Rosetown
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rosetown clear sky chart from 2005-11-06 to 2024-11-25.

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	8% 8% 3 8% 5% 5% 5% 4 6% 8% 38%	105570
	Night	7% 8% 3 9% 6% 5% 5% 4 6% 8% 38%	102454
Transparency	Day	42% 7% 16% 25% 9% 1	105316
	Night	42% 7% 15% 25% 10% 1	102355
Seeing	Day	12% 8% 27% 30% 18% 6%	15797
	Night	12% 6% 29% 36% 15% 2	25053

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	6% 12% 5% 13% 9% 6% 5% 4 6% 7% 27%	2219
	11th to 20th	Day	4 7% 4 13% 8% 7% 11% 7% 8% 11% 20%	2199
	21st to end	Day	6% 12% 4 8% 5% 5% 5% 4 6% 8% 35%	2541
February	1st to 10th	Day	9% 13% 5% 13% 7% 8% 6% 4 5% 7% 23%	1669
	11th to 20th	Day	7% 12% 4 11% 8% 7% 6% 4 7% 6% 29%	1665
	21st to end	Day	5% 11% 4 11% 10% 8% 7% 5% 7% 8% 24%	1413
March	1st to 10th	Day	7% 11% 5% 11% 9% 8% 7% 4 6% 6% 27%	3194
	11th to 20th	Day	4 12% 6% 12% 5% 5% 4 4 6% 10% 32%	3489
	21st to end	Day	6% 11% 5% 15% 7% 6% 6% 4 6% 8% 26%	3941
April	1st to 10th	Day	9% 10% 3 9% 6% 6% 5% 4 7% 7% 34%	2280
	11th to 20th	Day	10% 14% 5% 10% 6% 5% 5% 5% 6% 7% 28%	2393
	21st to end	Day	13% 10% 4 8% 5% 4 5% 3 6% 8% 34%	2584
May	1st to 10th	Day	20% 10% 3 7% 4 5% 4 3 5% 7% 33%	4430
	11th to 20th	Day	8% 7% 3 8% 6% 7% 6% 6% 8% 8% 33%	4388
	21st to end	Day	11% 8% 3 10% 6% 6% 6% 5% 7% 8% 30%	5158
June	1st to 10th	Day	13% 8% 3 7% 5% 5% 5% 4 6% 7% 38%	2869
	11th to 20th	Day	19% 7% 3 7% 7% 5% 5% 4 7% 7% 30%	3040
	21st to end	Day	9% 5% 2 7% 5% 5% 6% 5% 7% 9% 39%	2909
July	1st to 10th	Day	5% 4 2 6% 5% 5% 6% 5% 7% 10% 43%	4740
	11th to 20th	Day	8% 4 2 5% 4 4 4 4 7% 9% 49%	4740
	21st to end	Day	4 3 1 4 3 3 4 4 6% 9% 61%	5088
August	1st to 10th	Day	8% 6% 2 5% 4 4 4 4 6% 8% 49%	4412
	11th to 20th	Day	7% 4 2 5% 4 4 4 4 6% 10% 51%	4128
	21st to end	Day	10% 4 2 4 3 3 4 3 5% 8% 54%	4473
September	1st to 10th	Day	10% 5% 2 6% 4 4 4 3 6% 8% 49%	2280
	11th to 20th	Day	13% 7% 2 6% 4 4 4 4 6% 7% 43%	2280
	21st to end	Day	10% 5% 2 5% 3 4 3 3 5% 7% 53%	2001
October	1st to 10th	Day	7% 6% 2 6% 4 4 5% 4 6% 9% 48%	3170
	11th to 20th	Day	5% 5% 3 5% 4 5% 4 4 9% 13% 44%	3150
	21st to end	Day	6% 8% 4 9% 5% 4 5% 5% 6% 8% 40%	2959
November	1st to 10th	Day	11% 16% 4 11% 6% 4 4 4 5% 4 31%	1568
	11th to 20th	Day	6% 13% 7% 13% 7% 6% 5% 5% 6% 6% 27%	1600
	21st to end	Day	9% 13% 6% 11% 8% 6% 5% 4 5% 6% 27%	1552
December	1st to 10th	Day	8% 11% 4 12% 8% 7% 6% 5% 8% 8% 23%	1196
	11th to 20th	Day	7% 12% 4 11% 7% 8% 6% 4 7% 6% 28%	1439
	21st to end	Day	3 9% 3 9% 5% 5% 5% 5% 6% 8% 43%	2413
January	1st to 10th	Night	4 11% 5% 13% 7% 7% 7% 6% 7% 8% 25%	4726
	11th to 20th	Night	3 7% 4 14% 9% 9% 9% 6% 7% 8% 24%	4699
	21st to end	Night	6% 11% 4 9% 6% 6% 6% 5% 7% 9% 33%	5117
February	1st to 10th	Night	7% 13% 5% 12% 6% 5% 6% 5% 7% 8% 25%	2527
	11th to 20th	Night	6% 11% 5% 11% 7% 6% 7% 5% 6% 7% 29%	2402
	21st to end	Night	3 9% 5% 9% 8% 7% 6% 5% 7% 10% 31%	2041
March	1st to 10th	Night	6% 11% 5% 11% 8% 7% 8% 6% 7% 8% 24%	3668
	11th to 20th	Night	4 8% 5% 11% 6% 5% 6% 5% 7% 10% 33%	3490
	21st to end	Night	5% 9% 3 13% 7% 7% 6% 5% 7% 9% 29%	3707
April	1st to 10th	Night	6% 9% 2 7% 6% 5% 4 4 6% 9% 41%	1900
	11th to 20th	Night	10% 12% 4 9% 5% 5% 6% 5% 6% 7% 31%	1735
	21st to end	Night	12% 10% 3 9% 5% 5% 5% 5% 5% 7% 34%	1596
May	1st to 10th	Night	18% 11% 3 7% 5% 4 4 4 5% 6% 34%	2540
	11th to 20th	Night	11% 7% 2 8% 4 6% 6% 4 8% 8% 36%	2518
	21st to end	Night	13% 7% 3 8% 4 4 4 4 7% 7% 38%	2414
June	1st to 10th	Night	12% 6% 3 5% 4 5% 4 4 8% 10% 39%	1306
	11th to 20th	Night	18% 5% 2 6% 6% 6% 6% 4 7% 6% 34%	1140
	21st to end	Night	7% 5% 2 4 4 3 6% 5% 8% 9% 46%	1262
July	1st to 10th	Night	6% 4 1 5% 4 5% 5% 5% 8% 10% 47%	2220
	11th to 20th	Night	4 3 1 4 3 4 5% 4 7% 11% 55%	2220
	21st to end	Night	2 1 1 2 2 3 3 3 6% 9% 68%	2466
August	1st to 10th	Night	6% 4 2 5% 3 3 4 3 5% 8% 55%	2528
	11th to 20th	Night	5% 4 2 5% 4 5% 4 5% 6% 9% 51%	2710
	21st to end	Night	7% 4 2 5% 3 4 4 3 7% 9% 54%	3194
September	1st to 10th	Night	9% 4 2 6% 5% 4 4 3 6% 7% 51%	1900
	11th to 20th	Night	12% 5% 3 6% 4 3 4 4 5% 8% 46%	1900
	21st to end	Night	9% 6% 2 4 2 4 3 3 5% 8% 54%	2176
October	1st to 10th	Night	10% 8% 2 6% 5% 4 4 3 5% 7% 46%	3800
	11th to 20th	Night	6% 5% 2 6% 4 4 4 3 5% 8% 53%	3778
	21st to end	Night	8% 8% 3 7% 4 4 5% 4 7% 8% 42%	4552
November	1st to 10th	Night	14% 14% 4 9% 5% 4 4 3 5% 6% 32%	2730
	11th to 20th	Night	5% 11% 5% 13% 7% 6% 5% 3 7% 8% 29%	2800
	21st to end	Night	6% 14% 6% 12% 6% 6% 5% 4 5% 7% 30%	2723
December	1st to 10th	Night	8% 12% 4 11% 9% 7% 5% 4 7% 8% 26%	2979
	11th to 20th	Night	7% 13% 4 12% 8% 7% 6% 5% 6% 7% 25%	3753
	21st to end	Night	3 7% 2 7% 5% 5% 5% 4 5% 6% 52%	5237

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	56% 7% 14% 15% 8%	2219
	11th to 20th	Day	54% 9% 14% 18% 5% 1	2220
	21st to end	Day	46% 8% 20% 21% 5%	2541
February	1st to 10th	Day	60% 7% 10% 17% 7%	1669
	11th to 20th	Day	54% 6% 13% 17% 10% 1	1674
	21st to end	Day	55% 6% 14% 17% 7%	1413
March	1st to 10th	Day	55% 7% 17% 15% 6%	3194
	11th to 20th	Day	47% 9% 19% 17% 7%	3490
	21st to end	Day	52% 9% 15% 18% 5%	3941
April	1st to 10th	Day	46% 7% 14% 20% 12% 1	2280
	11th to 20th	Day	52% 6% 14% 19% 7% 1	2393
	21st to end	Day	47% 7% 14% 23% 8% 1	2584
May	1st to 10th	Day	51% 5% 14% 23% 5% 1	4430
	11th to 20th	Day	41% 10% 14% 23% 11% 1	4392
	21st to end	Day	47% 10% 16% 19% 8%	5159
June	1st to 10th	Day	43% 7% 13% 23% 12% 1	2869
	11th to 20th	Day	51% 8% 13% 20% 8% 1	3040
	21st to end	Day	38% 10% 19% 24% 9% 1	2909
July	1st to 10th	Day	32% 9% 19% 26% 13% 1	4666
	11th to 20th	Day	30% 7% 15% 36% 12% 1	4659
	21st to end	Day	20% 6% 15% 39% 16% 3	4927
August	1st to 10th	Day	32% 7% 20% 30% 10% 1	4396
	11th to 20th	Day	28% 7% 17% 37% 10%	4170
	21st to end	Day	29% 5% 18% 36% 12%	4472
September	1st to 10th	Day	33% 8% 14% 25% 15% 4	2280
	11th to 20th	Day	40% 6% 15% 27% 10% 2	2280
	21st to end	Day	30% 6% 15% 33% 14% 2	2001
October	1st to 10th	Day	33% 5% 21% 31% 9% 1	3170
	11th to 20th	Day	31% 5% 20% 34% 9%	3150
	21st to end	Day	41% 7% 17% 30% 6%	2959
November	1st to 10th	Day	56% 5% 13% 19% 7%	1568
	11th to 20th	Day	57% 7% 14% 17% 4	1600
	21st to end	Day	58% 7% 15% 17% 3	1552
December	1st to 10th	Day	56% 9% 14% 15% 6%	1196
	11th to 20th	Day	54% 8% 19% 11% 7%	1440
	21st to end	Day	37% 6% 15% 21% 16% 5%	2413
January	1st to 10th	Night	52% 9% 18% 17% 4	4726
	11th to 20th	Night	56% 8% 14% 16% 6% 1	4740
	21st to end	Night	46% 9% 18% 22% 5%	5117
February	1st to 10th	Night	54% 7% 13% 19% 7%	2527
	11th to 20th	Night	51% 7% 15% 16% 11%	2403
	21st to end	Night	46% 6% 15% 23% 10%	2041
March	1st to 10th	Night	52% 7% 16% 19% 6%	3668
	11th to 20th	Night	43% 9% 20% 20% 7%	3490
	21st to end	Night	49% 7% 14% 21% 8%	3707
April	1st to 10th	Night	39% 6% 14% 24% 16% 1	1900
	11th to 20th	Night	50% 6% 13% 18% 11% 2	1735
	21st to end	Night	48% 7% 10% 22% 11% 1	1596
May	1st to 10th	Night	49% 8% 12% 22% 9%	2540
	11th to 20th	Night	40% 9% 14% 21% 16% 1	2518
	21st to end	Night	42% 8% 17% 25% 9%	2414
June	1st to 10th	Night	37% 8% 16% 26% 12% 1	1306
	11th to 20th	Night	46% 10% 11% 19% 13% 1	1140
	21st to end	Night	31% 8% 20% 30% 9% 2	1262
July	1st to 10th	Night	28% 10% 23% 27% 12% 1	2185
	11th to 20th	Night	23% 6% 15% 44% 12%	2178
	21st to end	Night	14% 5% 15% 44% 20% 2	2388
August	1st to 10th	Night	28% 6% 19% 32% 13% 2	2520
	11th to 20th	Night	28% 6% 17% 35% 13% 1	2734
	21st to end	Night	26% 6% 16% 34% 17% 1	3194
September	1st to 10th	Night	31% 6% 14% 27% 15% 7%	1900
	11th to 20th	Night	37% 6% 14% 28% 12% 3	1900
	21st to end	Night	29% 6% 13% 33% 17% 3	2176
October	1st to 10th	Night	38% 4 17% 29% 11%	3800
	11th to 20th	Night	30% 4 14% 37% 14% 1	3778
	21st to end	Night	40% 5% 13% 35% 7% 1	4552
November	1st to 10th	Night	53% 6% 12% 20% 7% 1	2730
	11th to 20th	Night	52% 8% 17% 17% 6%	2800
	21st to end	Night	53% 7% 16% 19% 4	2723
December	1st to 10th	Night	55% 7% 15% 16% 6% 1	2979
	11th to 20th	Night	56% 8% 15% 15% 5%	3751
	21st to end	Night	32% 5% 14% 26% 17% 5%	5237

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	13% 6% 26% 31% 18% 6%	180
	11th to 20th	Day	13% 7% 24% 30% 21% 5%	180
	21st to end	Day	11% 11% 26% 33% 16% 4	227
February	1st to 10th	Day	15% 9% 35% 29% 11% 2	270
	11th to 20th	Day	11% 4 33% 31% 14% 6%	270
	21st to end	Day	6% 6% 27% 36% 20% 5%	225
March	1st to 10th	Day	10% 7% 33% 31% 15% 4	309
	11th to 20th	Day	10% 8% 31% 32% 13% 5%	460
	21st to end	Day	13% 9% 31% 26% 17% 3	506
April	1st to 10th	Day	10% 11% 36% 28% 11% 4	460
	11th to 20th	Day	13% 13% 33% 29% 9% 3	452
	21st to end	Day	17% 11% 28% 32% 12% 1	574
May	1st to 10th	Day	15% 7% 25% 28% 18% 6%	653
	11th to 20th	Day	10% 8% 22% 33% 20% 7%	675
	21st to end	Day	13% 9% 21% 27% 22% 7%	734
June	1st to 10th	Day	14% 10% 26% 28% 19% 5%	680
	11th to 20th	Day	18% 12% 27% 25% 13% 5%	680
	21st to end	Day	11% 9% 21% 31% 22% 7%	680
July	1st to 10th	Day	8% 4 23% 33% 24% 8%	671
	11th to 20th	Day	10% 6% 25% 28% 22% 8%	668
	21st to end	Day	8% 4 24% 28% 27% 10%	739
August	1st to 10th	Day	10% 5% 21% 32% 22% 10%	676
	11th to 20th	Day	9% 7% 19% 31% 27% 8%	541
	21st to end	Day	12% 6% 20% 33% 20% 7%	539
September	1st to 10th	Day	13% 7% 27% 27% 20% 6%	490
	11th to 20th	Day	19% 7% 26% 29% 17% 2	490
	21st to end	Day	15% 8% 30% 31% 11% 5%	396
October	1st to 10th	Day	18% 5% 27% 26% 19% 6%	300
	11th to 20th	Day	9% 8% 31% 32% 16% 5%	300
	21st to end	Day	11% 10% 41% 24% 11% 4	330
November	1st to 10th	Day	18% 8% 31% 31% 11% 1	300
	11th to 20th	Day	11% 12% 36% 30% 9% 2	300
	21st to end	Day	9% 9% 36% 30% 12% 5%	282
December	1st to 10th	Day	9% 3 34% 35% 13% 7%	182
	11th to 20th	Day	10% 13% 33% 32% 11% 1	180
	21st to end	Day	12% 3 33% 29% 20% 3	198
January	1st to 10th	Night	9% 7% 34% 36% 13% 2	950
	11th to 20th	Night	10% 9% 34% 34% 12% 1	950
	21st to end	Night	12% 7% 35% 34% 11% 1	1045
February	1st to 10th	Night	11% 6% 29% 35% 17% 3	817
	11th to 20th	Night	11% 7% 29% 36% 15% 2	744
	21st to end	Night	6% 4 25% 35% 25% 5%	628
March	1st to 10th	Night	10% 6% 30% 37% 14% 3	760
	11th to 20th	Night	9% 6% 31% 37% 15% 2	760
	21st to end	Night	11% 7% 28% 36% 15% 2	766
April	1st to 10th	Night	11% 9% 30% 38% 12% 1	570
	11th to 20th	Night	16% 10% 31% 30% 12% 1	563
	21st to end	Night	17% 7% 28% 34% 13%	570
May	1st to 10th	Night	15% 4 26% 37% 17% 2	570
	11th to 20th	Night	11% 7% 25% 36% 20% 2	561
	21st to end	Night	18% 8% 18% 33% 19% 3	411
June	1st to 10th	Night	13% 6% 27% 36% 16% 2	380
	11th to 20th	Night	19% 8% 19% 34% 18% 1	380
	21st to end	Night	9% 7% 20% 39% 23% 3	380
July	1st to 10th	Night	6% 3 21% 45% 23% 1	370
	11th to 20th	Night	8% 3 24% 45% 18% 2	368
	21st to end	Night	3 3 24% 43% 24% 2	444
August	1st to 10th	Night	6% 3 20% 42% 26% 3	567
	11th to 20th	Night	7% 3 18% 42% 27% 2	564
	21st to end	Night	9% 3 26% 37% 24%	627
September	1st to 10th	Night	11% 4 25% 42% 17% 2	570
	11th to 20th	Night	15% 4 23% 39% 19% 1	570
	21st to end	Night	11% 4 32% 36% 14% 2	753
October	1st to 10th	Night	17% 6% 26% 35% 16%	760
	11th to 20th	Night	11% 6% 31% 36% 15% 2	760
	21st to end	Night	15% 8% 34% 32% 11% 1	1002
November	1st to 10th	Night	20% 8% 29% 34% 8% 1	975
	11th to 20th	Night	10% 9% 33% 33% 12% 2	1000
	21st to end	Night	12% 7% 36% 34% 9% 1	973
December	1st to 10th	Night	13% 6% 33% 30% 15% 3	950
	11th to 20th	Night	11% 8% 36% 31% 12% 1	950
	21st to end	Night	12% 5% 29% 35% 16% 4	1045

Page generated at 2024-11-22 07:02:29. Version ac07

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