Getchell Mountain
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Getchell Mountain clear sky chart from 2005-11-06 to 2026-01-02.

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% 9% 3 7% 5% 4 4 4 5% 7% 33%	126925
	Night	18% 10% 3 7% 5% 4 4 4 5% 6% 34%	124494
Transparency	Day	49% 6% 11% 21% 12% 2	130426
	Night	48% 6% 12% 21% 12% 1	129081
Seeing	Day	27% 16% 31% 18% 6% 1	17450
	Night	25% 15% 32% 22% 6%	25658

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% 14% 4 9% 5% 5% 5% 5% 5% 6% 29%	3401
	11th to 20th	Day	14% 11% 3 10% 6% 5% 4 3 4 5% 35%	3570
	21st to end	Day	10% 10% 4 9% 6% 5% 5% 4 5% 6% 37%	4073
February	1st to 10th	Day	15% 12% 4 9% 6% 5% 5% 3 5% 7% 29%	1800
	11th to 20th	Day	14% 12% 5% 9% 5% 5% 5% 3 5% 5% 31%	1803
	21st to end	Day	12% 12% 4 8% 6% 5% 5% 4 4 7% 34%	1650
March	1st to 10th	Day	24% 13% 3 9% 5% 4 4 3 4 5% 27%	4567
	11th to 20th	Day	19% 15% 4 9% 6% 4 4 3 5% 6% 26%	4980
	21st to end	Day	26% 10% 4 8% 5% 4 4 3 5% 6% 25%	5466
April	1st to 10th	Day	21% 14% 3 8% 4 4 4 3 4 6% 29%	2359
	11th to 20th	Day	20% 10% 3 7% 5% 4 4 3 5% 5% 34%	2572
	21st to end	Day	23% 11% 3 7% 4 4 3 3 4 5% 34%	2600
May	1st to 10th	Day	27% 11% 3 7% 5% 4 4 3 4 5% 26%	5886
	11th to 20th	Day	22% 9% 3 7% 5% 5% 5% 4 6% 6% 28%	5861
	21st to end	Day	19% 9% 3 7% 6% 5% 5% 4 6% 7% 30%	7375
June	1st to 10th	Day	24% 8% 3 8% 4 5% 4 3 6% 7% 28%	3000
	11th to 20th	Day	20% 7% 2 5% 4 4 4 4 6% 8% 36%	3000
	21st to end	Day	25% 8% 3 7% 5% 4 4 4 5% 6% 28%	3000
July	1st to 10th	Day	14% 8% 3 7% 5% 6% 6% 5% 8% 9% 29%	6820
	11th to 20th	Day	16% 6% 2 7% 4 4 5% 4 6% 8% 37%	6420
	21st to end	Day	13% 6% 3 6% 4 4 5% 4 6% 9% 39%	6796
August	1st to 10th	Day	18% 8% 2 8% 5% 5% 5% 4 6% 7% 33%	4235
	11th to 20th	Day	16% 9% 3 8% 5% 5% 5% 5% 6% 8% 31%	4175
	21st to end	Day	13% 6% 2 7% 4 4 5% 4 5% 8% 42%	4675
September	1st to 10th	Day	11% 5% 2 6% 4 4 3 3 5% 8% 47%	2332
	11th to 20th	Day	14% 7% 2 4 3 4 3 4 4 5% 50%	2200
	21st to end	Day	17% 7% 2 6% 4 3 4 3 4 7% 44%	2200
October	1st to 10th	Day	17% 7% 2 7% 5% 3 3 3 5% 6% 41%	2105
	11th to 20th	Day	20% 7% 2 6% 4 5% 4 3 5% 6% 37%	2000
	21st to end	Day	21% 11% 3 8% 4 4 4 3 5% 6% 32%	1992
November	1st to 10th	Day	20% 8% 2 7% 4 4 5% 4 4 6% 37%	1851
	11th to 20th	Day	19% 9% 2 6% 3 3 5% 4 4 8% 37%	1742
	21st to end	Day	21% 10% 3 8% 5% 4 3 4 5% 6% 31%	1680
December	1st to 10th	Day	19% 11% 2 5% 4 4 4 4 6% 7% 34%	2498
	11th to 20th	Day	20% 9% 3 7% 5% 3 3 4 5% 5% 37%	2688
	21st to end	Day	19% 13% 4 7% 4 4 4 3 5% 6% 32%	3553
January	1st to 10th	Night	12% 12% 5% 10% 6% 5% 4 3 5% 7% 31%	6574
	11th to 20th	Night	14% 11% 4 10% 5% 5% 5% 4 6% 7% 29%	6315
	21st to end	Night	9% 11% 3 8% 5% 5% 5% 5% 5% 7% 38%	6881
February	1st to 10th	Night	15% 11% 4 8% 6% 5% 6% 4 6% 6% 29%	2600
	11th to 20th	Night	13% 12% 3 10% 6% 5% 4 4 5% 6% 31%	2480
	21st to end	Night	14% 12% 4 8% 4 4 4 3 4 5% 36%	1980
March	1st to 10th	Night	26% 13% 4 9% 4 4 3 3 4 4 26%	5273
	11th to 20th	Night	19% 13% 3 7% 5% 5% 5% 3 5% 6% 30%	4979
	21st to end	Night	27% 11% 3 6% 4 4 3 3 6% 7% 26%	5466
April	1st to 10th	Night	21% 13% 3 7% 5% 2 3 3 4 5% 33%	2036
	11th to 20th	Night	22% 10% 2 6% 5% 5% 3 3 5% 7% 33%	1778
	21st to end	Night	25% 10% 3 6% 5% 4 4 3 5% 6% 30%	1800
May	1st to 10th	Night	26% 10% 3 8% 5% 4 3 3 5% 6% 28%	4054
	11th to 20th	Night	20% 10% 3 7% 5% 5% 4 4 6% 6% 29%	4019
	21st to end	Night	17% 9% 2 6% 4 4 4 4 6% 8% 35%	3550
June	1st to 10th	Night	23% 9% 3 7% 5% 4 4 4 5% 8% 29%	1400
	11th to 20th	Night	17% 9% 3 7% 4 4 3 4 6% 8% 36%	1400
	21st to end	Night	25% 7% 3 7% 6% 4 4 3 5% 8% 30%	1400
July	1st to 10th	Night	14% 6% 3 8% 6% 5% 6% 5% 6% 7% 34%	3160
	11th to 20th	Night	18% 8% 3 7% 4 4 5% 4 6% 7% 34%	3526
	21st to end	Night	11% 7% 2 6% 4 4 4 4 7% 9% 41%	4011
August	1st to 10th	Night	20% 6% 3 8% 5% 5% 6% 4 5% 7% 31%	2915
	11th to 20th	Night	15% 9% 3 8% 5% 6% 5% 5% 6% 8% 31%	2872
	21st to end	Night	12% 7% 2 7% 3 4 3 3 5% 7% 46%	3223
September	1st to 10th	Night	14% 5% 1 5% 3 3 4 4 5% 6% 49%	2063
	11th to 20th	Night	15% 6% 2 4 3 3 3 3 5% 6% 50%	2200
	21st to end	Night	17% 6% 2 5% 3 3 4 3 5% 7% 44%	2200
October	1st to 10th	Night	18% 6% 2 5% 3 3 3 4 5% 6% 44%	2294
	11th to 20th	Night	17% 7% 2 7% 5% 4 4 4 5% 6% 39%	2400
	21st to end	Night	22% 10% 3 7% 4 4 4 3 5% 6% 33%	2845
November	1st to 10th	Night	19% 8% 3 7% 4 4 4 4 5% 6% 37%	2667
	11th to 20th	Night	18% 9% 2 6% 4 5% 4 4 5% 5% 37%	2877
	21st to end	Night	19% 10% 3 7% 5% 3 4 4 5% 6% 34%	2940
December	1st to 10th	Night	17% 9% 3 7% 5% 4 4 4 5% 7% 33%	4908
	11th to 20th	Night	23% 9% 2 5% 4 4 3 3 4 5% 37%	5741
	21st to end	Night	21% 11% 3 7% 4 4 4 3 4 5% 33%	7667

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	54% 4 12% 22% 7%	3402
	11th to 20th	Day	49% 5% 9% 24% 11% 1	3600
	21st to end	Day	46% 5% 9% 15% 20% 4	4073
February	1st to 10th	Day	53% 6% 11% 17% 12% 3	1800
	11th to 20th	Day	53% 5% 10% 18% 12% 1	1811
	21st to end	Day	49% 5% 10% 20% 11% 4	1650
March	1st to 10th	Day	59% 4 7% 11% 15% 4	4571
	11th to 20th	Day	56% 7% 13% 13% 10% 1	4980
	21st to end	Day	59% 3 7% 17% 12% 2	5466
April	1st to 10th	Day	57% 5% 8% 14% 13% 3	2359
	11th to 20th	Day	49% 5% 9% 21% 14% 1	2572
	21st to end	Day	51% 5% 8% 18% 14% 4	2600
May	1st to 10th	Day	60% 5% 9% 17% 7% 1	5897
	11th to 20th	Day	53% 6% 11% 20% 6% 3	5865
	21st to end	Day	50% 7% 12% 16% 13% 1	7375
June	1st to 10th	Day	53% 6% 12% 18% 10% 1	3000
	11th to 20th	Day	45% 6% 11% 21% 15% 2	3000
	21st to end	Day	54% 8% 10% 17% 10% 1	3000
July	1st to 10th	Day	47% 7% 15% 22% 9% 1	6745
	11th to 20th	Day	42% 7% 14% 23% 12% 1	6343
	21st to end	Day	40% 6% 13% 29% 12% 1	6600
August	1st to 10th	Day	49% 7% 12% 25% 7%	4222
	11th to 20th	Day	48% 8% 15% 21% 8%	4214
	21st to end	Day	37% 6% 13% 25% 18% 1	4675
September	1st to 10th	Day	34% 7% 12% 29% 18% 1	2332
	11th to 20th	Day	36% 4 9% 28% 20% 3	2200
	21st to end	Day	40% 5% 9% 28% 18% 1	2200
October	1st to 10th	Day	51% 5% 9% 24% 10%	3430
	11th to 20th	Day	40% 5% 10% 31% 13%	3240
	21st to end	Day	37% 4 17% 23% 18%	3192
November	1st to 10th	Day	47% 6% 13% 19% 14% 1	1851
	11th to 20th	Day	45% 6% 12% 22% 13% 2	1742
	21st to end	Day	52% 6% 14% 21% 7%	1680
December	1st to 10th	Day	48% 6% 18% 18% 10%	2498
	11th to 20th	Day	48% 5% 14% 16% 12% 6%	2688
	21st to end	Day	52% 5% 10% 19% 11% 4	3553
January	1st to 10th	Night	51% 6% 11% 25% 7% 1	6574
	11th to 20th	Night	52% 6% 13% 20% 9% 1	6360
	21st to end	Night	44% 5% 9% 21% 17% 4	6881
February	1st to 10th	Night	51% 6% 12% 17% 11% 2	2600
	11th to 20th	Night	52% 5% 10% 18% 13% 1	2483
	21st to end	Night	50% 3 8% 21% 15% 3	1980
March	1st to 10th	Night	62% 4 6% 13% 12% 4	5282
	11th to 20th	Night	53% 6% 16% 17% 7% 1	4980
	21st to end	Night	57% 3 7% 19% 14% 1	5466
April	1st to 10th	Night	53% 4 8% 15% 16% 4	2036
	11th to 20th	Night	49% 6% 10% 19% 14% 2	1778
	21st to end	Night	54% 6% 9% 15% 13% 3	1800
May	1st to 10th	Night	56% 6% 12% 16% 9% 1	4060
	11th to 20th	Night	52% 8% 11% 21% 6% 1	4020
	21st to end	Night	45% 8% 15% 21% 9% 1	3551
June	1st to 10th	Night	53% 6% 11% 21% 8% 1	1400
	11th to 20th	Night	46% 6% 13% 22% 12% 1	1400
	21st to end	Night	54% 7% 10% 19% 10% 2	1400
July	1st to 10th	Night	46% 7% 14% 23% 9%	3125
	11th to 20th	Night	48% 7% 12% 26% 7%	3480
	21st to end	Night	37% 8% 17% 26% 10% 1	3893
August	1st to 10th	Night	52% 7% 13% 21% 7%	2903
	11th to 20th	Night	47% 8% 17% 20% 7% 1	2899
	21st to end	Night	36% 8% 15% 23% 17% 1	3223
September	1st to 10th	Night	34% 7% 13% 30% 15% 1	2063
	11th to 20th	Night	35% 4 13% 28% 18% 1	2200
	21st to end	Night	39% 6% 10% 28% 16% 1	2200
October	1st to 10th	Night	43% 5% 12% 27% 13% 1	3749
	11th to 20th	Night	37% 6% 12% 30% 16%	3899
	21st to end	Night	41% 5% 14% 25% 14% 1	4595
November	1st to 10th	Night	45% 6% 12% 24% 12% 1	2667
	11th to 20th	Night	46% 6% 12% 22% 13% 2	2877
	21st to end	Night	50% 6% 14% 19% 10% 1	2940
December	1st to 10th	Night	49% 4 13% 25% 9%	4908
	11th to 20th	Night	49% 4 11% 19% 16% 1	5742
	21st to end	Night	53% 5% 10% 18% 12% 2	7667

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	38% 16% 31% 13% 2	202
	11th to 20th	Day	34% 20% 36% 6% 4 1	200
	21st to end	Day	24% 22% 34% 16% 4	268
February	1st to 10th	Day	25% 20% 35% 18% 3	400
	11th to 20th	Day	28% 28% 33% 10% 1	421
	21st to end	Day	26% 22% 35% 14% 2	414
March	1st to 10th	Day	31% 24% 30% 13% 2	500
	11th to 20th	Day	28% 21% 33% 14% 3 1	500
	21st to end	Day	34% 19% 30% 13% 3 1	550
April	1st to 10th	Day	39% 20% 25% 11% 3 1	500
	11th to 20th	Day	36% 21% 28% 11% 4	492
	21st to end	Day	35% 18% 32% 11% 3 1	500
May	1st to 10th	Day	35% 17% 29% 15% 3 1	503
	11th to 20th	Day	29% 18% 28% 20% 4 1	527
	21st to end	Day	25% 19% 33% 18% 5% 1	790
June	1st to 10th	Day	30% 13% 30% 19% 7% 1	730
	11th to 20th	Day	25% 15% 29% 21% 9% 2	730
	21st to end	Day	29% 11% 31% 22% 7% 1	730
July	1st to 10th	Day	19% 12% 34% 25% 8% 2	720
	11th to 20th	Day	21% 11% 35% 24% 8% 1	556
	21st to end	Day	17% 9% 38% 29% 6% 2	576
August	1st to 10th	Day	16% 9% 36% 27% 10% 2	526
	11th to 20th	Day	18% 10% 27% 31% 11% 3	519
	21st to end	Day	18% 14% 28% 28% 10% 2	583
September	1st to 10th	Day	15% 13% 35% 24% 10% 3	530
	11th to 20th	Day	22% 11% 29% 20% 13% 5%	530
	21st to end	Day	19% 15% 34% 19% 9% 4	530
October	1st to 10th	Day	23% 13% 28% 22% 11% 3	478
	11th to 20th	Day	26% 17% 32% 16% 8% 2	420
	21st to end	Day	29% 20% 30% 16% 4 1	462
November	1st to 10th	Day	30% 18% 31% 15% 5% 1	425
	11th to 20th	Day	30% 21% 30% 13% 6%	430
	21st to end	Day	31% 20% 30% 16% 3	430
December	1st to 10th	Day	28% 18% 35% 15% 3	316
	11th to 20th	Day	35% 24% 31% 9% 1	220
	21st to end	Day	34% 22% 29% 11% 5%	242
January	1st to 10th	Night	25% 20% 33% 20% 2	851
	11th to 20th	Night	27% 18% 32% 18% 5%	800
	21st to end	Night	19% 19% 39% 20% 3 1	880
February	1st to 10th	Night	25% 21% 34% 18% 2	800
	11th to 20th	Night	24% 24% 36% 13% 2 1	783
	21st to end	Night	24% 20% 32% 21% 3	660
March	1st to 10th	Night	29% 16% 35% 19% 1	800
	11th to 20th	Night	26% 19% 33% 19% 4	800
	21st to end	Night	26% 18% 32% 19% 5%	880
April	1st to 10th	Night	32% 18% 31% 16% 3	780
	11th to 20th	Night	28% 17% 34% 16% 5%	594
	21st to end	Night	34% 15% 30% 17% 5%	600
May	1st to 10th	Night	29% 13% 30% 24% 4	600
	11th to 20th	Night	25% 16% 35% 19% 5%	592
	21st to end	Night	20% 15% 35% 24% 6%	485
June	1st to 10th	Night	29% 9% 34% 24% 5%	400
	11th to 20th	Night	21% 8% 36% 27% 8%	400
	21st to end	Night	29% 7% 29% 30% 5%	400
July	1st to 10th	Night	17% 6% 38% 34% 6%	390
	11th to 20th	Night	19% 5% 30% 37% 7% 1	388
	21st to end	Night	18% 4 33% 36% 9%	473
August	1st to 10th	Night	19% 4 31% 36% 10%	598
	11th to 20th	Night	19% 6% 28% 34% 13% 1	592
	21st to end	Night	15% 9% 29% 33% 13% 1	660
September	1st to 10th	Night	17% 7% 35% 28% 13%	740
	11th to 20th	Night	18% 9% 27% 30% 14% 2	800
	21st to end	Night	21% 11% 31% 26% 11% 1	800
October	1st to 10th	Night	22% 10% 28% 27% 13%	800
	11th to 20th	Night	21% 15% 32% 24% 8% 1	800
	21st to end	Night	30% 16% 31% 20% 3	880
November	1st to 10th	Night	27% 17% 30% 20% 5% 1	820
	11th to 20th	Night	26% 18% 31% 18% 7% 1	917
	21st to end	Night	29% 19% 31% 17% 3 1	950
December	1st to 10th	Night	30% 15% 31% 19% 4 1	950
	11th to 20th	Night	30% 22% 29% 17% 2	950
	21st to end	Night	30% 19% 32% 15% 4	1045

Page generated at 2025-12-30 01:14:07. Version ac07

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