Ritter Butte
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ritter Butte 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	9% 10% 3 6% 4 4 4 3 4 6% 47%	105266
	Night	11% 12% 3 6% 4 4 4 3 4 6% 43%	102452
Transparency	Day	39% 5% 10% 19% 17% 10%	105011
	Night	43% 6% 11% 19% 15% 7%	102296
Seeing	Day	14% 12% 26% 27% 16% 5%	14493
	Night	17% 7% 17% 35% 21% 3	23609

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	15% 24% 8% 10% 5% 4 5% 4 4 5% 16%	2539
	11th to 20th	Day	18% 20% 5% 10% 5% 4 4 4 4 5% 22%	2540
	21st to end	Day	17% 18% 5% 9% 6% 5% 4 4 4 6% 23%	2794
February	1st to 10th	Day	15% 17% 5% 9% 6% 4 4 3 4 6% 25%	1691
	11th to 20th	Day	13% 19% 5% 9% 5% 4 4 5% 5% 6% 25%	1763
	21st to end	Day	11% 18% 8% 11% 5% 4 5% 3 5% 6% 23%	1570
March	1st to 10th	Day	7% 14% 6% 12% 6% 5% 6% 5% 6% 6% 27%	3138
	11th to 20th	Day	6% 11% 5% 6% 5% 4 4 3 4 5% 46%	3299
	21st to end	Day	9% 20% 6% 13% 7% 7% 6% 4 4 5% 20%	4151
April	1st to 10th	Day	12% 19% 6% 9% 5% 3 5% 3 5% 6% 26%	2280
	11th to 20th	Day	10% 13% 5% 8% 5% 5% 5% 4 5% 7% 33%	2249
	21st to end	Day	12% 15% 4 8% 5% 4 4 4 5% 6% 34%	2403
May	1st to 10th	Day	10% 15% 4 8% 5% 4 4 3 5% 6% 37%	4324
	11th to 20th	Day	8% 6% 2 5% 4 3 3 3 5% 6% 56%	4377
	21st to end	Day	10% 13% 3 6% 4 4 4 4 6% 8% 39%	4813
June	1st to 10th	Day	16% 8% 3 6% 5% 4 5% 4 5% 5% 40%	2660
	11th to 20th	Day	11% 9% 2 5% 4 3 3 4 5% 7% 46%	2660
	21st to end	Day	5% 4 1 4 3 2 3 3 5% 6% 63%	2660
July	1st to 10th	Day	1 1 2 2 2 2 2 3 4 81%	4420
	11th to 20th	Day	2 2 1 2 2 2 2 2 4 4 78%	4420
	21st to end	Day	1 1 1 2 2 2 2 2 3 5% 77%	4790
August	1st to 10th	Day	3 4 1 4 3 2 3 2 4 6% 68%	4400
	11th to 20th	Day	2 2 1 3 2 2 2 2 3 5% 76%	3923
	21st to end	Day	3 3 1 3 2 2 3 3 4 5% 71%	4180
September	1st to 10th	Day	4 2 1 3 2 3 3 2 4 6% 71%	2280
	11th to 20th	Day	7% 5% 2 5% 3 3 3 3 5% 6% 58%	2228
	21st to end	Day	8% 7% 2 6% 3 3 3 3 5% 5% 54%	2090
October	1st to 10th	Day	9% 6% 2 4 2 2 3 2 3 5% 61%	3248
	11th to 20th	Day	9% 7% 2 6% 4 4 4 3 6% 9% 47%	3161
	21st to end	Day	13% 12% 4 9% 5% 5% 5% 4 5% 6% 32%	3102
November	1st to 10th	Day	18% 14% 3 7% 5% 4 4 3 6% 8% 28%	1710
	11th to 20th	Day	16% 15% 4 9% 6% 5% 5% 4 5% 7% 24%	1641
	21st to end	Day	14% 17% 4 7% 5% 4 4 2 5% 6% 32%	1520
December	1st to 10th	Day	13% 17% 3 7% 5% 4 4 4 4 7% 32%	1520
	11th to 20th	Day	12% 18% 4 10% 5% 5% 4 4 6% 6% 26%	1928
	21st to end	Day	13% 18% 6% 10% 6% 5% 4 3 5% 6% 24%	2794
January	1st to 10th	Night	16% 25% 7% 9% 5% 4 4 3 4 5% 17%	4406
	11th to 20th	Night	21% 23% 6% 8% 4 4 3 2 3 5% 22%	4420
	21st to end	Night	17% 15% 4 9% 5% 5% 4 4 6% 7% 24%	4862
February	1st to 10th	Night	16% 17% 5% 9% 6% 4 3 3 6% 5% 25%	2485
	11th to 20th	Night	13% 20% 5% 9% 4 4 4 3 4 5% 29%	2302
	21st to end	Night	11% 21% 7% 9% 5% 5% 4 3 4 7% 24%	1884
March	1st to 10th	Night	8% 13% 5% 9% 5% 5% 5% 4 7% 8% 31%	3736
	11th to 20th	Night	8% 12% 3 6% 4 4 3 3 4 5% 46%	3676
	21st to end	Night	10% 20% 5% 10% 7% 6% 6% 4 6% 6% 19%	3502
April	1st to 10th	Night	12% 17% 4 7% 6% 5% 4 3 4 6% 32%	1900
	11th to 20th	Night	12% 13% 3 7% 5% 3 4 3 5% 7% 38%	1879
	21st to end	Night	11% 14% 3 7% 5% 5% 4 3 5% 7% 36%	1776
May	1st to 10th	Night	12% 18% 3 7% 4 3 4 4 4 4 38%	2636
	11th to 20th	Night	8% 5% 1 4 3 3 3 3 4 6% 60%	2516
	21st to end	Night	14% 11% 2 5% 3 4 3 3 3 6% 46%	2762
June	1st to 10th	Night	13% 8% 2 4 5% 4 4 4 5% 7% 45%	1520
	11th to 20th	Night	14% 7% 2 5% 3 3 3 3 4 7% 48%	1520
	21st to end	Night	5% 3 1 3 4 4 3 3 5% 6% 65%	1520
July	1st to 10th	Night	1 1 1 1 1 1 1 1 3 4 84%	2540
	11th to 20th	Night	1 1 1 3 2 2 2 2 4 5% 80%	2540
	21st to end	Night	2 2 1 2 2 2 3 3 3 5% 78%	2761
August	1st to 10th	Night	2 2 1 2 2 3 4 3 6% 7% 66%	2529
	11th to 20th	Night	1 1 1 3 2 3 3 2 4 6% 75%	2918
	21st to end	Night	2 3 1 3 2 2 3 3 4 5% 73%	3498
September	1st to 10th	Night	4 2 1 3 2 2 1 2 4 6% 73%	1900
	11th to 20th	Night	6% 5% 1 4 3 3 4 3 5% 6% 60%	1952
	21st to end	Night	8% 7% 2 5% 3 3 3 2 4 6% 57%	2090
October	1st to 10th	Night	7% 6% 2 4 2 2 2 2 3 4 66%	3728
	11th to 20th	Night	10% 7% 2 6% 4 3 4 3 5% 7% 51%	3777
	21st to end	Night	11% 12% 3 8% 4 4 4 3 5% 7% 39%	4454
November	1st to 10th	Night	18% 13% 3 7% 5% 5% 5% 3 4 6% 31%	2469
	11th to 20th	Night	20% 13% 3 7% 5% 4 4 4 5% 5% 30%	2536
	21st to end	Night	13% 17% 4 6% 4 3 5% 4 6% 6% 34%	2660
December	1st to 10th	Night	15% 14% 4 7% 4 3 5% 4 6% 7% 31%	2660
	11th to 20th	Night	14% 17% 5% 9% 5% 5% 5% 4 6% 6% 24%	3276
	21st to end	Night	14% 17% 5% 8% 5% 4 4 4 5% 5% 28%	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	69% 8% 9% 11% 2	2539
	11th to 20th	Day	64% 6% 8% 14% 6% 2	2540
	21st to end	Day	61% 10% 11% 13% 4 1	2794
February	1st to 10th	Day	61% 7% 11% 14% 6%	1691
	11th to 20th	Day	61% 7% 11% 13% 7% 1	1772
	21st to end	Day	63% 7% 9% 13% 7% 1	1570
March	1st to 10th	Day	55% 6% 13% 14% 12% 1	3138
	11th to 20th	Day	41% 6% 9% 31% 13%	3299
	21st to end	Day	66% 8% 10% 13% 3	4151
April	1st to 10th	Day	59% 6% 13% 15% 6% 1	2280
	11th to 20th	Day	53% 6% 12% 15% 11% 2	2252
	21st to end	Day	53% 6% 10% 19% 12% 1	2403
May	1st to 10th	Day	48% 6% 11% 24% 11% 1	4324
	11th to 20th	Day	31% 4 10% 29% 23% 4	4380
	21st to end	Day	43% 7% 18% 24% 7%	4814
June	1st to 10th	Day	47% 6% 11% 25% 11%	2660
	11th to 20th	Day	39% 6% 11% 26% 15% 3	2660
	21st to end	Day	23% 4 10% 28% 27% 8%	2660
July	1st to 10th	Day	10% 2 5% 13% 23% 47%	4351
	11th to 20th	Day	11% 3 5% 8% 21% 52%	4345
	21st to end	Day	11% 2 4 16% 37% 29%	4639
August	1st to 10th	Day	19% 3 5% 13% 34% 26%	4384
	11th to 20th	Day	14% 2 5% 26% 38% 15%	3964
	21st to end	Day	16% 3 7% 28% 24% 21%	4179
September	1st to 10th	Day	17% 3 6% 24% 31% 20%	2280
	11th to 20th	Day	28% 5% 9% 22% 25% 11%	2228
	21st to end	Day	32% 5% 9% 23% 22% 8%	2090
October	1st to 10th	Day	27% 4 10% 18% 29% 12%	3248
	11th to 20th	Day	35% 4 14% 26% 18% 2	3161
	21st to end	Day	52% 4 9% 22% 13% 1	3102
November	1st to 10th	Day	55% 6% 13% 17% 9% 1	1710
	11th to 20th	Day	59% 8% 11% 17% 6%	1641
	21st to end	Day	55% 6% 10% 15% 13% 2	1520
December	1st to 10th	Day	53% 8% 14% 14% 8% 2	1520
	11th to 20th	Day	57% 9% 16% 12% 6%	1928
	21st to end	Day	60% 6% 13% 16% 4	2794
January	1st to 10th	Night	70% 7% 8% 12% 3	4406
	11th to 20th	Night	66% 5% 9% 12% 6% 2	4420
	21st to end	Night	57% 10% 15% 11% 5% 1	4862
February	1st to 10th	Night	61% 9% 11% 13% 7%	2485
	11th to 20th	Night	59% 6% 11% 14% 7% 3	2304
	21st to end	Night	62% 6% 9% 14% 7% 2	1884
March	1st to 10th	Night	48% 6% 12% 21% 12% 1	3736
	11th to 20th	Night	41% 6% 11% 34% 8%	3676
	21st to end	Night	63% 10% 11% 12% 3 1	3502
April	1st to 10th	Night	55% 7% 13% 19% 6% 1	1900
	11th to 20th	Night	49% 7% 13% 20% 10% 2	1879
	21st to end	Night	47% 9% 13% 16% 14% 1	1776
May	1st to 10th	Night	50% 5% 13% 21% 12% 1	2636
	11th to 20th	Night	28% 4 12% 36% 20% 1	2516
	21st to end	Night	41% 7% 20% 24% 7%	2762
June	1st to 10th	Night	40% 8% 12% 27% 12% 1	1520
	11th to 20th	Night	37% 6% 13% 28% 12% 4	1520
	21st to end	Night	22% 5% 13% 29% 23% 8%	1520
July	1st to 10th	Night	8% 3 7% 13% 25% 44%	2500
	11th to 20th	Night	10% 2 7% 10% 24% 46%	2492
	21st to end	Night	12% 2 4 16% 38% 28%	2674
August	1st to 10th	Night	17% 3 7% 16% 37% 20%	2521
	11th to 20th	Night	13% 3 5% 34% 33% 12%	2943
	21st to end	Night	15% 3 8% 29% 25% 19%	3498
September	1st to 10th	Night	15% 3 8% 26% 32% 17%	1900
	11th to 20th	Night	25% 5% 8% 26% 24% 13%	1952
	21st to end	Night	30% 4 9% 24% 23% 9%	2090
October	1st to 10th	Night	26% 3 6% 23% 32% 10%	3728
	11th to 20th	Night	34% 4 17% 19% 23% 3	3777
	21st to end	Night	45% 5% 9% 24% 15% 2	4454
November	1st to 10th	Night	54% 7% 9% 18% 11% 2	2469
	11th to 20th	Night	56% 7% 10% 17% 10%	2536
	21st to end	Night	51% 7% 9% 14% 17% 2	2660
December	1st to 10th	Night	52% 9% 13% 14% 9% 2	2660
	11th to 20th	Night	58% 8% 13% 13% 7% 1	3276
	21st to end	Night	56% 8% 13% 16% 7% 1	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	24% 22% 22% 17% 12% 3	180
	11th to 20th	Day	19% 18% 27% 21% 11% 4	180
	21st to end	Day	18% 17% 29% 22% 14% 1	198
February	1st to 10th	Day	24% 21% 26% 20% 7% 2	351
	11th to 20th	Day	23% 20% 27% 19% 10% 1	412
	21st to end	Day	21% 20% 27% 23% 8% 1	382
March	1st to 10th	Day	19% 17% 33% 23% 6% 1	460
	11th to 20th	Day	16% 18% 27% 25% 10% 3	460
	21st to end	Day	22% 16% 34% 22% 6% 1	506
April	1st to 10th	Day	22% 19% 23% 23% 10% 3	460
	11th to 20th	Day	17% 20% 30% 18% 11% 4	452
	21st to end	Day	16% 18% 26% 25% 12% 2	460
May	1st to 10th	Day	13% 18% 28% 24% 14% 3	463
	11th to 20th	Day	22% 12% 23% 23% 15% 5%	488
	21st to end	Day	17% 10% 24% 23% 20% 7%	529
June	1st to 10th	Day	17% 10% 23% 25% 18% 8%	490
	11th to 20th	Day	12% 17% 30% 24% 14% 3	490
	21st to end	Day	4 8% 28% 33% 19% 7%	490
July	1st to 10th	Day	3 5% 29% 38% 20% 5%	486
	11th to 20th	Day	2 6% 31% 34% 21% 7%	484
	21st to end	Day	2 5% 30% 34% 22% 8%	531
August	1st to 10th	Day	5% 5% 24% 37% 22% 8%	487
	11th to 20th	Day	2 4 22% 33% 26% 14%	477
	21st to end	Day	5% 7% 23% 33% 21% 10%	539
September	1st to 10th	Day	4 4 24% 31% 26% 11%	490
	11th to 20th	Day	8% 6% 24% 33% 23% 6%	490
	21st to end	Day	12% 9% 24% 28% 20% 7%	490
October	1st to 10th	Day	14% 10% 21% 27% 19% 8%	490
	11th to 20th	Day	14% 13% 23% 26% 18% 8%	490
	21st to end	Day	21% 12% 24% 23% 15% 5%	331
November	1st to 10th	Day	20% 17% 27% 24% 12% 1	282
	11th to 20th	Day	19% 15% 24% 24% 14% 3	237
	21st to end	Day	22% 8% 27% 30% 10% 3	180
December	1st to 10th	Day	20% 19% 20% 23% 11% 8%	180
	11th to 20th	Day	27% 15% 34% 15% 9%	180
	21st to end	Day	22% 14% 30% 22% 11% 1	198
January	1st to 10th	Night	24% 12% 24% 24% 15% 2	760
	11th to 20th	Night	27% 11% 18% 26% 17% 2	760
	21st to end	Night	23% 8% 18% 34% 16% 2	836
February	1st to 10th	Night	24% 9% 23% 31% 11% 1	760
	11th to 20th	Night	22% 10% 20% 31% 16% 2	744
	21st to end	Night	20% 14% 24% 31% 10% 2	628
March	1st to 10th	Night	19% 11% 24% 31% 12% 2	760
	11th to 20th	Night	17% 8% 23% 33% 17% 2	760
	21st to end	Night	20% 10% 23% 33% 13% 1	836
April	1st to 10th	Night	19% 11% 17% 34% 16% 2	760
	11th to 20th	Night	17% 9% 25% 29% 17% 3	751
	21st to end	Night	18% 8% 19% 35% 19% 2	636
May	1st to 10th	Night	13% 8% 18% 37% 21% 2	437
	11th to 20th	Night	14% 4 13% 34% 30% 4	374
	21st to end	Night	19% 7% 12% 31% 28% 3	411
June	1st to 10th	Night	14% 6% 14% 41% 22% 3	380
	11th to 20th	Night	16% 5% 16% 41% 21% 2	380
	21st to end	Night	5% 2 12% 47% 32% 2	380
July	1st to 10th	Night	3 1 9% 54% 31% 2	370
	11th to 20th	Night	2 10% 61% 26% 1	368
	21st to end	Night	1 8% 52% 35% 3	416
August	1st to 10th	Night	3 1 5% 48% 41% 2	378
	11th to 20th	Night	2 1 7% 38% 43% 9%	616
	21st to end	Night	5% 3 11% 44% 33% 4	836
September	1st to 10th	Night	5% 2 9% 42% 38% 4	760
	11th to 20th	Night	7% 3 9% 38% 34% 8%	760
	21st to end	Night	12% 4 12% 38% 28% 7%	760
October	1st to 10th	Night	15% 3 11% 42% 26% 4	760
	11th to 20th	Night	15% 5% 17% 36% 21% 5%	760
	21st to end	Night	18% 9% 17% 35% 16% 5%	836
November	1st to 10th	Night	23% 8% 19% 35% 14% 1	760
	11th to 20th	Night	25% 8% 19% 31% 14% 2	760
	21st to end	Night	20% 9% 20% 31% 16% 5%	760
December	1st to 10th	Night	21% 9% 20% 31% 16% 2	760
	11th to 20th	Night	25% 9% 23% 29% 13% 1	760
	21st to end	Night	28% 11% 27% 24% 9% 1	836

Page generated at 2024-11-02 23:11:23. Version ac07

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