Jump to content


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


alt-az + accessories or gem?

  • Please log in to reply
4 replies to this topic

#1 lsfinn


    Explorer 1

  • *****
  • topic starter
  • Posts: 86
  • Joined: 28 Jan 2013
  • Loc: State College, PA

Posted 02 February 2013 - 10:37 AM

Ok - I'm torn. I'm trying to decide between a cpc 925 with accessories or a cgem 925 w/o. I'm going to be visual for a while, but have a burning desire to move into imaging. My previous experience (years ago) was always with an equatorial mount.

I understand that alt-az goto mounts are fantastically convenient, and that the alt-az system will be much lighter (and, very possibly, more likely to get out and about). I suppose that when I move toward imaging I can get a wedge; but, will it be as good as a good equatorial mount?

Of course, I could always go cpc 1100 w/o accessories...

I'd appreciate hearing anyone weigh-in with the kind of choice they'd make . . . and why (understanding always that many of the reasons will be subjective!)



#2 fmhill



  • -----
  • Posts: 436
  • Joined: 17 Jul 2012
  • Loc: Cape Cod, Massachusetts, USA

Posted 02 February 2013 - 10:50 AM

If you intend to get into astrophotography, put your money into the best GEM mount you can afford...

Alt/Az motions are intended for terrestrial viewing and are adapted to astronomical viewing however the motions are all wrong for astronomical tracking.

The GEM mount was developed for astronomical viewing and has the correct motions to compensate for the rotation of the earth relative to the position of Stars, DSO's, and other astronomical objects.

Attempting astroimaging with an Alt/Az mount can be done with short exposures and often reduced image quality however an accurate stable GEM mount allows you virtually unlimited exposure times when astroimaging, exposures times are only limited by sky conditions and light pollution provided the GEM mount is polar aligned accurately...

#3 csrlice12



  • *****
  • Posts: 16390
  • Joined: 22 May 2012
  • Loc: Denver, CO

Posted 02 February 2013 - 11:09 AM

Yup, if AP is in your future, go with the EQ Mount.

#4 Midnight Dan

Midnight Dan

    Voyager 1

  • *****
  • Posts: 12280
  • Joined: 23 Jan 2008
  • Loc: Hilton, NY, Yellow Zone (Bortle 4.5)

Posted 02 February 2013 - 11:17 AM

Alt/az mounts CAN be lightweight and easy to use but the CPC series combines the OTA and mount head into one unit that is not separable. At 60 pounds, I would personally not consider that lightweight, especially when you have to hoist it onto a tripod.

A GEM will certainly weigh more as a complete unit, but breaks down into manageable pieces. And a GEM will do a lot better when you get into AP.


#5 Gargoyle


    Ranger 4

  • *****
  • Posts: 350
  • Joined: 13 Mar 2008
  • Loc: Long Island, New York

Posted 02 February 2013 - 10:34 PM

Go with a GEM, and get the best one you can afford.


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics