Avyatha Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Avyatha Observatory clear sky chart from 2005-11-06 to 2024-11-25.

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	3 6% 3 7% 5% 4 5% 4 6% 8% 49%	105375
	Night	2 5% 2 5% 3 3 4 3 6% 8% 60%	102831
Transparency	Day	30% 9% 13% 21% 20% 8%	105121
	Night	21% 8% 14% 27% 23% 8%	102675
Seeing	Day	14% 27% 29% 19% 8% 2	15638
	Night	10% 28% 28% 22% 10% 2	25696

By Month

Percentage Cloud Cover SW (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	3 2 9% 5% 4 3 4 5% 9% 54%	2538
	11th to 20th	Day	3 2 8% 4 3 3 3 6% 11% 57%	2670
	21st to end	Day	6% 5% 8% 4 4 3 3 5% 7% 54%	3146
February	1st to 10th	Day	4 3 9% 4 4 5% 4 6% 10% 53%	1710
	11th to 20th	Day	3 2 5% 5% 3 5% 3 5% 7% 60%	1793
	21st to end	Day	5% 3 8% 5% 4 4 3 4 6% 56%	1570
March	1st to 10th	Day	1 8% 4 11% 4 3 3 3 5% 6% 52%	3151
	11th to 20th	Day	1 12% 7% 9% 4 4 4 3 5% 8% 41%	3490
	21st to end	Day	1 9% 5% 8% 5% 6% 5% 5% 7% 8% 42%	4027
April	1st to 10th	Day	2 8% 3 7% 4 5% 4 4 7% 8% 49%	2280
	11th to 20th	Day	5% 13% 4 8% 4 4 5% 4 5% 8% 39%	2251
	21st to end	Day	5% 13% 3 7% 5% 5% 6% 4 7% 8% 38%	2280
May	1st to 10th	Day	5% 14% 3 6% 5% 5% 5% 5% 7% 9% 34%	4008
	11th to 20th	Day	7% 9% 2 6% 5% 5% 5% 5% 8% 9% 39%	4388
	21st to end	Day	4 5% 1 5% 4 4 5% 4 7% 10% 49%	4825
June	1st to 10th	Day	4 5% 2 6% 5% 5% 6% 6% 8% 8% 45%	2660
	11th to 20th	Day	6% 6% 2 5% 5% 5% 5% 5% 6% 8% 48%	2660
	21st to end	Day	4 5% 2 5% 6% 6% 6% 5% 8% 10% 44%	2660
July	1st to 10th	Day	5% 4 1 5% 5% 5% 4 5% 6% 7% 52%	4430
	11th to 20th	Day	4 3 2 6% 6% 6% 7% 6% 9% 9% 43%	4430
	21st to end	Day	6% 5% 2 7% 6% 5% 6% 6% 7% 8% 43%	4651
August	1st to 10th	Day	6% 6% 3 8% 6% 6% 7% 6% 8% 11% 34%	4092
	11th to 20th	Day	5% 5% 2 7% 4 5% 6% 5% 7% 8% 44%	3768
	21st to end	Day	5% 5% 3 8% 5% 6% 6% 5% 7% 8% 41%	4180
September	1st to 10th	Day	5% 5% 2 6% 5% 4 4 4 5% 7% 53%	2280
	11th to 20th	Day	6% 5% 2 6% 4 4 4 4 4 7% 54%	2280
	21st to end	Day	6% 6% 2 5% 3 3 3 3 5% 6% 59%	2068
October	1st to 10th	Day	3 3 1 4 3 2 2 2 3 5% 71%	3170
	11th to 20th	Day	3 5% 2 6% 5% 5% 5% 4 7% 8% 51%	3150
	21st to end	Day	2 4 2 5% 3 3 3 3 5% 7% 64%	3359
November	1st to 10th	Day	1 5% 2 4 3 3 3 3 4 7% 66%	1763
	11th to 20th	Day	1 4 2 3 3 3 2 3 5% 9% 66%	1800
	21st to end	Day	3 3 8% 4 3 4 2 6% 7% 59%	1607
December	1st to 10th	Day	4 2 7% 4 4 4 3 5% 9% 59%	1520
	11th to 20th	Day	5% 2 5% 4 3 4 3 7% 11% 56%	1926
	21st to end	Day	5% 3 8% 4 4 4 4 6% 7% 55%	2794
January	1st to 10th	Night	2 2 10% 5% 4 4 3 5% 8% 57%	4417
	11th to 20th	Night	2 1 3 5% 3 3 4 5% 8% 66%	4330
	21st to end	Night	1 5% 3 7% 4 3 3 2 4 7% 60%	4521
February	1st to 10th	Night	3 2 6% 4 3 3 3 6% 8% 63%	2470
	11th to 20th	Night	3 2 5% 4 3 3 3 6% 7% 64%	2273
	21st to end	Night	4 3 6% 4 3 4 3 5% 7% 60%	1884
March	1st to 10th	Night	6% 4 6% 4 3 3 3 4 7% 59%	3711
	11th to 20th	Night	1 10% 6% 8% 3 3 3 3 4 6% 54%	3490
	21st to end	Night	1 6% 2 6% 3 3 4 4 7% 8% 56%	3619
April	1st to 10th	Night	1 6% 1 4 3 3 4 3 5% 7% 61%	1900
	11th to 20th	Night	4 7% 3 6% 3 4 4 4 6% 7% 52%	1877
	21st to end	Night	5% 11% 3 5% 4 3 3 3 6% 9% 50%	1900
May	1st to 10th	Night	5% 8% 2 5% 3 4 4 3 6% 9% 51%	2955
	11th to 20th	Night	6% 10% 2 5% 4 4 4 5% 6% 8% 46%	2517
	21st to end	Night	2 4 2 4 4 3 4 3 5% 7% 63%	2762
June	1st to 10th	Night	4 3 1 3 3 3 4 3 6% 9% 61%	1520
	11th to 20th	Night	4 3 1 4 2 3 4 4 6% 8% 62%	1520
	21st to end	Night	3 2 1 3 3 3 4 4 7% 8% 60%	1520
July	1st to 10th	Night	3 5% 1 4 3 3 3 3 5% 7% 62%	2540
	11th to 20th	Night	1 2 1 4 3 4 5% 4 9% 12% 55%	2540
	21st to end	Night	3 3 1 3 3 4 4 4 8% 9% 58%	2908
August	1st to 10th	Night	4 5% 2 6% 3 4 5% 5% 8% 10% 48%	2847
	11th to 20th	Night	3 3 1 3 3 3 5% 4 8% 10% 55%	3069
	21st to end	Night	2 4 2 6% 4 4 5% 5% 6% 9% 52%	3487
September	1st to 10th	Night	6% 3 1 4 3 3 4 4 5% 7% 60%	1900
	11th to 20th	Night	5% 4 2 3 3 3 3 3 5% 7% 63%	1900
	21st to end	Night	5% 5% 2 4 3 3 3 3 4 6% 64%	2108
October	1st to 10th	Night	2 3 1 2 2 2 2 2 4 5% 75%	3800
	11th to 20th	Night	1 4 2 4 2 3 3 3 5% 6% 67%	3778
	21st to end	Night	2 5% 2 5% 3 2 2 3 4 6% 68%	4166
November	1st to 10th	Night	1 3 1 3 3 3 3 3 4 7% 69%	2535
	11th to 20th	Night	4 1 3 3 3 3 3 5% 8% 67%	2600
	21st to end	Night	1 4 2 6% 3 3 3 3 6% 7% 62%	2663
December	1st to 10th	Night	3 2 5% 3 2 3 3 5% 8% 65%	2660
	11th to 20th	Night	4 2 6% 4 4 3 3 6% 10% 56%	3271
	21st to end	Night	5% 2 6% 4 4 4 4 7% 8% 56%	4873

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	22% 10% 21% 22% 20% 5%	2539
	11th to 20th	Day	27% 12% 20% 24% 13% 4	2670
	21st to end	Day	29% 8% 14% 25% 18% 6%	3146
February	1st to 10th	Day	27% 8% 19% 24% 16% 6%	1710
	11th to 20th	Day	23% 10% 12% 26% 23% 6%	1803
	21st to end	Day	28% 8% 12% 22% 22% 8%	1570
March	1st to 10th	Day	32% 6% 10% 22% 24% 6%	3151
	11th to 20th	Day	38% 7% 14% 27% 11% 2	3490
	21st to end	Day	35% 12% 12% 25% 14% 2	4027
April	1st to 10th	Day	31% 8% 14% 22% 18% 7%	2280
	11th to 20th	Day	41% 9% 12% 18% 16% 4	2254
	21st to end	Day	40% 9% 11% 25% 13% 1	2280
May	1st to 10th	Day	40% 12% 12% 17% 17% 2	4008
	11th to 20th	Day	35% 11% 15% 23% 16% 1	4392
	21st to end	Day	27% 8% 12% 24% 24% 5%	4825
June	1st to 10th	Day	31% 12% 14% 21% 17% 6%	2660
	11th to 20th	Day	31% 8% 11% 17% 22% 11%	2660
	21st to end	Day	30% 10% 12% 19% 20% 9%	2660
July	1st to 10th	Day	27% 8% 9% 14% 19% 24%	4361
	11th to 20th	Day	30% 9% 13% 20% 18% 10%	4355
	21st to end	Day	33% 10% 12% 15% 14% 15%	4504
August	1st to 10th	Day	39% 12% 15% 16% 13% 4	4078
	11th to 20th	Day	33% 10% 13% 15% 18% 11%	3804
	21st to end	Day	34% 10% 12% 16% 20% 9%	4179
September	1st to 10th	Day	30% 8% 9% 17% 24% 12%	2280
	11th to 20th	Day	28% 7% 11% 19% 25% 9%	2280
	21st to end	Day	25% 6% 8% 24% 31% 7%	2068
October	1st to 10th	Day	18% 4 6% 14% 39% 19%	3170
	11th to 20th	Day	24% 9% 11% 26% 24% 5%	3150
	21st to end	Day	19% 5% 9% 24% 38% 6%	3359
November	1st to 10th	Day	18% 6% 14% 22% 31% 8%	1763
	11th to 20th	Day	18% 5% 14% 30% 24% 9%	1800
	21st to end	Day	23% 6% 12% 28% 21% 10%	1607
December	1st to 10th	Day	24% 8% 16% 29% 17% 5%	1520
	11th to 20th	Day	19% 10% 14% 33% 21% 3	1924
	21st to end	Day	26% 8% 13% 22% 23% 7%	2794
January	1st to 10th	Night	25% 8% 14% 28% 21% 4	4417
	11th to 20th	Night	17% 13% 20% 27% 16% 8%	4330
	21st to end	Night	23% 7% 14% 29% 20% 6%	4521
February	1st to 10th	Night	20% 8% 18% 30% 20% 5%	2470
	11th to 20th	Night	20% 6% 16% 29% 24% 5%	2273
	21st to end	Night	21% 7% 12% 26% 23% 10%	1884
March	1st to 10th	Night	23% 7% 10% 24% 29% 8%	3711
	11th to 20th	Night	31% 7% 11% 29% 18% 4	3490
	21st to end	Night	22% 9% 19% 33% 16% 2	3619
April	1st to 10th	Night	21% 9% 15% 29% 21% 5%	1900
	11th to 20th	Night	30% 8% 13% 26% 19% 4	1877
	21st to end	Night	30% 7% 14% 29% 19% 1	1900
May	1st to 10th	Night	27% 8% 15% 28% 16% 5%	2955
	11th to 20th	Night	30% 11% 17% 25% 17%	2518
	21st to end	Night	20% 8% 14% 30% 25% 3	2762
June	1st to 10th	Night	18% 8% 21% 29% 17% 6%	1520
	11th to 20th	Night	18% 7% 12% 22% 25% 15%	1520
	21st to end	Night	18% 8% 12% 25% 25% 12%	1520
July	1st to 10th	Night	22% 6% 10% 20% 21% 22%	2500
	11th to 20th	Night	17% 8% 15% 33% 20% 7%	2492
	21st to end	Night	18% 9% 17% 27% 12% 16%	2817
August	1st to 10th	Night	27% 11% 21% 20% 17% 3	2838
	11th to 20th	Night	20% 8% 25% 19% 18% 10%	3099
	21st to end	Night	26% 8% 15% 21% 25% 5%	3487
September	1st to 10th	Night	23% 6% 12% 22% 26% 10%	1900
	11th to 20th	Night	20% 7% 12% 24% 25% 13%	1900
	21st to end	Night	21% 6% 9% 28% 28% 7%	2108
October	1st to 10th	Night	13% 4 8% 24% 36% 15%	3800
	11th to 20th	Night	16% 5% 11% 37% 24% 7%	3778
	21st to end	Night	17% 4 9% 27% 33% 11%	4166
November	1st to 10th	Night	15% 6% 14% 25% 32% 9%	2535
	11th to 20th	Night	16% 5% 14% 30% 26% 9%	2600
	21st to end	Night	21% 6% 12% 27% 25% 9%	2663
December	1st to 10th	Night	18% 7% 19% 28% 21% 7%	2660
	11th to 20th	Night	20% 8% 18% 25% 24% 5%	3272
	21st to end	Night	23% 10% 13% 23% 23% 8%	4873

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	18% 42% 20% 12% 6% 2	270
	11th to 20th	Day	17% 51% 18% 12% 1 1	270
	21st to end	Day	12% 51% 23% 10% 4	297
February	1st to 10th	Day	19% 57% 20% 4 1 1	270
	11th to 20th	Day	24% 47% 22% 6% 2	270
	21st to end	Day	28% 50% 15% 7%	225
March	1st to 10th	Day	20% 44% 22% 13% 2	278
	11th to 20th	Day	17% 35% 32% 13% 2	460
	21st to end	Day	20% 43% 28% 7% 2	506
April	1st to 10th	Day	23% 38% 29% 7% 3	460
	11th to 20th	Day	26% 38% 26% 8% 2	452
	21st to end	Day	20% 35% 32% 11% 2	460
May	1st to 10th	Day	23% 28% 31% 12% 4 1	548
	11th to 20th	Day	18% 19% 35% 19% 7% 1	675
	21st to end	Day	15% 21% 28% 25% 9% 2	734
June	1st to 10th	Day	9% 18% 31% 26% 12% 4	680
	11th to 20th	Day	11% 21% 33% 25% 8% 2	680
	21st to end	Day	7% 18% 34% 23% 13% 5%	680
July	1st to 10th	Day	8% 8% 30% 32% 18% 4	671
	11th to 20th	Day	6% 10% 31% 30% 17% 6%	668
	21st to end	Day	8% 10% 25% 33% 19% 5%	650
August	1st to 10th	Day	13% 13% 30% 31% 10% 3	487
	11th to 20th	Day	9% 14% 31% 32% 12% 3	477
	21st to end	Day	9% 13% 32% 30% 13% 3	539
September	1st to 10th	Day	9% 15% 32% 26% 14% 3	490
	11th to 20th	Day	8% 19% 39% 25% 8% 1	490
	21st to end	Day	12% 20% 34% 21% 11% 3	302
October	1st to 10th	Day	8% 26% 30% 24% 11% 3	300
	11th to 20th	Day	13% 37% 28% 13% 7% 2	300
	21st to end	Day	16% 38% 29% 13% 4	330
November	1st to 10th	Day	15% 44% 25% 9% 7%	300
	11th to 20th	Day	17% 42% 30% 5% 4 1	300
	21st to end	Day	15% 39% 36% 9% 1	282
December	1st to 10th	Day	22% 42% 23% 9% 3	270
	11th to 20th	Day	15% 56% 19% 8% 2	270
	21st to end	Day	20% 43% 27% 7% 2	297
January	1st to 10th	Night	15% 38% 26% 14% 6% 1	950
	11th to 20th	Night	17% 43% 22% 12% 5% 1	889
	21st to end	Night	12% 43% 28% 12% 4	836
February	1st to 10th	Night	11% 49% 26% 11% 4	760
	11th to 20th	Night	12% 44% 28% 13% 3	744
	21st to end	Night	12% 47% 27% 12% 1	628
March	1st to 10th	Night	11% 39% 30% 15% 5%	760
	11th to 20th	Night	9% 32% 31% 22% 5% 1	760
	21st to end	Night	12% 37% 31% 17% 3 1	717
April	1st to 10th	Night	11% 34% 34% 17% 3	570
	11th to 20th	Night	11% 32% 31% 18% 6% 1	563
	21st to end	Night	15% 26% 34% 19% 6% 1	570
May	1st to 10th	Night	13% 18% 39% 21% 8% 1	570
	11th to 20th	Night	16% 10% 30% 32% 11% 1	561
	21st to end	Night	9% 14% 31% 29% 15% 2	617
June	1st to 10th	Night	5% 9% 31% 34% 19% 3	570
	11th to 20th	Night	6% 12% 36% 33% 12% 1	570
	21st to end	Night	5% 7% 23% 40% 23% 2	570
July	1st to 10th	Night	6% 4 18% 39% 30% 3	555
	11th to 20th	Night	2 3 20% 37% 33% 5%	552
	21st to end	Night	7% 3 12% 38% 36% 5%	624
August	1st to 10th	Night	6% 5% 16% 40% 29% 3	567
	11th to 20th	Night	6% 4 18% 44% 24% 4	564
	21st to end	Night	5% 5% 17% 41% 27% 5%	627
September	1st to 10th	Night	6% 4 24% 38% 22% 6%	570
	11th to 20th	Night	7% 8% 31% 32% 17% 4	570
	21st to end	Night	9% 12% 30% 29% 15% 4	591
October	1st to 10th	Night	7% 23% 29% 28% 10% 3	760
	11th to 20th	Night	8% 33% 28% 22% 7% 2	760
	21st to end	Night	12% 31% 32% 17% 7% 2	858
November	1st to 10th	Night	8% 41% 29% 15% 6% 1	975
	11th to 20th	Night	13% 42% 31% 10% 3 1	1000
	21st to end	Night	8% 38% 33% 17% 3	973
December	1st to 10th	Night	15% 39% 31% 11% 3	950
	11th to 20th	Night	12% 45% 27% 12% 3 1	950
	21st to end	Night	13% 42% 26% 13% 4 1	1045

Page generated at 2024-11-22 06:02:25. Version ac07

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