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 2024-01-13.

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% 7% 3 5% 5% 3 4 4 5% 7% 39%	74575
	Night	19% 8% 3 5% 5% 3 4 4 5% 6% 39%	75145
Transparency	Day	45% 5% 11% 23% 14% 2	74281
	Night	46% 4 11% 22% 15% 2	74973
Seeing	Day	21% 13% 31% 25% 9% 2	14492
	Night	22% 12% 30% 26% 9% 1	23065

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% 4 6% 5% 3 4 4 4 6% 41%	1517
	11th to 20th	Day	21% 8% 3 6% 5% 2 3 3 4 7% 37%	1462
	21st to end	Day	14% 9% 4 6% 5% 2 4 4 5% 6% 41%	1606
February	1st to 10th	Day	17% 11% 3 5% 5% 3 5% 5% 5% 6% 35%	1620
	11th to 20th	Day	15% 8% 3 6% 6% 3 5% 6% 5% 6% 39%	1688
	21st to end	Day	14% 10% 3 7% 5% 3 5% 5% 5% 6% 35%	1480
March	1st to 10th	Day	16% 9% 3 6% 5% 3 5% 5% 5% 7% 37%	1797
	11th to 20th	Day	17% 6% 3 5% 6% 3 5% 4 4 6% 42%	1980
	21st to end	Day	18% 9% 3 4 4 4 4 4 4 5% 40%	2178
April	1st to 10th	Day	21% 8% 3 6% 5% 3 4 4 4 6% 34%	2151
	11th to 20th	Day	18% 7% 3 6% 5% 3 4 4 4 6% 40%	2276
	21st to end	Day	22% 9% 3 6% 5% 3 4 4 4 6% 34%	2340
May	1st to 10th	Day	23% 8% 2 6% 5% 3 5% 5% 5% 6% 33%	2340
	11th to 20th	Day	20% 7% 2 6% 5% 3 4 5% 4 6% 39%	2301
	21st to end	Day	18% 7% 3 5% 4 3 4 4 7% 9% 36%	2725
June	1st to 10th	Day	22% 8% 3 6% 5% 3 5% 4 5% 7% 32%	2700
	11th to 20th	Day	18% 6% 4 5% 5% 3 3 5% 5% 8% 38%	2700
	21st to end	Day	24% 6% 3 6% 5% 3 5% 5% 6% 7% 31%	2700
July	1st to 10th	Day	17% 6% 3 4 5% 3 5% 4 6% 9% 39%	2533
	11th to 20th	Day	14% 7% 2 6% 6% 3 5% 6% 6% 9% 38%	2520
	21st to end	Day	14% 6% 2 5% 5% 4 6% 6% 6% 10% 36%	2711
August	1st to 10th	Day	13% 6% 2 4 5% 2 5% 6% 7% 9% 39%	2327
	11th to 20th	Day	14% 6% 3 6% 5% 4 5% 5% 7% 9% 37%	2304
	21st to end	Day	14% 4 2 4 4 3 4 5% 7% 9% 45%	2546
September	1st to 10th	Day	10% 5% 2 5% 5% 3 4 4 5% 8% 49%	2080
	11th to 20th	Day	13% 5% 2 4 3 2 3 4 4 6% 54%	1980
	21st to end	Day	17% 5% 2 5% 4 2 3 4 5% 7% 45%	1980
October	1st to 10th	Day	16% 6% 3 5% 5% 3 5% 5% 5% 5% 42%	1944
	11th to 20th	Day	20% 4 2 5% 5% 4 4 3 5% 6% 42%	1778
	21st to end	Day	23% 8% 2 4 5% 3 3 4 4 5% 37%	1782
November	1st to 10th	Day	17% 6% 3 4 4 3 4 3 4 8% 43%	1671
	11th to 20th	Day	20% 6% 2 4 3 2 4 4 4 6% 44%	1710
	21st to end	Day	19% 9% 3 4 3 3 3 4 4 5% 44%	1531
December	1st to 10th	Day	22% 9% 3 5% 6% 3 3 3 4 6% 36%	1411
	11th to 20th	Day	23% 9% 3 3 4 3 3 4 4 5% 40%	1668
	21st to end	Day	26% 9% 2 5% 5% 3 4 4 5% 6% 32%	2538
January	1st to 10th	Night	16% 8% 3 5% 6% 3 4 4 5% 6% 39%	2649
	11th to 20th	Night	17% 11% 3 7% 7% 3 4 4 5% 6% 33%	2560
	21st to end	Night	11% 10% 4 6% 5% 3 5% 5% 4 7% 41%	2750
February	1st to 10th	Night	18% 8% 3 6% 5% 4 6% 5% 5% 6% 35%	2340
	11th to 20th	Night	15% 9% 4 6% 5% 4 5% 4 5% 6% 39%	2155
	21st to end	Night	14% 9% 3 5% 5% 4 4 4 4 6% 41%	1776
March	1st to 10th	Night	15% 11% 3 6% 5% 3 4 4 4 5% 39%	2148
	11th to 20th	Night	17% 8% 3 6% 6% 3 4 6% 5% 7% 35%	1979
	21st to end	Night	18% 8% 3 5% 5% 3 4 4 4 6% 42%	2178
April	1st to 10th	Night	23% 10% 3 5% 5% 3 4 4 4 6% 34%	1805
	11th to 20th	Night	19% 7% 3 5% 5% 3 4 4 6% 9% 36%	1633
	21st to end	Night	25% 9% 4 5% 5% 2 4 4 4 6% 33%	1620
May	1st to 10th	Night	22% 8% 4 6% 5% 3 4 5% 5% 7% 31%	1620
	11th to 20th	Night	22% 7% 3 5% 5% 3 5% 5% 6% 7% 32%	1593
	21st to end	Night	19% 8% 3 7% 5% 3 5% 3 5% 7% 35%	1559
June	1st to 10th	Night	24% 8% 3 5% 6% 3 5% 5% 6% 7% 29%	1260
	11th to 20th	Night	17% 8% 2 7% 5% 2 5% 4 5% 7% 39%	1260
	21st to end	Night	23% 9% 3 6% 5% 2 6% 4 5% 6% 31%	1260
July	1st to 10th	Night	18% 6% 3 5% 4 3 5% 5% 5% 9% 36%	1422
	11th to 20th	Night	17% 7% 2 6% 5% 3 5% 5% 5% 8% 37%	1440
	21st to end	Night	17% 7% 3 6% 5% 3 5% 6% 5% 8% 36%	1587
August	1st to 10th	Night	14% 7% 3 4 4 3 5% 6% 5% 7% 41%	1612
	11th to 20th	Night	15% 8% 2 5% 5% 4 4 5% 6% 8% 37%	1596
	21st to end	Night	14% 5% 2 4 4 2 4 4 5% 8% 47%	1808
September	1st to 10th	Night	13% 5% 2 4 4 2 4 5% 5% 6% 49%	1880
	11th to 20th	Night	16% 6% 2 3 2 1 3 3 4 7% 52%	1980
	21st to end	Night	17% 5% 2 4 3 3 4 4 4 6% 46%	1980
October	1st to 10th	Night	19% 6% 2 5% 5% 3 5% 4 5% 6% 41%	2016
	11th to 20th	Night	19% 5% 2 4 5% 3 4 4 4 7% 44%	2180
	21st to end	Night	25% 7% 2 5% 4 3 3 3 4 6% 37%	2574
November	1st to 10th	Night	18% 6% 2 5% 4 2 3 4 5% 5% 44%	2407
	11th to 20th	Night	18% 6% 2 4 4 3 5% 4 4 7% 43%	2470
	21st to end	Night	19% 6% 2 5% 4 3 4 4 5% 6% 42%	2645
December	1st to 10th	Night	22% 9% 3 5% 5% 3 4 4 5% 5% 35%	2764
	11th to 20th	Night	22% 8% 2 4 4 3 3 3 4 6% 41%	3531
	21st to end	Night	24% 9% 2 4 4 3 3 4 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	46% 3 10% 23% 15% 2	1518
	11th to 20th	Day	50% 5% 11% 21% 12% 2	1462
	21st to end	Day	45% 2 11% 23% 18% 2	1606
February	1st to 10th	Day	51% 3 11% 18% 15% 2	1620
	11th to 20th	Day	46% 4 12% 20% 15% 2	1696
	21st to end	Day	49% 4 10% 21% 12% 5%	1480
March	1st to 10th	Day	46% 5% 12% 19% 16% 4	1800
	11th to 20th	Day	43% 4 8% 22% 17% 6%	1980
	21st to end	Day	43% 4 10% 18% 18% 6%	2178
April	1st to 10th	Day	51% 3 8% 18% 16% 4	2151
	11th to 20th	Day	45% 4 9% 23% 16% 3	2276
	21st to end	Day	51% 4 9% 18% 15% 4	2340
May	1st to 10th	Day	51% 3 8% 21% 14% 3	2340
	11th to 20th	Day	45% 5% 9% 23% 16% 2	2305
	21st to end	Day	46% 6% 13% 22% 11% 2	2725
June	1st to 10th	Day	50% 5% 13% 22% 10% 1	2700
	11th to 20th	Day	45% 6% 10% 21% 16% 2	2700
	21st to end	Day	53% 7% 10% 19% 10% 2	2700
July	1st to 10th	Day	42% 7% 13% 24% 13% 1	2463
	11th to 20th	Day	43% 6% 14% 25% 11% 1	2445
	21st to end	Day	42% 7% 14% 25% 11% 1	2559
August	1st to 10th	Day	38% 8% 15% 29% 9%	2314
	11th to 20th	Day	42% 7% 14% 23% 13%	2304
	21st to end	Day	35% 6% 13% 27% 18% 1	2546
September	1st to 10th	Day	34% 6% 14% 28% 18% 1	2080
	11th to 20th	Day	33% 5% 10% 28% 21% 3	1980
	21st to end	Day	41% 3 9% 28% 18% 1	1980
October	1st to 10th	Day	43% 5% 10% 24% 15% 2	1944
	11th to 20th	Day	43% 4 13% 28% 12% 1	1778
	21st to end	Day	49% 3 10% 21% 15% 2	1782
November	1st to 10th	Day	41% 3 13% 25% 16% 2	1671
	11th to 20th	Day	43% 3 9% 23% 19% 3	1710
	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	46% 4 11% 23% 13% 2	2649
	11th to 20th	Night	53% 5% 12% 18% 10% 2	2560
	21st to end	Night	45% 4 10% 22% 17% 2	2750
February	1st to 10th	Night	52% 3 11% 18% 13% 3	2340
	11th to 20th	Night	48% 4 8% 21% 16% 3	2157
	21st to end	Night	45% 4 9% 21% 16% 5%	1776
March	1st to 10th	Night	48% 3 8% 21% 17% 3	2158
	11th to 20th	Night	48% 4 10% 18% 16% 4	1980
	21st to end	Night	45% 4 8% 19% 20% 4	2178
April	1st to 10th	Night	52% 4 7% 14% 18% 4	1805
	11th to 20th	Night	46% 4 8% 23% 17% 1	1633
	21st to end	Night	53% 3 10% 17% 13% 4	1620
May	1st to 10th	Night	53% 4 10% 19% 14% 1	1620
	11th to 20th	Night	51% 5% 10% 19% 12% 3	1594
	21st to end	Night	51% 4 11% 19% 14% 1	1560
June	1st to 10th	Night	53% 5% 11% 21% 9% 2	1260
	11th to 20th	Night	47% 5% 12% 21% 12% 2	1260
	21st to end	Night	54% 4 9% 20% 10% 2	1260
July	1st to 10th	Night	45% 7% 13% 23% 12% 1	1382
	11th to 20th	Night	46% 6% 14% 23% 11% 1	1392
	21st to end	Night	45% 5% 14% 25% 9% 1	1499
August	1st to 10th	Night	43% 5% 15% 28% 10% 1	1600
	11th to 20th	Night	45% 6% 14% 22% 13%	1596
	21st to end	Night	38% 4 11% 27% 19% 1	1808
September	1st to 10th	Night	36% 4 14% 29% 17% 1	1880
	11th to 20th	Night	35% 3 11% 28% 21% 2	1980
	21st to end	Night	38% 5% 9% 30% 17% 2	1980
October	1st to 10th	Night	45% 4 10% 25% 14% 2	2016
	11th to 20th	Night	41% 4 12% 29% 13% 1	2180
	21st to end	Night	49% 4 10% 21% 14% 1	2574
November	1st to 10th	Night	42% 4 11% 25% 16% 1	2407
	11th to 20th	Night	43% 3 9% 24% 18% 2	2470
	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% 21% 31% 17% 8%	180
	11th to 20th	Day	25% 23% 30% 16% 5% 1	166
	21st to end	Day	18% 20% 35% 23% 4	198
February	1st to 10th	Day	24% 20% 34% 18% 3	340
	11th to 20th	Day	23% 23% 37% 14% 3	389
	21st to end	Day	18% 21% 36% 22% 3	346
March	1st to 10th	Day	23% 17% 39% 20% 1	420
	11th to 20th	Day	18% 20% 38% 18% 4	420
	21st to end	Day	24% 20% 29% 18% 8% 2	462
April	1st to 10th	Day	29% 19% 31% 16% 5% 1	420
	11th to 20th	Day	23% 18% 34% 17% 6% 1	412
	21st to end	Day	26% 14% 36% 17% 6% 1	420
May	1st to 10th	Day	27% 16% 30% 21% 5% 1	423
	11th to 20th	Day	16% 15% 36% 24% 7% 2	447
	21st to end	Day	20% 12% 35% 25% 7% 1	507
June	1st to 10th	Day	23% 8% 30% 27% 11% 1	630
	11th to 20th	Day	18% 9% 30% 28% 12% 3	630
	21st to end	Day	25% 5% 27% 29% 12% 2	630
July	1st to 10th	Day	19% 7% 29% 32% 11% 2	458
	11th to 20th	Day	16% 4 27% 36% 14% 3	444
	21st to end	Day	14% 4 30% 35% 15% 2	488
August	1st to 10th	Day	14% 5% 26% 36% 18% 2	446
	11th to 20th	Day	18% 4 21% 38% 16% 3	439
	21st to end	Day	16% 8% 24% 34% 15% 3	495
September	1st to 10th	Day	12% 6% 29% 32% 19% 2	450
	11th to 20th	Day	17% 9% 28% 25% 16% 6%	450
	21st to end	Day	16% 10% 30% 26% 13% 5%	450
October	1st to 10th	Day	19% 12% 24% 28% 13% 4	432
	11th to 20th	Day	21% 13% 31% 21% 11% 3	360
	21st to end	Day	30% 13% 29% 23% 6% 1	396
November	1st to 10th	Day	18% 18% 26% 28% 9% 2	365
	11th to 20th	Day	24% 15% 34% 22% 4 1	370
	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	24% 20% 33% 18% 4	732
	21st to end	Night	18% 21% 38% 20% 3	792
February	1st to 10th	Night	23% 20% 34% 20% 3	720
	11th to 20th	Night	20% 22% 36% 19% 3	703
	21st to end	Night	21% 15% 38% 22% 4	592
March	1st to 10th	Night	23% 17% 37% 22% 2	720
	11th to 20th	Night	21% 15% 33% 24% 7%	720
	21st to end	Night	22% 14% 34% 23% 6% 1	792
April	1st to 10th	Night	27% 13% 35% 19% 5% 1	720
	11th to 20th	Night	22% 11% 30% 30% 6%	569
	21st to end	Night	30% 10% 27% 26% 6% 1	540
May	1st to 10th	Night	26% 4 31% 28% 9% 1	540
	11th to 20th	Night	24% 5% 34% 30% 6%	532
	21st to end	Night	21% 7% 25% 34% 10% 1	424
June	1st to 10th	Night	26% 7% 21% 34% 10% 1	360
	11th to 20th	Night	18% 6% 23% 36% 17%	360
	21st to end	Night	26% 6% 19% 38% 11% 1	360
July	1st to 10th	Night	20% 3 18% 42% 17% 1	350
	11th to 20th	Night	20% 4 16% 40% 19% 1	348
	21st to end	Night	17% 3 18% 41% 18% 2	407
August	1st to 10th	Night	16% 5% 16% 44% 18% 1	538
	11th to 20th	Night	18% 4 18% 41% 17% 2	532
	21st to end	Night	16% 5% 19% 37% 21% 2	620
September	1st to 10th	Night	15% 3 27% 35% 18% 2	720
	11th to 20th	Night	19% 6% 26% 28% 17% 5%	720
	21st to end	Night	18% 7% 28% 28% 16% 3	720
October	1st to 10th	Night	21% 8% 24% 29% 16% 1	720
	11th to 20th	Night	20% 8% 32% 25% 12% 2	720
	21st to end	Night	28% 13% 30% 23% 6% 1	792
November	1st to 10th	Night	23% 11% 30% 27% 8% 2	740
	11th to 20th	Night	20% 17% 32% 22% 8% 1	760
	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 2024-01-10 19:35:23. Version ac07

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