Machias
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Machias clear sky chart from 2005-11-06 to 2024-02-10.

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	20% 8% 3 5% 5% 3 4 4 5% 7% 37%	77977
	Night	20% 8% 3 6% 5% 3 4 4 5% 6% 36%	80989
Transparency	Day	48% 7% 12% 20% 11% 2	77682
	Night	50% 6% 12% 20% 11% 1	80819
Seeing	Day	24% 18% 32% 19% 6% 1	15052
	Night	25% 15% 31% 22% 6% 1	23330

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	19% 9% 3 5% 5% 3 4 4 4 5% 39%	2366
	11th to 20th	Day	19% 7% 3 5% 4 2 4 3 3 4 45%	2520
	21st to end	Day	17% 9% 4 7% 6% 3 4 5% 5% 6% 34%	2973
February	1st to 10th	Day	18% 11% 3 6% 5% 3 4 5% 4 7% 32%	1701
	11th to 20th	Day	16% 9% 4 6% 5% 3 5% 5% 4 7% 34%	1601
	21st to end	Day	14% 9% 3 6% 5% 4 5% 4 5% 7% 36%	1480
March	1st to 10th	Day	18% 11% 4 6% 5% 2 5% 4 5% 7% 34%	1858
	11th to 20th	Day	17% 9% 3 5% 5% 3 4 4 4 7% 38%	1980
	21st to end	Day	19% 11% 3 6% 6% 3 3 3 3 6% 37%	2178
April	1st to 10th	Day	22% 11% 4 6% 5% 3 4 4 4 7% 30%	2096
	11th to 20th	Day	22% 9% 2 5% 4 3 4 4 5% 6% 37%	2312
	21st to end	Day	24% 8% 3 6% 4 3 3 3 5% 6% 35%	2340
May	1st to 10th	Day	23% 10% 3 6% 5% 3 4 4 5% 6% 30%	2340
	11th to 20th	Day	23% 6% 3 4 5% 2 4 3 5% 6% 40%	2305
	21st to end	Day	21% 8% 3 6% 6% 2 4 5% 5% 8% 32%	2804
June	1st to 10th	Day	24% 7% 4 6% 5% 2 4 4 5% 7% 30%	2700
	11th to 20th	Day	22% 7% 3 5% 5% 2 4 4 5% 8% 36%	2700
	21st to end	Day	27% 9% 3 5% 5% 3 4 4 5% 7% 28%	2700
July	1st to 10th	Day	18% 7% 3 5% 5% 3 5% 5% 6% 10% 34%	2700
	11th to 20th	Day	18% 7% 2 5% 5% 3 4 4 5% 10% 37%	2552
	21st to end	Day	16% 6% 3 5% 5% 4 5% 6% 7% 9% 34%	2625
August	1st to 10th	Day	16% 6% 2 5% 5% 2 5% 5% 6% 9% 38%	2327
	11th to 20th	Day	17% 7% 2 5% 5% 4 5% 5% 6% 10% 34%	2304
	21st to end	Day	14% 6% 2 4 5% 3 4 5% 6% 8% 44%	2574
September	1st to 10th	Day	13% 5% 2 4 4 3 4 4 6% 8% 47%	2097
	11th to 20th	Day	18% 5% 2 4 4 2 3 4 3 6% 49%	1980
	21st to end	Day	20% 5% 2 5% 4 3 4 4 4 6% 43%	1980
October	1st to 10th	Day	17% 7% 2 5% 4 3 4 5% 5% 7% 41%	1877
	11th to 20th	Day	20% 5% 2 5% 4 3 5% 4 5% 8% 40%	1800
	21st to end	Day	23% 7% 2 5% 4 3 3 4 5% 5% 38%	1839
November	1st to 10th	Day	21% 6% 2 6% 4 2 4 4 5% 6% 39%	1671
	11th to 20th	Day	20% 6% 2 4 3 3 4 3 5% 7% 42%	1567
	21st to end	Day	22% 9% 3 4 3 2 3 4 4 6% 39%	1520
December	1st to 10th	Day	25% 8% 3 5% 4 3 4 5% 5% 6% 34%	1511
	11th to 20th	Day	26% 9% 3 6% 6% 3 4 3 4 5% 31%	1668
	21st to end	Day	26% 7% 2 5% 4 3 4 3 4 5% 36%	2431
January	1st to 10th	Night	15% 9% 4 6% 5% 3 4 4 4 5% 41%	4581
	11th to 20th	Night	15% 10% 3 8% 6% 3 5% 4 5% 5% 36%	4440
	21st to end	Night	17% 10% 4 7% 5% 3 4 4 5% 6% 33%	4680
February	1st to 10th	Night	19% 9% 3 5% 5% 3 5% 5% 5% 7% 34%	2464
	11th to 20th	Night	17% 9% 3 6% 5% 4 4 4 4 6% 36%	2241
	21st to end	Night	16% 10% 3 6% 5% 2 4 4 4 6% 38%	1776
March	1st to 10th	Night	15% 11% 3 8% 5% 3 4 4 4 7% 37%	2089
	11th to 20th	Night	18% 9% 4 7% 5% 3 4 5% 4 7% 32%	1979
	21st to end	Night	18% 10% 3 5% 6% 3 4 3 4 5% 38%	2178
April	1st to 10th	Night	26% 9% 3 5% 4 2 4 5% 5% 5% 31%	1861
	11th to 20th	Night	23% 8% 3 6% 4 2 4 4 5% 6% 33%	1598
	21st to end	Night	27% 8% 3 5% 4 3 4 4 5% 6% 30%	1620
May	1st to 10th	Night	24% 9% 3 5% 5% 3 3 4 4 7% 33%	1620
	11th to 20th	Night	27% 7% 2 6% 5% 4 3 5% 4 5% 32%	1586
	21st to end	Night	22% 9% 3 5% 6% 3 4 4 7% 7% 32%	1484
June	1st to 10th	Night	27% 8% 3 6% 5% 3 5% 4 5% 7% 26%	1260
	11th to 20th	Night	24% 8% 3 6% 4 3 4 4 4 7% 34%	1260
	21st to end	Night	30% 9% 3 5% 5% 2 4 2 5% 5% 29%	1260
July	1st to 10th	Night	19% 11% 3 6% 5% 3 5% 5% 7% 7% 29%	1260
	11th to 20th	Night	22% 7% 3 4 5% 4 5% 4 5% 7% 32%	1404
	21st to end	Night	22% 9% 4 6% 5% 3 5% 5% 5% 6% 31%	1672
August	1st to 10th	Night	18% 8% 3 5% 5% 3 5% 6% 6% 8% 33%	1612
	11th to 20th	Night	19% 10% 3 4 5% 3 5% 4 6% 8% 32%	1596
	21st to end	Night	18% 6% 3 4 4 3 4 5% 4 6% 42%	1782
September	1st to 10th	Night	17% 6% 3 5% 3 2 4 4 4 7% 45%	1858
	11th to 20th	Night	18% 6% 2 4 4 2 4 3 3 6% 47%	1980
	21st to end	Night	19% 7% 1 5% 4 2 3 3 5% 7% 44%	1980
October	1st to 10th	Night	20% 5% 2 4 5% 3 4 5% 5% 7% 40%	2082
	11th to 20th	Night	20% 5% 2 5% 4 3 4 4 4 7% 42%	2160
	21st to end	Night	24% 8% 2 4 5% 2 3 3 4 6% 38%	2515
November	1st to 10th	Night	20% 6% 2 5% 4 3 5% 4 5% 5% 41%	2407
	11th to 20th	Night	20% 7% 2 5% 4 3 4 4 5% 6% 41%	2612
	21st to end	Night	20% 7% 2 5% 4 2 4 5% 6% 7% 37%	2660
December	1st to 10th	Night	26% 10% 3 6% 4 3 3 4 4 5% 31%	2665
	11th to 20th	Night	26% 8% 3 4 3 3 4 5% 4 5% 35%	3531
	21st to end	Night	24% 9% 3 5% 5% 3 3 4 4 6% 36%	5236

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	49% 6% 17% 22% 6% 1	2367
	11th to 20th	Day	45% 6% 13% 24% 10% 2	2520
	21st to end	Day	51% 8% 16% 18% 7%	2973
February	1st to 10th	Day	53% 7% 14% 16% 9% 1	1701
	11th to 20th	Day	51% 7% 15% 17% 9% 1	1609
	21st to end	Day	46% 8% 13% 20% 9% 4	1480
March	1st to 10th	Day	49% 7% 11% 19% 11% 3	1862
	11th to 20th	Day	43% 7% 13% 18% 16% 3	1980
	21st to end	Day	47% 6% 10% 18% 15% 4	2178
April	1st to 10th	Day	51% 6% 11% 16% 14% 3	2096
	11th to 20th	Day	45% 6% 11% 22% 13% 2	2312
	21st to end	Day	49% 6% 11% 16% 16% 2	2340
May	1st to 10th	Day	53% 6% 10% 18% 11% 2	2340
	11th to 20th	Day	45% 6% 10% 22% 15% 1	2309
	21st to end	Day	52% 7% 12% 20% 9% 1	2804
June	1st to 10th	Day	54% 6% 12% 18% 9% 1	2700
	11th to 20th	Day	50% 6% 10% 17% 15% 2	2700
	21st to end	Day	57% 6% 10% 15% 10% 2	2700
July	1st to 10th	Day	51% 7% 12% 19% 11% 1	2625
	11th to 20th	Day	51% 7% 13% 19% 9% 1	2475
	21st to end	Day	50% 8% 14% 20% 7% 1	2478
August	1st to 10th	Day	46% 8% 13% 24% 9% 1	2314
	11th to 20th	Day	50% 8% 13% 19% 10%	2304
	21st to end	Day	40% 6% 13% 24% 15% 1	2574
September	1st to 10th	Day	37% 7% 13% 24% 17% 1	2097
	11th to 20th	Day	38% 6% 10% 25% 18% 3	1980
	21st to end	Day	41% 5% 10% 28% 14% 1	1980
October	1st to 10th	Day	40% 7% 13% 25% 15% 1	1877
	11th to 20th	Day	41% 7% 15% 27% 11%	1800
	21st to end	Day	47% 6% 12% 21% 13% 1	1839
November	1st to 10th	Day	46% 6% 13% 22% 12% 1	1671
	11th to 20th	Day	42% 6% 13% 22% 15% 2	1567
	21st to end	Day	48% 7% 16% 21% 7% 1	1520
December	1st to 10th	Day	53% 7% 16% 16% 8%	1511
	11th to 20th	Day	58% 5% 11% 18% 7%	1668
	21st to end	Day	51% 9% 13% 16% 9% 2	2431
January	1st to 10th	Night	47% 6% 14% 26% 6% 1	4581
	11th to 20th	Night	51% 8% 14% 19% 7% 1	4440
	21st to end	Night	53% 8% 15% 18% 6%	4680
February	1st to 10th	Night	53% 7% 14% 15% 9% 2	2464
	11th to 20th	Night	51% 6% 11% 19% 11% 2	2244
	21st to end	Night	48% 6% 11% 20% 13% 3	1776
March	1st to 10th	Night	50% 5% 10% 17% 15% 2	2098
	11th to 20th	Night	53% 5% 12% 14% 14% 2	1980
	21st to end	Night	48% 4 9% 21% 16% 2	2178
April	1st to 10th	Night	53% 7% 8% 15% 14% 4	1861
	11th to 20th	Night	50% 5% 10% 20% 14% 2	1598
	21st to end	Night	55% 4 11% 15% 13% 2	1620
May	1st to 10th	Night	52% 6% 8% 20% 13% 1	1620
	11th to 20th	Night	54% 6% 9% 18% 11% 2	1587
	21st to end	Night	52% 6% 12% 17% 12% 1	1485
June	1st to 10th	Night	58% 5% 11% 17% 7% 1	1260
	11th to 20th	Night	53% 6% 9% 20% 10% 2	1260
	21st to end	Night	58% 6% 8% 18% 8% 3	1260
July	1st to 10th	Night	55% 8% 11% 15% 11%	1225
	11th to 20th	Night	53% 6% 12% 17% 11% 1	1358
	21st to end	Night	55% 7% 11% 17% 8% 1	1579
August	1st to 10th	Night	48% 8% 14% 21% 8%	1600
	11th to 20th	Night	54% 7% 12% 18% 8%	1596
	21st to end	Night	43% 6% 12% 22% 16% 1	1782
September	1st to 10th	Night	39% 6% 12% 26% 16% 1	1858
	11th to 20th	Night	41% 4 10% 24% 19% 2	1980
	21st to end	Night	41% 4 9% 27% 17% 1	1980
October	1st to 10th	Night	42% 7% 10% 24% 14% 2	2082
	11th to 20th	Night	42% 6% 14% 25% 12% 1	2160
	21st to end	Night	49% 5% 12% 21% 12% 1	2515
November	1st to 10th	Night	46% 6% 13% 22% 14% 1	2407
	11th to 20th	Night	46% 6% 12% 20% 14% 2	2612
	21st to end	Night	47% 7% 15% 20% 10% 1	2660
December	1st to 10th	Night	58% 5% 14% 15% 7%	2665
	11th to 20th	Night	52% 6% 14% 18% 8% 1	3532
	21st to end	Night	51% 8% 14% 16% 8% 2	5236

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	27% 24% 33% 12% 3	180
	11th to 20th	Day	31% 21% 37% 8% 3	180
	21st to end	Day	19% 26% 33% 20% 2	321
February	1st to 10th	Day	26% 25% 29% 16% 3	367
	11th to 20th	Day	25% 32% 30% 11% 2	349
	21st to end	Day	23% 26% 34% 15% 3	346
March	1st to 10th	Day	25% 27% 32% 13% 2	420
	11th to 20th	Day	24% 27% 30% 15% 4	420
	21st to end	Day	28% 25% 28% 13% 4 2	462
April	1st to 10th	Day	32% 25% 31% 8% 3 1	420
	11th to 20th	Day	28% 25% 30% 12% 4 1	412
	21st to end	Day	26% 21% 34% 14% 4 1	420
May	1st to 10th	Day	27% 22% 33% 15% 3	423
	11th to 20th	Day	24% 19% 34% 17% 5% 1	451
	21st to end	Day	27% 17% 29% 19% 8% 1	680
June	1st to 10th	Day	26% 15% 31% 21% 6%	630
	11th to 20th	Day	24% 13% 32% 22% 8% 1	630
	21st to end	Day	31% 10% 29% 22% 7% 1	630
July	1st to 10th	Day	23% 10% 35% 22% 9% 1	620
	11th to 20th	Day	23% 8% 34% 26% 8% 2	474
	21st to end	Day	16% 11% 37% 26% 8% 1	488
August	1st to 10th	Day	15% 10% 33% 31% 10% 1	446
	11th to 20th	Day	21% 9% 32% 28% 10% 1	439
	21st to end	Day	16% 13% 31% 26% 11% 2	495
September	1st to 10th	Day	14% 11% 34% 30% 9% 1	450
	11th to 20th	Day	22% 16% 29% 21% 10% 3	450
	21st to end	Day	20% 14% 31% 21% 10% 3	450
October	1st to 10th	Day	19% 18% 30% 22% 9% 2	399
	11th to 20th	Day	21% 18% 29% 22% 8% 1	360
	21st to end	Day	26% 17% 34% 18% 5% 1	396
November	1st to 10th	Day	23% 20% 29% 20% 6% 2	365
	11th to 20th	Day	25% 22% 32% 15% 5%	370
	21st to end	Day	27% 25% 30% 15% 3	370
December	1st to 10th	Day	28% 22% 31% 16% 4	361
	11th to 20th	Day	36% 29% 25% 8% 2	180
	21st to end	Day	32% 29% 23% 13% 2 1	198
January	1st to 10th	Night	23% 22% 34% 17% 3	801
	11th to 20th	Night	27% 21% 34% 16% 3	760
	21st to end	Night	20% 25% 36% 15% 4	836
February	1st to 10th	Night	25% 22% 34% 15% 3	759
	11th to 20th	Night	24% 26% 31% 16% 2 1	703
	21st to end	Night	23% 20% 36% 17% 4	592
March	1st to 10th	Night	23% 21% 36% 18% 2	720
	11th to 20th	Night	25% 20% 30% 20% 5%	720
	21st to end	Night	23% 19% 35% 18% 5% 1	792
April	1st to 10th	Night	30% 19% 33% 15% 3	687
	11th to 20th	Night	28% 13% 35% 21% 2	534
	21st to end	Night	31% 14% 31% 18% 7%	540
May	1st to 10th	Night	26% 10% 31% 26% 6%	540
	11th to 20th	Night	31% 9% 36% 20% 3 1	532
	21st to end	Night	25% 10% 33% 24% 7% 1	517
June	1st to 10th	Night	30% 7% 30% 25% 7% 1	360
	11th to 20th	Night	26% 7% 30% 30% 6% 1	360
	21st to end	Night	33% 3 22% 36% 6%	360
July	1st to 10th	Night	24% 6% 27% 35% 8%	350
	11th to 20th	Night	26% 4 23% 36% 9% 1	348
	21st to end	Night	25% 6% 27% 31% 11%	492
August	1st to 10th	Night	19% 7% 29% 35% 10%	538
	11th to 20th	Night	23% 5% 26% 35% 10% 1	532
	21st to end	Night	19% 5% 28% 34% 12% 1	594
September	1st to 10th	Night	19% 5% 35% 29% 10% 1	639
	11th to 20th	Night	20% 8% 29% 27% 13% 2	720
	21st to end	Night	22% 10% 31% 25% 11% 2	720
October	1st to 10th	Night	23% 8% 28% 27% 12% 1	720
	11th to 20th	Night	23% 13% 29% 24% 10% 1	720
	21st to end	Night	28% 17% 30% 20% 5%	792
November	1st to 10th	Night	24% 15% 29% 24% 6% 1	740
	11th to 20th	Night	25% 20% 29% 18% 7% 1	827
	21st to end	Night	26% 21% 29% 18% 5% 1	850
December	1st to 10th	Night	32% 17% 33% 15% 3	850
	11th to 20th	Night	29% 24% 29% 14% 3	850
	21st to end	Night	28% 24% 30% 15% 3	935

Page generated at 2024-02-07 06:11:55. Version ac07

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