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 2024-01-15.

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	4 6% 3 6% 5% 3 5% 5% 6% 8% 49%	74775
	Night	2 4 2 4 4 2 4 4 5% 8% 60%	75016
Transparency	Day	32% 9% 13% 22% 19% 6%	74484
	Night	22% 7% 15% 27% 22% 7%	74829
Seeing	Day	14% 28% 29% 19% 8% 2	14416
	Night	10% 29% 27% 22% 11% 2	24593

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	2 3 5% 4 3 3 4 6% 9% 60%	1518
	11th to 20th	Day	4 3 6% 5% 3 4 5% 5% 9% 56%	1546
	21st to end	Day	3 3 8% 6% 4 4 4 6% 9% 52%	1782
February	1st to 10th	Day	4 2 7% 5% 3 4 5% 5% 11% 54%	1620
	11th to 20th	Day	3 2 5% 6% 2 6% 4 5% 8% 59%	1696
	21st to end	Day	5% 4 7% 7% 3 5% 4 4 7% 55%	1480
March	1st to 10th	Day	1 8% 3 6% 4 3 4 5% 6% 7% 52%	1807
	11th to 20th	Day	2 9% 4 7% 5% 3 4 4 6% 10% 46%	1980
	21st to end	Day	2 10% 5% 6% 5% 4 5% 4 7% 10% 42%	2290
April	1st to 10th	Day	3 7% 3 6% 5% 3 5% 5% 6% 8% 48%	2160
	11th to 20th	Day	5% 12% 4 7% 5% 3 5% 5% 5% 8% 39%	2131
	21st to end	Day	6% 11% 3 6% 5% 3 6% 6% 6% 9% 38%	2160
May	1st to 10th	Day	8% 12% 4 5% 5% 4 6% 6% 6% 8% 36%	2272
	11th to 20th	Day	11% 11% 3 5% 6% 4 5% 6% 7% 8% 34%	2478
	21st to end	Day	8% 7% 2 6% 7% 4 6% 6% 7% 9% 37%	2724
June	1st to 10th	Day	5% 4 2 5% 6% 4 6% 8% 7% 9% 45%	2520
	11th to 20th	Day	6% 6% 2 5% 5% 3 6% 5% 6% 8% 48%	2520
	21st to end	Day	5% 4 2 5% 6% 4 6% 6% 8% 10% 45%	2520
July	1st to 10th	Day	7% 5% 2 6% 6% 5% 6% 7% 8% 8% 40%	2520
	11th to 20th	Day	6% 4 3 5% 7% 4 6% 6% 8% 8% 43%	2520
	21st to end	Day	8% 5% 3 7% 7% 5% 7% 8% 7% 8% 35%	2658
August	1st to 10th	Day	9% 6% 3 7% 7% 4 6% 6% 7% 9% 35%	2328
	11th to 20th	Day	7% 5% 2 6% 5% 4 6% 5% 6% 8% 45%	2153
	21st to end	Day	6% 5% 3 7% 6% 4 6% 7% 7% 8% 42%	2376
September	1st to 10th	Day	6% 5% 2 5% 6% 3 4 5% 5% 7% 53%	2160
	11th to 20th	Day	7% 4 2 5% 5% 3 4 5% 4 7% 54%	2160
	21st to end	Day	6% 6% 2 4 4 2 3 4 5% 6% 59%	1960
October	1st to 10th	Day	5% 6% 2 6% 6% 3 4 5% 5% 7% 52%	1800
	11th to 20th	Day	3 4 2 3 3 2 4 3 5% 7% 64%	1800
	21st to end	Day	3 5% 2 4 4 2 4 4 5% 8% 59%	1940
November	1st to 10th	Day	1 4 1 3 3 2 3 4 4 8% 68%	1673
	11th to 20th	Day	1 3 2 2 4 2 3 4 5% 9% 66%	1710
	21st to end	Day	3 3 8% 4 2 4 3 5% 8% 60%	1573
December	1st to 10th	Day	4 2 6% 5% 3 4 4 4 9% 59%	1520
	11th to 20th	Day	1 4 3 4 4 2 4 4 6% 10% 57%	1926
	21st to end	Day	4 3 7% 5% 3 5% 5% 6% 8% 55%	2794
January	1st to 10th	Night	2 2 4 4 2 4 4 5% 9% 64%	2647
	11th to 20th	Night	2 2 3 4 3 3 4 4 8% 67%	2519
	21st to end	Night	1 3 3 4 4 3 4 3 5% 8% 62%	2574
February	1st to 10th	Night	2 2 5% 4 2 3 4 5% 8% 65%	2340
	11th to 20th	Night	3 2 4 4 3 3 3 6% 8% 63%	2150
	21st to end	Night	4 3 6% 5% 2 5% 4 5% 7% 60%	1776
March	1st to 10th	Night	1 4 2 3 3 2 4 4 5% 10% 61%	2150
	11th to 20th	Night	2 6% 2 5% 4 2 4 4 5% 7% 59%	1980
	21st to end	Night	2 6% 3 6% 3 2 4 3 5% 8% 58%	2066
April	1st to 10th	Night	1 6% 1 4 4 2 4 5% 4 7% 62%	1800
	11th to 20th	Night	3 7% 3 5% 4 2 4 4 6% 7% 53%	1777
	21st to end	Night	5% 10% 3 4 5% 2 3 4 5% 10% 50%	1800
May	1st to 10th	Night	7% 7% 3 4 4 3 4 5% 5% 9% 48%	1681
	11th to 20th	Night	8% 10% 3 4 3 2 4 6% 6% 8% 46%	1417
	21st to end	Night	4 5% 3 4 4 2 4 4 5% 8% 57%	1552
June	1st to 10th	Night	4 3 1 3 3 2 4 4 6% 10% 62%	1440
	11th to 20th	Night	4 3 1 3 2 2 4 5% 5% 8% 61%	1440
	21st to end	Night	3 2 1 3 3 2 4 5% 7% 9% 61%	1440
July	1st to 10th	Night	4 4 2 4 4 3 5% 5% 7% 9% 53%	1440
	11th to 20th	Night	2 2 1 3 4 3 6% 5% 7% 11% 57%	1440
	21st to end	Night	4 4 2 4 4 4 6% 6% 8% 11% 47%	1656
August	1st to 10th	Night	5% 4 1 5% 4 3 4 5% 7% 8% 53%	1611
	11th to 20th	Night	5% 3 1 3 4 3 5% 5% 6% 8% 56%	1746
	21st to end	Night	3 3 2 4 4 3 4 7% 6% 8% 54%	1980
September	1st to 10th	Night	6% 3 1 3 4 3 4 4 5% 7% 60%	1800
	11th to 20th	Night	5% 3 2 2 3 2 3 4 5% 7% 63%	1800
	21st to end	Night	5% 5% 2 3 3 2 3 3 4 6% 63%	1996
October	1st to 10th	Night	3 5% 2 3 4 2 4 4 5% 8% 61%	2160
	11th to 20th	Night	2 2 1 4 2 2 2 3 3 5% 74%	2160
	21st to end	Night	2 7% 2 6% 3 2 3 4 4 8% 59%	2396
November	1st to 10th	Night	1 3 1 2 2 2 3 4 4 7% 71%	2405
	11th to 20th	Night	4 1 3 4 2 3 3 5% 8% 66%	2470
	21st to end	Night	1 4 2 5% 4 2 3 4 5% 7% 62%	2603
December	1st to 10th	Night	3 2 5% 3 1 3 4 5% 8% 65%	2660
	11th to 20th	Night	1 3 2 5% 5% 3 4 4 6% 10% 57%	3271
	21st to end	Night	1 4 3 5% 5% 3 4 5% 6% 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	20% 7% 22% 26% 20% 5%	1519
	11th to 20th	Day	27% 8% 18% 24% 19% 5%	1546
	21st to end	Day	29% 7% 17% 26% 15% 6%	1782
February	1st to 10th	Day	26% 8% 19% 25% 15% 6%	1620
	11th to 20th	Day	24% 10% 13% 26% 22% 5%	1706
	21st to end	Day	29% 7% 13% 23% 21% 7%	1480
March	1st to 10th	Day	30% 7% 12% 27% 21% 2	1807
	11th to 20th	Day	34% 6% 14% 26% 17% 4	1980
	21st to end	Day	36% 10% 12% 24% 14% 3	2290
April	1st to 10th	Day	32% 8% 14% 22% 17% 7%	2160
	11th to 20th	Day	41% 8% 13% 18% 16% 3	2134
	21st to end	Day	41% 9% 11% 25% 13% 1	2160
May	1st to 10th	Day	45% 9% 10% 20% 14% 1	2272
	11th to 20th	Day	47% 10% 13% 21% 9% 1	2482
	21st to end	Day	41% 9% 12% 19% 14% 4	2724
June	1st to 10th	Day	32% 11% 14% 20% 17% 6%	2520
	11th to 20th	Day	32% 8% 11% 17% 22% 11%	2520
	21st to end	Day	30% 10% 12% 20% 20% 9%	2520
July	1st to 10th	Day	37% 10% 11% 16% 17% 7%	2451
	11th to 20th	Day	35% 10% 13% 20% 14% 7%	2445
	21st to end	Day	42% 13% 16% 15% 10% 3	2510
August	1st to 10th	Day	44% 11% 14% 15% 12% 4	2313
	11th to 20th	Day	36% 9% 11% 18% 19% 7%	2153
	21st to end	Day	37% 10% 10% 18% 19% 5%	2376
September	1st to 10th	Day	30% 8% 9% 16% 24% 13%	2160
	11th to 20th	Day	29% 7% 12% 19% 25% 9%	2160
	21st to end	Day	25% 6% 8% 24% 30% 7%	1960
October	1st to 10th	Day	32% 6% 10% 19% 26% 7%	1800
	11th to 20th	Day	20% 6% 10% 27% 29% 8%	1800
	21st to end	Day	24% 7% 11% 27% 23% 8%	1940
November	1st to 10th	Day	16% 6% 15% 23% 32% 8%	1673
	11th to 20th	Day	18% 5% 14% 31% 24% 7%	1710
	21st to end	Day	23% 6% 12% 28% 21% 11%	1573
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	19% 7% 17% 31% 21% 5%	2647
	11th to 20th	Night	16% 8% 20% 27% 22% 7%	2519
	21st to end	Night	21% 5% 16% 31% 20% 6%	2574
February	1st to 10th	Night	19% 8% 18% 31% 20% 5%	2340
	11th to 20th	Night	20% 6% 16% 29% 24% 5%	2150
	21st to end	Night	22% 7% 13% 27% 22% 9%	1776
March	1st to 10th	Night	19% 6% 14% 31% 26% 4	2150
	11th to 20th	Night	24% 6% 13% 31% 20% 6%	1980
	21st to end	Night	25% 8% 15% 30% 19% 3	2066
April	1st to 10th	Night	21% 9% 15% 29% 21% 6%	1800
	11th to 20th	Night	29% 8% 14% 27% 19% 4	1777
	21st to end	Night	30% 7% 14% 29% 19% 1	1800
May	1st to 10th	Night	33% 8% 15% 26% 15% 2	1681
	11th to 20th	Night	34% 10% 19% 25% 12% 1	1418
	21st to end	Night	26% 9% 16% 25% 20% 4	1552
June	1st to 10th	Night	19% 8% 21% 28% 17% 6%	1440
	11th to 20th	Night	19% 8% 12% 21% 25% 15%	1440
	21st to end	Night	18% 8% 12% 25% 25% 12%	1440
July	1st to 10th	Night	27% 9% 14% 23% 19% 8%	1400
	11th to 20th	Night	20% 9% 16% 27% 21% 8%	1392
	21st to end	Night	26% 12% 24% 24% 11% 3	1564
August	1st to 10th	Night	28% 11% 21% 22% 14% 5%	1602
	11th to 20th	Night	24% 8% 16% 21% 24% 8%	1746
	21st to end	Night	25% 10% 13% 25% 22% 5%	1980
September	1st to 10th	Night	24% 7% 12% 21% 26% 11%	1800
	11th to 20th	Night	20% 7% 12% 24% 24% 13%	1800
	21st to end	Night	21% 6% 10% 29% 27% 7%	1996
October	1st to 10th	Night	22% 7% 12% 25% 26% 9%	2160
	11th to 20th	Night	13% 4 13% 28% 30% 11%	2160
	21st to end	Night	24% 5% 13% 27% 24% 7%	2396
November	1st to 10th	Night	13% 6% 15% 25% 31% 9%	2405
	11th to 20th	Night	16% 5% 14% 31% 25% 8%	2470
	21st to end	Night	21% 6% 12% 27% 25% 9%	2603
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	16% 51% 19% 12% 1 1	252
	21st to end	Day	13% 55% 23% 8% 1	264
February	1st to 10th	Day	18% 60% 18% 3 1	240
	11th to 20th	Day	22% 48% 23% 6% 2	240
	21st to end	Day	22% 53% 17% 8% 1	198
March	1st to 10th	Day	19% 45% 23% 11% 1	247
	11th to 20th	Day	18% 37% 31% 12% 2	420
	21st to end	Day	19% 45% 27% 7% 2	462
April	1st to 10th	Day	22% 37% 30% 8% 2	420
	11th to 20th	Day	26% 37% 27% 7% 2	412
	21st to end	Day	20% 35% 30% 11% 2	420
May	1st to 10th	Day	21% 28% 33% 13% 5% 1	503
	11th to 20th	Day	19% 18% 34% 20% 7% 2	625
	21st to end	Day	15% 19% 28% 26% 9% 2	679
June	1st to 10th	Day	9% 17% 30% 27% 13% 4	630
	11th to 20th	Day	10% 21% 32% 26% 8% 3	630
	21st to end	Day	7% 17% 34% 24% 14% 5%	630
July	1st to 10th	Day	7% 7% 29% 33% 19% 4	621
	11th to 20th	Day	7% 9% 30% 30% 18% 6%	618
	21st to end	Day	9% 9% 25% 34% 19% 5%	600
August	1st to 10th	Day	13% 12% 30% 32% 10% 3	447
	11th to 20th	Day	9% 13% 30% 32% 12% 3	437
	21st to end	Day	8% 12% 32% 31% 14% 3	495
September	1st to 10th	Day	10% 16% 32% 25% 14% 3	450
	11th to 20th	Day	8% 18% 39% 25% 9% 1	450
	21st to end	Day	12% 19% 34% 20% 11% 3	272
October	1st to 10th	Day	8% 26% 29% 24% 11% 3	270
	11th to 20th	Day	13% 39% 28% 12% 6% 2	270
	21st to end	Day	15% 39% 28% 12% 5%	297
November	1st to 10th	Day	14% 46% 23% 10% 7%	270
	11th to 20th	Day	14% 46% 30% 5% 4 1	270
	21st to end	Day	15% 39% 35% 9% 1	270
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	16% 43% 22% 12% 5% 1	863
	21st to end	Night	12% 45% 28% 11% 3 1	792
February	1st to 10th	Night	12% 50% 25% 10% 3	720
	11th to 20th	Night	11% 44% 28% 13% 3	704
	21st to end	Night	10% 47% 28% 13% 2	592
March	1st to 10th	Night	10% 39% 30% 15% 5%	720
	11th to 20th	Night	9% 33% 31% 21% 5% 1	720
	21st to end	Night	12% 37% 30% 18% 3 1	680
April	1st to 10th	Night	11% 33% 36% 18% 3	540
	11th to 20th	Night	10% 33% 30% 19% 7% 1	533
	21st to end	Night	14% 26% 33% 19% 6% 1	540
May	1st to 10th	Night	11% 18% 39% 22% 9% 1	540
	11th to 20th	Night	17% 10% 28% 33% 11% 2	531
	21st to end	Night	9% 14% 31% 30% 15% 2	584
June	1st to 10th	Night	5% 7% 30% 34% 20% 3	540
	11th to 20th	Night	6% 13% 34% 33% 13% 1	540
	21st to end	Night	5% 7% 21% 40% 25% 2	540
July	1st to 10th	Night	7% 3 16% 39% 32% 4	525
	11th to 20th	Night	2 3 19% 36% 34% 5%	522
	21st to end	Night	7% 3 11% 37% 37% 6%	591
August	1st to 10th	Night	7% 5% 16% 39% 31% 3	537
	11th to 20th	Night	7% 3 16% 44% 25% 5%	534
	21st to end	Night	5% 5% 16% 40% 28% 6%	594
September	1st to 10th	Night	6% 4 25% 37% 22% 6%	540
	11th to 20th	Night	8% 8% 30% 32% 18% 4	540
	21st to end	Night	9% 13% 30% 29% 16% 4	559
October	1st to 10th	Night	7% 24% 27% 28% 11% 3	720
	11th to 20th	Night	8% 34% 27% 21% 7% 2	720
	21st to end	Night	12% 33% 30% 17% 7% 2	812
November	1st to 10th	Night	7% 42% 28% 16% 6% 1	925
	11th to 20th	Night	12% 43% 30% 10% 4 1	950
	21st to end	Night	8% 39% 32% 18% 3	950
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 2024-01-11 20:33:52. Version ac07

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