Why not use a polar mount?

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Why not use a polar mount?

Postby Sophiecentaur » Thu Apr 21, 2016 10:19 pm

If you have no Goto help then is there any advantage in not having a polar mount?
Is it a matter of cost and simplicity?
I am considering buying an astronomical telescope (at long last) because we now live out in the country and our Essex skies are often clear and there is so little local light pollution.
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Re: Why not use a polar mount?

Postby Aratus » Fri Apr 22, 2016 10:48 am

If you DON'T have a goto then an equatorial (polar) mount has one very important advantage, and that is that once you have found your object, the mount will keep that object in view with no further adjustment (If properly aligned with a motor drive, of course). With an alt-azimuth you would have to constantly keep nudging the telescope to keep it in view.
Goto telescopes with alt-azimuths automatically make those little nudges to keep the object in view and so removes that particular advantage.

So to sum up if the telescope does NOT have a Goto then it would be best to get an equatorial

However bear in mind that if it does have a goto then alt-azimuth is much easier to set up. Locating the pole star everytime is a bit of a bind although you get used to doing it.

Also bear in mind that if you are wanting (eventually?) to do quite advanced photography with very long exposures then an equatorial is a must because it eliminates the very slow rotation of an object in the field of view. Having said that, more sensitive CCDs and modern stacking technology, especially with large deep space objects has reduced the advantage of an equatorial mount quite a bit. Exposures of up to a couple of minutes with quite faint objects are possible with an alt-azimuth. Beyond that and you will still need an equatorial.
I use an 11" Celestron SCT (CPC 1100) on an equatorial wedge, housed in a 2.2m Pulsar observatory. I use a ZWO ASI1600MC and Canon 500D for imaging.
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Re: Why not use a polar mount?

Postby Sophiecentaur » Fri Apr 22, 2016 8:17 pm

Thanks for the reply. Looking through the adverts, there are several 8" Dobs at very reasonable prices but Would I be right in thinking that I will not find a goto control for a Dob? Bearing in mind how convenient Goto is, I would need to think along and hard about my choice and I know there is no perfect answer. If I start with a non-Goto scope then I will be struggling to find things at the very time that a Goto would help me most.
But would it be overkill to think in terms of 8" to start with?
Aaaarrrgh! Decisions.
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Re: Why not use a polar mount?

Postby Aratus » Fri Apr 22, 2016 9:12 pm

It is possible to adapt a Dobsonian to use a 'goto'. I've not seen one in action myself though.
Maybe someone here has one

For example . . .
https://www.firstlightoptics.com/dobsonians/skywatcher-skyliner-350p-flextube-goto.html
Image
I use an 11" Celestron SCT (CPC 1100) on an equatorial wedge, housed in a 2.2m Pulsar observatory. I use a ZWO ASI1600MC and Canon 500D for imaging.
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Re: Why not use a polar mount?

Postby The Man with the Corrugated Iron Roof » Sun May 15, 2016 9:14 pm

It's largely "horses for courses". A driven equatorial mount (with or without GOTO) costs more money than a simple alt-az mount. I was once quoted as saying I don't like GOTO mounts. Not strictly true! What I have said is that if you have a fixed budget, as most of us do, you get more optics for your money. I'm on quite a low budget, so prefer a larger, higher optical quality telescope with less "wizardry" than a GOTO 'scope that is smaller.

I tend to agree that a tracking mount is best for long exposure photography but I find more than enough to "snap". I love fiddling about with a DSLR on its own.

I would also suggest a decent pair of binoculars. I once heard it said that an astronomer is someone who owns a £500 telescope but spends most of their time looking through £30 binoculars.
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