Halfmoon Campground
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Halfmoon Campground clear sky chart from 2005-11-06 to 2024-12-09.

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	5% 7% 3 7% 5% 5% 6% 5% 8% 10% 40%	105756
	Night	4 6% 3 7% 5% 5% 5% 5% 8% 11% 41%	102725
Transparency	Day	33% 9% 13% 23% 16% 6%	105493
	Night	32% 8% 15% 25% 15% 4	102578
Seeing	Day	16% 26% 32% 18% 7% 2	15681
	Night	12% 28% 28% 21% 10% 1	25216

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	3 3 8% 6% 6% 8% 9% 13% 15% 28%	2219
	11th to 20th	Day	3 2 11% 11% 10% 8% 6% 9% 12% 27%	2384
	21st to end	Day	5% 2 7% 4 5% 6% 5% 9% 14% 41%	3146
February	1st to 10th	Day	1 7% 3 9% 7% 8% 7% 5% 12% 15% 23%	1710
	11th to 20th	Day	1 6% 4 13% 7% 7% 7% 6% 11% 13% 26%	1665
	21st to end	Day	1 5% 5% 13% 8% 8% 6% 5% 13% 14% 23%	1439
March	1st to 10th	Day	1 6% 4 8% 5% 5% 6% 5% 8% 11% 40%	3384
	11th to 20th	Day	2 10% 3 8% 5% 4 5% 5% 8% 10% 41%	3490
	21st to end	Day	4 13% 6% 14% 8% 7% 7% 6% 10% 10% 16%	3825
April	1st to 10th	Day	5% 15% 3 8% 5% 6% 6% 5% 9% 11% 25%	2232
	11th to 20th	Day	6% 13% 5% 10% 7% 7% 7% 5% 7% 9% 26%	2400
	21st to end	Day	12% 15% 4 9% 6% 5% 5% 4 6% 8% 28%	2470
May	1st to 10th	Day	10% 17% 5% 10% 6% 5% 6% 4 6% 7% 24%	4168
	11th to 20th	Day	9% 12% 3 7% 5% 5% 6% 5% 8% 10% 30%	4388
	21st to end	Day	13% 9% 2 8% 6% 5% 5% 4 8% 10% 30%	4825
June	1st to 10th	Day	12% 9% 3 8% 5% 6% 5% 6% 7% 8% 31%	2831
	11th to 20th	Day	10% 8% 3 8% 7% 5% 5% 5% 8% 9% 32%	2850
	21st to end	Day	5% 4 2 5% 4 5% 6% 5% 7% 9% 48%	2850
July	1st to 10th	Day	3 3 2 5% 5% 5% 6% 6% 9% 9% 46%	4740
	11th to 20th	Day	2 1 1 3 3 3 6% 5% 8% 10% 58%	4740
	21st to end	Day	2 2 1 3 4 4 6% 6% 7% 8% 57%	4628
August	1st to 10th	Day	5% 7% 1 6% 5% 5% 6% 4 8% 9% 45%	4092
	11th to 20th	Day	5% 3 1 5% 4 5% 5% 5% 7% 9% 51%	4028
	21st to end	Day	5% 3 2 5% 4 4 5% 4 6% 6% 56%	4491
September	1st to 10th	Day	8% 4 1 4 3 3 5% 3 5% 7% 57%	2280
	11th to 20th	Day	8% 7% 2 7% 4 4 5% 4 4 7% 48%	2136
	21st to end	Day	9% 6% 1 4 3 3 4 4 6% 8% 50%	2090
October	1st to 10th	Day	6% 7% 1 6% 4 3 3 3 4 6% 59%	3171
	11th to 20th	Day	4 8% 2 5% 3 3 3 4 6% 9% 54%	3150
	21st to end	Day	3 7% 3 7% 4 5% 5% 4 8% 11% 42%	3331
November	1st to 10th	Day	5% 6% 3 8% 5% 6% 6% 5% 8% 11% 36%	1616
	11th to 20th	Day	2 6% 3 7% 6% 7% 6% 5% 9% 15% 36%	1600
	21st to end	Day	1 6% 2 6% 5% 5% 6% 5% 10% 13% 40%	1600
December	1st to 10th	Day	1 4 2 6% 6% 6% 7% 6% 13% 13% 37%	1584
	11th to 20th	Day	1 5% 3 8% 6% 6% 6% 5% 11% 16% 33%	1761
	21st to end	Day	1 6% 3 9% 6% 6% 5% 5% 8% 11% 40%	2442
January	1st to 10th	Night	3 2 9% 5% 5% 6% 6% 12% 18% 34%	4726
	11th to 20th	Night	2 2 10% 9% 8% 8% 6% 10% 13% 31%	4602
	21st to end	Night	1 5% 3 7% 5% 5% 6% 7% 11% 15% 37%	4521
February	1st to 10th	Night	1 7% 5% 10% 7% 6% 6% 6% 11% 16% 24%	2470
	11th to 20th	Night	1 5% 4 9% 6% 6% 6% 7% 10% 16% 30%	2402
	21st to end	Night	5% 4 12% 6% 6% 5% 6% 12% 14% 30%	2013
March	1st to 10th	Night	1 6% 3 6% 4 6% 6% 5% 8% 13% 42%	3489
	11th to 20th	Night	2 6% 3 5% 5% 4 5% 4 7% 12% 48%	3490
	21st to end	Night	2 12% 5% 13% 8% 7% 6% 5% 9% 11% 21%	3828
April	1st to 10th	Night	7% 12% 3 7% 5% 6% 5% 5% 8% 10% 33%	1948
	11th to 20th	Night	5% 10% 3 9% 6% 6% 7% 5% 8% 11% 30%	1724
	21st to end	Night	12% 12% 3 8% 5% 3 5% 4 6% 8% 36%	1710
May	1st to 10th	Night	9% 16% 5% 10% 6% 4 5% 4 6% 7% 27%	2801
	11th to 20th	Night	10% 10% 4 6% 4 5% 4 3 6% 9% 38%	2517
	21st to end	Night	12% 9% 2 7% 6% 6% 6% 5% 7% 9% 30%	2762
June	1st to 10th	Night	13% 7% 2 7% 6% 6% 7% 6% 7% 8% 31%	1344
	11th to 20th	Night	13% 8% 2 6% 6% 4 5% 5% 6% 8% 38%	1330
	21st to end	Night	6% 4 2 4 4 3 4 4 6% 8% 54%	1330
July	1st to 10th	Night	4 3 1 4 3 4 5% 4 7% 7% 56%	2220
	11th to 20th	Night	2 2 1 4 3 3 4 3 6% 6% 64%	2220
	21st to end	Night	3 3 2 6% 4 5% 5% 4 7% 8% 54%	2929
August	1st to 10th	Night	6% 8% 2 6% 4 4 5% 5% 7% 8% 46%	2847
	11th to 20th	Night	4 4 2 5% 5% 5% 6% 5% 8% 8% 47%	2811
	21st to end	Night	6% 3 1 5% 3 4 4 4 6% 7% 58%	3174
September	1st to 10th	Night	8% 6% 2 4 3 3 4 4 4 5% 55%	1900
	11th to 20th	Night	10% 6% 2 5% 4 4 5% 4 6% 9% 46%	2042
	21st to end	Night	9% 6% 2 4 3 3 4 3 6% 8% 53%	2090
October	1st to 10th	Night	7% 5% 1 3 2 3 4 3 5% 6% 60%	3798
	11th to 20th	Night	5% 8% 2 4 3 3 4 4 7% 8% 52%	3778
	21st to end	Night	3 6% 2 6% 4 5% 5% 5% 7% 12% 45%	4226
November	1st to 10th	Night	4 6% 2 7% 4 5% 5% 6% 10% 15% 38%	2663
	11th to 20th	Night	1 5% 2 5% 4 5% 7% 6% 11% 15% 39%	2800
	21st to end	Night	1 6% 2 6% 5% 5% 5% 5% 10% 15% 40%	2800
December	1st to 10th	Night	3 3 7% 5% 5% 6% 7% 11% 16% 37%	2779
	11th to 20th	Night	1 5% 2 6% 4 4 6% 5% 9% 16% 42%	3427
	21st to end	Night	6% 3 7% 4 4 5% 5% 8% 12% 45%	5214

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	33% 14% 18% 24% 10% 1	2219
	11th to 20th	Day	44% 10% 17% 13% 11% 5%	2384
	21st to end	Day	29% 8% 25% 25% 11% 1	3146
February	1st to 10th	Day	40% 15% 19% 18% 8% 1	1710
	11th to 20th	Day	41% 13% 18% 20% 6% 2	1674
	21st to end	Day	42% 13% 13% 17% 11% 3	1439
March	1st to 10th	Day	33% 11% 12% 22% 21% 2	3384
	11th to 20th	Day	32% 9% 21% 28% 9% 1	3490
	21st to end	Day	56% 9% 17% 15% 3 1	3825
April	1st to 10th	Day	44% 12% 15% 21% 7% 1	2232
	11th to 20th	Day	48% 10% 15% 18% 8%	2403
	21st to end	Day	52% 7% 14% 19% 8%	2470
May	1st to 10th	Day	55% 6% 11% 21% 6% 1	4168
	11th to 20th	Day	44% 7% 16% 22% 8% 2	4392
	21st to end	Day	45% 8% 16% 22% 10%	4825
June	1st to 10th	Day	45% 9% 18% 20% 7% 1	2831
	11th to 20th	Day	41% 10% 12% 20% 14% 3	2850
	21st to end	Day	25% 9% 14% 27% 21% 4	2850
July	1st to 10th	Day	22% 8% 9% 24% 29% 8%	4666
	11th to 20th	Day	14% 6% 7% 21% 28% 24%	4659
	21st to end	Day	18% 8% 5% 17% 34% 17%	4481
August	1st to 10th	Day	28% 6% 11% 21% 22% 12%	4078
	11th to 20th	Day	23% 7% 7% 30% 27% 6%	4067
	21st to end	Day	23% 7% 6% 29% 24% 12%	4490
September	1st to 10th	Day	24% 6% 7% 24% 28% 11%	2280
	11th to 20th	Day	31% 7% 9% 26% 22% 5%	2136
	21st to end	Day	28% 6% 12% 29% 19% 6%	2090
October	1st to 10th	Day	25% 6% 8% 22% 29% 11%	3171
	11th to 20th	Day	25% 5% 16% 33% 18% 4	3150
	21st to end	Day	28% 10% 13% 25% 21% 3	3331
November	1st to 10th	Day	37% 9% 14% 24% 12% 4	1616
	11th to 20th	Day	32% 12% 19% 24% 10% 3	1600
	21st to end	Day	29% 10% 19% 25% 14% 3	1600
December	1st to 10th	Day	31% 12% 22% 19% 12% 4	1584
	11th to 20th	Day	32% 13% 29% 19% 6% 1	1760
	21st to end	Day	32% 11% 10% 24% 10% 13%	2442
January	1st to 10th	Night	31% 11% 17% 27% 12% 1	4726
	11th to 20th	Night	41% 10% 18% 17% 11% 4	4602
	21st to end	Night	31% 8% 22% 26% 12% 1	4521
February	1st to 10th	Night	43% 12% 16% 19% 8% 1	2470
	11th to 20th	Night	36% 11% 21% 21% 8% 2	2403
	21st to end	Night	37% 13% 16% 19% 13% 3	2013
March	1st to 10th	Night	31% 10% 12% 26% 18% 2	3489
	11th to 20th	Night	28% 7% 26% 31% 8% 1	3490
	21st to end	Night	54% 6% 20% 16% 3	3828
April	1st to 10th	Night	42% 9% 16% 23% 10% 1	1948
	11th to 20th	Night	42% 9% 17% 23% 8% 1	1724
	21st to end	Night	45% 6% 18% 22% 8%	1710
May	1st to 10th	Night	52% 7% 12% 20% 9%	2801
	11th to 20th	Night	40% 7% 15% 26% 9% 3	2518
	21st to end	Night	45% 8% 17% 24% 7%	2762
June	1st to 10th	Night	45% 10% 19% 19% 6% 1	1344
	11th to 20th	Night	41% 9% 12% 24% 12% 3	1330
	21st to end	Night	25% 6% 17% 28% 19% 4	1330
July	1st to 10th	Night	20% 6% 8% 34% 28% 5%	2185
	11th to 20th	Night	15% 5% 7% 22% 30% 21%	2178
	21st to end	Night	24% 4 7% 26% 25% 13%	2838
August	1st to 10th	Night	29% 6% 13% 24% 19% 10%	2838
	11th to 20th	Night	27% 8% 9% 30% 21% 5%	2838
	21st to end	Night	24% 5% 6% 32% 26% 7%	3174
September	1st to 10th	Night	29% 4 9% 21% 27% 10%	1900
	11th to 20th	Night	32% 6% 12% 26% 19% 3	2042
	21st to end	Night	28% 5% 11% 31% 22% 4	2090
October	1st to 10th	Night	23% 5% 8% 26% 28% 10%	3798
	11th to 20th	Night	27% 5% 14% 27% 20% 6%	3778
	21st to end	Night	26% 8% 12% 26% 22% 5%	4226
November	1st to 10th	Night	31% 10% 18% 25% 13% 4	2663
	11th to 20th	Night	26% 13% 21% 26% 12% 2	2800
	21st to end	Night	27% 9% 20% 28% 11% 4	2800
December	1st to 10th	Night	30% 13% 20% 22% 12% 3	2779
	11th to 20th	Night	28% 10% 27% 26% 8% 1	3428
	21st to end	Night	29% 7% 13% 27% 11% 12%	5214

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	14% 40% 27% 12% 5% 2	180
	11th to 20th	Day	14% 46% 24% 8% 4 4	191
	21st to end	Day	9% 45% 35% 7% 2 1	297
February	1st to 10th	Day	18% 46% 28% 7% 1	270
	11th to 20th	Day	14% 43% 33% 7% 3 1	270
	21st to end	Day	19% 38% 30% 8% 4	251
March	1st to 10th	Day	13% 41% 35% 8% 2	460
	11th to 20th	Day	12% 36% 32% 15% 5% 1	460
	21st to end	Day	19% 30% 35% 12% 3 1	506
April	1st to 10th	Day	25% 32% 33% 9% 1	460
	11th to 20th	Day	17% 35% 31% 12% 3	452
	21st to end	Day	25% 24% 28% 16% 5% 1	460
May	1st to 10th	Day	21% 20% 32% 20% 6% 2	495
	11th to 20th	Day	29% 13% 25% 19% 11% 3	675
	21st to end	Day	23% 15% 25% 20% 14% 3	734
June	1st to 10th	Day	15% 19% 29% 22% 12% 3	680
	11th to 20th	Day	20% 26% 30% 16% 7% 1	680
	21st to end	Day	10% 16% 33% 28% 11% 2	680
July	1st to 10th	Day	8% 13% 34% 27% 14% 4	671
	11th to 20th	Day	4 18% 35% 29% 13% 1	668
	21st to end	Day	5% 13% 39% 30% 12% 2	629
August	1st to 10th	Day	11% 15% 39% 26% 8% 1	487
	11th to 20th	Day	11% 14% 36% 28% 9% 2	477
	21st to end	Day	9% 20% 37% 22% 10% 3	539
September	1st to 10th	Day	9% 19% 40% 24% 7% 1	490
	11th to 20th	Day	17% 23% 34% 20% 4 2	490
	21st to end	Day	21% 26% 28% 18% 7% 1	490
October	1st to 10th	Day	22% 23% 32% 13% 11% 1	301
	11th to 20th	Day	14% 33% 34% 11% 6% 2	300
	21st to end	Day	22% 35% 27% 8% 5% 2	330
November	1st to 10th	Day	24% 33% 26% 11% 4 1	300
	11th to 20th	Day	19% 44% 28% 6% 2	300
	21st to end	Day	20% 36% 32% 10% 3	300
December	1st to 10th	Day	21% 45% 21% 8% 5% 1	294
	11th to 20th	Day	16% 46% 28% 8% 2	216
	21st to end	Day	17% 40% 28% 9% 5% 1	198
January	1st to 10th	Night	8% 41% 31% 14% 4 1	950
	11th to 20th	Night	8% 46% 29% 11% 5% 1	889
	21st to end	Night	8% 48% 28% 10% 5% 1	836
February	1st to 10th	Night	9% 45% 26% 15% 5%	760
	11th to 20th	Night	8% 41% 32% 13% 5% 1	744
	21st to end	Night	11% 33% 33% 15% 6% 1	628
March	1st to 10th	Night	8% 32% 35% 17% 6% 1	760
	11th to 20th	Night	9% 30% 30% 23% 6% 2	760
	21st to end	Night	11% 24% 31% 25% 8% 1	836
April	1st to 10th	Night	16% 24% 32% 19% 7% 1	618
	11th to 20th	Night	12% 24% 37% 20% 7% 1	563
	21st to end	Night	20% 17% 27% 24% 11% 2	570
May	1st to 10th	Night	19% 16% 26% 27% 11% 1	570
	11th to 20th	Night	22% 11% 18% 29% 18% 2	561
	21st to end	Night	23% 10% 23% 28% 15% 2	617
June	1st to 10th	Night	14% 15% 21% 30% 18% 2	394
	11th to 20th	Night	18% 17% 29% 25% 10%	380
	21st to end	Night	9% 9% 21% 42% 18% 1	380
July	1st to 10th	Night	7% 5% 22% 37% 27% 2	370
	11th to 20th	Night	3 8% 29% 44% 15% 1	368
	21st to end	Night	7% 5% 27% 40% 20% 2	610
August	1st to 10th	Night	9% 6% 27% 38% 19% 2	567
	11th to 20th	Night	7% 7% 26% 37% 20% 2	564
	21st to end	Night	9% 10% 25% 33% 21% 2	627
September	1st to 10th	Night	11% 10% 24% 34% 19% 2	570
	11th to 20th	Night	15% 9% 24% 31% 17% 4	712
	21st to end	Night	16% 16% 25% 25% 15% 3	760
October	1st to 10th	Night	17% 18% 25% 25% 13% 2	760
	11th to 20th	Night	14% 29% 27% 18% 9% 3	760
	21st to end	Night	15% 31% 30% 15% 8% 2	836
November	1st to 10th	Night	15% 35% 29% 14% 5% 1	908
	11th to 20th	Night	14% 44% 29% 12% 2	1000
	21st to end	Night	11% 38% 34% 14% 4	1000
December	1st to 10th	Night	12% 40% 31% 13% 4 1	993
	11th to 20th	Night	10% 48% 29% 10% 3 1	950
	21st to end	Night	9% 45% 26% 12% 7%	1045

Page generated at 2024-12-06 01:54:53. Version ac07

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