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I've owned my AstroMaster 114EQ for about a year now, and feel like I know my way around pretty well, but I'm only just becoming aware that collimation is recommended. The user manual has instructions on basic collimation. Does this look sufficient? Or should I invest in a celestron 94183 collimation cap, a celestron collimation eyepiece, or something fancy like an Orion LaserMate Deluxe II? The telescope itself cost less than $200 so I can't help but wonder if the fancier collimators are overkill. I've watched this longish video and one must apparently perform some disassembly on the telescope to user the laser collimator. This doesn't seem like the easy 'couple of minutes' adjustment I've seen described.

I'm also confused about the process of adjusting the secondary mirror. If anyone has good instructions about my specific model, I would greatly appreciate it. I'd really like to get it tuned up now that Mars is looking so good.

S. Imp
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  • It's not clear if the telescope actually needs collimating. You don't need any fancy gear to check. The picture in fig 7.2 of the manual shows what to look for. – Dr Chuck Jun 25 '18 at 20:56
  • @DrChuck That section, titled "Night Time Star Collimating" says It is best to use the optional collimation tool or collimating eyepiece. I have neither tool. The instructions also say this step is to be performed after the daytime collimation, which requires one of the collimation tools, neither of which came with the telescope. – S. Imp Jun 26 '18 at 02:02
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    Have a read through of https://astronomy.stackexchange.com/questions/150/how-can-i-collimate-a-dobsonian-telescope-with-a-laser-collimator?rq=1 – Mick Jun 26 '18 at 08:03
  • @s.imp. I am just that you check the current state of collimation. It may be ok in which case you don’t need to do anything. No expensive kit required to check collimation. – Dr Chuck Jun 26 '18 at 12:37
  • @DrChuck I finally got around to the star check last night and the pattern I see with a start inside & outside focus looks pretty symmetrical, but not perfect. I don't really see the concentric circle pattern described in so many places. I wish that I could share an image of it but don't know how to take a picture of it. – S. Imp Jul 18 '18 at 19:22

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With a tube length of 46 cm and a focal length of 100 cm, probably the AstroMaster 114EQ is not a classical Newtonian but uses a fast (e.g. f/4) spherical primary mirror and a corrector lens built into the base of the focuser to reduce spherical aberration and increase the effective focal length (e.g. to f/8.8). This is a variant of the Jones-Bird design of some custom telescopes. There is some doubt about how well the corrector actually works in budget-priced telescopes.

Most collimation instructions (e.g. Seronik or Carlin) assume a classical Newtonian design. Jones-Bird collimation is similar in theory but more complicated in practice. In particular, the corrector hinders the use of a laser device. Try a collimation cap; anything that fits a 1.25 inch focuser is fine. You can even get decent results with a homemade one. If you decide to invest in a Cheshire sight tube, it can be used with any Newtonian reflector.

Mike G
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  • Thank you for this post. You are correct that there's a lens in the bottom of the focuser. Your suggestion to use a collimation cap is appreciated, but I would like to see some detailed instructions for how to do so. Do you have any thoughts on this collimation tool sold by my scope manafacturer? It sounds like you are saying that I cannot use it with my scope due to the extra lens beneath the focuser: https://www.celestron.com/products/collimation-eyepiece-125-in – S. Imp Jul 18 '18 at 19:29
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    Celestron's collimation eyepiece is a Cheshire sight tube, and they provide an instruction sheet. Linked in this answer, Carlin explains such tools, and Seronik explains collimation caps. Either should work in your scope. – Mike G Jul 18 '18 at 19:46
  • Thanks for your prompt response. I called Celestron tech support and they confirmed that the Celestron 94182 should work with the Astromaster 114. I was concerned that, because this telescope is evidently a Jones-Bird variant of the Newtonian telescope, that this piece would not work due to the extra lense at the bottom of the focuser. As I described in my original post, one has to remove the extra lens to use a laser collimator. – S. Imp Jul 18 '18 at 21:38