Rimrock Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rimrock Observatory 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	13% 10% 3 6% 4 4 4 3 5% 6% 42%	105179
	Night	15% 11% 3 6% 4 4 4 3 5% 6% 39%	102418
Transparency	Day	44% 5% 12% 21% 13% 5%	104947
	Night	46% 6% 12% 20% 12% 5%	102296
Seeing	Day	20% 10% 24% 25% 16% 5%	14912
	Night	23% 5% 16% 32% 21% 3	24041

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	25% 28% 6% 9% 4 4 3 3 5% 4 10%	2539
	11th to 20th	Day	24% 16% 3 7% 6% 5% 5% 3 4 6% 21%	2516
	21st to end	Day	30% 20% 4 8% 5% 4 4 3 4 4 15%	2794
February	1st to 10th	Day	24% 19% 4 9% 6% 3 4 3 5% 4 20%	1520
	11th to 20th	Day	19% 19% 5% 9% 4 3 4 4 4 6% 23%	1768
	21st to end	Day	18% 22% 4 9% 6% 5% 4 3 4 4 21%	1570
March	1st to 10th	Day	14% 17% 4 8% 5% 4 5% 4 5% 6% 28%	3138
	11th to 20th	Day	12% 12% 3 7% 4 4 4 3 4 5% 44%	3302
	21st to end	Day	20% 19% 5% 9% 7% 5% 4 3 4 5% 20%	4072
April	1st to 10th	Day	18% 14% 3 8% 6% 5% 5% 4 6% 6% 24%	2280
	11th to 20th	Day	14% 12% 4 9% 6% 5% 5% 4 5% 6% 32%	2342
	21st to end	Day	15% 10% 3 8% 6% 6% 5% 4 5% 6% 32%	2470
May	1st to 10th	Day	11% 9% 3 9% 5% 5% 5% 4 5% 7% 36%	4286
	11th to 20th	Day	8% 7% 2 5% 4 5% 5% 4 6% 11% 43%	4377
	21st to end	Day	12% 9% 3 8% 6% 6% 6% 5% 7% 8% 32%	4955
June	1st to 10th	Day	17% 8% 3 7% 5% 4 4 4 5% 7% 36%	2850
	11th to 20th	Day	17% 7% 2 6% 6% 5% 4 4 7% 8% 35%	2850
	21st to end	Day	7% 4 1 4 4 4 5% 4 6% 7% 54%	2850
July	1st to 10th	Day	3 2 1 3 2 2 2 2 3 4 75%	4566
	11th to 20th	Day	2 1 1 2 1 2 2 2 3 5% 79%	4420
	21st to end	Day	2 1 1 2 2 2 3 3 5% 5% 75%	4790
August	1st to 10th	Day	4 2 1 3 3 2 3 3 5% 6% 69%	4401
	11th to 20th	Day	3 3 1 3 2 2 4 3 5% 8% 65%	4102
	21st to end	Day	4 3 1 3 2 4 4 3 6% 7% 62%	4318
September	1st to 10th	Day	6% 3 1 3 2 3 3 3 5% 6% 64%	2280
	11th to 20th	Day	10% 5% 2 6% 4 3 4 4 5% 7% 50%	2152
	21st to end	Day	10% 6% 3 6% 3 4 5% 4 5% 8% 46%	2090
October	1st to 10th	Day	10% 5% 1 4 4 3 4 3 4 6% 56%	3411
	11th to 20th	Day	14% 8% 3 5% 4 4 5% 3 5% 7% 42%	2920
	21st to end	Day	20% 13% 4 7% 5% 4 4 3 5% 6% 28%	3101
November	1st to 10th	Day	30% 15% 4 7% 4 3 3 3 4 5% 23%	1710
	11th to 20th	Day	25% 16% 5% 8% 5% 4 4 3 4 4 22%	1644
	21st to end	Day	21% 20% 5% 10% 5% 4 3 3 4 4 21%	1330
December	1st to 10th	Day	21% 18% 6% 9% 5% 4 5% 2 4 6% 20%	1330
	11th to 20th	Day	26% 24% 6% 9% 5% 4 4 2 4 4 11%	1682
	21st to end	Day	21% 21% 4 10% 5% 5% 4 3 4 6% 17%	2453
January	1st to 10th	Night	27% 24% 5% 8% 4 3 4 3 4 5% 13%	4424
	11th to 20th	Night	21% 16% 4 8% 4 4 4 2 4 7% 27%	4382
	21st to end	Night	32% 19% 4 6% 4 3 3 2 3 5% 18%	4862
February	1st to 10th	Night	23% 19% 5% 7% 5% 3 3 3 4 5% 25%	2660
	11th to 20th	Night	18% 15% 5% 9% 5% 4 3 3 5% 6% 28%	2294
	21st to end	Night	15% 17% 4 8% 5% 4 5% 3 5% 5% 28%	1884
March	1st to 10th	Night	11% 13% 3 7% 5% 5% 4 4 5% 7% 35%	3736
	11th to 20th	Night	14% 10% 2 5% 3 4 3 3 3 4 49%	3676
	21st to end	Night	16% 13% 4 9% 6% 6% 6% 5% 6% 6% 23%	3565
April	1st to 10th	Night	12% 12% 3 7% 5% 5% 5% 5% 7% 8% 33%	1900
	11th to 20th	Night	14% 11% 2 8% 5% 5% 5% 3 4 6% 38%	1788
	21st to end	Night	12% 10% 3 7% 5% 4 4 5% 5% 7% 38%	1710
May	1st to 10th	Night	12% 8% 3 7% 6% 5% 6% 5% 6% 8% 34%	2674
	11th to 20th	Night	7% 6% 3 5% 4 3 5% 4 6% 10% 47%	2516
	21st to end	Night	16% 8% 2 7% 5% 5% 6% 4 6% 8% 33%	2616
June	1st to 10th	Night	13% 7% 2 6% 5% 5% 5% 4 5% 6% 43%	1330
	11th to 20th	Night	12% 6% 2 6% 5% 5% 5% 5% 7% 6% 42%	1330
	21st to end	Night	6% 5% 2 5% 4 3 4 4 6% 6% 55%	1330
July	1st to 10th	Night	2 2 1 3 2 2 3 3 4 5% 74%	2376
	11th to 20th	Night	2 1 1 2 2 1 1 1 3 3 82%	2540
	21st to end	Night	4 2 2 2 1 2 3 4 5% 76%	2762
August	1st to 10th	Night	3 3 1 2 2 2 3 2 5% 6% 72%	2529
	11th to 20th	Night	3 4 1 5% 4 3 4 3 5% 6% 63%	2720
	21st to end	Night	3 3 1 4 3 4 4 4 5% 6% 63%	3354
September	1st to 10th	Night	5% 3 1 3 3 3 3 3 5% 6% 66%	1900
	11th to 20th	Night	8% 6% 1 5% 4 4 4 3 6% 8% 50%	2028
	21st to end	Night	12% 5% 1 5% 3 4 3 3 6% 7% 53%	2090
October	1st to 10th	Night	8% 4 1 4 3 3 4 2 5% 7% 58%	3569
	11th to 20th	Night	13% 5% 2 5% 4 4 4 3 5% 7% 47%	4010
	21st to end	Night	16% 7% 2 6% 4 4 4 4 6% 7% 39%	4457
November	1st to 10th	Night	25% 13% 3 7% 4 3 4 4 5% 7% 26%	2469
	11th to 20th	Night	22% 15% 4 8% 5% 4 4 4 4 5% 26%	2534
	21st to end	Night	24% 14% 3 6% 5% 4 4 3 5% 5% 26%	2829
December	1st to 10th	Night	21% 15% 4 9% 5% 3 4 3 4 6% 25%	2850
	11th to 20th	Night	25% 22% 4 8% 6% 4 4 3 4 5% 15%	3510
	21st to end	Night	21% 17% 5% 9% 5% 5% 5% 4 6% 7% 16%	5214

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	78% 7% 9% 5% 2	2539
	11th to 20th	Day	64% 5% 12% 13% 4 2	2540
	21st to end	Day	74% 6% 12% 7% 1 1	2794
February	1st to 10th	Day	69% 6% 11% 10% 3 1	1520
	11th to 20th	Day	65% 6% 12% 10% 6%	1778
	21st to end	Day	68% 5% 8% 14% 4	1570
March	1st to 10th	Day	56% 5% 13% 16% 9%	3138
	11th to 20th	Day	45% 5% 20% 29% 2	3303
	21st to end	Day	67% 7% 12% 9% 4	4072
April	1st to 10th	Day	61% 6% 16% 14% 3	2280
	11th to 20th	Day	53% 5% 14% 17% 9% 1	2342
	21st to end	Day	54% 6% 14% 18% 7% 1	2470
May	1st to 10th	Day	46% 7% 13% 27% 7%	4286
	11th to 20th	Day	33% 6% 18% 33% 8%	4380
	21st to end	Day	47% 10% 18% 21% 4	4956
June	1st to 10th	Day	49% 5% 14% 22% 10% 1	2850
	11th to 20th	Day	47% 6% 14% 22% 9% 2	2850
	21st to end	Day	29% 6% 15% 29% 18% 3	2850
July	1st to 10th	Day	14% 3 6% 22% 34% 21%	4497
	11th to 20th	Day	11% 2 7% 15% 27% 39%	4345
	21st to end	Day	13% 3 5% 22% 37% 20%	4639
August	1st to 10th	Day	18% 2 5% 26% 36% 12%	4384
	11th to 20th	Day	19% 4 9% 41% 24% 3	4142
	21st to end	Day	22% 3 12% 35% 25% 3	4317
September	1st to 10th	Day	22% 4 11% 31% 22% 9%	2280
	11th to 20th	Day	34% 5% 14% 23% 21% 3	2152
	21st to end	Day	37% 7% 19% 23% 11% 3	2090
October	1st to 10th	Day	31% 3 13% 37% 16%	3411
	11th to 20th	Day	44% 4 18% 23% 11%	2920
	21st to end	Day	59% 5% 12% 19% 5%	3101
November	1st to 10th	Day	65% 6% 14% 11% 3	1710
	11th to 20th	Day	68% 5% 13% 9% 4 1	1644
	21st to end	Day	67% 5% 11% 13% 4	1330
December	1st to 10th	Day	66% 7% 11% 13% 3	1330
	11th to 20th	Day	78% 6% 9% 6% 1	1684
	21st to end	Day	69% 6% 13% 8% 4	2453
January	1st to 10th	Night	74% 8% 9% 8% 1	4424
	11th to 20th	Night	60% 5% 14% 15% 3 3	4420
	21st to end	Night	71% 6% 12% 9% 2 1	4862
February	1st to 10th	Night	64% 5% 12% 12% 4 1	2660
	11th to 20th	Night	59% 5% 16% 13% 6%	2295
	21st to end	Night	58% 6% 12% 17% 7% 1	1884
March	1st to 10th	Night	46% 7% 14% 23% 9% 1	3736
	11th to 20th	Night	41% 4 19% 30% 6%	3676
	21st to end	Night	57% 11% 13% 15% 3	3565
April	1st to 10th	Night	48% 6% 15% 23% 6%	1900
	11th to 20th	Night	49% 4 11% 22% 12% 1	1788
	21st to end	Night	45% 7% 12% 24% 10% 1	1710
May	1st to 10th	Night	44% 8% 14% 22% 12%	2674
	11th to 20th	Night	29% 6% 15% 33% 16% 1	2516
	21st to end	Night	45% 10% 16% 20% 9%	2616
June	1st to 10th	Night	41% 6% 11% 24% 16% 1	1330
	11th to 20th	Night	40% 5% 12% 24% 14% 4	1330
	21st to end	Night	28% 5% 12% 27% 22% 6%	1330
July	1st to 10th	Night	15% 2 4 17% 33% 29%	2337
	11th to 20th	Night	10% 1 4 13% 21% 51%	2492
	21st to end	Night	12% 1 3 17% 33% 32%	2674
August	1st to 10th	Night	15% 2 5% 20% 37% 21%	2521
	11th to 20th	Night	24% 2 7% 32% 28% 7%	2745
	21st to end	Night	23% 4 9% 27% 31% 7%	3354
September	1st to 10th	Night	19% 3 9% 28% 27% 12%	1900
	11th to 20th	Night	32% 5% 10% 24% 22% 6%	2028
	21st to end	Night	32% 4 17% 27% 16% 5%	2090
October	1st to 10th	Night	27% 3 11% 40% 18% 1	3569
	11th to 20th	Night	38% 4 14% 24% 19% 1	4010
	21st to end	Night	45% 6% 13% 27% 8% 2	4457
November	1st to 10th	Night	59% 7% 15% 14% 4 1	2469
	11th to 20th	Night	63% 6% 14% 11% 5% 2	2534
	21st to end	Night	60% 6% 16% 14% 5%	2829
December	1st to 10th	Night	63% 7% 12% 15% 3	2850
	11th to 20th	Night	72% 6% 12% 9% 1	3507
	21st to end	Night	66% 9% 12% 9% 3	5214

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	36% 13% 17% 18% 12% 4	180
	11th to 20th	Day	40% 11% 13% 18% 11% 7%	180
	21st to end	Day	35% 8% 27% 18% 12% 1	198
February	1st to 10th	Day	37% 14% 28% 12% 8% 1	180
	11th to 20th	Day	34% 13% 22% 21% 8% 1	398
	21st to end	Day	32% 14% 24% 20% 8% 1	382
March	1st to 10th	Day	30% 17% 22% 19% 10% 2	460
	11th to 20th	Day	25% 11% 24% 21% 17% 2	460
	21st to end	Day	32% 13% 24% 21% 9% 1	506
April	1st to 10th	Day	29% 12% 28% 20% 9% 3	460
	11th to 20th	Day	22% 18% 24% 21% 11% 3	452
	21st to end	Day	21% 14% 27% 25% 10% 3	460
May	1st to 10th	Day	17% 12% 26% 29% 12% 4	463
	11th to 20th	Day	20% 9% 26% 25% 15% 6%	488
	21st to end	Day	16% 9% 21% 29% 18% 7%	606
June	1st to 10th	Day	21% 8% 23% 24% 19% 5%	680
	11th to 20th	Day	19% 15% 28% 22% 14% 3	680
	21st to end	Day	9% 8% 23% 30% 23% 6%	680
July	1st to 10th	Day	7% 5% 26% 34% 24% 3	580
	11th to 20th	Day	5% 9% 27% 36% 18% 5%	484
	21st to end	Day	4 8% 26% 35% 20% 7%	531
August	1st to 10th	Day	7% 4 23% 35% 23% 8%	487
	11th to 20th	Day	6% 4 21% 36% 24% 9%	477
	21st to end	Day	9% 8% 28% 26% 20% 9%	539
September	1st to 10th	Day	8% 10% 27% 26% 21% 8%	490
	11th to 20th	Day	14% 8% 27% 24% 19% 7%	490
	21st to end	Day	14% 13% 26% 21% 20% 5%	490
October	1st to 10th	Day	17% 8% 26% 26% 16% 7%	490
	11th to 20th	Day	23% 12% 19% 25% 13% 8%	352
	21st to end	Day	33% 9% 22% 23% 10% 3	330
November	1st to 10th	Day	42% 8% 18% 23% 9%	282
	11th to 20th	Day	38% 10% 15% 19% 16%	239
	21st to end	Day	29% 9% 25% 21% 14% 2	180
December	1st to 10th	Day	36% 10% 21% 16% 14% 3	180
	11th to 20th	Day	42% 9% 21% 19% 7% 2	180
	21st to end	Day	40% 10% 16% 23% 11% 1	198
January	1st to 10th	Night	42% 8% 15% 23% 10% 2	765
	11th to 20th	Night	34% 7% 15% 28% 14% 2	760
	21st to end	Night	32% 6% 15% 30% 15% 2	836
February	1st to 10th	Night	36% 7% 19% 26% 10% 2	760
	11th to 20th	Night	31% 6% 16% 31% 15% 1	744
	21st to end	Night	26% 8% 19% 28% 18% 2	628
March	1st to 10th	Night	25% 8% 17% 32% 17% 2	760
	11th to 20th	Night	26% 8% 16% 31% 19% 1	760
	21st to end	Night	25% 7% 20% 33% 13% 2	836
April	1st to 10th	Night	21% 6% 17% 38% 17% 2	760
	11th to 20th	Night	21% 7% 24% 32% 14% 2	660
	21st to end	Night	19% 6% 20% 34% 19% 2	570
May	1st to 10th	Night	13% 5% 19% 34% 27% 3	462
	11th to 20th	Night	14% 4 15% 30% 29% 9%	374
	21st to end	Night	17% 4 15% 29% 29% 5%	411
June	1st to 10th	Night	17% 5% 13% 36% 24% 5%	380
	11th to 20th	Night	17% 4 23% 32% 21% 3	380
	21st to end	Night	7% 3 13% 38% 35% 4	380
July	1st to 10th	Night	4 1 10% 41% 41% 3	370
	11th to 20th	Night	4 1 15% 45% 33% 2	368
	21st to end	Night	2 2 10% 43% 40% 4	416
August	1st to 10th	Night	4 1 10% 37% 40% 7%	378
	11th to 20th	Night	4 2 7% 37% 39% 10%	509
	21st to end	Night	6% 4 14% 35% 38% 3	744
September	1st to 10th	Night	7% 2 12% 39% 34% 6%	760
	11th to 20th	Night	12% 3 13% 31% 34% 8%	760
	21st to end	Night	15% 4 15% 35% 26% 5%	760
October	1st to 10th	Night	18% 4 12% 37% 27% 2	760
	11th to 20th	Night	23% 4 14% 30% 27% 3	760
	21st to end	Night	26% 5% 19% 30% 18% 3	836
November	1st to 10th	Night	36% 6% 13% 32% 14%	760
	11th to 20th	Night	33% 9% 16% 28% 14% 1	760
	21st to end	Night	34% 6% 14% 27% 16% 2	929
December	1st to 10th	Night	30% 6% 16% 31% 16% 1	950
	11th to 20th	Night	38% 5% 17% 30% 10%	950
	21st to end	Night	41% 7% 16% 27% 9% 1	1045

Page generated at 2024-11-02 23:11:08. Version ac07

Copyright © 2024 Attilla Danko.