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 2025-01-07.

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 4 3 3 3 3 5% 7% 59%	109084
	Night	6% 5% 2 4 3 3 4 3 5% 7% 58%	108623
Transparency	Day	25% 4 11% 26% 26% 9%	108839
	Night	26% 5% 11% 24% 25% 9%	108458
Seeing	Day	9% 7% 30% 34% 17% 3	15733
	Night	8% 9% 36% 36% 10% 1	25763

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% 9% 3 5% 4 4 4 2 4 6% 52%	2586
	11th to 20th	Day	5% 6% 2 6% 4 5% 7% 4 5% 6% 51%	2585
	21st to end	Day	7% 7% 2 6% 4 3 3 3 5% 6% 55%	3207
February	1st to 10th	Day	5% 9% 2 7% 4 3 3 3 4 7% 53%	1900
	11th to 20th	Day	4 5% 2 7% 4 3 5% 3 5% 6% 56%	1849
	21st to end	Day	4 5% 2 6% 4 3 3 3 5% 6% 59%	1570
March	1st to 10th	Day	5% 7% 1 4 2 2 2 2 4 6% 64%	3130
	11th to 20th	Day	8% 4 1 5% 3 3 3 2 5% 6% 61%	3404
	21st to end	Day	7% 6% 2 4 3 3 4 3 6% 7% 53%	3895
April	1st to 10th	Day	8% 5% 2 3 3 2 3 3 5% 6% 61%	2280
	11th to 20th	Day	11% 6% 2 4 4 2 4 3 5% 6% 54%	2251
	21st to end	Day	10% 5% 1 5% 4 3 4 4 5% 6% 52%	2419
May	1st to 10th	Day	11% 6% 2 5% 4 3 4 3 5% 6% 51%	4120
	11th to 20th	Day	7% 5% 2 5% 3 4 5% 4 6% 8% 51%	4082
	21st to end	Day	7% 4 2 4 3 3 4 3 6% 7% 57%	4489
June	1st to 10th	Day	4 3 1 3 3 3 3 3 6% 10% 60%	2534
	11th to 20th	Day	5% 4 1 3 3 3 3 3 5% 8% 61%	2660
	21st to end	Day	4 3 1 4 4 4 3 3 5% 8% 61%	2660
July	1st to 10th	Day	7% 4 1 4 4 4 5% 3 6% 7% 56%	4430
	11th to 20th	Day	2 2 1 3 2 3 3 4 6% 9% 65%	4399
	21st to end	Day	3 2 1 4 3 4 4 4 7% 10% 58%	4466
August	1st to 10th	Day	11% 4 2 4 3 3 4 4 6% 8% 51%	4103
	11th to 20th	Day	5% 3 2 3 4 3 3 3 5% 9% 59%	3792
	21st to end	Day	4 3 1 3 3 3 4 3 5% 9% 62%	4180
September	1st to 10th	Day	8% 4 1 3 3 2 4 3 5% 6% 59%	2238
	11th to 20th	Day	7% 3 1 4 2 3 4 3 5% 5% 63%	2090
	21st to end	Day	6% 3 1 4 3 3 2 2 4 6% 66%	2090
October	1st to 10th	Day	7% 2 1 3 2 2 1 1 3 4 74%	3480
	11th to 20th	Day	5% 3 1 4 3 3 3 2 4 6% 67%	3318
	21st to end	Day	6% 4 1 3 2 2 1 2 3 5% 71%	3091
November	1st to 10th	Day	7% 4 1 4 2 2 3 2 4 5% 65%	1763
	11th to 20th	Day	3 4 1 4 3 3 3 2 3 6% 67%	1800
	21st to end	Day	7% 6% 2 3 3 3 2 2 3 5% 64%	1800
December	1st to 10th	Day	3 4 1 4 2 2 2 2 4 5% 72%	2940
	11th to 20th	Day	4 5% 1 4 2 2 2 3 3 6% 68%	3391
	21st to end	Day	7% 13% 4 7% 3 3 3 2 4 6% 47%	4092
January	1st to 10th	Night	5% 7% 4 6% 4 4 4 2 4 6% 53%	4502
	11th to 20th	Night	3 5% 2 5% 4 3 4 4 5% 7% 58%	4368
	21st to end	Night	6% 9% 3 6% 3 4 3 3 4 5% 55%	4490
February	1st to 10th	Night	7% 9% 3 5% 4 4 2 3 4 6% 53%	2280
	11th to 20th	Night	5% 8% 2 6% 4 4 5% 3 5% 6% 53%	2218
	21st to end	Night	6% 6% 2 5% 2 2 3 2 4 6% 62%	1884
March	1st to 10th	Night	6% 4 1 3 2 2 3 3 4 6% 65%	3734
	11th to 20th	Night	6% 5% 2 4 3 3 3 3 5% 7% 58%	3557
	21st to end	Night	7% 5% 2 4 3 3 4 4 5% 6% 56%	3735
April	1st to 10th	Night	7% 5% 1 5% 3 3 4 3 6% 9% 55%	1900
	11th to 20th	Night	10% 5% 1 4 3 3 4 4 5% 7% 53%	1877
	21st to end	Night	9% 6% 2 4 4 3 4 3 5% 7% 52%	1758
May	1st to 10th	Night	10% 6% 2 5% 3 3 4 3 6% 7% 51%	2850
	11th to 20th	Night	9% 6% 2 6% 5% 4 4 4 6% 7% 48%	2823
	21st to end	Night	9% 5% 1 5% 4 4 5% 4 6% 9% 50%	3098
June	1st to 10th	Night	5% 3 2 4 3 3 5% 5% 7% 12% 53%	1640
	11th to 20th	Night	4 3 1 4 4 4 3 4 6% 9% 57%	1520
	21st to end	Night	6% 3 1 5% 5% 4 5% 4 6% 9% 54%	1520
July	1st to 10th	Night	6% 4 2 5% 5% 4 4 4 6% 9% 52%	2540
	11th to 20th	Night	3 3 1 4 4 4 5% 5% 8% 10% 52%	2566
	21st to end	Night	4 3 1 4 3 4 5% 5% 9% 11% 51%	3097
August	1st to 10th	Night	8% 6% 2 5% 4 3 5% 4 7% 10% 45%	2836
	11th to 20th	Night	7% 5% 2 5% 3 4 4 5% 7% 10% 47%	3043
	21st to end	Night	3 3 1 5% 4 4 5% 5% 9% 11% 48%	3487
September	1st to 10th	Night	6% 4 1 4 2 4 4 4 5% 8% 59%	1940
	11th to 20th	Night	7% 2 1 3 3 3 3 3 6% 8% 61%	2090
	21st to end	Night	7% 3 1 3 3 3 2 3 5% 6% 65%	2090
October	1st to 10th	Night	6% 3 1 2 1 2 2 2 3 4 75%	3480
	11th to 20th	Night	6% 2 1 3 2 3 3 2 4 6% 69%	3566
	21st to end	Night	7% 3 1 3 3 3 3 3 3 3 69%	4467
November	1st to 10th	Night	5% 3 1 3 2 2 2 3 4 6% 67%	2535
	11th to 20th	Night	4 3 1 3 2 3 3 2 4 5% 69%	2600
	21st to end	Night	6% 4 1 3 3 3 3 3 5% 7% 62%	2600
December	1st to 10th	Night	3 4 1 4 3 2 2 2 4 6% 69%	4250
	11th to 20th	Night	4 4 1 4 3 3 3 3 4 6% 66%	4816
	21st to end	Night	8% 11% 3 6% 4 3 4 3 4 5% 50%	6866

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	34% 3 10% 28% 22% 3	2587
	11th to 20th	Day	34% 4 12% 21% 22% 6%	2585
	21st to end	Day	31% 3 12% 28% 22% 3	3207
February	1st to 10th	Day	33% 3 11% 26% 19% 8%	1900
	11th to 20th	Day	29% 4 11% 27% 20% 9%	1859
	21st to end	Day	26% 3 8% 25% 25% 13%	1570
March	1st to 10th	Day	23% 2 9% 17% 28% 21%	3130
	11th to 20th	Day	25% 4 10% 24% 32% 5%	3404
	21st to end	Day	29% 4 12% 31% 18% 5%	3895
April	1st to 10th	Day	24% 4 9% 23% 26% 13%	2280
	11th to 20th	Day	31% 4 11% 24% 21% 8%	2254
	21st to end	Day	31% 6% 10% 25% 23% 5%	2419
May	1st to 10th	Day	32% 6% 10% 23% 17% 12%	4120
	11th to 20th	Day	28% 8% 14% 27% 20% 3	4086
	21st to end	Day	26% 7% 13% 20% 25% 10%	4489
June	1st to 10th	Day	19% 6% 20% 31% 18% 6%	2534
	11th to 20th	Day	21% 6% 11% 25% 26% 11%	2660
	21st to end	Day	21% 5% 11% 27% 26% 10%	2660
July	1st to 10th	Day	27% 6% 11% 21% 29% 6%	4361
	11th to 20th	Day	15% 5% 14% 30% 29% 7%	4324
	21st to end	Day	20% 6% 14% 28% 23% 9%	4325
August	1st to 10th	Day	30% 6% 14% 30% 17% 3	4090
	11th to 20th	Day	22% 6% 14% 26% 25% 6%	3830
	21st to end	Day	20% 5% 12% 29% 26% 8%	4179
September	1st to 10th	Day	25% 6% 8% 24% 24% 14%	2238
	11th to 20th	Day	23% 4 8% 24% 30% 10%	2090
	21st to end	Day	21% 3 9% 26% 27% 13%	2090
October	1st to 10th	Day	17% 2 6% 18% 41% 16%	3480
	11th to 20th	Day	20% 3 8% 25% 31% 13%	3318
	21st to end	Day	18% 1 6% 23% 38% 14%	3091
November	1st to 10th	Day	23% 3 8% 23% 31% 12%	1763
	11th to 20th	Day	20% 3 8% 28% 31% 11%	1800
	21st to end	Day	25% 2 8% 21% 31% 13%	1800
December	1st to 10th	Day	17% 3 8% 35% 29% 9%	2940
	11th to 20th	Day	20% 2 5% 34% 34% 5%	3389
	21st to end	Day	40% 3 7% 21% 22% 7%	4092
January	1st to 10th	Night	33% 3 12% 28% 21% 3	4502
	11th to 20th	Night	26% 5% 14% 25% 23% 7%	4368
	21st to end	Night	32% 4 11% 23% 25% 4	4490
February	1st to 10th	Night	33% 4 11% 23% 22% 8%	2280
	11th to 20th	Night	32% 4 11% 23% 23% 7%	2218
	21st to end	Night	25% 3 6% 22% 28% 16%	1884
March	1st to 10th	Night	20% 3 6% 21% 29% 20%	3734
	11th to 20th	Night	26% 4 11% 23% 25% 11%	3557
	21st to end	Night	27% 6% 14% 31% 16% 6%	3735
April	1st to 10th	Night	25% 4 12% 23% 23% 13%	1900
	11th to 20th	Night	29% 5% 11% 25% 20% 9%	1877
	21st to end	Night	31% 6% 12% 25% 23% 4	1758
May	1st to 10th	Night	30% 8% 15% 17% 19% 10%	2850
	11th to 20th	Night	34% 8% 13% 21% 19% 5%	2824
	21st to end	Night	30% 7% 14% 21% 17% 11%	3099
June	1st to 10th	Night	22% 8% 19% 31% 15% 5%	1640
	11th to 20th	Night	23% 7% 14% 26% 22% 8%	1520
	21st to end	Night	25% 7% 12% 25% 22% 9%	1520
July	1st to 10th	Night	28% 6% 15% 20% 27% 4	2500
	11th to 20th	Night	23% 7% 16% 22% 25% 7%	2518
	21st to end	Night	22% 7% 16% 25% 21% 9%	2999
August	1st to 10th	Night	33% 5% 13% 27% 20% 3	2826
	11th to 20th	Night	30% 7% 13% 27% 19% 4	3071
	21st to end	Night	26% 6% 15% 23% 23% 6%	3487
September	1st to 10th	Night	24% 6% 10% 23% 25% 13%	1940
	11th to 20th	Night	21% 5% 10% 23% 29% 11%	2090
	21st to end	Night	21% 4 7% 22% 31% 14%	2090
October	1st to 10th	Night	15% 3 6% 18% 43% 15%	3480
	11th to 20th	Night	18% 3 11% 23% 31% 13%	3566
	21st to end	Night	21% 3 5% 21% 37% 13%	4467
November	1st to 10th	Night	19% 4 9% 25% 27% 16%	2535
	11th to 20th	Night	18% 3 7% 26% 34% 13%	2600
	21st to end	Night	23% 3 9% 23% 27% 14%	2600
December	1st to 10th	Night	19% 3 8% 36% 27% 7%	4250
	11th to 20th	Night	20% 3 5% 30% 34% 8%	4817
	21st to end	Night	37% 3 8% 25% 22% 5%	6866

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	10% 7% 36% 32% 13% 2	288
	11th to 20th	Day	14% 7% 39% 28% 11% 1	270
	21st to end	Day	6% 9% 37% 34% 11% 2	297
February	1st to 10th	Day	9% 11% 47% 26% 7%	270
	11th to 20th	Day	7% 11% 45% 25% 11% 1	270
	21st to end	Day	6% 15% 49% 26% 4	225
March	1st to 10th	Day	10% 10% 38% 33% 9%	270
	11th to 20th	Day	14% 13% 34% 26% 10% 2	270
	21st to end	Day	14% 18% 37% 24% 6% 1	340
April	1st to 10th	Day	12% 15% 41% 25% 6% 1	460
	11th to 20th	Day	15% 18% 36% 24% 5% 1	452
	21st to end	Day	15% 14% 38% 25% 7% 1	599
May	1st to 10th	Day	11% 11% 38% 28% 11% 1	653
	11th to 20th	Day	15% 8% 27% 32% 15% 3	675
	21st to end	Day	11% 10% 37% 29% 13% 1	734
June	1st to 10th	Day	4 5% 28% 37% 19% 7%	680
	11th to 20th	Day	6% 7% 33% 37% 15% 2	680
	21st to end	Day	4 5% 29% 39% 20% 2	680
July	1st to 10th	Day	8% 2 18% 41% 25% 6%	671
	11th to 20th	Day	3 1 16% 43% 30% 7%	668
	21st to end	Day	6% 1 14% 38% 33% 8%	739
August	1st to 10th	Day	7% 1 14% 42% 31% 5%	676
	11th to 20th	Day	5% 1 20% 46% 26% 3	519
	21st to end	Day	5% 3 20% 41% 25% 6%	539
September	1st to 10th	Day	9% 2 20% 40% 24% 5%	448
	11th to 20th	Day	4 4 25% 37% 23% 7%	300
	21st to end	Day	9% 7% 24% 33% 21% 6%	300
October	1st to 10th	Day	15% 6% 20% 33% 20% 6%	300
	11th to 20th	Day	5% 5% 40% 28% 18% 4	300
	21st to end	Day	15% 11% 30% 27% 15% 3	330
November	1st to 10th	Day	12% 9% 33% 29% 15% 3	300
	11th to 20th	Day	9% 11% 34% 29% 15% 2	300
	21st to end	Day	14% 11% 28% 27% 15% 4	300
December	1st to 10th	Day	7% 6% 35% 32% 15% 4	300
	11th to 20th	Day	9% 10% 37% 32% 10% 1	300
	21st to end	Day	15% 12% 33% 33% 6% 1	330
January	1st to 10th	Night	8% 8% 37% 38% 9% 1	981
	11th to 20th	Night	8% 8% 37% 36% 9% 1	950
	21st to end	Night	6% 8% 40% 37% 8%	1016
February	1st to 10th	Night	11% 10% 38% 35% 6% 1	760
	11th to 20th	Night	8% 10% 49% 27% 6%	744
	21st to end	Night	9% 13% 47% 28% 3	628
March	1st to 10th	Night	8% 13% 42% 31% 6%	760
	11th to 20th	Night	12% 11% 36% 32% 8% 1	621
	21st to end	Night	13% 15% 44% 23% 4	627
April	1st to 10th	Night	9% 17% 44% 26% 4	570
	11th to 20th	Night	13% 18% 43% 24% 3	563
	21st to end	Night	13% 14% 40% 24% 8% 1	570
May	1st to 10th	Night	12% 12% 43% 26% 6%	570
	11th to 20th	Night	11% 10% 36% 32% 11% 1	561
	21st to end	Night	9% 15% 43% 26% 7%	617
June	1st to 10th	Night	4 7% 41% 34% 13% 1	570
	11th to 20th	Night	5% 11% 46% 31% 6% 1	570
	21st to end	Night	6% 5% 38% 41% 9%	570
July	1st to 10th	Night	5% 3 29% 45% 18%	555
	11th to 20th	Night	4 2 28% 46% 20% 1	552
	21st to end	Night	7% 2 18% 51% 20% 1	624
August	1st to 10th	Night	8% 3 20% 47% 22% 1	567
	11th to 20th	Night	9% 2 27% 48% 14%	564
	21st to end	Night	4 3 29% 44% 19% 1	627
September	1st to 10th	Night	6% 1 31% 47% 14%	570
	11th to 20th	Night	8% 3 39% 37% 12% 1	570
	21st to end	Night	8% 7% 30% 40% 15%	570
October	1st to 10th	Night	12% 8% 30% 38% 11%	570
	11th to 20th	Night	7% 8% 39% 34% 11% 1	626
	21st to end	Night	11% 8% 33% 32% 15% 1	1045
November	1st to 10th	Night	8% 8% 34% 41% 9% 1	975
	11th to 20th	Night	6% 9% 39% 35% 10%	1000
	21st to end	Night	8% 10% 29% 39% 11% 2	1000
December	1st to 10th	Night	8% 8% 35% 40% 8% 1	1000
	11th to 20th	Night	9% 11% 36% 36% 8%	1000
	21st to end	Night	11% 11% 35% 35% 8%	1100

Page generated at 2025-01-04 02:24:03. Version ac07

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