Rummy's Stargazing Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rummy's Stargazing Site clear sky chart from 2005-11-06 to 2024-04-03.

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% 3 6% 5% 3 5% 5% 5% 7% 37%	78766
	Night	17% 7% 2 5% 5% 3 4 4 5% 7% 40%	81352
Transparency	Day	45% 7% 12% 21% 13% 2	78471
	Night	43% 7% 13% 22% 13% 2	81181
Seeing	Day	24% 18% 29% 18% 8% 2	14036
	Night	22% 17% 29% 23% 8% 1	23414

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	13% 11% 3 4 5% 4 3 5% 4 5% 42%	2517
	11th to 20th	Day	14% 10% 6% 10% 7% 3 4 4 4 6% 30%	2520
	21st to end	Day	19% 11% 5% 6% 5% 3 5% 4 5% 6% 31%	3101
February	1st to 10th	Day	16% 8% 4 7% 6% 4 5% 6% 5% 5% 35%	1710
	11th to 20th	Day	13% 8% 3 7% 6% 3 5% 5% 5% 7% 38%	1782
	21st to end	Day	20% 10% 3 6% 5% 3 4 5% 4 5% 35%	1570
March	1st to 10th	Day	14% 8% 3 6% 5% 3 4 5% 5% 7% 40%	1897
	11th to 20th	Day	13% 8% 3 7% 7% 4 4 5% 5% 7% 36%	2076
	21st to end	Day	19% 7% 4 5% 5% 3 4 5% 4 6% 38%	2438
April	1st to 10th	Day	17% 8% 3 5% 5% 3 5% 5% 5% 6% 37%	2184
	11th to 20th	Day	17% 7% 3 6% 4 3 4 4 5% 6% 40%	2134
	21st to end	Day	18% 6% 2 4 6% 4 6% 4 6% 6% 38%	2160
May	1st to 10th	Day	20% 7% 3 7% 6% 4 5% 4 5% 6% 33%	2381
	11th to 20th	Day	20% 7% 3 5% 6% 3 5% 5% 5% 7% 34%	2478
	21st to end	Day	15% 6% 2 5% 6% 3 5% 5% 5% 8% 39%	2725
June	1st to 10th	Day	15% 4 3 6% 6% 3 5% 5% 6% 8% 36%	2520
	11th to 20th	Day	16% 6% 3 5% 5% 5% 5% 5% 6% 9% 34%	2520
	21st to end	Day	14% 5% 2 5% 6% 4 5% 6% 6% 8% 39%	2520
July	1st to 10th	Day	12% 5% 3 6% 6% 4 6% 5% 6% 9% 37%	2520
	11th to 20th	Day	12% 4 2 4 5% 3 6% 6% 6% 10% 41%	2520
	21st to end	Day	13% 6% 3 6% 7% 4 5% 5% 6% 8% 38%	2744
August	1st to 10th	Day	13% 5% 3 6% 7% 4 6% 6% 7% 8% 35%	2343
	11th to 20th	Day	12% 6% 3 6% 6% 5% 6% 5% 6% 9% 36%	2152
	21st to end	Day	15% 6% 2 5% 5% 3 5% 5% 7% 8% 40%	2376
September	1st to 10th	Day	17% 5% 3 5% 4 3 5% 5% 5% 8% 39%	2160
	11th to 20th	Day	14% 4 2 5% 4 2 4 5% 5% 6% 49%	2129
	21st to end	Day	18% 6% 3 5% 5% 3 4 6% 5% 5% 40%	1980
October	1st to 10th	Day	21% 6% 2 5% 4 2 4 4 4 7% 40%	1800
	11th to 20th	Day	17% 4 3 5% 5% 3 5% 4 4 7% 43%	1800
	21st to end	Day	23% 6% 2 5% 5% 3 4 5% 6% 6% 36%	1887
November	1st to 10th	Day	15% 7% 2 4 4 2 3 3 4 6% 51%	1671
	11th to 20th	Day	19% 7% 2 4 4 2 4 4 6% 5% 44%	1710
	21st to end	Day	17% 6% 2 5% 6% 3 5% 4 6% 7% 39%	1543
December	1st to 10th	Day	19% 10% 3 6% 5% 3 4 5% 4 6% 34%	1520
	11th to 20th	Day	21% 9% 3 5% 4 3 5% 4 5% 7% 35%	1906
	21st to end	Day	19% 11% 5% 9% 6% 4 5% 5% 6% 6% 25%	2772
January	1st to 10th	Night	16% 6% 3 5% 5% 3 4 5% 6% 7% 41%	4429
	11th to 20th	Night	15% 9% 4 9% 6% 3 4 4 5% 6% 34%	4440
	21st to end	Night	22% 11% 3 5% 5% 3 4 4 4 5% 33%	4553
February	1st to 10th	Night	16% 9% 3 5% 4 2 4 4 5% 6% 40%	2470
	11th to 20th	Night	14% 7% 3 6% 5% 3 4 6% 5% 6% 39%	2283
	21st to end	Night	19% 7% 3 6% 4 4 4 4 5% 6% 39%	1884
March	1st to 10th	Night	16% 6% 3 6% 5% 2 3 5% 5% 7% 42%	2270
	11th to 20th	Night	16% 7% 3 5% 5% 3 5% 4 5% 6% 42%	2100
	21st to end	Night	16% 7% 3 5% 5% 3 4 4 6% 6% 41%	2159
April	1st to 10th	Night	17% 8% 4 6% 5% 3 5% 5% 5% 7% 35%	1821
	11th to 20th	Night	18% 6% 3 5% 4 3 4 5% 5% 7% 40%	1775
	21st to end	Night	21% 6% 2 4 4 3 4 4 6% 7% 40%	1800
May	1st to 10th	Night	21% 8% 3 7% 6% 3 5% 5% 4 5% 34%	1593
	11th to 20th	Night	18% 6% 2 5% 5% 3 5% 5% 5% 6% 41%	1415
	21st to end	Night	16% 5% 2 4 5% 3 4 5% 6% 8% 43%	1550
June	1st to 10th	Night	17% 5% 2 4 5% 2 5% 5% 5% 8% 43%	1440
	11th to 20th	Night	17% 4 2 4 4 3 5% 5% 6% 9% 41%	1440
	21st to end	Night	12% 4 1 3 5% 2 4 4 8% 10% 46%	1440
July	1st to 10th	Night	13% 5% 2 5% 6% 3 5% 5% 5% 9% 42%	1440
	11th to 20th	Night	11% 5% 2 4 5% 2 4 6% 7% 10% 42%	1440
	21st to end	Night	12% 4 2 4 4 3 6% 5% 7% 9% 44%	1574
August	1st to 10th	Night	11% 4 2 4 5% 3 5% 6% 6% 11% 43%	1592
	11th to 20th	Night	13% 6% 2 6% 6% 4 6% 6% 5% 7% 39%	1729
	21st to end	Night	16% 5% 2 4 4 2 3 5% 6% 8% 44%	1980
September	1st to 10th	Night	16% 6% 2 4 5% 3 4 3 4 7% 45%	1800
	11th to 20th	Night	13% 6% 2 5% 3 2 3 3 4 7% 52%	1829
	21st to end	Night	17% 5% 2 5% 4 2 4 4 5% 6% 45%	1980
October	1st to 10th	Night	24% 5% 2 5% 4 2 4 3 4 6% 43%	2155
	11th to 20th	Night	18% 6% 2 5% 3 2 3 4 5% 6% 46%	2160
	21st to end	Night	23% 7% 2 3 3 3 3 4 5% 6% 41%	2467
November	1st to 10th	Night	14% 5% 2 5% 3 3 4 5% 5% 6% 50%	2407
	11th to 20th	Night	19% 7% 2 4 4 2 3 4 5% 6% 44%	2470
	21st to end	Night	15% 5% 2 4 5% 3 4 5% 5% 8% 44%	2635
December	1st to 10th	Night	19% 7% 3 5% 6% 3 5% 4 5% 7% 35%	2660
	11th to 20th	Night	18% 9% 2 5% 4 3 5% 5% 6% 6% 38%	3288
	21st to end	Night	21% 10% 4 6% 5% 3 4 4 4 6% 33%	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	45% 6% 11% 28% 8% 2	2518
	11th to 20th	Day	55% 6% 10% 19% 8% 2	2520
	21st to end	Day	54% 7% 10% 19% 9% 1	3101
February	1st to 10th	Day	50% 7% 13% 18% 11% 1	1710
	11th to 20th	Day	46% 7% 10% 21% 14% 2	1791
	21st to end	Day	50% 6% 10% 21% 10% 3	1570
March	1st to 10th	Day	44% 6% 14% 22% 12% 3	1900
	11th to 20th	Day	46% 6% 11% 23% 13% 2	2076
	21st to end	Day	48% 5% 10% 15% 17% 4	2438
April	1st to 10th	Day	46% 7% 10% 19% 13% 4	2184
	11th to 20th	Day	45% 5% 11% 22% 14% 3	2134
	21st to end	Day	45% 7% 11% 19% 13% 4	2160
May	1st to 10th	Day	51% 6% 10% 18% 13% 2	2381
	11th to 20th	Day	49% 7% 11% 19% 13% 2	2482
	21st to end	Day	43% 9% 14% 20% 13% 2	2725
June	1st to 10th	Day	45% 8% 14% 19% 13% 1	2520
	11th to 20th	Day	46% 9% 14% 20% 10% 2	2520
	21st to end	Day	41% 9% 13% 25% 11%	2520
July	1st to 10th	Day	43% 9% 12% 20% 14% 1	2450
	11th to 20th	Day	35% 10% 17% 23% 13% 1	2445
	21st to end	Day	43% 8% 12% 19% 16% 2	2591
August	1st to 10th	Day	43% 9% 14% 21% 13%	2329
	11th to 20th	Day	43% 9% 14% 22% 11% 1	2152
	21st to end	Day	40% 8% 11% 22% 16% 3	2376
September	1st to 10th	Day	43% 7% 13% 20% 16% 2	2160
	11th to 20th	Day	35% 7% 11% 22% 24% 2	2129
	21st to end	Day	43% 7% 11% 18% 20% 2	1980
October	1st to 10th	Day	45% 7% 12% 20% 14% 2	1800
	11th to 20th	Day	42% 6% 12% 24% 15% 1	1800
	21st to end	Day	48% 6% 12% 20% 12% 2	1887
November	1st to 10th	Day	36% 5% 13% 25% 18% 3	1671
	11th to 20th	Day	42% 6% 11% 23% 16% 2	1710
	21st to end	Day	44% 7% 15% 24% 9% 1	1543
December	1st to 10th	Day	52% 6% 14% 16% 11% 1	1520
	11th to 20th	Day	49% 6% 15% 22% 8%	1906
	21st to end	Day	59% 8% 10% 16% 7%	2772
January	1st to 10th	Night	42% 7% 13% 26% 9% 3	4429
	11th to 20th	Night	49% 7% 13% 21% 9% 1	4440
	21st to end	Night	52% 8% 10% 20% 10% 1	4553
February	1st to 10th	Night	44% 6% 15% 22% 11% 1	2470
	11th to 20th	Night	44% 7% 11% 20% 15% 3	2285
	21st to end	Night	46% 6% 10% 22% 13% 3	1884
March	1st to 10th	Night	41% 7% 14% 23% 12% 3	2280
	11th to 20th	Night	42% 6% 13% 24% 14% 2	2101
	21st to end	Night	43% 7% 10% 17% 18% 4	2159
April	1st to 10th	Night	48% 6% 12% 19% 12% 3	1821
	11th to 20th	Night	42% 8% 11% 21% 17% 1	1775
	21st to end	Night	43% 7% 11% 20% 15% 4	1800
May	1st to 10th	Night	52% 7% 9% 17% 13% 2	1593
	11th to 20th	Night	44% 7% 11% 19% 17% 2	1416
	21st to end	Night	40% 8% 16% 21% 12% 2	1551
June	1st to 10th	Night	40% 9% 11% 24% 16% 1	1440
	11th to 20th	Night	39% 9% 17% 23% 11% 1	1440
	21st to end	Night	32% 10% 15% 29% 13% 1	1440
July	1st to 10th	Night	39% 9% 14% 23% 13% 2	1400
	11th to 20th	Night	35% 10% 16% 27% 10% 1	1392
	21st to end	Night	34% 11% 18% 20% 16% 2	1486
August	1st to 10th	Night	34% 11% 16% 26% 13% 1	1582
	11th to 20th	Night	42% 10% 15% 21% 12%	1729
	21st to end	Night	36% 9% 13% 21% 18% 2	1980
September	1st to 10th	Night	39% 6% 13% 25% 16% 1	1800
	11th to 20th	Night	34% 6% 10% 23% 25% 2	1829
	21st to end	Night	39% 6% 11% 22% 21% 1	1980
October	1st to 10th	Night	44% 6% 12% 22% 15% 1	2155
	11th to 20th	Night	39% 6% 14% 27% 13% 1	2160
	21st to end	Night	43% 6% 13% 23% 14% 1	2467
November	1st to 10th	Night	35% 6% 14% 22% 19% 3	2407
	11th to 20th	Night	41% 4 12% 22% 17% 3	2470
	21st to end	Night	38% 7% 16% 26% 11% 1	2635
December	1st to 10th	Night	49% 7% 13% 21% 10% 1	2660
	11th to 20th	Night	47% 5% 15% 19% 12% 1	3288
	21st to end	Night	52% 7% 13% 20% 8%	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	37% 26% 26% 11% 2	180
	11th to 20th	Day	39% 27% 24% 8% 2	180
	21st to end	Day	25% 34% 29% 9% 3 1	292
February	1st to 10th	Day	32% 33% 26% 8% 1	270
	11th to 20th	Day	35% 28% 30% 6% 1	390
	21st to end	Day	37% 24% 28% 9% 2	382
March	1st to 10th	Day	32% 21% 33% 11% 2	460
	11th to 20th	Day	30% 27% 28% 12% 3 1	460
	21st to end	Day	33% 25% 27% 10% 3 1	506
April	1st to 10th	Day	30% 26% 28% 11% 5%	428
	11th to 20th	Day	27% 25% 26% 13% 7% 2	412
	21st to end	Day	29% 22% 34% 10% 4 2	420
May	1st to 10th	Day	32% 22% 26% 11% 8% 1	423
	11th to 20th	Day	25% 19% 32% 17% 6% 1	447
	21st to end	Day	20% 12% 28% 25% 13% 2	485
June	1st to 10th	Day	19% 15% 31% 23% 10% 2	450
	11th to 20th	Day	20% 17% 27% 24% 11% 1	450
	21st to end	Day	14% 16% 32% 26% 10% 2	450
July	1st to 10th	Day	13% 10% 28% 26% 18% 5%	445
	11th to 20th	Day	11% 5% 29% 31% 20% 2	444
	21st to end	Day	16% 9% 36% 26% 11% 3	488
August	1st to 10th	Day	12% 7% 30% 28% 16% 6%	446
	11th to 20th	Day	14% 7% 26% 33% 15% 5%	439
	21st to end	Day	14% 11% 29% 26% 12% 7%	495
September	1st to 10th	Day	20% 12% 24% 22% 15% 6%	450
	11th to 20th	Day	13% 11% 31% 22% 14% 10%	450
	21st to end	Day	22% 14% 28% 23% 10% 4	450
October	1st to 10th	Day	29% 11% 23% 21% 12% 4	450
	11th to 20th	Day	21% 19% 30% 22% 7% 1	450
	21st to end	Day	29% 18% 29% 19% 5% 1	448
November	1st to 10th	Day	22% 19% 28% 21% 8% 2	365
	11th to 20th	Day	28% 24% 28% 16% 4 1	370
	21st to end	Day	27% 24% 33% 14% 2	203
December	1st to 10th	Day	29% 32% 25% 10% 4 1	180
	11th to 20th	Day	38% 24% 27% 8% 2	180
	21st to end	Day	31% 24% 32% 10% 3	198
January	1st to 10th	Night	23% 25% 36% 13% 3	760
	11th to 20th	Night	28% 23% 31% 17% 1	760
	21st to end	Night	20% 27% 35% 16% 2	836
February	1st to 10th	Night	25% 23% 36% 15% 1	760
	11th to 20th	Night	26% 30% 35% 9% 1	743
	21st to end	Night	32% 23% 29% 14% 2	628
March	1st to 10th	Night	27% 23% 33% 14% 3	760
	11th to 20th	Night	25% 25% 29% 17% 4	760
	21st to end	Night	23% 26% 33% 14% 4 1	836
April	1st to 10th	Night	24% 24% 32% 18% 3	729
	11th to 20th	Night	22% 20% 31% 21% 6%	711
	21st to end	Night	26% 17% 31% 22% 4	720
May	1st to 10th	Night	27% 13% 29% 24% 6% 1	513
	11th to 20th	Night	20% 12% 36% 25% 5% 1	354
	21st to end	Night	17% 6% 26% 38% 13%	389
June	1st to 10th	Night	17% 7% 25% 36% 15%	360
	11th to 20th	Night	17% 6% 31% 34% 12%	360
	21st to end	Night	13% 6% 26% 44% 11%	360
July	1st to 10th	Night	13% 5% 23% 39% 19% 1	350
	11th to 20th	Night	12% 4 23% 44% 15% 2	348
	21st to end	Night	12% 6% 24% 43% 14% 1	394
August	1st to 10th	Night	13% 2 23% 38% 22% 2	518
	11th to 20th	Night	15% 5% 18% 37% 23% 2	665
	21st to end	Night	18% 5% 21% 34% 21% 1	792
September	1st to 10th	Night	18% 7% 26% 31% 16% 2	720
	11th to 20th	Night	17% 6% 26% 27% 18% 5%	720
	21st to end	Night	20% 8% 26% 29% 15% 2	720
October	1st to 10th	Night	26% 11% 22% 24% 15% 1	720
	11th to 20th	Night	21% 14% 29% 30% 6%	720
	21st to end	Night	29% 16% 30% 19% 6%	792
November	1st to 10th	Night	19% 18% 30% 24% 9%	740
	11th to 20th	Night	27% 18% 28% 20% 5% 1	760
	21st to end	Night	21% 22% 32% 20% 5%	760
December	1st to 10th	Night	26% 21% 33% 15% 4	760
	11th to 20th	Night	26% 21% 33% 18% 2	760
	21st to end	Night	27% 22% 33% 16% 2	836

Page generated at 2024-03-31 06:08:55. Version ac07

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