Shediac River Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Shediac River Observatory clear sky chart from 2005-11-06 to 2025-01-22.

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% 10% 3 8% 5% 4 4 4 5% 6% 32%	105227
	Night	18% 11% 3 8% 5% 4 4 3 5% 6% 33%	104216
Transparency	Day	51% 6% 12% 21% 10% 1	108790
	Night	51% 5% 12% 21% 10% 1	108742
Seeing	Day	22% 16% 31% 23% 7% 1	17032
	Night	24% 15% 32% 23% 6%	24737

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	15% 13% 4 11% 5% 4 5% 3 4 5% 30%	2277
	11th to 20th	Day	13% 15% 4 10% 5% 3 4 3 4 6% 34%	2431
	21st to end	Day	12% 10% 5% 9% 8% 4 4 3 5% 6% 34%	3133
February	1st to 10th	Day	16% 12% 4 9% 5% 5% 4 3 5% 5% 31%	1710
	11th to 20th	Day	17% 12% 4 11% 5% 4 5% 5% 3 5% 28%	1663
	21st to end	Day	11% 14% 4 8% 5% 4 3 4 5% 7% 34%	1418
March	1st to 10th	Day	22% 15% 5% 8% 4 3 4 3 4 5% 26%	3400
	11th to 20th	Day	15% 19% 5% 12% 6% 5% 5% 3 5% 5% 21%	3480
	21st to end	Day	27% 15% 5% 7% 4 3 4 3 5% 5% 21%	3816
April	1st to 10th	Day	21% 13% 4 8% 6% 5% 4 4 4 5% 26%	2256
	11th to 20th	Day	20% 12% 3 7% 4 4 4 4 4 6% 31%	2390
	21st to end	Day	23% 11% 3 7% 4 3 4 3 4 7% 29%	2470
May	1st to 10th	Day	23% 17% 3 8% 5% 3 4 3 4 6% 26%	4230
	11th to 20th	Day	17% 9% 3 7% 5% 4 4 4 5% 7% 37%	4398
	21st to end	Day	16% 10% 3 8% 6% 6% 5% 5% 6% 7% 28%	4836
June	1st to 10th	Day	26% 9% 2 6% 5% 4 5% 3 5% 6% 27%	2812
	11th to 20th	Day	20% 7% 2 7% 5% 5% 5% 4 6% 7% 32%	2850
	21st to end	Day	25% 10% 3 7% 5% 4 4 3 4 6% 29%	2850
July	1st to 10th	Day	14% 7% 3 7% 5% 6% 6% 5% 6% 8% 31%	4760
	11th to 20th	Day	14% 7% 2 7% 5% 5% 5% 5% 6% 9% 34%	4680
	21st to end	Day	12% 7% 3 7% 5% 5% 5% 4 7% 9% 37%	4725
August	1st to 10th	Day	17% 9% 3 7% 5% 5% 5% 4 6% 7% 31%	4105
	11th to 20th	Day	13% 6% 3 6% 4 6% 6% 4 7% 9% 36%	4045
	21st to end	Day	14% 4 2 5% 4 4 5% 4 6% 8% 45%	4436
September	1st to 10th	Day	16% 5% 2 6% 4 5% 4 3 6% 7% 43%	2280
	11th to 20th	Day	18% 6% 3 7% 4 4 3 3 5% 5% 42%	2177
	21st to end	Day	17% 7% 2 6% 4 4 4 3 4 6% 43%	2049
October	1st to 10th	Day	18% 8% 2 6% 3 3 4 4 5% 7% 41%	1900
	11th to 20th	Day	19% 9% 3 7% 4 4 5% 4 4 6% 36%	1900
	21st to end	Day	21% 9% 2 7% 5% 5% 5% 3 4 6% 33%	2057
November	1st to 10th	Day	19% 10% 3 9% 5% 5% 4 3 4 6% 32%	1575
	11th to 20th	Day	20% 14% 3 6% 4 5% 4 4 4 6% 30%	1600
	21st to end	Day	18% 15% 3 8% 5% 4 4 4 5% 6% 29%	1600
December	1st to 10th	Day	18% 12% 4 7% 4 4 3 3 5% 7% 33%	2610
	11th to 20th	Day	17% 16% 4 7% 5% 3 3 2 3 4 35%	2832
	21st to end	Day	16% 11% 5% 13% 6% 4 4 3 4 4 30%	3476
January	1st to 10th	Night	14% 12% 4 7% 5% 4 3 3 5% 6% 36%	4898
	11th to 20th	Night	15% 12% 4 9% 5% 5% 4 3 4 5% 32%	4749
	21st to end	Night	13% 14% 4 9% 8% 4 3 3 4 6% 33%	4546
February	1st to 10th	Night	16% 14% 3 8% 5% 5% 5% 4 6% 6% 29%	2470
	11th to 20th	Night	16% 14% 4 9% 6% 5% 5% 3 6% 5% 28%	2403
	21st to end	Night	14% 13% 4 7% 6% 4 4 3 5% 6% 34%	2032
March	1st to 10th	Night	23% 15% 4 11% 5% 5% 4 2 3 4 24%	3428
	11th to 20th	Night	21% 18% 4 9% 5% 4 5% 3 4 5% 21%	3479
	21st to end	Night	28% 12% 3 8% 5% 4 5% 3 5% 3 24%	3816
April	1st to 10th	Night	23% 13% 3 8% 4 4 4 3 5% 4 27%	1924
	11th to 20th	Night	22% 11% 2 7% 5% 4 3 3 4 6% 32%	1737
	21st to end	Night	21% 12% 3 8% 4 4 4 2 4 6% 32%	1710
May	1st to 10th	Night	25% 14% 3 7% 5% 4 4 4 6% 6% 24%	2712
	11th to 20th	Night	17% 9% 2 6% 3 3 3 4 5% 8% 40%	2506
	21st to end	Night	14% 11% 3 8% 5% 6% 6% 5% 6% 7% 30%	2749
June	1st to 10th	Night	26% 8% 2 6% 4 5% 4 4 5% 7% 29%	1383
	11th to 20th	Night	20% 7% 4 5% 5% 4 5% 3 4 8% 34%	1330
	21st to end	Night	24% 9% 3 7% 5% 5% 4 4 5% 5% 28%	1330
July	1st to 10th	Night	14% 8% 3 9% 5% 5% 6% 5% 7% 7% 31%	2210
	11th to 20th	Night	12% 8% 3 7% 5% 6% 6% 4 6% 8% 34%	2242
	21st to end	Night	12% 6% 2 6% 4 5% 5% 4 7% 7% 41%	2834
August	1st to 10th	Night	16% 8% 4 9% 6% 6% 6% 3 7% 7% 28%	2825
	11th to 20th	Night	11% 6% 3 8% 6% 6% 6% 5% 6% 8% 37%	2782
	21st to end	Night	13% 5% 2 5% 4 4 4 3 5% 7% 48%	3219
September	1st to 10th	Night	16% 6% 2 5% 4 3 4 3 5% 7% 45%	1900
	11th to 20th	Night	16% 7% 3 5% 3 3 3 3 4 6% 46%	2000
	21st to end	Night	16% 5% 3 6% 4 4 4 3 6% 5% 44%	2130
October	1st to 10th	Night	19% 7% 3 7% 4 4 4 3 4 6% 40%	2280
	11th to 20th	Night	17% 9% 3 6% 4 3 3 3 5% 6% 40%	2280
	21st to end	Night	23% 9% 3 7% 5% 4 4 3 5% 5% 34%	2538
November	1st to 10th	Night	20% 10% 2 6% 4 5% 4 3 5% 5% 35%	2720
	11th to 20th	Night	20% 12% 3 7% 5% 4 4 3 5% 6% 31%	2800
	21st to end	Night	24% 12% 3 6% 5% 4 4 3 4 6% 31%	2800
December	1st to 10th	Night	15% 9% 3 7% 5% 4 4 4 5% 6% 38%	4580
	11th to 20th	Night	18% 16% 4 7% 3 3 3 3 4 4 37%	5372
	21st to end	Night	20% 14% 5% 11% 4 4 4 3 4 5% 28%	7502

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	58% 4 13% 17% 7% 1	2278
	11th to 20th	Day	52% 7% 6% 19% 16% 1	2431
	21st to end	Day	50% 6% 13% 15% 15% 1	3133
February	1st to 10th	Day	55% 4 11% 17% 11% 2	1710
	11th to 20th	Day	57% 7% 8% 17% 9% 1	1671
	21st to end	Day	49% 4 11% 21% 13% 3	1418
March	1st to 10th	Day	60% 5% 9% 18% 6% 2	3404
	11th to 20th	Day	62% 6% 10% 14% 6% 1	3480
	21st to end	Day	64% 5% 5% 16% 8% 2	3816
April	1st to 10th	Day	60% 5% 7% 16% 11% 3	2256
	11th to 20th	Day	52% 7% 8% 20% 12% 2	2390
	21st to end	Day	55% 5% 9% 16% 12% 3	2470
May	1st to 10th	Day	60% 6% 8% 18% 8% 1	4244
	11th to 20th	Day	46% 6% 14% 25% 8%	4402
	21st to end	Day	50% 10% 13% 18% 9%	4836
June	1st to 10th	Day	57% 5% 12% 19% 8%	2812
	11th to 20th	Day	50% 7% 11% 23% 9% 1	2850
	21st to end	Day	57% 5% 11% 17% 9% 1	2850
July	1st to 10th	Day	48% 7% 16% 18% 10% 1	4685
	11th to 20th	Day	45% 7% 15% 25% 8%	4599
	21st to end	Day	42% 9% 17% 26% 7%	4574
August	1st to 10th	Day	52% 7% 10% 25% 6%	4092
	11th to 20th	Day	43% 7% 14% 25% 11%	4084
	21st to end	Day	36% 6% 15% 26% 17% 1	4436
September	1st to 10th	Day	39% 6% 15% 26% 13%	2280
	11th to 20th	Day	44% 4 12% 25% 13% 1	2177
	21st to end	Day	43% 5% 10% 26% 15% 1	2049
October	1st to 10th	Day	44% 7% 12% 28% 9% 1	3160
	11th to 20th	Day	44% 5% 10% 31% 9% 1	3140
	21st to end	Day	41% 5% 16% 20% 18%	3371
November	1st to 10th	Day	54% 5% 11% 22% 8% 1	1575
	11th to 20th	Day	56% 4 14% 15% 10% 1	1600
	21st to end	Day	57% 6% 14% 17% 7%	1600
December	1st to 10th	Day	51% 5% 14% 23% 7%	2610
	11th to 20th	Day	55% 4 11% 18% 11% 2	2831
	21st to end	Day	59% 3 12% 18% 7% 1	3476
January	1st to 10th	Night	50% 3 16% 25% 5% 1	4898
	11th to 20th	Night	52% 7% 9% 21% 10% 1	4749
	21st to end	Night	53% 4 10% 22% 10% 1	4546
February	1st to 10th	Night	56% 4 10% 17% 11% 2	2470
	11th to 20th	Night	58% 4 9% 17% 11% 1	2406
	21st to end	Night	52% 4 9% 20% 13% 3	2032
March	1st to 10th	Night	66% 4 6% 15% 8% 2	3437
	11th to 20th	Night	66% 5% 7% 14% 8% 1	3480
	21st to end	Night	64% 3 4 16% 10% 2	3816
April	1st to 10th	Night	59% 5% 8% 14% 11% 3	1924
	11th to 20th	Night	53% 4 9% 21% 12% 1	1737
	21st to end	Night	56% 3 9% 15% 15% 2	1710
May	1st to 10th	Night	60% 5% 12% 14% 7% 1	2718
	11th to 20th	Night	44% 5% 18% 25% 8% 1	2507
	21st to end	Night	49% 9% 19% 16% 7%	2750
June	1st to 10th	Night	54% 6% 13% 18% 8%	1383
	11th to 20th	Night	49% 6% 11% 23% 9% 1	1330
	21st to end	Night	57% 6% 11% 16% 9% 1	1330
July	1st to 10th	Night	48% 7% 14% 20% 11%	2175
	11th to 20th	Night	47% 7% 17% 21% 8%	2200
	21st to end	Night	39% 9% 17% 24% 11%	2745
August	1st to 10th	Night	54% 8% 12% 20% 5%	2813
	11th to 20th	Night	42% 7% 17% 23% 10%	2809
	21st to end	Night	35% 5% 17% 27% 15% 1	3218
September	1st to 10th	Night	40% 5% 12% 29% 14%	1900
	11th to 20th	Night	39% 5% 13% 28% 13% 1	2000
	21st to end	Night	41% 5% 12% 27% 14% 1	2130
October	1st to 10th	Night	50% 4 11% 27% 8%	3800
	11th to 20th	Night	36% 5% 13% 34% 12%	3779
	21st to end	Night	44% 4 14% 23% 14%	4174
November	1st to 10th	Night	51% 5% 13% 20% 10% 1	2720
	11th to 20th	Night	55% 4 13% 17% 9% 1	2800
	21st to end	Night	56% 5% 14% 18% 7%	2800
December	1st to 10th	Night	46% 4 15% 25% 10%	4580
	11th to 20th	Night	52% 3 11% 22% 11% 2	5374
	21st to end	Night	61% 3 12% 16% 8% 1	7502

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% 24% 31% 16% 1	200
	11th to 20th	Day	26% 23% 30% 16% 4	270
	21st to end	Day	17% 18% 37% 23% 4	410
February	1st to 10th	Day	24% 19% 34% 19% 5%	370
	11th to 20th	Day	23% 25% 34% 14% 3 1	366
	21st to end	Day	17% 23% 37% 19% 5%	310
March	1st to 10th	Day	25% 22% 36% 15% 2 1	460
	11th to 20th	Day	19% 25% 32% 20% 5%	460
	21st to end	Day	29% 19% 31% 16% 3 2	506
April	1st to 10th	Day	27% 24% 32% 13% 3	460
	11th to 20th	Day	24% 19% 34% 17% 5%	452
	21st to end	Day	26% 18% 29% 20% 5% 1	460
May	1st to 10th	Day	29% 17% 28% 20% 5%	535
	11th to 20th	Day	23% 13% 29% 24% 9% 1	674
	21st to end	Day	22% 16% 32% 24% 5%	735
June	1st to 10th	Day	31% 12% 28% 23% 6%	680
	11th to 20th	Day	22% 11% 30% 28% 7% 1	680
	21st to end	Day	26% 9% 29% 27% 8% 1	680
July	1st to 10th	Day	19% 8% 33% 29% 10% 1	670
	11th to 20th	Day	16% 6% 30% 36% 11% 1	668
	21st to end	Day	16% 5% 30% 36% 12% 1	686
August	1st to 10th	Day	16% 8% 26% 38% 10% 1	486
	11th to 20th	Day	17% 8% 25% 33% 15% 2	479
	21st to end	Day	15% 11% 26% 33% 13% 3	539
September	1st to 10th	Day	12% 9% 37% 30% 10% 2	490
	11th to 20th	Day	21% 15% 23% 27% 12% 1	490
	21st to end	Day	19% 14% 31% 24% 9% 2	467
October	1st to 10th	Day	19% 14% 29% 22% 14% 1	390
	11th to 20th	Day	20% 21% 30% 20% 9% 1	390
	21st to end	Day	24% 21% 31% 18% 5% 1	429
November	1st to 10th	Day	24% 22% 30% 18% 6% 1	395
	11th to 20th	Day	31% 21% 31% 14% 4 1	400
	21st to end	Day	30% 23% 33% 13% 3	400
December	1st to 10th	Day	29% 18% 34% 16% 4	400
	11th to 20th	Day	29% 32% 26% 12% 1	325
	21st to end	Day	20% 28% 35% 14% 2	220
January	1st to 10th	Night	25% 20% 34% 17% 4	900
	11th to 20th	Night	23% 20% 32% 20% 6%	883
	21st to end	Night	17% 20% 36% 20% 6%	841
February	1st to 10th	Night	25% 16% 37% 18% 4	760
	11th to 20th	Night	25% 21% 34% 17% 2 1	743
	21st to end	Night	22% 16% 34% 24% 4 1	628
March	1st to 10th	Night	24% 17% 37% 20% 2	760
	11th to 20th	Night	24% 18% 30% 22% 6% 1	760
	21st to end	Night	27% 15% 33% 20% 5% 1	836
April	1st to 10th	Night	29% 17% 29% 22% 3	594
	11th to 20th	Night	27% 13% 32% 22% 6%	564
	21st to end	Night	27% 15% 31% 19% 8%	570
May	1st to 10th	Night	30% 11% 27% 23% 7% 1	570
	11th to 20th	Night	27% 8% 30% 25% 9%	562
	21st to end	Night	19% 11% 40% 27% 4	616
June	1st to 10th	Night	28% 6% 27% 32% 7%	433
	11th to 20th	Night	21% 8% 32% 32% 7% 1	380
	21st to end	Night	26% 7% 30% 29% 7% 1	380
July	1st to 10th	Night	18% 5% 39% 27% 11%	370
	11th to 20th	Night	15% 8% 30% 34% 12% 1	387
	21st to end	Night	17% 5% 30% 38% 9%	623
August	1st to 10th	Night	16% 3 31% 37% 11% 1	568
	11th to 20th	Night	17% 6% 27% 34% 15% 1	562
	21st to end	Night	16% 6% 29% 36% 12% 1	627
September	1st to 10th	Night	18% 7% 37% 29% 8%	570
	11th to 20th	Night	18% 10% 27% 35% 10% 1	670
	21st to end	Night	18% 11% 33% 29% 9%	760
October	1st to 10th	Night	22% 9% 32% 26% 10%	760
	11th to 20th	Night	20% 15% 36% 21% 7%	760
	21st to end	Night	27% 21% 30% 18% 3	836
November	1st to 10th	Night	26% 19% 32% 18% 5%	874
	11th to 20th	Night	27% 20% 30% 17% 5% 1	900
	21st to end	Night	31% 21% 30% 16% 3	900
December	1st to 10th	Night	29% 17% 33% 18% 3	900
	11th to 20th	Night	28% 23% 34% 12% 3	900
	21st to end	Night	29% 21% 27% 20% 3 1	990

Page generated at 2025-01-19 04:06:47. Version ac07

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