Mill Ridge
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mill Ridge clear sky chart from 2005-11-06 to 2024-02-15.

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	11% 8% 4 7% 6% 4 6% 5% 6% 7% 34%	78703
	Night	11% 9% 4 7% 6% 3 5% 5% 6% 7% 36%	80391
Transparency	Day	45% 10% 11% 17% 14% 3	78426
	Night	44% 9% 12% 18% 14% 3	80187
Seeing	Day	19% 15% 25% 21% 14% 6%	13971
	Night	18% 12% 22% 29% 17% 3	24132

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% 9% 6% 13% 7% 4 4 3 6% 7% 30%	2836
	11th to 20th	Day	10% 11% 6% 13% 7% 5% 5% 4 4 4 30%	2840
	21st to end	Day	13% 16% 7% 8% 5% 3 4 4 4 5% 31%	3124
February	1st to 10th	Day	12% 10% 6% 8% 7% 4 4 5% 4 6% 33%	1800
	11th to 20th	Day	14% 11% 6% 9% 7% 4 5% 4 4 6% 32%	1788
	21st to end	Day	15% 12% 3 8% 5% 3 4 4 5% 6% 35%	1480
March	1st to 10th	Day	12% 10% 5% 5% 5% 4 4 4 5% 6% 40%	1916
	11th to 20th	Day	14% 11% 4 8% 6% 4 5% 5% 5% 6% 32%	1980
	21st to end	Day	13% 11% 5% 7% 6% 3 5% 5% 5% 7% 32%	2178
April	1st to 10th	Day	9% 8% 3 5% 6% 3 5% 5% 6% 9% 41%	1980
	11th to 20th	Day	14% 7% 2 6% 5% 4 5% 5% 5% 7% 40%	2171
	21st to end	Day	12% 7% 4 6% 6% 3 5% 6% 5% 8% 38%	2340
May	1st to 10th	Day	11% 6% 3 7% 6% 4 6% 5% 6% 8% 37%	2340
	11th to 20th	Day	13% 9% 3 7% 7% 5% 6% 7% 6% 7% 31%	2301
	21st to end	Day	10% 7% 2 7% 6% 5% 7% 5% 8% 10% 32%	2531
June	1st to 10th	Day	10% 6% 3 6% 7% 5% 7% 7% 7% 9% 32%	2340
	11th to 20th	Day	6% 6% 3 8% 8% 5% 8% 7% 8% 9% 32%	2340
	21st to end	Day	9% 6% 3 6% 7% 5% 8% 6% 8% 9% 32%	2340
July	1st to 10th	Day	9% 6% 4 9% 9% 6% 8% 8% 7% 8% 26%	2340
	11th to 20th	Day	11% 6% 4 7% 8% 5% 9% 7% 9% 8% 26%	2340
	21st to end	Day	9% 7% 3 8% 9% 5% 7% 8% 8% 10% 26%	2547
August	1st to 10th	Day	10% 6% 3 7% 10% 5% 9% 8% 7% 10% 24%	2327
	11th to 20th	Day	10% 8% 3 8% 8% 5% 7% 8% 8% 9% 26%	2303
	21st to end	Day	10% 7% 3 8% 8% 4 7% 7% 7% 10% 30%	2394
September	1st to 10th	Day	9% 7% 4 7% 7% 4 6% 6% 7% 8% 37%	1980
	11th to 20th	Day	13% 7% 3 8% 7% 4 5% 5% 5% 7% 35%	1980
	21st to end	Day	13% 6% 3 6% 6% 4 5% 6% 6% 7% 39%	1980
October	1st to 10th	Day	13% 6% 3 6% 5% 3 4 4 5% 7% 45%	1958
	11th to 20th	Day	11% 7% 3 6% 4 3 3 5% 5% 6% 48%	1800
	21st to end	Day	12% 8% 3 4 4 3 4 4 5% 6% 48%	1980
November	1st to 10th	Day	10% 6% 3 4 4 2 4 4 4 6% 53%	1742
	11th to 20th	Day	9% 9% 2 6% 6% 2 5% 4 6% 6% 46%	1710
	21st to end	Day	10% 9% 3 5% 5% 3 4 4 5% 7% 44%	1710
December	1st to 10th	Day	14% 11% 5% 8% 6% 3 4 6% 6% 6% 33%	1710
	11th to 20th	Day	10% 11% 5% 8% 4 2 5% 6% 7% 6% 36%	2153
	21st to end	Day	14% 10% 7% 7% 5% 4 5% 6% 5% 6% 30%	3124
January	1st to 10th	Night	13% 10% 7% 14% 7% 3 4 4 4 6% 28%	4109
	11th to 20th	Night	13% 10% 5% 10% 8% 5% 5% 4 4 6% 31%	4120
	21st to end	Night	14% 16% 5% 8% 6% 3 4 5% 5% 5% 30%	4532
February	1st to 10th	Night	11% 10% 5% 8% 6% 3 5% 5% 6% 7% 36%	2377
	11th to 20th	Night	16% 11% 5% 9% 6% 3 4 3 5% 5% 32%	2153
	21st to end	Night	14% 13% 5% 8% 5% 3 5% 4 5% 6% 33%	1776
March	1st to 10th	Night	11% 11% 5% 7% 6% 3 5% 4 4 6% 39%	2043
	11th to 20th	Night	13% 12% 4 7% 5% 4 5% 5% 5% 7% 32%	1980
	21st to end	Night	11% 10% 4 7% 6% 4 4 5% 7% 7% 36%	2178
April	1st to 10th	Night	11% 7% 4 5% 5% 3 5% 5% 6% 8% 42%	1980
	11th to 20th	Night	10% 9% 4 5% 5% 4 4 5% 4 7% 43%	1752
	21st to end	Night	11% 7% 3 6% 6% 3 4 6% 6% 6% 42%	1620
May	1st to 10th	Night	10% 8% 3 6% 6% 2 5% 5% 7% 9% 38%	1620
	11th to 20th	Night	11% 6% 3 7% 6% 5% 5% 7% 7% 10% 33%	1592
	21st to end	Night	7% 6% 3 7% 8% 3 6% 7% 8% 9% 37%	1744
June	1st to 10th	Night	7% 5% 3 6% 6% 4 6% 6% 9% 12% 35%	1620
	11th to 20th	Night	5% 4 3 6% 6% 4 6% 5% 8% 14% 38%	1620
	21st to end	Night	8% 5% 3 5% 6% 4 6% 5% 8% 11% 40%	1620
July	1st to 10th	Night	9% 7% 3 6% 6% 4 6% 7% 7% 11% 33%	1620
	11th to 20th	Night	8% 4 3 7% 7% 3 7% 7% 11% 13% 30%	1620
	21st to end	Night	6% 6% 3 7% 7% 5% 7% 9% 9% 11% 31%	1771
August	1st to 10th	Night	8% 5% 3 7% 7% 4 6% 8% 8% 11% 34%	1611
	11th to 20th	Night	8% 8% 3 7% 8% 3 7% 5% 8% 8% 35%	1598
	21st to end	Night	9% 6% 3 7% 7% 3 6% 6% 8% 9% 35%	1940
September	1st to 10th	Night	9% 6% 3 7% 6% 4 5% 6% 7% 8% 40%	1980
	11th to 20th	Night	12% 8% 4 7% 6% 3 5% 5% 5% 8% 37%	1980
	21st to end	Night	10% 7% 3 6% 6% 3 4 4 4 6% 46%	1980
October	1st to 10th	Night	13% 7% 2 5% 5% 2 4 3 4 6% 48%	2001
	11th to 20th	Night	12% 7% 2 5% 5% 4 4 4 5% 6% 47%	2160
	21st to end	Night	10% 9% 3 5% 4 2 4 4 4 7% 48%	2376
November	1st to 10th	Night	11% 7% 3 5% 5% 3 4 4 5% 6% 48%	2334
	11th to 20th	Night	10% 10% 3 6% 4 2 4 4 5% 7% 45%	2470
	21st to end	Night	10% 9% 4 6% 5% 2 4 4 5% 7% 45%	2470
December	1st to 10th	Night	13% 11% 6% 10% 6% 3 5% 5% 5% 6% 28%	2470
	11th to 20th	Night	13% 11% 5% 11% 5% 3 4 4 4 5% 35%	3042
	21st to end	Night	14% 10% 6% 10% 8% 4 5% 6% 6% 7% 25%	4532

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	45% 9% 10% 18% 15% 3	2837
	11th to 20th	Day	51% 8% 8% 14% 17% 2	2840
	21st to end	Day	53% 6% 7% 15% 18% 1	3124
February	1st to 10th	Day	52% 7% 9% 15% 16% 3	1800
	11th to 20th	Day	54% 7% 9% 15% 13% 3	1798
	21st to end	Day	49% 7% 10% 14% 14% 6%	1480
March	1st to 10th	Day	42% 7% 8% 19% 18% 5%	1916
	11th to 20th	Day	52% 7% 10% 15% 13% 3	1980
	21st to end	Day	50% 8% 10% 19% 11% 2	2178
April	1st to 10th	Day	39% 9% 12% 22% 16% 3	1980
	11th to 20th	Day	41% 8% 8% 18% 20% 4	2171
	21st to end	Day	42% 9% 12% 22% 12% 2	2340
May	1st to 10th	Day	43% 11% 14% 21% 10% 2	2340
	11th to 20th	Day	50% 12% 12% 16% 8% 1	2305
	21st to end	Day	43% 13% 13% 20% 10% 1	2531
June	1st to 10th	Day	44% 14% 17% 16% 8% 1	2340
	11th to 20th	Day	43% 15% 16% 13% 11% 1	2340
	21st to end	Day	44% 13% 14% 18% 10% 2	2340
July	1st to 10th	Day	50% 14% 13% 14% 7% 1	2275
	11th to 20th	Day	48% 16% 14% 11% 9% 2	2271
	21st to end	Day	47% 18% 14% 14% 7% 1	2405
August	1st to 10th	Day	49% 16% 15% 15% 5%	2314
	11th to 20th	Day	48% 15% 15% 13% 8% 1	2303
	21st to end	Day	46% 13% 13% 16% 9% 2	2394
September	1st to 10th	Day	42% 12% 12% 17% 13% 3	1980
	11th to 20th	Day	47% 9% 10% 18% 14% 2	1980
	21st to end	Day	43% 8% 12% 17% 15% 4	1980
October	1st to 10th	Day	37% 8% 10% 18% 22% 4	1958
	11th to 20th	Day	36% 7% 10% 21% 20% 6%	1800
	21st to end	Day	37% 6% 8% 23% 22% 6%	1980
November	1st to 10th	Day	33% 6% 8% 19% 26% 8%	1742
	11th to 20th	Day	37% 6% 8% 20% 23% 5%	1710
	21st to end	Day	39% 6% 9% 22% 19% 5%	1710
December	1st to 10th	Day	51% 8% 9% 17% 13% 3	1710
	11th to 20th	Day	43% 7% 10% 17% 19% 3	2150
	21st to end	Day	48% 9% 10% 21% 10% 1	3124
January	1st to 10th	Night	53% 8% 8% 13% 14% 3	4109
	11th to 20th	Night	50% 6% 7% 12% 20% 4	4120
	21st to end	Night	53% 7% 7% 13% 18% 1	4532
February	1st to 10th	Night	46% 7% 11% 18% 15% 3	2377
	11th to 20th	Night	54% 5% 8% 17% 12% 4	2154
	21st to end	Night	51% 8% 10% 15% 12% 4	1776
March	1st to 10th	Night	47% 5% 9% 15% 19% 5%	2043
	11th to 20th	Night	49% 9% 11% 18% 12% 2	1980
	21st to end	Night	47% 9% 11% 20% 12% 2	2178
April	1st to 10th	Night	39% 7% 14% 22% 16% 2	1980
	11th to 20th	Night	40% 8% 10% 20% 19% 4	1752
	21st to end	Night	40% 9% 12% 26% 12% 1	1620
May	1st to 10th	Night	40% 10% 17% 23% 9% 2	1620
	11th to 20th	Night	42% 16% 14% 21% 7% 1	1593
	21st to end	Night	38% 15% 16% 22% 8% 1	1745
June	1st to 10th	Night	37% 13% 22% 19% 9%	1620
	11th to 20th	Night	32% 15% 23% 20% 9% 1	1620
	21st to end	Night	35% 13% 20% 19% 10% 2	1620
July	1st to 10th	Night	42% 13% 17% 17% 10%	1575
	11th to 20th	Night	37% 18% 21% 14% 7% 2	1566
	21st to end	Night	38% 19% 17% 19% 6%	1672
August	1st to 10th	Night	38% 16% 21% 18% 7%	1600
	11th to 20th	Night	42% 16% 16% 17% 9% 1	1598
	21st to end	Night	41% 12% 19% 19% 8% 1	1940
September	1st to 10th	Night	40% 10% 15% 19% 12% 3	1980
	11th to 20th	Night	43% 10% 14% 16% 16% 1	1980
	21st to end	Night	37% 8% 11% 22% 18% 3	1980
October	1st to 10th	Night	37% 7% 12% 18% 23% 4	2001
	11th to 20th	Night	37% 8% 10% 22% 18% 4	2160
	21st to end	Night	35% 6% 7% 21% 23% 7%	2376
November	1st to 10th	Night	36% 8% 9% 20% 22% 6%	2334
	11th to 20th	Night	38% 7% 7% 20% 22% 6%	2470
	21st to end	Night	39% 7% 7% 25% 18% 4	2470
December	1st to 10th	Night	53% 9% 10% 15% 10% 3	2470
	11th to 20th	Night	50% 7% 8% 13% 18% 4	3044
	21st to end	Night	50% 11% 13% 15% 10% 1	4532

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	31% 29% 29% 10% 1	270
	11th to 20th	Day	39% 22% 26% 11% 1	270
	21st to end	Day	32% 29% 29% 7% 3	297
February	1st to 10th	Day	29% 26% 34% 10% 1	270
	11th to 20th	Day	39% 35% 22% 3	252
	21st to end	Day	40% 27% 27% 5% 1	198
March	1st to 10th	Day	25% 25% 32% 13% 5%	356
	11th to 20th	Day	29% 28% 23% 14% 5% 1	420
	21st to end	Day	27% 25% 27% 16% 5%	462
April	1st to 10th	Day	24% 21% 26% 20% 9% 1	420
	11th to 20th	Day	21% 21% 25% 21% 10% 2	412
	21st to end	Day	21% 18% 26% 21% 11% 4	420
May	1st to 10th	Day	22% 17% 30% 16% 11% 5%	423
	11th to 20th	Day	19% 13% 25% 25% 12% 6%	447
	21st to end	Day	14% 10% 23% 27% 17% 10%	485
June	1st to 10th	Day	12% 8% 27% 25% 19% 8%	450
	11th to 20th	Day	9% 6% 26% 26% 24% 10%	450
	21st to end	Day	10% 9% 30% 25% 16% 10%	450
July	1st to 10th	Day	10% 4 18% 28% 24% 16%	445
	11th to 20th	Day	9% 5% 16% 30% 25% 15%	444
	21st to end	Day	8% 3 18% 28% 27% 14%	488
August	1st to 10th	Day	14% 8% 20% 24% 21% 14%	446
	11th to 20th	Day	11% 4 20% 28% 24% 13%	439
	21st to end	Day	12% 3 16% 28% 26% 15%	495
September	1st to 10th	Day	9% 6% 15% 31% 26% 12%	450
	11th to 20th	Day	13% 6% 18% 25% 28% 10%	450
	21st to end	Day	18% 6% 20% 30% 22% 4	450
October	1st to 10th	Day	18% 8% 23% 26% 19% 6%	450
	11th to 20th	Day	16% 17% 24% 24% 17% 2	450
	21st to end	Day	20% 17% 22% 29% 11% 2	495
November	1st to 10th	Day	16% 18% 28% 26% 10% 2	340
	11th to 20th	Day	23% 20% 34% 18% 4	270
	21st to end	Day	20% 21% 36% 16% 6% 1	270
December	1st to 10th	Day	29% 27% 30% 11% 3	270
	11th to 20th	Day	25% 23% 32% 16% 5%	270
	21st to end	Day	26% 23% 36% 12% 3	297
January	1st to 10th	Night	25% 21% 28% 22% 4	760
	11th to 20th	Night	26% 20% 28% 21% 5%	760
	21st to end	Night	22% 21% 32% 22% 2	836
February	1st to 10th	Night	21% 18% 30% 27% 4	760
	11th to 20th	Night	30% 23% 30% 17% 1	722
	21st to end	Night	27% 25% 30% 18% 1	592
March	1st to 10th	Night	21% 20% 30% 25% 4	720
	11th to 20th	Night	24% 19% 28% 20% 8% 1	720
	21st to end	Night	21% 17% 31% 24% 7%	792
April	1st to 10th	Night	22% 16% 28% 26% 8%	720
	11th to 20th	Night	18% 15% 27% 27% 11% 2	593
	21st to end	Night	16% 12% 24% 36% 11% 1	540
May	1st to 10th	Night	16% 11% 26% 28% 17% 1	540
	11th to 20th	Night	13% 7% 23% 34% 21% 2	531
	21st to end	Night	11% 3 13% 37% 31% 4	584
June	1st to 10th	Night	8% 3 14% 41% 29% 5%	540
	11th to 20th	Night	6% 4 14% 35% 32% 8%	540
	21st to end	Night	8% 3 13% 38% 33% 4	540
July	1st to 10th	Night	12% 2 10% 30% 40% 6%	525
	11th to 20th	Night	9% 3 9% 31% 40% 8%	522
	21st to end	Night	7% 3 7% 31% 41% 11%	591
August	1st to 10th	Night	8% 2 9% 32% 42% 6%	537
	11th to 20th	Night	10% 4 10% 33% 37% 6%	534
	21st to end	Night	11% 3 8% 33% 38% 7%	625
September	1st to 10th	Night	11% 4 12% 32% 34% 7%	720
	11th to 20th	Night	15% 5% 14% 31% 30% 5%	720
	21st to end	Night	15% 5% 18% 33% 27% 3	720
October	1st to 10th	Night	16% 8% 19% 27% 23% 6%	720
	11th to 20th	Night	16% 12% 23% 31% 17% 3	720
	21st to end	Night	16% 15% 21% 32% 12% 3	792
November	1st to 10th	Night	16% 9% 21% 34% 16% 3	740
	11th to 20th	Night	20% 14% 24% 31% 10% 1	760
	21st to end	Night	18% 15% 25% 29% 11% 1	760
December	1st to 10th	Night	24% 18% 26% 27% 6%	760
	11th to 20th	Night	20% 18% 26% 29% 7% 1	760
	21st to end	Night	25% 18% 27% 26% 4	836

Page generated at 2024-02-12 06:35:35. Version ac07

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