	Day	22% 15% 4 8% 6% 4 5% 4 4 6% 22%	1671
	21st to end	Day	28% 18% 5% 7% 5% 3 3 3 4 5% 19%	1782
November	1st to 10th	Day	19% 18% 4 7% 6% 2 4 3 4 5% 28%	1671
	11th to 20th	Day	19% 16% 7% 10% 7% 2 3 4 4 6% 22%	1710
	21st to end	Day	18% 21% 8% 9% 6% 3 4 4 4 5% 18%	1522
December	1st to 10th	Day	22% 21% 9% 12% 7% 3 4 3 3 3 14%	1330
	11th to 20th	Day	20% 16% 8% 10% 7% 3 4 2 3 3 22%	1668
	21st to end	Day	22% 21% 7% 11% 9% 2 3 3 3 3 16%	2755
January	1st to 10th	Night	16% 19% 11% 13% 10% 5% 5% 4 3 4 13%	2649
	11th to 20th	Night	15% 18% 7% 14% 10% 4 6% 4 3 3 17%	2660
	21st to end	Night	10% 15% 7% 13% 9% 5% 7% 5% 4 4 20%	2919
February	1st to 10th	Night	13% 15% 7% 12% 11% 4 5% 4 3 5% 19%	2484
	11th to 20th	Night	14% 15% 8% 13% 8% 5% 5% 4 4 4 20%	2098
	21st to end	Night	14% 15% 6% 11% 8% 3 5% 4 4 3 26%	1776
March	1st to 10th	Night	14% 15% 7% 9% 8% 4 5% 4 4 5% 26%	2150
	11th to 20th	Night	17% 14% 6% 10% 7% 3 4 5% 4 4 27%	2083
	21st to end	Night	17% 12% 5% 8% 6% 3 4 6% 3 4 31%	2026
April	1st to 10th	Night	24% 12% 5% 8% 5% 2 5% 4 4 4 28%	1800
	11th to 20th	Night	21% 9% 3 7% 5% 3 4 4 5% 5% 34%	1718
	21st to end	Night	23% 11% 4 6% 5% 3 4 4 4 5% 29%	1620
May	1st to 10th	Night	25% 9% 3 5% 6% 3 3 4 5% 6% 31%	1598
	11th to 20th	Night	19% 9% 4 5% 5% 3 5% 4 4 6% 35%	1415
	21st to end	Night	20% 7% 3 6% 5% 2 5% 5% 5% 7% 35%	1550
June	1st to 10th	Night	24% 9% 4 5% 5% 3 5% 4 7% 8% 27%	1437
	11th to 20th	Night	21% 6% 2 5% 5% 3 5% 5% 6% 8% 36%	1261
	21st to end	Night	21% 7% 3 7% 6% 3 5% 5% 6% 7% 30%	1440
July	1st to 10th	Night	15% 7% 3 6% 5% 4 5% 5% 6% 9% 36%	1440
	11th to 20th	Night	15% 6% 3 5% 6% 3 6% 6% 6% 8% 35%	1440
	21st to end	Night	17% 7% 3 6% 6% 3 6% 5% 5% 8% 34%	1574
August	1st to 10th	Night	17% 5% 2 4 5% 3 5% 6% 6% 9% 37%	1432
	11th to 20th	Night	16% 7% 3 6% 6% 3 4 4 5% 8% 36%	1596
	21st to end	Night	17% 7% 2 5% 5% 3 5% 4 5% 7% 39%	1929
September	1st to 10th	Night	18% 8% 2 5% 4 3 5% 4 5% 6% 39%	1800
	11th to 20th	Night	18% 6% 2 4 4 2 3 5% 5% 6% 45%	1951
	21st to end	Night	20% 7% 2 5% 4 2 3 4 3 6% 42%	1980
October	1st to 10th	Night	19% 9% 3 6% 5% 3 4 4 5% 6% 35%	1988
	11th to 20th	Night	24% 11% 3 7% 6% 3 5% 4 4 5% 28%	2288
	21st to end	Night	26% 14% 4 6% 5% 3 4 4 4 5% 24%	2574
November	1st to 10th	Night	20% 14% 5% 7% 6% 3 3 5% 4 5% 27%	2407
	11th to 20th	Night	18% 13% 6% 10% 7% 4 5% 3 4 4 26%	2470
	21st to end	Night	19% 17% 7% 11% 7% 3 3 3 3 4 22%	2649
December	1st to 10th	Night	21% 21% 9% 12% 7% 3 4 3 3 3 14%	2850
	11th to 20th	Night	20% 18% 8% 14% 8% 4 4 3 3 3 16%	3530
	21st to end	Night	23% 21% 5% 10% 7% 3 3 3 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% 7% 8% 3	1518
	11th to 20th	Day	74% 3 6% 12% 4 1	1520
	21st to end	Day	66% 4 8% 13% 7% 1	1664
February	1st to 10th	Day	74% 4 5% 10% 6% 1	1472
	11th to 20th	Day	73% 3 8% 9% 5% 1	1757
	21st to end	Day	68% 4 7% 14% 6% 1	1480
March	1st to 10th	Day	64% 5% 8% 14% 8% 2	1800
	11th to 20th	Day	61% 5% 10% 13% 10% 1	1876
	21st to end	Day	62% 4 8% 15% 9% 2	2326
April	1st to 10th	Day	64% 5% 9% 13% 7% 2	2160
	11th to 20th	Day	53% 5% 9% 19% 13% 1	2190
	21st to end	Day	60% 5% 8% 15% 10% 2	2340
May	1st to 10th	Day	55% 5% 8% 18% 13% 2	2376
	11th to 20th	Day	51% 6% 13% 18% 10% 1	2482
	21st to end	Day	53% 8% 11% 17% 11%	2725
June	1st to 10th	Day	55% 8% 11% 18% 7% 1	2520
	11th to 20th	Day	48% 7% 13% 21% 10% 1	2672
	21st to end	Day	57% 8% 11% 17% 7%	2520
July	1st to 10th	Day	47% 10% 14% 22% 7%	2450
	11th to 20th	Day	48% 8% 15% 22% 6%	2445
	21st to end	Day	51% 9% 13% 21% 6%	2591
August	1st to 10th	Day	51% 9% 17% 20% 3	2473
	11th to 20th	Day	47% 10% 15% 19% 8%	2304
	21st to end	Day	47% 7% 14% 21% 10%	2425
September	1st to 10th	Day	46% 7% 15% 22% 9% 1	2160
	11th to 20th	Day	43% 6% 13% 27% 11%	2008
	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	77% 4 8% 9% 3	2649
	11th to 20th	Night	74% 5% 6% 10% 4 1	2660
	21st to end	Night	66% 7% 8% 13% 5% 1	2919
February	1st to 10th	Night	69% 4 8% 12% 6% 1	2484
	11th to 20th	Night	68% 5% 7% 11% 7%	2100
	21st to end	Night	63% 5% 7% 14% 10% 1	1776
March	1st to 10th	Night	63% 5% 8% 15% 8% 1	2160
	11th to 20th	Night	61% 6% 8% 12% 12% 2	2084
	21st to end	Night	57% 4 9% 17% 9% 3	2026
April	1st to 10th	Night	59% 5% 9% 14% 11% 1	1800
	11th to 20th	Night	51% 5% 10% 21% 11% 2	1718
	21st to end	Night	56% 7% 9% 16% 10% 2	1620
May	1st to 10th	Night	53% 5% 8% 19% 13% 2	1598
	11th to 20th	Night	50% 5% 13% 19% 13% 2	1416
	21st to end	Night	47% 8% 12% 19% 12% 1	1551
June	1st to 10th	Night	53% 8% 12% 18% 8%	1437
	11th to 20th	Night	45% 7% 11% 24% 11% 2	1261
	21st to end	Night	52% 8% 12% 18% 9%	1440
July	1st to 10th	Night	43% 10% 15% 21% 10%	1400
	11th to 20th	Night	43% 10% 16% 21% 9%	1392
	21st to end	Night	47% 9% 14% 22% 8%	1486
August	1st to 10th	Night	41% 10% 18% 25% 5%	1422
	11th to 20th	Night	44% 11% 16% 21% 8%	1596
	21st to end	Night	43% 8% 15% 25% 9%	1929
September	1st to 10th	Night	46% 8% 13% 23% 10% 1	1800
	11th to 20th	Night	39% 6% 15% 30% 9% 1	1951
	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	23% 27% 29% 16% 4 1	196
February	1st to 10th	Day	37% 29% 28% 6% 1	177
	11th to 20th	Day	30% 27% 32% 9% 2	416
	21st to end	Day	30% 25% 26% 17% 2	346
March	1st to 10th	Day	26% 26% 28% 16% 4	420
	11th to 20th	Day	28% 26% 27% 14% 4 1	420
	21st to end	Day	30% 21% 26% 13% 9% 1	462
April	1st to 10th	Day	37% 18% 25% 14% 4 2	420
	11th to 20th	Day	31% 21% 23% 16% 7% 2	412
	21st to end	Day	34% 19% 28% 13% 5% 2	420
May	1st to 10th	Day	31% 19% 28% 16% 5% 1	423
	11th to 20th	Day	25% 15% 32% 20% 6% 2	447
	21st to end	Day	24% 20% 33% 16% 7% 1	485
June	1st to 10th	Day	29% 20% 29% 15% 6% 1	450
	11th to 20th	Day	23% 14% 28% 24% 11%	602
	21st to end	Day	25% 13% 34% 18% 8% 2	450
July	1st to 10th	Day	20% 9% 33% 26% 10% 1	445
	11th to 20th	Day	20% 11% 39% 21% 8% 2	444
	21st to end	Day	23% 9% 33% 26% 6% 1	488
August	1st to 10th	Day	21% 13% 28% 24% 12% 2	446
	11th to 20th	Day	21% 8% 27% 25% 16% 2	439
	21st to end	Day	22% 14% 25% 20% 12% 6%	495
September	1st to 10th	Day	20% 12% 30% 22% 10% 5%	450
	11th to 20th	Day	23% 11% 22% 22% 15% 6%	450
	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% 31% 22% 5% 1	835
February	1st to 10th	Night	23% 23% 32% 19% 4	720
	11th to 20th	Night	24% 22% 33% 18% 3	703
	21st to end	Night	25% 21% 32% 20% 3	592
March	1st to 10th	Night	25% 18% 34% 20% 3	720
	11th to 20th	Night	28% 21% 27% 19% 5% 1	720
	21st to end	Night	24% 16% 28% 24% 7% 1	792
April	1st to 10th	Night	32% 15% 28% 20% 5%	720
	11th to 20th	Night	27% 16% 27% 23% 7%	654
	21st to end	Night	31% 14% 29% 20% 6% 1	540
May	1st to 10th	Night	28% 12% 29% 23% 7% 1	518
	11th to 20th	Night	21% 11% 32% 29% 6% 1	354
	21st to end	Night	24% 9% 30% 29% 8%	389
June	1st to 10th	Night	28% 10% 27% 27% 8% 1	360
	11th to 20th	Night	21% 7% 25% 36% 11%	360
	21st to end	Night	21% 7% 26% 33% 12% 1	360
July	1st to 10th	Night	16% 7% 29% 34% 14% 1	350
	11th to 20th	Night	16% 5% 26% 37% 14% 1	348
	21st to end	Night	17% 6% 24% 39% 14%	394
August	1st to 10th	Night	19% 4 18% 38% 20% 1	358
	11th to 20th	Night	19% 6% 19% 37% 19% 1	532
	21st to end	Night	21% 5% 22% 31% 18% 3	741
September	1st to 10th	Night	22% 7% 24% 31% 14% 2	720
	11th to 20th	Night	21% 8% 21% 29% 18% 3	720
	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 2024-01-28 05:26:37. Version ac07

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