Goat Shed Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Goat Shed Observatory clear sky chart from 2005-11-06 to 2024-03-01.

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	6% 5% 2 5% 5% 3 4 4 5% 7% 54%	78460
	Night	7% 6% 3 5% 5% 3 4 5% 5% 7% 50%	80961
Transparency	Day	28% 6% 13% 22% 19% 12%	78164
	Night	33% 7% 14% 21% 16% 9%	80779
Seeing	Day	8% 10% 24% 30% 21% 7%	13518
	Night	9% 5% 22% 41% 21% 2	23083

By Month

Percentage Cloud Cover SW (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	7% 10% 5% 7% 7% 4 6% 6% 7% 6% 35%	2539
	11th to 20th	Day	9% 13% 5% 10% 8% 4 6% 6% 6% 7% 27%	2540
	21st to end	Day	11% 9% 4 9% 6% 4 5% 5% 6% 7% 33%	2794
February	1st to 10th	Day	7% 7% 3 5% 6% 4 5% 5% 7% 9% 42%	1729
	11th to 20th	Day	7% 8% 3 6% 6% 4 6% 5% 6% 8% 41%	1850
	21st to end	Day	5% 8% 3 6% 5% 4 6% 6% 6% 8% 42%	1570
March	1st to 10th	Day	6% 7% 3 7% 6% 4 7% 6% 7% 7% 40%	1801
	11th to 20th	Day	6% 6% 3 7% 4 2 4 6% 7% 9% 44%	1938
	21st to end	Day	8% 7% 3 7% 6% 4 5% 6% 6% 8% 42%	2218
April	1st to 10th	Day	7% 6% 2 6% 6% 3 5% 6% 6% 9% 45%	2160
	11th to 20th	Day	4 6% 2 5% 6% 2 4 4 6% 8% 52%	2199
	21st to end	Day	5% 5% 3 4 5% 3 4 5% 5% 8% 54%	2340
May	1st to 10th	Day	4 4 2 5% 4 3 5% 4 6% 7% 57%	2340
	11th to 20th	Day	5% 4 2 5% 5% 4 4 5% 7% 9% 51%	2301
	21st to end	Day	6% 5% 2 4 5% 3 5% 5% 8% 10% 48%	2701
June	1st to 10th	Day	6% 3 2 4 5% 3 5% 5% 6% 10% 52%	2520
	11th to 20th	Day	4 3 1 3 4 2 3 3 4 7% 64%	2520
	21st to end	Day	3 2 1 2 3 1 3 3 3 6% 74%	2520
July	1st to 10th	Day	2 2 1 2 2 2 3 3 4 7% 73%	2520
	11th to 20th	Day	3 1 1 1 2 1 2 2 3 5% 79%	2520
	21st to end	Day	3 2 1 2 3 2 3 3 4 5% 71%	2741
August	1st to 10th	Day	4 3 1 3 3 2 4 3 4 6% 66%	2332
	11th to 20th	Day	1 1 1 2 2 2 2 3 4 6% 75%	2299
	21st to end	Day	2 2 1 2 2 2 2 2 4 5% 76%	2430
September	1st to 10th	Day	1 2 1 2 2 2 3 3 3 5% 77%	2134
	11th to 20th	Day	4 3 1 3 3 2 2 3 4 5% 69%	1980
	21st to end	Day	5% 3 1 2 3 2 3 3 4 6% 69%	1980
October	1st to 10th	Day	6% 4 2 4 4 2 3 4 5% 7% 61%	1980
	11th to 20th	Day	4 3 2 3 4 2 3 4 4 7% 63%	1774
	21st to end	Day	4 3 1 4 3 3 4 4 6% 9% 58%	1782
November	1st to 10th	Day	8% 5% 2 5% 6% 4 4 4 5% 9% 47%	1674
	11th to 20th	Day	7% 5% 2 5% 6% 4 5% 5% 7% 8% 46%	1710
	21st to end	Day	8% 7% 2 7% 6% 3 5% 6% 6% 8% 43%	1710
December	1st to 10th	Day	11% 9% 3 5% 6% 3 5% 5% 4 7% 42%	1592
	11th to 20th	Day	10% 8% 4 8% 7% 4 4 6% 7% 8% 33%	1928
	21st to end	Day	8% 8% 4 9% 6% 4 5% 6% 6% 7% 38%	2794
January	1st to 10th	Night	9% 10% 4 8% 6% 4 5% 6% 6% 8% 34%	4406
	11th to 20th	Night	13% 15% 5% 9% 9% 4 5% 5% 4 6% 25%	4420
	21st to end	Night	12% 10% 5% 9% 7% 4 5% 4 5% 6% 34%	4862
February	1st to 10th	Night	10% 8% 3 7% 6% 3 5% 6% 6% 8% 40%	2443
	11th to 20th	Night	8% 6% 3 5% 5% 2 5% 4 4 7% 49%	2218
	21st to end	Night	8% 7% 3 5% 5% 3 5% 5% 7% 9% 42%	1884
March	1st to 10th	Night	6% 8% 3 7% 6% 4 5% 5% 7% 8% 41%	2165
	11th to 20th	Night	7% 6% 3 6% 6% 3 5% 6% 6% 8% 46%	2021
	21st to end	Night	7% 8% 3 6% 6% 3 6% 5% 5% 7% 42%	2134
April	1st to 10th	Night	7% 5% 3 5% 5% 3 6% 5% 6% 7% 48%	1800
	11th to 20th	Night	6% 5% 3 6% 6% 2 5% 6% 6% 7% 49%	1709
	21st to end	Night	4 4 2 5% 4 3 4 5% 6% 7% 56%	1620
May	1st to 10th	Night	6% 5% 2 4 4 2 3 4 6% 7% 57%	1620
	11th to 20th	Night	6% 4 2 5% 4 3 5% 6% 6% 10% 51%	1594
	21st to end	Night	7% 4 3 5% 5% 3 6% 5% 7% 8% 47%	1571
June	1st to 10th	Night	5% 4 2 5% 4 3 4 6% 7% 9% 50%	1440
	11th to 20th	Night	4 3 1 3 3 2 3 4 4 8% 64%	1440
	21st to end	Night	1 1 1 3 3 2 4 3 4 6% 74%	1440
July	1st to 10th	Night	2 1 2 2 1 4 4 5% 8% 70%	1440
	11th to 20th	Night	1 1 1 2 2 1 3 3 4 4 78%	1440
	21st to end	Night	2 2 1 2 3 2 3 3 5% 6% 70%	1576
August	1st to 10th	Night	4 3 1 3 3 2 3 3 5% 7% 66%	1606
	11th to 20th	Night	1 1 1 2 1 3 5% 4 7% 73%	1602
	21st to end	Night	2 2 1 2 3 1 3 3 4 5% 74%	1922
September	1st to 10th	Night	2 2 1 3 2 1 3 3 3 4 76%	1825
	11th to 20th	Night	4 2 1 2 2 2 4 4 5% 6% 67%	1980
	21st to end	Night	5% 3 1 2 3 2 3 3 3 5% 69%	1980
October	1st to 10th	Night	7% 3 2 3 3 2 4 3 4 7% 63%	1980
	11th to 20th	Night	7% 2 2 4 4 3 3 3 4 8% 61%	2182
	21st to end	Night	5% 3 1 4 4 3 4 5% 6% 7% 58%	2574
November	1st to 10th	Night	10% 5% 2 5% 4 2 5% 4 5% 7% 49%	2405
	11th to 20th	Night	9% 5% 3 6% 5% 3 4 5% 6% 7% 46%	2470
	21st to end	Night	7% 5% 2 6% 5% 3 5% 5% 6% 8% 47%	2470
December	1st to 10th	Night	10% 8% 4 7% 6% 3 4 4 5% 8% 40%	2584
	11th to 20th	Night	12% 10% 4 9% 7% 3 5% 5% 6% 7% 32%	3276
	21st to end	Night	9% 8% 3 7% 6% 4 5% 6% 5% 7% 40%	4862

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	44% 12% 23% 17% 4	2539
	11th to 20th	Day	52% 14% 19% 13% 2	2540
	21st to end	Day	48% 11% 23% 15% 2	2794
February	1st to 10th	Day	37% 11% 23% 23% 5% 1	1729
	11th to 20th	Day	38% 10% 20% 22% 9%	1860
	21st to end	Day	38% 8% 18% 27% 9% 1	1570
March	1st to 10th	Day	40% 11% 15% 24% 9% 2	1801
	11th to 20th	Day	33% 8% 17% 29% 12% 2	1938
	21st to end	Day	39% 8% 19% 23% 9% 2	2218
April	1st to 10th	Day	34% 6% 15% 22% 17% 4	2160
	11th to 20th	Day	28% 6% 13% 29% 19% 4	2202
	21st to end	Day	28% 4 13% 27% 25% 3	2340
May	1st to 10th	Day	25% 6% 10% 27% 26% 6%	2340
	11th to 20th	Day	26% 8% 11% 29% 20% 6%	2304
	21st to end	Day	29% 7% 15% 26% 19% 4	2701
June	1st to 10th	Day	27% 6% 12% 25% 25% 4	2520
	11th to 20th	Day	21% 4 7% 21% 33% 14%	2520
	21st to end	Day	13% 3 5% 17% 33% 29%	2520
July	1st to 10th	Day	12% 3 6% 15% 30% 35%	2451
	11th to 20th	Day	10% 2 4 10% 24% 50%	2445
	21st to end	Day	15% 3 4 9% 24% 45%	2589
August	1st to 10th	Day	20% 3 7% 14% 26% 30%	2316
	11th to 20th	Day	11% 2 5% 17% 34% 31%	2299
	21st to end	Day	12% 2 4 16% 37% 28%	2430
September	1st to 10th	Day	12% 3 5% 14% 31% 35%	2134
	11th to 20th	Day	18% 3 7% 26% 26% 21%	1980
	21st to end	Day	18% 4 7% 22% 35% 14%	1980
October	1st to 10th	Day	24% 4 12% 27% 24% 8%	1980
	11th to 20th	Day	22% 5% 11% 34% 24% 5%	1774
	21st to end	Day	22% 6% 17% 32% 20% 2	1782
November	1st to 10th	Day	36% 6% 14% 27% 15% 2	1674
	11th to 20th	Day	34% 8% 22% 29% 6% 1	1710
	21st to end	Day	38% 7% 21% 27% 7%	1710
December	1st to 10th	Day	41% 10% 21% 21% 8%	1592
	11th to 20th	Day	45% 11% 27% 15% 2	1928
	21st to end	Day	42% 8% 20% 23% 7%	2794
January	1st to 10th	Night	45% 9% 23% 18% 4	4406
	11th to 20th	Night	55% 11% 18% 13% 3	4420
	21st to end	Night	48% 10% 20% 18% 4	4862
February	1st to 10th	Night	41% 10% 21% 22% 4 1	2443
	11th to 20th	Night	35% 7% 22% 26% 10% 1	2219
	21st to end	Night	36% 8% 19% 28% 9% 1	1884
March	1st to 10th	Night	38% 9% 17% 26% 9% 2	2165
	11th to 20th	Night	35% 7% 13% 29% 15% 1	2021
	21st to end	Night	40% 7% 17% 23% 11% 1	2134
April	1st to 10th	Night	35% 5% 14% 23% 17% 5%	1800
	11th to 20th	Night	33% 6% 10% 26% 22% 3	1709
	21st to end	Night	26% 5% 14% 27% 23% 4	1620
May	1st to 10th	Night	25% 5% 9% 24% 31% 6%	1620
	11th to 20th	Night	27% 6% 12% 28% 22% 5%	1595
	21st to end	Night	32% 8% 13% 24% 20% 4	1571
June	1st to 10th	Night	29% 8% 11% 23% 25% 5%	1440
	11th to 20th	Night	20% 4 8% 20% 35% 13%	1440
	21st to end	Night	12% 3 6% 16% 31% 32%	1440
July	1st to 10th	Night	13% 3 5% 12% 29% 38%	1400
	11th to 20th	Night	11% 3 5% 7% 21% 54%	1392
	21st to end	Night	15% 3 4 9% 22% 48%	1488
August	1st to 10th	Night	19% 4 6% 14% 21% 37%	1598
	11th to 20th	Night	11% 3 6% 12% 28% 40%	1602
	21st to end	Night	14% 3 5% 13% 29% 36%	1922
September	1st to 10th	Night	13% 3 4 12% 28% 40%	1825
	11th to 20th	Night	18% 4 6% 18% 27% 27%	1980
	21st to end	Night	19% 3 5% 19% 33% 21%	1980
October	1st to 10th	Night	23% 3 8% 25% 27% 13%	1980
	11th to 20th	Night	24% 4 8% 31% 28% 6%	2182
	21st to end	Night	23% 7% 13% 30% 23% 3	2574
November	1st to 10th	Night	34% 7% 13% 25% 19% 2	2405
	11th to 20th	Night	34% 8% 15% 31% 11% 1	2470
	21st to end	Night	34% 6% 20% 31% 9%	2470
December	1st to 10th	Night	41% 9% 23% 19% 8% 1	2584
	11th to 20th	Night	49% 8% 20% 20% 2	3276
	21st to end	Night	41% 9% 21% 23% 7%	4862

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	17% 12% 24% 29% 14% 4	180
	11th to 20th	Day	8% 9% 32% 29% 17% 4	180
	21st to end	Day	11% 8% 27% 30% 20% 4	198
February	1st to 10th	Day	12% 14% 31% 29% 13% 1	291
	11th to 20th	Day	12% 14% 30% 29% 12% 3	455
	21st to end	Day	9% 16% 30% 36% 9%	382
March	1st to 10th	Day	7% 11% 38% 32% 10% 1	421
	11th to 20th	Day	9% 14% 30% 30% 15% 2	420
	21st to end	Day	11% 18% 34% 24% 12% 2	462
April	1st to 10th	Day	15% 17% 27% 21% 15% 5%	420
	11th to 20th	Day	10% 21% 32% 23% 11% 4	412
	21st to end	Day	8% 21% 30% 23% 15% 2	420
May	1st to 10th	Day	6% 14% 33% 28% 15% 4	423
	11th to 20th	Day	10% 13% 25% 27% 19% 5%	448
	21st to end	Day	8% 9% 21% 26% 23% 13%	485
June	1st to 10th	Day	5% 10% 26% 27% 21% 10%	450
	11th to 20th	Day	7% 16% 29% 25% 17% 5%	450
	21st to end	Day	3 7% 26% 34% 22% 8%	450
July	1st to 10th	Day	2 4 22% 35% 27% 9%	446
	11th to 20th	Day	3 4 22% 37% 29% 6%	444
	21st to end	Day	2 3 17% 35% 35% 8%	487
August	1st to 10th	Day	6% 4 18% 36% 26% 10%	447
	11th to 20th	Day	2 5% 13% 31% 33% 15%	437
	21st to end	Day	2 5% 18% 29% 30% 15%	495
September	1st to 10th	Day	3 6% 16% 25% 35% 16%	450
	11th to 20th	Day	5% 5% 17% 30% 31% 12%	450
	21st to end	Day	6% 10% 19% 28% 28% 9%	450
October	1st to 10th	Day	9% 9% 18% 26% 28% 11%	450
	11th to 20th	Day	6% 11% 23% 25% 25% 11%	316
	21st to end	Day	8% 9% 19% 42% 18% 5%	297
November	1st to 10th	Day	14% 10% 23% 29% 23%	270
	11th to 20th	Day	8% 8% 25% 33% 22% 4	270
	21st to end	Day	15% 8% 18% 36% 19% 4	270
December	1st to 10th	Day	18% 9% 21% 29% 17% 6%	214
	11th to 20th	Day	12% 12% 27% 32% 15% 2	180
	21st to end	Day	15% 13% 21% 34% 11% 7%	198
January	1st to 10th	Night	11% 6% 23% 39% 18% 2	760
	11th to 20th	Night	13% 4 23% 38% 20% 1	760
	21st to end	Night	10% 4 23% 39% 22% 2	836
February	1st to 10th	Night	14% 6% 27% 40% 13%	760
	11th to 20th	Night	10% 6% 27% 39% 17% 1	744
	21st to end	Night	10% 7% 27% 41% 14%	628
March	1st to 10th	Night	8% 7% 27% 44% 13% 1	722
	11th to 20th	Night	9% 6% 26% 41% 16% 2	720
	21st to end	Night	12% 9% 30% 36% 12% 1	792
April	1st to 10th	Night	10% 8% 26% 40% 15% 2	720
	11th to 20th	Night	6% 11% 30% 38% 13% 2	641
	21st to end	Night	5% 8% 30% 39% 15% 2	540
May	1st to 10th	Night	7% 9% 28% 38% 16% 2	540
	11th to 20th	Night	8% 7% 17% 43% 22% 3	531
	21st to end	Night	8% 5% 19% 37% 27% 4	409
June	1st to 10th	Night	8% 6% 16% 42% 25% 4	360
	11th to 20th	Night	5% 8% 20% 46% 21% 1	360
	21st to end	Night	1 4 19% 51% 23% 1	360
July	1st to 10th	Night	1 1 13% 55% 29% 1	350
	11th to 20th	Night	1 1 17% 55% 25% 1	348
	21st to end	Night	2 1 8% 54% 33% 1	394
August	1st to 10th	Night	5% 2 13% 52% 28% 1	532
	11th to 20th	Night	2 1 11% 53% 32% 1	534
	21st to end	Night	3 2 15% 46% 31% 3	734
September	1st to 10th	Night	3 2 11% 46% 33% 5%	720
	11th to 20th	Night	6% 2 13% 39% 35% 6%	720
	21st to end	Night	6% 5% 14% 37% 29% 8%	720
October	1st to 10th	Night	7% 4 18% 41% 27% 3	720
	11th to 20th	Night	8% 5% 18% 40% 26% 4	720
	21st to end	Night	6% 4 24% 38% 23% 4	792
November	1st to 10th	Night	12% 5% 19% 42% 21% 1	740
	11th to 20th	Night	10% 6% 26% 41% 16% 1	760
	21st to end	Night	10% 4 24% 38% 22% 3	760
December	1st to 10th	Night	13% 5% 23% 40% 16% 2	760
	11th to 20th	Night	17% 6% 20% 39% 16% 2	760
	21st to end	Night	18% 7% 28% 35% 10% 1	836

Page generated at 2024-02-27 04:30:12. Version ac07

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