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

AstroMaster 114 - Is This Fixable

  • Please log in to reply
8 replies to this topic

#1 Equacken

Equacken

    Lift Off

  • -----
  • topic starter
  • Posts: 2
  • Joined: 30 Nov 2020

Posted 30 November 2020 - 11:23 PM

So I pulled out my son's Celestron AstroMaster for our first good cold weather stargazing session... and I heard something rattling around inside. Something big. I pulled off the cap, and it was the main mirror. I took it apart and the attached photo is what we've got.

 

20201130_200031a.jpg

 

No idea how this happened while it was just sitting in the pantry, but since that room isn't conditioned, maybe the hot/cold cycle did it? Looks like the pot metal the mirror base plate is mounted to just snapped. Considering the general quality of the telescope, I was thinking of calling it dead and getting an Orion XT8 Plus, but that's not really the point of this post. Is this something I can glue, or will it forever affect the quality of the optics? If it just re-snaps every time I try to tighten down the mirror, there's not much point in it.

 

 



#2 wrnchhead

wrnchhead

    Mercury-Atlas

  • *****
  • Posts: 2,733
  • Joined: 28 Aug 2017
  • Loc: NE Kansas

Posted 01 December 2020 - 12:21 AM

That shouldn’t be tight at all. There should be a business card gap between the mirror and the bottom of that rubber foot, no actual contact. It will distort the mirror. I would back them all off, properly apply epoxy to that part, and after letting it cure (24 hr+ depending on epoxy and temperature, 48 is better) and put it back together.

Edited by wrnchhead, 01 December 2020 - 12:21 AM.

  • SteveG and Dark cloud like this

#3 Dark cloud

Dark cloud

    Sputnik

  • -----
  • Posts: 41
  • Joined: 25 Sep 2018
  • Loc: Northwest Illinois

Posted 01 December 2020 - 12:44 AM

Wow! I second the epoxy and back off screws might also be a good time to center mark the mirror.



#4 verycoldtoday

verycoldtoday

    Explorer 1

  • -----
  • Posts: 60
  • Joined: 01 Dec 2010
  • Loc: Ontario, Canada

Posted 01 December 2020 - 01:00 AM

Wrnchhead is correct. The mirror should be slightly loose in the cell. The clips are there in case you inadvertently turn the tube upside down. You will see a lot of these pictures on buy and sell internet sites, but don't copy them. If the metal is aluminum you can get it welded. If you don't want to do that, you can reinforce the clip mounting with a small L shaped shelf bracket and a couple of small bolts. Next idea is to replace the mirror base with a circle of plywood and three of those shelf brackets I mentioned before. You will need to bend the ends over to form the clip. I recommend an adjustable crescent type wrench for the job. Do not let the metal end touch the mirror surface, use a small sliver of cork or rubber as a separator. The mirrors are the expensive part of any scope, everything else can be jury-rigged in a pinch. Good Luck.



#5 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 90,369
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 01 December 2020 - 08:41 AM

So I pulled out my son's Celestron AstroMaster for our first good cold weather stargazing session... and I heard something rattling around inside. Something big. I pulled off the cap, and it was the main mirror. I took it apart and the attached photo is what we've got.

 

 

 

No idea how this happened while it was just sitting in the pantry, but since that room isn't conditioned, maybe the hot/cold cycle did it? Looks like the pot metal the mirror base plate is mounted to just snapped. Considering the general quality of the telescope, I was thinking of calling it dead and getting an Orion XT8 Plus, but that's not really the point of this post. Is this something I can glue, or will it forever affect the quality of the optics? If it just re-snaps every time I try to tighten down the mirror, there's not much point in it.

 

Hello and :welcome: to Cloudy Nights. 

 

I think there are ways that you can repair it. Probably the easiest is to make an L-Bracket that fits behind the broken piece and reinforces it.  This would then be bonded with Epoxy.  You could also use a plate on the back side and Epoxy that in place, there's enough surface area to give it some strength.

 

I do think calling it dead and getting something like an XT-8 is a reasonable plan.  The Astromaster 114 EQ is what is known as a Jones-Bird scope, it has a 1000mm focal length but it's only about 500mm in length.  These scopes are generally compromised, they use a fast F/4 spherical mirror and a Barlow like corrector to increase the effective focal length from about 500mm to 1000mm.  

 

But your 114mm is fixable and I would fix it.

 

Jon


  • wrnchhead likes this

#6 Barlowbill

Barlowbill

    Apollo

  • *****
  • Posts: 1,205
  • Joined: 05 Apr 2018
  • Loc: Tulsa, Oklahoma

Posted 01 December 2020 - 11:21 AM

An AstroMaster 114 was the first scope I ever dealt with.  My son-in-law lent me his because he never used it.  I quickly learned why he never used it.  Get the 8" Dob.


  • BSJ likes this

#7 KerryR

KerryR

    Skylab

  • *****
  • Posts: 4,003
  • Joined: 05 Dec 2007
  • Loc: West Michigan

Posted 01 December 2020 - 02:21 PM

A simple fix would be to silicone-glue the mirror to the remainder of the cell, and remove the remaining clips. HERE's the gist of how this can be done on Stellfane's website. Make sure surfaces are clean, use high quality non-water soluble silicone adhesive, and sand the paint away where the glue goes. 

However: As others have mentioned, this optical design, where there's a "corrector" lens mounted at the bottom of the focus tube (Bird-Jones), rarely produces a good image, partly because of poor execution, and partly because you need to remove the lens to collimate, which can't be done if it's glued, as is sometimes the case. I've never heard of anyone being happy with these scopes, even after extensive work, and no one has a good explanation for why these scopes continue to be sold-- they're established "hobby killers". (The design -can- be done well, but it's difficult to execute correctly, and no one is currently doing so.) Consequently, if the astro-bug is biting, it'd be a good idea to get something better. You're XT8 idea would be a great direction to go in! 



#8 Equacken

Equacken

    Lift Off

  • -----
  • topic starter
  • Posts: 2
  • Joined: 30 Nov 2020

Posted 01 December 2020 - 05:10 PM

I had a feeling this was going to be a good forum - you guys don't disappoint. I think my favorite comment so far has been Jon's recommendation of calling it dead immediately after telling me it's easily fixed. I'll give it a whirl when I have some time and see if I can fix it. Thanks!



#9 SteveG

SteveG

    Cosmos

  • *****
  • Posts: 9,616
  • Joined: 27 Sep 2006
  • Loc: Seattle, WA

Posted 01 December 2020 - 05:20 PM

I had a feeling this was going to be a good forum - you guys don't disappoint. I think my favorite comment so far has been Jon's recommendation of calling it dead immediately after telling me it's easily fixed. I'll give it a whirl when I have some time and see if I can fix it. Thanks!

 

You will be hard-pressed to find better advise than what Jon offers. Note how many posts he has on these forums.




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






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics