Chisasibi
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Chisasibi clear sky chart from 2005-11-06 to 2024-11-10.

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	15% 13% 5% 11% 7% 6% 5% 4 5% 6% 23%	102102
	Night	13% 15% 5% 13% 8% 6% 6% 5% 5% 5% 18%	97179
Transparency	Day	61% 5% 11% 17% 6%	105412
	Night	66% 6% 9% 14% 5%	101959
Seeing	Day	21% 7% 25% 28% 15% 5%	16144
	Night	20% 7% 23% 31% 16% 3	24502

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	9% 13% 6% 21% 12% 10% 9% 8% 6% 2 3	2186
	11th to 20th	Day	5% 14% 8% 23% 16% 11% 8% 5% 5% 3 3	2210
	21st to end	Day	7% 14% 6% 16% 9% 8% 9% 7% 10% 4 12%	2431
February	1st to 10th	Day	5% 11% 4 12% 10% 10% 13% 12% 11% 4 7%	1553
	11th to 20th	Day	5% 12% 6% 13% 9% 8% 11% 11% 12% 5% 7%	1663
	21st to end	Day	5% 11% 4 11% 7% 7% 11% 10% 10% 9% 15%	1413
March	1st to 10th	Day	8% 12% 5% 13% 10% 9% 8% 7% 8% 7% 14%	3138
	11th to 20th	Day	4 14% 8% 17% 16% 6% 7% 7% 5% 4 13%	3480
	21st to end	Day	11% 11% 5% 13% 9% 8% 8% 5% 5% 4 21%	3903
April	1st to 10th	Day	11% 15% 4 12% 7% 6% 7% 3 4 5% 26%	2330
	11th to 20th	Day	10% 12% 6% 11% 7% 6% 5% 4 4 6% 31%	2442
	21st to end	Day	13% 12% 4 11% 9% 5% 4 3 4 6% 30%	2603
May	1st to 10th	Day	13% 13% 7% 13% 7% 5% 5% 3 4 6% 24%	4426
	11th to 20th	Day	17% 13% 7% 14% 6% 4 4 3 5% 6% 22%	4671
	21st to end	Day	13% 9% 4 9% 5% 5% 5% 4 6% 8% 33%	5279
June	1st to 10th	Day	14% 9% 3 7% 4 5% 5% 3 5% 7% 37%	3040
	11th to 20th	Day	14% 7% 3 6% 5% 4 4 4 5% 8% 39%	3040
	21st to end	Day	15% 9% 3 6% 3 4 4 3 6% 7% 39%	3040
July	1st to 10th	Day	16% 8% 3 7% 5% 5% 5% 4 7% 7% 31%	4961
	11th to 20th	Day	22% 11% 3 8% 5% 5% 4 3 5% 7% 27%	4760
	21st to end	Day	17% 11% 3 9% 6% 5% 5% 3 6% 7% 27%	5162
August	1st to 10th	Day	21% 14% 5% 10% 5% 5% 5% 4 6% 7% 19%	4596
	11th to 20th	Day	14% 9% 3 6% 3 4 4 4 6% 9% 38%	4204
	21st to end	Day	19% 8% 2 6% 4 4 4 4 5% 8% 35%	4532
September	1st to 10th	Day	25% 11% 4 8% 5% 4 4 4 5% 9% 21%	2299
	11th to 20th	Day	25% 14% 4 9% 6% 4 4 3 4 5% 21%	2251
	21st to end	Day	25% 15% 4 9% 6% 4 4 3 4 6% 20%	2005
October	1st to 10th	Day	25% 16% 4 9% 5% 4 5% 3 4 6% 19%	1900
	11th to 20th	Day	27% 22% 5% 10% 6% 4 3 3 3 4 13%	1900
	21st to end	Day	23% 23% 7% 12% 6% 6% 4 3 3 4 10%	1707
November	1st to 10th	Day	19% 28% 7% 13% 6% 5% 4 2 4 4 7%	1558
	11th to 20th	Day	22% 25% 8% 17% 6% 3 3 2 3 3 7%	1520
	21st to end	Day	13% 22% 8% 22% 10% 5% 3 2 4 3 9%	1236
December	1st to 10th	Day	9% 23% 10% 19% 13% 7% 4 3 3 3 7%	1140
	11th to 20th	Day	8% 17% 8% 16% 14% 10% 9% 3 3 2 11%	1433
	21st to end	Day	9% 22% 8% 19% 11% 7% 7% 4 4 4 6%	2090
January	1st to 10th	Night	9% 16% 7% 20% 12% 9% 8% 7% 7% 2 3	4768
	11th to 20th	Night	6% 16% 7% 22% 14% 9% 8% 6% 6% 2 4	4760
	21st to end	Night	7% 14% 5% 14% 11% 9% 10% 7% 10% 3 11%	5236
February	1st to 10th	Night	4 12% 5% 13% 10% 10% 14% 10% 11% 5% 5%	2623
	11th to 20th	Night	5% 11% 5% 11% 9% 7% 11% 11% 13% 5% 10%	2403
	21st to end	Night	4 13% 6% 12% 7% 7% 8% 10% 10% 9% 14%	2041
March	1st to 10th	Night	6% 11% 4 13% 8% 8% 11% 8% 9% 6% 15%	3698
	11th to 20th	Night	4 13% 7% 16% 17% 9% 7% 5% 5% 6% 12%	3479
	21st to end	Night	8% 10% 5% 13% 8% 7% 9% 8% 5% 7% 20%	3728
April	1st to 10th	Night	14% 13% 4 11% 6% 6% 6% 3 5% 6% 27%	1867
	11th to 20th	Night	10% 11% 5% 9% 7% 6% 4 4 5% 7% 33%	1687
	21st to end	Night	12% 11% 5% 9% 5% 6% 4 3 6% 7% 34%	1576
May	1st to 10th	Night	17% 14% 6% 10% 5% 3 4 3 4 5% 27%	2514
	11th to 20th	Night	20% 13% 4 13% 5% 5% 4 3 4 7% 21%	2230
	21st to end	Night	14% 10% 4 10% 5% 4 5% 4 7% 7% 31%	2309
June	1st to 10th	Night	16% 8% 3 7% 4 4 5% 4 5% 6% 38%	1140
	11th to 20th	Night	14% 7% 3 6% 4 4 5% 3 6% 6% 42%	1140
	21st to end	Night	14% 9% 2 8% 5% 4 4 4 4 7% 39%	1140
July	1st to 10th	Night	14% 8% 2 6% 3 4 6% 4 7% 10% 34%	2012
	11th to 20th	Night	19% 12% 4 10% 6% 4 4 4 4 5% 28%	2210
	21st to end	Night	18% 13% 4 9% 5% 4 4 4 5% 6% 28%	2402
August	1st to 10th	Night	20% 13% 3 10% 6% 5% 5% 3 6% 5% 25%	2338
	11th to 20th	Night	15% 9% 3 6% 4 4 4 4 5% 8% 38%	2623
	21st to end	Night	16% 9% 2 6% 4 3 3 3 4 7% 42%	3124
September	1st to 10th	Night	25% 12% 4 8% 5% 4 4 3 5% 5% 24%	1861
	11th to 20th	Night	22% 13% 4 8% 5% 5% 5% 4 5% 6% 23%	1928
	21st to end	Night	22% 14% 4 9% 5% 5% 4 3 4 7% 23%	2175
October	1st to 10th	Night	24% 16% 4 10% 6% 5% 5% 3 4 5% 19%	2280
	11th to 20th	Night	25% 22% 4 10% 5% 5% 3 3 3 5% 15%	2280
	21st to end	Night	22% 21% 7% 12% 5% 5% 4 3 4 5% 12%	2888
November	1st to 10th	Night	23% 27% 8% 14% 5% 4 3 3 2 3 8%	2725
	11th to 20th	Night	22% 25% 9% 16% 6% 5% 3 3 3 3 7%	2660
	21st to end	Night	14% 24% 9% 19% 7% 5% 4 3 3 3 8%	2937
December	1st to 10th	Night	11% 22% 10% 23% 12% 7% 3 2 2 2 6%	3040
	11th to 20th	Night	9% 15% 8% 19% 13% 9% 7% 3 2 3 12%	3769
	21st to end	Night	10% 21% 5% 18% 14% 9% 7% 4 3 2 6%	5588

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	79% 9% 7% 4 1	2187
	11th to 20th	Day	84% 4 4 6% 2	2210
	21st to end	Day	67% 5% 9% 10% 8%	2431
February	1st to 10th	Day	65% 9% 8% 12% 5%	1553
	11th to 20th	Day	65% 8% 9% 13% 5%	1672
	21st to end	Day	57% 6% 15% 15% 6%	1413
March	1st to 10th	Day	64% 6% 8% 18% 5%	3141
	11th to 20th	Day	71% 5% 8% 12% 4	3480
	21st to end	Day	64% 5% 9% 15% 6%	3903
April	1st to 10th	Day	62% 3 6% 19% 9% 1	2330
	11th to 20th	Day	55% 4 9% 21% 11%	2442
	21st to end	Day	57% 4 9% 18% 12% 1	2603
May	1st to 10th	Day	61% 5% 9% 20% 5%	4440
	11th to 20th	Day	61% 7% 9% 18% 5%	4675
	21st to end	Day	47% 6% 11% 19% 17%	5279
June	1st to 10th	Day	45% 6% 10% 26% 11% 1	3040
	11th to 20th	Day	44% 5% 9% 26% 15% 1	3040
	21st to end	Day	45% 5% 13% 26% 11% 1	3040
July	1st to 10th	Day	50% 6% 15% 24% 5%	4885
	11th to 20th	Day	55% 5% 12% 21% 7%	4679
	21st to end	Day	55% 6% 17% 19% 2 1	4999
August	1st to 10th	Day	65% 6% 17% 11% 2	4580
	11th to 20th	Day	42% 4 19% 28% 6%	4246
	21st to end	Day	47% 5% 13% 27% 8%	4531
September	1st to 10th	Day	61% 6% 15% 15% 3	2299
	11th to 20th	Day	65% 6% 13% 14% 2	2251
	21st to end	Day	66% 6% 12% 12% 4	2005
October	1st to 10th	Day	61% 4 15% 17% 2	3160
	11th to 20th	Day	76% 4 10% 9% 1	3140
	21st to end	Day	80% 5% 7% 8% 1	2781
November	1st to 10th	Day	82% 6% 7% 5% 1	1558
	11th to 20th	Day	83% 5% 6% 4 2	1520
	21st to end	Day	81% 5% 7% 7% 1	1236
December	1st to 10th	Day	85% 4 5% 5% 1	1140
	11th to 20th	Day	79% 6% 6% 6% 2	1433
	21st to end	Day	81% 5% 5% 6% 2	2090
January	1st to 10th	Night	82% 5% 6% 6% 1	4768
	11th to 20th	Night	82% 5% 5% 6% 2	4760
	21st to end	Night	68% 6% 6% 11% 9%	5236
February	1st to 10th	Night	68% 9% 7% 11% 5%	2623
	11th to 20th	Night	61% 7% 11% 15% 6%	2405
	21st to end	Night	57% 7% 12% 17% 7%	2041
March	1st to 10th	Night	60% 7% 8% 18% 6%	3708
	11th to 20th	Night	71% 6% 8% 9% 6%	3480
	21st to end	Night	58% 7% 10% 18% 7%	3728
April	1st to 10th	Night	58% 5% 7% 18% 11% 1	1867
	11th to 20th	Night	51% 4 10% 22% 13% 1	1687
	21st to end	Night	50% 4 9% 20% 16%	1576
May	1st to 10th	Night	57% 6% 8% 21% 6% 1	2520
	11th to 20th	Night	63% 5% 7% 18% 6% 1	2231
	21st to end	Night	48% 8% 11% 20% 13%	2310
June	1st to 10th	Night	45% 5% 8% 26% 14% 1	1140
	11th to 20th	Night	40% 4 10% 25% 19% 1	1140
	21st to end	Night	45% 5% 11% 24% 14% 1	1140
July	1st to 10th	Night	44% 7% 13% 29% 7%	1979
	11th to 20th	Night	57% 5% 12% 21% 5%	2168
	21st to end	Night	57% 4 18% 18% 4	2325
August	1st to 10th	Night	59% 5% 20% 15% 2	2330
	11th to 20th	Night	44% 5% 16% 30% 4	2647
	21st to end	Night	44% 4 13% 27% 11% 1	3124
September	1st to 10th	Night	62% 6% 16% 14% 2	1861
	11th to 20th	Night	61% 7% 16% 14% 3	1928
	21st to end	Night	62% 5% 14% 14% 4	2175
October	1st to 10th	Night	65% 4 13% 14% 3	3800
	11th to 20th	Night	75% 4 12% 7% 1	3779
	21st to end	Night	77% 5% 8% 8% 2	4764
November	1st to 10th	Night	82% 5% 6% 6% 1	2725
	11th to 20th	Night	84% 5% 5% 4 1	2660
	21st to end	Night	81% 6% 5% 7% 1	2937
December	1st to 10th	Night	87% 3 4 4 1	3040
	11th to 20th	Night	78% 6% 6% 8% 3	3769
	21st to end	Night	81% 7% 5% 6% 2	5588

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	12% 6% 27% 34% 16% 6%	180
	11th to 20th	Day	9% 7% 27% 30% 21% 6%	180
	21st to end	Day	14% 8% 20% 30% 22% 7%	198
February	1st to 10th	Day	10% 4 23% 35% 19% 8%	231
	11th to 20th	Day	9% 4 30% 30% 20% 8%	270
	21st to end	Day	9% 10% 30% 30% 15% 6%	225
March	1st to 10th	Day	12% 8% 24% 28% 15% 13%	391
	11th to 20th	Day	9% 7% 27% 30% 18% 8%	460
	21st to end	Day	15% 6% 25% 33% 16% 5%	506
April	1st to 10th	Day	13% 6% 18% 34% 22% 8%	460
	11th to 20th	Day	15% 8% 25% 26% 19% 7%	452
	21st to end	Day	17% 7% 25% 26% 16% 10%	460
May	1st to 10th	Day	17% 7% 22% 28% 20% 6%	463
	11th to 20th	Day	17% 9% 27% 29% 15% 3	643
	21st to end	Day	19% 9% 31% 28% 11% 2	789
June	1st to 10th	Day	17% 6% 27% 29% 15% 5%	870
	11th to 20th	Day	19% 6% 29% 28% 13% 5%	870
	21st to end	Day	19% 7% 24% 32% 14% 5%	870
July	1st to 10th	Day	19% 6% 26% 30% 15% 4	792
	11th to 20th	Day	21% 5% 26% 29% 15% 3	668
	21st to end	Day	26% 4 19% 28% 16% 7%	739
August	1st to 10th	Day	31% 5% 17% 27% 14% 6%	595
	11th to 20th	Day	27% 7% 15% 26% 17% 8%	479
	21st to end	Day	22% 7% 20% 27% 15% 8%	539
September	1st to 10th	Day	32% 8% 26% 22% 10% 3	490
	11th to 20th	Day	26% 10% 26% 21% 13% 3	490
	21st to end	Day	33% 8% 26% 18% 11% 4	490
October	1st to 10th	Day	31% 10% 27% 20% 8% 3	490
	11th to 20th	Day	38% 6% 27% 17% 9% 4	490
	21st to end	Day	26% 12% 21% 25% 12% 4	248
November	1st to 10th	Day	29% 14% 22% 20% 11% 4	198
	11th to 20th	Day	27% 14% 19% 22% 13% 4	180
	21st to end	Day	21% 7% 23% 27% 17% 6%	180
December	1st to 10th	Day	17% 8% 24% 31% 18% 2	180
	11th to 20th	Day	15% 13% 24% 29% 14% 4	180
	21st to end	Day	16% 7% 27% 30% 18% 3	198
January	1st to 10th	Night	18% 7% 24% 31% 15% 4	953
	11th to 20th	Night	14% 6% 20% 35% 21% 4	950
	21st to end	Night	11% 4 17% 34% 26% 7%	1045
February	1st to 10th	Night	8% 6% 20% 38% 23% 5%	836
	11th to 20th	Night	10% 5% 20% 36% 22% 7%	743
	21st to end	Night	9% 5% 22% 34% 22% 7%	628
March	1st to 10th	Night	11% 6% 22% 34% 23% 5%	760
	11th to 20th	Night	11% 7% 27% 34% 17% 4	760
	21st to end	Night	14% 7% 28% 31% 18% 3	836
April	1st to 10th	Night	18% 5% 23% 35% 16% 3	727
	11th to 20th	Night	14% 4 23% 34% 20% 4	563
	21st to end	Night	18% 5% 22% 35% 18% 1	436
May	1st to 10th	Night	22% 5% 24% 32% 13% 3	380
	11th to 20th	Night	21% 8% 25% 32% 12% 1	374
	21st to end	Night	19% 9% 27% 34% 11%	411
June	1st to 10th	Night	20% 4 25% 34% 16% 1	380
	11th to 20th	Night	18% 6% 26% 34% 14% 2	380
	21st to end	Night	17% 6% 26% 36% 14% 2	380
July	1st to 10th	Night	19% 4 21% 35% 20% 1	370
	11th to 20th	Night	20% 5% 23% 37% 14% 1	368
	21st to end	Night	24% 4 14% 33% 22% 4	416
August	1st to 10th	Night	25% 5% 16% 33% 19% 2	378
	11th to 20th	Night	27% 4 17% 31% 17% 4	464
	21st to end	Night	25% 3 21% 29% 19% 3	627
September	1st to 10th	Night	31% 7% 25% 24% 12% 1	721
	11th to 20th	Night	29% 8% 22% 30% 12%	760
	21st to end	Night	30% 8% 23% 26% 13% 1	760
October	1st to 10th	Night	35% 10% 22% 23% 9% 1	760
	11th to 20th	Night	35% 8% 24% 21% 8% 3	760
	21st to end	Night	32% 8% 23% 22% 13% 2	836
November	1st to 10th	Night	35% 12% 20% 23% 9% 1	779
	11th to 20th	Night	31% 12% 22% 23% 11% 1	760
	21st to end	Night	23% 10% 26% 25% 13% 3	977
December	1st to 10th	Night	19% 9% 29% 28% 14% 2	1040
	11th to 20th	Night	15% 9% 23% 29% 18% 5%	1040
	21st to end	Night	16% 8% 24% 33% 15% 5%	1144

Page generated at 2024-11-07 06:55:43. Version ac07

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