[jman17]

Hi,


Sorry about the long post but I just have some questions about a SkyWatcher Black Diamond reflector (8inch aperture and 1000m focal length) that I am thinking of buying with a HEQ5 GOTO mount, if anyone can help me out. I want it for astrophotography mainly (with a Canon 450D now and maybe CCD in the future) and also visual use of mainly DSOs. I know that observing would not be ideal with a Newtonian on this equatorial mount due to the eyepiece position.


So far all I have used is a DSLR with telephoto lens on a star tracker and I am concerned about the difficulty of using a reflector like this with a 1000mm focal length. I am weighing up between this reflector and a SkyWatcher ED80. How much harder is the tracking of this reflector compared to an SkyWatcher ED80 with 600mm focal length, given that it is quite a bit faster? Would the shorter exposures needed for the same amount of light onto the camera sensor compared to the ED80 reduce this difference in difficulty quite a bit? What I am most interested in filming are DSOs, especially galaxies and nebulae (including the small ones) so I am leaning towards the reflector to get good scale on these targets, just don’t want to increase the difficulty too much as I am pretty inexperienced. How well would the ED80 perform on smaller galaxies and nebulae, would it do a good enough job or would I need more focal length for these targets? I know there are plenty of bigger DSOs, I just find the smaller ones something I really want to have the capacity to shoot too. Would using this reflector give too much magnification for many DSOs that are a little bigger to be imaged effectively?



If I want to use an automatic focuser, coma corrector/field flattener and CCD with filter wheel as well will this all fit without sagging or other problems on these scopes? How much could be put on scopes like these with no problems? Would differential flexure or front or back focus be a problem? I do want to use guiding so when using this reflector would the weight limit of the HEQ5 be an issue (if I balance well) once a guide scope and autoguider etc is attached? I am looking at a SkyWatcher guidescope that is around 2kg for a guide scope and this reflector weighs around 9kg. I know there is lighter ones with shorter focal length but read that I shouldn’t go too short for a longer focal length scope. Also, if I use a coma corrector with a focal reducer does this make the scope harder to collimate, given that fast Newtonians are very hard to collimate accurately?




Thanks for any advice that anyone can give me. I am open to recommendations of other scopes/mounts too.



jman17