McKim Alpena County Observation Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the McKim Alpena County Observation Site clear sky chart from 2005-11-06 to 2024-12-09.

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 5% 7% 32%	101560
	Night	13% 12% 4 9% 5% 5% 5% 4 5% 6% 32%	98304
Transparency	Day	49% 7% 11% 20% 12% 1	105083
	Night	50% 7% 13% 20% 10% 1	102857
Seeing	Day	20% 16% 32% 20% 8% 3	15597
	Night	19% 13% 32% 26% 9% 1	25116

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	14% 17% 8% 14% 6% 5% 4 4 4 5% 19%	2527
	11th to 20th	Day	13% 17% 7% 17% 10% 7% 5% 4 4 4 11%	2530
	21st to end	Day	18% 21% 7% 12% 6% 5% 4 3 6% 4 13%	2814
February	1st to 10th	Day	11% 16% 6% 12% 11% 7% 4 4 4 5% 19%	1710
	11th to 20th	Day	11% 15% 6% 14% 8% 4 6% 3 5% 5% 22%	1760
	21st to end	Day	11% 17% 6% 13% 8% 6% 5% 4 4 5% 22%	1570
March	1st to 10th	Day	13% 13% 4 10% 5% 5% 5% 4 5% 5% 32%	3141
	11th to 20th	Day	10% 14% 6% 11% 6% 5% 5% 3 5% 6% 27%	3480
	21st to end	Day	15% 14% 5% 11% 7% 5% 5% 3 5% 5% 24%	3815
April	1st to 10th	Day	17% 17% 4 8% 5% 4 3 3 5% 5% 28%	2262
	11th to 20th	Day	19% 13% 3 7% 4 4 4 3 5% 6% 33%	2423
	21st to end	Day	16% 12% 3 8% 5% 4 3 4 4 7% 33%	2470
May	1st to 10th	Day	15% 8% 3 7% 5% 4 5% 4 5% 8% 36%	4108
	11th to 20th	Day	13% 7% 2 6% 4 4 5% 4 5% 8% 42%	4081
	21st to end	Day	11% 6% 2 5% 4 4 4 3 5% 8% 47%	4983
June	1st to 10th	Day	12% 6% 3 8% 5% 5% 5% 4 6% 8% 39%	2850
	11th to 20th	Day	12% 6% 2 7% 5% 5% 4 5% 6% 9% 39%	2850
	21st to end	Day	13% 7% 2 7% 6% 5% 5% 4 6% 7% 38%	2850
July	1st to 10th	Day	14% 7% 3 8% 5% 5% 5% 4 5% 8% 36%	4613
	11th to 20th	Day	9% 4 3 7% 5% 6% 6% 5% 7% 9% 41%	4440
	21st to end	Day	8% 6% 2 6% 5% 5% 6% 4 7% 8% 42%	4793
August	1st to 10th	Day	9% 5% 2 6% 5% 5% 5% 4 9% 9% 39%	4104
	11th to 20th	Day	13% 6% 2 7% 4 3 5% 4 6% 8% 41%	4044
	21st to end	Day	12% 6% 3 8% 5% 4 5% 4 6% 7% 39%	4516
September	1st to 10th	Day	11% 7% 2 7% 5% 4 5% 4 6% 8% 40%	2187
	11th to 20th	Day	12% 6% 2 5% 4 4 5% 3 5% 7% 46%	2090
	21st to end	Day	17% 8% 3 7% 5% 4 5% 3 6% 8% 35%	2090
October	1st to 10th	Day	17% 9% 2 7% 5% 4 4 3 5% 7% 37%	2033
	11th to 20th	Day	21% 12% 4 9% 6% 5% 5% 3 4 5% 25%	1880
	21st to end	Day	21% 14% 4 9% 7% 5% 4 4 6% 7% 19%	1881
November	1st to 10th	Day	13% 17% 4 8% 5% 4 5% 4 5% 7% 28%	1762
	11th to 20th	Day	13% 16% 5% 11% 6% 5% 6% 4 5% 6% 23%	1745
	21st to end	Day	17% 18% 7% 11% 6% 5% 3 3 5% 5% 20%	1600
December	1st to 10th	Day	13% 20% 7% 14% 7% 5% 5% 3 5% 5% 16%	1456
	11th to 20th	Day	13% 18% 7% 13% 8% 5% 5% 4 4 6% 17%	1671
	21st to end	Day	23% 26% 9% 14% 6% 4 3 2 3 3 7%	2431
January	1st to 10th	Night	14% 15% 6% 16% 8% 5% 5% 4 5% 6% 17%	4428
	11th to 20th	Night	12% 15% 8% 17% 9% 8% 5% 4 4 4 14%	4440
	21st to end	Night	14% 20% 8% 15% 7% 6% 5% 3 4 4 13%	4852
February	1st to 10th	Night	9% 17% 5% 13% 9% 6% 6% 4 5% 5% 20%	2470
	11th to 20th	Night	11% 14% 5% 12% 9% 5% 5% 4 5% 7% 23%	2305
	21st to end	Night	14% 16% 6% 12% 7% 4 4 3 5% 5% 24%	1884
March	1st to 10th	Night	13% 11% 4 7% 4 4 4 3 5% 7% 39%	3698
	11th to 20th	Night	9% 13% 5% 7% 4 4 4 4 5% 7% 37%	3479
	21st to end	Night	14% 13% 4 10% 6% 4 5% 3 5% 6% 31%	3817
April	1st to 10th	Night	17% 13% 4 7% 4 3 3 5% 6% 6% 32%	1933
	11th to 20th	Night	18% 9% 3 6% 4 5% 4 4 5% 6% 36%	1705
	21st to end	Night	15% 12% 4 7% 5% 5% 5% 3 5% 6% 35%	1710
May	1st to 10th	Night	12% 8% 3 7% 6% 5% 5% 4 5% 7% 38%	2833
	11th to 20th	Night	13% 7% 2 6% 4 4 5% 4 6% 8% 41%	2812
	21st to end	Night	14% 6% 2 5% 3 4 4 4 5% 7% 45%	2596
June	1st to 10th	Night	13% 6% 2 5% 5% 4 5% 4 5% 8% 43%	1330
	11th to 20th	Night	8% 5% 2 5% 5% 5% 5% 5% 8% 9% 44%	1330
	21st to end	Night	11% 7% 2 6% 4 4 4 3 6% 7% 46%	1330
July	1st to 10th	Night	10% 6% 2 6% 5% 4 4 4 7% 9% 43%	2353
	11th to 20th	Night	8% 4 2 6% 4 4 4 4 5% 8% 51%	2530
	21st to end	Night	9% 6% 2 5% 4 4 4 4 6% 8% 50%	2770
August	1st to 10th	Night	9% 5% 2 6% 4 4 4 5% 6% 8% 47%	2825
	11th to 20th	Night	15% 5% 2 4 3 3 3 3 6% 8% 49%	2785
	21st to end	Night	9% 6% 2 6% 3 4 5% 3 6% 8% 49%	3124
September	1st to 10th	Night	9% 6% 2 5% 4 3 5% 4 5% 7% 48%	1973
	11th to 20th	Night	11% 5% 1 5% 4 4 3 3 5% 7% 50%	2090
	21st to end	Night	17% 7% 2 7% 5% 4 4 3 6% 6% 40%	2090
October	1st to 10th	Night	16% 7% 2 7% 4 4 4 3 5% 5% 42%	2146
	11th to 20th	Night	18% 12% 4 8% 5% 4 4 3 5% 6% 32%	2298
	21st to end	Night	23% 12% 4 8% 5% 4 4 4 4 6% 27%	2717
November	1st to 10th	Night	12% 12% 4 9% 5% 4 5% 3 7% 7% 32%	2536
	11th to 20th	Night	13% 15% 5% 10% 6% 5% 6% 4 6% 7% 24%	2653
	21st to end	Night	17% 17% 6% 9% 6% 4 5% 3 5% 7% 22%	2800
December	1st to 10th	Night	14% 16% 6% 14% 6% 5% 5% 4 6% 6% 19%	2904
	11th to 20th	Night	13% 17% 6% 15% 8% 6% 6% 4 5% 5% 15%	3526
	21st to end	Night	22% 26% 8% 12% 5% 5% 4 2 3 3 9%	5232

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	65% 7% 14% 12% 2	2528
	11th to 20th	Day	73% 8% 8% 9% 2	2530
	21st to end	Day	73% 6% 12% 6% 2	2814
February	1st to 10th	Day	66% 6% 9% 14% 4	1710
	11th to 20th	Day	61% 7% 10% 13% 9% 1	1769
	21st to end	Day	62% 7% 10% 14% 6% 1	1570
March	1st to 10th	Day	53% 6% 12% 20% 8% 1	3143
	11th to 20th	Day	55% 7% 11% 19% 6% 2	3480
	21st to end	Day	58% 7% 10% 15% 9% 1	3815
April	1st to 10th	Day	58% 6% 10% 15% 10% 1	2262
	11th to 20th	Day	51% 5% 10% 18% 15% 1	2423
	21st to end	Day	50% 6% 12% 15% 14% 3	2470
May	1st to 10th	Day	44% 8% 11% 18% 18% 2	4120
	11th to 20th	Day	38% 8% 13% 25% 14% 2	4085
	21st to end	Day	35% 7% 12% 19% 22% 5%	4983
June	1st to 10th	Day	41% 7% 11% 24% 14% 3	2850
	11th to 20th	Day	39% 7% 11% 22% 18% 2	2850
	21st to end	Day	43% 7% 12% 22% 13% 2	2850
July	1st to 10th	Day	46% 6% 11% 20% 15% 1	4543
	11th to 20th	Day	36% 7% 12% 27% 15% 2	4365
	21st to end	Day	36% 8% 12% 22% 21% 1	4641
August	1st to 10th	Day	38% 8% 13% 26% 14% 1	4091
	11th to 20th	Day	40% 6% 13% 26% 13% 1	4083
	21st to end	Day	42% 6% 13% 27% 10% 1	4515
September	1st to 10th	Day	40% 7% 12% 24% 15% 1	2187
	11th to 20th	Day	36% 7% 12% 29% 15% 1	2090
	21st to end	Day	46% 7% 14% 23% 11%	2090
October	1st to 10th	Day	35% 5% 9% 33% 17% 1	3384
	11th to 20th	Day	53% 5% 8% 20% 14%	3096
	21st to end	Day	59% 6% 10% 18% 7%	3081
November	1st to 10th	Day	54% 7% 12% 19% 8%	1762
	11th to 20th	Day	59% 7% 14% 14% 5%	1745
	21st to end	Day	65% 7% 14% 11% 3 1	1600
December	1st to 10th	Day	68% 7% 11% 11% 2	1456
	11th to 20th	Day	67% 7% 12% 12% 2	1671
	21st to end	Day	84% 5% 5% 4 2	2431
January	1st to 10th	Night	63% 10% 12% 12% 3	4428
	11th to 20th	Night	71% 8% 8% 10% 3	4440
	21st to end	Night	72% 7% 10% 8% 2	4852
February	1st to 10th	Night	62% 6% 11% 14% 6% 1	2470
	11th to 20th	Night	58% 6% 11% 18% 5% 1	2307
	21st to end	Night	61% 5% 12% 15% 7%	1884
March	1st to 10th	Night	44% 6% 17% 23% 9% 1	3709
	11th to 20th	Night	43% 8% 15% 24% 9% 2	3480
	21st to end	Night	51% 7% 12% 20% 9% 1	3817
April	1st to 10th	Night	52% 6% 9% 19% 13% 2	1933
	11th to 20th	Night	47% 5% 8% 23% 14% 2	1705
	21st to end	Night	49% 7% 10% 16% 15% 3	1710
May	1st to 10th	Night	40% 10% 13% 18% 17% 2	2840
	11th to 20th	Night	37% 9% 12% 26% 15% 1	2813
	21st to end	Night	36% 7% 14% 20% 17% 5%	2597
June	1st to 10th	Night	38% 7% 13% 26% 15% 1	1330
	11th to 20th	Night	33% 9% 14% 25% 18% 2	1330
	21st to end	Night	36% 8% 12% 25% 15% 3	1330
July	1st to 10th	Night	36% 7% 15% 23% 16% 3	2314
	11th to 20th	Night	31% 7% 11% 35% 16% 1	2482
	21st to end	Night	31% 7% 17% 25% 19% 1	2682
August	1st to 10th	Night	34% 7% 15% 28% 15% 1	2814
	11th to 20th	Night	33% 6% 17% 30% 14% 1	2812
	21st to end	Night	33% 6% 15% 32% 13% 1	3124
September	1st to 10th	Night	32% 8% 12% 28% 17% 2	1973
	11th to 20th	Night	33% 5% 15% 33% 14%	2090
	21st to end	Night	42% 7% 15% 25% 10%	2090
October	1st to 10th	Night	31% 5% 13% 33% 17% 1	3575
	11th to 20th	Night	46% 4 12% 24% 14%	3809
	21st to end	Night	50% 6% 14% 24% 6%	4467
November	1st to 10th	Night	48% 7% 15% 23% 7% 1	2536
	11th to 20th	Night	57% 7% 14% 16% 6% 1	2653
	21st to end	Night	62% 7% 15% 13% 3	2800
December	1st to 10th	Night	64% 7% 13% 12% 3	2904
	11th to 20th	Night	67% 9% 12% 9% 3	3525
	21st to end	Night	79% 7% 6% 5% 2	5232

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	24% 19% 39% 15% 4	270
	11th to 20th	Day	19% 24% 38% 17% 2	270
	21st to end	Day	30% 15% 37% 11% 6% 1	297
February	1st to 10th	Day	26% 27% 31% 13% 2 1	270
	11th to 20th	Day	27% 31% 31% 9% 1	270
	21st to end	Day	31% 28% 32% 8% 1	225
March	1st to 10th	Day	27% 25% 35% 11% 2	280
	11th to 20th	Day	24% 17% 38% 15% 6% 1	460
	21st to end	Day	30% 16% 30% 19% 5%	506
April	1st to 10th	Day	25% 20% 32% 18% 4 1	460
	11th to 20th	Day	32% 20% 27% 12% 8% 2	452
	21st to end	Day	25% 18% 33% 15% 7% 2	460
May	1st to 10th	Day	24% 20% 31% 14% 7% 3	463
	11th to 20th	Day	18% 16% 31% 23% 8% 4	487
	21st to end	Day	14% 13% 36% 26% 7% 3	707
June	1st to 10th	Day	15% 18% 36% 22% 8% 1	680
	11th to 20th	Day	16% 16% 36% 23% 7% 2	680
	21st to end	Day	18% 13% 36% 24% 6% 2	680
July	1st to 10th	Day	11% 11% 35% 28% 13% 2	671
	11th to 20th	Day	11% 13% 33% 27% 11% 4	668
	21st to end	Day	12% 8% 36% 27% 12% 5%	730
August	1st to 10th	Day	12% 9% 26% 29% 16% 8%	486
	11th to 20th	Day	13% 6% 24% 29% 16% 11%	479
	21st to end	Day	18% 7% 29% 28% 14% 4	539
September	1st to 10th	Day	16% 12% 28% 24% 12% 8%	490
	11th to 20th	Day	12% 10% 22% 32% 17% 8%	490
	21st to end	Day	21% 12% 24% 24% 13% 6%	490
October	1st to 10th	Day	23% 18% 27% 18% 13% 2	490
	11th to 20th	Day	27% 19% 31% 17% 5% 1	470
	21st to end	Day	32% 24% 32% 11% 2	330
November	1st to 10th	Day	27% 20% 34% 15% 4	300
	11th to 20th	Day	25% 26% 33% 12% 3 1	273
	21st to end	Day	30% 19% 36% 14% 2	200
December	1st to 10th	Day	30% 15% 39% 11% 5% 1	196
	11th to 20th	Day	26% 24% 38% 9% 2	180
	21st to end	Day	30% 27% 27% 13% 2 1	198
January	1st to 10th	Night	20% 19% 36% 20% 4	950
	11th to 20th	Night	22% 19% 33% 20% 6%	950
	21st to end	Night	18% 14% 36% 25% 6% 1	1026
February	1st to 10th	Night	18% 20% 38% 20% 4	760
	11th to 20th	Night	21% 20% 31% 23% 4	743
	21st to end	Night	25% 18% 34% 21% 2	628
March	1st to 10th	Night	19% 16% 37% 22% 6%	760
	11th to 20th	Night	19% 18% 35% 22% 5%	760
	21st to end	Night	22% 14% 33% 24% 5% 1	836
April	1st to 10th	Night	25% 14% 36% 20% 5% 1	603
	11th to 20th	Night	24% 14% 29% 25% 6% 2	563
	21st to end	Night	18% 13% 31% 29% 8% 1	570
May	1st to 10th	Night	14% 10% 37% 30% 8% 1	570
	11th to 20th	Night	19% 9% 29% 32% 10% 1	561
	21st to end	Night	13% 8% 30% 35% 14%	504
June	1st to 10th	Night	15% 8% 32% 37% 8%	380
	11th to 20th	Night	9% 11% 34% 33% 12% 1	380
	21st to end	Night	12% 9% 28% 37% 13% 1	380
July	1st to 10th	Night	7% 4 29% 45% 14% 1	444
	11th to 20th	Night	9% 4 26% 38% 20% 3	552
	21st to end	Night	10% 5% 22% 43% 18% 1	624
August	1st to 10th	Night	9% 3 25% 39% 23% 1	567
	11th to 20th	Night	12% 3 21% 33% 27% 4	564
	21st to end	Night	15% 5% 21% 37% 20% 2	627
September	1st to 10th	Night	12% 7% 26% 33% 19% 4	643
	11th to 20th	Night	13% 6% 27% 33% 18% 4	760
	21st to end	Night	20% 9% 23% 28% 17% 3	760
October	1st to 10th	Night	19% 11% 29% 29% 11% 1	760
	11th to 20th	Night	24% 13% 34% 22% 7%	760
	21st to end	Night	29% 14% 31% 21% 4 1	836
November	1st to 10th	Night	20% 15% 36% 21% 7% 1	780
	11th to 20th	Night	22% 20% 33% 21% 5%	800
	21st to end	Night	25% 15% 40% 16% 3	800
December	1st to 10th	Night	22% 18% 36% 19% 4	920
	11th to 20th	Night	23% 19% 36% 17% 4 1	950
	21st to end	Night	28% 16% 37% 17% 3	1045

Page generated at 2024-12-06 03:54:49. Version ac07

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