5 replies to this topic

[BenBroad]

After some frustrations with my meade DS-2909 & Celestoron 10” (made too small and not very great aligning..) and Celestron just too big and hard to fine aim) Is there much of a difference in what can be seen between the Nexstar 6” and the 8”, I’m half tempted to go for the 8” but it is a big price difference.

[dogfish]

Hi Ben

Having owned both (or at least the OTA's), I can say that there is a difference in what you can see, although it varies somewhat. I have been able to make direct head-to-head comparisons on objects such as M13 (noticable improvement in the 8"), M31 (couldn't see much of a difference), M51 (slight improvement in the 8"). M42 (couldn't see much of a difference).

Whilst it looks like the difference is slight, it really depends on you and your personality how much this might bother you. Astronomers, when they've been doing this hobby for a bit, start trying to get any improvement they can out of their viewing instruments, even though this might be costly. You may well find that you're tempted to kick yourself later if you don't go for the bigger scope, but it might also be the case that if you get the 8" you find yourself hankering after more aperture a bit further down the road. One thing I would say is that the difference between decent dark skies compared to moderately light polluted suburbia is more pronounced than the difference in 2" of aperture. So think about what you can physically (be bothered to) transport.

There has been some concern about the stability of the 8SE on the single arm mount, but I've not heard a really convincing opinion on this one way or the other. My C8 is mounted on the CG5-GT mount, and that's solid. Also remember that if you have ambitions for astrophotography, at some point in the future you'll need an equatorial mount.

Hope that helps, Martin

[BenBroad]

Thanks for the good tips Martin,

After considering it I'll got for the 6" its something I could afford right away. Of course could just change my mind when I'm ordering it...

[centroid]

The all important light gathering power of one telescope aperture against another, is calculated by the ratio of the square of their apertures.

Therefore, 6 squared = 36, and 8 squared = 64, so 64/36 = 1.777.

Therefore, the 8" scope has a theoretical light gathering advantage of 1.8 times that of the 6".

In round figures, the 8" has almost twice the light gathering power of the 6", which is a very useful gain.

Hope this helps.

Dave

[mdstuart]

Whilst I agree with the Maths I do have to say going from a 6 to 10 inch whilst an impovement it was not as dramatic as the maths woudl suggest.

Whilst the 8 might get 1.8 times as much light it does not make everything twice as bright. So a very faint galaxy in the 6 inch might only be a faint galaxy in the 8 inch etc.

To be honest even if you get the 8 inch you will then want a 10 inch one anyway...

Mark

[steve_bham]

If you do got for the 6" now and  want a 8" later down the road you can always sell the 6" OTA and mount the 8" on the arm. I think no matter what scope you want you will always hanker for the next size up!

I personally think the 6" is a really portable scope, its the one im going to go for