Pine River Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pine River Observatory clear sky chart from 2005-11-06 to 2024-12-06.

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	13% 10% 4 9% 6% 5% 5% 4 6% 7% 31%	102390
	Night	13% 11% 4 9% 6% 5% 5% 4 5% 7% 32%	97318
Transparency	Day	51% 5% 12% 20% 10% 1	105990
	Night	51% 5% 13% 20% 10% 1	101808
Seeing	Day	20% 20% 30% 19% 8% 3	14983
	Night	19% 18% 31% 22% 8% 1	23901

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% 13% 7% 16% 8% 5% 6% 5% 5% 5% 16%	2517
	11th to 20th	Day	9% 18% 8% 21% 11% 7% 6% 4 3 4 11%	2779
	21st to end	Day	18% 21% 7% 12% 7% 5% 4 4 5% 4 13%	3124
February	1st to 10th	Day	11% 17% 4 14% 10% 7% 7% 4 5% 5% 17%	1710
	11th to 20th	Day	10% 13% 7% 15% 9% 6% 6% 4 6% 6% 19%	1663
	21st to end	Day	14% 16% 5% 12% 8% 4 5% 3 5% 5% 23%	1475
March	1st to 10th	Day	15% 13% 5% 10% 6% 5% 4 4 4 5% 28%	3419
	11th to 20th	Day	9% 16% 6% 12% 6% 5% 5% 4 4 5% 27%	3480
	21st to end	Day	12% 12% 4 8% 6% 5% 5% 4 5% 5% 34%	3815
April	1st to 10th	Day	15% 14% 4 9% 6% 5% 4 3 4 6% 29%	2223
	11th to 20th	Day	18% 10% 4 7% 4 4 3 4 5% 6% 36%	2371
	21st to end	Day	19% 10% 4 7% 5% 4 4 3 5% 6% 34%	2470
May	1st to 10th	Day	15% 10% 3 7% 4 4 4 3 5% 8% 36%	4108
	11th to 20th	Day	16% 9% 3 7% 5% 5% 5% 4 6% 8% 32%	4351
	21st to end	Day	11% 6% 2 6% 4 4 5% 4 5% 8% 46%	4837
June	1st to 10th	Day	15% 7% 2 6% 4 4 5% 4 7% 9% 36%	2660
	11th to 20th	Day	10% 6% 2 6% 5% 5% 5% 5% 7% 9% 41%	2806
	21st to end	Day	13% 6% 2 6% 5% 5% 6% 4 7% 8% 39%	2850
July	1st to 10th	Day	10% 5% 3 8% 6% 5% 6% 5% 8% 9% 36%	4760
	11th to 20th	Day	10% 5% 2 5% 5% 4 5% 5% 7% 8% 42%	4458
	21st to end	Day	8% 5% 2 6% 5% 5% 6% 4 6% 9% 43%	4476
August	1st to 10th	Day	13% 7% 3 7% 4 4 5% 5% 7% 8% 37%	4104
	11th to 20th	Day	10% 8% 3 8% 5% 6% 6% 5% 8% 10% 33%	4044
	21st to end	Day	10% 5% 2 7% 4 4 6% 4 7% 8% 42%	4410
September	1st to 10th	Day	14% 7% 3 7% 5% 5% 5% 4 5% 8% 39%	2280
	11th to 20th	Day	11% 6% 3 6% 5% 4 4 3 6% 8% 44%	2134
	21st to end	Day	13% 7% 3 9% 6% 5% 5% 5% 6% 7% 33%	2072
October	1st to 10th	Day	17% 9% 3 7% 5% 5% 5% 4 5% 7% 33%	1900
	11th to 20th	Day	15% 11% 4 10% 7% 6% 4 5% 5% 7% 25%	1900
	21st to end	Day	22% 17% 4 9% 5% 4 5% 4 5% 5% 19%	2090
November	1st to 10th	Day	11% 15% 5% 10% 7% 6% 4 4 5% 7% 28%	1666
	11th to 20th	Day	11% 15% 6% 12% 7% 6% 6% 5% 6% 6% 21%	1600
	21st to end	Day	14% 17% 7% 13% 7% 7% 6% 3 4 7% 15%	1600
December	1st to 10th	Day	13% 19% 6% 19% 7% 5% 5% 5% 7% 5% 10%	1560
	11th to 20th	Day	15% 16% 7% 14% 7% 6% 5% 4 6% 6% 15%	1906
	21st to end	Day	23% 19% 8% 18% 6% 4 3 3 4 3 9%	2772
January	1st to 10th	Night	14% 16% 6% 14% 8% 6% 6% 4 5% 5% 17%	4429
	11th to 20th	Night	12% 12% 7% 17% 12% 9% 6% 5% 5% 5% 11%	4180
	21st to end	Night	16% 15% 7% 13% 10% 7% 5% 4 4 6% 12%	4532
February	1st to 10th	Night	11% 15% 4 13% 8% 6% 5% 5% 6% 6% 20%	2470
	11th to 20th	Night	9% 13% 6% 12% 7% 7% 6% 4 6% 7% 23%	2403
	21st to end	Night	11% 13% 4 11% 9% 6% 5% 5% 5% 7% 25%	1975
March	1st to 10th	Night	15% 11% 5% 9% 6% 5% 5% 4 5% 6% 30%	3419
	11th to 20th	Night	10% 12% 4 9% 6% 4 4 4 5% 6% 35%	3479
	21st to end	Night	14% 8% 3 8% 5% 4 4 4 6% 7% 37%	3817
April	1st to 10th	Night	16% 13% 3 8% 5% 4 5% 4 6% 6% 30%	1957
	11th to 20th	Night	16% 9% 2 8% 5% 4 5% 3 5% 7% 38%	1773
	21st to end	Night	14% 11% 3 9% 5% 5% 4 4 5% 6% 35%	1710
May	1st to 10th	Night	15% 8% 2 6% 4 4 5% 3 5% 6% 41%	2833
	11th to 20th	Night	15% 7% 3 6% 4 4 4 4 6% 8% 41%	2541
	21st to end	Night	8% 5% 2 6% 4 4 4 4 5% 8% 52%	2738
June	1st to 10th	Night	12% 6% 2 7% 5% 4 4 4 6% 8% 41%	1520
	11th to 20th	Night	8% 5% 1 5% 5% 5% 4 4 8% 10% 45%	1368
	21st to end	Night	11% 6% 2 6% 4 4 4 3 6% 9% 45%	1330
July	1st to 10th	Night	5% 5% 3 6% 4 4 4 4 6% 7% 52%	2210
	11th to 20th	Night	10% 4 1 4 4 4 4 4 5% 7% 54%	2486
	21st to end	Night	6% 5% 2 5% 4 4 5% 5% 6% 8% 50%	3074
August	1st to 10th	Night	8% 6% 2 6% 4 4 5% 4 5% 8% 49%	2825
	11th to 20th	Night	11% 5% 2 5% 4 4 4 3 5% 8% 50%	2785
	21st to end	Night	10% 5% 2 5% 4 4 4 4 5% 8% 49%	3212
September	1st to 10th	Night	9% 5% 2 6% 4 4 5% 4 6% 8% 48%	1900
	11th to 20th	Night	10% 4 2 5% 3 3 4 3 5% 7% 55%	2042
	21st to end	Night	16% 7% 3 7% 6% 4 4 4 4 6% 40%	2107
October	1st to 10th	Night	17% 7% 3 6% 5% 5% 4 3 6% 6% 38%	2280
	11th to 20th	Night	17% 10% 3 7% 5% 4 5% 4 6% 6% 33%	2280
	21st to end	Night	19% 14% 3 8% 6% 5% 6% 4 6% 5% 25%	2508
November	1st to 10th	Night	14% 10% 3 8% 5% 6% 6% 4 6% 6% 33%	2626
	11th to 20th	Night	13% 15% 5% 9% 5% 5% 5% 5% 5% 8% 25%	2800
	21st to end	Night	15% 15% 6% 10% 6% 5% 6% 4 6% 7% 20%	2800
December	1st to 10th	Night	15% 14% 6% 13% 8% 6% 6% 5% 7% 5% 15%	2737
	11th to 20th	Night	13% 16% 6% 13% 8% 5% 5% 5% 7% 6% 17%	3288
	21st to end	Night	22% 22% 7% 16% 6% 5% 4 3 3 4 8%	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	68% 4 14% 11% 3	2518
	11th to 20th	Day	78% 6% 7% 6% 3	2779
	21st to end	Day	75% 4 10% 8% 3	3124
February	1st to 10th	Day	71% 4 8% 13% 3	1710
	11th to 20th	Day	65% 6% 10% 13% 5% 1	1672
	21st to end	Day	64% 4 9% 14% 8% 1	1475
March	1st to 10th	Day	60% 3 12% 15% 9%	3422
	11th to 20th	Day	59% 3 10% 19% 7% 1	3480
	21st to end	Day	50% 5% 11% 19% 12% 2	3815
April	1st to 10th	Day	57% 4 10% 17% 10% 1	2223
	11th to 20th	Day	49% 4 9% 22% 15% 1	2371
	21st to end	Day	52% 5% 10% 19% 12% 2	2470
May	1st to 10th	Day	46% 5% 12% 21% 15% 1	4120
	11th to 20th	Day	49% 5% 16% 20% 9% 1	4355
	21st to end	Day	38% 4 14% 22% 19% 4	4837
June	1st to 10th	Day	43% 6% 12% 22% 15% 1	2660
	11th to 20th	Day	39% 6% 13% 24% 17% 1	2806
	21st to end	Day	42% 6% 13% 24% 14% 1	2850
July	1st to 10th	Day	42% 7% 15% 20% 15% 1	4686
	11th to 20th	Day	36% 7% 13% 33% 11% 1	4382
	21st to end	Day	36% 7% 13% 25% 18% 1	4333
August	1st to 10th	Day	42% 6% 15% 25% 11% 1	4091
	11th to 20th	Day	43% 7% 17% 24% 9%	4083
	21st to end	Day	37% 7% 12% 33% 10% 1	4410
September	1st to 10th	Day	44% 6% 12% 26% 11% 2	2280
	11th to 20th	Day	39% 4 14% 28% 14%	2134
	21st to end	Day	49% 6% 12% 25% 8% 1	2072
October	1st to 10th	Day	45% 6% 12% 24% 11% 1	3160
	11th to 20th	Day	47% 6% 13% 20% 13%	3140
	21st to end	Day	61% 5% 13% 16% 5%	3428
November	1st to 10th	Day	56% 6% 13% 17% 7%	1666
	11th to 20th	Day	62% 6% 13% 13% 6% 1	1600
	21st to end	Day	69% 6% 12% 11% 2	1600
December	1st to 10th	Day	74% 5% 11% 8% 2	1560
	11th to 20th	Day	70% 8% 11% 9% 2	1906
	21st to end	Day	82% 3 7% 7% 1	2772
January	1st to 10th	Night	68% 5% 16% 9% 2	4429
	11th to 20th	Night	76% 6% 9% 7% 2	4180
	21st to end	Night	72% 4 13% 7% 3	4532
February	1st to 10th	Night	63% 6% 11% 16% 3	2470
	11th to 20th	Night	60% 6% 12% 17% 5%	2405
	21st to end	Night	58% 5% 14% 15% 8% 1	1975
March	1st to 10th	Night	54% 5% 12% 21% 7% 1	3429
	11th to 20th	Night	49% 4 15% 22% 9% 2	3480
	21st to end	Night	47% 4 13% 23% 12% 1	3817
April	1st to 10th	Night	54% 4 9% 19% 13% 1	1957
	11th to 20th	Night	48% 3 10% 21% 16% 2	1773
	21st to end	Night	51% 4 11% 16% 16% 2	1710
May	1st to 10th	Night	43% 3 14% 19% 15% 5%	2840
	11th to 20th	Night	42% 5% 15% 25% 12% 2	2542
	21st to end	Night	32% 3 15% 25% 22% 2	2739
June	1st to 10th	Night	40% 5% 13% 22% 18% 2	1520
	11th to 20th	Night	33% 5% 16% 26% 20% 1	1368
	21st to end	Night	37% 5% 15% 28% 15% 1	1330
July	1st to 10th	Night	30% 5% 15% 27% 19% 3	2175
	11th to 20th	Night	30% 5% 13% 36% 16% 1	2440
	21st to end	Night	31% 7% 14% 31% 16% 2	2976
August	1st to 10th	Night	34% 4 15% 29% 16% 2	2814
	11th to 20th	Night	34% 5% 18% 29% 14% 1	2812
	21st to end	Night	34% 5% 15% 32% 14% 1	3212
September	1st to 10th	Night	33% 7% 17% 29% 13% 1	1900
	11th to 20th	Night	30% 4 14% 32% 19% 1	2042
	21st to end	Night	45% 4 14% 26% 10%	2107
October	1st to 10th	Night	37% 5% 11% 26% 20% 1	3800
	11th to 20th	Night	45% 5% 14% 22% 14% 1	3779
	21st to end	Night	49% 6% 16% 21% 8%	4120
November	1st to 10th	Night	51% 6% 13% 20% 9% 1	2626
	11th to 20th	Night	58% 5% 15% 14% 7% 1	2800
	21st to end	Night	63% 9% 15% 11% 2 1	2800
December	1st to 10th	Night	70% 6% 14% 8% 2	2737
	11th to 20th	Night	68% 6% 13% 10% 2	3288
	21st to end	Night	83% 3 7% 6% 1	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	20% 29% 30% 17% 4 1	180
	11th to 20th	Day	21% 33% 31% 11% 3 1	254
	21st to end	Day	25% 28% 33% 12% 2	297
February	1st to 10th	Day	27% 36% 28% 6% 3	270
	11th to 20th	Day	23% 34% 37% 6% 1	270
	21st to end	Day	35% 31% 29% 4	225
March	1st to 10th	Day	24% 27% 32% 13% 3	447
	11th to 20th	Day	23% 27% 34% 12% 4 1	460
	21st to end	Day	31% 23% 27% 14% 5%	506
April	1st to 10th	Day	27% 23% 33% 12% 5%	460
	11th to 20th	Day	33% 21% 23% 12% 7% 3	452
	21st to end	Day	30% 20% 30% 13% 6% 2	460
May	1st to 10th	Day	23% 18% 31% 17% 8% 2	463
	11th to 20th	Day	18% 16% 30% 23% 9% 3	487
	21st to end	Day	14% 17% 32% 23% 10% 4	529
June	1st to 10th	Day	18% 18% 29% 26% 8% 2	490
	11th to 20th	Day	13% 16% 32% 28% 9% 2	636
	21st to end	Day	17% 15% 36% 21% 8% 3	680
July	1st to 10th	Day	11% 11% 32% 27% 15% 3	671
	11th to 20th	Day	12% 12% 33% 25% 12% 7%	501
	21st to end	Day	9% 10% 36% 29% 11% 6%	532
August	1st to 10th	Day	9% 12% 28% 29% 15% 7%	486
	11th to 20th	Day	9% 9% 29% 26% 18% 9%	479
	21st to end	Day	15% 10% 28% 28% 14% 5%	539
September	1st to 10th	Day	15% 13% 27% 25% 13% 6%	490
	11th to 20th	Day	9% 12% 25% 24% 19% 11%	490
	21st to end	Day	15% 18% 26% 23% 15% 4	490
October	1st to 10th	Day	21% 18% 27% 18% 11% 4	490
	11th to 20th	Day	18% 28% 31% 16% 5% 1	490
	21st to end	Day	28% 29% 26% 14% 3	539
November	1st to 10th	Day	29% 25% 28% 15% 3 1	252
	11th to 20th	Day	24% 29% 33% 11% 3 2	200
	21st to end	Day	27% 26% 36% 12% 1	200
December	1st to 10th	Day	26% 30% 32% 11% 1	190
	11th to 20th	Day	31% 24% 29% 12% 3 1	180
	21st to end	Day	29% 32% 30% 8% 2	198
January	1st to 10th	Night	23% 29% 31% 14% 3	760
	11th to 20th	Night	25% 24% 30% 19% 2 1	760
	21st to end	Night	17% 19% 39% 19% 5%	836
February	1st to 10th	Night	21% 30% 32% 15% 1	760
	11th to 20th	Night	20% 25% 38% 14% 3	743
	21st to end	Night	22% 28% 32% 15% 3	628
March	1st to 10th	Night	21% 23% 36% 17% 3	760
	11th to 20th	Night	22% 24% 33% 16% 5%	760
	21st to end	Night	21% 19% 33% 22% 5%	836
April	1st to 10th	Night	24% 21% 35% 18% 2	760
	11th to 20th	Night	21% 20% 31% 20% 7% 1	649
	21st to end	Night	21% 18% 31% 22% 8%	570
May	1st to 10th	Night	18% 12% 28% 32% 9% 1	570
	11th to 20th	Night	18% 11% 33% 26% 11%	407
	21st to end	Night	11% 11% 31% 35% 11%	411
June	1st to 10th	Night	15% 10% 36% 30% 8% 1	380
	11th to 20th	Night	12% 9% 30% 37% 11%	380
	21st to end	Night	14% 8% 31% 32% 13% 1	380
July	1st to 10th	Night	6% 6% 28% 39% 20% 1	370
	11th to 20th	Night	11% 8% 31% 31% 19% 1	368
	21st to end	Night	9% 5% 32% 37% 16% 1	611
August	1st to 10th	Night	10% 5% 28% 34% 21% 2	567
	11th to 20th	Night	7% 6% 23% 38% 24% 2	564
	21st to end	Night	13% 8% 29% 29% 20% 1	676
September	1st to 10th	Night	11% 10% 28% 30% 17% 4	760
	11th to 20th	Night	12% 9% 26% 29% 19% 4	760
	21st to end	Night	19% 12% 21% 28% 16% 4	760
October	1st to 10th	Night	19% 13% 31% 22% 13% 2	760
	11th to 20th	Night	24% 18% 30% 20% 7% 1	760
	21st to end	Night	27% 21% 32% 17% 3	836
November	1st to 10th	Night	23% 20% 32% 18% 7%	780
	11th to 20th	Night	24% 27% 27% 15% 6% 1	800
	21st to end	Night	25% 25% 31% 16% 3	800
December	1st to 10th	Night	25% 26% 32% 13% 4	783
	11th to 20th	Night	21% 27% 37% 12% 3	760
	21st to end	Night	30% 26% 30% 14% 1	836

Page generated at 2024-12-03 06:45:10. Version ac07

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