Massacre Rim
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Massacre Rim clear sky chart from 2005-11-06 to 2024-11-01.

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	3 6% 3 6% 4 4 4 3 5% 6% 55%	101356
	Night	4 8% 3 7% 4 4 4 4 5% 7% 51%	97768
Transparency	Day	29% 5% 8% 19% 21% 17%	101097
	Night	32% 6% 10% 19% 20% 13%	97616
Seeing	Day	7% 9% 22% 30% 23% 9%	14795
	Night	7% 7% 20% 38% 24% 5%	24010

By Month

Percentage Cloud Cover SW (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	4 12% 7% 13% 7% 6% 7% 5% 6% 8% 27%	2539
	11th to 20th	Day	4 12% 7% 15% 7% 6% 6% 5% 7% 8% 23%	2540
	21st to end	Day	4 17% 5% 12% 7% 7% 5% 4 6% 6% 27%	3018
February	1st to 10th	Day	4 8% 4 10% 5% 4 5% 5% 8% 10% 39%	1710
	11th to 20th	Day	2 8% 3 10% 6% 6% 5% 5% 7% 8% 39%	1807
	21st to end	Day	2 9% 4 8% 4 5% 7% 7% 8% 9% 37%	1570
March	1st to 10th	Day	2 13% 5% 13% 6% 6% 5% 5% 6% 7% 30%	3138
	11th to 20th	Day	2 6% 3 6% 4 4 4 3 5% 6% 56%	3384
	21st to end	Day	2 9% 4 10% 6% 6% 6% 5% 7% 10% 33%	4098
April	1st to 10th	Day	4 10% 5% 8% 6% 5% 5% 4 6% 8% 39%	2280
	11th to 20th	Day	5% 9% 3 8% 4 4 5% 4 6% 8% 46%	2249
	21st to end	Day	4 9% 2 6% 4 4 4 4 6% 9% 46%	2294
May	1st to 10th	Day	4 8% 3 5% 3 3 3 3 5% 8% 56%	4185
	11th to 20th	Day	4 4 1 4 3 2 3 2 3 5% 69%	4377
	21st to end	Day	4 5% 2 5% 4 4 4 3 5% 7% 56%	4813
June	1st to 10th	Day	5% 5% 2 6% 5% 4 4 5% 6% 8% 50%	2660
	11th to 20th	Day	4 4 1 4 3 3 3 3 5% 6% 64%	2660
	21st to end	Day	3 2 1 2 3 2 3 2 3 5% 73%	2660
July	1st to 10th	Day	1 1 1 2 1 2 1 3 3 84%	4420
	11th to 20th	Day	2 2 1 3 2 2 3 2 4 5% 74%	4420
	21st to end	Day	2 2 1 3 3 3 3 3 4 5% 71%	4790
August	1st to 10th	Day	3 2 1 4 3 3 3 3 5% 7% 66%	4202
	11th to 20th	Day	1 2 2 2 2 3 2 3 4 79%	3762
	21st to end	Day	2 2 1 2 2 2 2 1 3 3 80%	4180
September	1st to 10th	Day	2 1 1 3 2 2 2 2 4 4 77%	2280
	11th to 20th	Day	4 3 1 4 3 3 3 3 4 5% 65%	2242
	21st to end	Day	4 4 1 3 2 2 3 2 4 4 70%	2090
October	1st to 10th	Day	6% 5% 2 5% 3 3 4 3 4 5% 61%	1933
	11th to 20th	Day	5% 5% 2 4 3 3 3 3 4 6% 61%	1900
	21st to end	Day	4 4 2 6% 4 4 4 4 7% 7% 54%	1971
November	1st to 10th	Day	7% 9% 3 8% 4 3 4 4 5% 7% 43%	1674
	11th to 20th	Day	6% 9% 3 6% 6% 5% 6% 5% 8% 9% 38%	1710
	21st to end	Day	4 10% 3 7% 5% 4 6% 5% 7% 7% 43%	1558
December	1st to 10th	Day	5% 11% 4 10% 6% 5% 5% 4 5% 6% 39%	1520
	11th to 20th	Day	6% 12% 4 10% 6% 6% 7% 6% 8% 10% 26%	1928
	21st to end	Day	5% 10% 5% 10% 6% 6% 6% 5% 7% 9% 30%	2794
January	1st to 10th	Night	4 12% 5% 11% 6% 6% 6% 6% 8% 8% 28%	4406
	11th to 20th	Night	4 16% 6% 13% 6% 5% 6% 5% 6% 8% 25%	4420
	21st to end	Night	5% 15% 6% 12% 7% 6% 5% 4 5% 7% 28%	4644
February	1st to 10th	Night	4 9% 3 8% 5% 5% 6% 4 7% 8% 42%	2470
	11th to 20th	Night	2 8% 4 9% 7% 5% 5% 4 6% 8% 41%	2260
	21st to end	Night	3 9% 3 8% 6% 6% 6% 5% 7% 9% 38%	1884
March	1st to 10th	Night	3 16% 7% 12% 6% 4 5% 4 6% 7% 31%	3736
	11th to 20th	Night	2 8% 3 7% 6% 4 3 3 4 5% 53%	3593
	21st to end	Night	3 12% 4 8% 6% 7% 6% 6% 8% 10% 30%	3554
April	1st to 10th	Night	6% 8% 3 7% 6% 5% 5% 5% 7% 9% 41%	1900
	11th to 20th	Night	5% 8% 3 6% 5% 4 5% 3 5% 7% 50%	1879
	21st to end	Night	4 7% 2 6% 4 3 4 2 5% 7% 54%	1886
May	1st to 10th	Night	4 6% 4 5% 3 3 3 3 5% 7% 57%	2778
	11th to 20th	Night	4 3 1 3 3 3 3 3 4 5% 69%	2516
	21st to end	Night	4 4 2 5% 4 4 4 3 5% 7% 59%	2762
June	1st to 10th	Night	5% 6% 2 5% 4 3 4 5% 5% 8% 53%	1520
	11th to 20th	Night	4 5% 2 4 2 2 3 2 5% 6% 66%	1520
	21st to end	Night	3 3 1 3 2 2 2 3 4 5% 71%	1520
July	1st to 10th	Night	1 1 2 2 1 2 2 3 4 84%	2540
	11th to 20th	Night	3 2 1 3 2 2 3 2 3 4 75%	2540
	21st to end	Night	1 2 1 3 2 3 3 2 4 5% 74%	2761
August	1st to 10th	Night	3 3 1 4 3 3 3 2 4 7% 66%	2717
	11th to 20th	Night	2 2 1 2 2 2 2 2 3 3 80%	3087
	21st to end	Night	2 3 1 2 2 2 2 2 2 4 79%	3498
September	1st to 10th	Night	2 2 1 3 2 2 2 2 2 4 78%	1900
	11th to 20th	Night	4 4 1 3 2 2 2 3 4 5% 69%	1938
	21st to end	Night	3 3 1 3 2 2 2 2 4 6% 72%	2090
October	1st to 10th	Night	4 5% 2 4 3 3 3 2 4 5% 66%	2242
	11th to 20th	Night	3 4 1 5% 3 3 4 3 5% 5% 64%	2280
	21st to end	Night	4 5% 2 5% 3 3 4 4 6% 7% 58%	2627
November	1st to 10th	Night	7% 7% 3 7% 5% 4 5% 4 6% 8% 44%	2411
	11th to 20th	Night	5% 8% 2 6% 6% 6% 6% 4 7% 10% 41%	2470
	21st to end	Night	4 9% 3 8% 4 5% 4 3 6% 8% 45%	2621
December	1st to 10th	Night	7% 9% 3 9% 5% 5% 5% 4 6% 10% 38%	2660
	11th to 20th	Night	6% 13% 4 10% 6% 6% 5% 5% 7% 9% 28%	3276
	21st to end	Night	5% 11% 4 12% 7% 6% 6% 5% 7% 8% 29%	4862

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	53% 9% 12% 20% 6% 1	2539
	11th to 20th	Day	58% 9% 10% 12% 7% 5%	2540
	21st to end	Day	55% 8% 10% 17% 7% 2	3018
February	1st to 10th	Day	37% 8% 14% 24% 12% 4	1710
	11th to 20th	Day	38% 8% 15% 20% 14% 4	1817
	21st to end	Day	38% 10% 16% 22% 11% 4	1570
March	1st to 10th	Day	48% 11% 10% 14% 16% 1	3138
	11th to 20th	Day	27% 7% 9% 32% 23% 1	3384
	21st to end	Day	41% 12% 14% 24% 7% 2	4098
April	1st to 10th	Day	42% 8% 15% 22% 12% 2	2280
	11th to 20th	Day	35% 7% 11% 26% 18% 3	2252
	21st to end	Day	33% 7% 14% 27% 17% 2	2294
May	1st to 10th	Day	27% 6% 9% 33% 22% 3	4185
	11th to 20th	Day	20% 4 6% 20% 45% 5%	4380
	21st to end	Day	27% 6% 10% 34% 21% 2	4814
June	1st to 10th	Day	31% 7% 12% 26% 21% 3	2660
	11th to 20th	Day	21% 4 8% 24% 31% 12%	2660
	21st to end	Day	15% 2 5% 18% 36% 24%	2660
July	1st to 10th	Day	8% 1 2 7% 16% 65%	4351
	11th to 20th	Day	15% 1 3 7% 18% 55%	4345
	21st to end	Day	16% 2 3 8% 28% 42%	4639
August	1st to 10th	Day	19% 2 3 8% 22% 46%	4186
	11th to 20th	Day	12% 2 2 9% 34% 41%	3798
	21st to end	Day	12% 1 2 14% 38% 33%	4179
September	1st to 10th	Day	12% 2 3 11% 30% 41%	2280
	11th to 20th	Day	20% 4 6% 18% 27% 24%	2242
	21st to end	Day	18% 3 6% 21% 31% 21%	2090
October	1st to 10th	Day	25% 4 7% 20% 25% 19%	1933
	11th to 20th	Day	25% 3 8% 24% 27% 13%	1900
	21st to end	Day	26% 6% 11% 24% 21% 10%	1971
November	1st to 10th	Day	38% 6% 12% 18% 20% 6%	1674
	11th to 20th	Day	39% 7% 12% 23% 15% 3	1710
	21st to end	Day	37% 6% 13% 19% 20% 6%	1558
December	1st to 10th	Day	45% 7% 11% 19% 14% 5%	1520
	11th to 20th	Day	49% 9% 14% 15% 11% 2	1928
	21st to end	Day	48% 9% 11% 20% 11% 1	2794
January	1st to 10th	Night	49% 11% 13% 20% 5% 1	4406
	11th to 20th	Night	56% 7% 9% 13% 10% 4	4420
	21st to end	Night	54% 7% 11% 16% 9% 3	4644
February	1st to 10th	Night	37% 7% 15% 22% 17% 3	2470
	11th to 20th	Night	38% 8% 14% 21% 16% 5%	2261
	21st to end	Night	39% 10% 14% 21% 12% 3	1884
March	1st to 10th	Night	50% 9% 11% 15% 13% 2	3736
	11th to 20th	Night	33% 5% 7% 32% 22% 1	3593
	21st to end	Night	42% 11% 15% 22% 8% 1	3554
April	1st to 10th	Night	36% 11% 15% 23% 12% 3	1900
	11th to 20th	Night	32% 9% 15% 23% 17% 4	1879
	21st to end	Night	29% 7% 16% 30% 15% 3	1886
May	1st to 10th	Night	25% 8% 9% 30% 22% 5%	2778
	11th to 20th	Night	18% 4 7% 23% 39% 9%	2516
	21st to end	Night	24% 6% 12% 35% 21% 2	2762
June	1st to 10th	Night	28% 7% 13% 30% 19% 2	1520
	11th to 20th	Night	20% 4 8% 26% 33% 9%	1520
	21st to end	Night	16% 3 5% 19% 35% 22%	1520
July	1st to 10th	Night	8% 2 3 8% 18% 62%	2500
	11th to 20th	Night	15% 1 3 7% 18% 55%	2492
	21st to end	Night	12% 2 4 7% 32% 42%	2674
August	1st to 10th	Night	19% 2 4 10% 21% 44%	2709
	11th to 20th	Night	11% 2 3 9% 39% 36%	3117
	21st to end	Night	12% 1 3 18% 35% 31%	3498
September	1st to 10th	Night	12% 3 3 11% 28% 43%	1900
	11th to 20th	Night	18% 3 5% 18% 31% 25%	1938
	21st to end	Night	15% 3 4 23% 31% 23%	2090
October	1st to 10th	Night	22% 3 8% 21% 29% 18%	2242
	11th to 20th	Night	21% 5% 8% 25% 27% 14%	2280
	21st to end	Night	24% 5% 13% 24% 23% 10%	2627
November	1st to 10th	Night	36% 7% 11% 20% 18% 6%	2411
	11th to 20th	Night	37% 8% 14% 20% 19% 3	2470
	21st to end	Night	37% 5% 14% 18% 19% 7%	2621
December	1st to 10th	Night	41% 7% 13% 18% 16% 4	2660
	11th to 20th	Night	50% 8% 11% 16% 13% 3	3276
	21st to end	Night	48% 10% 12% 16% 13% 2	4862

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	17% 16% 21% 25% 17% 4	180
	11th to 20th	Day	8% 16% 20% 27% 23% 7%	180
	21st to end	Day	8% 8% 21% 31% 24% 8%	331
February	1st to 10th	Day	7% 12% 24% 31% 22% 5%	370
	11th to 20th	Day	8% 16% 23% 32% 19% 3	434
	21st to end	Day	6% 15% 25% 33% 18% 4	382
March	1st to 10th	Day	10% 10% 34% 29% 15% 3	460
	11th to 20th	Day	8% 12% 22% 29% 22% 7%	460
	21st to end	Day	8% 15% 25% 31% 17% 4	506
April	1st to 10th	Day	7% 11% 24% 34% 20% 4	460
	11th to 20th	Day	10% 10% 23% 30% 20% 7%	452
	21st to end	Day	7% 9% 20% 31% 25% 8%	460
May	1st to 10th	Day	5% 9% 21% 32% 23% 10%	463
	11th to 20th	Day	12% 7% 21% 28% 19% 13%	488
	21st to end	Day	10% 7% 16% 24% 24% 19%	529
June	1st to 10th	Day	5% 9% 22% 23% 27% 14%	490
	11th to 20th	Day	7% 12% 29% 26% 19% 7%	490
	21st to end	Day	4 7% 20% 31% 26% 13%	490
July	1st to 10th	Day	3 3 20% 34% 29% 11%	486
	11th to 20th	Day	2 3 18% 37% 29% 11%	484
	21st to end	Day	4 2 17% 35% 29% 14%	531
August	1st to 10th	Day	4 3 18% 33% 28% 14%	487
	11th to 20th	Day	4 5% 19% 29% 27% 16%	477
	21st to end	Day	2 5% 20% 32% 27% 13%	539
September	1st to 10th	Day	3 3 19% 29% 31% 15%	490
	11th to 20th	Day	7% 8% 21% 28% 25% 12%	490
	21st to end	Day	5% 6% 25% 30% 27% 8%	490
October	1st to 10th	Day	7% 10% 24% 24% 23% 11%	490
	11th to 20th	Day	10% 12% 17% 28% 26% 8%	490
	21st to end	Day	7% 14% 26% 28% 19% 7%	420
November	1st to 10th	Day	11% 12% 22% 27% 20% 7%	270
	11th to 20th	Day	7% 13% 23% 30% 23% 4	270
	21st to end	Day	7% 13% 19% 34% 20% 7%	198
December	1st to 10th	Day	13% 12% 20% 22% 21% 13%	180
	11th to 20th	Day	8% 8% 32% 26% 19% 7%	180
	21st to end	Day	8% 15% 21% 30% 21% 5%	198
January	1st to 10th	Night	11% 8% 25% 33% 19% 5%	760
	11th to 20th	Night	9% 10% 22% 32% 21% 6%	760
	21st to end	Night	10% 7% 20% 34% 23% 6%	836
February	1st to 10th	Night	7% 8% 24% 37% 21% 3	760
	11th to 20th	Night	6% 10% 21% 40% 19% 4	744
	21st to end	Night	6% 8% 24% 40% 20% 2	628
March	1st to 10th	Night	10% 11% 25% 35% 16% 4	760
	11th to 20th	Night	8% 8% 23% 31% 26% 4	760
	21st to end	Night	8% 12% 26% 35% 17% 2	836
April	1st to 10th	Night	8% 7% 25% 37% 21% 2	760
	11th to 20th	Night	8% 10% 23% 32% 22% 5%	751
	21st to end	Night	7% 7% 19% 38% 24% 5%	746
May	1st to 10th	Night	7% 7% 28% 35% 20% 4	527
	11th to 20th	Night	9% 5% 20% 32% 27% 8%	374
	21st to end	Night	8% 5% 18% 34% 29% 5%	411
June	1st to 10th	Night	5% 5% 19% 40% 28% 3	380
	11th to 20th	Night	5% 5% 24% 43% 21% 2	380
	21st to end	Night	4 2 16% 51% 26% 2	380
July	1st to 10th	Night	2 1 14% 54% 28% 2	370
	11th to 20th	Night	3 1 14% 56% 25% 1	368
	21st to end	Night	2 10% 50% 35% 2	416
August	1st to 10th	Night	3 1 11% 48% 34% 3	488
	11th to 20th	Night	3 2 11% 45% 34% 4	725
	21st to end	Night	2 1 11% 47% 35% 4	836
September	1st to 10th	Night	3 1 12% 41% 37% 6%	760
	11th to 20th	Night	5% 3 13% 34% 34% 11%	760
	21st to end	Night	5% 4 15% 35% 30% 12%	760
October	1st to 10th	Night	6% 4 17% 37% 29% 8%	760
	11th to 20th	Night	5% 8% 15% 37% 28% 8%	760
	21st to end	Night	6% 8% 17% 38% 23% 8%	836
November	1st to 10th	Night	9% 7% 19% 38% 20% 6%	742
	11th to 20th	Night	9% 7% 25% 34% 22% 3	760
	21st to end	Night	8% 7% 23% 34% 23% 5%	760
December	1st to 10th	Night	9% 10% 20% 37% 19% 4	760
	11th to 20th	Night	12% 10% 20% 34% 21% 3	760
	21st to end	Night	12% 11% 29% 33% 13% 2	836

Page generated at 2024-10-29 08:20:50. Version ac07

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