Hope Slide
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hope Slide clear sky chart from 2005-11-06 to 2024-01-17.

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 TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(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

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
24%
22437
9%
74741
6%
22376
28%
22376
12%
57230

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 10thNight
10%
850
8%
2836
3%
846
17%
846
7%
2393
January11th to 20thNight
15%
776
9%
2676
4%
776
22%
776
9%
2143
January21st to endNight
16%
792
9%
2772
4%
792
22%
792
9%
2195
February1st to 10thNight
10%
720
6%
2394
2%
720
15%
720
7%
2002
February11th to 20thNight
12%
701
7%
2274
3%
700
19%
700
8%
1901
February21st to endNight
17%
592
9%
1848
4%
592
23%
592
8%
1546
March1st to 10thNight
22%
720
8%
2160
5%
720
25%
720
11%
1752
March11th to 20thNight
18%
720
9%
1998
4%
720
22%
720
11%
1645
March21st to endNight
15%
792
5%
2064
2%
792
18%
792
8%
1783
April1st to 10thNight
21%
720
6%
1800
3%
720
22%
720
11%
1491
April11th to 20thNight
21%
698
9%
1766
4%
698
24%
698
12%
1445
April21st to endNight
20%
416
6%
1496
4%
416
23%
416
8%
1193
May1st to 10thNight
31%
360
8%
1440
9%
360
35%
360
11%
1076
May11th to 20thNight
40%
354
8%
1416
12%
354
42%
354
13%
1007
May21st to endNight
34%
389
5%
1552
8%
388
35%
388
12%
1158
June1st to 10thNight
29%
360
3%
1324
2%
360
30%
360
12%
996
June11th to 20thNight
28%
360
2%
1260
1%
360
29%
360
11%
987
June21st to endNight
41%
360
6%
1260
2%
360
42%
360
20%
825
July1st to 10thNight
52%
350
6%
1225
5%
350
52%
350
25%
750
July11th to 20thNight
52%
348
12%
1275
12%
348
55%
348
30%
702
July21st to endNight
66%
394
17%
1488
27%
372
71%
372
42%
642
August1st to 10thNight
63%
358
16%
1424
22%
356
67%
356
35%
694
August11th to 20thNight
62%
461
22%
1529
21%
461
67%
461
39%
798
August21st to endNight
45%
710
19%
1898
13%
710
48%
710
31%
1231
September1st to 10thNight
40%
720
16%
1800
8%
720
43%
720
32%
1195
September11th to 20thNight
44%
720
19%
1800
11%
720
45%
720
25%
1274
September21st to endNight
34%
720
15%
2038
10%
720
38%
720
19%
1479
October1st to 10thNight
32%
720
10%
2160
9%
720
34%
720
16%
1597
October11th to 20thNight
26%
720
11%
2160
8%
720
31%
720
13%
1656
October21st to endNight
17%
792
9%
2556
5%
792
23%
792
10%
2008
November1st to 10thNight
11%
740
6%
2549
3%
740
16%
740
7%
2138
November11th to 20thNight
12%
760
7%
2660
3%
760
17%
760
8%
2181
November21st to endNight
13%
760
6%
2660
2%
760
17%
760
7%
2182
December1st to 10thNight
15%
760
9%
2660
4%
760
21%
760
9%
2100
December11th to 20thNight
8%
789
5%
3357
2%
788
12%
788
4%
2851
December21st to endNight
5%
935
4%
5166
1%
905
10%
905
3%
4214

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 ForecastData
Points
Cloud CoverDay
20%17%47%5%34445%27%
74855
Night
20%18%5%7%5%34445%25%
74980
TransparencyDay
61%310%16%8%2
74546
Night
63%311%15%8%1
74807
SeeingDay
27%20%29%17%6%1
13921
Night
29%14%28%22%7%
22440

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
24%24%5%8%6%2334416%
1329
11th to 20thDay
17%21%5%11%6%34445%21%
1424
21st to endDay
18%23%6%7%6%22346%22%
1584
February1st to 10thDay
21%23%6%10%6%34346%14%
1564
11th to 20thDay
15%26%6%8%6%34445%18%
1575
21st to endDay
12%27%10%9%7%45%44316%
1408
March1st to 10thDay
15%24%9%10%7%4344418%
1800
11th to 20thDay
16%30%8%7%6%4433415%
1958
21st to endDay
18%27%8%9%6%35%44412%
2291
April1st to 10thDay
18%29%8%8%5%3445%412%
2160
11th to 20thDay
17%28%5%8%6%4444416%
2141
21st to endDay
22%28%48%5%3344416%
2462
May1st to 10thDay
19%23%47%5%34435%24%
2520
11th to 20thDay
20%17%36%5%35%6%6%6%23%
2477
21st to endDay
31%14%46%43443422%
2723
June1st to 10thDay
29%15%46%5%4443422%
2632
11th to 20thDay
37%15%47%5%3334416%
2700
21st to endDay
24%8%35%6%4445%5%32%
2700
July1st to 10thDay
16%7%36%5%34445%44%
2700
11th to 20thDay
15%5%25%5%2445%6%47%
2642
21st to endDay
11%423323346%59%
2741
August1st to 10thDay
14%5%1333445%6%52%
2507
11th to 20thDay
11%42442445%7%54%
2368
21st to endDay
19%6%26%5%345%6%6%39%
2458
September1st to 10thDay
17%6%26%433446%45%
2160
11th to 20thDay
21%8%37%6%2434438%
2160
21st to endDay
23%12%26%5%24335%34%
1921
October1st to 10thDay
23%13%36%44435%6%29%
1800
11th to 20thDay
23%14%47%5%34445%26%
1800
21st to endDay
26%19%35%5%34345%22%
1800
November1st to 10thDay
27%22%5%7%5%3444415%
1526
11th to 20thDay
24%26%5%6%5%2333320%
1520
21st to endDay
21%22%6%7%6%34345%20%
1520
December1st to 10thDay
18%21%7%7%5%35%435%23%
1520
11th to 20thDay
14%24%6%10%7%44445%18%
1822
21st to endDay
16%24%9%10%8%45%5%4312%
2442
January1st to 10thNight
24%25%6%7%5%33335%15%
2836
11th to 20thNight
20%20%6%9%5%34446%19%
2676
21st to endNight
17%22%6%9%6%3335%6%20%
2772
February1st to 10thNight
23%22%7%9%5%34445%16%
2394
11th to 20thNight
17%27%7%9%6%3433419%
2272
21st to endNight
14%24%7%9%7%345%45%17%
1848
March1st to 10thNight
14%22%7%8%6%345%5%421%
2160
11th to 20thNight
18%25%7%7%6%4434420%
1997
21st to endNight
19%25%7%8%5%34435%17%
2064
April1st to 10thNight
14%25%7%9%7%45%435%18%
1800
11th to 20thNight
16%27%47%6%4444421%
1766
21st to endNight
21%25%5%7%5%24445%18%
1496
May1st to 10thNight
18%22%47%335%43428%
1440
11th to 20thNight
17%14%46%5%36%5%6%7%27%
1416
21st to endNight
29%13%34424446%26%
1552
June1st to 10thNight
26%10%35%6%445%5%5%26%
1324
11th to 20thNight
26%15%37%6%345%5%5%21%
1260
21st to endNight
20%8%36%6%33447%38%
1260
July1st to 10thNight
18%8%24433345%45%
1260
11th to 20thNight
14%5%25%435%45%6%49%
1317
21st to endNight
10%313323447%60%
1576
August1st to 10thNight
10%6%1333435%6%57%
1432
11th to 20thNight
10%6%1432335%6%58%
1529
21st to endNight
15%7%25%5%346%6%8%39%
1898
September1st to 10thNight
16%8%35%434335%46%
1800
11th to 20thNight
24%7%25%433336%39%
1800
21st to endNight
22%12%45%5%24346%33%
2038
October1st to 10thNight
21%14%36%5%44436%31%
2160
11th to 20thNight
27%14%37%5%4443327%
2160
21st to endNight
27%18%46%5%33445%22%
2556
November1st to 10thNight
29%19%5%7%5%3443417%
2549
11th to 20thNight
24%23%5%6%5%4433418%
2660
21st to endNight
23%24%6%6%5%4434418%
2660
December1st to 10thNight
18%18%6%8%5%35%445%23%
2660
11th to 20thNight
21%23%6%10%8%35%34413%
3378
21st to endNight
16%24%8%11%7%4445%5%12%
5214

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
74%37%10%41
1329
11th to 20thDay
65%6%9%11%5%3
1424
21st to endDay
66%29%12%10%
1584
February1st to 10thDay
72%48%10%5%1
1564
11th to 20thDay
70%39%10%6%1
1584
21st to endDay
74%47%12%3
1408
March1st to 10thDay
72%48%10%5%1
1800
11th to 20thDay
74%38%11%3
1958
21st to endDay
78%310%7%2
2291
April1st to 10thDay
77%310%8%1
2160
11th to 20thDay
71%5%8%8%7%1
2141
21st to endDay
73%39%9%6%
2462
May1st to 10thDay
64%5%12%14%6%
2520
11th to 20thDay
61%5%14%16%3
2480
21st to endDay
68%411%13%3
2724
June1st to 10thDay
67%311%13%43
2632
11th to 20thDay
74%39%11%3
2700
21st to endDay
54%414%20%8%1
2700
July1st to 10thDay
45%410%25%13%3
2626
11th to 20thDay
37%312%29%16%3
2561
21st to endDay
26%212%32%22%6%
2589
August1st to 10thDay
33%314%28%18%4
2490
11th to 20thDay
30%317%28%18%3
2368
21st to endDay
45%312%29%9%2
2458
September1st to 10thDay
42%212%26%13%4
2160
11th to 20thDay
52%27%18%18%2
2160
21st to endDay
55%212%17%11%2
1921
October1st to 10thDay
58%312%19%8%
1800
11th to 20thDay
61%39%19%7%1
1800
21st to endDay
66%310%14%8%
1800
November1st to 10thDay
75%46%10%5%
1526
11th to 20thDay
69%48%12%6%2
1520
21st to endDay
68%47%11%8%2
1520
December1st to 10thDay
66%5%8%11%8%1
1520
11th to 20thDay
70%39%13%5%1
1824
21st to endDay
77%36%10%4
2442
January1st to 10thNight
75%35%12%42
2836
11th to 20thNight
69%38%12%5%3
2676
21st to endNight
67%38%11%9%2
2772
February1st to 10thNight
74%36%11%5%1
2394
11th to 20thNight
73%37%10%5%2
2274
21st to endNight
73%37%13%4
1848
March1st to 10thNight
67%411%10%7%1
2160
11th to 20thNight
70%39%14%5%
1998
21st to endNight
73%5%12%9%2
2064
April1st to 10thNight
70%313%12%3
1800
11th to 20thNight
66%411%10%9%
1766
21st to endNight
69%310%12%5%
1496
May1st to 10thNight
62%5%12%16%5%1
1440
11th to 20thNight
55%6%18%15%5%
1416
21st to endNight
61%5%15%16%3
1552
June1st to 10thNight
59%6%15%13%5%2
1324
11th to 20thNight
62%6%14%14%3
1260
21st to endNight
46%6%20%20%7%2
1260
July1st to 10thNight
41%316%24%14%2
1225
11th to 20thNight
33%417%31%12%3
1275
21st to endNight
21%317%30%25%4
1488
August1st to 10thNight
27%420%27%20%3
1424
11th to 20thNight
27%420%27%19%2
1529
21st to endNight
39%417%27%10%2
1898
September1st to 10thNight
41%414%24%15%3
1800
11th to 20thNight
49%310%18%17%3
1800
21st to endNight
54%313%18%10%2
2038
October1st to 10thNight
58%310%21%8%
2160
11th to 20thNight
63%39%16%9%1
2160
21st to endNight
67%28%14%9%
2556
November1st to 10thNight
73%48%9%5%1
2549
11th to 20thNight
71%49%9%6%2
2660
21st to endNight
73%26%10%7%3
2660
December1st to 10thNight
67%49%13%7%1
2660
11th to 20thNight
77%38%8%41
3375
21st to endNight
75%27%10%5%
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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
26%29%27%13%5%1
180
11th to 20thDay
26%21%33%16%5%
172
21st to endDay
23%24%30%19%3
176
February1st to 10thDay
41%25%24%9%1
284
11th to 20thDay
34%21%29%13%21
335
21st to endDay
29%24%32%13%3
314
March1st to 10thDay
30%25%31%11%4
420
11th to 20thDay
31%24%25%16%4
420
21st to endDay
32%24%26%13%3
462
April1st to 10thDay
38%22%23%14%3
420
11th to 20thDay
30%26%24%12%7%1
412
21st to endDay
37%22%23%13%5%1
420
May1st to 10thDay
26%17%34%18%31
423
11th to 20thDay
29%12%29%22%7%1
448
21st to endDay
35%18%24%16%6%2
485
June1st to 10thDay
31%22%26%16%4
562
11th to 20thDay
38%22%25%12%3
630
21st to endDay
26%18%30%19%7%1
630
July1st to 10thDay
19%16%39%20%5%1
621
11th to 20thDay
18%20%37%20%41
560
21st to endDay
9%15%38%26%10%3
487
August1st to 10thDay
15%12%34%27%9%4
447
11th to 20thDay
11%13%35%29%10%2
437
21st to endDay
18%20%35%18%9%1
495
September1st to 10thDay
18%24%32%20%6%
450
11th to 20thDay
26%18%28%21%7%
450
21st to endDay
29%18%27%18%7%1
450
October1st to 10thDay
27%18%27%17%10%1
450
11th to 20thDay
33%19%20%19%7%1
450
21st to endDay
36%17%27%17%4
315
November1st to 10thDay
37%16%27%18%2
198
11th to 20thDay
37%19%22%14%7%
180
21st to endDay
33%25%23%9%9%1
180
December1st to 10thDay
32%19%23%18%7%1
180
11th to 20thDay
32%22%30%11%32
180
21st to endDay
29%24%33%15%
198
January1st to 10thNight
35%24%28%12%2
850
11th to 20thNight
33%17%32%17%2
776
21st to endNight
26%19%35%18%2
792
February1st to 10thNight
35%18%33%13%2
720
11th to 20thNight
30%19%33%16%1
704
21st to endNight
28%17%32%19%4
592
March1st to 10thNight
27%17%28%22%5%
720
11th to 20thNight
29%19%29%18%5%
720
21st to endNight
29%19%29%17%6%
792
April1st to 10thNight
27%16%27%24%5%1
720
11th to 20thNight
30%14%28%23%5%
698
21st to endNight
30%13%30%19%7%
416
May1st to 10thNight
24%11%26%28%11%
360
11th to 20thNight
25%7%20%34%13%1
354
21st to endNight
31%7%23%28%12%
389
June1st to 10thNight
29%8%29%25%10%
360
11th to 20thNight
31%8%25%26%10%1
360
21st to endNight
21%6%25%34%13%1
360
July1st to 10thNight
19%7%17%40%17%1
350
11th to 20thNight
12%7%23%40%18%
348
21st to endNight
8%5%18%43%25%1
394
August1st to 10thNight
12%316%36%31%2
358
11th to 20thNight
12%418%39%26%1
461
21st to endNight
16%7%26%34%16%
710
September1st to 10thNight
18%8%29%28%18%
720
11th to 20thNight
24%9%19%27%20%2
720
21st to endNight
28%12%22%29%9%
720
October1st to 10thNight
27%10%25%28%10%
720
11th to 20thNight
34%12%24%24%6%
720
21st to endNight
39%13%27%17%4
792
November1st to 10thNight
39%16%32%12%1
740
11th to 20thNight
39%16%30%13%2
760
21st to endNight
37%19%26%15%3
760
December1st to 10thNight
26%17%37%17%3
760
11th to 20thNight
35%21%32%11%1
789
21st to endNight
33%21%37%8%
935
Page generated at 2024-01-14 06:55:03. Version ac07

Copyright 2024 Attilla Danko


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