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 2024-11-02.

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%	101721
	Night	8% 9% 3 9% 6% 5% 5% 4 6% 7% 38%	97346
Transparency	Day	42% 7% 16% 25% 10% 1	101478
	Night	43% 6% 15% 24% 10% 1	97235
Seeing	Day	12% 9% 29% 30% 17% 4	15981
	Night	12% 7% 31% 35% 13% 1	25399

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	8% 13% 4 11% 8% 7% 7% 6% 7% 6% 23%	2219
	11th to 20th	Day	5% 7% 4 11% 9% 10% 11% 7% 8% 7% 20%	2425
	21st to end	Day	5% 12% 4 12% 6% 6% 6% 4 5% 7% 33%	2794
February	1st to 10th	Day	9% 13% 6% 13% 9% 6% 7% 5% 5% 7% 22%	1577
	11th to 20th	Day	8% 14% 4 9% 7% 7% 8% 6% 6% 5% 25%	1665
	21st to end	Day	5% 11% 6% 14% 9% 7% 7% 6% 7% 6% 23%	1525
March	1st to 10th	Day	7% 13% 5% 12% 9% 5% 7% 4 5% 6% 26%	3130
	11th to 20th	Day	4 12% 5% 11% 5% 4 5% 4 5% 8% 36%	3347
	21st to end	Day	6% 11% 5% 12% 7% 5% 5% 5% 6% 8% 29%	4098
April	1st to 10th	Day	6% 9% 3 7% 6% 4 6% 5% 7% 8% 38%	2280
	11th to 20th	Day	13% 13% 4 10% 7% 5% 5% 4 7% 6% 28%	2268
	21st to end	Day	14% 11% 3 7% 6% 5% 4 3 5% 7% 35%	2636
May	1st to 10th	Day	18% 11% 3 6% 4 4 4 3 5% 6% 35%	4430
	11th to 20th	Day	8% 8% 3 7% 5% 6% 7% 5% 7% 8% 36%	4388
	21st to end	Day	13% 7% 2 8% 6% 6% 6% 5% 7% 8% 33%	4884
June	1st to 10th	Day	15% 7% 2 7% 4 4 4 4 6% 8% 38%	2969
	11th to 20th	Day	18% 7% 3 7% 5% 5% 5% 4 6% 8% 32%	3040
	21st to end	Day	9% 6% 2 6% 4 5% 5% 5% 7% 9% 42%	3040
July	1st to 10th	Day	5% 4 2 6% 5% 5% 6% 5% 8% 9% 45%	4850
	11th to 20th	Day	5% 3 1 4 3 4 5% 5% 7% 10% 53%	4622
	21st to end	Day	3 3 1 4 3 3 4 3 5% 8% 62%	4802
August	1st to 10th	Day	8% 5% 2 5% 3 4 4 4 6% 7% 52%	4412
	11th to 20th	Day	7% 4 2 5% 3 4 4 4 7% 10% 52%	4318
	21st to end	Day	9% 5% 2 5% 4 3 4 3 4 8% 55%	4273
September	1st to 10th	Day	11% 5% 2 6% 3 4 4 4 5% 9% 49%	2280
	11th to 20th	Day	13% 7% 2 6% 4 5% 5% 3 4 7% 44%	2275
	21st to end	Day	12% 5% 2 5% 3 3 3 3 6% 9% 48%	2050
October	1st to 10th	Day	15% 10% 3 7% 4 4 4 3 5% 6% 40%	1900
	11th to 20th	Day	8% 10% 3 8% 5% 3 4 4 5% 8% 42%	1833
	21st to end	Day	10% 12% 5% 11% 6% 4 4 3 5% 7% 34%	1881
November	1st to 10th	Day	12% 15% 5% 10% 6% 5% 4 3 4 6% 31%	1561
	11th to 20th	Day	6% 11% 5% 14% 8% 6% 5% 4 5% 7% 30%	1520
	21st to end	Day	10% 12% 5% 9% 7% 6% 5% 5% 6% 6% 29%	1392
December	1st to 10th	Day	8% 14% 4 14% 9% 6% 6% 5% 6% 6% 23%	1330
	11th to 20th	Day	6% 15% 7% 13% 8% 6% 6% 5% 5% 7% 21%	1571
	21st to end	Day	5% 8% 4 9% 6% 4 5% 4 4 6% 46%	2136
January	1st to 10th	Night	4 12% 5% 14% 8% 6% 6% 5% 7% 6% 28%	4726
	11th to 20th	Night	4 8% 4 14% 10% 11% 10% 6% 6% 5% 22%	4476
	21st to end	Night	6% 13% 4 10% 5% 6% 6% 4 5% 7% 34%	4873
February	1st to 10th	Night	7% 12% 5% 12% 9% 7% 7% 4 6% 7% 25%	2618
	11th to 20th	Night	6% 12% 4 10% 8% 6% 7% 6% 6% 7% 28%	2402
	21st to end	Night	4 8% 4 13% 7% 6% 7% 4 7% 8% 32%	1928
March	1st to 10th	Night	7% 11% 5% 13% 7% 6% 6% 4 6% 7% 28%	3734
	11th to 20th	Night	5% 10% 4 8% 6% 6% 5% 4 6% 9% 37%	3624
	21st to end	Night	6% 10% 4 14% 7% 6% 6% 4 6% 7% 30%	3545
April	1st to 10th	Night	6% 9% 2 7% 4 5% 5% 4 7% 9% 43%	1900
	11th to 20th	Night	12% 12% 4 8% 4 5% 5% 4 6% 8% 32%	1863
	21st to end	Night	12% 9% 4 7% 6% 5% 6% 5% 6% 7% 34%	1541
May	1st to 10th	Night	20% 14% 3 6% 4 4 4 3 5% 6% 32%	2540
	11th to 20th	Night	12% 8% 2 6% 4 4 5% 4 7% 8% 41%	2518
	21st to end	Night	14% 6% 2 7% 5% 5% 5% 4 7% 8% 39%	2699
June	1st to 10th	Night	12% 5% 2 5% 4 4 4 4 7% 9% 44%	1208
	11th to 20th	Night	14% 7% 2 5% 4 5% 4 3 6% 9% 41%	1140
	21st to end	Night	8% 5% 2 4 4 4 6% 5% 7% 9% 47%	1140
July	1st to 10th	Night	6% 4 1 4 4 4 5% 4 7% 10% 52%	2106
	11th to 20th	Night	5% 3 1 4 3 3 4 3 6% 8% 59%	2338
	21st to end	Night	3 3 1 4 2 3 3 3 5% 8% 64%	2762
August	1st to 10th	Night	7% 4 1 4 4 4 3 3 5% 8% 56%	2528
	11th to 20th	Night	4 3 2 5% 4 4 5% 5% 8% 9% 53%	2518
	21st to end	Night	7% 4 2 4 3 4 5% 4 6% 9% 53%	3393
September	1st to 10th	Night	9% 4 2 4 3 4 4 4 5% 7% 54%	1900
	11th to 20th	Night	10% 5% 2 5% 4 4 4 4 5% 8% 48%	1905
	21st to end	Night	10% 6% 2 5% 4 4 3 4 6% 7% 50%	2128
October	1st to 10th	Night	13% 9% 3 5% 4 4 4 3 5% 8% 42%	2280
	11th to 20th	Night	8% 9% 2 7% 3 3 4 4 5% 7% 47%	2327
	21st to end	Night	9% 12% 4 9% 6% 5% 4 4 5% 7% 35%	2717
November	1st to 10th	Night	14% 14% 5% 8% 5% 4 4 4 4 6% 32%	2552
	11th to 20th	Night	7% 12% 4 12% 7% 6% 6% 4 6% 7% 29%	2660
	21st to end	Night	8% 12% 5% 11% 6% 5% 5% 3 6% 8% 32%	2786
December	1st to 10th	Night	7% 13% 5% 12% 9% 7% 6% 5% 5% 6% 26%	2850
	11th to 20th	Night	8% 13% 6% 14% 7% 6% 6% 5% 5% 7% 24%	3618
	21st to end	Night	5% 8% 3 7% 5% 4 4 4 5% 7% 49%	5503

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	58% 8% 15% 14% 5%	2219
	11th to 20th	Day	59% 7% 16% 13% 6%	2449
	21st to end	Day	51% 6% 15% 24% 4	2794
February	1st to 10th	Day	62% 5% 12% 16% 6%	1577
	11th to 20th	Day	57% 8% 11% 13% 10% 1	1674
	21st to end	Day	57% 8% 13% 14% 8%	1525
March	1st to 10th	Day	57% 6% 16% 17% 4	3130
	11th to 20th	Day	46% 9% 22% 19% 5%	3348
	21st to end	Day	50% 8% 15% 17% 9% 1	4098
April	1st to 10th	Day	40% 8% 17% 23% 11% 1	2280
	11th to 20th	Day	54% 6% 13% 19% 6% 2	2268
	21st to end	Day	48% 5% 15% 22% 8% 1	2636
May	1st to 10th	Day	49% 5% 14% 24% 8% 1	4430
	11th to 20th	Day	40% 9% 12% 24% 14%	4392
	21st to end	Day	45% 9% 14% 25% 8%	4884
June	1st to 10th	Day	42% 7% 14% 27% 10% 1	2969
	11th to 20th	Day	49% 7% 14% 19% 10% 1	3040
	21st to end	Day	35% 9% 17% 29% 10% 1	3040
July	1st to 10th	Day	30% 10% 24% 28% 8% 1	4776
	11th to 20th	Day	25% 7% 18% 36% 14% 1	4541
	21st to end	Day	20% 6% 13% 40% 18% 3	4651
August	1st to 10th	Day	30% 7% 19% 26% 17% 1	4396
	11th to 20th	Day	27% 6% 18% 38% 10% 1	4360
	21st to end	Day	29% 5% 14% 38% 12% 1	4272
September	1st to 10th	Day	32% 7% 14% 28% 16% 2	2280
	11th to 20th	Day	39% 5% 14% 28% 11% 2	2275
	21st to end	Day	33% 5% 14% 32% 14% 2	2050
October	1st to 10th	Day	45% 5% 15% 25% 10% 1	1900
	11th to 20th	Day	40% 4 13% 31% 10% 1	1833
	21st to end	Day	51% 5% 17% 20% 7%	1881
November	1st to 10th	Day	56% 5% 13% 18% 7%	1561
	11th to 20th	Day	54% 6% 15% 18% 7% 1	1520
	21st to end	Day	54% 8% 17% 17% 4	1392
December	1st to 10th	Day	60% 6% 13% 15% 5% 1	1330
	11th to 20th	Day	60% 7% 19% 10% 4	1571
	21st to end	Day	40% 4 12% 24% 13% 7%	2136
January	1st to 10th	Night	53% 7% 17% 19% 4	4726
	11th to 20th	Night	61% 6% 16% 13% 4	4514
	21st to end	Night	49% 6% 18% 22% 4	4873
February	1st to 10th	Night	57% 6% 12% 18% 7%	2618
	11th to 20th	Night	52% 7% 13% 18% 9% 1	2403
	21st to end	Night	48% 5% 16% 22% 9%	1928
March	1st to 10th	Night	53% 7% 18% 18% 4	3734
	11th to 20th	Night	42% 8% 24% 20% 6%	3624
	21st to end	Night	51% 6% 14% 19% 9%	3545
April	1st to 10th	Night	37% 5% 16% 25% 16% 1	1900
	11th to 20th	Night	48% 7% 10% 21% 10% 3	1863
	21st to end	Night	46% 7% 11% 25% 10% 1	1541
May	1st to 10th	Night	51% 6% 10% 21% 11% 1	2540
	11th to 20th	Night	38% 7% 12% 23% 16% 3	2518
	21st to end	Night	39% 9% 13% 29% 9% 1	2699
June	1st to 10th	Night	34% 6% 15% 29% 14% 2	1208
	11th to 20th	Night	39% 8% 16% 23% 13% 1	1140
	21st to end	Night	31% 9% 17% 31% 11% 1	1140
July	1st to 10th	Night	25% 9% 29% 29% 7%	2071
	11th to 20th	Night	21% 6% 14% 39% 17% 2	2296
	21st to end	Night	18% 5% 14% 40% 18% 6%	2674
August	1st to 10th	Night	26% 7% 19% 31% 17% 1	2520
	11th to 20th	Night	24% 7% 17% 37% 13% 1	2542
	21st to end	Night	27% 6% 14% 37% 14% 2	3393
September	1st to 10th	Night	29% 6% 11% 30% 22% 3	1900
	11th to 20th	Night	33% 6% 15% 28% 16% 2	1905
	21st to end	Night	34% 5% 13% 31% 16% 2	2128
October	1st to 10th	Night	41% 5% 17% 25% 11% 1	2280
	11th to 20th	Night	36% 5% 16% 30% 12% 1	2327
	21st to end	Night	49% 5% 14% 24% 8% 1	2717
November	1st to 10th	Night	54% 6% 13% 18% 7% 2	2552
	11th to 20th	Night	54% 7% 17% 16% 6%	2660
	21st to end	Night	51% 6% 20% 19% 4	2786
December	1st to 10th	Night	59% 5% 15% 16% 6%	2850
	11th to 20th	Night	59% 7% 13% 16% 5% 1	3617
	21st to end	Night	36% 4 12% 26% 16% 5%	5503

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% 9% 28% 28% 16% 5%	180
	11th to 20th	Day	10% 10% 29% 31% 17% 2	246
	21st to end	Day	13% 9% 31% 34% 11% 1	297
February	1st to 10th	Day	14% 8% 34% 31% 11% 1	270
	11th to 20th	Day	14% 7% 38% 25% 14% 2	270
	21st to end	Day	7% 5% 31% 38% 16% 3	225
March	1st to 10th	Day	13% 8% 36% 27% 13% 3	270
	11th to 20th	Day	11% 11% 37% 25% 11% 5%	370
	21st to end	Day	13% 11% 30% 29% 15% 2	506
April	1st to 10th	Day	10% 15% 36% 27% 10% 2	460
	11th to 20th	Day	17% 14% 32% 25% 11% 2	466
	21st to end	Day	16% 9% 30% 28% 16% 1	650
May	1st to 10th	Day	13% 7% 28% 30% 19% 3	653
	11th to 20th	Day	12% 6% 26% 31% 17% 7%	675
	21st to end	Day	16% 9% 24% 28% 18% 6%	734
June	1st to 10th	Day	16% 11% 28% 24% 17% 4	680
	11th to 20th	Day	19% 13% 29% 25% 12% 3	680
	21st to end	Day	10% 8% 24% 32% 20% 5%	680
July	1st to 10th	Day	7% 5% 22% 35% 24% 7%	671
	11th to 20th	Day	7% 6% 28% 31% 21% 6%	668
	21st to end	Day	6% 6% 26% 31% 22% 9%	739
August	1st to 10th	Day	8% 6% 20% 38% 21% 6%	676
	11th to 20th	Day	8% 4 21% 35% 24% 8%	653
	21st to end	Day	10% 7% 24% 32% 21% 6%	539
September	1st to 10th	Day	11% 12% 29% 30% 13% 4	490
	11th to 20th	Day	16% 9% 28% 29% 16% 1	485
	21st to end	Day	14% 9% 30% 30% 14% 2	300
October	1st to 10th	Day	17% 8% 28% 26% 19% 2	300
	11th to 20th	Day	10% 12% 35% 25% 16% 1	300
	21st to end	Day	13% 11% 37% 27% 10% 2	330
November	1st to 10th	Day	22% 10% 26% 28% 11% 3	273
	11th to 20th	Day	13% 9% 39% 29% 11%	270
	21st to end	Day	14% 10% 36% 27% 13% 1	270
December	1st to 10th	Day	12% 6% 36% 31% 10% 4	270
	11th to 20th	Day	10% 10% 50% 23% 6% 1	237
	21st to end	Day	13% 6% 33% 32% 14% 3	198
January	1st to 10th	Night	8% 11% 35% 32% 13% 1	950
	11th to 20th	Night	12% 11% 34% 34% 8% 1	950
	21st to end	Night	12% 10% 37% 30% 11% 1	1045
February	1st to 10th	Night	11% 8% 33% 33% 14% 1	908
	11th to 20th	Night	11% 7% 36% 34% 10% 2	744
	21st to end	Night	5% 5% 25% 41% 20% 4	628
March	1st to 10th	Night	10% 8% 34% 34% 13% 2	760
	11th to 20th	Night	10% 7% 35% 32% 14% 1	760
	21st to end	Night	14% 7% 30% 35% 14% 1	669
April	1st to 10th	Night	9% 7% 36% 36% 11% 1	570
	11th to 20th	Night	17% 10% 32% 34% 6% 1	563
	21st to end	Night	17% 8% 31% 37% 7% 1	570
May	1st to 10th	Night	15% 5% 26% 36% 16% 1	570
	11th to 20th	Night	14% 6% 29% 35% 15% 1	561
	21st to end	Night	19% 5% 27% 32% 16% 2	617
June	1st to 10th	Night	13% 6% 29% 35% 16% 1	448
	11th to 20th	Night	17% 7% 28% 36% 12% 1	380
	21st to end	Night	10% 7% 25% 41% 16% 1	380
July	1st to 10th	Night	8% 4 19% 47% 19% 1	370
	11th to 20th	Night	7% 3 26% 45% 18% 1	434
	21st to end	Night	5% 3 25% 43% 22% 2	624
August	1st to 10th	Night	7% 3 24% 42% 21% 2	567
	11th to 20th	Night	6% 4 21% 42% 24% 3	564
	21st to end	Night	8% 4 27% 40% 19% 1	627
September	1st to 10th	Night	9% 6% 26% 39% 17% 3	570
	11th to 20th	Night	11% 6% 25% 42% 16% 1	570
	21st to end	Night	13% 5% 31% 39% 11% 1	608
October	1st to 10th	Night	18% 6% 27% 33% 15% 1	760
	11th to 20th	Night	12% 6% 30% 37% 14% 1	807
	21st to end	Night	16% 9% 32% 32% 10% 1	1045
November	1st to 10th	Night	20% 8% 32% 32% 8%	935
	11th to 20th	Night	14% 10% 33% 31% 9% 2	950
	21st to end	Night	13% 10% 37% 33% 6% 1	950
December	1st to 10th	Night	13% 6% 35% 30% 13% 3	950
	11th to 20th	Night	13% 11% 34% 29% 13% 1	950
	21st to end	Night	13% 6% 32% 34% 13% 2	1045

Page generated at 2024-10-30 11:19:23. Version ac07

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