Elton Moonshine Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Elton Moonshine Observatory clear sky chart from 2005-11-06 to 2025-10-19.

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	14% 11% 4 10% 6% 5% 5% 4 5% 7% 30%	126520
	Night	14% 11% 5% 11% 6% 5% 4 3 5% 6% 30%	123194
Transparency	Day	53% 5% 10% 21% 10% 1	130118
	Night	54% 5% 10% 20% 10% 2	127665
Seeing	Day	25% 17% 26% 19% 10% 4	16016
	Night	22% 17% 25% 24% 10% 1	25558

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	13% 16% 8% 21% 9% 5% 4 2 3 3 15%	3844
	11th to 20th	Day	11% 16% 10% 22% 10% 8% 4 2 2 3 12%	4060
	21st to end	Day	17% 14% 10% 12% 8% 5% 4 3 3 4 19%	4466
February	1st to 10th	Day	14% 19% 5% 11% 9% 6% 4 3 4 6% 20%	1800
	11th to 20th	Day	14% 13% 7% 15% 7% 4 5% 3 4 5% 21%	1753
	21st to end	Day	16% 14% 5% 13% 6% 5% 4 3 4 5% 24%	1642
March	1st to 10th	Day	14% 11% 9% 10% 5% 4 4 3 4 5% 31%	4935
	11th to 20th	Day	12% 10% 5% 11% 5% 5% 5% 4 7% 7% 32%	4980
	21st to end	Day	14% 12% 4 9% 5% 5% 4 4 5% 5% 33%	5465
April	1st to 10th	Day	15% 15% 4 9% 5% 4 5% 4 5% 7% 27%	2365
	11th to 20th	Day	15% 13% 4 7% 5% 5% 4 3 5% 6% 33%	2374
	21st to end	Day	19% 10% 4 7% 4 4 5% 3 5% 7% 31%	2530
May	1st to 10th	Day	19% 10% 3 9% 7% 6% 6% 4 5% 6% 25%	5862
	11th to 20th	Day	18% 9% 3 8% 6% 5% 6% 5% 6% 8% 26%	5988
	21st to end	Day	19% 9% 3 7% 5% 4 5% 5% 6% 8% 29%	6934
June	1st to 10th	Day	15% 8% 3 6% 6% 6% 5% 4 6% 8% 34%	2800
	11th to 20th	Day	13% 8% 3 8% 6% 5% 5% 6% 8% 8% 31%	2800
	21st to end	Day	13% 6% 2 7% 6% 5% 5% 4 7% 10% 35%	2800
July	1st to 10th	Day	9% 7% 3 7% 5% 6% 6% 4 5% 8% 39%	6360
	11th to 20th	Day	10% 8% 3 8% 5% 5% 6% 5% 8% 10% 31%	5994
	21st to end	Day	12% 8% 3 8% 5% 4 4 4 6% 8% 39%	6424
August	1st to 10th	Day	13% 10% 3 9% 6% 5% 6% 5% 7% 9% 29%	4234
	11th to 20th	Day	13% 7% 3 7% 6% 5% 6% 5% 7% 8% 33%	4174
	21st to end	Day	9% 5% 2 7% 5% 6% 5% 5% 8% 9% 39%	4327
September	1st to 10th	Day	15% 6% 2 6% 5% 4 5% 3 5% 7% 42%	2400
	11th to 20th	Day	12% 5% 3 7% 4 4 4 4 5% 7% 45%	2307
	21st to end	Day	20% 10% 3 8% 5% 4 4 4 4 6% 32%	2140
October	1st to 10th	Day	14% 9% 3 6% 5% 5% 4 3 6% 7% 39%	2000
	11th to 20th	Day	17% 11% 3 8% 4 4 5% 4 4 5% 36%	1980
	21st to end	Day	16% 15% 3 7% 5% 4 3 3 4 6% 33%	2090
November	1st to 10th	Day	11% 11% 4 8% 4 4 4 4 4 6% 41%	1929
	11th to 20th	Day	13% 13% 6% 9% 5% 5% 5% 4 5% 6% 29%	1613
	21st to end	Day	15% 16% 7% 11% 6% 5% 5% 3 4 5% 23%	1600
December	1st to 10th	Day	14% 12% 6% 28% 7% 4 3 2 4 4 16%	2600
	11th to 20th	Day	19% 16% 6% 11% 4 4 4 3 4 4 23%	2990
	21st to end	Day	17% 20% 8% 13% 6% 5% 4 3 4 4 16%	3960
January	1st to 10th	Night	9% 15% 7% 24% 13% 5% 4 3 3 3 14%	6100
	11th to 20th	Night	10% 14% 8% 22% 11% 8% 3 3 3 4 15%	5900
	21st to end	Night	15% 15% 7% 14% 9% 5% 4 2 4 5% 21%	6490
February	1st to 10th	Night	15% 12% 6% 12% 7% 6% 4 4 5% 4 25%	2600
	11th to 20th	Night	15% 13% 5% 13% 8% 6% 5% 4 5% 6% 21%	2533
	21st to end	Night	13% 14% 6% 13% 6% 5% 5% 3 5% 5% 25%	1981
March	1st to 10th	Night	15% 13% 6% 10% 8% 5% 3 3 4 4 28%	4918
	11th to 20th	Night	10% 9% 6% 9% 4 3 3 3 5% 7% 41%	4980
	21st to end	Night	11% 12% 5% 10% 6% 4 4 3 4 6% 34%	5467
April	1st to 10th	Night	16% 15% 4 9% 6% 4 4 3 4 5% 30%	2035
	11th to 20th	Night	15% 10% 3 7% 4 4 5% 3 6% 7% 35%	1975
	21st to end	Night	14% 10% 3 9% 5% 5% 4 3 5% 8% 35%	1885
May	1st to 10th	Night	24% 11% 4 8% 5% 4 4 4 5% 7% 24%	4033
	11th to 20th	Night	18% 11% 4 8% 5% 4 5% 3 5% 7% 30%	3901
	21st to end	Night	19% 12% 4 7% 4 5% 4 4 5% 8% 30%	3920
June	1st to 10th	Night	12% 8% 2 6% 6% 4 5% 4 5% 7% 43%	1600
	11th to 20th	Night	12% 7% 4 6% 6% 5% 5% 3 7% 7% 38%	1600
	21st to end	Night	11% 5% 2 6% 4 4 5% 5% 7% 10% 41%	1600
July	1st to 10th	Night	9% 10% 3 8% 5% 4 5% 4 7% 8% 38%	3598
	11th to 20th	Night	11% 8% 3 7% 5% 5% 6% 5% 8% 8% 34%	3958
	21st to end	Night	11% 9% 2 7% 5% 4 4 4 5% 8% 41%	4427
August	1st to 10th	Night	12% 8% 3 7% 5% 5% 6% 4 6% 9% 34%	2915
	11th to 20th	Night	14% 8% 2 7% 4 5% 4 4 5% 7% 40%	2875
	21st to end	Night	8% 5% 2 5% 4 5% 6% 5% 6% 8% 45%	3536
September	1st to 10th	Night	12% 7% 3 5% 3 4 4 3 5% 6% 46%	2000
	11th to 20th	Night	9% 7% 2 5% 4 4 4 4 6% 7% 49%	2090
	21st to end	Night	15% 9% 3 7% 5% 5% 4 3 5% 6% 37%	2260
October	1st to 10th	Night	15% 7% 2 5% 4 4 5% 3 5% 6% 43%	2400
	11th to 20th	Night	14% 10% 3 6% 5% 5% 4 4 5% 6% 39%	2377
	21st to end	Night	19% 13% 3 7% 4 4 3 3 4 6% 34%	2508
November	1st to 10th	Night	10% 11% 3 7% 4 4 4 3 5% 6% 43%	2366
	11th to 20th	Night	15% 13% 4 9% 6% 4 4 3 5% 6% 30%	2785
	21st to end	Night	15% 15% 6% 10% 5% 4 4 4 4 5% 27%	2800
December	1st to 10th	Night	15% 12% 6% 24% 6% 4 4 3 3 4 19%	4580
	11th to 20th	Night	19% 12% 7% 14% 5% 5% 4 3 4 4 22%	5205
	21st to end	Night	15% 19% 8% 14% 7% 5% 4 3 5% 5% 15%	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	75% 3 7% 10% 4 1	3845
	11th to 20th	Day	80% 2 5% 8% 4 1	4060
	21st to end	Day	70% 3 7% 12% 8% 1	4466
February	1st to 10th	Day	66% 4 9% 13% 7% 1	1800
	11th to 20th	Day	65% 5% 8% 15% 7%	1762
	21st to end	Day	63% 4 10% 14% 7% 2	1642
March	1st to 10th	Day	55% 3 8% 23% 8% 2	4935
	11th to 20th	Day	51% 4 11% 25% 7% 2	4980
	21st to end	Day	53% 3 10% 21% 13% 2	5465
April	1st to 10th	Day	56% 4 10% 17% 11% 2	2365
	11th to 20th	Day	52% 3 11% 17% 15% 2	2374
	21st to end	Day	53% 4 9% 23% 10% 1	2530
May	1st to 10th	Day	58% 6% 9% 17% 8% 2	5897
	11th to 20th	Day	55% 5% 9% 22% 8% 1	5992
	21st to end	Day	53% 5% 12% 19% 10% 2	6949
June	1st to 10th	Day	48% 5% 11% 25% 10% 1	2800
	11th to 20th	Day	48% 6% 14% 21% 11% 1	2800
	21st to end	Day	43% 6% 13% 26% 12%	2800
July	1st to 10th	Day	42% 6% 10% 27% 12% 2	6290
	11th to 20th	Day	45% 8% 15% 22% 10%	5922
	21st to end	Day	43% 5% 8% 26% 17% 1	6240
August	1st to 10th	Day	50% 7% 14% 22% 7%	4221
	11th to 20th	Day	45% 6% 11% 29% 9%	4213
	21st to end	Day	38% 7% 12% 28% 13% 2	4327
September	1st to 10th	Day	42% 5% 10% 22% 17% 3	2400
	11th to 20th	Day	38% 4 11% 29% 17% 1	2307
	21st to end	Day	53% 4 11% 18% 13% 1	2140
October	1st to 10th	Day	37% 4 8% 29% 19% 3	3260
	11th to 20th	Day	46% 4 9% 22% 10% 9%	3220
	21st to end	Day	36% 4 10% 29% 21% 1	3428
November	1st to 10th	Day	45% 4 11% 19% 16% 4	1929
	11th to 20th	Day	56% 4 9% 17% 11% 3	1613
	21st to end	Day	64% 4 8% 16% 7%	1600
December	1st to 10th	Day	74% 4 11% 9% 3	2600
	11th to 20th	Day	64% 5% 10% 17% 5%	2986
	21st to end	Day	72% 3 7% 12% 5%	3960
January	1st to 10th	Night	75% 3 5% 10% 6%	6100
	11th to 20th	Night	75% 4 6% 11% 4 1	5900
	21st to end	Night	68% 4 7% 14% 6% 1	6490
February	1st to 10th	Night	61% 4 8% 18% 8% 1	2600
	11th to 20th	Night	63% 5% 7% 16% 8%	2535
	21st to end	Night	61% 4 9% 16% 8% 2	1981
March	1st to 10th	Night	59% 3 8% 21% 8% 1	4918
	11th to 20th	Night	44% 4 14% 27% 8% 4	4980
	21st to end	Night	50% 5% 9% 19% 15% 2	5467
April	1st to 10th	Night	57% 3 9% 17% 13% 1	2035
	11th to 20th	Night	48% 4 11% 20% 15% 2	1975
	21st to end	Night	49% 4 9% 25% 11% 2	1885
May	1st to 10th	Night	60% 5% 8% 14% 9% 3	4060
	11th to 20th	Night	56% 4 8% 25% 7% 1	3902
	21st to end	Night	53% 5% 11% 21% 7% 2	3927
June	1st to 10th	Night	41% 5% 11% 28% 14% 1	1600
	11th to 20th	Night	43% 6% 13% 26% 10% 2	1600
	21st to end	Night	37% 7% 15% 25% 15% 1	1600
July	1st to 10th	Night	43% 6% 12% 25% 12% 2	3560
	11th to 20th	Night	44% 7% 17% 20% 11% 1	3910
	21st to end	Night	40% 6% 11% 23% 19% 1	4297
August	1st to 10th	Night	44% 8% 16% 22% 9%	2904
	11th to 20th	Night	42% 5% 11% 30% 12% 1	2902
	21st to end	Night	34% 8% 13% 30% 13% 2	3536
September	1st to 10th	Night	38% 5% 12% 25% 17% 3	2000
	11th to 20th	Night	33% 4 11% 31% 19% 1	2090
	21st to end	Night	48% 4 10% 22% 15% 1	2260
October	1st to 10th	Night	38% 4 9% 26% 22% 1	3920
	11th to 20th	Night	38% 4 9% 23% 16% 9%	3876
	21st to end	Night	38% 3 9% 26% 20% 3	4120
November	1st to 10th	Night	43% 3 10% 21% 19% 4	2366
	11th to 20th	Night	56% 4 7% 18% 12% 3	2785
	21st to end	Night	60% 4 9% 18% 8% 1	2800
December	1st to 10th	Night	70% 4 11% 12% 3	4580
	11th to 20th	Night	65% 5% 11% 16% 4	5208
	21st to end	Night	71% 4 8% 11% 5%	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	37% 26% 24% 8% 4	253
	11th to 20th	Day	43% 25% 26% 5% 2	300
	21st to end	Day	36% 22% 31% 9% 1	330
February	1st to 10th	Day	35% 27% 29% 8% 1	300
	11th to 20th	Day	42% 27% 25% 5%	300
	21st to end	Day	36% 27% 25% 11% 1	351
March	1st to 10th	Day	33% 24% 27% 13% 2	500
	11th to 20th	Day	32% 25% 25% 14% 3 1	500
	21st to end	Day	32% 26% 27% 11% 3 1	550
April	1st to 10th	Day	33% 20% 27% 15% 4 1	500
	11th to 20th	Day	26% 21% 28% 14% 7% 4	492
	21st to end	Day	32% 17% 30% 14% 7% 1	500
May	1st to 10th	Day	32% 20% 23% 15% 7% 3	503
	11th to 20th	Day	25% 17% 29% 16% 9% 4	527
	21st to end	Day	22% 12% 27% 21% 12% 6%	573
June	1st to 10th	Day	20% 18% 24% 21% 13% 3	530
	11th to 20th	Day	21% 11% 27% 22% 15% 4	530
	21st to end	Day	15% 13% 31% 24% 13% 3	530
July	1st to 10th	Day	13% 8% 27% 25% 18% 10%	525
	11th to 20th	Day	10% 9% 29% 27% 17% 7%	524
	21st to end	Day	16% 8% 27% 28% 15% 6%	576
August	1st to 10th	Day	12% 8% 25% 27% 19% 8%	526
	11th to 20th	Day	17% 8% 23% 25% 16% 11%	519
	21st to end	Day	13% 9% 24% 27% 17% 10%	583
September	1st to 10th	Day	21% 9% 20% 23% 18% 11%	530
	11th to 20th	Day	14% 4 22% 32% 20% 9%	530
	21st to end	Day	28% 13% 23% 18% 13% 5%	530
October	1st to 10th	Day	20% 12% 23% 26% 17% 4	530
	11th to 20th	Day	24% 20% 26% 19% 10% 1	522
	21st to end	Day	24% 21% 31% 17% 6% 1	539
November	1st to 10th	Day	20% 20% 29% 19% 10% 2	480
	11th to 20th	Day	28% 24% 30% 13% 4	213
	21st to end	Day	32% 26% 30% 12% 2	200
December	1st to 10th	Day	32% 33% 24% 10% 2 1	200
	11th to 20th	Day	40% 21% 29% 9% 2	200
	21st to end	Day	35% 25% 25% 11% 4	220
January	1st to 10th	Night	26% 32% 28% 11% 3	800
	11th to 20th	Night	31% 26% 27% 14% 2	800
	21st to end	Night	26% 29% 30% 13% 1	880
February	1st to 10th	Night	27% 26% 27% 18% 2	800
	11th to 20th	Night	29% 31% 28% 11% 1	783
	21st to end	Night	29% 26% 29% 14% 2	660
March	1st to 10th	Night	24% 26% 29% 20% 2	800
	11th to 20th	Night	28% 25% 25% 17% 6% 1	800
	21st to end	Night	26% 21% 32% 15% 5%	880
April	1st to 10th	Night	28% 20% 30% 18% 4	800
	11th to 20th	Night	23% 18% 28% 23% 8% 1	791
	21st to end	Night	21% 14% 29% 29% 6%	685
May	1st to 10th	Night	27% 11% 22% 30% 9% 1	600
	11th to 20th	Night	23% 11% 25% 30% 10%	538
	21st to end	Night	14% 8% 21% 36% 19% 2	433
June	1st to 10th	Night	14% 9% 23% 36% 17% 1	400
	11th to 20th	Night	13% 9% 23% 37% 18% 1	400
	21st to end	Night	13% 5% 25% 39% 16% 2	400
July	1st to 10th	Night	13% 5% 18% 40% 22% 2	390
	11th to 20th	Night	10% 5% 18% 37% 27% 3	538
	21st to end	Night	11% 5% 19% 40% 23% 2	657
August	1st to 10th	Night	10% 3 18% 39% 28% 2	597
	11th to 20th	Night	11% 5% 14% 39% 26% 4	594
	21st to end	Night	12% 5% 19% 35% 23% 5%	843
September	1st to 10th	Night	16% 6% 17% 35% 22% 4	800
	11th to 20th	Night	12% 6% 17% 35% 27% 4	800
	21st to end	Night	23% 11% 20% 26% 18% 3	800
October	1st to 10th	Night	19% 7% 22% 31% 19% 2	800
	11th to 20th	Night	20% 15% 32% 23% 9% 2	793
	21st to end	Night	25% 19% 25% 24% 6% 1	836
November	1st to 10th	Night	18% 16% 28% 27% 10% 1	780
	11th to 20th	Night	27% 21% 26% 20% 5% 1	800
	21st to end	Night	26% 22% 29% 18% 5%	800
December	1st to 10th	Night	31% 26% 23% 16% 3	800
	11th to 20th	Night	26% 29% 25% 17% 2	800
	21st to end	Night	27% 25% 28% 18% 2	880

Page generated at 2025-10-16 01:50:24. Version ac07

Copyright © 2025 Attilla Danko.