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Aperture: Do 13-16 more mm make a difference?

Started by Lee_S, 01/14/2006 04:42PM
Posted 01/14/2006 04:42PM Opening Post
I really appreciate everyone's feedback on my reflector questions. smile Here's my next one, how much more can I see by going for a 127 or 130mm scope versus a 114mm scope of moderate focal length say F/8 or so? 8O

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I have several telescopes, but none are semi-APO, APO, or in anyway valuable.
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Posted 01/14/2006 07:44PM #1
Not much improvement. With differences that small, it's best to go with the best quality scope on the best mount. Small changes in aperture like that rarely make much difference that you will notice.
Posted 01/15/2006 04:34AM #2
>>>I really appreciate everyone's feedback on my reflector questions. Here's my next one, how much more can I see by going for a 127 or 130mm scope versus a 114mm scope of moderate focal length say F/8 or so?
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This is a somewhat complicated issue. As Roger says, go with the better equipment. There are several factors to address here though.

IN general 114 mm F8 Newtonians use spherical mirrors rather than Parabolic. At this focal length it is acceptable, not ideal but it is the standard.

The standard 130mm F7 Orion SpaceProbe 130 also has a spherical mirror but a heavier mount. This is pushing the spherical mirror thing IMHO.

The 130mm SpaceProbeST has a 130mm F5 Parabolic mirror and in my experience does a nice job but one can buy and XT-6 with a 6 inch F8 Parabolic mirror on a solid DOB mount for about the same money and it will definitely out perform any of thesemaller scopes.

So... Looking a small reflectors (and I have owned/still own a few, this is my thinking:

1. GOTO can be nice but you are trading optics and aperture for electronics, not a good trade IMHO.

2. In general, small reflectors in the 114mm -130mm class are undermounted, they are quite shaky which makes focusing getting a solid view somewhat difficult.

Often the reason behind purchasing an EQ mount is "so I can do Astrophotography later" but none of these mounts are stable enough for astrophotography.

3. I think the best bet for an astronomer on a budget is a 6 inch F8 DOB. New these are around $250 and used somewhere between $150 and $200.

A 6 inch DOB is on a solid mount that will not shake at the slightest touch, is easy to use and setup, has nice optics and enough aperture to keep some entranced for a long time to come.

It is a simple scope but a scope suitable for a serious observer, it doesn't pretend to be anything it isn't, it just does what it needs to do, you do the rest. Pretty hard to beat.

Jon