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I've used a 150mm Dobsonian reflector for a few years and have decided to move to a Goto system. I'd like to try a different type of scope as an alternative to the Dobsonian. Looking at the Celestron website I see a classic case of confusion marketing, where there are so many options and variants that selecting a good telescope package is quite challenging. I'd appreciate any advice from those that have successfully navigated product specs to get a good telescope. My reason for interest in Goto technology is just to make the most of observation time, track planetary motion and explore new parts of the sky. I'm interested in using a DSLR but that is secondary to enjoying the view.

I've looked at the  Celestron Advanced VX 9.25" Schmidt-Cassegrain Telescope which looks good, although potentially heavy. I've seen posts here that say a more solid mount/tripod may be required. Also this is a step up in terms of magnification from the Dobsonian, so want to be sure it is easy to use, which is where Goto performance is relevant. So potentially an 8" is a contender.

Any help appreciated.

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Don’t confuse the mount type with the telescope type :). You have a 150mm Newtonian reflector on a Dobsian mount. The 150 is an excellent scope IMO and with the addition of some tube rings and a bit of fettling, you could plop it on a goto mount and have a nice set up.

The scope your looking at is an SCT type scope on an EQ goto mount. SCT’s have the advantage of having a very long focal length for their size meaning you can put nice wide view long focal length eyepieces in and still get good magnification. Their disadvantage is price. You could get a much larger aperture Newtonian for the same money so more photon capturing ability.

Much comes down to what you want to use it for? Visual, AP, deep space, planets and double stars, lunar etc? For what it’s worth I bought a 10” SCT and barely used it as it’s cumbersome and it mists up at the drop of a hat. It’s bloody heavy too, sure it’s in a relatively short tube but by god it takes some man handling to get it mounted. I wanted to love, I still do, but right now it doesn’t get used. My 4” frac and 150 Newtonian do get used.

I have some bits coming that I hope will mean I get to start liking the SCT and using it a bit more but we’ll see.  

Edited by dannybgoode
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After experiencing Celestron's 8SE goto system (single arm mount) I wouldn't buy a similar system again, not with an 8" SCT on it at least (6" might be that mount's realistic limit).

My two (or three) pence would be to look at an EQ system as it will allow you to mount different scope types, if looking at 8" SCT then probably HEQ5 Pro or equivalent as a minimum.  With the EQ mounts that offer goto or simple motorised tracking versions, you can normally just upgrade the hand controller to make a tracking mount a goto mount.  Personally I feel this is a good route to go from a manual push-to (dobsonian), get used to an EQ with simple motor drive first and all the setup that entails (polar alignment), a non-goto EQ mount is perfectly capable of long or short exposure photography, the initial setup required will be the same if you intend to do photography with goto.  Once you have goto then there'll be the extra steps required to calibrate the goto system each time it is moved (i.e. taken outside), and as with any complex system this is where errors and problems can occur, leading to frustrations and lost evenings, so having that fall-back of the simple motor driven tracking can certainly save an evening.

If you're keen to splash the cash then there are all manner of automation gadgets (more things to potentially go wrong!) but in my experience they tend to be tied to specific setups, e.g. Celestron StarSense, which may not offer much by way of customisation or upgrade, e.g. one might be limited to a medium or small mount.  Even a 'basic' goto setup can be quite a big jump from a manual dobsonian, a steep learning curve!

An SCT is a compromise of aperture vs size, to get a similar aperture you'd normally need a much larger newtonian, but an SCT has it's pecularities and is more susceptible to dew and less than ideal seeing conditions.  Expect to require a dew shield as a standard minimum, and also at least one dew heater tape.

Just as a PS, the difference between an 8" and 9.25" SCT with the same coatings etc will be almost nothing, don't get hung up on size too much.  I'd say 9.25" is a comfortable size to handle, bigger than this becomes tricky especially when the tube is covered in frozen dew and your hands are cold!

 

Edited by jonathan
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13 minutes ago, jonathan said:

An SCT is a compromise of aperture vs size, to get a similar aperture you'd normally need a much larger newtonian, but an SCT has it's pecularities and is more susceptible to dew and less than ideal seeing conditions.  Expect to require a dew shield as a standard minimum, and also at least one dew heater tape.

Oh and they take some cooling - by crikey can they take a while to stabilise!!

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11 hours ago, dannybgoode said:

Oh and they take some cooling - by crikey can they take a while to stabilise!!

Indeed, typically 20 minutes minimum, possibly up to 40 minutes.  It's been a while though, I just haven't been out much at all in the past year or two and when I have it's usually been with a refractor.

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Be clear about what you want to do with the new outfit.  You could have another Newtonian, but a SCT of the same aperture while more expensive will be shorter, lighter and easier to mount.  If you did not have dew problems with your 6" Newt, a SCT should be fine with just a dew shield.

  Do you intend to do deep space imaging at any point? If you don't, you don't have to contend with the added bother of an equatorial mount: polar alignment, odd eyepiece positions, counterweights and meridian flip.  Note that SCTs with their 'slow' focal ratios are not well suited to deep space imaging, particularly for beginners. If you want to do the latter, a small refractor or small f5 Newtonian would be much more suitable.

An alt-azimuth Goto will do fine for most use, including planetary imaging, but is not suited to the long exposures needed for deep space imaging.

You don't need to buy the scope and mount as a package, but this is usually cheaper than buying separately.

Give some thought to what GoTo system you want to invest in, as they aren't all the same.  The most often bought are the Celestron Nexstar and Sky-watcher Synscan, but there are others.  I have found the Nexstar (alt-azimuth version) easy to use and with some handy features, while the Synscan (equatorial version) is poorly designed and hard to align with sufficient accuracy for all-sky use.  Just look at the number of posts from newbies complaining that they can't make sense of Synscan, followed by the posts from experienced users who have found some workaround to get the thing to deliver a useful result.

How important is ease of setup to you? If you really want, you can have a setup with SCT + alt-az Goto + Starsense that you can carry out assembled and have going in a few minutes. If it's not a priority, you could spend the best part of an hour assembling a Newt + equatorial GoTo from its stored sub-assemblies, polar aligning it and sky aligning it.

Edited by Cosmic Geoff
SCT not well suited for deep space imaging.
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Ease of setup is the most important to me, so tracking an object once found with Goto would be the goal for observation. Is there a recommendation for the mount type to enable this? Astro photography is not the goal at this point, and would be a phase 2 project as this seems to be an art in itself.

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The upcoming GOTO / Push to / WiFi / GPS upgrade for the Rowan AZ100 mount will allow that sort of thing. Will be able to use full GOTO or just push to the target and tracking will kick in when you find it. Going to be super flexible. 👍🏻

Edited by johninderby
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Thanks for all the comments, it's very helpful to get the views of people of who been through the challenges of understanding this subject and implementing it.

I prefer to have a system that can be used without a substantial setup/alignment process. This would initially be for observation but later for photography. If this is a contradiction then maybe I'll need to get 2 systems each for a specific purpose, although that may be cost prohibitive.

I have a few more 'beginner' questions:

Do Goto systems also track?

What are the benefits or problems using Goto with Eq or Az mounts?

Are the setup processes substantially longer/more difficult with Goto on Eq or Az mounts?

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9 minutes ago, random said:

Do Goto systems also track?

Goto is usually "upgrade" to tracking mount. Once you have motors that are capable of tracking the sky - you can add small computer to use those motors to navigate the sky.

With AltAz mounts - this usually comes together as there is no simple way to track the sky without controller (small computer that calculates needed motor speeds depending where scope is pointing).

10 minutes ago, random said:

What are the benefits or problems using Goto with Eq or Az mounts?

Benefit of AltAz is that your eyepiece is pretty much in same position with all scopes. With EQ mounts, newtonians are a bit awkward to use as eyepiece and finder rotate with tube and can end up in weird positions - you need to rotate OTA in rings to get eyepiece in comfortable position.

Goto EQ is almost a must for astrophotography (at least long exposure) - as Alt AZ suffers from field rotation. Completely irrelevant for observation but ruins long exposure. Planetary astrophotography will not suffer from field rotation as exposures are very short in comparison to rotation speed.

If comfort of use is primary concern - go with Alt Az.

If long exposure photography is in plans - consider EQ

13 minutes ago, random said:

Are the setup processes substantially longer/more difficult with Goto on Eq or Az mounts?

No - about the same. EQ does require polar alignment, but for visual that can be rather crude.

With both types there will be procedure to complete that lasts about 3-4 minutes (maybe a bit longer due to polar alignment on EQ). Procedure consists of selecting an object (usually star but can be planet) - mount will try to locate it and then you have to help it by centering selected object in your eyepiece. This is repeated 2-3 times with different stars.

If every minute counts - go with Alt Az as you only need to make sure mount is level and scope is pointing north. With EQ mount - you'll also need to make sure mount RA axis is pointing at NCP (north celestial pole - close to polaris), and that can take additional minute or two.

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GOTO also means tracking.  GOTO has simpler options with Alt-Az. With a Synscan Alt-Az sertuo I often just used the solar system align if just wanted a quick look at the moon ot planets. Just move the scope to the target and start tracking. Not as good as keeping things centred in the fov but perfectly adequate for solar system viewing and quicker than doind a full alignment.

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On 07/03/2021 at 21:46, Cosmic Geoff said:

If the original poster has settled on a particular telescope, we can suggest a GoTo mount for it.

Indeed.  My advice there would be to look at the complete approximate telescope weight including any typical accessories such as finder, diagonal, and eyepiece, then look at the weight carrying capacity of a mount - it needs to ideally have at least 1/4 additional capacity over what the telescope weighs in order to be stable, preferably 1/3 more.  e.g. if the telescope weighs around 10lb then a mount carrying capacity of 15lb would be ideal.  I quote lb because that's a typical weight unit used by Celestron in their mount specs.  This is relevant to visual and photography, though with visual maybe 1/4 would be acceptable but the more spare capacity there is then the less affected the scope will be when it comes to vibrations from touching the scope (focusing), wind, or vibrations through the ground.

When it comes to wind, obviously the bigger the scope the more it will be affected.  I've had an 8SE on an NEQ6 out in quite strong winds on a hillside and it's been rock solid, as it's quite a short scope there's less for the wind to grab hold of and 'twist'.  Had it been on an HEQ5 Pro there would have been more chance of vibration from the gusts of wind.  A slim, long refractor will catch the wind at the ends more, and the basic principles of leverage physics come into play, although on an NEQ6 I wouldn't expect any significant difference as that is such a heavy solid mount.

Edited by jonathan
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For visual observing I greatly prefer an alt-az mount to a German Equatorial. The Equatorial needs polar aligning and balancing and the necessary counterweights almost double the weight of the whole payload. Then, in use, the scope changes position radically between objects, the eyepiece ends up at odd angles and needs rotating, and the sky is divided into two halves requiring a meridian flip. What a palaver, even when permanently mounted! So I have always enjoyed my fork-mounted alt-az SCTs for their ease and comfort of use and fast setup. I've previously had 8 and 10 inch and now have a 14 inch. (All Meade. I have no opinion on the Meade-Celestron debate.)

The 8 inch was fine to manhandle and set up.  The 10 inch was not. It was 'possible' but stressful. In the end I mounted its tripod on a wooden platform or 'sled' under which I could roll a sack truck. I stored it in the garage and rolled it out as one on the sack truck, after which it was quick to align.

Another alternative is the driven Dobsonian. This is just another kind of Alt-Az Go To and has to be an attractive proposition which would also lend itself to the wheeled principle. Dobs can easily have 'wheelbarrow handles' attached. A Newt, with its shorter focal length, has a much wider field of view and thus a wider range of targets than an SCT, which can leave you feeling very boxed in. I would certainly want an SCT with a 2 inch visual back so as to allow an ultra-wide two-inch EP to open things up a bit. (The focal reducer is a bit of a non-solution in that you can get the same FOV with a 2 inch EP and the view is distinctly better.)

Olly

Edited by ollypenrice
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I agree with Olly @ollypenrice about avoiding Eq mounts for visual.  (Had one when I started out, and it almost put me right off.)

Concerning GoTo, the advantages are considerable in terms of not only finding targets, but also tracking, esp. at high magnification.  I have the Celestron single fork GoTo mount that came with the 8SE.  The 'scope and mount are easy to manage (as two separate pieces) and use.  The tube doesn't take too long to cool, esp. as it normally lives in a shed.  It doesn't wobble any more than my other 'scopes,  The mount is also used with the small ED80 frac, which is very handy.

As for alignment, it is quick and easy (esp. with the GPS module).  I usually just use one-star or solar system alignment.  Two-star is more accurate.  I've never bothered with three-star, as the previous approaches put me on or very close to targets.

Doug.

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GOTO can be great but also has a greater chance of technical issues.

The weight can be a big factor if you don't have a permanent setup

Most users often under estimate what their mounts will carry

Its tempting to add larger guide/finder scopes, EP's, imagers etc

I like to stick with a rule (often broken!) that your scope should be around half the carrying capacity of the mount

That leaves the other half for your accessories and not using it near capacity

AP is much improved with reduced loads

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Update - I'm now considering a SkyWatcher HEQ5 Pro with the the 6" Newtonian I already have. I appreciate the viewing position will shift but it will give me some experience of using a Goto and astrophotography is something I want to try. I take the point raised about the lower payload of this mount but I'm not comfortable handling the HEQ6 due to its 17Kg weight. I haven't decided whether leaving the mount in position outside is a good plan as I don't have a flat surface in the right position, just grass. Presumably it can be protected against the weather so a heavier mount could be an option. The comment about the potential difficulties with SynScan is also noted. So more research needed. Thanks again for all the comments.

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