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What EQ GoTo mount for my 8" newt

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#1 nexguy

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Posted 13 February 2011 - 10:13 PM

I have an 8" Zhumell dob. I would like to switch to an EQ mount and try some imaging.

The OTA is about 29 lbs. What mount would you recommend? I saw the Atlas and Sirius, but not sure if I need the Atlas since the Sirius says it can handle 30lb (and ppl say it can handle more). Others? iOptron SmartStar-PR?

I appreciate any advice.
Chris

#2 Eddgie

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Posted 13 February 2011 - 10:25 PM

I am going to go out on a limb and say that I think an Atlas class mount would be strained to hold an 8" Newt for imagaing.

By the time you add rings and a dovetail, the weight will be 34 lbs.

Put a camera on it, and you are adding more weight.

And it isn't just the weight itself, it is how the weight is distributed and the amount of area of the tube.

If the weight is distributed over a long tube (refractor or Newtonian), it makes far more demands on the rigidity of the mount than say a small refractor or SCT/MCT. These short tubes don't start vibtating as easy as long tubes, and they dampen much faster.

The area of the big Newtonian telescope is like a big sail. Even a slight breeze will induce oscillations.

Others may say differently, but even for visual use, the I think that an 8" Newtonian is pushing it on an Atlas. But for visual, the observer can tolerate some shaking.

For imaging though, I think you would be pushing it.

I would recommend a CGE or G11 as a better choice.

#3 nexguy

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Posted 13 February 2011 - 11:57 PM

I wanted to mention that it's an F/5.9 1200mm 8" Zhumell. I've read that these mounts can easily hold that..(but I have yet to see an image of the scope, or an astro image from the setup) and that the Atlas could hold over 50lbs without issue.

#4 jmasin

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Posted 14 February 2011 - 12:19 AM

I can comment for sure on an Atlas.

I mounted Orion's 8" F4.9 on there. In the early days of trying to image with a DSLR it was ok.

As my setup grew and approached 30 lbs (CCD, filterwheel, guidescope etc) the Atlas began to struggle a bit. Some days things were perfect, others I threw out half my subs... I spent a lot of time debugging.

The Atlas can handle 30 lbs for imaging, but you will be doing some debugging and you will lose some subs...

If your scope is starting at 30, then you'll be up above that with imaging hardware, I don't recommend an Atlas.

#5 Doug76

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Posted 14 February 2011 - 02:12 AM

I have an 8" Zhumell dob. I would like to switch to an EQ mount and try some imaging.

The OTA is about 29 lbs. What mount would you recommend? I saw the Atlas and Sirius, but not sure if I need the Atlas since the Sirius says it can handle 30lb (and ppl say it can handle more). Others? iOptron SmartStar-PR?

I appreciate any advice.
Chris


An 8" Dob OTA 29lbs? I don't think so. 29lbs is more in the neighborhood of a 10" OTA.

An 8" f/4 goes about 16lbs.
An 8" f/5 goes about 17lbs.
Keeping with that progression, your Dob tube should be no more than 18lbs.
At that weight even a CG-5 will carry it, but the length of the tube will give it trouble. But an Atlas, no trouble at all.
And if you are going to image, you need a mount capable of about twice the weight the scope it carries weighs. The Atlas covers that, but not the Sirius or CG-5.

#6 alpal

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Posted 14 February 2011 - 02:58 AM

I am about to connect up an 8" Newt soon after getting
some results finally with a little 4.5" Newt.
see here:

http://www.cloudynig...5/o/all/fpart/4

#7 EricJD

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Posted 14 February 2011 - 10:17 AM

I've been imaging with an AT8IN on my Atlas for a while now. On top of it is an Orion 80ED for guiding. Recently I upgraded to a Parsec 8300M camera and 2" automatic filter wheel. I am set up in a permanent observatory on a pier, so I imagine that helps. I've been doing 10 minute exposures with no bad subs.

If you're talking 1200mm focal length and on a tripod I can see where you might have some issues because I believe I'm at the limit of what the Atlas can handle.

#8 RAKing

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Posted 14 February 2011 - 12:05 PM

My 8 inch, f/5.9 (1200mm fl) Newt weighs 27 pounds RTG with rings and Losmandy dovetail. I could easily see this on an Atlas for visual use, but unless you upgrade the tripod I don't think it will be as good for imaging.

Personally, I suggest you get a faster Newt, such as one of the f/4 Imaging Newts, if you want to do some imaging. These would easily work on an Atlas, possibly even the Sirius.

Save your long Newt for visual work.

Cheers,

Ron

#9 Bowmoreman

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Posted 14 February 2011 - 12:53 PM

Lets keep in mind that OP has the 8" f5.9 OTA, a far far different beastie than the 8" f4.0 Newts out there...

for starters f4 newts are far more forgiving imaging wise due to much shorter focal lengths AND shorter exposure for same amount of photons (faster f ratio)...

8" f5.9 would need at LEAST an Atlas IMHO... and it'd be frustrating... especially STARTING out imaging...

starting out imaging, you really are hard pressed to beat shorter, faster scopes...

you want focal lengths 800mm or less, and f5 or faster (if possible)...

short refractors (80mm f6ish or faster) are also good...

Others have mentioned the tradeoffs/issues...

#10 avarakin

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Posted 14 February 2011 - 08:42 PM

Chris,

It is not possible to get "jack of all trades" telescope, the best is to have at least 2 setups. I currently have 10" dob for visual and 5" F5 reflector on LXD75 for imaging. So far this combination works very well: when I go to dark site, I can setup my imaging rig and it will be shooting the object I want and at the same time I will be doing visual with the dob. Small reflector like AT6IN + LXD75 + MPCC will be around $1000, still far less than Atlas or Sirius. Once you grow out of your small imaging setup, then you can get Atlas for imaging and keep LXD75 for visual with your 8" dob OTA

Alex

#11 gnowellsct

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Posted 14 February 2011 - 08:50 PM

accept no substitutes

(it's a 10" f/6)

#12 Kellogg

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Posted 15 February 2011 - 09:49 AM

I've recently put an 8" skywatcher newtonian (former dobsonian) on an EQ6 Pro (Atlas) mount and it seems good to me.

Initial attempts at astrophotography seem good, but this is new to me so its a learning curve.

I dont see the point in buying one setup just to learn on then sell it to buy something to handle the scope you want to image with. This way you'll end up paying far more to get to the same point.

#13 avarakin

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Posted 15 February 2011 - 10:26 AM

Forgot to mention - the dob may not come to the focus with DSLR because it was not designed for AP. I suggest to do a quick test and then decide what to do.

Alex

#14 nexguy

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Posted 15 February 2011 - 11:24 PM

Ok, obviously I am not going to be able to *reuse* my 8" 1200mm reflector for imaging. I was willing to shell out around $1400 for the Atlas mount so...

What complete imaging setup could I get for around $1000 to $1400? Keep in mind that I already have a unmodified Canon 1000D. Some sort of setup with parts I could reuse when(if) I decide that I like it and want to upgrade.

I really appreciate the advice!

#15 Kellogg

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Posted 16 February 2011 - 09:14 AM

I wouldn't write off the scope just yet. I thought I might have to get a new focuser for my SkyWatcher 8" when I moved it from the Dobsonian base to the EQ mount to start imaging, but found with a Barlow I could reach focus easily enough. Then to get around having to use the Barlow lens (which is not ideal) I just moved the mirror up the tube a fraction using some 6mm bolts and washers from a hardware store. It saved me ~$150 or more on a focuser and works great.

If you have any questions let me know.

Ok, obviously I am not going to be able to *reuse* my 8" 1200mm reflector for imaging. I was willing to shell out around $1400 for the Atlas mount so...

What complete imaging setup could I get for around $1000 to $1400? Keep in mind that I already have a unmodified Canon 1000D. Some sort of setup with parts I could reuse when(if) I decide that I like it and want to upgrade.

I really appreciate the advice!



#16 nexguy

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Posted 17 February 2011 - 10:13 AM

Would my f/5.9 8" newt work better on an Atlas if I placed it on a pier instead of the tripod?

#17 RAKing

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Posted 17 February 2011 - 10:45 AM

Would my f/5.9 8" newt work better on an Atlas if I placed it on a pier instead of the tripod?


Yes. I had an adapter made so I could use my Atlas on an Astro-Physics 6 inch Portable Pier. It worked very well and I was able to use it closer to its rated capacity.

IMHO, many of the mounts on the market could benefit from sturdier foundations. Plus - most of the current crop of tripods don't do down far enough so you can comfortably use a Newt on them anymore. :)

Cheers,

Ron

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