Rabbit Hole Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rabbit Hole Observatory clear sky chart from 2005-11-06 to 2024-03-06.

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% 9% 4 6% 6% 3 5% 5% 6% 8% 35%	78906
	Night	15% 9% 3 6% 5% 3 4 5% 5% 7% 37%	80621
Transparency	Day	47% 8% 10% 18% 13% 2	78629
	Night	46% 8% 11% 19% 14% 3	80417
Seeing	Day	18% 12% 21% 23% 17% 8%	14063
	Night	18% 9% 21% 31% 18% 2	24247

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% 15% 9% 9% 6% 2 3 4 4 6% 27%	2836
	11th to 20th	Day	15% 16% 8% 10% 8% 4 3 4 4 4 25%	2840
	21st to end	Day	17% 18% 4 7% 5% 3 4 4 4 5% 29%	3124
February	1st to 10th	Day	17% 12% 5% 7% 6% 3 4 4 4 7% 31%	1762
	11th to 20th	Day	21% 13% 6% 8% 4 3 3 3 4 6% 29%	1848
	21st to end	Day	22% 11% 4 6% 5% 3 3 3 4 7% 32%	1570
March	1st to 10th	Day	14% 11% 4 5% 4 3 4 4 5% 6% 40%	1985
	11th to 20th	Day	20% 10% 4 6% 5% 3 5% 5% 5% 6% 32%	1980
	21st to end	Day	19% 11% 3 6% 5% 3 5% 4 5% 7% 33%	2178
April	1st to 10th	Day	13% 8% 2 5% 5% 3 5% 4 7% 8% 40%	1980
	11th to 20th	Day	15% 6% 2 5% 4 3 4 5% 5% 7% 41%	2173
	21st to end	Day	16% 6% 2 5% 6% 4 5% 6% 5% 7% 38%	2340
May	1st to 10th	Day	16% 5% 3 6% 6% 4 6% 5% 6% 8% 35%	2340
	11th to 20th	Day	17% 6% 3 7% 7% 4 6% 6% 6% 7% 31%	2301
	21st to end	Day	12% 6% 3 6% 6% 4 6% 6% 7% 11% 34%	2531
June	1st to 10th	Day	11% 6% 3 5% 6% 4 6% 7% 6% 10% 35%	2340
	11th to 20th	Day	7% 6% 3 7% 7% 5% 8% 7% 8% 10% 32%	2340
	21st to end	Day	10% 6% 3 6% 6% 3 7% 7% 9% 9% 33%	2340
July	1st to 10th	Day	10% 6% 3 8% 8% 4 7% 7% 8% 9% 30%	2340
	11th to 20th	Day	12% 6% 3 6% 9% 4 6% 6% 7% 10% 30%	2340
	21st to end	Day	12% 7% 3 7% 7% 5% 7% 7% 8% 10% 27%	2547
August	1st to 10th	Day	11% 6% 3 6% 7% 4 7% 8% 7% 12% 29%	2327
	11th to 20th	Day	14% 5% 3 7% 8% 5% 8% 7% 7% 8% 29%	2303
	21st to end	Day	10% 7% 2 5% 7% 4 6% 7% 8% 8% 36%	2423
September	1st to 10th	Day	9% 5% 2 7% 6% 4 6% 6% 6% 8% 41%	1980
	11th to 20th	Day	14% 6% 2 5% 5% 3 6% 6% 5% 7% 40%	1980
	21st to end	Day	14% 6% 3 6% 7% 3 4 5% 6% 7% 40%	1980
October	1st to 10th	Day	14% 5% 2 4 4 2 4 4 5% 6% 49%	1936
	11th to 20th	Day	15% 6% 2 4 4 3 4 3 5% 7% 48%	1800
	21st to end	Day	17% 8% 2 4 3 2 3 4 4 7% 46%	1980
November	1st to 10th	Day	13% 5% 2 4 4 2 3 3 4 7% 53%	1755
	11th to 20th	Day	12% 8% 3 5% 4 4 4 5% 5% 7% 45%	1710
	21st to end	Day	15% 8% 4 5% 4 2 4 4 5% 7% 43%	1710
December	1st to 10th	Day	18% 14% 4 6% 5% 3 5% 5% 4 5% 32%	1710
	11th to 20th	Day	16% 14% 3 5% 4 2 4 5% 5% 8% 33%	2153
	21st to end	Day	13% 15% 5% 6% 7% 4 6% 5% 5% 6% 28%	3124
January	1st to 10th	Night	18% 17% 6% 8% 5% 2 4 4 4 5% 27%	4109
	11th to 20th	Night	18% 12% 3 8% 6% 3 4 3 4 5% 32%	4120
	21st to end	Night	20% 12% 5% 6% 6% 2 4 4 4 5% 32%	4532
February	1st to 10th	Night	16% 11% 3 6% 5% 2 5% 4 5% 7% 36%	2414
	11th to 20th	Night	21% 11% 5% 7% 5% 3 3 4 5% 5% 31%	2218
	21st to end	Night	20% 12% 4 8% 4 2 4 5% 4 6% 32%	1884
March	1st to 10th	Night	15% 13% 3 6% 5% 2 4 3 4 5% 40%	2090
	11th to 20th	Night	18% 11% 4 6% 4 4 4 5% 5% 7% 33%	1980
	21st to end	Night	16% 9% 4 4 5% 4 4 4 5% 7% 37%	2178
April	1st to 10th	Night	14% 7% 3 5% 4 3 4 4 4 8% 42%	1980
	11th to 20th	Night	14% 7% 2 5% 5% 3 5% 5% 5% 7% 43%	1748
	21st to end	Night	15% 7% 2 6% 5% 4 5% 4 5% 6% 41%	1620
May	1st to 10th	Night	15% 6% 3 6% 6% 3 5% 4 6% 9% 36%	1620
	11th to 20th	Night	15% 6% 2 6% 6% 3 6% 5% 6% 10% 33%	1592
	21st to end	Night	10% 6% 2 6% 6% 4 6% 5% 7% 9% 39%	1744
June	1st to 10th	Night	10% 4 2 6% 7% 4 5% 5% 6% 12% 39%	1620
	11th to 20th	Night	6% 4 3 5% 7% 4 6% 6% 8% 12% 41%	1620
	21st to end	Night	9% 5% 3 6% 6% 4 5% 6% 7% 11% 39%	1620
July	1st to 10th	Night	10% 7% 3 5% 7% 4 5% 6% 7% 10% 36%	1620
	11th to 20th	Night	9% 5% 3 6% 5% 4 6% 7% 8% 11% 36%	1620
	21st to end	Night	9% 5% 4 6% 7% 4 7% 7% 8% 11% 32%	1771
August	1st to 10th	Night	9% 5% 2 5% 6% 4 5% 6% 7% 11% 39%	1611
	11th to 20th	Night	11% 6% 3 6% 8% 5% 6% 6% 7% 8% 35%	1598
	21st to end	Night	10% 5% 2 5% 6% 3 6% 6% 8% 11% 39%	1910
September	1st to 10th	Night	12% 5% 2 6% 5% 3 4 5% 6% 7% 44%	1980
	11th to 20th	Night	15% 7% 2 5% 5% 3 5% 4 5% 8% 41%	1980
	21st to end	Night	13% 5% 2 5% 5% 3 3 4 4 7% 49%	1980
October	1st to 10th	Night	15% 6% 2 5% 4 2 4 3 5% 6% 48%	2022
	11th to 20th	Night	16% 7% 2 4 3 2 3 4 5% 7% 48%	2160
	21st to end	Night	15% 7% 2 4 3 2 4 4 5% 7% 47%	2376
November	1st to 10th	Night	15% 7% 2 4 3 2 3 4 5% 6% 50%	2320
	11th to 20th	Night	13% 8% 3 4 4 2 4 4 6% 7% 45%	2470
	21st to end	Night	13% 8% 3 5% 4 3 4 4 5% 6% 47%	2470
December	1st to 10th	Night	19% 11% 5% 8% 5% 3 4 4 5% 6% 30%	2470
	11th to 20th	Night	18% 11% 4 8% 5% 3 3 4 4 5% 34%	3042
	21st to end	Night	14% 16% 6% 7% 6% 3 5% 5% 6% 8% 24%	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	57% 6% 5% 15% 14% 3	2837
	11th to 20th	Day	62% 5% 6% 12% 14% 1	2840
	21st to end	Day	58% 5% 6% 14% 16% 1	3124
February	1st to 10th	Day	55% 5% 7% 16% 15% 2	1762
	11th to 20th	Day	58% 5% 6% 15% 14% 2	1858
	21st to end	Day	54% 5% 7% 14% 15% 5%	1570
March	1st to 10th	Day	45% 5% 6% 22% 18% 4	1985
	11th to 20th	Day	53% 6% 9% 17% 11% 3	1980
	21st to end	Day	52% 6% 11% 21% 9% 1	2178
April	1st to 10th	Day	41% 7% 12% 23% 14% 3	1980
	11th to 20th	Day	42% 7% 8% 19% 20% 5%	2173
	21st to end	Day	46% 8% 10% 23% 11% 2	2340
May	1st to 10th	Day	46% 9% 12% 21% 11% 2	2340
	11th to 20th	Day	51% 10% 13% 18% 7% 1	2305
	21st to end	Day	43% 11% 15% 22% 9% 1	2531
June	1st to 10th	Day	42% 12% 15% 20% 10% 1	2340
	11th to 20th	Day	44% 13% 14% 15% 12% 1	2340
	21st to end	Day	43% 12% 13% 19% 12% 2	2340
July	1st to 10th	Day	46% 14% 14% 15% 9% 1	2275
	11th to 20th	Day	46% 15% 14% 12% 11% 2	2271
	21st to end	Day	48% 15% 13% 17% 7% 1	2405
August	1st to 10th	Day	46% 15% 15% 18% 7%	2314
	11th to 20th	Day	51% 13% 12% 14% 9%	2303
	21st to end	Day	44% 12% 13% 19% 11% 2	2423
September	1st to 10th	Day	41% 11% 13% 19% 13% 4	1980
	11th to 20th	Day	44% 10% 9% 21% 15% 2	1980
	21st to end	Day	42% 9% 11% 18% 15% 4	1980
October	1st to 10th	Day	37% 7% 9% 22% 22% 4	1936
	11th to 20th	Day	37% 6% 9% 24% 20% 5%	1800
	21st to end	Day	40% 5% 7% 23% 19% 5%	1980
November	1st to 10th	Day	34% 5% 7% 20% 28% 6%	1755
	11th to 20th	Day	40% 5% 7% 20% 22% 5%	1710
	21st to end	Day	42% 5% 8% 21% 19% 4	1710
December	1st to 10th	Day	55% 6% 8% 17% 12% 2	1710
	11th to 20th	Day	49% 5% 11% 15% 17% 3	2150
	21st to end	Day	56% 6% 8% 20% 9% 1	3124
January	1st to 10th	Night	60% 6% 6% 13% 12% 4	4109
	11th to 20th	Night	54% 6% 8% 12% 17% 3	4120
	21st to end	Night	55% 7% 7% 13% 16% 2	4532
February	1st to 10th	Night	50% 5% 9% 19% 15% 2	2414
	11th to 20th	Night	57% 5% 7% 16% 12% 4	2219
	21st to end	Night	54% 6% 8% 17% 12% 4	1884
March	1st to 10th	Night	48% 5% 8% 17% 19% 4	2090
	11th to 20th	Night	51% 7% 11% 19% 11% 2	1980
	21st to end	Night	48% 8% 10% 21% 12% 2	2178
April	1st to 10th	Night	42% 7% 12% 22% 14% 3	1980
	11th to 20th	Night	39% 7% 10% 21% 18% 5%	1748
	21st to end	Night	43% 5% 12% 26% 12% 1	1620
May	1st to 10th	Night	44% 10% 14% 22% 9% 1	1620
	11th to 20th	Night	44% 13% 15% 21% 6% 1	1593
	21st to end	Night	39% 12% 16% 23% 9% 1	1745
June	1st to 10th	Night	39% 12% 17% 20% 11% 1	1620
	11th to 20th	Night	35% 12% 21% 22% 10% 1	1620
	21st to end	Night	38% 14% 14% 20% 12% 3	1620
July	1st to 10th	Night	41% 11% 17% 17% 12% 1	1575
	11th to 20th	Night	37% 16% 21% 15% 9% 3	1566
	21st to end	Night	40% 14% 17% 20% 8%	1672
August	1st to 10th	Night	38% 13% 20% 20% 8% 1	1600
	11th to 20th	Night	43% 12% 16% 18% 10% 1	1598
	21st to end	Night	36% 12% 16% 24% 11% 1	1910
September	1st to 10th	Night	38% 9% 14% 21% 15% 3	1980
	11th to 20th	Night	41% 9% 12% 20% 17% 1	1980
	21st to end	Night	36% 8% 11% 24% 18% 3	1980
October	1st to 10th	Night	37% 6% 10% 20% 23% 4	2022
	11th to 20th	Night	36% 6% 9% 26% 18% 4	2160
	21st to end	Night	38% 5% 6% 22% 22% 6%	2376
November	1st to 10th	Night	36% 6% 8% 20% 24% 6%	2320
	11th to 20th	Night	39% 5% 7% 21% 22% 6%	2470
	21st to end	Night	40% 5% 6% 26% 19% 3	2470
December	1st to 10th	Night	56% 7% 8% 16% 11% 3	2470
	11th to 20th	Night	53% 5% 7% 15% 16% 3	3044
	21st to end	Night	57% 9% 8% 15% 11% 1	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	23% 30% 27% 17% 2	270
	11th to 20th	Day	32% 27% 24% 15% 2	270
	21st to end	Day	25% 27% 32% 11% 4	297
February	1st to 10th	Day	26% 21% 31% 17% 4	270
	11th to 20th	Day	36% 29% 25% 9% 1	270
	21st to end	Day	36% 23% 31% 9% 2	225
March	1st to 10th	Day	21% 22% 27% 22% 8% 1	390
	11th to 20th	Day	27% 20% 28% 20% 4 1	420
	21st to end	Day	26% 19% 25% 22% 8%	462
April	1st to 10th	Day	19% 19% 26% 23% 11% 2	420
	11th to 20th	Day	18% 16% 25% 25% 14% 3	412
	21st to end	Day	23% 13% 26% 21% 13% 4	420
May	1st to 10th	Day	20% 17% 26% 20% 12% 5%	423
	11th to 20th	Day	19% 9% 19% 29% 15% 9%	447
	21st to end	Day	14% 8% 18% 21% 24% 15%	485
June	1st to 10th	Day	12% 5% 19% 30% 24% 10%	450
	11th to 20th	Day	9% 7% 16% 28% 26% 14%	450
	21st to end	Day	13% 6% 22% 24% 23% 11%	450
July	1st to 10th	Day	14% 3 14% 24% 27% 19%	445
	11th to 20th	Day	11% 4 12% 27% 29% 16%	444
	21st to end	Day	12% 4 10% 31% 28% 15%	488
August	1st to 10th	Day	14% 4 16% 25% 25% 16%	446
	11th to 20th	Day	14% 4 12% 26% 28% 16%	439
	21st to end	Day	13% 3 9% 23% 31% 21%	495
September	1st to 10th	Day	10% 4 14% 24% 32% 17%	450
	11th to 20th	Day	15% 5% 10% 22% 32% 16%	450
	21st to end	Day	17% 8% 14% 27% 28% 6%	450
October	1st to 10th	Day	16% 8% 17% 30% 21% 9%	450
	11th to 20th	Day	15% 14% 22% 26% 20% 3	450
	21st to end	Day	22% 11% 21% 29% 14% 3	495
November	1st to 10th	Day	18% 12% 24% 28% 15% 3	353
	11th to 20th	Day	17% 21% 25% 27% 10%	270
	21st to end	Day	16% 19% 29% 25% 10% 1	270
December	1st to 10th	Day	29% 19% 30% 19% 4	270
	11th to 20th	Day	24% 17% 29% 23% 7% 1	270
	21st to end	Day	21% 23% 30% 18% 8%	297
January	1st to 10th	Night	23% 18% 26% 28% 4	760
	11th to 20th	Night	26% 15% 28% 26% 4	760
	21st to end	Night	22% 15% 33% 27% 3	836
February	1st to 10th	Night	22% 14% 29% 32% 4	760
	11th to 20th	Night	27% 17% 35% 20% 1	743
	21st to end	Night	26% 20% 31% 22% 1	628
March	1st to 10th	Night	21% 14% 30% 30% 5%	743
	11th to 20th	Night	23% 15% 28% 25% 8%	720
	21st to end	Night	20% 11% 30% 29% 9%	792
April	1st to 10th	Night	19% 15% 26% 30% 10%	720
	11th to 20th	Night	15% 12% 29% 30% 13%	615
	21st to end	Night	18% 7% 26% 39% 9% 1	540
May	1st to 10th	Night	16% 10% 26% 32% 15% 1	540
	11th to 20th	Night	17% 4 20% 36% 22% 2	531
	21st to end	Night	11% 2 13% 34% 35% 5%	584
June	1st to 10th	Night	10% 3 10% 41% 32% 4	540
	11th to 20th	Night	6% 3 13% 39% 33% 6%	540
	21st to end	Night	11% 2 13% 37% 34% 4	540
July	1st to 10th	Night	13% 2 9% 28% 43% 5%	525
	11th to 20th	Night	11% 2 6% 30% 43% 8%	522
	21st to end	Night	9% 3 7% 31% 41% 8%	591
August	1st to 10th	Night	10% 2 9% 28% 45% 6%	537
	11th to 20th	Night	12% 3 7% 31% 43% 4	534
	21st to end	Night	12% 2 5% 33% 40% 8%	638
September	1st to 10th	Night	12% 2 10% 31% 37% 8%	720
	11th to 20th	Night	18% 3 11% 27% 36% 6%	720
	21st to end	Night	16% 3 14% 34% 30% 2	720
October	1st to 10th	Night	17% 5% 16% 29% 27% 6%	720
	11th to 20th	Night	18% 6% 22% 34% 17% 2	720
	21st to end	Night	18% 9% 20% 37% 14% 2	792
November	1st to 10th	Night	17% 7% 19% 38% 17% 2	740
	11th to 20th	Night	19% 11% 21% 37% 11% 1	760
	21st to end	Night	18% 12% 25% 34% 10% 1	760
December	1st to 10th	Night	25% 13% 26% 30% 7%	760
	11th to 20th	Night	23% 11% 24% 35% 7% 1	760
	21st to end	Night	25% 14% 26% 31% 4	836

Page generated at 2024-03-03 05:28:58. Version ac07

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