Park Place Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Park Place Observatory clear sky chart from 2005-11-06 to 2024-11-25.

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	17% 7% 2 6% 4 4 5% 4 6% 7% 38%	101560
	Night	18% 7% 2 6% 4 4 4 3 5% 7% 41%	97907
Transparency	Day	42% 7% 13% 22% 14% 2	105109
	Night	42% 6% 12% 23% 15% 2	102447
Seeing	Day	21% 16% 28% 21% 11% 3	14967
	Night	20% 12% 30% 28% 10% 1	24240

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% 8% 2 5% 4 4 4 3 5% 5% 43%	2517
	11th to 20th	Day	14% 11% 6% 9% 6% 5% 5% 4 6% 6% 28%	2581
	21st to end	Day	21% 11% 4 7% 4 4 4 4 4 5% 32%	3124
February	1st to 10th	Day	16% 7% 3 7% 6% 5% 5% 4 6% 8% 34%	1710
	11th to 20th	Day	15% 8% 2 6% 5% 4 5% 4 6% 7% 38%	1770
	21st to end	Day	20% 8% 3 6% 5% 5% 4 4 6% 6% 35%	1570
March	1st to 10th	Day	27% 7% 2 6% 4 4 4 3 5% 6% 34%	3148
	11th to 20th	Day	10% 5% 2 6% 6% 5% 5% 4 6% 8% 43%	3480
	21st to end	Day	21% 8% 2 5% 3 3 3 3 4 6% 42%	4024
April	1st to 10th	Day	17% 8% 3 6% 4 5% 5% 3 7% 7% 35%	2280
	11th to 20th	Day	17% 7% 2 6% 4 5% 4 3 6% 6% 39%	2254
	21st to end	Day	17% 6% 2 6% 4 4 4 5% 7% 7% 38%	2280
May	1st to 10th	Day	28% 7% 2 6% 3 4 4 4 5% 7% 30%	4150
	11th to 20th	Day	25% 8% 3 8% 5% 5% 4 4 5% 6% 28%	4398
	21st to end	Day	14% 5% 2 4 4 4 5% 4 7% 9% 43%	4837
June	1st to 10th	Day	14% 6% 2 6% 5% 5% 5% 5% 7% 9% 37%	2660
	11th to 20th	Day	15% 5% 2 6% 4 5% 6% 5% 7% 9% 36%	2660
	21st to end	Day	12% 6% 2 5% 5% 4 5% 4 6% 9% 41%	2660
July	1st to 10th	Day	8% 5% 2 7% 6% 5% 6% 5% 8% 10% 36%	4440
	11th to 20th	Day	10% 6% 2 6% 5% 5% 5% 5% 7% 10% 40%	4440
	21st to end	Day	13% 8% 3 7% 6% 5% 6% 4 6% 8% 33%	4739
August	1st to 10th	Day	21% 6% 2 7% 4 5% 6% 4 7% 8% 31%	4104
	11th to 20th	Day	14% 5% 3 6% 5% 4 5% 4 7% 9% 40%	3793
	21st to end	Day	15% 5% 2 4 3 3 4 3 6% 9% 46%	4180
September	1st to 10th	Day	17% 4 2 5% 5% 4 5% 3 5% 7% 42%	2280
	11th to 20th	Day	14% 4 2 5% 3 3 4 3 6% 6% 51%	2266
	21st to end	Day	21% 8% 2 5% 3 3 4 3 5% 5% 39%	2062
October	1st to 10th	Day	19% 6% 2 5% 3 4 4 3 6% 6% 41%	1900
	11th to 20th	Day	17% 5% 2 4 4 4 5% 3 5% 7% 45%	1900
	21st to end	Day	20% 6% 3 5% 3 3 4 4 5% 7% 40%	2027
November	1st to 10th	Day	14% 7% 2 4 2 3 3 2 3 7% 52%	1761
	11th to 20th	Day	17% 6% 2 5% 4 4 4 4 6% 6% 43%	1800
	21st to end	Day	18% 6% 2 5% 3 4 3 4 6% 7% 41%	1567
December	1st to 10th	Day	20% 8% 2 7% 5% 5% 4 4 5% 6% 34%	1520
	11th to 20th	Day	21% 7% 2 5% 4 4 4 5% 6% 6% 38%	1906
	21st to end	Day	20% 9% 4 8% 6% 4 5% 4 6% 6% 28%	2772
January	1st to 10th	Night	16% 6% 2 6% 5% 3 4 3 5% 7% 42%	4429
	11th to 20th	Night	16% 9% 3 7% 4 4 5% 4 6% 6% 36%	4376
	21st to end	Night	24% 10% 2 5% 4 4 4 3 5% 5% 35%	4532
February	1st to 10th	Night	17% 8% 3 5% 4 4 4 4 5% 7% 40%	2470
	11th to 20th	Night	16% 7% 3 6% 4 4 4 4 5% 5% 40%	2294
	21st to end	Night	20% 8% 2 5% 4 3 4 3 5% 5% 41%	1884
March	1st to 10th	Night	23% 10% 3 6% 3 3 3 3 4 5% 37%	3678
	11th to 20th	Night	11% 6% 2 6% 5% 4 4 3 5% 6% 48%	3479
	21st to end	Night	17% 8% 3 6% 4 3 3 2 4 5% 44%	3608
April	1st to 10th	Night	18% 7% 3 7% 5% 4 4 4 5% 6% 37%	1900
	11th to 20th	Night	16% 7% 2 6% 4 4 5% 4 5% 7% 40%	1875
	21st to end	Night	20% 5% 2 5% 3 3 4 3 5% 6% 44%	1900
May	1st to 10th	Night	28% 8% 2 6% 4 3 4 3 6% 6% 31%	2818
	11th to 20th	Night	24% 10% 3 7% 4 4 4 3 5% 6% 30%	2495
	21st to end	Night	15% 6% 2 6% 3 4 4 4 5% 8% 41%	2738
June	1st to 10th	Night	17% 6% 2 5% 4 4 3 4 4 8% 43%	1520
	11th to 20th	Night	14% 5% 2 4 4 5% 5% 4 6% 8% 43%	1520
	21st to end	Night	12% 4 1 5% 3 4 5% 5% 6% 9% 44%	1520
July	1st to 10th	Night	9% 5% 2 8% 5% 6% 7% 5% 6% 9% 39%	2520
	11th to 20th	Night	12% 6% 3 6% 5% 4 7% 4 7% 10% 38%	2520
	21st to end	Night	17% 6% 2 6% 3 5% 4 4 6% 8% 39%	2798
August	1st to 10th	Night	21% 7% 3 6% 4 4 5% 3 6% 7% 33%	2825
	11th to 20th	Night	17% 7% 3 6% 5% 4 4 3 4 7% 41%	3002
	21st to end	Night	13% 5% 2 4 3 3 4 4 6% 8% 48%	3476
September	1st to 10th	Night	15% 7% 2 6% 4 4 3 3 4 6% 47%	1900
	11th to 20th	Night	13% 6% 2 4 4 4 3 3 4 6% 52%	1914
	21st to end	Night	19% 6% 2 6% 3 3 3 3 5% 5% 44%	2114
October	1st to 10th	Night	23% 5% 2 5% 3 3 3 2 4 6% 44%	2280
	11th to 20th	Night	18% 5% 2 4 3 4 4 3 4 6% 49%	2280
	21st to end	Night	21% 5% 2 4 3 4 3 3 5% 6% 46%	2570
November	1st to 10th	Night	13% 5% 2 5% 3 4 4 4 5% 5% 52%	2537
	11th to 20th	Night	17% 7% 2 5% 4 3 4 3 4 6% 46%	2600
	21st to end	Night	16% 6% 2 6% 4 4 4 3 5% 7% 42%	2703
December	1st to 10th	Night	20% 7% 2 7% 5% 5% 5% 4 5% 6% 35%	2660
	11th to 20th	Night	19% 7% 2 5% 4 4 5% 3 6% 7% 38%	3288
	21st to end	Night	21% 8% 3 7% 5% 4 4 3 5% 5% 36%	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	41% 6% 14% 27% 10% 2	2518
	11th to 20th	Day	53% 7% 12% 17% 10% 2	2581
	21st to end	Day	52% 7% 11% 20% 8% 1	3124
February	1st to 10th	Day	46% 7% 14% 20% 12% 1	1710
	11th to 20th	Day	44% 7% 11% 22% 14% 2	1779
	21st to end	Day	49% 6% 10% 22% 10% 3	1570
March	1st to 10th	Day	50% 5% 11% 25% 7% 2	3151
	11th to 20th	Day	36% 6% 15% 28% 13% 2	3480
	21st to end	Day	43% 5% 11% 17% 20% 3	4024
April	1st to 10th	Day	45% 6% 11% 20% 14% 4	2280
	11th to 20th	Day	43% 6% 11% 22% 15% 3	2254
	21st to end	Day	42% 7% 11% 21% 15% 4	2280
May	1st to 10th	Day	53% 6% 11% 18% 10% 2	4163
	11th to 20th	Day	56% 7% 12% 16% 8% 1	4402
	21st to end	Day	35% 8% 13% 25% 16% 2	4837
June	1st to 10th	Day	41% 9% 15% 22% 13% 1	2660
	11th to 20th	Day	41% 10% 14% 22% 11% 2	2660
	21st to end	Day	37% 10% 14% 25% 13%	2660
July	1st to 10th	Day	39% 11% 14% 21% 13% 1	4370
	11th to 20th	Day	36% 10% 17% 24% 13% 1	4365
	21st to end	Day	46% 9% 11% 17% 15% 1	4588
August	1st to 10th	Day	48% 10% 13% 20% 9%	4091
	11th to 20th	Day	38% 8% 13% 29% 12% 1	3831
	21st to end	Day	34% 7% 13% 30% 15% 2	4180
September	1st to 10th	Day	41% 6% 12% 21% 19% 2	2280
	11th to 20th	Day	32% 6% 11% 23% 25% 3	2266
	21st to end	Day	46% 6% 9% 17% 19% 2	2062
October	1st to 10th	Day	38% 6% 10% 19% 22% 5%	3160
	11th to 20th	Day	28% 6% 12% 28% 22% 4	3140
	21st to end	Day	28% 4 16% 24% 25% 3	3317
November	1st to 10th	Day	34% 4 15% 24% 20% 3	1761
	11th to 20th	Day	39% 7% 10% 25% 18% 2	1800
	21st to end	Day	40% 5% 15% 29% 9% 2	1567
December	1st to 10th	Day	50% 6% 15% 18% 10% 1	1520
	11th to 20th	Day	45% 6% 17% 23% 8% 1	1906
	21st to end	Day	53% 7% 13% 19% 7%	2772
January	1st to 10th	Night	41% 6% 12% 29% 10% 3	4429
	11th to 20th	Night	46% 6% 14% 22% 10% 2	4376
	21st to end	Night	51% 5% 11% 23% 10% 1	4532
February	1st to 10th	Night	44% 5% 14% 24% 11% 2	2470
	11th to 20th	Night	45% 5% 12% 20% 16% 3	2296
	21st to end	Night	44% 4 10% 23% 16% 3	1884
March	1st to 10th	Night	50% 5% 9% 23% 11% 2	3688
	11th to 20th	Night	34% 6% 15% 27% 16% 2	3480
	21st to end	Night	43% 4 8% 17% 22% 6%	3608
April	1st to 10th	Night	45% 6% 11% 22% 14% 3	1900
	11th to 20th	Night	42% 7% 10% 20% 19% 1	1875
	21st to end	Night	40% 6% 11% 21% 18% 4	1900
May	1st to 10th	Night	53% 6% 10% 21% 9% 2	2824
	11th to 20th	Night	54% 8% 13% 14% 10% 1	2496
	21st to end	Night	39% 9% 14% 22% 13% 3	2739
June	1st to 10th	Night	40% 6% 11% 24% 18% 1	1520
	11th to 20th	Night	37% 9% 15% 25% 13% 1	1520
	21st to end	Night	34% 9% 15% 28% 13% 1	1520
July	1st to 10th	Night	40% 10% 15% 17% 15% 2	2480
	11th to 20th	Night	39% 9% 16% 23% 13% 1	2472
	21st to end	Night	41% 8% 15% 18% 17% 1	2709
August	1st to 10th	Night	48% 9% 16% 18% 9% 1	2814
	11th to 20th	Night	42% 7% 12% 23% 15% 1	3030
	21st to end	Night	33% 7% 11% 30% 17% 1	3476
September	1st to 10th	Night	38% 6% 10% 23% 20% 2	1900
	11th to 20th	Night	34% 5% 9% 23% 26% 3	1914
	21st to end	Night	42% 5% 10% 21% 21% 1	2114
October	1st to 10th	Night	42% 6% 10% 21% 20% 2	3800
	11th to 20th	Night	27% 5% 9% 30% 25% 4	3779
	21st to end	Night	28% 4 14% 29% 23% 2	4230
November	1st to 10th	Night	33% 6% 14% 23% 20% 4	2537
	11th to 20th	Night	41% 4 10% 24% 18% 3	2600
	21st to end	Night	41% 5% 13% 27% 13% 2	2703
December	1st to 10th	Night	48% 6% 13% 21% 11% 1	2660
	11th to 20th	Night	45% 5% 15% 20% 14% 2	3288
	21st to end	Night	49% 6% 13% 23% 9%	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% 28% 16% 3	180
	11th to 20th	Day	32% 29% 26% 10% 2 1	197
	21st to end	Day	21% 30% 31% 13% 5% 1	297
February	1st to 10th	Day	21% 33% 33% 10% 3	270
	11th to 20th	Day	25% 26% 37% 10% 1	378
	21st to end	Day	31% 21% 29% 17% 2	382
March	1st to 10th	Day	26% 24% 29% 18% 3	460
	11th to 20th	Day	25% 25% 30% 15% 4 1	460
	21st to end	Day	28% 22% 31% 12% 5% 1	506
April	1st to 10th	Day	24% 27% 27% 16% 5% 1	460
	11th to 20th	Day	23% 24% 27% 16% 7% 3	452
	21st to end	Day	27% 19% 32% 15% 5% 3	460
May	1st to 10th	Day	29% 21% 25% 14% 7% 3	463
	11th to 20th	Day	23% 16% 31% 20% 9% 2	487
	21st to end	Day	19% 9% 30% 21% 18% 4	529
June	1st to 10th	Day	17% 16% 27% 24% 14% 2	490
	11th to 20th	Day	19% 13% 27% 26% 13% 3	490
	21st to end	Day	14% 12% 33% 25% 14% 2	490
July	1st to 10th	Day	12% 6% 25% 28% 22% 6%	485
	11th to 20th	Day	10% 5% 25% 33% 23% 5%	484
	21st to end	Day	14% 8% 29% 31% 13% 5%	532
August	1st to 10th	Day	14% 6% 22% 31% 20% 7%	486
	11th to 20th	Day	14% 6% 22% 32% 20% 6%	479
	21st to end	Day	14% 8% 28% 24% 16% 10%	539
September	1st to 10th	Day	19% 10% 20% 24% 19% 8%	490
	11th to 20th	Day	15% 4 27% 26% 17% 12%	490
	21st to end	Day	26% 13% 21% 21% 13% 5%	490
October	1st to 10th	Day	24% 10% 24% 22% 15% 5%	490
	11th to 20th	Day	18% 16% 29% 23% 11% 3	490
	21st to end	Day	23% 14% 32% 19% 9% 1	505
November	1st to 10th	Day	18% 16% 29% 24% 10% 3	395
	11th to 20th	Day	23% 21% 30% 22% 5% 1	400
	21st to end	Day	25% 23% 35% 14% 4	203
December	1st to 10th	Day	24% 31% 28% 12% 5% 1	180
	11th to 20th	Day	30% 28% 26% 12% 4	180
	21st to end	Day	27% 22% 34% 12% 4 2	198
January	1st to 10th	Night	19% 19% 41% 18% 3	760
	11th to 20th	Night	25% 18% 31% 23% 3	760
	21st to end	Night	18% 19% 38% 23% 1	836
February	1st to 10th	Night	21% 17% 36% 23% 2	760
	11th to 20th	Night	22% 23% 38% 16% 1	743
	21st to end	Night	24% 20% 35% 19% 2	628
March	1st to 10th	Night	22% 19% 33% 23% 3	760
	11th to 20th	Night	22% 19% 33% 21% 5% 1	760
	21st to end	Night	22% 15% 38% 20% 4	836
April	1st to 10th	Night	22% 18% 36% 20% 4	760
	11th to 20th	Night	20% 14% 36% 23% 7%	751
	21st to end	Night	23% 11% 34% 25% 7%	760
May	1st to 10th	Night	26% 10% 30% 26% 8% 1	567
	11th to 20th	Night	19% 8% 34% 31% 8%	374
	21st to end	Night	17% 5% 22% 41% 14% 1	411
June	1st to 10th	Night	18% 6% 24% 34% 18%	380
	11th to 20th	Night	13% 8% 25% 41% 11% 1	380
	21st to end	Night	12% 4 26% 43% 14%	380
July	1st to 10th	Night	11% 4 19% 42% 22% 2	370
	11th to 20th	Night	10% 4 20% 41% 24% 1	368
	21st to end	Night	13% 3 21% 40% 22% 1	451
August	1st to 10th	Night	14% 4 14% 43% 24% 2	567
	11th to 20th	Night	16% 5% 16% 36% 25% 2	691
	21st to end	Night	16% 4 18% 35% 25% 2	836
September	1st to 10th	Night	17% 4 25% 33% 20% 1	760
	11th to 20th	Night	15% 5% 19% 33% 23% 5%	760
	21st to end	Night	22% 7% 21% 31% 18% 1	760
October	1st to 10th	Night	23% 8% 24% 25% 17% 3	760
	11th to 20th	Night	19% 10% 27% 33% 10% 1	760
	21st to end	Night	24% 10% 30% 27% 9%	836
November	1st to 10th	Night	16% 12% 34% 27% 11% 1	780
	11th to 20th	Night	20% 17% 29% 26% 7% 1	800
	21st to end	Night	18% 16% 34% 26% 6%	779
December	1st to 10th	Night	25% 16% 32% 22% 5% 1	760
	11th to 20th	Night	21% 15% 35% 24% 4	760
	21st to end	Night	23% 16% 34% 25% 3	836

Page generated at 2024-11-22 08:02:26. Version ac07

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