Cheboygan
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cheboygan 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% 10% 4 9% 5% 5% 4 4 5% 7% 34%	101633
	Night	14% 12% 4 10% 6% 4 4 3 5% 6% 30%	98252
Transparency	Day	26% 47% 7% 13% 6% 1	105141
	Night	29% 47% 7% 11% 5%	102832
Seeing	Day	17% 6% 24% 30% 18% 5%	15672
	Night	20% 8% 27% 30% 14% 2	25208

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	13% 18% 12% 20% 7% 6% 5% 3 4 4 7%	2527
	11th to 20th	Day	13% 18% 6% 19% 17% 7% 4 3 3 3 7%	2530
	21st to end	Day	15% 22% 8% 14% 7% 6% 5% 4 4 6% 10%	2783
February	1st to 10th	Day	9% 16% 6% 13% 9% 6% 5% 3 5% 6% 21%	1653
	11th to 20th	Day	12% 14% 7% 13% 8% 5% 4 3 5% 5% 23%	1777
	21st to end	Day	11% 15% 6% 11% 8% 6% 4 4 5% 7% 24%	1570
March	1st to 10th	Day	13% 12% 3 8% 5% 4 4 3 5% 6% 36%	3118
	11th to 20th	Day	9% 13% 5% 12% 7% 6% 4 4 5% 6% 30%	3445
	21st to end	Day	14% 12% 8% 11% 7% 6% 5% 4 4 5% 23%	3869
April	1st to 10th	Day	17% 14% 4 8% 5% 5% 3 3 5% 6% 30%	2280
	11th to 20th	Day	19% 11% 3 7% 4 4 4 4 5% 5% 33%	2404
	21st to end	Day	16% 11% 3 7% 4 4 4 4 5% 7% 33%	2470
May	1st to 10th	Day	15% 8% 3 6% 4 4 4 4 6% 7% 39%	4108
	11th to 20th	Day	11% 7% 2 7% 4 4 4 3 4 7% 46%	4193
	21st to end	Day	13% 6% 2 5% 4 4 4 3 5% 8% 46%	5019
June	1st to 10th	Day	14% 5% 2 6% 4 4 4 4 6% 7% 43%	2850
	11th to 20th	Day	12% 6% 3 6% 5% 5% 5% 4 7% 8% 40%	2850
	21st to end	Day	15% 7% 2 5% 4 3 4 4 5% 8% 43%	2850
July	1st to 10th	Day	17% 7% 3 5% 3 3 4 3 5% 8% 41%	4614
	11th to 20th	Day	8% 5% 2 5% 4 4 4 4 6% 8% 50%	4440
	21st to end	Day	9% 5% 2 6% 4 3 4 4 5% 8% 49%	4814
August	1st to 10th	Day	8% 5% 2 6% 5% 5% 5% 4 7% 9% 43%	4204
	11th to 20th	Day	12% 6% 2 6% 4 5% 4 3 5% 8% 45%	4044
	21st to end	Day	12% 7% 3 7% 4 4 4 4 4 7% 45%	4476
September	1st to 10th	Day	15% 7% 3 6% 4 4 4 4 5% 8% 42%	2222
	11th to 20th	Day	13% 7% 2 6% 4 5% 4 3 6% 8% 43%	2090
	21st to end	Day	16% 8% 3 7% 4 3 4 4 5% 8% 38%	2090
October	1st to 10th	Day	20% 9% 3 6% 4 5% 4 2 5% 8% 35%	2057
	11th to 20th	Day	23% 14% 4 11% 5% 5% 4 3 4 6% 21%	1825
	21st to end	Day	23% 15% 4 9% 5% 5% 5% 3 6% 6% 19%	1881
November	1st to 10th	Day	18% 15% 4 9% 5% 5% 5% 3 5% 8% 24%	1762
	11th to 20th	Day	14% 16% 7% 12% 7% 6% 6% 5% 6% 6% 17%	1755
	21st to end	Day	19% 19% 8% 13% 6% 4 4 3 5% 5% 13%	1575
December	1st to 10th	Day	12% 22% 10% 16% 10% 5% 5% 3 4 4 9%	1386
	11th to 20th	Day	17% 17% 7% 16% 9% 6% 5% 4 4 4 11%	1671
	21st to end	Day	21% 23% 8% 17% 6% 4 4 2 3 3 7%	2431
January	1st to 10th	Night	14% 18% 8% 18% 8% 5% 5% 4 4 5% 13%	4428
	11th to 20th	Night	12% 16% 7% 19% 13% 6% 5% 4 4 4 11%	4440
	21st to end	Night	14% 21% 8% 14% 7% 5% 5% 3 4 5% 13%	4884
February	1st to 10th	Night	10% 17% 5% 12% 8% 7% 5% 4 6% 5% 21%	2525
	11th to 20th	Night	11% 14% 5% 12% 8% 6% 5% 4 5% 6% 25%	2287
	21st to end	Night	14% 15% 5% 10% 7% 5% 4 4 4 5% 25%	1884
March	1st to 10th	Night	15% 10% 3 6% 4 3 3 3 4 6% 42%	3722
	11th to 20th	Night	8% 14% 5% 9% 4 4 4 4 4 6% 37%	3512
	21st to end	Night	14% 11% 6% 8% 5% 4 4 3 6% 7% 31%	3791
April	1st to 10th	Night	20% 12% 2 7% 5% 5% 5% 4 6% 6% 29%	1900
	11th to 20th	Night	19% 10% 3 8% 4 3 4 3 5% 6% 36%	1725
	21st to end	Night	17% 9% 3 8% 5% 4 5% 4 5% 5% 35%	1710
May	1st to 10th	Night	15% 8% 3 7% 6% 5% 5% 4 5% 5% 37%	2833
	11th to 20th	Night	12% 7% 3 7% 5% 5% 4 3 6% 7% 40%	2703
	21st to end	Night	17% 7% 2 5% 4 3 3 3 6% 7% 43%	2564
June	1st to 10th	Night	13% 5% 2 7% 5% 5% 4 4 7% 8% 40%	1330
	11th to 20th	Night	10% 5% 2 5% 5% 4 6% 4 7% 9% 41%	1330
	21st to end	Night	14% 7% 2 6% 4 3 4 3 5% 7% 45%	1330
July	1st to 10th	Night	13% 6% 2 6% 5% 4 4 4 6% 7% 44%	2338
	11th to 20th	Night	9% 5% 2 6% 4 4 5% 4 5% 6% 51%	2530
	21st to end	Night	9% 5% 2 5% 4 4 4 4 5% 7% 51%	2750
August	1st to 10th	Night	10% 6% 2 6% 4 5% 4 3 6% 8% 45%	2726
	11th to 20th	Night	13% 6% 2 4 2 3 4 2 5% 8% 51%	2785
	21st to end	Night	10% 5% 2 5% 4 4 4 3 5% 7% 52%	3178
September	1st to 10th	Night	13% 6% 2 6% 4 4 4 3 4 7% 48%	1938
	11th to 20th	Night	14% 6% 2 6% 4 4 3 4 5% 7% 45%	2090
	21st to end	Night	17% 7% 3 6% 3 4 4 4 5% 7% 40%	2090
October	1st to 10th	Night	16% 9% 3 6% 4 4 3 4 6% 7% 39%	2123
	11th to 20th	Night	21% 12% 4 8% 5% 5% 4 4 5% 7% 24%	2351
	21st to end	Night	25% 14% 3 9% 5% 4 4 3 5% 6% 22%	2717
November	1st to 10th	Night	16% 14% 5% 9% 5% 4 5% 4 5% 7% 27%	2536
	11th to 20th	Night	15% 17% 5% 11% 7% 5% 6% 4 5% 5% 20%	2643
	21st to end	Night	18% 21% 6% 12% 7% 4 5% 4 5% 4 14%	2824
December	1st to 10th	Night	12% 20% 8% 16% 8% 6% 5% 4 5% 5% 12%	2977
	11th to 20th	Night	16% 19% 6% 17% 9% 4 5% 4 4 5% 13%	3526
	21st to end	Night	22% 23% 8% 16% 6% 4 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	52% 42% 3 3	2528
	11th to 20th	Day	55% 39% 3 2 1	2530
	21st to end	Day	48% 43% 6% 2 1	2783
February	1st to 10th	Day	20% 65% 5% 6% 3	1653
	11th to 20th	Day	22% 65% 4 5% 4	1786
	21st to end	Day	19% 65% 4 8% 4	1570
March	1st to 10th	Day	27% 41% 8% 16% 7% 1	3120
	11th to 20th	Day	33% 44% 7% 12% 4 1	3445
	21st to end	Day	37% 45% 5% 7% 6% 1	3869
April	1st to 10th	Day	20% 65% 3 8% 4	2280
	11th to 20th	Day	17% 66% 3 7% 5% 1	2404
	21st to end	Day	16% 65% 3 8% 6% 1	2470
May	1st to 10th	Day	24% 42% 6% 15% 11% 1	4120
	11th to 20th	Day	21% 42% 8% 20% 8%	4197
	21st to end	Day	22% 41% 7% 14% 13% 2	5019
June	1st to 10th	Day	14% 65% 4 10% 6% 1	2850
	11th to 20th	Day	16% 65% 5% 8% 5% 1	2850
	21st to end	Day	14% 64% 5% 11% 5% 1	2850
July	1st to 10th	Day	30% 36% 11% 15% 7% 1	4544
	11th to 20th	Day	18% 36% 11% 28% 6%	4365
	21st to end	Day	18% 36% 6% 26% 13%	4662
August	1st to 10th	Day	20% 40% 9% 23% 8%	4189
	11th to 20th	Day	25% 39% 10% 20% 6%	4083
	21st to end	Day	25% 38% 11% 22% 4	4475
September	1st to 10th	Day	16% 61% 6% 12% 4	2222
	11th to 20th	Day	13% 61% 5% 15% 6%	2090
	21st to end	Day	17% 60% 7% 11% 4	2090
October	1st to 10th	Day	20% 37% 8% 23% 13%	3421
	11th to 20th	Day	32% 38% 7% 18% 6%	3015
	21st to end	Day	38% 37% 9% 12% 4	3081
November	1st to 10th	Day	29% 56% 5% 8% 2	1762
	11th to 20th	Day	30% 57% 6% 5% 2	1755
	21st to end	Day	34% 58% 3 3 1	1575
December	1st to 10th	Day	34% 58% 4 3 1	1386
	11th to 20th	Day	41% 49% 4 5% 1	1671
	21st to end	Day	54% 39% 2 2 2	2431
January	1st to 10th	Night	45% 40% 8% 6% 1	4428
	11th to 20th	Night	50% 40% 6% 4 1	4440
	21st to end	Night	47% 42% 6% 4 1	4884
February	1st to 10th	Night	21% 66% 4 5% 4	2525
	11th to 20th	Night	20% 65% 4 9% 2	2289
	21st to end	Night	19% 65% 5% 6% 5%	1884
March	1st to 10th	Night	26% 41% 11% 15% 6%	3733
	11th to 20th	Night	27% 42% 10% 16% 5% 1	3513
	21st to end	Night	31% 43% 8% 12% 5% 1	3791
April	1st to 10th	Night	22% 65% 2 7% 3	1900
	11th to 20th	Night	19% 65% 2 9% 4 2	1725
	21st to end	Night	19% 65% 3 7% 6% 1	1710
May	1st to 10th	Night	28% 41% 7% 15% 8% 1	2840
	11th to 20th	Night	23% 42% 6% 20% 9%	2704
	21st to end	Night	27% 42% 9% 10% 10% 3	2565
June	1st to 10th	Night	14% 65% 4 10% 7%	1330
	11th to 20th	Night	16% 65% 3 9% 5% 2	1330
	21st to end	Night	15% 64% 4 11% 5% 2	1330
July	1st to 10th	Night	29% 37% 11% 13% 10% 1	2299
	11th to 20th	Night	19% 36% 12% 21% 11%	2482
	21st to end	Night	20% 37% 9% 18% 16%	2662
August	1st to 10th	Night	25% 39% 9% 18% 9%	2717
	11th to 20th	Night	24% 38% 9% 21% 7% 1	2812
	21st to end	Night	20% 38% 8% 24% 10%	3178
September	1st to 10th	Night	15% 61% 5% 12% 6%	1938
	11th to 20th	Night	14% 60% 6% 13% 7%	2090
	21st to end	Night	16% 61% 7% 12% 4	2090
October	1st to 10th	Night	24% 38% 7% 22% 9%	3539
	11th to 20th	Night	24% 37% 13% 16% 10%	3900
	21st to end	Night	34% 38% 10% 14% 4	4467
November	1st to 10th	Night	29% 56% 5% 8% 2	2536
	11th to 20th	Night	28% 57% 6% 6% 3	2643
	21st to end	Night	35% 57% 4 3 1	2824
December	1st to 10th	Night	32% 58% 5% 5%	2977
	11th to 20th	Night	39% 51% 5% 3 1	3525
	21st to end	Night	54% 39% 2 4 1	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	17% 13% 34% 26% 10%	270
	11th to 20th	Day	20% 9% 33% 29% 7% 2	270
	21st to end	Day	23% 7% 25% 32% 13% 1	297
February	1st to 10th	Day	16% 11% 36% 25% 10% 1	270
	11th to 20th	Day	17% 8% 41% 23% 9% 1	270
	21st to end	Day	16% 13% 36% 30% 5%	225
March	1st to 10th	Day	14% 8% 33% 31% 13%	270
	11th to 20th	Day	16% 9% 32% 30% 12% 2	438
	21st to end	Day	23% 8% 28% 29% 10% 2	506
April	1st to 10th	Day	21% 9% 27% 32% 9% 2	460
	11th to 20th	Day	24% 8% 28% 26% 12% 2	452
	21st to end	Day	20% 6% 31% 29% 12% 2	460
May	1st to 10th	Day	22% 3 29% 28% 15% 3	463
	11th to 20th	Day	16% 3 21% 37% 18% 4	547
	21st to end	Day	12% 4 20% 36% 21% 6%	734
June	1st to 10th	Day	12% 2 25% 37% 20% 4	680
	11th to 20th	Day	12% 3 24% 35% 22% 4	680
	21st to end	Day	18% 5% 17% 36% 21% 4	680
July	1st to 10th	Day	9% 2 16% 40% 26% 7%	671
	11th to 20th	Day	11% 2 18% 33% 28% 7%	668
	21st to end	Day	11% 3 15% 34% 29% 8%	739
August	1st to 10th	Day	11% 3 13% 33% 30% 9%	548
	11th to 20th	Day	10% 3 13% 29% 32% 13%	479
	21st to end	Day	15% 4 15% 32% 28% 7%	539
September	1st to 10th	Day	16% 4 19% 27% 26% 9%	490
	11th to 20th	Day	13% 4 15% 29% 28% 12%	490
	21st to end	Day	19% 6% 18% 27% 24% 6%	490
October	1st to 10th	Day	22% 8% 26% 22% 17% 5%	490
	11th to 20th	Day	24% 11% 27% 25% 12% 1	415
	21st to end	Day	34% 6% 23% 28% 8% 2	330
November	1st to 10th	Day	21% 14% 27% 27% 10% 2	300
	11th to 20th	Day	21% 15% 34% 23% 6% 1	277
	21st to end	Day	26% 18% 34% 20% 3	200
December	1st to 10th	Day	26% 13% 34% 18% 8% 1	196
	11th to 20th	Day	21% 18% 34% 19% 7% 1	180
	21st to end	Day	29% 13% 36% 16% 4 2	198
January	1st to 10th	Night	21% 11% 36% 24% 6% 1	950
	11th to 20th	Night	23% 11% 33% 25% 8%	950
	21st to end	Night	18% 8% 32% 32% 8% 2	1045
February	1st to 10th	Night	16% 10% 38% 27% 7% 1	815
	11th to 20th	Night	18% 9% 34% 28% 10%	743
	21st to end	Night	20% 8% 35% 31% 7%	628
March	1st to 10th	Night	17% 7% 35% 31% 10% 1	760
	11th to 20th	Night	16% 10% 34% 31% 9% 1	760
	21st to end	Night	18% 6% 30% 34% 11% 1	822
April	1st to 10th	Night	23% 8% 27% 32% 8% 1	570
	11th to 20th	Night	24% 4 27% 32% 12% 2	563
	21st to end	Night	20% 6% 26% 34% 14% 1	570
May	1st to 10th	Night	17% 3 24% 37% 18% 1	570
	11th to 20th	Night	18% 4 17% 39% 20% 2	561
	21st to end	Night	15% 3 20% 34% 25% 3	509
June	1st to 10th	Night	13% 4 20% 38% 24% 1	380
	11th to 20th	Night	12% 2 21% 39% 26% 2	380
	21st to end	Night	16% 3 17% 36% 25% 3	380
July	1st to 10th	Night	12% 1 13% 41% 30% 4	442
	11th to 20th	Night	9% 3 13% 37% 30% 8%	552
	21st to end	Night	11% 2 14% 42% 28% 4	624
August	1st to 10th	Night	12% 3 15% 39% 27% 4	567
	11th to 20th	Night	10% 2 17% 31% 30% 9%	564
	21st to end	Night	15% 4 14% 37% 27% 3	627
September	1st to 10th	Night	16% 4 18% 30% 26% 6%	608
	11th to 20th	Night	15% 3 18% 31% 26% 7%	760
	21st to end	Night	20% 6% 17% 30% 21% 6%	760
October	1st to 10th	Night	21% 8% 22% 31% 17% 2	760
	11th to 20th	Night	28% 9% 24% 30% 7% 1	760
	21st to end	Night	32% 11% 24% 27% 6% 1	836
November	1st to 10th	Night	24% 11% 31% 25% 9% 1	780
	11th to 20th	Night	23% 16% 32% 23% 6%	800
	21st to end	Night	31% 15% 30% 20% 4	824
December	1st to 10th	Night	22% 14% 37% 21% 6% 1	993
	11th to 20th	Night	23% 16% 36% 17% 6% 2	950
	21st to end	Night	31% 12% 33% 19% 4	1045

Page generated at 2024-12-06 03:54:52. Version ac07

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