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[Centaur]

On December 6th some observers will have an opportunity to spot the New Moon while it is little more than a day old at the same time it is occulting Mars. Chicagolanders will be able to watch the immersion shortly after sunset, however the emersion will occur after moonset. The Dark Moon will be in geocentric longitudinal conjunction with the Sun on 2010 DEC 05 at 17:36 UT (11:36 CST). Mercury will serve as a guide star about 6° to the upper left of the Moon during the evening of the 6th.

I’ve made a graphic previewing the southwestern sky from Chicagoland after sunset on December 6th. It should well serve most North American observers. I’ve also created a North American graze map for the Mars occultation, and specific occultation info for observers at Chicago’s Adler Planetarium. They can all be seen by clicking: www.curtrenz.com/astronomical then going to the Moon page.

If you would like Mars occultation or graze data for a specific location, please reply to this post with a longitude, latitude, time zone and elevation above sea level.

Photos and descriptions of the December New Moon and Mars occultation would be welcome additions to this thread. Please include the date, time, time zone and location. Good Luck!

Below is a photo I took from Arlington Heights, Illinois after sunset on 2008 DEC 28 of a 1.5-day-old Moon with Venus at the top and Mercury in the center.

[patrickm]

If this British weather keeps up, new moon spotting may also be January full moon spotting!

Centaur, could you please do a graze map for Austin? 30d 16' N 97d 45' W 253m

Maybe I'll have a crack at it there. Thanks much!!
P

[Centaur]

Dec 2, 2010 10:15:10 GMT -6 patrickm said:

If this British weather keeps up, new moon spotting may also be January full moon spotting!

Centaur, could you please do a graze map for Austin? 30d 16' N 97d 45' W 253m

Maybe I'll have a crack at it there. Thanks much!!
P

Patrick, the graze map on my website for North America includes Austin which is far from either graze path. You are in the zone for a full occultation, however the immersion will occur during the daytime. But the emersion will occur shortly after sunset. The zenith angle is the position of Mars on the lunar limb measured counterclockwise from the zenith.

Immersion
16:26:44 CST at Zenith Angle 23.4°

Emersion
17:41:12 CST at Zenith Angle 209.9°

[Paulie pchris00]

I haven't run it by Hillary yet, but assuming good conditions Monday, I want to go all out to capture this. My computer is working normally again, and I will need her help to get everything documented.

[patrickm]

This will be a tough one from my Mom's place. May have to take a dinner break and head to higher ground with better horizon!

Thanks for the tips, Centaur! Much appreciated, as always.

[Chicago Astronomer - Astro Joe]

If clear and not too cold...and things are good at home...I will set up a telescope by the Adler for this and try and video the event.

Very cool.

[Paulie pchris00]

Joe, if you head out to Adler, we could be persuaded to join you.

[Centaur]

Dec 3, 2010 2:08:45 GMT -6 Chicago Astronomer - Astro Joe said:

If clear and not too cold...and things are good at home...I will set up a telescope by the Adler for this and try and video the event.

Very cool.

Dec 3, 2010 9:24:27 GMT -6 Paulie pchris00 said:

Joe, if you head out to Adler, we could be persuaded to join you.

The December 6th observation from the Adler Planetarium of the occultation of magnitude +1.3 Mars by the 1.6% illuminated waxing crescent Moon may be something of a challenge, even if clouds or buildings do not interfere. I calculate that the immersion of the center of 3.9-arcsecond Mars into the Moon’s dark limb will occur at 16:31:59 CST, which will be only 12 minutes after sunset. Optical aid will almost certainly be required during bright twilight, despite Mars being at first magnitude. The emersion will occur after moonset.

Please be extra careful, if trying to observe while the Sun is still out. My only occultation observation occurred on 1958 JUN 18 as a 12-year-old. It was serendipitous. With my 3-inch refractor I was seeking to spot a quite young Moon low in the west moments after sunset, when I realized the Moon’s limb was approaching a star. I didn’t learn which star it was until I wrote an occultation program 40 years later. It was magnitude +3.6 Lambda Geminorum. Magnitude +1.3 Mars should present a somewhat easier target on Monday.

At the time of the immersion at the Adler, here will be Mars’ coordinates.

Equatorial
RA 17:56.5
Dec S 24° 17’

Horizontal (Alt-Azm)
Azm 230.1° (5.1° to the right of southwest)
Alt 5.7° (atmospheric refraction corrected)

Good luck, guys. Your reports are much anticipated!

[Chicago Astronomer - Astro Joe]

Curt,

How high off the horizon is this event?

I ask due to the skyscrapers.

[Centaur]

Dec 5, 2010 11:59:48 GMT -6 Chicago Astronomer - Astro Joe said:

Curt,

How high off the horizon is this event?

I ask due to the skyscrapers.

Joe, please read the altitude information near the bottom of my previous post.

[Chicago Astronomer - Astro Joe]

It was hard to read on the road on Smartphone.

Thanks anyway.

[Centaur]

Dec 5, 2010 15:43:50 GMT -6 Chicago Astronomer - Astro Joe said:

It was hard to read on the road on Smartphone.

Thanks anyway.

I understand, Joe. You’re welcome.

Chicagoland lies on a very narrow strip of the Earth’s surface for which either the immersion or emersion will occur after sunset. For most people, both of these events will occur either in daylight or while the Moon is beneath the horizon. So photos or descriptions of the event will be coming from those few of us in the favorable zone. We’ll be serving as the eyes for the rest of the world despite imperfect circumstances. Good luck!

BTW, there will be no other nighttime or twilight occultations of first magnitude planets or stars visible from North America until 2015.

[Centaur]

The New Moon Spotting image linked at the top of my Moon webpage is now drawn specifically for the Adler Planetarium twelve minutes after sunset today (December 6) and thirteen seconds before the occultation.

[Paulie pchris00]

It looks like Monday's weather kept everybody from seeing the lunar occultation of Mars, huh? Yesterday afternoon I got my first glimpse of the new Moon at 16:42 (4:42 PM) CST. Not meaning to tease, I may have an occultation story from 7DEC 2010 to share later. Sorry, but I don't have time to post the entire story right now, but will try to get it posted this afternoon.

[patrickm]

No luck here in Austin. Cloudy. Still haven't seen the moon yet. MAYBE tonight.

[Paulie pchris00]

Monday night's forecast for the lunar occultation of Mars was so bad that I decided to catch up on sleep rather than fight the weather. Tuesday evening, however, I was going to meet Hillary and her dad for dinner, but had to run around town on errands first. As soon as I went outside I was greeted by a clear sky. I turned around and saw an old friend I hadn't seen for two weeks: Luna! I checked the time (4:42 CST), took some pictures. I even texted Hillary to make sure she saw it too. I decided to bring along my Dobsonian, just in case the sky stayed clear later.






4:42 PM CST.




I took this picture at a stop sign.


I cut my errands a little bit short, and stopped at Woodland Park in Portage before I met Hillary. Luna's disk, lit by sunlight and Earth-shine, was tempting me for a closer look. I only meant to stay a few minutes. It was very cold, with wind chills approaching zero degrees, and I wasn't dressed well enough to be outside for long.

Getting a few pictures through the telescope, I was ready to pack up and head to dinner, but I noticed something interesting. Less than half a degree east of the Moon were two similarly bright stars, estimated about 4th magnitude, and only about 1/4 degree from each other. I quickly noted them in my notebook- very sloppily with frozen fingers. Luna observed and the stars noted, I put the telescope away at 5:19 PM and started to leave. One last look to the soon-setting Moon as I was backing out made me realize I'd overlooked something.







I tried to get pictures of the two stars with the Moon, but they were too faint for my camera to capture.


While I was observing the two stars near the Moon, I was paying attention to the inverted image at the eyepiece, and not recognizing that they were ahead of the leading lunar limb. I hadn't been thinking- blame it on the cold- and had assumed there had already been an occultation of these stars. Now I realized I was wrong.

The Moon was already low on the horizon, so I drove around to different areas of the park looking for the best place to observe from again. It turned out that I had already been in the best place to be, so I parked near the spot I had started from, and hauled out the telescope all over again.

It had only been about ten minutes since concluding the first observation, but already one of the stars had disappeared. I watched the remaining star for about ten more minutes, and concluded that Luna's path would pass above it, not in front of it. I wasn't 100% sure, but in a few more minutes it wouldn't matter anyway; I would be totally frozen, and the Moon would drop out of sight.

My notes are terrible, but considering the observing conditions, and that I hadn't planned on any serious observations at all, I'm satisfied that I made an attempt to document the situation. Checking my redshift planetarium software this morning, I think the two stars I observed may have been 32 & 35 Sgr, with 32 being the one that was occulted. The times don't mesh up with what I observed. The times on Redshift are almost exactly one hour behind what I observed, so maybe there is a problem with the time on my program? Any help in figuring this out would be greatly appreciated. The observation site details are:

41 Deg. 35' 21" North

87 Deg. 11' 04" West

Elevation: 191 Meters


Okay, my images from photobucket are not showing up, and I don't know why. They can be seen on my blog page.

pchris00pnc.blogspot.com/2010/12/greeting-two-day-old-luna-and.html

[Centaur]

Nice descriptions, Paulie, but your pictures are not appearing. Here’s a link to a picture on spaceweather.com of the emersion of Mars from behind the Moon: www.spaceweather.com/submissions/pics/d/Doug-Zubenel-IMG_0029_1291683340.jpg

[patrickm]

Looks to me like 32+35 Sgr with 32 disappearing around 17:26, but oddly being occluded by trailing edge, dark section of the Moon. 35 wouldn't have been swallowed until only 2deg above horizon at about 1759. Because of my ignorance, I ASSumed that they would have been occluded earlier by the leading edge, but WRONG potato breath!

So, I second your interpretation of your observations.

[Paulie pchris00]

Okay, I don't know what was wrong with the images before, but I deleted the entire album, and uploaded them again.

Patrick, unless I'm misunderstanding, I think you're making the same mistake I did initially. The dark edge was the leading edge.

32 & 35 Sgr seem to be the best guesses. Their magnitudes are about right, and their relative positions are accurate. the only problem I was having was with time that Redshift showed.

[Paulie pchris00]

Dec 8, 2010 18:14:51 GMT -6 Centaur said:

Nice descriptions, Paulie, but your pictures are not appearing. Here’s a link to a picture on spaceweather.com of the emersion of Mars from behind the Moon: www.spaceweather.com/submissions/pics/d/Doug-Zubenel-IMG_0029_1291683340.jpg

Congratulations to Doug Zubenel for getting that great image! Thanks Centaur!

[patrickm]

Not on my software!

Attachments:

[patrickm]

A few mins later. Definitely setting down and to the right, toward the crescent.

Attachments:

[Centaur]

To clear up some apparent confusion here: When the Moon is waxing, occultation immersions generally take place on the lunar dark limb, while emersions follow on the bright limb. The reverse is normally true for a waning Moon.

[patrickm]

Centaur,
Please do tell! Why?! I was confused looking at my software for a few minutes, and still am as to the reason.
Thanks!
P

[Centaur]

Dec 9, 2010 19:00:35 GMT -6 patrickm said:

Centaur,
Please do tell! Why?! I was confused looking at my software for a few minutes, and still am as to the reason.
Thanks!
P

Patrick, it’s because the bright limb of the Moon is always facing the Sun; it’s bathed in sunlight. The dark limb of the Moon is in the nighttime portion facing away from the Sun. When the Moon is waxing it appears to be moving away from the Sun with the Moon’s nighttime side leading. When the Moon is waning it appears to be moving toward the Sun with the Moon’s daytime side leading.

[patrickm]

Are occultations always on the backside of the moon? Sorry to be so dense!!!

[patrickm]

NASA APOD
A Twilight Occultation
apod.nasa.gov/apod/ap101210.html

Image Credit & Copyright: Doug Zubenel (TWAN)

Attachments:

[Centaur]

Dec 10, 2010 1:42:37 GMT -6 patrickm said:

Are occultations always on the backside of the moon? Sorry to be so dense!!!

I’m not sure what you mean by “backside”, Patrick. Normally that might refer to the far side that cannot be seen from Earth. It’s always the selenographic western limb of the Moon on which occultation immersions occur, and the eastern limb for emersions. That is using a standard similar to viewing a globe of the Earth with the prime meridian in the center. To add to the confusion, the modern selenographic western limb is the traditional astronomical eastern limb, i.e. the side to the left (toward your eastern horizon) when facing the Moon while it is transiting in the south. That is the direction toward which the Moon always appears to be plowing through the celestial sphere and stars as it orbits the Earth. More confusion comes from the fact that the Earth’s rotation makes it appear that the Moon is moving in the opposite direction.

[Paulie pchris00]

If I may throw some more confusion into the mix, from the southern hemisphere the modern eastern selenographic limb correlates to the traditional astronomical eastern limb, and the same goes for the western limb.

The Apollo astronauts screwed it all up. They were the ones who pushed to reverse what (northern hemisphere) astronomers had established as east and west on the Moon's Earth-facing hemisphere. I'm not even sure if they had a good reason...

[patrickm]

OK guys. Thanks.

Now explain it so a third grader can understand it! (and me!)

What I thought I saw on the software is this:

The Moon is plowing down toward the horizon and from SW toward S. The leading edge is a crescent. But even though the moon is apparently moving forward and down, stars (and a planet) behind it are being swallowed.

So this is my confusion, and I think Paulie's too originally. I would expect it to be catching up with stars instead of being caught. So thinking out loud, this means that the Earth (and thus the star) is spinning faster than the moon is rotating. However, if this is true, then it would seem that the moon would be moving in apparent retrograde motion, which it is not, at least compared to the horizon.

I also don't get how it could swallow objects from the trailing edge the first half of the month and the leading edge the second. I have thought about this with no successful conclusion for going on three days now and I keep getting stuck.

(argh)