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 2024-11-12.

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% 12% 4 9% 5% 4 4 3 5% 6% 30%	101965
	Night	17% 14% 5% 10% 5% 5% 4 3 4 5% 28%	97226
Transparency	Day	56% 3 10% 22% 8% 1	105527
	Night	59% 3 11% 19% 8% 1	101753
Seeing	Day	25% 14% 30% 20% 8% 2	14981
	Night	25% 12% 29% 24% 9% 1	23847

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 4 3 5% 7% 38%	4837
June	1st to 10th	Day	22% 9% 3 7% 5% 5% 5% 3 5% 6% 30%	2707
	11th to 20th	Day	16% 6% 2 6% 5% 5% 5% 5% 6% 7% 37%	2850
	21st to end	Day	20% 7% 3 6% 5% 5% 5% 4 6% 7% 31%	2850
July	1st to 10th	Day	18% 7% 2 7% 5% 5% 5% 4 6% 8% 33%	4760
	11th to 20th	Day	16% 6% 3 6% 5% 4 5% 4 6% 8% 37%	4578
	21st to end	Day	13% 6% 2 6% 4 4 4 4 5% 7% 45%	4814
August	1st to 10th	Day	15% 7% 3 8% 6% 5% 6% 4 6% 8% 32%	4111
	11th to 20th	Day	19% 8% 2 6% 5% 4 5% 4 6% 8% 35%	4044
	21st to end	Day	11% 6% 2 7% 5% 5% 5% 4 6% 7% 42%	4372
September	1st to 10th	Day	18% 7% 3 6% 4 4 4 4 5% 7% 39%	2280
	11th to 20th	Day	19% 6% 2 6% 4 4 4 4 5% 7% 41%	2233
	21st to end	Day	23% 9% 3 6% 5% 4 4 4 5% 6% 32%	2014
October	1st to 10th	Day	20% 12% 4 7% 4 3 3 4 5% 6% 32%	1900
	11th to 20th	Day	25% 16% 3 8% 5% 4 4 3 4 5% 23%	1900
	21st to end	Day	28% 17% 5% 8% 4 5% 4 2 4 5% 18%	2053
November	1st to 10th	Day	20% 15% 5% 9% 4 4 3 3 4 7% 27%	1579
	11th to 20th	Day	18% 19% 5% 10% 6% 5% 4 3 4 5% 20%	1528
	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%	2738
June	1st to 10th	Night	17% 9% 3 8% 6% 6% 5% 3 5% 5% 34%	1469
	11th to 20th	Night	18% 6% 2 5% 3 5% 5% 3 5% 8% 41%	1330
	21st to end	Night	16% 9% 2 7% 5% 4 5% 5% 5% 7% 35%	1330
July	1st to 10th	Night	17% 7% 3 7% 4 5% 4 3 4 7% 39%	2210
	11th to 20th	Night	19% 6% 2 6% 4 4 4 3 4 7% 40%	2382
	21st to end	Night	13% 5% 2 5% 3 4 4 4 6% 7% 48%	2739
August	1st to 10th	Night	13% 6% 2 6% 4 4 4 4 7% 7% 43%	2815
	11th to 20th	Night	18% 6% 3 5% 4 4 5% 3 5% 6% 40%	2785
	21st to end	Night	17% 6% 2 5% 3 3 4 3 6% 8% 44%	3251
September	1st to 10th	Night	16% 5% 2 6% 3 4 4 3 5% 6% 47%	1900
	11th to 20th	Night	18% 7% 2 5% 3 3 3 3 6% 5% 46%	1946
	21st to end	Night	20% 8% 2 6% 3 5% 3 3 4 7% 39%	2166
October	1st to 10th	Night	20% 9% 3 8% 4 4 5% 4 4 6% 34%	2280
	11th to 20th	Night	25% 14% 3 8% 5% 4 4 2 3 4 28%	2280
	21st to end	Night	27% 16% 4 8% 4 4 3 3 5% 5% 22%	2544
November	1st to 10th	Night	20% 16% 4 7% 4 4 4 3 4 5% 28%	2718
	11th to 20th	Night	19% 18% 5% 11% 6% 5% 4 3 4 5% 21%	2675
	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% 17% 2	4837
June	1st to 10th	Day	55% 3 8% 22% 11% 1	2707
	11th to 20th	Day	46% 3 11% 26% 12% 2	2850
	21st to end	Day	51% 4 12% 22% 10% 1	2850
July	1st to 10th	Day	49% 4 13% 25% 8% 1	4686
	11th to 20th	Day	43% 5% 15% 29% 7%	4498
	21st to end	Day	39% 4 13% 32% 13%	4661
August	1st to 10th	Day	47% 5% 13% 28% 7%	4097
	11th to 20th	Day	47% 5% 14% 27% 7%	4083
	21st to end	Day	40% 4 12% 33% 9% 1	4372
September	1st to 10th	Day	46% 3 12% 26% 12%	2280
	11th to 20th	Day	44% 3 13% 30% 9%	2233
	21st to end	Day	53% 5% 11% 24% 7%	2014
October	1st to 10th	Day	54% 4 10% 25% 7%	3160
	11th to 20th	Day	57% 4 12% 21% 6%	3140
	21st to end	Day	69% 3 13% 12% 4	3367
November	1st to 10th	Day	60% 3 13% 19% 5%	1579
	11th to 20th	Day	67% 3 11% 11% 7% 1	1528
	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	2739
June	1st to 10th	Night	51% 4 9% 22% 12% 1	1469
	11th to 20th	Night	43% 3 11% 26% 16% 1	1330
	21st to end	Night	47% 6% 13% 22% 12% 1	1330
July	1st to 10th	Night	45% 4 13% 24% 13% 1	2175
	11th to 20th	Night	45% 4 16% 26% 8% 1	2339
	21st to end	Night	35% 4 13% 33% 15%	2651
August	1st to 10th	Night	38% 6% 16% 29% 11%	2805
	11th to 20th	Night	43% 6% 18% 26% 7% 1	2812
	21st to end	Night	38% 5% 15% 30% 10% 3	3251
September	1st to 10th	Night	39% 3 16% 29% 12% 1	1900
	11th to 20th	Night	41% 3 15% 32% 10%	1946
	21st to end	Night	46% 4 13% 29% 8%	2166
October	1st to 10th	Night	48% 4 11% 28% 9%	3800
	11th to 20th	Night	55% 3 13% 21% 7%	3779
	21st to end	Night	60% 5% 16% 13% 5%	4180
November	1st to 10th	Night	59% 3 13% 18% 7%	2718
	11th to 20th	Night	67% 3 11% 14% 5% 1	2675
	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% 33% 19% 9% 3	529
June	1st to 10th	Day	26% 10% 33% 23% 7% 1	537
	11th to 20th	Day	21% 14% 29% 24% 10% 2	680
	21st to end	Day	21% 14% 31% 23% 9% 2	680
July	1st to 10th	Day	15% 12% 30% 32% 10% 1	671
	11th to 20th	Day	17% 12% 29% 28% 12% 1	565
	21st to end	Day	14% 9% 32% 30% 12% 3	532
August	1st to 10th	Day	20% 6% 30% 26% 13% 5%	486
	11th to 20th	Day	18% 6% 24% 29% 15% 8%	479
	21st to end	Day	18% 12% 29% 23% 12% 6%	539
September	1st to 10th	Day	23% 9% 31% 20% 11% 6%	490
	11th to 20th	Day	20% 8% 24% 26% 14% 8%	490
	21st to end	Day	27% 11% 23% 22% 13% 3	490
October	1st to 10th	Day	28% 13% 25% 19% 11% 3	490
	11th to 20th	Day	29% 20% 30% 17% 4 1	490
	21st to end	Day	36% 14% 30% 16% 4	519
November	1st to 10th	Day	33% 17% 36% 11% 2	213
	11th to 20th	Day	28% 20% 33% 14% 5%	182
	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% 8% 31% 32% 8%	380
	11th to 20th	Night	20% 7% 27% 35% 11%	380
	21st to end	Night	20% 8% 27% 32% 12% 1	380
July	1st to 10th	Night	14% 5% 31% 36% 14% 1	370
	11th to 20th	Night	14% 5% 27% 37% 17% 1	368
	21st to end	Night	12% 6% 29% 38% 14% 1	416
August	1st to 10th	Night	17% 7% 20% 36% 20%	557
	11th to 20th	Night	13% 4 21% 40% 20% 2	564
	21st to end	Night	20% 7% 24% 30% 16% 2	702
September	1st to 10th	Night	20% 5% 25% 31% 18% 1	760
	11th to 20th	Night	21% 6% 24% 24% 21% 3	760
	21st to end	Night	25% 6% 23% 29% 15% 1	760
October	1st to 10th	Night	25% 10% 28% 25% 10% 1	760
	11th to 20th	Night	31% 12% 28% 21% 8% 1	760
	21st to end	Night	37% 12% 26% 21% 4	836
November	1st to 10th	Night	31% 12% 28% 21% 7% 1	780
	11th to 20th	Night	27% 18% 32% 15% 7%	765
	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 2024-11-08 22:45:36. Version ac07

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