Chambersburg
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Chambersburg clear sky chart from 2005-11-06 to 2024-02-25.

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	14% 7% 3 6% 6% 3 5% 5% 6% 7% 38%	78452
	Night	14% 7% 3 6% 6% 3 5% 5% 5% 7% 39%	80850
Transparency	Day	43% 8% 13% 21% 13% 2	78162
	Night	42% 7% 12% 22% 14% 2	80659
Seeing	Day	20% 14% 26% 22% 13% 4	13857
	Night	18% 13% 27% 29% 12% 1	23507

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	16% 9% 4 8% 6% 4 4 5% 4 5% 35%	2558
	11th to 20th	Day	13% 13% 5% 10% 9% 4 5% 4 4 5% 27%	2840
	21st to end	Day	17% 13% 5% 8% 7% 3 5% 4 4 6% 29%	3124
February	1st to 10th	Day	15% 10% 3 7% 6% 3 5% 5% 5% 7% 33%	1710
	11th to 20th	Day	14% 10% 4 7% 7% 3 5% 4 6% 6% 35%	1671
	21st to end	Day	18% 10% 4 8% 5% 3 4 4 5% 5% 35%	1520
March	1st to 10th	Day	13% 7% 3 6% 6% 3 4 4 5% 6% 44%	1962
	11th to 20th	Day	17% 8% 3 6% 5% 4 4 5% 5% 7% 35%	1980
	21st to end	Day	19% 8% 4 6% 6% 3 5% 4 5% 6% 35%	2196
April	1st to 10th	Day	14% 9% 3 5% 7% 3 5% 5% 6% 6% 37%	2160
	11th to 20th	Day	14% 6% 4 7% 4 3 5% 4 4 6% 42%	2134
	21st to end	Day	18% 7% 2 6% 5% 3 5% 5% 6% 6% 38%	2185
May	1st to 10th	Day	18% 6% 3 6% 5% 3 5% 6% 6% 8% 34%	2340
	11th to 20th	Day	19% 7% 4 4 5% 4 5% 4 5% 6% 36%	2419
	21st to end	Day	14% 6% 2 5% 6% 4 6% 4 6% 7% 39%	2725
June	1st to 10th	Day	12% 5% 2 5% 5% 3 6% 5% 7% 11% 39%	2520
	11th to 20th	Day	13% 6% 3 5% 5% 4 5% 5% 7% 9% 38%	2520
	21st to end	Day	11% 4 2 5% 5% 3 4 5% 7% 10% 43%	2520
July	1st to 10th	Day	9% 5% 2 5% 6% 3 6% 6% 6% 9% 42%	2520
	11th to 20th	Day	7% 5% 3 5% 5% 3 7% 6% 7% 9% 44%	2464
	21st to end	Day	10% 7% 3 5% 6% 4 6% 6% 7% 9% 38%	2547
August	1st to 10th	Day	11% 5% 2 5% 6% 4 7% 6% 7% 9% 38%	2327
	11th to 20th	Day	12% 6% 2 5% 5% 3 6% 6% 7% 9% 39%	2254
	21st to end	Day	12% 5% 2 5% 5% 3 5% 6% 7% 9% 41%	2376
September	1st to 10th	Day	16% 5% 2 5% 5% 3 5% 4 5% 7% 44%	2160
	11th to 20th	Day	11% 4 2 5% 4 3 4 5% 6% 8% 48%	2160
	21st to end	Day	17% 8% 2 5% 5% 3 5% 3 5% 7% 40%	1879
October	1st to 10th	Day	15% 6% 2 6% 4 3 5% 5% 4 7% 43%	1800
	11th to 20th	Day	16% 5% 3 5% 5% 3 4 5% 5% 7% 43%	1800
	21st to end	Day	16% 7% 3 5% 5% 3 4 5% 5% 6% 43%	1980
November	1st to 10th	Day	12% 7% 3 4 5% 3 4 5% 4 8% 48%	1759
	11th to 20th	Day	15% 7% 3 5% 4 3 5% 5% 5% 6% 43%	1620
	21st to end	Day	16% 6% 3 5% 6% 3 4 5% 4 7% 39%	1520
December	1st to 10th	Day	18% 9% 3 6% 6% 3 5% 6% 6% 8% 30%	1520
	11th to 20th	Day	16% 12% 4 6% 5% 4 4 4 5% 6% 34%	1910
	21st to end	Day	19% 11% 4 7% 6% 4 5% 6% 6% 7% 26%	2772
January	1st to 10th	Night	12% 10% 4 9% 7% 4 5% 5% 5% 7% 33%	4384
	11th to 20th	Night	16% 9% 5% 8% 7% 3 4 4 4 6% 34%	4120
	21st to end	Night	21% 10% 4 8% 7% 3 4 4 4 6% 30%	4532
February	1st to 10th	Night	15% 8% 4 7% 6% 3 5% 4 5% 6% 37%	2470
	11th to 20th	Night	16% 9% 3 6% 6% 3 4 6% 6% 6% 35%	2394
	21st to end	Night	17% 9% 4 7% 5% 3 5% 4 4 7% 34%	1831
March	1st to 10th	Night	14% 6% 3 5% 6% 2 4 4 5% 7% 45%	1995
	11th to 20th	Night	18% 8% 3 5% 5% 3 4 4 5% 6% 40%	1980
	21st to end	Night	16% 7% 4 6% 6% 3 5% 4 5% 6% 39%	2160
April	1st to 10th	Night	16% 8% 4 7% 6% 3 5% 5% 5% 5% 35%	1800
	11th to 20th	Night	13% 6% 3 5% 5% 3 5% 4 6% 9% 42%	1775
	21st to end	Night	18% 5% 2 4 6% 3 5% 5% 5% 6% 41%	1790
May	1st to 10th	Night	17% 6% 3 6% 5% 3 5% 4 6% 8% 38%	1620
	11th to 20th	Night	17% 6% 4 5% 5% 3 5% 5% 6% 8% 36%	1473
	21st to end	Night	11% 6% 2 5% 6% 3 5% 5% 6% 10% 42%	1550
June	1st to 10th	Night	12% 6% 2 5% 4 3 4 5% 6% 7% 47%	1440
	11th to 20th	Night	12% 5% 2 7% 5% 4 5% 6% 5% 9% 40%	1440
	21st to end	Night	9% 4 2 5% 5% 3 5% 5% 7% 10% 45%	1440
July	1st to 10th	Night	9% 6% 3 5% 5% 4 5% 6% 6% 10% 41%	1440
	11th to 20th	Night	7% 4 2 4 5% 3 5% 5% 7% 10% 48%	1492
	21st to end	Night	9% 4 2 4 6% 3 5% 5% 8% 11% 43%	1771
August	1st to 10th	Night	9% 6% 2 5% 6% 3 5% 7% 8% 10% 41%	1611
	11th to 20th	Night	11% 6% 3 5% 6% 4 5% 5% 6% 8% 43%	1629
	21st to end	Night	11% 5% 2 5% 5% 3 5% 5% 6% 9% 44%	1980
September	1st to 10th	Night	14% 5% 2 5% 5% 3 4 4 5% 7% 45%	1800
	11th to 20th	Night	10% 6% 2 4 4 2 3 4 4 7% 53%	1800
	21st to end	Night	16% 7% 3 5% 4 3 5% 5% 5% 6% 42%	2077
October	1st to 10th	Night	16% 6% 2 5% 5% 3 4 4 5% 6% 43%	2160
	11th to 20th	Night	14% 5% 3 4 5% 4 4 4 5% 6% 46%	2160
	21st to end	Night	16% 6% 2 4 5% 3 4 4 5% 7% 43%	2376
November	1st to 10th	Night	10% 6% 2 6% 4 3 4 4 4 6% 52%	2316
	11th to 20th	Night	14% 7% 3 5% 5% 3 4 4 6% 6% 43%	2555
	21st to end	Night	14% 6% 3 5% 7% 3 5% 5% 5% 8% 39%	2660
December	1st to 10th	Night	16% 9% 3 7% 5% 3 5% 5% 6% 6% 34%	2660
	11th to 20th	Night	17% 9% 3 6% 6% 4 4 5% 5% 7% 35%	3285
	21st to end	Night	17% 9% 4 7% 7% 4 6% 6% 6% 8% 27%	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	47% 6% 13% 23% 8% 3	2559
	11th to 20th	Day	53% 9% 12% 14% 11% 2	2840
	21st to end	Day	54% 7% 9% 21% 6% 1	3124
February	1st to 10th	Day	50% 6% 12% 21% 10% 1	1710
	11th to 20th	Day	48% 7% 11% 22% 11% 2	1680
	21st to end	Day	50% 5% 12% 18% 11% 4	1520
March	1st to 10th	Day	40% 6% 12% 24% 16% 2	1962
	11th to 20th	Day	47% 5% 14% 16% 13% 5%	1980
	21st to end	Day	50% 6% 10% 18% 15% 2	2196
April	1st to 10th	Day	45% 6% 13% 18% 15% 3	2160
	11th to 20th	Day	41% 7% 10% 21% 17% 3	2134
	21st to end	Day	46% 8% 9% 20% 15% 3	2185
May	1st to 10th	Day	46% 9% 11% 19% 14% 2	2340
	11th to 20th	Day	49% 8% 11% 17% 12% 3	2423
	21st to end	Day	42% 9% 16% 20% 11% 2	2725
June	1st to 10th	Day	39% 8% 15% 22% 14% 1	2520
	11th to 20th	Day	41% 11% 15% 19% 13% 1	2520
	21st to end	Day	34% 9% 16% 28% 13% 1	2520
July	1st to 10th	Day	37% 11% 14% 22% 14% 3	2450
	11th to 20th	Day	33% 9% 16% 24% 16% 2	2389
	21st to end	Day	40% 10% 12% 21% 15% 2	2405
August	1st to 10th	Day	39% 11% 16% 23% 10%	2314
	11th to 20th	Day	39% 9% 15% 23% 14% 1	2254
	21st to end	Day	38% 9% 15% 23% 12% 3	2376
September	1st to 10th	Day	40% 8% 11% 20% 18% 3	2160
	11th to 20th	Day	33% 8% 12% 25% 19% 3	2160
	21st to end	Day	44% 5% 11% 18% 20% 2	1879
October	1st to 10th	Day	41% 7% 12% 22% 16% 2	1800
	11th to 20th	Day	39% 7% 13% 24% 17% 1	1800
	21st to end	Day	40% 6% 12% 24% 16% 2	1980
November	1st to 10th	Day	35% 5% 14% 23% 19% 4	1759
	11th to 20th	Day	41% 6% 12% 21% 17% 3	1620
	21st to end	Day	44% 6% 12% 27% 10% 1	1520
December	1st to 10th	Day	50% 8% 13% 20% 8% 1	1520
	11th to 20th	Day	48% 6% 13% 26% 6% 1	1906
	21st to end	Day	51% 11% 15% 16% 8%	2772
January	1st to 10th	Night	45% 8% 12% 22% 10% 2	4384
	11th to 20th	Night	47% 7% 14% 21% 9% 2	4120
	21st to end	Night	53% 6% 10% 22% 7% 1	4532
February	1st to 10th	Night	47% 6% 13% 22% 11% 1	2470
	11th to 20th	Night	47% 7% 10% 18% 16% 2	2396
	21st to end	Night	49% 6% 11% 18% 12% 4	1831
March	1st to 10th	Night	39% 5% 12% 26% 16% 2	1995
	11th to 20th	Night	44% 6% 11% 21% 15% 3	1980
	21st to end	Night	45% 6% 11% 19% 15% 4	2160
April	1st to 10th	Night	49% 7% 10% 17% 15% 3	1800
	11th to 20th	Night	38% 7% 10% 22% 17% 5%	1775
	21st to end	Night	40% 8% 11% 22% 15% 4	1790
May	1st to 10th	Night	45% 7% 10% 20% 13% 4	1620
	11th to 20th	Night	45% 8% 11% 17% 16% 2	1474
	21st to end	Night	38% 10% 15% 25% 11% 2	1551
June	1st to 10th	Night	34% 9% 11% 27% 16% 3	1440
	11th to 20th	Night	40% 9% 13% 23% 13% 2	1440
	21st to end	Night	34% 9% 15% 25% 16% 2	1440
July	1st to 10th	Night	38% 11% 15% 20% 14% 3	1400
	11th to 20th	Night	28% 11% 17% 25% 16% 3	1444
	21st to end	Night	31% 11% 19% 21% 16% 2	1672
August	1st to 10th	Night	34% 11% 17% 24% 13% 1	1600
	11th to 20th	Night	37% 10% 14% 21% 17% 1	1629
	21st to end	Night	35% 10% 14% 23% 15% 3	1980
September	1st to 10th	Night	37% 8% 13% 21% 17% 4	1800
	11th to 20th	Night	31% 5% 11% 28% 22% 3	1800
	21st to end	Night	41% 7% 12% 21% 18% 2	2077
October	1st to 10th	Night	41% 7% 12% 23% 16% 2	2160
	11th to 20th	Night	38% 6% 10% 27% 17% 2	2160
	21st to end	Night	40% 6% 9% 27% 17% 2	2376
November	1st to 10th	Night	34% 6% 10% 27% 19% 4	2316
	11th to 20th	Night	41% 5% 10% 24% 17% 4	2555
	21st to end	Night	41% 6% 13% 24% 14% 2	2660
December	1st to 10th	Night	48% 7% 13% 21% 10% 1	2660
	11th to 20th	Night	46% 6% 13% 21% 12% 2	3288
	21st to end	Night	49% 11% 15% 18% 7%	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	31% 24% 27% 13% 4 2	193
	11th to 20th	Day	36% 22% 30% 10% 2	270
	21st to end	Day	26% 29% 28% 14% 3	297
February	1st to 10th	Day	30% 25% 31% 11% 3	270
	11th to 20th	Day	38% 26% 31% 4 1	278
	21st to end	Day	31% 20% 31% 16% 1	362
March	1st to 10th	Day	27% 23% 28% 20% 3	420
	11th to 20th	Day	28% 22% 29% 14% 5% 1	420
	21st to end	Day	29% 21% 27% 16% 5% 2	462
April	1st to 10th	Day	26% 21% 28% 18% 5% 2	420
	11th to 20th	Day	20% 19% 29% 16% 11% 4	412
	21st to end	Day	29% 16% 31% 15% 7% 2	420
May	1st to 10th	Day	27% 18% 28% 15% 8% 3	423
	11th to 20th	Day	23% 16% 26% 22% 9% 3	447
	21st to end	Day	18% 11% 22% 26% 16% 7%	485
June	1st to 10th	Day	15% 12% 27% 23% 18% 5%	450
	11th to 20th	Day	16% 11% 30% 26% 14% 4	450
	21st to end	Day	11% 10% 31% 26% 19% 4	450
July	1st to 10th	Day	10% 5% 22% 30% 23% 11%	445
	11th to 20th	Day	6% 4 26% 30% 25% 9%	444
	21st to end	Day	13% 5% 23% 30% 22% 7%	488
August	1st to 10th	Day	10% 4 20% 31% 25% 10%	446
	11th to 20th	Day	12% 5% 20% 31% 22% 11%	439
	21st to end	Day	12% 5% 21% 30% 21% 12%	495
September	1st to 10th	Day	19% 8% 18% 24% 20% 10%	450
	11th to 20th	Day	12% 6% 20% 30% 21% 10%	450
	21st to end	Day	23% 12% 24% 22% 14% 5%	450
October	1st to 10th	Day	20% 10% 22% 24% 19% 4	450
	11th to 20th	Day	19% 17% 25% 26% 11% 2	450
	21st to end	Day	19% 17% 32% 23% 8% 1	495
November	1st to 10th	Day	16% 14% 29% 25% 13% 2	408
	11th to 20th	Day	25% 19% 27% 20% 8% 1	280
	21st to end	Day	22% 25% 29% 19% 5%	180
December	1st to 10th	Day	29% 24% 30% 12% 4 1	180
	11th to 20th	Day	28% 21% 32% 14% 6%	180
	21st to end	Day	27% 19% 31% 20% 4	198
January	1st to 10th	Night	18% 22% 36% 20% 4	760
	11th to 20th	Night	22% 18% 32% 25% 3	760
	21st to end	Night	19% 20% 36% 23% 2	836
February	1st to 10th	Night	20% 20% 30% 28% 2	760
	11th to 20th	Night	23% 25% 33% 18% 1	743
	21st to end	Night	23% 22% 34% 18% 2	611
March	1st to 10th	Night	21% 19% 36% 21% 4	720
	11th to 20th	Night	26% 18% 28% 22% 6%	720
	21st to end	Night	21% 17% 35% 22% 5% 1	792
April	1st to 10th	Night	21% 20% 31% 23% 5%	720
	11th to 20th	Night	16% 15% 30% 30% 9%	711
	21st to end	Night	21% 13% 29% 27% 9%	710
May	1st to 10th	Night	21% 10% 25% 28% 15% 1	540
	11th to 20th	Night	19% 7% 27% 38% 9%	412
	21st to end	Night	15% 4 22% 36% 21% 2	389
June	1st to 10th	Night	13% 4 24% 36% 23% 1	360
	11th to 20th	Night	13% 6% 22% 39% 19%	360
	21st to end	Night	11% 3 20% 46% 20%	360
July	1st to 10th	Night	11% 1 20% 35% 29% 3	350
	11th to 20th	Night	8% 1 15% 43% 31% 3	400
	21st to end	Night	9% 2 15% 42% 28% 3	591
August	1st to 10th	Night	10% 2 11% 44% 30% 3	537
	11th to 20th	Night	12% 4 12% 39% 30% 4	565
	21st to end	Night	12% 3 15% 38% 28% 4	792
September	1st to 10th	Night	17% 3 17% 34% 26% 3	720
	11th to 20th	Night	13% 4 17% 34% 28% 5%	720
	21st to end	Night	19% 6% 22% 29% 22% 3	720
October	1st to 10th	Night	21% 6% 22% 28% 21% 3	720
	11th to 20th	Night	17% 12% 25% 33% 11% 1	720
	21st to end	Night	20% 10% 31% 30% 10%	792
November	1st to 10th	Night	13% 11% 29% 35% 11% 1	740
	11th to 20th	Night	18% 20% 25% 28% 7% 1	760
	21st to end	Night	18% 19% 29% 29% 6% 1	760
December	1st to 10th	Night	23% 16% 32% 22% 6%	760
	11th to 20th	Night	21% 15% 32% 28% 3	760
	21st to end	Night	19% 16% 33% 29% 3	836

Page generated at 2024-02-22 06:05:44. Version ac07

Copyright 2024 Attilla Danko