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70 inch Dob sneak peek

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#26 Chuck Hards

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Posted 20 October 2013 - 11:31 AM

Do you think one of the folks involved could do an article? A lot of ATM's would like to have more details I expect.

JimC


Mike and I are talking about writing an article at present.

#27 Chuck Hards

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Posted 20 October 2013 - 11:40 AM

OK, I've got last nights images WELL BELOW the CN size limit, but it won't let me post them. I'll see what I can do to work around it. Stay tuned. Grrr....

#28 Edward E

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Posted 20 October 2013 - 12:04 PM

That is one big scope! My 20" would make a nice finder for this monster. :grin:

It must have a GOTO system on it and tracking. I cannot image star hopping with such a behemoth.

I tried to view the video but it was not functional :( .

#29 Chuck Hards

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Posted 20 October 2013 - 12:20 PM

Steve Dodds (L) and Mike Clements ® standing in front of the 70-inch.
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#30 Chuck Hards

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Posted 20 October 2013 - 12:21 PM

Steve Dodds (L), myself ® next to the 70-inch.
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#31 Chuck Hards

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Posted 20 October 2013 - 12:22 PM

The 70-inch primary mirror. f/6.1 Mike silvered the mirror in quadrants, and has masked-off the borders, in line with the secondary supports. The central shadowed area of the secondary is also masked-off. Note the streaks of condensation which formed on the steel structure and dripped onto the mirror. Mike is working on a fix for that.
Posted Image

#32 Chuck Hards

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Posted 20 October 2013 - 12:22 PM

Looking up at the secondary mirror from the observing postion. From left to right are a sight tube (no optics), a conventional finderscope, and an empty refractor OTA aimed at the secondary, which holds the focuser. A 2-inch star diagonal serves as tertiary mirror.
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#33 Chuck Hards

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Posted 20 October 2013 - 12:23 PM

Rear view. 9 point mirror cell. Steve said it supports the cellular mirror adequately. At the eyepiece, star images were nicely round, no hint of astigmatism, and displayed a textbook diffraction pattern. Note the hanging barbell weights, which must be changed depending on the scopes altitude. Mike is still working on fine-tuning balance.
Posted Image

#34 Chuck Hards

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Posted 20 October 2013 - 12:24 PM

Note the multiple sight tubes used for initial aiming, spaced all along the back end. You can also see the hanging weights in the rear (a temporary work-around)
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#35 Chuck Hards

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Posted 20 October 2013 - 12:25 PM

Right side. The azimuth ring is blocked-up on timbers at present.
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#36 Chuck Hards

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Posted 20 October 2013 - 12:26 PM

Bearing detail.
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#37 Chuck Hards

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Posted 20 October 2013 - 12:27 PM

Another view of the observing station.
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#38 Chuck Hards

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Posted 20 October 2013 - 12:29 PM

That's all the photos for now. It wouldn't let me post them all in a single post.

Remember that this telescope is a work in progress. It's only been operational for several weeks and Mike has many adjustments and changes to make before it can hit the road next year. He plans to add motorized tracking as well.

He has no email or online presence, but I will be happy to forward questions as long as it doesn't become overwhelming.

#39 gatorengineer

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Posted 20 October 2013 - 01:54 PM

I cant see any means of stray light control. A low rider with that amount of angle I would think would get drowned in stray light. What am I missing? I have a 36 in the works and this is the second steep angle low rider recently seen, its a great idea.... I am just not understanding how it works. Kinda like a cass or SCT without a baffle tube.

#40 Chuck Hards

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Posted 20 October 2013 - 02:17 PM

The long tube that the focuser is attached to, aimed at the secondary, is an effective baffle.

As I said above though, it is very much incomplete and a work in progress. I'll ask Mike about it next time I see him. Probably next weekend.

#41 Pinbout

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Posted 20 October 2013 - 02:23 PM

thanks for the pics, they're great additional info.

#42 Chuck Hards

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Posted 20 October 2013 - 02:30 PM

Thanks Danny, I'm just helping Mike spread the word. I took many more pics but the low light level made most of them too grainy or blurred. It was a lot darker when I arrived than you would think, looking at the pics. I had to really up the ISO setting on the DSLR to brighten them, and still had to tweak them on the computer after uploading them.

More next weekend if the weather holds.

#43 Pinbout

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Posted 20 October 2013 - 02:35 PM

if he takes it on the road he could get funding by making it a traveling exhibit to all the hands on science centers.

also there are companies that could get involved like intel backs the creator projects. you guys should contact their marketing department before the year ends to get funding for next year.

OMSI in portland as well as the exploriturium in san fran were the 1st.

I was apart of the startup in 93 for liberty science center in jersey city nj.

#44 the1andonlyfinn

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Posted 20 October 2013 - 03:10 PM

Every star party in America is going to want that there!

#45 Zamboni

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Posted 20 October 2013 - 03:24 PM

I think I need to go change...

#46 Alan A.

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Posted 20 October 2013 - 03:29 PM

That's all the photos for now. It wouldn't let me post them all in a single post.

Remember that this telescope is a work in progress. It's only been operational for several weeks and Mike has many adjustments and changes to make before it can hit the road next year. He plans to add motorized tracking as well.

He has no email or online presence, but I will be happy to forward questions as long as it doesn't become overwhelming.


Hi Chuck, thanks for posting all the beautiful photos. If he can tell us the story of how he acquired the mirror, and some of the specs of the mirror I think it would be of interest to everyone.

Best,

Alan

#47 Jeff Morgan

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Posted 20 October 2013 - 03:36 PM

Every star party in America is going to want that there!


Imagine the lines.

I would fork over $20 for a few minutes at the eyepiece.

#48 saemark30

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Posted 20 October 2013 - 04:55 PM

What is this silver solution that they are spraying on?
I like to try some.

#49 jpcannavo

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Posted 20 October 2013 - 05:43 PM

Rear view. 9 point mirror cell. Steve said it supports the cellular mirror adequately. At the eyepiece, star images were nicely round, no hint of astigmatism, and displayed a textbook diffraction pattern. Note the hanging barbell weights, which must be changed depending on the scopes altitude. Mike is still working on fine-tuning balance.
Posted Image


Mega Kudos on an absolutely astronomical achievement!!
But, one question: "textbook diffraction pattern ", i.e. Airy disk and all - with 70" of aperture? You guys must have some record setting seeing out there.

Joe

#50 Chuck Hards

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Posted 20 October 2013 - 06:24 PM

The seeing came and went, actually you got me there. It was as good as I'd expect for a good mirror under those conditions.

Keeping the scope outside means no cool-down issues, as well.






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