18 votes
Accepted

Why are segmented mirrors lighter than monolithic mirrors?

A telescope's precision mirror needs to be very large, to collect lots of light, and needs to be very precisely shaped. Holding that proper shape is based on the mirror's ability to resist stress on ...
Darth Pseudonym's user avatar
7 votes

Instead of a 4 meter diameter, 50 liter spinning pool of dangerous mercury, why didn't the ILMT just use an ionic liquid? Or gallium?

Ionic liquids are not reflective. An ionic liquid being poured, from )source( They have different properties, but may are toxic, note the nitrile gloves, the researcher doesn't want to get any of ...
James K's user avatar
  • 121k
6 votes

Instead of a 4 meter diameter, 50 liter spinning pool of dangerous mercury, why didn't the ILMT just use an ionic liquid? Or gallium?

I'll add this to point out that the mercury is managed such that choosing something else might not be worth the bother. The paper by Brajesh Kumar et al. (Monthly Notices of the Royal Astronomical ...
Jon Custer's user avatar
6 votes

Why are segmented mirrors lighter than monolithic mirrors?

When creating a mirror, you need to take a block of glass and grind and polish it until it has the desired shape. For telescopes this is typically a parabolic shape. So The thickness of the slab of ...
planetmaker's user avatar
  • 19.4k
4 votes

Is there a reflecting telescope like as a Newtonian telescope but with a negative lens before the diagonal mirror?

Yes! Those with a Coudé focus and others The following this answer to Why aren't reflector telescopes built with an offset secondary mirror? this answer to Do telescopes exist that reflect the ...
uhoh's user avatar
  • 31.1k
3 votes

Why is plasma used to deposit aluminum on the VLT's four large mirrors?

As shown in an ESO image, the mirrors are coated in a giant plasma sputter system, where ions produced in a (presumably argon) plasma are accelerated and strike the pure aluminum, freeing neutral ...
Jon Custer's user avatar
3 votes

Can telescopes under $200 help you see saturn clearly by eye without editing the image on a computer?

My simple answer to your question is that you're probably going to have to increase your budget to find something worthwhile. But there are some options. For planetary and lunar observing, there's a ...
J.M. Haynes's user avatar
  • 1,058
2 votes

Why are segmented mirrors lighter than monolithic mirrors?

The bottom line is that an (active) support mechanism to hold a segment in the right position will be lighter than the (passive) glass required if the mirror were not segmented. There have been ...
Mark Morgan Lloyd's user avatar

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