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Guys!
How about a little respect for the OP? He came on here asking about possible upgrades from a 130mm newt with a budget of $2000 and here we are arguing about the optical merits of LX 200's and SDM's.
There are lots of different scopes out there and each has its merits, drawbacks, strengths, weaknesses etc. And it is human nature once we have made a choice (especially if it involves large quantities of cash) to defend that choice vigorously. That applies to scopes, footy teams, cars, spouses etc.
So I suggest we all calm down, have a read of our previous posts and think to ourselves are we actually helping Richard? What he needs are some idea to spend his $2k and what the strengths and weaknesses of the various options are.
Here is a quick summary of my views.
8" Go To SCT
Strengths
Small portable scope
Usually good go to performance
OTA can be deforked and attached to a EQ mount for imaging if required
Eyepiece is always at a comfortable height for viewing
Long focal length makes high power observing easy
Weaknesses
Relatively high cost per inch of aperture so less $$ left to accesorise
Corrector plate is susceptible to dew (but this as with most dew problems can be solved with dew shields or heaters!)
Longer cool down time that open tube models
Relies on electronics, motors etc. which may fail from time to time necessitating repairs
Long focal length can mean that for the same EP, the view is degraded compared to a shorter scope.
8" or 10" dob
Strengths
Low cost per inch of aperture so $$ are available to spend on accessories or to get a Go To version
Smaller dobs are still compact instruments
Solid tube dobs can be used on an EQ mount if desired.
Primary mirror is not usually susceptible to dewing especially in solid tube models. (as an aside here, I have used both solid and truss tube dobs and only once had a dew issue on my primary and that was on the solid tube 12", and I never use the fan while observing, only while cooling!)
Non go to dobs have simple mechanics and even the go to versions can still be used in manual mode if electronics or motors break down or fail
Non goto dobs are easy to upgrade to push to systems such as Argo Navis
Collimation is an easy thing to learn and fairly painless in small dobs
A non go to dob is a great way to learn your way around the sky
Eyepiece height is usually at a comfortable position and can be used which seated if chair has adjustable height
Optically robust system that can give wonderful views
Weaknesses
Larger dobs can be quite large and heavy
Go to performance in some go to dobs has been less than stellar I have heard and as with all go to scopes there are electronics and motors that may breakdown or fail then requiring repair
Non go to dobs require charts and star hopping which is not everyones cup of tea
Require collimation on regular basis
Secondary, finder and eyepieces can be susceptible to dew ( but this as with most dew problems can be solved with dew shields or heaters!)
Eyepiece height can be uncomfortable at low elevations and in larger dobs (eg 16" plus) may need a stepladder.
Many cheaper dobs come with chipboard mounts that are susceptible to damage and moisture (although my old 12" GSO survived several years with no issues)
Shorter focal length means best views are at low to medium power. I found with my 12" f5 that I rarely pushed it much beyond 115X, but then I rarely needed to!
This list obviously is based on my experience and knowledge and there are MANY others with more of both. Note I have not mentioned collimation in regard to an SCT as I have no experience of how often it is needed or how easy it is. Also my comments on optical performance is not based on a rigorous analysis, only on what I have found but in relation to SCTs is based on a very limited sample that I have looked through at star parties.
Also I have tried to keep the points relevant to smaller apertures, although I have mentioned larger dobs in a couple of places for clarity. IMHO in larger apertures is where dobs really come into their own but the OP is budget limited.
Malcolm
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