Actual Magnification Celestron Astromaster 130EQ-MD

[mickopla]

I have a Celestron Astromaster 130EQ-MD and am a bit confused at what the actual Magnification limits of the scope. I have seen 217x and 350x in different reviews on the internet. From people in the know what is the max magnification i can expect and also what lens would i need to achieve this ??? Thanks guys

Mike

[NGC 1502]

Hi Mike. There's not a straightforward answer to your question. A lot depends

on what type of object you are viewing, how high above the horizon it is, how

steady the atmosphere is, and user prefererence (some like smaller and sharper,

rather than bigger and fuzzier)

However, here is my own take on what would work with your scope. At the low

end I would have a 32mm EP - 20x and 2.5 degree field of view, gives a large

exit pupil, but good for Pleiades/Beehive etc. At the high end a 5mm EP should

be ok most nights - a sharp Saturn at 130x is a wonderful sight. Many will say

you could go higher, but I'm a smaller/sharper is best viewer. One or two EPs

in between would be good too.

With my 10" Dob, most of the time I use 44x, 85x and 150x, and find this does

fine, occasionaly go to 200x for planets/double stars on a good night.

There are lots of opinions on this, but thats my take, hope it's at least of some

help, Ed.

[stardad]

I cant explain the magnification or how they get the figures. All I can explain is the practical application.

With the 10mm lense that comes with the scope Saturn is a very small pin head in the optic. Using a ultima barlow x2 its about the size of a pea that takes about a minute to move across the optic.

With a 12inch Dob its about the size of a sprout and last in the scope for several minutes before realining....

Clusters and such like are like dim clouds on the 130 and a 12in dob you can start to see that they are whirlpools or groups of stars.

If you imagine that your scope and eyepieces are a set of blinkers for a horse, the smaller the eye piece you fit in the narrower the feild of vision.

Hope that makes some sort of sense to you.

[NGC 1502]

Hi Mike & stardad. I should have included the following.

The Astromaster is a 130mm scope, with a focal length of 650mm.

Divide 650 by the focal length of the eyepiece to get the magnification.

So, 650/5 = 130x, 650/32 = 20x, etc.

To find how much actual sky will be visible, divide the apparent field of the EP

by the magnification. A 32mm plossl EP has an apparent field of about 50 degrees.

So 50/20 = 2.5 degrees of sky - enough to see all of the Pleiades.

To find the exit pupil ( the diameter of the column of light coming out of the EP)

divide the aperture of the scope by the magnification.

Using a 32mm EP with the Astromaster 130 gives 20x, 130/20 = 6.5mm exit pupil.

Too large an exit pupil can waste light if your eye pupil is smaller, can also give

a greyer sky background under our light polluted skies. But to me it's a shame not

to see all of the Pleiades etc if your scope can get to those low magnifications.

HTH, Ed.

[John]

With a 130mm scope you will find around 200x the maximum practical magnification. Higher figures are theoretical maximums only and won't be useful in practice.

I often find 150x - 180x the best magnification for Saturn and Jupiter in much larger scopes than yours - it's the atmospheric conditions that limit this.

Crisp, contrasty views are much more satisfying than large blurry ones !.

For deep sky objects low to medium magnifications (30x - 70x) are the most useful.

Your scope is primarily a light gathering tool rather than a magnifying one. Many DSO's are larger that you would expect, eg: M32 (the Andromeda galaxy) is, in total, nearly 4 degrees across, which is the same as 8 full moon diameters !.

So don't get hung up on max magnification, but rather go for a sharp and contrasty image.

[mickopla]

Cheers guys for all that great information. It would mostly be for planets that i would be looking for increased magnification. At the moment i have a 20mm, 12.5mm 10.0mm and 6.5mm and a 3x barlow which was cheap and is rubbish. In your opinion what would i get next ? Thanks Again

Mike

[NGC 1502]

Hi again Mike. You seem to have the fairly low and mid range covered,

as those give you 32.5x, 52x, 65x & 100x. Not sure of your budget.

One option is a good 2x barlow, but that would turn your 20mm into

a 10mm, your 12.5 into a 6.25, already covered by what you have.

So maybe a 5mm for 130x or if you think that's too conservative,

a 4mm for 163x. It's tough to know whats best for you until you

actually try it. One option before you spend your money is to contact

or join an astronomy club, many would be happy to let you try EPs in

your scope. The snag is of course getting a clear night that coincides

with a clubs observing session.

Some buy stuff to try, and then sell on if it doesn't meet their needs,

you need 50 posts to access the buy/sell section here on SGL. If you

do buy used, then you should be able to sell on at little loss, unlike

buying new and then selling.

Hope that helps a bit, Ed,

[mickopla]

Thanks NGC 1502 i think i will go for the 4mm and see how i get on and as you said i can always sell it on if i'm not happy with the results.