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Newtonian v. Dob

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#1 reimk4526

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Posted 05 April 2010 - 12:45 AM

I am thinking of converting my 6" reflector from a Dob mount to a Newtonian mount at sum point, what I am wondering is there really an advantage to doing this or would I just be wasting my time and money.

#2 Chris Rowland

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Posted 05 April 2010 - 04:15 AM

It's not clear what you mean, a Newtonian is a type of telescope, not a mount.

Chris

#3 Eddgie

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Posted 05 April 2010 - 09:01 AM

If you mean converting it to a GEM mount, the advantage will be that you can do tracking.

This is only really beneficial if you use high powers a lot and have trouble keeping the target in the feild of view.

The downside is that even for a small reflector, the mount can introduce some instability. You may find the view shaky when focusing and such.

Regards.

#4 reimk4526

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Posted 05 April 2010 - 01:38 PM

If you mean converting it to a GEM mount

That's what I meant:foreheadslap:, sorry for the confusion and thatnks for the help.

#5 LLEEGE

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Posted 05 April 2010 - 01:41 PM

Mounting on a GEM can also put the EP in some awkward positions. I'd suggest a set of rotating rings to solve that problem.

#6 gnowellsct

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Posted 05 April 2010 - 11:10 PM

come on in the water's fine...don't skimp on the GEM!

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#7 PJ Anway

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Posted 06 April 2010 - 05:45 PM

Though I have used several dobs (friend's and daughter's), I have never owned one personally. I tend to look at objects for more than a few seconds and I just don't enjoy the constant nudging. I've had equatorial mounts for many years and find I couldn't live without tracking ability, especially when observing at higher powers.

#8 gnowellsct

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Posted 06 April 2010 - 06:04 PM

Though I have used several dobs (friend's and daughter's), I have never owned one personally. I tend to look at objects for more than a few seconds and I just don't enjoy the constant nudging. I've had equatorial mounts for many years and find I couldn't live without tracking ability, especially when observing at higher powers.


ServoCat or an equatorial platform does take care of these issues, but the "handling" is not as precise on servoCAT as a good EQ mount. However, it probably equals or exceeds a cheap EQ mount.

For what it's worth, I would prefer a good Dob to a cheap GEM. I think cheap, unsteady GEMs with lots of slop in the mechanics are one of the worst things out there in amateur astronomy.

Greg N

#9 MorningStar1969

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Posted 07 April 2010 - 02:21 PM

A CG-5 will give you goto and tracking, i think very well worth the upgrade.

#10 Javier1978

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Posted 07 April 2010 - 03:40 PM

Hi,

I would only consider to switch to a GEM if you are getting into AP or if you love planetary observing at really high powers.

Dob mounts are really comfortable to observe and set up.

#11 ewave

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Posted 07 April 2010 - 05:30 PM

Looks like Orion Telescopes now have introduced the tracking go to dob:

http://www.telescope...ory_id=gotodobs

Can't wait to see the reviews and bugs on these when they get to market.

#12 gnowellsct

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Posted 07 April 2010 - 07:42 PM

Looks like Orion Telescopes now have introduced the tracking go to dob:
Can't wait to see the reviews and bugs on these when they get to market.


It's the kind of thing that you'd want to wait two years for them to get it right, IMHO. I am extremely skeptical that they fineness of control will equal or exceed the servoCAT, which as I have mentioned, doesn't really do what a top notch GEM does.

In fact so far....I haven't tried every known scope with a paddle, but so far: my stepper version G11 and stepper version AP900 blow away of the competitors in turns of giving you fine control of the object in the eyepiece. I'll put the Vixen Super Polaris in there too. I'm sure the GP and DX versions are just as good.

All three of these mounts have the ability to "turn on a dime" when you want to switch directions and have no perceptible backlash.

regards
Greg N

#13 ewave

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Posted 07 April 2010 - 08:58 PM

Greg

Good insight. I can't imagine how good the mechanics of the mount are as this appears to be the very first go-to dob ever made. But it is a step in the right direction for amateur observers and perhaps down the road for more discrete folks if the idea ever catches momentum.

If I can comment on the alt-az mount on my CPC 11 SCT, it is just incredible.....there was a time I had 2x barlowed my 17mm hyperion went in the house for 30minutes and came out and Mars was still in the field of view...(this without a precise alignment).

Clear skies and appreciate your posts.

#14 jsiska

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Posted 08 April 2010 - 03:00 PM

I like the classic looks of a Newtonian on a low slung beefy GEM better than a Dob. Dobs look so unscientific.

Jim

#15 RAKing

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Posted 08 April 2010 - 03:52 PM

I like the classic looks of a Newtonian on a low slung beefy GEM better than a Dob. Dobs look so unscientific.


I agree about the aesthetics -- but unless you are willing to invest in some rotating rings, be prepared to face some ergonomic "challenges".

That eyepiece can wind up in some very uncomfortable places and I sometimes spent more time climbing around the mount like a kid's Jungle Gym than looking through the eyepiece. :)

Ron

#16 gnowellsct

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Posted 08 April 2010 - 08:26 PM

I like the classic looks of a Newtonian on a low slung beefy GEM better than a Dob. Dobs look so unscientific.

Jim


It isn't just about the looks. If you consider the picture above carefully, you'll see that the tube is sticking out only about three feet past the axis of rotation. If the GEM is solid and well proportioned, it makes for a lot more solidity than the usual dob configuration, because there is less leveraging. Eyepiece balance is not an issue because the mount clutches handle that. (But servoCAT relieves one of eyepiece balance issues too).

I guess I could go to a 12" f/4.5 Newt and use it on the same mount--would actually be a bit shorter. But GEMs have their limits, and a 12" f/4.5 would make for easier viewing positions than the rig above.

greg N

#17 MorningStar1969

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Posted 08 April 2010 - 09:44 PM

Orion has there act together and than some. While normally i see the wisdom of avoiding first generation technology, i would not hesitate to purchase one of these right out of the gate. I have no doubt that they do exactly what they are supposed to, goto and track, at a break through price point. To support this, Sky at Night tested the tracking SkyWatcher version and found it to be first rate.

#18 gnowellsct

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Posted 09 April 2010 - 02:20 PM

Orion has there act together and than some. While normally i see the wisdom of avoiding first generation technology, i would not hesitate to purchase one of these right out of the gate. I have no doubt that they do exactly what they are supposed to, goto and track, at a break through price point. To support this, Sky at Night tested the tracking SkyWatcher version and found it to be first rate.


Hmmmm. Well good luck with that. We'll see what happens right here on CN I suppose. I still do buy Orion products, and have given 3 star blasts as presents. These are very simple in comparison to what we're talking about. But they all had performance and cosmetic issues, including the one that went away to a friend just this past week. Truth is, I wouldn't even want a new Astro-Physics mount design until it had been out for a year. At a minimum I want to know how the product will perform at -10F (and I'm dead serious).

regards
Greg N

#19 gnowellsct

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Posted 09 April 2010 - 02:27 PM

Greg

Good insight. I can't imagine how good the mechanics of the mount are as this appears to be the very first go-to dob ever made. But it is a step in the right direction for amateur observers and perhaps down the road for more discrete folks if the idea ever catches momentum.

Clear skies and appreciate your posts.


Sean: I just wanted to be clear that this is not the first go-to Dob ever made. Argo Navis/Obsession/ServoCat have been selling them for at least 5 years, probably more like 7. ServoCat has been installed in a wide variety of scopes.

But the Orion go-to is certainly a breakthrough in the lower price points, though of course, the lower price points won't be so low now. I guess I don't see the point to go-to other than the gimmick on these inexpensive dobs. Near as I have read the intelliscopes are only accurate to about a degree or so in pointing. That works at lower powers on bright objects, but better encoders and a pointing model might have done more for helping amateurs find stuff. Near as I can see go-to at this price level is just going to be one more thing to break in not very much time. I've seen the simple azimuth base particle board crumble on these units after not too much time.

So I'm by no means sure cheap go-to is a boon.

But one thing is for sure: it is the dominant trend in the industry at all levels, and my views on the matter are sour, curmudgeonly, retrograde. But I do think there will be a lot of nice dobs that get sent to the closets once their go-to system breaks.

Greg N

#20 TexomaAU.Obs.

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Posted 11 April 2010 - 11:44 PM

GEM vs Dob..
Im sure that this was the big question that brought about the JMI GEM split ring platform on the NGT's . I wish Celestron, Meade and Orion would make a similar split ring GEM for their Dobs to make it more affordable for those of us that can't cash out for a Cadillac 12" plus aperture NGT......I'm gonna go out side now and look up and wish upon that star.....






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