Amanda
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Amanda clear sky chart from 2005-11-06 to 2024-04-03.

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	16% 10% 4 7% 6% 3 5% 5% 5% 7% 32%	79197
	Night	15% 10% 4 7% 5% 3 4 4 5% 7% 35%	80943
Transparency	Day	51% 6% 11% 20% 12% 2	78920
	Night	50% 5% 10% 20% 13% 2	80739
Seeing	Day	20% 13% 27% 21% 14% 6%	14010
	Night	19% 10% 27% 29% 14% 2	24209

By Month

Percentage Cloud Cover SE (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% 6% 11% 6% 3 4 4 4 5% 20%	2836
	11th to 20th	Day	15% 20% 9% 11% 7% 8% 5% 3 4 3 16%	2840
	21st to end	Day	27% 18% 10% 8% 6% 3 4 3 3 4 12%	3124
February	1st to 10th	Day	22% 12% 5% 9% 7% 4 4 4 4 6% 25%	1710
	11th to 20th	Day	18% 12% 5% 11% 7% 3 4 4 4 6% 26%	1826
	21st to end	Day	20% 14% 5% 8% 6% 2 3 3 4 5% 30%	1570
March	1st to 10th	Day	18% 11% 5% 7% 6% 3 4 3 5% 7% 31%	1994
	11th to 20th	Day	19% 11% 5% 8% 5% 3 5% 4 5% 6% 29%	2090
	21st to end	Day	22% 10% 5% 7% 6% 3 5% 4 4 7% 29%	2299
April	1st to 10th	Day	15% 11% 4 6% 6% 4 4 4 4 6% 34%	2026
	11th to 20th	Day	18% 9% 3 6% 5% 3 4 4 5% 6% 36%	2271
	21st to end	Day	19% 9% 4 5% 6% 4 5% 5% 5% 7% 32%	2340
May	1st to 10th	Day	20% 9% 3 6% 6% 3 5% 5% 5% 7% 31%	2340
	11th to 20th	Day	21% 7% 3 6% 5% 3 6% 5% 5% 7% 31%	2301
	21st to end	Day	8% 5% 2 6% 7% 4 7% 5% 8% 11% 37%	2531
June	1st to 10th	Day	13% 6% 2 5% 5% 4 6% 5% 6% 9% 39%	2340
	11th to 20th	Day	10% 5% 3 6% 6% 4 6% 5% 7% 10% 38%	2340
	21st to end	Day	11% 6% 3 5% 6% 4 6% 6% 8% 10% 36%	2340
July	1st to 10th	Day	12% 6% 3 6% 6% 5% 5% 5% 6% 9% 38%	2340
	11th to 20th	Day	10% 6% 2 6% 6% 4 7% 6% 7% 9% 38%	2340
	21st to end	Day	10% 5% 3 5% 6% 4 6% 6% 8% 9% 38%	2547
August	1st to 10th	Day	9% 5% 3 5% 6% 4 6% 7% 8% 11% 37%	2327
	11th to 20th	Day	10% 7% 2 6% 6% 4 6% 7% 8% 10% 35%	2303
	21st to end	Day	8% 5% 2 6% 5% 4 5% 5% 6% 10% 45%	2534
September	1st to 10th	Day	15% 5% 2 4 3 2 4 5% 7% 8% 45%	1980
	11th to 20th	Day	10% 4 2 5% 5% 3 5% 4 5% 8% 48%	1980
	21st to end	Day	17% 7% 3 5% 4 3 4 4 4 5% 44%	1980
October	1st to 10th	Day	13% 7% 3 6% 5% 2 4 5% 6% 6% 42%	1925
	11th to 20th	Day	16% 7% 3 5% 6% 3 4 4 5% 7% 42%	1800
	21st to end	Day	23% 8% 3 6% 5% 3 3 4 4 6% 35%	1944
November	1st to 10th	Day	10% 7% 3 5% 5% 2 3 4 5% 6% 50%	1672
	11th to 20th	Day	16% 11% 6% 7% 5% 3 4 4 4 6% 34%	1710
	21st to end	Day	19% 10% 4 8% 5% 4 5% 4 4 7% 31%	1710
December	1st to 10th	Day	22% 15% 7% 9% 6% 3 4 4 4 5% 20%	1710
	11th to 20th	Day	19% 16% 6% 10% 6% 2 4 4 5% 6% 22%	2153
	21st to end	Day	19% 22% 8% 9% 8% 4 5% 5% 4 5% 12%	3124
January	1st to 10th	Night	15% 20% 8% 12% 7% 3 4 3 4 4 19%	4109
	11th to 20th	Night	14% 17% 6% 16% 8% 4 5% 4 4 5% 18%	4120
	21st to end	Night	26% 17% 9% 9% 8% 3 3 3 2 3 18%	4532
February	1st to 10th	Night	22% 13% 4 9% 5% 4 4 3 4 4 29%	2470
	11th to 20th	Night	18% 13% 4 8% 6% 3 5% 5% 4 6% 28%	2237
	21st to end	Night	20% 14% 6% 9% 5% 3 4 3 3 5% 28%	1884
March	1st to 10th	Night	18% 9% 4 6% 6% 3 4 4 4 5% 36%	2185
	11th to 20th	Night	18% 10% 4 5% 5% 3 4 4 5% 7% 36%	2090
	21st to end	Night	20% 9% 4 7% 5% 2 4 4 4 6% 34%	2299
April	1st to 10th	Night	16% 9% 4 5% 4 3 5% 4 5% 8% 38%	1995
	11th to 20th	Night	14% 7% 3 6% 6% 3 4 5% 7% 7% 38%	1636
	21st to end	Night	16% 7% 3 7% 5% 3 5% 4 6% 8% 36%	1620
May	1st to 10th	Night	18% 8% 2 6% 6% 3 6% 6% 6% 8% 32%	1620
	11th to 20th	Night	17% 9% 2 6% 5% 3 4 5% 6% 8% 36%	1592
	21st to end	Night	7% 5% 2 6% 5% 3 5% 6% 8% 12% 42%	1744
June	1st to 10th	Night	8% 6% 3 5% 5% 3 5% 5% 5% 10% 46%	1620
	11th to 20th	Night	9% 4 3 5% 3 3 5% 5% 8% 11% 44%	1620
	21st to end	Night	10% 5% 2 4 5% 2 5% 6% 6% 10% 44%	1620
July	1st to 10th	Night	10% 4 3 6% 4 3 5% 4 6% 8% 48%	1620
	11th to 20th	Night	7% 4 3 5% 4 4 5% 4 7% 10% 47%	1620
	21st to end	Night	7% 5% 3 6% 6% 3 5% 6% 8% 8% 43%	1771
August	1st to 10th	Night	4 5% 2 6% 5% 4 5% 6% 7% 11% 44%	1611
	11th to 20th	Night	6% 6% 3 6% 6% 3 6% 5% 6% 8% 46%	1598
	21st to end	Night	7% 4 2 5% 4 3 3 4 7% 9% 53%	1813
September	1st to 10th	Night	13% 5% 2 4 4 2 4 4 5% 7% 51%	1966
	11th to 20th	Night	9% 4 2 4 4 2 4 4 5% 7% 55%	1980
	21st to end	Night	13% 7% 2 4 4 2 3 4 4 6% 49%	1980
October	1st to 10th	Night	10% 6% 3 4 4 3 4 5% 5% 7% 49%	2034
	11th to 20th	Night	16% 8% 2 5% 5% 3 3 4 5% 7% 43%	2160
	21st to end	Night	21% 8% 3 5% 4 3 4 4 5% 5% 38%	2407
November	1st to 10th	Night	14% 7% 2 4 4 3 3 3 4 6% 49%	2406
	11th to 20th	Night	16% 10% 4 7% 5% 3 4 4 4 7% 36%	2470
	21st to end	Night	20% 11% 4 6% 5% 3 4 4 4 6% 31%	2470
December	1st to 10th	Night	21% 14% 7% 9% 5% 2 4 4 4 5% 24%	2470
	11th to 20th	Night	18% 14% 7% 7% 5% 2 4 3 5% 6% 28%	3042
	21st to end	Night	20% 20% 8% 9% 7% 3 5% 4 4 5% 16%	4532

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	67% 5% 10% 12% 6%	2837
	11th to 20th	Day	74% 4 8% 10% 4	2840
	21st to end	Day	76% 4 7% 9% 3 1	3124
February	1st to 10th	Day	61% 4 11% 14% 9%	1710
	11th to 20th	Day	61% 4 9% 17% 9%	1836
	21st to end	Day	58% 4 10% 19% 8% 1	1570
March	1st to 10th	Day	54% 5% 10% 24% 7% 1	1994
	11th to 20th	Day	56% 5% 9% 19% 9% 1	2090
	21st to end	Day	56% 4 10% 20% 9% 1	2299
April	1st to 10th	Day	51% 4 10% 20% 11% 2	2026
	11th to 20th	Day	48% 4 11% 19% 14% 4	2271
	21st to end	Day	52% 5% 10% 20% 11% 3	2340
May	1st to 10th	Day	53% 5% 10% 21% 9% 2	2340
	11th to 20th	Day	51% 8% 12% 17% 11% 1	2305
	21st to end	Day	40% 8% 15% 22% 14% 1	2531
June	1st to 10th	Day	42% 7% 11% 24% 16% 2	2340
	11th to 20th	Day	41% 8% 14% 21% 15% 1	2340
	21st to end	Day	42% 7% 14% 21% 14% 2	2340
July	1st to 10th	Day	44% 7% 11% 20% 16% 1	2275
	11th to 20th	Day	40% 9% 13% 23% 14% 1	2271
	21st to end	Day	39% 8% 12% 24% 14% 3	2405
August	1st to 10th	Day	39% 8% 15% 25% 12% 1	2314
	11th to 20th	Day	42% 7% 13% 27% 10% 2	2303
	21st to end	Day	35% 7% 15% 22% 16% 5%	2534
September	1st to 10th	Day	37% 7% 11% 22% 21% 4	1980
	11th to 20th	Day	34% 5% 12% 26% 21% 2	1980
	21st to end	Day	43% 4 9% 22% 21% 1	1980
October	1st to 10th	Day	40% 6% 10% 23% 20% 1	1925
	11th to 20th	Day	43% 4 10% 25% 18% 2	1800
	21st to end	Day	51% 4 10% 22% 12% 2	1944
November	1st to 10th	Day	36% 5% 9% 29% 18% 3	1672
	11th to 20th	Day	52% 4 7% 20% 14% 3	1710
	21st to end	Day	54% 4 10% 20% 11% 1	1710
December	1st to 10th	Day	67% 4 9% 15% 4	1710
	11th to 20th	Day	63% 4 8% 17% 7%	2150
	21st to end	Day	74% 5% 9% 8% 4	3124
January	1st to 10th	Night	69% 4 8% 14% 5%	4109
	11th to 20th	Night	69% 4 10% 12% 3 1	4120
	21st to end	Night	74% 3 6% 13% 3 1	4532
February	1st to 10th	Night	59% 4 10% 18% 8% 1	2470
	11th to 20th	Night	59% 4 8% 17% 11% 1	2238
	21st to end	Night	61% 4 9% 16% 9% 2	1884
March	1st to 10th	Night	51% 5% 7% 23% 13% 1	2185
	11th to 20th	Night	49% 5% 10% 24% 10% 2	2090
	21st to end	Night	52% 4 8% 22% 12% 2	2299
April	1st to 10th	Night	46% 5% 11% 21% 15% 2	1995
	11th to 20th	Night	43% 6% 11% 17% 19% 5%	1636
	21st to end	Night	46% 5% 9% 23% 14% 2	1620
May	1st to 10th	Night	49% 7% 11% 20% 10% 3	1620
	11th to 20th	Night	46% 7% 11% 21% 12% 3	1593
	21st to end	Night	35% 8% 17% 26% 12% 3	1745
June	1st to 10th	Night	35% 7% 13% 24% 20% 2	1620
	11th to 20th	Night	32% 8% 17% 23% 18% 2	1620
	21st to end	Night	33% 8% 13% 24% 19% 3	1620
July	1st to 10th	Night	36% 7% 12% 23% 20% 3	1575
	11th to 20th	Night	31% 9% 13% 26% 19% 3	1566
	21st to end	Night	36% 8% 13% 25% 16% 2	1672
August	1st to 10th	Night	33% 8% 15% 28% 15% 2	1600
	11th to 20th	Night	35% 8% 14% 23% 19% 1	1598
	21st to end	Night	28% 7% 12% 27% 21% 5%	1813
September	1st to 10th	Night	33% 4 13% 24% 20% 6%	1966
	11th to 20th	Night	29% 6% 11% 26% 25% 3	1980
	21st to end	Night	37% 4 10% 21% 27% 1	1980
October	1st to 10th	Night	34% 6% 10% 25% 21% 3	2034
	11th to 20th	Night	41% 5% 9% 25% 18% 2	2160
	21st to end	Night	48% 4 9% 23% 14% 3	2407
November	1st to 10th	Night	38% 3 10% 24% 20% 3	2406
	11th to 20th	Night	49% 3 8% 21% 16% 2	2470
	21st to end	Night	55% 4 10% 19% 11% 1	2470
December	1st to 10th	Night	62% 4 9% 17% 7% 1	2470
	11th to 20th	Night	59% 3 11% 21% 6%	3044
	21st to end	Night	70% 5% 8% 12% 4	4532

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	25% 23% 37% 11% 4 1	270
	11th to 20th	Day	30% 22% 37% 9% 2	270
	21st to end	Day	32% 22% 31% 11% 4	297
February	1st to 10th	Day	31% 23% 31% 13% 2	270
	11th to 20th	Day	33% 27% 29% 9% 2	270
	21st to end	Day	32% 26% 35% 7%	225
March	1st to 10th	Day	24% 26% 29% 18% 4	364
	11th to 20th	Day	27% 20% 33% 15% 6%	460
	21st to end	Day	31% 17% 31% 17% 4	506
April	1st to 10th	Day	22% 17% 33% 16% 10% 2	428
	11th to 20th	Day	25% 15% 29% 19% 7% 4	412
	21st to end	Day	24% 17% 32% 18% 8% 1	420
May	1st to 10th	Day	28% 18% 27% 15% 9% 3	423
	11th to 20th	Day	21% 12% 29% 22% 11% 5%	447
	21st to end	Day	12% 7% 24% 29% 20% 7%	485
June	1st to 10th	Day	13% 6% 26% 30% 18% 7%	450
	11th to 20th	Day	14% 7% 25% 28% 20% 6%	450
	21st to end	Day	13% 6% 28% 28% 17% 8%	450
July	1st to 10th	Day	16% 3 17% 21% 22% 21%	445
	11th to 20th	Day	10% 6% 20% 26% 27% 11%	444
	21st to end	Day	13% 3 16% 29% 24% 14%	488
August	1st to 10th	Day	11% 3 16% 28% 28% 14%	446
	11th to 20th	Day	13% 3 22% 29% 20% 12%	439
	21st to end	Day	10% 4 18% 29% 26% 13%	495
September	1st to 10th	Day	13% 7% 16% 25% 26% 13%	450
	11th to 20th	Day	12% 2 15% 25% 32% 14%	450
	21st to end	Day	20% 9% 19% 26% 21% 6%	450
October	1st to 10th	Day	13% 9% 26% 28% 17% 7%	450
	11th to 20th	Day	16% 14% 32% 23% 13% 2	450
	21st to end	Day	25% 16% 32% 19% 7%	459
November	1st to 10th	Day	15% 17% 36% 21% 9% 2	270
	11th to 20th	Day	27% 21% 26% 18% 7% 1	270
	21st to end	Day	24% 20% 34% 19% 3	270
December	1st to 10th	Day	26% 21% 33% 13% 4 2	270
	11th to 20th	Day	26% 24% 34% 11% 5%	270
	21st to end	Day	30% 22% 31% 14% 3	297
January	1st to 10th	Night	23% 21% 34% 18% 5%	760
	11th to 20th	Night	28% 19% 30% 20% 2	760
	21st to end	Night	26% 16% 33% 23% 2	836
February	1st to 10th	Night	28% 13% 32% 25% 2	760
	11th to 20th	Night	27% 16% 35% 21% 1	743
	21st to end	Night	28% 15% 36% 19% 2	628
March	1st to 10th	Night	23% 15% 33% 24% 4	760
	11th to 20th	Night	21% 16% 33% 23% 6%	760
	21st to end	Night	25% 13% 31% 23% 7%	836
April	1st to 10th	Night	20% 14% 34% 25% 7%	721
	11th to 20th	Night	18% 10% 36% 24% 12% 1	533
	21st to end	Night	18% 9% 40% 26% 7% 1	540
May	1st to 10th	Night	20% 9% 32% 25% 13%	540
	11th to 20th	Night	20% 7% 25% 32% 15% 1	531
	21st to end	Night	9% 3 23% 34% 28% 2	584
June	1st to 10th	Night	9% 2 26% 41% 20% 1	540
	11th to 20th	Night	10% 2 22% 41% 24% 1	540
	21st to end	Night	11% 4 22% 39% 23% 2	540
July	1st to 10th	Night	10% 3 16% 36% 28% 8%	525
	11th to 20th	Night	6% 3 15% 36% 35% 6%	522
	21st to end	Night	9% 3 14% 37% 36% 2	591
August	1st to 10th	Night	6% 2 13% 41% 35% 3	537
	11th to 20th	Night	9% 2 11% 40% 33% 4	534
	21st to end	Night	9% 1 15% 33% 34% 7%	594
September	1st to 10th	Night	14% 3 16% 35% 28% 4	706
	11th to 20th	Night	11% 2 14% 35% 33% 6%	720
	21st to end	Night	16% 6% 21% 32% 22% 3	720
October	1st to 10th	Night	12% 6% 25% 33% 21% 4	720
	11th to 20th	Night	18% 9% 29% 30% 11% 1	720
	21st to end	Night	25% 11% 26% 28% 9%	792
November	1st to 10th	Night	19% 9% 25% 30% 16% 1	740
	11th to 20th	Night	22% 15% 28% 26% 9% 1	760
	21st to end	Night	26% 11% 27% 29% 6% 1	760
December	1st to 10th	Night	30% 16% 26% 24% 4	760
	11th to 20th	Night	26% 13% 32% 23% 5% 1	760
	21st to end	Night	28% 15% 31% 23% 3	836

Page generated at 2024-03-31 06:08:52. Version ac07

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