Point Petre
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Point Petre 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	15% 9% 3 8% 5% 4 4 3 5% 7% 35%	108748
	Night	17% 12% 4 9% 5% 4 4 3 5% 7% 29%	109807
Transparency	Day	48% 5% 13% 23% 11% 1	112338
	Night	55% 4 11% 19% 10% 1	114380
Seeing	Day	20% 4 17% 31% 22% 6%	14788
	Night	23% 7% 23% 28% 16% 3	24181

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	14% 18% 9% 12% 6% 5% 4 3 4 7% 18%	3597
	11th to 20th	Day	14% 21% 10% 22% 6% 4 3 3 4 4 11%	3570
	21st to end	Day	14% 17% 6% 13% 9% 5% 5% 4 5% 7% 15%	4448
February	1st to 10th	Day	15% 16% 6% 14% 6% 4 5% 4 5% 5% 20%	1800
	11th to 20th	Day	14% 13% 5% 13% 6% 5% 4 3 5% 6% 26%	1753
	21st to end	Day	20% 12% 4 10% 5% 4 4 4 5% 6% 25%	1537
March	1st to 10th	Day	20% 10% 4 8% 5% 4 4 3 5% 6% 32%	3269
	11th to 20th	Day	9% 12% 4 10% 6% 5% 4 3 5% 6% 36%	3480
	21st to end	Day	14% 8% 2 6% 4 3 4 3 6% 6% 43%	3928
April	1st to 10th	Day	18% 9% 2 7% 5% 4 4 3 5% 7% 35%	2280
	11th to 20th	Day	18% 8% 2 6% 4 4 4 3 4 5% 42%	2254
	21st to end	Day	19% 7% 3 7% 5% 4 5% 3 5% 6% 35%	2398
May	1st to 10th	Day	18% 8% 2 7% 4 5% 4 4 5% 7% 35%	4326
	11th to 20th	Day	13% 10% 3 8% 5% 5% 5% 4 6% 8% 33%	4398
	21st to end	Day	11% 4 2 6% 4 4 4 4 6% 8% 46%	4837
June	1st to 10th	Day	16% 6% 2 7% 4 5% 4 4 6% 7% 39%	2660
	11th to 20th	Day	12% 5% 2 6% 4 4 4 4 6% 10% 44%	2660
	21st to end	Day	13% 7% 2 6% 4 4 4 3 5% 8% 44%	2660
July	1st to 10th	Day	10% 4 2 5% 4 4 5% 4 6% 9% 46%	4440
	11th to 20th	Day	10% 4 2 4 3 3 3 3 6% 8% 52%	4440
	21st to end	Day	8% 4 2 6% 5% 4 5% 4 6% 9% 48%	4797
August	1st to 10th	Day	17% 6% 2 6% 4 4 3 3 5% 7% 44%	4104
	11th to 20th	Day	14% 5% 2 6% 4 3 4 4 6% 9% 42%	4044
	21st to end	Day	12% 6% 2 4 4 4 4 3 6% 8% 48%	4182
September	1st to 10th	Day	12% 6% 2 6% 3 3 4 3 5% 8% 47%	2280
	11th to 20th	Day	10% 4 2 6% 3 3 4 4 5% 8% 50%	2280
	21st to end	Day	16% 6% 3 6% 4 5% 4 4 6% 7% 39%	1998
October	1st to 10th	Day	18% 7% 4 7% 5% 4 4 4 5% 7% 36%	1900
	11th to 20th	Day	21% 7% 2 7% 4 5% 4 4 6% 8% 33%	1900
	21st to end	Day	26% 10% 2 7% 5% 5% 5% 3 5% 5% 27%	2036
November	1st to 10th	Day	15% 11% 4 7% 5% 5% 5% 4 5% 8% 34%	1746
	11th to 20th	Day	15% 14% 4 9% 5% 5% 5% 4 5% 6% 28%	1600
	21st to end	Day	22% 18% 3 8% 4 4 4 4 5% 6% 21%	1600
December	1st to 10th	Day	20% 21% 5% 9% 4 5% 5% 3 5% 6% 16%	2600
	11th to 20th	Day	20% 17% 5% 15% 5% 4 4 3 5% 6% 16%	2986
	21st to end	Day	25% 14% 4 11% 5% 4 5% 3 5% 7% 16%	3960
January	1st to 10th	Night	17% 21% 7% 10% 6% 4 4 3 4 7% 17%	6349
	11th to 20th	Night	14% 18% 9% 26% 7% 5% 4 3 3 4 7%	6315
	21st to end	Night	18% 17% 9% 14% 9% 5% 4 3 4 6% 13%	6490
February	1st to 10th	Night	17% 16% 6% 14% 6% 5% 4 3 4 5% 20%	2600
	11th to 20th	Night	17% 15% 5% 10% 5% 5% 4 3 5% 7% 24%	2533
	21st to end	Night	18% 12% 4 9% 5% 5% 6% 4 6% 6% 24%	1916
March	1st to 10th	Night	18% 10% 3 9% 6% 5% 4 4 6% 6% 30%	3569
	11th to 20th	Night	19% 15% 3 8% 4 3 4 3 5% 6% 29%	3479
	21st to end	Night	17% 7% 3 6% 4 3 4 3 4 6% 44%	3702
April	1st to 10th	Night	21% 9% 2 6% 5% 4 5% 3 5% 7% 33%	1900
	11th to 20th	Night	18% 8% 4 6% 4 3 4 4 5% 6% 37%	1875
	21st to end	Night	19% 8% 2 7% 4 3 4 4 5% 6% 37%	1800
May	1st to 10th	Night	24% 10% 3 7% 4 3 4 3 5% 6% 32%	2615
	11th to 20th	Night	19% 7% 2 6% 5% 5% 5% 5% 7% 7% 33%	2495
	21st to end	Night	12% 5% 2 6% 4 4 4 4 6% 9% 43%	2738
June	1st to 10th	Night	15% 6% 2 7% 6% 4 5% 5% 7% 9% 35%	1520
	11th to 20th	Night	9% 6% 3 7% 4 4 6% 3 6% 9% 43%	1520
	21st to end	Night	11% 8% 3 7% 5% 5% 3 4 6% 7% 40%	1520
July	1st to 10th	Night	10% 6% 3 6% 5% 5% 5% 4 6% 7% 42%	2520
	11th to 20th	Night	11% 6% 2 6% 4 4 4 4 6% 9% 44%	2520
	21st to end	Night	11% 5% 2 5% 4 4 4 3 6% 7% 48%	2752
August	1st to 10th	Night	11% 6% 2 6% 4 4 4 4 6% 8% 45%	2825
	11th to 20th	Night	12% 6% 2 7% 4 4 5% 4 5% 9% 41%	2785
	21st to end	Night	8% 4 2 6% 4 5% 5% 4 7% 9% 48%	3440
September	1st to 10th	Night	12% 6% 3 6% 4 3 3 3 5% 8% 47%	1900
	11th to 20th	Night	12% 5% 2 5% 5% 3 4 3 5% 6% 51%	1900
	21st to end	Night	16% 6% 2 7% 5% 5% 4 4 6% 7% 40%	2178
October	1st to 10th	Night	18% 7% 3 8% 5% 4 5% 4 5% 6% 35%	2280
	11th to 20th	Night	21% 9% 3 8% 5% 5% 5% 3 5% 6% 30%	2280
	21st to end	Night	24% 9% 4 8% 5% 4 4 3 5% 6% 27%	2560
November	1st to 10th	Night	18% 11% 3 6% 5% 4 5% 3 5% 6% 34%	2547
	11th to 20th	Night	18% 13% 4 7% 4 4 5% 4 5% 7% 28%	2800
	21st to end	Night	23% 16% 4 8% 5% 4 4 4 5% 7% 20%	2800
December	1st to 10th	Night	22% 24% 4 8% 5% 4 4 3 4 6% 15%	4580
	11th to 20th	Night	24% 18% 6% 12% 4 4 4 3 4 6% 16%	5208
	21st to end	Night	28% 14% 5% 10% 5% 4 4 3 5% 6% 16%	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	69% 7% 11% 8% 5% 1	3598
	11th to 20th	Day	79% 3 8% 7% 2	3600
	21st to end	Day	69% 5% 14% 7% 4 1	4448
February	1st to 10th	Day	67% 4 11% 15% 3 1	1800
	11th to 20th	Day	61% 4 9% 17% 8% 1	1762
	21st to end	Day	61% 3 11% 16% 8%	1537
March	1st to 10th	Day	53% 4 12% 21% 9% 1	3272
	11th to 20th	Day	49% 4 16% 19% 11% 2	3480
	21st to end	Day	41% 3 10% 30% 14% 2	3928
April	1st to 10th	Day	48% 4 9% 23% 14% 2	2280
	11th to 20th	Day	45% 4 8% 25% 16% 2	2254
	21st to end	Day	48% 4 10% 20% 15% 3	2398
May	1st to 10th	Day	48% 4 11% 22% 13% 2	4339
	11th to 20th	Day	50% 4 14% 21% 9% 2	4402
	21st to end	Day	35% 4 15% 28% 16% 2	4837
June	1st to 10th	Day	42% 5% 12% 24% 16% 2	2660
	11th to 20th	Day	36% 4 14% 29% 15% 2	2660
	21st to end	Day	38% 5% 15% 26% 15% 1	2660
July	1st to 10th	Day	34% 5% 14% 31% 16% 1	4370
	11th to 20th	Day	29% 4 16% 37% 13% 1	4365
	21st to end	Day	33% 6% 18% 28% 15% 1	4644
August	1st to 10th	Day	41% 5% 14% 26% 14% 1	4091
	11th to 20th	Day	37% 5% 19% 28% 10%	4083
	21st to end	Day	33% 5% 14% 38% 9% 1	4182
September	1st to 10th	Day	36% 5% 14% 32% 12% 1	2280
	11th to 20th	Day	34% 3 13% 33% 16% 1	2280
	21st to end	Day	43% 4 14% 28% 10%	1998
October	1st to 10th	Day	38% 7% 14% 29% 12%	3160
	11th to 20th	Day	42% 5% 16% 27% 10%	3140
	21st to end	Day	48% 7% 13% 24% 9%	3338
November	1st to 10th	Day	49% 5% 14% 20% 11%	1746
	11th to 20th	Day	56% 5% 14% 15% 9% 1	1600
	21st to end	Day	66% 3 13% 13% 5%	1600
December	1st to 10th	Day	70% 6% 15% 8% 2	2600
	11th to 20th	Day	70% 7% 13% 8% 2	2986
	21st to end	Day	69% 8% 10% 10% 3	3960
January	1st to 10th	Night	72% 5% 9% 10% 4	6349
	11th to 20th	Night	83% 4 5% 5% 2	6360
	21st to end	Night	74% 4 11% 7% 4	6490
February	1st to 10th	Night	69% 4 10% 13% 4	2600
	11th to 20th	Night	62% 3 9% 18% 7%	2535
	21st to end	Night	60% 3 14% 17% 6% 1	1916
March	1st to 10th	Night	55% 3 10% 22% 8% 1	3579
	11th to 20th	Night	57% 3 13% 17% 9% 1	3480
	21st to end	Night	42% 3 7% 26% 19% 3	3702
April	1st to 10th	Night	51% 4 8% 22% 12% 2	1900
	11th to 20th	Night	48% 4 11% 18% 18% 2	1875
	21st to end	Night	47% 4 10% 19% 16% 3	1800
May	1st to 10th	Night	54% 3 11% 16% 13% 2	2621
	11th to 20th	Night	49% 5% 14% 21% 10% 2	2496
	21st to end	Night	36% 4 12% 23% 22% 2	2739
June	1st to 10th	Night	43% 6% 10% 24% 13% 3	1520
	11th to 20th	Night	38% 4 12% 22% 21% 3	1520
	21st to end	Night	42% 6% 11% 23% 16% 1	1520
July	1st to 10th	Night	39% 6% 11% 22% 20% 1	2480
	11th to 20th	Night	36% 7% 12% 30% 15%	2472
	21st to end	Night	34% 6% 14% 30% 14% 1	2664
August	1st to 10th	Night	36% 5% 15% 29% 14% 1	2814
	11th to 20th	Night	39% 6% 17% 26% 11% 1	2812
	21st to end	Night	31% 6% 14% 37% 11% 1	3440
September	1st to 10th	Night	37% 4 14% 31% 13% 2	1900
	11th to 20th	Night	34% 4 12% 32% 17% 1	1900
	21st to end	Night	43% 5% 12% 27% 12% 1	2178
October	1st to 10th	Night	39% 5% 11% 28% 17% 1	3800
	11th to 20th	Night	44% 5% 15% 25% 10%	3779
	21st to end	Night	47% 5% 12% 26% 9% 1	4208
November	1st to 10th	Night	53% 4 11% 20% 12% 2	2547
	11th to 20th	Night	57% 4 11% 18% 9% 1	2800
	21st to end	Night	67% 3 13% 13% 4	2800
December	1st to 10th	Night	73% 5% 9% 11% 1	4580
	11th to 20th	Night	73% 5% 10% 9% 3	5208
	21st to end	Night	71% 6% 11% 8% 4	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	22% 15% 26% 27% 8% 3	200
	11th to 20th	Day	28% 11% 30% 23% 8% 1	200
	21st to end	Day	24% 10% 25% 28% 12% 1	327
February	1st to 10th	Day	25% 12% 28% 27% 8%	300
	11th to 20th	Day	20% 11% 29% 34% 5% 1	300
	21st to end	Day	28% 10% 28% 29% 5%	349
March	1st to 10th	Day	22% 7% 27% 35% 9% 2	460
	11th to 20th	Day	21% 7% 28% 32% 10% 1	460
	21st to end	Day	27% 4 25% 30% 11% 3	506
April	1st to 10th	Day	21% 6% 22% 36% 12% 2	460
	11th to 20th	Day	23% 4 23% 28% 16% 5%	452
	21st to end	Day	24% 3 19% 34% 17% 3	460
May	1st to 10th	Day	22% 2 13% 35% 23% 5%	463
	11th to 20th	Day	16% 2 12% 34% 27% 9%	487
	21st to end	Day	14% 1 8% 37% 29% 12%	529
June	1st to 10th	Day	18% 1 11% 34% 29% 7%	490
	11th to 20th	Day	13% 1 11% 31% 36% 8%	490
	21st to end	Day	18% 1 12% 33% 30% 7%	490
July	1st to 10th	Day	11% 1 5% 32% 39% 12%	485
	11th to 20th	Day	13% 1 9% 29% 38% 10%	484
	21st to end	Day	11% 1 9% 39% 33% 8%	532
August	1st to 10th	Day	15% 2 7% 27% 38% 10%	486
	11th to 20th	Day	12% 1 9% 29% 36% 12%	479
	21st to end	Day	13% 2 10% 31% 35% 9%	539
September	1st to 10th	Day	14% 3 11% 31% 29% 12%	490
	11th to 20th	Day	11% 10% 31% 27% 21%	490
	21st to end	Day	17% 3 14% 32% 26% 9%	490
October	1st to 10th	Day	23% 3 17% 26% 21% 9%	490
	11th to 20th	Day	23% 7% 25% 26% 14% 5%	490
	21st to end	Day	31% 5% 22% 28% 13% 1	510
November	1st to 10th	Day	21% 13% 23% 26% 16% 1	380
	11th to 20th	Day	22% 11% 26% 29% 11% 2	200
	21st to end	Day	31% 8% 30% 23% 7% 2	200
December	1st to 10th	Day	32% 9% 25% 24% 9% 2	200
	11th to 20th	Day	27% 17% 33% 19% 4 2	200
	21st to end	Day	36% 8% 29% 22% 5%	220
January	1st to 10th	Night	32% 13% 31% 16% 7%	800
	11th to 20th	Night	29% 12% 29% 22% 7%	800
	21st to end	Night	24% 12% 29% 27% 9% 1	880
February	1st to 10th	Night	26% 13% 31% 25% 5%	800
	11th to 20th	Night	25% 12% 34% 23% 7%	783
	21st to end	Night	24% 8% 36% 25% 6%	629
March	1st to 10th	Night	22% 7% 30% 31% 9% 1	760
	11th to 20th	Night	25% 8% 27% 30% 9% 1	760
	21st to end	Night	22% 4 29% 29% 13% 3	836
April	1st to 10th	Night	25% 4 23% 35% 12% 1	760
	11th to 20th	Night	23% 4 23% 35% 13% 3	751
	21st to end	Night	24% 3 20% 34% 16% 4	660
May	1st to 10th	Night	25% 15% 31% 22% 5%	442
	11th to 20th	Night	16% 2 13% 43% 23% 3	374
	21st to end	Night	11% 2 12% 38% 28% 8%	411
June	1st to 10th	Night	15% 2 12% 39% 26% 5%	380
	11th to 20th	Night	11% 2 13% 37% 32% 6%	380
	21st to end	Night	17% 2 12% 34% 30% 4	380
July	1st to 10th	Night	7% 2 9% 36% 37% 9%	370
	11th to 20th	Night	11% 11% 36% 34% 8%	368
	21st to end	Night	11% 2 9% 41% 32% 5%	417
August	1st to 10th	Night	12% 1 10% 36% 33% 8%	567
	11th to 20th	Night	13% 2 11% 33% 32% 9%	564
	21st to end	Night	11% 2 12% 34% 34% 6%	813
September	1st to 10th	Night	16% 3 14% 30% 31% 8%	760
	11th to 20th	Night	15% 2 12% 28% 30% 13%	760
	21st to end	Night	19% 4 17% 29% 23% 9%	760
October	1st to 10th	Night	23% 5% 22% 24% 18% 7%	760
	11th to 20th	Night	24% 7% 25% 29% 12% 2	760
	21st to end	Night	30% 6% 27% 27% 10% 1	836
November	1st to 10th	Night	24% 8% 26% 28% 13% 2	780
	11th to 20th	Night	25% 11% 30% 24% 8% 2	800
	21st to end	Night	34% 10% 27% 22% 7% 1	800
December	1st to 10th	Night	37% 13% 27% 18% 5% 1	800
	11th to 20th	Night	28% 14% 34% 18% 5% 1	800
	21st to end	Night	36% 10% 30% 18% 6%	880

Page generated at 2025-02-18 03:26:29. Version ac07

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