Macomb
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Macomb clear sky chart from 2005-11-06 to 2024-12-24.

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	12% 8% 3 7% 5% 4 4 4 6% 7% 39%	101795
	Night	13% 9% 3 7% 4 4 4 3 5% 7% 41%	98396
Transparency	Day	42% 4 12% 24% 15% 2	105387
	Night	42% 4 11% 24% 16% 2	102944
Seeing	Day	15% 11% 28% 26% 16% 4	15903
	Night	16% 10% 31% 30% 12% 1	25800

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	11% 12% 6% 14% 6% 4 4 4 4 7% 27%	2527
	11th to 20th	Day	12% 11% 4 11% 8% 6% 8% 5% 7% 6% 22%	2623
	21st to end	Day	15% 20% 10% 12% 6% 3 3 2 4 4 20%	3135
February	1st to 10th	Day	14% 13% 5% 10% 5% 4 5% 4 5% 5% 30%	1710
	11th to 20th	Day	14% 9% 4 7% 6% 5% 5% 4 5% 6% 35%	1773
	21st to end	Day	14% 13% 5% 9% 5% 3 3 4 5% 5% 35%	1570
March	1st to 10th	Day	16% 14% 4 7% 4 4 3 3 4 5% 38%	3173
	11th to 20th	Day	10% 8% 2 6% 4 3 5% 3 6% 7% 45%	3480
	21st to end	Day	18% 13% 3 9% 6% 4 4 4 5% 7% 29%	4005
April	1st to 10th	Day	16% 10% 3 7% 5% 4 4 3 5% 6% 37%	2280
	11th to 20th	Day	15% 9% 3 7% 5% 4 4 4 5% 6% 39%	2254
	21st to end	Day	19% 7% 3 8% 5% 5% 4 4 5% 6% 34%	2280
May	1st to 10th	Day	15% 8% 2 7% 5% 5% 5% 4 7% 9% 33%	4065
	11th to 20th	Day	17% 8% 3 6% 5% 4 4 3 5% 8% 39%	4399
	21st to end	Day	12% 6% 2 6% 4 4 4 3 5% 6% 46%	4824
June	1st to 10th	Day	8% 5% 2 7% 5% 5% 4 4 6% 8% 46%	2660
	11th to 20th	Day	7% 5% 2 7% 5% 4 5% 3 6% 8% 48%	2660
	21st to end	Day	8% 6% 2 6% 5% 5% 6% 4 7% 9% 42%	2660
July	1st to 10th	Day	11% 6% 2 7% 6% 5% 5% 4 7% 10% 38%	4440
	11th to 20th	Day	6% 5% 2 5% 4 5% 5% 4 7% 10% 48%	4440
	21st to end	Day	7% 5% 2 6% 5% 4 6% 5% 8% 10% 41%	4702
August	1st to 10th	Day	6% 4 2 6% 5% 5% 5% 5% 8% 10% 46%	4104
	11th to 20th	Day	10% 6% 2 7% 4 4 5% 5% 6% 10% 41%	3819
	21st to end	Day	6% 5% 2 5% 4 4 4 4 6% 9% 50%	4180
September	1st to 10th	Day	12% 5% 2 5% 3 3 3 4 6% 7% 50%	2280
	11th to 20th	Day	10% 4 1 4 3 4 4 3 5% 8% 53%	2270
	21st to end	Day	8% 5% 2 5% 4 5% 4 4 6% 8% 48%	2057
October	1st to 10th	Day	12% 5% 3 4 4 4 4 3 5% 5% 52%	1900
	11th to 20th	Day	16% 8% 3 6% 4 3 3 2 4 5% 46%	1900
	21st to end	Day	18% 8% 3 7% 4 3 4 3 5% 6% 41%	2038
November	1st to 10th	Day	10% 8% 2 6% 4 3 4 3 5% 7% 48%	1762
	11th to 20th	Day	16% 10% 3 7% 3 4 3 2 5% 6% 41%	1800
	21st to end	Day	16% 13% 3 9% 5% 2 3 4 4 6% 37%	1620
December	1st to 10th	Day	12% 12% 4 9% 4 3 4 4 5% 6% 36%	1600
	11th to 20th	Day	14% 13% 3 8% 4 3 4 4 6% 6% 34%	1998
	21st to end	Day	23% 18% 6% 12% 4 3 4 3 4 5% 18%	2807
January	1st to 10th	Night	13% 12% 7% 12% 5% 5% 4 3 4 5% 31%	4428
	11th to 20th	Night	13% 16% 6% 11% 5% 5% 6% 4 6% 4 23%	4344
	21st to end	Night	20% 16% 6% 12% 5% 4 3 3 4 6% 23%	4532
February	1st to 10th	Night	15% 11% 5% 8% 5% 5% 4 3 5% 6% 34%	2470
	11th to 20th	Night	14% 10% 3 7% 5% 3 4 3 5% 7% 38%	2292
	21st to end	Night	15% 10% 4 8% 4 3 2 3 4 5% 42%	1884
March	1st to 10th	Night	17% 12% 3 6% 4 4 4 3 4 5% 39%	3709
	11th to 20th	Night	13% 8% 2 5% 3 3 3 3 5% 5% 51%	3480
	21st to end	Night	20% 13% 5% 8% 5% 4 4 3 5% 5% 28%	3612
April	1st to 10th	Night	13% 10% 3 6% 5% 4 4 3 6% 6% 42%	1900
	11th to 20th	Night	14% 8% 3 6% 4 4 4 3 5% 7% 43%	1875
	21st to end	Night	19% 6% 3 7% 5% 4 4 3 6% 6% 39%	1900
May	1st to 10th	Night	17% 9% 3 7% 5% 4 4 4 6% 7% 34%	2829
	11th to 20th	Night	13% 6% 2 6% 4 4 4 4 6% 9% 42%	2506
	21st to end	Night	9% 5% 2 5% 4 4 4 4 5% 8% 49%	2743
June	1st to 10th	Night	7% 4 2 5% 4 3 4 3 6% 9% 52%	1520
	11th to 20th	Night	8% 4 2 5% 4 5% 3 3 5% 9% 51%	1520
	21st to end	Night	7% 6% 2 6% 5% 3 4 4 6% 7% 48%	1520
July	1st to 10th	Night	12% 6% 3 6% 5% 4 4 4 6% 10% 42%	2530
	11th to 20th	Night	3 3 1 4 4 3 5% 4 6% 8% 57%	2530
	21st to end	Night	7% 5% 2 5% 4 4 5% 4 6% 9% 48%	2857
August	1st to 10th	Night	4 3 1 4 3 3 4 4 6% 10% 57%	2836
	11th to 20th	Night	8% 5% 2 5% 4 4 4 3 6% 7% 53%	3012
	21st to end	Night	5% 3 2 5% 4 5% 4 3 6% 9% 54%	3476
September	1st to 10th	Night	10% 5% 1 5% 3 3 2 2 5% 6% 58%	1900
	11th to 20th	Night	8% 4 1 6% 4 4 3 3 5% 7% 53%	1900
	21st to end	Night	8% 5% 2 5% 5% 5% 5% 3 6% 7% 50%	2109
October	1st to 10th	Night	9% 5% 2 5% 3 3 4 3 5% 6% 55%	2280
	11th to 20th	Night	13% 5% 2 5% 3 3 3 3 4 6% 52%	2280
	21st to end	Night	17% 7% 3 5% 4 3 4 3 5% 6% 42%	2559
November	1st to 10th	Night	12% 7% 2 4 4 3 3 3 5% 6% 52%	2536
	11th to 20th	Night	14% 8% 3 7% 3 4 3 3 5% 7% 43%	2600
	21st to end	Night	15% 11% 4 6% 4 4 3 3 5% 6% 39%	2775
December	1st to 10th	Night	14% 11% 4 7% 5% 4 4 3 5% 7% 36%	2800
	11th to 20th	Night	15% 11% 4 9% 5% 4 3 2 4 6% 37%	3419
	21st to end	Night	22% 18% 8% 11% 6% 4 3 3 3 4 19%	4933

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	59% 3 10% 21% 7%	2528
	11th to 20th	Day	61% 2 12% 17% 7%	2623
	21st to end	Day	69% 2 9% 13% 6%	3135
February	1st to 10th	Day	57% 3 12% 19% 7% 2	1710
	11th to 20th	Day	49% 4 12% 22% 12% 1	1782
	21st to end	Day	51% 4 10% 23% 11% 2	1570
March	1st to 10th	Day	51% 3 10% 20% 15% 1	3173
	11th to 20th	Day	38% 3 14% 27% 18% 1	3480
	21st to end	Day	57% 3 15% 21% 4 1	4005
April	1st to 10th	Day	47% 4 12% 24% 13%	2280
	11th to 20th	Day	45% 4 10% 26% 13% 2	2254
	21st to end	Day	50% 4 10% 21% 13% 2	2280
May	1st to 10th	Day	47% 4 13% 23% 13% 1	4100
	11th to 20th	Day	45% 3 11% 31% 9% 1	4403
	21st to end	Day	39% 4 9% 23% 23% 1	4837
June	1st to 10th	Day	35% 5% 13% 30% 15% 3	2660
	11th to 20th	Day	34% 6% 10% 26% 22% 2	2660
	21st to end	Day	35% 6% 16% 23% 17% 3	2660
July	1st to 10th	Day	40% 6% 13% 27% 12% 2	4371
	11th to 20th	Day	30% 7% 16% 27% 20% 1	4365
	21st to end	Day	34% 8% 21% 22% 14% 1	4554
August	1st to 10th	Day	31% 6% 17% 34% 12% 1	4090
	11th to 20th	Day	37% 6% 13% 29% 13% 1	3857
	21st to end	Day	30% 6% 15% 31% 15% 4	4179
September	1st to 10th	Day	33% 4 10% 27% 20% 5%	2280
	11th to 20th	Day	29% 4 10% 29% 23% 4	2270
	21st to end	Day	33% 4 10% 30% 20% 2	2057
October	1st to 10th	Day	24% 2 6% 18% 46% 3	3160
	11th to 20th	Day	28% 2 7% 23% 35% 6%	3140
	21st to end	Day	42% 3 8% 26% 20% 2	3340
November	1st to 10th	Day	36% 3 15% 26% 17% 3	1762
	11th to 20th	Day	46% 2 10% 25% 14% 3	1800
	21st to end	Day	50% 4 13% 22% 10%	1620
December	1st to 10th	Day	50% 4 14% 22% 10% 1	1600
	11th to 20th	Day	50% 3 9% 26% 9% 2	1995
	21st to end	Day	70% 3 9% 13% 6%	2807
January	1st to 10th	Night	57% 2 11% 21% 9%	4428
	11th to 20th	Night	62% 3 9% 16% 8% 1	4344
	21st to end	Night	65% 2 10% 17% 6%	4532
February	1st to 10th	Night	53% 4 11% 20% 12% 2	2470
	11th to 20th	Night	46% 3 11% 26% 12% 2	2293
	21st to end	Night	46% 3 8% 25% 15% 3	1884
March	1st to 10th	Night	49% 3 8% 25% 13% 1	3709
	11th to 20th	Night	36% 3 10% 29% 17% 5%	3480
	21st to end	Night	58% 3 14% 20% 5%	3612
April	1st to 10th	Night	43% 4 11% 26% 14% 3	1900
	11th to 20th	Night	42% 5% 8% 25% 17% 4	1875
	21st to end	Night	47% 3 10% 21% 15% 3	1900
May	1st to 10th	Night	49% 4 13% 21% 12% 1	2859
	11th to 20th	Night	40% 5% 15% 28% 12%	2507
	21st to end	Night	33% 4 12% 22% 25% 3	2751
June	1st to 10th	Night	29% 4 16% 27% 19% 4	1520
	11th to 20th	Night	31% 4 11% 26% 23% 5%	1520
	21st to end	Night	33% 7% 14% 22% 20% 3	1520
July	1st to 10th	Night	39% 6% 13% 27% 13% 2	2490
	11th to 20th	Night	22% 7% 13% 33% 24% 2	2482
	21st to end	Night	30% 7% 18% 24% 19% 2	2766
August	1st to 10th	Night	23% 6% 18% 33% 18% 2	2826
	11th to 20th	Night	30% 5% 13% 33% 17% 1	3040
	21st to end	Night	26% 6% 16% 31% 16% 5%	3476
September	1st to 10th	Night	30% 3 10% 26% 25% 7%	1900
	11th to 20th	Night	31% 3 10% 26% 24% 6%	1900
	21st to end	Night	31% 5% 9% 26% 25% 3	2109
October	1st to 10th	Night	22% 3 7% 23% 42% 4	3800
	11th to 20th	Night	25% 2 9% 22% 37% 5%	3779
	21st to end	Night	39% 3 10% 21% 23% 4	4207
November	1st to 10th	Night	35% 4 11% 26% 20% 4	2536
	11th to 20th	Night	42% 3 11% 24% 18% 2	2600
	21st to end	Night	47% 3 10% 25% 14% 1	2775
December	1st to 10th	Night	49% 3 12% 24% 10% 1	2800
	11th to 20th	Night	50% 3 11% 25% 10% 1	3421
	21st to end	Night	71% 2 8% 13% 5% 1	4933

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% 19% 30% 21% 9%	270
	11th to 20th	Day	23% 21% 39% 15% 3	270
	21st to end	Day	18% 23% 35% 17% 7%	297
February	1st to 10th	Day	22% 18% 40% 16% 5%	270
	11th to 20th	Day	20% 21% 32% 19% 6% 1	270
	21st to end	Day	21% 20% 41% 16% 2	225
March	1st to 10th	Day	19% 24% 37% 17% 2	270
	11th to 20th	Day	26% 17% 34% 16% 6%	270
	21st to end	Day	32% 15% 33% 16% 4 1	411
April	1st to 10th	Day	22% 17% 32% 22% 6% 1	460
	11th to 20th	Day	18% 16% 35% 21% 9% 2	452
	21st to end	Day	21% 14% 34% 22% 8% 1	460
May	1st to 10th	Day	21% 12% 34% 25% 7% 2	530
	11th to 20th	Day	19% 12% 28% 26% 12% 2	675
	21st to end	Day	16% 6% 30% 26% 14% 7%	734
June	1st to 10th	Day	8% 5% 25% 33% 23% 6%	680
	11th to 20th	Day	8% 5% 26% 36% 21% 4	680
	21st to end	Day	9% 10% 31% 29% 17% 4	680
July	1st to 10th	Day	11% 4 15% 31% 27% 13%	671
	11th to 20th	Day	8% 3 23% 36% 23% 8%	668
	21st to end	Day	9% 2 20% 34% 29% 6%	739
August	1st to 10th	Day	7% 3 19% 38% 24% 9%	676
	11th to 20th	Day	10% 4 19% 29% 27% 11%	533
	21st to end	Day	6% 2 17% 31% 32% 11%	539
September	1st to 10th	Day	12% 5% 19% 30% 27% 7%	490
	11th to 20th	Day	8% 2 17% 34% 30% 9%	490
	21st to end	Day	9% 11% 25% 26% 21% 8%	457
October	1st to 10th	Day	13% 9% 31% 26% 16% 5%	300
	11th to 20th	Day	15% 22% 34% 20% 9%	300
	21st to end	Day	28% 14% 36% 18% 4	330
November	1st to 10th	Day	14% 12% 39% 21% 12% 3	300
	11th to 20th	Day	20% 19% 31% 21% 7% 2	300
	21st to end	Day	24% 14% 34% 23% 5%	300
December	1st to 10th	Day	12% 18% 43% 19% 6% 2	300
	11th to 20th	Day	21% 15% 37% 21% 4	300
	21st to end	Day	25% 22% 36% 16% 2	306
January	1st to 10th	Night	16% 16% 41% 20% 7%	950
	11th to 20th	Night	18% 16% 39% 22% 5%	950
	21st to end	Night	19% 16% 36% 27% 3	1045
February	1st to 10th	Night	21% 13% 39% 23% 4	950
	11th to 20th	Night	20% 15% 36% 27% 3	817
	21st to end	Night	22% 15% 40% 21% 2	628
March	1st to 10th	Night	19% 14% 41% 21% 4	749
	11th to 20th	Night	19% 13% 34% 27% 6%	570
	21st to end	Night	24% 13% 35% 22% 5%	627
April	1st to 10th	Night	17% 16% 36% 26% 4	570
	11th to 20th	Night	17% 13% 32% 29% 7% 1	563
	21st to end	Night	22% 10% 34% 27% 7%	570
May	1st to 10th	Night	17% 7% 37% 30% 7% 1	570
	11th to 20th	Night	17% 6% 30% 34% 12% 1	561
	21st to end	Night	12% 6% 28% 33% 19% 2	617
June	1st to 10th	Night	9% 3 22% 45% 20% 1	570
	11th to 20th	Night	9% 4 24% 44% 18% 1	570
	21st to end	Night	7% 4 31% 38% 18% 1	570
July	1st to 10th	Night	10% 3 13% 40% 31% 3	555
	11th to 20th	Night	5% 2 17% 49% 26% 2	552
	21st to end	Night	7% 1 14% 45% 31% 2	624
August	1st to 10th	Night	7% 2 12% 48% 28% 3	567
	11th to 20th	Night	8% 3 14% 40% 31% 4	564
	21st to end	Night	8% 14% 37% 39% 2	627
September	1st to 10th	Night	13% 4 15% 39% 26% 3	570
	11th to 20th	Night	9% 3 18% 37% 29% 4	570
	21st to end	Night	9% 8% 23% 36% 21% 4	750
October	1st to 10th	Night	11% 6% 27% 32% 21% 2	760
	11th to 20th	Night	16% 11% 32% 29% 12%	760
	21st to end	Night	20% 14% 32% 27% 7%	836
November	1st to 10th	Night	15% 10% 38% 27% 9% 1	780
	11th to 20th	Night	18% 14% 37% 25% 6% 1	800
	21st to end	Night	21% 13% 36% 24% 6%	975
December	1st to 10th	Night	19% 13% 38% 25% 4 1	1000
	11th to 20th	Night	23% 12% 34% 26% 6%	1000
	21st to end	Night	25% 17% 34% 22% 2	1063

Page generated at 2024-12-21 03:13:49. Version ac07

Copyright © 2024 Attilla Danko.