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 2024-11-05.

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	15% 11% 4 9% 6% 5% 5% 4 5% 7% 30%	101220
	Night	14% 12% 5% 10% 6% 5% 4 4 5% 6% 31%	97767
Transparency	Day	52% 4 10% 21% 10% 1	104862
	Night	53% 4 10% 21% 11% 2	102264
Seeing	Day	24% 16% 26% 19% 10% 4	14787
	Night	21% 17% 25% 25% 10% 1	24345

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	15% 17% 9% 17% 5% 4 5% 2 3 4 19%	2680
	11th to 20th	Day	11% 18% 9% 19% 9% 6% 4 2 2 4 16%	2840
	21st to end	Day	20% 16% 11% 15% 8% 5% 4 3 3 4 12%	3124
February	1st to 10th	Day	14% 19% 5% 10% 9% 6% 4 3 4 6% 20%	1710
	11th to 20th	Day	14% 13% 7% 15% 7% 4 5% 3 4 5% 22%	1663
	21st to end	Day	17% 15% 5% 13% 6% 5% 4 3 4 5% 24%	1562
March	1st to 10th	Day	17% 11% 6% 10% 5% 5% 4 4 5% 6% 26%	3435
	11th to 20th	Day	12% 11% 5% 13% 6% 5% 5% 4 6% 6% 29%	3480
	21st to end	Day	16% 11% 4 8% 5% 5% 4 4 5% 6% 33%	3815
April	1st to 10th	Day	13% 15% 4 8% 5% 4 5% 4 5% 7% 28%	2247
	11th to 20th	Day	15% 13% 4 7% 5% 5% 4 3 5% 6% 33%	2254
	21st to end	Day	20% 10% 4 7% 5% 4 5% 3 5% 6% 31%	2403
May	1st to 10th	Day	24% 10% 3 8% 6% 5% 4 3 4 6% 27%	4082
	11th to 20th	Day	20% 10% 3 7% 5% 5% 5% 5% 6% 7% 27%	4166
	21st to end	Day	12% 7% 3 7% 5% 5% 5% 4 7% 9% 36%	4823
June	1st to 10th	Day	15% 8% 3 6% 6% 5% 5% 5% 6% 8% 33%	2660
	11th to 20th	Day	13% 8% 3 7% 6% 5% 5% 6% 8% 8% 31%	2660
	21st to end	Day	14% 6% 2 7% 6% 5% 5% 4 7% 9% 34%	2660
July	1st to 10th	Day	9% 6% 3 7% 5% 6% 7% 4 6% 8% 39%	4440
	11th to 20th	Day	10% 7% 3 7% 4 4 5% 5% 7% 10% 38%	4186
	21st to end	Day	13% 9% 3 8% 5% 5% 4 4 5% 7% 36%	4466
August	1st to 10th	Day	13% 10% 3 9% 6% 6% 6% 5% 7% 9% 28%	4104
	11th to 20th	Day	13% 7% 3 7% 6% 5% 6% 5% 7% 8% 33%	4044
	21st to end	Day	9% 5% 2 7% 5% 6% 5% 5% 8% 9% 39%	4194
September	1st to 10th	Day	16% 6% 2 7% 5% 5% 5% 3 6% 7% 41%	2280
	11th to 20th	Day	13% 5% 3 7% 4 4 4 4 5% 7% 44%	2192
	21st to end	Day	20% 9% 3 8% 5% 4 4 4 4 6% 33%	2033
October	1st to 10th	Day	15% 9% 3 7% 5% 5% 4 3 6% 7% 37%	1900
	11th to 20th	Day	17% 11% 3 8% 4 4 5% 4 5% 5% 35%	1900
	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%	1872
	11th to 20th	Day	13% 13% 6% 9% 5% 5% 5% 4 5% 6% 29%	1533
	21st to end	Day	15% 15% 7% 11% 6% 5% 5% 3 4 6% 24%	1520
December	1st to 10th	Day	16% 18% 9% 15% 6% 5% 4 3 4 4 17%	1520
	11th to 20th	Day	16% 17% 7% 14% 5% 4 3 3 4 5% 22%	1910
	21st to end	Day	20% 19% 9% 12% 5% 4 4 3 4 4 16%	2772
January	1st to 10th	Night	10% 16% 9% 19% 6% 6% 5% 4 4 4 18%	4264
	11th to 20th	Night	13% 16% 8% 18% 8% 7% 4 3 4 4 17%	4120
	21st to end	Night	20% 18% 8% 14% 9% 4 3 2 3 3 17%	4532
February	1st to 10th	Night	14% 12% 6% 13% 7% 6% 4 4 5% 4 25%	2470
	11th to 20th	Night	15% 13% 5% 12% 8% 6% 5% 4 5% 5% 21%	2403
	21st to end	Night	14% 14% 7% 12% 6% 5% 5% 3 5% 5% 25%	1885
March	1st to 10th	Night	19% 13% 5% 8% 6% 5% 3 3 4 5% 27%	3418
	11th to 20th	Night	12% 10% 7% 12% 5% 4 4 3 5% 7% 32%	3480
	21st to end	Night	12% 12% 4 8% 5% 4 4 3 4 6% 37%	3817
April	1st to 10th	Night	15% 15% 4 9% 6% 4 4 4 4 6% 31%	1933
	11th to 20th	Night	15% 10% 3 7% 4 4 5% 3 6% 7% 36%	1875
	21st to end	Night	14% 9% 3 9% 6% 5% 4 3 5% 7% 35%	1791
May	1st to 10th	Night	26% 11% 3 7% 4 4 4 3 5% 6% 26%	2813
	11th to 20th	Night	21% 13% 4 7% 5% 4 4 3 5% 6% 30%	2723
	21st to end	Night	11% 10% 3 8% 5% 5% 4 4 6% 9% 35%	2732
June	1st to 10th	Night	12% 7% 2 6% 6% 4 5% 4 5% 7% 42%	1520
	11th to 20th	Night	11% 6% 3 6% 6% 5% 6% 4 8% 8% 38%	1520
	21st to end	Night	11% 5% 2 6% 4 4 5% 5% 7% 10% 41%	1520
July	1st to 10th	Night	9% 9% 3 9% 5% 4 5% 4 8% 8% 37%	2520
	11th to 20th	Night	9% 6% 2 6% 4 5% 5% 5% 8% 9% 42%	2769
	21st to end	Night	11% 8% 3 7% 6% 5% 5% 4 5% 7% 40%	3087
August	1st to 10th	Night	13% 8% 3 7% 5% 5% 6% 4 6% 9% 34%	2825
	11th to 20th	Night	14% 8% 2 7% 4 5% 4 4 5% 7% 40%	2785
	21st to end	Night	8% 5% 2 5% 4 5% 5% 5% 6% 8% 45%	3428
September	1st to 10th	Night	13% 7% 3 5% 3 4 5% 3 5% 6% 45%	1900
	11th to 20th	Night	9% 7% 2 5% 3 3 3 4 6% 8% 49%	1985
	21st to end	Night	15% 9% 3 7% 4 5% 4 3 5% 7% 38%	2147
October	1st to 10th	Night	15% 8% 2 6% 4 4 5% 3 5% 7% 42%	2280
	11th to 20th	Night	15% 10% 3 6% 4 5% 4 4 5% 6% 39%	2280
	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%	2303
	11th to 20th	Night	15% 13% 4 9% 7% 4 4 3 5% 6% 31%	2645
	21st to end	Night	15% 14% 6% 10% 5% 4 4 4 4 5% 28%	2660
December	1st to 10th	Night	18% 16% 8% 13% 6% 5% 5% 3 4 5% 17%	2660
	11th to 20th	Night	16% 13% 7% 14% 6% 5% 4 3 4 4 22%	3285
	21st to end	Night	18% 18% 9% 13% 7% 5% 4 4 5% 5% 14%	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	71% 3 7% 13% 4 1	2681
	11th to 20th	Day	76% 2 6% 10% 6% 1	2840
	21st to end	Day	79% 2 5% 10% 4 1	3124
February	1st to 10th	Day	66% 4 9% 13% 7% 1	1710
	11th to 20th	Day	65% 5% 8% 15% 7%	1672
	21st to end	Day	63% 4 10% 14% 7% 2	1562
March	1st to 10th	Day	58% 3 8% 24% 6%	3435
	11th to 20th	Day	57% 3 11% 23% 6% 1	3480
	21st to end	Day	52% 2 12% 21% 12% 1	3815
April	1st to 10th	Day	55% 4 10% 18% 11% 2	2247
	11th to 20th	Day	52% 3 11% 17% 15% 2	2254
	21st to end	Day	54% 3 9% 22% 10% 2	2403
May	1st to 10th	Day	60% 3 8% 20% 8% 1	4120
	11th to 20th	Day	57% 4 10% 22% 7% 1	4170
	21st to end	Day	44% 4 14% 24% 12% 2	4837
June	1st to 10th	Day	48% 5% 12% 25% 10% 1	2660
	11th to 20th	Day	47% 6% 14% 22% 11% 1	2660
	21st to end	Day	44% 6% 13% 26% 11%	2660
July	1st to 10th	Day	43% 6% 12% 26% 11% 3	4370
	11th to 20th	Day	39% 6% 15% 26% 13% 1	4114
	21st to end	Day	47% 5% 8% 23% 16% 1	4324
August	1st to 10th	Day	50% 7% 14% 21% 7%	4091
	11th to 20th	Day	46% 6% 11% 29% 9%	4083
	21st to end	Day	38% 7% 13% 27% 13% 2	4194
September	1st to 10th	Day	43% 5% 10% 22% 16% 4	2280
	11th to 20th	Day	39% 3 10% 29% 17% 2	2192
	21st to end	Day	53% 4 11% 19% 13% 1	2033
October	1st to 10th	Day	38% 4 8% 29% 18% 3	3160
	11th to 20th	Day	46% 4 9% 22% 10% 9%	3140
	21st to end	Day	36% 4 10% 29% 21% 1	3428
November	1st to 10th	Day	45% 4 11% 20% 16% 4	1872
	11th to 20th	Day	56% 4 10% 17% 11% 3	1533
	21st to end	Day	63% 4 9% 17% 7%	1520
December	1st to 10th	Day	72% 3 9% 11% 4	1520
	11th to 20th	Day	66% 3 8% 19% 5%	1906
	21st to end	Day	74% 3 8% 12% 4	2772
January	1st to 10th	Night	70% 3 6% 13% 7% 1	4264
	11th to 20th	Night	72% 4 8% 12% 4	4120
	21st to end	Night	75% 2 5% 13% 4 1	4532
February	1st to 10th	Night	61% 4 8% 18% 8% 1	2470
	11th to 20th	Night	63% 6% 7% 16% 8%	2405
	21st to end	Night	61% 4 9% 16% 9% 2	1885
March	1st to 10th	Night	59% 2 7% 23% 7% 1	3418
	11th to 20th	Night	52% 3 10% 26% 8% 1	3480
	21st to end	Night	49% 3 8% 23% 15% 2	3817
April	1st to 10th	Night	56% 3 9% 17% 13% 1	1933
	11th to 20th	Night	48% 4 11% 20% 15% 2	1875
	21st to end	Night	49% 4 9% 24% 11% 3	1791
May	1st to 10th	Night	60% 3 7% 18% 9% 2	2840
	11th to 20th	Night	57% 3 9% 21% 8% 1	2724
	21st to end	Night	46% 5% 14% 23% 9% 4	2739
June	1st to 10th	Night	41% 5% 11% 29% 13% 1	1520
	11th to 20th	Night	42% 6% 14% 26% 10% 2	1520
	21st to end	Night	37% 7% 15% 26% 14% 1	1520
July	1st to 10th	Night	43% 7% 12% 22% 13% 3	2480
	11th to 20th	Night	36% 7% 17% 24% 15% 1	2718
	21st to end	Night	43% 6% 11% 21% 17% 2	2988
August	1st to 10th	Night	45% 8% 16% 22% 8%	2814
	11th to 20th	Night	43% 5% 11% 30% 11% 1	2812
	21st to end	Night	34% 8% 13% 30% 13% 2	3428
September	1st to 10th	Night	39% 4 12% 25% 17% 3	1900
	11th to 20th	Night	33% 4 11% 31% 20% 1	1985
	21st to end	Night	47% 4 10% 23% 15% 1	2147
October	1st to 10th	Night	38% 4 9% 26% 21% 1	3800
	11th to 20th	Night	38% 4 9% 23% 16% 10%	3779
	21st to end	Night	38% 3 9% 26% 20% 3	4120
November	1st to 10th	Night	43% 4 10% 21% 18% 4	2303
	11th to 20th	Night	55% 4 8% 19% 12% 3	2645
	21st to end	Night	59% 4 9% 19% 8% 1	2660
December	1st to 10th	Night	70% 4 8% 12% 5% 1	2660
	11th to 20th	Night	65% 5% 7% 17% 5%	3288
	21st to end	Night	73% 3 9% 11% 4	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	34% 27% 25% 9% 5%	227
	11th to 20th	Day	41% 26% 26% 5% 2	270
	21st to end	Day	35% 21% 33% 10% 1	297
February	1st to 10th	Day	31% 28% 31% 9% 1	270
	11th to 20th	Day	38% 28% 28% 6%	270
	21st to end	Day	37% 26% 24% 11% 1	322
March	1st to 10th	Day	32% 24% 26% 15% 3	460
	11th to 20th	Day	32% 25% 25% 14% 3 1	460
	21st to end	Day	30% 27% 27% 12% 3 1	506
April	1st to 10th	Day	30% 21% 29% 16% 4 1	460
	11th to 20th	Day	24% 21% 30% 14% 8% 4	452
	21st to end	Day	32% 17% 30% 13% 7% 1	460
May	1st to 10th	Day	32% 17% 25% 15% 8% 4	463
	11th to 20th	Day	25% 16% 28% 17% 9% 4	487
	21st to end	Day	18% 12% 28% 23% 13% 6%	529
June	1st to 10th	Day	20% 17% 24% 21% 14% 3	490
	11th to 20th	Day	21% 10% 26% 23% 16% 4	490
	21st to end	Day	16% 14% 31% 22% 14% 3	490
July	1st to 10th	Day	12% 8% 26% 25% 18% 10%	485
	11th to 20th	Day	10% 8% 30% 28% 16% 8%	484
	21st to end	Day	16% 8% 27% 28% 15% 6%	532
August	1st to 10th	Day	13% 8% 24% 27% 20% 8%	486
	11th to 20th	Day	17% 8% 23% 25% 16% 11%	479
	21st to end	Day	13% 8% 24% 27% 18% 10%	539
September	1st to 10th	Day	21% 8% 20% 22% 18% 11%	490
	11th to 20th	Day	14% 4 22% 31% 19% 10%	490
	21st to end	Day	28% 13% 22% 18% 14% 5%	490
October	1st to 10th	Day	20% 12% 23% 24% 17% 3	490
	11th to 20th	Day	24% 19% 26% 20% 11% 1	490
	21st to end	Day	24% 21% 31% 17% 6% 1	539
November	1st to 10th	Day	19% 19% 29% 20% 11% 2	459
	11th to 20th	Day	27% 24% 29% 15% 5% 1	193
	21st to end	Day	29% 26% 31% 13% 2	180
December	1st to 10th	Day	30% 33% 23% 11% 2 1	180
	11th to 20th	Day	39% 22% 28% 9% 2	180
	21st to end	Day	35% 25% 23% 12% 4	198
January	1st to 10th	Night	25% 31% 29% 11% 3	760
	11th to 20th	Night	30% 25% 28% 15% 2	760
	21st to end	Night	25% 29% 31% 14% 2	836
February	1st to 10th	Night	25% 26% 28% 18% 2	760
	11th to 20th	Night	27% 33% 28% 12% 1	743
	21st to end	Night	30% 25% 30% 14% 2	628
March	1st to 10th	Night	23% 25% 30% 20% 2	760
	11th to 20th	Night	28% 25% 24% 17% 6% 1	760
	21st to end	Night	25% 21% 32% 16% 5%	836
April	1st to 10th	Night	26% 20% 31% 18% 4	760
	11th to 20th	Night	22% 18% 28% 24% 8% 1	751
	21st to end	Night	21% 14% 29% 30% 6%	651
May	1st to 10th	Night	26% 10% 22% 31% 10% 1	570
	11th to 20th	Night	23% 10% 25% 32% 10%	511
	21st to end	Night	11% 8% 21% 38% 20% 2	411
June	1st to 10th	Night	14% 8% 24% 35% 18% 1	380
	11th to 20th	Night	12% 7% 22% 39% 18% 1	380
	21st to end	Night	13% 6% 26% 39% 15% 1	380
July	1st to 10th	Night	13% 5% 18% 40% 22% 2	370
	11th to 20th	Night	10% 4 18% 37% 27% 4	510
	21st to end	Night	11% 5% 19% 40% 22% 2	624
August	1st to 10th	Night	10% 3 17% 40% 28% 2	567
	11th to 20th	Night	11% 5% 14% 38% 27% 4	564
	21st to end	Night	12% 5% 18% 36% 24% 5%	801
September	1st to 10th	Night	16% 6% 17% 35% 23% 4	760
	11th to 20th	Night	12% 6% 18% 34% 26% 4	760
	21st to end	Night	22% 10% 20% 25% 19% 3	760
October	1st to 10th	Night	19% 8% 23% 29% 19% 2	760
	11th to 20th	Night	20% 15% 31% 24% 9% 2	760
	21st to end	Night	25% 19% 25% 24% 6% 1	836
November	1st to 10th	Night	18% 16% 28% 28% 10% 1	760
	11th to 20th	Night	26% 22% 25% 21% 6% 1	760
	21st to end	Night	25% 21% 30% 18% 5%	760
December	1st to 10th	Night	31% 26% 23% 17% 3	760
	11th to 20th	Night	24% 30% 25% 18% 3	760
	21st to end	Night	26% 25% 28% 18% 2	836

Page generated at 2024-11-03 02:11:12. Version ac07

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