Mattawa
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mattawa clear sky chart from 2005-11-06 to 2024-01-13.

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% 5% 8% 6% 3 5% 4 5% 6% 29%	74902
	Night	18% 13% 5% 8% 6% 3 4 4 4 5% 28%	74825
Transparency	Day	57% 3 10% 20% 9% 1	74598
	Night	59% 3 10% 18% 9% 1	74664
Seeing	Day	25% 14% 30% 20% 8% 2	13809
	Night	25% 12% 29% 24% 9% 1	22856

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	13% 22% 9% 12% 9% 4 5% 4 3 5% 14%	1328
	11th to 20th	Day	17% 17% 7% 10% 8% 3 7% 5% 4 4 19%	1456
	21st to end	Day	14% 15% 7% 12% 9% 5% 5% 5% 4 5% 19%	1762
February	1st to 10th	Day	10% 20% 8% 13% 12% 4 6% 4 4 4 16%	1620
	11th to 20th	Day	12% 19% 7% 9% 9% 3 6% 4 4 5% 21%	1573
	21st to end	Day	17% 16% 7% 12% 9% 4 5% 3 4 5% 20%	1350
March	1st to 10th	Day	16% 15% 6% 11% 5% 3 5% 4 4 5% 27%	1936
	11th to 20th	Day	13% 13% 6% 11% 9% 4 5% 4 4 4 27%	1980
	21st to end	Day	19% 11% 4 7% 6% 2 4 3 4 5% 35%	2190
April	1st to 10th	Day	22% 14% 4 7% 6% 2 5% 4 5% 6% 25%	2160
	11th to 20th	Day	21% 11% 4 6% 5% 3 3 4 4 5% 34%	2213
	21st to end	Day	23% 12% 4 6% 5% 3 3 3 4 4 34%	2340
May	1st to 10th	Day	21% 8% 3 6% 6% 3 4 4 5% 6% 34%	2456
	11th to 20th	Day	20% 11% 4 6% 5% 3 4 4 4 5% 33%	2478
	21st to end	Day	17% 6% 4 5% 4 3 5% 4 5% 8% 38%	2725
June	1st to 10th	Day	22% 8% 4 6% 5% 3 5% 5% 5% 6% 31%	2564
	11th to 20th	Day	17% 5% 3 5% 6% 4 6% 5% 6% 7% 37%	2700
	21st to end	Day	19% 6% 3 6% 5% 4 5% 6% 6% 7% 32%	2700
July	1st to 10th	Day	14% 6% 2 5% 5% 3 5% 4 6% 8% 40%	2700
	11th to 20th	Day	16% 6% 3 5% 6% 4 4 5% 6% 9% 37%	2602
	21st to end	Day	15% 6% 3 6% 5% 4 5% 5% 6% 10% 35%	2744
August	1st to 10th	Day	17% 6% 2 6% 6% 4 6% 5% 5% 8% 34%	2334
	11th to 20th	Day	17% 7% 3 6% 7% 3 5% 5% 6% 7% 36%	2303
	21st to end	Day	16% 8% 3 6% 6% 4 5% 5% 6% 7% 33%	2484
September	1st to 10th	Day	18% 6% 3 6% 5% 3 5% 4 5% 7% 38%	2160
	11th to 20th	Day	20% 6% 3 5% 4 3 4 4 5% 7% 39%	2116
	21st to end	Day	24% 8% 3 6% 5% 3 5% 4 5% 6% 32%	1908
October	1st to 10th	Day	20% 11% 4 6% 5% 3 4 4 5% 6% 33%	1800
	11th to 20th	Day	27% 15% 4 7% 7% 3 5% 4 4 5% 21%	1800
	21st to end	Day	29% 16% 5% 7% 6% 4 3 4 4 5% 18%	1945
November	1st to 10th	Day	20% 14% 6% 8% 5% 3 3 4 4 7% 27%	1499
	11th to 20th	Day	19% 17% 6% 9% 7% 4 5% 3 4 5% 20%	1520
	21st to end	Day	23% 21% 6% 12% 7% 3 4 3 3 3 14%	1520
December	1st to 10th	Day	19% 21% 9% 12% 7% 3 4 4 4 4 13%	1520
	11th to 20th	Day	19% 19% 7% 11% 9% 4 5% 3 3 5% 16%	1906
	21st to end	Day	21% 22% 9% 15% 6% 2 2 3 2 3 15%	2510
January	1st to 10th	Night	18% 20% 10% 12% 9% 4 5% 4 3 4 12%	2838
	11th to 20th	Night	18% 17% 6% 13% 9% 4 5% 4 4 4 15%	2560
	21st to end	Night	11% 15% 7% 11% 8% 5% 6% 6% 5% 5% 22%	2592
February	1st to 10th	Night	12% 15% 8% 12% 12% 5% 5% 5% 5% 5% 17%	2340
	11th to 20th	Night	13% 15% 8% 11% 8% 4 5% 4 4 4 24%	2273
	21st to end	Night	15% 17% 7% 11% 7% 5% 5% 4 4 4 20%	1905
March	1st to 10th	Night	15% 15% 6% 10% 7% 3 5% 4 3 4 29%	2007
	11th to 20th	Night	16% 13% 6% 9% 6% 3 5% 4 4 6% 29%	1979
	21st to end	Night	17% 13% 4 7% 5% 3 4 3 4 5% 37%	2165
April	1st to 10th	Night	21% 15% 4 6% 5% 3 3 3 5% 4 29%	1800
	11th to 20th	Night	21% 9% 5% 6% 5% 3 5% 3 4 5% 34%	1710
	21st to end	Night	23% 12% 3 6% 5% 2 5% 4 4 5% 31%	1620
May	1st to 10th	Night	18% 9% 4 5% 5% 3 4 3 5% 5% 39%	1504
	11th to 20th	Night	20% 6% 3 6% 5% 2 5% 4 5% 7% 37%	1415
	21st to end	Night	16% 6% 3 5% 5% 2 5% 5% 5% 8% 41%	1550
June	1st to 10th	Night	17% 7% 3 7% 6% 5% 6% 4 5% 5% 35%	1392
	11th to 20th	Night	18% 5% 3 4 4 3 4 4 6% 7% 42%	1260
	21st to end	Night	16% 8% 2 6% 6% 3 5% 6% 5% 8% 35%	1260
July	1st to 10th	Night	13% 4 2 4 4 3 5% 4 5% 10% 44%	1260
	11th to 20th	Night	13% 5% 2 5% 6% 3 4 4 6% 7% 45%	1354
	21st to end	Night	11% 6% 3 5% 5% 4 5% 6% 7% 7% 42%	1574
August	1st to 10th	Night	15% 6% 3 5% 5% 3 4 6% 7% 7% 40%	1601
	11th to 20th	Night	12% 5% 3 5% 5% 3 6% 6% 6% 8% 42%	1598
	21st to end	Night	17% 6% 3 5% 5% 2 4 4 5% 8% 39%	1853
September	1st to 10th	Night	16% 5% 2 5% 4 3 4 4 4 6% 46%	1800
	11th to 20th	Night	19% 7% 2 4 4 3 3 4 6% 5% 44%	1843
	21st to end	Night	20% 8% 2 5% 4 4 4 4 4 7% 39%	2052
October	1st to 10th	Night	20% 9% 3 7% 5% 3 5% 4 4 6% 34%	2160
	11th to 20th	Night	26% 13% 3 6% 7% 3 4 3 3 4 27%	2160
	21st to end	Night	28% 15% 4 6% 5% 2 4 4 4 5% 22%	2410
November	1st to 10th	Night	20% 15% 4 7% 5% 3 4 4 4 5% 29%	2578
	11th to 20th	Night	19% 17% 5% 9% 7% 4 5% 4 4 5% 21%	2660
	21st to end	Night	24% 19% 6% 10% 7% 3 4 3 4 4 16%	2660
December	1st to 10th	Night	20% 23% 8% 11% 8% 3 3 4 3 4 13%	2660
	11th to 20th	Night	18% 20% 7% 12% 8% 4 4 4 3 4 17%	3288
	21st to end	Night	22% 20% 7% 14% 9% 3 3 3 3 4 13%	5144

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	74% 2 7% 13% 3	1329
	11th to 20th	Day	70% 3 7% 10% 10%	1456
	21st to end	Day	67% 4 6% 14% 8% 1	1762
February	1st to 10th	Day	73% 3 6% 12% 6% 1	1620
	11th to 20th	Day	67% 2 8% 13% 9% 1	1582
	21st to end	Day	69% 2 5% 16% 8%	1350
March	1st to 10th	Day	61% 2 9% 17% 9% 1	1939
	11th to 20th	Day	61% 3 7% 18% 10% 1	1980
	21st to end	Day	53% 3 8% 19% 14% 4	2190
April	1st to 10th	Day	61% 2 7% 18% 9% 2	2160
	11th to 20th	Day	54% 2 6% 24% 12% 2	2213
	21st to end	Day	56% 2 6% 18% 14% 3	2340
May	1st to 10th	Day	52% 3 8% 20% 14% 3	2456
	11th to 20th	Day	54% 2 7% 21% 14% 2	2482
	21st to end	Day	45% 4 12% 21% 14% 3	2725
June	1st to 10th	Day	55% 3 9% 22% 11% 1	2564
	11th to 20th	Day	46% 3 10% 26% 12% 2	2700
	21st to end	Day	50% 4 12% 23% 10% 1	2700
July	1st to 10th	Day	42% 4 11% 29% 13% 1	2626
	11th to 20th	Day	44% 4 12% 30% 9% 1	2522
	21st to end	Day	46% 4 13% 29% 8%	2591
August	1st to 10th	Day	48% 4 14% 24% 10%	2320
	11th to 20th	Day	46% 4 15% 26% 7% 1	2303
	21st to end	Day	49% 4 12% 25% 9%	2484
September	1st to 10th	Day	46% 4 12% 26% 12%	2160
	11th to 20th	Day	46% 3 13% 29% 8% 1	2116
	21st to end	Day	54% 4 11% 26% 5%	1908
October	1st to 10th	Day	54% 3 12% 21% 11%	1800
	11th to 20th	Day	67% 3 11% 14% 5%	1800
	21st to end	Day	71% 3 9% 12% 5%	1945
November	1st to 10th	Day	60% 3 13% 19% 6%	1499
	11th to 20th	Day	67% 3 11% 12% 7% 1	1520
	21st to end	Day	78% 3 9% 7% 3	1520
December	1st to 10th	Day	76% 2 8% 11% 3	1520
	11th to 20th	Day	75% 2 7% 12% 4	1906
	21st to end	Day	77% 1 5% 15% 2	2510
January	1st to 10th	Night	78% 3 7% 9% 4	2838
	11th to 20th	Night	73% 3 7% 10% 6% 1	2560
	21st to end	Night	64% 4 6% 16% 10% 1	2592
February	1st to 10th	Night	69% 3 8% 13% 6%	2340
	11th to 20th	Night	65% 3 9% 16% 6% 1	2275
	21st to end	Night	67% 3 7% 15% 6% 1	1905
March	1st to 10th	Night	61% 2 9% 16% 10% 2	2017
	11th to 20th	Night	58% 3 10% 17% 11% 1	1980
	21st to end	Night	52% 3 8% 19% 15% 3	2165
April	1st to 10th	Night	58% 3 6% 19% 12% 2	1800
	11th to 20th	Night	54% 2 6% 22% 14% 1	1710
	21st to end	Night	56% 4 6% 15% 15% 3	1620
May	1st to 10th	Night	48% 2 8% 23% 15% 3	1504
	11th to 20th	Night	47% 3 7% 24% 17% 2	1416
	21st to end	Night	42% 4 15% 20% 16% 3	1551
June	1st to 10th	Night	51% 4 9% 22% 12% 2	1392
	11th to 20th	Night	42% 3 11% 25% 16% 2	1260
	21st to end	Night	47% 6% 13% 22% 12% 1	1260
July	1st to 10th	Night	36% 3 14% 28% 18% 1	1225
	11th to 20th	Night	39% 3 15% 29% 12% 1	1311
	21st to end	Night	40% 4 17% 30% 9%	1486
August	1st to 10th	Night	41% 6% 16% 26% 11% 1	1591
	11th to 20th	Night	38% 6% 19% 26% 10% 1	1598
	21st to end	Night	43% 4 16% 27% 9% 1	1853
September	1st to 10th	Night	39% 4 16% 28% 12% 1	1800
	11th to 20th	Night	43% 3 15% 31% 9%	1843
	21st to end	Night	46% 4 14% 30% 7%	2052
October	1st to 10th	Night	52% 3 12% 22% 10%	2160
	11th to 20th	Night	63% 2 11% 19% 5%	2160
	21st to end	Night	65% 4 10% 14% 7% 1	2410
November	1st to 10th	Night	59% 3 13% 18% 7%	2578
	11th to 20th	Night	67% 3 11% 14% 5% 1	2660
	21st to end	Night	74% 3 10% 10% 3	2660
December	1st to 10th	Night	77% 2 7% 10% 3	2660
	11th to 20th	Night	73% 2 5% 13% 6%	3288
	21st to end	Night	79% 2 5% 10% 3	5144

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	23% 24% 33% 15% 5% 1	180
	11th to 20th	Day	27% 14% 35% 16% 8%	166
	21st to end	Day	24% 18% 33% 15% 8% 2	256
February	1st to 10th	Day	30% 26% 32% 7% 4	240
	11th to 20th	Day	27% 24% 38% 10% 1	240
	21st to end	Day	41% 16% 32% 10% 1	216
March	1st to 10th	Day	28% 16% 38% 15% 2 1	420
	11th to 20th	Day	25% 17% 37% 15% 5% 1	420
	21st to end	Day	29% 18% 29% 17% 6% 1	462
April	1st to 10th	Day	31% 18% 30% 15% 6% 1	420
	11th to 20th	Day	33% 16% 23% 17% 8% 3	412
	21st to end	Day	32% 16% 29% 14% 7% 1	420
May	1st to 10th	Day	28% 16% 27% 19% 8% 2	423
	11th to 20th	Day	26% 15% 28% 19% 9% 3	447
	21st to end	Day	20% 16% 33% 19% 9% 3	485
June	1st to 10th	Day	26% 10% 33% 23% 7% 1	494
	11th to 20th	Day	21% 14% 28% 25% 10% 2	630
	21st to end	Day	20% 14% 31% 24% 10% 2	630
July	1st to 10th	Day	14% 12% 30% 33% 10% 1	621
	11th to 20th	Day	17% 12% 28% 29% 13% 2	521
	21st to end	Day	14% 9% 32% 30% 12% 3	488
August	1st to 10th	Day	21% 5% 30% 26% 12% 6%	446
	11th to 20th	Day	18% 4 26% 29% 15% 8%	439
	21st to end	Day	19% 13% 29% 21% 12% 6%	495
September	1st to 10th	Day	23% 9% 30% 20% 12% 6%	450
	11th to 20th	Day	22% 9% 26% 25% 12% 6%	450
	21st to end	Day	27% 11% 23% 22% 13% 3	450
October	1st to 10th	Day	28% 12% 25% 20% 11% 3	450
	11th to 20th	Day	30% 19% 30% 16% 4 1	450
	21st to end	Day	36% 14% 30% 17% 4	477
November	1st to 10th	Day	32% 18% 36% 11% 3	193
	11th to 20th	Day	28% 19% 33% 14% 5%	180
	21st to end	Day	37% 19% 33% 8% 1 1	180
December	1st to 10th	Day	36% 13% 32% 14% 4	180
	11th to 20th	Day	33% 21% 34% 9% 3 1	180
	21st to end	Day	31% 22% 31% 12% 4 1	198
January	1st to 10th	Night	29% 15% 33% 19% 5%	950
	11th to 20th	Night	29% 13% 31% 22% 5%	732
	21st to end	Night	17% 11% 35% 25% 9% 1	792
February	1st to 10th	Night	21% 18% 38% 18% 5%	720
	11th to 20th	Night	23% 14% 37% 19% 6%	703
	21st to end	Night	24% 19% 32% 22% 3	592
March	1st to 10th	Night	24% 18% 32% 22% 4	720
	11th to 20th	Night	24% 20% 31% 18% 6% 1	720
	21st to end	Night	24% 11% 32% 25% 7% 1	792
April	1st to 10th	Night	29% 14% 29% 24% 4	720
	11th to 20th	Night	28% 15% 24% 24% 8%	646
	21st to end	Night	28% 11% 27% 25% 8% 1	540
May	1st to 10th	Night	24% 7% 28% 32% 9%	424
	11th to 20th	Night	23% 8% 33% 25% 10%	354
	21st to end	Night	19% 8% 31% 32% 9%	389
June	1st to 10th	Night	21% 7% 32% 31% 8%	360
	11th to 20th	Night	21% 7% 27% 35% 11%	360
	21st to end	Night	19% 8% 27% 33% 13% 1	360
July	1st to 10th	Night	13% 5% 32% 35% 15% 1	350
	11th to 20th	Night	13% 6% 26% 36% 18% 1	348
	21st to end	Night	12% 6% 30% 37% 14% 1	394
August	1st to 10th	Night	17% 6% 21% 35% 20%	527
	11th to 20th	Night	12% 4 21% 40% 20% 2	534
	21st to end	Night	20% 7% 25% 29% 16% 3	665
September	1st to 10th	Night	20% 5% 25% 30% 19% 1	720
	11th to 20th	Night	22% 6% 26% 25% 18% 3	720
	21st to end	Night	25% 6% 23% 29% 15% 1	720
October	1st to 10th	Night	26% 10% 28% 25% 10% 2	720
	11th to 20th	Night	32% 12% 28% 20% 8% 1	720
	21st to end	Night	37% 12% 26% 21% 4 1	792
November	1st to 10th	Night	30% 12% 29% 21% 7% 1	740
	11th to 20th	Night	27% 18% 32% 16% 8%	760
	21st to end	Night	36% 13% 24% 20% 6%	760
December	1st to 10th	Night	33% 14% 31% 15% 6% 1	760
	11th to 20th	Night	30% 16% 31% 18% 4 1	760
	21st to end	Night	33% 14% 31% 18% 4	992

Page generated at 2024-01-10 19:35:22. Version ac07

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