Rustic Lake Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rustic Lake 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	14% 11% 4 9% 5% 5% 5% 4 6% 7% 31%	101274
	Night	14% 11% 4 9% 5% 4 4 4 5% 7% 33%	97694
Transparency	Day	49% 7% 11% 20% 12% 1	104950
	Night	49% 6% 11% 21% 12% 2	102158
Seeing	Day	18% 12% 28% 22% 14% 6%	15057
	Night	18% 10% 28% 29% 13% 2	24933

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	18% 20% 9% 14% 5% 5% 4 3 4 5% 14%	2836
	11th to 20th	Day	14% 22% 7% 13% 6% 5% 8% 3 4 5% 13%	2840
	21st to end	Day	25% 20% 11% 13% 7% 5% 3 2 2 3 9%	3124
February	1st to 10th	Day	17% 17% 6% 10% 7% 5% 4 3 4 5% 22%	1710
	11th to 20th	Day	14% 12% 6% 14% 7% 5% 6% 4 4 5% 23%	1775
	21st to end	Day	17% 14% 4 10% 6% 4 6% 4 5% 6% 26%	1570
March	1st to 10th	Day	21% 14% 7% 10% 5% 4 4 3 4 5% 24%	3298
	11th to 20th	Day	12% 13% 5% 10% 5% 4 4 3 4 5% 33%	3480
	21st to end	Day	19% 11% 6% 11% 5% 4 4 3 4 5% 28%	3815
April	1st to 10th	Day	13% 13% 5% 10% 6% 5% 4 4 5% 7% 30%	2114
	11th to 20th	Day	16% 10% 4 8% 6% 5% 4 3 4 7% 34%	2432
	21st to end	Day	20% 10% 3 7% 5% 4 4 3 4 7% 32%	2470
May	1st to 10th	Day	18% 10% 3 9% 5% 5% 4 4 5% 7% 30%	4082
	11th to 20th	Day	18% 9% 3 7% 4 4 4 3 6% 8% 33%	4081
	21st to end	Day	10% 6% 3 7% 5% 5% 6% 5% 7% 9% 37%	4476
June	1st to 10th	Day	12% 8% 2 7% 5% 4 5% 4 6% 8% 37%	2470
	11th to 20th	Day	12% 7% 2 7% 5% 5% 5% 4 8% 9% 36%	2521
	21st to end	Day	10% 6% 2 6% 6% 5% 5% 5% 8% 9% 38%	2660
July	1st to 10th	Day	10% 6% 3 8% 5% 5% 6% 4 7% 11% 35%	4358
	11th to 20th	Day	7% 5% 2 7% 5% 5% 6% 5% 7% 10% 41%	4120
	21st to end	Day	10% 7% 3 7% 5% 6% 6% 5% 6% 8% 38%	4466
August	1st to 10th	Day	12% 7% 3 8% 5% 5% 6% 4 6% 9% 36%	4104
	11th to 20th	Day	9% 7% 2 8% 5% 5% 6% 5% 8% 10% 36%	4044
	21st to end	Day	8% 6% 2 7% 5% 5% 6% 5% 7% 9% 40%	4513
September	1st to 10th	Day	13% 5% 2 6% 4 5% 4 4 5% 7% 44%	2105
	11th to 20th	Day	9% 8% 2 6% 4 4 4 3 6% 9% 43%	2090
	21st to end	Day	18% 8% 3 7% 4 5% 3 3 5% 6% 39%	2090
October	1st to 10th	Day	13% 7% 3 7% 4 4 4 4 6% 7% 42%	2005
	11th to 20th	Day	15% 10% 2 7% 4 4 5% 4 6% 7% 37%	1900
	21st to end	Day	19% 11% 3 8% 5% 5% 4 3 5% 6% 30%	2042
November	1st to 10th	Day	9% 10% 3 7% 6% 4 4 3 6% 7% 41%	1708
	11th to 20th	Day	17% 14% 4 9% 5% 4 4 3 4 7% 31%	1710
	21st to end	Day	17% 16% 5% 9% 5% 5% 5% 3 5% 6% 25%	1647
December	1st to 10th	Day	16% 19% 8% 11% 6% 4 3 3 3 5% 20%	1520
	11th to 20th	Day	16% 15% 6% 14% 6% 5% 3 4 6% 7% 19%	1974
	21st to end	Day	21% 24% 8% 11% 6% 5% 3 3 4 4 11%	3124
January	1st to 10th	Night	14% 20% 7% 15% 6% 5% 4 3 4 4 17%	4109
	11th to 20th	Night	13% 18% 9% 18% 7% 5% 7% 6% 3 4 12%	4120
	21st to end	Night	24% 20% 7% 14% 6% 3 3 2 3 3 15%	4532
February	1st to 10th	Night	18% 14% 5% 12% 7% 5% 4 3 4 5% 22%	2470
	11th to 20th	Night	14% 15% 6% 11% 6% 4 5% 4 6% 6% 24%	2287
	21st to end	Night	18% 15% 4 11% 7% 4 4 4 4 5% 24%	1884
March	1st to 10th	Night	19% 15% 5% 8% 4 4 4 3 4 4 32%	3555
	11th to 20th	Night	12% 9% 3 7% 5% 4 5% 4 5% 7% 38%	3480
	21st to end	Night	17% 10% 3 8% 4 5% 3 3 5% 5% 35%	3817
April	1st to 10th	Night	14% 13% 3 8% 5% 5% 5% 4 6% 6% 33%	2082
	11th to 20th	Night	15% 9% 2 8% 5% 5% 4 4 6% 6% 36%	1695
	21st to end	Night	15% 9% 4 7% 5% 4 4 4 6% 7% 35%	1710
May	1st to 10th	Night	21% 10% 4 8% 6% 4 5% 3 5% 6% 27%	2813
	11th to 20th	Night	18% 8% 3 6% 5% 4 4 4 5% 7% 38%	2812
	21st to end	Night	9% 5% 2 5% 4 3 5% 5% 8% 10% 45%	3079
June	1st to 10th	Night	10% 7% 3 7% 5% 5% 4 4 5% 7% 44%	1710
	11th to 20th	Night	7% 5% 3 7% 5% 4 5% 5% 8% 8% 43%	1649
	21st to end	Night	9% 5% 2 6% 6% 4 4 5% 7% 9% 43%	1520
July	1st to 10th	Night	9% 5% 2 6% 5% 4 5% 4 5% 10% 45%	2592
	11th to 20th	Night	7% 4 2 5% 4 4 5% 4 6% 9% 50%	2840
	21st to end	Night	6% 5% 2 7% 5% 4 5% 4 7% 9% 44%	3087
August	1st to 10th	Night	11% 7% 3 7% 5% 5% 5% 4 6% 9% 38%	2825
	11th to 20th	Night	10% 8% 3 8% 4 4 4 3 5% 8% 44%	2785
	21st to end	Night	5% 5% 2 5% 4 5% 5% 4 6% 9% 49%	3124
September	1st to 10th	Night	11% 6% 2 5% 3 3 4 4 5% 7% 50%	2057
	11th to 20th	Night	9% 5% 1 4 4 3 4 3 4 8% 55%	2090
	21st to end	Night	14% 8% 2 6% 4 4 4 3 6% 6% 42%	2090
October	1st to 10th	Night	12% 6% 2 5% 4 3 5% 3 6% 6% 47%	2174
	11th to 20th	Night	16% 8% 3 7% 5% 5% 3 3 4 6% 40%	2280
	21st to end	Night	19% 9% 3 6% 5% 5% 4 3 4 7% 34%	2555
November	1st to 10th	Night	11% 9% 3 6% 4 4 5% 4 5% 7% 42%	2470
	11th to 20th	Night	14% 13% 4 8% 5% 4 3 3 5% 6% 34%	2470
	21st to end	Night	18% 13% 4 8% 5% 4 4 4 5% 6% 27%	2527
December	1st to 10th	Night	17% 19% 6% 10% 5% 4 4 3 5% 5% 21%	2660
	11th to 20th	Night	16% 15% 5% 12% 5% 5% 4 3 5% 6% 24%	3212
	21st to end	Night	21% 20% 8% 11% 6% 5% 4 3 4 5% 13%	4532

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	73% 5% 8% 11% 3	2837
	11th to 20th	Day	72% 5% 10% 9% 3	2840
	21st to end	Day	81% 5% 5% 6% 2	3124
February	1st to 10th	Day	66% 5% 10% 13% 6% 1	1710
	11th to 20th	Day	63% 6% 8% 14% 8% 1	1784
	21st to end	Day	58% 7% 12% 14% 7% 2	1570
March	1st to 10th	Day	62% 5% 9% 19% 5%	3298
	11th to 20th	Day	52% 6% 9% 24% 8% 1	3480
	21st to end	Day	57% 5% 11% 18% 8%	3815
April	1st to 10th	Day	53% 6% 11% 17% 11% 1	2114
	11th to 20th	Day	51% 6% 11% 17% 14% 2	2432
	21st to end	Day	51% 6% 10% 20% 11% 2	2470
May	1st to 10th	Day	53% 8% 10% 21% 8% 1	4120
	11th to 20th	Day	48% 7% 13% 23% 8% 1	4085
	21st to end	Day	38% 11% 11% 21% 13% 5%	4489
June	1st to 10th	Day	42% 8% 11% 25% 13% 1	2470
	11th to 20th	Day	43% 9% 12% 22% 14% 1	2521
	21st to end	Day	39% 9% 13% 21% 15% 3	2660
July	1st to 10th	Day	42% 7% 11% 22% 16% 2	4291
	11th to 20th	Day	34% 8% 14% 24% 19% 1	4051
	21st to end	Day	40% 8% 13% 17% 19% 3	4324
August	1st to 10th	Day	43% 8% 13% 22% 14%	4091
	11th to 20th	Day	38% 9% 11% 29% 11% 1	4083
	21st to end	Day	37% 8% 14% 27% 12% 2	4513
September	1st to 10th	Day	37% 7% 13% 22% 17% 4	2105
	11th to 20th	Day	37% 7% 11% 24% 18% 2	2090
	21st to end	Day	46% 6% 9% 20% 18% 1	2090
October	1st to 10th	Day	29% 6% 13% 31% 21% 1	3330
	11th to 20th	Day	41% 6% 10% 22% 19% 2	3140
	21st to end	Day	40% 5% 12% 24% 18% 1	3344
November	1st to 10th	Day	43% 5% 12% 23% 15% 2	1708
	11th to 20th	Day	53% 5% 10% 20% 10% 2	1710
	21st to end	Day	60% 5% 10% 16% 7% 1	1647
December	1st to 10th	Day	67% 6% 9% 13% 4	1520
	11th to 20th	Day	64% 5% 10% 16% 5%	1970
	21st to end	Day	78% 5% 8% 6% 3	3124
January	1st to 10th	Night	70% 5% 8% 13% 4	4109
	11th to 20th	Night	77% 5% 7% 8% 3	4120
	21st to end	Night	76% 3 6% 11% 3	4532
February	1st to 10th	Night	63% 6% 9% 14% 7% 1	2470
	11th to 20th	Night	59% 6% 9% 16% 9% 1	2289
	21st to end	Night	62% 5% 9% 14% 8% 2	1884
March	1st to 10th	Night	55% 5% 10% 21% 9%	3555
	11th to 20th	Night	44% 6% 13% 25% 10% 2	3480
	21st to end	Night	50% 5% 10% 25% 10% 1	3817
April	1st to 10th	Night	50% 6% 11% 17% 14% 2	2082
	11th to 20th	Night	47% 6% 11% 17% 16% 3	1695
	21st to end	Night	47% 5% 11% 21% 14% 2	1710
May	1st to 10th	Night	56% 7% 9% 19% 8% 1	2840
	11th to 20th	Night	44% 7% 11% 24% 12% 2	2813
	21st to end	Night	31% 9% 14% 28% 16% 3	3087
June	1st to 10th	Night	38% 7% 11% 23% 18% 3	1710
	11th to 20th	Night	34% 8% 14% 24% 17% 2	1649
	21st to end	Night	34% 8% 14% 25% 15% 3	1520
July	1st to 10th	Night	34% 6% 13% 25% 16% 6%	2550
	11th to 20th	Night	29% 7% 14% 30% 18% 1	2786
	21st to end	Night	33% 8% 15% 21% 20% 3	2988
August	1st to 10th	Night	41% 7% 13% 23% 15% 1	2814
	11th to 20th	Night	38% 7% 11% 27% 17% 1	2812
	21st to end	Night	31% 7% 14% 30% 15% 3	3124
September	1st to 10th	Night	32% 7% 12% 26% 17% 5%	2057
	11th to 20th	Night	28% 6% 11% 27% 26% 2	2090
	21st to end	Night	41% 7% 10% 21% 20% 2	2090
October	1st to 10th	Night	29% 5% 8% 30% 27% 1	3629
	11th to 20th	Night	37% 5% 11% 23% 21% 3	3779
	21st to end	Night	38% 4 10% 28% 18% 3	4203
November	1st to 10th	Night	40% 7% 11% 22% 17% 3	2470
	11th to 20th	Night	51% 4 10% 21% 13% 2	2470
	21st to end	Night	57% 6% 12% 18% 7% 1	2527
December	1st to 10th	Night	65% 5% 10% 14% 6%	2660
	11th to 20th	Night	60% 5% 12% 18% 4	3215
	21st to end	Night	72% 6% 10% 9% 3	4532

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	25% 21% 36% 11% 5% 1	270
	11th to 20th	Day	26% 24% 37% 9% 4	270
	21st to end	Day	28% 19% 37% 14% 3	297
February	1st to 10th	Day	30% 20% 32% 14% 3 1	270
	11th to 20th	Day	26% 28% 32% 12% 2	270
	21st to end	Day	26% 30% 34% 10%	225
March	1st to 10th	Day	25% 19% 33% 18% 4	370
	11th to 20th	Day	25% 16% 34% 19% 5% 1	460
	21st to end	Day	29% 14% 31% 20% 5%	506
April	1st to 10th	Day	19% 18% 33% 19% 9% 2	460
	11th to 20th	Day	23% 20% 26% 17% 10% 5%	452
	21st to end	Day	23% 16% 32% 19% 9% 2	460
May	1st to 10th	Day	23% 13% 32% 21% 8% 3	463
	11th to 20th	Day	19% 9% 32% 20% 14% 6%	487
	21st to end	Day	11% 7% 25% 28% 21% 8%	529
June	1st to 10th	Day	14% 7% 28% 29% 17% 4	490
	11th to 20th	Day	14% 9% 23% 29% 20% 5%	541
	21st to end	Day	10% 9% 30% 32% 14% 5%	680
July	1st to 10th	Day	13% 3 20% 27% 23% 14%	630
	11th to 20th	Day	11% 4 21% 28% 23% 13%	484
	21st to end	Day	11% 4 20% 27% 26% 11%	532
August	1st to 10th	Day	12% 5% 15% 28% 25% 14%	486
	11th to 20th	Day	11% 5% 22% 27% 23% 12%	479
	21st to end	Day	11% 4 17% 27% 26% 16%	539
September	1st to 10th	Day	12% 5% 20% 25% 25% 13%	490
	11th to 20th	Day	9% 3 15% 24% 33% 16%	490
	21st to end	Day	21% 11% 22% 20% 19% 8%	490
October	1st to 10th	Day	11% 8% 28% 25% 20% 8%	490
	11th to 20th	Day	15% 16% 32% 23% 9% 4	490
	21st to end	Day	25% 16% 33% 20% 5% 1	491
November	1st to 10th	Day	13% 18% 36% 19% 12% 2	282
	11th to 20th	Day	28% 16% 33% 16% 7%	270
	21st to end	Day	26% 18% 40% 15% 2	239
December	1st to 10th	Day	21% 22% 37% 14% 4 2	180
	11th to 20th	Day	22% 20% 36% 18% 4	198
	21st to end	Day	28% 21% 32% 16% 3	297
January	1st to 10th	Night	23% 18% 36% 18% 5%	760
	11th to 20th	Night	26% 19% 34% 16% 4	760
	21st to end	Night	24% 16% 34% 22% 4	836
February	1st to 10th	Night	25% 16% 35% 22% 3	760
	11th to 20th	Night	24% 17% 34% 22% 3	743
	21st to end	Night	26% 17% 36% 19% 3	628
March	1st to 10th	Night	23% 14% 33% 25% 6%	760
	11th to 20th	Night	19% 15% 35% 24% 7% 1	760
	21st to end	Night	23% 10% 33% 26% 7% 1	836
April	1st to 10th	Night	21% 14% 34% 26% 6% 1	752
	11th to 20th	Night	20% 11% 32% 26% 9% 2	563
	21st to end	Night	18% 9% 36% 29% 7% 1	570
May	1st to 10th	Night	19% 10% 29% 32% 10% 1	570
	11th to 20th	Night	20% 6% 25% 33% 13% 2	561
	21st to end	Night	10% 3 21% 41% 23% 3	617
June	1st to 10th	Night	11% 3 26% 40% 20% 1	570
	11th to 20th	Night	9% 4 21% 43% 20% 3	570
	21st to end	Night	10% 3 22% 42% 22% 1	570
July	1st to 10th	Night	8% 3 15% 41% 28% 4	555
	11th to 20th	Night	8% 3 16% 42% 28% 4	552
	21st to end	Night	8% 2 15% 42% 30% 2	624
August	1st to 10th	Night	9% 1 14% 43% 29% 4	567
	11th to 20th	Night	10% 2 13% 40% 30% 5%	564
	21st to end	Night	8% 2 14% 38% 32% 6%	627
September	1st to 10th	Night	13% 4 17% 32% 29% 5%	746
	11th to 20th	Night	11% 2 13% 34% 34% 6%	760
	21st to end	Night	18% 7% 21% 31% 20% 4	760
October	1st to 10th	Night	14% 6% 24% 35% 19% 3	760
	11th to 20th	Night	20% 10% 30% 27% 10% 2	760
	21st to end	Night	23% 12% 29% 28% 8%	836
November	1st to 10th	Night	16% 12% 29% 29% 13% 1	760
	11th to 20th	Night	20% 16% 33% 23% 8% 1	760
	21st to end	Night	24% 14% 31% 24% 6%	760
December	1st to 10th	Night	26% 16% 33% 21% 4	760
	11th to 20th	Night	25% 15% 35% 22% 4	760
	21st to end	Night	26% 17% 33% 21% 3	836

Page generated at 2024-11-03 02:11:30. Version ac07

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