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Centaur
2018-Jul-14, 04:55 PM
Mars will appear at a perihelic opposition from the Sun during the night of 2018 JUL 26-27. Greatest brilliance at magnitude -2.8 is expected on JUL 28, with closest approach to Earth on JUL 31. It will be nearly as bright and close as in 2003, which was its closest in more than 60,000 years.

My related graphics and more details can be found on my Mars webpage: https://www.CurtRenz.com/mars.html

Photos and descriptions of Mars during its current apparition would be welcome additions to this thread.

grapes
2018-Jul-14, 05:23 PM
Full internet cycle! We're back to "Mars as big as the moon"

Almost August!

https://www.space.com/33869-mars-size-of-moon-hoax-tonight.html

My nephew noticed it peeking through the trees last night, my first reaction was "it's back!"

chornedsnorkack
2018-Jul-15, 12:41 PM
Full internet cycle! We're back to "Mars as big as the moon"

Almost August!

https://www.space.com/33869-mars-size-of-moon-hoax-tonight.html
But it shall be literally true this time!
What shall be the angular distance from opposed (but not even penumbrally eclipsed) Mars to totally eclipsed Moon?
How shall the magnitude integrated over the totally eclipsed disc of Moon compare against the magnitude of fully lit Mars?

grapes
2018-Jul-19, 08:16 PM
But it shall be literally true this time!

You mean, you expect the brightness of the eclipsed full moon to be less than that of mars? Is that what you mean by literally? :)



What shall be the angular distance from opposed (but not even penumbrally eclipsed) Mars to totally eclipsed Moon?
How shall the magnitude integrated over the totally eclipsed disc of Moon compare against the magnitude of fully lit Mars?

Hornblower
2018-Jul-19, 09:16 PM
I have seen the eclipsed Moon get much fainter than what Mars is right now. The extremely dark eclipse of December 30, 1963 was around magnitude +4 and invisible to the unaided eye. The one 19 years to the day later came close.

Spacedude
2018-Jul-19, 09:29 PM
Every few years I have to set my sister straight on this issue and remind her that Mars will not appear as visibly large as the moon in the sky, and that if it were that she might feel it without having to see it.

grapes
2018-Jul-20, 09:41 AM
Every few years I have to set my sister straight on this issue and remind her that Mars will not appear as visibly large as the moon in the sky, and that if it were that she might feel it without having to see it.
The "original" email somehow left off the "through a telescope" explanatory phrase.

But what do you mean by feel it?

KaiYeves
2018-Jul-20, 11:26 AM
The "original" email somehow left off the "through a telescope" explanatory phrase.

But what do you mean by feel it?

If Mars appeared that big from Earth, it would mean it was extremely close to us and would affect us gravitationally.

We can see it in the south from our dig house, it looks very bright. Sadly we don't really have much time for stargazing any night besides Saturday because every day except Sunday we have to wake up at 5:30.

Spacedude
2018-Jul-20, 11:52 AM
If Mars appeared that big from Earth, it would mean it was extremely close to us and would affect us gravitationally

Yes, that's what I meant.
Anyone here up to task of calculating the distance Mars would need to be from Earth to appear as the same size as the moon?

profloater
2018-Jul-20, 12:04 PM
Yes, that's what I meant.
Anyone here up to task of calculating the distance Mars would need to be from Earth to appear as the same size as the moon?
loosely speaking twice the distance; based on diameter 6794 and 3475 km.

Spacedude
2018-Jul-20, 02:36 PM
Thx Profloater, that's a bit closer than I may have guessed but it makes sense. So Mars at ~1/2 million miles distant would seem to be pretty darn close, close enough to at least influence some tidal pressures on the Earth similar to the moon's effects? Or possibly even influence the moon too if the moon were in-between the 2 planets.

grapes
2018-Jul-20, 05:28 PM
Thx Profloater, that's a bit closer than I may have guessed but it makes sense. So Mars at ~1/2 million miles distant would seem to be pretty darn close, close enough to at least influence some tidal pressures on the Earth similar to the moon's effects? Or possibly even influence the moon too if the moon were in-between the 2 planets.
For objects with similar densities, their gravitational effect is proportional to their arc area in the sky (so the sun has half the tidal effect of the moon because it has half the density of the moon).

chornedsnorkack
2018-Jul-20, 05:29 PM
Mars is 20 % denser than Moon.
Therefore, if Mars had the same angular size, it would cause 20 % higher tides.

However, Mars being brighter than Moon is not really common. Perihelion oppositions recur once in 15 or so years, and total lunar eclipses rarely coincide with them.

megrfl
2018-Jul-20, 09:54 PM
We've been enjoying Mars for the last two nights starting around 1:30am. An orange tinged star to the naked eye.

chornedsnorkack
2018-Jul-27, 11:44 PM
As could be feared, a lot of air masses for Mars. At the end of complete eclipse, I could fit three fingers of outstretched hand between Moon and Mars, two between Mars and horizon.

Trebuchet
2018-Jul-28, 01:58 PM
I've not seen it yet at all. It's quite low in the sky from here and our view to the south is obstructed. I actually got up at about 3:00 AM to look but, alas, a cloud had rolled in. There's not been a cloud in our sky for a couple of weeks.

Hornblower
2018-Jul-28, 03:06 PM
I saw the Moon and Mars near midnight last night. It really showed how far south of the ecliptic Mars is right now, as the Moon had just emerged from an eclipse a few hours earlier. Southern hemisphere observers definitely have an advantage.

grapes
2018-Jul-28, 04:18 PM
I saw the Moon and Mars near midnight last night. It really showed how far south of the ecliptic Mars is right now, as the Moon had just emerged from an eclipse a few hours earlier. Southern hemisphere observers definitely have an advantage.
Good point. Since the sun is high in the northern summer sky, the ecliptic dips low in the night sky. Mars' orbit is inclined less than two degrees from the ecliptic but its farther away, its declination would have been -25, the moon's only -19.

George
2018-Jul-28, 06:07 PM
I saw the Moon and Mars near midnight last night. It really showed how far south of the ecliptic Mars is right now, as the Moon had just emerged from an eclipse a few hours earlier. Southern hemisphere observers definitely have an advantage.
That's interesting. I didn't think Mars wandered so far. It looks to be about 6-2/3o max in a couple days, swinging across the ecliptic not until January.

Trebuchet
2018-Jul-29, 01:15 AM
I don't think it's so much that Mars is below the ecliptic, but that the ecliptic is low in the Northern sky at this time of year due to the tilt of the earth.

Centaur
2018-Jul-29, 03:20 AM
I don't think it's so much that Mars is below the ecliptic, but that the ecliptic is low in the Northern sky at this time of year due to the tilt of the earth.

It's both, although as you note the time of year is the greater factor. The anti-solar point is currently at declination S 19.77. Even though the inclination of Mars' orbital plane from the ecliptic is only 1.85, Mars is currently at ecliptical latitude S 6.52, i.e. 6.52 in ecliptical latitude south of the anit-solar point. The increase is due to the current closeness between Mars and Earth. Mars' maximum heliocentric ecliptical latitude of 1.85 is relative to the Sun, not Earth. Mars' current declination is S 25.67, which is 5.90 in declination south of the anti-solar point.

chornedsnorkack
2018-Jul-29, 08:02 AM
A dim red spot low on the red background (of sky above city lights) could be seen with effort. Not with naked eye - with glasses.
Moon was also a dim red patch on red background, but it was higher and bigger.

grapes
2018-Jul-29, 07:58 PM
A dim red spot low on the red background (of sky above city lights) could be seen with effort. Not with naked eye - with glasses.

What? Mars is -3 magnitude! so sorry ...


Moon was also a dim red patch on red background, but it was higher and bigger.

Centaur
2018-Jul-29, 08:41 PM
A dim red spot low on the red background (of sky above city lights) could be seen with effort. Not with naked eye - with glasses.
Moon was also a dim red patch on red background, but it was higher and bigger.
'
That wasn't the Moon. That was Mars appearing as big as the Moon. Didn't you get this year's email notification? ;)

George
2018-Jul-30, 01:57 PM
It's both, although as you note the time of year is the greater factor. The anti-solar point is currently at declination S 19.77. Even though the inclination of Mars' orbital plane from the ecliptic is only 1.85, Mars is currently at ecliptical latitude S 6.52, i.e. 6.52 in ecliptical latitude south of the anit-solar point. The increase is due to the current closeness between Mars and Earth. Mars' maximum heliocentric ecliptical latitude of 1.85 is relative to the Sun, not Earth. Mars' current declination is S 25.67, which is 5.90 in declination south of the anti-solar point.

Yep...

23469

The distances are scaled.

I did look at Mars last night through my old, dusty 16" Dob. Seeing was poor and only a murky orange disk was observed, no ice cap.