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Equipment Discussions >> ATM, Optics and DIY Forum

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Napersky
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Reged: 01/27/10

Loc: Chicagoland
Re: My 16" f7.2 Newt project code named "Grace" new [Re: bremms]
      #5604240 - 01/04/13 08:36 AM

Sean,

With that F Ratio your scope should be excellent for Planetary and blow away anything else around including short focal length Dobs of larger apertures!

Mark


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Napersky
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Reged: 01/27/10

Loc: Chicagoland
Re: My 16" f7.2 Newt project code named "Grace" new [Re: Napersky]
      #5604243 - 01/04/13 08:37 AM

Hey we got to call the Internet Police and the Thread Police!

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Mike I. Jones
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Reged: 07/02/06

Loc: Fort Worth TX
Re: My 16" f7.2 Newt project code named "Grace" new [Re: Napersky]
      #5604289 - 01/04/13 08:58 AM

and don't click on a spam link, EVER!

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Napersky
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Reged: 01/27/10

Loc: Chicagoland
Re: My 16" f7.2 Newt project code named "Grace" new [Re: Mike I. Jones]
      #5604367 - 01/04/13 09:23 AM

Very scary!

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Jeff Morgan
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Reged: 09/28/03

Loc: Prescott, AZ
Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5604509 - 01/04/13 10:41 AM

Quote:

So I know that I like to have a very quick setup. I don't like fiddling with lots of pieces. When my scope breaks down, it has to break down into 3 or four manageable parts.




An admirable goal, but I would not make it the top of the list.

Realistically, the limiting factor on getting the evenings observing started is the primary mirror. Even with fans, there is not a lot to be done for the first hour anyway. While it's nice to be set up in five minutes and then have time to sip a coffee as twilight progresses, ultimately you're always waiting on the mirror.

A different story at the end of the night of course, but still not enough to make it the #1 design criteria.


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Sean Cunneen
Let Me Think
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Reged: 08/01/07

Loc: Blue Island Illinois
Re: My 16" f7.2 Newt project code named "Grace" new [Re: Jeff Morgan]
      #5604522 - 01/04/13 10:47 AM Attachment (114 downloads)

Attached is a PDF of a simple sketch, 1:9 showing the general proportions. Kinda diggin the long look!

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Sean Cunneen
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Reged: 08/01/07

Loc: Blue Island Illinois
Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5611046 - 01/07/13 10:29 PM Attachment (68 downloads)

It's heeeerrrrreeeeeee!

Whew!

Rather than have this thing ride in a truck and sit by my door I opted to pick it up at the shippers store. I had to wait the weekend and picked it up this afternoon. It's a Pegasus mirror and came with the specs on the mirror. The numbers are very good, I am all tingly...


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bremms
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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5611113 - 01/07/13 10:57 PM

+1 racing terms for up one lap.

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Sean Cunneen
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Reged: 08/01/07

Loc: Blue Island Illinois
Re: My 16" f7.2 Newt project code named "Grace" new [Re: bremms]
      #5611240 - 01/08/13 12:21 AM Attachment (48 downloads)

Here are some of the parts congregating:

The sides of the rocker box: I'll strip them and clean them up over the weekend...


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Sean Cunneen
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Reged: 08/01/07

Loc: Blue Island Illinois
Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5611243 - 01/08/13 12:22 AM Attachment (53 downloads)

The poor donor:

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Sean Cunneen
Let Me Think
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Reged: 08/01/07

Loc: Blue Island Illinois
Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5611248 - 01/08/13 12:24 AM Attachment (44 downloads)

Finally a beautiful piece of 18"x18"x2" pine which will become the bottom of the rocker box. This piece was give to me by my good friend Tom, I figure this is a good enough use!

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Darren Drake
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Loc: Chicagoland
Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5611874 - 01/08/13 12:35 PM

Yea both you and Napersky (Mark) got a major package yesterday. (He just gotta 6 inch AP superplanetary on a Losmandy mount.)That explains the week of clouds we have coming. Thanks a lot. lol.

Edited by Darren Drake (01/08/13 03:11 PM)


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magic612
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Reged: 09/30/08

Loc: S. of Chicago's light dome
Re: My 16" f7.2 Newt project code named "Grace" new [Re: Darren Drake]
      #5611919 - 01/08/13 01:10 PM

Quote:

Yea both you and Napersky (Mark) got a major package yesterday. That explains the week of clouds we have coming. Thanks a lot. lol.




As a Chicago-area observer myself, I will second that - especially since the clouds are coming right when I have time in the evening this week!

Seriously, congrats on the mirror, Sean. Looks like you've got some good pieces of this already thought out and in-process.


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JohnH
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Reged: 10/04/05

Loc: Squamish BC Moved!!!!!
Re: My 16" f7.2 Newt project code named "Grace" new [Re: MKV]
      #5612007 - 01/08/13 02:03 PM

Quote:

Jeff, simply beautiful! The split truss is the way to go for resistance to misalignment. It should be an awesome all-purpose telescope. Do you have a 3 or a 4 wave spider. A 3-vane is better diffraction-wise. How big is your central obstruction?

Mladen




I would say four vanes is somewhat better diffraction-wise.

The four vane type consisting of two pairs of two perpendicular vanes with make a four-point pattern, whereas a three vane one will generate a six-point pattern.


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Howie Glatter
Vendor


Reged: 07/04/06

Re: My 16" f7.2 Newt project code named "Grace" new [Re: JohnH]
      #5612158 - 01/08/13 03:22 PM

> I would say four vanes is somewhat better diffraction-wise.

If all vanes are the same size, there will be less light in the six spikes produced by the three vane spider than in the four spikes of a four-vane spider.


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niteskystargazer
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Reged: 10/05/09

Loc: 41-43'-28" N 87-42'-39" W
Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5612493 - 01/08/13 06:45 PM

Sean,

I knew, that some day, you would have a use for that piece of wood, that's why we hung on to it. We knew you would come-long, and need it.

CS,KLU,

,

Tom


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gatorengineer
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Reged: 02/28/05

Loc: Hellertown, PA
Re: My 16" f7.2 Newt project code named "Grace" new [Re: niteskystargazer]
      #5612702 - 01/08/13 08:58 PM

You might want to rethink the secondary a bit, 2.6 is a bit large, 2.14 would be plenty.....

http://www.loptics.com/ATM/diagonals.html

I have run 3.1 in the several 16"s I have had over the years. Your building a great planetary instrument.... keep the secondary down, and consider a protostar curved vane spider.

Just thoughts looks like a great project....


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Jeff Morgan
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Reged: 09/28/03

Loc: Prescott, AZ
Re: My 16" f7.2 Newt project code named "Grace" new [Re: Howie Glatter]
      #5612919 - 01/08/13 11:25 PM

Quote:

> I would say four vanes is somewhat better diffraction-wise.

If all vanes are the same size, there will be less light in the six spikes produced by the three vane spider than in the four spikes of a four-vane spider.




I do slightly prefer the 3 vane pattern. The complication in my case was the size/weight of the secondary was a bit more than I have previously used. So, I opted for the stability of the four.

Once the scope goes operational and I have completed a few finishing touches, I would like to go back and see if I could build a wire spider. If I like the result, I can retrofit it to the existing cage during some full moon period.


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Sean Cunneen
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Reged: 08/01/07

Loc: Blue Island Illinois
Re: My 16" f7.2 Newt project code named "Grace" new [Re: Jeff Morgan]
      #5613302 - 01/09/13 08:44 AM

I haven't decided on a secondary or secondary arrangement yet. I wanted to put off buying expensive stuff until the mirror arrived safe and sound.

I've built a couple of curved vane spiders for smaller scopes and I was never able to get them stiff enough to my liking. I've done a fair amount of reading about wire spiders and I've collected parts for one. I love the look but for an 18" expanse, I'm not sure if the wire can be thin enough to do it's job. For a big scope, I don't think you can do better than a thin 4 vane spider in terms of elegance.


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gatorengineer
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Reged: 02/28/05

Loc: Hellertown, PA
Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5614446 - 01/09/13 08:14 PM

The other thing you will want to factor in is that you will want to have a very large piece of flock board opposite the focuser. This makes it very difficult for wire spiders, as you have more points to work around.

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