TWASC Eggshatch Observatorium
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the TWASC Eggshatch Observatorium clear sky chart from 2005-11-06 to 2024-01-14.

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	13% 9% 4 7% 6% 3 5% 5% 5% 7% 36%	74804
	Night	13% 9% 4 7% 5% 3 4 4 5% 7% 38%	74978
Transparency	Day	46% 7% 13% 22% 12% 1	74505
	Night	45% 6% 12% 22% 13% 2	74798
Seeing	Day	16% 12% 30% 25% 13% 4	14730
	Night	17% 10% 32% 29% 11% 1	24726

By Month

Percentage Cloud Cover SE (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	11% 12% 6% 8% 7% 4 5% 5% 5% 6% 30%	1517
	11th to 20th	Day	13% 15% 7% 15% 7% 3 5% 3 5% 6% 21%	1464
	21st to end	Day	12% 13% 8% 12% 7% 4 5% 4 5% 7% 23%	1598
February	1st to 10th	Day	11% 13% 8% 8% 6% 4 6% 5% 4 7% 30%	1620
	11th to 20th	Day	13% 12% 4 7% 6% 4 5% 4 5% 5% 36%	1730
	21st to end	Day	12% 14% 6% 9% 6% 4 6% 5% 5% 6% 28%	1480
March	1st to 10th	Day	14% 11% 5% 7% 5% 4 6% 5% 5% 6% 33%	1800
	11th to 20th	Day	12% 9% 4 8% 6% 3 5% 4 6% 6% 38%	1858
	21st to end	Day	18% 12% 5% 7% 7% 3 4 4 4 7% 30%	2376
April	1st to 10th	Day	18% 11% 6% 6% 6% 3 4 5% 5% 7% 29%	2160
	11th to 20th	Day	17% 12% 4 5% 6% 3 4 4 5% 6% 34%	2134
	21st to end	Day	18% 10% 3 6% 5% 4 5% 5% 5% 7% 32%	2275
May	1st to 10th	Day	16% 9% 3 6% 6% 4 5% 5% 6% 8% 32%	2362
	11th to 20th	Day	17% 7% 3 6% 6% 3 4 5% 5% 7% 37%	2479
	21st to end	Day	13% 7% 2 6% 5% 4 5% 5% 6% 8% 39%	2725
June	1st to 10th	Day	10% 5% 2 6% 6% 3 4 5% 6% 8% 45%	2520
	11th to 20th	Day	12% 5% 3 5% 5% 3 6% 4 5% 8% 43%	2520
	21st to end	Day	10% 6% 2 6% 4 3 5% 6% 6% 10% 42%	2520
July	1st to 10th	Day	7% 4 2 4 4 3 5% 6% 7% 9% 47%	2520
	11th to 20th	Day	8% 5% 2 5% 5% 4 5% 5% 7% 9% 45%	2520
	21st to end	Day	7% 4 2 4 5% 3 6% 5% 6% 11% 47%	2743
August	1st to 10th	Day	8% 4 2 5% 5% 4 7% 7% 7% 9% 43%	2507
	11th to 20th	Day	11% 6% 2 5% 5% 4 5% 6% 6% 8% 42%	2177
	21st to end	Day	12% 5% 3 5% 4 3 5% 5% 6% 7% 44%	2376
September	1st to 10th	Day	12% 6% 2 6% 6% 3 5% 5% 6% 7% 43%	2160
	11th to 20th	Day	13% 5% 2 5% 4 3 4 4 5% 8% 48%	2062
	21st to end	Day	12% 8% 3 6% 5% 3 4 5% 5% 7% 42%	1980
October	1st to 10th	Day	14% 7% 3 7% 4 3 3 4 5% 8% 43%	1900
	11th to 20th	Day	20% 11% 3 7% 6% 3 5% 4 5% 7% 31%	1778
	21st to end	Day	17% 10% 4 6% 6% 3 4 5% 5% 5% 35%	1782
November	1st to 10th	Day	11% 10% 4 6% 5% 2 4 4 5% 6% 43%	1672
	11th to 20th	Day	11% 12% 4 9% 8% 4 5% 5% 5% 7% 31%	1710
	21st to end	Day	17% 10% 4 8% 6% 3 3 3 4 6% 35%	1558
December	1st to 10th	Day	13% 13% 5% 9% 8% 4 5% 4 5% 7% 28%	1520
	11th to 20th	Day	12% 14% 4 9% 7% 4 5% 5% 5% 7% 27%	1918
	21st to end	Day	18% 19% 9% 12% 6% 3 4 4 4 5% 15%	2783
January	1st to 10th	Night	12% 13% 6% 8% 7% 4 4 4 4 4 34%	2648
	11th to 20th	Night	14% 13% 7% 10% 6% 4 5% 5% 5% 6% 25%	2569
	21st to end	Night	12% 12% 6% 11% 8% 4 6% 4 6% 6% 26%	2757
February	1st to 10th	Night	11% 14% 6% 9% 6% 4 4 4 5% 5% 33%	2340
	11th to 20th	Night	12% 9% 4 8% 6% 4 5% 5% 4 5% 38%	2115
	21st to end	Night	16% 11% 5% 7% 6% 3 3 4 5% 5% 34%	1776
March	1st to 10th	Night	16% 9% 3 6% 5% 3 5% 5% 5% 7% 35%	2160
	11th to 20th	Night	12% 8% 3 6% 5% 3 4 5% 6% 8% 41%	2116
	21st to end	Night	18% 9% 4 7% 6% 3 5% 4 5% 6% 33%	1980
April	1st to 10th	Night	17% 11% 4 7% 4 3 4 5% 6% 6% 35%	1800
	11th to 20th	Night	21% 8% 3 6% 5% 3 4 4 3 5% 38%	1775
	21st to end	Night	18% 8% 3 5% 5% 3 4 5% 5% 7% 37%	1684
May	1st to 10th	Night	15% 9% 3 7% 5% 3 5% 5% 6% 9% 33%	1594
	11th to 20th	Night	15% 7% 3 6% 5% 3 5% 5% 5% 7% 39%	1416
	21st to end	Night	10% 7% 3 5% 4 4 5% 5% 6% 10% 41%	1551
June	1st to 10th	Night	10% 4 2 5% 4 3 4 5% 6% 8% 48%	1440
	11th to 20th	Night	11% 4 2 6% 4 3 4 5% 7% 9% 46%	1440
	21st to end	Night	9% 5% 2 5% 4 3 4 4 6% 7% 49%	1440
July	1st to 10th	Night	7% 3 1 4 4 2 4 5% 6% 10% 54%	1440
	11th to 20th	Night	6% 3 2 4 4 3 4 6% 6% 8% 54%	1440
	21st to end	Night	6% 3 2 3 4 3 5% 5% 7% 9% 52%	1575
August	1st to 10th	Night	6% 3 2 5% 5% 3 4 5% 8% 9% 49%	1432
	11th to 20th	Night	9% 4 2 4 4 3 3 5% 5% 8% 53%	1720
	21st to end	Night	9% 5% 2 4 5% 3 4 4 4 8% 52%	1980
September	1st to 10th	Night	10% 6% 1 5% 4 3 3 4 4 8% 54%	1800
	11th to 20th	Night	12% 4 2 4 5% 2 4 4 4 7% 53%	1878
	21st to end	Night	12% 7% 3 5% 5% 3 3 4 4 7% 48%	1980
October	1st to 10th	Night	12% 7% 3 6% 5% 3 3 4 4 6% 47%	2059
	11th to 20th	Night	17% 9% 4 5% 5% 3 4 3 4 6% 40%	2181
	21st to end	Night	19% 10% 3 5% 5% 3 4 4 5% 7% 34%	2574
November	1st to 10th	Night	12% 8% 3 5% 4 3 4 4 4 7% 46%	2406
	11th to 20th	Night	14% 10% 5% 8% 5% 4 5% 5% 4 7% 33%	2470
	21st to end	Night	16% 8% 4 6% 6% 3 4 5% 4 6% 37%	2619
December	1st to 10th	Night	14% 12% 5% 8% 7% 3 5% 4 5% 7% 31%	2660
	11th to 20th	Night	14% 13% 6% 9% 7% 4 5% 4 4 5% 29%	3279
	21st to end	Night	20% 17% 6% 10% 6% 4 4 4 4 5% 20%	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	53% 6% 13% 18% 10% 1	1518
	11th to 20th	Day	64% 5% 9% 14% 7%	1464
	21st to end	Day	62% 5% 12% 13% 8% 1	1598
February	1st to 10th	Day	54% 5% 13% 19% 8% 1	1620
	11th to 20th	Day	49% 5% 11% 22% 11% 2	1740
	21st to end	Day	57% 5% 10% 16% 10% 2	1480
March	1st to 10th	Day	52% 7% 11% 21% 8% 2	1800
	11th to 20th	Day	45% 7% 12% 21% 14% 2	1858
	21st to end	Day	56% 5% 12% 19% 7% 1	2376
April	1st to 10th	Day	54% 7% 11% 19% 10%	2160
	11th to 20th	Day	50% 6% 10% 19% 12% 3	2134
	21st to end	Day	50% 8% 12% 18% 11% 1	2275
May	1st to 10th	Day	48% 8% 13% 22% 8% 1	2362
	11th to 20th	Day	46% 7% 12% 22% 12% 1	2483
	21st to end	Day	42% 8% 12% 22% 14% 2	2725
June	1st to 10th	Day	35% 7% 14% 26% 15% 2	2520
	11th to 20th	Day	37% 7% 13% 24% 17% 1	2520
	21st to end	Day	37% 8% 16% 23% 15% 1	2520
July	1st to 10th	Day	31% 8% 14% 31% 14% 3	2451
	11th to 20th	Day	33% 9% 15% 26% 16% 2	2445
	21st to end	Day	30% 9% 16% 26% 16% 3	2591
August	1st to 10th	Day	34% 10% 17% 26% 12% 2	2492
	11th to 20th	Day	38% 8% 15% 26% 13% 1	2177
	21st to end	Day	36% 7% 13% 24% 18% 2	2376
September	1st to 10th	Day	38% 9% 11% 25% 16% 1	2160
	11th to 20th	Day	35% 6% 13% 30% 15% 1	2062
	21st to end	Day	41% 6% 12% 28% 12%	1980
October	1st to 10th	Day	40% 7% 9% 28% 15% 1	1900
	11th to 20th	Day	52% 6% 11% 20% 10% 1	1778
	21st to end	Day	49% 6% 12% 20% 11% 1	1782
November	1st to 10th	Day	42% 5% 15% 23% 14% 2	1672
	11th to 20th	Day	51% 6% 14% 20% 8% 1	1710
	21st to end	Day	50% 4 14% 23% 7%	1558
December	1st to 10th	Day	56% 6% 14% 16% 7% 1	1520
	11th to 20th	Day	55% 5% 16% 16% 7% 2	1915
	21st to end	Day	71% 6% 9% 8% 5%	2783
January	1st to 10th	Night	53% 6% 9% 20% 12% 1	2648
	11th to 20th	Night	59% 6% 12% 14% 8%	2569
	21st to end	Night	57% 6% 12% 15% 10% 1	2757
February	1st to 10th	Night	54% 4 10% 18% 12% 2	2340
	11th to 20th	Night	48% 5% 11% 20% 15% 2	2116
	21st to end	Night	51% 5% 12% 18% 12% 2	1776
March	1st to 10th	Night	48% 6% 14% 19% 11% 2	2160
	11th to 20th	Night	39% 6% 14% 22% 16% 3	2116
	21st to end	Night	51% 6% 9% 22% 10% 2	1980
April	1st to 10th	Night	48% 7% 10% 19% 15% 1	1800
	11th to 20th	Night	49% 4 8% 18% 17% 3	1775
	21st to end	Night	44% 7% 13% 20% 14% 2	1684
May	1st to 10th	Night	46% 8% 12% 22% 11% 1	1594
	11th to 20th	Night	43% 7% 12% 23% 13% 2	1417
	21st to end	Night	38% 8% 13% 24% 14% 3	1552
June	1st to 10th	Night	32% 8% 14% 28% 17% 1	1440
	11th to 20th	Night	35% 7% 10% 26% 20% 2	1440
	21st to end	Night	33% 6% 17% 24% 18% 2	1440
July	1st to 10th	Night	26% 7% 15% 31% 19% 4	1400
	11th to 20th	Night	26% 7% 15% 29% 19% 3	1392
	21st to end	Night	25% 9% 17% 27% 18% 5%	1487
August	1st to 10th	Night	29% 8% 17% 28% 16% 3	1423
	11th to 20th	Night	29% 7% 17% 31% 16% 1	1720
	21st to end	Night	30% 6% 12% 29% 20% 3	1980
September	1st to 10th	Night	30% 8% 11% 25% 24% 2	1800
	11th to 20th	Night	32% 6% 10% 34% 17% 1	1878
	21st to end	Night	37% 5% 11% 30% 16% 1	1980
October	1st to 10th	Night	38% 6% 9% 29% 17% 1	2059
	11th to 20th	Night	45% 5% 13% 21% 15% 1	2181
	21st to end	Night	49% 5% 13% 22% 11% 1	2574
November	1st to 10th	Night	39% 5% 11% 25% 17% 2	2406
	11th to 20th	Night	49% 7% 14% 19% 10% 1	2470
	21st to end	Night	47% 7% 14% 22% 9% 1	2619
December	1st to 10th	Night	53% 6% 13% 19% 9% 1	2660
	11th to 20th	Night	57% 6% 11% 16% 9% 1	3281
	21st to end	Night	66% 6% 10% 13% 5%	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	16% 17% 37% 23% 6% 1	270
	11th to 20th	Day	18% 17% 33% 24% 6% 1	249
	21st to end	Day	23% 12% 40% 19% 6%	264
February	1st to 10th	Day	14% 20% 46% 15% 4	240
	11th to 20th	Day	20% 27% 33% 15% 5%	240
	21st to end	Day	21% 24% 42% 13% 1	198
March	1st to 10th	Day	18% 23% 43% 13% 3	240
	11th to 20th	Day	22% 19% 29% 21% 7% 2	250
	21st to end	Day	27% 13% 29% 22% 7% 1	462
April	1st to 10th	Day	26% 13% 35% 21% 5%	420
	11th to 20th	Day	21% 21% 26% 20% 9% 2	412
	21st to end	Day	23% 11% 29% 23% 13% 1	420
May	1st to 10th	Day	23% 13% 32% 21% 8% 2	445
	11th to 20th	Day	20% 12% 32% 23% 10% 3	625
	21st to end	Day	16% 11% 28% 27% 13% 6%	679
June	1st to 10th	Day	8% 9% 35% 30% 15% 5%	630
	11th to 20th	Day	13% 10% 28% 31% 13% 5%	630
	21st to end	Day	10% 9% 30% 31% 16% 3	630
July	1st to 10th	Day	8% 4 21% 32% 26% 10%	621
	11th to 20th	Day	8% 6% 29% 32% 19% 6%	618
	21st to end	Day	6% 3 30% 35% 20% 7%	684
August	1st to 10th	Day	8% 3 24% 37% 19% 10%	626
	11th to 20th	Day	12% 4 18% 28% 25% 13%	448
	21st to end	Day	12% 7% 21% 30% 19% 10%	495
September	1st to 10th	Day	13% 8% 25% 26% 20% 8%	450
	11th to 20th	Day	12% 5% 21% 30% 22% 10%	450
	21st to end	Day	16% 13% 26% 23% 18% 5%	450
October	1st to 10th	Day	20% 9% 26% 28% 12% 5%	370
	11th to 20th	Day	22% 22% 31% 16% 9%	270
	21st to end	Day	24% 17% 38% 16% 4 1	297
November	1st to 10th	Day	18% 17% 34% 21% 9% 1	270
	11th to 20th	Day	15% 21% 37% 19% 8%	270
	21st to end	Day	23% 14% 39% 20% 5%	270
December	1st to 10th	Day	19% 21% 40% 13% 6% 1	270
	11th to 20th	Day	19% 19% 39% 15% 7% 1	270
	21st to end	Day	25% 22% 34% 16% 3	297
January	1st to 10th	Night	17% 17% 36% 23% 6%	950
	11th to 20th	Night	21% 13% 39% 20% 7% 1	918
	21st to end	Night	18% 12% 40% 24% 5% 1	990
February	1st to 10th	Night	19% 14% 38% 24% 5%	900
	11th to 20th	Night	18% 16% 36% 24% 5%	720
	21st to end	Night	25% 15% 38% 18% 4	592
March	1st to 10th	Night	20% 14% 33% 24% 8% 1	720
	11th to 20th	Night	17% 13% 36% 26% 7% 1	687
	21st to end	Night	22% 7% 29% 32% 8% 2	594
April	1st to 10th	Night	22% 13% 34% 24% 7%	540
	11th to 20th	Night	24% 10% 33% 26% 7% 1	533
	21st to end	Night	20% 9% 32% 29% 9% 1	540
May	1st to 10th	Night	18% 10% 33% 32% 6% 1	540
	11th to 20th	Night	19% 7% 31% 30% 13%	531
	21st to end	Night	11% 5% 26% 38% 18% 1	584
June	1st to 10th	Night	10% 4 27% 41% 17% 1	540
	11th to 20th	Night	12% 5% 31% 37% 14% 1	540
	21st to end	Night	10% 4 25% 44% 16%	540
July	1st to 10th	Night	7% 2 18% 40% 30% 3	525
	11th to 20th	Night	6% 2 25% 42% 23% 2	522
	21st to end	Night	7% 1 21% 45% 24% 1	591
August	1st to 10th	Night	6% 2 18% 45% 25% 3	537
	11th to 20th	Night	10% 3 16% 39% 27% 5%	534
	21st to end	Night	10% 2 20% 41% 24% 3	594
September	1st to 10th	Night	11% 3 22% 36% 23% 5%	540
	11th to 20th	Night	12% 4 22% 32% 25% 5%	618
	21st to end	Night	15% 8% 26% 27% 21% 3	720
October	1st to 10th	Night	16% 8% 28% 31% 16% 1	720
	11th to 20th	Night	22% 12% 32% 25% 8%	720
	21st to end	Night	23% 12% 31% 26% 8% 1	792
November	1st to 10th	Night	15% 12% 38% 24% 10% 1	740
	11th to 20th	Night	19% 17% 36% 22% 6%	760
	21st to end	Night	21% 13% 37% 23% 6%	909
December	1st to 10th	Night	22% 15% 37% 21% 5%	950
	11th to 20th	Night	21% 13% 38% 21% 6% 1	950
	21st to end	Night	28% 14% 36% 19% 3	1045

Page generated at 2024-01-11 03:22:41. Version ac07

Copyright 2024 Attilla Danko