10" SCT versus 12" Newtonian - what are the differences?

[naskies (Dave)]

Hi everyone,

I was just wondering if anyone could explain what differences there would be between say a 10" f/10 SCT (e.g. Meade LX200) and 12" f/4 imaging Newtonian (e.g. GSO) for planetary imaging and visual observing on an EQ6 mount?

(If it helps... I currently have a 132 mm apo refractor.)

Thanks!


Dave

[rider]

12' newt:

plus:
significantly more light coming in.
its lighter than an equiv. SCT for size.
much easier to collimate.

minus:
Wind effected of long tube
focusser can end up at some weird angles if you don't pre-rotate the tube for the object.

The SCT has a longer focal length.


I've had an SCT and Ive currently got a f4.9 12 inch newt which is IMHO a clear winner for visual work, but if you think you will spend a lot of time taking happy snaps, I'd probably go for the SCT.

BTW the HEQ6pro handles either of them with no probs, but you will need an counterweight bar extention if you dont want about 5 weights on the bar.

[Alchemy (Clive)]

The 12 inch should give more detail in both cases, Smaller secondary, plus larger mirror should win over ( assuming mirror quality average here).

10 inch scope more compact and maneuverable,

For planetary and visual, id go the 12 inch, if I was doing deep sky, it's going to depend on the tube and focuser of the newt..... But thats not a consideration here.

For planetary just bolt on a powermate, and for visual varying eyepieces will give all you need.

[icytailmark (Mark)]

the sct has more focal length which is better suited for planet imaging. However newts gather slightly more light. There isnt a huge difference tho. I have used a 12" Dob and now i have a 14" sct and there isnt a huge difference in terms of visual.

[Poita (Peter)]

I find SCTs just as easy, or easier to collimate than a Newtonian. I've also found planetary better in the SCT as well, probably due to the longer focal length though. SCT is also more compact and doesn't get diffraction spikes on stars, though some like that look.

For DSO work, some SCTs allow you to use a hyperstar attachment and image at F1.9 which is a real benefit. Otherwise the newt has the advantage in being cheaper and some of the other advantages listed here already.

[Paul Haese]

As you might imagine I am a big advocate for the SCT for planetary imaging. However, you cannot compare the 12" Newtonian with the 10" SCT. The light gathering power of the 12" will have benefits to planetary imaging over the 10" in this particular case. If you compared it to a 12" SCT then I would say the 12" SCT. The SCT has planetary viewing and imaging as its main strength.

The bottom line is though; the larger the diameter the better for planetary imaging. If your only choice is a 12' Newtonian or a 10" SCT then the Newtonian should be your first choice. If you can buy a larger SCT of the same aperture I would go with the SCT. Every thing is budget related.

[naskies (Dave)]

Thanks guys - very helpful tips.

I already have a 5x PowerMate, so I think the 12" Newt is the go for me.

I'm aware that it's not really a "fair" comparison, but given a limited budget it's what I have to consider.

[Poita (Peter)]

My experience is extremely limited, but I have been playing with a 14" SCT and an 8" and a 10" SCT over the past few weeks.

One thing is, that for imaging the planets, seeing appears to be everything.
If your seeing is pretty average, the planets can actually come out worse in the 14" vs the 8".
I'm not sure why this would be, but when the seeing gets close to perfect, the bigger scope smokes the smaller ones, but in average to poor seeing there doesn't seem to be a lot of advantage to a C14 vs a C8.

[Gem (Grant)]

I can compare a 10" reflector (solid tube) to a 9.25" SCT...

The SCT is much easier to transport, move around, store, etc...
Visually there isn't a big difference. I had my 10" in the country and I have my SCT in town, so it is hard to give a very accurate comparison.
The SCT takes much longer to cool!!

I prefer my SCT, but if I had a permanent site I would probably have a huge reflector. But in terms of moving around, I take the SCT.

I know its not the size you were asking, but it might help...

[Satchmo]

I would never advocate a 40% obstructed instrument at the secondary baffle , like an SCT for viewing low contrast planetary detail in real time. If you are imaging via frame stacking the difference won't be so great to a Newtonian- cooling and seeing are probably bigger factors.