Quiet Pond Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Quiet Pond Observatory clear sky chart from 2005-11-06 to 2025-02-21.

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% 6% 2 5% 4 4 4 4 6% 8% 45%	108633
	Night	15% 6% 2 6% 4 4 4 3 5% 7% 44%	109961
Transparency	Day	21% 45% 7% 15% 10% 2	112266
	Night	23% 43% 7% 14% 11% 2	114467
Seeing	Day	16% 8% 25% 27% 18% 6%	15315
	Night	17% 9% 29% 29% 14% 2	24857

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	14% 5% 1 4 3 3 3 3 5% 6% 53%	3597
	11th to 20th	Day	14% 9% 3 8% 3 4 3 2 3 4 47%	3985
	21st to end	Day	16% 6% 2 5% 4 4 4 3 5% 6% 46%	4466
February	1st to 10th	Day	16% 7% 2 6% 4 4 5% 4 5% 8% 40%	1800
	11th to 20th	Day	18% 7% 2 5% 4 3 4 2 6% 7% 41%	1864
	21st to end	Day	18% 9% 2 6% 4 3 3 3 5% 6% 40%	1570
March	1st to 10th	Day	22% 6% 2 4 3 3 4 3 5% 7% 41%	3265
	11th to 20th	Day	10% 4 2 4 4 4 4 4 5% 7% 51%	3480
	21st to end	Day	21% 6% 2 5% 4 3 3 3 4 5% 44%	3961
April	1st to 10th	Day	14% 6% 2 5% 3 4 4 4 6% 7% 44%	2280
	11th to 20th	Day	12% 6% 2 5% 3 3 4 4 6% 6% 49%	2254
	21st to end	Day	16% 6% 2 5% 3 3 4 4 5% 8% 44%	2280
May	1st to 10th	Day	24% 7% 2 6% 4 4 4 4 5% 8% 33%	3918
	11th to 20th	Day	21% 7% 3 6% 4 4 5% 4 6% 8% 34%	4398
	21st to end	Day	11% 4 2 5% 3 4 4 3 7% 9% 48%	4823
June	1st to 10th	Day	10% 4 2 5% 5% 3 5% 5% 7% 10% 44%	2660
	11th to 20th	Day	10% 4 2 5% 4 4 5% 4 8% 10% 44%	2660
	21st to end	Day	9% 4 1 4 3 3 5% 4 7% 11% 48%	2660
July	1st to 10th	Day	5% 3 2 5% 5% 5% 6% 5% 8% 11% 45%	4440
	11th to 20th	Day	9% 5% 2 5% 4 4 5% 5% 8% 11% 42%	4440
	21st to end	Day	9% 6% 2 6% 4 5% 6% 5% 8% 9% 39%	4503
August	1st to 10th	Day	15% 6% 2 6% 4 3 5% 4 9% 10% 37%	4104
	11th to 20th	Day	10% 4 2 6% 5% 4 4 4 6% 9% 46%	3790
	21st to end	Day	8% 4 2 5% 4 4 4 4 6% 8% 50%	4180
September	1st to 10th	Day	13% 5% 2 5% 4 4 4 3 5% 8% 48%	2280
	11th to 20th	Day	11% 6% 1 5% 3 3 4 2 5% 7% 51%	2280
	21st to end	Day	19% 8% 2 6% 4 3 5% 4 5% 7% 39%	2032
October	1st to 10th	Day	16% 5% 1 6% 3 3 3 3 4 7% 49%	1900
	11th to 20th	Day	15% 5% 2 4 2 3 3 3 5% 6% 53%	1900
	21st to end	Day	14% 6% 2 5% 3 3 3 3 4 6% 50%	2090
November	1st to 10th	Day	13% 6% 1 4 3 3 4 2 5% 7% 52%	1781
	11th to 20th	Day	13% 5% 2 4 4 4 4 4 5% 7% 49%	1800
	21st to end	Day	14% 6% 2 4 5% 3 4 3 5% 5% 49%	1642
December	1st to 10th	Day	11% 5% 3 6% 4 3 2 4 5% 8% 49%	2600
	11th to 20th	Day	18% 9% 2 6% 3 3 3 3 4 7% 43%	2990
	21st to end	Day	13% 7% 2 6% 4 4 4 3 5% 8% 43%	3960
January	1st to 10th	Night	14% 7% 2 5% 4 4 4 3 5% 6% 48%	6349
	11th to 20th	Night	13% 7% 2 5% 3 3 3 3 4 5% 51%	5974
	21st to end	Night	16% 7% 2 6% 3 4 3 3 4 5% 46%	6490
February	1st to 10th	Night	17% 7% 2 6% 4 4 4 3 5% 6% 41%	2600
	11th to 20th	Night	20% 7% 3 5% 3 4 3 3 5% 6% 42%	2421
	21st to end	Night	18% 8% 2 6% 3 3 4 3 5% 6% 43%	1885
March	1st to 10th	Night	21% 8% 3 6% 3 3 4 3 4 6% 39%	3585
	11th to 20th	Night	12% 5% 2 5% 4 4 4 4 6% 7% 49%	3480
	21st to end	Night	16% 8% 3 6% 4 3 3 3 4 5% 46%	3670
April	1st to 10th	Night	16% 7% 2 5% 5% 4 4 3 5% 7% 42%	1900
	11th to 20th	Night	12% 6% 2 6% 5% 4 4 4 5% 7% 45%	1875
	21st to end	Night	19% 5% 2 4 3 3 4 3 5% 7% 44%	1900
May	1st to 10th	Night	21% 7% 3 7% 5% 4 4 5% 5% 7% 32%	2990
	11th to 20th	Night	22% 8% 3 7% 4 4 5% 4 5% 6% 31%	2495
	21st to end	Night	11% 5% 2 6% 4 4 5% 4 5% 9% 44%	2732
June	1st to 10th	Night	11% 4 3 5% 5% 4 4 3 6% 10% 45%	1520
	11th to 20th	Night	9% 6% 3 6% 5% 5% 4 5% 8% 9% 41%	1520
	21st to end	Night	10% 4 2 5% 5% 5% 5% 4 7% 11% 42%	1520
July	1st to 10th	Night	7% 5% 2 7% 5% 6% 6% 5% 8% 9% 40%	2520
	11th to 20th	Night	10% 5% 2 6% 6% 5% 5% 4 8% 10% 39%	2520
	21st to end	Night	13% 8% 3 7% 5% 5% 5% 5% 6% 8% 36%	3045
August	1st to 10th	Night	18% 6% 3 6% 4 5% 6% 4 7% 10% 32%	2825
	11th to 20th	Night	11% 7% 3 8% 5% 5% 6% 4 7% 8% 36%	3007
	21st to end	Night	9% 5% 2 6% 4 4 5% 3 5% 9% 48%	3476
September	1st to 10th	Night	14% 6% 2 5% 5% 4 4 3 6% 7% 45%	1900
	11th to 20th	Night	10% 5% 2 5% 4 4 4 3 4 8% 50%	1900
	21st to end	Night	19% 7% 3 6% 5% 4 4 3 5% 6% 39%	2144
October	1st to 10th	Night	18% 7% 2 6% 3 3 4 3 4 6% 43%	2280
	11th to 20th	Night	15% 5% 2 5% 3 2 3 3 5% 6% 51%	2280
	21st to end	Night	17% 5% 2 4 4 3 3 3 4 6% 50%	2508
November	1st to 10th	Night	11% 5% 2 5% 4 3 4 3 5% 6% 52%	2514
	11th to 20th	Night	16% 6% 2 5% 4 3 3 3 4 6% 47%	2600
	21st to end	Night	13% 5% 2 5% 4 4 4 4 5% 6% 49%	2755
December	1st to 10th	Night	11% 5% 2 5% 3 4 3 3 5% 7% 50%	4580
	11th to 20th	Night	21% 6% 2 5% 4 3 4 3 6% 7% 39%	5205
	21st to end	Night	16% 7% 2 6% 4 4 4 4 6% 7% 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	23% 27% 4 21% 21% 4	3598
	11th to 20th	Day	31% 27% 4 17% 15% 6%	3985
	21st to end	Day	29% 30% 8% 21% 10% 2	4466
February	1st to 10th	Day	18% 63% 7% 8% 3 1	1800
	11th to 20th	Day	18% 61% 3 9% 7% 1	1873
	21st to end	Day	18% 65% 4 6% 6% 1	1570
March	1st to 10th	Day	31% 43% 4 13% 6% 3	3265
	11th to 20th	Day	15% 42% 5% 22% 14% 2	3480
	21st to end	Day	27% 42% 5% 11% 13% 3	3961
April	1st to 10th	Day	15% 66% 4 7% 6% 1	2280
	11th to 20th	Day	12% 67% 5% 9% 6% 1	2254
	21st to end	Day	14% 65% 5% 9% 6% 1	2280
May	1st to 10th	Day	35% 43% 6% 12% 3 1	3953
	11th to 20th	Day	32% 43% 10% 12% 2	4402
	21st to end	Day	18% 43% 9% 17% 13% 1	4837
June	1st to 10th	Day	13% 67% 4 9% 6%	2660
	11th to 20th	Day	10% 67% 4 10% 7% 1	2660
	21st to end	Day	10% 65% 7% 10% 8% 1	2660
July	1st to 10th	Day	21% 41% 19% 8% 8% 4	4370
	11th to 20th	Day	25% 39% 13% 18% 5% 1	4365
	21st to end	Day	27% 39% 9% 14% 10% 1	4359
August	1st to 10th	Day	27% 39% 12% 18% 3	4091
	11th to 20th	Day	21% 39% 9% 23% 8%	3828
	21st to end	Day	17% 38% 9% 21% 14% 1	4180
September	1st to 10th	Day	15% 61% 7% 10% 6% 2	2280
	11th to 20th	Day	13% 61% 5% 10% 9% 2	2280
	21st to end	Day	22% 60% 3 9% 4 1	2032
October	1st to 10th	Day	22% 37% 5% 12% 21% 4	3160
	11th to 20th	Day	11% 36% 4 19% 22% 8%	3140
	21st to end	Day	8% 36% 6% 23% 20% 7%	3428
November	1st to 10th	Day	16% 56% 7% 10% 7% 3	1781
	11th to 20th	Day	13% 58% 4 12% 12% 2	1800
	21st to end	Day	15% 57% 4 16% 8% 1	1642
December	1st to 10th	Day	23% 36% 13% 17% 8% 3	2600
	11th to 20th	Day	29% 33% 8% 21% 7% 2	2986
	21st to end	Day	29% 29% 12% 16% 13% 1	3960
January	1st to 10th	Night	28% 27% 5% 17% 19% 4	6349
	11th to 20th	Night	25% 26% 6% 20% 16% 7%	5974
	21st to end	Night	30% 29% 5% 21% 14% 1	6490
February	1st to 10th	Night	17% 63% 6% 9% 4 1	2600
	11th to 20th	Night	18% 60% 2 9% 10% 1	2423
	21st to end	Night	15% 64% 4 9% 5% 3	1885
March	1st to 10th	Night	33% 42% 4 14% 6% 1	3585
	11th to 20th	Night	16% 42% 7% 21% 12% 3	3480
	21st to end	Night	24% 41% 5% 12% 15% 3	3670
April	1st to 10th	Night	15% 65% 3 8% 7% 1	1900
	11th to 20th	Night	14% 66% 4 9% 5% 2	1875
	21st to end	Night	15% 66% 4 7% 7% 1	1900
May	1st to 10th	Night	34% 44% 6% 12% 4	3020
	11th to 20th	Night	34% 43% 9% 11% 2	2496
	21st to end	Night	21% 43% 10% 13% 11% 2	2739
June	1st to 10th	Night	14% 66% 4 8% 7%	1520
	11th to 20th	Night	13% 66% 4 11% 6%	1520
	21st to end	Night	11% 64% 6% 11% 6% 1	1520
July	1st to 10th	Night	24% 41% 16% 10% 8% 1	2480
	11th to 20th	Night	27% 37% 15% 16% 4 1	2472
	21st to end	Night	34% 37% 8% 12% 9%	2948
August	1st to 10th	Night	33% 40% 12% 12% 4	2814
	11th to 20th	Night	26% 40% 7% 21% 6%	3035
	21st to end	Night	19% 38% 6% 21% 16% 1	3476
September	1st to 10th	Night	15% 61% 7% 10% 5% 2	1900
	11th to 20th	Night	13% 61% 3 10% 10% 2	1900
	21st to end	Night	22% 61% 4 8% 5%	2144
October	1st to 10th	Night	27% 38% 6% 13% 13% 3	3800
	11th to 20th	Night	10% 37% 8% 12% 26% 7%	3779
	21st to end	Night	10% 36% 7% 23% 18% 6%	4120
November	1st to 10th	Night	16% 57% 6% 11% 8% 3	2514
	11th to 20th	Night	16% 57% 4 10% 11% 3	2600
	21st to end	Night	14% 57% 5% 13% 9% 1	2755
December	1st to 10th	Night	20% 36% 9% 21% 12% 2	4580
	11th to 20th	Night	31% 32% 9% 13% 11% 4	5208
	21st to end	Night	32% 29% 9% 15% 14% 1	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	17% 19% 40% 18% 7% 1	200
	11th to 20th	Day	17% 21% 35% 23% 4	283
	21st to end	Day	18% 15% 38% 22% 6% 1	330
February	1st to 10th	Day	21% 10% 42% 19% 8%	300
	11th to 20th	Day	26% 16% 41% 16% 2	412
	21st to end	Day	24% 14% 37% 20% 5%	382
March	1st to 10th	Day	18% 18% 34% 22% 7% 1	460
	11th to 20th	Day	19% 15% 33% 24% 7% 2	460
	21st to end	Day	21% 11% 36% 25% 6% 2	506
April	1st to 10th	Day	18% 13% 37% 23% 8% 1	460
	11th to 20th	Day	13% 15% 31% 25% 11% 5%	452
	21st to end	Day	19% 11% 30% 27% 12% 2	460
May	1st to 10th	Day	22% 9% 30% 25% 12% 2	463
	11th to 20th	Day	18% 6% 27% 28% 15% 5%	487
	21st to end	Day	16% 4 19% 26% 25% 10%	529
June	1st to 10th	Day	11% 4 24% 26% 24% 10%	490
	11th to 20th	Day	11% 5% 19% 28% 26% 11%	490
	21st to end	Day	10% 2 17% 36% 28% 8%	490
July	1st to 10th	Day	9% 2 10% 31% 34% 15%	485
	11th to 20th	Day	5% 1 6% 37% 37% 14%	484
	21st to end	Day	10% 3 12% 33% 33% 10%	532
August	1st to 10th	Day	11% 2 9% 31% 34% 13%	486
	11th to 20th	Day	10% 3 12% 31% 33% 13%	479
	21st to end	Day	8% 2 15% 28% 30% 16%	539
September	1st to 10th	Day	17% 3 15% 23% 28% 14%	490
	11th to 20th	Day	12% 3 14% 29% 29% 12%	490
	21st to end	Day	25% 6% 20% 28% 17% 4	490
October	1st to 10th	Day	20% 6% 16% 28% 21% 9%	490
	11th to 20th	Day	15% 8% 26% 28% 17% 5%	490
	21st to end	Day	16% 8% 30% 28% 13% 6%	539
November	1st to 10th	Day	15% 9% 32% 25% 13% 5%	405
	11th to 20th	Day	13% 14% 34% 28% 10% 2	400
	21st to end	Day	14% 17% 33% 21% 13% 2	242
December	1st to 10th	Day	18% 12% 35% 26% 8% 2	200
	11th to 20th	Day	21% 15% 32% 23% 11%	200
	21st to end	Day	20% 12% 29% 29% 10% 1	220
January	1st to 10th	Night	19% 17% 41% 20% 3	800
	11th to 20th	Night	21% 15% 33% 27% 5%	800
	21st to end	Night	18% 15% 38% 26% 3	880
February	1st to 10th	Night	20% 12% 36% 28% 4	800
	11th to 20th	Night	23% 17% 39% 19% 1	783
	21st to end	Night	22% 15% 38% 22% 3	629
March	1st to 10th	Night	17% 14% 39% 24% 5%	760
	11th to 20th	Night	19% 14% 36% 23% 6% 1	760
	21st to end	Night	18% 10% 39% 27% 6% 1	836
April	1st to 10th	Night	20% 12% 40% 22% 6%	760
	11th to 20th	Night	15% 9% 34% 32% 10%	751
	21st to end	Night	20% 8% 34% 27% 11% 1	760
May	1st to 10th	Night	18% 8% 28% 32% 13% 1	685
	11th to 20th	Night	19% 6% 27% 32% 14% 1	374
	21st to end	Night	13% 4 19% 37% 25% 2	411
June	1st to 10th	Night	12% 2 24% 38% 24% 1	380
	11th to 20th	Night	8% 4 22% 41% 23% 1	380
	21st to end	Night	11% 1 19% 45% 22% 3	380
July	1st to 10th	Night	9% 2 16% 36% 33% 4	370
	11th to 20th	Night	7% 1 11% 41% 38% 3	368
	21st to end	Night	9% 2 15% 41% 31% 3	595
August	1st to 10th	Night	11% 2 10% 41% 32% 3	567
	11th to 20th	Night	11% 3 15% 34% 32% 5%	696
	21st to end	Night	12% 2 12% 35% 31% 7%	836
September	1st to 10th	Night	16% 3 14% 32% 29% 5%	760
	11th to 20th	Night	11% 4 14% 34% 32% 6%	760
	21st to end	Night	22% 5% 19% 30% 21% 3	760
October	1st to 10th	Night	21% 5% 22% 27% 20% 5%	760
	11th to 20th	Night	17% 8% 27% 30% 16% 2	760
	21st to end	Night	18% 10% 29% 26% 16% 1	836
November	1st to 10th	Night	14% 7% 32% 32% 13% 2	780
	11th to 20th	Night	19% 13% 31% 27% 9%	800
	21st to end	Night	16% 14% 34% 27% 8% 1	800
December	1st to 10th	Night	21% 14% 33% 23% 9% 1	800
	11th to 20th	Night	18% 12% 39% 25% 6%	800
	21st to end	Night	18% 10% 35% 32% 4	880

Page generated at 2025-02-18 03:26:28. Version ac07

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