Mirrors and lenses

[Ganymede12]

Would a 150mm diameter Objective lens in a Newtonian give the same view as a 150mm diameter objective lens in a refractor?

[Ags]

No. The Newt has a central obstruction that will reduce contrast to a certain extent. The newt also has coma that reduces sharpness away from the middle of the FOV.

The refractor will have chromatic aberations that are expensive to control - a 150mm apochromatic refractor costs as much as a new car! The 150mm newt, even a luxury one, costs a tenth or less than that.

Finally the 150mm newt is light enough to be a grab and go. The 150mm refractor probably lives in an observatory. Unless it is an StarTravel 150 - still big but small in comparison to some - but it has the worst chromatic aberation of any telescope, bar none!

[Moonshane]

I agree with Ags to some extent. The answer depends on focal length / ratio. I have a 6" f11 newtonian and a 6" f5 newtonian. In principle the views should be the same if one used eyepieces to get to the same magnification. This however is not the case with my scopes. the f11 provides far better planetary and lunar views at the same magnifications. the reason for this is the smaller secondary in the f11 due to the focal length.

DSOs are about the same and the stars are possibly slightly sharper across the field on the f11; double stars are more defined too with the f11.

there is no chromatic aberration with newtonians other than that from the eyepieces.

I agree with Ags comments on the refractor. personally, I would have a newt at 6" over a refractor at 6" any day.