Jump to content


Photo

Why an EQ?

This topic has been archived. This means that you cannot reply to this topic.
28 replies to this topic

#1 BobH

BobH

    Messenger

  • *****
  • Posts: 433
  • Joined: 03 Jan 2008

Posted 28 November 2008 - 08:59 AM

I'm still agonizing over which mount to get for my forthcoming refractor.

Initially, I just assumed it should be an equitorial because most of the photos I see of refractors have them mounted on an EQ. But, the more reserach I do, the more of a pain these eqs seem to be. Balance and stability; meridian tracking; polar alignment (rough or otherwise); change in balance and apparent motion when shifting from east to west configuration, etc. Seems like everytime I read more about the eqs, I find another little glitch that needs to be dealt with.

I'm a spoiled newbee with an LX 200 GPS GOTO on alt-az. To set up, I just get the tripod level, mount the scope, turn it on and go for a beer. By the time I get back, the scope has downloaded time, date, and location, found north, level, and tilt, and is pointing toward the first aligment star.

GOTO and visual tracking performance are exceptional (to me) and the mount is rock solid with no noticable movement while focusing.

So, I ask, is there an eq mount that convenient?

Assuming one is not going to do AP, what would be the advantage of an eq over alt-za?

Thanks,

#2 GJJim

GJJim

    Surveyor 1

  • -----
  • Posts: 1756
  • Joined: 09 Sep 2006

Posted 28 November 2008 - 09:55 AM

For imaging with exposures longer than a few seconds, an alt/az mount means you'll need to add a field rotator to the scope.

Could you assemble a system consisting of alt/az mount + field rotator + guider + software? Sure. Would it work reliably in the real world? I doubt it. There is a reason why almost all refractors end up on a EQ mount.

#3 Applal

Applal

    Messenger

  • -----
  • Posts: 435
  • Joined: 23 Jan 2006

Posted 28 November 2008 - 10:11 AM

Assuming one is not going to do AP, there is NO advantage for you to use an EQ over what you have... you have a perfect mount for your needs and uses. Just enjoy the sky (and the beer!)

:lol:

#4 watcher

watcher

    Vanguard

  • *****
  • Posts: 2120
  • Joined: 21 Nov 2007

Posted 28 November 2008 - 10:15 AM

If a mount can handle the refractor, (length and weight), an EQ won't have any advantage over an Alt-Az, for visual. Personally, I don't find an EQ difficult to setup.It's a process that becomes easier the more you do it. Kinda like a child learning to tie his shoes.

#5 hudson_yak

hudson_yak

    Surveyor 1

  • -----
  • Posts: 1580
  • Joined: 15 Nov 2007

Posted 28 November 2008 - 10:33 AM

I'm not much into GoTo but I won't be without motorized tracking, for planets anyway. I've tried manual tracking and motorized is better. Well worth the minimal increase in setup time. It's also good if you want to offer a look to someone else.

Another advantage is an eq mount allows me to engage in one of my favorite pursuits, finding planets in the late afternoon sky before you can see them naked-eye. The manual eq setting circles are what you want for this.

Besides, there's just a certain rightness to using an equatorial mount for astronomy.

Mike

#6 Jared

Jared

    Fly Me to the Moon

  • *****
  • Posts: 5077
  • Joined: 11 Oct 2005

Posted 28 November 2008 - 10:39 AM

Most of the disadvantages you mention only come to the forefront when imaging. Shifting balance and meridian flip are not going to be problems for a visual observer, for example. GEM's have become the standard for refractors primarily because of their flexibility--able to handle a range of optical tubes--and because a fork mount like the one on your LX200 can not handle longer OTA's since there isn't room for "swing through.". However, you could consider something like the iOptron mounts if you want toto in an alt-az configuration.

I'm still agonizing over which mount to get for my forthcoming refractor.

Initially, I just assumed it should be an equitorial because most of the photos I see of refractors have them mounted on an EQ. But, the more reserach I do, the more of a pain these eqs seem to be. Balance and stability; meridian tracking; polar alignment (rough or otherwise); change in balance and apparent motion when shifting from east to west configuration, etc. Seems like everytime I read more about the eqs, I find another little glitch that needs to be dealt with.

I'm a spoiled newbee with an LX 200 GPS GOTO on alt-az. To set up, I just get the tripod level, mount the scope, turn it on and go for a beer. By the time I get back, the scope has downloaded time, date, and location, found north, level, and tilt, and is pointing toward the first aligment star.

GOTO and visual tracking performance are exceptional (to me) and the mount is rock solid with no noticable movement while focusing.

So, I ask, is there an eq mount that convenient?

Assuming one is not going to do AP, what would be the advantage of an eq over alt-za?

Thanks,



#7 DeanS

DeanS

    Gemini

  • *****
  • Posts: 3347
  • Joined: 12 Jul 2005

Posted 28 November 2008 - 10:40 AM

Look at the Disc Mounts if you are just doing visual observing. They look very well made and stable.

#8 Daniel Mounsey

Daniel Mounsey

    Vendor (Woodland Hills)

  • *****
  • Vendors
  • Posts: 5511
  • Joined: 12 Jun 2002

Posted 28 November 2008 - 11:11 AM

Bob,

Maybe I can help. What is it you're trying to do? If you're happy with your scope, then what's the issue?

#9 Jeff Morgan

Jeff Morgan

    Fly Me to the Moon

  • *****
  • Posts: 5788
  • Joined: 28 Sep 2003

Posted 28 November 2008 - 11:28 AM

I'm still agonizing over which mount to get for my forthcoming refractor.

Initially, I just assumed it should be an equitorial because most of the photos I see of refractors have them mounted on an EQ. But, the more reserach I do, the more of a pain these eqs seem to be. Balance and stability; meridian tracking; polar alignment (rough or otherwise); change in balance and apparent motion when shifting from east to west configuration, etc. Seems like everytime I read more about the eqs, I find another little glitch that needs to be dealt with.

I'm a spoiled newbee with an LX 200 GPS GOTO on alt-az. To set up, I just get the tripod level, mount the scope, turn it on and go for a beer. By the time I get back, the scope has downloaded time, date, and location, found north, level, and tilt, and is pointing toward the first aligment star.

GOTO and visual tracking performance are exceptional (to me) and the mount is rock solid with no noticable movement while focusing.

So, I ask, is there an eq mount that convenient?

Assuming one is not going to do AP, what would be the advantage of an eq over alt-za?

Thanks,


It's largely personal preference. In my mind, the biggest advantages of the eq mount are in tracking and star hopping. I know you have a driven goto mount. And not to turn this into a goto thread, but let me say that they do fail (frequently judging from the public sessions I attend), leaving the observer to basic star hopping (assuming they know how, and there mount is actually operable without goto). With an eq mount, north is always north, east is east, etc. With an alt-az mount, up-down-right-left only corresponds with north-south-east-west when the scope points at the zenith. The farther away one moves from that point, the less scope motions correspond to chart directions.

#10 letimotif

letimotif

    No Complaints

  • *****
  • Posts: 3225
  • Joined: 19 May 2007

Posted 28 November 2008 - 11:47 AM

Hey Bob,

Ioptron makes a nice series of AA mounts, and their Mini-Tower has gotten some great reviews. I think there's even a review in our forum under mounts.

I've been looking at an AA for my refractors because I don't see myself doing any imaging anytime in the near future, and--for me--the challenge of an EQ mount is the odd positions in which it sometimes places the EP for viewing. Stand up sometimes, sit down sometimes, even with a chair it can be a problem.

#11 Doug76

Doug76

    Long Achro Junkie

  • *****
  • Posts: 10839
  • Joined: 05 Dec 2007

Posted 28 November 2008 - 12:04 PM

Assuming one is not going to do AP, there is NO advantage for you to use an EQ over what you have.


Agreed. I like EQ mounts, but not for Newtonian Reflectors. The eyepiece can and does wind up in some very awkward positions to view from. As was said, if your not doing AP with it, leave the reflector on an Alt-Az mount.

#12 Eddgie

Eddgie

    Voyager 1

  • *****
  • Posts: 13178
  • Joined: 01 Feb 2006

Posted 28 November 2008 - 01:42 PM

You know Bob, these things can be as simple or as complex as you make them.

You did not really say what kind of refractor you were going to get, or what your intended purpose was.

If the scope is small and you are a purely visual observer, there are a number of simple Alt-az mounts on the market that will do fine.

On the other hand, a GOOD alt-az mount for a larger refractor can become VERY expensive, and often, you STILL need to resort to counterweigts to keep it balanced. So, if you are going to have to manage counterweights anyway, the difference between the Alt-az and the GEM are not so great in terms of setting up.

A GEM mount doesn't NEED to be complicated to use.. You can buy a basic GEM (CG5) for LESS than a decent quality Alt-az mount and get the benefit of slow motion controls and single control tracking.. You don't need to accuratly align a GEM to get the benefit of the design. If you just plop it down and do a rough alignment, you can easily keep a target centered with just the RA slow motion control. YOu now don't have to worry about clutches and center of gravity shift when changing from big eyepieces to small ones.

And for only a LITTLE more money, you can get a Go-to GEM (used LXD55s sell for less that $250). This way EVEN IF YOU DON'T USE the Go-to, you STILL get tracking and electronic slow motion.. This helps you prevent touching the telescope so that when viewing at high powers you aren't always waiting for the telescope to settle every time you touch it to re-center your target. And you get the benefit of multile slew rates for times when you wish to just sweep the sky. I use my 6" Refractor on a giant GEM, and half the time I use it, mostly I have a very low power eyepiece and I am sweeping.. The GEM lets me make very controlled sweeps.. I sweep about 30 degrees of declination, then move the scope a couple of minutes in RA, then make another long sweep. None of this requires precise alignment or anything.

And of course if you get the Go-to, it COMES with the equivilent of Digital Setting Circles BUILT IN! If you add these to an Alt-az, you will spend MORE ON THE EQUIPMENT to upgrade an Alt-az than you would spend just BUYING a GEM mount.

And of course there is Go-To.. When I use my big refractor for Double Stars, I can do 20 in an hour. I don't have to star hop or hunt and peck around the sky.. I plug in the coordinates and the scope goes to the target.

So, You can still get great value out of a GEM mount even if it is not Go-to.

All that being said? If you don't want to MESS with it, then that is an entirely different issue. Just buy the best Alt-az you can afford and be done with it.

Good luck with the decision.

#13 BobH

BobH

    Messenger

  • *****
  • Posts: 433
  • Joined: 03 Jan 2008

Posted 28 November 2008 - 06:53 PM

The new mount, GEM or otherwise, is for an SV115ST that I have on order.

I want GOTO for regular star gazing because I'm lazy, but a good set up for star hopping because, #1 I need to learn to do it, and #2 I want to do the Messier thing.

I want the capability to eventually do some AP.

On top of all that, I want a good, solid setup, that doesn't bounce all around, or at least settles down quickly when I focus.

Finally, a good-looking blond to hand me the eyepices.
Ok, forget the blond.

Bob

#14 jrbarnett

jrbarnett

    Eyepiece Hooligan

  • *****
  • Posts: 20631
  • Joined: 28 Feb 2006

Posted 28 November 2008 - 10:47 PM

Much simpler for automated tracking (one axis rather than two are in motion). With an EQ only a sidereal rate drive on the RA axis is needed. To track with an alt-az requires movements in both axes. Besides, with a little practice, EQ mounts are really easy to set up and use. All that polar aligning, balancing and other set-up stuff you dread takes about 5-7 minutes for visual use. :grin:

Regards,

Jim

#15 Rusty

Rusty

    Hubble

  • *****
  • Posts: 19883
  • Joined: 06 Aug 2003

Posted 28 November 2008 - 11:20 PM

I want GOTO for regular star gazing because I'm lazy, but a good set up for star hopping because, #1 I need to learn to do it, and #2 I want to do the Messier thing.

I want the capability to eventually do some AP.

Bob


You've nailed down the mount - unless all the AP you'd want to do is solar system, an EQ mount is the choice.

#16 BobH

BobH

    Messenger

  • *****
  • Posts: 433
  • Joined: 03 Jan 2008

Posted 29 November 2008 - 05:43 AM


Another advantage is an eq mount allows me to engage in one of my favorite pursuits, finding planets in the late afternoon sky before you can see them naked-eye. The manual eq setting circles are what you want for this.

Besides, there's just a certain rightness to using an equatorial mount for astronomy.

Mike



Mike,

Of all the great advice I've gotten here, your comment hits the nail on the head...the certain rightness about having a refracter on a GEM.

But, I have a questopn for you. If you set up in late afternoon, as I frequently do, you can't see Polaris. How do you align?

Thanks,

Bob

#17 hudson_yak

hudson_yak

    Surveyor 1

  • -----
  • Posts: 1580
  • Joined: 15 Nov 2007

Posted 29 November 2008 - 09:13 AM

But, I have a questopn for you. If you set up in late afternoon, as I frequently do, you can't see Polaris. How do you align?



I'm on fairly level ground so the latitude setting will be in the ballpark and since this neighborhood is built on a E-W N-S grid (close, anyway) pointing the tripod roughly north isn't too hard.

Then use a planetarium program to find local sidereal time (what the RA is straight up) and set the RA circle so it indicates that when the scope is pointing straight up. If you have a motor drive and driven RA circle you can switch it on though if you work fast this isn't really necessary. My mount is marked so that the Dec circle can be set correctly as well.

Then it's just a matter of looking up the coords for Juputer or Venus, pushing the scope to indicate one and seeing if it's in a widefield eyepiece. My widest gives me a 2.5 degree field and frequently the target is in there somewhere. You also need to have your focus tube marked so the scope will be roughly in focus to start with.

Right now, this is a piece of cake, with Venus and Jupiter so close you can probably find Venus naked-eye before finding Jupiter in the scope. Takes some of the fun out of it...

Mike

#18 Bob Griffiths

Bob Griffiths

    Getting Grouchy

  • *****
  • Posts: 10674
  • Joined: 10 Oct 2005

Posted 29 November 2008 - 09:31 AM

Bob:

I own 2 fork mounted SCTS and 2 refractors on Gems...I am seriously thinking of buying a Mini Tower and replace both Gem mounts... My reason is that the Gems are heavier, more difficult for me to lug outside and set up...and also they are not nearly as comfortable for "me" to use...

BUT I DO NOT IMAGE and have absolutely no desire to image..for my use I can set up one of the Gems at high noon and place everything in the correct position so that when it gets dark I have no problem tracking

For me the comfort using a Alt/Azm mount is my main reason for converting and the Mini Tower is not that more expensive then a good manual alt/azm mount..

Bob G

#19 Jeff Morgan

Jeff Morgan

    Fly Me to the Moon

  • *****
  • Posts: 5788
  • Joined: 28 Sep 2003

Posted 29 November 2008 - 01:18 PM

A GEM mount doesn't NEED to be complicated to use.. You can buy a basic GEM (CG5) for LESS than a decent quality Alt-az mount and get the benefit of slow motion controls and single control tracking.. You don't need to accuratly align a GEM to get the benefit of the design. If you just plop it down and do a rough alignment, you can easily keep a target centered with just the RA slow motion control. YOu now don't have to worry about clutches and center of gravity shift when changing from big eyepieces to small ones.


Not at all! I picked up an old Super Polaris on Astromart, then removed and sold the drive motors and Vixen SkySensor (a 1st generation GOTO system about the size of a shoebox). After the sale I have an excellent smooth mount with slo-mo tracking for about $150. Still light enough to carry in one piece from basement to yard.

Attached Files



#20 Jeff Morgan

Jeff Morgan

    Fly Me to the Moon

  • *****
  • Posts: 5788
  • Joined: 28 Sep 2003

Posted 29 November 2008 - 01:26 PM

Of all the great advice I've gotten here, your comment hits the nail on the head...the certain rightness about having a refracter on a GEM.

But, I have a questopn for you. If you set up in late afternoon, as I frequently do, you can't see Polaris. How do you align?


It is a myth that a GEM will not work if not aligned on the north pole. Basically, you just guess the direction of north. For visual use this is just fine. Worst case is that every now and again you have to turn the declination slow motion knob a bit. At this point, the mount is functioning as a two-axis mount, just like an alt-az. If it bothers you, adjust the mount in azimuth to get it closer to true north, then the adjustments in declination become smaller and less frequent.

If you are a perfectionist and need it dead-on you can look up the star-drift alignment method. Once you have it, make a small mark on the ground or wall, then next time align to that.

#21 BobH

BobH

    Messenger

  • *****
  • Posts: 433
  • Joined: 03 Jan 2008

Posted 29 November 2008 - 03:51 PM

Well, my apologies to the alt-az fans, and thanks to everyone who pitched in their 2 cents to help a newbee....I've decided to start with a GEM, just don't know which one yet, and when the budget allows, maybe an alt-az as a backup.

#22 Mike Holland

Mike Holland

    Apollo

  • -----
  • Posts: 1284
  • Joined: 22 Dec 2006

Posted 30 November 2008 - 04:27 PM

...

If you are a perfectionist and need it dead-on you can look up the star-drift alignment method. Once you have it, make a small mark on the ground or wall, then next time align to that.


Are many people using this method? I can't see Polaris from where I observe, and don't need precise alignment since I'm strictly visual. I've often wondered if getting the alignment once and then marking the spots for the tripod's feet would work well. Thanks.

Mike

#23 Jeff Morgan

Jeff Morgan

    Fly Me to the Moon

  • *****
  • Posts: 5788
  • Joined: 28 Sep 2003

Posted 30 November 2008 - 07:17 PM

Star drift is mainly used by imagers for very precise alignment. Personally, I just rough it in, even when I have a good view of Polaris. But if you were a perfectionist ....

#24 GJJim

GJJim

    Surveyor 1

  • -----
  • Posts: 1756
  • Joined: 09 Sep 2006

Posted 01 December 2008 - 09:54 AM

Star drift is mainly used by imagers for very precise alignment.


Nothing wrong with the drift method, but many of the newer systems use software for fine polar alignment. Programs like TPoint create a model that takes into account flexure of the mount and pier as the scope looks in different directions, corrects for slight errors between the optical axis of the scope and the mount, and even the small pole offset caused by refraction in the atmosphere. So instead of hours of tedious drift measurements on a star, it's possible to get near perfect polar alignment in less than half an hour.

#25 Kim Miau

Kim Miau

    Apollo

  • -----
  • Posts: 1264
  • Joined: 17 Jul 2006

Posted 22 February 2009 - 11:34 AM

It's largely personal preference. In my mind, the biggest advantages of the eq mount are in tracking and star hopping. I know you have a driven goto mount. And not to turn this into a goto thread, but let me say that they do fail (frequently judging from the public sessions I attend), leaving the observer to basic star hopping (assuming they know how, and there mount is actually operable without goto). With an eq mount, north is always north, east is east, etc. With an alt-az mount, up-down-right-left only corresponds with north-south-east-west when the scope points at the zenith. The farther away one moves from that point, the less scope motions correspond to chart directions.

Yeah, the characteristic of the GEM that corresponds to the celestial coordination tempted me to get it. In my opinion, this make thing easier to learn about the sky.

Frankly speaking, I still don't have a clear idea where are north, south, east and west when I look at the sky. Well, I know the terrestial direction but not the celestial's. I guess the problem is that I relied on the Alt-Az GOTO too much. It could be that I never really look into it too. :p






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics