New Glasgow
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the New Glasgow 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	18% 12% 4 9% 5% 5% 4 4 5% 6% 27%	101648
	Night	18% 13% 4 10% 5% 4 4 3 5% 6% 27%	97511
Transparency	Day	56% 7% 12% 17% 7% 1	105199
	Night	57% 6% 13% 17% 7% 1	102053
Seeing	Day	26% 21% 31% 16% 4 1	17519
	Night	25% 19% 31% 20% 4	25108

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	13% 17% 7% 23% 5% 5% 3 3 3 5% 17%	2526
	11th to 20th	Day	11% 18% 7% 14% 6% 5% 5% 3 4 4 24%	2530
	21st to end	Day	14% 16% 7% 14% 6% 5% 4 3 4 5% 23%	3040
February	1st to 10th	Day	16% 17% 5% 11% 7% 5% 4 3 4 5% 23%	1710
	11th to 20th	Day	16% 16% 6% 11% 6% 5% 4 4 4 4 24%	1663
	21st to end	Day	10% 17% 4 10% 7% 6% 5% 3 5% 6% 27%	1489
March	1st to 10th	Day	22% 15% 4 8% 5% 5% 3 3 4 4 26%	3290
	11th to 20th	Day	11% 23% 8% 11% 7% 5% 4 4 4 4 20%	3480
	21st to end	Day	21% 23% 8% 11% 5% 3 3 2 3 3 18%	3904
April	1st to 10th	Day	19% 18% 4 8% 5% 3 4 4 4 5% 25%	2280
	11th to 20th	Day	22% 14% 4 7% 4 4 4 3 4 5% 29%	2260
	21st to end	Day	23% 16% 3 6% 5% 4 4 3 5% 6% 26%	2470
May	1st to 10th	Day	27% 18% 3 6% 4 3 3 3 5% 6% 22%	4377
	11th to 20th	Day	20% 11% 3 7% 5% 4 4 3 6% 7% 31%	4398
	21st to end	Day	17% 9% 3 8% 6% 5% 6% 4 7% 8% 28%	4836
June	1st to 10th	Day	29% 10% 2 7% 5% 4 5% 4 5% 7% 22%	2660
	11th to 20th	Day	24% 8% 3 6% 5% 4 4 3 5% 6% 32%	2660
	21st to end	Day	24% 9% 3 7% 6% 4 5% 4 6% 6% 26%	2660
July	1st to 10th	Day	20% 7% 3 6% 5% 5% 5% 5% 6% 8% 30%	4440
	11th to 20th	Day	13% 6% 3 8% 5% 5% 6% 4 7% 10% 33%	4440
	21st to end	Day	13% 7% 3 7% 5% 5% 6% 5% 7% 9% 33%	4815
August	1st to 10th	Day	18% 9% 3 9% 5% 5% 6% 5% 6% 8% 26%	4174
	11th to 20th	Day	14% 8% 3 8% 5% 5% 6% 5% 6% 8% 34%	4045
	21st to end	Day	11% 5% 2 7% 5% 5% 5% 4 7% 8% 43%	4277
September	1st to 10th	Day	19% 5% 3 6% 4 3 4 4 5% 7% 38%	2280
	11th to 20th	Day	20% 7% 2 7% 5% 4 4 4 6% 6% 36%	2280
	21st to end	Day	19% 7% 3 6% 5% 5% 4 4 6% 6% 36%	1987
October	1st to 10th	Day	20% 7% 3 7% 5% 5% 4 4 6% 7% 32%	1900
	11th to 20th	Day	19% 10% 3 8% 6% 5% 5% 3 6% 8% 28%	1900
	21st to end	Day	20% 15% 3 9% 6% 5% 4 3 4 6% 24%	2020
November	1st to 10th	Day	22% 14% 4 7% 5% 5% 5% 4 5% 5% 23%	1608
	11th to 20th	Day	17% 21% 4 9% 5% 4 4 2 5% 7% 21%	1520
	21st to end	Day	16% 17% 5% 9% 6% 5% 5% 4 5% 6% 21%	1520
December	1st to 10th	Day	21% 19% 5% 11% 5% 5% 3 4 5% 4 18%	1520
	11th to 20th	Day	24% 18% 5% 13% 6% 4 4 3 4 5% 14%	1906
	21st to end	Day	20% 15% 11% 12% 4 4 4 3 4 5% 19%	2783
January	1st to 10th	Night	13% 14% 6% 20% 8% 5% 4 3 5% 5% 18%	4429
	11th to 20th	Night	13% 13% 6% 14% 8% 5% 5% 3 4 5% 25%	4440
	21st to end	Night	14% 14% 6% 19% 7% 5% 4 3 5% 5% 19%	4618
February	1st to 10th	Night	18% 14% 5% 12% 6% 5% 4 3 5% 3 24%	2470
	11th to 20th	Night	16% 16% 4 12% 8% 5% 4 4 4 5% 22%	2403
	21st to end	Night	11% 17% 5% 10% 6% 5% 4 4 4 4 29%	1965
March	1st to 10th	Night	21% 17% 5% 10% 5% 4 4 3 4 4 23%	3548
	11th to 20th	Night	16% 22% 6% 10% 6% 4 4 3 4 4 21%	3479
	21st to end	Night	20% 18% 7% 12% 5% 4 4 3 3 3 21%	3727
April	1st to 10th	Night	20% 15% 4 9% 5% 5% 4 4 3 5% 25%	1900
	11th to 20th	Night	19% 13% 3 6% 4 4 4 4 4 5% 32%	1867
	21st to end	Night	22% 15% 4 7% 5% 4 4 4 5% 4 26%	1710
May	1st to 10th	Night	25% 22% 3 6% 4 4 4 3 4 5% 20%	2570
	11th to 20th	Night	19% 11% 2 7% 5% 5% 4 4 5% 6% 32%	2506
	21st to end	Night	16% 11% 3 9% 6% 5% 6% 4 6% 8% 26%	2749
June	1st to 10th	Night	25% 9% 3 8% 5% 4 5% 3 5% 8% 25%	1520
	11th to 20th	Night	20% 7% 2 6% 4 4 4 3 6% 6% 38%	1520
	21st to end	Night	21% 7% 3 7% 5% 6% 5% 4 6% 7% 29%	1520
July	1st to 10th	Night	16% 8% 2 8% 6% 5% 6% 5% 7% 9% 29%	2530
	11th to 20th	Night	13% 7% 2 7% 5% 6% 5% 4 7% 10% 34%	2530
	21st to end	Night	12% 6% 2 8% 5% 4 5% 4 6% 8% 40%	2750
August	1st to 10th	Night	13% 8% 4 8% 6% 6% 5% 4 6% 9% 32%	2754
	11th to 20th	Night	12% 8% 3 7% 5% 5% 5% 4 7% 8% 36%	2782
	21st to end	Night	13% 5% 2 5% 4 4 5% 3 6% 8% 43%	3378
September	1st to 10th	Night	13% 7% 2 6% 5% 4 5% 4 5% 8% 41%	1900
	11th to 20th	Night	17% 8% 2 6% 3 4 3 3 5% 6% 43%	1900
	21st to end	Night	20% 7% 2 7% 4 4 4 2 6% 6% 37%	2188
October	1st to 10th	Night	20% 7% 2 6% 5% 4 5% 4 5% 7% 37%	2280
	11th to 20th	Night	18% 8% 3 7% 5% 4 5% 3 6% 7% 34%	2280
	21st to end	Night	25% 11% 3 7% 4 4 5% 4 5% 5% 27%	2576
November	1st to 10th	Night	19% 15% 4 8% 5% 5% 4 3 5% 5% 27%	2565
	11th to 20th	Night	18% 15% 4 9% 6% 4 5% 4 6% 6% 23%	2660
	21st to end	Night	19% 17% 6% 9% 5% 4 5% 4 5% 6% 21%	2660
December	1st to 10th	Night	19% 20% 5% 11% 5% 5% 4 3 5% 6% 17%	2660
	11th to 20th	Night	24% 17% 5% 12% 6% 4 4 3 3 4 18%	3293
	21st to end	Night	26% 16% 6% 13% 4 3 3 3 3 4 20%	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	73% 6% 12% 7% 2	2527
	11th to 20th	Day	61% 9% 8% 14% 7%	2530
	21st to end	Day	65% 5% 11% 12% 7% 1	3040
February	1st to 10th	Day	65% 4 10% 14% 6% 1	1710
	11th to 20th	Day	64% 6% 9% 15% 6%	1671
	21st to end	Day	56% 7% 11% 16% 9% 2	1489
March	1st to 10th	Day	61% 5% 8% 16% 9%	3294
	11th to 20th	Day	66% 8% 9% 12% 5% 1	3480
	21st to end	Day	71% 6% 7% 10% 5% 1	3904
April	1st to 10th	Day	61% 6% 8% 13% 10% 2	2280
	11th to 20th	Day	57% 6% 8% 18% 11% 1	2260
	21st to end	Day	58% 7% 10% 15% 9% 1	2470
May	1st to 10th	Day	63% 7% 11% 13% 5% 1	4392
	11th to 20th	Day	52% 8% 14% 19% 7%	4402
	21st to end	Day	50% 10% 16% 16% 7%	4836
June	1st to 10th	Day	60% 7% 12% 16% 4	2660
	11th to 20th	Day	51% 7% 11% 21% 9% 1	2660
	21st to end	Day	58% 8% 9% 15% 9% 1	2660
July	1st to 10th	Day	50% 7% 15% 17% 11%	4370
	11th to 20th	Day	44% 9% 18% 22% 7%	4364
	21st to end	Day	44% 10% 18% 22% 7%	4662
August	1st to 10th	Day	54% 9% 12% 20% 5%	4160
	11th to 20th	Day	46% 8% 14% 24% 8%	4084
	21st to end	Day	36% 7% 15% 29% 13%	4277
September	1st to 10th	Day	45% 7% 13% 24% 11% 1	2280
	11th to 20th	Day	48% 6% 12% 22% 11% 1	2280
	21st to end	Day	47% 7% 11% 24% 11%	1987
October	1st to 10th	Day	49% 9% 14% 20% 8%	3160
	11th to 20th	Day	50% 7% 12% 22% 9%	3140
	21st to end	Day	52% 5% 15% 19% 8% 1	3314
November	1st to 10th	Day	64% 6% 10% 15% 5%	1608
	11th to 20th	Day	65% 6% 14% 11% 4	1520
	21st to end	Day	65% 7% 16% 10% 2	1520
December	1st to 10th	Day	70% 6% 14% 8% 2	1520
	11th to 20th	Day	75% 4 11% 7% 2 1	1905
	21st to end	Day	69% 5% 16% 7% 2	2783
January	1st to 10th	Night	70% 4 15% 9% 2	4429
	11th to 20th	Night	61% 7% 10% 15% 5%	4440
	21st to end	Night	67% 6% 11% 11% 4	4618
February	1st to 10th	Night	64% 4 9% 13% 8% 1	2470
	11th to 20th	Night	66% 5% 10% 14% 6% 1	2406
	21st to end	Night	57% 6% 9% 18% 9% 1	1965
March	1st to 10th	Night	64% 6% 6% 13% 9% 1	3557
	11th to 20th	Night	66% 6% 9% 13% 5% 1	3480
	21st to end	Night	68% 5% 6% 14% 6% 1	3727
April	1st to 10th	Night	62% 6% 9% 13% 9% 2	1900
	11th to 20th	Night	53% 5% 9% 19% 11% 1	1867
	21st to end	Night	59% 7% 9% 14% 11% 1	1710
May	1st to 10th	Night	67% 4 9% 14% 5%	2575
	11th to 20th	Night	51% 7% 14% 20% 7%	2507
	21st to end	Night	54% 9% 18% 14% 5%	2750
June	1st to 10th	Night	57% 8% 10% 19% 5%	1520
	11th to 20th	Night	46% 6% 13% 21% 13%	1520
	21st to end	Night	52% 8% 13% 17% 8% 1	1520
July	1st to 10th	Night	50% 8% 17% 17% 8% 1	2491
	11th to 20th	Night	44% 8% 21% 19% 9%	2482
	21st to end	Night	41% 8% 17% 24% 9%	2663
August	1st to 10th	Night	49% 9% 17% 22% 4	2743
	11th to 20th	Night	44% 9% 15% 26% 5%	2809
	21st to end	Night	37% 8% 18% 25% 11% 1	3377
September	1st to 10th	Night	40% 8% 13% 28% 11% 1	1900
	11th to 20th	Night	42% 5% 13% 27% 11% 1	1900
	21st to end	Night	46% 7% 12% 25% 9% 1	2188
October	1st to 10th	Night	50% 8% 13% 19% 9%	3800
	11th to 20th	Night	44% 7% 14% 26% 10%	3779
	21st to end	Night	51% 6% 14% 19% 9% 1	4236
November	1st to 10th	Night	59% 6% 13% 16% 6%	2565
	11th to 20th	Night	62% 8% 13% 12% 5%	2660
	21st to end	Night	64% 8% 15% 11% 2	2660
December	1st to 10th	Night	70% 5% 13% 9% 2	2660
	11th to 20th	Night	74% 4 10% 9% 3	3295
	21st to end	Night	71% 4 13% 10% 2	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	30% 26% 31% 11% 2	370
	11th to 20th	Day	30% 29% 26% 12% 4	370
	21st to end	Day	24% 29% 33% 12% 1	407
February	1st to 10th	Day	29% 28% 29% 12% 2	370
	11th to 20th	Day	30% 31% 27% 11% 1	366
	21st to end	Day	22% 25% 36% 12% 4 1	307
March	1st to 10th	Day	25% 28% 33% 13% 1	418
	11th to 20th	Day	25% 31% 29% 12% 3	460
	21st to end	Day	33% 30% 24% 10% 2	506
April	1st to 10th	Day	36% 29% 25% 7% 2	460
	11th to 20th	Day	32% 30% 25% 10% 3	452
	21st to end	Day	29% 23% 31% 14% 3	460
May	1st to 10th	Day	36% 23% 25% 11% 3 2	618
	11th to 20th	Day	23% 19% 33% 18% 6% 1	674
	21st to end	Day	25% 21% 35% 15% 3	735
June	1st to 10th	Day	34% 18% 28% 16% 4	680
	11th to 20th	Day	24% 17% 37% 18% 4 1	680
	21st to end	Day	26% 14% 34% 20% 6% 1	680
July	1st to 10th	Day	20% 12% 38% 24% 4 1	670
	11th to 20th	Day	15% 11% 40% 25% 8%	668
	21st to end	Day	20% 10% 36% 27% 7% 1	740
August	1st to 10th	Day	17% 9% 38% 27% 7% 2	529
	11th to 20th	Day	23% 13% 32% 21% 10% 2	479
	21st to end	Day	17% 12% 34% 26% 9% 1	539
September	1st to 10th	Day	19% 17% 37% 20% 6% 1	490
	11th to 20th	Day	26% 14% 30% 21% 7% 1	490
	21st to end	Day	22% 19% 32% 18% 8% 2	427
October	1st to 10th	Day	22% 17% 30% 22% 7% 2	390
	11th to 20th	Day	26% 24% 27% 15% 6% 1	390
	21st to end	Day	28% 27% 28% 12% 4 1	429
November	1st to 10th	Day	30% 28% 26% 11% 3 1	378
	11th to 20th	Day	36% 25% 24% 12% 2 1	370
	21st to end	Day	35% 30% 22% 10% 2 1	370
December	1st to 10th	Day	35% 26% 29% 9% 1	370
	11th to 20th	Day	39% 30% 24% 7%	370
	21st to end	Day	28% 31% 27% 12% 2	407
January	1st to 10th	Night	26% 26% 31% 15% 2	850
	11th to 20th	Night	26% 26% 32% 14% 2	850
	21st to end	Night	22% 27% 31% 16% 3	858
February	1st to 10th	Night	28% 22% 31% 18% 2	760
	11th to 20th	Night	29% 30% 26% 13% 2	743
	21st to end	Night	22% 22% 32% 18% 5%	628
March	1st to 10th	Night	25% 25% 32% 17% 1	760
	11th to 20th	Night	22% 24% 27% 21% 6%	760
	21st to end	Night	27% 23% 28% 19% 3	785
April	1st to 10th	Night	30% 22% 28% 17% 3	570
	11th to 20th	Night	27% 21% 30% 18% 4	564
	21st to end	Night	29% 17% 29% 19% 5%	570
May	1st to 10th	Night	33% 16% 26% 18% 6% 1	570
	11th to 20th	Night	26% 14% 30% 25% 5% 1	562
	21st to end	Night	22% 16% 40% 19% 3	616
June	1st to 10th	Night	30% 13% 35% 19% 4	570
	11th to 20th	Night	23% 11% 40% 23% 4	570
	21st to end	Night	21% 11% 36% 27% 4	570
July	1st to 10th	Night	17% 8% 40% 29% 5%	556
	11th to 20th	Night	14% 8% 39% 31% 7%	552
	21st to end	Night	19% 7% 35% 33% 6%	623
August	1st to 10th	Night	15% 8% 36% 33% 8% 1	568
	11th to 20th	Night	20% 9% 31% 30% 9% 1	562
	21st to end	Night	15% 8% 32% 36% 8%	627
September	1st to 10th	Night	16% 8% 41% 29% 6%	570
	11th to 20th	Night	22% 11% 30% 29% 8%	570
	21st to end	Night	22% 16% 30% 25% 6% 1	742
October	1st to 10th	Night	24% 14% 28% 25% 8%	760
	11th to 20th	Night	22% 19% 32% 21% 6% 1	760
	21st to end	Night	32% 23% 27% 14% 3	873
November	1st to 10th	Night	29% 23% 28% 15% 3 1	854
	11th to 20th	Night	30% 25% 26% 15% 4 1	850
	21st to end	Night	32% 25% 26% 16% 2	850
December	1st to 10th	Night	30% 26% 29% 12% 2	850
	11th to 20th	Night	33% 29% 26% 9% 2	850
	21st to end	Night	32% 28% 24% 13% 2 1	935

Page generated at 2024-11-03 03:11:23. Version ac07

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