Jump to content


Photo

which mount is the most suitable for me?

  • Please log in to reply
21 replies to this topic

#1 dongchina

dongchina

    Sputnik

  • -----
  • Posts: 42
  • Joined: 19 Aug 2008
  • Loc: Tianjin, CHINA

Posted 02 June 2009 - 01:49 AM

Hi~~ :

I am going to make a Newtonian D=305mm,F=4,and make the tube with aluminium alloy [No. #6063]. Then its weight will be about 22kg.[includes dovetail;tube holders; guidingscope;etc.. all miscellaneousness]

At the beginning I want to use Vixen's NEW ATLUX, but its preload is just about 22kg! Then I think of CGE & CGE Pro.
I'd like to ask help and useful advice~~~ CGE or CGE Pro, which is the best one for me?

#2 dongchina

dongchina

    Sputnik

  • -----
  • Posts: 42
  • Joined: 19 Aug 2008
  • Loc: Tianjin, CHINA

Posted 02 June 2009 - 03:18 AM

P.S. How much shall the thickness of the aluminium alloy board be? Which is the best? 2mm or 2.5mm?

#3 Bowmoreman

Bowmoreman

    Clear enough skies

  • *****
  • Posts: 9162
  • Joined: 11 Sep 2006
  • Loc: Bolton, MA

Posted 02 June 2009 - 06:20 AM

Your challenge won't be only weight... a 12" f4 Newt is going to have a HUGE moment arm, not to mention "sail area"...

IMO there is no way you should mount that on any mount not in at least the CGE-Pro/Titan/MI-250 class... And, quite frankly, if AP with that setup is in the cards, you may want to step up to AP900/1200 class...

That is a big scope, whether or not you end up using 2mm or 2.5mm metal...

Good luck and enjoy the build!

clear enough skies

#4 Luigi

Luigi

    Fly Me to the Moon

  • *****
  • Posts: 5320
  • Joined: 03 Jul 2007
  • Loc: MA

Posted 02 June 2009 - 06:37 AM

I've seen and observed with 10" Newts on Atlas mounts and they were pretty marginal. If your 12" comes out the same weight and moment as those 10" Newts, it'll be marginal too. If it's more, it'll be over the limit. A G11 or CGE would be better, though still not really adequate. Like recommended above CGE-Pro etc are better.

#5 GaryML

GaryML

    Ranger 4

  • *****
  • Posts: 348
  • Joined: 16 Feb 2009
  • Loc: San Diego, California

Posted 02 June 2009 - 08:58 AM

Hi~~ :

I am going to make a Newtonian D=305mm,F=4,and make the tube with aluminium alloy [No. #6063]. Then its weight will be about 22kg.[includes dovetail;tube holders; guidingscope;etc.. all miscellaneousness]

At the beginning I want to use Vixen's NEW ATLUX, but its preload is just about 22kg! Then I think of CGE & CGE Pro.


The Altux is rated for a load of 75 lb./34 kg:

http://www.vixenopti...ounts/atlux.htm

If you want more load capacity in a Vixen mount, then get the Gaiax which is rated for a load of 100 lb./45 kg:

http://www.vixenopti...unts/gaiax.html

#6 Chris Curran

Chris Curran

    Viking 1

  • *****
  • Posts: 827
  • Joined: 14 Jun 2005
  • Loc: Brandon, FL

Posted 02 June 2009 - 10:18 AM

That's a long(ish) tube of large diameter == wind sail. I have a 10" f/6 mounted to an AP 1200 for imaging use - I wouldn't think of using a smaller mount.

#7 dongchina

dongchina

    Sputnik

  • -----
  • Posts: 42
  • Joined: 19 Aug 2008
  • Loc: Tianjin, CHINA

Posted 02 June 2009 - 09:56 PM

Thank you! GaryML & others. But please have a look at this address-----http://www.vixen.co.jp/English/at/spec/atlux_e.html
I have ever sent an E-MAIL to Vixen's Japanese company, and their answer is just 22kg! not 35kg~~~

The tube is about 1200mm long. If I increase the length of the dovetail and the distance between the 2 tube holders, will this decrease the vibrance of the tube?

Have a look at my draw.

Attached Files



#8 Bowmoreman

Bowmoreman

    Clear enough skies

  • *****
  • Posts: 9162
  • Joined: 11 Sep 2006
  • Loc: Bolton, MA

Posted 03 June 2009 - 06:15 AM

Hi Dongchina... two points:

1) Vixen and "ratings"

Vixen JP *always* rate things FAR more conservatively than Vixen USA (or others). For SOME reason, non JP Vixen seem to rate their mounts for "total load" (which INCLUDES counterweights)... The most recent incarnation of this "behavior" was with the introduction of the Vixen Sphinx SXD

When in doubt - go with Vixen Japan ratings

2) The "issue" with mounting a scope of the size you are contemplating is only partially a function of the rigidity with which you clamp it to the mount.

Most of the issue is that it's just very, VERY long, with most of its weight close to one end (i.e. not intrinsically balanced). This then means that to balance it, you will have a LOT of its length hanging WAY out there away from the Center of Gravity of the mounting point. that is going to create quite a "sail"/moment arm for vibrations.

Also, its just plan huge and heavy... You are going to need a mount that can "muscle it around"...

Having had a CGE (and now an MI-250), I wouldn't even attempt to mount my f4.7 254mm Newt on my old CGE... I might - as a thought experiment sometime - TRY it on my MI-250... but I'm pretty sure it won't be ideal at least for AP, Visual will be fine I'm sure. And your 12" mirror is gonna be way heavier than my 10"!

Final point: if you are at all going to be using this system for visual, you are going to want/need rotating rings. And, if you are also going to do AP, then those rotating rings need to be sturdy. Sturdy, rotating rings for a 12" OTA are BIG and Heavy; at least another6-8Kg of weight.

So, again, I think your mount needs to be in a bigger class than you had originally considered.

Clear enough skies

#9 Ian Robinson

Ian Robinson

    Soyuz

  • -----
  • Posts: 3916
  • Joined: 29 Jan 2009
  • Loc: 33S , 151E

Posted 03 June 2009 - 06:40 AM

Hi~~ :

I am going to make a Newtonian D=305mm,F=4,and make the tube with aluminium alloy [No. #6063]. Then its weight will be about 22kg.[includes dovetail;tube holders; guidingscope;etc.. all miscellaneousness]

At the beginning I want to use Vixen's NEW ATLUX, but its preload is just about 22kg! Then I think of CGE & CGE Pro.


The Altux is rated for a load of 75 lb./34 kg:

http://www.vixenopti...ounts/atlux.htm

If you want more load capacity in a Vixen mount, then get the Gaiax which is rated for a load of 100 lb./45 kg:

http://www.vixenopti...unts/gaiax.html


I was going to say the same thing , the Atlux is build like a tank ....

You'd have no problem mounting a 12" f4 newt onto a New Atlux , I reckon you'd probably be able mount a RF newt up to 15" on one without overloading it .... unlike some companies GEMs I think Vixen is very concervative on max loading capabilities on their GEMs , they have are overengineered.

You'll likely find a Vixen New Atlux will out perform any off the shelf Celestron or Losmandy GEM of comparable size.
This is why I bought mine.

#10 Ian Robinson

Ian Robinson

    Soyuz

  • -----
  • Posts: 3916
  • Joined: 29 Jan 2009
  • Loc: 33S , 151E

Posted 03 June 2009 - 06:41 AM

duplicated post

#11 ericsolo

ericsolo

    Explorer 1

  • -----
  • Posts: 71
  • Joined: 27 Dec 2005
  • Loc: Edmonton, AB, Canada

Posted 03 June 2009 - 07:56 AM

A few months ago, I emailed Vixen Optics (USA) to confirm the payload of the New Atlux, and was told that it is rated at 75 pounds (34 kg) for "photographic capabilities", with the counterweights included.

It is my experience that the while the New Atlux may be mechanically "overengineered", the tripods are not so capable. There is a great deal of flex in my DP95 tripod.

Eric

#12 GaryML

GaryML

    Ranger 4

  • *****
  • Posts: 348
  • Joined: 16 Feb 2009
  • Loc: San Diego, California

Posted 03 June 2009 - 01:46 PM

Thank you! GaryML & others. But please have a look at this address-----http://www.vixen.co.jp/English/at/spec/atlux_e.html
I have ever sent an E-MAIL to Vixen's Japanese company, and their answer is just 22kg! not 35kg~~~

The tube is about 1200mm long. If I increase the length of the dovetail and the distance between the 2 tube holders, will this decrease the vibrance of the tube?

Have a look at my draw.


I don't have any experience with these big Vixen mounts -- I was just pointing you to the specs I found. Most manufacturers quote the load rating as NOT including counterweights. Vixen makes some nice products (and I like my Vixen VMC200L telescope), but they often do not provide enough information about their products. If Vixen says use the 22 kg number and to include counterweights in the 35 kg figure, then that is what you should use.

My strategy for mounts is to go oversize if possible. I like minimal vibration, and under-stressed components are more reliable and last longer. If possible, I would get a mount rated for double the load it will carry. In any event, leave yourself a healthy margin for extra capacity for best stability and for future additions to the system.

As others have pointed out, a long telescope puts added strain on the mount even if it is perfectly balanced. A longer dovetail won't change this. Cutting some weight by using a lighter tube (carbon fiber or an open truss?) may help.

Whatever you get, it is going to be a very large, very heavy set-up. If this is a permanent installation in an observatory, then you will want a sturdy pier set in concrete. If you want to transport the telescope, then you're going to need a truck and a couple of helpers to move it and set it up!

#13 Bowmoreman

Bowmoreman

    Clear enough skies

  • *****
  • Posts: 9162
  • Joined: 11 Sep 2006
  • Loc: Bolton, MA

Posted 03 June 2009 - 02:47 PM

This is the SAME issue we all went through about 18 months to 2 years ago when Vixen introduced the Sphinx SXW to replace/adjunct the Sphinx SXD

At that time, Vixen Optics (in the US they had *just* changed distributors from Vixen North America - which was a Televue company) started rating the Vixen mounts "INCLUDING Counterweights"... when, simultaneously, if one went to Vixen.co.jp website and poked around, it was easy to find that they were rated LESS - NOT including counterweights...

Every other manufacturer rates by LOAD (and doesn't include the CW weight in that load). Vixen JP even do it that way.

Vixen Optics (US) was claiming 50# load on a Sphinx SXD, which, for anyone who has owned a Sphinx/HAL combination, you could tell was NUTS... until we discovered they were saying 50 pounds of LOAD + CW... Oh, I get it... change the metric!

Go back and do some CN searches (research) on the whole Sphinx situation: It's fascinating. Basically the SXW was rated (in Japan) at 12Kg - and at 25# capacity in the US (which from my experience with one - WAS its true limit)...

Then they came out with the SXD, wherein the only significant change was to make the bearings/spindle assembly out of steel instead of brass - NOTHING was made bigger/beefier...

And yet Vixen Optics (America) rated it at 50# (by INCLUDING CW in the rating)... I.e. changing the "rules"

So, if Vixen Optics is rating the New Atlux at 75# for load and counterweights; and your OTA weighs more than 40# (which I believe highly likely given that a 254mm f4.7 Newt OTA weighs about 30#), then when you add in the CW to balance it, you are OVER.

And that is before factoring enough stability for AP, weight for rings, plates, camera(s), EP's, etc...

I think the class of mount needed to successfully and sturdily mount a scope of OP's size/weight/dimensions, is going to be in your basic AP900 class and above. Obviously IMHO.

Motto: always read all the fine print.

clear enough skies

#14 jouster

jouster

    Viking 1

  • -----
  • Posts: 947
  • Joined: 27 Nov 2005

Posted 03 June 2009 - 06:32 PM

Hi~~ :

I am going to make a Newtonian D=305mm,F=4,and make the tube with aluminium alloy [No. #6063]. Then its weight will be about 22kg.[includes dovetail;tube holders; guidingscope;etc.. all miscellaneousness]

That seems light for a newt that size plus all accessories.

I hadn't heard of the Vixen Gaiax mentioned earlier. Seems like $15,000 is a lot for a 100lb capacity mount. Not saying it isn't good; just that for that price, I'm getting a Paramount or an AP 1200, or investigating Parallax, Iott or MI.

#15 dongchina

dongchina

    Sputnik

  • -----
  • Posts: 42
  • Joined: 19 Aug 2008
  • Loc: Tianjin, CHINA

Posted 03 June 2009 - 09:57 PM

Dear Bowmoreman,

Thank you VERY MUCH for so much useful help & advice!

Now I am still a bit sad...... you know, I want to do both visual & AP, and i do know that the aperture of a telescope is such important for watching much more faint objects.

I ONLY have 30000 RMB, equal to 3750 dollars, this sum of money is the budget for me to buy a good mount that I can afford. Those famous brands, such as ME,AP,TAKAHASHI etc., for me are so expensive~~~~ :bawling: And I have no my own car,but my good friends are to buy a car recently, we have no dome, usually, we are going to observe in wild mountain regions.

http://www.telescope...de=PON08F000001
So have a look at this, I think that this telescope is only for visual, not very suitable for AP maybe, is it right???

I have found the homepage of MI 250. wow!!! :bawling: :bawling: 7000dollars~~~ for me it is ABSOLUTELY an astronomical number!!! And this do not include necessories~~~ :tonofbricks:

How shall I do???? :bawling:


I list a form bellow:
1). mirror: net diameter=305mm; thickness=38mm; net weight=6kg
2). mirror cell: aluminium, net weight=2.4kg. it has 9 points of nylon support, 3 screws are for push and 3 for pull
3). the tube: #6063 aluminium alloy, density is 2.7g/cm3; thickness=2mm; I give up both up cover and rear cover.
4). focuser: 1.25''
5). ORION's SSDS, about 500g; or Nikon FA camera body + lens + teleconvertor + flip mirror, etc...... other necessories-----1kg
6). secondary mirror + spider: about 600g
7). guidingscope + support: about 2kg
8). dovetail board: #6063 aluminium alloy, thickness=2~3cm; tube rings. All are about 3~4kg

It is said that CGE's maxload is 65 pound, about 29kg. So Bowmoreman, Why do you say that CGE is not suitable for my Newtonian? I do not understand,yet.

I do want to buy C14~~~ but it is too expensive :bawling:

#16 dongchina

dongchina

    Sputnik

  • -----
  • Posts: 42
  • Joined: 19 Aug 2008
  • Loc: Tianjin, CHINA

Posted 03 June 2009 - 10:43 PM

Maybe I begin to see the truth:

New ATLUX's maxload is 22kg + 7kg & 3.5kg [2 CWs] =32.5kg, about 34kg

So New ATLUX can ONLY carry a telescope of 22kg!!! Perhaps less than 22kg, because we all know that it is always good for a mount that leaving some loading-capability to the mount, or there will be harmful to the gears and bearings.

Then 65 pound for CGE.....

65 = 1. tube + CWs? or
2. ONLY tube & other necessories?

#17 dongchina

dongchina

    Sputnik

  • -----
  • Posts: 42
  • Joined: 19 Aug 2008
  • Loc: Tianjin, CHINA

Posted 03 June 2009 - 10:52 PM

AND ESPECIALLY I FIND A STRANGE THING:

At Celestron's homepage, all mounts' spec give their max loading, such as CGEM; CGE Pro; CG5. BUT IT IS CGE that has no this item!!!

WHY DOES CELESTRON DO LIKE THIS???????? WHY DOES CELESTRON HIDE THIS FROM US???

#18 Bowmoreman

Bowmoreman

    Clear enough skies

  • *****
  • Posts: 9162
  • Joined: 11 Sep 2006
  • Loc: Bolton, MA

Posted 04 June 2009 - 08:34 AM

Dear Bowmoreman,

Thank you VERY MUCH for so much useful help & advice!

Now I am still a bit sad...... you know, I want to do both visual & AP, and i do know that the aperture of a telescope is such important for watching much more faint objects.

OK, I'll try and answer each of your points/questions separately


I ONLY have 30000 RMB, equal to 3750 dollars, this sum of money is the budget for me to buy a good mount that I can afford. Those famous brands, such as ME,AP,TAKAHASHI etc., for me are so expensive~~~~ :bawling: And I have no my own car,but my good friends are to buy a car recently, we have no dome, usually, we are going to observe in wild mountain regions.


Got it. So that means it MUST be something that is - relatively - easy to breakdown, transport, and then setup again


http://www.telescope...de=PON08F000001
So have a look at this, I think that this telescope is only for visual, not very suitable for AP maybe, is it right???


That scope is WICKED undermounted, in my opinion, even for visual. A 12" Newt on an EQ6/Atlas!!! Yikes! I can't imagine the shakes!

Here is the OTHER problem with Newtonians on EQ mounts: the eyepiece will end up in some INCREDIBLY difficult (impossible!) locations depending on what you are trying to look at. This then MANDATES (in my opinion again) that you must use rotating rings (for visual).

If you want to be able to quickly/easily go between visual and AP, then those rings need to be very rigid and solid. That means: 1) expense, and 2) significant additional weight.


I have found the homepage of MI 250. wow!!! :bawling: :bawling: 7000dollars~~~ for me it is ABSOLUTELY an astronomical number!!! And this do not include necessories~~~ :tonofbricks:

How shall I do???? :bawling:


Not to worry! ;)

I list a form bellow:
1). mirror: net diameter=305mm; thickness=38mm; net weight=6kg
2). mirror cell: aluminium, net weight=2.4kg. it has 9 points of nylon support, 3 screws are for push and 3 for pull
3). the tube: #6063 aluminium alloy, density is 2.7g/cm3; thickness=2mm; I give up both up cover and rear cover.
4). focuser: 1.25''
5). ORION's SSDS, about 500g; or Nikon FA camera body + lens + teleconvertor + flip mirror, etc...... other necessories-----1kg
6). secondary mirror + spider: about 600g
7). guidingscope + support: about 2kg
8). dovetail board: #6063 aluminium alloy, thickness=2~3cm; tube rings. All are about 3~4kg

It is said that CGE's maxload is 65 pound, about 29kg. So Bowmoreman, Why do you say that CGE is not suitable for my Newtonian? I do not understand,yet.


Ok, here's my experience. I had no issues loading my CGE up to 55# for either visual or imaging. But, my setup was NOT with an OTA 1200mm+ long. So I didn't have the moment-arm issues or wind/sail issues you will likely run into.

I think with careful balancing you might be able to make it work for AP (at shorter exposures)... You will almost certainly have a fair proportion of your shots you will have to throw out due to things like breezes moving the tube etc... Since you are NOT in a protected observatory (like I am)... So, this is not impossible. Expect challenges on the AP side of things.

Go Widefield, short exposures, and it probably will work fine.

There are those who've successfully loaded CGE's up to, and even beyond the rated 65# (at least with the CGE the rating is for the Load - and doesn't include CWs!) for imaging.

It would certainly work reasonably well for visual. My concern, ultimately, is that a 12" f5 Newtonian is a VERY large scope.


I do want to buy C14~~~ but it is too expensive :bawling:


Certainly, given your pricing situation, the CGE is the only potential candidate (in my opinion). It is, I think, on the low-ish side of what you need.

I hope this is helpful to you. Perhaps you can find a used CGE in China somehow, and then use funds saved to acquire a good set of solid rotating rings (e.g. Parallax) - which as I noted before are NOT cheap, and are heavy.

good luck

clear enough skies

#19 Bowmoreman

Bowmoreman

    Clear enough skies

  • *****
  • Posts: 9162
  • Joined: 11 Sep 2006
  • Loc: Bolton, MA

Posted 04 June 2009 - 08:42 AM

AND ESPECIALLY I FIND A STRANGE THING:

At Celestron's homepage, all mounts' spec give their max loading, such as CGEM; CGE Pro; CG5. BUT IT IS CGE that has no this item!!!

WHY DOES CELESTRON DO LIKE THIS???????? WHY DOES CELESTRON HIDE THIS FROM US???


Can't say. My experience with Celestron and virtually every other mount maker other than Vixen (America - not Japan!) is that they rate the load as the "LOAD" and do NOT consider CW's as "Load"...

Now, why Celestron no longer talk about the load capacity of the CGE??? Don't know. Not to worry. It is, in my direct, and may other's experiences, quite capable of loads up to to the 55-65# or more (not including CWs).

Careful balance is the key. As low a center of gravity as possible (for the load) is key. As minimal moment arm of the load as possible is the key.

Believe me, a CGE is "just about" at the limit of "transportable" (at least for me!)... Anything bigger starts to get into the serious hassle to transport range...

Obviously, weight lifters, etc. may feel differently. But I wouldn't want to constantly be transporting a CGE Pro, AP900, MI250, Losmandy Titan, etc... on a frequent basis...

Ever lift just the tripod for something like a CGE? :lol:


Clear enough skies

#20 jrcrilly

jrcrilly

    Refractor wienie no more

  • *****
  • Administrators
  • Posts: 33757
  • Joined: 30 Apr 2003
  • Loc: NE Ohio

Posted 04 June 2009 - 12:32 PM

Then 65 pound for CGE.....

65 = 1. tube + CWs? or
2. ONLY tube & other necessories?


2. ONLY tube & other necessories?

That's for visual use, though. For imaging, most folks would derate it to 22kg or so. With the Japanese mounts (and with other premium brands) the stated load is usable for imaging so derating is not necessary.

#21 Bowmoreman

Bowmoreman

    Clear enough skies

  • *****
  • Posts: 9162
  • Joined: 11 Sep 2006
  • Loc: Bolton, MA

Posted 04 June 2009 - 01:35 PM

Then 65 pound for CGE.....

65 = 1. tube + CWs? or
2. ONLY tube & other necessories?


2. ONLY tube & other necessories?

That's for visual use, though. For imaging, most folks would derate it to 22kg or so. With the Japanese mounts (and with other premium brands) the stated load is usable for imaging so derating is not necessary.


Agreed, but with the sole exception that you must use the Japanese sourced ratings in the case of Vixen, and NOT the importer: Vixen Optics! (because of the CW "counting issue")...

Clear enough skies

#22 dongchina

dongchina

    Sputnik

  • -----
  • Posts: 42
  • Joined: 19 Aug 2008
  • Loc: Tianjin, CHINA

Posted 04 June 2009 - 10:28 PM

Thank you Bowmnoreman & other friends!

Last night I made an experiment on my EQ-2 made in China 10 years ago~~ it looks good, yes! just like those you have told me, "careful and perfect balance is so important!" After a good balance, the mount works so fluently & smoothly~~ :) And I add some lubrecant between the worm gear and other gears. There is hardly any vibrance,you know, I have no motor driver, I drive the mount by my hand~~

my newt is 114--900,its weight is 3kg. then I put these things onto it:
1.)70--350 refractor for guiding + 9mm guiding lens + a ring. about 2kg

2.)Nikon FA body + teleconveror + eyepiece

I just wanted to carry out this experiment on eq-2, if this little mount can perform well, then I think that CGE will be much better~~

Just wait for some time, I will put some photoes here. Hope all friends give me helpful advice~~~






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics