This page made possible by the sponsorship of:

Gardner Camp Youth Astronomy Club

.

Gardner Camp
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gardner Camp clear sky chart from 2005-11-06 to 2025-09-19.

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	13% 7% 3 7% 4 4 4 4 6% 7% 41%	126422
	Night	13% 8% 3 7% 4 4 4 3 5% 6% 42%	122866
Transparency	Day	41% 6% 12% 24% 16% 2	130016
	Night	41% 5% 11% 24% 17% 3	127349
Seeing	Day	15% 11% 28% 27% 16% 4	16935
	Night	16% 10% 30% 30% 13% 1	26679

By Month

Percentage Cloud Cover SE (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	14% 11% 6% 14% 7% 4 4 3 5% 6% 27%	3617
	11th to 20th	Day	9% 10% 4 10% 6% 6% 5% 4 5% 5% 36%	3924
	21st to end	Day	16% 16% 7% 9% 5% 3 3 2 3 4 31%	4488
February	1st to 10th	Day	15% 11% 5% 8% 5% 4 4 3 5% 7% 32%	1800
	11th to 20th	Day	13% 11% 3 7% 4 5% 5% 4 6% 6% 35%	1856
	21st to end	Day	14% 11% 3 7% 5% 3 4 3 4 6% 39%	1650
March	1st to 10th	Day	18% 9% 3 5% 3 3 3 2 3 4 48%	4663
	11th to 20th	Day	8% 6% 2 5% 4 4 4 4 5% 8% 50%	4980
	21st to end	Day	17% 10% 3 8% 5% 5% 4 3 5% 7% 33%	5681
April	1st to 10th	Day	15% 9% 3 7% 5% 3 4 4 5% 6% 39%	2400
	11th to 20th	Day	16% 8% 3 7% 4 4 4 3 5% 6% 40%	2374
	21st to end	Day	19% 6% 3 7% 4 4 5% 4 5% 8% 35%	2400
May	1st to 10th	Day	14% 7% 3 7% 5% 5% 5% 4 6% 9% 35%	5691
	11th to 20th	Day	15% 7% 3 6% 4 4 4 3 5% 7% 41%	6319
	21st to end	Day	15% 7% 3 6% 5% 4 4 4 5% 7% 40%	6935
June	1st to 10th	Day	7% 4 2 6% 4 5% 5% 5% 7% 10% 46%	2800
	11th to 20th	Day	8% 5% 2 6% 4 4 5% 4 7% 9% 46%	2800
	21st to end	Day	8% 5% 3 6% 4 5% 5% 4 6% 9% 45%	2800
July	1st to 10th	Day	11% 5% 2 6% 4 4 5% 4 6% 9% 43%	6360
	11th to 20th	Day	9% 5% 3 7% 5% 5% 5% 5% 7% 10% 40%	6360
	21st to end	Day	9% 5% 3 6% 5% 5% 6% 5% 8% 11% 38%	6544
August	1st to 10th	Day	5% 4 2 5% 4 4 5% 5% 7% 9% 49%	4234
	11th to 20th	Day	13% 5% 2 6% 4 4 5% 4 7% 9% 42%	3952
	21st to end	Day	6% 3 2 5% 3 4 5% 5% 7% 10% 51%	4312
September	1st to 10th	Day	11% 5% 2 5% 3 4 3 4 5% 7% 52%	2400
	11th to 20th	Day	9% 5% 2 5% 3 4 3 4 5% 8% 52%	2376
	21st to end	Day	8% 4 2 5% 4 5% 4 4 6% 7% 51%	2030
October	1st to 10th	Day	12% 5% 2 5% 3 3 3 3 4 7% 53%	1900
	11th to 20th	Day	16% 6% 2 6% 3 3 3 3 5% 6% 48%	1900
	21st to end	Day	19% 7% 3 6% 4 3 3 3 4 6% 43%	2090
November	1st to 10th	Day	11% 8% 2 5% 4 3 3 3 5% 6% 51%	1767
	11th to 20th	Day	16% 7% 3 7% 3 3 3 3 4 6% 44%	1800
	21st to end	Day	16% 11% 3 7% 4 4 3 4 4 6% 38%	1619
December	1st to 10th	Day	8% 9% 3 7% 5% 3 3 3 3 6% 51%	2610
	11th to 20th	Day	13% 10% 7% 9% 4 5% 4 3 4 6% 34%	3008
	21st to end	Day	24% 19% 6% 10% 4 4 4 3 4 4 20%	3982
January	1st to 10th	Night	14% 12% 6% 13% 5% 4 4 3 4 4 30%	6348
	11th to 20th	Night	12% 12% 5% 12% 5% 4 6% 4 5% 4 31%	6038
	21st to end	Night	16% 15% 5% 9% 4 3 3 2 4 5% 32%	6490
February	1st to 10th	Night	15% 12% 4 7% 6% 4 4 4 5% 6% 33%	2600
	11th to 20th	Night	15% 8% 4 7% 6% 4 4 4 5% 6% 38%	2429
	21st to end	Night	16% 9% 3 7% 4 3 3 3 4 5% 42%	1980
March	1st to 10th	Night	19% 10% 3 5% 4 2 3 2 4 5% 42%	5221
	11th to 20th	Night	12% 7% 2 5% 3 3 3 3 4 5% 52%	4980
	21st to end	Night	18% 9% 3 8% 5% 5% 5% 4 5% 7% 32%	5248
April	1st to 10th	Night	13% 7% 3 6% 5% 4 4 3 5% 6% 45%	2000
	11th to 20th	Night	14% 7% 3 5% 4 4 4 4 5% 7% 44%	1975
	21st to end	Night	17% 7% 2 7% 4 4 4 3 4 6% 41%	2000
May	1st to 10th	Night	18% 8% 3 6% 5% 4 5% 4 5% 7% 36%	4205
	11th to 20th	Night	13% 6% 2 6% 5% 4 4 3 5% 7% 45%	3596
	21st to end	Night	14% 6% 2 6% 4 4 4 4 5% 8% 44%	3942
June	1st to 10th	Night	7% 5% 2 4 3 3 4 4 6% 9% 52%	1600
	11th to 20th	Night	8% 4 2 7% 4 4 4 4 6% 8% 49%	1600
	21st to end	Night	6% 3 1 6% 3 4 5% 5% 6% 10% 51%	1600
July	1st to 10th	Night	10% 5% 2 7% 4 4 4 3 7% 9% 45%	3618
	11th to 20th	Night	7% 4 2 6% 4 5% 5% 4 6% 8% 49%	3617
	21st to end	Night	10% 5% 2 6% 4 4 5% 4 7% 11% 41%	4310
August	1st to 10th	Night	4 2 1 4 4 3 4 3 6% 10% 59%	2926
	11th to 20th	Night	10% 4 2 5% 4 4 4 3 5% 7% 52%	3097
	21st to end	Night	4 3 1 5% 3 4 4 5% 6% 10% 55%	3586
September	1st to 10th	Night	10% 5% 2 4 3 3 4 3 5% 6% 56%	2000
	11th to 20th	Night	8% 5% 2 6% 3 3 5% 3 6% 7% 52%	1980
	21st to end	Night	7% 4 2 6% 4 4 4 3 4 7% 55%	2127
October	1st to 10th	Night	9% 4 1 5% 3 3 3 3 5% 6% 57%	2280
	11th to 20th	Night	14% 5% 2 5% 3 3 3 3 4 6% 53%	2280
	21st to end	Night	17% 8% 2 5% 3 4 4 3 5% 6% 44%	2508
November	1st to 10th	Night	12% 5% 2 5% 3 3 3 3 5% 6% 53%	2531
	11th to 20th	Night	12% 8% 3 7% 4 4 3 2 4 6% 47%	2600
	21st to end	Night	17% 10% 3 6% 3 3 4 3 5% 6% 41%	2779
December	1st to 10th	Night	11% 8% 3 7% 4 4 4 3 4 6% 47%	4580
	11th to 20th	Night	16% 10% 3 6% 4 4 3 3 5% 6% 40%	5199
	21st to end	Night	25% 17% 7% 10% 4 4 3 3 3 4 21%	6996

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	57% 5% 10% 18% 9% 1	3618
	11th to 20th	Day	49% 4 12% 17% 13% 5%	3924
	21st to end	Day	57% 4 8% 17% 12% 2	4488
February	1st to 10th	Day	52% 5% 13% 19% 10% 2	1800
	11th to 20th	Day	49% 6% 11% 19% 13% 2	1865
	21st to end	Day	47% 4 10% 24% 12% 3	1650
March	1st to 10th	Day	42% 3 7% 24% 22% 2	4663
	11th to 20th	Day	32% 5% 10% 29% 22% 3	4980
	21st to end	Day	49% 6% 16% 22% 6% 1	5683
April	1st to 10th	Day	45% 5% 11% 24% 14% 1	2400
	11th to 20th	Day	45% 5% 9% 25% 14% 2	2374
	21st to end	Day	47% 6% 14% 19% 13% 1	2400
May	1st to 10th	Day	44% 8% 13% 21% 12% 1	5726
	11th to 20th	Day	42% 6% 10% 26% 13% 3	6323
	21st to end	Day	43% 6% 9% 23% 18% 1	6949
June	1st to 10th	Day	31% 8% 16% 28% 15% 3	2800
	11th to 20th	Day	33% 8% 12% 24% 20% 3	2800
	21st to end	Day	34% 7% 15% 24% 17% 3	2800
July	1st to 10th	Day	36% 6% 13% 28% 16% 2	6291
	11th to 20th	Day	39% 7% 15% 25% 14% 1	6285
	21st to end	Day	38% 7% 19% 27% 9% 1	6359
August	1st to 10th	Day	29% 8% 16% 35% 12% 1	4220
	11th to 20th	Day	37% 6% 14% 28% 14% 1	3990
	21st to end	Day	27% 7% 17% 31% 14% 4	4311
September	1st to 10th	Day	31% 6% 11% 26% 21% 5%	2400
	11th to 20th	Day	30% 4 10% 30% 21% 4	2376
	21st to end	Day	31% 6% 10% 28% 23% 2	2030
October	1st to 10th	Day	21% 3 7% 17% 46% 6%	3160
	11th to 20th	Day	25% 3 7% 21% 37% 7%	3140
	21st to end	Day	40% 3 7% 24% 24% 2	3428
November	1st to 10th	Day	34% 4 13% 24% 20% 4	1767
	11th to 20th	Day	41% 4 10% 24% 18% 3	1800
	21st to end	Day	48% 5% 10% 25% 11%	1619
December	1st to 10th	Day	36% 3 17% 30% 14%	2610
	11th to 20th	Day	51% 5% 12% 21% 10% 1	3005
	21st to end	Day	68% 4 12% 11% 4	3982
January	1st to 10th	Night	57% 4 10% 21% 7%	6348
	11th to 20th	Night	56% 4 9% 17% 12% 2	6038
	21st to end	Night	55% 4 9% 19% 11% 2	6490
February	1st to 10th	Night	52% 5% 12% 19% 11% 2	2600
	11th to 20th	Night	47% 5% 11% 22% 14% 2	2430
	21st to end	Night	44% 5% 10% 24% 15% 3	1980
March	1st to 10th	Night	46% 4 7% 22% 20% 2	5221
	11th to 20th	Night	36% 4 6% 28% 21% 6%	4980
	21st to end	Night	50% 6% 11% 23% 8% 2	5248
April	1st to 10th	Night	40% 5% 13% 23% 16% 4	2000
	11th to 20th	Night	40% 4 11% 24% 17% 4	1975
	21st to end	Night	45% 6% 10% 21% 16% 2	2000
May	1st to 10th	Night	46% 7% 12% 23% 10% 2	4235
	11th to 20th	Night	39% 6% 12% 26% 13% 4	3597
	21st to end	Night	38% 7% 12% 22% 20% 2	3950
June	1st to 10th	Night	27% 7% 16% 30% 18% 3	1600
	11th to 20th	Night	31% 6% 11% 23% 25% 4	1600
	21st to end	Night	28% 8% 17% 23% 20% 5%	1600
July	1st to 10th	Night	36% 6% 11% 29% 16% 2	3580
	11th to 20th	Night	32% 6% 13% 30% 17% 1	3572
	21st to end	Night	34% 7% 19% 27% 12% 1	4185
August	1st to 10th	Night	20% 6% 20% 36% 17% 2	2916
	11th to 20th	Night	32% 5% 13% 29% 21% 1	3125
	21st to end	Night	24% 6% 19% 30% 16% 4	3586
September	1st to 10th	Night	28% 5% 12% 23% 25% 7%	2000
	11th to 20th	Night	29% 6% 10% 25% 26% 4	1980
	21st to end	Night	29% 5% 9% 26% 27% 4	2127
October	1st to 10th	Night	19% 4 7% 21% 45% 5%	3800
	11th to 20th	Night	25% 3 9% 21% 36% 7%	3779
	21st to end	Night	36% 4 8% 23% 25% 4	4120
November	1st to 10th	Night	32% 5% 12% 27% 20% 5%	2531
	11th to 20th	Night	39% 4 10% 25% 20% 3	2600
	21st to end	Night	45% 4 11% 25% 14% 1	2779
December	1st to 10th	Night	39% 4 11% 33% 12%	4580
	11th to 20th	Night	46% 5% 12% 23% 14% 1	5201
	21st to end	Night	69% 4 11% 11% 5% 1	6996

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	19% 20% 35% 19% 6% 1	300
	11th to 20th	Day	24% 21% 41% 12% 2	300
	21st to end	Day	16% 20% 45% 15% 3	330
February	1st to 10th	Day	23% 17% 42% 15% 3	300
	11th to 20th	Day	23% 25% 32% 14% 5%	300
	21st to end	Day	21% 22% 39% 16% 2	249
March	1st to 10th	Day	18% 24% 44% 12% 1	300
	11th to 20th	Day	26% 19% 33% 19% 3	300
	21st to end	Day	30% 20% 32% 14% 4	420
April	1st to 10th	Day	22% 17% 33% 21% 7% 1	500
	11th to 20th	Day	21% 17% 31% 21% 9% 1	492
	21st to end	Day	19% 15% 36% 23% 5% 1	500
May	1st to 10th	Day	15% 13% 38% 23% 9% 2	584
	11th to 20th	Day	18% 11% 28% 27% 13% 2	725
	21st to end	Day	13% 10% 30% 28% 14% 6%	789
June	1st to 10th	Day	8% 5% 24% 33% 23% 7%	730
	11th to 20th	Day	10% 3 23% 36% 23% 5%	730
	21st to end	Day	8% 7% 29% 35% 18% 4	730
July	1st to 10th	Day	9% 4 16% 33% 25% 13%	721
	11th to 20th	Day	7% 4 20% 37% 25% 7%	718
	21st to end	Day	9% 3 18% 32% 32% 7%	794
August	1st to 10th	Day	7% 4 17% 41% 24% 7%	726
	11th to 20th	Day	7% 3 17% 33% 30% 9%	586
	21st to end	Day	8% 2 15% 35% 31% 10%	583
September	1st to 10th	Day	11% 4 16% 33% 28% 9%	530
	11th to 20th	Day	8% 3 15% 32% 30% 13%	522
	21st to end	Day	9% 10% 21% 32% 19% 8%	416
October	1st to 10th	Day	12% 8% 31% 28% 14% 7%	300
	11th to 20th	Day	15% 21% 34% 20% 10%	300
	21st to end	Day	26% 18% 32% 19% 5%	330
November	1st to 10th	Day	12% 12% 39% 24% 9% 3	300
	11th to 20th	Day	22% 17% 33% 18% 9% 1	300
	21st to end	Day	28% 13% 33% 20% 7%	300
December	1st to 10th	Day	13% 19% 45% 14% 6% 3	300
	11th to 20th	Day	21% 18% 36% 19% 5%	300
	21st to end	Day	27% 21% 36% 13% 4	330
January	1st to 10th	Night	17% 16% 40% 22% 6%	1000
	11th to 20th	Night	18% 19% 36% 23% 4	1000
	21st to end	Night	19% 13% 40% 25% 2	1100
February	1st to 10th	Night	22% 13% 40% 23% 3	1000
	11th to 20th	Night	19% 16% 37% 25% 3	875
	21st to end	Night	22% 16% 37% 23% 2	660
March	1st to 10th	Night	20% 14% 39% 22% 5%	739
	11th to 20th	Night	21% 12% 34% 28% 5%	600
	21st to end	Night	25% 13% 34% 25% 4	660
April	1st to 10th	Night	17% 15% 37% 28% 4	600
	11th to 20th	Night	17% 12% 34% 28% 8% 1	593
	21st to end	Night	21% 10% 36% 29% 5%	600
May	1st to 10th	Night	16% 8% 34% 33% 8% 1	600
	11th to 20th	Night	16% 6% 27% 38% 12% 1	591
	21st to end	Night	12% 5% 26% 36% 20% 2	650
June	1st to 10th	Night	8% 4 21% 42% 24% 1	600
	11th to 20th	Night	10% 3 20% 48% 19% 2	600
	21st to end	Night	7% 3 25% 44% 21% 1	600
July	1st to 10th	Night	9% 4 9% 37% 37% 4	585
	11th to 20th	Night	5% 2 16% 45% 29% 3	582
	21st to end	Night	9% 1 13% 43% 33% 1	657
August	1st to 10th	Night	6% 3 11% 46% 32% 2	597
	11th to 20th	Night	8% 2 12% 40% 34% 4	594
	21st to end	Night	5% 2 15% 35% 40% 3	660
September	1st to 10th	Night	13% 2 18% 36% 27% 4	600
	11th to 20th	Night	9% 2 16% 38% 28% 6%	594
	21st to end	Night	8% 7% 24% 34% 22% 5%	727
October	1st to 10th	Night	11% 4 28% 32% 23% 3	760
	11th to 20th	Night	16% 10% 32% 30% 10% 1	760
	21st to end	Night	22% 11% 34% 27% 6%	836
November	1st to 10th	Night	14% 9% 36% 32% 9% 1	780
	11th to 20th	Night	16% 15% 38% 26% 5% 1	800
	21st to end	Night	22% 13% 34% 24% 6%	979
December	1st to 10th	Night	19% 12% 39% 25% 5% 1	1000
	11th to 20th	Night	24% 11% 33% 27% 6%	1000
	21st to end	Night	25% 16% 34% 22% 3	1100

Page generated at 2025-09-16 00:49:14. Version ac07

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