Mancamp Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mancamp Observatory clear sky chart from 2005-11-06 to 2024-01-13.

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	18% 7% 3 5% 5% 3 5% 5% 5% 7% 37%	74539
	Night	18% 8% 3 5% 5% 3 4 5% 5% 6% 38%	75160
Transparency	Day	46% 6% 11% 21% 13% 2	74244
	Night	46% 6% 11% 21% 13% 2	74990
Seeing	Day	24% 14% 30% 20% 9% 2	14095
	Night	23% 11% 31% 27% 8% 1	22916

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	15% 8% 3 6% 7% 4 5% 6% 5% 7% 34%	1517
	11th to 20th	Day	18% 10% 4 5% 5% 3 5% 4 4 7% 35%	1456
	21st to end	Day	12% 11% 4 6% 5% 4 5% 4 5% 7% 39%	1584
February	1st to 10th	Day	17% 10% 3 7% 6% 4 5% 4 6% 6% 33%	1566
	11th to 20th	Day	13% 10% 3 8% 7% 4 5% 4 5% 6% 33%	1734
	21st to end	Day	14% 12% 4 6% 6% 4 6% 5% 5% 6% 32%	1480
March	1st to 10th	Day	15% 10% 4 6% 5% 3 6% 5% 5% 6% 36%	1797
	11th to 20th	Day	16% 7% 3 5% 6% 3 5% 4 4 5% 41%	1938
	21st to end	Day	16% 8% 3 6% 6% 4 4 3 4 5% 40%	2234
April	1st to 10th	Day	20% 10% 3 7% 6% 2 4 3 4 6% 34%	2160
	11th to 20th	Day	18% 7% 2 5% 6% 3 5% 5% 5% 7% 38%	2234
	21st to end	Day	23% 9% 3 7% 6% 4 4 4 4 5% 31%	2340
May	1st to 10th	Day	24% 7% 3 6% 6% 3 4 3 5% 6% 32%	2340
	11th to 20th	Day	21% 6% 3 6% 6% 3 6% 3 5% 6% 35%	2362
	21st to end	Day	17% 6% 3 5% 5% 3 5% 5% 6% 8% 37%	2725
June	1st to 10th	Day	24% 7% 3 5% 5% 3 4 6% 7% 8% 29%	2587
	11th to 20th	Day	18% 6% 2 5% 5% 3 5% 4 5% 7% 38%	2700
	21st to end	Day	24% 7% 3 5% 5% 3 4 6% 5% 7% 31%	2572
July	1st to 10th	Day	16% 5% 3 5% 6% 4 5% 5% 7% 8% 37%	2520
	11th to 20th	Day	13% 6% 2 6% 6% 4 6% 7% 5% 8% 36%	2520
	21st to end	Day	15% 5% 2 6% 7% 4 6% 5% 7% 10% 34%	2744
August	1st to 10th	Day	15% 5% 2 5% 6% 4 5% 6% 6% 9% 37%	2365
	11th to 20th	Day	13% 5% 2 6% 5% 4 6% 6% 6% 9% 38%	2304
	21st to end	Day	13% 5% 2 4 4 3 4 5% 6% 8% 45%	2484
September	1st to 10th	Day	12% 5% 2 4 6% 3 4 4 5% 8% 46%	2123
	11th to 20th	Day	13% 4 2 4 4 3 4 4 4 6% 52%	1980
	21st to end	Day	16% 4 2 4 5% 3 3 5% 5% 8% 44%	1980
October	1st to 10th	Day	19% 7% 3 5% 6% 3 4 5% 4 6% 39%	1980
	11th to 20th	Day	18% 7% 2 5% 4 4 4 4 5% 7% 40%	1720
	21st to end	Day	25% 9% 3 6% 5% 2 4 4 4 5% 33%	1782
November	1st to 10th	Day	17% 6% 3 6% 3 3 5% 4 5% 6% 42%	1671
	11th to 20th	Day	21% 6% 2 5% 4 3 4 5% 5% 8% 38%	1710
	21st to end	Day	21% 7% 2 4 4 2 3 3 4 6% 42%	1626
December	1st to 10th	Day	22% 11% 4 6% 5% 2 5% 4 4 5% 33%	1330
	11th to 20th	Day	23% 9% 3 4 4 3 3 4 5% 5% 36%	1668
	21st to end	Day	24% 12% 2 6% 5% 3 5% 5% 6% 5% 28%	2706
January	1st to 10th	Night	15% 9% 4 6% 5% 3 5% 5% 5% 7% 37%	2649
	11th to 20th	Night	16% 13% 4 8% 5% 3 6% 4 4 5% 31%	2549
	21st to end	Night	12% 8% 4 7% 6% 3 5% 5% 6% 6% 39%	2772
February	1st to 10th	Night	15% 9% 4 8% 6% 3 5% 6% 6% 7% 31%	2393
	11th to 20th	Night	11% 11% 4 7% 6% 3 5% 5% 5% 5% 38%	2107
	21st to end	Night	14% 10% 4 6% 5% 3 5% 5% 5% 6% 38%	1776
March	1st to 10th	Night	14% 11% 4 6% 6% 3 6% 6% 4 6% 35%	2150
	11th to 20th	Night	16% 8% 4 6% 5% 4 5% 5% 5% 6% 37%	2020
	21st to end	Night	18% 8% 2 6% 5% 3 4 5% 4 6% 40%	2120
April	1st to 10th	Night	20% 11% 4 6% 5% 2 4 4 3 5% 36%	1800
	11th to 20th	Night	18% 6% 2 6% 6% 3 5% 5% 5% 6% 38%	1674
	21st to end	Night	26% 8% 2 6% 5% 2 3 4 5% 6% 33%	1620
May	1st to 10th	Night	21% 9% 4 6% 5% 3 4 5% 5% 6% 32%	1620
	11th to 20th	Night	22% 7% 2 5% 5% 4 5% 4 5% 7% 33%	1546
	21st to end	Night	18% 8% 2 6% 5% 3 5% 5% 6% 7% 34%	1550
June	1st to 10th	Night	25% 7% 2 4 5% 4 4 4 4 7% 33%	1364
	11th to 20th	Night	18% 7% 3 5% 4 3 3 6% 5% 8% 39%	1260
	21st to end	Night	23% 6% 3 5% 5% 2 4 4 6% 7% 34%	1378
July	1st to 10th	Night	16% 5% 2 4 5% 3 5% 6% 6% 9% 39%	1440
	11th to 20th	Night	15% 5% 2 6% 5% 3 4 4 5% 10% 41%	1440
	21st to end	Night	14% 6% 3 4 4 3 5% 6% 6% 9% 40%	1574
August	1st to 10th	Night	15% 5% 2 5% 5% 3 6% 6% 6% 7% 42%	1553
	11th to 20th	Night	13% 7% 3 6% 6% 4 5% 4 7% 8% 38%	1596
	21st to end	Night	14% 5% 1 4 5% 2 3 4 5% 7% 48%	1869
September	1st to 10th	Night	13% 5% 2 5% 4 3 4 4 5% 7% 49%	1836
	11th to 20th	Night	17% 5% 2 4 3 2 4 3 4 6% 51%	1980
	21st to end	Night	17% 6% 2 4 3 3 4 3 5% 7% 46%	1980
October	1st to 10th	Night	18% 7% 2 6% 5% 3 4 5% 5% 6% 39%	1980
	11th to 20th	Night	17% 7% 2 4 5% 3 6% 5% 5% 7% 39%	2238
	21st to end	Night	25% 9% 2 4 5% 3 3 5% 5% 7% 33%	2574
November	1st to 10th	Night	18% 7% 2 5% 5% 3 4 3 5% 7% 41%	2407
	11th to 20th	Night	18% 5% 2 5% 5% 3 5% 4 5% 7% 40%	2470
	21st to end	Night	17% 7% 2 6% 4 3 5% 4 5% 7% 39%	2550
December	1st to 10th	Night	22% 10% 4 6% 5% 3 4 5% 4 6% 32%	2850
	11th to 20th	Night	22% 8% 3 5% 4 3 4 4 5% 5% 37%	3531
	21st to end	Night	24% 10% 3 5% 5% 2 4 4 5% 5% 34%	4944

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% 7% 10% 20% 15% 1	1518
	11th to 20th	Day	51% 6% 11% 17% 12% 3	1456
	21st to end	Day	45% 5% 11% 19% 17% 2	1584
February	1st to 10th	Day	52% 6% 9% 19% 12% 2	1566
	11th to 20th	Day	51% 6% 11% 17% 12% 3	1743
	21st to end	Day	51% 6% 9% 17% 11% 5%	1480
March	1st to 10th	Day	49% 6% 11% 16% 14% 4	1800
	11th to 20th	Day	45% 4 9% 20% 17% 5%	1938
	21st to end	Day	46% 5% 9% 17% 18% 5%	2234
April	1st to 10th	Day	53% 4 8% 17% 15% 5%	2160
	11th to 20th	Day	45% 6% 9% 22% 15% 2	2234
	21st to end	Day	55% 5% 7% 17% 12% 4	2340
May	1st to 10th	Day	53% 5% 7% 20% 13% 2	2340
	11th to 20th	Day	50% 5% 7% 20% 15% 3	2366
	21st to end	Day	45% 8% 12% 21% 13% 2	2725
June	1st to 10th	Day	52% 7% 12% 20% 8% 1	2587
	11th to 20th	Day	44% 7% 11% 20% 15% 2	2700
	21st to end	Day	51% 9% 12% 17% 10% 1	2572
July	1st to 10th	Day	41% 9% 14% 22% 13%	2450
	11th to 20th	Day	44% 9% 13% 24% 10% 1	2445
	21st to end	Day	43% 8% 15% 22% 12%	2591
August	1st to 10th	Day	41% 9% 14% 26% 9%	2351
	11th to 20th	Day	42% 8% 14% 25% 11%	2304
	21st to end	Day	36% 8% 13% 24% 18% 1	2484
September	1st to 10th	Day	36% 7% 14% 26% 16% 1	2123
	11th to 20th	Day	33% 5% 8% 31% 20% 2	1980
	21st to end	Day	38% 6% 11% 28% 16% 1	1980
October	1st to 10th	Day	46% 6% 11% 22% 14% 1	1980
	11th to 20th	Day	44% 7% 13% 27% 9% 1	1720
	21st to end	Day	54% 5% 10% 16% 13% 1	1782
November	1st to 10th	Day	42% 5% 14% 22% 15% 2	1671
	11th to 20th	Day	44% 6% 10% 20% 16% 3	1710
	21st to end	Day	45% 4 16% 22% 12% 1	1626
December	1st to 10th	Day	54% 5% 9% 20% 11% 1	1330
	11th to 20th	Day	50% 5% 9% 19% 15% 3	1668
	21st to end	Day	57% 5% 10% 17% 8% 3	2706
January	1st to 10th	Night	47% 6% 11% 23% 13% 1	2649
	11th to 20th	Night	56% 5% 12% 16% 10% 2	2549
	21st to end	Night	45% 6% 9% 21% 17% 3	2772
February	1st to 10th	Night	52% 5% 12% 17% 12% 2	2393
	11th to 20th	Night	47% 5% 11% 20% 15% 3	2109
	21st to end	Night	47% 5% 9% 20% 15% 4	1776
March	1st to 10th	Night	49% 6% 8% 20% 14% 3	2160
	11th to 20th	Night	49% 7% 10% 16% 14% 4	2021
	21st to end	Night	46% 4 9% 18% 18% 4	2120
April	1st to 10th	Night	53% 4 8% 18% 15% 3	1800
	11th to 20th	Night	46% 6% 9% 22% 17% 1	1674
	21st to end	Night	52% 5% 11% 17% 12% 3	1620
May	1st to 10th	Night	51% 7% 8% 19% 14% 1	1620
	11th to 20th	Night	50% 5% 10% 19% 13% 3	1547
	21st to end	Night	49% 7% 12% 20% 11% 1	1551
June	1st to 10th	Night	51% 7% 11% 21% 9% 1	1364
	11th to 20th	Night	43% 7% 13% 23% 13% 2	1260
	21st to end	Night	49% 8% 14% 18% 10% 1	1378
July	1st to 10th	Night	41% 9% 15% 22% 12% 1	1400
	11th to 20th	Night	40% 5% 17% 28% 10%	1392
	21st to end	Night	40% 9% 16% 23% 11% 1	1486
August	1st to 10th	Night	40% 9% 15% 27% 9%	1543
	11th to 20th	Night	43% 7% 17% 20% 12%	1596
	21st to end	Night	35% 7% 14% 27% 16% 1	1869
September	1st to 10th	Night	34% 7% 14% 29% 15%	1836
	11th to 20th	Night	35% 5% 9% 32% 17% 2	1980
	21st to end	Night	39% 6% 10% 30% 14% 2	1980
October	1st to 10th	Night	44% 7% 11% 23% 14% 1	1980
	11th to 20th	Night	44% 7% 13% 25% 11% 1	2238
	21st to end	Night	51% 6% 11% 18% 13% 1	2574
November	1st to 10th	Night	44% 5% 12% 24% 14% 1	2407
	11th to 20th	Night	44% 5% 10% 23% 15% 3	2470
	21st to end	Night	44% 6% 14% 21% 13% 2	2550
December	1st to 10th	Night	54% 6% 9% 20% 11% 1	2850
	11th to 20th	Night	49% 5% 9% 18% 17% 1	3532
	21st to end	Night	51% 6% 11% 19% 11% 1	4944

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% 17% 33% 14% 5%	180
	11th to 20th	Day	32% 16% 33% 13% 5% 2	164
	21st to end	Day	22% 21% 32% 19% 6%	176
February	1st to 10th	Day	33% 16% 30% 19% 3	286
	11th to 20th	Day	27% 22% 32% 17% 2	410
	21st to end	Day	23% 21% 32% 20% 3	346
March	1st to 10th	Day	25% 20% 35% 16% 4	420
	11th to 20th	Day	28% 20% 32% 15% 3 1	420
	21st to end	Day	26% 19% 30% 15% 7% 3	462
April	1st to 10th	Day	35% 18% 28% 12% 6% 1	420
	11th to 20th	Day	30% 17% 31% 13% 6% 2	412
	21st to end	Day	33% 19% 29% 13% 5% 2	420
May	1st to 10th	Day	34% 18% 24% 18% 4 1	423
	11th to 20th	Day	23% 18% 34% 17% 6% 1	447
	21st to end	Day	22% 16% 34% 21% 6% 1	485
June	1st to 10th	Day	25% 13% 32% 20% 8% 2	517
	11th to 20th	Day	23% 13% 27% 23% 13% 2	630
	21st to end	Day	24% 12% 28% 23% 12% 2	502
July	1st to 10th	Day	20% 11% 31% 24% 12% 2	445
	11th to 20th	Day	16% 7% 36% 25% 12% 4	444
	21st to end	Day	15% 8% 35% 27% 10% 4	488
August	1st to 10th	Day	14% 9% 29% 29% 15% 3	446
	11th to 20th	Day	17% 9% 28% 26% 14% 6%	439
	21st to end	Day	15% 12% 30% 26% 13% 4	495
September	1st to 10th	Day	16% 10% 28% 24% 17% 4	450
	11th to 20th	Day	20% 9% 27% 22% 13% 8%	450
	21st to end	Day	18% 12% 29% 23% 14% 5%	450
October	1st to 10th	Day	22% 16% 22% 24% 12% 4	450
	11th to 20th	Day	26% 13% 29% 18% 12% 2	363
	21st to end	Day	35% 12% 26% 18% 9%	396
November	1st to 10th	Day	24% 12% 28% 24% 9% 2	365
	11th to 20th	Day	31% 12% 30% 19% 7% 1	370
	21st to end	Day	30% 19% 22% 22% 7% 1	366
December	1st to 10th	Day	33% 12% 34% 14% 7%	180
	11th to 20th	Day	34% 17% 35% 9% 4	180
	21st to end	Day	30% 20% 28% 16% 4 2	198
January	1st to 10th	Night	22% 13% 36% 25% 3	760
	11th to 20th	Night	26% 15% 32% 24% 4	729
	21st to end	Night	17% 17% 38% 25% 4	792
February	1st to 10th	Night	23% 16% 31% 26% 3	720
	11th to 20th	Night	21% 18% 37% 21% 3	703
	21st to end	Night	23% 13% 35% 27% 3	592
March	1st to 10th	Night	25% 13% 35% 25% 2	720
	11th to 20th	Night	24% 15% 32% 23% 7%	720
	21st to end	Night	24% 16% 32% 21% 6% 1	792
April	1st to 10th	Night	29% 15% 30% 22% 3	720
	11th to 20th	Night	22% 15% 35% 22% 6%	610
	21st to end	Night	32% 11% 32% 20% 4	540
May	1st to 10th	Night	27% 12% 29% 27% 5%	540
	11th to 20th	Night	25% 13% 33% 24% 5% 1	485
	21st to end	Night	20% 7% 33% 34% 5% 1	389
June	1st to 10th	Night	26% 6% 31% 31% 5%	360
	11th to 20th	Night	19% 6% 28% 35% 11%	360
	21st to end	Night	24% 2 29% 36% 8%	360
July	1st to 10th	Night	18% 3 28% 36% 15%	350
	11th to 20th	Night	18% 1 23% 42% 15% 1	348
	21st to end	Night	15% 3 26% 40% 15% 1	394
August	1st to 10th	Night	15% 4 23% 41% 17% 1	479
	11th to 20th	Night	16% 4 28% 36% 15% 1	532
	21st to end	Night	17% 5% 23% 37% 16% 2	681
September	1st to 10th	Night	14% 5% 31% 33% 16% 1	720
	11th to 20th	Night	20% 7% 24% 29% 16% 3	720
	21st to end	Night	20% 8% 28% 28% 14% 1	720
October	1st to 10th	Night	21% 9% 25% 31% 13% 1	720
	11th to 20th	Night	21% 11% 31% 27% 10% 1	720
	21st to end	Night	32% 11% 27% 24% 5%	792
November	1st to 10th	Night	23% 10% 30% 28% 8% 1	740
	11th to 20th	Night	23% 11% 30% 26% 9% 1	760
	21st to end	Night	24% 15% 28% 27% 6% 1	796
December	1st to 10th	Night	29% 10% 33% 22% 6%	850
	11th to 20th	Night	27% 14% 33% 22% 5%	850
	21st to end	Night	29% 14% 30% 23% 3	852

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