Copper Harbor
Clear Sky Chart
History

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

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% 11% 5% 11% 6% 5% 4 3 5% 6% 32%	101733
	Night	12% 12% 5% 13% 7% 6% 5% 3 5% 5% 26%	98104
Transparency	Day	29% 46% 7% 13% 5%	105167
	Night	32% 46% 7% 11% 4	102757
Seeing	Day	19% 12% 31% 25% 11% 3	15994
	Night	20% 10% 28% 28% 12% 1	25777

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	9% 21% 14% 26% 7% 7% 4 3 2 2 5%	2527
	11th to 20th	Day	8% 15% 7% 22% 23% 11% 5% 2 2 1 4	2530
	21st to end	Day	8% 19% 13% 19% 10% 8% 5% 4 4 2 7%	2783
February	1st to 10th	Day	8% 14% 6% 16% 15% 12% 8% 3 4 4 12%	1567
	11th to 20th	Day	7% 13% 7% 16% 12% 10% 6% 4 4 4 17%	1759
	21st to end	Day	9% 15% 5% 16% 12% 8% 5% 4 6% 5% 15%	1570
March	1st to 10th	Day	8% 10% 5% 15% 7% 5% 5% 3 4 5% 32%	3118
	11th to 20th	Day	7% 11% 8% 15% 10% 5% 3 3 4 6% 28%	3262
	21st to end	Day	17% 13% 6% 18% 6% 4 4 3 3 5% 21%	4165
April	1st to 10th	Day	13% 14% 4 9% 5% 5% 4 4 6% 6% 30%	2280
	11th to 20th	Day	17% 12% 4 9% 6% 5% 5% 3 4 6% 29%	2291
	21st to end	Day	16% 11% 4 6% 5% 5% 4 4 5% 6% 35%	2470
May	1st to 10th	Day	15% 9% 3 6% 4 4 3 3 4 7% 41%	4381
	11th to 20th	Day	12% 8% 3 7% 4 5% 5% 3 6% 7% 40%	4399
	21st to end	Day	13% 8% 3 8% 5% 5% 4 3 5% 7% 39%	4837
June	1st to 10th	Day	11% 6% 3 6% 4 4 5% 4 5% 7% 45%	2741
	11th to 20th	Day	12% 6% 2 6% 5% 5% 5% 4 6% 7% 41%	2850
	21st to end	Day	13% 6% 3 6% 5% 4 4 3 6% 8% 42%	2750
July	1st to 10th	Day	11% 5% 2 6% 4 4 5% 4 5% 8% 47%	4440
	11th to 20th	Day	7% 4 2 5% 3 3 4 4 6% 9% 53%	4440
	21st to end	Day	7% 5% 2 5% 4 3 3 3 4 8% 56%	4814
August	1st to 10th	Day	8% 6% 2 7% 5% 5% 5% 4 6% 8% 43%	4423
	11th to 20th	Day	12% 6% 2 4 3 3 3 3 5% 7% 52%	4202
	21st to end	Day	12% 7% 3 6% 3 4 4 4 5% 8% 46%	4198
September	1st to 10th	Day	12% 7% 3 5% 4 4 4 3 5% 7% 44%	2280
	11th to 20th	Day	14% 7% 2 6% 5% 4 5% 4 6% 8% 39%	2176
	21st to end	Day	17% 10% 3 7% 5% 4 4 3 5% 7% 34%	2090
October	1st to 10th	Day	16% 12% 3 10% 5% 5% 4 3 5% 6% 31%	1990
	11th to 20th	Day	20% 19% 4 11% 5% 4 5% 3 4 5% 20%	1795
	21st to end	Day	20% 19% 6% 13% 5% 5% 4 3 4 4 17%	1881
November	1st to 10th	Day	16% 23% 4 12% 5% 5% 4 4 4 5% 19%	1762
	11th to 20th	Day	15% 21% 8% 17% 8% 5% 5% 3 3 4 12%	1685
	21st to end	Day	14% 21% 9% 22% 9% 6% 3 3 2 3 8%	1550
December	1st to 10th	Day	9% 20% 12% 25% 10% 5% 4 3 4 3 5%	1365
	11th to 20th	Day	15% 18% 8% 23% 11% 6% 5% 3 3 2 7%	1671
	21st to end	Day	20% 21% 9% 19% 7% 4 5% 2 3 3 7%	2691
January	1st to 10th	Night	8% 20% 10% 28% 9% 6% 5% 2 2 2 7%	4428
	11th to 20th	Night	7% 15% 9% 23% 18% 11% 5% 3 3 2 4	4440
	21st to end	Night	8% 16% 11% 19% 11% 9% 5% 4 4 4 10%	4884
February	1st to 10th	Night	9% 14% 5% 14% 13% 12% 6% 4 3 4 15%	2608
	11th to 20th	Night	10% 12% 5% 15% 11% 11% 7% 5% 5% 4 16%	2306
	21st to end	Night	11% 15% 5% 11% 9% 7% 5% 3 5% 5% 22%	1884
March	1st to 10th	Night	6% 10% 4 11% 7% 6% 6% 5% 7% 9% 30%	3722
	11th to 20th	Night	7% 12% 5% 15% 6% 5% 5% 3 5% 7% 31%	3724
	21st to end	Night	16% 12% 6% 14% 8% 5% 5% 3 5% 6% 21%	3466
April	1st to 10th	Night	14% 11% 4 9% 7% 7% 6% 4 5% 5% 27%	1900
	11th to 20th	Night	19% 11% 3 7% 6% 4 5% 3 5% 6% 32%	1836
	21st to end	Night	17% 10% 4 7% 4 4 4 4 5% 6% 34%	1710
May	1st to 10th	Night	16% 8% 3 7% 4 4 4 3 5% 7% 40%	2568
	11th to 20th	Night	12% 7% 3 8% 6% 4 4 5% 6% 6% 39%	2506
	21st to end	Night	14% 9% 4 8% 6% 5% 4 4 5% 6% 35%	2750
June	1st to 10th	Night	13% 6% 2 8% 6% 5% 4 3 7% 8% 38%	1431
	11th to 20th	Night	12% 7% 3 7% 5% 5% 6% 5% 8% 9% 34%	1330
	21st to end	Night	14% 7% 2 6% 5% 6% 4 5% 6% 8% 39%	1422
July	1st to 10th	Night	9% 6% 3 7% 5% 6% 5% 4 6% 7% 43%	2530
	11th to 20th	Night	6% 4 2 5% 4 4 4 5% 7% 9% 51%	2530
	21st to end	Night	7% 4 2 5% 4 3 5% 5% 6% 8% 52%	2750
August	1st to 10th	Night	10% 5% 3 6% 5% 5% 4 4 6% 10% 42%	2517
	11th to 20th	Night	11% 5% 2 5% 3 4 4 3 5% 6% 51%	2632
	21st to end	Night	13% 6% 2 7% 5% 4 3 3 5% 6% 45%	3443
September	1st to 10th	Night	11% 6% 2 6% 4 4 4 3 6% 6% 47%	1900
	11th to 20th	Night	11% 7% 3 7% 6% 4 5% 4 6% 8% 41%	1985
	21st to end	Night	17% 9% 3 8% 5% 3 4 3 5% 6% 37%	2090
October	1st to 10th	Night	17% 9% 3 8% 4 5% 4 3 5% 6% 36%	2187
	11th to 20th	Night	16% 15% 4 10% 5% 5% 5% 4 6% 6% 25%	2384
	21st to end	Night	18% 16% 5% 11% 7% 5% 4 3 4 4 21%	2717
November	1st to 10th	Night	15% 20% 6% 10% 5% 5% 5% 3 5% 6% 21%	2536
	11th to 20th	Night	15% 19% 7% 16% 7% 4 4 3 4 4 16%	2713
	21st to end	Night	14% 19% 8% 19% 9% 5% 4 3 4 4 12%	2846
December	1st to 10th	Night	10% 19% 10% 24% 11% 5% 3 2 2 3 9%	2932
	11th to 20th	Night	10% 18% 8% 20% 11% 7% 5% 3 4 3 11%	3526
	21st to end	Night	18% 22% 9% 18% 8% 5% 4 2 2 3 9%	4971

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	58% 36% 2 3	2528
	11th to 20th	Day	60% 36% 3 2	2530
	21st to end	Day	52% 39% 7% 2	2783
February	1st to 10th	Day	26% 65% 4 3 1	1567
	11th to 20th	Day	24% 64% 3 7% 2	1768
	21st to end	Day	22% 64% 3 6% 4	1570
March	1st to 10th	Day	30% 39% 8% 16% 7%	3120
	11th to 20th	Day	39% 39% 10% 8% 3 1	3262
	21st to end	Day	44% 39% 3 9% 3 1	4165
April	1st to 10th	Day	21% 64% 4 6% 4	2280
	11th to 20th	Day	20% 65% 2 8% 3 1	2291
	21st to end	Day	18% 64% 2 11% 4 1	2470
May	1st to 10th	Day	26% 39% 6% 16% 12% 1	4393
	11th to 20th	Day	27% 39% 8% 20% 6%	4403
	21st to end	Day	30% 40% 9% 11% 10% 1	4837
June	1st to 10th	Day	13% 65% 6% 8% 6% 1	2741
	11th to 20th	Day	16% 66% 4 9% 4 1	2850
	21st to end	Day	15% 64% 5% 11% 4	2750
July	1st to 10th	Day	25% 37% 13% 16% 8% 1	4371
	11th to 20th	Day	17% 37% 12% 25% 8%	4365
	21st to end	Day	16% 35% 8% 29% 11%	4662
August	1st to 10th	Day	27% 37% 11% 18% 6%	4408
	11th to 20th	Day	22% 37% 16% 21% 4	4244
	21st to end	Day	24% 38% 12% 18% 8%	4197
September	1st to 10th	Day	16% 61% 7% 12% 4	2280
	11th to 20th	Day	16% 61% 10% 10% 3	2176
	21st to end	Day	18% 60% 9% 11% 3	2090
October	1st to 10th	Day	22% 38% 8% 26% 6%	3302
	11th to 20th	Day	36% 36% 7% 10% 10%	2959
	21st to end	Day	39% 38% 10% 10% 2	3081
November	1st to 10th	Day	32% 56% 6% 5% 2	1762
	11th to 20th	Day	34% 56% 5% 4 1	1685
	21st to end	Day	39% 57% 2 2 1	1550
December	1st to 10th	Day	34% 58% 5% 3	1365
	11th to 20th	Day	46% 48% 3 2 1	1671
	21st to end	Day	53% 36% 4 7%	2691
January	1st to 10th	Night	56% 36% 3 4	4428
	11th to 20th	Night	59% 36% 3 2	4440
	21st to end	Night	47% 38% 12% 3	4884
February	1st to 10th	Night	24% 65% 5% 4 1	2608
	11th to 20th	Night	24% 63% 5% 7% 1	2307
	21st to end	Night	20% 65% 5% 6% 4	1884
March	1st to 10th	Night	27% 41% 13% 12% 7%	3733
	11th to 20th	Night	35% 39% 7% 15% 4	3725
	21st to end	Night	44% 40% 4 9% 3 1	3466
April	1st to 10th	Night	20% 64% 4 6% 5%	1900
	11th to 20th	Night	18% 65% 3 8% 4 1	1836
	21st to end	Night	18% 64% 3 8% 7%	1710
May	1st to 10th	Night	24% 40% 7% 20% 9% 1	2575
	11th to 20th	Night	27% 39% 6% 17% 10% 1	2507
	21st to end	Night	34% 39% 7% 9% 10% 1	2751
June	1st to 10th	Night	16% 65% 4 8% 7%	1431
	11th to 20th	Night	19% 66% 5% 6% 4	1330
	21st to end	Night	17% 64% 5% 9% 4 1	1422
July	1st to 10th	Night	27% 38% 11% 15% 7% 2	2490
	11th to 20th	Night	14% 38% 11% 28% 9%	2482
	21st to end	Night	17% 36% 7% 22% 17% 1	2662
August	1st to 10th	Night	26% 37% 8% 20% 8% 1	2508
	11th to 20th	Night	24% 38% 12% 20% 6%	2656
	21st to end	Night	27% 39% 10% 17% 7%	3443
September	1st to 10th	Night	16% 61% 6% 13% 4	1900
	11th to 20th	Night	17% 60% 7% 13% 2	1985
	21st to end	Night	18% 60% 8% 11% 2 1	2090
October	1st to 10th	Night	20% 37% 7% 26% 11%	3655
	11th to 20th	Night	28% 37% 8% 18% 9%	3959
	21st to end	Night	37% 38% 12% 11% 3	4467
November	1st to 10th	Night	31% 55% 6% 7% 1	2536
	11th to 20th	Night	32% 57% 5% 4 2	2713
	21st to end	Night	37% 57% 4 2	2846
December	1st to 10th	Night	34% 58% 4 3 1	2932
	11th to 20th	Night	39% 49% 6% 5% 1	3525
	21st to end	Night	51% 36% 6% 6%	4971

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% 15% 40% 21% 6% 1	270
	11th to 20th	Day	17% 14% 38% 23% 7% 1	270
	21st to end	Day	22% 12% 45% 18% 2	297
February	1st to 10th	Day	20% 22% 37% 16% 4 1	270
	11th to 20th	Day	15% 29% 32% 17% 7%	270
	21st to end	Day	20% 25% 40% 14% 1	225
March	1st to 10th	Day	13% 20% 43% 19% 4 1	270
	11th to 20th	Day	16% 19% 34% 24% 7% 1	300
	21st to end	Day	23% 15% 30% 22% 8% 2	506
April	1st to 10th	Day	22% 11% 34% 25% 7% 1	460
	11th to 20th	Day	29% 13% 25% 23% 8% 2	452
	21st to end	Day	27% 10% 29% 21% 10% 3	460
May	1st to 10th	Day	17% 13% 35% 24% 8% 2	619
	11th to 20th	Day	16% 9% 37% 25% 9% 3	675
	21st to end	Day	18% 8% 30% 30% 13% 1	734
June	1st to 10th	Day	14% 8% 32% 31% 13% 2	680
	11th to 20th	Day	17% 9% 31% 28% 12% 3	680
	21st to end	Day	17% 8% 26% 30% 15% 4	680
July	1st to 10th	Day	9% 5% 30% 35% 16% 5%	671
	11th to 20th	Day	10% 8% 29% 30% 18% 5%	668
	21st to end	Day	9% 6% 28% 35% 16% 6%	739
August	1st to 10th	Day	13% 8% 26% 31% 18% 4	676
	11th to 20th	Day	14% 6% 19% 31% 23% 7%	576
	21st to end	Day	17% 11% 21% 27% 20% 4	539
September	1st to 10th	Day	18% 7% 26% 28% 17% 5%	490
	11th to 20th	Day	15% 8% 27% 30% 17% 2	490
	21st to end	Day	23% 10% 24% 27% 13% 3	490
October	1st to 10th	Day	24% 13% 27% 23% 10% 3	390
	11th to 20th	Day	31% 19% 31% 16% 3	300
	21st to end	Day	36% 18% 32% 12% 2	330
November	1st to 10th	Day	28% 17% 29% 19% 5% 1	300
	11th to 20th	Day	25% 21% 38% 11% 4	300
	21st to end	Day	26% 19% 36% 13% 4 1	275
December	1st to 10th	Day	24% 14% 37% 17% 7% 1	190
	11th to 20th	Day	29% 18% 33% 16% 3 1	180
	21st to end	Day	27% 16% 36% 17% 3	272
January	1st to 10th	Night	17% 16% 39% 22% 5% 1	950
	11th to 20th	Night	19% 12% 39% 22% 7% 2	950
	21st to end	Night	19% 13% 35% 26% 8%	1045
February	1st to 10th	Night	17% 16% 33% 25% 7% 1	950
	11th to 20th	Night	18% 15% 33% 23% 9% 1	832
	21st to end	Night	19% 11% 36% 28% 6%	628
March	1st to 10th	Night	14% 11% 31% 33% 10% 2	760
	11th to 20th	Night	19% 12% 30% 29% 9% 1	755
	21st to end	Night	22% 9% 23% 30% 14% 2	627
April	1st to 10th	Night	24% 5% 29% 32% 8% 2	570
	11th to 20th	Night	23% 10% 26% 30% 10% 1	563
	21st to end	Night	22% 6% 24% 32% 13% 2	570
May	1st to 10th	Night	18% 8% 27% 31% 14% 1	570
	11th to 20th	Night	19% 5% 27% 35% 12% 3	561
	21st to end	Night	15% 7% 20% 37% 18% 1	617
June	1st to 10th	Night	17% 6% 18% 43% 14% 2	481
	11th to 20th	Night	14% 5% 24% 42% 13% 1	380
	21st to end	Night	17% 4 20% 38% 19% 2	472
July	1st to 10th	Night	9% 4 18% 43% 24% 3	555
	11th to 20th	Night	11% 6% 25% 32% 24% 3	552
	21st to end	Night	10% 3 21% 40% 24% 3	624
August	1st to 10th	Night	11% 2 20% 39% 26% 2	567
	11th to 20th	Night	12% 3 18% 31% 30% 5%	564
	21st to end	Night	16% 5% 21% 33% 22% 2	627
September	1st to 10th	Night	17% 6% 20% 31% 22% 4	570
	11th to 20th	Night	16% 5% 24% 34% 18% 2	655
	21st to end	Night	23% 7% 22% 31% 16% 1	760
October	1st to 10th	Night	25% 11% 25% 25% 13% 1	760
	11th to 20th	Night	29% 11% 27% 24% 9% 1	760
	21st to end	Night	33% 10% 24% 26% 7% 1	836
November	1st to 10th	Night	28% 12% 27% 27% 6% 1	780
	11th to 20th	Night	26% 16% 30% 19% 8% 1	913
	21st to end	Night	26% 17% 30% 23% 4	1000
December	1st to 10th	Night	22% 19% 34% 19% 6% 1	978
	11th to 20th	Night	20% 17% 34% 20% 8% 1	950
	21st to end	Night	29% 14% 33% 19% 5% 1	1045

Page generated at 2024-12-03 06:45:11. Version ac07

Copyright © 2024 Attilla Danko.