Muskegon Astronomical Society
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Muskegon Astronomical Society clear sky chart from 2005-11-06 to 2024-11-08.

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	13% 10% 4 8% 5% 5% 4 4 5% 7% 35%	101315
	Night	15% 12% 4 9% 5% 4 4 3 5% 6% 32%	97840
Transparency	Day	49% 4 11% 22% 13% 1	104886
	Night	53% 3 10% 21% 12% 1	102410
Seeing	Day	19% 15% 30% 22% 11% 4	15869
	Night	19% 10% 28% 29% 12% 1	25717

By Month

Percentage Cloud Cover SE (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	14% 25% 12% 13% 7% 5% 4 3 3 4 10%	2527
	11th to 20th	Day	13% 18% 8% 19% 14% 9% 4 3 3 3 6%	2530
	21st to end	Day	20% 24% 9% 17% 6% 4 4 2 2 3 8%	2783
February	1st to 10th	Day	11% 18% 6% 14% 11% 7% 5% 3 4 4 17%	1718
	11th to 20th	Day	12% 16% 7% 15% 9% 6% 5% 3 5% 5% 19%	1848
	21st to end	Day	13% 17% 6% 12% 6% 6% 5% 4 5% 5% 21%	1570
March	1st to 10th	Day	15% 13% 5% 8% 5% 5% 4 4 5% 6% 31%	3120
	11th to 20th	Day	11% 7% 6% 11% 7% 5% 4 4 4 6% 35%	3351
	21st to end	Day	20% 12% 6% 9% 5% 3 4 3 4 5% 28%	4000
April	1st to 10th	Day	18% 13% 4 8% 4 3 4 4 4 7% 30%	2280
	11th to 20th	Day	18% 11% 3 6% 4 4 4 3 4 6% 35%	2298
	21st to end	Day	17% 8% 3 7% 5% 4 4 3 5% 7% 35%	2470
May	1st to 10th	Day	17% 7% 2 6% 4 4 5% 4 5% 8% 39%	4082
	11th to 20th	Day	13% 7% 2 6% 4 4 4 3 6% 8% 42%	4163
	21st to end	Day	10% 6% 2 6% 4 4 4 4 6% 9% 45%	4824
June	1st to 10th	Day	10% 6% 2 6% 4 5% 5% 4 6% 8% 44%	2660
	11th to 20th	Day	11% 4 2 6% 4 5% 4 4 5% 9% 47%	2660
	21st to end	Day	13% 5% 2 5% 4 4 5% 3 6% 9% 43%	2660
July	1st to 10th	Day	12% 7% 3 7% 4 4 5% 4 5% 9% 40%	4440
	11th to 20th	Day	6% 4 1 4 3 4 4 4 6% 9% 54%	4440
	21st to end	Day	7% 5% 2 6% 4 5% 5% 4 7% 9% 47%	4813
August	1st to 10th	Day	11% 5% 2 6% 5% 5% 6% 4 6% 8% 42%	4204
	11th to 20th	Day	12% 5% 1 5% 4 4 4 3 6% 7% 49%	4044
	21st to end	Day	9% 6% 2 6% 4 5% 5% 4 6% 8% 46%	4197
September	1st to 10th	Day	10% 6% 2 7% 5% 5% 5% 3 5% 7% 46%	2267
	11th to 20th	Day	12% 4 1 6% 4 4 4 3 6% 8% 47%	2090
	21st to end	Day	13% 7% 2 6% 5% 4 5% 4 5% 7% 41%	2090
October	1st to 10th	Day	16% 6% 2 7% 4 4 4 3 5% 7% 42%	2090
	11th to 20th	Day	20% 11% 3 8% 5% 5% 5% 5% 5% 7% 25%	1834
	21st to end	Day	22% 12% 3 9% 6% 6% 5% 3 4 7% 24%	1881
November	1st to 10th	Day	14% 11% 4 8% 4 4 5% 3 5% 6% 34%	1735
	11th to 20th	Day	15% 21% 6% 10% 6% 4 4 3 5% 6% 21%	1710
	21st to end	Day	21% 20% 5% 9% 5% 4 4 2 4 6% 21%	1710
December	1st to 10th	Day	14% 23% 9% 15% 7% 4 4 2 4 4 13%	1525
	11th to 20th	Day	14% 21% 9% 14% 8% 4 5% 4 5% 5% 12%	1918
	21st to end	Day	22% 24% 8% 13% 6% 5% 3 3 4 4 9%	2783
January	1st to 10th	Night	14% 24% 9% 15% 7% 5% 3 2 4 3 14%	4428
	11th to 20th	Night	13% 18% 10% 19% 11% 8% 4 2 3 3 9%	4440
	21st to end	Night	20% 22% 9% 16% 7% 4 4 3 3 3 9%	4884
February	1st to 10th	Night	12% 17% 6% 14% 11% 5% 5% 3 4 5% 18%	2458
	11th to 20th	Night	13% 15% 7% 12% 8% 6% 5% 4 5% 6% 22%	2218
	21st to end	Night	16% 14% 5% 11% 6% 6% 4 4 5% 5% 24%	1884
March	1st to 10th	Night	17% 10% 4 7% 5% 4 4 3 4 6% 36%	3733
	11th to 20th	Night	9% 8% 3 7% 5% 4 4 3 6% 8% 42%	3608
	21st to end	Night	16% 13% 5% 9% 6% 5% 5% 3 5% 6% 27%	3660
April	1st to 10th	Night	16% 11% 3 7% 4 5% 4 3 5% 7% 34%	1900
	11th to 20th	Night	19% 9% 4 6% 4 4 5% 3 5% 5% 36%	1829
	21st to end	Night	16% 10% 3 7% 4 4 4 3 5% 7% 38%	1710
May	1st to 10th	Night	14% 8% 3 8% 5% 5% 5% 3 5% 7% 37%	2813
	11th to 20th	Night	16% 6% 2 6% 5% 4 5% 4 5% 8% 38%	2730
	21st to end	Night	16% 8% 3 7% 4 4 3 4 4 6% 41%	2743
June	1st to 10th	Night	12% 5% 2 4 5% 3 4 5% 7% 8% 44%	1520
	11th to 20th	Night	10% 5% 2 6% 4 4 4 4 6% 8% 46%	1520
	21st to end	Night	10% 6% 2 6% 4 5% 3 4 6% 9% 46%	1520
July	1st to 10th	Night	10% 7% 2 7% 6% 4 6% 4 6% 8% 40%	2530
	11th to 20th	Night	6% 4 1 5% 4 4 4 4 5% 8% 55%	2530
	21st to end	Night	7% 5% 3 6% 4 4 4 3 6% 7% 51%	2750
August	1st to 10th	Night	9% 5% 2 6% 3 3 4 3 5% 9% 50%	2726
	11th to 20th	Night	11% 4 2 5% 3 3 5% 3 5% 7% 51%	2785
	21st to end	Night	8% 6% 3 6% 4 4 5% 4 6% 8% 47%	3442
September	1st to 10th	Night	9% 5% 2 6% 3 4 5% 4 5% 7% 51%	1900
	11th to 20th	Night	10% 5% 2 5% 3 3 4 3 5% 6% 55%	2082
	21st to end	Night	14% 6% 3 7% 4 4 4 3 5% 8% 42%	2090
October	1st to 10th	Night	17% 6% 2 6% 3 3 3 3 5% 6% 47%	2090
	11th to 20th	Night	21% 11% 3 7% 4 4 3 3 4 6% 34%	2343
	21st to end	Night	23% 9% 3 7% 4 4 4 3 4 8% 31%	2717
November	1st to 10th	Night	16% 10% 3 7% 5% 4 4 4 5% 6% 36%	2504
	11th to 20th	Night	16% 15% 5% 9% 6% 5% 5% 4 7% 7% 21%	2470
	21st to end	Night	18% 18% 5% 9% 6% 4 3 3 5% 6% 23%	2470
December	1st to 10th	Night	16% 19% 8% 14% 7% 5% 4 4 4 5% 14%	2650
	11th to 20th	Night	15% 22% 7% 13% 7% 5% 5% 3 5% 4 15%	3279
	21st to end	Night	25% 22% 7% 11% 5% 4 4 3 4 4 13%	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	82% 2 7% 8% 1	2528
	11th to 20th	Day	85% 3 5% 5% 2	2530
	21st to end	Day	85% 2 7% 5% 2	2783
February	1st to 10th	Day	71% 4 7% 15% 3	1718
	11th to 20th	Day	68% 4 8% 14% 6%	1858
	21st to end	Day	65% 4 11% 15% 5%	1570
March	1st to 10th	Day	55% 3 13% 21% 8% 1	3120
	11th to 20th	Day	51% 3 15% 20% 11% 1	3351
	21st to end	Day	59% 2 10% 20% 8% 1	4000
April	1st to 10th	Day	55% 3 9% 21% 11%	2280
	11th to 20th	Day	50% 4 9% 21% 14% 2	2298
	21st to end	Day	49% 3 12% 21% 14% 2	2470
May	1st to 10th	Day	44% 2 9% 27% 17% 1	4120
	11th to 20th	Day	40% 2 13% 25% 17% 3	4167
	21st to end	Day	36% 3 12% 25% 23% 2	4837
June	1st to 10th	Day	36% 4 11% 29% 18% 2	2660
	11th to 20th	Day	34% 4 14% 25% 22% 1	2660
	21st to end	Day	37% 4 15% 25% 17% 2	2660
July	1st to 10th	Day	42% 4 13% 24% 14% 3	4371
	11th to 20th	Day	26% 5% 15% 33% 20% 2	4365
	21st to end	Day	32% 6% 14% 24% 22% 2	4662
August	1st to 10th	Day	38% 4 11% 31% 14% 1	4189
	11th to 20th	Day	33% 5% 12% 32% 17% 1	4083
	21st to end	Day	35% 5% 15% 26% 17% 2	4196
September	1st to 10th	Day	38% 4 13% 28% 15% 2	2267
	11th to 20th	Day	35% 4 12% 31% 16% 2	2090
	21st to end	Day	42% 5% 11% 27% 15%	2090
October	1st to 10th	Day	29% 3 8% 39% 19% 2	3480
	11th to 20th	Day	45% 4 13% 25% 13%	3024
	21st to end	Day	53% 3 14% 21% 8%	3081
November	1st to 10th	Day	51% 5% 12% 21% 11%	1735
	11th to 20th	Day	66% 3 12% 14% 5%	1710
	21st to end	Day	66% 4 13% 13% 4	1710
December	1st to 10th	Day	76% 4 8% 10% 2	1525
	11th to 20th	Day	77% 3 11% 8% 1	1915
	21st to end	Day	81% 2 7% 7% 2	2783
January	1st to 10th	Night	77% 3 6% 9% 4	4428
	11th to 20th	Night	84% 3 5% 6% 2	4440
	21st to end	Night	83% 3 7% 6% 2	4884
February	1st to 10th	Night	70% 3 8% 13% 6%	2458
	11th to 20th	Night	65% 4 7% 17% 7%	2219
	21st to end	Night	62% 4 12% 15% 7% 1	1884
March	1st to 10th	Night	50% 3 14% 25% 7% 1	3733
	11th to 20th	Night	41% 3 13% 26% 15% 2	3608
	21st to end	Night	60% 1 8% 20% 9% 1	3660
April	1st to 10th	Night	50% 3 10% 22% 14% 1	1900
	11th to 20th	Night	50% 3 6% 20% 18% 3	1829
	21st to end	Night	47% 3 10% 22% 14% 4	1710
May	1st to 10th	Night	49% 2 12% 20% 15% 3	2840
	11th to 20th	Night	45% 3 8% 25% 16% 3	2731
	21st to end	Night	46% 3 8% 19% 20% 4	2751
June	1st to 10th	Night	36% 4 11% 30% 15% 3	1520
	11th to 20th	Night	35% 4 13% 26% 20% 2	1520
	21st to end	Night	35% 4 15% 26% 16% 3	1520
July	1st to 10th	Night	42% 5% 10% 25% 12% 7%	2490
	11th to 20th	Night	28% 4 13% 30% 23% 2	2482
	21st to end	Night	33% 4 13% 22% 25% 2	2662
August	1st to 10th	Night	32% 4 13% 29% 20% 1	2717
	11th to 20th	Night	33% 4 9% 35% 18% 1	2812
	21st to end	Night	35% 5% 10% 28% 20% 2	3442
September	1st to 10th	Night	33% 5% 10% 31% 19% 2	1900
	11th to 20th	Night	30% 3 10% 36% 19% 1	2082
	21st to end	Night	42% 3 11% 29% 13% 1	2090
October	1st to 10th	Night	32% 2 8% 36% 20% 2	3480
	11th to 20th	Night	41% 3 12% 28% 16%	3892
	21st to end	Night	45% 3 11% 29% 13%	4467
November	1st to 10th	Night	50% 4 10% 23% 12% 1	2504
	11th to 20th	Night	62% 4 11% 16% 6% 1	2470
	21st to end	Night	64% 3 14% 14% 3	2470
December	1st to 10th	Night	74% 4 9% 10% 3	2650
	11th to 20th	Night	73% 4 10% 9% 3	3281
	21st to end	Night	77% 3 10% 7% 2	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	21% 18% 35% 19% 5% 1	270
	11th to 20th	Day	27% 16% 37% 15% 4 1	270
	21st to end	Day	28% 19% 32% 18% 3	297
February	1st to 10th	Day	21% 29% 29% 16% 4 1	270
	11th to 20th	Day	22% 29% 32% 14% 2	270
	21st to end	Day	27% 31% 34% 6% 2	225
March	1st to 10th	Day	23% 32% 34% 9% 2	270
	11th to 20th	Day	24% 19% 31% 18% 9%	383
	21st to end	Day	30% 15% 29% 19% 5% 1	506
April	1st to 10th	Day	28% 17% 32% 17% 5% 1	460
	11th to 20th	Day	30% 23% 23% 15% 7% 2	452
	21st to end	Day	24% 17% 30% 18% 9% 1	460
May	1st to 10th	Day	23% 16% 33% 19% 6% 2	463
	11th to 20th	Day	20% 13% 31% 21% 11% 3	530
	21st to end	Day	15% 14% 29% 26% 12% 4	734
June	1st to 10th	Day	12% 12% 39% 25% 9% 4	680
	11th to 20th	Day	15% 10% 34% 26% 10% 4	680
	21st to end	Day	16% 9% 37% 24% 9% 4	680
July	1st to 10th	Day	8% 7% 30% 31% 18% 7%	671
	11th to 20th	Day	7% 9% 30% 33% 14% 6%	668
	21st to end	Day	9% 6% 32% 30% 16% 7%	739
August	1st to 10th	Day	11% 6% 26% 28% 20% 10%	548
	11th to 20th	Day	12% 4 22% 31% 20% 11%	479
	21st to end	Day	13% 7% 24% 30% 18% 8%	539
September	1st to 10th	Day	14% 9% 27% 26% 19% 6%	490
	11th to 20th	Day	10% 6% 23% 26% 27% 8%	490
	21st to end	Day	16% 13% 24% 26% 16% 6%	490
October	1st to 10th	Day	18% 13% 25% 26% 16% 3	490
	11th to 20th	Day	26% 19% 30% 22% 4	367
	21st to end	Day	33% 20% 31% 11% 3 2	330
November	1st to 10th	Day	25% 22% 31% 15% 5% 2	291
	11th to 20th	Day	23% 27% 37% 9% 4	270
	21st to end	Day	29% 20% 37% 12% 2	270
December	1st to 10th	Day	28% 25% 28% 14% 6%	270
	11th to 20th	Day	24% 29% 31% 12% 3 1	270
	21st to end	Day	29% 23% 35% 10% 3	297
January	1st to 10th	Night	22% 15% 31% 25% 6% 1	950
	11th to 20th	Night	25% 15% 31% 23% 6% 1	950
	21st to end	Night	22% 10% 34% 28% 6%	1045
February	1st to 10th	Night	18% 16% 35% 26% 4 1	824
	11th to 20th	Night	21% 15% 32% 26% 5% 1	743
	21st to end	Night	25% 16% 35% 21% 3	628
March	1st to 10th	Night	20% 13% 32% 26% 8% 1	760
	11th to 20th	Night	19% 13% 34% 26% 8% 1	760
	21st to end	Night	22% 10% 29% 30% 8% 1	743
April	1st to 10th	Night	19% 10% 34% 29% 6% 1	570
	11th to 20th	Night	27% 10% 30% 25% 7% 1	563
	21st to end	Night	22% 10% 33% 26% 9% 1	570
May	1st to 10th	Night	19% 8% 32% 32% 8% 1	570
	11th to 20th	Night	18% 8% 31% 30% 12% 1	561
	21st to end	Night	16% 6% 26% 34% 17% 2	617
June	1st to 10th	Night	12% 5% 29% 39% 13% 1	570
	11th to 20th	Night	13% 4 30% 36% 16% 1	570
	21st to end	Night	12% 6% 23% 40% 18% 1	570
July	1st to 10th	Night	9% 2 19% 41% 27% 3	555
	11th to 20th	Night	6% 4 22% 39% 26% 2	552
	21st to end	Night	9% 2 19% 40% 27% 2	624
August	1st to 10th	Night	8% 2 17% 45% 26% 2	567
	11th to 20th	Night	10% 3 13% 43% 26% 5%	564
	21st to end	Night	11% 2 19% 41% 25% 2	627
September	1st to 10th	Night	10% 5% 19% 39% 23% 4	570
	11th to 20th	Night	11% 5% 20% 33% 27% 4	752
	21st to end	Night	16% 9% 22% 30% 19% 4	760
October	1st to 10th	Night	19% 6% 23% 34% 16% 1	760
	11th to 20th	Night	26% 11% 27% 26% 10% 1	760
	21st to end	Night	27% 11% 29% 25% 8%	836
November	1st to 10th	Night	22% 11% 32% 26% 9% 1	771
	11th to 20th	Night	25% 17% 31% 21% 5% 1	760
	21st to end	Night	26% 13% 29% 27% 4	760
December	1st to 10th	Night	24% 15% 33% 22% 5%	940
	11th to 20th	Night	25% 15% 33% 21% 4 1	950
	21st to end	Night	30% 14% 33% 20% 3	1045

Page generated at 2024-11-05 08:15:49. Version ac07

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