Camp Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Camp Observatory clear sky chart from 2005-11-06 to 2024-01-17.

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% 10% 4 8% 6% 4 5% 5% 5% 7% 31%	74788
	Night	14% 10% 4 7% 6% 3 5% 5% 6% 7% 33%	75031
Transparency	Day	51% 8% 11% 19% 10% 1	74493
	Night	50% 8% 12% 19% 10% 1	74860
Seeing	Day	24% 21% 28% 17% 7% 3	13690
	Night	23% 21% 27% 21% 8% 1	22931

By Month

Percentage Cloud Cover NE (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	9% 12% 7% 11% 7% 4 5% 5% 7% 8% 27%	1517
	11th to 20th	Day	12% 14% 5% 10% 9% 4 6% 5% 5% 6% 23%	1488
	21st to end	Day	9% 11% 7% 11% 9% 5% 7% 5% 5% 7% 25%	1683
February	1st to 10th	Day	14% 13% 7% 10% 10% 4 6% 6% 5% 6% 20%	1620
	11th to 20th	Day	9% 10% 6% 12% 9% 4 5% 5% 6% 6% 27%	1695
	21st to end	Day	16% 13% 4 9% 8% 4 5% 4 4 5% 26%	1480
March	1st to 10th	Day	11% 12% 5% 10% 9% 3 4 4 5% 7% 29%	1797
	11th to 20th	Day	14% 14% 6% 8% 6% 4 5% 4 4 5% 30%	1914
	21st to end	Day	17% 12% 5% 7% 6% 3 4 3 4 5% 33%	2341
April	1st to 10th	Day	14% 12% 6% 8% 7% 4 5% 4 5% 5% 31%	2160
	11th to 20th	Day	15% 10% 4 6% 6% 3 4 5% 4 6% 36%	2134
	21st to end	Day	20% 11% 5% 7% 6% 3 4 4 4 6% 31%	2200
May	1st to 10th	Day	20% 12% 3 7% 5% 4 5% 4 4 6% 30%	2416
	11th to 20th	Day	17% 9% 3 6% 4 3 5% 5% 5% 7% 36%	2478
	21st to end	Day	13% 6% 3 7% 6% 4 6% 5% 6% 9% 37%	2725
June	1st to 10th	Day	17% 8% 3 7% 6% 3 6% 6% 6% 8% 30%	2520
	11th to 20th	Day	17% 7% 3 7% 5% 3 6% 6% 6% 10% 31%	2520
	21st to end	Day	15% 8% 3 7% 6% 5% 6% 4 6% 9% 32%	2520
July	1st to 10th	Day	11% 6% 4 7% 6% 4 7% 6% 7% 8% 34%	2520
	11th to 20th	Day	10% 5% 2 6% 7% 4 6% 7% 7% 11% 35%	2520
	21st to end	Day	12% 7% 3 7% 7% 4 7% 5% 6% 9% 33%	2744
August	1st to 10th	Day	10% 6% 3 8% 7% 5% 6% 7% 6% 9% 35%	2449
	11th to 20th	Day	12% 7% 3 6% 7% 5% 7% 6% 8% 9% 30%	2150
	21st to end	Day	15% 6% 3 5% 5% 4 6% 6% 6% 9% 36%	2376
September	1st to 10th	Day	15% 6% 3 6% 5% 4 5% 5% 6% 7% 39%	2160
	11th to 20th	Day	14% 6% 3 5% 5% 3 4 5% 5% 7% 44%	2103
	21st to end	Day	15% 7% 2 4 5% 3 5% 5% 7% 9% 39%	1980
October	1st to 10th	Day	18% 9% 3 7% 6% 3 4 5% 5% 6% 33%	1840
	11th to 20th	Day	13% 10% 3 7% 6% 3 4 6% 6% 7% 35%	1800
	21st to end	Day	21% 14% 3 6% 5% 3 4 5% 5% 6% 27%	1828
November	1st to 10th	Day	13% 11% 3 6% 4 3 4 5% 5% 6% 39%	1671
	11th to 20th	Day	14% 14% 4 8% 7% 4 6% 5% 4 5% 31%	1710
	21st to end	Day	14% 13% 5% 7% 7% 4 5% 6% 5% 7% 29%	1531
December	1st to 10th	Day	12% 17% 7% 12% 7% 4 6% 4 6% 6% 20%	1520
	11th to 20th	Day	19% 14% 6% 9% 6% 3 4 4 3 5% 27%	1906
	21st to end	Day	18% 17% 8% 10% 6% 2 4 5% 5% 6% 18%	2772
January	1st to 10th	Night	11% 12% 7% 11% 6% 3 5% 6% 6% 8% 26%	2649
	11th to 20th	Night	12% 12% 5% 10% 9% 4 6% 5% 6% 7% 22%	2616
	21st to end	Night	8% 9% 7% 10% 9% 5% 6% 5% 6% 8% 26%	2669
February	1st to 10th	Night	12% 13% 6% 9% 9% 4 6% 6% 7% 7% 22%	2340
	11th to 20th	Night	11% 9% 7% 10% 10% 4 7% 6% 6% 7% 23%	2150
	21st to end	Night	15% 10% 6% 11% 7% 4 5% 6% 5% 6% 25%	1776
March	1st to 10th	Night	13% 11% 5% 11% 6% 4 5% 5% 5% 6% 29%	2150
	11th to 20th	Night	14% 9% 6% 9% 9% 5% 5% 5% 5% 6% 28%	2043
	21st to end	Night	15% 12% 4 7% 5% 3 4 5% 6% 7% 33%	2013
April	1st to 10th	Night	15% 12% 4 7% 7% 4 6% 5% 6% 7% 28%	1800
	11th to 20th	Night	17% 10% 3 5% 5% 3 4 4 5% 7% 36%	1775
	21st to end	Night	20% 10% 4 6% 4 3 4 4 5% 7% 33%	1757
May	1st to 10th	Night	20% 13% 4 6% 6% 3 4 3 5% 5% 31%	1560
	11th to 20th	Night	15% 8% 3 7% 5% 4 5% 4 6% 6% 37%	1415
	21st to end	Night	11% 6% 3 5% 6% 4 5% 4 7% 8% 41%	1550
June	1st to 10th	Night	15% 7% 3 4 5% 3 5% 5% 6% 7% 41%	1440
	11th to 20th	Night	15% 6% 3 6% 4 3 3 5% 6% 9% 40%	1440
	21st to end	Night	10% 4 2 5% 6% 3 6% 5% 7% 10% 42%	1440
July	1st to 10th	Night	10% 5% 3 3 5% 2 6% 6% 7% 7% 46%	1440
	11th to 20th	Night	11% 5% 2 5% 5% 3 5% 6% 7% 9% 42%	1440
	21st to end	Night	11% 5% 3 5% 6% 2 4 5% 6% 7% 46%	1574
August	1st to 10th	Night	9% 5% 2 5% 6% 4 5% 5% 7% 9% 45%	1487
	11th to 20th	Night	12% 7% 3 6% 6% 3 5% 5% 6% 7% 40%	1732
	21st to end	Night	13% 6% 2 5% 5% 3 4 4 6% 8% 44%	1980
September	1st to 10th	Night	14% 6% 2 4 5% 3 5% 5% 5% 8% 43%	1800
	11th to 20th	Night	14% 6% 2 4 3 2 3 3 4 7% 52%	1856
	21st to end	Night	13% 6% 2 5% 6% 4 4 5% 5% 6% 44%	1980
October	1st to 10th	Night	19% 9% 2 6% 5% 3 3 5% 5% 6% 37%	2117
	11th to 20th	Night	16% 8% 3 5% 5% 3 5% 5% 5% 6% 38%	2160
	21st to end	Night	21% 13% 3 5% 4 4 4 4 5% 8% 29%	2528
November	1st to 10th	Night	12% 11% 4 7% 5% 3 5% 4 6% 7% 38%	2407
	11th to 20th	Night	15% 12% 4 7% 6% 4 5% 5% 6% 6% 30%	2470
	21st to end	Night	12% 10% 7% 8% 6% 4 5% 4 6% 7% 31%	2645
December	1st to 10th	Night	13% 14% 6% 10% 6% 3 6% 6% 6% 7% 22%	2660
	11th to 20th	Night	17% 13% 5% 10% 7% 4 5% 5% 5% 6% 25%	3288
	21st to end	Night	21% 14% 7% 11% 5% 3 4 4 4 6% 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	54% 6% 13% 17% 9% 1	1518
	11th to 20th	Day	61% 9% 9% 13% 6% 2	1488
	21st to end	Day	58% 8% 9% 14% 9% 2	1683
February	1st to 10th	Day	64% 7% 10% 12% 7% 1	1620
	11th to 20th	Day	56% 8% 8% 18% 9% 1	1704
	21st to end	Day	59% 7% 9% 15% 10%	1480
March	1st to 10th	Day	53% 7% 11% 17% 9% 2	1800
	11th to 20th	Day	57% 5% 8% 17% 11% 2	1914
	21st to end	Day	54% 5% 6% 16% 15% 4	2341
April	1st to 10th	Day	54% 6% 8% 20% 10% 2	2160
	11th to 20th	Day	49% 6% 11% 19% 13% 1	2134
	21st to end	Day	55% 5% 9% 17% 11% 3	2200
May	1st to 10th	Day	56% 6% 7% 19% 9% 2	2416
	11th to 20th	Day	47% 7% 9% 22% 13% 2	2482
	21st to end	Day	44% 10% 15% 21% 9% 1	2725
June	1st to 10th	Day	50% 7% 14% 18% 10%	2520
	11th to 20th	Day	48% 9% 14% 19% 10% 1	2520
	21st to end	Day	50% 7% 14% 19% 9% 1	2520
July	1st to 10th	Day	45% 9% 12% 20% 12% 1	2450
	11th to 20th	Day	40% 11% 16% 22% 9%	2445
	21st to end	Day	47% 8% 13% 21% 11% 1	2591
August	1st to 10th	Day	44% 10% 13% 21% 11% 1	2435
	11th to 20th	Day	47% 10% 14% 22% 6%	2150
	21st to end	Day	42% 9% 12% 23% 12% 1	2376
September	1st to 10th	Day	43% 8% 13% 24% 12% 1	2160
	11th to 20th	Day	39% 7% 10% 23% 19% 2	2103
	21st to end	Day	40% 8% 13% 23% 14% 2	1980
October	1st to 10th	Day	51% 7% 9% 19% 13% 2	1840
	11th to 20th	Day	45% 8% 13% 22% 10% 1	1800
	21st to end	Day	57% 7% 11% 13% 9% 2	1828
November	1st to 10th	Day	44% 8% 12% 22% 13% 2	1671
	11th to 20th	Day	55% 7% 10% 16% 11% 2	1710
	21st to end	Day	54% 7% 14% 17% 7% 1	1531
December	1st to 10th	Day	65% 7% 10% 12% 6%	1520
	11th to 20th	Day	60% 7% 12% 15% 5%	1906
	21st to end	Day	66% 8% 8% 11% 7%	2772
January	1st to 10th	Night	53% 8% 11% 16% 11% 1	2649
	11th to 20th	Night	59% 10% 11% 12% 7% 2	2616
	21st to end	Night	55% 8% 10% 16% 10% 2	2669
February	1st to 10th	Night	59% 9% 10% 13% 7% 1	2340
	11th to 20th	Night	58% 9% 10% 14% 8% 1	2152
	21st to end	Night	57% 7% 10% 16% 8% 2	1776
March	1st to 10th	Night	55% 7% 10% 18% 9% 1	2160
	11th to 20th	Night	55% 7% 10% 18% 9% 1	2044
	21st to end	Night	49% 7% 9% 18% 14% 3	2013
April	1st to 10th	Night	54% 8% 11% 18% 8% 1	1800
	11th to 20th	Night	48% 7% 12% 20% 14%	1775
	21st to end	Night	51% 7% 11% 17% 12% 2	1757
May	1st to 10th	Night	56% 5% 9% 14% 13% 2	1560
	11th to 20th	Night	46% 7% 10% 22% 13% 1	1416
	21st to end	Night	40% 10% 15% 23% 10% 2	1551
June	1st to 10th	Night	43% 6% 13% 25% 12% 1	1440
	11th to 20th	Night	41% 7% 16% 26% 10%	1440
	21st to end	Night	36% 10% 17% 26% 11%	1440
July	1st to 10th	Night	35% 9% 16% 24% 14% 2	1400
	11th to 20th	Night	36% 8% 18% 28% 9%	1392
	21st to end	Night	36% 9% 16% 24% 13% 2	1486
August	1st to 10th	Night	34% 10% 18% 28% 10% 1	1477
	11th to 20th	Night	42% 8% 17% 24% 9%	1732
	21st to end	Night	38% 8% 13% 27% 13% 1	1980
September	1st to 10th	Night	39% 7% 14% 27% 12% 1	1800
	11th to 20th	Night	34% 6% 12% 24% 23% 1	1856
	21st to end	Night	41% 8% 11% 23% 16% 1	1980
October	1st to 10th	Night	47% 8% 12% 20% 12% 1	2117
	11th to 20th	Night	45% 8% 15% 21% 10% 1	2160
	21st to end	Night	55% 7% 12% 17% 9% 1	2528
November	1st to 10th	Night	46% 7% 12% 18% 15% 3	2407
	11th to 20th	Night	51% 9% 10% 17% 10% 2	2470
	21st to end	Night	52% 7% 14% 19% 7% 1	2645
December	1st to 10th	Night	60% 10% 11% 14% 5%	2660
	11th to 20th	Night	60% 7% 11% 13% 9%	3288
	21st to end	Night	64% 7% 8% 14% 6%	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% 29% 24% 12% 4	180
	11th to 20th	Day	38% 27% 26% 8% 1 1	172
	21st to end	Day	25% 32% 31% 8% 3	220
February	1st to 10th	Day	38% 35% 24% 4	240
	11th to 20th	Day	32% 38% 22% 7% 2	363
	21st to end	Day	34% 28% 27% 10% 1	346
March	1st to 10th	Day	29% 29% 30% 11% 2	420
	11th to 20th	Day	35% 25% 27% 10% 3	420
	21st to end	Day	33% 29% 21% 10% 5% 2	462
April	1st to 10th	Day	30% 29% 22% 13% 6%	420
	11th to 20th	Day	28% 28% 24% 12% 6% 2	412
	21st to end	Day	34% 21% 27% 11% 5% 2	420
May	1st to 10th	Day	31% 23% 27% 9% 6% 3	423
	11th to 20th	Day	22% 21% 32% 17% 6% 2	447
	21st to end	Day	20% 13% 31% 21% 11% 4	485
June	1st to 10th	Day	20% 17% 34% 21% 7% 1	450
	11th to 20th	Day	18% 17% 32% 21% 10% 2	450
	21st to end	Day	18% 19% 31% 22% 8% 1	450
July	1st to 10th	Day	13% 11% 33% 26% 13% 4	445
	11th to 20th	Day	10% 9% 37% 29% 11% 3	444
	21st to end	Day	14% 12% 39% 25% 8% 3	488
August	1st to 10th	Day	9% 11% 33% 25% 16% 4	446
	11th to 20th	Day	16% 9% 30% 28% 11% 7%	439
	21st to end	Day	15% 15% 29% 24% 12% 6%	495
September	1st to 10th	Day	20% 11% 25% 22% 15% 7%	450
	11th to 20th	Day	15% 12% 27% 21% 15% 9%	450
	21st to end	Day	20% 14% 27% 23% 10% 6%	450
October	1st to 10th	Day	22% 18% 27% 17% 12% 4	450
	11th to 20th	Day	24% 21% 26% 20% 8% 1	450
	21st to end	Day	30% 22% 29% 14% 5%	419
November	1st to 10th	Day	27% 21% 24% 17% 11%	365
	11th to 20th	Day	30% 28% 22% 14% 4 1	370
	21st to end	Day	31% 26% 30% 12% 1	191
December	1st to 10th	Day	34% 32% 20% 9% 4	180
	11th to 20th	Day	37% 26% 27% 8% 1	180
	21st to end	Day	29% 34% 29% 6% 2	198
January	1st to 10th	Night	25% 33% 30% 11% 1	760
	11th to 20th	Night	27% 28% 29% 13% 2	748
	21st to end	Night	18% 35% 30% 16% 2	792
February	1st to 10th	Night	27% 28% 34% 10% 1	720
	11th to 20th	Night	25% 32% 29% 13% 1	703
	21st to end	Night	31% 27% 27% 13% 2	592
March	1st to 10th	Night	27% 29% 28% 14% 3	720
	11th to 20th	Night	27% 28% 27% 15% 2 1	720
	21st to end	Night	27% 22% 29% 16% 5% 1	792
April	1st to 10th	Night	25% 25% 29% 18% 3	720
	11th to 20th	Night	25% 24% 27% 16% 7%	711
	21st to end	Night	28% 19% 26% 20% 7% 1	677
May	1st to 10th	Night	29% 16% 26% 20% 8% 1	480
	11th to 20th	Night	23% 15% 28% 29% 5% 1	354
	21st to end	Night	16% 8% 31% 30% 14% 1	389
June	1st to 10th	Night	18% 12% 27% 31% 12% 1	360
	11th to 20th	Night	17% 11% 22% 36% 13%	360
	21st to end	Night	13% 8% 30% 36% 12% 1	360
July	1st to 10th	Night	12% 9% 22% 42% 14% 2	350
	11th to 20th	Night	11% 6% 27% 37% 18% 1	348
	21st to end	Night	12% 6% 26% 41% 14% 1	394
August	1st to 10th	Night	9% 7% 28% 34% 21% 1	413
	11th to 20th	Night	16% 5% 21% 35% 19% 3	668
	21st to end	Night	15% 9% 20% 34% 20% 2	792
September	1st to 10th	Night	16% 10% 25% 33% 15% 2	720
	11th to 20th	Night	17% 11% 23% 26% 17% 6%	720
	21st to end	Night	16% 13% 26% 27% 15% 3	720
October	1st to 10th	Night	25% 17% 20% 23% 14% 2	720
	11th to 20th	Night	21% 18% 28% 25% 7% 1	720
	21st to end	Night	29% 21% 27% 19% 4	792
November	1st to 10th	Night	22% 22% 27% 22% 6% 1	740
	11th to 20th	Night	26% 25% 25% 16% 6% 2	760
	21st to end	Night	23% 27% 27% 18% 4 1	760
December	1st to 10th	Night	26% 31% 26% 13% 4	760
	11th to 20th	Night	27% 29% 27% 15% 2	760
	21st to end	Night	30% 31% 25% 12% 2	836

Page generated at 2024-01-14 09:55:01. Version ac07

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