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 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	18% 8% 2 6% 4 4 4 4 5% 7% 38%	101154
	Night	19% 8% 2 6% 4 4 4 3 5% 6% 38%	98032
Transparency	Day	45% 5% 12% 23% 14% 2	104693
	Night	46% 4 11% 22% 14% 2	102582
Seeing	Day	21% 13% 31% 24% 9% 2	15653
	Night	22% 12% 30% 26% 9% 1	24070

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	17% 8% 3 6% 5% 4 4 3 4 5% 42%	2517
	11th to 20th	Day	18% 7% 2 6% 3 3 3 3 5% 6% 44%	2520
	21st to end	Day	16% 11% 4 7% 4 3 3 3 5% 6% 38%	2808
February	1st to 10th	Day	16% 11% 2 6% 5% 5% 4 4 5% 6% 36%	1710
	11th to 20th	Day	14% 9% 3 6% 5% 5% 5% 4 5% 5% 40%	1784
	21st to end	Day	14% 10% 3 8% 5% 4 4 5% 6% 6% 36%	1570
March	1st to 10th	Day	25% 12% 2 6% 4 4 4 3 5% 5% 30%	3130
	11th to 20th	Day	18% 9% 3 7% 5% 4 4 4 5% 6% 36%	3480
	21st to end	Day	26% 9% 3 5% 4 4 4 3 6% 6% 30%	3816
April	1st to 10th	Day	20% 10% 3 7% 5% 4 3 3 5% 6% 34%	2271
	11th to 20th	Day	18% 8% 3 7% 4 4 4 3 4 6% 40%	2404
	21st to end	Day	21% 9% 3 7% 4 4 4 4 5% 6% 35%	2470
May	1st to 10th	Day	21% 9% 2 6% 4 4 4 4 6% 6% 33%	4106
	11th to 20th	Day	18% 7% 2 7% 4 4 5% 4 4 7% 37%	4081
	21st to end	Day	17% 7% 2 5% 4 4 4 4 6% 9% 37%	4851
June	1st to 10th	Day	22% 8% 2 6% 5% 5% 4 4 5% 7% 32%	2850
	11th to 20th	Day	18% 7% 3 6% 4 4 3 4 6% 7% 38%	2850
	21st to end	Day	24% 7% 2 7% 4 4 5% 4 6% 6% 30%	2850
July	1st to 10th	Day	15% 6% 2 7% 5% 5% 5% 4 6% 9% 36%	4453
	11th to 20th	Day	12% 6% 2 6% 4 4 5% 4 6% 10% 40%	4440
	21st to end	Day	20% 7% 2 6% 4 4 4 4 5% 8% 36%	4755
August	1st to 10th	Day	16% 8% 3 7% 4 4 5% 4 7% 8% 34%	4105
	11th to 20th	Day	16% 9% 3 7% 4 4 5% 4 6% 7% 35%	4045
	21st to end	Day	10% 5% 2 5% 5% 4 4 4 7% 8% 46%	4476
September	1st to 10th	Day	10% 5% 2 5% 4 4 4 3 5% 8% 50%	2195
	11th to 20th	Day	12% 5% 1 5% 3 3 3 3 5% 6% 54%	2090
	21st to end	Day	17% 6% 2 6% 3 3 3 3 5% 7% 44%	2090
October	1st to 10th	Day	16% 7% 3 6% 4 5% 5% 4 5% 5% 41%	2052
	11th to 20th	Day	19% 5% 2 6% 4 4 3 3 4 6% 43%	1876
	21st to end	Day	22% 8% 2 5% 4 4 4 3 4 5% 39%	1881
November	1st to 10th	Day	16% 6% 3 5% 4 4 4 3 4 8% 43%	1761
	11th to 20th	Day	20% 6% 1 5% 3 3 3 4 5% 6% 43%	1719
	21st to end	Day	19% 9% 2 5% 2 3 3 3 3 5% 44%	1531
December	1st to 10th	Day	21% 10% 3 5% 5% 4 3 3 4 6% 36%	1411
	11th to 20th	Day	22% 10% 2 3 4 4 3 3 4 5% 40%	1668
	21st to end	Day	26% 10% 2 5% 4 4 4 3 5% 6% 32%	2538
January	1st to 10th	Night	16% 9% 2 7% 5% 3 3 3 5% 6% 41%	4429
	11th to 20th	Night	13% 9% 3 9% 5% 4 4 3 5% 6% 39%	4440
	21st to end	Night	17% 13% 4 9% 4 4 4 3 4 5% 35%	4848
February	1st to 10th	Night	17% 9% 3 7% 4 6% 5% 4 5% 5% 36%	2470
	11th to 20th	Night	14% 9% 3 7% 5% 5% 4 3 5% 6% 39%	2279
	21st to end	Night	15% 10% 3 6% 4 4 4 3 4 6% 41%	1884
March	1st to 10th	Night	28% 12% 2 6% 3 4 3 2 4 4 32%	3708
	11th to 20th	Night	13% 9% 3 8% 6% 5% 5% 5% 7% 7% 33%	3479
	21st to end	Night	27% 9% 3 6% 4 4 5% 4 5% 5% 30%	3816
April	1st to 10th	Night	22% 11% 2 6% 4 4 3 3 4 6% 35%	1905
	11th to 20th	Night	19% 8% 2 6% 4 4 4 3 6% 9% 35%	1725
	21st to end	Night	23% 9% 3 6% 5% 3 4 3 4 6% 35%	1710
May	1st to 10th	Night	24% 8% 3 5% 3 4 3 4 5% 8% 34%	2834
	11th to 20th	Night	19% 7% 3 7% 5% 6% 5% 4 7% 8% 29%	2813
	21st to end	Night	17% 7% 3 7% 5% 4 5% 3 5% 7% 37%	2749
June	1st to 10th	Night	23% 8% 2 6% 5% 4 4 4 6% 7% 30%	1330
	11th to 20th	Night	16% 8% 2 8% 4 4 5% 3 5% 7% 39%	1330
	21st to end	Night	23% 10% 2 7% 5% 4 5% 3 5% 5% 30%	1330
July	1st to 10th	Night	14% 7% 2 7% 5% 6% 6% 5% 7% 9% 32%	2502
	11th to 20th	Night	15% 6% 2 7% 4 5% 5% 5% 6% 8% 37%	2520
	21st to end	Night	15% 8% 2 7% 4 4 5% 4 6% 8% 39%	2765
August	1st to 10th	Night	21% 9% 3 7% 5% 4 5% 4 5% 7% 30%	2825
	11th to 20th	Night	17% 10% 2 7% 4 5% 5% 4 6% 7% 33%	2782
	21st to end	Night	10% 5% 2 6% 4 4 4 4 6% 8% 48%	3178
September	1st to 10th	Night	13% 6% 2 4 4 3 4 4 5% 6% 49%	1985
	11th to 20th	Night	16% 6% 2 4 2 2 3 2 5% 6% 53%	2090
	21st to end	Night	17% 6% 2 6% 3 4 4 3 4 6% 46%	2090
October	1st to 10th	Night	19% 6% 2 6% 4 4 4 3 5% 6% 41%	2128
	11th to 20th	Night	18% 5% 2 5% 4 3 4 3 4 7% 45%	2302
	21st to end	Night	24% 8% 2 5% 4 4 3 2 4 6% 38%	2717
November	1st to 10th	Night	17% 6% 2 6% 4 3 3 4 5% 5% 44%	2537
	11th to 20th	Night	18% 7% 2 5% 4 5% 4 3 4 6% 43%	2484
	21st to end	Night	18% 7% 2 5% 4 4 3 3 6% 6% 42%	2645
December	1st to 10th	Night	22% 9% 2 5% 5% 4 4 3 5% 5% 35%	2764
	11th to 20th	Night	22% 8% 2 4 4 4 3 2 4 5% 41%	3531
	21st to end	Night	24% 9% 2 4 3 3 3 3 5% 5% 37%	5108

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	45% 4 12% 27% 10% 1	2518
	11th to 20th	Day	43% 3 12% 27% 13% 3	2520
	21st to end	Day	48% 4 13% 21% 13% 1	2808
February	1st to 10th	Day	49% 3 11% 19% 15% 2	1710
	11th to 20th	Day	45% 4 12% 21% 16% 2	1792
	21st to end	Day	48% 3 10% 22% 12% 5%	1570
March	1st to 10th	Day	56% 5% 8% 13% 14% 3	3133
	11th to 20th	Day	46% 6% 10% 22% 13% 3	3480
	21st to end	Day	52% 5% 6% 15% 17% 5%	3816
April	1st to 10th	Day	51% 4 8% 18% 15% 4	2271
	11th to 20th	Day	45% 4 9% 24% 16% 2	2404
	21st to end	Day	49% 4 8% 19% 16% 3	2470
May	1st to 10th	Day	48% 8% 14% 20% 9% 1	4120
	11th to 20th	Day	46% 7% 14% 23% 9% 1	4085
	21st to end	Day	43% 8% 14% 21% 14% 1	4851
June	1st to 10th	Day	50% 5% 13% 22% 9% 1	2850
	11th to 20th	Day	45% 6% 11% 21% 15% 2	2850
	21st to end	Day	53% 7% 9% 19% 10% 2	2850
July	1st to 10th	Day	46% 6% 11% 25% 12%	4383
	11th to 20th	Day	40% 5% 17% 27% 11% 1	4365
	21st to end	Day	46% 5% 12% 23% 12% 1	4603
August	1st to 10th	Day	47% 6% 15% 26% 7%	4092
	11th to 20th	Day	46% 5% 18% 21% 9%	4084
	21st to end	Day	32% 5% 13% 29% 20% 1	4476
September	1st to 10th	Day	33% 6% 13% 28% 19% 1	2195
	11th to 20th	Day	32% 4 11% 29% 21% 3	2090
	21st to end	Day	41% 3 9% 28% 18% 1	2090
October	1st to 10th	Day	48% 4 12% 23% 13% 1	3416
	11th to 20th	Day	32% 3 9% 33% 24%	3092
	21st to end	Day	35% 2 14% 25% 20% 4	3081
November	1st to 10th	Day	41% 3 13% 25% 16% 2	1761
	11th to 20th	Day	43% 3 9% 23% 19% 3	1719
	21st to end	Day	45% 3 16% 22% 13% 1	1531
December	1st to 10th	Day	51% 4 9% 23% 12% 1	1411
	11th to 20th	Day	49% 4 8% 21% 15% 3	1668
	21st to end	Day	54% 6% 11% 17% 9% 2	2538
January	1st to 10th	Night	45% 4 12% 27% 10% 2	4429
	11th to 20th	Night	47% 5% 12% 22% 12% 2	4440
	21st to end	Night	53% 3 10% 22% 11% 1	4848
February	1st to 10th	Night	51% 3 11% 19% 13% 3	2470
	11th to 20th	Night	47% 4 8% 22% 17% 3	2281
	21st to end	Night	45% 4 9% 21% 15% 5%	1884
March	1st to 10th	Night	57% 3 8% 16% 11% 4	3718
	11th to 20th	Night	47% 7% 13% 19% 11% 3	3480
	21st to end	Night	56% 4 5% 15% 17% 3	3816
April	1st to 10th	Night	52% 4 7% 15% 19% 4	1905
	11th to 20th	Night	46% 4 8% 23% 17% 2	1725
	21st to end	Night	51% 3 10% 17% 15% 3	1710
May	1st to 10th	Night	49% 6% 18% 19% 8% 1	2840
	11th to 20th	Night	51% 7% 15% 18% 7% 1	2814
	21st to end	Night	46% 8% 13% 19% 13% 1	2750
June	1st to 10th	Night	51% 6% 11% 22% 8% 2	1330
	11th to 20th	Night	46% 5% 14% 21% 12% 2	1330
	21st to end	Night	55% 4 9% 20% 9% 3	1330
July	1st to 10th	Night	49% 6% 12% 20% 12%	2462
	11th to 20th	Night	45% 5% 15% 24% 11%	2472
	21st to end	Night	43% 5% 13% 25% 12% 1	2677
August	1st to 10th	Night	55% 5% 13% 20% 7%	2813
	11th to 20th	Night	49% 5% 13% 22% 10%	2809
	21st to end	Night	33% 5% 14% 26% 21% 1	3178
September	1st to 10th	Night	35% 4 13% 29% 18% 1	1985
	11th to 20th	Night	34% 3 11% 29% 21% 2	2090
	21st to end	Night	39% 4 9% 29% 17% 2	2090
October	1st to 10th	Night	42% 4 14% 24% 15% 1	3544
	11th to 20th	Night	31% 3 9% 31% 24% 2	3825
	21st to end	Night	38% 3 10% 29% 17% 3	4467
November	1st to 10th	Night	41% 4 11% 27% 16% 1	2537
	11th to 20th	Night	44% 3 9% 24% 18% 2	2484
	21st to end	Night	44% 4 14% 21% 16% 2	2645
December	1st to 10th	Night	52% 4 9% 21% 13%	2764
	11th to 20th	Night	46% 4 10% 21% 18% 1	3532
	21st to end	Night	50% 5% 13% 18% 13% 1	5108

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% 22% 31% 17% 8%	180
	11th to 20th	Day	23% 24% 30% 17% 5% 1	180
	21st to end	Day	18% 20% 34% 24% 5%	221
February	1st to 10th	Day	22% 21% 34% 19% 4	370
	11th to 20th	Day	21% 25% 37% 14% 3	425
	21st to end	Day	18% 21% 34% 23% 4	382
March	1st to 10th	Day	23% 18% 37% 20% 2	460
	11th to 20th	Day	18% 21% 38% 18% 4	460
	21st to end	Day	25% 21% 29% 17% 7% 1	506
April	1st to 10th	Day	28% 19% 31% 17% 5% 1	460
	11th to 20th	Day	24% 18% 34% 17% 6% 1	452
	21st to end	Day	24% 15% 37% 17% 6% 1	460
May	1st to 10th	Day	26% 17% 30% 21% 6% 1	463
	11th to 20th	Day	15% 14% 35% 26% 8% 2	487
	21st to end	Day	20% 12% 34% 27% 7% 1	553
June	1st to 10th	Day	22% 8% 30% 27% 11% 1	680
	11th to 20th	Day	18% 9% 31% 27% 13% 3	680
	21st to end	Day	26% 6% 27% 27% 11% 2	680
July	1st to 10th	Day	19% 7% 31% 31% 10% 2	498
	11th to 20th	Day	16% 5% 29% 35% 13% 3	484
	21st to end	Day	16% 5% 30% 33% 14% 2	532
August	1st to 10th	Day	15% 5% 27% 35% 17% 1	486
	11th to 20th	Day	19% 5% 21% 37% 15% 3	479
	21st to end	Day	16% 8% 26% 33% 14% 4	539
September	1st to 10th	Day	13% 7% 29% 31% 18% 2	490
	11th to 20th	Day	16% 8% 27% 26% 17% 7%	490
	21st to end	Day	16% 11% 29% 26% 12% 5%	490
October	1st to 10th	Day	19% 12% 26% 27% 13% 3	470
	11th to 20th	Day	22% 13% 29% 22% 11% 3	390
	21st to end	Day	29% 13% 29% 22% 5% 1	429
November	1st to 10th	Day	19% 18% 26% 26% 8% 2	395
	11th to 20th	Day	24% 16% 34% 21% 4 1	373
	21st to end	Day	24% 19% 30% 19% 7%	370
December	1st to 10th	Day	25% 13% 38% 17% 6% 1	261
	11th to 20th	Day	27% 28% 31% 11% 3 1	180
	21st to end	Day	27% 25% 28% 13% 7%	198
January	1st to 10th	Night	20% 20% 36% 20% 3	760
	11th to 20th	Night	23% 21% 34% 18% 4	760
	21st to end	Night	18% 20% 39% 20% 3	836
February	1st to 10th	Night	22% 20% 34% 20% 4	760
	11th to 20th	Night	19% 22% 37% 19% 3	743
	21st to end	Night	21% 14% 37% 23% 4	628
March	1st to 10th	Night	24% 17% 35% 22% 2	760
	11th to 20th	Night	20% 16% 34% 24% 7%	760
	21st to end	Night	23% 14% 34% 22% 6% 1	836
April	1st to 10th	Night	28% 13% 34% 20% 5% 1	760
	11th to 20th	Night	23% 11% 30% 30% 6%	601
	21st to end	Night	28% 11% 28% 26% 6% 1	570
May	1st to 10th	Night	26% 4 30% 29% 10% 1	570
	11th to 20th	Night	24% 5% 32% 31% 8% 1	562
	21st to end	Night	21% 7% 25% 35% 10% 1	448
June	1st to 10th	Night	26% 7% 22% 34% 11% 1	380
	11th to 20th	Night	17% 6% 24% 36% 17% 1	380
	21st to end	Night	27% 7% 19% 36% 11% 1	380
July	1st to 10th	Night	19% 4 18% 42% 17% 1	370
	11th to 20th	Night	20% 4 17% 40% 18% 1	368
	21st to end	Night	17% 3 19% 42% 18% 2	430
August	1st to 10th	Night	17% 5% 17% 43% 17% 1	568
	11th to 20th	Night	18% 4 18% 41% 17% 2	562
	21st to end	Night	15% 5% 20% 37% 21% 2	655
September	1st to 10th	Night	14% 4 28% 35% 18% 2	760
	11th to 20th	Night	18% 6% 25% 29% 17% 5%	760
	21st to end	Night	19% 7% 28% 28% 16% 3	760
October	1st to 10th	Night	21% 8% 24% 29% 16% 1	760
	11th to 20th	Night	20% 10% 32% 24% 12% 2	760
	21st to end	Night	27% 14% 30% 23% 6%	836
November	1st to 10th	Night	22% 12% 30% 27% 7% 2	780
	11th to 20th	Night	20% 18% 32% 22% 8% 1	765
	21st to end	Night	22% 20% 32% 20% 7%	843
December	1st to 10th	Night	26% 16% 36% 17% 5%	850
	11th to 20th	Night	25% 20% 33% 19% 3	850
	21st to end	Night	27% 19% 33% 17% 4	899

Page generated at 2024-11-08 22:45:35. Version ac07

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