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 2024-12-09.

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% 8% 3 7% 5% 5% 5% 4 5% 7% 39%	105813
	Night	16% 9% 3 8% 5% 5% 5% 4 5% 7% 33%	102569
Transparency	Day	42% 9% 19% 20% 8% 1	105563
	Night	46% 10% 16% 19% 8% 1	102466
Seeing	Day	15% 6% 17% 29% 25% 8%	15504
	Night	19% 7% 18% 29% 22% 6%	23742

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	25% 14% 5% 13% 6% 6% 5% 4 4 6% 12%	2219
	11th to 20th	Day	21% 13% 4 10% 6% 5% 5% 4 5% 5% 21%	2199
	21st to end	Day	26% 15% 7% 14% 7% 6% 5% 3 5% 4 9%	2926
February	1st to 10th	Day	24% 12% 4 9% 7% 6% 4 4 5% 8% 15%	1710
	11th to 20th	Day	20% 13% 4 10% 6% 6% 5% 4 5% 7% 22%	1665
	21st to end	Day	15% 13% 3 10% 8% 5% 7% 4 6% 6% 22%	1418
March	1st to 10th	Day	10% 11% 4 10% 7% 7% 8% 6% 7% 9% 21%	3310
	11th to 20th	Day	10% 10% 4 8% 5% 5% 4 4 5% 8% 36%	3490
	21st to end	Day	16% 11% 4 10% 6% 5% 6% 4 6% 6% 26%	3881
April	1st to 10th	Day	15% 11% 4 9% 6% 6% 6% 5% 6% 8% 24%	2280
	11th to 20th	Day	12% 11% 3 8% 5% 5% 5% 5% 7% 8% 30%	2356
	21st to end	Day	13% 10% 3 7% 5% 5% 5% 5% 7% 8% 32%	2475
May	1st to 10th	Day	11% 6% 2 6% 4 5% 4 3 5% 7% 46%	4420
	11th to 20th	Day	6% 4 2 5% 3 4 5% 5% 7% 12% 48%	4377
	21st to end	Day	16% 9% 3 7% 4 4 5% 4 5% 7% 35%	4868
June	1st to 10th	Day	12% 7% 3 7% 5% 5% 4 4 6% 9% 37%	2850
	11th to 20th	Day	8% 6% 3 7% 5% 5% 5% 5% 7% 9% 41%	2850
	21st to end	Day	7% 5% 2 5% 4 4 5% 4 6% 8% 48%	2850
July	1st to 10th	Day	4 2 1 3 2 2 3 2 3 5% 74%	4740
	11th to 20th	Day	3 2 1 2 2 2 3 2 4 7% 72%	4740
	21st to end	Day	8% 3 1 2 2 2 2 3 5% 7% 65%	4853
August	1st to 10th	Day	3 2 1 2 2 2 2 2 4 10% 69%	4255
	11th to 20th	Day	7% 6% 3 7% 4 5% 5% 4 5% 7% 48%	4026
	21st to end	Day	10% 6% 2 6% 4 4 4 3 5% 7% 50%	4433
September	1st to 10th	Day	6% 4 2 5% 4 4 4 3 6% 9% 53%	2280
	11th to 20th	Day	10% 8% 2 5% 4 4 5% 3 5% 8% 45%	2245
	21st to end	Day	14% 7% 2 6% 4 4 5% 4 6% 7% 41%	2021
October	1st to 10th	Day	14% 7% 2 6% 6% 6% 7% 5% 7% 9% 31%	3180
	11th to 20th	Day	22% 10% 4 9% 5% 5% 4 4 5% 6% 26%	3161
	21st to end	Day	16% 11% 3 9% 6% 6% 6% 4 7% 8% 26%	3246
November	1st to 10th	Day	24% 13% 5% 10% 6% 6% 5% 4 5% 6% 17%	1568
	11th to 20th	Day	20% 14% 4 10% 7% 6% 5% 3 3 5% 24%	1600
	21st to end	Day	22% 12% 5% 10% 7% 6% 6% 4 4 5% 18%	1600
December	1st to 10th	Day	19% 13% 4 10% 6% 5% 5% 3 5% 6% 23%	1584
	11th to 20th	Day	23% 13% 5% 13% 6% 6% 6% 4 5% 5% 13%	1695
	21st to end	Day	21% 17% 6% 13% 6% 5% 6% 4 4 5% 13%	2442
January	1st to 10th	Night	23% 15% 5% 12% 8% 7% 5% 4 5% 5% 11%	4726
	11th to 20th	Night	23% 12% 4 8% 6% 4 4 3 5% 6% 24%	4698
	21st to end	Night	27% 16% 6% 12% 6% 5% 4 3 4 5% 12%	4729
February	1st to 10th	Night	23% 13% 4 9% 6% 6% 5% 5% 4 6% 20%	2470
	11th to 20th	Night	18% 12% 3 9% 6% 5% 4 4 4 7% 27%	2402
	21st to end	Night	21% 13% 4 8% 6% 4 5% 4 5% 7% 22%	2036
March	1st to 10th	Night	12% 11% 4 9% 7% 8% 8% 5% 8% 7% 22%	3562
	11th to 20th	Night	11% 8% 2 7% 5% 5% 4 5% 7% 8% 39%	3489
	21st to end	Night	17% 13% 5% 11% 7% 6% 5% 4 5% 6% 22%	3772
April	1st to 10th	Night	16% 10% 4 9% 6% 5% 5% 4 7% 7% 28%	1900
	11th to 20th	Night	13% 9% 3 8% 5% 5% 5% 5% 8% 7% 33%	1772
	21st to end	Night	15% 10% 3 8% 5% 4 6% 4 5% 9% 31%	1704
May	1st to 10th	Night	11% 8% 2 5% 4 4 4 4 5% 6% 48%	2540
	11th to 20th	Night	7% 4 2 5% 4 5% 5% 4 7% 9% 48%	2516
	21st to end	Night	10% 8% 3 8% 6% 6% 6% 5% 8% 9% 32%	2703
June	1st to 10th	Night	12% 7% 3 7% 6% 4 5% 4 5% 6% 40%	1330
	11th to 20th	Night	9% 6% 2 6% 3 4 5% 5% 8% 10% 40%	1330
	21st to end	Night	6% 4 2 5% 3 3 4 4 6% 11% 52%	1330
July	1st to 10th	Night	3 2 1 4 3 3 3 3 4 7% 68%	2220
	11th to 20th	Night	2 2 2 2 2 2 2 3 7% 75%	2220
	21st to end	Night	7% 3 1 3 2 3 5% 2 5% 9% 60%	2697
August	1st to 10th	Night	2 1 1 2 2 2 2 2 5% 8% 72%	2678
	11th to 20th	Night	7% 4 2 5% 4 4 3 3 5% 9% 53%	2812
	21st to end	Night	10% 3 2 5% 4 4 4 4 7% 9% 48%	3236
September	1st to 10th	Night	5% 3 2 4 2 3 3 3 6% 9% 60%	1900
	11th to 20th	Night	11% 7% 3 6% 4 3 4 3 5% 7% 46%	1933
	21st to end	Night	11% 7% 3 7% 4 4 4 3 5% 8% 44%	2158
October	1st to 10th	Night	11% 6% 2 7% 5% 5% 5% 4 6% 8% 40%	3800
	11th to 20th	Night	20% 9% 4 8% 5% 4 4 3 5% 7% 30%	3777
	21st to end	Night	19% 9% 3 8% 5% 5% 5% 3 5% 7% 30%	4302
November	1st to 10th	Night	24% 12% 4 8% 6% 6% 5% 4 5% 5% 21%	2730
	11th to 20th	Night	23% 11% 4 9% 6% 5% 5% 4 6% 6% 22%	2800
	21st to end	Night	21% 13% 4 11% 7% 5% 6% 4 5% 5% 19%	2800
December	1st to 10th	Night	21% 12% 3 9% 6% 5% 5% 4 5% 6% 23%	2778
	11th to 20th	Night	23% 15% 5% 11% 7% 6% 6% 5% 4 5% 14%	3505
	21st to end	Night	24% 15% 5% 10% 7% 5% 5% 4 5% 6% 16%	5214

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	65% 13% 10% 10% 2	2219
	11th to 20th	Day	61% 11% 17% 9% 3	2220
	21st to end	Day	71% 14% 8% 6% 1	2926
February	1st to 10th	Day	63% 13% 12% 8% 4	1710
	11th to 20th	Day	61% 8% 15% 12% 4	1674
	21st to end	Day	58% 10% 13% 14% 4	1418
March	1st to 10th	Day	49% 15% 15% 16% 5%	3310
	11th to 20th	Day	43% 9% 18% 27% 3 1	3490
	21st to end	Day	53% 13% 19% 13% 2	3881
April	1st to 10th	Day	52% 12% 20% 13% 3	2280
	11th to 20th	Day	47% 9% 18% 16% 8% 1	2356
	21st to end	Day	46% 10% 20% 18% 5% 1	2475
May	1st to 10th	Day	37% 7% 23% 25% 8% 1	4420
	11th to 20th	Day	27% 11% 34% 23% 5%	4380
	21st to end	Day	48% 12% 22% 15% 4	4869
June	1st to 10th	Day	41% 10% 25% 16% 6% 1	2850
	11th to 20th	Day	37% 12% 26% 21% 4	2850
	21st to end	Day	32% 10% 27% 21% 9% 1	2850
July	1st to 10th	Day	15% 5% 13% 29% 26% 12%	4666
	11th to 20th	Day	15% 5% 15% 36% 28% 1	4659
	21st to end	Day	19% 5% 27% 30% 16% 2	4700
August	1st to 10th	Day	16% 5% 19% 42% 16% 1	4238
	11th to 20th	Day	35% 6% 29% 21% 7% 1	4065
	21st to end	Day	35% 6% 20% 29% 9%	4432
September	1st to 10th	Day	28% 7% 23% 24% 14% 2	2280
	11th to 20th	Day	39% 9% 17% 20% 14% 1	2245
	21st to end	Day	41% 8% 20% 21% 10% 1	2021
October	1st to 10th	Day	50% 6% 18% 21% 5%	3180
	11th to 20th	Day	57% 7% 14% 17% 5%	3161
	21st to end	Day	52% 9% 17% 15% 7% 1	3246
November	1st to 10th	Day	68% 6% 12% 10% 3 1	1568
	11th to 20th	Day	62% 7% 12% 14% 4 1	1600
	21st to end	Day	63% 11% 9% 12% 4	1600
December	1st to 10th	Day	62% 7% 12% 15% 4	1584
	11th to 20th	Day	65% 14% 12% 7% 2	1698
	21st to end	Day	64% 14% 12% 7% 3	2442
January	1st to 10th	Night	67% 14% 9% 8% 3	4726
	11th to 20th	Night	57% 11% 14% 15% 3 1	4739
	21st to end	Night	69% 12% 7% 9% 2	4729
February	1st to 10th	Night	62% 10% 12% 10% 6%	2470
	11th to 20th	Night	55% 9% 15% 15% 6%	2404
	21st to end	Night	59% 8% 13% 15% 5% 1	2036
March	1st to 10th	Night	45% 19% 14% 18% 4	3562
	11th to 20th	Night	36% 11% 21% 28% 3 1	3490
	21st to end	Night	58% 11% 17% 13% 1	3772
April	1st to 10th	Night	51% 10% 19% 15% 4	1900
	11th to 20th	Night	45% 9% 16% 20% 7% 2	1772
	21st to end	Night	48% 8% 17% 17% 9% 1	1704
May	1st to 10th	Night	34% 6% 19% 29% 11% 1	2540
	11th to 20th	Night	27% 9% 28% 28% 8%	2516
	21st to end	Night	41% 14% 22% 19% 4	2703
June	1st to 10th	Night	42% 7% 19% 23% 6% 2	1330
	11th to 20th	Night	34% 9% 26% 25% 5%	1330
	21st to end	Night	25% 8% 30% 25% 9% 3	1330
July	1st to 10th	Night	16% 5% 12% 32% 21% 13%	2185
	11th to 20th	Night	12% 3 15% 36% 32% 2	2178
	21st to end	Night	19% 5% 18% 34% 22% 3	2612
August	1st to 10th	Night	13% 4 18% 37% 25% 2	2670
	11th to 20th	Night	29% 6% 30% 22% 9% 3	2839
	21st to end	Night	31% 7% 17% 34% 11%	3236
September	1st to 10th	Night	21% 6% 22% 30% 17% 4	1900
	11th to 20th	Night	36% 8% 15% 20% 17% 4	1933
	21st to end	Night	37% 7% 16% 24% 13% 1	2158
October	1st to 10th	Night	40% 5% 22% 26% 7%	3800
	11th to 20th	Night	51% 6% 17% 22% 4	3777
	21st to end	Night	52% 6% 16% 17% 8% 1	4302
November	1st to 10th	Night	61% 9% 13% 13% 4	2730
	11th to 20th	Night	58% 9% 15% 11% 5% 2	2800
	21st to end	Night	62% 10% 13% 10% 5%	2800
December	1st to 10th	Night	59% 10% 12% 14% 5%	2778
	11th to 20th	Night	63% 15% 13% 6% 2	3501
	21st to end	Night	60% 16% 11% 10% 4	5214

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	33% 8% 22% 25% 12% 1	180
	11th to 20th	Day	27% 10% 22% 24% 17% 1	180
	21st to end	Day	28% 8% 18% 27% 17% 3	278
February	1st to 10th	Day	28% 13% 20% 25% 14% 1	370
	11th to 20th	Day	25% 11% 16% 32% 16% 1	365
	21st to end	Day	19% 16% 19% 28% 15% 2	310
March	1st to 10th	Day	19% 9% 18% 30% 20% 3	460
	11th to 20th	Day	19% 9% 17% 28% 21% 6%	460
	21st to end	Day	18% 9% 20% 32% 19% 3	506
April	1st to 10th	Day	18% 11% 20% 25% 21% 5%	460
	11th to 20th	Day	16% 8% 17% 33% 19% 7%	452
	21st to end	Day	18% 8% 22% 26% 22% 4	460
May	1st to 10th	Day	13% 6% 15% 31% 30% 5%	463
	11th to 20th	Day	13% 5% 14% 28% 33% 7%	488
	21st to end	Day	13% 3 20% 31% 25% 8%	558
June	1st to 10th	Day	15% 5% 22% 33% 21% 5%	680
	11th to 20th	Day	9% 7% 27% 35% 17% 5%	680
	21st to end	Day	7% 4 21% 33% 24% 11%	680
July	1st to 10th	Day	8% 2 15% 33% 31% 11%	671
	11th to 20th	Day	4 4 19% 31% 31% 11%	668
	21st to end	Day	3 2 15% 30% 30% 19%	568
August	1st to 10th	Day	6% 2 10% 23% 38% 21%	487
	11th to 20th	Day	3 1 8% 24% 42% 22%	477
	21st to end	Day	9% 4 13% 29% 33% 14%	539
September	1st to 10th	Day	10% 2 8% 31% 37% 12%	490
	11th to 20th	Day	13% 3 10% 25% 36% 12%	490
	21st to end	Day	14% 4 14% 30% 29% 9%	490
October	1st to 10th	Day	18% 5% 13% 27% 27% 10%	490
	11th to 20th	Day	24% 7% 9% 30% 25% 5%	490
	21st to end	Day	21% 10% 19% 32% 15% 3	440
November	1st to 10th	Day	30% 9% 19% 26% 17%	200
	11th to 20th	Day	23% 8% 19% 23% 26% 2	200
	21st to end	Day	24% 12% 17% 29% 16% 4	200
December	1st to 10th	Day	23% 9% 13% 33% 20% 3	196
	11th to 20th	Day	31% 8% 20% 27% 14% 1	180
	21st to end	Day	34% 7% 21% 30% 8% 1	198
January	1st to 10th	Night	29% 12% 19% 25% 13% 1	850
	11th to 20th	Night	28% 11% 14% 27% 19% 2	849
	21st to end	Night	26% 7% 15% 28% 19% 4	836
February	1st to 10th	Night	26% 12% 17% 28% 14% 3	760
	11th to 20th	Night	23% 9% 18% 28% 18% 4	744
	21st to end	Night	26% 12% 18% 23% 16% 4	628
March	1st to 10th	Night	17% 12% 16% 31% 19% 6%	760
	11th to 20th	Night	19% 9% 22% 25% 19% 5%	760
	21st to end	Night	19% 8% 19% 31% 19% 5%	836
April	1st to 10th	Night	20% 7% 20% 28% 21% 3	760
	11th to 20th	Night	16% 8% 22% 31% 18% 5%	644
	21st to end	Night	15% 9% 26% 32% 15% 4	564
May	1st to 10th	Night	12% 5% 24% 32% 24% 3	380
	11th to 20th	Night	10% 6% 18% 33% 26% 6%	374
	21st to end	Night	12% 4 23% 34% 25% 2	411
June	1st to 10th	Night	15% 4 24% 33% 21% 3	380
	11th to 20th	Night	11% 3 30% 37% 17% 3	380
	21st to end	Night	8% 3 27% 29% 26% 7%	380
July	1st to 10th	Night	6% 2 19% 39% 30% 4	370
	11th to 20th	Night	4 2 21% 41% 29% 3	368
	21st to end	Night	4 2 22% 35% 31% 7%	416
August	1st to 10th	Night	3 3 12% 33% 40% 10%	462
	11th to 20th	Night	5% 1 7% 34% 38% 15%	564
	21st to end	Night	8% 3 18% 32% 32% 8%	678
September	1st to 10th	Night	8% 2 12% 33% 33% 13%	760
	11th to 20th	Night	13% 2 9% 28% 31% 17%	760
	21st to end	Night	14% 3 14% 31% 28% 10%	760
October	1st to 10th	Night	15% 4 11% 27% 30% 13%	760
	11th to 20th	Night	19% 6% 11% 29% 24% 11%	760
	21st to end	Night	25% 7% 13% 30% 20% 5%	836
November	1st to 10th	Night	28% 8% 17% 28% 18% 2	780
	11th to 20th	Night	23% 12% 20% 25% 17% 4	800
	21st to end	Night	25% 9% 19% 25% 17% 5%	800
December	1st to 10th	Night	23% 9% 17% 28% 20% 3	794
	11th to 20th	Night	27% 11% 19% 30% 12% 1	843
	21st to end	Night	28% 12% 24% 26% 9% 1	935

Page generated at 2024-12-06 00:54:53. Version ac07

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