SAPM à Hemmingford
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the SAPM à Hemmingford 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	17% 10% 3 8% 5% 5% 5% 4 5% 7% 32%	100985
	Night	18% 11% 4 8% 5% 5% 4 3 5% 6% 31%	96918
Transparency	Day	51% 7% 12% 20% 9% 1	100745
	Night	54% 7% 11% 18% 9% 1	96778
Seeing	Day	23% 16% 29% 21% 9% 2	14437
	Night	23% 14% 29% 25% 9% 1	23369

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	17% 17% 6% 13% 6% 6% 4 3 4 4 21%	2517
	11th to 20th	Day	14% 17% 7% 14% 7% 5% 4 4 5% 4 18%	2520
	21st to end	Day	16% 18% 5% 12% 6% 6% 5% 4 5% 6% 18%	2772
February	1st to 10th	Day	16% 17% 5% 13% 7% 4 5% 3 5% 5% 21%	1676
	11th to 20th	Day	12% 15% 4 13% 7% 4 4 5% 4 5% 25%	1778
	21st to end	Day	17% 17% 4 8% 7% 5% 5% 3 5% 6% 24%	1570
March	1st to 10th	Day	21% 12% 4 10% 6% 5% 5% 3 4 5% 25%	3116
	11th to 20th	Day	15% 17% 6% 10% 7% 5% 4 3 4 5% 25%	3290
	21st to end	Day	16% 10% 3 8% 5% 3 4 3 4 6% 39%	4166
April	1st to 10th	Day	23% 12% 3 7% 4 4 4 3 5% 5% 30%	2280
	11th to 20th	Day	21% 10% 3 7% 5% 4 4 3 4 5% 35%	2254
	21st to end	Day	23% 9% 3 7% 5% 4 3 4 4 6% 32%	2429
May	1st to 10th	Day	23% 10% 3 7% 4 4 5% 3 6% 6% 29%	4320
	11th to 20th	Day	18% 8% 3 7% 5% 5% 5% 4 6% 6% 32%	4398
	21st to end	Day	14% 6% 3 7% 5% 5% 6% 4 7% 9% 35%	4837
June	1st to 10th	Day	22% 7% 3 7% 5% 5% 4 4 6% 7% 30%	2660
	11th to 20th	Day	14% 7% 2 6% 5% 5% 5% 5% 6% 8% 37%	2660
	21st to end	Day	22% 7% 2 7% 5% 5% 4 4 6% 7% 31%	2660
July	1st to 10th	Day	12% 6% 2 8% 5% 5% 6% 5% 7% 9% 36%	4440
	11th to 20th	Day	11% 6% 2 6% 5% 5% 6% 5% 7% 10% 37%	4440
	21st to end	Day	12% 6% 3 6% 4 4 5% 4 6% 8% 41%	4814
August	1st to 10th	Day	15% 7% 3 9% 5% 5% 6% 5% 7% 8% 32%	4423
	11th to 20th	Day	14% 6% 2 6% 4 5% 5% 4 6% 8% 38%	3942
	21st to end	Day	15% 5% 2 6% 4 4 4 4 6% 9% 41%	4180
September	1st to 10th	Day	12% 6% 2 5% 5% 4 5% 4 5% 8% 44%	2280
	11th to 20th	Day	15% 6% 2 5% 4 3 4 3 4 7% 47%	2116
	21st to end	Day	14% 6% 2 7% 4 4 5% 4 6% 8% 41%	1980
October	1st to 10th	Day	22% 7% 3 7% 4 5% 5% 4 5% 7% 31%	1871
	11th to 20th	Day	18% 8% 3 8% 6% 6% 6% 4 6% 5% 30%	1762
	21st to end	Day	25% 13% 3 6% 4 5% 3 3 4 6% 27%	1782
November	1st to 10th	Day	17% 12% 3 8% 5% 5% 4 3 6% 5% 32%	1671
	11th to 20th	Day	17% 14% 4 7% 5% 5% 4 5% 5% 6% 28%	1663
	21st to end	Day	20% 15% 5% 9% 6% 4 5% 4 6% 6% 22%	1520
December	1st to 10th	Day	21% 18% 5% 11% 6% 5% 4 3 5% 5% 18%	1520
	11th to 20th	Day	21% 15% 6% 9% 5% 4 5% 3 5% 4 23%	1906
	21st to end	Day	26% 16% 3 11% 6% 5% 4 3 4 3 19%	2772
January	1st to 10th	Night	16% 18% 6% 11% 7% 5% 5% 3 5% 4 20%	4429
	11th to 20th	Night	13% 15% 6% 14% 8% 6% 6% 4 6% 5% 19%	4440
	21st to end	Night	19% 18% 5% 10% 7% 5% 4 3 4 4 22%	4884
February	1st to 10th	Night	15% 15% 5% 13% 8% 6% 5% 3 4 5% 20%	2502
	11th to 20th	Night	15% 11% 5% 10% 6% 6% 5% 4 6% 5% 27%	2288
	21st to end	Night	16% 13% 4 9% 6% 4 5% 3 4 5% 30%	1884
March	1st to 10th	Night	21% 11% 4 7% 5% 4 4 3 5% 5% 32%	3724
	11th to 20th	Night	17% 16% 5% 10% 5% 4 4 3 4 4 27%	3667
	21st to end	Night	14% 11% 4 9% 6% 5% 5% 3 5% 5% 35%	3466
April	1st to 10th	Night	22% 11% 3 7% 5% 5% 4 3 5% 5% 30%	1900
	11th to 20th	Night	25% 9% 3 7% 4 4 4 3 4 5% 32%	1875
	21st to end	Night	19% 9% 3 8% 5% 5% 5% 3 4 5% 35%	1749
May	1st to 10th	Night	23% 11% 3 7% 4 4 5% 3 5% 7% 28%	2647
	11th to 20th	Night	21% 9% 3 7% 4 4 3 3 5% 6% 35%	2495
	21st to end	Night	16% 6% 3 7% 4 5% 5% 3 5% 9% 37%	2738
June	1st to 10th	Night	22% 6% 3 5% 5% 6% 5% 3 7% 7% 30%	1520
	11th to 20th	Night	17% 5% 3 7% 4 4 5% 4 7% 8% 37%	1520
	21st to end	Night	18% 8% 2 7% 5% 4 4 4 6% 6% 35%	1520
July	1st to 10th	Night	14% 6% 3 8% 5% 5% 6% 4 6% 7% 36%	2520
	11th to 20th	Night	13% 5% 2 5% 4 4 5% 4 7% 8% 43%	2520
	21st to end	Night	11% 7% 3 7% 5% 5% 5% 3 6% 7% 41%	2739
August	1st to 10th	Night	16% 7% 4 8% 4 4 4 3 5% 7% 38%	2506
	11th to 20th	Night	14% 7% 2 8% 4 5% 5% 4 6% 6% 38%	2837
	21st to end	Night	16% 5% 2 6% 4 4 5% 4 5% 8% 42%	3476
September	1st to 10th	Night	12% 6% 2 6% 5% 4 4 3 6% 7% 45%	1900
	11th to 20th	Night	14% 6% 2 5% 4 4 3 3 4 6% 49%	1921
	21st to end	Night	17% 7% 2 4 4 4 4 3 5% 7% 42%	1980
October	1st to 10th	Night	18% 8% 3 7% 4 4 4 4 5% 5% 37%	2087
	11th to 20th	Night	20% 9% 2 7% 5% 4 5% 4 6% 6% 32%	2196
	21st to end	Night	24% 10% 4 8% 5% 4 4 3 5% 6% 28%	2574
November	1st to 10th	Night	19% 10% 4 7% 5% 4 4 4 5% 6% 31%	2407
	11th to 20th	Night	19% 10% 4 9% 5% 4 4 3 4 5% 32%	2515
	21st to end	Night	20% 14% 4 9% 5% 4 5% 3 5% 6% 24%	2660
December	1st to 10th	Night	22% 17% 5% 9% 7% 4 5% 3 5% 6% 16%	2660
	11th to 20th	Night	22% 15% 5% 10% 5% 4 4 3 4 4 22%	3288
	21st to end	Night	28% 14% 5% 12% 4 4 4 3 3 4 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	64% 8% 14% 12% 2	2518
	11th to 20th	Day	65% 9% 12% 8% 5%	2520
	21st to end	Day	64% 12% 11% 8% 5%	2772
February	1st to 10th	Day	66% 5% 9% 14% 4 1	1676
	11th to 20th	Day	59% 7% 10% 15% 7% 1	1787
	21st to end	Day	61% 5% 11% 14% 8% 1	1570
March	1st to 10th	Day	59% 8% 9% 17% 6% 1	3119
	11th to 20th	Day	59% 8% 11% 12% 9% 1	3290
	21st to end	Day	47% 4 10% 19% 17% 2	4166
April	1st to 10th	Day	55% 5% 8% 19% 11% 2	2280
	11th to 20th	Day	51% 5% 8% 20% 15% 2	2254
	21st to end	Day	54% 6% 9% 17% 12% 3	2429
May	1st to 10th	Day	53% 8% 10% 18% 10% 1	4334
	11th to 20th	Day	48% 9% 14% 19% 8% 2	4402
	21st to end	Day	42% 9% 13% 23% 12% 1	4837
June	1st to 10th	Day	52% 8% 10% 18% 11% 1	2660
	11th to 20th	Day	43% 7% 11% 23% 14% 2	2660
	21st to end	Day	51% 8% 11% 21% 9% 1	2660
July	1st to 10th	Day	42% 6% 15% 26% 11%	4370
	11th to 20th	Day	41% 6% 15% 32% 6%	4365
	21st to end	Day	40% 7% 12% 32% 9%	4661
August	1st to 10th	Day	48% 7% 15% 21% 8%	4409
	11th to 20th	Day	40% 8% 18% 27% 6%	3983
	21st to end	Day	40% 6% 18% 22% 14%	4180
September	1st to 10th	Day	37% 8% 13% 28% 13%	2280
	11th to 20th	Day	37% 5% 12% 33% 13% 1	2116
	21st to end	Day	41% 8% 15% 26% 9% 1	1980
October	1st to 10th	Day	52% 7% 12% 20% 9%	1871
	11th to 20th	Day	51% 9% 15% 17% 8%	1762
	21st to end	Day	60% 6% 11% 16% 7% 1	1782
November	1st to 10th	Day	52% 7% 13% 20% 7% 1	1671
	11th to 20th	Day	56% 8% 12% 14% 10% 1	1663
	21st to end	Day	61% 9% 12% 13% 4	1520
December	1st to 10th	Day	69% 7% 11% 12% 2	1520
	11th to 20th	Day	63% 7% 11% 14% 5%	1906
	21st to end	Day	69% 6% 11% 10% 4	2772
January	1st to 10th	Night	65% 8% 13% 10% 4	4429
	11th to 20th	Night	64% 9% 11% 11% 4	4440
	21st to end	Night	65% 6% 12% 11% 6% 1	4884
February	1st to 10th	Night	65% 7% 8% 13% 6% 1	2502
	11th to 20th	Night	57% 7% 11% 17% 9%	2290
	21st to end	Night	56% 6% 10% 16% 12% 1	1884
March	1st to 10th	Night	54% 7% 9% 19% 10% 2	3734
	11th to 20th	Night	60% 6% 9% 14% 10% 1	3668
	21st to end	Night	49% 6% 7% 21% 14% 2	3466
April	1st to 10th	Night	56% 5% 9% 17% 12% 1	1900
	11th to 20th	Night	55% 5% 9% 18% 12% 1	1875
	21st to end	Night	52% 7% 8% 17% 13% 4	1749
May	1st to 10th	Night	54% 8% 9% 18% 9% 3	2653
	11th to 20th	Night	48% 8% 11% 21% 11% 2	2496
	21st to end	Night	42% 9% 10% 20% 17% 1	2739
June	1st to 10th	Night	50% 8% 11% 20% 10% 1	1520
	11th to 20th	Night	44% 6% 14% 19% 15% 2	1520
	21st to end	Night	47% 9% 12% 19% 12% 1	1520
July	1st to 10th	Night	46% 7% 12% 21% 13%	2480
	11th to 20th	Night	37% 7% 15% 31% 9%	2472
	21st to end	Night	43% 7% 14% 24% 13%	2651
August	1st to 10th	Night	47% 6% 12% 26% 9%	2496
	11th to 20th	Night	44% 7% 19% 21% 9%	2862
	21st to end	Night	40% 7% 15% 23% 15% 1	3476
September	1st to 10th	Night	37% 8% 12% 28% 14% 1	1900
	11th to 20th	Night	35% 7% 14% 32% 11% 1	1921
	21st to end	Night	41% 7% 12% 25% 14% 1	1980
October	1st to 10th	Night	47% 8% 11% 22% 12%	2087
	11th to 20th	Night	50% 8% 11% 22% 8%	2196
	21st to end	Night	57% 7% 12% 14% 9% 1	2574
November	1st to 10th	Night	52% 7% 12% 18% 9% 1	2407
	11th to 20th	Night	54% 7% 11% 18% 9% 1	2515
	21st to end	Night	60% 8% 12% 15% 5%	2660
December	1st to 10th	Night	70% 7% 10% 12% 2	2660
	11th to 20th	Night	66% 6% 9% 13% 6%	3288
	21st to end	Night	69% 7% 9% 13% 3	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% 23% 21% 21% 7% 1	180
	11th to 20th	Day	31% 26% 28% 12% 3 1	180
	21st to end	Day	25% 17% 34% 17% 7% 1	198
February	1st to 10th	Day	34% 23% 35% 6% 1	254
	11th to 20th	Day	25% 25% 37% 12% 2	386
	21st to end	Day	30% 20% 30% 18% 2	382
March	1st to 10th	Day	30% 18% 30% 18% 5%	460
	11th to 20th	Day	26% 23% 30% 14% 5% 1	460
	21st to end	Day	32% 22% 24% 16% 6%	506
April	1st to 10th	Day	35% 17% 25% 16% 7%	460
	11th to 20th	Day	31% 20% 27% 13% 7% 3	452
	21st to end	Day	30% 17% 30% 14% 9% 1	460
May	1st to 10th	Day	27% 16% 32% 16% 8% 1	463
	11th to 20th	Day	20% 17% 30% 24% 9% 1	487
	21st to end	Day	17% 16% 31% 26% 8% 1	529
June	1st to 10th	Day	24% 16% 27% 25% 7% 1	490
	11th to 20th	Day	16% 14% 31% 26% 11% 2	490
	21st to end	Day	24% 13% 32% 20% 8% 2	490
July	1st to 10th	Day	15% 7% 30% 29% 16% 2	485
	11th to 20th	Day	14% 7% 35% 30% 12% 3	484
	21st to end	Day	13% 9% 29% 34% 13% 2	532
August	1st to 10th	Day	16% 8% 27% 30% 15% 4	486
	11th to 20th	Day	15% 7% 27% 29% 16% 6%	479
	21st to end	Day	17% 10% 28% 24% 15% 6%	539
September	1st to 10th	Day	15% 11% 28% 26% 14% 6%	490
	11th to 20th	Day	16% 11% 21% 26% 18% 8%	463
	21st to end	Day	15% 14% 29% 21% 16% 5%	450
October	1st to 10th	Day	23% 16% 23% 20% 14% 5%	450
	11th to 20th	Day	22% 20% 28% 20% 7% 2	430
	21st to end	Day	34% 17% 25% 20% 4	396
November	1st to 10th	Day	26% 18% 30% 20% 5% 1	365
	11th to 20th	Day	28% 24% 28% 14% 6% 1	323
	21st to end	Day	32% 20% 26% 17% 6% 1	180
December	1st to 10th	Day	34% 14% 26% 18% 7% 1	180
	11th to 20th	Day	28% 23% 33% 13% 3	180
	21st to end	Day	29% 26% 28% 11% 4 1	198
January	1st to 10th	Night	25% 20% 33% 18% 4	760
	11th to 20th	Night	25% 19% 33% 19% 5%	760
	21st to end	Night	21% 15% 35% 24% 5% 1	836
February	1st to 10th	Night	23% 17% 33% 23% 4	760
	11th to 20th	Night	23% 18% 37% 20% 2	743
	21st to end	Night	25% 17% 32% 23% 4	628
March	1st to 10th	Night	28% 16% 30% 23% 4	760
	11th to 20th	Night	28% 18% 29% 21% 4	760
	21st to end	Night	27% 17% 27% 23% 6%	836
April	1st to 10th	Night	28% 17% 27% 24% 4	760
	11th to 20th	Night	30% 16% 26% 21% 5%	751
	21st to end	Night	24% 19% 28% 21% 8%	609
May	1st to 10th	Night	28% 10% 29% 23% 10%	461
	11th to 20th	Night	21% 12% 33% 26% 8% 1	374
	21st to end	Night	17% 12% 32% 30% 9%	411
June	1st to 10th	Night	23% 10% 26% 30% 10% 1	380
	11th to 20th	Night	18% 9% 27% 32% 13% 1	380
	21st to end	Night	20% 7% 28% 32% 13% 1	380
July	1st to 10th	Night	12% 5% 32% 34% 18%	370
	11th to 20th	Night	9% 4 26% 44% 16% 1	368
	21st to end	Night	13% 4 22% 43% 17% 1	416
August	1st to 10th	Night	16% 4 18% 44% 17% 1	378
	11th to 20th	Night	16% 4 23% 35% 20% 2	588
	21st to end	Night	17% 6% 22% 36% 17% 2	836
September	1st to 10th	Night	15% 7% 27% 35% 14% 1	760
	11th to 20th	Night	16% 7% 21% 32% 20% 3	736
	21st to end	Night	19% 8% 29% 25% 17% 2	720
October	1st to 10th	Night	22% 12% 27% 25% 14% 1	720
	11th to 20th	Night	24% 13% 29% 25% 8%	720
	21st to end	Night	29% 13% 32% 22% 5%	792
November	1st to 10th	Night	25% 19% 29% 20% 7% 1	740
	11th to 20th	Night	24% 19% 31% 17% 8% 1	760
	21st to end	Night	29% 18% 30% 17% 7%	760
December	1st to 10th	Night	30% 19% 29% 18% 4	760
	11th to 20th	Night	31% 17% 30% 16% 5% 1	760
	21st to end	Night	34% 17% 30% 16% 3	836

Page generated at 2024-09-11 10:00:05. Version ac07

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