Any Reason Why Newtonian Scopes Can Not Be Made with Fixed Mirrors?

[refractordude]

Hello There


Just curious. Thanks to you all

[AstroViking (Steve)]

My guess is collimation (alignment) of the mirrors - you can't tune the optics and get everything lined up correctly if you can't move the mirrors.

V.

[refractordude]

Hello There Steve


My thinking is why cant the alignment be made fixed? Kinda like the head lights on a car and eye glasses.

[N1 (Mirko)]

Car headlights and glasses aren't telescopes. All telescopes require collimation, including refractors. The ability to easily collimate a Newtonian is actually one of its great strengths. Fixed, non-collimatable optics would mean the tube and mounts for the mirrors would have to be designed and built so much stronger that the extra cost, weight and hassle of doing that would absolutely dwarf the relatively simple job of collimating a Newtonian every now and then (which is really part of setting it up). The fact that Newtonian optics have to be aligned along not one but two axes perpendicular to each other probably doesn't help either.

[Stefan Buda]

I agree with Mirko, the main reason is cost.

[doug mc]

A lot of recent 130 f/5 newtonians from Skywatcher and Celestron have fixed, uncollimateable mirror cells.

[Startrek (Martin)]

Thermal dynamics
All materials expand and contract at different rates due to internal and external temperatures.
My carbon newts hold collimation much better than my old metal tube and truss newts but still require re collimation throughout the year due to temperatures fluctuating throughout summer and winter. My 12” is worse than the 10” and the 10” is worse than the 8”.
Some folk around the globe would experience huge fluctuations in temperature between summer and winter.
For visual work a fixed scope at say 1000 to 1200mm fl probably wouldn’t affect your view to greatly, but for imaging it can and does.
Collimating that 6” Dob should be easy and completed in a minute or two , not that big of a deal.

[JA]

Originally Posted by refractordude

Hello There Steve


My thinking is why cant the alignment be made fixed? Kinda like the head lights on a car and eye glasses.

By the by, car headlights do not have fixed alignment they can be adjusted Left/right and up/down, usually together for both low and high beams, but sometimes separately. This is necessary to take account of vehicle chassis variation and to a lesser extent headlamp unit variation in manufacture and its effect on beam position in order to properly illuminate the road and not dazzle other oncoming drivers and meet the relevant ADRs or other regulations. There are usually sufficiently tight tolerances on bulb filament position and reflector or optic shape and location to ensure that fore/aft adjustment (focus) is not necessary in a properly designed and certified headlamp. Additionally headlamps also often employ vehicle load based adjustments / levelling, so that when you're carrying a heavy load in the back the headlights don't point upwards illuminating the sky (exag) or oncoming vehicles.

Best
JA

[refractordude]

Hello There


Thanks for all the great replies.

[By.Jove (Jove)]

Originally Posted by AstroViking

My guess is collimation (alignment) of the mirrors - you can't tune the optics and get everything lined up correctly if you can't move the mirrors.
V.

That was exactly how Ceravolo built their mak-newtonians. Totally fixed, no adjustments allowed by the user.

Exquisite but they had a very high price few were prepared to pay.