Newton/Godin Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Newton/Godin Observatory clear sky chart from 2005-11-06 to 2026-04-02.

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	12% 8% 3 7% 5% 5% 5% 4 5% 7% 38%	135174
	Night	16% 10% 3 8% 5% 5% 5% 4 5% 7% 32%	135357
Transparency	Day	44% 8% 20% 20% 8% 1	134883
	Night	48% 8% 16% 19% 7% 1	135227
Seeing	Day	15% 6% 16% 29% 25% 8%	17131
	Night	19% 7% 17% 30% 21% 5%	25502

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	24% 15% 5% 13% 6% 6% 5% 4 5% 6% 11%	4125
	11th to 20th	Day	14% 10% 4 10% 5% 5% 5% 4 5% 8% 31%	4119
	21st to end	Day	20% 13% 5% 12% 6% 5% 5% 3 5% 5% 22%	5456
February	1st to 10th	Day	23% 12% 4 10% 8% 6% 5% 4 5% 8% 15%	1890
	11th to 20th	Day	20% 13% 4 10% 5% 6% 5% 4 5% 7% 22%	1845
	21st to end	Day	15% 13% 4 10% 8% 6% 7% 4 6% 6% 21%	1562
March	1st to 10th	Day	12% 13% 4 11% 7% 6% 7% 5% 7% 8% 21%	4860
	11th to 20th	Day	12% 13% 4 9% 6% 6% 5% 4 5% 7% 28%	5110
	21st to end	Day	17% 13% 4 10% 7% 6% 6% 4 6% 6% 21%	5691
April	1st to 10th	Day	15% 11% 4 9% 6% 6% 6% 5% 7% 8% 24%	2413
	11th to 20th	Day	11% 10% 3 8% 5% 5% 6% 5% 7% 8% 31%	2482
	21st to end	Day	13% 10% 3 7% 5% 5% 4 4 7% 8% 34%	2605
May	1st to 10th	Day	9% 6% 3 6% 5% 5% 5% 3 4 7% 48%	6320
	11th to 20th	Day	8% 7% 3 6% 4 4 5% 4 7% 10% 42%	6277
	21st to end	Day	13% 7% 2 6% 4 4 6% 4 6% 8% 38%	6986
June	1st to 10th	Day	12% 6% 3 7% 5% 5% 4 4 6% 9% 39%	3000
	11th to 20th	Day	8% 6% 3 7% 5% 5% 5% 5% 7% 9% 41%	3000
	21st to end	Day	8% 6% 2 5% 4 4 5% 4 6% 8% 47%	3000
July	1st to 10th	Day	4 2 1 3 2 2 3 2 4 6% 70%	6780
	11th to 20th	Day	2 2 1 2 2 2 3 2 4 6% 74%	6780
	21st to end	Day	5% 2 1 2 2 2 3 3 5% 8% 68%	6965
August	1st to 10th	Day	3 2 1 2 2 2 2 2 5% 10% 68%	4390
	11th to 20th	Day	7% 6% 3 7% 4 4 5% 4 5% 7% 48%	4156
	21st to end	Day	10% 5% 2 6% 4 4 4 3 5% 7% 50%	4573
September	1st to 10th	Day	6% 4 2 6% 4 4 4 3 6% 10% 53%	2400
	11th to 20th	Day	10% 8% 2 5% 4 4 5% 3 5% 8% 45%	2363
	21st to end	Day	14% 6% 2 6% 5% 4 5% 3 6% 7% 41%	2127
October	1st to 10th	Day	14% 7% 2 6% 6% 6% 7% 5% 7% 9% 31%	3280
	11th to 20th	Day	22% 10% 4 9% 5% 5% 4 4 5% 6% 27%	3261
	21st to end	Day	16% 11% 3 9% 6% 6% 6% 4 7% 8% 25%	3350
November	1st to 10th	Day	23% 13% 5% 10% 6% 6% 5% 4 6% 6% 16%	1648
	11th to 20th	Day	21% 14% 4 9% 6% 6% 5% 3 4 5% 23%	1680
	21st to end	Day	23% 12% 5% 10% 7% 6% 6% 3 4 6% 18%	1680
December	1st to 10th	Day	15% 11% 5% 13% 6% 6% 6% 3 7% 9% 19%	2700
	11th to 20th	Day	27% 13% 5% 11% 6% 5% 5% 4 6% 6% 13%	2725
	21st to end	Day	22% 18% 6% 13% 6% 5% 5% 4 4 5% 11%	3575
January	1st to 10th	Night	26% 16% 5% 12% 7% 7% 5% 4 5% 5% 9%	8770
	11th to 20th	Night	17% 10% 4 7% 4 3 3 3 5% 8% 37%	8764
	21st to end	Night	19% 13% 5% 10% 5% 4 4 3 4 6% 27%	8733
February	1st to 10th	Night	22% 13% 4 9% 6% 6% 5% 5% 4 6% 20%	2730
	11th to 20th	Night	18% 13% 4 9% 6% 5% 4 4 4 7% 27%	2662
	21st to end	Night	21% 12% 4 9% 6% 4 5% 4 5% 7% 22%	2244
March	1st to 10th	Night	12% 10% 3 9% 7% 8% 7% 5% 8% 8% 24%	5239
	11th to 20th	Night	12% 10% 3 8% 6% 6% 5% 5% 7% 8% 31%	5109
	21st to end	Night	20% 14% 5% 11% 6% 6% 5% 4 5% 6% 17%	5526
April	1st to 10th	Night	15% 10% 4 9% 6% 5% 6% 4 7% 7% 27%	2010
	11th to 20th	Night	13% 9% 3 8% 5% 5% 5% 5% 8% 7% 33%	1866
	21st to end	Night	14% 10% 3 8% 4 4 6% 4 5% 9% 33%	1793
May	1st to 10th	Night	10% 7% 2 6% 4 4 4 3 4 6% 50%	3640
	11th to 20th	Night	9% 5% 2 7% 5% 5% 7% 4 7% 9% 39%	3616
	21st to end	Night	9% 7% 3 8% 5% 7% 7% 5% 9% 9% 32%	3885
June	1st to 10th	Night	11% 7% 3 7% 6% 4 4 4 6% 7% 41%	1400
	11th to 20th	Night	9% 6% 2 6% 3 4 5% 5% 8% 10% 41%	1400
	21st to end	Night	7% 4 2 5% 3 4 4 4 6% 11% 52%	1400
July	1st to 10th	Night	4 3 1 4 3 3 4 3 4 6% 67%	3180
	11th to 20th	Night	1 1 1 1 2 1 3 2 4 6% 77%	3180
	21st to end	Night	5% 2 1 2 2 3 5% 2 5% 9% 64%	3876
August	1st to 10th	Night	2 1 1 2 2 2 2 2 5% 9% 72%	2763
	11th to 20th	Night	8% 4 2 5% 4 4 4 3 5% 9% 53%	2902
	21st to end	Night	10% 3 2 5% 4 4 4 4 7% 9% 49%	3338
September	1st to 10th	Night	5% 2 2 4 3 3 4 4 6% 9% 59%	2000
	11th to 20th	Night	10% 7% 2 6% 4 3 4 3 5% 7% 47%	2035
	21st to end	Night	12% 7% 3 7% 4 4 4 3 5% 7% 44%	2272
October	1st to 10th	Night	11% 6% 3 7% 5% 5% 5% 4 6% 8% 41%	3920
	11th to 20th	Night	20% 9% 3 8% 5% 4 4 3 5% 7% 31%	3897
	21st to end	Night	19% 8% 3 8% 5% 5% 5% 4 5% 7% 29%	4440
November	1st to 10th	Night	24% 12% 4 8% 6% 6% 5% 4 5% 5% 21%	2870
	11th to 20th	Night	23% 11% 4 10% 6% 5% 5% 4 6% 6% 21%	2940
	21st to end	Night	21% 13% 4 11% 7% 5% 6% 4 5% 5% 19%	2940
December	1st to 10th	Night	17% 11% 3 10% 7% 6% 6% 5% 7% 9% 21%	4700
	11th to 20th	Night	27% 16% 6% 11% 6% 5% 5% 4 4 5% 11%	5694
	21st to end	Night	23% 14% 5% 11% 7% 6% 5% 4 5% 6% 15%	7623

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	70% 9% 9% 10% 2	4125
	11th to 20th	Day	53% 7% 16% 19% 4	4140
	21st to end	Day	63% 8% 11% 15% 4	5457
February	1st to 10th	Day	63% 12% 11% 9% 4 1	1890
	11th to 20th	Day	61% 7% 14% 13% 4	1854
	21st to end	Day	59% 10% 14% 13% 4	1562
March	1st to 10th	Day	55% 11% 14% 16% 4	4860
	11th to 20th	Day	52% 7% 14% 23% 4	5110
	21st to end	Day	61% 10% 16% 11% 2	5691
April	1st to 10th	Day	53% 12% 20% 13% 2	2413
	11th to 20th	Day	46% 9% 19% 17% 8% 1	2482
	21st to end	Day	44% 10% 21% 19% 5% 1	2605
May	1st to 10th	Day	36% 6% 22% 26% 9%	6320
	11th to 20th	Day	35% 9% 30% 22% 4	6280
	21st to end	Day	42% 10% 26% 17% 4 1	6987
June	1st to 10th	Day	40% 10% 26% 17% 6% 1	3000
	11th to 20th	Day	38% 12% 25% 21% 4	3000
	21st to end	Day	33% 9% 27% 21% 8% 1	3000
July	1st to 10th	Day	17% 5% 24% 26% 21% 8%	6706
	11th to 20th	Day	14% 3 21% 35% 26% 2	6699
	21st to end	Day	16% 4 36% 31% 12% 2	6770
August	1st to 10th	Day	17% 5% 20% 41% 16% 1	4373
	11th to 20th	Day	36% 6% 29% 21% 7% 1	4195
	21st to end	Day	35% 6% 20% 29% 10% 1	4572
September	1st to 10th	Day	29% 7% 25% 24% 14% 2	2400
	11th to 20th	Day	38% 9% 17% 21% 14% 1	2363
	21st to end	Day	41% 8% 20% 20% 10% 1	2127
October	1st to 10th	Day	50% 6% 19% 21% 4	3280
	11th to 20th	Day	56% 7% 14% 18% 5%	3261
	21st to end	Day	53% 9% 17% 15% 7% 1	3350
November	1st to 10th	Day	67% 6% 13% 10% 3	1648
	11th to 20th	Day	63% 6% 12% 14% 4 1	1680
	21st to end	Day	63% 11% 9% 12% 4	1680
December	1st to 10th	Day	65% 5% 11% 15% 3	2700
	11th to 20th	Day	67% 10% 12% 9% 1	2728
	21st to end	Day	68% 11% 11% 8% 2	3575
January	1st to 10th	Night	75% 8% 9% 7% 2	8770
	11th to 20th	Night	48% 7% 15% 21% 9%	8805
	21st to end	Night	58% 8% 12% 18% 5%	8733
February	1st to 10th	Night	62% 10% 11% 9% 7%	2730
	11th to 20th	Night	55% 8% 14% 16% 6%	2664
	21st to end	Night	60% 8% 13% 14% 5% 1	2244
March	1st to 10th	Night	46% 15% 14% 19% 6%	5239
	11th to 20th	Night	45% 9% 16% 25% 4 1	5110
	21st to end	Night	63% 9% 15% 12% 2	5526
April	1st to 10th	Night	52% 10% 19% 15% 4	2010
	11th to 20th	Night	44% 9% 17% 21% 7% 2	1866
	21st to end	Night	46% 8% 18% 18% 9% 1	1793
May	1st to 10th	Night	35% 5% 16% 31% 13%	3637
	11th to 20th	Night	35% 8% 27% 24% 6%	3616
	21st to end	Night	41% 12% 23% 20% 4	3885
June	1st to 10th	Night	40% 7% 21% 23% 8% 2	1400
	11th to 20th	Night	34% 9% 26% 27% 5%	1400
	21st to end	Night	25% 8% 30% 24% 9% 3	1400
July	1st to 10th	Night	17% 4 22% 32% 16% 9%	3145
	11th to 20th	Night	10% 4 20% 37% 28% 3	3138
	21st to end	Night	16% 3 27% 36% 16% 2	3767
August	1st to 10th	Night	14% 4 19% 37% 24% 2	2755
	11th to 20th	Night	30% 6% 30% 22% 10% 3	2929
	21st to end	Night	30% 7% 17% 34% 11% 1	3338
September	1st to 10th	Night	22% 6% 22% 29% 16% 4	2000
	11th to 20th	Night	36% 7% 16% 21% 17% 3	2035
	21st to end	Night	38% 7% 17% 24% 13% 1	2272
October	1st to 10th	Night	40% 5% 22% 26% 7%	3920
	11th to 20th	Night	51% 6% 17% 22% 5%	3897
	21st to end	Night	52% 6% 16% 18% 8% 1	4440
November	1st to 10th	Night	61% 8% 13% 13% 4	2870
	11th to 20th	Night	60% 9% 15% 10% 5% 2	2940
	21st to end	Night	63% 9% 13% 10% 5%	2940
December	1st to 10th	Night	62% 8% 12% 15% 3	4700
	11th to 20th	Night	69% 10% 11% 7% 3	5690
	21st to end	Night	63% 12% 12% 10% 3	7623

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	35% 8% 21% 25% 10%	220
	11th to 20th	Day	23% 10% 19% 27% 20% 2	220
	21st to end	Day	28% 7% 15% 30% 16% 5%	332
February	1st to 10th	Day	27% 11% 19% 27% 14% 2	430
	11th to 20th	Day	24% 10% 16% 30% 18% 1	425
	21st to end	Day	20% 15% 21% 28% 14% 2	358
March	1st to 10th	Day	19% 9% 18% 30% 20% 3	540
	11th to 20th	Day	21% 9% 18% 28% 19% 6%	540
	21st to end	Day	19% 8% 19% 32% 19% 3	594
April	1st to 10th	Day	17% 11% 19% 26% 22% 5%	505
	11th to 20th	Day	15% 7% 18% 32% 21% 7%	492
	21st to end	Day	17% 8% 21% 25% 23% 7%	500
May	1st to 10th	Day	13% 6% 15% 30% 30% 6%	503
	11th to 20th	Day	13% 5% 14% 29% 32% 8%	528
	21st to end	Day	13% 3 20% 31% 26% 8%	604
June	1st to 10th	Day	14% 5% 20% 32% 23% 7%	730
	11th to 20th	Day	9% 7% 26% 34% 19% 6%	730
	21st to end	Day	8% 3 20% 31% 25% 12%	730
July	1st to 10th	Day	8% 2 16% 33% 31% 10%	721
	11th to 20th	Day	4 3 19% 31% 32% 12%	718
	21st to end	Day	3 1 14% 30% 32% 20%	614
August	1st to 10th	Day	6% 2 10% 24% 38% 21%	527
	11th to 20th	Day	4 1 8% 24% 42% 21%	517
	21st to end	Day	8% 3 12% 28% 33% 16%	583
September	1st to 10th	Day	9% 2 8% 29% 37% 15%	530
	11th to 20th	Day	13% 3 10% 24% 37% 13%	530
	21st to end	Day	14% 4 15% 29% 30% 8%	530
October	1st to 10th	Day	17% 5% 12% 28% 28% 10%	530
	11th to 20th	Day	23% 7% 10% 29% 25% 5%	530
	21st to end	Day	23% 10% 18% 32% 15% 3	478
November	1st to 10th	Day	28% 9% 18% 29% 16%	220
	11th to 20th	Day	25% 8% 18% 23% 25% 2	220
	21st to end	Day	26% 10% 17% 29% 15% 3	220
December	1st to 10th	Day	26% 9% 13% 30% 19% 2	220
	11th to 20th	Day	34% 10% 19% 24% 13%	220
	21st to end	Day	31% 8% 21% 31% 8% 1	242
January	1st to 10th	Night	31% 12% 19% 25% 12% 1	950
	11th to 20th	Night	27% 10% 14% 28% 20% 2	948
	21st to end	Night	25% 7% 14% 30% 20% 4	924
February	1st to 10th	Night	26% 12% 17% 27% 15% 3	840
	11th to 20th	Night	23% 9% 17% 29% 18% 4	824
	21st to end	Night	26% 11% 18% 25% 15% 4	692
March	1st to 10th	Night	17% 12% 15% 30% 20% 5%	840
	11th to 20th	Night	21% 9% 22% 26% 18% 4	840
	21st to end	Night	18% 9% 20% 30% 18% 5%	924
April	1st to 10th	Night	20% 7% 20% 29% 20% 4	804
	11th to 20th	Night	15% 8% 22% 31% 19% 5%	678
	21st to end	Night	15% 8% 25% 31% 16% 5%	593
May	1st to 10th	Night	12% 5% 24% 32% 25% 3	400
	11th to 20th	Night	11% 7% 19% 32% 25% 6%	394
	21st to end	Night	12% 4 23% 35% 25% 2	433
June	1st to 10th	Night	14% 4 24% 33% 22% 4	400
	11th to 20th	Night	11% 3 29% 38% 17% 3	400
	21st to end	Night	8% 3 27% 29% 27% 7%	400
July	1st to 10th	Night	6% 2 19% 39% 30% 4	390
	11th to 20th	Night	4 2 21% 42% 29% 3	388
	21st to end	Night	3 2 22% 35% 31% 7%	438
August	1st to 10th	Night	4 3 12% 33% 39% 9%	487
	11th to 20th	Night	6% 1 7% 34% 37% 14%	594
	21st to end	Night	8% 3 17% 31% 34% 8%	714
September	1st to 10th	Night	8% 2 12% 33% 33% 13%	800
	11th to 20th	Night	13% 2 9% 28% 31% 17%	800
	21st to end	Night	14% 3 14% 31% 28% 10%	800
October	1st to 10th	Night	15% 4 10% 29% 29% 13%	800
	11th to 20th	Night	19% 6% 11% 29% 24% 11%	800
	21st to end	Night	24% 7% 14% 31% 20% 5%	880
November	1st to 10th	Night	28% 8% 17% 28% 17% 2	820
	11th to 20th	Night	23% 12% 19% 26% 16% 4	840
	21st to end	Night	25% 9% 19% 26% 16% 4	840
December	1st to 10th	Night	24% 9% 17% 28% 19% 3	840
	11th to 20th	Night	28% 12% 19% 29% 11% 1	942
	21st to end	Night	27% 12% 23% 28% 9% 1	1045

Page generated at 2026-03-29 23:18:43. Version ac07

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