Montauk Point State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Montauk Point State Park 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	16% 7% 2 5% 4 3 4 4 5% 7% 42%	78524
	Night	18% 8% 3 5% 5% 3 4 4 5% 6% 39%	81253
Transparency	Day	41% 7% 13% 22% 15% 2	78229
	Night	45% 6% 12% 21% 14% 2	81082
Seeing	Day	19% 7% 24% 30% 17% 4	14253
	Night	21% 9% 27% 27% 13% 2	23380

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	17% 7% 2 5% 5% 4 5% 4 5% 6% 41%	2517
	11th to 20th	Day	19% 8% 2 5% 4 3 5% 4 6% 6% 38%	2520
	21st to end	Day	23% 10% 4 6% 5% 2 4 3 4 5% 33%	2772
February	1st to 10th	Day	18% 7% 4 5% 6% 3 5% 5% 5% 7% 35%	1860
	11th to 20th	Day	14% 7% 3 6% 4 3 4 4 5% 6% 42%	1848
	21st to end	Day	20% 8% 3 5% 3 2 4 3 5% 7% 38%	1570
March	1st to 10th	Day	17% 6% 1 4 4 2 4 4 5% 8% 45%	1897
	11th to 20th	Day	16% 7% 2 4 4 3 5% 4 6% 7% 43%	1950
	21st to end	Day	18% 8% 3 5% 5% 3 4 4 3 4 43%	2324
April	1st to 10th	Day	18% 7% 2 4 4 2 4 5% 5% 6% 43%	2160
	11th to 20th	Day	17% 6% 2 4 3 2 4 4 5% 7% 45%	2134
	21st to end	Day	19% 5% 2 5% 5% 2 4 5% 5% 6% 41%	2302
May	1st to 10th	Day	23% 9% 3 6% 3 2 4 3 4 6% 37%	2340
	11th to 20th	Day	18% 7% 3 5% 4 2 4 4 5% 8% 42%	2307
	21st to end	Day	15% 7% 2 5% 4 2 4 5% 5% 8% 42%	2725
June	1st to 10th	Day	17% 6% 2 4 5% 3 5% 5% 6% 8% 38%	2520
	11th to 20th	Day	13% 6% 3 6% 4 3 5% 4 6% 9% 40%	2520
	21st to end	Day	12% 6% 2 4 4 3 4 5% 6% 9% 44%	2520
July	1st to 10th	Day	12% 5% 2 4 4 3 5% 5% 6% 9% 45%	2520
	11th to 20th	Day	10% 5% 3 4 5% 3 4 5% 5% 9% 46%	2520
	21st to end	Day	12% 5% 2 5% 4 3 4 5% 6% 9% 44%	2744
August	1st to 10th	Day	10% 5% 2 4 4 3 5% 4 6% 10% 46%	2339
	11th to 20th	Day	13% 5% 2 5% 5% 3 4 4 6% 7% 46%	2198
	21st to end	Day	11% 4 2 4 5% 3 4 5% 5% 8% 48%	2376
September	1st to 10th	Day	13% 6% 2 5% 5% 3 3 4 5% 8% 46%	2160
	11th to 20th	Day	11% 6% 2 4 3 2 3 3 4 7% 54%	1990
	21st to end	Day	18% 6% 2 4 5% 2 3 4 5% 7% 43%	1980
October	1st to 10th	Day	21% 6% 2 5% 3 2 3 3 4 6% 44%	1980
	11th to 20th	Day	15% 7% 3 5% 3 2 3 4 5% 8% 47%	1788
	21st to end	Day	19% 6% 2 5% 4 3 3 4 6% 6% 41%	1782
November	1st to 10th	Day	18% 5% 2 4 4 3 4 4 3 5% 47%	1671
	11th to 20th	Day	17% 6% 3 4 4 2 4 5% 5% 7% 44%	1710
	21st to end	Day	17% 7% 3 4 5% 3 4 4 5% 6% 41%	1710
December	1st to 10th	Day	20% 8% 3 6% 5% 3 4 4 5% 6% 35%	1592
	11th to 20th	Day	22% 7% 2 4 3 3 3 4 4 7% 42%	1906
	21st to end	Day	20% 11% 4 8% 6% 2 3 3 4 7% 33%	2772
January	1st to 10th	Night	19% 7% 3 4 4 2 3 3 5% 6% 44%	4429
	11th to 20th	Night	19% 10% 3 7% 4 3 3 4 4 5% 39%	4440
	21st to end	Night	25% 11% 4 7% 6% 3 4 4 5% 5% 28%	4880
February	1st to 10th	Night	16% 10% 3 7% 6% 3 4 4 5% 7% 36%	2318
	11th to 20th	Night	19% 7% 2 5% 5% 3 4 5% 6% 7% 38%	2218
	21st to end	Night	19% 7% 3 5% 6% 3 4 4 5% 6% 38%	1884
March	1st to 10th	Night	18% 7% 2 4 4 3 4 4 5% 7% 41%	2270
	11th to 20th	Night	16% 7% 3 6% 4 2 5% 4 5% 7% 40%	2175
	21st to end	Night	17% 9% 2 5% 4 2 4 3 5% 6% 42%	2030
April	1st to 10th	Night	19% 9% 3 5% 4 2 4 4 5% 6% 40%	1800
	11th to 20th	Night	17% 6% 2 6% 4 3 4 4 4 6% 43%	1775
	21st to end	Night	20% 8% 3 4 5% 2 4 4 4 7% 38%	1656
May	1st to 10th	Night	20% 9% 4 6% 5% 3 5% 4 5% 7% 32%	1620
	11th to 20th	Night	19% 8% 3 4 6% 4 4 4 5% 8% 35%	1593
	21st to end	Night	19% 8% 2 7% 5% 2 6% 5% 5% 8% 33%	1558
June	1st to 10th	Night	17% 8% 4 5% 5% 3 5% 4 5% 6% 37%	1440
	11th to 20th	Night	18% 6% 2 5% 4 3 4 4 6% 8% 39%	1440
	21st to end	Night	13% 7% 3 5% 5% 3 4 4 6% 9% 40%	1440
July	1st to 10th	Night	11% 7% 2 5% 6% 3 6% 6% 7% 9% 37%	1440
	11th to 20th	Night	12% 6% 3 4 5% 4 5% 6% 7% 9% 39%	1440
	21st to end	Night	12% 6% 4 5% 5% 3 6% 5% 7% 8% 39%	1574
August	1st to 10th	Night	8% 5% 2 5% 4 3 6% 7% 7% 8% 44%	1580
	11th to 20th	Night	11% 6% 2 4 5% 4 5% 6% 7% 8% 41%	1699
	21st to end	Night	12% 5% 2 4 4 3 5% 4 5% 8% 46%	1980
September	1st to 10th	Night	15% 7% 3 6% 4 4 5% 5% 6% 7% 39%	1800
	11th to 20th	Night	14% 5% 2 5% 4 2 4 3 4 7% 50%	1969
	21st to end	Night	18% 7% 2 5% 6% 3 4 4 4 5% 42%	1980
October	1st to 10th	Night	21% 7% 3 5% 5% 3 4 4 4 6% 39%	1980
	11th to 20th	Night	16% 6% 2 5% 4 2 4 4 5% 6% 45%	2168
	21st to end	Night	21% 7% 3 5% 5% 3 4 4 4 6% 38%	2574
November	1st to 10th	Night	16% 6% 3 6% 5% 3 4 3 4 7% 44%	2407
	11th to 20th	Night	19% 8% 3 5% 4 3 3 4 5% 6% 41%	2470
	21st to end	Night	16% 6% 3 4 4 4 4 5% 5% 7% 42%	2470
December	1st to 10th	Night	21% 9% 3 6% 5% 3 5% 5% 5% 6% 33%	2584
	11th to 20th	Night	20% 8% 2 6% 5% 3 4 3 6% 7% 38%	3288
	21st to end	Night	21% 11% 3 6% 5% 2 4 4 4 5% 36%	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	43% 6% 12% 27% 12% 1	2518
	11th to 20th	Day	46% 7% 12% 23% 11% 2	2520
	21st to end	Day	53% 7% 9% 21% 9% 1	2772
February	1st to 10th	Day	47% 6% 15% 19% 12% 1	1860
	11th to 20th	Day	42% 6% 11% 24% 14% 2	1857
	21st to end	Day	47% 5% 13% 19% 14% 3	1570
March	1st to 10th	Day	38% 5% 15% 23% 14% 3	1900
	11th to 20th	Day	39% 5% 13% 26% 15% 2	1950
	21st to end	Day	45% 5% 10% 20% 17% 4	2324
April	1st to 10th	Day	41% 6% 12% 20% 18% 3	2160
	11th to 20th	Day	39% 5% 10% 23% 20% 3	2134
	21st to end	Day	43% 7% 10% 20% 17% 4	2302
May	1st to 10th	Day	49% 5% 11% 20% 12% 2	2340
	11th to 20th	Day	42% 6% 11% 21% 17% 3	2311
	21st to end	Day	41% 9% 15% 21% 13% 2	2725
June	1st to 10th	Day	43% 9% 12% 22% 13% 1	2520
	11th to 20th	Day	40% 8% 13% 23% 14% 1	2520
	21st to end	Day	36% 9% 14% 26% 14% 1	2520
July	1st to 10th	Day	35% 10% 16% 21% 16% 2	2450
	11th to 20th	Day	35% 8% 15% 29% 12% 2	2445
	21st to end	Day	35% 9% 14% 23% 16% 3	2591
August	1st to 10th	Day	33% 10% 17% 24% 15% 1	2325
	11th to 20th	Day	37% 9% 13% 26% 13% 2	2198
	21st to end	Day	34% 9% 14% 22% 19% 2	2376
September	1st to 10th	Day	37% 7% 13% 22% 19% 1	2160
	11th to 20th	Day	31% 7% 13% 24% 23% 3	1990
	21st to end	Day	41% 7% 9% 22% 19% 2	1980
October	1st to 10th	Day	42% 7% 11% 22% 16% 3	1980
	11th to 20th	Day	37% 5% 14% 26% 17% 1	1788
	21st to end	Day	42% 7% 13% 21% 14% 3	1782
November	1st to 10th	Day	41% 5% 15% 20% 18% 2	1671
	11th to 20th	Day	39% 6% 15% 21% 17% 2	1710
	21st to end	Day	43% 6% 14% 25% 10% 2	1710
December	1st to 10th	Day	50% 6% 13% 17% 13% 1	1592
	11th to 20th	Day	45% 4 15% 16% 17% 3	1906
	21st to end	Day	52% 6% 11% 21% 9%	2772
January	1st to 10th	Night	41% 5% 12% 30% 10% 3	4429
	11th to 20th	Night	48% 5% 14% 21% 10% 2	4440
	21st to end	Night	57% 6% 10% 16% 9% 1	4880
February	1st to 10th	Night	48% 6% 13% 20% 11% 2	2318
	11th to 20th	Night	46% 5% 11% 21% 14% 3	2220
	21st to end	Night	47% 5% 9% 22% 14% 3	1884
March	1st to 10th	Night	43% 5% 12% 21% 15% 3	2280
	11th to 20th	Night	43% 6% 11% 21% 14% 4	2176
	21st to end	Night	44% 4 9% 18% 19% 6%	2030
April	1st to 10th	Night	45% 5% 10% 19% 17% 4	1800
	11th to 20th	Night	43% 5% 11% 19% 20% 2	1775
	21st to end	Night	47% 5% 10% 19% 15% 4	1656
May	1st to 10th	Night	52% 7% 10% 16% 13% 2	1620
	11th to 20th	Night	48% 7% 10% 18% 13% 3	1594
	21st to end	Night	50% 9% 13% 16% 11% 1	1559
June	1st to 10th	Night	47% 8% 12% 17% 15% 1	1440
	11th to 20th	Night	42% 8% 13% 22% 14% 1	1440
	21st to end	Night	40% 7% 13% 25% 14% 1	1440
July	1st to 10th	Night	41% 10% 16% 19% 14% 1	1400
	11th to 20th	Night	37% 10% 16% 25% 10% 1	1392
	21st to end	Night	38% 9% 15% 23% 13% 2	1486
August	1st to 10th	Night	32% 10% 20% 23% 13% 2	1570
	11th to 20th	Night	37% 11% 16% 24% 12%	1699
	21st to end	Night	35% 8% 14% 24% 18% 2	1980
September	1st to 10th	Night	43% 6% 10% 23% 16% 2	1800
	11th to 20th	Night	36% 5% 12% 22% 23% 2	1969
	21st to end	Night	45% 6% 8% 19% 19% 3	1980
October	1st to 10th	Night	47% 6% 10% 19% 14% 4	1980
	11th to 20th	Night	39% 6% 14% 27% 14% 1	2168
	21st to end	Night	48% 6% 13% 19% 13% 2	2574
November	1st to 10th	Night	41% 6% 12% 21% 17% 4	2407
	11th to 20th	Night	45% 5% 12% 20% 15% 3	2470
	21st to end	Night	40% 7% 14% 26% 11% 2	2470
December	1st to 10th	Night	51% 6% 13% 17% 11% 1	2584
	11th to 20th	Night	47% 6% 14% 17% 16% 1	3288
	21st to end	Night	51% 6% 12% 20% 11% 1	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	19% 19% 32% 22% 8% 1	180
	11th to 20th	Day	19% 17% 40% 18% 5%	180
	21st to end	Day	20% 11% 39% 20% 8% 2	198
February	1st to 10th	Day	25% 9% 38% 21% 7%	420
	11th to 20th	Day	21% 14% 42% 21% 2	456
	21st to end	Day	23% 14% 32% 24% 6% 1	382
March	1st to 10th	Day	20% 10% 36% 27% 7%	460
	11th to 20th	Day	15% 13% 37% 28% 6% 1	449
	21st to end	Day	22% 8% 33% 26% 9% 2	462
April	1st to 10th	Day	23% 8% 32% 25% 11% 1	420
	11th to 20th	Day	19% 8% 28% 36% 9% 1	412
	21st to end	Day	24% 7% 23% 36% 9% 2	420
May	1st to 10th	Day	25% 8% 27% 29% 10% 1	423
	11th to 20th	Day	17% 4 30% 34% 14% 2	447
	21st to end	Day	21% 2 14% 29% 28% 6%	485
June	1st to 10th	Day	18% 2 18% 35% 25% 3	450
	11th to 20th	Day	14% 2 20% 36% 24% 3	450
	21st to end	Day	15% 2 15% 38% 25% 5%	450
July	1st to 10th	Day	15% 3 9% 36% 31% 7%	445
	11th to 20th	Day	9% 2 9% 37% 34% 10%	444
	21st to end	Day	13% 2 12% 39% 31% 3	488
August	1st to 10th	Day	12% 2 12% 36% 32% 7%	446
	11th to 20th	Day	16% 2 9% 34% 32% 8%	439
	21st to end	Day	12% 1 14% 36% 27% 11%	495
September	1st to 10th	Day	18% 2 16% 30% 23% 11%	450
	11th to 20th	Day	16% 3 18% 31% 23% 10%	450
	21st to end	Day	24% 2 21% 32% 18% 4	450
October	1st to 10th	Day	26% 7% 18% 27% 17% 6%	450
	11th to 20th	Day	16% 8% 24% 31% 19% 3	421
	21st to end	Day	26% 8% 26% 27% 11% 2	396
November	1st to 10th	Day	17% 8% 24% 32% 15% 4	365
	11th to 20th	Day	22% 13% 30% 26% 9%	370
	21st to end	Day	18% 15% 32% 24% 10% 1	370
December	1st to 10th	Day	19% 14% 34% 25% 7%	252
	11th to 20th	Day	23% 16% 36% 19% 6%	180
	21st to end	Day	24% 12% 35% 20% 8% 2	198
January	1st to 10th	Night	21% 18% 35% 21% 4	760
	11th to 20th	Night	28% 16% 33% 19% 4	760
	21st to end	Night	22% 15% 39% 20% 3 1	836
February	1st to 10th	Night	20% 15% 39% 23% 2	760
	11th to 20th	Night	23% 15% 43% 16% 3	743
	21st to end	Night	23% 16% 35% 20% 5%	628
March	1st to 10th	Night	23% 13% 34% 23% 6%	760
	11th to 20th	Night	20% 9% 36% 28% 6% 1	752
	21st to end	Night	22% 8% 35% 26% 9% 1	792
April	1st to 10th	Night	23% 8% 31% 30% 7% 1	720
	11th to 20th	Night	20% 6% 28% 33% 12% 1	711
	21st to end	Night	24% 4 27% 30% 14% 1	576
May	1st to 10th	Night	23% 6% 22% 32% 13% 4	540
	11th to 20th	Night	20% 4 29% 34% 12% 1	532
	21st to end	Night	23% 3 14% 29% 27% 4	397
June	1st to 10th	Night	18% 3 18% 35% 24% 3	360
	11th to 20th	Night	21% 3 16% 32% 28% 1	360
	21st to end	Night	16% 3 11% 41% 28% 1	360
July	1st to 10th	Night	14% 3 11% 39% 29% 4	350
	11th to 20th	Night	13% 2 8% 39% 33% 5%	348
	21st to end	Night	13% 2 12% 40% 30% 3	394
August	1st to 10th	Night	9% 1 12% 40% 32% 5%	506
	11th to 20th	Night	12% 3 9% 36% 33% 7%	635
	21st to end	Night	14% 2 11% 33% 31% 9%	792
September	1st to 10th	Night	18% 1 16% 32% 27% 7%	720
	11th to 20th	Night	17% 3 18% 31% 24% 8%	720
	21st to end	Night	21% 4 20% 31% 19% 4	720
October	1st to 10th	Night	26% 6% 21% 24% 18% 4	720
	11th to 20th	Night	19% 8% 26% 30% 15% 2	720
	21st to end	Night	23% 10% 33% 24% 9% 1	792
November	1st to 10th	Night	19% 10% 28% 28% 13% 3	740
	11th to 20th	Night	24% 14% 31% 23% 8% 1	760
	21st to end	Night	19% 16% 31% 24% 8% 1	760
December	1st to 10th	Night	25% 17% 31% 21% 6% 1	760
	11th to 20th	Night	23% 19% 33% 19% 5%	760
	21st to end	Night	24% 15% 38% 20% 4	836

Page generated at 2024-03-15 14:01:38. Version ac07

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