Galaxy Quest Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Galaxy Quest Observatory 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% 8% 3 6% 4 4 4 3 5% 7% 38%	126450
	Night	18% 9% 3 6% 4 4 4 3 5% 6% 38%	124904
Transparency	Day	46% 5% 11% 22% 14% 2	129971
	Night	47% 4 11% 22% 14% 2	129470
Seeing	Day	21% 14% 31% 24% 9% 2	17085
	Night	22% 13% 30% 26% 9% 1	25600

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% 8% 3 7% 5% 5% 5% 4 5% 6% 38%	3605
	11th to 20th	Day	14% 8% 3 6% 3 3 3 3 5% 7% 45%	3570
	21st to end	Day	13% 9% 4 7% 4 3 3 3 4 5% 45%	4024
February	1st to 10th	Day	16% 11% 2 6% 4 5% 4 4 5% 6% 37%	1800
	11th to 20th	Day	14% 8% 2 6% 5% 4 5% 5% 5% 6% 40%	1881
	21st to end	Day	14% 10% 3 8% 5% 4 4 5% 5% 6% 37%	1650
March	1st to 10th	Day	23% 12% 2 6% 4 4 5% 3 5% 5% 31%	4490
	11th to 20th	Day	18% 12% 3 6% 4 4 4 3 5% 6% 35%	4980
	21st to end	Day	27% 9% 3 5% 4 4 4 3 6% 6% 30%	5466
April	1st to 10th	Day	20% 10% 3 7% 5% 4 3 3 5% 6% 34%	2391
	11th to 20th	Day	19% 8% 3 7% 4 4 4 3 4 6% 39%	2532
	21st to end	Day	21% 8% 2 7% 4 4 4 4 5% 6% 36%	2600
May	1st to 10th	Day	30% 10% 3 7% 4 3 4 3 5% 5% 26%	5886
	11th to 20th	Day	19% 8% 3 8% 5% 5% 5% 4 4 6% 34%	5861
	21st to end	Day	20% 7% 2 6% 4 4 4 4 6% 8% 34%	6963
June	1st to 10th	Day	22% 8% 2 6% 5% 5% 4 4 5% 7% 32%	3000
	11th to 20th	Day	17% 7% 3 6% 4 4 3 4 5% 7% 38%	3000
	21st to end	Day	24% 7% 2 7% 4 4 5% 4 6% 6% 31%	3000
July	1st to 10th	Day	16% 8% 3 7% 5% 5% 5% 4 6% 9% 32%	6373
	11th to 20th	Day	12% 9% 3 7% 4 4 4 4 5% 8% 38%	6360
	21st to end	Day	15% 6% 2 5% 3 4 4 4 5% 9% 43%	6839
August	1st to 10th	Day	16% 7% 3 7% 4 4 5% 4 6% 8% 35%	4235
	11th to 20th	Day	16% 8% 3 7% 4 4 5% 4 6% 7% 35%	4175
	21st to end	Day	10% 5% 2 5% 4 4 4 4 7% 8% 47%	4617
September	1st to 10th	Day	10% 5% 2 5% 4 4 4 3 5% 8% 50%	2310
	11th to 20th	Day	12% 5% 1 4 3 3 3 3 5% 6% 54%	2200
	21st to end	Day	17% 6% 2 6% 3 3 3 3 5% 7% 45%	2200
October	1st to 10th	Day	15% 7% 3 6% 4 4 5% 4 5% 5% 43%	2160
	11th to 20th	Day	19% 5% 2 6% 4 4 3 3 4 6% 43%	1975
	21st to end	Day	22% 8% 2 5% 4 4 4 3 4 6% 39%	1980
November	1st to 10th	Day	16% 6% 3 6% 4 4 4 3 5% 8% 42%	1851
	11th to 20th	Day	19% 6% 2 5% 3 3 4 4 5% 6% 44%	1890
	21st to end	Day	19% 9% 3 5% 2 3 3 3 3 5% 43%	1691
December	1st to 10th	Day	16% 11% 2 4 3 3 3 2 5% 6% 45%	2491
	11th to 20th	Day	18% 8% 2 3 4 3 3 3 4 5% 46%	2688
	21st to end	Day	21% 12% 4 6% 3 3 3 3 5% 5% 35%	3716
January	1st to 10th	Night	13% 9% 3 8% 5% 4 3 3 5% 6% 41%	6364
	11th to 20th	Night	14% 10% 4 9% 5% 4 5% 3 5% 6% 36%	6315
	21st to end	Night	12% 11% 3 8% 4 4 4 4 4 6% 41%	6932
February	1st to 10th	Night	17% 9% 3 7% 4 6% 5% 4 5% 5% 36%	2600
	11th to 20th	Night	14% 9% 3 7% 5% 5% 4 3 5% 6% 39%	2402
	21st to end	Night	14% 10% 3 7% 4 4 4 3 4 6% 41%	1980
March	1st to 10th	Night	26% 11% 2 6% 4 4 3 2 4 5% 31%	5348
	11th to 20th	Night	16% 10% 3 7% 5% 4 5% 4 6% 7% 34%	4979
	21st to end	Night	26% 9% 2 6% 4 3 5% 4 6% 6% 31%	5466
April	1st to 10th	Night	22% 11% 2 6% 4 4 3 3 5% 6% 34%	2005
	11th to 20th	Night	19% 8% 2 6% 4 4 4 4 6% 8% 34%	1817
	21st to end	Night	23% 9% 3 6% 5% 3 4 3 4 6% 35%	1800
May	1st to 10th	Night	30% 10% 4 7% 4 3 3 3 4 6% 27%	4054
	11th to 20th	Night	21% 9% 3 7% 4 5% 4 3 6% 7% 30%	4033
	21st to end	Night	16% 8% 4 8% 5% 4 5% 3 5% 7% 34%	3939
June	1st to 10th	Night	23% 9% 2 6% 5% 4 4 4 6% 8% 30%	1400
	11th to 20th	Night	16% 8% 2 7% 4 4 5% 3 5% 7% 39%	1400
	21st to end	Night	22% 10% 2 7% 5% 4 5% 3 6% 6% 31%	1400
July	1st to 10th	Night	13% 8% 3 7% 5% 5% 6% 5% 6% 8% 33%	3569
	11th to 20th	Night	15% 10% 2 6% 4 5% 6% 5% 6% 7% 34%	3600
	21st to end	Night	11% 6% 2 5% 4 4 5% 4 7% 9% 43%	3966
August	1st to 10th	Night	21% 9% 3 7% 5% 4 6% 4 5% 7% 31%	2915
	11th to 20th	Night	17% 10% 2 7% 4 5% 5% 4 6% 7% 34%	2872
	21st to end	Night	10% 5% 2 6% 4 4 4 4 6% 8% 48%	3279
September	1st to 10th	Night	12% 6% 2 4 4 3 4 4 5% 6% 50%	2090
	11th to 20th	Night	15% 6% 2 4 2 2 3 2 5% 6% 53%	2200
	21st to end	Night	16% 6% 2 5% 3 4 4 3 5% 6% 46%	2200
October	1st to 10th	Night	18% 6% 2 6% 4 4 4 3 5% 5% 43%	2240
	11th to 20th	Night	18% 5% 2 5% 4 3 4 3 4 7% 44%	2423
	21st to end	Night	23% 7% 2 6% 4 4 3 3 4 6% 38%	2860
November	1st to 10th	Night	18% 6% 2 5% 3 3 3 4 5% 5% 45%	2667
	11th to 20th	Night	17% 6% 2 5% 4 5% 4 3 4 6% 44%	2730
	21st to end	Night	18% 7% 2 5% 4 4 3 3 6% 6% 42%	2925
December	1st to 10th	Night	17% 10% 3 5% 4 4 4 3 5% 7% 39%	4914
	11th to 20th	Night	22% 8% 2 4 3 3 3 2 4 5% 43%	5741
	21st to end	Night	21% 10% 2 6% 4 3 3 3 4 5% 39%	7479

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	48% 4 9% 28% 11% 1	3606
	11th to 20th	Day	41% 3 11% 29% 13% 3	3600
	21st to end	Day	43% 3 10% 19% 18% 7%	4024
February	1st to 10th	Day	49% 3 10% 19% 16% 3	1800
	11th to 20th	Day	45% 4 12% 20% 15% 3	1889
	21st to end	Day	47% 3 10% 21% 13% 5%	1650
March	1st to 10th	Day	54% 4 8% 11% 15% 7%	4493
	11th to 20th	Day	49% 4 13% 20% 11% 2	4980
	21st to end	Day	53% 4 5% 17% 16% 4	5466
April	1st to 10th	Day	51% 3 7% 18% 16% 4	2391
	11th to 20th	Day	45% 4 9% 24% 16% 3	2532
	21st to end	Day	48% 4 8% 20% 16% 4	2600
May	1st to 10th	Day	59% 6% 11% 17% 6% 1	5897
	11th to 20th	Day	51% 6% 11% 21% 8% 3	5865
	21st to end	Day	47% 6% 13% 21% 11% 1	6963
June	1st to 10th	Day	49% 5% 13% 22% 11% 1	3000
	11th to 20th	Day	44% 6% 11% 22% 15% 2	3000
	21st to end	Day	52% 7% 9% 20% 10% 2	3000
July	1st to 10th	Day	50% 5% 12% 22% 10%	6303
	11th to 20th	Day	44% 5% 14% 23% 13% 1	6285
	21st to end	Day	39% 5% 13% 28% 14% 1	6642
August	1st to 10th	Day	46% 6% 14% 26% 7%	4222
	11th to 20th	Day	46% 5% 18% 21% 9%	4214
	21st to end	Day	32% 5% 13% 29% 20% 1	4617
September	1st to 10th	Day	33% 6% 13% 28% 19% 1	2310
	11th to 20th	Day	32% 4 11% 29% 22% 3	2200
	21st to end	Day	41% 3 9% 28% 18% 1	2200
October	1st to 10th	Day	47% 4 11% 24% 13% 1	3524
	11th to 20th	Day	32% 3 9% 32% 23%	3191
	21st to end	Day	35% 2 14% 25% 20% 3	3180
November	1st to 10th	Day	41% 3 13% 24% 17% 2	1851
	11th to 20th	Day	42% 3 9% 23% 19% 3	1890
	21st to end	Day	46% 3 15% 23% 12% 1	1691
December	1st to 10th	Day	41% 3 13% 28% 13% 1	2491
	11th to 20th	Day	42% 3 11% 19% 17% 7%	2688
	21st to end	Day	52% 5% 10% 18% 13% 3	3716
January	1st to 10th	Night	45% 3 11% 28% 12% 1	6364
	11th to 20th	Night	50% 4 11% 22% 11% 2	6360
	21st to end	Night	46% 3 8% 21% 17% 5%	6932
February	1st to 10th	Night	51% 3 11% 18% 14% 3	2600
	11th to 20th	Night	47% 4 9% 21% 17% 3	2404
	21st to end	Night	45% 4 9% 22% 15% 5%	1980
March	1st to 10th	Night	56% 3 6% 13% 13% 9%	5358
	11th to 20th	Night	48% 6% 17% 19% 9% 2	4980
	21st to end	Night	53% 3 5% 16% 19% 3	5466
April	1st to 10th	Night	52% 4 7% 15% 18% 4	2005
	11th to 20th	Night	47% 4 9% 22% 17% 2	1817
	21st to end	Night	52% 3 9% 17% 15% 3	1800
May	1st to 10th	Night	59% 5% 13% 15% 7% 1	4060
	11th to 20th	Night	53% 6% 12% 19% 8% 1	4034
	21st to end	Night	50% 7% 12% 20% 11% 1	3940
June	1st to 10th	Night	51% 6% 11% 22% 9% 2	1400
	11th to 20th	Night	45% 5% 14% 22% 12% 2	1400
	21st to end	Night	54% 4 9% 21% 10% 2	1400
July	1st to 10th	Night	49% 5% 12% 23% 10%	3529
	11th to 20th	Night	50% 4 13% 21% 12%	3552
	21st to end	Night	37% 5% 17% 30% 11% 1	3849
August	1st to 10th	Night	55% 5% 12% 20% 8%	2903
	11th to 20th	Night	49% 5% 13% 22% 10%	2899
	21st to end	Night	33% 5% 14% 27% 21% 1	3279
September	1st to 10th	Night	35% 4 13% 29% 18% 1	2090
	11th to 20th	Night	34% 3 11% 29% 22% 2	2200
	21st to end	Night	39% 5% 9% 29% 17% 2	2200
October	1st to 10th	Night	41% 4 13% 25% 16% 1	3656
	11th to 20th	Night	32% 3 9% 31% 24% 2	3946
	21st to end	Night	39% 3 10% 29% 17% 3	4610
November	1st to 10th	Night	41% 4 10% 26% 17% 2	2667
	11th to 20th	Night	43% 3 9% 24% 18% 3	2730
	21st to end	Night	45% 4 14% 21% 15% 2	2925
December	1st to 10th	Night	45% 3 8% 30% 13%	4914
	11th to 20th	Night	45% 3 11% 20% 19% 3	5742
	21st to end	Night	49% 4 10% 18% 17% 1	7479

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% 30% 16% 7%	202
	11th to 20th	Day	23% 25% 30% 18% 5% 1	200
	21st to end	Day	20% 21% 33% 22% 4	245
February	1st to 10th	Day	23% 22% 33% 18% 4	400
	11th to 20th	Day	23% 24% 37% 13% 3	462
	21st to end	Day	19% 22% 35% 21% 4	414
March	1st to 10th	Day	25% 20% 35% 19% 1	500
	11th to 20th	Day	19% 22% 37% 18% 4	500
	21st to end	Day	27% 21% 29% 16% 6% 1	550
April	1st to 10th	Day	29% 20% 30% 15% 4 1	500
	11th to 20th	Day	26% 19% 33% 16% 5% 1	492
	21st to end	Day	25% 16% 37% 17% 6% 1	500
May	1st to 10th	Day	28% 16% 29% 20% 5% 1	503
	11th to 20th	Day	17% 13% 34% 26% 7% 2	527
	21st to end	Day	21% 12% 34% 26% 6% 1	598
June	1st to 10th	Day	22% 9% 30% 27% 11% 1	730
	11th to 20th	Day	19% 9% 31% 26% 12% 3	730
	21st to end	Day	26% 7% 28% 27% 11% 2	730
July	1st to 10th	Day	19% 8% 31% 30% 10% 2	538
	11th to 20th	Day	17% 6% 29% 33% 13% 3	524
	21st to end	Day	16% 6% 30% 32% 13% 2	576
August	1st to 10th	Day	13% 5% 28% 36% 16% 2	526
	11th to 20th	Day	18% 6% 21% 36% 15% 4	519
	21st to end	Day	15% 9% 27% 32% 14% 3	583
September	1st to 10th	Day	13% 8% 30% 31% 17% 2	530
	11th to 20th	Day	15% 8% 27% 26% 16% 7%	530
	21st to end	Day	16% 11% 30% 25% 12% 5%	530
October	1st to 10th	Day	19% 12% 25% 27% 14% 3	508
	11th to 20th	Day	23% 14% 30% 21% 10% 3	420
	21st to end	Day	29% 14% 30% 21% 5% 1	462
November	1st to 10th	Day	20% 20% 26% 25% 8% 2	425
	11th to 20th	Day	24% 17% 34% 20% 5% 1	430
	21st to end	Day	26% 19% 30% 18% 7%	430
December	1st to 10th	Day	25% 16% 35% 17% 6% 1	309
	11th to 20th	Day	29% 26% 31% 10% 3	220
	21st to end	Day	28% 23% 30% 13% 6%	242
January	1st to 10th	Night	20% 20% 36% 20% 3	805
	11th to 20th	Night	23% 21% 33% 18% 5%	800
	21st to end	Night	18% 20% 39% 20% 3	880
February	1st to 10th	Night	23% 20% 33% 20% 4	800
	11th to 20th	Night	20% 22% 37% 18% 3	783
	21st to end	Night	22% 14% 37% 23% 4	660
March	1st to 10th	Night	25% 17% 35% 21% 2	800
	11th to 20th	Night	20% 15% 34% 24% 7%	800
	21st to end	Night	23% 14% 34% 22% 6% 1	880
April	1st to 10th	Night	28% 14% 33% 19% 5% 1	800
	11th to 20th	Night	23% 11% 30% 29% 6%	633
	21st to end	Night	29% 11% 28% 26% 6% 1	600
May	1st to 10th	Night	27% 5% 30% 28% 9% 1	600
	11th to 20th	Night	24% 6% 32% 30% 8% 1	592
	21st to end	Night	21% 7% 26% 34% 10% 1	472
June	1st to 10th	Night	26% 7% 22% 34% 10% 1	400
	11th to 20th	Night	17% 6% 24% 36% 17% 1	400
	21st to end	Night	26% 7% 20% 37% 10% 1	400
July	1st to 10th	Night	18% 4 18% 43% 16% 1	390
	11th to 20th	Night	20% 4 17% 41% 18% 1	388
	21st to end	Night	17% 3 21% 41% 17% 2	453
August	1st to 10th	Night	17% 5% 17% 43% 17% 1	598
	11th to 20th	Night	18% 4 19% 40% 17% 2	592
	21st to end	Night	15% 5% 20% 37% 20% 2	690
September	1st to 10th	Night	14% 4 27% 35% 18% 2	800
	11th to 20th	Night	18% 6% 25% 30% 17% 5%	800
	21st to end	Night	18% 7% 28% 30% 16% 3	800
October	1st to 10th	Night	21% 9% 25% 29% 16% 1	800
	11th to 20th	Night	20% 10% 32% 24% 12% 2	800
	21st to end	Night	27% 14% 30% 23% 6%	880
November	1st to 10th	Night	23% 13% 29% 26% 7% 2	820
	11th to 20th	Night	21% 18% 33% 21% 7% 1	840
	21st to end	Night	23% 20% 31% 19% 7%	943
December	1st to 10th	Night	25% 16% 35% 18% 5%	950
	11th to 20th	Night	26% 22% 32% 17% 3	950
	21st to end	Night	26% 19% 33% 17% 4	1001

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

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