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 2024-11-03.

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% 9% 5% 5% 4 4 5% 6% 27%	101455
	Night	17% 12% 5% 10% 6% 4 4 3 4 5% 28%	97538
Transparency	Day	56% 4 10% 19% 9% 1	101213
	Night	58% 4 9% 18% 9% 1	97400
Seeing	Day	27% 17% 28% 17% 8% 3	14706
	Night	25% 16% 26% 22% 9% 1	23777

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% 19% 10% 18% 6% 4 4 3 3 3 17%	2517
	11th to 20th	Day	14% 19% 9% 18% 8% 8% 3 2 3 3 13%	2520
	21st to end	Day	15% 19% 11% 14% 6% 5% 5% 3 4 4 13%	2909
February	1st to 10th	Day	14% 18% 6% 13% 10% 7% 4 3 4 3 17%	1710
	11th to 20th	Day	12% 15% 9% 17% 9% 4 3 3 4 4 20%	1761
	21st to end	Day	17% 18% 7% 12% 7% 4 3 3 5% 4 20%	1570
March	1st to 10th	Day	21% 19% 6% 11% 5% 4 3 2 4 4 21%	3116
	11th to 20th	Day	11% 19% 11% 13% 5% 4 4 3 4 4 23%	3383
	21st to end	Day	17% 14% 4 11% 6% 3 3 3 3 4 31%	4096
April	1st to 10th	Day	19% 17% 4 8% 4 3 4 3 4 5% 29%	2280
	11th to 20th	Day	18% 13% 4 8% 4 5% 3 4 4 5% 31%	2254
	21st to end	Day	21% 14% 4 8% 4 4 4 3 4 5% 28%	2337
May	1st to 10th	Day	25% 11% 3 7% 4 4 4 3 5% 6% 28%	4327
	11th to 20th	Day	19% 10% 3 8% 5% 5% 6% 5% 6% 7% 26%	4398
	21st to end	Day	15% 7% 3 7% 5% 4 5% 4 6% 8% 36%	4837
June	1st to 10th	Day	19% 9% 4 7% 6% 5% 5% 5% 6% 7% 27%	2660
	11th to 20th	Day	20% 8% 2 7% 5% 4 5% 5% 7% 8% 29%	2660
	21st to end	Day	21% 8% 3 8% 5% 5% 5% 4 6% 7% 28%	2660
July	1st to 10th	Day	14% 7% 2 7% 5% 5% 6% 5% 7% 9% 33%	4440
	11th to 20th	Day	13% 8% 3 7% 5% 5% 6% 5% 9% 10% 30%	4440
	21st to end	Day	16% 6% 3 7% 6% 6% 5% 5% 6% 7% 33%	4814
August	1st to 10th	Day	20% 6% 2 6% 5% 5% 5% 4 7% 8% 32%	4342
	11th to 20th	Day	18% 8% 3 9% 5% 5% 6% 5% 7% 8% 26%	3826
	21st to end	Day	19% 6% 2 5% 4 5% 5% 5% 7% 8% 35%	4180
September	1st to 10th	Day	17% 6% 2 6% 4 5% 5% 4 5% 7% 38%	2280
	11th to 20th	Day	16% 7% 2 6% 4 4 4 3 6% 7% 41%	2233
	21st to end	Day	20% 8% 3 8% 4 5% 4 3 5% 8% 34%	2090
October	1st to 10th	Day	24% 12% 2 8% 5% 4 4 3 4 5% 27%	1919
	11th to 20th	Day	20% 13% 3 8% 4 3 4 3 6% 5% 31%	1900
	21st to end	Day	25% 17% 3 6% 5% 5% 5% 3 4 5% 23%	1921
November	1st to 10th	Day	14% 17% 3 9% 4 5% 4 4 5% 6% 29%	1689
	11th to 20th	Day	18% 17% 5% 10% 5% 3 3 4 4 5% 27%	1668
	21st to end	Day	19% 18% 7% 10% 5% 4 4 3 4 5% 21%	1520
December	1st to 10th	Day	18% 25% 9% 10% 5% 3 4 3 4 4 14%	1520
	11th to 20th	Day	21% 16% 7% 14% 6% 4 4 2 4 4 17%	1906
	21st to end	Day	19% 22% 10% 14% 4 3 4 2 3 4 15%	2772
January	1st to 10th	Night	15% 15% 10% 17% 8% 6% 4 3 3 3 17%	4429
	11th to 20th	Night	12% 13% 10% 19% 15% 6% 4 2 3 3 12%	4440
	21st to end	Night	18% 18% 7% 15% 6% 6% 5% 3 3 4 16%	4746
February	1st to 10th	Night	13% 15% 7% 16% 10% 6% 5% 3 5% 4 16%	2470
	11th to 20th	Night	12% 11% 6% 16% 8% 7% 5% 4 6% 5% 20%	2304
	21st to end	Night	15% 14% 5% 14% 7% 5% 5% 3 6% 6% 20%	1884
March	1st to 10th	Night	19% 15% 4 11% 6% 6% 4 3 4 5% 23%	3724
	11th to 20th	Night	14% 16% 8% 13% 5% 4 4 3 3 3 27%	3561
	21st to end	Night	16% 12% 6% 11% 6% 4 3 3 4 5% 30%	3535
April	1st to 10th	Night	20% 14% 5% 8% 4 4 4 4 4 6% 27%	1900
	11th to 20th	Night	18% 13% 4 6% 4 4 4 4 5% 7% 31%	1875
	21st to end	Night	19% 12% 4 7% 4 4 4 3 4 6% 33%	1843
May	1st to 10th	Night	24% 11% 3 7% 5% 4 4 3 5% 6% 28%	2642
	11th to 20th	Night	17% 12% 4 9% 5% 5% 4 3 4 5% 32%	2495
	21st to end	Night	16% 8% 3 6% 4 4 5% 5% 5% 7% 37%	2738
June	1st to 10th	Night	18% 8% 3 6% 4 4 5% 4 5% 8% 35%	1520
	11th to 20th	Night	20% 7% 2 5% 3 4 3 3 5% 8% 39%	1520
	21st to end	Night	18% 6% 3 7% 4 4 3 5% 6% 8% 36%	1520
July	1st to 10th	Night	12% 6% 2 9% 6% 5% 5% 5% 7% 6% 36%	2520
	11th to 20th	Night	17% 8% 2 6% 4 4 3 4 5% 7% 40%	2520
	21st to end	Night	14% 9% 3 6% 4 4 4 3 6% 7% 40%	2739
August	1st to 10th	Night	25% 8% 2 6% 4 3 4 3 4 5% 36%	2583
	11th to 20th	Night	21% 9% 2 7% 4 4 4 3 4 6% 38%	2971
	21st to end	Night	14% 6% 2 5% 5% 4 4 4 6% 7% 43%	3476
September	1st to 10th	Night	14% 7% 3 7% 4 4 4 4 5% 6% 42%	1900
	11th to 20th	Night	16% 7% 2 5% 3 4 3 3 4 5% 48%	1947
	21st to end	Night	19% 7% 2 6% 4 4 4 4 6% 8% 38%	2090
October	1st to 10th	Night	22% 9% 4 8% 5% 5% 4 3 5% 5% 30%	2257
	11th to 20th	Night	19% 12% 3 7% 5% 4 3 4 5% 5% 33%	2280
	21st to end	Night	23% 14% 3 8% 5% 4 5% 3 5% 5% 24%	2675
November	1st to 10th	Night	14% 14% 4 8% 5% 5% 4 3 5% 5% 33%	2434
	11th to 20th	Night	18% 15% 4 9% 5% 3 4 4 4 6% 27%	2508
	21st to end	Night	16% 16% 6% 10% 6% 4 5% 3 5% 6% 23%	2660
December	1st to 10th	Night	19% 20% 8% 12% 6% 4 4 3 5% 3 15%	2660
	11th to 20th	Night	19% 17% 7% 14% 6% 5% 4 3 4 4 16%	3288
	21st to end	Night	23% 18% 6% 14% 5% 4 3 3 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	68% 2 8% 12% 9% 1	3119
	11th to 20th	Day	64% 3 13% 11% 8% 2	3383
	21st to end	Day	58% 3 5% 16% 16% 2	4096
April	1st to 10th	Day	57% 4 6% 19% 11% 2	2280
	11th to 20th	Day	56% 3 8% 21% 11% 1	2254
	21st to end	Day	59% 3 7% 16% 11% 3	2337
May	1st to 10th	Day	58% 3 9% 21% 8% 1	4341
	11th to 20th	Day	56% 2 11% 22% 7% 1	4402
	21st to end	Day	46% 4 13% 27% 10% 1	4837
June	1st to 10th	Day	54% 5% 12% 20% 10%	2660
	11th to 20th	Day	50% 4 13% 22% 9% 1	2660
	21st to end	Day	54% 5% 13% 19% 8% 1	2660
July	1st to 10th	Day	43% 7% 15% 24% 10%	4370
	11th to 20th	Day	43% 7% 15% 27% 7%	4365
	21st to end	Day	48% 6% 13% 25% 8%	4661
August	1st to 10th	Day	48% 5% 15% 20% 12%	4328
	11th to 20th	Day	50% 8% 15% 22% 5%	3865
	21st to end	Day	43% 7% 14% 29% 7%	4180
September	1st to 10th	Day	44% 5% 10% 29% 11% 1	2280
	11th to 20th	Day	42% 4 10% 27% 16% 1	2233
	21st to end	Day	49% 3 10% 24% 12% 1	2090
October	1st to 10th	Day	58% 4 8% 18% 11% 1	1919
	11th to 20th	Day	54% 4 12% 21% 8% 1	1900
	21st to end	Day	63% 5% 8% 14% 9% 1	1921
November	1st to 10th	Day	54% 5% 11% 18% 11%	1689
	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	65% 3 6% 16% 9% 2	3734
	11th to 20th	Night	63% 3 8% 19% 7% 1	3562
	21st to end	Night	58% 3 6% 17% 14% 3	3535
April	1st to 10th	Night	57% 5% 9% 19% 9% 2	1900
	11th to 20th	Night	52% 5% 9% 20% 13%	1875
	21st to end	Night	53% 3 9% 18% 14% 3	1843
May	1st to 10th	Night	59% 2 9% 18% 11% 1	2648
	11th to 20th	Night	55% 2 11% 22% 8% 1	2496
	21st to end	Night	47% 3 12% 22% 14% 1	2739
June	1st to 10th	Night	46% 4 12% 24% 12% 1	1520
	11th to 20th	Night	44% 4 15% 25% 11% 1	1520
	21st to end	Night	45% 6% 14% 25% 10%	1520
July	1st to 10th	Night	45% 6% 13% 20% 14% 1	2480
	11th to 20th	Night	43% 7% 13% 25% 12%	2472
	21st to end	Night	42% 5% 11% 30% 11% 1	2651
August	1st to 10th	Night	51% 4 14% 23% 8%	2573
	11th to 20th	Night	48% 4 14% 27% 7%	2998
	21st to end	Night	36% 6% 15% 33% 9%	3476
September	1st to 10th	Night	41% 5% 13% 28% 12% 1	1900
	11th to 20th	Night	38% 3 10% 30% 18% 1	1947
	21st to end	Night	44% 4 12% 25% 13% 2	2090
October	1st to 10th	Night	56% 3 10% 19% 12% 1	2257
	11th to 20th	Night	52% 5% 13% 20% 8% 2	2280
	21st to end	Night	60% 5% 10% 14% 9% 1	2675
November	1st to 10th	Night	52% 4 11% 17% 14% 2	2434
	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% 27% 10% 4 1	460
	21st to end	Day	35% 23% 22% 12% 6% 1	506
April	1st to 10th	Day	37% 23% 21% 13% 5% 1	460
	11th to 20th	Day	36% 21% 20% 14% 8% 2	452
	21st to end	Day	34% 18% 28% 12% 5% 2	460
May	1st to 10th	Day	35% 17% 26% 12% 5% 4	463
	11th to 20th	Day	23% 18% 31% 18% 8% 1	487
	21st to end	Day	22% 15% 29% 20% 12% 3	529
June	1st to 10th	Day	24% 15% 32% 19% 9% 1	490
	11th to 20th	Day	22% 14% 31% 23% 9% 1	490
	21st to end	Day	25% 16% 29% 21% 6% 2	490
July	1st to 10th	Day	18% 9% 29% 28% 13% 2	485
	11th to 20th	Day	16% 8% 33% 29% 12% 2	484
	21st to end	Day	17% 10% 37% 25% 9% 2	532
August	1st to 10th	Day	19% 10% 26% 28% 12% 6%	486
	11th to 20th	Day	21% 11% 25% 24% 13% 6%	479
	21st to end	Day	17% 14% 29% 22% 11% 7%	539
September	1st to 10th	Day	19% 9% 26% 21% 17% 8%	490
	11th to 20th	Day	16% 10% 27% 20% 14% 13%	490
	21st to end	Day	22% 12% 29% 19% 13% 5%	490
October	1st to 10th	Day	30% 13% 24% 17% 12% 3	490
	11th to 20th	Day	27% 18% 26% 21% 7% 1	490
	21st to end	Day	36% 15% 26% 18% 5%	449
November	1st to 10th	Day	32% 16% 24% 18% 9%	371
	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% 22% 28% 19% 6% 1	836
April	1st to 10th	Night	29% 17% 32% 20% 3	760
	11th to 20th	Night	26% 18% 32% 17% 7% 1	751
	21st to end	Night	29% 16% 26% 22% 6% 1	703
May	1st to 10th	Night	29% 13% 25% 23% 9% 1	456
	11th to 20th	Night	20% 14% 28% 32% 7% 1	374
	21st to end	Night	19% 7% 27% 32% 14% 1	411
June	1st to 10th	Night	21% 9% 24% 32% 13% 1	380
	11th to 20th	Night	20% 11% 21% 34% 14%	380
	21st to end	Night	21% 6% 27% 31% 14%	380
July	1st to 10th	Night	15% 5% 19% 38% 22% 1	370
	11th to 20th	Night	14% 6% 21% 39% 19% 2	368
	21st to end	Night	14% 6% 23% 41% 15% 1	416
August	1st to 10th	Night	16% 6% 19% 35% 23% 2	416
	11th to 20th	Night	19% 6% 19% 30% 23% 3	672
	21st to end	Night	17% 6% 20% 36% 19% 2	836
September	1st to 10th	Night	17% 9% 22% 30% 20% 2	760
	11th to 20th	Night	19% 8% 19% 28% 21% 6%	760
	21st to end	Night	21% 11% 24% 26% 17% 2	760
October	1st to 10th	Night	27% 14% 22% 22% 15% 1	760
	11th to 20th	Night	27% 14% 24% 27% 8% 1	760
	21st to end	Night	32% 15% 28% 20% 5%	836
November	1st to 10th	Night	22% 19% 28% 23% 8% 1	749
	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 2024-10-31 03:39:27. Version ac07

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