Arunah Hill
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Arunah Hill clear sky chart from 2005-11-06 to 2024-11-04.

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% 8% 3 7% 5% 5% 5% 4 6% 7% 33%	101319
	Night	16% 9% 3 7% 5% 4 5% 4 6% 7% 36%	97718
Transparency	Day	44% 8% 14% 20% 12% 2	104843
	Night	42% 9% 14% 21% 12% 2	102283
Seeing	Day	24% 20% 29% 17% 7% 2	14906
	Night	22% 20% 27% 22% 8% 1	23901

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	12% 9% 4 7% 6% 6% 5% 5% 6% 6% 34%	2517
	11th to 20th	Day	16% 10% 5% 11% 7% 6% 6% 3 6% 7% 25%	2520
	21st to end	Day	18% 15% 7% 10% 4 4 3 3 4 5% 26%	2804
February	1st to 10th	Day	14% 10% 4 8% 7% 6% 6% 4 6% 7% 28%	1738
	11th to 20th	Day	11% 8% 3 10% 6% 6% 6% 4 6% 7% 33%	1848
	21st to end	Day	18% 11% 3 9% 5% 4 5% 3 5% 5% 32%	1570
March	1st to 10th	Day	21% 15% 3 8% 5% 4 3 2 4 5% 29%	3116
	11th to 20th	Day	12% 9% 3 8% 7% 7% 6% 4 6% 7% 32%	3264
	21st to end	Day	19% 10% 3 8% 5% 4 4 3 4 6% 35%	4166
April	1st to 10th	Day	17% 11% 3 8% 5% 5% 4 3 5% 6% 33%	2280
	11th to 20th	Day	16% 9% 3 7% 5% 5% 4 4 6% 6% 36%	2254
	21st to end	Day	18% 8% 3 8% 5% 5% 5% 4 5% 6% 33%	2403
May	1st to 10th	Day	25% 10% 3 8% 5% 4 4 3 4 6% 28%	4106
	11th to 20th	Day	22% 9% 3 7% 4 4 4 3 6% 8% 31%	4360
	21st to end	Day	13% 6% 2 6% 4 5% 5% 5% 7% 8% 39%	4837
June	1st to 10th	Day	17% 7% 2 7% 6% 6% 6% 5% 6% 8% 31%	2660
	11th to 20th	Day	18% 6% 3 6% 4 5% 5% 5% 6% 9% 34%	2660
	21st to end	Day	17% 7% 3 6% 6% 6% 5% 4 6% 8% 31%	2660
July	1st to 10th	Day	11% 6% 3 7% 5% 5% 6% 6% 7% 9% 34%	4440
	11th to 20th	Day	10% 5% 2 6% 6% 6% 6% 5% 7% 11% 36%	4440
	21st to end	Day	16% 8% 3 7% 5% 5% 5% 4 7% 8% 32%	4814
August	1st to 10th	Day	16% 7% 3 8% 5% 5% 5% 4 6% 9% 31%	4329
	11th to 20th	Day	13% 7% 3 8% 5% 4 6% 5% 7% 10% 33%	3799
	21st to end	Day	11% 5% 2 6% 4 5% 7% 6% 8% 9% 38%	4180
September	1st to 10th	Day	13% 5% 2 6% 5% 5% 4 4 5% 8% 41%	2280
	11th to 20th	Day	15% 5% 2 5% 4 4 4 3 5% 7% 46%	2157
	21st to end	Day	17% 6% 2 6% 4 4 4 5% 7% 7% 39%	2090
October	1st to 10th	Day	22% 7% 3 6% 5% 4 4 4 4 5% 35%	2043
	11th to 20th	Day	15% 8% 3 6% 5% 4 4 4 6% 7% 40%	1872
	21st to end	Day	21% 10% 3 7% 3 4 4 4 5% 7% 31%	1881
November	1st to 10th	Day	11% 9% 2 7% 4 3 3 4 5% 6% 45%	1698
	11th to 20th	Day	17% 8% 3 6% 4 4 4 4 6% 7% 39%	1710
	21st to end	Day	17% 9% 3 5% 5% 4 4 4 5% 7% 36%	1625
December	1st to 10th	Day	17% 11% 4 9% 6% 6% 5% 3 5% 6% 28%	1520
	11th to 20th	Day	20% 9% 3 6% 5% 4 4 2 4 5% 36%	1906
	21st to end	Day	18% 12% 3 10% 6% 5% 5% 4 5% 8% 25%	2772
January	1st to 10th	Night	15% 9% 4 6% 4 3 4 4 6% 8% 37%	4429
	11th to 20th	Night	13% 9% 3 10% 8% 6% 6% 4 6% 7% 28%	4440
	21st to end	Night	18% 15% 4 9% 5% 5% 5% 4 5% 5% 25%	4852
February	1st to 10th	Night	14% 9% 3 7% 5% 5% 6% 5% 6% 7% 33%	2441
	11th to 20th	Night	11% 9% 3 7% 5% 7% 6% 4 7% 7% 34%	2218
	21st to end	Night	16% 10% 3 7% 5% 5% 4 4 6% 6% 34%	1884
March	1st to 10th	Night	22% 13% 2 6% 5% 4 4 4 5% 6% 28%	3724
	11th to 20th	Night	12% 9% 3 6% 5% 6% 5% 4 6% 8% 34%	3691
	21st to end	Night	17% 10% 4 8% 5% 4 4 3 6% 6% 33%	3466
April	1st to 10th	Night	16% 9% 3 8% 4 5% 5% 4 6% 7% 33%	1900
	11th to 20th	Night	19% 8% 2 7% 4 4 3 4 5% 7% 36%	1875
	21st to end	Night	20% 10% 3 6% 4 3 3 3 5% 6% 37%	1777
May	1st to 10th	Night	25% 11% 2 6% 4 4 5% 3 5% 6% 29%	2834
	11th to 20th	Night	18% 9% 3 9% 5% 6% 4 4 6% 8% 28%	2561
	21st to end	Night	15% 6% 2 6% 4 5% 5% 4 6% 9% 39%	2738
June	1st to 10th	Night	17% 8% 3 6% 4 3 4 2 6% 7% 39%	1520
	11th to 20th	Night	18% 6% 2 5% 4 4 5% 4 6% 7% 39%	1520
	21st to end	Night	15% 7% 2 5% 4 4 5% 3 5% 8% 42%	1520
July	1st to 10th	Night	11% 6% 2 7% 6% 4 5% 4 7% 9% 39%	2520
	11th to 20th	Night	14% 5% 3 7% 4 5% 4 4 6% 8% 41%	2520
	21st to end	Night	15% 8% 3 6% 4 3 4 3 7% 7% 40%	2739
August	1st to 10th	Night	22% 6% 3 7% 4 4 4 3 5% 6% 36%	2569
	11th to 20th	Night	15% 7% 3 8% 4 4 4 4 6% 7% 39%	3026
	21st to end	Night	10% 4 1 4 3 4 4 4 7% 8% 51%	3476
September	1st to 10th	Night	13% 6% 2 6% 4 4 4 4 6% 7% 45%	1900
	11th to 20th	Night	12% 5% 2 5% 3 3 4 3 4 7% 51%	2023
	21st to end	Night	17% 7% 2 5% 3 4 5% 3 5% 6% 43%	2090
October	1st to 10th	Night	21% 7% 2 7% 4 4 4 3 4 5% 39%	2135
	11th to 20th	Night	15% 7% 2 6% 4 4 5% 3 5% 6% 44%	2308
	21st to end	Night	21% 8% 3 6% 4 4 4 3 4 6% 37%	2717
November	1st to 10th	Night	13% 7% 2 6% 4 3 4 3 5% 6% 45%	2453
	11th to 20th	Night	17% 8% 3 5% 5% 4 4 4 5% 6% 39%	2470
	21st to end	Night	13% 8% 3 6% 6% 5% 5% 4 6% 7% 38%	2550
December	1st to 10th	Night	17% 9% 4 7% 5% 4 5% 4 6% 8% 30%	2660
	11th to 20th	Night	18% 9% 3 6% 5% 4 5% 5% 6% 7% 31%	3288
	21st to end	Night	19% 11% 5% 10% 5% 5% 4 4 5% 6% 26%	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% 9% 18% 25% 6% 1	2518
	11th to 20th	Day	51% 10% 15% 17% 6% 1	2520
	21st to end	Day	58% 6% 11% 17% 7% 1	2804
February	1st to 10th	Day	51% 8% 16% 15% 10% 1	1738
	11th to 20th	Day	45% 8% 12% 21% 12% 2	1857
	21st to end	Day	51% 8% 11% 18% 11% 2	1570
March	1st to 10th	Day	55% 7% 12% 14% 10% 2	3119
	11th to 20th	Day	40% 13% 18% 18% 9% 2	3264
	21st to end	Day	47% 6% 8% 17% 18% 4	4166
April	1st to 10th	Day	48% 7% 10% 21% 11% 3	2280
	11th to 20th	Day	44% 9% 11% 19% 15% 2	2254
	21st to end	Day	47% 9% 10% 18% 13% 3	2403
May	1st to 10th	Day	54% 9% 11% 14% 11% 1	4120
	11th to 20th	Day	48% 8% 16% 17% 9% 1	4364
	21st to end	Day	34% 10% 16% 23% 15% 1	4837
June	1st to 10th	Day	45% 10% 16% 19% 10% 1	2660
	11th to 20th	Day	43% 9% 15% 19% 12% 1	2660
	21st to end	Day	46% 9% 15% 18% 11% 1	2660
July	1st to 10th	Day	43% 9% 12% 22% 14% 1	4370
	11th to 20th	Day	38% 10% 17% 23% 12% 1	4365
	21st to end	Day	47% 8% 13% 18% 13% 1	4661
August	1st to 10th	Day	46% 9% 15% 20% 9% 1	4315
	11th to 20th	Day	41% 10% 16% 26% 7% 1	3837
	21st to end	Day	35% 8% 15% 28% 12% 1	4180
September	1st to 10th	Day	39% 8% 13% 24% 15% 1	2280
	11th to 20th	Day	36% 7% 11% 24% 20% 2	2157
	21st to end	Day	40% 8% 13% 22% 15% 2	2090
October	1st to 10th	Day	42% 7% 10% 19% 20% 2	3394
	11th to 20th	Day	34% 6% 11% 23% 21% 5%	3088
	21st to end	Day	35% 6% 14% 27% 14% 4	3081
November	1st to 10th	Day	37% 8% 16% 24% 13% 2	1698
	11th to 20th	Day	41% 8% 15% 20% 15% 2	1710
	21st to end	Day	44% 7% 16% 23% 9% 2	1625
December	1st to 10th	Day	52% 9% 16% 12% 11% 1	1520
	11th to 20th	Day	45% 9% 16% 18% 12% 1	1906
	21st to end	Day	52% 10% 15% 13% 10%	2772
January	1st to 10th	Night	40% 9% 16% 23% 10% 2	4429
	11th to 20th	Night	46% 10% 17% 17% 8% 2	4440
	21st to end	Night	55% 8% 13% 15% 8% 1	4852
February	1st to 10th	Night	46% 8% 16% 19% 9% 2	2441
	11th to 20th	Night	43% 8% 15% 19% 13% 2	2220
	21st to end	Night	45% 7% 14% 21% 9% 3	1884
March	1st to 10th	Night	51% 9% 13% 17% 9% 1	3734
	11th to 20th	Night	39% 11% 16% 22% 9% 2	3692
	21st to end	Night	45% 9% 9% 14% 20% 4	3466
April	1st to 10th	Night	46% 7% 13% 19% 13% 2	1900
	11th to 20th	Night	46% 8% 11% 19% 16% 1	1875
	21st to end	Night	45% 7% 12% 18% 14% 4	1777
May	1st to 10th	Night	52% 9% 13% 14% 10% 1	2840
	11th to 20th	Night	49% 13% 14% 14% 8% 1	2562
	21st to end	Night	37% 10% 17% 21% 14% 1	2739
June	1st to 10th	Night	43% 7% 15% 23% 12%	1520
	11th to 20th	Night	42% 10% 15% 22% 11%	1520
	21st to end	Night	38% 10% 15% 23% 13%	1520
July	1st to 10th	Night	39% 8% 17% 22% 15%	2480
	11th to 20th	Night	39% 7% 14% 26% 13%	2472
	21st to end	Night	43% 7% 13% 21% 15% 1	2651
August	1st to 10th	Night	48% 8% 14% 21% 9% 1	2559
	11th to 20th	Night	41% 7% 17% 27% 8%	3054
	21st to end	Night	26% 7% 14% 37% 16% 1	3476
September	1st to 10th	Night	37% 9% 12% 25% 17% 1	1900
	11th to 20th	Night	33% 6% 14% 24% 22% 2	2023
	21st to end	Night	39% 8% 11% 23% 17% 2	2090
October	1st to 10th	Night	40% 8% 13% 22% 17% 1	3564
	11th to 20th	Night	29% 6% 14% 23% 22% 6%	3831
	21st to end	Night	35% 6% 15% 30% 13% 2	4467
November	1st to 10th	Night	37% 7% 13% 22% 18% 3	2453
	11th to 20th	Night	42% 8% 14% 20% 15% 3	2470
	21st to end	Night	39% 9% 18% 23% 10% 1	2550
December	1st to 10th	Night	45% 11% 16% 18% 10%	2660
	11th to 20th	Night	43% 11% 18% 16% 11% 2	3288
	21st to end	Night	52% 10% 13% 17% 8% 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	30% 27% 32% 7% 3 1	180
	11th to 20th	Day	30% 33% 27% 7% 2	180
	21st to end	Day	20% 32% 32% 13% 2	207
February	1st to 10th	Day	33% 34% 25% 6% 1	298
	11th to 20th	Day	31% 32% 27% 9% 1	456
	21st to end	Day	31% 27% 28% 13% 1	382
March	1st to 10th	Day	29% 28% 29% 12% 2	460
	11th to 20th	Day	33% 28% 27% 9% 3 1	460
	21st to end	Day	34% 25% 25% 8% 5% 2	506
April	1st to 10th	Day	34% 23% 26% 10% 6% 1	460
	11th to 20th	Day	32% 25% 26% 10% 4 2	452
	21st to end	Day	27% 23% 30% 13% 5% 2	460
May	1st to 10th	Day	34% 21% 26% 11% 5% 3	463
	11th to 20th	Day	21% 24% 33% 17% 5% 1	487
	21st to end	Day	20% 15% 31% 22% 9% 2	529
June	1st to 10th	Day	19% 18% 32% 20% 10% 1	490
	11th to 20th	Day	20% 15% 32% 21% 10% 1	490
	21st to end	Day	18% 21% 31% 20% 7% 3	490
July	1st to 10th	Day	16% 11% 34% 26% 12% 2	485
	11th to 20th	Day	13% 8% 35% 31% 10% 2	484
	21st to end	Day	16% 11% 38% 23% 10% 2	532
August	1st to 10th	Day	13% 13% 29% 29% 13% 4	486
	11th to 20th	Day	16% 12% 30% 24% 11% 7%	479
	21st to end	Day	13% 14% 27% 27% 13% 6%	539
September	1st to 10th	Day	19% 12% 27% 21% 15% 6%	490
	11th to 20th	Day	17% 13% 24% 21% 14% 11%	490
	21st to end	Day	20% 14% 29% 21% 10% 6%	490
October	1st to 10th	Day	28% 16% 24% 16% 13% 3	490
	11th to 20th	Day	21% 21% 28% 21% 8% 2	475
	21st to end	Day	31% 20% 27% 17% 6% 1	429
November	1st to 10th	Day	24% 24% 23% 21% 9% 1	374
	11th to 20th	Day	29% 28% 22% 15% 5% 1	370
	21st to end	Day	30% 24% 25% 16% 4 1	285
December	1st to 10th	Day	29% 31% 24% 12% 3	180
	11th to 20th	Day	38% 24% 29% 7% 2	180
	21st to end	Day	29% 28% 27% 12% 3 1	198
January	1st to 10th	Night	22% 28% 32% 14% 2	760
	11th to 20th	Night	26% 26% 29% 17% 2	760
	21st to end	Night	19% 30% 31% 17% 3	836
February	1st to 10th	Night	23% 26% 35% 15% 1	760
	11th to 20th	Night	24% 30% 30% 14% 1	743
	21st to end	Night	28% 27% 28% 16% 2	628
March	1st to 10th	Night	26% 25% 30% 16% 3	760
	11th to 20th	Night	24% 27% 29% 17% 2 1	760
	21st to end	Night	25% 23% 27% 19% 5%	836
April	1st to 10th	Night	25% 22% 32% 16% 4	760
	11th to 20th	Night	23% 24% 26% 20% 6%	751
	21st to end	Night	29% 21% 25% 20% 5%	637
May	1st to 10th	Night	28% 15% 29% 20% 7%	570
	11th to 20th	Night	20% 17% 32% 26% 5%	414
	21st to end	Night	19% 9% 28% 30% 13%	411
June	1st to 10th	Night	19% 12% 30% 28% 11%	380
	11th to 20th	Night	18% 9% 27% 35% 9% 1	380
	21st to end	Night	18% 9% 26% 34% 13% 1	380
July	1st to 10th	Night	15% 6% 25% 38% 16% 1	370
	11th to 20th	Night	15% 5% 24% 39% 16% 1	368
	21st to end	Night	11% 8% 24% 39% 17%	416
August	1st to 10th	Night	14% 5% 23% 39% 19%	415
	11th to 20th	Night	15% 8% 24% 31% 20% 3	703
	21st to end	Night	16% 8% 22% 32% 21% 2	836
September	1st to 10th	Night	15% 9% 27% 32% 16% 2	760
	11th to 20th	Night	15% 9% 23% 27% 21% 5%	760
	21st to end	Night	20% 12% 24% 28% 14% 2	760
October	1st to 10th	Night	26% 12% 25% 25% 11% 1	760
	11th to 20th	Night	21% 19% 25% 24% 10% 1	760
	21st to end	Night	26% 20% 27% 22% 5%	836
November	1st to 10th	Night	18% 20% 30% 22% 9% 1	755
	11th to 20th	Night	24% 25% 24% 18% 6% 1	760
	21st to end	Night	21% 25% 28% 21% 4 1	760
December	1st to 10th	Night	25% 30% 27% 14% 4	760
	11th to 20th	Night	25% 28% 27% 17% 3	760
	21st to end	Night	26% 31% 26% 15% 2	836

Page generated at 2024-11-01 22:47:34. Version ac07

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