Bend
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bend 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	4 6% 2 6% 4 4 4 4 6% 7% 53%	105408
	Night	4 7% 2 6% 4 4 4 4 6% 7% 51%	102323
Transparency	Day	28% 10% 12% 21% 18% 11%	105151
	Night	29% 12% 14% 22% 16% 7%	102169
Seeing	Day	9% 16% 27% 27% 17% 5%	14679
	Night	7% 12% 24% 36% 19% 2	23714

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	7% 12% 4 9% 7% 6% 7% 5% 8% 9% 28%	2539
	11th to 20th	Day	9% 11% 4 9% 6% 7% 7% 5% 8% 7% 26%	2540
	21st to end	Day	8% 11% 4 8% 6% 6% 6% 4 6% 9% 32%	3018
February	1st to 10th	Day	4 10% 3 8% 6% 7% 5% 5% 7% 9% 36%	1710
	11th to 20th	Day	5% 10% 4 7% 5% 5% 5% 4 7% 9% 40%	1670
	21st to end	Day	2 11% 5% 9% 5% 6% 6% 6% 7% 8% 32%	1570
March	1st to 10th	Day	3 7% 3 7% 5% 6% 6% 5% 9% 11% 37%	3182
	11th to 20th	Day	2 7% 2 6% 4 4 4 3 6% 7% 54%	3490
	21st to end	Day	3 9% 3 9% 8% 7% 8% 5% 7% 9% 31%	3996
April	1st to 10th	Day	6% 12% 4 10% 6% 5% 5% 4 6% 8% 34%	2280
	11th to 20th	Day	6% 10% 3 8% 6% 5% 5% 4 5% 8% 39%	2249
	21st to end	Day	6% 8% 2 7% 5% 4 4 3 6% 8% 46%	2335
May	1st to 10th	Day	8% 8% 3 7% 4 4 4 3 5% 6% 47%	4410
	11th to 20th	Day	5% 4 2 4 3 3 3 3 4 5% 63%	4377
	21st to end	Day	8% 6% 2 5% 4 4 5% 4 6% 7% 49%	4813
June	1st to 10th	Day	9% 7% 2 6% 5% 5% 5% 4 6% 7% 44%	2660
	11th to 20th	Day	7% 5% 2 5% 4 3 4 4 5% 7% 55%	2660
	21st to end	Day	3 3 2 3 3 3 3 3 5% 5% 66%	2660
July	1st to 10th	Day	1 1 1 2 1 2 2 3 3 85%	4420
	11th to 20th	Day	2 1 1 2 2 1 2 2 3 4 80%	4420
	21st to end	Day	1 1 2 2 2 2 2 3 4 82%	4790
August	1st to 10th	Day	3 3 1 2 2 2 4 3 5% 6% 68%	4188
	11th to 20th	Day	2 2 1 3 3 3 3 3 4 6% 71%	4000
	21st to end	Day	3 3 1 3 2 2 3 2 3 4 74%	4180
September	1st to 10th	Day	2 2 1 2 2 2 3 2 4 6% 75%	2280
	11th to 20th	Day	3 4 2 5% 4 4 4 4 5% 7% 60%	2280
	21st to end	Day	6% 5% 2 5% 3 3 3 2 5% 6% 61%	2033
October	1st to 10th	Day	4 4 1 4 3 3 3 3 3 5% 67%	3180
	11th to 20th	Day	3 4 2 5% 4 4 5% 5% 6% 9% 52%	3161
	21st to end	Day	7% 8% 2 7% 5% 5% 5% 4 6% 7% 44%	3301
November	1st to 10th	Day	5% 9% 3 8% 5% 6% 6% 4 7% 8% 40%	1710
	11th to 20th	Day	4 7% 2 8% 7% 5% 6% 6% 9% 9% 36%	1544
	21st to end	Day	5% 8% 4 6% 5% 4 5% 7% 8% 9% 39%	1520
December	1st to 10th	Day	4 8% 4 6% 6% 4 3 5% 8% 8% 44%	1520
	11th to 20th	Day	4 10% 4 9% 6% 6% 5% 6% 8% 9% 33%	1928
	21st to end	Day	4 11% 4 11% 7% 6% 5% 5% 7% 9% 31%	2794
January	1st to 10th	Night	4 10% 3 9% 7% 8% 8% 6% 8% 9% 27%	4406
	11th to 20th	Night	6% 10% 4 11% 7% 6% 6% 6% 7% 9% 28%	4420
	21st to end	Night	8% 14% 5% 10% 5% 5% 5% 4 6% 7% 30%	4641
February	1st to 10th	Night	4 11% 4 9% 6% 4 5% 5% 7% 8% 38%	2470
	11th to 20th	Night	4 10% 3 9% 5% 4 5% 5% 7% 9% 40%	2395
	21st to end	Night	4 10% 4 9% 6% 6% 6% 4 6% 9% 37%	1884
March	1st to 10th	Night	3 8% 2 5% 5% 6% 7% 7% 9% 11% 37%	3688
	11th to 20th	Night	2 5% 2 5% 4 4 4 4 6% 7% 58%	3490
	21st to end	Night	5% 11% 4 9% 6% 5% 6% 6% 8% 10% 30%	3657
April	1st to 10th	Night	7% 11% 3 7% 5% 5% 5% 4 6% 7% 39%	1900
	11th to 20th	Night	6% 10% 3 6% 5% 5% 5% 5% 8% 7% 41%	1879
	21st to end	Night	6% 8% 3 5% 4 4 5% 4 7% 9% 43%	1842
May	1st to 10th	Night	9% 9% 2 6% 4 4 3 3 5% 7% 47%	2549
	11th to 20th	Night	4 4 1 4 3 3 4 3 4 5% 64%	2516
	21st to end	Night	7% 6% 2 4 4 3 4 4 5% 6% 54%	2762
June	1st to 10th	Night	10% 6% 3 5% 5% 3 4 4 4 7% 48%	1520
	11th to 20th	Night	6% 5% 2 4 3 2 3 3 5% 7% 60%	1520
	21st to end	Night	3 3 1 2 3 2 3 3 3 6% 70%	1520
July	1st to 10th	Night	1 1 1 1 1 2 2 2 3 86%	2540
	11th to 20th	Night	2 1 2 2 1 2 2 2 3 82%	2540
	21st to end	Night	1 1 2 1 2 2 2 3 3 84%	2761
August	1st to 10th	Night	2 2 1 3 3 3 2 2 4 5% 72%	2745
	11th to 20th	Night	1 2 1 2 2 2 2 3 4 5% 75%	2839
	21st to end	Night	2 2 1 3 2 2 2 2 3 4 78%	3498
September	1st to 10th	Night	2 1 1 2 1 2 2 2 3 4 80%	1900
	11th to 20th	Night	3 3 1 5% 3 3 4 2 6% 6% 64%	1900
	21st to end	Night	6% 4 1 4 3 2 2 3 5% 6% 64%	2142
October	1st to 10th	Night	4 4 1 4 2 2 3 2 3 4 71%	3800
	11th to 20th	Night	4 4 2 5% 4 4 4 4 5% 8% 55%	3777
	21st to end	Night	4 6% 2 8% 6% 5% 5% 5% 6% 8% 45%	4262
November	1st to 10th	Night	6% 9% 3 7% 6% 4 5% 5% 7% 7% 40%	2469
	11th to 20th	Night	6% 7% 3 8% 6% 5% 5% 5% 8% 8% 38%	2633
	21st to end	Night	3 8% 3 6% 4 4 5% 6% 8% 8% 45%	2660
December	1st to 10th	Night	5% 9% 3 7% 5% 4 5% 4 7% 8% 43%	2660
	11th to 20th	Night	4 9% 4 10% 7% 6% 6% 5% 8% 9% 32%	3276
	21st to end	Night	4 10% 3 8% 6% 6% 6% 5% 6% 7% 37%	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	41% 22% 20% 13% 5%	2539
	11th to 20th	Day	48% 18% 13% 13% 5% 3	2540
	21st to end	Day	42% 20% 14% 16% 6% 1	3018
February	1st to 10th	Day	43% 15% 15% 18% 8% 1	1710
	11th to 20th	Day	37% 15% 17% 19% 10% 2	1679
	21st to end	Day	43% 18% 16% 14% 8% 1	1570
March	1st to 10th	Day	31% 16% 20% 20% 12% 1	3182
	11th to 20th	Day	26% 14% 15% 31% 14%	3490
	21st to end	Day	38% 22% 16% 18% 6%	3996
April	1st to 10th	Day	45% 13% 14% 17% 9% 2	2280
	11th to 20th	Day	42% 10% 15% 18% 12% 3	2252
	21st to end	Day	34% 11% 17% 24% 12% 2	2335
May	1st to 10th	Day	32% 12% 13% 24% 18% 1	4410
	11th to 20th	Day	23% 6% 10% 27% 31% 3	4380
	21st to end	Day	30% 12% 19% 28% 10%	4814
June	1st to 10th	Day	38% 9% 13% 28% 12% 1	2660
	11th to 20th	Day	29% 7% 12% 31% 18% 3	2660
	21st to end	Day	19% 6% 10% 28% 26% 10%	2660
July	1st to 10th	Day	8% 3 6% 12% 19% 52%	4351
	11th to 20th	Day	10% 2 5% 8% 20% 55%	4345
	21st to end	Day	8% 2 4 16% 39% 31%	4639
August	1st to 10th	Day	17% 3 7% 15% 36% 22%	4172
	11th to 20th	Day	15% 3 6% 26% 35% 15%	4039
	21st to end	Day	16% 3 7% 27% 28% 20%	4179
September	1st to 10th	Day	11% 4 6% 24% 34% 21%	2280
	11th to 20th	Day	23% 7% 11% 24% 24% 11%	2280
	21st to end	Day	23% 7% 12% 25% 22% 10%	2033
October	1st to 10th	Day	22% 5% 10% 21% 25% 17%	3180
	11th to 20th	Day	26% 9% 16% 26% 20% 3	3161
	21st to end	Day	35% 10% 9% 25% 20% 2	3301
November	1st to 10th	Day	39% 12% 15% 20% 13% 1	1710
	11th to 20th	Day	38% 19% 19% 15% 9% 1	1544
	21st to end	Day	37% 16% 15% 15% 15% 2	1520
December	1st to 10th	Day	33% 17% 16% 22% 11% 1	1520
	11th to 20th	Day	43% 17% 17% 15% 7% 1	1928
	21st to end	Day	44% 17% 15% 18% 4 1	2794
January	1st to 10th	Night	41% 22% 19% 12% 5%	4406
	11th to 20th	Night	45% 18% 15% 14% 5% 4	4420
	21st to end	Night	49% 15% 15% 13% 7% 1	4641
February	1st to 10th	Night	40% 17% 18% 16% 9% 1	2470
	11th to 20th	Night	38% 14% 19% 19% 8% 3	2397
	21st to end	Night	40% 20% 15% 16% 8% 1	1884
March	1st to 10th	Night	29% 18% 19% 23% 10% 1	3688
	11th to 20th	Night	22% 14% 17% 33% 13%	3490
	21st to end	Night	38% 22% 19% 16% 4	3657
April	1st to 10th	Night	40% 14% 20% 17% 8% 1	1900
	11th to 20th	Night	36% 14% 18% 20% 11% 2	1879
	21st to end	Night	35% 14% 18% 22% 10% 1	1842
May	1st to 10th	Night	30% 14% 18% 26% 12%	2549
	11th to 20th	Night	18% 10% 12% 35% 23% 2	2516
	21st to end	Night	26% 16% 27% 27% 5%	2762
June	1st to 10th	Night	36% 10% 13% 29% 11% 1	1520
	11th to 20th	Night	23% 8% 16% 34% 16% 3	1520
	21st to end	Night	16% 6% 12% 33% 26% 7%	1520
July	1st to 10th	Night	6% 2 7% 15% 23% 47%	2500
	11th to 20th	Night	10% 2 4 14% 22% 47%	2492
	21st to end	Night	7% 3 4 18% 41% 28%	2674
August	1st to 10th	Night	15% 2 6% 18% 42% 17%	2737
	11th to 20th	Night	12% 4 5% 35% 34% 9%	2866
	21st to end	Night	12% 3 9% 30% 31% 15%	3498
September	1st to 10th	Night	10% 3 6% 27% 37% 17%	1900
	11th to 20th	Night	20% 8% 11% 24% 27% 11%	1900
	21st to end	Night	21% 7% 11% 24% 25% 12%	2142
October	1st to 10th	Night	19% 5% 8% 23% 32% 14%	3800
	11th to 20th	Night	26% 9% 19% 26% 17% 4	3777
	21st to end	Night	31% 11% 12% 28% 15% 2	4262
November	1st to 10th	Night	39% 14% 15% 16% 13% 3	2469
	11th to 20th	Night	38% 17% 16% 19% 9% 1	2633
	21st to end	Night	33% 17% 15% 16% 16% 3	2660
December	1st to 10th	Night	36% 16% 15% 20% 11% 2	2660
	11th to 20th	Night	41% 19% 15% 16% 9%	3276
	21st to end	Night	40% 18% 15% 20% 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	16% 24% 32% 19% 8% 2	180
	11th to 20th	Day	19% 13% 30% 24% 11% 2	180
	21st to end	Day	10% 24% 26% 27% 11% 2	331
February	1st to 10th	Day	14% 23% 27% 27% 8% 1	370
	11th to 20th	Day	12% 28% 32% 19% 8% 1	368
	21st to end	Day	12% 26% 29% 24% 9% 1	382
March	1st to 10th	Day	11% 25% 32% 27% 5%	460
	11th to 20th	Day	10% 24% 27% 27% 12% 1	460
	21st to end	Day	12% 28% 29% 24% 7%	506
April	1st to 10th	Day	13% 23% 30% 21% 11% 3	460
	11th to 20th	Day	14% 24% 29% 21% 7% 4	452
	21st to end	Day	9% 24% 30% 22% 12% 3	460
May	1st to 10th	Day	10% 20% 27% 26% 13% 3	463
	11th to 20th	Day	16% 15% 28% 19% 16% 5%	488
	21st to end	Day	12% 13% 25% 27% 18% 5%	529
June	1st to 10th	Day	9% 15% 27% 25% 19% 6%	490
	11th to 20th	Day	8% 18% 31% 25% 16% 3	490
	21st to end	Day	4 8% 27% 32% 23% 8%	490
July	1st to 10th	Day	2 6% 27% 37% 21% 6%	486
	11th to 20th	Day	1 5% 33% 30% 23% 8%	484
	21st to end	Day	1 5% 28% 35% 21% 9%	531
August	1st to 10th	Day	2 5% 25% 35% 23% 11%	487
	11th to 20th	Day	2 5% 22% 32% 26% 13%	477
	21st to end	Day	4 9% 22% 32% 24% 10%	539
September	1st to 10th	Day	3 5% 22% 34% 28% 8%	490
	11th to 20th	Day	4 10% 22% 33% 24% 6%	490
	21st to end	Day	7% 13% 21% 33% 22% 3	490
October	1st to 10th	Day	9% 15% 23% 28% 22% 4	490
	11th to 20th	Day	9% 17% 22% 25% 23% 4	490
	21st to end	Day	11% 18% 30% 21% 16% 5%	454
November	1st to 10th	Day	11% 18% 29% 28% 11% 2	282
	11th to 20th	Day	8% 24% 26% 25% 15% 3	192
	21st to end	Day	13% 23% 20% 29% 13% 2	180
December	1st to 10th	Day	10% 19% 24% 26% 14% 6%	180
	11th to 20th	Day	12% 25% 34% 23% 6% 1	180
	21st to end	Day	14% 20% 30% 25% 9% 2	198
January	1st to 10th	Night	9% 20% 31% 26% 12% 2	760
	11th to 20th	Night	8% 20% 29% 25% 17% 2	760
	21st to end	Night	11% 15% 25% 33% 14% 2	836
February	1st to 10th	Night	7% 18% 31% 32% 11% 1	760
	11th to 20th	Night	8% 14% 32% 33% 12% 1	744
	21st to end	Night	8% 18% 31% 34% 8%	628
March	1st to 10th	Night	9% 20% 27% 32% 10% 2	760
	11th to 20th	Night	6% 16% 28% 35% 15% 1	760
	21st to end	Night	7% 18% 32% 30% 12% 1	836
April	1st to 10th	Night	11% 14% 28% 31% 14% 1	760
	11th to 20th	Night	9% 13% 31% 29% 15% 3	751
	21st to end	Night	10% 11% 28% 35% 15% 1	702
May	1st to 10th	Night	9% 8% 24% 39% 19% 1	389
	11th to 20th	Night	8% 7% 19% 43% 22% 1	374
	21st to end	Night	10% 7% 21% 36% 24% 2	411
June	1st to 10th	Night	9% 7% 21% 42% 19% 1	380
	11th to 20th	Night	7% 6% 22% 44% 21% 1	380
	21st to end	Night	4 1 14% 59% 22%	380
July	1st to 10th	Night	2 1 9% 60% 27% 1	370
	11th to 20th	Night	2 12% 64% 21% 1	368
	21st to end	Night	1 10% 58% 30% 1	416
August	1st to 10th	Night	2 1 6% 51% 36% 3	503
	11th to 20th	Night	1 1 7% 43% 42% 6%	578
	21st to end	Night	2 2 17% 46% 30% 2	836
September	1st to 10th	Night	2 2 15% 47% 31% 3	760
	11th to 20th	Night	4 3 14% 42% 31% 5%	760
	21st to end	Night	8% 5% 18% 38% 26% 5%	760
October	1st to 10th	Night	8% 5% 22% 38% 24% 3	760
	11th to 20th	Night	7% 10% 21% 35% 24% 4	760
	21st to end	Night	8% 13% 25% 33% 15% 6%	836
November	1st to 10th	Night	9% 14% 30% 33% 13% 2	760
	11th to 20th	Night	9% 19% 28% 27% 15% 2	760
	21st to end	Night	7% 17% 24% 33% 15% 3	760
December	1st to 10th	Night	9% 14% 26% 33% 17% 2	760
	11th to 20th	Night	8% 19% 30% 30% 13% 1	760
	21st to end	Night	8% 24% 32% 25% 10%	836

Page generated at 2024-11-02 23:11:20. Version ac07

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