How much magnification can I do ?

[Cloengaa]

I have a SW Explorer 130m and it says that max magnification on it is 256x.

If I magnify 300x will that be doable or just be out of focus blurry ?

[RikM]

Unless you have nice dark skies and good seeing (stable air) I suspect your view will turn to mush at much above 150x in that scope.

I observe from the edge of a housing estate on the outskirts of Gloucester. LP is average but the heat rising from the roof tops messes things up a bit. mag 4.5 sky. I tend to get the sharpest view at about 1x per mm of apperture in all of my scopes:

120x in my Skymax 127

136x in my Phenix 127 refractor

150x in my 150P

240x in my 250PX Dob

[twotter]

To get up to x300 you're going to need ideal conditions and a target like the Moon. I can think of only one occasion in the last three years when I managed to go up to x375, observing Mars in January 2010.

Most nights I'm comfortable with the view at x100, with better nights allowing x133.

[brantuk]

I go for 200x-250x max in any scope - much more just isn't worth it cos the view deteriorates too much. It's quite comfortable around 150x or 180x on a good clear night

[Cloengaa]

Hehe Yeah I allready have problems when viewing Jupiter with a 10mm and x2 barlow. Really hard to get focus spot on.

Brantuk I can see you are using a SPC900, do you know how much magnification this cam gives without anything ?

[spaceboy]

I may be wrong but I think the 130m design performs better on larger objects in the night sky like open clusters and so high magnifications will not yield the best results. There are nights that I can barely get over x100 and my observing turns to the larger clusters that do not need much magnification but still make for an impressive session. As Rik said I would stick to a maximum of x150 and only then on nights of good seeing.

[spaceboy]

Hehe Yeah I allready have problems when viewing Jupiter with a 10mm and x2 barlow. Really hard to get focus spot on.

Brantuk I can see you are using a SPC900, do you know how much magnification this cam gives without anything ?

Equal to a 6mm EP in your scope

[JimStan]

At first it sounded like the old "XXXX Magnification" ploy. The advertising types ( we call them the "Madison Avenue Boys" here in the States), have always tried to push scopes on the unsuspecting public by filling the boxes with images taken from the Hubble and similar telescopes, and trying to make you believe that you could possibly see such images by peering through the eyepiece of the scope they just sold you. The sad reality is that unless the scope is attached to a really solid mount, has superior optics, and a good clock drive, it is quite likely that you will end up being very frustrated with it, and relegating it to a closet in short time! "Cheap dimestore telescopes" is the discription most often associated with those types of scopes.

But then, I found a link, showing this telescope here:

Sky-Watcher EXPLORER-130PM 130mm (5.1") f/650 Motorised Parabolic Newtonian Reflector

This certainly seems to be in a catagory above the 1st scopes I was think of.

A telescope with a 130mm main mirror, and a 650mm Focal Length is not going to give you all that much magnification, but it probably will offer some reasonably wide fields of view and useably bright images. This would make it ideal for viewing such things as open star clusters and the larger, brighter nebula.

If you want a scope that will provide reasonable scale on smaller objects such as galaxies and planets, you will probably have to go to an 8 inch F:10 design or larger. That would be 200mm objective with a 2000mm FL. Such a scope would give you a magnification of around 400X using a 5mm eyepiece. But other conditions such as "seeing" ( how turbulent is the air ? ) would often limit you to something less than that, fairly often. I find an eyepiece of 8mm to 15mm offering the most satisfactory views with my 2000mm FL telescope, with a 12 being the eypiece of choice almost all of the time.

[JimStan]

BTW, the formula for magnification is FL of the main objective ( mirror or lens ) divided by the FL of the eyepiece . Therefore, as stated in the post just above this one, a 2000mm FL telescope with a 5mm eyepiece would give you 400X magnification.

The way to figure out magnification using a camera at the prime focus is to consider what FL lens is used with the camera ( if it does, indeed use a lens ! ) and substitute that number in place of the eyepiece. A camera using a "normal" 50mm eyepiece would see the equivilent of 40X magnification if it were being attached to the prime focus of a 2000mm FL scope ! To achieve a larger image scale, the technique called "Eyepiece Projection" can be used. But we won't get into figuring out the magnification factor of that setup, since there are several other variables that enter into the equation!

Jim