Jump to content


Photo

GEM for 6" f/8 Newt

  • Please log in to reply
24 replies to this topic

#1 moynihan

moynihan

    Vanguard

  • -----
  • Posts: 2315
  • Joined: 22 Jul 2003
  • Loc: Lake Michigan Watershed

Posted 10 April 2013 - 03:36 PM

Hello,
What German equatorial mounty would you pic for mounting a 6" f/8 newtonian ota?

For visual use only.

To anticipate one line of answer, I am familiar with dob mounts, i use a dob, do not want to mount it on a dob, thanks.

#2 Falcon-

Falcon-

    Aurora

  • *****
  • Posts: 4942
  • Joined: 11 Sep 2009
  • Loc: Gambier Island, BC, Canada

Posted 10 April 2013 - 05:37 PM

I would guess my M606 should be similar in weight/length to your 6" f/8 newt. I have used that on a CG-5 successfully. Perhaps then a Celestron AVX (the CG5's sucessor) might be the way to go, or for a slightly more beefy mount, an Orion Atlas.

If you are budget constrained a Celestron Omni-CG4 might work (not quite as beefy as an AVX, manual, no automatic go-to). If you just won the lottery a Losmandy GM8 or G11 are *excellent* quality mounts.

Ya, I know... not exactly a single answer ;)

#3 Mel M

Mel M

    Mariner 2

  • *****
  • Posts: 204
  • Joined: 04 May 2008
  • Loc: southern Oregon

Posted 10 April 2013 - 05:46 PM

My 6" f/6 newt is a little under-mounted on a GM-8. Usable but not solid.

#4 Kendahl

Kendahl

    Vostok 1

  • -----
  • Posts: 144
  • Joined: 02 Feb 2013

Posted 10 April 2013 - 06:48 PM

Orion used to sell a 6 inch f/8 Newtonian on their Skyview Pro GEM. (It's still available as a dob.) The combination works well for strictly visual observation. Current price for the mount alone is $400. The mount really benefits from spending another $60 for a polar alignment scope and $150 for dual axis drive. That increases the total to $610 and it's still not a GoTo mount. OPT will sell you a left over CG-5 GoTo for $550. That strikes me as the better deal. An Advanced VX mount would be even better but, with a price of $800, it's not as good a bargain.

#5 skywolf856

skywolf856

    Ranger 4

  • -----
  • Posts: 309
  • Joined: 25 Jan 2008
  • Loc: SE Michigan

Posted 10 April 2013 - 07:21 PM

I mount my 8" f7 on my CG5.
It works for visual use.

Attached Files



#6 moynihan

moynihan

    Vanguard

  • -----
  • Posts: 2315
  • Joined: 22 Jul 2003
  • Loc: Lake Michigan Watershed

Posted 10 April 2013 - 09:09 PM

My 6" f/6 newt is a little under-mounted on a GM-8. Usable but not solid.


I find that very interesting, given its stated load capacity. Is it the standard legs?

#7 moynihan

moynihan

    Vanguard

  • -----
  • Posts: 2315
  • Joined: 22 Jul 2003
  • Loc: Lake Michigan Watershed

Posted 10 April 2013 - 09:11 PM

I mount my 8" f7 on my CG5.
It works for visual use.


That is a beautiful scope.

#8 MikeCMP

MikeCMP

    Vostok 1

  • *****
  • Posts: 185
  • Joined: 12 Jul 2011
  • Loc: Chardon OH

Posted 10 April 2013 - 09:16 PM

I use an atlas for my 5" newt. Works for visual and photography. But I bet it is way more mount than you need.

Do you need go-to for your mount? If not, the. An eq-4 might fit the bill for you too.

Mike

#9 moynihan

moynihan

    Vanguard

  • -----
  • Posts: 2315
  • Joined: 22 Jul 2003
  • Loc: Lake Michigan Watershed

Posted 10 April 2013 - 09:37 PM

Do you need go-to for your mount?

Nope. do not need go to.

#10 Falcon-

Falcon-

    Aurora

  • *****
  • Posts: 4942
  • Joined: 11 Sep 2009
  • Loc: Gambier Island, BC, Canada

Posted 10 April 2013 - 11:30 PM

Well... if you do not need go-to...

Check out the classifieds here and other such places and keep an eye out for a used non-goto Orion Atlas (aka Skywatcher EQ6) or non-goto Losmandy G11. If one of those fit in your budget you would end up with a much more stable mount then a CG4 would give you.

(what counts as "stable" and vibration-free is a matter of personal preference of course. You may find the OmniCG4 or an older used non-goto CG5 would be perfectly fine for you. Just stay away from the EQ1/CG2 or EQ2/CG3 - those tend to be quite shaky even with smaller scopes)

#11 Husbyggarn

Husbyggarn

    Mariner 2

  • -----
  • Posts: 216
  • Joined: 12 Dec 2008
  • Loc: Sweden

Posted 11 April 2013 - 01:38 AM

I have my 6" F5 on the old black non-goto skywatcher Heq5 (Orion sirius).
Works great for photo and visual.
I understand F8 is much longer than F5 but for visual i think it would work.

Attached Files



#12 moynihan

moynihan

    Vanguard

  • -----
  • Posts: 2315
  • Joined: 22 Jul 2003
  • Loc: Lake Michigan Watershed

Posted 11 April 2013 - 07:06 AM

Thanks for all the input folks

jay

#13 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 44804
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 11 April 2013 - 07:19 AM

Thanks for all the input folks

jay


Jay:

It really depends on the weight of the OTA. The classic 6 inch F/8 Newtonian is the RV-6. The RV-6 tube is phenolic and the complete OTA minus rings weighs 8 pounds. It rides reasonably well on the original mount, a AstroView or CG-4 does a reasonable job with it as well.

A CG-5ASGT would be overkill but do a nice job. I find that a CG-5ASGT is fine for my 8 inch F/5, people put 10 inch F/5s on them and C-11s, the 10 inch F/5 OTA is around 30lbs... Not me.. That's what Altas's are for, not for 6 inch F/8's...

How heavy is your OTA???

Jon

#14 moynihan

moynihan

    Vanguard

  • -----
  • Posts: 2315
  • Joined: 22 Jul 2003
  • Loc: Lake Michigan Watershed

Posted 11 April 2013 - 07:36 AM


How heavy is your OTA???

Jon


Fully loaded it will be about 17-18 pounds.

#15 obin robinson

obin robinson

    Mercury-Atlas

  • *****
  • Posts: 2667
  • Joined: 25 Oct 2012
  • Loc: League City, TX

Posted 11 April 2013 - 07:47 AM

If you are on a budget look for a used Meade Starfinder EQ. I have a 10" scope on it and the mount swings it smoothly without a problem.

obin ;)

#16 Mirzam

Mirzam

    Skylab

  • *****
  • Posts: 4459
  • Joined: 01 Apr 2008
  • Loc: Lovettsville, VA

Posted 11 April 2013 - 08:17 AM

RV-6 on a GM8. Works great, although as mentioned above the RV-6 OTA is exceptionally light weight.

JimC

Attached Files



#17 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 44804
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 11 April 2013 - 11:52 AM



How heavy is your OTA???

Jon


Fully loaded it will be about 17-18 pounds.


Something to consider:

The old Equatorially mounted Newtonians were all pier mounted. There is good reason for this. With a Newtonian on an EQ mount, the mirror end of the tube and a tripod often want to be occupying the same space... this happens much less frequently with a pier.

Also, tripods achieve their stability by having their legs widely spread, this requires that the mount itself be higher than is optimal. To keep from being tippy, the legs must be spread wide. With a pier, the stability comes from the arms and not the triangulated height so the mount can be at the optimal height for observing.

I just don't see a need for a heavy mount for a 18 lbs 6 inch F/8 OTA.

Jon

Posted Image

#18 moynihan

moynihan

    Vanguard

  • -----
  • Posts: 2315
  • Joined: 22 Jul 2003
  • Loc: Lake Michigan Watershed

Posted 11 April 2013 - 01:17 PM

The old Equatorially mounted Newtonians were all pier mounted. There is good reason for this. ...


Indeed there is good reason for it. I have wondered about that approach, now. Orion (U.S.A.) used to offer mounting piers, as did Antares. I am not aware of a modern source, other than on the used market. :question:Are you aware of any?

#19 Patrick

Patrick

    Voyager 1

  • *****
  • Posts: 11444
  • Joined: 15 May 2003
  • Loc: Franklin, Ohio

Posted 11 April 2013 - 03:12 PM

I used a 6" f/8 Orion Newt for a couple of years mounted on a CG5-GT mount. I'd give it an 8 out of 10 for stability. Right now you can pick up a new CG-5 for under $600.

Patrick

#20 hottr6

hottr6

    Mercury-Atlas

  • *****
  • Posts: 2529
  • Joined: 28 Jun 2009
  • Loc: 7,500', Magdalena Mtns, NM

Posted 11 April 2013 - 04:24 PM

You can pick up old Starfinder pier-mounted GEMS for $100-200. A 6" f/8 would be rock solid on that mount.

#21 moynihan

moynihan

    Vanguard

  • -----
  • Posts: 2315
  • Joined: 22 Jul 2003
  • Loc: Lake Michigan Watershed

Posted 12 April 2013 - 07:34 AM

Jon,
Re your 6" classic mounting there:
What is the height of the pier/pedestal (at the bottom of the GEM head) and the width of the pedestal?

Thank you in advance.

#22 cuir

cuir

    Surveyor 1

  • -----
  • Posts: 1746
  • Joined: 03 Mar 2007
  • Loc: Up north.

Posted 12 April 2013 - 10:05 AM

Long post, but required for context, so please don't begrudge me for it.

I used to have an 8" Newtonian on a EQ5, and considered it to be a lot of gymnastics, though I still found it serviceable, but it required a dual-speed focuser to achieve focus at hight powers, and quiet, wind-free weather. Eventually sold the newt for a C8, though. I later ended up trading my way to a 10" newt because of a bout of aperture fever. By then I had changed my mount to a Skywatcher EQ6 Pro, but I soon realized the efforts required to use a 10" on a GEM got me overwhelmed and bummed-out. I Thought of a GoTo dob for a while, but on all 3 which I had tried at star parties, the tracking was "skippy" and not sufficiently smooth for observing with Orthos. At high powers, the slight stutters in motion got very distracting.

That was, more or less, about a year ago. The Lx80 was announced, but I had not seen it, and wasn't sure about it being bulky enough for a 10" Newt, even in Alt-Az mode. Other factors kept me away from the hobby for a while, and forced me to liquidate a lot of my gear. I still had the 10" Newt and a few T6 Naglers, though. Last week, I got wind of the AZ/EQ6 being available. I have ordered one the very same day.

If the EQ6 Pro I used to own is a good hint of what this new mount is capable of, I'm quite confident it's AZ function will be a winner for big reflectors. I should be getting my new mount within 10 days. I also ordered an extra counter-weight and a pier extension to go with it. I will most certainly post my first impressions here on CN, so if you have not yet chosen and acquired your mount, perhaps I'll have some hands-on time and first impressions about the Az/EQ6 solution for a big Newt.

#23 Geo.

Geo.

    Gemini

  • *****
  • Posts: 3065
  • Joined: 01 Oct 2008
  • Loc: Upstate NY

Posted 12 April 2013 - 06:06 PM

I think windage is the real concern not weight. Getting it low on a Newt height pier will probably do more for stability than a heavy mount.

#24 Mel M

Mel M

    Mariner 2

  • *****
  • Posts: 204
  • Joined: 04 May 2008
  • Loc: southern Oregon

Posted 12 April 2013 - 07:49 PM

My 6" f/6 newt is a little under-mounted on a GM-8. Usable but not solid.


I find that very interesting, given its stated load capacity. Is it the standard legs?


Standard legs. Sure, a GM-8 can hold 30 pounds but with how much image shake? If the wind blows you need to wait for the image to settle. Touch to focus? Wait for image to settle. A more solid mount would really help the high-power views.

#25 hottr6

hottr6

    Mercury-Atlas

  • *****
  • Posts: 2529
  • Joined: 28 Jun 2009
  • Loc: 7,500', Magdalena Mtns, NM

Posted 13 April 2013 - 09:21 AM

My 6" f/6 newt is a little under-mounted on a GM-8. Usable but not solid.


I find that very interesting, given its stated load capacity. Is it the standard legs?


Standard legs. Sure, a GM-8 can hold 30 pounds but with how much image shake? If the wind blows you need to wait for the image to settle. Touch to focus? Wait for image to settle. A more solid mount would really help the high-power views.

Wow, that surprises me. Someone who is even more sensitive to mount shake than I am. Inconceivable! :bigshock:

Shock and awe aside, how is the backlash on your G8? When I first mounted my 6" f/8 'frac on the G8, it definitely felt like the G8 was not up for the job. I paid a lot of attention to eliminating backlash without too much preload on the worm face and now I am quite happy with the C6R on the G8. It is not perfect, but light-years ahead of the same OTA on a CG5-class, which some folk are perfectly happy with.






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics