Gardner
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gardner clear sky chart from 2005-11-06 to 2024-11-08.

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	2 4 2 4 3 4 4 4 6% 8% 57%	105073
	Night	3 5% 2 4 3 3 3 3 5% 7% 62%	102743
Transparency	Day	21% 8% 12% 23% 25% 11%	104823
	Night	20% 7% 12% 25% 26% 10%	102583
Seeing	Day	8% 17% 32% 26% 13% 3	15429
	Night	5% 13% 35% 31% 14% 2	25452

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	1 5% 2 6% 2 2 3 3 4 9% 63%	2538
	11th to 20th	Day	3 2 4 2 2 3 3 5% 6% 69%	2773
	21st to end	Day	1 10% 3 5% 2 2 2 3 5% 6% 60%	3146
February	1st to 10th	Day	5% 3 6% 3 2 3 2 4 7% 64%	1734
	11th to 20th	Day	1 4 2 4 3 2 3 3 6% 8% 66%	1849
	21st to end	Day	1 4 2 6% 2 3 4 3 7% 7% 60%	1570
March	1st to 10th	Day	1 5% 3 4 3 3 3 3 5% 7% 64%	3130
	11th to 20th	Day	3 14% 4 7% 3 4 3 4 4 6% 49%	3484
	21st to end	Day	1 6% 2 4 3 3 4 4 6% 8% 59%	4041
April	1st to 10th	Day	2 5% 1 5% 3 4 4 3 7% 8% 58%	2280
	11th to 20th	Day	3 6% 2 5% 3 4 4 3 5% 9% 55%	2251
	21st to end	Day	4 8% 2 5% 4 4 5% 5% 6% 8% 50%	2280
May	1st to 10th	Day	5% 8% 2 5% 3 3 4 3 6% 7% 53%	3880
	11th to 20th	Day	5% 6% 2 5% 4 4 4 5% 7% 9% 49%	4233
	21st to end	Day	3 3 1 3 3 3 4 4 6% 8% 63%	4825
June	1st to 10th	Day	3 4 1 4 4 5% 5% 5% 7% 10% 52%	2660
	11th to 20th	Day	3 2 1 3 3 3 4 4 7% 8% 62%	2660
	21st to end	Day	2 4 1 4 5% 5% 6% 6% 8% 9% 50%	2660
July	1st to 10th	Day	3 3 2 3 3 5% 6% 6% 9% 8% 53%	4430
	11th to 20th	Day	1 3 1 5% 6% 7% 8% 7% 10% 10% 42%	4430
	21st to end	Day	3 3 1 5% 5% 5% 6% 5% 8% 9% 49%	4523
August	1st to 10th	Day	3 3 1 6% 6% 7% 9% 8% 10% 11% 36%	4002
	11th to 20th	Day	3 2 1 4 3 4 5% 5% 8% 10% 54%	3726
	21st to end	Day	4 3 2 5% 4 5% 6% 5% 9% 12% 46%	4180
September	1st to 10th	Day	4 4 2 5% 4 4 5% 4 7% 8% 53%	2280
	11th to 20th	Day	4 3 1 3 3 3 4 3 5% 8% 63%	2258
	21st to end	Day	4 3 2 4 3 3 3 3 4 6% 66%	2090
October	1st to 10th	Day	3 3 1 2 2 2 2 2 4 5% 73%	3206
	11th to 20th	Day	2 3 1 4 3 3 3 3 5% 7% 66%	3150
	21st to end	Day	2 3 1 3 1 2 2 2 3 5% 77%	3412
November	1st to 10th	Day	1 3 2 3 2 2 2 3 5% 8% 70%	1736
	11th to 20th	Day	3 1 4 2 2 3 3 5% 7% 69%	1710
	21st to end	Day	1 5% 2 5% 2 2 2 4 5% 7% 65%	1706
December	1st to 10th	Day	1 4 1 4 3 3 3 2 4 7% 68%	1520
	11th to 20th	Day	1 4 2 3 2 3 2 3 6% 10% 64%	1926
	21st to end	Day	1 4 3 6% 4 3 3 3 5% 7% 62%	2794
January	1st to 10th	Night	5% 3 7% 3 3 3 3 4 7% 61%	4417
	11th to 20th	Night	3 1 4 3 3 3 3 4 7% 69%	4224
	21st to end	Night	1 5% 2 5% 3 3 3 3 4 8% 62%	4521
February	1st to 10th	Night	1 5% 3 6% 4 2 2 2 4 5% 65%	2443
	11th to 20th	Night	1 4 2 7% 4 2 3 3 4 6% 65%	2218
	21st to end	Night	1 4 3 5% 4 2 3 3 4 6% 66%	1884
March	1st to 10th	Night	1 7% 2 3 2 2 2 2 4 6% 68%	3734
	11th to 20th	Night	3 12% 3 4 2 3 3 3 5% 5% 56%	3494
	21st to end	Night	2 6% 2 4 3 2 3 2 4 6% 65%	3605
April	1st to 10th	Night	1 4 2 4 3 2 2 2 5% 7% 67%	1900
	11th to 20th	Night	3 7% 2 4 3 3 3 4 4 8% 60%	1877
	21st to end	Night	4 7% 2 5% 3 3 3 3 5% 8% 58%	1900
May	1st to 10th	Night	6% 7% 2 4 2 3 3 2 4 4 63%	3088
	11th to 20th	Night	9% 7% 2 4 3 3 3 3 5% 7% 54%	2656
	21st to end	Night	4 4 1 3 2 3 3 2 6% 6% 65%	2762
June	1st to 10th	Night	4 4 1 3 3 3 4 4 6% 9% 58%	1520
	11th to 20th	Night	2 3 1 3 3 3 3 4 5% 9% 65%	1520
	21st to end	Night	3 3 1 4 3 4 6% 5% 8% 10% 53%	1520
July	1st to 10th	Night	6% 4 1 4 4 4 6% 5% 7% 8% 51%	2540
	11th to 20th	Night	3 3 1 4 4 5% 6% 6% 9% 13% 47%	2540
	21st to end	Night	4 3 1 4 4 5% 5% 5% 8% 10% 51%	3036
August	1st to 10th	Night	4 4 2 7% 6% 6% 7% 6% 9% 10% 38%	2934
	11th to 20th	Night	3 2 1 4 4 5% 6% 6% 9% 14% 45%	3113
	21st to end	Night	3 3 2 5% 4 5% 6% 6% 9% 13% 42%	3487
September	1st to 10th	Night	4 4 2 4 3 4 5% 4 6% 9% 55%	1900
	11th to 20th	Night	5% 3 1 2 2 2 3 4 4 7% 66%	1921
	21st to end	Night	5% 4 1 3 2 2 3 3 5% 6% 66%	2090
October	1st to 10th	Night	3 3 1 2 2 2 2 2 3 5% 76%	3758
	11th to 20th	Night	3 3 1 3 3 3 3 3 4 6% 68%	3778
	21st to end	Night	2 3 1 3 1 2 2 2 3 5% 75%	4120
November	1st to 10th	Night	1 3 2 3 2 2 2 2 4 6% 72%	2497
	11th to 20th	Night	1 3 1 3 2 2 2 2 3 5% 74%	2470
	21st to end	Night	2 5% 1 4 2 2 2 2 4 8% 67%	2472
December	1st to 10th	Night	1 3 1 4 3 3 3 3 5% 7% 67%	2660
	11th to 20th	Night	1 5% 1 4 3 2 2 3 6% 8% 65%	3271
	21st to end	Night	1 5% 2 5% 3 3 3 3 6% 7% 62%	4873

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	15% 9% 13% 29% 24% 8%	2539
	11th to 20th	Day	14% 6% 12% 31% 31% 6%	2773
	21st to end	Day	22% 8% 10% 29% 25% 6%	3146
February	1st to 10th	Day	21% 4 11% 30% 24% 10%	1734
	11th to 20th	Day	15% 5% 11% 28% 31% 9%	1859
	21st to end	Day	20% 5% 10% 21% 29% 15%	1570
March	1st to 10th	Day	17% 6% 8% 20% 38% 11%	3130
	11th to 20th	Day	31% 9% 11% 26% 19% 5%	3484
	21st to end	Day	19% 7% 9% 34% 26% 5%	4041
April	1st to 10th	Day	20% 7% 12% 23% 24% 14%	2280
	11th to 20th	Day	25% 8% 8% 26% 22% 11%	2254
	21st to end	Day	27% 9% 11% 22% 24% 7%	2280
May	1st to 10th	Day	25% 9% 9% 17% 25% 16%	3880
	11th to 20th	Day	26% 11% 13% 22% 18% 10%	4237
	21st to end	Day	15% 8% 11% 18% 27% 22%	4825
June	1st to 10th	Day	22% 9% 14% 22% 21% 12%	2660
	11th to 20th	Day	16% 8% 11% 17% 24% 24%	2660
	21st to end	Day	23% 9% 12% 23% 21% 12%	2660
July	1st to 10th	Day	21% 10% 13% 17% 21% 18%	4361
	11th to 20th	Day	27% 14% 15% 27% 14% 4	4355
	21st to end	Day	25% 12% 16% 23% 15% 10%	4380
August	1st to 10th	Day	33% 15% 22% 17% 9% 5%	3988
	11th to 20th	Day	20% 10% 17% 20% 18% 14%	3762
	21st to end	Day	24% 10% 20% 22% 21% 3	4179
September	1st to 10th	Day	25% 9% 12% 23% 21% 10%	2280
	11th to 20th	Day	18% 7% 11% 19% 29% 16%	2258
	21st to end	Day	19% 6% 8% 21% 35% 12%	2090
October	1st to 10th	Day	14% 5% 7% 16% 35% 22%	3206
	11th to 20th	Day	17% 5% 8% 26% 34% 11%	3150
	21st to end	Day	12% 3 5% 19% 43% 17%	3412
November	1st to 10th	Day	12% 5% 10% 23% 36% 15%	1736
	11th to 20th	Day	14% 4 9% 31% 32% 10%	1710
	21st to end	Day	18% 4 9% 21% 32% 16%	1706
December	1st to 10th	Day	16% 6% 14% 30% 24% 10%	1520
	11th to 20th	Day	15% 6% 15% 24% 31% 10%	1924
	21st to end	Day	19% 6% 11% 26% 25% 14%	2794
January	1st to 10th	Night	20% 6% 12% 27% 29% 6%	4417
	11th to 20th	Night	13% 5% 11% 36% 29% 6%	4224
	21st to end	Night	19% 8% 12% 32% 25% 5%	4521
February	1st to 10th	Night	21% 4 10% 30% 25% 10%	2443
	11th to 20th	Night	20% 4 11% 30% 27% 8%	2218
	21st to end	Night	18% 3 9% 23% 35% 12%	1884
March	1st to 10th	Night	17% 4 7% 18% 44% 10%	3734
	11th to 20th	Night	28% 6% 11% 27% 23% 4	3494
	21st to end	Night	19% 4 12% 37% 24% 3	3605
April	1st to 10th	Night	16% 5% 11% 29% 26% 12%	1900
	11th to 20th	Night	23% 6% 11% 24% 27% 9%	1877
	21st to end	Night	24% 8% 13% 26% 22% 6%	1900
May	1st to 10th	Night	22% 7% 7% 21% 27% 16%	3088
	11th to 20th	Night	28% 8% 12% 29% 16% 8%	2657
	21st to end	Night	16% 6% 12% 19% 33% 15%	2762
June	1st to 10th	Night	20% 8% 15% 22% 18% 16%	1520
	11th to 20th	Night	15% 8% 11% 19% 25% 23%	1520
	21st to end	Night	23% 10% 13% 19% 21% 13%	1520
July	1st to 10th	Night	26% 12% 12% 19% 15% 16%	2500
	11th to 20th	Night	22% 11% 24% 29% 10% 4	2492
	21st to end	Night	24% 12% 17% 23% 18% 6%	2941
August	1st to 10th	Night	37% 14% 20% 16% 9% 4	2925
	11th to 20th	Night	25% 11% 24% 17% 15% 8%	3143
	21st to end	Night	27% 12% 20% 23% 15% 3	3487
September	1st to 10th	Night	23% 8% 15% 25% 21% 9%	1900
	11th to 20th	Night	17% 7% 11% 20% 26% 19%	1921
	21st to end	Night	18% 6% 10% 22% 34% 10%	2090
October	1st to 10th	Night	13% 4 8% 22% 35% 18%	3758
	11th to 20th	Night	18% 5% 10% 24% 32% 10%	3778
	21st to end	Night	14% 4 5% 23% 39% 16%	4120
November	1st to 10th	Night	12% 3 9% 26% 34% 16%	2497
	11th to 20th	Night	13% 3 7% 33% 32% 12%	2470
	21st to end	Night	17% 4 9% 22% 35% 13%	2472
December	1st to 10th	Night	16% 5% 13% 32% 24% 9%	2660
	11th to 20th	Night	15% 7% 11% 25% 34% 8%	3272
	21st to end	Night	18% 8% 14% 22% 27% 11%	4873

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	12% 24% 29% 23% 9% 2	270
	11th to 20th	Day	13% 24% 42% 16% 5% 1	270
	21st to end	Day	6% 22% 41% 21% 9% 1	297
February	1st to 10th	Day	7% 34% 42% 13% 2 2	270
	11th to 20th	Day	8% 34% 40% 12% 4 1	270
	21st to end	Day	17% 29% 37% 16% 1	225
March	1st to 10th	Day	10% 34% 29% 23% 4	270
	11th to 20th	Day	11% 27% 37% 19% 4 1	454
	21st to end	Day	16% 36% 34% 11% 3	506
April	1st to 10th	Day	11% 31% 38% 15% 4 1	460
	11th to 20th	Day	16% 31% 37% 12% 3 1	452
	21st to end	Day	13% 31% 37% 15% 3 1	460
May	1st to 10th	Day	13% 24% 40% 17% 5% 1	504
	11th to 20th	Day	11% 14% 34% 28% 11% 2	675
	21st to end	Day	8% 16% 31% 30% 13% 2	734
June	1st to 10th	Day	4 13% 26% 33% 19% 4	680
	11th to 20th	Day	5% 12% 35% 29% 15% 5%	680
	21st to end	Day	4 10% 34% 30% 18% 5%	680
July	1st to 10th	Day	6% 4 25% 38% 21% 7%	671
	11th to 20th	Day	4 3 16% 34% 34% 9%	668
	21st to end	Day	6% 3 14% 37% 30% 10%	574
August	1st to 10th	Day	5% 3 23% 36% 24% 9%	487
	11th to 20th	Day	6% 4 28% 34% 24% 4	477
	21st to end	Day	7% 5% 24% 39% 20% 5%	539
September	1st to 10th	Day	5% 9% 25% 33% 21% 7%	490
	11th to 20th	Day	4 12% 37% 30% 15% 3	468
	21st to end	Day	5% 12% 24% 33% 19% 6%	300
October	1st to 10th	Day	6% 16% 26% 27% 19% 6%	300
	11th to 20th	Day	6% 19% 38% 22% 10% 4	300
	21st to end	Day	11% 16% 41% 21% 10% 2	330
November	1st to 10th	Day	7% 25% 35% 25% 7% 1	291
	11th to 20th	Day	4 23% 42% 17% 12% 2	270
	21st to end	Day	4 21% 40% 26% 7% 1	270
December	1st to 10th	Day	10% 23% 37% 20% 9% 1	270
	11th to 20th	Day	7% 33% 37% 17% 6% 1	270
	21st to end	Day	11% 26% 40% 19% 3	297
January	1st to 10th	Night	3 21% 39% 26% 10% 1	950
	11th to 20th	Night	4 23% 41% 23% 7% 2	822
	21st to end	Night	4 13% 44% 30% 8% 1	836
February	1st to 10th	Night	3 19% 51% 23% 4	760
	11th to 20th	Night	3 22% 48% 20% 6%	744
	21st to end	Night	4 18% 54% 21% 3	628
March	1st to 10th	Night	4 23% 46% 21% 5% 1	760
	11th to 20th	Night	6% 15% 37% 33% 9% 1	760
	21st to end	Night	4 21% 43% 27% 4	703
April	1st to 10th	Night	6% 18% 47% 25% 3	570
	11th to 20th	Night	10% 14% 41% 28% 7%	563
	21st to end	Night	10% 15% 36% 31% 8% 1	570
May	1st to 10th	Night	10% 9% 41% 31% 9%	570
	11th to 20th	Night	12% 7% 31% 35% 14% 2	561
	21st to end	Night	9% 11% 32% 32% 14% 2	617
June	1st to 10th	Night	4 8% 24% 43% 19% 2	570
	11th to 20th	Night	3 8% 33% 39% 16% 1	570
	21st to end	Night	5% 2 26% 39% 27% 2	570
July	1st to 10th	Night	8% 2 15% 41% 31% 4	555
	11th to 20th	Night	6% 1 10% 38% 39% 6%	552
	21st to end	Night	7% 2 6% 37% 42% 6%	624
August	1st to 10th	Night	6% 2 11% 36% 40% 5%	567
	11th to 20th	Night	5% 2 11% 45% 34% 3	564
	21st to end	Night	6% 2 13% 42% 32% 5%	627
September	1st to 10th	Night	6% 2 16% 44% 27% 5%	570
	11th to 20th	Night	6% 5% 23% 40% 21% 5%	570
	21st to end	Night	6% 7% 25% 41% 16% 4	570
October	1st to 10th	Night	7% 7% 32% 38% 14% 3	731
	11th to 20th	Night	3 9% 39% 32% 15% 3	760
	21st to end	Night	6% 12% 36% 30% 13% 3	836
November	1st to 10th	Night	3 13% 39% 33% 11% 1	957
	11th to 20th	Night	3 17% 40% 30% 10% 1	950
	21st to end	Night	6% 13% 40% 31% 9% 1	950
December	1st to 10th	Night	5% 16% 42% 28% 7% 1	950
	11th to 20th	Night	4 19% 45% 22% 10%	950
	21st to end	Night	4 21% 45% 24% 4 1	1045

Page generated at 2024-11-05 06:15:48. Version ac07

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