Palmer Junction
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Palmer Junction clear sky chart from 2005-11-06 to 2024-02-10.

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	9% 10% 4 7% 6% 4 5% 5% 5% 6% 40%	78194
	Night	9% 10% 4 7% 6% 4 5% 5% 5% 7% 38%	80790
Transparency	Day	44% 8% 12% 17% 13% 5%	77898
	Night	46% 9% 14% 18% 10% 4	80607
Seeing	Day	15% 14% 26% 26% 14% 4	13318
	Night	15% 8% 19% 34% 21% 3	22648

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	7% 23% 9% 12% 10% 5% 7% 5% 4 5% 12%	2539
	11th to 20th	Day	9% 17% 8% 11% 8% 4 5% 4 5% 7% 22%	2540
	21st to end	Day	11% 16% 5% 11% 9% 5% 7% 6% 5% 5% 19%	2794
February	1st to 10th	Day	10% 18% 7% 10% 7% 4 6% 5% 7% 5% 22%	1592
	11th to 20th	Day	10% 19% 6% 8% 8% 4 6% 5% 5% 5% 24%	1705
	21st to end	Day	9% 17% 8% 10% 8% 4 6% 5% 5% 6% 22%	1480
March	1st to 10th	Day	9% 16% 7% 9% 9% 4 5% 5% 6% 6% 23%	1800
	11th to 20th	Day	9% 15% 5% 10% 9% 5% 6% 6% 7% 7% 23%	1833
	21st to end	Day	13% 17% 7% 10% 7% 4 6% 6% 5% 6% 19%	2376
April	1st to 10th	Day	10% 15% 6% 8% 8% 5% 5% 5% 6% 8% 23%	2160
	11th to 20th	Day	10% 12% 5% 8% 7% 4 5% 5% 5% 7% 32%	2137
	21st to end	Day	11% 12% 4 8% 6% 4 6% 5% 5% 7% 32%	2340
May	1st to 10th	Day	8% 10% 3 7% 6% 4 4 5% 6% 8% 38%	2422
	11th to 20th	Day	12% 8% 3 8% 7% 5% 6% 5% 7% 7% 34%	2477
	21st to end	Day	14% 9% 3 7% 6% 4 5% 5% 7% 6% 34%	2723
June	1st to 10th	Day	14% 8% 3 6% 6% 4 5% 5% 5% 7% 37%	2520
	11th to 20th	Day	13% 7% 3 5% 4 3 5% 5% 5% 6% 42%	2520
	21st to end	Day	6% 3 2 3 4 2 3 3 4 7% 63%	2520
July	1st to 10th	Day	3 2 1 3 3 2 3 4 5% 6% 69%	2520
	11th to 20th	Day	2 2 1 2 3 2 3 3 4 6% 73%	2520
	21st to end	Day	1 1 2 2 2 2 3 4 5% 77%	2741
August	1st to 10th	Day	3 2 1 2 3 2 3 4 4 6% 69%	2507
	11th to 20th	Day	3 2 1 3 3 1 3 3 4 6% 72%	2312
	21st to end	Day	5% 2 1 3 4 3 3 3 4 7% 66%	2376
September	1st to 10th	Day	3 2 2 3 3 2 3 2 3 6% 70%	2160
	11th to 20th	Day	7% 4 2 4 4 3 5% 4 5% 7% 56%	2068
	21st to end	Day	8% 5% 2 5% 4 3 4 5% 4 6% 53%	1980
October	1st to 10th	Day	12% 7% 3 5% 5% 2 4 4 4 6% 48%	1904
	11th to 20th	Day	10% 8% 3 6% 5% 2 5% 4 7% 8% 42%	1738
	21st to end	Day	11% 12% 3 7% 8% 4 6% 4 4 5% 36%	1782
November	1st to 10th	Day	14% 14% 3 10% 7% 4 5% 5% 5% 7% 27%	1674
	11th to 20th	Day	10% 17% 5% 10% 8% 4 6% 6% 6% 8% 19%	1672
	21st to end	Day	8% 15% 5% 7% 7% 4 6% 6% 8% 7% 27%	1520
December	1st to 10th	Day	9% 14% 6% 8% 7% 5% 7% 6% 6% 7% 24%	1520
	11th to 20th	Day	9% 13% 5% 11% 9% 5% 6% 6% 7% 7% 23%	1928
	21st to end	Day	8% 13% 6% 11% 8% 4 6% 6% 6% 7% 26%	2794
January	1st to 10th	Night	9% 20% 8% 12% 9% 5% 5% 5% 5% 6% 16%	4406
	11th to 20th	Night	11% 19% 7% 9% 7% 4 5% 4 4 6% 24%	4420
	21st to end	Night	10% 14% 5% 11% 9% 5% 6% 6% 6% 7% 21%	4862
February	1st to 10th	Night	11% 18% 6% 9% 7% 4 4 5% 5% 6% 24%	2570
	11th to 20th	Night	8% 14% 5% 9% 7% 4 4 5% 6% 6% 31%	2143
	21st to end	Night	7% 15% 7% 8% 8% 4 6% 5% 6% 7% 24%	1776
March	1st to 10th	Night	11% 12% 5% 8% 8% 4 5% 5% 6% 7% 30%	2160
	11th to 20th	Night	9% 11% 4 7% 7% 4 7% 6% 6% 8% 30%	2123
	21st to end	Night	9% 15% 4 7% 7% 4 6% 6% 6% 7% 26%	1980
April	1st to 10th	Night	10% 10% 3 7% 7% 3 7% 5% 6% 9% 33%	1800
	11th to 20th	Night	11% 9% 4 6% 7% 3 5% 5% 4 5% 40%	1771
	21st to end	Night	8% 8% 3 7% 6% 3 5% 6% 6% 7% 43%	1620
May	1st to 10th	Night	8% 5% 3 5% 5% 3 4 5% 5% 8% 49%	1535
	11th to 20th	Night	10% 6% 3 5% 5% 3 4 6% 8% 9% 40%	1416
	21st to end	Night	12% 7% 3 6% 5% 4 5% 5% 6% 8% 39%	1552
June	1st to 10th	Night	12% 6% 2 5% 6% 3 4 5% 7% 9% 41%	1440
	11th to 20th	Night	10% 6% 1 4 5% 4 4 5% 5% 7% 49%	1440
	21st to end	Night	4 4 2 4 4 2 4 4 5% 6% 61%	1440
July	1st to 10th	Night	3 2 1 2 3 2 2 4 5% 6% 70%	1440
	11th to 20th	Night	1 1 1 2 2 2 2 3 3 6% 77%	1440
	21st to end	Night	1 1 1 2 1 3 3 4 6% 77%	1576
August	1st to 10th	Night	4 1 1 2 2 2 3 3 5% 7% 70%	1432
	11th to 20th	Night	1 2 1 2 3 2 2 3 4 6% 74%	1583
	21st to end	Night	4 3 1 2 3 1 3 3 4 6% 70%	1980
September	1st to 10th	Night	4 2 1 3 2 1 2 2 4 4 73%	1800
	11th to 20th	Night	5% 3 2 4 4 4 5% 4 4 6% 60%	1891
	21st to end	Night	8% 5% 2 4 5% 3 3 4 4 7% 56%	1980
October	1st to 10th	Night	9% 5% 2 6% 5% 4 4 4 5% 6% 50%	2052
	11th to 20th	Night	10% 7% 2 6% 6% 3 5% 6% 4 7% 44%	2222
	21st to end	Night	11% 9% 3 5% 7% 4 5% 5% 6% 5% 40%	2574
November	1st to 10th	Night	14% 11% 4 7% 7% 4 6% 5% 5% 5% 31%	2405
	11th to 20th	Night	13% 13% 4 7% 7% 5% 6% 6% 6% 6% 27%	2503
	21st to end	Night	8% 11% 5% 7% 7% 5% 6% 5% 6% 7% 33%	2660
December	1st to 10th	Night	10% 12% 5% 8% 7% 5% 7% 6% 6% 6% 27%	2660
	11th to 20th	Night	9% 13% 5% 10% 10% 6% 7% 5% 7% 8% 20%	3276
	21st to end	Night	8% 13% 5% 10% 8% 4 6% 6% 5% 6% 26%	4862

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	72% 12% 8% 7% 1	2539
	11th to 20th	Day	64% 8% 12% 13% 3 1	2540
	21st to end	Day	66% 11% 13% 8% 2	2794
February	1st to 10th	Day	63% 10% 12% 11% 3	1592
	11th to 20th	Day	62% 10% 11% 11% 6%	1715
	21st to end	Day	62% 11% 10% 11% 5% 1	1480
March	1st to 10th	Day	59% 10% 13% 12% 6%	1800
	11th to 20th	Day	58% 9% 15% 16% 3	1833
	21st to end	Day	65% 10% 13% 11% 2	2376
April	1st to 10th	Day	59% 9% 14% 14% 4	2160
	11th to 20th	Day	51% 9% 14% 15% 9% 1	2140
	21st to end	Day	51% 9% 11% 19% 10%	2340
May	1st to 10th	Day	41% 10% 15% 25% 9%	2422
	11th to 20th	Day	48% 10% 15% 20% 8% 1	2480
	21st to end	Day	48% 10% 16% 19% 6%	2724
June	1st to 10th	Day	46% 9% 14% 23% 8%	2520
	11th to 20th	Day	41% 8% 15% 21% 13% 2	2520
	21st to end	Day	22% 6% 12% 33% 21% 6%	2520
July	1st to 10th	Day	16% 6% 11% 22% 28% 17%	2451
	11th to 20th	Day	13% 4 10% 15% 32% 26%	2445
	21st to end	Day	10% 3 6% 15% 40% 26%	2589
August	1st to 10th	Day	17% 4 9% 20% 36% 14%	2490
	11th to 20th	Day	14% 5% 9% 25% 32% 16%	2312
	21st to end	Day	19% 4 10% 25% 31% 10%	2376
September	1st to 10th	Day	16% 4 11% 25% 28% 15%	2160
	11th to 20th	Day	27% 6% 11% 20% 23% 12%	2068
	21st to end	Day	31% 8% 14% 24% 19% 5%	1980
October	1st to 10th	Day	39% 7% 11% 23% 17% 3	1904
	11th to 20th	Day	38% 8% 14% 24% 14% 1	1738
	21st to end	Day	51% 8% 11% 20% 10%	1782
November	1st to 10th	Day	57% 9% 12% 16% 6%	1674
	11th to 20th	Day	62% 10% 14% 11% 3	1672
	21st to end	Day	54% 12% 14% 13% 7% 1	1520
December	1st to 10th	Day	57% 12% 13% 13% 4 1	1520
	11th to 20th	Day	58% 14% 17% 10% 2	1928
	21st to end	Day	54% 12% 21% 11% 3	2794
January	1st to 10th	Night	66% 14% 10% 8% 1	4406
	11th to 20th	Night	63% 7% 14% 13% 3	4420
	21st to end	Night	60% 13% 15% 9% 2	4862
February	1st to 10th	Night	61% 10% 15% 11% 3	2570
	11th to 20th	Night	55% 9% 15% 15% 6%	2144
	21st to end	Night	60% 8% 11% 14% 5% 1	1776
March	1st to 10th	Night	54% 8% 15% 17% 6% 1	2160
	11th to 20th	Night	51% 10% 16% 19% 4	2123
	21st to end	Night	57% 12% 16% 15% 1	1980
April	1st to 10th	Night	51% 10% 16% 18% 5%	1800
	11th to 20th	Night	46% 8% 15% 18% 11% 1	1771
	21st to end	Night	41% 10% 17% 18% 12% 1	1620
May	1st to 10th	Night	33% 11% 15% 29% 12%	1535
	11th to 20th	Night	37% 11% 18% 25% 8% 1	1416
	21st to end	Night	42% 10% 18% 23% 7%	1552
June	1st to 10th	Night	38% 12% 12% 28% 9% 1	1440
	11th to 20th	Night	35% 9% 17% 27% 11% 2	1440
	21st to end	Night	23% 7% 13% 30% 21% 6%	1440
July	1st to 10th	Night	15% 5% 10% 23% 30% 17%	1400
	11th to 20th	Night	10% 5% 10% 22% 26% 26%	1392
	21st to end	Night	9% 3 5% 20% 34% 29%	1488
August	1st to 10th	Night	13% 4 9% 26% 32% 15%	1424
	11th to 20th	Night	13% 5% 9% 23% 33% 17%	1583
	21st to end	Night	16% 6% 8% 28% 31% 12%	1980
September	1st to 10th	Night	16% 3 10% 27% 28% 16%	1800
	11th to 20th	Night	25% 8% 10% 23% 24% 11%	1891
	21st to end	Night	29% 7% 12% 27% 18% 7%	1980
October	1st to 10th	Night	36% 7% 12% 25% 18% 2	2052
	11th to 20th	Night	40% 9% 11% 22% 17% 2	2222
	21st to end	Night	45% 9% 13% 18% 13% 1	2574
November	1st to 10th	Night	53% 10% 12% 18% 6% 1	2405
	11th to 20th	Night	56% 10% 15% 15% 3	2503
	21st to end	Night	51% 8% 14% 18% 8% 1	2660
December	1st to 10th	Night	56% 12% 15% 13% 3 1	2660
	11th to 20th	Night	61% 12% 14% 12% 1	3276
	21st to end	Night	55% 10% 20% 10% 4	4862

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% 18% 28% 24% 12% 3	180
	11th to 20th	Day	21% 11% 37% 14% 12% 4	180
	21st to end	Day	18% 11% 33% 25% 13% 1	198
February	1st to 10th	Day	26% 21% 28% 17% 7% 1	258
	11th to 20th	Day	26% 17% 28% 19% 9%	395
	21st to end	Day	20% 22% 28% 22% 7% 1	346
March	1st to 10th	Day	22% 23% 30% 18% 7%	420
	11th to 20th	Day	20% 21% 23% 23% 12% 1	420
	21st to end	Day	25% 24% 25% 19% 5% 1	462
April	1st to 10th	Day	25% 20% 26% 18% 8% 4	420
	11th to 20th	Day	21% 24% 27% 15% 9% 4	412
	21st to end	Day	20% 18% 26% 21% 13% 2	420
May	1st to 10th	Day	16% 13% 29% 29% 11% 3	423
	11th to 20th	Day	21% 13% 24% 21% 14% 7%	448
	21st to end	Day	16% 11% 23% 28% 15% 6%	485
June	1st to 10th	Day	16% 13% 23% 22% 18% 7%	450
	11th to 20th	Day	16% 18% 29% 24% 10% 3	450
	21st to end	Day	6% 11% 28% 32% 16% 7%	450
July	1st to 10th	Day	4 8% 28% 35% 22% 3	446
	11th to 20th	Day	4 10% 30% 34% 18% 4	444
	21st to end	Day	2 8% 28% 32% 22% 8%	487
August	1st to 10th	Day	6% 6% 28% 32% 19% 9%	447
	11th to 20th	Day	3 7% 19% 38% 22% 12%	437
	21st to end	Day	7% 12% 26% 28% 17% 8%	495
September	1st to 10th	Day	5% 11% 24% 29% 23% 8%	450
	11th to 20th	Day	11% 10% 26% 28% 19% 6%	450
	21st to end	Day	13% 10% 28% 28% 16% 6%	450
October	1st to 10th	Day	16% 13% 21% 24% 21% 5%	450
	11th to 20th	Day	19% 11% 21% 25% 17% 7%	388
	21st to end	Day	16% 18% 23% 26% 11% 5%	297
November	1st to 10th	Day	22% 14% 24% 32% 8%	270
	11th to 20th	Day	21% 13% 20% 28% 16% 2	252
	21st to end	Day	18% 14% 22% 34% 12% 1	180
December	1st to 10th	Day	17% 14% 28% 23% 13% 4	180
	11th to 20th	Day	24% 19% 29% 22% 4 1	180
	21st to end	Day	16% 18% 28% 29% 6% 3	198
January	1st to 10th	Night	21% 9% 26% 29% 13% 2	760
	11th to 20th	Night	22% 10% 22% 31% 14% 2	760
	21st to end	Night	17% 9% 22% 36% 15% 2	836
February	1st to 10th	Night	23% 10% 24% 32% 9% 2	758
	11th to 20th	Night	18% 13% 20% 33% 15% 2	704
	21st to end	Night	19% 17% 22% 28% 13% 2	592
March	1st to 10th	Night	20% 10% 22% 32% 15% 1	720
	11th to 20th	Night	16% 13% 22% 30% 18% 1	720
	21st to end	Night	19% 12% 24% 31% 13% 1	792
April	1st to 10th	Night	18% 10% 21% 32% 17% 2	720
	11th to 20th	Night	18% 12% 21% 29% 17% 3	703
	21st to end	Night	12% 11% 23% 32% 21% 2	540
May	1st to 10th	Night	12% 8% 21% 35% 22% 2	455
	11th to 20th	Night	14% 6% 14% 28% 32% 6%	354
	21st to end	Night	14% 6% 14% 30% 33% 3	389
June	1st to 10th	Night	15% 7% 14% 31% 28% 4	360
	11th to 20th	Night	13% 9% 21% 33% 23% 2	360
	21st to end	Night	7% 4 14% 40% 33% 3	360
July	1st to 10th	Night	5% 3 12% 39% 38% 3	350
	11th to 20th	Night	1 3 14% 50% 31% 2	348
	21st to end	Night	2 4 8% 44% 39% 3	394
August	1st to 10th	Night	4 3 9% 39% 41% 4	358
	11th to 20th	Night	3 2 11% 37% 41% 6%	515
	21st to end	Night	5% 4 16% 37% 33% 4	792
September	1st to 10th	Night	5% 3 13% 41% 33% 5%	720
	11th to 20th	Night	6% 3 11% 33% 39% 8%	720
	21st to end	Night	11% 5% 13% 37% 30% 5%	720
October	1st to 10th	Night	12% 5% 14% 40% 25% 4	720
	11th to 20th	Night	16% 7% 15% 34% 23% 6%	720
	21st to end	Night	17% 8% 17% 36% 17% 4	792
November	1st to 10th	Night	21% 9% 23% 35% 11% 1	740
	11th to 20th	Night	24% 9% 23% 30% 13% 2	760
	21st to end	Night	16% 10% 21% 33% 16% 3	760
December	1st to 10th	Night	17% 7% 25% 35% 15% 1	760
	11th to 20th	Night	20% 11% 25% 32% 11% 1	760
	21st to end	Night	22% 13% 26% 31% 8% 1	836

Page generated at 2024-02-07 03:11:59. Version ac07

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