Persimmon Gap
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Persimmon Gap clear sky chart from 2005-11-06 to 2026-09-14.

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	4 3 1 3 2 3 3 3 5% 7% 66%	156176
	Night	4 3 1 3 2 3 3 3 5% 7% 65%	152388
Transparency	Day	18% 4 9% 21% 25% 23%	151290
	Night	19% 4 9% 21% 24% 23%	148281
Seeing	Day	5% 6% 19% 33% 28% 10%	17024
	Night	6% 3 19% 46% 24% 1	27049

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	2 3 1 3 2 2 2 2 4 6% 73%	5885
	11th to 20th	Day	3 3 1 3 2 2 2 2 4 6% 72%	5910
	21st to end	Day	4 5% 2 5% 3 4 3 2 4 5% 63%	6468
February	1st to 10th	Day	3 4 1 4 3 3 3 3 4 6% 65%	2100
	11th to 20th	Day	4 5% 1 4 3 3 3 3 4 6% 64%	2049
	21st to end	Day	3 3 1 2 2 2 3 3 5% 8% 68%	1730
March	1st to 10th	Day	2 3 1 4 3 3 4 3 5% 7% 65%	4600
	11th to 20th	Day	8% 2 1 3 2 2 3 2 4 5% 68%	4791
	21st to end	Day	2 4 1 3 3 3 3 3 5% 6% 66%	6101
April	1st to 10th	Day	3 3 1 3 2 3 3 3 5% 7% 67%	2520
	11th to 20th	Day	3 3 1 3 3 2 3 3 4 6% 69%	2491
	21st to end	Day	4 4 1 3 3 2 3 3 4 6% 67%	2520
May	1st to 10th	Day	4 2 1 3 2 2 2 3 5% 6% 70%	7057
	11th to 20th	Day	4 2 1 4 2 3 4 3 6% 7% 64%	7068
	21st to end	Day	3 2 1 3 3 3 4 3 6% 8% 64%	8404
June	1st to 10th	Day	1 2 1 2 2 3 3 3 5% 9% 69%	2730
	11th to 20th	Day	3 2 1 3 3 3 4 3 5% 7% 66%	2730
	21st to end	Day	3 3 1 3 3 3 4 4 6% 9% 60%	2730
July	1st to 10th	Day	4 2 1 3 2 3 4 4 6% 11% 60%	7226
	11th to 20th	Day	7% 4 2 5% 4 4 4 4 7% 11% 50%	7080
	21st to end	Day	2 2 1 2 2 2 3 3 5% 8% 69%	7686
August	1st to 10th	Day	1 1 1 1 2 2 3 5% 10% 73%	6988
	11th to 20th	Day	2 1 1 2 3 3 5% 4 7% 11% 60%	7003
	21st to end	Day	2 1 1 2 2 2 3 3 5% 8% 71%	7751
September	1st to 10th	Day	7% 5% 1 6% 4 4 5% 4 6% 9% 49%	2520
	11th to 20th	Day	8% 4 1 4 4 4 5% 4 6% 9% 52%	2262
	21st to end	Day	7% 3 1 3 4 4 4 3 5% 6% 60%	2200
October	1st to 10th	Day	2 2 2 1 2 2 2 3 5% 80%	3590
	11th to 20th	Day	5% 3 1 3 2 2 3 2 4 5% 72%	3522
	21st to end	Day	4 1 1 1 1 1 1 1 2 3 82%	3548
November	1st to 10th	Day	6% 2 1 2 2 2 2 2 2 4 75%	1944
	11th to 20th	Day	5% 3 1 2 1 3 3 2 4 6% 69%	1890
	21st to end	Day	6% 4 1 4 3 2 3 3 4 5% 65%	1890
December	1st to 10th	Day	10% 10% 1 4 3 2 3 2 4 4 57%	3030
	11th to 20th	Day	2 3 1 3 2 3 3 3 4 5% 70%	3481
	21st to end	Day	2 2 1 2 2 2 2 2 4 5% 75%	4681
January	1st to 10th	Night	2 2 1 3 2 2 3 2 3 5% 75%	7038
	11th to 20th	Night	4 3 2 3 2 2 2 2 4 5% 73%	7080
	21st to end	Night	5% 8% 3 5% 3 3 3 3 5% 6% 57%	7746
February	1st to 10th	Night	4 4 1 3 3 3 3 3 5% 6% 64%	2520
	11th to 20th	Night	5% 4 2 5% 3 3 4 3 5% 7% 60%	2458
	21st to end	Night	4 5% 1 4 3 3 3 3 4 6% 65%	2076
March	1st to 10th	Night	3 4 1 4 3 4 4 3 5% 7% 63%	5494
	11th to 20th	Night	8% 4 1 3 2 2 3 2 4 5% 67%	5377
	21st to end	Night	3 4 1 2 2 3 4 3 5% 6% 67%	5094
April	1st to 10th	Night	4 4 1 4 3 3 4 3 6% 5% 63%	2100
	11th to 20th	Night	4 3 1 3 3 3 4 3 6% 6% 65%	2077
	21st to end	Night	3 3 1 2 3 3 3 3 4 6% 69%	2100
May	1st to 10th	Night	7% 4 1 3 3 2 3 2 4 6% 65%	5890
	11th to 20th	Night	5% 3 1 4 3 3 4 3 5% 7% 61%	5805
	21st to end	Night	4 3 1 4 3 4 5% 4 6% 7% 60%	5803
June	1st to 10th	Night	2 1 1 3 3 3 4 4 9% 12% 59%	1890
	11th to 20th	Night	2 2 1 4 3 4 4 5% 6% 10% 58%	1890
	21st to end	Night	3 3 1 3 2 3 4 4 8% 10% 59%	1890
July	1st to 10th	Night	3 3 1 3 3 3 4 4 8% 14% 53%	5728
	11th to 20th	Night	6% 3 1 4 3 3 4 4 7% 11% 55%	5910
	21st to end	Night	2 1 1 3 3 4 4 3 6% 9% 65%	6423
August	1st to 10th	Night	1 1 1 1 1 3 2 5% 11% 74%	5834
	11th to 20th	Night	1 1 1 2 2 3 4 4 7% 15% 59%	5853
	21st to end	Night	2 1 1 2 2 2 3 3 6% 10% 69%	6465
September	1st to 10th	Night	7% 3 1 4 4 5% 5% 4 6% 10% 52%	2100
	11th to 20th	Night	7% 4 1 5% 4 3 4 4 7% 11% 50%	2201
	21st to end	Night	8% 3 1 4 3 4 4 3 7% 9% 55%	2200
October	1st to 10th	Night	2 1 2 1 2 2 2 4 5% 79%	3590
	11th to 20th	Night	4 2 1 2 2 2 3 2 4 6% 73%	3600
	21st to end	Night	3 2 1 2 1 1 1 1 2 4 82%	4252
November	1st to 10th	Night	7% 2 1 2 1 2 2 2 4 4 74%	2550
	11th to 20th	Night	5% 4 1 3 2 2 3 2 4 5% 69%	2730
	21st to end	Night	5% 4 2 3 3 3 3 3 5% 6% 63%	2730
December	1st to 10th	Night	11% 9% 2 5% 3 3 4 3 4 6% 49%	4380
	11th to 20th	Night	2 3 1 3 2 2 3 2 4 6% 71%	4946
	21st to end	Night	2 3 1 3 2 2 2 2 4 6% 72%	6568

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	14% 2 5% 24% 28% 27%	5888
	11th to 20th	Day	17% 2 5% 16% 35% 25%	5910
	21st to end	Day	25% 3 5% 20% 29% 19%	6468
February	1st to 10th	Day	21% 3 6% 13% 25% 32%	2100
	11th to 20th	Day	23% 3 6% 15% 23% 29%	2059
	21st to end	Day	16% 3 5% 13% 29% 34%	1730
March	1st to 10th	Day	19% 2 5% 10% 21% 43%	4600
	11th to 20th	Day	19% 3 5% 9% 18% 46%	4791
	21st to end	Day	18% 2 5% 9% 24% 42%	6101
April	1st to 10th	Day	17% 4 8% 12% 22% 37%	2520
	11th to 20th	Day	16% 3 8% 14% 23% 36%	2494
	21st to end	Day	18% 3 6% 14% 23% 36%	2520
May	1st to 10th	Day	15% 4 6% 16% 21% 38%	7057
	11th to 20th	Day	18% 3 7% 11% 26% 34%	7071
	21st to end	Day	17% 5% 8% 23% 21% 26%	8405
June	1st to 10th	Day	12% 4 12% 26% 28% 17%	2730
	11th to 20th	Day	17% 5% 9% 17% 31% 21%	2730
	21st to end	Day	19% 7% 14% 22% 24% 14%	2730
July	1st to 10th	Day	19% 6% 16% 33% 22% 5%	7168
	11th to 20th	Day	27% 6% 15% 33% 14% 4	7017
	21st to end	Day	13% 5% 13% 30% 30% 8%	7516
August	1st to 10th	Day	9% 4 11% 33% 33% 9%	5532
	11th to 20th	Day	15% 6% 16% 42% 19% 3	5519
	21st to end	Day	14% 5% 12% 28% 33% 9%	6078
September	1st to 10th	Day	31% 7% 14% 22% 15% 11%	2520
	11th to 20th	Day	29% 7% 12% 21% 23% 8%	2262
	21st to end	Day	24% 6% 10% 19% 26% 15%	2200
October	1st to 10th	Day	10% 3 7% 15% 23% 42%	3590
	11th to 20th	Day	16% 4 11% 19% 17% 34%	3522
	21st to end	Day	11% 2 2 14% 38% 33%	3548
November	1st to 10th	Day	15% 2 7% 19% 29% 28%	1944
	11th to 20th	Day	18% 3 8% 19% 27% 25%	1890
	21st to end	Day	22% 3 7% 21% 25% 22%	1890
December	1st to 10th	Day	32% 3 7% 16% 24% 17%	3030
	11th to 20th	Day	17% 3 4 24% 32% 20%	3479
	21st to end	Day	12% 3 4 16% 36% 29%	4681
January	1st to 10th	Night	14% 2 4 24% 31% 25%	7038
	11th to 20th	Night	16% 2 5% 13% 31% 33%	7080
	21st to end	Night	28% 3 5% 17% 26% 20%	7746
February	1st to 10th	Night	21% 3 5% 13% 26% 32%	2520
	11th to 20th	Night	23% 4 7% 14% 23% 29%	2458
	21st to end	Night	21% 3 5% 9% 27% 35%	2076
March	1st to 10th	Night	22% 2 5% 11% 19% 40%	5494
	11th to 20th	Night	21% 4 5% 8% 16% 45%	5377
	21st to end	Night	17% 3 7% 11% 23% 40%	5094
April	1st to 10th	Night	21% 5% 7% 14% 19% 35%	2100
	11th to 20th	Night	19% 4 9% 17% 18% 33%	2077
	21st to end	Night	17% 4 8% 18% 22% 31%	2100
May	1st to 10th	Night	21% 3 9% 20% 17% 30%	5888
	11th to 20th	Night	21% 5% 8% 16% 23% 27%	5806
	21st to end	Night	21% 6% 13% 24% 16% 21%	5805
June	1st to 10th	Night	14% 6% 14% 30% 24% 11%	1890
	11th to 20th	Night	19% 6% 10% 20% 28% 15%	1890
	21st to end	Night	19% 6% 14% 23% 25% 13%	1890
July	1st to 10th	Night	20% 6% 18% 34% 19% 2	5678
	11th to 20th	Night	24% 6% 17% 33% 16% 4	5850
	21st to end	Night	15% 6% 15% 29% 31% 5%	6280
August	1st to 10th	Night	8% 4 9% 35% 39% 5%	4614
	11th to 20th	Night	13% 5% 18% 47% 15% 2	4613
	21st to end	Night	12% 6% 14% 28% 32% 7%	5069
September	1st to 10th	Night	28% 7% 16% 26% 14% 10%	2100
	11th to 20th	Night	26% 8% 18% 22% 19% 7%	2201
	21st to end	Night	25% 6% 14% 22% 19% 15%	2200
October	1st to 10th	Night	10% 4 8% 15% 22% 41%	3590
	11th to 20th	Night	14% 4 11% 20% 15% 36%	3600
	21st to end	Night	11% 1 3 19% 38% 28%	4252
November	1st to 10th	Night	16% 3 6% 16% 31% 29%	2550
	11th to 20th	Night	19% 3 7% 18% 26% 28%	2730
	21st to end	Night	22% 4 9% 15% 23% 26%	2730
December	1st to 10th	Night	37% 3 6% 16% 18% 20%	4380
	11th to 20th	Night	16% 2 5% 22% 31% 23%	4947
	21st to end	Night	15% 3 4 14% 37% 27%	6568

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	8% 8% 27% 38% 18% 2	330
	11th to 20th	Day	6% 9% 23% 41% 18% 3	330
	21st to end	Day	5% 10% 25% 42% 17% 2	363
February	1st to 10th	Day	7% 6% 22% 33% 28% 4	330
	11th to 20th	Day	12% 10% 25% 36% 14% 3	330
	21st to end	Day	5% 11% 30% 40% 11% 2	273
March	1st to 10th	Day	5% 9% 28% 34% 21% 2	330
	11th to 20th	Day	10% 11% 29% 31% 14% 4	367
	21st to end	Day	5% 15% 30% 32% 14% 3	594
April	1st to 10th	Day	4 14% 37% 31% 13% 2	540
	11th to 20th	Day	5% 17% 32% 32% 12% 3	532
	21st to end	Day	6% 14% 32% 36% 12% 1	540
May	1st to 10th	Day	2 12% 35% 33% 15% 3	543
	11th to 20th	Day	4 8% 31% 35% 18% 4	578
	21st to end	Day	5% 5% 22% 40% 27% 3	844
June	1st to 10th	Day	2 3 17% 35% 37% 6%	780
	11th to 20th	Day	3 1 13% 34% 43% 6%	780
	21st to end	Day	4 1 11% 29% 42% 13%	780
July	1st to 10th	Day	4 1 8% 28% 39% 19%	622
	11th to 20th	Day	2 9% 33% 36% 20%	564
	21st to end	Day	1 8% 35% 37% 18%	619
August	1st to 10th	Day	2 7% 30% 34% 28%	567
	11th to 20th	Day	6% 1 8% 29% 29% 26%	557
	21st to end	Day	3 1 8% 31% 34% 24%	627
September	1st to 10th	Day	7% 2 8% 34% 32% 17%	570
	11th to 20th	Day	6% 1 3 17% 43% 30%	368
	21st to end	Day	10% 1 6% 18% 38% 26%	330
October	1st to 10th	Day	4 2 10% 24% 39% 20%	330
	11th to 20th	Day	10% 2 10% 28% 37% 14%	330
	21st to end	Day	6% 5% 14% 28% 32% 15%	363
November	1st to 10th	Day	9% 4 13% 30% 31% 12%	330
	11th to 20th	Day	10% 6% 15% 27% 31% 11%	330
	21st to end	Day	7% 10% 21% 36% 21% 5%	330
December	1st to 10th	Day	9% 6% 15% 34% 29% 7%	330
	11th to 20th	Day	5% 7% 23% 36% 23% 5%	330
	21st to end	Day	4 6% 25% 36% 25% 4	363
January	1st to 10th	Night	6% 3 22% 52% 15% 1	840
	11th to 20th	Night	9% 3 21% 51% 16% 1	840
	21st to end	Night	8% 4 24% 51% 13%	924
February	1st to 10th	Night	7% 4 24% 49% 16%	840
	11th to 20th	Night	7% 4 29% 50% 10% 1	824
	21st to end	Night	5% 6% 32% 50% 7%	692
March	1st to 10th	Night	8% 4 32% 46% 9% 1	840
	11th to 20th	Night	8% 6% 29% 44% 12%	812
	21st to end	Night	5% 5% 36% 43% 11%	693
April	1st to 10th	Night	6% 5% 34% 47% 8%	630
	11th to 20th	Night	4 6% 40% 42% 8%	623
	21st to end	Night	4 6% 36% 47% 7%	630
May	1st to 10th	Night	6% 4 30% 51% 9%	630
	11th to 20th	Night	7% 5% 29% 48% 11%	621
	21st to end	Night	4 3 27% 49% 16%	683
June	1st to 10th	Night	2 2 17% 55% 24%	630
	11th to 20th	Night	2 1 15% 48% 34%	630
	21st to end	Night	3 2 12% 43% 40% 1	630
July	1st to 10th	Night	5% 1 8% 39% 45% 2	615
	11th to 20th	Night	2 7% 36% 53% 1	612
	21st to end	Night	3 1 6% 36% 51% 3	690
August	1st to 10th	Night	2 6% 33% 56% 3	627
	11th to 20th	Night	2 5% 28% 60% 5%	624
	21st to end	Night	3 1 5% 34% 54% 2	693
September	1st to 10th	Night	7% 1 5% 37% 48% 2	630
	11th to 20th	Night	9% 6% 38% 46% 1	609
	21st to end	Night	9% 1 8% 43% 37% 2	600
October	1st to 10th	Night	4 2 9% 47% 37% 1	600
	11th to 20th	Night	7% 11% 57% 23% 2	618
	21st to end	Night	6% 3 12% 47% 28% 4	880
November	1st to 10th	Night	8% 2 11% 47% 27% 4	910
	11th to 20th	Night	7% 3 14% 49% 24% 2	1050
	21st to end	Night	7% 3 23% 46% 19% 2	1050
December	1st to 10th	Night	9% 3 17% 51% 19% 1	1050
	11th to 20th	Night	6% 3 22% 53% 15% 1	1050
	21st to end	Night	5% 4 22% 53% 15% 1	1129

Page generated at 2026-09-11 03:11:57. Version ac07

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