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 2024-10-25.

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	5% 5% 2 5% 4 4 4 3 5% 7% 58%	101148
	Night	6% 6% 2 6% 4 4 4 4 5% 7% 52%	97835
Transparency	Day	26% 6% 12% 21% 20% 16%	100892
	Night	30% 6% 13% 21% 17% 13%	97681
Seeing	Day	7% 10% 24% 30% 21% 7%	14459
	Night	8% 5% 22% 42% 21% 2	23837

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% 11% 4 9% 6% 6% 5% 5% 7% 6% 34%	2539
	11th to 20th	Day	9% 14% 5% 11% 7% 6% 5% 5% 6% 6% 27%	2540
	21st to end	Day	11% 10% 4 10% 5% 5% 5% 4 6% 7% 32%	2794
February	1st to 10th	Day	7% 8% 3 6% 5% 5% 4 4 7% 9% 42%	1729
	11th to 20th	Day	7% 8% 2 7% 6% 5% 6% 4 6% 8% 41%	1850
	21st to end	Day	5% 9% 2 7% 4 5% 6% 5% 6% 8% 42%	1570
March	1st to 10th	Day	6% 9% 3 8% 5% 6% 6% 5% 7% 9% 34%	3138
	11th to 20th	Day	4 5% 2 5% 3 3 3 3 6% 6% 60%	3422
	21st to end	Day	6% 7% 3 8% 5% 6% 6% 5% 6% 8% 40%	3903
April	1st to 10th	Day	6% 7% 2 6% 5% 4 4 5% 6% 9% 45%	2280
	11th to 20th	Day	4 7% 2 6% 5% 3 3 4 6% 8% 53%	2323
	21st to end	Day	5% 5% 2 5% 3 4 4 4 6% 9% 54%	2470
May	1st to 10th	Day	6% 6% 2 6% 4 4 4 4 5% 6% 53%	4110
	11th to 20th	Day	3 2 1 3 3 3 3 3 5% 6% 69%	4071
	21st to end	Day	5% 4 1 4 3 3 4 3 6% 8% 59%	4778
June	1st to 10th	Day	6% 3 1 4 4 4 5% 4 7% 9% 52%	2660
	11th to 20th	Day	4 3 1 4 3 3 3 2 4 7% 65%	2660
	21st to end	Day	2 2 1 3 2 2 3 2 4 5% 74%	2660
July	1st to 10th	Day	1 1 1 1 1 2 2 2 3 4 82%	4420
	11th to 20th	Day	2 2 1 3 2 2 2 2 4 5% 75%	4420
	21st to end	Day	2 2 1 2 2 3 3 3 4 5% 74%	4790
August	1st to 10th	Day	3 3 1 4 3 3 4 3 5% 6% 65%	4096
	11th to 20th	Day	1 1 1 2 2 2 2 2 3 5% 78%	4028
	21st to end	Day	2 3 1 3 2 2 2 1 3 4 77%	4273
September	1st to 10th	Day	1 2 1 2 2 3 2 2 3 5% 76%	2252
	11th to 20th	Day	3 4 1 4 2 3 3 3 4 5% 68%	2090
	21st to end	Day	4 3 1 3 3 2 2 2 4 6% 70%	2090
October	1st to 10th	Day	5% 4 2 5% 3 3 3 3 5% 6% 62%	2090
	11th to 20th	Day	4 3 2 4 3 3 3 3 5% 7% 63%	1872
	21st to end	Day	4 3 1 4 3 3 4 4 6% 9% 58%	1822
November	1st to 10th	Day	8% 6% 2 6% 6% 4 4 4 5% 9% 47%	1674
	11th to 20th	Day	7% 6% 2 6% 5% 5% 5% 5% 7% 8% 46%	1710
	21st to end	Day	8% 7% 2 8% 5% 4 4 5% 6% 8% 43%	1710
December	1st to 10th	Day	11% 9% 4 6% 4 4 4 4 5% 7% 42%	1592
	11th to 20th	Day	10% 9% 4 9% 6% 6% 4 5% 7% 8% 33%	1928
	21st to end	Day	8% 9% 3 10% 5% 5% 5% 5% 6% 7% 38%	2794
January	1st to 10th	Night	8% 10% 4 9% 5% 6% 5% 5% 7% 7% 33%	4406
	11th to 20th	Night	13% 15% 4 10% 8% 5% 5% 4 4 6% 25%	4420
	21st to end	Night	12% 10% 5% 10% 5% 5% 5% 4 5% 6% 34%	4862
February	1st to 10th	Night	10% 8% 3 8% 5% 4 4 5% 6% 7% 39%	2443
	11th to 20th	Night	8% 7% 3 6% 5% 4 4 3 4 7% 49%	2218
	21st to end	Night	7% 8% 2 6% 5% 5% 5% 5% 7% 10% 42%	1884
March	1st to 10th	Night	6% 10% 3 8% 6% 5% 5% 4 7% 7% 40%	3736
	11th to 20th	Night	6% 6% 2 4 4 4 4 4 5% 5% 58%	3557
	21st to end	Night	6% 7% 2 7% 6% 6% 6% 4 5% 9% 42%	3746
April	1st to 10th	Night	7% 6% 3 5% 5% 5% 5% 5% 6% 7% 48%	1900
	11th to 20th	Night	5% 6% 2 6% 5% 4 5% 4 5% 7% 50%	1805
	21st to end	Night	4 5% 2 5% 4 4 4 4 6% 7% 55%	1710
May	1st to 10th	Night	8% 6% 2 5% 3 3 4 3 6% 7% 53%	2860
	11th to 20th	Night	4 2 1 3 2 3 3 3 4 7% 68%	2834
	21st to end	Night	4 4 2 5% 3 4 4 4 5% 6% 59%	2795
June	1st to 10th	Night	5% 4 2 5% 4 4 5% 5% 7% 8% 51%	1520
	11th to 20th	Night	4 3 1 3 3 3 3 3 4 8% 65%	1520
	21st to end	Night	1 1 1 3 3 2 4 2 4 5% 75%	1520
July	1st to 10th	Night	1 1 2 2 2 2 2 3 4 81%	2540
	11th to 20th	Night	1 1 2 2 2 3 3 4 5% 77%	2540
	21st to end	Night	2 2 1 3 3 3 4 3 4 6% 68%	2761
August	1st to 10th	Night	3 3 1 4 3 3 4 3 6% 7% 63%	2842
	11th to 20th	Night	2 1 1 2 2 3 3 4 5% 77%	2811
	21st to end	Night	2 3 1 3 2 2 3 2 3 4 76%	3398
September	1st to 10th	Night	2 2 1 3 2 2 3 2 4 4 76%	1927
	11th to 20th	Night	4 3 1 3 2 3 4 3 5% 6% 66%	2090
	21st to end	Night	5% 3 1 3 2 3 3 2 3 5% 71%	2090
October	1st to 10th	Night	6% 3 2 4 3 3 3 3 4 7% 64%	2090
	11th to 20th	Night	7% 3 1 4 3 3 3 3 5% 7% 61%	2304
	21st to end	Night	5% 3 1 5% 3 4 4 4 6% 7% 57%	2639
November	1st to 10th	Night	10% 6% 2 6% 4 4 5% 3 5% 7% 49%	2405
	11th to 20th	Night	9% 5% 3 7% 4 4 4 4 6% 7% 46%	2470
	21st to end	Night	7% 5% 2 7% 4 4 5% 4 6% 7% 47%	2470
December	1st to 10th	Night	10% 8% 4 9% 5% 4 4 3 5% 7% 40%	2584
	11th to 20th	Night	12% 10% 4 10% 6% 5% 5% 4 6% 7% 31%	3276
	21st to end	Night	9% 8% 3 8% 5% 5% 5% 5% 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% 26% 9% 1	1570
March	1st to 10th	Day	41% 11% 16% 24% 7% 1	3138
	11th to 20th	Day	22% 7% 15% 39% 16% 1	3422
	21st to end	Day	37% 9% 19% 25% 8% 1	3903
April	1st to 10th	Day	34% 7% 15% 23% 17% 4	2280
	11th to 20th	Day	27% 6% 14% 29% 20% 5%	2326
	21st to end	Day	27% 5% 13% 28% 24% 3	2470
May	1st to 10th	Day	28% 6% 9% 26% 24% 7%	4110
	11th to 20th	Day	16% 5% 7% 26% 33% 14%	4074
	21st to end	Day	21% 6% 13% 28% 27% 5%	4778
June	1st to 10th	Day	27% 7% 12% 25% 26% 4	2660
	11th to 20th	Day	20% 4 7% 21% 33% 15%	2660
	21st to end	Day	13% 3 5% 16% 33% 30%	2660
July	1st to 10th	Day	8% 2 3 9% 18% 61%	4351
	11th to 20th	Day	13% 2 2 6% 19% 58%	4345
	21st to end	Day	13% 3 3 7% 27% 47%	4639
August	1st to 10th	Day	20% 3 4 11% 26% 36%	4081
	11th to 20th	Day	11% 2 3 13% 35% 36%	4067
	21st to end	Day	13% 2 3 13% 36% 34%	4272
September	1st to 10th	Day	12% 3 5% 14% 32% 35%	2252
	11th to 20th	Day	19% 3 7% 26% 25% 20%	2090
	21st to end	Day	17% 3 7% 22% 36% 15%	2090
October	1st to 10th	Day	24% 4 11% 26% 26% 9%	2090
	11th to 20th	Day	21% 5% 11% 34% 24% 5%	1872
	21st to end	Day	22% 6% 18% 33% 19% 2	1822
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	35% 8% 19% 28% 9% 1	1884
March	1st to 10th	Night	36% 11% 17% 26% 9% 1	3736
	11th to 20th	Night	27% 5% 13% 34% 19% 2	3557
	21st to end	Night	36% 9% 18% 28% 8% 1	3746
April	1st to 10th	Night	35% 5% 15% 24% 16% 5%	1900
	11th to 20th	Night	32% 6% 10% 26% 22% 4	1805
	21st to end	Night	27% 5% 14% 27% 24% 4	1710
May	1st to 10th	Night	27% 6% 10% 26% 23% 9%	2860
	11th to 20th	Night	16% 4 8% 22% 37% 13%	2835
	21st to end	Night	24% 5% 11% 23% 32% 4	2795
June	1st to 10th	Night	28% 8% 11% 23% 25% 4	1520
	11th to 20th	Night	19% 4 8% 19% 36% 14%	1520
	21st to end	Night	12% 3 6% 15% 30% 33%	1520
July	1st to 10th	Night	9% 2 3 7% 17% 62%	2500
	11th to 20th	Night	11% 2 3 5% 17% 62%	2492
	21st to end	Night	17% 3 3 7% 28% 42%	2674
August	1st to 10th	Night	20% 3 3 9% 22% 42%	2834
	11th to 20th	Night	10% 3 3 11% 30% 42%	2838
	21st to end	Night	15% 2 3 12% 31% 38%	3398
September	1st to 10th	Night	13% 3 4 12% 30% 39%	1927
	11th to 20th	Night	19% 4 6% 20% 26% 25%	2090
	21st to end	Night	19% 3 5% 19% 33% 22%	2090
October	1st to 10th	Night	22% 3 8% 24% 28% 15%	2090
	11th to 20th	Night	24% 4 8% 31% 27% 6%	2304
	21st to end	Night	24% 7% 13% 31% 22% 3	2639
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% 15% 31% 36% 9%	382
March	1st to 10th	Day	7% 12% 39% 31% 10% 1	460
	11th to 20th	Day	8% 14% 29% 30% 16% 3	460
	21st to end	Day	10% 17% 34% 25% 13% 1	506
April	1st to 10th	Day	15% 17% 27% 22% 14% 5%	460
	11th to 20th	Day	10% 20% 32% 23% 11% 4	452
	21st to end	Day	8% 21% 29% 25% 15% 2	460
May	1st to 10th	Day	6% 16% 33% 27% 14% 4	463
	11th to 20th	Day	11% 13% 24% 28% 19% 5%	488
	21st to end	Day	7% 9% 22% 27% 22% 12%	529
June	1st to 10th	Day	5% 10% 26% 28% 22% 9%	490
	11th to 20th	Day	8% 16% 29% 25% 17% 5%	490
	21st to end	Day	3 7% 26% 34% 21% 8%	490
July	1st to 10th	Day	2 5% 23% 34% 28% 9%	486
	11th to 20th	Day	3 4 20% 37% 29% 7%	484
	21st to end	Day	2 3 17% 34% 36% 9%	531
August	1st to 10th	Day	5% 3 18% 38% 26% 9%	487
	11th to 20th	Day	2 5% 15% 31% 33% 14%	477
	21st to end	Day	2 6% 19% 29% 29% 15%	539
September	1st to 10th	Day	2 5% 16% 26% 36% 14%	490
	11th to 20th	Day	5% 5% 17% 29% 32% 12%	490
	21st to end	Day	6% 9% 19% 28% 28% 9%	490
October	1st to 10th	Day	8% 8% 18% 26% 28% 12%	490
	11th to 20th	Day	6% 11% 22% 24% 26% 12%	348
	21st to end	Day	7% 9% 19% 42% 19% 5%	311
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	9% 8% 27% 41% 14%	628
March	1st to 10th	Night	8% 7% 27% 44% 13% 1	760
	11th to 20th	Night	9% 6% 26% 41% 17% 2	760
	21st to end	Night	11% 9% 30% 37% 12% 1	836
April	1st to 10th	Night	9% 8% 26% 40% 15% 2	760
	11th to 20th	Night	6% 11% 31% 39% 13% 1	677
	21st to end	Night	5% 8% 30% 40% 15% 2	570
May	1st to 10th	Night	8% 9% 30% 36% 15% 2	570
	11th to 20th	Night	7% 7% 17% 44% 21% 3	561
	21st to end	Night	8% 5% 19% 38% 27% 4	432
June	1st to 10th	Night	8% 7% 16% 42% 24% 3	380
	11th to 20th	Night	5% 7% 20% 47% 20% 1	380
	21st to end	Night	1 3 19% 52% 23% 1	380
July	1st to 10th	Night	1 1 13% 55% 28% 1	370
	11th to 20th	Night	1 1 16% 55% 26% 1	368
	21st to end	Night	2 1 8% 54% 33% 1	416
August	1st to 10th	Night	4 2 13% 52% 28% 1	562
	11th to 20th	Night	2 2 12% 52% 30% 1	564
	21st to end	Night	3 2 15% 45% 31% 3	775
September	1st to 10th	Night	3 2 11% 46% 33% 4	760
	11th to 20th	Night	6% 2 13% 39% 34% 5%	760
	21st to end	Night	6% 5% 14% 38% 30% 8%	760
October	1st to 10th	Night	7% 4 18% 41% 28% 3	760
	11th to 20th	Night	8% 5% 17% 40% 27% 4	760
	21st to end	Night	6% 4 24% 38% 23% 4	812
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 2024-10-22 18:21:04. Version ac07

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