Morehouse Lake Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Morehouse Lake Observatory clear sky chart from 2005-11-06 to 2024-03-23.

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% 12% 5% 8% 6% 3 5% 5% 5% 6% 27%	78567
	Night	17% 12% 6% 9% 7% 4 4 4 4 5% 27%	81314
Transparency	Day	58% 4 10% 18% 9% 1	78272
	Night	58% 4 9% 17% 10% 1	81143
Seeing	Day	27% 17% 28% 17% 8% 3	13817
	Night	25% 17% 27% 22% 9% 1	23081

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	12% 18% 11% 16% 8% 3 4 4 3 3 17%	2517
	11th to 20th	Day	14% 19% 9% 16% 10% 7% 4 3 3 3 13%	2520
	21st to end	Day	16% 18% 11% 13% 8% 4 5% 4 4 4 14%	2909
February	1st to 10th	Day	14% 16% 7% 12% 11% 5% 6% 4 4 4 17%	1710
	11th to 20th	Day	12% 14% 9% 16% 10% 3 4 4 4 4 20%	1761
	21st to end	Day	18% 16% 8% 10% 8% 4 3 4 4 5% 20%	1570
March	1st to 10th	Day	14% 13% 8% 12% 8% 4 4 4 5% 5% 24%	1897
	11th to 20th	Day	14% 17% 8% 10% 5% 3 3 3 5% 4 27%	2032
	21st to end	Day	20% 12% 4 7% 6% 3 3 4 3 5% 32%	2356
April	1st to 10th	Day	19% 14% 6% 8% 5% 3 4 4 4 5% 30%	2160
	11th to 20th	Day	18% 12% 5% 7% 5% 3 4 4 4 6% 33%	2134
	21st to end	Day	22% 14% 4 7% 5% 3 4 4 4 5% 27%	2214
May	1st to 10th	Day	23% 12% 4 8% 5% 3 3 4 4 6% 30%	2463
	11th to 20th	Day	21% 9% 3 5% 5% 3 4 5% 4 7% 33%	2478
	21st to end	Day	18% 7% 3 6% 6% 3 5% 5% 6% 8% 33%	2725
June	1st to 10th	Day	20% 8% 4 6% 6% 4 4 6% 6% 8% 28%	2520
	11th to 20th	Day	21% 7% 3 6% 5% 3 5% 6% 6% 8% 29%	2520
	21st to end	Day	20% 8% 3 6% 7% 4 6% 5% 6% 7% 28%	2520
July	1st to 10th	Day	17% 7% 3 6% 6% 4 5% 6% 6% 7% 34%	2520
	11th to 20th	Day	14% 8% 3 6% 5% 3 6% 7% 7% 8% 31%	2520
	21st to end	Day	16% 7% 3 6% 7% 5% 6% 6% 6% 7% 30%	2744
August	1st to 10th	Day	16% 6% 2 6% 7% 4 6% 5% 6% 8% 33%	2467
	11th to 20th	Day	17% 8% 3 7% 6% 4 5% 6% 7% 8% 27%	2183
	21st to end	Day	18% 7% 2 4 5% 4 5% 6% 6% 8% 34%	2376
September	1st to 10th	Day	18% 5% 3 5% 5% 3 6% 5% 5% 8% 37%	2160
	11th to 20th	Day	17% 8% 2 6% 4 3 4 4 6% 7% 40%	2116
	21st to end	Day	19% 7% 3 7% 5% 3 4 4 5% 8% 34%	1980
October	1st to 10th	Day	25% 11% 3 7% 6% 3 4 4 4 5% 27%	1818
	11th to 20th	Day	20% 12% 3 7% 6% 3 4 4 6% 5% 30%	1800
	21st to end	Day	27% 16% 4 5% 6% 4 5% 4 4 4 21%	1820
November	1st to 10th	Day	14% 16% 4 7% 6% 4 4 5% 5% 6% 29%	1671
	11th to 20th	Day	18% 16% 5% 9% 5% 3 4 4 4 5% 27%	1668
	21st to end	Day	19% 16% 8% 10% 6% 3 4 4 4 5% 22%	1520
December	1st to 10th	Day	18% 23% 11% 10% 6% 3 4 4 3 4 14%	1520
	11th to 20th	Day	21% 15% 8% 13% 8% 3 4 3 4 5% 17%	1906
	21st to end	Day	19% 21% 10% 13% 6% 2 4 3 3 4 15%	2772
January	1st to 10th	Night	15% 14% 11% 15% 10% 5% 4 3 3 3 17%	4429
	11th to 20th	Night	12% 13% 11% 16% 18% 5% 4 3 3 3 12%	4440
	21st to end	Night	18% 18% 7% 13% 7% 5% 5% 4 3 4 16%	4746
February	1st to 10th	Night	13% 14% 8% 14% 11% 4 6% 4 5% 4 16%	2470
	11th to 20th	Night	12% 10% 7% 14% 10% 4 6% 5% 6% 5% 20%	2304
	21st to end	Night	15% 12% 6% 12% 8% 4 5% 5% 6% 7% 20%	1884
March	1st to 10th	Night	14% 10% 5% 11% 9% 5% 6% 5% 4 6% 25%	2270
	11th to 20th	Night	15% 14% 6% 10% 7% 3 5% 4 4 4 28%	2145
	21st to end	Night	17% 12% 5% 7% 6% 3 5% 4 5% 6% 32%	2044
April	1st to 10th	Night	20% 12% 6% 7% 5% 3 4 5% 5% 6% 27%	1800
	11th to 20th	Night	17% 11% 5% 6% 5% 3 4 5% 5% 8% 31%	1775
	21st to end	Night	20% 11% 4 7% 5% 3 4 4 4 7% 32%	1746
May	1st to 10th	Night	22% 11% 5% 7% 6% 2 4 4 4 5% 31%	1512
	11th to 20th	Night	15% 11% 3 6% 4 4 5% 4 5% 7% 36%	1415
	21st to end	Night	16% 7% 3 6% 6% 3 4 6% 4 6% 38%	1550
June	1st to 10th	Night	19% 6% 3 4 5% 3 6% 5% 5% 8% 35%	1440
	11th to 20th	Night	21% 7% 2 5% 4 3 4 3 5% 8% 39%	1440
	21st to end	Night	17% 5% 3 6% 5% 3 4 5% 6% 8% 37%	1440
July	1st to 10th	Night	14% 5% 2 5% 5% 3 5% 6% 6% 7% 41%	1440
	11th to 20th	Night	13% 6% 2 5% 5% 3 4 6% 5% 8% 41%	1440
	21st to end	Night	12% 7% 3 5% 6% 4 4 4 6% 8% 42%	1574
August	1st to 10th	Night	14% 6% 2 5% 5% 3 5% 5% 6% 7% 42%	1467
	11th to 20th	Night	16% 7% 2 7% 6% 4 5% 5% 5% 7% 37%	1700
	21st to end	Night	14% 6% 2 4 6% 3 4 4 6% 7% 44%	1980
September	1st to 10th	Night	14% 6% 3 6% 5% 3 4 5% 6% 6% 42%	1800
	11th to 20th	Night	16% 7% 2 5% 4 3 4 4 4 6% 47%	1844
	21st to end	Night	19% 6% 3 5% 4 3 4 5% 6% 8% 39%	1980
October	1st to 10th	Night	22% 8% 4 7% 6% 4 4 4 5% 5% 31%	2138
	11th to 20th	Night	20% 11% 3 6% 6% 3 4 5% 5% 6% 31%	2160
	21st to end	Night	25% 13% 4 7% 7% 4 4 4 5% 5% 22%	2534
November	1st to 10th	Night	14% 13% 5% 7% 6% 4 4 4 5% 5% 33%	2407
	11th to 20th	Night	18% 14% 5% 8% 6% 3 5% 5% 4 6% 27%	2508
	21st to end	Night	16% 15% 7% 9% 6% 3 5% 5% 5% 6% 23%	2660
December	1st to 10th	Night	19% 18% 10% 12% 6% 3 4 4 5% 4 15%	2660
	11th to 20th	Night	20% 16% 7% 13% 7% 4 5% 3 4 4 17%	3288
	21st to end	Night	23% 18% 7% 13% 6% 3 4 4 3 5% 15%	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	74% 2 5% 12% 5% 1	2518
	11th to 20th	Day	78% 3 6% 7% 5% 2	2520
	21st to end	Day	76% 3 6% 10% 4 2	2909
February	1st to 10th	Day	71% 5% 6% 13% 5% 1	1710
	11th to 20th	Day	68% 5% 5% 12% 9% 1	1770
	21st to end	Day	66% 4 8% 13% 8% 1	1570
March	1st to 10th	Day	62% 3 10% 15% 9% 2	1900
	11th to 20th	Day	60% 3 9% 13% 11% 3	2032
	21st to end	Day	57% 3 7% 15% 15% 3	2356
April	1st to 10th	Day	57% 4 6% 19% 11% 3	2160
	11th to 20th	Day	54% 3 9% 22% 12% 1	2134
	21st to end	Day	59% 3 7% 16% 11% 3	2214
May	1st to 10th	Day	58% 3 7% 19% 11% 2	2463
	11th to 20th	Day	51% 4 8% 24% 12% 2	2482
	21st to end	Day	49% 5% 16% 20% 9% 1	2725
June	1st to 10th	Day	53% 5% 13% 19% 10%	2520
	11th to 20th	Day	51% 4 12% 22% 9% 1	2520
	21st to end	Day	53% 5% 14% 19% 8% 1	2520
July	1st to 10th	Day	48% 4 12% 24% 11%	2450
	11th to 20th	Day	47% 5% 14% 27% 6%	2445
	21st to end	Day	51% 5% 12% 22% 10%	2591
August	1st to 10th	Day	48% 4 15% 23% 10%	2453
	11th to 20th	Day	51% 5% 14% 22% 8%	2183
	21st to end	Day	46% 5% 12% 26% 10% 1	2376
September	1st to 10th	Day	45% 5% 11% 28% 11% 1	2160
	11th to 20th	Day	44% 4 10% 25% 16% 1	2116
	21st to end	Day	49% 3 10% 24% 12% 1	1980
October	1st to 10th	Day	59% 4 7% 17% 11% 1	1818
	11th to 20th	Day	55% 4 12% 21% 7% 1	1800
	21st to end	Day	66% 4 8% 12% 8% 1	1820
November	1st to 10th	Day	54% 5% 11% 18% 11%	1671
	11th to 20th	Day	59% 4 8% 15% 12% 2	1668
	21st to end	Day	65% 4 12% 12% 6% 1	1520
December	1st to 10th	Day	73% 4 8% 10% 4 1	1520
	11th to 20th	Day	73% 3 8% 11% 5%	1906
	21st to end	Day	76% 3 5% 7% 10%	2772
January	1st to 10th	Night	73% 3 6% 10% 7% 1	4429
	11th to 20th	Night	78% 4 6% 6% 5% 1	4440
	21st to end	Night	74% 3 5% 12% 6% 2	4746
February	1st to 10th	Night	69% 5% 7% 12% 6% 1	2470
	11th to 20th	Night	64% 6% 5% 15% 10% 1	2306
	21st to end	Night	62% 5% 8% 16% 8% 1	1884
March	1st to 10th	Night	60% 5% 9% 17% 9% 1	2280
	11th to 20th	Night	59% 4 8% 18% 10% 1	2146
	21st to end	Night	54% 4 9% 17% 13% 4	2044
April	1st to 10th	Night	56% 5% 9% 19% 9% 2	1800
	11th to 20th	Night	51% 5% 10% 21% 13% 1	1775
	21st to end	Night	53% 3 9% 19% 13% 3	1746
May	1st to 10th	Night	56% 3 8% 16% 14% 2	1512
	11th to 20th	Night	47% 4 10% 24% 13% 2	1416
	21st to end	Night	46% 5% 14% 23% 10% 2	1551
June	1st to 10th	Night	46% 4 13% 23% 12% 1	1440
	11th to 20th	Night	44% 4 15% 25% 11% 1	1440
	21st to end	Night	43% 6% 15% 26% 10%	1440
July	1st to 10th	Night	41% 5% 14% 26% 12% 2	1400
	11th to 20th	Night	41% 5% 16% 28% 10% 1	1392
	21st to end	Night	41% 4 13% 29% 11% 1	1486
August	1st to 10th	Night	41% 5% 16% 28% 9% 1	1457
	11th to 20th	Night	46% 4 16% 25% 10%	1700
	21st to end	Night	38% 4 15% 30% 12% 1	1980
September	1st to 10th	Night	41% 5% 13% 28% 11% 1	1800
	11th to 20th	Night	40% 3 10% 29% 18% 1	1844
	21st to end	Night	44% 3 11% 26% 13% 2	1980
October	1st to 10th	Night	56% 3 10% 18% 12% 1	2138
	11th to 20th	Night	53% 5% 13% 20% 7% 1	2160
	21st to end	Night	62% 5% 10% 13% 9% 1	2534
November	1st to 10th	Night	52% 4 11% 17% 14% 2	2407
	11th to 20th	Night	57% 5% 7% 18% 10% 2	2508
	21st to end	Night	60% 5% 11% 16% 7% 1	2660
December	1st to 10th	Night	71% 4 9% 10% 6%	2660
	11th to 20th	Night	71% 5% 7% 10% 7%	3288
	21st to end	Night	73% 3 7% 10% 8%	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% 18% 33% 14% 3 1	180
	11th to 20th	Day	35% 28% 27% 7% 2 1	180
	21st to end	Day	23% 30% 33% 11% 4	238
February	1st to 10th	Day	37% 28% 30% 4 1	270
	11th to 20th	Day	35% 31% 28% 5% 1	368
	21st to end	Day	37% 21% 28% 12% 1	382
March	1st to 10th	Day	30% 24% 31% 12% 3	460
	11th to 20th	Day	32% 26% 28% 10% 4 1	460
	21st to end	Day	36% 23% 22% 13% 6% 1	470
April	1st to 10th	Day	35% 24% 20% 14% 5% 1	420
	11th to 20th	Day	33% 20% 22% 15% 8% 2	412
	21st to end	Day	35% 18% 29% 12% 5% 2	420
May	1st to 10th	Day	35% 18% 26% 11% 6% 4	423
	11th to 20th	Day	24% 19% 32% 17% 7% 2	447
	21st to end	Day	22% 14% 29% 19% 12% 3	485
June	1st to 10th	Day	25% 14% 32% 19% 9% 1	450
	11th to 20th	Day	23% 14% 31% 22% 9% 1	450
	21st to end	Day	23% 16% 30% 23% 7% 2	450
July	1st to 10th	Day	19% 9% 27% 29% 14% 2	445
	11th to 20th	Day	16% 8% 32% 29% 13% 2	444
	21st to end	Day	17% 10% 36% 25% 9% 2	488
August	1st to 10th	Day	17% 10% 25% 29% 13% 6%	446
	11th to 20th	Day	21% 10% 25% 24% 13% 7%	439
	21st to end	Day	17% 15% 27% 23% 11% 7%	495
September	1st to 10th	Day	19% 10% 26% 21% 17% 8%	450
	11th to 20th	Day	17% 10% 28% 19% 14% 12%	450
	21st to end	Day	21% 12% 29% 18% 14% 5%	450
October	1st to 10th	Day	31% 13% 23% 17% 13% 3	450
	11th to 20th	Day	27% 17% 27% 21% 7% 1	450
	21st to end	Day	37% 16% 24% 19% 5%	414
November	1st to 10th	Day	32% 16% 24% 19% 10%	365
	11th to 20th	Day	33% 24% 26% 13% 3 1	328
	21st to end	Day	38% 22% 27% 12% 1	180
December	1st to 10th	Day	36% 23% 31% 7% 3	180
	11th to 20th	Day	42% 18% 31% 7% 3	180
	21st to end	Day	38% 23% 28% 10% 2	198
January	1st to 10th	Night	29% 24% 29% 15% 3	760
	11th to 20th	Night	31% 20% 29% 16% 3	760
	21st to end	Night	22% 23% 33% 17% 4	836
February	1st to 10th	Night	24% 25% 34% 14% 1	760
	11th to 20th	Night	25% 28% 30% 14% 2	743
	21st to end	Night	29% 22% 32% 14% 2	628
March	1st to 10th	Night	25% 22% 32% 18% 2	760
	11th to 20th	Night	30% 21% 30% 16% 3 1	760
	21st to end	Night	25% 21% 28% 19% 6% 1	801
April	1st to 10th	Night	29% 16% 31% 20% 3	720
	11th to 20th	Night	25% 17% 32% 18% 7% 1	711
	21st to end	Night	29% 16% 26% 22% 7% 1	666
May	1st to 10th	Night	28% 13% 25% 23% 9% 1	432
	11th to 20th	Night	20% 14% 29% 30% 6% 1	354
	21st to end	Night	20% 6% 27% 33% 14% 1	389
June	1st to 10th	Night	22% 9% 24% 31% 14% 1	360
	11th to 20th	Night	20% 11% 21% 34% 14%	360
	21st to end	Night	19% 6% 27% 33% 15%	360
July	1st to 10th	Night	15% 5% 18% 37% 23% 1	350
	11th to 20th	Night	14% 5% 21% 38% 20% 2	348
	21st to end	Night	14% 6% 24% 40% 16% 1	394
August	1st to 10th	Night	14% 5% 19% 35% 24% 2	393
	11th to 20th	Night	18% 5% 19% 30% 23% 3	636
	21st to end	Night	16% 6% 20% 36% 19% 2	792
September	1st to 10th	Night	16% 9% 22% 31% 20% 2	720
	11th to 20th	Night	20% 8% 20% 28% 19% 5%	720
	21st to end	Night	21% 11% 24% 25% 17% 2	720
October	1st to 10th	Night	27% 14% 22% 22% 14% 1	720
	11th to 20th	Night	28% 14% 24% 27% 7% 1	720
	21st to end	Night	33% 15% 27% 21% 4	792
November	1st to 10th	Night	22% 18% 29% 23% 8% 1	740
	11th to 20th	Night	29% 18% 27% 18% 7% 1	760
	21st to end	Night	28% 19% 29% 18% 5% 1	760
December	1st to 10th	Night	32% 24% 25% 15% 3	760
	11th to 20th	Night	34% 23% 23% 16% 4 1	760
	21st to end	Night	33% 25% 26% 13% 2	836

Page generated at 2024-03-19 23:31:09. Version ac07

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