Another Newbie Scope question:Truss DOB with EQ5 & Images?

[macg]

Hey guys,

I am very keen to buy a new scope soon and have been a little confused by options.

I have been looking at two 2nd hand scopes, a solid tube 200p on eq5 and an Orion 8 Proview on equivalent eq mount. Both look ok and are a reasonable discount. Though it is a little hard to find much info on the Orion.

I am interested in an eq mount for both education purposes, mostly my education, and for occasional photos. The dob for ease of use and movement.

So now the local store is offering a collapsible truss rod dob, Skywatcher 8, with dob base and eq5 mount packaged.

So my question is: Are there any reasons a truss rod dob would be any worse for the occasional photos i would like to take? ie movement/flex? Or the way it might sit on an eq mount?

Or would i be better to go with the second hand and sort out a dob base after?

All and any assistance is greatly appreciated.

Glen

[VigdisVZ]

Hi

A dobsonian mount is higly unsuitable for photography because it's an alt-az setup (introduces field rotation) and it's unmotorized. You can however take lunar pictures and the occasional try at planetary with a bit of effort.

The EQ-5 mount is underpowered to carry a 8" truss OTA for photography. You might be able to do it more easily with a stronger mount like the NEQ-6. Keep in mind that if you get the EQ-5 it must be the motorized version if you're going to stand any chance of getting any worthwhile images from it. I assume an EQ-5 could carry an 8" for visual without any problems but I do not have the load weights of the EQ-5 in my head.

In this case I would recommend either to go fully visual with the truss dob, it's a marvelous instrument. Or if you want to go imaging more look into getting atleast HEQ-5 mount and pick a cheaper refractor to start out with. Telescopes are by nature very specialized and there is no clear jack of all trades. However a photographic setup will still serve as a good visual instrument while a fully visual one is hard to press into service as a photo rig.

I heartily suggest taking a look Steve Richards book "Making Every Photon Count" if you're at all interested in astrophotograpy. It's an excellent beginners guide and explains in great detail what you need and why you need it.

[ronin]

The 200P on an EQ5 mount is really a visual setup.

Couple of weekends back at Sidmouth there were a few EQ5's used for imaging, people put something like the WO 71mm refractor on them, one person was using a 66mm WO refractor on an HEQ5. A little different to the 200P.

A truss OTA from a dobsonian would need tube rings and I am not sure you could sensibly fit tube rings around a truss OTA. Thinking that by the time they grip they will also have bent something.

No mention of anything called a motor? To image you need a couple of motors on the EQ5.

[macg]

Thanks guys.

I have checked out some photos using the 200p eq5 set up from people on this forum and they are pretty good i have to say.

I do understand that it not sufficient for trouble free long exposures, but at this stage to keep the initial outlay lower and work up to greater expense.

Ronin: The 2nd hand 200p eq5 has the dual axis motors, but no the other two do not have any motors. Regarding the tube rings, i wouldn't have a clue if they would fit a truss rod dob sensibly. I sort of imagine they mustn't harm the scope as the retailer would probably go broke from returns if they did.

Carl: Thanks for the recommendation for the book, I'll be getting it as soon as i can. I am pretty sure that the eq5 can take the 200p, from reading this forum only, not from my own experience. I get the impression it becomes problematic after the addition of camera, guide scope and a slight breeze.

[VigdisVZ]

Carl: Thanks for the recommendation for the book, I'll be getting it as soon as i can. I am pretty sure that the eq5 can take the 200p, from reading this forum only, not from my own experience. I get the impression it becomes problematic after the addition of camera, guide scope and a slight breeze.

Yeah you can work with the 200p on the EQ-5 (if you figure out how to mount it if it's the truss version). Just as long as you are aware of the limitations, go ahead. Be aware that most people want to upgrade at some point but then there is a used market on mounts like the EQ-5 so you should be safe.