Edwelda Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Edwelda Observatory clear sky chart from 2005-11-06 to 2025-11-03.

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	17% 7% 2 6% 4 4 4 4 5% 7% 39%	126459
	Night	17% 8% 2 6% 4 4 4 3 5% 6% 40%	123584
Transparency	Day	44% 5% 11% 22% 15% 3	129992
	Night	44% 5% 11% 22% 16% 3	128138
Seeing	Day	24% 16% 33% 19% 7% 2	16330
	Night	22% 13% 34% 24% 7% 1	25181

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% 7% 2 8% 4 4 5% 4 5% 7% 42%	3597
	11th to 20th	Day	14% 7% 3 6% 3 3 3 4 4 5% 48%	3570
	21st to end	Day	17% 8% 3 5% 3 4 3 4 5% 6% 43%	3960
February	1st to 10th	Day	19% 8% 2 5% 4 4 5% 5% 6% 6% 37%	1860
	11th to 20th	Day	14% 8% 3 6% 4 4 5% 5% 6% 6% 39%	1948
	21st to end	Day	17% 9% 3 7% 5% 5% 4 4 5% 5% 38%	1650
March	1st to 10th	Day	22% 10% 2 6% 4 4 4 3 5% 5% 35%	4476
	11th to 20th	Day	15% 9% 2 6% 4 4 4 4 6% 6% 39%	4789
	21st to end	Day	26% 9% 2 6% 3 4 4 3 6% 6% 30%	5740
April	1st to 10th	Day	19% 9% 3 6% 4 5% 4 3 5% 6% 36%	2400
	11th to 20th	Day	19% 7% 2 5% 4 5% 4 4 5% 8% 38%	2399
	21st to end	Day	20% 6% 2 7% 5% 4 5% 3 5% 7% 37%	2600
May	1st to 10th	Day	30% 10% 3 7% 4 4 4 3 5% 6% 24%	5886
	11th to 20th	Day	19% 8% 3 8% 5% 5% 5% 3 5% 7% 31%	5945
	21st to end	Day	20% 6% 2 6% 4 5% 4 4 5% 8% 36%	6949
June	1st to 10th	Day	19% 7% 2 6% 4 4 5% 5% 6% 9% 34%	2800
	11th to 20th	Day	16% 6% 2 6% 4 5% 5% 4 6% 8% 38%	2800
	21st to end	Day	17% 6% 2 7% 5% 4 5% 4 6% 9% 35%	2800
July	1st to 10th	Day	17% 7% 2 7% 4 5% 5% 4 7% 9% 33%	6360
	11th to 20th	Day	9% 6% 2 7% 5% 5% 5% 4 7% 10% 39%	6360
	21st to end	Day	15% 6% 2 6% 4 4 4 3 5% 8% 44%	6926
August	1st to 10th	Day	14% 7% 2 7% 5% 5% 5% 5% 7% 10% 33%	4273
	11th to 20th	Day	14% 7% 3 6% 4 4 5% 4 6% 8% 38%	4145
	21st to end	Day	7% 4 2 5% 4 4 5% 4 7% 9% 47%	4312
September	1st to 10th	Day	13% 6% 2 5% 4 4 4 4 5% 8% 46%	2390
	11th to 20th	Day	14% 6% 2 5% 3 3 3 3 4 6% 51%	2200
	21st to end	Day	18% 6% 2 6% 5% 3 3 3 5% 7% 44%	2200
October	1st to 10th	Day	22% 5% 2 6% 3 3 4 3 5% 5% 42%	2200
	11th to 20th	Day	15% 5% 1 5% 3 5% 4 3 5% 7% 46%	1953
	21st to end	Day	20% 6% 2 6% 3 4 4 3 5% 6% 41%	1980
November	1st to 10th	Day	15% 6% 2 5% 4 3 3 2 3 6% 50%	1779
	11th to 20th	Day	18% 6% 2 4 4 3 3 2 4 6% 48%	1800
	21st to end	Day	18% 7% 2 5% 3 4 3 4 4 5% 44%	1800
December	1st to 10th	Day	15% 8% 2 4 3 3 4 2 4 5% 49%	2666
	11th to 20th	Day	20% 6% 2 4 3 3 3 3 4 6% 47%	2986
	21st to end	Day	20% 10% 3 6% 4 4 4 3 4 5% 38%	3960
January	1st to 10th	Night	14% 6% 2 5% 3 3 4 3 4 7% 49%	6349
	11th to 20th	Night	14% 9% 3 8% 5% 4 4 3 4 6% 40%	6315
	21st to end	Night	15% 10% 3 7% 4 4 4 3 4 5% 38%	6996
February	1st to 10th	Night	17% 9% 3 5% 5% 4 4 4 5% 6% 38%	2532
	11th to 20th	Night	15% 9% 3 6% 5% 3 4 4 5% 6% 40%	2338
	21st to end	Night	17% 10% 2 6% 4 3 4 3 5% 6% 41%	1980
March	1st to 10th	Night	24% 8% 2 5% 4 3 3 3 5% 5% 37%	5364
	11th to 20th	Night	15% 10% 3 7% 5% 4 5% 3 4 6% 38%	5169
	21st to end	Night	26% 9% 2 5% 4 4 4 4 4 5% 33%	5174
April	1st to 10th	Night	20% 8% 2 7% 4 5% 4 4 6% 6% 35%	2000
	11th to 20th	Night	21% 7% 2 6% 3 4 4 3 4 6% 40%	1950
	21st to end	Night	21% 6% 2 7% 4 4 4 3 5% 5% 40%	1800
May	1st to 10th	Night	31% 10% 3 7% 4 4 4 3 4 6% 25%	4054
	11th to 20th	Night	18% 8% 3 7% 5% 5% 5% 5% 7% 8% 28%	3991
	21st to end	Night	20% 9% 3 7% 5% 4 5% 4 5% 6% 33%	3926
June	1st to 10th	Night	17% 9% 3 7% 4 4 4 4 5% 5% 38%	1600
	11th to 20th	Night	18% 8% 2 6% 4 4 4 3 6% 8% 37%	1600
	21st to end	Night	15% 6% 3 5% 5% 4 4 4 7% 8% 39%	1600
July	1st to 10th	Night	13% 7% 2 7% 5% 5% 5% 4 6% 10% 37%	3600
	11th to 20th	Night	11% 7% 2 7% 5% 4 5% 5% 5% 9% 39%	3600
	21st to end	Night	12% 7% 2 6% 4 4 4 3 5% 7% 46%	3926
August	1st to 10th	Night	19% 6% 3 7% 5% 5% 4 4 6% 7% 33%	2845
	11th to 20th	Night	10% 7% 3 8% 6% 6% 6% 5% 7% 7% 37%	2898
	21st to end	Night	9% 3 2 4 3 4 4 4 5% 8% 54%	3586
September	1st to 10th	Night	13% 5% 2 6% 4 3 4 3 5% 7% 47%	2010
	11th to 20th	Night	14% 5% 2 5% 3 3 3 2 4 5% 54%	2200
	21st to end	Night	17% 6% 3 6% 4 3 3 4 5% 6% 43%	2200
October	1st to 10th	Night	20% 5% 3 5% 4 4 3 3 4 6% 43%	2200
	11th to 20th	Night	15% 5% 2 5% 3 3 4 4 4 7% 47%	2444
	21st to end	Night	21% 7% 3 5% 4 4 3 3 4 6% 40%	2860
November	1st to 10th	Night	14% 5% 2 6% 4 4 3 3 5% 5% 49%	2564
	11th to 20th	Night	18% 6% 2 5% 3 3 4 3 4 5% 47%	2600
	21st to end	Night	16% 8% 2 5% 4 4 4 3 5% 7% 44%	2600
December	1st to 10th	Night	18% 8% 2 5% 4 4 4 3 4 5% 43%	4509
	11th to 20th	Night	22% 7% 2 6% 3 3 3 3 4 4 42%	5208
	21st to end	Night	17% 10% 3 7% 4 4 3 3 4 5% 40%	6996

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% 4 7% 28% 18% 2	3598
	11th to 20th	Day	39% 5% 10% 23% 21% 3	3600
	21st to end	Day	42% 4 9% 22% 19% 3	3960
February	1st to 10th	Day	47% 4 12% 20% 15% 2	1860
	11th to 20th	Day	44% 6% 11% 21% 15% 3	1957
	21st to end	Day	48% 4 10% 20% 15% 3	1650
March	1st to 10th	Day	50% 4 10% 16% 11% 10%	4479
	11th to 20th	Day	44% 6% 12% 25% 11% 2	4789
	21st to end	Day	55% 3 7% 15% 14% 7%	5740
April	1st to 10th	Day	50% 4 9% 18% 17% 4	2400
	11th to 20th	Day	45% 5% 10% 20% 17% 3	2399
	21st to end	Day	47% 5% 8% 19% 18% 4	2600
May	1st to 10th	Day	60% 6% 11% 14% 8% 1	5897
	11th to 20th	Day	51% 7% 13% 17% 10% 2	5949
	21st to end	Day	46% 6% 11% 22% 14% 1	6949
June	1st to 10th	Day	46% 6% 12% 23% 12% 1	2800
	11th to 20th	Day	43% 7% 12% 19% 17% 2	2800
	21st to end	Day	45% 7% 12% 21% 15% 1	2800
July	1st to 10th	Day	47% 6% 11% 21% 14% 1	6290
	11th to 20th	Day	39% 6% 16% 25% 13% 1	6285
	21st to end	Day	40% 4 11% 28% 15% 1	6728
August	1st to 10th	Day	45% 8% 15% 22% 9% 1	4259
	11th to 20th	Day	43% 7% 13% 27% 10% 1	4184
	21st to end	Day	32% 6% 11% 30% 19% 1	4312
September	1st to 10th	Day	37% 6% 10% 24% 21% 2	2390
	11th to 20th	Day	35% 4 8% 27% 23% 3	2200
	21st to end	Day	41% 4 8% 23% 22% 3	2200
October	1st to 10th	Day	41% 5% 8% 24% 19% 3	3590
	11th to 20th	Day	32% 4 7% 29% 25% 3	3156
	21st to end	Day	34% 3 10% 30% 20% 3	3180
November	1st to 10th	Day	38% 3 12% 26% 18% 2	1779
	11th to 20th	Day	40% 3 9% 22% 23% 3	1800
	21st to end	Day	42% 5% 13% 24% 14% 2	1800
December	1st to 10th	Day	39% 3 15% 29% 13% 1	2666
	11th to 20th	Day	41% 3 13% 18% 20% 5%	2986
	21st to end	Day	50% 4 7% 21% 15% 4	3960
January	1st to 10th	Night	36% 3 10% 33% 16% 2	6349
	11th to 20th	Night	46% 4 11% 21% 14% 4	6360
	21st to end	Night	49% 4 9% 16% 18% 5%	6996
February	1st to 10th	Night	47% 4 12% 21% 14% 3	2532
	11th to 20th	Night	45% 4 9% 21% 16% 4	2340
	21st to end	Night	45% 4 7% 24% 16% 4	1980
March	1st to 10th	Night	49% 4 8% 16% 16% 7%	5374
	11th to 20th	Night	48% 5% 15% 18% 13% 2	5170
	21st to end	Night	55% 3 4 12% 21% 6%	5174
April	1st to 10th	Night	49% 4 10% 18% 16% 3	2000
	11th to 20th	Night	46% 5% 8% 19% 18% 3	1950
	21st to end	Night	47% 4 10% 18% 18% 4	1800
May	1st to 10th	Night	60% 6% 13% 12% 8% 2	4060
	11th to 20th	Night	51% 8% 14% 16% 9% 2	3992
	21st to end	Night	51% 7% 12% 19% 11% 1	3927
June	1st to 10th	Night	47% 7% 12% 22% 13% 1	1600
	11th to 20th	Night	44% 6% 13% 21% 14% 2	1600
	21st to end	Night	41% 7% 13% 23% 14% 1	1600
July	1st to 10th	Night	43% 5% 12% 22% 16%	3560
	11th to 20th	Night	41% 6% 18% 21% 14% 1	3552
	21st to end	Night	39% 5% 10% 30% 15% 1	3809
August	1st to 10th	Night	50% 6% 12% 19% 11% 1	2835
	11th to 20th	Night	43% 8% 13% 24% 10%	2925
	21st to end	Night	28% 6% 14% 29% 23% 1	3586
September	1st to 10th	Night	37% 5% 11% 26% 20% 1	2010
	11th to 20th	Night	34% 4 9% 23% 27% 2	2200
	21st to end	Night	42% 5% 7% 23% 20% 2	2200
October	1st to 10th	Night	40% 4 14% 24% 16% 3	3590
	11th to 20th	Night	28% 3 10% 28% 28% 3	3980
	21st to end	Night	35% 3 10% 31% 18% 2	4610
November	1st to 10th	Night	38% 5% 11% 23% 20% 4	2564
	11th to 20th	Night	41% 3 9% 22% 21% 4	2600
	21st to end	Night	41% 4 13% 25% 14% 2	2600
December	1st to 10th	Night	44% 4 11% 28% 13% 1	4509
	11th to 20th	Night	46% 4 13% 14% 21% 1	5208
	21st to end	Night	47% 4 7% 23% 17% 3	6996

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	28% 24% 30% 14% 5%	200
	11th to 20th	Day	33% 19% 35% 11% 3 1	200
	21st to end	Day	25% 22% 36% 12% 4	220
February	1st to 10th	Day	32% 17% 34% 15% 2	405
	11th to 20th	Day	27% 22% 36% 13% 2	496
	21st to end	Day	28% 17% 35% 15% 4	414
March	1st to 10th	Day	29% 20% 33% 15% 3	500
	11th to 20th	Day	28% 22% 33% 13% 4 1	500
	21st to end	Day	32% 20% 31% 8% 7% 1	550
April	1st to 10th	Day	34% 24% 23% 13% 5% 1	500
	11th to 20th	Day	31% 25% 30% 9% 5%	492
	21st to end	Day	28% 19% 34% 15% 3 1	500
May	1st to 10th	Day	33% 22% 29% 12% 3 1	503
	11th to 20th	Day	24% 18% 37% 15% 5% 1	527
	21st to end	Day	19% 13% 39% 21% 6% 1	573
June	1st to 10th	Day	21% 14% 38% 18% 7% 2	530
	11th to 20th	Day	18% 17% 38% 19% 7% 1	530
	21st to end	Day	17% 15% 36% 22% 7% 2	530
July	1st to 10th	Day	18% 10% 34% 26% 10% 2	525
	11th to 20th	Day	15% 7% 32% 30% 13% 2	524
	21st to end	Day	14% 8% 37% 31% 9% 1	576
August	1st to 10th	Day	12% 9% 34% 32% 12% 2	526
	11th to 20th	Day	17% 8% 31% 27% 13% 4	519
	21st to end	Day	13% 9% 35% 26% 13% 4	583
September	1st to 10th	Day	18% 10% 33% 22% 14% 3	530
	11th to 20th	Day	20% 12% 27% 21% 12% 8%	530
	21st to end	Day	20% 13% 32% 22% 8% 5%	530
October	1st to 10th	Day	25% 14% 24% 21% 11% 4	530
	11th to 20th	Day	22% 17% 29% 20% 10% 2	464
	21st to end	Day	27% 15% 32% 18% 7% 1	462
November	1st to 10th	Day	23% 13% 35% 18% 9% 1	401
	11th to 20th	Day	30% 18% 32% 15% 5% 1	400
	21st to end	Day	29% 19% 29% 17% 6% 1	400
December	1st to 10th	Day	23% 22% 35% 17% 3	240
	11th to 20th	Day	33% 23% 34% 9% 2	200
	21st to end	Day	25% 19% 36% 15% 3 2	220
January	1st to 10th	Night	23% 18% 39% 18% 3	800
	11th to 20th	Night	27% 17% 36% 18% 2	800
	21st to end	Night	20% 18% 38% 20% 4	880
February	1st to 10th	Night	23% 16% 38% 21% 1	800
	11th to 20th	Night	24% 16% 41% 16% 2	783
	21st to end	Night	25% 17% 35% 20% 3	660
March	1st to 10th	Night	26% 17% 35% 20% 4	800
	11th to 20th	Night	24% 16% 37% 19% 4	800
	21st to end	Night	27% 16% 33% 19% 5%	880
April	1st to 10th	Night	27% 18% 32% 19% 4	800
	11th to 20th	Night	26% 17% 34% 18% 5%	766
	21st to end	Night	24% 17% 35% 22% 2	600
May	1st to 10th	Night	29% 14% 32% 20% 5%	600
	11th to 20th	Night	22% 13% 38% 21% 5%	576
	21st to end	Night	23% 8% 33% 29% 6%	433
June	1st to 10th	Night	22% 5% 36% 30% 7% 1	400
	11th to 20th	Night	18% 8% 38% 31% 5% 1	400
	21st to end	Night	18% 5% 35% 33% 8%	400
July	1st to 10th	Night	15% 5% 32% 37% 11% 1	390
	11th to 20th	Night	13% 4 32% 36% 14%	388
	21st to end	Night	14% 4 32% 39% 9% 1	438
August	1st to 10th	Night	13% 5% 31% 41% 10% 1	553
	11th to 20th	Night	11% 7% 30% 38% 14%	605
	21st to end	Night	15% 4 26% 38% 15% 2	880
September	1st to 10th	Night	16% 5% 32% 33% 13% 1	800
	11th to 20th	Night	17% 7% 27% 29% 18% 3	800
	21st to end	Night	21% 7% 29% 29% 13% 2	800
October	1st to 10th	Night	23% 10% 26% 27% 13% 2	800
	11th to 20th	Night	19% 11% 33% 25% 11% 1	800
	21st to end	Night	27% 13% 32% 22% 6%	880
November	1st to 10th	Night	17% 14% 34% 26% 8% 1	789
	11th to 20th	Night	24% 16% 34% 20% 7%	800
	21st to end	Night	23% 19% 33% 20% 5% 1	800
December	1st to 10th	Night	26% 17% 35% 18% 4	800
	11th to 20th	Night	26% 16% 32% 22% 4	800
	21st to end	Night	25% 15% 36% 21% 3	880

Page generated at 2025-10-31 02:02:41. Version ac07

Copyright © 2025 Attilla Danko.