Planets Relative Sizes

[supernova1965]

I wondered if someone could post an image that shows how mars would look in size compared to Jupiter and the other planets. I am sure that I had mars in my scope using 25mm and a 9mm and it was quite small and I couldn't see any detail what was I doing wrong if anything? If I had a reference picture showing relative sizes through a scope I could keep trying if I wasn't getting the same results. I have found Telescope Calculator so that should solve my comparison problems but if anyone can tell me if iam doing anything wrong as I only just saw mars a disc. I am happy to have this thread removed if desired if there is no advise as to what I am doing wrong. :thanx:

[Paddy]

Can't post an image, but that sounds about right to me for Mars.

[Robh]

Try the NASA Solar System Simulator ...
http://space.jpl.nasa.gov/

You can get a comparison of the planets by restricting the field of view to say 0.2 degrees.
Also handy for moon positions.

Regards, Rob

[Rod66]

Well actually this is my favourite picture to compare sizes. I printed this and hung it on my son's wall when he was 7 years old.

http://onlyfunnyjokes.com/bestoftheweb/wp-uploads/earth_planets_size_comparison.jpg

And this is a good one for star comparisons.
http://www.funmint.com/images/planets/planet-size-comparison-sun-sirius-arcturus.jpg

I know that you're looking for relative sizes in a scope, but thought this may be of interest.

cheers

Rod

[StarGazing]

Nice thread guys ....... going to show the kids this afternoon.
Cheers Alex.

[pirate of skies]

Rod 66,
I love that pic of the planet comparisons.
Its really amazing to see the immense size of the sun compared to earth.
I read in a book by Paul Davies today, that the Black holes at the middle of the milky way galaxy is 1 million times the size of our sun.
Point to note, is there are more Black holes that are 1000 times that size again.
Mind boggling isnt it ?

[Paddy]

Mind boggling indeed, even more so since they are 1 million - 1 billion times the mass of the sun, but have no size at all. A black hole is a mathematical point as far as I understand.

[solissydney]

Type the heading in your web browser, and there you are

[toryglen-boy]

i think the o/p was looking for comparative sizes through an eyepiece

:)

[Robh]

In General Relativity, a black hole can be thought of as a massive singularity.
However, the physical size of the black hole is measured as the radius of the event horizon, the point of no return for matter and electromagnetic energy. Also known as the Schwarzschild radius. If the Sun were a black hole, its radius would be about 3 km.

Regards, Rob.

[supernova1965]

That's OK I am enjoying where this thread is going its an interesting discussion

[toryglen-boy]

i hear you, but i am quite interested in an answer to your original question !!

:lol:

[Robh]

Duncan,
I gave a solution to it in my first post (3).
However, you just can't put the planets side by side. Unless you want to open several windows at once!
Because the planets vary in distance, their relative sizes continually change.

Regards, Rob

[astro744]

Just look at the angular sizes of each planet and that will give you a difference in size in any telescope.

Currently Jupiter is just over 44 arcsec and Mars is less than 7.

Therefore Mars will appear about 6 times smaller than Jupiter in any telescope at the moment using the same magnification on each object.
Mars is tiny and serious visual observation is difficult under 10 arcsec.

Because of the highly elliptical orbit of Mars, its size varies with each opposition over about a 17-18 year cycle. The largest Mars is 25 arcsec and the smallest about 13 arcsec. The 2010 opposition will be 14.1 and the 2012 opposition will be 13.89 and go back up to 24.31 in 2018.

Also good news for us in the Southern hemisphere is that our closest oppositions are always south of the celestial equator (high in the sky) and the farthest are north of the equator (lowest in the sky).

Therefore to answer your question (without knowing what telescope you have); Yes, Mars is very small at the moment and a 25mm or even 9mm eyepiece in most telescope will show a very tiny disk.

The 2010 opposition of Mars is January 29 and the disk will slowly get bigger between now and opposition date.

[supernova1965]

That' great news it means I have stuff to look forward to :thumbsup: made my day I thought that that was as good as it got. I must admit I was disappointed because it was so small that any detail was not possible to see. So does this mean we are on an increase in apparent size for a while?:thanx:

[astro744]

Yes Mars will increase to 14 arcsec this opposition and larger again in 2012 until 2018 after which it will get smaller again for 2020. I did a web search for Oppositions of Mars and the found the following link:

http://seds.org/~spider/spider/Mars/marsopps.html

The 2003 opposition was hyped up as being the closest approach for some 25,000 years but you'd be hard pressed to spot the difference in 2018, 2035, 2050.

Any opposition over 15 arc seconds is good with those over 20 very good to excellent. The higher position in the southern sky at closest opposition is a bonus. Note even at 25 arc sec, Mars is half the size of Jupiter at its closest.

However, Mars is appealing to many because of its solid surface, dark features, dust storms and polar caps that can be cleary seen to change size over time (weeks to months). Filters can really help with Mars and if you only buy one get a #21 (Orange).

Enjoy!

[OneOfOne]

Do you mean this?

[supernova1965]

That looks very helpful thanks heaps:2thumbs::2thumbs:

[Starkler]

Cartes du Ciel tells you the angular size of planets at any point in time, which is what you wanted to know I believe.

[firstlight]

You can always look in the current Astronomy 2009 yearbook. They have the relative apparent size of the planets for each month. Lots of other good info as well.

[supernova1965]

AGHHHHHHHHHHHHHHHHHHHHHHHHHH its sold out :sadeyes:

[firstlight]

At the risk of breach of copyright... (Sorry Glenn, Ken and Peter)
65265

[supernova1965]

Thank you very much:thumbsup:

[astro744]

MICA from Willmann Bell is also very good for tabular data. Have a look at http://www.willbell.com/almanacs/almanac_mica.htm

[firstlight]

No problem. Cannot speak high enough about this particular publication... no amateur should be without a copy, no matter how advanced.

[mithrandir]

Along the roads leading to Siding Spring are a set of planet billboards at 1/38000000 scale distances. They have models of the planets on them and some history. I have a set of photos I took on Saturday, except Pluto which I couldn't find at either Dubbo or Tamworth. But then it isn't a planet anymore.

Yell if you want a copy.