Jump to content


Photo

Meade Advanced Coma Free (ACF) question

  • Please log in to reply
11 replies to this topic

#1 Hazel

Hazel

    Lift Off

  • -----
  • Posts: 16
  • Joined: 29 Oct 2012

Posted 08 November 2012 - 03:40 AM

Hi -- does anyone have experience with Advanced Coma Free w/UHTC optics that are available for an additional cost on the Meade LX scopes? On the Meade website the 12" LX90-ACF (f/10) Advanced Coma-Free w/UHTC is $3200 and the 12" LX90-SC (f/10) Schmidt-Cassegrain w/UHTC is $2900. Is the quality of the image noticably better with the ACF? Are there any negatives about ACF that I should be aware of? I am most interested in lunar and planetary observing but will probablay also use it for deep sky. Thanks.

#2 Bob Griffiths

Bob Griffiths

    Getting Grouchy

  • *****
  • Posts: 10620
  • Joined: 10 Oct 2005
  • Loc: Frederick Maryland

Posted 08 November 2012 - 10:21 AM

Oh boy...
a simple answer is YES the AFC optics are simply better then the standard optics.. no question about that fact at all..
The question you have to ask yourself is the AFC optics worth the extra money because on axis there is no difference.. the AFC opticx only do there thing at the edges of the FOV and I personally do not spend much time looking at the edges...

I own a CPC1100 .. mainly because I found the Lx90 12 inch scopes to be way-way under mounted IF I wanted to buy a 12 it would have to have been the Lx200 .. MONEY then became a big factor

The lx90 is fine with the 10 inch OTA BUT NOT with the 12..

Just my opinion

Bob G.

#3 faltered

faltered

    Viking 1

  • -----
  • Posts: 617
  • Joined: 01 Apr 2005

Posted 08 November 2012 - 11:39 AM

The other big question is if you ever plan on getting into astrophotography - then the ACF would be a worthwhile option. I would also think resale value would be better on the ACF option - in case you ever sell and upgrade.

#4 *skyguy*

*skyguy*

    Surveyor 1

  • *****
  • Posts: 1986
  • Joined: 31 Dec 2008
  • Loc: Western New York

Posted 08 November 2012 - 01:41 PM

The ACF optics were really designed for the astrophotographer. The major difference is the AFC will correct for coma along the edge of the image. The LX90 mount with the heavy 12" OTA is best suited for visual use and really demands the heavy duty LX200 mount if you are interested in imaging. Since both optical designs will ... essentially ...produce the same visual experience at the eyepiece, I would purchase the standard 12" SCT with the LX90 mount. I own the standard 12" SCT on a LX200 mount and the optics provide excellent views .... some of the best I've ever had ... of the moon and planets.

BTW, before you make the commitment to buy your scope ... read the recent CN posts on the quality control issues that have plagued Meade since the move to their new Mexican factory:

http://www.cloudynig...5493670/page...



#5 Hazel

Hazel

    Lift Off

  • -----
  • Posts: 16
  • Joined: 29 Oct 2012

Posted 10 November 2012 - 11:26 AM

If the ACF is better than the SC (even if just a little better), I do wonder why Meade still offers traditional SC optics after 7 years on the market with the ACF technology? Is there anything about the traditional SC that makes it actually preferable to the ACF other than a slightly lower price? Other than saving $300 (which is only a 10% difference with the 12" LX90 ACF vs. SC) is there any reason at all why I should buy the traditional SC version?

#6 rcdk

rcdk

    Vostok 1

  • -----
  • Posts: 171
  • Joined: 13 Nov 2010

Posted 10 November 2012 - 01:23 PM

I am bothered by edge of field defects so it was definitely worth it for me.

The 12" LX90 is not for everyone. I would be happy to have the LX200, but couldn't afford the extra $$$. I find the 12" LX90 to be...adequate...as far as the mount goes. You do need to make sure you don't hang on the focuser or bump the eyepiece when observing which is a good idea with any scope.

#7 *skyguy*

*skyguy*

    Surveyor 1

  • *****
  • Posts: 1986
  • Joined: 31 Dec 2008
  • Loc: Western New York

Posted 12 November 2012 - 10:14 AM

Is there anything about the traditional SC that makes it actually preferable to the ACF other than a slightly lower price?


The standard SCT has a 4" secondary mirror (33.3% central obstruction), while the ACF has a larger 4.6" secondary mirror (38.6% central obstruction)... (obstructions expressed as a percentage of the aperture's diameter, not area). This could be a factor when observing low contrast planetary features, however any differences would be very subtle ... but, that is what planetary observing is all about! It would be equivalent to the views between unobstructed telescopes of 7.9" (for the SCT) and 7.4" (for the ACF).

#8 Bill Barlow

Bill Barlow

    Vanguard

  • *****
  • Posts: 2352
  • Joined: 03 Dec 2007
  • Loc: Overland Park KS

Posted 12 November 2012 - 04:55 PM

My Meade 12" ACF secondary diameter/obstruction is exactly 4". But the clear aperture is 11.8"/300mm (distance from where the corrector glass first touches the corrector retaining ring on both sides). So the central obstruction by diameter is a little larger than 33%. Where did you get 4.6"?

Bill

#9 neotesla

neotesla

    Apollo

  • *****
  • Posts: 1121
  • Joined: 18 Nov 2010
  • Loc: Canada

Posted 12 November 2012 - 07:13 PM

The LX200R 12" is a full 12" aperature... Never measured the secondary housing though.

#10 Bill Barlow

Bill Barlow

    Vanguard

  • *****
  • Posts: 2352
  • Joined: 03 Dec 2007
  • Loc: Overland Park KS

Posted 12 November 2012 - 08:43 PM

The older "R" versions must have a slightly thinner corrector retaining ring than the newer "ACF" M12's.

Bill

#11 Hazel

Hazel

    Lift Off

  • -----
  • Posts: 16
  • Joined: 29 Oct 2012

Posted 14 November 2012 - 02:43 AM

So does the newer 12" LX90 SCT also have an 11.8 inch aperture like the newer 12" LX90 ACF? Thanks.

#12 Hazel

Hazel

    Lift Off

  • -----
  • Posts: 16
  • Joined: 29 Oct 2012

Posted 25 November 2012 - 10:26 PM

Skyguy -- I appreciate this information about the size of the secondary mirror obstruction in the ACF vs. the SCG. Can you please tell me your reference for this information? I checked with Meade and could not find it in their spec sheets (on line at least). Thank you very much.






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics