Palomar East
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Palomar East clear sky chart from 2005-11-06 to 2024-11-30.

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	16% 7% 2 6% 4 4 4 4 5% 7% 40%	101548
	Night	16% 7% 2 6% 4 4 4 3 5% 6% 42%	98046
Transparency	Day	40% 7% 12% 22% 16% 2	105081
	Night	40% 6% 12% 23% 16% 3	102588
Seeing	Day	21% 16% 29% 22% 10% 3	15058
	Night	19% 13% 31% 27% 9% 1	24329

By Month

Percentage Cloud Cover NE (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% 7% 2 6% 4 4 4 4 5% 5% 45%	2517
	11th to 20th	Day	14% 10% 3 9% 6% 4 4 3 5% 6% 36%	2561
	21st to end	Day	22% 8% 3 7% 5% 4 4 3 4 5% 35%	3124
February	1st to 10th	Day	17% 6% 3 7% 5% 3 4 4 5% 6% 39%	1710
	11th to 20th	Day	17% 8% 2 7% 5% 4 4 2 5% 6% 40%	1806
	21st to end	Day	19% 9% 4 7% 4 3 4 3 5% 5% 38%	1570
March	1st to 10th	Day	25% 6% 3 6% 4 4 3 3 3 5% 37%	3116
	11th to 20th	Day	10% 5% 2 6% 5% 5% 5% 4 6% 8% 45%	3470
	21st to end	Day	21% 7% 2 5% 4 3 3 2 3 5% 43%	4056
April	1st to 10th	Day	16% 7% 3 7% 5% 4 4 3 6% 7% 40%	2280
	11th to 20th	Day	15% 7% 3 6% 4 4 4 4 5% 7% 41%	2254
	21st to end	Day	16% 5% 2 7% 5% 4 4 4 6% 7% 40%	2280
May	1st to 10th	Day	28% 8% 2 6% 4 4 4 3 5% 7% 28%	4067
	11th to 20th	Day	24% 9% 3 7% 5% 5% 5% 4 4 6% 29%	4398
	21st to end	Day	12% 6% 2 6% 4 4 4 4 6% 9% 43%	4837
June	1st to 10th	Day	13% 5% 2 6% 5% 5% 5% 4 8% 9% 38%	2660
	11th to 20th	Day	12% 7% 2 6% 5% 5% 6% 4 7% 9% 37%	2660
	21st to end	Day	11% 6% 1 5% 4 4 6% 5% 6% 10% 41%	2660
July	1st to 10th	Day	8% 5% 2 7% 5% 6% 6% 5% 7% 10% 37%	4440
	11th to 20th	Day	10% 6% 2 6% 4 5% 5% 4 7% 10% 40%	4440
	21st to end	Day	13% 9% 3 7% 6% 5% 5% 4 6% 8% 34%	4763
August	1st to 10th	Day	20% 5% 2 7% 5% 5% 5% 4 6% 7% 34%	4104
	11th to 20th	Day	13% 5% 2 6% 4 4 4 4 6% 8% 43%	3731
	21st to end	Day	12% 5% 2 5% 3 4 4 3 5% 8% 49%	4180
September	1st to 10th	Day	14% 6% 2 6% 4 4 4 3 6% 6% 45%	2280
	11th to 20th	Day	12% 5% 2 4 3 3 4 3 5% 8% 50%	2245
	21st to end	Day	19% 7% 3 6% 4 5% 4 3 5% 6% 38%	2090
October	1st to 10th	Day	18% 6% 2 6% 2 4 4 4 5% 6% 43%	1910
	11th to 20th	Day	15% 5% 2 4 3 4 4 3 5% 7% 48%	1900
	21st to end	Day	19% 6% 2 5% 3 3 3 3 5% 6% 45%	2012
November	1st to 10th	Day	12% 7% 2 5% 3 3 3 3 4 5% 53%	1761
	11th to 20th	Day	16% 5% 2 5% 3 3 3 4 5% 6% 48%	1800
	21st to end	Day	15% 6% 3 4 3 3 3 4 5% 8% 45%	1668
December	1st to 10th	Day	19% 8% 2 6% 4 4 3 3 6% 8% 38%	1520
	11th to 20th	Day	21% 6% 2 4 4 4 3 3 5% 6% 41%	1906
	21st to end	Day	17% 7% 3 6% 5% 5% 6% 4 6% 6% 35%	2772
January	1st to 10th	Night	16% 6% 2 6% 3 4 4 3 5% 6% 45%	4429
	11th to 20th	Night	18% 9% 2 6% 4 3 4 3 4 5% 43%	4397
	21st to end	Night	23% 10% 2 6% 4 3 3 3 4 5% 37%	4532
February	1st to 10th	Night	16% 9% 3 5% 4 4 4 4 4 6% 41%	2470
	11th to 20th	Night	18% 9% 3 6% 4 4 4 3 5% 5% 41%	2258
	21st to end	Night	18% 8% 3 6% 4 3 3 3 4 6% 43%	1884
March	1st to 10th	Night	23% 9% 2 6% 3 4 3 3 4 5% 37%	3724
	11th to 20th	Night	11% 5% 2 7% 4 4 4 3 5% 6% 49%	3486
	21st to end	Night	17% 9% 3 6% 3 3 3 2 4 4 45%	3575
April	1st to 10th	Night	17% 6% 2 6% 5% 5% 3 4 5% 7% 40%	1900
	11th to 20th	Night	15% 6% 3 7% 6% 3 4 4 5% 6% 41%	1875
	21st to end	Night	18% 6% 2 5% 3 3 3 3 5% 8% 44%	1900
May	1st to 10th	Night	23% 9% 3 7% 4 4 4 4 5% 8% 30%	2886
	11th to 20th	Night	24% 9% 3 7% 4 4 4 3 5% 6% 30%	2495
	21st to end	Night	13% 6% 2 6% 4 4 3 4 6% 10% 42%	2738
June	1st to 10th	Night	16% 6% 2 5% 5% 3 4 3 5% 8% 42%	1520
	11th to 20th	Night	11% 6% 3 5% 5% 5% 5% 4 5% 8% 41%	1520
	21st to end	Night	11% 3 3 6% 4 5% 5% 5% 7% 9% 43%	1520
July	1st to 10th	Night	9% 5% 2 7% 6% 5% 5% 5% 7% 10% 39%	2520
	11th to 20th	Night	12% 6% 3 6% 4 5% 6% 4 7% 10% 37%	2520
	21st to end	Night	15% 7% 3 6% 5% 4 5% 5% 7% 8% 36%	2787
August	1st to 10th	Night	22% 7% 3 6% 4 4 4 4 6% 8% 33%	2825
	11th to 20th	Night	13% 7% 3 6% 4 4 4 3 6% 7% 42%	3063
	21st to end	Night	11% 5% 2 5% 4 3 4 4 6% 7% 49%	3476
September	1st to 10th	Night	14% 6% 2 6% 4 4 4 3 5% 6% 46%	1900
	11th to 20th	Night	11% 6% 2 5% 3 3 3 2 4 6% 54%	1934
	21st to end	Night	18% 7% 2 6% 4 4 4 4 5% 6% 40%	2090
October	1st to 10th	Night	18% 7% 3 5% 4 4 3 3 4 5% 44%	2266
	11th to 20th	Night	15% 5% 1 4 3 3 3 3 5% 6% 51%	2280
	21st to end	Night	17% 7% 2 5% 2 3 3 3 5% 5% 47%	2584
November	1st to 10th	Night	11% 6% 2 5% 3 3 3 3 4 6% 54%	2537
	11th to 20th	Night	17% 6% 2 5% 3 3 4 3 4 5% 48%	2600
	21st to end	Night	14% 6% 2 5% 5% 4 4 4 6% 7% 44%	2723
December	1st to 10th	Night	20% 7% 3 5% 4 4 3 3 5% 7% 39%	2660
	11th to 20th	Night	17% 6% 2 6% 4 4 5% 3 5% 7% 40%	3288
	21st to end	Night	18% 8% 3 7% 4 4 4 4 5% 5% 38%	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	38% 6% 13% 27% 13% 3	2518
	11th to 20th	Day	45% 8% 12% 20% 13% 2	2561
	21st to end	Day	50% 6% 12% 21% 10% 1	3124
February	1st to 10th	Day	44% 6% 15% 23% 11% 2	1710
	11th to 20th	Day	44% 5% 10% 23% 15% 2	1815
	21st to end	Day	47% 6% 11% 21% 12% 3	1570
March	1st to 10th	Day	48% 6% 10% 25% 8% 2	3119
	11th to 20th	Day	33% 8% 13% 29% 15% 3	3470
	21st to end	Day	44% 5% 9% 17% 22% 4	4056
April	1st to 10th	Day	42% 7% 11% 21% 15% 5%	2280
	11th to 20th	Day	40% 6% 12% 22% 16% 4	2254
	21st to end	Day	41% 6% 12% 19% 18% 4	2280
May	1st to 10th	Day	53% 8% 12% 16% 10% 2	4080
	11th to 20th	Day	53% 9% 12% 17% 8% 1	4402
	21st to end	Day	34% 8% 13% 25% 17% 2	4837
June	1st to 10th	Day	39% 10% 14% 22% 14% 1	2660
	11th to 20th	Day	40% 9% 14% 24% 11% 2	2660
	21st to end	Day	36% 10% 15% 23% 16% 1	2660
July	1st to 10th	Day	39% 11% 15% 19% 14% 3	4370
	11th to 20th	Day	37% 8% 16% 23% 14% 1	4365
	21st to end	Day	46% 7% 10% 18% 17% 1	4611
August	1st to 10th	Day	47% 9% 12% 22% 10%	4091
	11th to 20th	Day	36% 7% 12% 29% 14% 1	3767
	21st to end	Day	34% 6% 10% 26% 22% 2	4180
September	1st to 10th	Day	39% 7% 11% 19% 21% 3	2280
	11th to 20th	Day	32% 5% 11% 24% 24% 4	2245
	21st to end	Day	47% 5% 8% 17% 20% 2	2090
October	1st to 10th	Day	37% 5% 9% 17% 27% 5%	3170
	11th to 20th	Day	25% 4 11% 25% 28% 6%	3140
	21st to end	Day	25% 4 13% 24% 29% 5%	3289
November	1st to 10th	Day	34% 4 13% 25% 21% 4	1761
	11th to 20th	Day	37% 5% 11% 25% 20% 3	1800
	21st to end	Day	37% 5% 15% 30% 11% 2	1668
December	1st to 10th	Day	44% 5% 17% 22% 12%	1520
	11th to 20th	Day	42% 7% 13% 26% 10% 2	1906
	21st to end	Day	45% 9% 13% 22% 11% 1	2772
January	1st to 10th	Night	39% 5% 12% 28% 12% 3	4429
	11th to 20th	Night	44% 4 12% 25% 12% 3	4397
	21st to end	Night	49% 4 9% 24% 12% 2	4532
February	1st to 10th	Night	43% 6% 13% 25% 11% 2	2470
	11th to 20th	Night	45% 5% 9% 19% 18% 4	2260
	21st to end	Night	43% 5% 8% 22% 17% 4	1884
March	1st to 10th	Night	48% 6% 9% 23% 12% 2	3734
	11th to 20th	Night	33% 7% 14% 27% 16% 3	3487
	21st to end	Night	43% 4 8% 17% 22% 6%	3575
April	1st to 10th	Night	42% 6% 11% 20% 16% 4	1900
	11th to 20th	Night	42% 6% 10% 20% 19% 3	1875
	21st to end	Night	40% 6% 10% 21% 19% 5%	1900
May	1st to 10th	Night	51% 10% 10% 19% 9% 1	2892
	11th to 20th	Night	52% 9% 14% 13% 10% 2	2496
	21st to end	Night	36% 10% 16% 21% 15% 3	2739
June	1st to 10th	Night	39% 8% 11% 21% 19% 2	1520
	11th to 20th	Night	38% 10% 13% 25% 13% 1	1520
	21st to end	Night	34% 10% 16% 25% 14% 2	1520
July	1st to 10th	Night	39% 10% 19% 16% 14% 2	2480
	11th to 20th	Night	39% 10% 16% 22% 11% 1	2472
	21st to end	Night	44% 8% 14% 18% 16% 1	2698
August	1st to 10th	Night	48% 8% 19% 16% 9% 1	2814
	11th to 20th	Night	40% 7% 13% 25% 14% 1	3093
	21st to end	Night	33% 6% 11% 28% 21% 2	3476
September	1st to 10th	Night	39% 6% 12% 19% 22% 3	1900
	11th to 20th	Night	32% 5% 11% 21% 27% 4	1934
	21st to end	Night	43% 6% 9% 20% 21% 2	2090
October	1st to 10th	Night	41% 5% 10% 21% 21% 2	3786
	11th to 20th	Night	24% 4 10% 29% 29% 4	3779
	21st to end	Night	27% 4 11% 31% 23% 4	4244
November	1st to 10th	Night	32% 5% 13% 24% 21% 5%	2537
	11th to 20th	Night	39% 4 9% 23% 20% 5%	2600
	21st to end	Night	38% 5% 13% 27% 15% 2	2723
December	1st to 10th	Night	45% 5% 12% 23% 13% 1	2660
	11th to 20th	Night	41% 7% 13% 20% 16% 3	3288
	21st to end	Night	44% 7% 13% 24% 11% 1	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	27% 27% 31% 12% 3 1	180
	11th to 20th	Day	35% 24% 31% 9% 2	193
	21st to end	Day	27% 27% 30% 12% 4	297
February	1st to 10th	Day	29% 27% 32% 9% 3	270
	11th to 20th	Day	29% 25% 34% 11% 1	414
	21st to end	Day	30% 24% 31% 13% 2	382
March	1st to 10th	Day	29% 21% 31% 15% 4	460
	11th to 20th	Day	26% 26% 31% 14% 2 2	460
	21st to end	Day	29% 24% 30% 12% 5% 1	506
April	1st to 10th	Day	28% 23% 29% 14% 5% 1	460
	11th to 20th	Day	22% 26% 30% 14% 6% 2	452
	21st to end	Day	23% 20% 33% 18% 4 2	460
May	1st to 10th	Day	28% 19% 30% 15% 6% 2	463
	11th to 20th	Day	23% 15% 30% 23% 7% 2	487
	21st to end	Day	18% 9% 27% 28% 15% 3	529
June	1st to 10th	Day	15% 13% 31% 25% 12% 3	490
	11th to 20th	Day	16% 12% 28% 28% 12% 3	490
	21st to end	Day	16% 12% 30% 28% 12% 3	490
July	1st to 10th	Day	11% 6% 24% 31% 20% 7%	485
	11th to 20th	Day	9% 4 26% 35% 23% 4	484
	21st to end	Day	14% 7% 28% 32% 15% 4	532
August	1st to 10th	Day	12% 5% 27% 33% 17% 6%	486
	11th to 20th	Day	13% 6% 22% 35% 19% 6%	479
	21st to end	Day	13% 8% 25% 29% 16% 8%	539
September	1st to 10th	Day	17% 11% 24% 26% 16% 7%	490
	11th to 20th	Day	15% 5% 27% 29% 14% 10%	490
	21st to end	Day	25% 14% 22% 24% 11% 5%	490
October	1st to 10th	Day	23% 9% 27% 21% 12% 7%	490
	11th to 20th	Day	17% 16% 31% 23% 10% 3	490
	21st to end	Day	22% 17% 31% 18% 11% 2	497
November	1st to 10th	Day	19% 13% 34% 22% 11% 3	395
	11th to 20th	Day	21% 20% 34% 21% 4 1	400
	21st to end	Day	24% 21% 34% 16% 4	270
December	1st to 10th	Day	28% 27% 30% 9% 7%	180
	11th to 20th	Day	34% 23% 28% 11% 4	180
	21st to end	Day	28% 22% 31% 13% 6% 1	198
January	1st to 10th	Night	20% 22% 35% 20% 3	760
	11th to 20th	Night	24% 18% 32% 22% 3	760
	21st to end	Night	18% 21% 37% 22% 1	836
February	1st to 10th	Night	21% 17% 39% 22% 1	760
	11th to 20th	Night	26% 23% 35% 15% 1	743
	21st to end	Night	24% 20% 38% 16% 2	628
March	1st to 10th	Night	24% 19% 34% 20% 3	760
	11th to 20th	Night	23% 21% 34% 17% 4	760
	21st to end	Night	22% 15% 39% 19% 5%	836
April	1st to 10th	Night	21% 19% 39% 16% 5%	760
	11th to 20th	Night	18% 17% 38% 22% 6%	751
	21st to end	Night	22% 13% 34% 25% 5%	760
May	1st to 10th	Night	23% 14% 32% 25% 6%	609
	11th to 20th	Night	20% 9% 39% 26% 6%	374
	21st to end	Night	16% 6% 26% 38% 12% 1	411
June	1st to 10th	Night	17% 6% 28% 37% 12%	380
	11th to 20th	Night	10% 7% 30% 40% 12% 1	380
	21st to end	Night	9% 4 27% 49% 11%	380
July	1st to 10th	Night	12% 2 24% 43% 17% 1	370
	11th to 20th	Night	8% 3 22% 44% 20% 2	368
	21st to end	Night	9% 2 28% 41% 19% 1	440
August	1st to 10th	Night	14% 1 16% 45% 21% 2	567
	11th to 20th	Night	14% 4 19% 37% 24% 2	728
	21st to end	Night	15% 4 17% 38% 23% 2	836
September	1st to 10th	Night	16% 4 25% 36% 16% 2	760
	11th to 20th	Night	14% 5% 22% 35% 20% 4	760
	21st to end	Night	22% 5% 23% 31% 18% 1	760
October	1st to 10th	Night	21% 8% 26% 25% 16% 4	760
	11th to 20th	Night	17% 11% 27% 32% 13%	760
	21st to end	Night	21% 13% 32% 26% 8%	836
November	1st to 10th	Night	16% 10% 35% 28% 11% 1	780
	11th to 20th	Night	22% 16% 29% 26% 7% 1	800
	21st to end	Night	18% 17% 35% 25% 6% 1	800
December	1st to 10th	Night	25% 17% 32% 19% 6% 1	760
	11th to 20th	Night	21% 15% 36% 23% 5%	760
	21st to end	Night	21% 17% 34% 26% 3	836

Page generated at 2024-11-27 17:30:54. Version ac07

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