Poker Flat Research Range
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Poker Flat Research Range clear sky chart from 2005-11-06 to 2024-11-05.

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	14% 12% 4 10% 6% 6% 5% 4 6% 7% 26%	107070
	Night	8% 13% 5% 12% 7% 6% 5% 4 6% 6% 29%	100580
Transparency	Day	56% 8% 15% 16% 4 1	106720
	Night	54% 7% 13% 17% 8% 2	100577
Seeing	Day	16% 5% 17% 27% 25% 10%	18773
	Night	13% 4 15% 32% 28% 8%	22836

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	3 12% 4 12% 4 6% 4 2 3 5% 46%	780
	11th to 20th	Day	3 11% 5% 12% 7% 6% 6% 5% 7% 6% 33%	1258
	21st to end	Day	4 9% 5% 11% 8% 7% 7% 6% 8% 8% 28%	1659
February	1st to 10th	Day	2 11% 4 10% 5% 5% 5% 5% 6% 4 41%	1140
	11th to 20th	Day	4 11% 4 16% 9% 6% 7% 8% 5% 7% 23%	1381
	21st to end	Day	4 14% 8% 11% 8% 4 7% 4 6% 5% 28%	1256
March	1st to 10th	Day	3 15% 9% 19% 9% 6% 4 3 4 4 25%	3036
	11th to 20th	Day	3 10% 6% 13% 7% 6% 6% 4 6% 7% 32%	3224
	21st to end	Day	5% 14% 5% 9% 6% 5% 6% 4 6% 8% 31%	4161
April	1st to 10th	Day	5% 15% 6% 10% 9% 6% 6% 4 6% 7% 26%	2438
	11th to 20th	Day	5% 10% 4 9% 6% 4 4 5% 6% 7% 40%	2633
	21st to end	Day	5% 9% 3 7% 5% 6% 6% 5% 6% 7% 40%	2908
May	1st to 10th	Day	8% 16% 5% 13% 8% 7% 6% 5% 6% 6% 21%	5189
	11th to 20th	Day	5% 9% 3 9% 7% 6% 7% 5% 7% 8% 34%	5508
	21st to end	Day	14% 10% 4 9% 6% 6% 6% 5% 7% 7% 26%	6426
June	1st to 10th	Day	13% 8% 4 9% 7% 7% 7% 5% 7% 8% 26%	3768
	11th to 20th	Day	14% 8% 3 8% 7% 7% 6% 5% 7% 8% 27%	3800
	21st to end	Day	16% 7% 3 7% 5% 5% 7% 5% 7% 9% 29%	3800
July	1st to 10th	Day	30% 10% 3 7% 5% 5% 5% 4 5% 7% 19%	6330
	11th to 20th	Day	19% 9% 3 8% 5% 5% 7% 5% 7% 8% 25%	5910
	21st to end	Day	25% 10% 3 7% 4 5% 5% 4 5% 7% 26%	6165
August	1st to 10th	Day	28% 11% 4 7% 5% 5% 5% 4 5% 6% 20%	5091
	11th to 20th	Day	25% 14% 3 9% 6% 5% 5% 4 6% 7% 17%	4851
	21st to end	Day	26% 15% 4 9% 6% 5% 4 4 5% 6% 15%	4886
September	1st to 10th	Day	21% 11% 3 9% 5% 5% 5% 4 6% 7% 24%	2481
	11th to 20th	Day	22% 15% 4 10% 5% 4 5% 4 5% 5% 20%	2247
	21st to end	Day	18% 17% 4 10% 6% 5% 4 4 4 5% 23%	2062
October	1st to 10th	Day	9% 17% 6% 10% 6% 4 4 3 4 5% 32%	2984
	11th to 20th	Day	7% 17% 7% 16% 6% 6% 5% 3 5% 4 25%	2751
	21st to end	Day	11% 15% 7% 15% 7% 5% 5% 3 5% 5% 22%	2424
November	1st to 10th	Day	7% 15% 5% 13% 8% 6% 5% 4 5% 5% 26%	1158
	11th to 20th	Day	6% 12% 5% 14% 11% 8% 5% 3 3 5% 29%	950
	21st to end	Day	10% 12% 5% 12% 8% 6% 4 5% 5% 6% 27%	669
December	1st to 10th	Day	9% 16% 6% 9% 6% 5% 4 5% 4 6% 30%	556
	11th to 20th	Day	2 16% 7% 14% 6% 11% 3 5% 6% 8% 22%	486
	21st to end	Day	2 10% 5% 11% 6% 7% 7% 4 10% 9% 29%	704
January	1st to 10th	Night	3 10% 5% 10% 7% 6% 5% 4 4 6% 41%	6204
	11th to 20th	Night	3 14% 5% 12% 6% 6% 5% 4 6% 6% 32%	5650
	21st to end	Night	3 9% 4 11% 6% 5% 7% 6% 9% 7% 34%	6005
February	1st to 10th	Night	2 10% 6% 14% 6% 4 4 4 5% 4 42%	3040
	11th to 20th	Night	4 10% 5% 11% 7% 7% 7% 5% 8% 8% 29%	2684
	21st to end	Night	4 13% 7% 14% 8% 6% 6% 5% 5% 6% 26%	2198
March	1st to 10th	Night	3 15% 9% 18% 7% 6% 4 3 3 4 28%	3818
	11th to 20th	Night	4 10% 5% 12% 8% 6% 7% 5% 6% 8% 29%	3734
	21st to end	Night	5% 12% 4 8% 6% 6% 6% 4 6% 9% 33%	3467
April	1st to 10th	Night	5% 15% 5% 12% 6% 5% 6% 5% 7% 6% 28%	1739
	11th to 20th	Night	4 7% 4 9% 6% 5% 7% 6% 6% 7% 39%	1496
	21st to end	Night	6% 7% 3 8% 6% 4 4 4 7% 7% 43%	1270
May	1st to 10th	Night	7% 12% 4 11% 7% 8% 7% 6% 7% 8% 22%	1777
	11th to 20th	Night	5% 6% 3 9% 6% 5% 7% 6% 9% 11% 33%	1392
	21st to end	Night	16% 11% 3 10% 6% 5% 4 4 5% 6% 31%	1160
June	1st to 10th	Night	10% 6% 2 9% 7% 6% 6% 7% 8% 9% 30%	409
	11th to 20th	Night	13% 5% 3 10% 7% 7% 5% 5% 8% 8% 29%	380
	21st to end	Night	17% 4 3 8% 5% 7% 6% 7% 9% 8% 28%	380
July	1st to 10th	Night	26% 11% 4 8% 5% 4 3 3 6% 9% 20%	640
	11th to 20th	Night	17% 9% 2 8% 5% 5% 5% 4 5% 6% 34%	1058
	21st to end	Night	23% 8% 3 7% 5% 5% 4 4 6% 8% 28%	1397
August	1st to 10th	Night	23% 13% 3 9% 6% 4 6% 4 5% 7% 20%	1846
	11th to 20th	Night	31% 15% 4 8% 5% 4 3 3 5% 6% 16%	1987
	21st to end	Night	25% 16% 3 8% 6% 5% 5% 3 5% 4 20%	2778
September	1st to 10th	Night	17% 12% 2 8% 6% 5% 5% 4 6% 8% 27%	1697
	11th to 20th	Night	20% 15% 4 8% 5% 6% 5% 4 5% 6% 22%	1933
	21st to end	Night	18% 15% 4 9% 5% 5% 5% 4 6% 5% 25%	2117
October	1st to 10th	Night	9% 16% 5% 9% 5% 5% 6% 4 5% 7% 29%	3982
	11th to 20th	Night	9% 17% 6% 11% 6% 6% 5% 4 5% 6% 26%	4174
	21st to end	Night	9% 15% 7% 17% 8% 5% 4 3 4 4 23%	5135
November	1st to 10th	Night	7% 18% 6% 11% 7% 5% 4 3 5% 5% 29%	3018
	11th to 20th	Night	8% 13% 5% 14% 7% 5% 5% 4 5% 6% 27%	3230
	21st to end	Night	8% 13% 4 13% 8% 6% 5% 4 6% 5% 27%	3492
December	1st to 10th	Night	7% 14% 6% 13% 6% 6% 5% 4 5% 5% 27%	3622
	11th to 20th	Night	4 17% 7% 16% 8% 7% 6% 4 6% 5% 20%	4708
	21st to end	Night	3 11% 5% 12% 8% 7% 6% 5% 6% 7% 29%	6963

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	43% 4 11% 23% 10% 8%	780
	11th to 20th	Day	49% 7% 17% 13% 10% 5%	1270
	21st to end	Day	51% 5% 9% 13% 14% 8%	1659
February	1st to 10th	Day	44% 6% 7% 17% 20% 7%	1140
	11th to 20th	Day	56% 7% 10% 17% 9% 1	1387
	21st to end	Day	55% 6% 11% 16% 10% 2	1256
March	1st to 10th	Day	64% 4 8% 10% 13% 2	3036
	11th to 20th	Day	48% 7% 12% 21% 11% 1	3224
	21st to end	Day	49% 9% 18% 14% 8% 2	4161
April	1st to 10th	Day	57% 6% 12% 17% 7% 1	2438
	11th to 20th	Day	42% 7% 16% 25% 9% 2	2633
	21st to end	Day	41% 7% 13% 30% 8%	2908
May	1st to 10th	Day	60% 9% 11% 17% 4	5189
	11th to 20th	Day	43% 11% 14% 28% 5%	5511
	21st to end	Day	52% 12% 13% 19% 5%	6427
June	1st to 10th	Day	53% 10% 15% 19% 3	3768
	11th to 20th	Day	52% 11% 16% 19% 2	3800
	21st to end	Day	49% 11% 20% 19% 2	3800
July	1st to 10th	Day	65% 9% 16% 8% 1	6231
	11th to 20th	Day	54% 9% 18% 19% 1	5803
	21st to end	Day	56% 8% 18% 14% 4	5970
August	1st to 10th	Day	64% 7% 19% 9% 1	5071
	11th to 20th	Day	65% 9% 19% 8%	4899
	21st to end	Day	69% 8% 15% 7% 1	4885
September	1st to 10th	Day	58% 9% 20% 11% 1	2481
	11th to 20th	Day	64% 9% 15% 11%	2247
	21st to end	Day	62% 9% 11% 14% 3	2062
October	1st to 10th	Day	57% 5% 10% 23% 6%	2984
	11th to 20th	Day	63% 7% 11% 17% 2	2751
	21st to end	Day	66% 5% 12% 15% 3	2424
November	1st to 10th	Day	59% 7% 14% 15% 4 1	1158
	11th to 20th	Day	60% 7% 12% 16% 6%	950
	21st to end	Day	57% 7% 10% 18% 7%	669
December	1st to 10th	Day	54% 8% 13% 15% 7% 2	556
	11th to 20th	Day	60% 7% 11% 16% 5% 1	488
	21st to end	Day	46% 6% 16% 19% 12% 1	704
January	1st to 10th	Night	43% 6% 13% 26% 9% 3	6204
	11th to 20th	Night	51% 6% 14% 16% 9% 4	5700
	21st to end	Night	44% 5% 9% 15% 20% 7%	6005
February	1st to 10th	Night	46% 4 7% 16% 21% 7%	3040
	11th to 20th	Night	49% 7% 11% 21% 11% 1	2689
	21st to end	Night	58% 5% 11% 13% 11% 2	2198
March	1st to 10th	Night	61% 4 5% 15% 13% 2	3818
	11th to 20th	Night	52% 6% 12% 19% 10% 2	3736
	21st to end	Night	43% 10% 20% 15% 10% 2	3467
April	1st to 10th	Night	53% 7% 13% 19% 7% 1	1739
	11th to 20th	Night	42% 10% 15% 24% 7% 2	1496
	21st to end	Night	40% 5% 17% 29% 10%	1270
May	1st to 10th	Night	54% 12% 11% 20% 2	1777
	11th to 20th	Night	38% 12% 16% 30% 4	1392
	21st to end	Night	51% 10% 12% 20% 8%	1160
June	1st to 10th	Night	47% 10% 17% 21% 4	409
	11th to 20th	Night	51% 10% 15% 21% 3	380
	21st to end	Night	47% 13% 21% 18% 1	380
July	1st to 10th	Night	64% 8% 17% 8% 2	630
	11th to 20th	Night	52% 7% 17% 22% 2	1042
	21st to end	Night	54% 9% 17% 16% 4	1353
August	1st to 10th	Night	64% 7% 20% 7% 2	1841
	11th to 20th	Night	69% 7% 18% 7%	2005
	21st to end	Night	68% 6% 16% 9% 1	2778
September	1st to 10th	Night	55% 10% 20% 14% 1	1697
	11th to 20th	Night	62% 8% 16% 13% 1	1933
	21st to end	Night	60% 9% 11% 16% 3	2117
October	1st to 10th	Night	55% 6% 11% 22% 5%	3982
	11th to 20th	Night	59% 7% 15% 17% 2	4174
	21st to end	Night	66% 5% 11% 16% 2	5135
November	1st to 10th	Night	59% 6% 13% 18% 3 2	3018
	11th to 20th	Night	59% 7% 14% 17% 4	3230
	21st to end	Night	57% 6% 11% 17% 8%	3492
December	1st to 10th	Night	57% 7% 13% 14% 7% 2	3622
	11th to 20th	Night	65% 6% 10% 12% 6%	4705
	21st to end	Night	51% 7% 12% 13% 15% 2	6963

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	7% 4 18% 39% 28% 4	90
	11th to 20th	Day	2 4 19% 38% 30% 7%	90
	21st to end	Day	6% 6% 14% 35% 25% 14%	185
February	1st to 10th	Day	5% 5% 14% 30% 28% 19%	280
	11th to 20th	Day	6% 5% 20% 33% 26% 10%	335
	21st to end	Day	8% 7% 21% 34% 23% 7%	307
March	1st to 10th	Day	6% 5% 22% 31% 29% 7%	370
	11th to 20th	Day	8% 7% 25% 28% 22% 11%	370
	21st to end	Day	8% 9% 21% 32% 23% 8%	612
April	1st to 10th	Day	11% 9% 24% 31% 20% 5%	621
	11th to 20th	Day	10% 6% 22% 30% 28% 5%	640
	21st to end	Day	9% 4 18% 31% 28% 11%	650
May	1st to 10th	Day	9% 5% 22% 28% 27% 8%	653
	11th to 20th	Day	9% 6% 21% 32% 24% 8%	775
	21st to end	Day	16% 7% 18% 29% 23% 7%	1070
June	1st to 10th	Day	13% 5% 16% 28% 26% 13%	1060
	11th to 20th	Day	14% 4 15% 25% 30% 12%	1060
	21st to end	Day	16% 3 12% 25% 30% 14%	1060
July	1st to 10th	Day	19% 3 14% 24% 30% 10%	1041
	11th to 20th	Day	22% 4 14% 24% 24% 11%	939
	21st to end	Day	20% 3 15% 22% 25% 15%	942
August	1st to 10th	Day	29% 5% 17% 21% 20% 9%	676
	11th to 20th	Day	29% 6% 17% 25% 18% 5%	665
	21st to end	Day	32% 4 16% 22% 20% 7%	748
September	1st to 10th	Day	25% 7% 14% 20% 22% 11%	665
	11th to 20th	Day	28% 7% 16% 25% 18% 6%	547
	21st to end	Day	27% 7% 18% 18% 18% 12%	390
October	1st to 10th	Day	24% 8% 19% 20% 18% 11%	390
	11th to 20th	Day	14% 5% 19% 24% 23% 15%	390
	21st to end	Day	17% 6% 11% 23% 28% 14%	429
November	1st to 10th	Day	14% 6% 11% 30% 28% 11%	264
	11th to 20th	Day	6% 6% 10% 32% 30% 17%	90
	21st to end	Day	11% 2 11% 40% 31% 4	90
December	1st to 10th	Day	13% 4 16% 39% 20% 8%	90
	11th to 20th	Day	7% 6% 26% 31% 28% 3	90
	21st to end	Day	4 11% 21% 26% 33% 4	99
January	1st to 10th	Night	8% 3 16% 32% 31% 10%	1124
	11th to 20th	Night	9% 4 16% 40% 25% 7%	940
	21st to end	Night	8% 4 20% 37% 24% 8%	998
February	1st to 10th	Night	5% 7% 16% 33% 29% 10%	850
	11th to 20th	Night	7% 3 19% 37% 27% 6%	834
	21st to end	Night	8% 4 20% 38% 27% 3	703
March	1st to 10th	Night	8% 4 16% 39% 28% 5%	683
	11th to 20th	Night	8% 3 17% 39% 27% 5%	642
	21st to end	Night	9% 4 18% 33% 27% 9%	627
April	1st to 10th	Night	10% 4 20% 32% 29% 5%	570
	11th to 20th	Night	7% 3 16% 38% 29% 7%	563
	21st to end	Night	9% 3 11% 28% 41% 8%	510
May	1st to 10th	Night	13% 3 11% 27% 37% 9%	309
	11th to 20th	Night	10% 5% 13% 40% 30% 3	187
	21st to end	Night	15% 5% 9% 34% 31% 7%	206
June	1st to 10th	Night	10% 3 11% 29% 37% 9%	190
	11th to 20th	Night	13% 3 8% 29% 38% 9%	190
	21st to end	Night	17% 3 4 23% 44% 8%	190
July	1st to 10th	Night	13% 3 11% 24% 41% 9%	185
	11th to 20th	Night	21% 1 13% 23% 35% 8%	184
	21st to end	Night	24% 9% 22% 39% 6%	208
August	1st to 10th	Night	30% 3 6% 22% 34% 5%	343
	11th to 20th	Night	31% 4 9% 21% 30% 6%	441
	21st to end	Night	30% 3 9% 19% 28% 11%	627
September	1st to 10th	Night	24% 3 12% 22% 28% 11%	570
	11th to 20th	Night	27% 4 11% 26% 27% 5%	570
	21st to end	Night	24% 5% 15% 23% 28% 5%	585
October	1st to 10th	Night	22% 5% 17% 27% 25% 4	774
	11th to 20th	Night	16% 3 15% 28% 27% 11%	860
	21st to end	Night	14% 4 12% 33% 29% 9%	946
November	1st to 10th	Night	15% 5% 15% 32% 24% 8%	854
	11th to 20th	Night	14% 4 14% 28% 26% 14%	850
	21st to end	Night	12% 3 14% 33% 28% 9%	1020
December	1st to 10th	Night	13% 4 15% 38% 23% 8%	1130
	11th to 20th	Night	10% 3 19% 29% 30% 9%	1130
	21st to end	Night	8% 5% 15% 32% 29% 11%	1243

Page generated at 2024-11-02 22:11:28. Version ac07

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