Pense
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pense clear sky chart from 2005-11-06 to 2026-09-29.

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	9% 8% 3 8% 5% 5% 5% 4 6% 8% 39%	153594
	Night	7% 9% 3 9% 6% 5% 5% 4 6% 8% 37%	146643
Transparency	Day	41% 6% 15% 25% 11% 1	153309
	Night	44% 6% 15% 24% 10% 1	146513
Seeing	Day	12% 9% 30% 29% 16% 4	18637
	Night	12% 8% 31% 35% 13% 1	27925

By Month

Percentage Cloud Cover NW (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	7% 12% 5% 13% 9% 9% 7% 5% 6% 6% 21%	4125
	11th to 20th	Day	3 7% 4 11% 10% 8% 10% 7% 9% 9% 23%	4569
	21st to end	Day	5% 10% 4 13% 8% 7% 6% 4 6% 8% 30%	5188
February	1st to 10th	Day	8% 13% 6% 13% 8% 7% 7% 5% 6% 7% 21%	1744
	11th to 20th	Day	7% 13% 4 9% 7% 7% 8% 6% 7% 7% 25%	1845
	21st to end	Day	5% 10% 6% 13% 9% 7% 8% 6% 7% 6% 24%	1681
March	1st to 10th	Day	7% 11% 5% 14% 8% 4 5% 3 5% 7% 30%	4600
	11th to 20th	Day	5% 13% 6% 14% 6% 5% 5% 3 5% 7% 29%	4892
	21st to end	Day	8% 13% 5% 14% 7% 5% 5% 4 5% 7% 27%	6006
April	1st to 10th	Day	6% 10% 3 8% 6% 4 6% 5% 7% 8% 38%	2520
	11th to 20th	Day	12% 12% 4 10% 6% 5% 5% 4 7% 6% 29%	2510
	21st to end	Day	14% 11% 3 7% 5% 5% 4 3 5% 6% 36%	2914
May	1st to 10th	Day	11% 8% 2 6% 4 4 4 3 5% 7% 45%	8224
	11th to 20th	Day	15% 8% 3 6% 4 5% 6% 4 7% 8% 33%	8191
	21st to end	Day	10% 6% 2 7% 5% 5% 5% 4 5% 8% 45%	9142
June	1st to 10th	Day	14% 7% 2 7% 5% 4 5% 5% 6% 8% 38%	3281
	11th to 20th	Day	17% 7% 3 7% 5% 6% 5% 4 6% 9% 31%	3360
	21st to end	Day	10% 6% 2 6% 4 5% 5% 5% 7% 9% 41%	3360
July	1st to 10th	Day	5% 5% 2 6% 4 4 5% 4 8% 9% 48%	9028
	11th to 20th	Day	9% 5% 2 6% 4 5% 5% 5% 7% 9% 42%	8598
	21st to end	Day	4 3 1 4 3 3 3 3 5% 8% 61%	8952
August	1st to 10th	Day	7% 5% 2 6% 4 4 5% 4 6% 7% 51%	6462
	11th to 20th	Day	9% 4 2 6% 3 4 4 4 7% 10% 47%	6350
	21st to end	Day	10% 4 2 5% 4 3 4 3 5% 8% 52%	6211
September	1st to 10th	Day	10% 5% 2 6% 4 4 4 4 5% 8% 48%	2520
	11th to 20th	Day	13% 7% 2 6% 4 4 4 3 5% 8% 43%	2515
	21st to end	Day	11% 5% 2 5% 3 3 3 3 6% 8% 51%	2246
October	1st to 10th	Day	9% 7% 2 6% 5% 4 5% 3 6% 7% 45%	3270
	11th to 20th	Day	7% 7% 3 6% 3 3 4 4 7% 11% 47%	3129
	21st to end	Day	6% 10% 4 8% 6% 4 5% 4 6% 8% 39%	3190
November	1st to 10th	Day	11% 15% 5% 9% 6% 5% 5% 3 4 6% 31%	1718
	11th to 20th	Day	6% 12% 5% 14% 7% 6% 5% 4 5% 7% 29%	1680
	21st to end	Day	10% 11% 5% 11% 7% 7% 6% 5% 6% 6% 27%	1538
December	1st to 10th	Day	6% 13% 4 13% 8% 7% 6% 5% 6% 6% 25%	2360
	11th to 20th	Day	7% 16% 7% 13% 10% 7% 7% 4 5% 7% 18%	2541
	21st to end	Day	5% 8% 4 12% 8% 5% 5% 4 5% 6% 38%	3134
January	1st to 10th	Night	3 11% 5% 13% 10% 8% 8% 5% 7% 6% 24%	8768
	11th to 20th	Night	3 8% 5% 12% 9% 9% 8% 6% 8% 7% 25%	8348
	21st to end	Night	5% 11% 5% 12% 7% 6% 6% 4 6% 8% 31%	9026
February	1st to 10th	Night	7% 12% 5% 12% 8% 7% 7% 5% 6% 7% 24%	2893
	11th to 20th	Night	6% 11% 4 11% 7% 5% 7% 6% 6% 7% 29%	2662
	21st to end	Night	4 8% 3 13% 7% 6% 6% 4 7% 9% 33%	2124
March	1st to 10th	Night	6% 10% 6% 13% 6% 5% 6% 5% 6% 8% 29%	5494
	11th to 20th	Night	7% 11% 4 11% 7% 6% 5% 4 6% 8% 31%	5301
	21st to end	Night	8% 12% 5% 15% 7% 5% 6% 4 6% 7% 26%	5192
April	1st to 10th	Night	7% 9% 3 7% 4 5% 5% 4 6% 9% 41%	2100
	11th to 20th	Night	12% 12% 3 7% 4 5% 5% 4 6% 8% 33%	2061
	21st to end	Night	12% 9% 4 7% 5% 5% 5% 5% 5% 7% 34%	1703
May	1st to 10th	Night	11% 8% 2 5% 3 4 4 3 6% 7% 47%	4724
	11th to 20th	Night	18% 9% 3 7% 4 4 5% 4 7% 7% 34%	4702
	21st to end	Night	10% 6% 2 5% 4 4 4 4 7% 8% 46%	5059
June	1st to 10th	Night	11% 5% 2 6% 4 4 4 4 7% 9% 44%	1335
	11th to 20th	Night	14% 7% 2 5% 4 4 4 4 6% 9% 39%	1260
	21st to end	Night	10% 5% 2 4 4 4 6% 5% 7% 8% 46%	1260
July	1st to 10th	Night	6% 4 2 5% 4 4 5% 4 7% 10% 49%	3914
	11th to 20th	Night	9% 5% 2 6% 3 4 4 4 6% 8% 49%	4370
	21st to end	Night	5% 3 1 4 3 3 4 3 6% 8% 60%	5150
August	1st to 10th	Night	6% 3 1 4 3 3 4 4 6% 9% 57%	3708
	11th to 20th	Night	7% 3 2 5% 4 4 4 4 7% 9% 51%	3713
	21st to end	Night	8% 4 2 5% 4 5% 5% 4 6% 8% 50%	4936
September	1st to 10th	Night	9% 4 1 4 3 4 4 4 5% 7% 54%	2100
	11th to 20th	Night	10% 6% 2 6% 4 4 4 4 5% 8% 47%	2105
	21st to end	Night	9% 6% 2 5% 4 4 3 4 6% 6% 52%	2328
October	1st to 10th	Night	11% 7% 2 5% 4 3 3 3 5% 8% 49%	3920
	11th to 20th	Night	5% 7% 2 5% 3 4 4 4 6% 9% 50%	3986
	21st to end	Night	7% 9% 3 7% 5% 4 4 4 5% 7% 45%	4610
November	1st to 10th	Night	14% 13% 5% 8% 5% 4 4 4 4 6% 33%	2800
	11th to 20th	Night	7% 12% 4 11% 7% 5% 6% 4 6% 7% 30%	2940
	21st to end	Night	8% 12% 5% 12% 6% 6% 5% 3 6% 7% 30%	3080
December	1st to 10th	Night	7% 15% 6% 15% 9% 8% 5% 4 4 6% 21%	5050
	11th to 20th	Night	7% 14% 6% 14% 8% 7% 8% 5% 5% 6% 20%	5874
	21st to end	Night	4 7% 3 11% 8% 5% 5% 4 6% 6% 40%	8047

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	61% 6% 13% 12% 8%	4125
	11th to 20th	Day	54% 6% 16% 16% 9%	4593
	21st to end	Day	52% 5% 19% 18% 7%	5188
February	1st to 10th	Day	61% 5% 12% 16% 6%	1744
	11th to 20th	Day	55% 7% 11% 15% 11%	1854
	21st to end	Day	56% 8% 13% 15% 8%	1681
March	1st to 10th	Day	53% 6% 19% 17% 6%	4600
	11th to 20th	Day	53% 7% 18% 18% 4	4893
	21st to end	Day	55% 7% 13% 17% 8% 1	6006
April	1st to 10th	Day	41% 7% 17% 23% 11% 1	2520
	11th to 20th	Day	53% 6% 14% 19% 6% 1	2510
	21st to end	Day	48% 5% 15% 23% 8% 1	2914
May	1st to 10th	Day	38% 4 11% 31% 15% 1	8224
	11th to 20th	Day	45% 8% 13% 21% 13% 1	8195
	21st to end	Day	35% 7% 11% 28% 19% 1	9142
June	1st to 10th	Day	41% 7% 14% 27% 10% 1	3281
	11th to 20th	Day	48% 7% 14% 20% 10% 1	3360
	21st to end	Day	36% 9% 17% 28% 9% 1	3360
July	1st to 10th	Day	29% 9% 23% 29% 10%	8954
	11th to 20th	Day	35% 7% 15% 30% 10% 2	8517
	21st to end	Day	21% 6% 15% 34% 21% 3	8759
August	1st to 10th	Day	31% 7% 17% 28% 16% 1	6446
	11th to 20th	Day	31% 7% 19% 35% 8% 1	6392
	21st to end	Day	31% 6% 14% 35% 15% 1	6210
September	1st to 10th	Day	33% 7% 14% 29% 15% 2	2520
	11th to 20th	Day	40% 6% 15% 27% 11% 2	2515
	21st to end	Day	31% 4 14% 33% 15% 2	2246
October	1st to 10th	Day	37% 5% 15% 30% 11% 2	3270
	11th to 20th	Day	32% 4 15% 36% 11% 2	3129
	21st to end	Day	43% 5% 16% 28% 8%	3190
November	1st to 10th	Day	55% 5% 13% 19% 7% 1	1718
	11th to 20th	Day	54% 6% 15% 18% 7%	1680
	21st to end	Day	55% 8% 17% 16% 4	1538
December	1st to 10th	Day	58% 7% 18% 13% 4	2360
	11th to 20th	Day	65% 5% 19% 8% 3	2541
	21st to end	Day	47% 4 11% 22% 11% 4	3134
January	1st to 10th	Night	58% 6% 13% 17% 6%	8769
	11th to 20th	Night	54% 6% 16% 14% 9%	8386
	21st to end	Night	51% 5% 20% 17% 8%	9026
February	1st to 10th	Night	57% 6% 12% 17% 7%	2893
	11th to 20th	Night	51% 6% 13% 19% 11% 1	2663
	21st to end	Night	47% 5% 16% 23% 9%	2124
March	1st to 10th	Night	51% 7% 21% 18% 4	5494
	11th to 20th	Night	49% 7% 19% 20% 5%	5301
	21st to end	Night	57% 6% 12% 19% 7%	5192
April	1st to 10th	Night	38% 5% 15% 25% 16% 1	2100
	11th to 20th	Night	48% 6% 11% 22% 10% 3	2061
	21st to end	Night	46% 7% 11% 25% 10% 1	1703
May	1st to 10th	Night	35% 5% 10% 31% 17% 2	4724
	11th to 20th	Night	47% 7% 12% 22% 11% 2	4702
	21st to end	Night	32% 8% 11% 29% 18% 2	5063
June	1st to 10th	Night	34% 6% 15% 29% 15% 2	1335
	11th to 20th	Night	39% 8% 17% 23% 12% 1	1260
	21st to end	Night	33% 9% 17% 31% 10% 1	1260
July	1st to 10th	Night	29% 8% 25% 30% 6% 1	3879
	11th to 20th	Night	31% 6% 14% 35% 12% 2	4328
	21st to end	Night	22% 6% 17% 31% 19% 5%	5038
August	1st to 10th	Night	22% 7% 21% 34% 15% 1	3700
	11th to 20th	Night	27% 8% 20% 35% 9% 1	3737
	21st to end	Night	31% 6% 13% 31% 18% 1	4936
September	1st to 10th	Night	29% 6% 11% 32% 20% 3	2100
	11th to 20th	Night	35% 6% 15% 27% 15% 2	2105
	21st to end	Night	31% 5% 13% 33% 16% 2	2328
October	1st to 10th	Night	35% 4 16% 32% 12% 2	3920
	11th to 20th	Night	29% 4 14% 38% 13% 1	3986
	21st to end	Night	38% 4 11% 34% 12% 1	4610
November	1st to 10th	Night	53% 6% 13% 19% 7% 2	2800
	11th to 20th	Night	53% 7% 17% 17% 6%	2940
	21st to end	Night	53% 6% 19% 19% 4	3080
December	1st to 10th	Night	65% 6% 16% 10% 3	5050
	11th to 20th	Night	63% 7% 16% 11% 3	5873
	21st to end	Night	44% 4 11% 24% 13% 4	8047

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	13% 11% 28% 30% 14% 4	220
	11th to 20th	Day	10% 12% 34% 28% 14% 2	302
	21st to end	Day	12% 10% 33% 32% 11% 1	363
February	1st to 10th	Day	13% 9% 38% 28% 11% 1	330
	11th to 20th	Day	13% 6% 36% 25% 16% 3	330
	21st to end	Day	6% 7% 35% 34% 15% 3	273
March	1st to 10th	Day	12% 9% 35% 29% 12% 2	330
	11th to 20th	Day	10% 12% 37% 27% 10% 4	440
	21st to end	Day	14% 11% 33% 27% 13% 2	594
April	1st to 10th	Day	9% 15% 36% 28% 9% 2	540
	11th to 20th	Day	16% 15% 34% 25% 9% 1	548
	21st to end	Day	15% 10% 30% 28% 16% 1	750
May	1st to 10th	Day	12% 8% 28% 31% 18% 3	753
	11th to 20th	Day	15% 6% 28% 29% 16% 6%	775
	21st to end	Day	15% 8% 25% 29% 17% 5%	844
June	1st to 10th	Day	15% 13% 29% 23% 16% 4	780
	11th to 20th	Day	18% 13% 29% 26% 12% 2	780
	21st to end	Day	12% 8% 24% 31% 19% 5%	780
July	1st to 10th	Day	8% 5% 22% 36% 23% 6%	771
	11th to 20th	Day	8% 7% 29% 30% 20% 6%	768
	21st to end	Day	5% 6% 27% 32% 22% 8%	849
August	1st to 10th	Day	9% 7% 21% 37% 21% 6%	776
	11th to 20th	Day	8% 5% 22% 35% 23% 7%	751
	21st to end	Day	9% 8% 25% 30% 22% 6%	627
September	1st to 10th	Day	11% 12% 29% 29% 15% 5%	570
	11th to 20th	Day	16% 9% 27% 30% 16% 1	565
	21st to end	Day	13% 8% 30% 31% 16% 2	354
October	1st to 10th	Day	16% 9% 28% 26% 18% 2	330
	11th to 20th	Day	13% 12% 35% 25% 14% 1	330
	21st to end	Day	12% 11% 39% 27% 9% 2	363
November	1st to 10th	Day	19% 11% 30% 27% 10% 3	330
	11th to 20th	Day	14% 10% 37% 28% 10% 1	330
	21st to end	Day	13% 9% 38% 27% 12% 1	330
December	1st to 10th	Day	12% 9% 38% 29% 8% 3	330
	11th to 20th	Day	12% 10% 48% 24% 5% 1	289
	21st to end	Day	11% 6% 35% 32% 13% 2	242
January	1st to 10th	Night	7% 11% 36% 33% 12% 1	1050
	11th to 20th	Night	12% 12% 35% 32% 8% 1	1050
	21st to end	Night	12% 11% 38% 28% 10% 1	1155
February	1st to 10th	Night	11% 10% 33% 32% 13% 1	1003
	11th to 20th	Night	10% 7% 34% 36% 10% 2	824
	21st to end	Night	5% 7% 27% 40% 18% 4	692
March	1st to 10th	Night	10% 8% 35% 33% 12% 1	840
	11th to 20th	Night	11% 7% 36% 31% 13% 1	840
	21st to end	Night	14% 7% 31% 34% 13% 1	739
April	1st to 10th	Night	9% 7% 36% 37% 11% 1	630
	11th to 20th	Night	16% 10% 32% 35% 6% 1	623
	21st to end	Night	17% 8% 30% 37% 8%	630
May	1st to 10th	Night	14% 5% 27% 37% 16% 1	630
	11th to 20th	Night	16% 7% 28% 34% 14% 1	621
	21st to end	Night	17% 5% 28% 33% 15% 1	683
June	1st to 10th	Night	13% 6% 30% 35% 15% 1	495
	11th to 20th	Night	17% 6% 28% 37% 11%	420
	21st to end	Night	11% 7% 25% 40% 15% 1	420
July	1st to 10th	Night	8% 5% 20% 46% 19% 1	410
	11th to 20th	Night	8% 3 26% 45% 17% 1	482
	21st to end	Night	6% 3 25% 43% 21% 2	690
August	1st to 10th	Night	7% 3 24% 44% 20% 2	627
	11th to 20th	Night	5% 4 23% 43% 22% 3	624
	21st to end	Night	8% 5% 27% 41% 19% 1	693
September	1st to 10th	Night	9% 5% 27% 40% 16% 2	630
	11th to 20th	Night	10% 6% 25% 42% 16% 1	630
	21st to end	Night	12% 5% 31% 41% 11% 1	664
October	1st to 10th	Night	17% 6% 27% 35% 15% 1	800
	11th to 20th	Night	13% 6% 31% 36% 14% 1	850
	21st to end	Night	16% 10% 33% 32% 9% 1	1100
November	1st to 10th	Night	20% 8% 33% 31% 8%	1025
	11th to 20th	Night	14% 10% 34% 30% 9% 2	1050
	21st to end	Night	13% 10% 37% 34% 7% 1	1050
December	1st to 10th	Night	13% 7% 36% 30% 12% 3	1050
	11th to 20th	Night	13% 12% 34% 28% 11% 1	1050
	21st to end	Night	12% 6% 32% 35% 13% 2	1155

Page generated at 2026-09-26 02:18:38. Version ac07

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