Morris County Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Morris County Observatory clear sky chart from 2005-11-06 to 2024-03-18.

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	17% 6% 3 5% 5% 3 5% 5% 5% 7% 39%	78587
	Night	17% 7% 3 5% 4 3 4 4 5% 6% 42%	81192
Transparency	Day	43% 7% 12% 21% 15% 2	78292
	Night	42% 6% 12% 22% 15% 2	81021
Seeing	Day	23% 17% 30% 20% 8% 2	14050
	Night	21% 15% 32% 24% 8% 1	23393

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	15% 8% 2 5% 4 2 4 4 5% 5% 47%	2517
	11th to 20th	Day	15% 9% 3 7% 7% 4 5% 4 5% 6% 34%	2520
	21st to end	Day	21% 10% 5% 6% 5% 2 4 4 5% 5% 33%	3064
February	1st to 10th	Day	17% 8% 3 6% 5% 3 4 4 6% 6% 38%	1710
	11th to 20th	Day	15% 6% 3 6% 5% 2 4 5% 5% 6% 42%	1826
	21st to end	Day	20% 9% 3 4 5% 3 4 4 5% 6% 37%	1570
March	1st to 10th	Day	15% 7% 3 6% 5% 3 4 4 4 6% 43%	1897
	11th to 20th	Day	15% 7% 2 4 5% 4 6% 6% 6% 8% 38%	2005
	21st to end	Day	20% 7% 2 5% 5% 2 4 4 4 7% 39%	2335
April	1st to 10th	Day	17% 7% 4 5% 5% 3 4 4 5% 6% 39%	2160
	11th to 20th	Day	17% 5% 3 5% 5% 3 5% 4 5% 7% 41%	2134
	21st to end	Day	19% 5% 2 6% 5% 3 4 5% 5% 6% 39%	2160
May	1st to 10th	Day	23% 7% 2 5% 5% 3 4 4 5% 7% 34%	2348
	11th to 20th	Day	21% 5% 3 5% 5% 3 5% 5% 5% 7% 36%	2478
	21st to end	Day	15% 7% 3 5% 5% 3 5% 4 5% 9% 40%	2725
June	1st to 10th	Day	17% 5% 2 4 5% 3 6% 6% 6% 9% 36%	2520
	11th to 20th	Day	17% 6% 2 6% 5% 4 6% 6% 6% 8% 35%	2520
	21st to end	Day	14% 5% 2 5% 6% 4 4 5% 5% 9% 40%	2520
July	1st to 10th	Day	12% 6% 3 6% 6% 4 7% 4 7% 9% 37%	2520
	11th to 20th	Day	11% 4 2 5% 5% 3 6% 6% 7% 10% 41%	2520
	21st to end	Day	13% 6% 3 6% 6% 4 5% 6% 6% 8% 37%	2744
August	1st to 10th	Day	12% 5% 2 6% 6% 4 7% 7% 8% 8% 36%	2361
	11th to 20th	Day	13% 6% 2 6% 5% 4 6% 5% 6% 8% 38%	2126
	21st to end	Day	16% 5% 2 6% 6% 3 4 4 6% 8% 41%	2376
September	1st to 10th	Day	16% 5% 2 5% 4 4 5% 5% 5% 7% 42%	2160
	11th to 20th	Day	14% 4 2 4 4 3 3 3 4 8% 49%	2104
	21st to end	Day	18% 5% 3 5% 4 4 5% 4 5% 5% 41%	1980
October	1st to 10th	Day	21% 5% 2 4 4 2 4 5% 5% 6% 41%	1846
	11th to 20th	Day	16% 5% 2 5% 3 3 5% 4 5% 7% 45%	1800
	21st to end	Day	21% 5% 2 4 3 3 4 4 4 6% 42%	1864
November	1st to 10th	Day	14% 6% 3 4 4 2 3 3 4 6% 52%	1671
	11th to 20th	Day	19% 5% 2 3 4 2 3 5% 6% 5% 46%	1710
	21st to end	Day	15% 6% 2 4 4 3 5% 4 5% 7% 43%	1598
December	1st to 10th	Day	19% 8% 2 5% 5% 3 4 4 4 8% 37%	1520
	11th to 20th	Day	21% 6% 2 4 4 2 4 4 5% 6% 42%	1906
	21st to end	Day	18% 8% 4 6% 7% 4 5% 6% 6% 6% 29%	2772
January	1st to 10th	Night	16% 6% 2 4 4 2 3 4 5% 6% 45%	4429
	11th to 20th	Night	16% 9% 3 6% 5% 3 4 4 3 6% 41%	4440
	21st to end	Night	24% 10% 2 5% 4 2 4 4 4 6% 35%	4589
February	1st to 10th	Night	16% 9% 3 5% 4 3 4 4 4 6% 42%	2470
	11th to 20th	Night	16% 7% 4 5% 4 3 4 4 5% 5% 42%	2238
	21st to end	Night	19% 7% 3 4 5% 3 3 3 4 6% 42%	1884
March	1st to 10th	Night	17% 7% 3 4 4 3 4 4 5% 7% 44%	2270
	11th to 20th	Night	17% 6% 3 4 4 3 4 4 5% 5% 44%	2118
	21st to end	Night	17% 7% 3 5% 4 2 3 4 5% 6% 43%	2021
April	1st to 10th	Night	17% 7% 3 5% 5% 4 5% 5% 6% 7% 38%	1800
	11th to 20th	Night	19% 5% 2 5% 5% 2 5% 5% 4 7% 41%	1775
	21st to end	Night	21% 6% 2 5% 4 2 4 4 5% 6% 42%	1800
May	1st to 10th	Night	21% 8% 4 6% 5% 3 4 4 4 6% 35%	1624
	11th to 20th	Night	19% 7% 3 5% 5% 3 4 4 4 6% 40%	1415
	21st to end	Night	17% 5% 2 5% 4 3 5% 4 5% 8% 41%	1550
June	1st to 10th	Night	17% 5% 2 5% 4 3 4 5% 5% 7% 43%	1440
	11th to 20th	Night	14% 6% 4 5% 4 3 5% 5% 6% 8% 41%	1440
	21st to end	Night	12% 4 2 4 4 3 4 5% 7% 10% 44%	1440
July	1st to 10th	Night	13% 4 2 6% 5% 3 6% 5% 7% 9% 41%	1440
	11th to 20th	Night	11% 4 2 6% 6% 4 7% 6% 6% 11% 39%	1440
	21st to end	Night	11% 5% 2 4 4 3 5% 6% 7% 10% 43%	1574
August	1st to 10th	Night	10% 5% 3 5% 5% 3 5% 6% 7% 9% 42%	1561
	11th to 20th	Night	12% 6% 3 7% 7% 4 5% 6% 6% 8% 36%	1769
	21st to end	Night	14% 5% 3 7% 5% 3 4 4 6% 8% 42%	1980
September	1st to 10th	Night	17% 5% 3 5% 6% 3 4 4 4 6% 44%	1800
	11th to 20th	Night	15% 5% 2 4 4 2 3 4 4 7% 52%	1855
	21st to end	Night	18% 6% 2 5% 4 3 3 3 5% 7% 45%	1980
October	1st to 10th	Night	20% 7% 3 5% 4 3 3 3 5% 6% 42%	2110
	11th to 20th	Night	16% 5% 2 4 4 2 3 4 4 6% 49%	2160
	21st to end	Night	22% 6% 2 4 3 2 3 4 4 6% 44%	2492
November	1st to 10th	Night	13% 5% 2 4 4 2 4 3 5% 6% 52%	2407
	11th to 20th	Night	20% 6% 2 4 4 2 3 4 4 5% 48%	2470
	21st to end	Night	15% 5% 3 4 4 3 4 5% 5% 7% 45%	2579
December	1st to 10th	Night	19% 7% 3 5% 4 3 5% 4 5% 7% 39%	2660
	11th to 20th	Night	19% 7% 2 5% 4 2 4 4 5% 7% 42%	3288
	21st to end	Night	19% 10% 3 6% 5% 3 4 4 4 5% 37%	4884

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	41% 4 11% 30% 12% 3	2518
	11th to 20th	Day	50% 5% 13% 19% 12% 2	2520
	21st to end	Day	53% 6% 10% 20% 10% 2	3064
February	1st to 10th	Day	46% 6% 13% 21% 12% 2	1710
	11th to 20th	Day	43% 7% 9% 22% 16% 3	1835
	21st to end	Day	49% 5% 10% 21% 12% 3	1570
March	1st to 10th	Day	42% 5% 12% 25% 13% 3	1900
	11th to 20th	Day	43% 6% 12% 22% 15% 2	2005
	21st to end	Day	47% 4 9% 17% 17% 5%	2335
April	1st to 10th	Day	45% 5% 10% 20% 16% 5%	2160
	11th to 20th	Day	42% 5% 11% 21% 17% 3	2134
	21st to end	Day	45% 6% 10% 19% 16% 4	2160
May	1st to 10th	Day	50% 6% 9% 17% 15% 3	2348
	11th to 20th	Day	46% 7% 11% 20% 14% 3	2482
	21st to end	Day	41% 8% 14% 21% 14% 2	2725
June	1st to 10th	Day	42% 9% 14% 19% 14% 1	2520
	11th to 20th	Day	46% 8% 12% 21% 11% 2	2520
	21st to end	Day	41% 8% 13% 22% 15% 1	2520
July	1st to 10th	Day	43% 9% 11% 21% 15% 1	2450
	11th to 20th	Day	35% 9% 16% 23% 14% 2	2445
	21st to end	Day	42% 8% 12% 18% 17% 2	2591
August	1st to 10th	Day	40% 10% 14% 20% 14% 1	2347
	11th to 20th	Day	41% 9% 14% 23% 12% 1	2126
	21st to end	Day	41% 7% 10% 21% 18% 3	2376
September	1st to 10th	Day	40% 8% 11% 20% 18% 3	2160
	11th to 20th	Day	35% 6% 10% 22% 24% 3	2104
	21st to end	Day	44% 6% 10% 17% 20% 3	1980
October	1st to 10th	Day	44% 7% 11% 21% 16% 2	1846
	11th to 20th	Day	39% 5% 12% 24% 19% 1	1800
	21st to end	Day	44% 5% 10% 21% 17% 2	1864
November	1st to 10th	Day	35% 5% 12% 24% 21% 3	1671
	11th to 20th	Day	39% 5% 12% 22% 20% 3	1710
	21st to end	Day	41% 4 13% 28% 12% 2	1598
December	1st to 10th	Day	47% 5% 14% 19% 13% 1	1520
	11th to 20th	Day	43% 6% 16% 23% 11% 2	1906
	21st to end	Day	52% 8% 12% 21% 8%	2772
January	1st to 10th	Night	40% 5% 11% 30% 11% 3	4429
	11th to 20th	Night	45% 5% 13% 23% 11% 2	4440
	21st to end	Night	51% 5% 9% 21% 12% 2	4589
February	1st to 10th	Night	44% 6% 12% 24% 12% 2	2470
	11th to 20th	Night	45% 5% 11% 18% 17% 5%	2240
	21st to end	Night	44% 4 8% 24% 16% 3	1884
March	1st to 10th	Night	41% 5% 12% 24% 14% 4	2280
	11th to 20th	Night	42% 6% 10% 22% 17% 3	2119
	21st to end	Night	42% 6% 10% 18% 18% 5%	2021
April	1st to 10th	Night	45% 6% 11% 20% 14% 4	1800
	11th to 20th	Night	43% 6% 10% 19% 20% 2	1775
	21st to end	Night	43% 6% 10% 20% 17% 4	1800
May	1st to 10th	Night	50% 6% 10% 16% 15% 2	1624
	11th to 20th	Night	46% 6% 12% 17% 18% 3	1416
	21st to end	Night	41% 8% 15% 20% 13% 3	1551
June	1st to 10th	Night	41% 5% 12% 21% 18% 2	1440
	11th to 20th	Night	41% 8% 15% 23% 12% 1	1440
	21st to end	Night	33% 10% 16% 25% 16% 1	1440
July	1st to 10th	Night	39% 10% 14% 20% 15% 2	1400
	11th to 20th	Night	38% 10% 13% 25% 12% 2	1392
	21st to end	Night	32% 10% 17% 22% 16% 3	1486
August	1st to 10th	Night	36% 11% 16% 21% 15% 1	1551
	11th to 20th	Night	43% 10% 14% 21% 11% 1	1769
	21st to end	Night	40% 8% 12% 18% 20% 2	1980
September	1st to 10th	Night	41% 6% 11% 22% 18% 1	1800
	11th to 20th	Night	34% 5% 10% 22% 25% 3	1855
	21st to end	Night	40% 5% 8% 23% 23% 2	1980
October	1st to 10th	Night	44% 5% 11% 23% 14% 2	2110
	11th to 20th	Night	37% 6% 13% 27% 15% 2	2160
	21st to end	Night	43% 5% 11% 25% 15% 1	2492
November	1st to 10th	Night	34% 6% 11% 23% 22% 4	2407
	11th to 20th	Night	40% 5% 9% 24% 18% 4	2470
	21st to end	Night	38% 6% 14% 27% 14% 2	2579
December	1st to 10th	Night	45% 7% 12% 23% 12% 1	2660
	11th to 20th	Night	43% 6% 13% 19% 16% 3	3288
	21st to end	Night	49% 6% 12% 22% 11%	4884

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% 26% 33% 12% 1 1	180
	11th to 20th	Day	36% 27% 28% 9% 1	180
	21st to end	Day	25% 28% 32% 9% 5%	281
February	1st to 10th	Day	31% 27% 33% 8% 1	270
	11th to 20th	Day	28% 28% 35% 9%	434
	21st to end	Day	32% 24% 28% 12% 3	382
March	1st to 10th	Day	29% 22% 32% 13% 3	460
	11th to 20th	Day	26% 27% 30% 13% 3 1	449
	21st to end	Day	31% 22% 30% 12% 4 1	462
April	1st to 10th	Day	28% 24% 30% 11% 7%	420
	11th to 20th	Day	24% 23% 30% 15% 7% 1	412
	21st to end	Day	32% 20% 34% 11% 2 2	420
May	1st to 10th	Day	33% 19% 28% 13% 5% 1	423
	11th to 20th	Day	24% 16% 35% 17% 6% 1	447
	21st to end	Day	22% 9% 27% 29% 11% 1	485
June	1st to 10th	Day	18% 15% 31% 23% 11% 1	450
	11th to 20th	Day	20% 15% 31% 23% 10% 1	450
	21st to end	Day	16% 12% 33% 26% 12% 1	450
July	1st to 10th	Day	15% 7% 28% 28% 17% 5%	445
	11th to 20th	Day	12% 3 28% 36% 18% 2	444
	21st to end	Day	16% 8% 32% 29% 13% 2	488
August	1st to 10th	Day	13% 8% 25% 32% 16% 6%	446
	11th to 20th	Day	15% 7% 26% 33% 14% 5%	439
	21st to end	Day	13% 9% 32% 27% 13% 6%	495
September	1st to 10th	Day	19% 12% 25% 25% 14% 6%	450
	11th to 20th	Day	16% 8% 31% 22% 14% 10%	450
	21st to end	Day	20% 15% 29% 21% 11% 4	450
October	1st to 10th	Day	27% 9% 29% 20% 12% 4	450
	11th to 20th	Day	18% 18% 31% 22% 9% 1	450
	21st to end	Day	26% 17% 31% 17% 7% 1	437
November	1st to 10th	Day	20% 15% 31% 22% 9% 2	365
	11th to 20th	Day	28% 19% 31% 18% 4	370
	21st to end	Day	23% 21% 36% 16% 4	258
December	1st to 10th	Day	28% 27% 28% 11% 6%	180
	11th to 20th	Day	35% 24% 27% 11% 3	180
	21st to end	Day	29% 22% 32% 13% 4 1	198
January	1st to 10th	Night	22% 22% 37% 16% 3	760
	11th to 20th	Night	27% 19% 33% 18% 3	760
	21st to end	Night	21% 22% 38% 17% 2	836
February	1st to 10th	Night	22% 21% 37% 18% 2	760
	11th to 20th	Night	24% 26% 36% 12% 1	743
	21st to end	Night	28% 19% 34% 16% 2	628
March	1st to 10th	Night	24% 23% 32% 18% 4	760
	11th to 20th	Night	23% 23% 34% 17% 3 1	752
	21st to end	Night	21% 21% 38% 15% 5% 1	792
April	1st to 10th	Night	23% 22% 34% 16% 4	720
	11th to 20th	Night	21% 18% 36% 20% 4	711
	21st to end	Night	24% 16% 34% 23% 4	720
May	1st to 10th	Night	26% 17% 33% 20% 6%	544
	11th to 20th	Night	22% 13% 36% 23% 6%	354
	21st to end	Night	18% 8% 25% 36% 13% 1	389
June	1st to 10th	Night	19% 7% 29% 32% 12%	360
	11th to 20th	Night	15% 6% 33% 34% 11%	360
	21st to end	Night	12% 4 28% 46% 10%	360
July	1st to 10th	Night	13% 6% 26% 35% 18% 2	350
	11th to 20th	Night	11% 4 24% 42% 18% 1	348
	21st to end	Night	14% 4 25% 43% 13% 1	394
August	1st to 10th	Night	13% 2 23% 40% 20% 2	487
	11th to 20th	Night	14% 4 22% 37% 23% 1	705
	21st to end	Night	15% 4 24% 38% 18% 2	792
September	1st to 10th	Night	18% 4 27% 34% 15% 2	720
	11th to 20th	Night	17% 6% 25% 32% 18% 3	720
	21st to end	Night	20% 7% 27% 31% 13% 2	720
October	1st to 10th	Night	22% 9% 29% 25% 13% 2	720
	11th to 20th	Night	18% 15% 29% 29% 8%	720
	21st to end	Night	25% 15% 32% 21% 6% 1	792
November	1st to 10th	Night	17% 14% 33% 26% 9% 1	740
	11th to 20th	Night	24% 15% 31% 23% 6%	760
	21st to end	Night	18% 19% 35% 21% 6% 1	760
December	1st to 10th	Night	25% 18% 32% 20% 4 1	760
	11th to 20th	Night	22% 19% 36% 20% 3	760
	21st to end	Night	23% 19% 36% 19% 2	836

Page generated at 2024-03-15 14:01:39. Version ac07

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