Jump to content


Photo

Non-Goto EQ with fast slewing speeds?

  • Please log in to reply
10 replies to this topic

#1 Michael Rapp

Michael Rapp

    Gemini

  • *****
  • Posts: 3326
  • Joined: 26 Apr 2004
  • Loc: Dickinson, TX

Posted 03 September 2013 - 11:12 AM

Hi all,

I hope my LXD-75 (EC controller, non Autostar) mount continues to run for years, but I'm wondering what I would replace it with if it dies.

Are there any non-Goto equatorial mounts around the LXD-75's class that have slewing speeds of 180x siderial (0.75 deg/sec)? I can't find any. GM-8 tops out at 32x sideral, good for centering, but not slewing.

I suppose a related question would be, can the VX mount be operated easily in non-goto mode? That is, can you just tell it to track without doing any alignment?

#2 orlyandico

orlyandico

    Fly Me to the Moon

  • *****
  • Posts: 5630
  • Joined: 10 Aug 2009
  • Loc: Singapore

Posted 03 September 2013 - 11:13 AM

You can tell the VX to track without alignment. Turn it on then keep pressing Cancel until it stops bugging you.

To answer your question: the Takahashi EM11 (or EM200) USD-3 has fairly fast slew speeds but no GoTo.

#3 obin robinson

obin robinson

    Mercury-Atlas

  • *****
  • Posts: 2656
  • Joined: 25 Oct 2012
  • Loc: League City, TX

Posted 03 September 2013 - 12:01 PM

If your LXD fries why not consider upgrading the motors to something faster and even more precise?

http://www.siderealtechnology.com/

obin ;)

#4 orlyandico

orlyandico

    Fly Me to the Moon

  • *****
  • Posts: 5630
  • Joined: 10 Aug 2009
  • Loc: Singapore

Posted 03 September 2013 - 08:17 PM

well a SiderealTech box and motors costs about as much as an AVX...

#5 jrcrilly

jrcrilly

    Refractor wienie no more

  • *****
  • Administrators
  • Posts: 33881
  • Joined: 30 Apr 2003
  • Loc: NE Ohio

Posted 03 September 2013 - 08:22 PM

well a SiderealTech box and motors costs about as much as an AVX...


Yes. Plus the costs of fabricating motor brackets, etc.

#6 Eddgie

Eddgie

    Voyager 1

  • *****
  • Posts: 12924
  • Joined: 01 Feb 2006

Posted 03 September 2013 - 09:22 PM

While the GM8 may top out at 32X, remember that a GM8 with digital circles can be pushed to position very quietly, quickly and easily.

The GM8 design dives the encoders off of the axis shafts so position information is independent of motor function.

If you don't really need Hi Speed Go-To by motor, the GM8 can often "Go To" more quickly than most Go-to mounts.

Also, if you are really concerned, you can often buy used LXD75s for next to nothing. If you really like the mount just buy a used one for a parts machine. You can buy a used LXD75 for less than the cost of the encoder and Delrin covers for a GM8.

#7 Michael Rapp

Michael Rapp

    Gemini

  • *****
  • Posts: 3326
  • Joined: 26 Apr 2004
  • Loc: Dickinson, TX

Posted 04 September 2013 - 08:15 AM

I've been thinking about this and with the GM-8 I may not need the high speed slewing for another reason.

With my LXD-75 and refractor, as I get up from my crouch to tighten the RA and DEC locks, I sometimes move the tube a noticeable amount. So what I've been going is manually getting the scope in the area of the target, then using the faster (then slower) slews to get the red dot finder on my first star-hopping star.

With the GM-8, if my understanding of it is correct, I don't need to adjust any locks to engage the tracking, so I can be more accurate in my manual alignment, even to the point of putting it right on that first star. The built in speeds should take me from there.

And I may just buy a used LXD-75. Thankfully, there is a plethora of material on how to tear down and rebuild one on the web.

#8 Tapio

Tapio

    Apollo

  • -----
  • Posts: 1327
  • Joined: 24 Sep 2006
  • Loc: Tampere, Finland

Posted 04 September 2013 - 08:28 AM

There's Syntrek mounts HEQ5 & EQ6:
http://www.skywatche...s1=3&class2=302

#9 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 44289
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 04 September 2013 - 08:34 AM

I suppose a related question would be, can the VX mount be operated easily in non-goto mode? That is, can you just tell it to track without doing any alignment?



I don't know about the VX mount but it's very easy with the CG-5 ASGT. You just go into the tracking menu and select EQ-North.

Jon

#10 Eddgie

Eddgie

    Voyager 1

  • *****
  • Posts: 12924
  • Joined: 01 Feb 2006

Posted 04 September 2013 - 10:02 AM

Right.

The GM8 uses a very big clutch disk that allows for delicate adjustment of the friction, and is as close to "Premium Dob" manual movement as you can get.

There is no need to unlock anything. You turn a collar on each axis to set the friction on the clutch faces and you can adjust it to very firm, or very light, or anywhere in between.

The gears mount on the shafts so the DSC tracks all the time, and if you move the scope manually, it does not loose position.

If you really don't need "Go-To" and can be happy with "Push-To" the GM8 is one of the sweetest mounts out there.

But here is the catch. The GM8 with a DSC computer is not cheap.

It will run all night on a small bettery pack though, so you completely cut the cord, it is inaudible even during the highest speed slews (unless you start breathing hard from the effort), It is fully supported by Losmanday and you can buy any part that should ever break (don't expect to have to do this, but I have two mounts now that are getting hard to get parts for).

They are beautifully made, and function superbly.Oh, and this. If you do a careful polar alignment, you don't even need DSCs. While the setting circles are rather small, they are decently legible. It is surprising how quickly and accurately you can get to objects using manual setting circles. If you are using a small refractor or other scope with a 2 degree field capability, manual cricles are quite good on the GM8.

#11 Michael Rapp

Michael Rapp

    Gemini

  • *****
  • Posts: 3326
  • Joined: 26 Apr 2004
  • Loc: Dickinson, TX

Posted 05 September 2013 - 01:10 PM

That's good to hear, Eddgie. I grew up on a Meade 826C mount, which was friction-clutch and push-to. Makes star-hopping a lovely experience.

They are expensive....but as you indicated they are lifetime mounts. Every member of my club that bought a GM-8 or GM-11 two decades ago are still using them.






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics