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Newby Lunar Observing List Questions

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#1 shrevestan

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Posted 13 January 2013 - 07:59 PM

Hi everyone,

I've recently decided to branch out from just astrophotography and do a few Astronomical League observing lists, and had a question about the Lunar one.

Under naked eye objects, there is Old/New Moon in New/Old Moon Arms and Waning/Waxing Crescent.

I had a brief break in the clouds tonight and was able to observe the crescent moon and the old moon slightly illuminated.

Does this count as both Old Moon in New Moons Arms and Waxing Crescent or just Waxing Crescent?

Is there something else in particular the list means when it mentions Within 48/72 hours?

Thanks for the help.

#2 azure1961p

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Posted 14 January 2013 - 09:39 PM

I'm not clear on the terms either -decades later, but I'd highly recommend Virtual Moon Atlas. There's also lunar terminator visualization tool or LTVT but the ultimately simple install is such a convoluted mess even some pretty bright folks give up on it . Still if you wade thru it - and it's ultimately straightforward after the long swim, it's about the best lunar program in the world. VMA is nice but LTVT is another realm.

Just mentioning it.

Pete

#3 edosaurusrex

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Posted 14 January 2013 - 10:23 PM

The Old Moon in the New Moon's Arms and the New Moon in the Old Moon's Arms are the appearance of the thin cresent Moon when the "dark" portion is ashen because it is being lit by light from the Earth. The Moon looks round and the ashen "dark" side is easily visible. This happens a few days before and after a New Moon (sorry Curt).

Check APOD Mar 24, 2012 for a good photo of the effect.

Hope this helps.

Ed

#4 Dave Chapman

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Posted 16 January 2013 - 12:04 PM

Stan, let me help answer your question. Lunation 1114 started on Friday at 19:44 UT. The two waxing crescent observations (40 h, 48 h) should have been made before Sunday, 11:44 UT and 19:44 UT, respectively. The Old/New observation (72 h) should have been be made before Monday, 19:44 UT.

I am not sure of your time zone, but I am guessing "continental USA", so your observation would not qualify for either of the "waxing" objectives (not sure why AL has two!) but it would qualify for the "old/new" objective, IF you saw earthshine (which you said you did).

The problem with seeing earthshine soon after New Moon is that the sky may not get dark enough until after moonset, but I do think it would be possible in some circumstances to snag a waxing crescent observation and an earthshine observation at the same time.

Myself, I observed an photographed a waning crescent on Thursday as it rose here (Nova Scotia) about 33 h before the end of the lunation, hoping to capture it with Venus, but the clouds foiled me (again). Perhaps I will post that photo.

clear skies

Dave

#5 Dave Chapman

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Posted 16 January 2013 - 12:10 PM

Here is my waning Moon photo from Thursday past.

Attached Files



#6 THEPLOUGH

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Posted 16 January 2013 - 08:05 PM

Nice shot Dave... :waytogo:

#7 shrevestan

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Posted 17 January 2013 - 04:54 PM

Stan, let me help answer your question. Lunation 1114 started on Friday at 19:44 UT. The two waxing crescent observations (40 h, 48 h) should have been made before Sunday, 11:44 UT and 19:44 UT, respectively. The Old/New observation (72 h) should have been be made before Monday, 19:44 UT.

I am not sure of your time zone, but I am guessing "continental USA", so your observation would not qualify for either of the "waxing" objectives (not sure why AL has two!) but it would qualify for the "old/new" objective, IF you saw earthshine (which you said you did).

The problem with seeing earthshine soon after New Moon is that the sky may not get dark enough until after moonset, but I do think it would be possible in some circumstances to snag a waxing crescent observation and an earthshine observation at the same time.

Myself, I observed an photographed a waning crescent on Thursday as it rose here (Nova Scotia) about 33 h before the end of the lunation, hoping to capture it with Venus, but the clouds foiled me (again). Perhaps I will post that photo.

clear skies

Dave


Thanks Dave. It's still a little bit confusing.

The first observation I made was 6:21 PM CST/1220AM UTC on 13JAN13 and the second was 14JAN13 at 1755CST. Both times I could see the dark part of the moon as a dark brown in the sky. So I missed the waxing crescent by 40 minutes but that observation would still be valid for Old/New?

#8 Dave Chapman

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Posted 18 January 2013 - 11:30 AM

Hi Stan,

I'm a bit confused myself! I am not an AL member, and I have not completed the AL Lunar Club list, but I have completed the RASC's Isabel Williamson Lunar Observing Program. But here goes...

Stick to UT for clarity: observation 1 was on Mon 14 Jan at 00:21 UT (not 13 Jan); observation 2 was on Mon 14 Jan at 23:55 UT, almost a day later. You saw a crescent both times, and earthshine both times. According to AL, they wanted the crescent observations before Sun 13 Jan at 11:44 UT (40 h) and Sun 13 Jan at 19:44 UT (48 h), so both your observations were outside the window for the AL crescent requirements; however, your first observation was well within the AL window for "Old Moon in New Moon's Arms", which expired on Mon 14 Jan at 19:44 UT (72 h).

When you convert to and from UT, be mindful of the possible date change! I think that is part of the confusion.

Certificate requirements aside, the evening of Mon 14 Jan was a perfect night to observe a crescent Moon with earthshine from North America. It is documented (but not well known) that earthshine is brighter at an elongation angle of 41º +/- 3º, which roughly corresponds to 3.4 d (82 h +/- 6 h). I do not know the origin of the 72 h cutoff for Old/New, but I would be tempted to change it to 96 h (4 d) so observers would not miss such opportunities. Just one observer's opinion!

cielos claros

Dave

#9 shrevestan

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Posted 18 January 2013 - 09:24 PM

Thanks! I'll have to plan better on the next cycle!






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