Saddle Mountain Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Saddle Mountain Site clear sky chart from 2005-11-05 to 2017-09-24.

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
77%
15807
39%
47013
33%
15771
82%
15771
59%
21427

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 15thNight
75%
716
35%
2327
35%
716
80%
716
51%
1074
January16th to endNight
69%
768
38%
2496
36%
768
77%
768
47%
1204
February1st to 15thNight
74%
699
40%
2121
37%
699
83%
699
56%
975
February16th to endNight
67%
632
36%
1895
35%
632
73%
632
47%
968
March1st to 15thNight
68%
720
41%
2013
33%
720
77%
720
60%
948
March16th to endNight
74%
768
41%
2112
31%
768
82%
768
64%
972
April1st to 15thNight
65%
719
34%
1978
22%
719
74%
719
58%
960
April16th to endNight
67%
579
47%
1662
30%
579
79%
579
75%
671
May1st to 15thNight
73%
539
39%
1619
30%
539
79%
539
68%
679
May16th to endNight
74%
561
41%
1684
30%
561
80%
561
74%
667
June1st to 15thNight
82%
540
36%
1620
30%
540
84%
540
73%
646
June16th to endNight
90%
540
36%
1620
31%
540
90%
540
77%
639
July1st to 15thNight
85%
510
28%
1530
23%
510
86%
510
58%
702
July16th to endNight
87%
564
32%
1593
26%
531
88%
531
48%
816
August1st to 15thNight
86%
539
35%
1611
29%
536
86%
536
54%
769
August16th to endNight
85%
729
38%
1911
30%
729
86%
729
56%
994
September1st to 15thNight
81%
720
34%
1980
28%
720
84%
720
56%
997
September16th to endNight
86%
692
47%
1914
38%
692
91%
692
76%
813
October1st to 15thNight
79%
660
45%
1849
36%
660
85%
660
68%
828
October16th to endNight
83%
704
45%
2112
41%
704
88%
704
68%
892
November1st to 15thNight
83%
700
42%
2190
41%
700
87%
700
66%
917
November16th to endNight
77%
720
42%
2340
42%
720
83%
720
59%
1002
December1st to 15thNight
77%
720
38%
2340
38%
720
82%
720
51%
1074
December16th to endNight
72%
768
38%
2496
39%
768
76%
768
45%
1220

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
2112212335%72%
47914
Night
2212212335%71%
47209
TransparencyDay
14%2311%24%43%
47609
Night
15%2210%22%45%
47015
SeeingDay
3314%30%33%14%
5589
Night
3112%40%37%4
15819

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
3312223226%68%
1611
16th to endDay
7%113212336%66%
1728
February1st to 15thDay
2312213336%69%
1742
16th to endDay
421232325%6%64%
1579
March1st to 15thDay
3212123245%71%
1945
16th to endDay
221221234473%
2112
April1st to 15thDay
111213347%72%
1970
16th to endDay
1111112483%
2294
May1st to 15thDay
111112225%80%
2331
16th to endDay
1111112384%
2429
June1st to 15thDay
111112384%
2340
16th to endDay
121112384%
2340
July1st to 15thDay
1213213447%66%
2340
16th to endDay
43145%25%7%6%10%48%
2467
August1st to 15thDay
321232346%9%61%
2340
16th to endDay
311231345%7%65%
2288
September1st to 15thDay
421231345%6%64%
1980
16th to endDay
1111112382%
1904
October1st to 15thDay
111112225%79%
1779
16th to endDay
111123480%
1760
November1st to 15thDay
11221232478%
1667
16th to endDay
41122235%74%
1620
December1st to 15thDay
3313423345%65%
1620
16th to endDay
43232235%7%63%
1728
January1st to 15thNight
3313323345%66%
2327
16th to endNight
6%31332224466%
2496
February1st to 15thNight
3211212335%69%
2110
16th to endNight
4213424346%62%
1895
March1st to 15thNight
322211345%71%
2013
16th to endNight
212112235%73%
2112
April1st to 15thNight
311321233472%
1978
16th to endNight
11111484%
1662
May1st to 15thNight
232235%77%
1619
16th to endNight
1111211284%
1684
June1st to 15thNight
1111222481%
1620
16th to endNight
1112384%
1620
July1st to 15thNight
111231436%7%65%
1620
16th to endNight
2112325%6%7%11%54%
1701
August1st to 15thNight
121332347%9%60%
1620
16th to endNight
22332345%8%63%
1911
September1st to 15thNight
3212314447%65%
1980
16th to endNight
11222382%
1914
October1st to 15thNight
22111222477%
1849
16th to endNight
11121232478%
2112
November1st to 15thNight
1111212235%75%
2190
16th to endNight
32221123475%
2340
December1st to 15thNight
322323336%66%
2340
16th to endNight
5%323323335%64%
2496

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 15thDay
20%1414%29%30%
1612
16th to endDay
20%2314%27%31%
1728
February1st to 15thDay
17%2414%29%31%
1742
16th to endDay
19%2216%31%27%
1579
March1st to 15thDay
16%118%29%42%
1945
16th to endDay
14%228%30%41%
2112
April1st to 15thDay
12%118%32%43%
1970
16th to endDay
8%7%22%60%
2294
May1st to 15thDay
8%117%22%58%
2331
16th to endDay
8%15%20%63%
2432
June1st to 15thDay
6%1315%72%
2340
16th to endDay
8%1139%77%
2340
July1st to 15thDay
16%45%13%19%40%
2201
16th to endDay
26%5%9%22%21%13%
2312
August1st to 15thDay
18%36%19%19%33%
2325
16th to endDay
17%4414%30%29%
2288
September1st to 15thDay
20%35%12%23%34%
1980
16th to endDay
9%1322%61%
1904
October1st to 15thDay
10%228%25%50%
1779
16th to endDay
9%237%25%52%
1760
November1st to 15thDay
11%1111%28%44%
1667
16th to endDay
14%1111%28%42%
1620
December1st to 15thDay
21%1317%28%26%
1620
16th to endDay
20%25%21%30%18%
1728
January1st to 15thNight
19%2411%24%37%
2327
16th to endNight
23%1212%23%36%
2496
February1st to 15thNight
17%1314%24%38%
2121
16th to endNight
23%2211%24%33%
1895
March1st to 15thNight
15%117%21%51%
2013
16th to endNight
14%128%28%45%
2112
April1st to 15thNight
16%116%26%46%
1978
16th to endNight
7%115%24%60%
1662
May1st to 15thNight
10%116%23%56%
1620
16th to endNight
8%16%17%65%
1685
June1st to 15thNight
9%1415%70%
1620
16th to endNight
8%26%81%
1620
July1st to 15thNight
15%38%13%20%39%
1530
16th to endNight
19%6%8%23%22%19%
1593
August1st to 15thNight
17%4319%22%32%
1611
16th to endNight
18%35%14%26%30%
1911
September1st to 15thNight
17%3416%23%33%
1980
16th to endNight
8%16%20%62%
1914
October1st to 15thNight
12%1110%22%51%
1849
16th to endNight
11%128%16%58%
2112
November1st to 15thNight
12%118%26%49%
2190
16th to endNight
15%128%24%48%
2340
December1st to 15thNight
20%1413%25%34%
2340
16th to endNight
23%2317%26%26%
2496

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 15thDay
16%118%43%18%1
90
16th to endDay
5%116%36%29%11%
96
February1st to 15thDay
35%17%31%34%8%
257
16th to endDay
9%7%24%30%23%4
238
March1st to 15thDay
39%17%31%21%15%
270
16th to endDay
27%24%29%25%11%
288
April1st to 15thDay
5%10%22%29%21%10%
269
16th to endDay
210%32%27%19%8%
270
May1st to 15thDay
27%25%33%22%8%
288
16th to endDay
2420%31%33%6%
330
June1st to 15thDay
2217%37%31%8%
315
16th to endDay
116%35%35%18%
315
July1st to 15thDay
27%30%42%17%
305
16th to endDay
3122%42%29%
327
August1st to 15thDay
2321%41%30%
315
16th to endDay
1121%47%27%
332
September1st to 15thDay
5%6%26%44%15%
315
16th to endDay
2215%33%32%13%
288
October1st to 15thDay
1418%26%36%13%
219
16th to endDay
31425%51%15%
96
November1st to 15thDay
213%33%40%11%
90
16th to endDay
5%117%43%26%5%
90
December1st to 15thDay
43435%46%5%
90
16th to endDay
10%316%42%25%2
96
January1st to 15thNight
4211%47%30%3
720
16th to endNight
7%213%43%28%4
768
February1st to 15thNight
4212%44%33%3
704
16th to endNight
5%118%46%25%1
632
March1st to 15thNight
4319%38%29%4
720
16th to endNight
2315%42%32%4
768
April1st to 15thNight
4321%41%26%2
719
16th to endNight
1424%43%23%3
579
May1st to 15thNight
1219%43%30%2
540
16th to endNight
1218%41%34%2
563
June1st to 15thNight
1112%55%28%1
540
16th to endNight
16%44%44%1
540
July1st to 15thNight
35%37%50%3
510
16th to endNight
2331%54%7%
564
August1st to 15thNight
2234%52%6%
539
16th to endNight
4324%55%11%
729
September1st to 15thNight
417%25%52%8%
720
16th to endNight
29%35%46%6%
692
October1st to 15thNight
1112%40%39%3
660
16th to endNight
218%38%41%7%
704
November1st to 15thNight
29%41%39%6%
700
16th to endNight
3110%39%37%6%
720
December1st to 15thNight
5%110%44%34%2
720
16th to endNight
6%110%48%29%3
768
Page generated at 2017-09-25 06:02:17. Version ac04

Copyright 2017 A. Danko


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