Telescopes

[John K Jordan]

…I’ve been spoiled all these years by images from various big scopes, Hubble and orbiters. Those samples were a great reality check.

I have an 8” scope. A friend told me you don’t even start to see color in nebulas until you get to 12”. After that you get to the realm where it starts to make sense to add a an observatory to the house. Maybe after relocating way out in the countryside! It’s an addiction worse than woodturning.

[Myk Rian]

We're visiting Flagstaff this week, and went to the Lowell Observatory here. Those are real big telescopes.
Here is the 13" astrograph that was used to discover Pluto.
https://lowell.edu/discover/telescop...ery-telescope/

I own a 13.1" Coulter Newt on a dob base, among 7-8 other scopes.
Bertha Butt is her name. She has a big butt.
https://drive.google.com/file/d/1KhI...w?usp=drivesdk

The hobby is capable of growing on you. First you get a scope, then eyepieces, filters, more eyepieces, etc. You get the idea.

[Alan Rutherford]

When I was a young teenager, early 1950's, I had a pamphlet that gave detailed instructions on how you could make the reflector for a telescope with 2 glass blanks and some grinding compound. I didn't have the patience for something like that then and still don't, but I've always been fascinated by the thought that it's possible. I'm also fascinated with this thread and what you can do for less than $1,000. Interesting stuff.

[Tom M King]

Alan, that's what my best friend and I did when we were teenagers. We ordered the mirror blanks from Edmund Scientific from an ad in the back of Boys Life magazine. We built a 6" f/8, 4-1/4" f/4, 8" f/8, 4-1/4" f/15, and a 12-1/2" f/6. For the 12-1/2" we built a 12x12 building that the roof rolled off of for an observatory in a cow pasture where I grew up. The observatory was complete with concrete footings, and built like a house. We received a lot of help for people in the community for things like welding, and machine work and learned a lot in the process. My bedroom at home when I was in High School was a mirror grinding lab, and darkroom.

My BF became a professional Astronomer, and had a career at NASA. When they had trouble with the Hubble, he carried our 12-1/2" mirror in to their optics lab, and it was better than anything they had. Harvey was put on the team to fix the Hubble. He went on to be one of the lead project scientists on the JWST.

We were eating dinner with a group of people once, and the head of the SpaceX project was there. He had been a Summer intern a long time ago working for Harvey. He asked me who I was. I told him that Harvey and I built telescopes when we were teenagers. He laughed and said, "Yeah, he still is."

[John K Jordan]

Alan, that's what my best friend and I did when we were teenagers. We ordered the mirror blanks from Edmund Scientific from an ad in the back of Boys Life magazine. We built a 6" f/8, 4-1/4" f/4, 8" f/8, 4-1/4" f/15, and a 12-1/2" f/6. For the 12-1/2" we built a 12x12 building that the roof rolled off of for an observatory in a cow pasture where I grew up. The observatory was complete with concrete footings, and built like a house. We received a lot of help for people in the community for things like welding, and machine work and learned a lot in the process. My bedroom at home when I was in High School was a mirror grinding lab, and darkroom.

Ack, just imagine what you missed by not sitting and playing video games every day!! You had to suffer being exposed to and learn all that stuff.

I did nothing with optics in JH and HS but did play with chemicals, fire, molten metals, home-made rockets and explosives, and all the old electronics I could get my hands on. Some I learned to fix, some I just took apart, built a radio from scratch. Sure had a lot of fun at Science Fair time. And an "elderly" guy down the road with two fingers missing spent some much-appreciated time teaching me some woodworking and letting me use his shop (with supervision). Pay it forward.

JKJ

[Tom M King]

Here are the books we used to find out how to do it, only ours were an earlier printing than these and became very dog eared from being handled and read, sometimes with wet hands from the grinding process. We both got 60mm refractors for Christmas in 1962, and were disappointed with what we could see with them. We were lucky that we lived so far out at the end of nowhere, before the lake came, that we had really dark skies back then.

https://www.amazon.com/Amateur-Teles.../dp/B000H4LWMO

The test used to do the measuring in changing from a Spherical shape to a Parabola is called the Foucault test. In one of the books is a drawing of a scale that you used to put on the outside of a wooden spool, and a 1/4-20 bolt provided the axis for the homemade micrometer used for the Foucault test. A razor blade cut into the image made by the blank, after you got it to spherical shape for the focal length you wanted, to measure the spherical aberration shadow bands formed when you changed the shape from a sphere to a parabola.

Our 12-1/2" mirror was better than 1/12th of a wavelength of light, as determined by the NASA lab, and had been shaped by our hands with the help of the homemade
1/4-20 bolt micrometer.

edited to add: pictures of Foucault test shadows and how it's measured: https://www.telescope-optics.net/foucault_test.htm

[Bill Dufour]

Nasa version
Bill D

[Simon Foley]

For the night sky, diameter is most important. I know nothing of the current market. I built them from mirror blanks when I was a teenager, and my best friends just built one called the JWST.

Is actually James Webb?

[Tom M King]

Yes. James Webb Space Telescope. JWST

[Andy Gold]

It's amazing what kit amateurs possess reading this thread. I'm envious