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 2025-01-07.

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% 11% 4 9% 5% 5% 5% 4 6% 7% 30%	105056
	Night	14% 11% 4 9% 5% 4 4 4 5% 6% 32%	103995
Transparency	Day	51% 7% 11% 20% 10% 1	108563
	Night	52% 7% 11% 19% 10% 1	108577
Seeing	Day	24% 20% 28% 17% 7% 2	14953
	Night	23% 21% 27% 21% 8% 1	24153

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	11% 14% 10% 15% 5% 4 4 3 5% 5% 24%	2565
	11th to 20th	Day	11% 17% 6% 12% 8% 5% 5% 4 4 4 22%	2520
	21st to end	Day	17% 18% 8% 11% 6% 6% 4 4 4 5% 19%	2941
February	1st to 10th	Day	13% 15% 5% 11% 9% 5% 5% 5% 5% 6% 22%	1710
	11th to 20th	Day	9% 11% 6% 14% 8% 5% 5% 4 6% 6% 27%	1792
	21st to end	Day	15% 14% 4 11% 7% 5% 4 4 4 5% 27%	1570
March	1st to 10th	Day	21% 16% 5% 9% 5% 3 3 3 4 5% 26%	3116
	11th to 20th	Day	10% 16% 8% 10% 5% 5% 5% 3 4 5% 28%	3372
	21st to end	Day	18% 10% 4 10% 5% 4 4 3 4 5% 33%	4117
April	1st to 10th	Day	14% 14% 5% 9% 6% 5% 5% 3 5% 5% 31%	2280
	11th to 20th	Day	15% 12% 4 6% 5% 4 5% 4 5% 6% 35%	2254
	21st to end	Day	19% 11% 4 8% 5% 4 3 3 4 6% 31%	2323
May	1st to 10th	Day	23% 11% 3 7% 5% 4 4 3 5% 6% 30%	4252
	11th to 20th	Day	18% 10% 2 7% 5% 5% 5% 4 5% 7% 30%	4398
	21st to end	Day	11% 6% 2 7% 5% 5% 5% 4 7% 9% 38%	4837
June	1st to 10th	Day	17% 8% 3 8% 5% 5% 5% 5% 7% 8% 30%	2660
	11th to 20th	Day	16% 7% 2 7% 5% 5% 6% 4 7% 10% 31%	2660
	21st to end	Day	15% 8% 3 8% 5% 6% 5% 4 6% 8% 31%	2660
July	1st to 10th	Day	10% 7% 3 8% 5% 6% 6% 5% 8% 10% 33%	4440
	11th to 20th	Day	9% 6% 2 7% 6% 7% 6% 6% 9% 12% 32%	4440
	21st to end	Day	12% 8% 3 9% 6% 6% 6% 4 6% 7% 32%	4814
August	1st to 10th	Day	18% 7% 3 9% 5% 5% 5% 4 6% 7% 30%	4310
	11th to 20th	Day	12% 8% 3 8% 5% 6% 6% 5% 8% 10% 29%	3767
	21st to end	Day	13% 8% 3 6% 5% 5% 5% 4 7% 9% 35%	4180
September	1st to 10th	Day	14% 6% 2 7% 4 5% 5% 4 6% 7% 41%	2280
	11th to 20th	Day	13% 6% 2 5% 4 4 4 4 5% 7% 46%	2219
	21st to end	Day	15% 7% 3 6% 4 5% 4 4 6% 9% 37%	2090
October	1st to 10th	Day	17% 10% 3 9% 4 5% 4 4 5% 6% 33%	1942
	11th to 20th	Day	13% 10% 3 8% 4 4 4 4 6% 6% 36%	1900
	21st to end	Day	20% 14% 3 7% 4 5% 4 4 5% 6% 29%	1929
November	1st to 10th	Day	12% 12% 3 6% 4 4 4 3 6% 6% 40%	1761
	11th to 20th	Day	13% 14% 3 9% 6% 6% 5% 4 4 5% 31%	1800
	21st to end	Day	15% 14% 5% 8% 5% 5% 4 4 5% 6% 28%	1611
December	1st to 10th	Day	9% 17% 9% 17% 6% 5% 5% 3 5% 6% 18%	2600
	11th to 20th	Day	16% 15% 6% 11% 5% 5% 4 4 4 5% 26%	2986
	21st to end	Day	14% 14% 7% 13% 6% 4 4 4 5% 6% 22%	3960
January	1st to 10th	Night	13% 13% 6% 13% 5% 4 4 4 5% 7% 26%	4514
	11th to 20th	Night	10% 16% 6% 13% 9% 6% 4 4 5% 5% 21%	4440
	21st to end	Night	16% 16% 6% 13% 7% 5% 4 3 4 5% 20%	4711
February	1st to 10th	Night	12% 13% 4 11% 8% 5% 6% 4 7% 7% 24%	2470
	11th to 20th	Night	10% 10% 7% 12% 9% 6% 6% 5% 6% 7% 23%	2273
	21st to end	Night	15% 11% 5% 11% 6% 5% 5% 4 5% 6% 26%	1884
March	1st to 10th	Night	19% 11% 4 10% 5% 5% 5% 3 5% 5% 28%	3724
	11th to 20th	Night	10% 14% 7% 10% 6% 5% 5% 4 5% 5% 28%	3585
	21st to end	Night	14% 14% 5% 10% 5% 4 3 3 5% 4 32%	3513
April	1st to 10th	Night	15% 13% 4 8% 6% 5% 5% 4 6% 7% 28%	1900
	11th to 20th	Night	17% 11% 3 6% 4 4 4 3 5% 7% 35%	1875
	21st to end	Night	19% 10% 3 7% 4 4 4 3 5% 6% 34%	1854
May	1st to 10th	Night	23% 12% 3 7% 4 3 3 3 5% 6% 31%	2718
	11th to 20th	Night	16% 12% 3 8% 5% 5% 5% 3 5% 6% 32%	2495
	21st to end	Night	11% 8% 3 7% 5% 5% 5% 4 6% 9% 37%	2738
June	1st to 10th	Night	14% 8% 2 6% 5% 4 4 4 6% 7% 40%	1520
	11th to 20th	Night	15% 7% 2 6% 4 3 4 4 6% 9% 40%	1520
	21st to end	Night	11% 5% 2 6% 5% 4 5% 4 7% 10% 41%	1520
July	1st to 10th	Night	9% 7% 3 7% 6% 5% 6% 5% 7% 7% 40%	2520
	11th to 20th	Night	11% 7% 3 6% 5% 4 5% 4 6% 9% 41%	2520
	21st to end	Night	13% 7% 3 6% 5% 5% 5% 4 6% 6% 41%	2739
August	1st to 10th	Night	19% 9% 2 6% 5% 4 4 3 5% 6% 35%	2617
	11th to 20th	Night	14% 7% 3 7% 5% 4 4 4 6% 7% 40%	3029
	21st to end	Night	11% 8% 2 6% 4 4 4 3 6% 7% 46%	3476
September	1st to 10th	Night	13% 7% 2 6% 3 4 4 4 5% 7% 44%	1900
	11th to 20th	Night	14% 6% 2 5% 2 3 3 3 4 7% 52%	1960
	21st to end	Night	13% 7% 2 6% 5% 5% 5% 4 5% 6% 42%	2090
October	1st to 10th	Night	18% 9% 3 7% 4 4 3 4 5% 6% 37%	2235
	11th to 20th	Night	16% 9% 2 6% 4 4 5% 4 5% 6% 39%	2280
	21st to end	Night	20% 13% 2 6% 3 4 4 3 5% 8% 30%	2669
November	1st to 10th	Night	12% 11% 3 7% 4 4 4 3 6% 7% 38%	2537
	11th to 20th	Night	14% 13% 4 8% 5% 5% 5% 4 6% 6% 31%	2600
	21st to end	Night	12% 12% 7% 9% 5% 5% 5% 3 6% 6% 30%	2785
December	1st to 10th	Night	12% 15% 6% 15% 5% 5% 5% 4 6% 7% 20%	4580
	11th to 20th	Night	19% 13% 6% 10% 5% 5% 4 3 4 4 27%	5208
	21st to end	Night	17% 15% 6% 12% 5% 4 4 3 5% 5% 23%	6996

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	58% 9% 10% 16% 6% 1	2566
	11th to 20th	Day	63% 9% 8% 14% 5% 1	2520
	21st to end	Day	65% 8% 8% 13% 5% 1	2941
February	1st to 10th	Day	61% 7% 10% 14% 7% 1	1710
	11th to 20th	Day	55% 8% 8% 18% 10% 1	1801
	21st to end	Day	57% 7% 10% 16% 10%	1570
March	1st to 10th	Day	61% 5% 10% 14% 9% 1	3119
	11th to 20th	Day	56% 8% 12% 15% 8% 1	3372
	21st to end	Day	52% 7% 5% 16% 17% 3	4117
April	1st to 10th	Day	55% 6% 8% 20% 10% 2	2280
	11th to 20th	Day	50% 6% 11% 19% 13% 1	2254
	21st to end	Day	55% 5% 9% 16% 12% 3	2323
May	1st to 10th	Day	56% 6% 9% 18% 10% 1	4266
	11th to 20th	Day	51% 8% 12% 21% 7% 1	4402
	21st to end	Day	39% 10% 13% 25% 12% 1	4837
June	1st to 10th	Day	50% 8% 13% 18% 10%	2660
	11th to 20th	Day	47% 8% 14% 19% 10% 1	2660
	21st to end	Day	50% 7% 14% 19% 9% 1	2660
July	1st to 10th	Day	45% 7% 14% 23% 11%	4370
	11th to 20th	Day	43% 7% 16% 24% 10%	4365
	21st to end	Day	50% 5% 13% 20% 11%	4661
August	1st to 10th	Day	53% 6% 13% 18% 10%	4296
	11th to 20th	Day	49% 6% 16% 25% 5%	3804
	21st to end	Day	44% 5% 12% 30% 8% 1	4180
September	1st to 10th	Day	42% 7% 12% 24% 14% 1	2280
	11th to 20th	Day	38% 7% 10% 25% 19% 1	2219
	21st to end	Day	42% 7% 13% 22% 14% 2	2090
October	1st to 10th	Day	51% 4 6% 21% 17% 1	3228
	11th to 20th	Day	42% 5% 9% 22% 18% 4	3140
	21st to end	Day	41% 5% 13% 26% 11% 3	3154
November	1st to 10th	Day	43% 7% 12% 22% 14% 2	1761
	11th to 20th	Day	54% 7% 9% 16% 13% 2	1800
	21st to end	Day	55% 7% 13% 17% 7% 1	1611
December	1st to 10th	Day	68% 4 9% 15% 4	2600
	11th to 20th	Day	61% 4 11% 15% 8%	2986
	21st to end	Day	62% 6% 8% 12% 12% 2	3960
January	1st to 10th	Night	54% 11% 12% 15% 8% 1	4514
	11th to 20th	Night	63% 8% 10% 12% 6% 1	4440
	21st to end	Night	67% 6% 8% 13% 5% 1	4711
February	1st to 10th	Night	57% 8% 10% 15% 8% 1	2470
	11th to 20th	Night	57% 10% 10% 14% 9% 1	2275
	21st to end	Night	57% 7% 10% 16% 8% 2	1884
March	1st to 10th	Night	58% 7% 9% 17% 9% 1	3734
	11th to 20th	Night	53% 9% 12% 19% 6% 1	3586
	21st to end	Night	54% 6% 7% 16% 16% 2	3513
April	1st to 10th	Night	54% 7% 12% 17% 8% 1	1900
	11th to 20th	Night	49% 7% 11% 19% 14%	1875
	21st to end	Night	50% 7% 11% 18% 13% 2	1854
May	1st to 10th	Night	55% 6% 10% 17% 10% 2	2724
	11th to 20th	Night	51% 10% 11% 20% 8% 1	2496
	21st to end	Night	41% 11% 14% 21% 13% 1	2739
June	1st to 10th	Night	43% 6% 12% 25% 12% 1	1520
	11th to 20th	Night	40% 7% 16% 27% 9%	1520
	21st to end	Night	37% 10% 16% 26% 11%	1520
July	1st to 10th	Night	43% 6% 16% 21% 13% 1	2480
	11th to 20th	Night	40% 5% 17% 25% 12%	2472
	21st to end	Night	44% 6% 12% 26% 11% 1	2651
August	1st to 10th	Night	49% 6% 14% 22% 8% 1	2607
	11th to 20th	Night	44% 5% 17% 26% 8%	3058
	21st to end	Night	39% 5% 12% 34% 10%	3476
September	1st to 10th	Night	38% 7% 14% 27% 13% 1	1900
	11th to 20th	Night	34% 6% 11% 26% 22% 1	1960
	21st to end	Night	43% 7% 11% 22% 15% 1	2090
October	1st to 10th	Night	51% 5% 11% 22% 11% 1	3729
	11th to 20th	Night	41% 5% 12% 21% 17% 4	3779
	21st to end	Night	43% 5% 15% 27% 10% 1	4394
November	1st to 10th	Night	45% 7% 12% 19% 15% 3	2537
	11th to 20th	Night	51% 8% 10% 17% 11% 2	2600
	21st to end	Night	53% 7% 14% 19% 6% 1	2785
December	1st to 10th	Night	64% 6% 9% 19% 3	4580
	11th to 20th	Night	62% 4 10% 13% 12%	5208
	21st to end	Night	64% 5% 6% 11% 11% 2	6996

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	32% 29% 24% 11% 4	192
	11th to 20th	Day	38% 27% 25% 8% 1 1	180
	21st to end	Day	26% 31% 32% 8% 3	247
February	1st to 10th	Day	34% 34% 26% 6%	270
	11th to 20th	Day	34% 37% 21% 7% 2	400
	21st to end	Day	34% 27% 28% 10% 1	382
March	1st to 10th	Day	30% 27% 29% 11% 2	460
	11th to 20th	Day	36% 24% 26% 10% 3	460
	21st to end	Day	34% 29% 22% 9% 4 2	506
April	1st to 10th	Day	32% 28% 22% 12% 5%	460
	11th to 20th	Day	30% 28% 23% 11% 5% 2	452
	21st to end	Day	33% 21% 28% 11% 5% 2	460
May	1st to 10th	Day	32% 22% 27% 10% 6% 3	463
	11th to 20th	Day	22% 20% 32% 18% 7% 2	487
	21st to end	Day	20% 13% 32% 22% 10% 3	529
June	1st to 10th	Day	20% 17% 34% 22% 7% 1	490
	11th to 20th	Day	17% 17% 32% 21% 11% 2	490
	21st to end	Day	20% 19% 31% 22% 7% 1	490
July	1st to 10th	Day	13% 11% 35% 26% 12% 4	485
	11th to 20th	Day	11% 9% 37% 30% 10% 3	484
	21st to end	Day	14% 11% 39% 25% 8% 3	532
August	1st to 10th	Day	12% 12% 33% 25% 15% 4	486
	11th to 20th	Day	16% 10% 29% 28% 10% 7%	479
	21st to end	Day	15% 14% 29% 24% 12% 6%	539
September	1st to 10th	Day	20% 11% 25% 22% 14% 7%	490
	11th to 20th	Day	14% 11% 26% 21% 17% 10%	490
	21st to end	Day	21% 13% 27% 23% 11% 5%	490
October	1st to 10th	Day	22% 18% 26% 17% 12% 4	490
	11th to 20th	Day	25% 21% 25% 20% 8% 2	490
	21st to end	Day	28% 22% 29% 15% 5%	454
November	1st to 10th	Day	27% 22% 25% 16% 10%	395
	11th to 20th	Day	30% 27% 23% 15% 5% 1	400
	21st to end	Day	34% 26% 29% 11% 1	211
December	1st to 10th	Day	34% 31% 22% 9% 4	200
	11th to 20th	Day	37% 27% 26% 10% 1	200
	21st to end	Day	28% 32% 30% 8% 2	220
January	1st to 10th	Night	25% 33% 29% 11% 1	785
	11th to 20th	Night	27% 28% 29% 13% 3	760
	21st to end	Night	19% 34% 29% 16% 2	836
February	1st to 10th	Night	26% 27% 35% 12% 1	760
	11th to 20th	Night	26% 32% 29% 13% 1	743
	21st to end	Night	31% 27% 27% 13% 2	628
March	1st to 10th	Night	27% 28% 29% 13% 3	760
	11th to 20th	Night	27% 28% 28% 15% 2 1	760
	21st to end	Night	28% 23% 28% 16% 5%	836
April	1st to 10th	Night	26% 25% 29% 17% 3	760
	11th to 20th	Night	26% 24% 27% 16% 7%	751
	21st to end	Night	28% 19% 25% 20% 7% 1	714
May	1st to 10th	Night	29% 16% 27% 20% 7% 1	506
	11th to 20th	Night	22% 14% 27% 29% 6% 1	374
	21st to end	Night	16% 9% 31% 30% 14% 1	411
June	1st to 10th	Night	17% 11% 28% 31% 12% 1	380
	11th to 20th	Night	16% 11% 22% 37% 13%	380
	21st to end	Night	14% 8% 31% 35% 12% 1	380
July	1st to 10th	Night	12% 8% 21% 43% 14% 2	370
	11th to 20th	Night	11% 7% 26% 37% 17% 1	368
	21st to end	Night	12% 6% 26% 41% 15% 1	416
August	1st to 10th	Night	12% 6% 26% 34% 20% 1	437
	11th to 20th	Night	16% 5% 21% 35% 19% 3	706
	21st to end	Night	16% 9% 20% 34% 20% 2	836
September	1st to 10th	Night	16% 9% 25% 31% 16% 2	760
	11th to 20th	Night	16% 10% 22% 26% 20% 6%	760
	21st to end	Night	17% 12% 25% 27% 15% 3	760
October	1st to 10th	Night	24% 16% 20% 24% 14% 2	760
	11th to 20th	Night	21% 18% 28% 25% 8% 1	760
	21st to end	Night	28% 21% 27% 20% 4	836
November	1st to 10th	Night	22% 22% 27% 22% 6% 1	780
	11th to 20th	Night	27% 24% 25% 16% 6% 2	800
	21st to end	Night	25% 26% 26% 18% 4 1	800
December	1st to 10th	Night	26% 31% 26% 13% 4	800
	11th to 20th	Night	28% 28% 27% 15% 2	800
	21st to end	Night	30% 30% 25% 13% 3	880

Page generated at 2025-01-04 03:23:59. Version ac07

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