Dobsonians do not make good astrophotography scopes because they are mounted in alt-azimuth (altaz), which means that any exposure over a minute or two will begin to show field rotation.  That's why a good equatorial mounted scope or fork mounted scope on a wedge is essential for photography.  Even so, most dobsonians are not motorized anyway, meaning you couldn't track the objects.

However, if you took the same newtonian reflector and mounted it on an EQ mount (expensive for big aperture scopes) or a Poncet/Equatorial Platform (again, very expensive for good ones), you could have a pretty good AP platform due to the fact that such newts are very fast. But there are problems with this.

One problem is that the field would show too much curvature to obtain sharp stars at the edges of your exposures. Good photographic scopes have flat fields.  In fact, this makes the SCT less desirable as a photographic scope as well.  The flatest fields comes from refractors and dedicated astrographs.  However, a Televue Parrcorr (coma corrector) could be used with the scope to flatten the field with newts.

Another problem with a newt is that the focal point of the scope tends to fall too short of a camera's film plane.  In other words, there is not enough back focus in some newts.  Then again, a coma corrector would probably correct this problem as well, though I'm not personally experienced with this type of setup.

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