Garden City
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Garden City clear sky chart from 2005-11-06 to 2024-03-06.

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	3 5% 3 5% 6% 4 6% 6% 7% 9% 47%	78952
	Night	2 5% 2 6% 6% 4 6% 6% 7% 9% 47%	80600
Transparency	Day	31% 10% 13% 20% 18% 7%	78677
	Night	31% 11% 15% 22% 16% 6%	80397
Seeing	Day	7% 15% 29% 28% 17% 4	14431
	Night	5% 9% 23% 38% 23% 3	24511

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	5% 4 10% 8% 6% 8% 10% 10% 9% 30%	2858
	11th to 20th	Day	4 3 8% 9% 5% 8% 10% 10% 10% 32%	2860
	21st to end	Day	1 8% 6% 11% 9% 6% 8% 8% 6% 8% 28%	3146
February	1st to 10th	Day	1 5% 5% 8% 8% 5% 8% 7% 11% 10% 32%	1710
	11th to 20th	Day	1 8% 4 8% 7% 5% 8% 7% 8% 10% 34%	1674
	21st to end	Day	1 7% 4 10% 7% 5% 7% 7% 9% 9% 33%	1570
March	1st to 10th	Day	1 6% 3 8% 8% 5% 7% 8% 9% 9% 36%	1988
	11th to 20th	Day	2 6% 2 5% 6% 5% 8% 8% 8% 12% 38%	1980
	21st to end	Day	4 8% 4 7% 8% 4 7% 7% 8% 9% 34%	2178
April	1st to 10th	Day	4 6% 3 6% 7% 4 7% 6% 8% 9% 40%	2030
	11th to 20th	Day	4 7% 3 6% 6% 4 8% 7% 7% 9% 40%	2262
	21st to end	Day	4 5% 3 5% 6% 4 6% 6% 6% 9% 46%	2340
May	1st to 10th	Day	6% 6% 2 4 6% 4 7% 7% 7% 9% 41%	2340
	11th to 20th	Day	5% 5% 2 5% 6% 3 6% 7% 8% 10% 43%	2301
	21st to end	Day	7% 5% 2 6% 7% 4 6% 7% 8% 8% 40%	2637
June	1st to 10th	Day	3 3 2 4 4 3 5% 6% 6% 10% 55%	2520
	11th to 20th	Day	5% 3 1 4 4 3 4 5% 6% 7% 58%	2523
	21st to end	Day	1 2 1 2 3 2 3 4 4 7% 71%	2700
July	1st to 10th	Day	2 1 1 3 3 2 4 5% 6% 8% 65%	2502
	11th to 20th	Day	3 2 1 2 2 1 4 4 5% 7% 68%	2340
	21st to end	Day	3 2 1 3 3 3 4 4 5% 8% 62%	2545
August	1st to 10th	Day	4 2 1 3 3 3 4 5% 6% 8% 61%	2328
	11th to 20th	Day	3 2 1 3 3 2 3 3 6% 8% 68%	2299
	21st to end	Day	3 2 1 3 3 3 3 4 5% 7% 67%	2552
September	1st to 10th	Day	3 2 1 2 3 2 3 4 5% 7% 68%	2085
	11th to 20th	Day	4 2 1 2 3 3 4 4 4 8% 64%	1980
	21st to end	Day	4 3 1 2 3 2 4 5% 4 6% 65%	1980
October	1st to 10th	Day	6% 6% 2 5% 5% 3 5% 6% 7% 7% 48%	1866
	11th to 20th	Day	4 4 2 3 4 3 5% 7% 6% 8% 55%	1800
	21st to end	Day	2 5% 2 5% 5% 4 6% 5% 6% 10% 50%	1967
November	1st to 10th	Day	3 6% 3 7% 5% 4 6% 6% 7% 9% 44%	1674
	11th to 20th	Day	2 5% 3 5% 5% 4 7% 7% 6% 11% 45%	1625
	21st to end	Day	2 6% 4 6% 6% 4 6% 7% 7% 8% 43%	1520
December	1st to 10th	Day	1 6% 5% 8% 7% 5% 7% 8% 9% 9% 36%	1520
	11th to 20th	Day	1 6% 5% 9% 8% 6% 9% 10% 9% 10% 27%	1926
	21st to end	Day	1 7% 4 8% 9% 6% 8% 10% 9% 9% 28%	2826
January	1st to 10th	Night	1 5% 4 11% 7% 5% 7% 10% 8% 9% 34%	4097
	11th to 20th	Night	1 4 3 7% 8% 5% 7% 8% 11% 12% 35%	4110
	21st to end	Night	1 11% 5% 11% 11% 6% 7% 6% 7% 9% 26%	4521
February	1st to 10th	Night	1 6% 3 7% 8% 5% 7% 8% 9% 11% 36%	2470
	11th to 20th	Night	2 6% 4 6% 6% 4 6% 7% 9% 9% 42%	2388
	21st to end	Night	1 5% 3 6% 6% 4 6% 7% 11% 12% 39%	1884
March	1st to 10th	Night	1 6% 3 6% 7% 4 8% 7% 10% 10% 38%	2088
	11th to 20th	Night	2 5% 2 3 4 4 7% 7% 8% 10% 49%	1980
	21st to end	Night	4 6% 3 6% 5% 3 6% 7% 7% 9% 44%	2178
April	1st to 10th	Night	3 6% 3 5% 5% 3 6% 7% 7% 8% 47%	1928
	11th to 20th	Night	4 6% 3 4 6% 4 5% 6% 7% 8% 48%	1643
	21st to end	Night	4 4 2 3 6% 3 4 5% 6% 9% 53%	1620
May	1st to 10th	Night	6% 6% 2 5% 4 3 5% 6% 6% 9% 48%	1620
	11th to 20th	Night	7% 4 2 6% 4 3 5% 5% 6% 9% 48%	1594
	21st to end	Night	7% 5% 1 5% 6% 3 5% 5% 6% 9% 47%	1635
June	1st to 10th	Night	3 2 2 4 3 3 5% 4 6% 10% 58%	1440
	11th to 20th	Night	4 2 1 3 3 2 2 4 6% 9% 64%	1425
	21st to end	Night	2 2 1 2 3 2 3 3 5% 6% 70%	1260
July	1st to 10th	Night	1 2 1 4 4 2 4 6% 6% 6% 63%	1443
	11th to 20th	Night	2 2 1 3 3 2 4 4 5% 7% 66%	1620
	21st to end	Night	2 2 1 3 4 2 4 4 7% 8% 63%	1773
August	1st to 10th	Night	3 3 1 4 4 3 4 4 6% 9% 59%	1611
	11th to 20th	Night	3 3 1 3 3 1 3 4 4 6% 68%	1602
	21st to end	Night	3 2 1 2 3 2 4 5% 5% 7% 67%	1804
September	1st to 10th	Night	2 2 1 3 3 2 3 2 5% 6% 70%	1872
	11th to 20th	Night	4 2 1 3 3 2 4 4 4 7% 65%	1980
	21st to end	Night	5% 3 1 3 3 2 3 3 5% 5% 68%	1980
October	1st to 10th	Night	5% 5% 2 4 5% 3 3 5% 5% 7% 57%	2093
	11th to 20th	Night	4 5% 2 4 4 2 4 5% 5% 8% 58%	2160
	21st to end	Night	3 4 1 4 4 3 5% 5% 6% 8% 57%	2384
November	1st to 10th	Night	3 5% 3 5% 4 3 6% 6% 7% 9% 48%	2405
	11th to 20th	Night	2 4 2 4 5% 4 7% 8% 8% 10% 46%	2532
	21st to end	Night	1 5% 2 5% 6% 4 8% 8% 8% 10% 45%	2660
December	1st to 10th	Night	2 5% 3 7% 7% 4 8% 8% 8% 9% 40%	2660
	11th to 20th	Night	2 5% 4 8% 7% 5% 8% 10% 10% 11% 30%	3271
	21st to end	Night	1 6% 4 10% 10% 6% 8% 11% 8% 9% 27%	4869

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% 15% 17% 17% 6% 1	2859
	11th to 20th	Day	45% 19% 16% 14% 5% 1	2860
	21st to end	Day	47% 17% 14% 13% 7% 1	3146
February	1st to 10th	Day	43% 14% 18% 16% 7% 1	1710
	11th to 20th	Day	43% 12% 16% 18% 8% 2	1683
	21st to end	Day	43% 14% 16% 17% 9% 1	1570
March	1st to 10th	Day	39% 14% 17% 20% 9% 1	1988
	11th to 20th	Day	37% 13% 20% 19% 12% 1	1980
	21st to end	Day	44% 12% 17% 18% 7% 1	2178
April	1st to 10th	Day	39% 11% 15% 20% 12% 3	2030
	11th to 20th	Day	39% 10% 14% 24% 14%	2265
	21st to end	Day	34% 10% 15% 28% 13%	2340
May	1st to 10th	Day	37% 10% 13% 22% 16% 2	2340
	11th to 20th	Day	33% 10% 13% 27% 14% 3	2304
	21st to end	Day	38% 12% 14% 26% 10% 1	2637
June	1st to 10th	Day	24% 9% 15% 26% 23% 3	2520
	11th to 20th	Day	24% 7% 9% 21% 27% 12%	2523
	21st to end	Day	13% 5% 7% 19% 33% 23%	2700
July	1st to 10th	Day	16% 6% 7% 20% 28% 24%	2438
	11th to 20th	Day	15% 5% 7% 17% 28% 28%	2271
	21st to end	Day	19% 5% 8% 16% 30% 22%	2404
August	1st to 10th	Day	20% 5% 8% 20% 24% 22%	2313
	11th to 20th	Day	15% 5% 7% 21% 33% 19%	2299
	21st to end	Day	16% 6% 8% 16% 35% 19%	2552
September	1st to 10th	Day	15% 6% 7% 18% 32% 22%	2085
	11th to 20th	Day	20% 6% 9% 21% 29% 15%	1980
	21st to end	Day	19% 6% 8% 27% 33% 7%	1980
October	1st to 10th	Day	33% 7% 11% 26% 19% 5%	1866
	11th to 20th	Day	25% 8% 17% 28% 19% 3	1800
	21st to end	Day	27% 9% 19% 26% 17% 1	1967
November	1st to 10th	Day	36% 10% 17% 23% 13% 2	1674
	11th to 20th	Day	32% 12% 21% 23% 12% 1	1625
	21st to end	Day	35% 9% 17% 23% 14% 1	1520
December	1st to 10th	Day	40% 15% 19% 16% 7% 3	1520
	11th to 20th	Day	44% 14% 19% 16% 7%	1924
	21st to end	Day	42% 14% 14% 17% 12% 2	2826
January	1st to 10th	Night	41% 16% 15% 19% 8% 1	4097
	11th to 20th	Night	44% 19% 15% 15% 6% 1	4110
	21st to end	Night	48% 17% 15% 14% 5% 2	4521
February	1st to 10th	Night	39% 17% 17% 19% 7%	2470
	11th to 20th	Night	34% 13% 17% 21% 13% 2	2389
	21st to end	Night	35% 15% 16% 23% 10% 2	1884
March	1st to 10th	Night	35% 13% 19% 23% 9%	2088
	11th to 20th	Night	27% 11% 21% 26% 14% 1	1980
	21st to end	Night	35% 13% 20% 22% 8% 1	2178
April	1st to 10th	Night	33% 12% 19% 20% 11% 6%	1928
	11th to 20th	Night	32% 9% 15% 27% 17%	1643
	21st to end	Night	28% 8% 16% 30% 17%	1620
May	1st to 10th	Night	31% 10% 12% 25% 19% 2	1620
	11th to 20th	Night	31% 8% 16% 26% 15% 4	1595
	21st to end	Night	31% 11% 16% 28% 12% 1	1635
June	1st to 10th	Night	21% 9% 18% 25% 24% 3	1440
	11th to 20th	Night	17% 7% 11% 25% 28% 13%	1425
	21st to end	Night	14% 4 6% 18% 32% 26%	1260
July	1st to 10th	Night	18% 7% 9% 17% 25% 25%	1399
	11th to 20th	Night	16% 5% 7% 17% 27% 28%	1566
	21st to end	Night	18% 4 9% 17% 29% 24%	1674
August	1st to 10th	Night	21% 7% 10% 16% 24% 22%	1602
	11th to 20th	Night	17% 5% 5% 18% 33% 22%	1602
	21st to end	Night	17% 6% 8% 16% 33% 21%	1804
September	1st to 10th	Night	16% 4 7% 19% 27% 27%	1872
	11th to 20th	Night	18% 6% 9% 21% 29% 17%	1980
	21st to end	Night	19% 5% 8% 25% 35% 8%	1980
October	1st to 10th	Night	26% 7% 11% 28% 23% 6%	2093
	11th to 20th	Night	25% 6% 12% 31% 21% 5%	2160
	21st to end	Night	22% 8% 20% 30% 17% 3	2384
November	1st to 10th	Night	30% 10% 17% 23% 17% 4	2405
	11th to 20th	Night	29% 11% 20% 26% 12% 2	2532
	21st to end	Night	31% 10% 17% 26% 13% 3	2660
December	1st to 10th	Night	37% 13% 20% 18% 8% 3	2660
	11th to 20th	Night	39% 14% 17% 22% 8%	3272
	21st to end	Night	43% 12% 15% 18% 9% 3	4869

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	7% 20% 24% 24% 22% 3	270
	11th to 20th	Day	7% 17% 28% 31% 16% 2	270
	21st to end	Day	6% 15% 25% 35% 16% 3	297
February	1st to 10th	Day	7% 27% 36% 24% 6%	270
	11th to 20th	Day	9% 20% 36% 24% 10% 2	279
	21st to end	Day	8% 24% 38% 23% 6%	382
March	1st to 10th	Day	7% 27% 35% 24% 6% 1	441
	11th to 20th	Day	8% 19% 34% 28% 11% 1	420
	21st to end	Day	11% 28% 35% 21% 5%	462
April	1st to 10th	Day	12% 25% 30% 20% 13% 1	420
	11th to 20th	Day	12% 27% 38% 14% 7% 2	412
	21st to end	Day	11% 27% 28% 19% 12% 4	420
May	1st to 10th	Day	9% 22% 34% 22% 11% 3	423
	11th to 20th	Day	11% 13% 33% 29% 13% 2	448
	21st to end	Day	10% 11% 26% 26% 21% 5%	592
June	1st to 10th	Day	5% 11% 24% 30% 24% 6%	630
	11th to 20th	Day	7% 14% 29% 32% 17% 2	630
	21st to end	Day	2 7% 27% 37% 22% 5%	630
July	1st to 10th	Day	2 5% 25% 40% 22% 6%	525
	11th to 20th	Day	4 5% 30% 35% 21% 4	444
	21st to end	Day	4 3 23% 38% 25% 7%	487
August	1st to 10th	Day	5% 4 31% 31% 21% 7%	447
	11th to 20th	Day	3 5% 27% 32% 27% 6%	437
	21st to end	Day	4 6% 24% 36% 23% 8%	495
September	1st to 10th	Day	3 10% 24% 30% 20% 12%	450
	11th to 20th	Day	6% 13% 28% 24% 18% 10%	450
	21st to end	Day	5% 14% 24% 27% 23% 7%	450
October	1st to 10th	Day	5% 13% 24% 21% 26% 10%	336
	11th to 20th	Day	9% 15% 21% 27% 21% 8%	270
	21st to end	Day	7% 20% 28% 27% 15% 2	297
November	1st to 10th	Day	13% 17% 27% 24% 12% 8%	270
	11th to 20th	Day	9% 15% 28% 31% 13% 4	270
	21st to end	Day	7% 14% 24% 33% 17% 5%	270
December	1st to 10th	Day	6% 16% 26% 33% 16% 4	270
	11th to 20th	Day	8% 17% 27% 34% 13% 1	270
	21st to end	Day	9% 17% 34% 25% 11% 4	297
January	1st to 10th	Night	4 9% 26% 39% 20% 2	760
	11th to 20th	Night	4 11% 27% 36% 19% 2	760
	21st to end	Night	3 8% 31% 41% 15% 2	836
February	1st to 10th	Night	4 15% 33% 35% 12% 1	760
	11th to 20th	Night	3 12% 30% 38% 14% 2	744
	21st to end	Night	5% 13% 33% 37% 12% 1	628
March	1st to 10th	Night	3 12% 31% 40% 12% 2	742
	11th to 20th	Night	3 8% 26% 45% 17% 1	720
	21st to end	Night	6% 11% 32% 37% 14% 1	792
April	1st to 10th	Night	6% 11% 29% 38% 15% 1	668
	11th to 20th	Night	8% 13% 29% 35% 14% 1	533
	21st to end	Night	6% 10% 27% 34% 20% 2	540
May	1st to 10th	Night	10% 9% 23% 38% 19% 1	540
	11th to 20th	Night	10% 5% 19% 35% 30% 3	531
	21st to end	Night	8% 6% 21% 34% 28% 3	584
June	1st to 10th	Night	3 7% 21% 36% 31% 3	540
	11th to 20th	Night	5% 7% 23% 39% 25%	525
	21st to end	Night	3 2 14% 42% 36% 4	360
July	1st to 10th	Night	1 12% 37% 48% 2	433
	11th to 20th	Night	2 2 13% 45% 37% 1	522
	21st to end	Night	3 1 6% 42% 44% 4	591
August	1st to 10th	Night	2 1 9% 45% 40% 2	537
	11th to 20th	Night	4 2 8% 44% 39% 3	534
	21st to end	Night	4 3 11% 38% 41% 4	594
September	1st to 10th	Night	4 4 14% 38% 36% 5%	612
	11th to 20th	Night	3 6% 12% 35% 37% 7%	720
	21st to end	Night	6% 5% 16% 32% 33% 8%	720
October	1st to 10th	Night	6% 6% 21% 36% 27% 4	720
	11th to 20th	Night	6% 9% 19% 36% 26% 4	720
	21st to end	Night	5% 9% 23% 38% 22% 4	792
November	1st to 10th	Night	6% 9% 24% 38% 20% 3	740
	11th to 20th	Night	4 12% 27% 39% 15% 3	822
	21st to end	Night	5% 12% 25% 37% 18% 3	950
December	1st to 10th	Night	6% 11% 27% 41% 14% 1	950
	11th to 20th	Night	4 11% 30% 41% 12% 1	950
	21st to end	Night	5% 16% 31% 36% 12% 1	1041

Page generated at 2024-03-03 04:29:00. Version ac07

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