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 2024-06-03.

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	18% 13% 4 9% 5% 4 4 3 5% 6% 28%	89259
	Night	17% 14% 5% 10% 5% 5% 4 3 4 5% 27%	89237
Transparency	Day	58% 3 10% 20% 9% 1	88968
	Night	61% 3 10% 18% 8% 1	89082
Seeing	Day	25% 14% 30% 20% 8% 2	14320
	Night	25% 12% 29% 24% 9% 1	23345

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	15% 22% 10% 16% 6% 4 4 2 3 4 13%	2208
	11th to 20th	Day	11% 15% 7% 21% 8% 4 5% 3 4 5% 17%	2502
	21st to end	Day	16% 23% 10% 12% 5% 4 4 2 3 4 16%	3090
February	1st to 10th	Day	9% 21% 7% 15% 9% 6% 5% 3 4 4 17%	1710
	11th to 20th	Day	11% 20% 6% 11% 8% 5% 5% 3 4 5% 20%	1663
	21st to end	Day	17% 17% 5% 12% 8% 5% 4 3 4 4 20%	1433
March	1st to 10th	Day	20% 16% 4 9% 4 5% 4 3 4 5% 26%	3366
	11th to 20th	Day	11% 17% 7% 15% 6% 5% 4 3 4 4 24%	3480
	21st to end	Day	13% 11% 5% 10% 7% 6% 4 3 4 4 33%	3840
April	1st to 10th	Day	22% 15% 4 8% 4 3 4 3 5% 6% 26%	2280
	11th to 20th	Day	21% 13% 4 7% 4 3 3 3 4 5% 33%	2338
	21st to end	Day	22% 12% 3 7% 4 4 3 2 4 4 34%	2470
May	1st to 10th	Day	21% 9% 3 8% 5% 5% 5% 4 4 6% 31%	4321
	11th to 20th	Day	17% 10% 3 7% 4 4 4 4 5% 7% 35%	4398
	21st to end	Day	19% 7% 2 6% 4 4 5% 3 5% 7% 38%	4797
June	1st to 10th	Day	22% 9% 3 6% 5% 5% 5% 4 5% 6% 31%	2592
	11th to 20th	Day	17% 5% 2 6% 5% 5% 5% 5% 6% 7% 37%	2700
	21st to end	Day	19% 7% 3 6% 5% 5% 5% 4 7% 7% 32%	2700
July	1st to 10th	Day	14% 7% 2 6% 5% 4 5% 4 6% 8% 40%	2700
	11th to 20th	Day	16% 7% 2 6% 5% 5% 4 4 6% 8% 36%	2602
	21st to end	Day	15% 7% 2 7% 5% 5% 5% 4 6% 9% 35%	2744
August	1st to 10th	Day	17% 7% 2 7% 5% 5% 5% 4 5% 8% 34%	2334
	11th to 20th	Day	16% 7% 2 7% 6% 4 5% 4 6% 7% 36%	2303
	21st to end	Day	16% 9% 3 7% 5% 5% 5% 4 6% 7% 33%	2484
September	1st to 10th	Day	18% 7% 3 6% 4 4 4 4 5% 7% 38%	2160
	11th to 20th	Day	20% 6% 2 6% 4 4 4 4 5% 7% 39%	2116
	21st to end	Day	23% 9% 3 6% 5% 4 4 3 5% 6% 32%	1908
October	1st to 10th	Day	20% 11% 4 7% 4 4 4 4 5% 6% 32%	1800
	11th to 20th	Day	26% 16% 3 8% 6% 4 4 3 4 5% 21%	1800
	21st to end	Day	28% 17% 5% 8% 4 4 4 3 4 5% 18%	1945
November	1st to 10th	Day	20% 15% 5% 9% 3 4 3 3 4 7% 27%	1499
	11th to 20th	Day	18% 19% 6% 10% 6% 5% 4 3 4 5% 20%	1520
	21st to end	Day	23% 22% 6% 14% 5% 4 4 3 2 3 14%	1520
December	1st to 10th	Day	18% 23% 8% 12% 6% 5% 3 3 4 3 13%	1520
	11th to 20th	Day	18% 20% 6% 13% 7% 5% 4 2 3 5% 15%	1906
	21st to end	Day	20% 23% 8% 17% 4 3 2 2 2 3 15%	2510
January	1st to 10th	Night	16% 20% 9% 16% 7% 5% 5% 3 3 4 11%	4748
	11th to 20th	Night	12% 14% 5% 19% 10% 7% 6% 3 5% 4 15%	4440
	21st to end	Night	12% 24% 10% 13% 5% 7% 5% 3 4 3 13%	4564
February	1st to 10th	Night	11% 16% 7% 13% 10% 6% 4 4 5% 5% 18%	2470
	11th to 20th	Night	12% 17% 7% 13% 6% 6% 4 4 4 4 23%	2403
	21st to end	Night	15% 18% 6% 12% 6% 6% 4 3 4 5% 20%	2020
March	1st to 10th	Night	15% 17% 4 8% 4 3 4 4 4 6% 30%	3470
	11th to 20th	Night	16% 20% 6% 10% 5% 4 4 3 4 5% 24%	3479
	21st to end	Night	13% 12% 6% 10% 6% 5% 4 3 4 4 33%	3791
April	1st to 10th	Night	21% 16% 4 7% 5% 3 3 3 5% 4 29%	1900
	11th to 20th	Night	21% 11% 4 7% 4 4 4 3 4 5% 34%	1806
	21st to end	Night	23% 12% 3 7% 5% 4 4 3 4 5% 31%	1710
May	1st to 10th	Night	20% 9% 3 7% 4 4 3 3 5% 5% 35%	2620
	11th to 20th	Night	17% 8% 3 7% 4 4 5% 4 5% 7% 37%	2495
	21st to end	Night	14% 8% 3 7% 5% 5% 4 3 5% 8% 39%	2732
June	1st to 10th	Night	16% 8% 3 7% 6% 6% 5% 4 5% 5% 35%	1414
	11th to 20th	Night	18% 6% 2 5% 3 4 4 3 5% 8% 41%	1260
	21st to end	Night	16% 9% 2 7% 5% 4 6% 5% 6% 7% 35%	1260
July	1st to 10th	Night	13% 5% 2 5% 3 5% 4 4 6% 9% 44%	1260
	11th to 20th	Night	13% 5% 2 6% 5% 4 4 3 6% 7% 45%	1354
	21st to end	Night	11% 6% 3 5% 5% 5% 5% 5% 7% 7% 41%	1574
August	1st to 10th	Night	15% 6% 3 6% 4 4 4 4 7% 6% 40%	1601
	11th to 20th	Night	12% 5% 3 6% 4 4 6% 4 6% 8% 42%	1598
	21st to end	Night	17% 7% 2 6% 4 4 4 3 6% 8% 39%	1853
September	1st to 10th	Night	16% 5% 2 6% 4 4 4 3 5% 6% 46%	1800
	11th to 20th	Night	19% 7% 2 5% 3 3 3 3 6% 5% 44%	1843
	21st to end	Night	20% 8% 1 6% 3 5% 3 3 4 7% 39%	2052
October	1st to 10th	Night	20% 9% 3 8% 3 4 5% 4 4 6% 34%	2160
	11th to 20th	Night	26% 13% 3 8% 5% 4 4 2 3 4 27%	2160
	21st to end	Night	27% 16% 4 8% 4 3 3 3 5% 5% 22%	2410
November	1st to 10th	Night	20% 16% 4 7% 4 5% 4 3 4 5% 29%	2578
	11th to 20th	Night	18% 18% 5% 11% 6% 5% 4 3 4 5% 21%	2660
	21st to end	Night	24% 21% 5% 11% 6% 3 4 3 4 4 16%	2660
December	1st to 10th	Night	20% 25% 6% 12% 7% 4 3 3 3 4 12%	2660
	11th to 20th	Night	18% 21% 6% 14% 6% 4 4 3 3 4 17%	3288
	21st to end	Night	22% 21% 7% 17% 6% 3 3 2 3 3 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	77% 2 9% 10% 3	2209
	11th to 20th	Day	72% 2 10% 11% 6%	2502
	21st to end	Day	75% 2 6% 12% 5% 1	3090
February	1st to 10th	Day	71% 2 7% 13% 6% 1	1710
	11th to 20th	Day	67% 2 8% 13% 9% 1	1672
	21st to end	Day	68% 2 5% 16% 8% 1	1433
March	1st to 10th	Day	63% 1 11% 15% 9% 1	3369
	11th to 20th	Day	65% 2 9% 15% 8% 1	3480
	21st to end	Day	56% 2 7% 21% 11% 2	3840
April	1st to 10th	Day	61% 2 7% 20% 9% 2	2280
	11th to 20th	Day	55% 2 6% 23% 12% 2	2338
	21st to end	Day	56% 2 6% 18% 14% 3	2470
May	1st to 10th	Day	56% 2 6% 23% 10% 2	4334
	11th to 20th	Day	50% 1 9% 30% 8% 1	4402
	21st to end	Day	47% 2 13% 19% 16% 2	4797
June	1st to 10th	Day	55% 3 8% 22% 11% 1	2592
	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	80% 2 9% 7% 2	4748
	11th to 20th	Night	74% 2 9% 11% 4	4440
	21st to end	Night	76% 2 6% 10% 6%	4564
February	1st to 10th	Night	69% 3 9% 14% 6%	2470
	11th to 20th	Night	66% 2 9% 16% 6% 1	2405
	21st to end	Night	67% 3 8% 15% 6% 1	2020
March	1st to 10th	Night	57% 2 12% 18% 10% 1	3480
	11th to 20th	Night	65% 2 10% 16% 7% 1	3480
	21st to end	Night	56% 2 7% 20% 13% 2	3791
April	1st to 10th	Night	58% 3 6% 19% 11% 2	1900
	11th to 20th	Night	54% 2 6% 22% 14% 1	1806
	21st to end	Night	56% 3 7% 16% 15% 3	1710
May	1st to 10th	Night	52% 2 10% 23% 12% 2	2626
	11th to 20th	Night	48% 2 10% 27% 11% 1	2496
	21st to end	Night	46% 2 11% 23% 15% 2	2733
June	1st to 10th	Night	51% 4 9% 22% 12% 1	1414
	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% 23% 33% 15% 5% 1	180
	11th to 20th	Day	26% 16% 35% 16% 7%	180
	21st to end	Day	24% 18% 34% 16% 8% 1	288
February	1st to 10th	Day	29% 23% 34% 8% 6%	270
	11th to 20th	Day	25% 26% 38% 9% 1	270
	21st to end	Day	42% 16% 31% 10% 1	245
March	1st to 10th	Day	27% 17% 38% 15% 2 1	460
	11th to 20th	Day	25% 18% 37% 15% 5% 1	460
	21st to end	Day	28% 18% 30% 17% 5% 1	506
April	1st to 10th	Day	32% 18% 28% 15% 6% 1	460
	11th to 20th	Day	35% 16% 22% 16% 8% 3	452
	21st to end	Day	32% 17% 28% 14% 7% 1	460
May	1st to 10th	Day	27% 16% 29% 19% 8% 2	463
	11th to 20th	Day	24% 15% 28% 21% 10% 3	487
	21st to end	Day	22% 15% 32% 19% 9% 3	529
June	1st to 10th	Day	26% 10% 33% 23% 7% 1	502
	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% 14% 31% 21% 5%	760
	21st to end	Night	17% 11% 36% 25% 9% 1	836
February	1st to 10th	Night	21% 18% 36% 19% 5%	760
	11th to 20th	Night	23% 14% 38% 19% 6%	743
	21st to end	Night	25% 19% 32% 21% 3	628
March	1st to 10th	Night	23% 18% 33% 23% 4	760
	11th to 20th	Night	24% 19% 32% 19% 6% 1	760
	21st to end	Night	23% 12% 33% 24% 6% 1	836
April	1st to 10th	Night	30% 14% 29% 23% 4	760
	11th to 20th	Night	29% 15% 25% 23% 8%	682
	21st to end	Night	28% 11% 27% 25% 8% 1	570
May	1st to 10th	Night	24% 9% 27% 32% 9%	447
	11th to 20th	Night	22% 9% 33% 26% 10%	374
	21st to end	Night	19% 9% 30% 33% 9%	411
June	1st to 10th	Night	21% 7% 32% 31% 9%	366
	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 2024-05-31 06:01:38. Version ac07

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