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 2024-01-15.

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 6% 5% 3 4 5% 5% 7% 41%	74753
	Night	13% 8% 3 6% 5% 3 4 4 5% 7% 43%	75058
Transparency	Day	41% 6% 12% 23% 14% 2	74462
	Night	41% 6% 12% 23% 16% 3	74870
Seeing	Day	15% 10% 28% 27% 16% 5%	14539
	Night	16% 9% 30% 30% 13% 1	24509

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	13% 11% 4 9% 7% 3 4 5% 5% 7% 33%	1517
	11th to 20th	Day	15% 12% 7% 10% 6% 4 4 4 4 5% 29%	1599
	21st to end	Day	14% 12% 5% 8% 7% 3 5% 4 5% 6% 32%	1782
February	1st to 10th	Day	16% 10% 6% 8% 6% 4 4 4 5% 6% 32%	1620
	11th to 20th	Day	13% 11% 3 6% 5% 4 5% 5% 6% 7% 34%	1665
	21st to end	Day	16% 11% 3 7% 6% 3 4 4 4 6% 35%	1480
March	1st to 10th	Day	15% 11% 5% 6% 6% 3 4 3 4 5% 38%	1871
	11th to 20th	Day	16% 9% 3 6% 5% 4 4 4 5% 6% 37%	1980
	21st to end	Day	20% 11% 5% 7% 6% 3 5% 4 4 6% 29%	2258
April	1st to 10th	Day	14% 8% 3 6% 6% 2 4 4 5% 7% 41%	2160
	11th to 20th	Day	17% 7% 3 6% 5% 3 4 3 5% 6% 40%	2134
	21st to end	Day	20% 6% 3 6% 6% 3 5% 5% 5% 7% 35%	2160
May	1st to 10th	Day	16% 8% 3 6% 6% 3 6% 4 6% 7% 35%	2264
	11th to 20th	Day	17% 6% 3 6% 5% 4 4 4 5% 7% 38%	2479
	21st to end	Day	13% 6% 3 6% 7% 4 5% 6% 6% 8% 37%	2725
June	1st to 10th	Day	6% 4 2 5% 5% 3 5% 6% 7% 10% 46%	2520
	11th to 20th	Day	8% 4 2 5% 4 3 5% 6% 6% 9% 46%	2520
	21st to end	Day	8% 4 3 5% 5% 4 5% 5% 6% 10% 45%	2520
July	1st to 10th	Day	8% 4 2 4 4 4 6% 6% 7% 11% 45%	2520
	11th to 20th	Day	5% 4 2 4 5% 3 5% 6% 8% 10% 48%	2520
	21st to end	Day	8% 4 2 4 5% 3 6% 5% 7% 9% 46%	2598
August	1st to 10th	Day	7% 5% 3 5% 6% 4 5% 7% 7% 9% 42%	2328
	11th to 20th	Day	8% 4 2 5% 6% 3 6% 6% 7% 9% 44%	2186
	21st to end	Day	9% 3 2 4 4 3 4 6% 7% 9% 49%	2376
September	1st to 10th	Day	12% 5% 2 4 3 3 4 5% 6% 7% 50%	2160
	11th to 20th	Day	10% 5% 1 4 4 2 3 4 5% 7% 54%	2160
	21st to end	Day	6% 4 2 5% 4 3 5% 5% 6% 7% 52%	1924
October	1st to 10th	Day	13% 5% 2 5% 4 3 3 4 4 7% 51%	1800
	11th to 20th	Day	17% 6% 2 6% 4 2 3 4 5% 5% 47%	1800
	21st to end	Day	20% 7% 3 5% 5% 2 3 4 4 6% 42%	1980
November	1st to 10th	Day	11% 7% 2 4 4 2 3 3 5% 6% 52%	1677
	11th to 20th	Day	16% 6% 4 6% 4 2 3 3 4 7% 44%	1710
	21st to end	Day	16% 11% 3 6% 5% 2 4 4 4 6% 38%	1539
December	1st to 10th	Day	13% 10% 4 6% 6% 3 4 3 4 7% 39%	1520
	11th to 20th	Day	14% 9% 4 6% 5% 4 5% 5% 5% 6% 38%	1918
	21st to end	Day	21% 15% 6% 10% 6% 3 4 4 4 4 22%	2783
January	1st to 10th	Night	12% 11% 4 7% 5% 3 5% 4 4 5% 38%	2648
	11th to 20th	Night	14% 11% 5% 8% 6% 3 4 4 4 5% 35%	2462
	21st to end	Night	13% 12% 6% 7% 5% 3 4 4 5% 6% 34%	2574
February	1st to 10th	Night	16% 12% 5% 7% 5% 4 4 4 4 6% 33%	2340
	11th to 20th	Night	15% 8% 4 6% 6% 3 4 4 5% 6% 39%	2180
	21st to end	Night	17% 9% 4 6% 5% 2 4 4 4 6% 40%	1776
March	1st to 10th	Night	15% 10% 4 5% 5% 2 4 4 4 6% 43%	2106
	11th to 20th	Night	18% 8% 4 6% 4 3 5% 5% 4 6% 37%	1980
	21st to end	Night	22% 9% 4 7% 7% 3 6% 4 5% 6% 27%	2098
April	1st to 10th	Night	13% 6% 3 5% 5% 3 4 5% 5% 6% 45%	1800
	11th to 20th	Night	14% 7% 3 5% 5% 2 4 4 5% 7% 44%	1775
	21st to end	Night	18% 7% 3 6% 4 3 4 5% 4 6% 41%	1800
May	1st to 10th	Night	14% 5% 3 6% 6% 3 5% 5% 6% 8% 39%	1688
	11th to 20th	Night	15% 7% 3 6% 5% 3 3 4 4 6% 43%	1416
	21st to end	Night	10% 5% 3 6% 6% 3 4 6% 5% 9% 43%	1551
June	1st to 10th	Night	7% 5% 2 3 4 2 4 5% 6% 9% 53%	1440
	11th to 20th	Night	8% 3 2 6% 5% 3 4 6% 6% 8% 49%	1440
	21st to end	Night	6% 3 1 5% 4 3 5% 6% 6% 10% 50%	1440
July	1st to 10th	Night	8% 4 2 5% 5% 3 4 5% 6% 9% 49%	1440
	11th to 20th	Night	6% 4 2 4 4 3 4 5% 5% 7% 56%	1440
	21st to end	Night	7% 4 2 4 4 3 5% 4 5% 9% 54%	1717
August	1st to 10th	Night	6% 3 1 4 5% 3 4 5% 7% 11% 51%	1611
	11th to 20th	Night	8% 4 2 5% 4 2 5% 4 6% 7% 53%	1712
	21st to end	Night	5% 3 1 4 4 3 4 6% 6% 8% 56%	1980
September	1st to 10th	Night	11% 5% 2 4 3 2 3 4 5% 7% 55%	1800
	11th to 20th	Night	8% 4 2 5% 4 2 4 4 5% 7% 53%	1800
	21st to end	Night	6% 3 2 5% 4 3 5% 5% 4 7% 56%	2014
October	1st to 10th	Night	9% 4 1 4 4 2 4 3 5% 7% 56%	2160
	11th to 20th	Night	14% 5% 2 5% 4 2 4 4 4 6% 51%	2160
	21st to end	Night	18% 7% 2 5% 3 3 3 4 5% 5% 44%	2376
November	1st to 10th	Night	11% 5% 2 4 4 2 3 4 4 7% 54%	2401
	11th to 20th	Night	13% 7% 3 6% 5% 3 3 3 4 6% 48%	2470
	21st to end	Night	18% 8% 3 4 4 2 3 4 4 6% 43%	2640
December	1st to 10th	Night	14% 10% 3 7% 5% 3 5% 5% 5% 6% 35%	2660
	11th to 20th	Night	16% 9% 3 6% 5% 3 3 3 4 6% 42%	3279
	21st to end	Night	21% 17% 8% 10% 6% 3 4 3 3 4 21%	4884

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	49% 6% 11% 19% 13% 1	1518
	11th to 20th	Day	58% 5% 10% 20% 7%	1599
	21st to end	Day	52% 6% 13% 19% 9% 2	1782
February	1st to 10th	Day	54% 5% 12% 19% 9% 1	1620
	11th to 20th	Day	49% 7% 12% 20% 12% 1	1674
	21st to end	Day	51% 4 11% 21% 10% 2	1480
March	1st to 10th	Day	49% 5% 11% 25% 10% 2	1871
	11th to 20th	Day	49% 6% 12% 21% 11% 2	1980
	21st to end	Day	56% 6% 12% 16% 8% 1	2258
April	1st to 10th	Day	43% 5% 12% 25% 14%	2160
	11th to 20th	Day	46% 5% 9% 25% 13% 3	2134
	21st to end	Day	47% 7% 13% 19% 13% 1	2160
May	1st to 10th	Day	48% 7% 12% 22% 10% 1	2264
	11th to 20th	Day	46% 7% 12% 22% 12% 1	2483
	21st to end	Day	43% 9% 12% 19% 15% 2	2725
June	1st to 10th	Day	31% 8% 16% 28% 15% 2	2520
	11th to 20th	Day	33% 9% 12% 23% 20% 3	2520
	21st to end	Day	34% 8% 15% 24% 16% 3	2520
July	1st to 10th	Day	31% 9% 16% 27% 13% 3	2451
	11th to 20th	Day	29% 9% 17% 26% 15% 3	2445
	21st to end	Day	32% 7% 14% 31% 15% 1	2454
August	1st to 10th	Day	35% 9% 16% 26% 12% 2	2314
	11th to 20th	Day	34% 9% 14% 28% 14% 1	2186
	21st to end	Day	28% 8% 13% 26% 19% 5%	2376
September	1st to 10th	Day	32% 7% 11% 26% 18% 6%	2160
	11th to 20th	Day	30% 4 11% 29% 22% 4	2160
	21st to end	Day	29% 6% 10% 29% 23% 2	1924
October	1st to 10th	Day	34% 4 11% 26% 21% 4	1800
	11th to 20th	Day	38% 5% 10% 23% 20% 4	1800
	21st to end	Day	44% 4 9% 24% 16% 3	1980
November	1st to 10th	Day	33% 4 14% 24% 20% 4	1677
	11th to 20th	Day	41% 4 10% 25% 18% 3	1710
	21st to end	Day	48% 6% 10% 25% 12%	1539
December	1st to 10th	Day	47% 4 14% 22% 12% 1	1520
	11th to 20th	Day	45% 7% 12% 24% 10% 2	1915
	21st to end	Day	63% 6% 10% 14% 6% 1	2783
January	1st to 10th	Night	47% 5% 10% 23% 14% 1	2648
	11th to 20th	Night	52% 5% 10% 23% 9%	2462
	21st to end	Night	51% 5% 14% 19% 10% 1	2574
February	1st to 10th	Night	53% 5% 12% 18% 10% 2	2340
	11th to 20th	Night	46% 5% 11% 22% 14% 2	2181
	21st to end	Night	47% 5% 11% 24% 11% 4	1776
March	1st to 10th	Night	44% 5% 10% 25% 15% 2	2106
	11th to 20th	Night	47% 6% 11% 20% 13% 3	1980
	21st to end	Night	56% 7% 11% 18% 7% 1	2098
April	1st to 10th	Night	39% 5% 13% 24% 15% 4	1800
	11th to 20th	Night	40% 4 11% 24% 16% 4	1775
	21st to end	Night	45% 6% 10% 21% 17% 2	1800
May	1st to 10th	Night	41% 8% 14% 22% 14% 1	1688
	11th to 20th	Night	43% 6% 10% 22% 18% 1	1417
	21st to end	Night	38% 7% 13% 20% 18% 3	1552
June	1st to 10th	Night	26% 7% 16% 29% 18% 3	1440
	11th to 20th	Night	31% 7% 11% 22% 24% 4	1440
	21st to end	Night	28% 8% 17% 23% 20% 4	1440
July	1st to 10th	Night	32% 7% 15% 28% 14% 4	1400
	11th to 20th	Night	26% 6% 13% 32% 20% 3	1392
	21st to end	Night	25% 7% 14% 30% 21% 2	1622
August	1st to 10th	Night	26% 7% 17% 32% 15% 2	1601
	11th to 20th	Night	30% 6% 12% 31% 20% 1	1712
	21st to end	Night	24% 7% 16% 25% 22% 7%	1980
September	1st to 10th	Night	29% 5% 12% 23% 24% 6%	1800
	11th to 20th	Night	29% 6% 10% 25% 25% 4	1800
	21st to end	Night	28% 5% 10% 26% 28% 4	2014
October	1st to 10th	Night	29% 6% 11% 24% 25% 5%	2160
	11th to 20th	Night	35% 4 9% 26% 21% 5%	2160
	21st to end	Night	42% 6% 9% 20% 21% 3	2376
November	1st to 10th	Night	31% 5% 12% 27% 20% 5%	2401
	11th to 20th	Night	38% 4 10% 26% 20% 3	2470
	21st to end	Night	44% 4 11% 25% 14% 1	2640
December	1st to 10th	Night	48% 5% 14% 22% 10% 1	2660
	11th to 20th	Night	45% 5% 11% 25% 13% 1	3281
	21st to end	Night	68% 5% 8% 12% 6% 1	4884

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	18% 20% 34% 20% 7% 1	270
	11th to 20th	Day	27% 19% 39% 13% 2	254
	21st to end	Day	14% 22% 45% 16% 3	264
February	1st to 10th	Day	26% 18% 40% 14% 3	240
	11th to 20th	Day	24% 24% 32% 15% 5%	240
	21st to end	Day	24% 21% 36% 17% 2	198
March	1st to 10th	Day	19% 24% 45% 11% 2	240
	11th to 20th	Day	29% 15% 33% 19% 4	240
	21st to end	Day	32% 18% 31% 13% 5%	344
April	1st to 10th	Day	20% 14% 35% 23% 7% 1	420
	11th to 20th	Day	21% 14% 31% 23% 10% 1	412
	21st to end	Day	21% 15% 34% 24% 5% 1	420
May	1st to 10th	Day	16% 13% 38% 22% 9% 2	495
	11th to 20th	Day	20% 10% 28% 27% 12% 2	625
	21st to end	Day	13% 8% 29% 28% 16% 7%	679
June	1st to 10th	Day	7% 5% 21% 34% 25% 8%	630
	11th to 20th	Day	10% 3 23% 35% 23% 5%	630
	21st to end	Day	8% 7% 28% 35% 18% 4	630
July	1st to 10th	Day	9% 3 15% 33% 26% 14%	621
	11th to 20th	Day	7% 4 19% 37% 27% 7%	618
	21st to end	Day	9% 2 19% 33% 30% 7%	684
August	1st to 10th	Day	7% 4 16% 41% 25% 8%	626
	11th to 20th	Day	7% 3 17% 34% 29% 10%	500
	21st to end	Day	9% 2 14% 34% 31% 11%	495
September	1st to 10th	Day	12% 4 16% 32% 28% 8%	450
	11th to 20th	Day	9% 2 16% 32% 28% 12%	450
	21st to end	Day	6% 10% 22% 32% 21% 9%	380
October	1st to 10th	Day	14% 9% 31% 29% 13% 5%	270
	11th to 20th	Day	17% 21% 36% 19% 7%	270
	21st to end	Day	29% 17% 31% 19% 5%	297
November	1st to 10th	Day	10% 11% 42% 24% 10% 4	270
	11th to 20th	Day	21% 17% 33% 20% 9% 1	270
	21st to end	Day	27% 11% 34% 20% 7%	270
December	1st to 10th	Day	13% 17% 44% 15% 7% 3	270
	11th to 20th	Day	21% 15% 38% 20% 5%	270
	21st to end	Day	26% 22% 36% 13% 3	297
January	1st to 10th	Night	16% 16% 40% 22% 6%	950
	11th to 20th	Night	18% 18% 36% 23% 4	925
	21st to end	Night	19% 13% 40% 25% 2	990
February	1st to 10th	Night	23% 12% 40% 23% 3	900
	11th to 20th	Night	19% 15% 37% 26% 3	786
	21st to end	Night	23% 17% 35% 22% 2	592
March	1st to 10th	Night	20% 14% 39% 22% 5%	666
	11th to 20th	Night	23% 10% 33% 28% 6%	540
	21st to end	Night	25% 11% 34% 25% 4	594
April	1st to 10th	Night	16% 14% 37% 28% 5%	540
	11th to 20th	Night	17% 10% 35% 29% 9% 1	533
	21st to end	Night	22% 9% 35% 29% 6%	540
May	1st to 10th	Night	16% 7% 34% 34% 9% 1	540
	11th to 20th	Night	17% 6% 26% 37% 12% 1	531
	21st to end	Night	11% 4 25% 36% 21% 2	584
June	1st to 10th	Night	7% 3 21% 43% 25% 1	540
	11th to 20th	Night	10% 3 19% 47% 19% 2	540
	21st to end	Night	6% 3 26% 44% 20% 1	540
July	1st to 10th	Night	9% 4 9% 37% 37% 4	525
	11th to 20th	Night	5% 2 16% 46% 28% 3	522
	21st to end	Night	8% 1 14% 44% 32% 1	591
August	1st to 10th	Night	6% 3 9% 46% 33% 2	537
	11th to 20th	Night	9% 2 12% 39% 34% 4	534
	21st to end	Night	4 2 15% 34% 41% 3	594
September	1st to 10th	Night	14% 2 18% 36% 26% 4	540
	11th to 20th	Night	10% 2 17% 37% 27% 7%	540
	21st to end	Night	7% 6% 24% 35% 23% 5%	688
October	1st to 10th	Night	11% 5% 28% 32% 22% 3	720
	11th to 20th	Night	17% 11% 33% 29% 10% 1	720
	21st to end	Night	23% 11% 34% 26% 7%	792
November	1st to 10th	Night	13% 9% 36% 31% 9% 1	740
	11th to 20th	Night	16% 14% 37% 26% 6% 1	760
	21st to end	Night	22% 13% 34% 25% 6%	930
December	1st to 10th	Night	19% 12% 39% 25% 5% 1	950
	11th to 20th	Night	23% 10% 32% 28% 6%	950
	21st to end	Night	24% 17% 34% 22% 3	1045

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