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.

Photo

upgrading astrotec 12 inch mirror cell

ATM collimation dob mirror making optics reflector
  • Please log in to reply
3 replies to this topic

#1 fender2547886

fender2547886

    Sputnik

  • *****
  • topic starter
  • Posts: 48
  • Joined: 27 Aug 2006

Posted 08 December 2019 - 01:54 AM

Hi everyone,

    I am looking for some help. I own the astro tec 12" imaging newtonian and have owned it for a few years. I shelved the scope due to major mirror flop. The mirror flop is so significant for example, on a goto slew the object is not in the ccd fov, whereas the previous object was centered and sync'd . My goto's are dead accurate with another other optical tube, it is defintily the mirror shift.

   I have already upgraded the focuser to a moonlite with the hi res motor and was wondering on everyone thoughts on does it make sense to upgrade the mirror cell, or are the modifications that can be made to the stock cell.  any recommendations on rock solid cells that are better than the current cell.  Are there any concerns or "watch-outs" please let me know. I have an extra mount and would love to image with this scope.

dan
 



#2 CCD-Freak

CCD-Freak

    Vendor - Portable Observatories

  • *****
  • Vendors
  • Posts: 1,925
  • Joined: 17 Jan 2008
  • Loc: Whitesboro,Texas

Posted 08 December 2019 - 04:31 PM

I just traded for one of the 12" F4 (TPO  variant) so I will be watching this thread.  I have not had mine out yet so it will be interesting to see if I  have similar issues.

 

 

John

CCD-Freak

WD5IKX


Edited by CCD-Freak, 08 December 2019 - 04:53 PM.


#3 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 85,632
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 08 December 2019 - 05:45 PM

It's my understanding that the tube wall flexes under the weight of the camera. You could test this by using an eyepiece to see if the drives are more accurate.

 

Primary mirror shift should result in collimation shift which should be identifiable, I use a laser.   The secondary also maybe shifting, the vanes not being tight is an issue. 

 

I would try to identify the cause of the problem before trying to fix it. It could be the springs in the cell are weak or not sufficiently compressed.

 

Jon


  • psandelle likes this

#4 MitchAlsup

MitchAlsup

    Skylab

  • -----
  • Posts: 4,453
  • Joined: 31 Aug 2009

Posted 08 December 2019 - 07:52 PM

 

    I am looking for some help. I own the astro tec 12" imaging newtonian and have owned it for a few years. I shelved the scope due to major mirror flop. The mirror flop is so significant for example, on a goto slew the object is not in the ccd fov, whereas the previous object was centered and sync'd . My goto's are dead accurate with another other optical tube, it is defintily the mirror shift.

   I have already upgraded the focuser to a moonlite with the hi res motor and was wondering on everyone thoughts on does it make sense to upgrade the mirror cell,

It is certainly useful to dig into the mirror cell and see if it is the source of <part of> the problem. Only after such digging should you consider replacing the cell.

 

What I would do is put a laser in the focuser and run the scope through zenith -to- horizon slews.

a) does the laser remain at the center (to a fraction of a millimeter) of the primary at all angles of scope pointing?

b) does the laser return to the center of the focuser (to a fraction of a millimeter) at all angles of scope pointing?

 

if the (a) test above does not stay centered, the problem is in the secondary or spider or upper end of the scope.

 

if (a) above passes, but (b) does not, then the mirror cell and everything at the back of the scope is suspect. Not just the mirror cell.


  • Jon Isaacs likes this


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.


Recent Topics





Also tagged with one or more of these keywords: ATM, collimation, dob, mirror making, optics, reflector



Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics