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Amateur Telescope Making (UPDATED 9/23/18) - 20" f/4 Nearly Complete

_Augustus_

By _Augustus_
in Science & Spaceflight

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Green Baron

Green Baron

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Brass ? Hmm, depending on the kind of brass, it can break when you bend it cold. Brass is more brittle than steel.

Best would be to warm it (~500°C) and then bend it over a mold, depending on what radii or torsion you have ... if it is a hollow profile you can fill it with dry sand and seal the ends before bending to avoid kinks.

Attention: if you heat it too much(*) it looses a lot of its strength permanently !

If i think about it, is there any possibility to avoid bending it and adjust the fittings in a respective way ?

(*) edit: ... which can happen very quickly locally if you use an acetylene soldering torch on a thin profile ...

Edited by Green Baron
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  • 4 weeks later...
_Augustus_

_Augustus_

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Sorry for the long overdue update. I was busy for a while and unable to work on the scope, and I had to redesign the spider.

I managed to test focus and balance. I don't have enough in-travel but I can hold the eyepiece inside the focuser and I have a lower-profile one on the way now. The Moon looks great. Will have a base and aluminize the primary soon.

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  • 2 weeks later...
_Augustus_

_Augustus_

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I went a little crazy......

  • Moon - Ridiculously good. Limb looks really awesome with this high resolution.
  • M38 - Quite decent, though it was behind clouds when I first saw it.
  • M3 - A real treat. Resolved right to the center at low power, while high power showed many individual stars.
  • M51 - Both the main galaxy and the companion were extremely obvious. No spiral structure, though.
  • M108 - Lots of mottling, remarkable considering it's barely visible in my 6" at all.
  • M94 - Ridiculously bright, but that's about it. A hint of the lenticular structure perhaps?
  • NGC 4490 - Very nice, some elongation/spiral structure, companion 4485 visible.
  • M63 - No detail at all, but visible (have never been able to see it in my 6").
  • Leo Triplet - M65 and M66 were quite bright with some spiral structure, but the Hamburger was barely visible as little more than an averted-vision cloud. No clue why.
  • Virgo Cluster - I spent about 20 minutes randomly panning around here. For any given field there were at least ten galaxies. I probably observed about 50 in all? When I return I'm going to try to identify individual galaxies.
  • M13 - Very nice resolution, with NGC 6207 nearby.
  • M92 - Resolved, very nice.
  • M102 - One of my new favorite galaxies, "spindle" structure very obvious.
  • NGC 3190 group (Leo Quadruplet) - Very nice, magnitude 13.5 NGC 3187 was just visible.
  • NGC 3226/7 - Nice little pairing, 3226 is around magnitude 13.3. NGC 3222 is barely visible nearby as a smudge.
  • M105 group - M105 and and NGC 3384 were quite bright, and NGC 3389 was faintly visible next to them.
  • M95/96 - Bright, but little to no detail.

I have to add a better baffle and tweak a couple things, but I'm considering this scope done.

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_Augustus_

_Augustus_

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Have used this scope a couple more times sporadically over the past month, though not lately due to poor conditions/near-full Moon.

Jupiter is really good and shows detail inside the Great Red Spot. Ganymede has an albedo feature or two.

M81 shows a spiral arm.

M82 is similar to the photographs with lots of mottling/filaments.

M51 does show its spiral arms under slightly darker skies/under great conditions at home. Absolutely spectacular.

Hamburger Galaxy under slightly darker skies is decent with lots of dust lanes.

Theophilus on the Moon has craterlets.

 

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_Augustus_

_Augustus_

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Haven't done a whole lot of observing with the 16" lately thanks to weather and being away for a week - I think I've used it once or twice since my last post. For shorter sessions, I use my Celestron C8. The only thing that I can say wasn't either a repeat or really boring observation is that the Blinking Planetary is a green dot similar in appearance to Uranus. I've knocked out a few boring globulars, but they're nothing to rave about - most of them were unresolved or really dim.

I'm building a custom 10" f/5.6 for a friend at the moment, and I'm getting ready to rebuild the 6" in time for Stellafane.

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_Augustus_

_Augustus_

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Had the 16" out tonight and it clouded over right as it got dark.

I've found a 24" Pyrex blank for sale on Cloudy Nights for a very reasonable price, but it's still a bit outside my budget. Going to have to raise the funds for that thing.

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_Augustus_

_Augustus_

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It's been a while!

Finished the 10" but the customer didn't want it. Trying to sell it at the moment.

1VYgEQl.jpg

Rebuilt the 6":

SpZ5jCN.jpg

Brought all three Dobs to Stellafane:

f7gyWJj.jpg

Won the first and third place Junior awards there.

 

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Gargamel

Gargamel

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On 8/13/2018 at 9:51 AM, _Augustus_ said:

Finished the 10" but the customer didn't want it. Trying to sell it at the moment.

Lesson learned.  In the future, a half now, half on delivery is a good way to ensure your costs are covered when building bespoke items, and gives the customer incentive to actually take delivery.  Taking half now will cover your material costs and time, and the half on delivery should be almost all profit. 

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_Augustus_

_Augustus_

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On 8/23/2018 at 7:40 PM, Gargamel said:

Lesson learned.  In the future, a half now, half on delivery is a good way to ensure your costs are covered when building bespoke items, and gives the customer incentive to actually take delivery.  Taking half now will cover your material costs and time, and the half on delivery should be almost all profit. 

That's what I did.

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