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

Loc: Blue Island Illinois
My 16" f7.2 Newt project code named "Grace"
      #5601069 - 01/02/13 11:18 AM

I am awaiting delivery of a 16" f7.2 mirror I've seen listed on and off for the past year on Amart.

I've decided to dedicate this project to My Grandma Grace who passed away this past Thanksgiving. She and my Grandpa always encouraged my love of the night sky which started at their farm in Indiana. When we would visit, I would sleep on the floor in a sleeping bag. They would turn up the heat before bed and I would just swelter. I took to opening the sliding screen door a crack to let some cool air in and I always told them it was to look at the stars! When I first became interested in telescopes, my first experience was the their farm with a 90mm refractor. My first view? Jupiter. The big guy just blew me away and she was amazed as well. After that my scopes grew and I would always set one up on my visits.

Needless to say, This scope is going to be huge. For my last big project each component had to pass the lift test. For this project, each piece has to pass the doorway test!

Parts and pieces are still arriving, so this will evolve slowly and there are some features that will have to develop as we go.

The quick summary is that I am putting together an open truss Newt on an equatorial platform using as many "found" objects as I can. So far I have the arms from a mission style recliner, some tripod legs and a moonlight focuser.

I picked up a load of wood last night and I'll start showing pictures soon... Stay tuned!

Sean


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Darren Drake
Carpal Tunnel
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Reged: 10/09/02

Loc: Chicagoland
Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5601129 - 01/02/13 11:53 AM

This will be fun. Looking forward to it.

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MessiToM
scholastic sledgehammer
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Reged: 12/21/09

Loc: Huntingdon PA
Re: My 16" f7.2 Newt project code named "Grace" new [Re: Darren Drake]
      #5601144 - 01/02/13 12:09 PM

I am as well

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bremms
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Reged: 08/31/12

Loc: SC
Re: My 16" f7.2 Newt project code named "Grace" new [Re: MessiToM]
      #5601220 - 01/02/13 01:00 PM

Yes.. one BIG telescope. Will make my 12.5 F8 project look tiny. Looking forward to seeing this one.

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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: bremms]
      #5601384 - 01/02/13 02:49 PM

Do you have the hydraulic lift to reach the eyepiece yet?

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Jeff Morgan
Postmaster
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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]
      #5601425 - 01/02/13 03:24 PM Attachment (187 downloads)

Congratulations Sean, and best of luck on the project. My 16" f/7 can see first light any night now, depending upon whether or not I want to wait for a bracket for my ServoCAT control box. My feeling is that such a scope deserves better than duct tape for it's maiden voyage.

The fact that northern Arizona temperatures are getting into mid-teens has nothing to do with my delays

I thought about an equatorial platform for mine. I have first-hand experience with the Osypowski platform and nothing but good things to say about them. But given the scale of my project ServoCAT seemed like a better choice. And GOTO will be very handy with 2800 mm focal length. Driving the whole thing wirelessly with SkySafari and an iPad was icing on the cake.


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MKV
Carpal Tunnel
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Reged: 01/20/11

Re: My 16" f7.2 Newt project code named "Grace" new [Re: Jeff Morgan]
      #5601515 - 01/02/13 04:14 PM

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


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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: magic612]
      #5601687 - 01/02/13 06:08 PM

Quote:

Do you have the hydraulic lift to reach the eyepiece yet?




I spent my Morning at Menards asking each sales associate if any of the ladders were ASCOM compliant, none of them could tell me.


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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]
      #5601692 - 01/02/13 06:12 PM

Quote:

Congratulations Sean, and best of luck on the project. My 16" f/7 can see first light any night now, depending upon whether or not I want to wait for a bracket for my ServoCAT control box. My feeling is that such a scope deserves better than duct tape for it's maiden voyage.

The fact that northern Arizona temperatures are getting into mid-teens has nothing to do with my delays

I thought about an equatorial platform for mine. I have first-hand experience with the Osypowski platform and nothing but good things to say about them. But given the scale of my project ServoCAT seemed like a better choice. And GOTO will be very handy with 2800 mm focal length. Driving the whole thing wirelessly with SkySafari and an iPad was icing on the cake.




Other bands, their scopes only go up to 7. Ours go up to 7.2, for when you want to get just a little longer. Seriously, Jeff, that scope is beautiful. That truss looks so light and effortless. Here in the Midwest, we have to dress ours up a little more for the crazy winters.

I have always wanted to build a platform and this scope being as cumbersome as it is, I felt this was the project for it. If my jigs work out, I make make a couple for my other scopes.


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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: MKV]
      #5601823 - 01/02/13 07:45 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




Thanks. That picture was taken during tube trimming, still a few finishing touches to go.

I played around with wire spiders for a month, then broke down and got a 4 vane. The diagonal mirror is 2.6", for about 16% obstruction. If Mel Bartels diagonal calculator is correct, it should fully illuminate a 31 Nagler. Going with the next smallest size (2.14") was starting to get a little chancy. You see, there was another consideration - I used a Moonlight focuser and filter slide, and I wanted to have enough room to mount the slide completely outside the aperture defined by the tube rings so as not to create additional diffraction.


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Jeff Morgan
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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5601841 - 01/02/13 07:52 PM

Sean, will this be a permanent installation? If not what do you have to transport it?

An option you might want to look at is a rolling platform ladder (McMaster-Carr). They are incredibly comfortable and stable. And surprisingly easy to move around too. I could post a few pics, but I don't want to hijack your thread (pm me if you want me to email them). I bought one for my scope, and Jon Issacs has been using one with his 25" scope, which I believe has just a bit more focal length than you or I have.

The only downsides of this approach is transporting it. Easy if you have a trailer. Perhaps easy if you have a pick-up truck or a van. Impossible with a car or SUV.

If you are looking more of a standard ladder, the Little Giant ladders look like a good option. If you have a roof rack on your car that would be workable.


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Darren Drake
Carpal Tunnel
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Reged: 10/09/02

Loc: Chicagoland
Re: My 16" f7.2 Newt project code named "Grace" new [Re: Jeff Morgan]
      #5602133 - 01/02/13 11:15 PM Attachment (114 downloads)

Sean is quite an experienced atmer. Tonight he brought his homemade 12 inch dob to my back yard. It is quite unique looking. The trusses are made of shower pipes. The 16 will be a fun project to follow.

Edited by Darren Drake (01/02/13 11:17 PM)


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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: Darren Drake]
      #5602190 - 01/02/13 11:50 PM

Jeff, the scope will dissemble into 3 main pieces and everything should just fit into the back of our caravan. Kids will ride on the roof.

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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: Sean Cunneen]
      #5602673 - 01/03/13 10:18 AM

Which is rather unfair too, given that Sean's kids are sweethearts, and his scopes - well, let's just say they don't hold a conversation very well.

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StarryHost
member
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Reged: 01/13/09

Loc: Vista, CA
Re: My 16" f7.2 Newt project code named "Grace" new [Re: magic612]
      #5602700 - 01/03/13 10:38 AM

Can't wait to see this come about. When it's done, we can play "Patriot" vs. "Scud" with our two rocket scopes. ;-)

Jack


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k9yr
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Reged: 05/21/08

Loc: Far North suburbs of Chicago
Re: My 16" f7.2 Newt project code named "Grace" new [Re: StarryHost]
      #5603696 - 01/03/13 09:05 PM

Jeff and Sean, killer scopes! Much braver than my little 16" F4.5.

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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: k9yr]
      #5603756 - 01/03/13 09:52 PM Attachment (132 downloads)

So I thought I'd start with some of my ideas behind my design aspects. I've been fortunate enough to have built a lot of scopes and I've also spent a fair amount of time traveling with, setting up and viewing through scopes that I have built.

So to massacre one of my favorite speeches ever, There are knowns I know and knowns I don't know. There unknowns I know and unknowns I don't know, you know?

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.

I know from where I usually observe that stray light is a constant problem. The 12" dob Darren took a picture of was built to be as open as can be. It was since rebuilt to shield the mirror from as much ambient light as possible.

I like for my scopes to be as stiff and "tight" as I can manage. No wobbles.

stuff either has to move or it has to never ever move with nothing in between.

I don't mind heavy scopes (once they are set up)
Fans are important.
Baffles are important.
Having the mirror protected is important.

As I learned from my 12", crazy looking scopes are great but take a walk around a star party and check out which scopes are getting used and they all tend to look the same.

Here is a photo of "Big Tom" in his original form:

Edited by Sean Cunneen (01/03/13 10:01 PM)


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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]
      #5603768 - 01/03/13 09:58 PM

I've decided to make my platform in the style of Warren Peters. You can find his article here:
Warren Peters Platform

There are three or four different designs, all have some strengths and weaknesses. The Warren Peters design is a little harder to make as there are two arcs of different radius you have to cut out but the plusses for a large heavy scope is that the actual platform can be a square or slight rectangle and the weight is supported on all four corners. A Poncet platform is a little simpler as the back arc is replaced by a single angled pivot but for a scope this size and weight, the extra stability should more than pay for the extra work.


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Napersky
Carpal Tunnel
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Reged: 01/27/10

Loc: Chicagoland
Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5603957 - 01/04/13 12:39 AM

Very cool Sean I admire your craftsmanship especially the equatorial mount you made for your 6" refractors.

I can't wait to look through your 6" Jaeger's although I won't be building mine any too soon. I am totally occupied with my Interferometer project and have the 6" AP for my observing.

Mark


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bremms
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Reged: 08/31/12

Loc: SC
Re: My 16" f7.2 Newt project code named "Grace" new [Re: Napersky]
      #5604218 - 01/04/13 08:18 AM

Yes, TOOOO many projects. I suffer the same. I did get a Jaegers 6" F10 from SS and need to make a cell and all the fixins. My 4" F15 Jaegers is almost done.
On a side note, What do a lot of you use for artificial stars?
I was going to make pinholes like the old days, but it's hard to control the size. We do have a laser at work I could make some holes with. I cold shoot some spots at some copper foil.


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Napersky
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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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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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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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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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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
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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 (108 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
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]
      #5611046 - 01/07/13 10:29 PM Attachment (65 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 (47 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 (52 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 (43 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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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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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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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


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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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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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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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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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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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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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Sean Cunneen
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Re: My 16" f7.2 Newt project code named "Grace" new [Re: gatorengineer]
      #5614642 - 01/09/13 10:46 PM

The secondary cage will be 2ft long and I am seriously considering an extendable dew shield as well. Where I observe there is a lot of stray light!

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Jeff Morgan
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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5615184 - 01/10/13 10:22 AM

Quote:

The secondary cage will be 2ft long and I am seriously considering an extendable dew shield as well. Where I observe there is a lot of stray light!




Will you be using a filter slide?


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gatorengineer
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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Jeff Morgan]
      #5615216 - 01/10/13 10:38 AM

The Deep upper ring is great. The other thing to factor into the design is that you are going to need a Ton of tail weight, especially if you put a grenade in the focuser. You will want something that you easily adjust, so a sliding weight on the top of the mirror box may be in order. in addition to several lead counterweights in the mirror box Even at F5 on large dobs its tough to find the balance between a 31 Nagler and 6 orthoscopic. F7 will even be more challenging, unless you depart from a traditional rocker and move the bearing substantially cageward.....

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Jeff Morgan]
      #5615400 - 01/10/13 12:10 PM

Quote:

Will you be using a filter slide?




I like to build adjustability into my dobs. Either the mirror has been adjustable 4-6" or the top of the OTA has been adjustable to accomodate filter slides, polarizer filters, binoviewers (perhaps not all at once, one does have to keep humble)

Edited by Sean Cunneen (01/10/13 12:16 PM)


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Re: My 16" f7.2 Newt project code named "Grace" new [Re: gatorengineer]
      #5615409 - 01/10/13 12:14 PM

The bearings are 3-1/2ft up the tube because for planetary/highpower viewing the moments have to be kept as short as possible to minimize vibrations and maximize stiffness.

for this scope, imagine a 10ft long teeter-totter with 45lbs 3ft away from the balance point and 7ft of poles and a cage on the other. My concern is coming up with enough weight on the top end so I can avoid having counterweights suspended above the mirror.

I am considering going with conduit for truss poles as the added weight in this case is a benefit.


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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5615788 - 01/10/13 03:58 PM

Balance is a tough nut to crack for the longer focus scope. Extending the mirror box upwards can be done, but the with diminishing returns.

I've been immensely pleased with the double truss layout. Building the center box for the attachment of altitude trunnions and trusses frees you to make the mirror box exceptionally light. Which just makes the whole concept work even better. In hindsight, I should have ordered an aluminum mirror cell for mine to eliminate even more of the dead weight.

To keep the rocker box stiff I use thicker upright sections. Usually I use hollow core construction for weight, although in my current project I used the cut-outs you saw in the photo. The hollow core approach is light, but lacks hand holds. The cut-out approach is slightly heavier, but is easy to grab and handle. Both approaches take several hours extra work in the shop.

There is another balance idea I'll past you. For my next project I was considering an RFT - something like a 8" f/4.5 with a focuser coincident with the center of balance. The reason is to make eyepiece balance irrelevant, and put the focuser at a fixed and comfortable height of around 40 inches. The issue here of course is balancing a scope that effectively rotates around the focuser! To make it work without using forward weight extensions I was thinking of something like a pulley. That is, suspend a weight on a chord that wraps around the altitude trunnion on the side of the scope opposite the focuser. The issue of course is that the arm of the weight is limited to the radius of the altitude trunnion. I haven't fleshed it out yet, but from that position it would not at any time be suspended above the primary mirror.


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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Jeff Morgan]
      #5620867 - 01/13/13 02:01 PM Attachment (41 downloads)

Spent most of my weekend in my basement practicing my stripping. It's been a while and I am a little rusty but after an hour session last night, I can state confidently that I am stripping like a pro. If you are unfamiliar, stripping can be pretty dangerous. I wear gloves and I always keep my hat on.

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5620888 - 01/13/13 02:12 PM Attachment (40 downloads)

I received a Windows phone last week and there are all sorts of doodads I can play with picture-wise, so please be patient with me while I figure things out...

Here are the parts for the dob base stripped and partially dressed before finishing. Looking dapper!

Edited by Sean Cunneen (01/13/13 02:18 PM)


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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5636664 - 01/22/13 11:14 AM

This project rocks, awaiting further updates.

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: droid]
      #5637114 - 01/22/13 03:06 PM

I've been busy! Currently I'm gathering parts. My Antares 1/16th PV Secondary just came in, I picked up a bunch of plywood and hard-board and I'll be cutting lots of circles in the next week.

I also had a bunch of projects to get out of the way the past couple of weeks. I rebuilt a Criterion RV-6 Mount and an old Edmund Equatorial. I am waiting for a brass Crawmach focuser which has been shipped to complete my Chester Brandon/Max Bray 3" f15.3 Objective (which you may see in this forum soon!)

I can hardly wait to get back to this thing myself!


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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5782393 - 04/06/13 06:45 PM Attachment (26 downloads)

Goings have been slow, but I am making progress now, I hit some snags and made some twists and turns in my initial design, working out some of those took quite some time...

I picked up three sheets of 18"x4' planked pine sheets. These are narrow pine boards glued together to make larger sheets, they are finished sanded and look nice, though they are on the heavy side. I cut 12" off of three, then glued the scrap up to make a 4th 3' section. I do love being frugal. Some sweating with a plane and some sanding, and the franken-piece will work fine.

Edited by Sean Cunneen (04/06/13 06:47 PM)


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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5782401 - 04/06/13 06:49 PM Attachment (17 downloads)

Next up is an 8' x24" sheet of birch ply... This will be cut into 24" squares and the scrap used for support pieces for the cell. A couple are used for the rings of the UTA, and 3 are cut for baffles for the LTA. Below is my circle jig for the OTA... The clamping knob makes it look so... so... classy.

Edited by Sean Cunneen (04/06/13 06:51 PM)


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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5782415 - 04/06/13 06:52 PM Attachment (19 downloads)

For the baffles, I then ran the router around the inner circle with an angle bit to rough cut what will be knife edges after some finish sanding...

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5782417 - 04/06/13 06:56 PM Attachment (20 downloads)

Next I had to make a jig to true and flatten the circle that will become the altitude bearings. I picked up a planked pine 24" round that had been dropped. It split in half so the floor manager let me have it for $2. I'll take that any day. Some glue, some clamping, wood putty and sanding and it looked like new.

For the jig I made a radius extension for my router table...


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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5782418 - 04/06/13 06:58 PM Attachment (15 downloads)

The circle mounts onto the threaded shaft then I spun the wheel against the cutting bit of the router. That gave me a true circle with an accurate center hole!

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5782421 - 04/06/13 07:00 PM Attachment (22 downloads)

A shot of my rigged radius control knob assembly...

Crawford Machining, beware, I'm coming for ya...


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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5782664 - 04/06/13 09:38 PM Attachment (26 downloads)

Now that I have the LTA sides cut, baffles cut, side trim cut, UTA rings cut, base cut, base sides cut, it's time for the cell. The mirror is a stout 40#, 1.75" thick Pyrex, so it won't be overly sensitive to mounting supports, but it will take a while to cool. After some Plop research and some Kriege and Berry(sp?) research, I've decided on a 6pt cell with 3 each 2 points on a teeter/totter. I am constructing the cell out of the rounds from the routing of the UTA with a stiffening structure in between that will hold the mirror supports. This design took a while to work itself out dimensions-wise. There was more than a few times I searched for a ready-made 16" cell. My children are cute however, and I am not allowed to trade them for Telescope parts.

Below shows the upper cell round getting slots routed for the mirror supports. If you look close you can see all the geometry worked out and you might get a hint of what's to come!


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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5782667 - 04/06/13 09:38 PM Attachment (22 downloads)

and one more...

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5782708 - 04/06/13 09:55 PM

What a neat project! My 16.5" is an f/6.5. I ground it long to give me a good chance at producing a good figure and allow me to use a small, affordable, diagonal. I've since bought a 16" f/4.5 to serve as a more compact companion, but I love my biggo 16.5".

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5783485 - 04/07/13 10:28 AM

Quote:

Goings have been slow, but I am making progress now, I hit some snags and made some twists and turns in my initial design, working out some of those took quite some time...

I picked up three sheets of 18"x4' planked pine sheets. These are narrow pine boards glued together to make larger sheets, they are finished sanded and look nice, though they are on the heavy side. I cut 12" off of three, then glued the scrap up to make a 4th 3' section. I do love being frugal. Some sweating with a plane and some sanding, and the franken-piece will work fine.




Thanks for the progress report Sean, it's fun to watch your progress.

I'm starting a rebuild on my 16" f/7 today. The explanation is lengthy and I don't want to hijack your thread, perhaps I'll start a new thread.

The design allows me to build up some of the larger wood sheets like you're doing from the numerous scraps I have laying around. I'm done with furniture-quality clear/poly finishes, going with paint so the seams will never show.

Have you made a decision on truss connectors? I just got a set of quick release clamps from Aurora Precision, a clever design with excellent build quality. Check out their video on Youtube. Pretty reasonable on cost too if you go with the simple lower clamp system vs. the more traditional design.


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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Jeff Morgan]
      #5783632 - 04/07/13 11:49 AM

Thanks Jeff, I am going to have my trusses fasten semi-permenantly to the top baffle which will then bolt to my LTA. Because of the overall size of the scope, I had to think about construction and transportationo in terms of sub-assembly, so the scope will break down into 3 main pieces that should *just* fit in the back of my Caravan. If I should be forced to carry passengers or another scope, then the truss assembly will break down more traditionally and I'll assemble the trusses on the field. When the trusses look to be in the 7'-8' long range, I think you should evaluate traditional dob set up and breakdown proceedures very carefully. I'll be putting this thing together myself in low-light conditions and since the weights and moments of these long pieces will bend or snap their mounting points if something bad happens, I have to have some options!

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5789261 - 04/09/13 10:26 PM Attachment (37 downloads)

Some more progress:
The cell support is built from angle iron scavenged from the chair and some 3/4" square iron stock. I can't weld, so some drilling, tapping and pretty stainless steel socket head screws. The cell and mirror will ride on this frame and I am going to hinge the assembly so that I can insert the mirror easily once the whole scope is assembled on the field.

Edited by Sean Cunneen (04/09/13 10:29 PM)


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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5789269 - 04/09/13 10:34 PM Attachment (35 downloads)

Now, here is where we get to some fun stuff. Lets be honest, there is not a whole lot you can do with a newt these days, so I had to have some fun somewhere! Bear in mind, the pictures that follow are only rough-fit, nothing is glued yet so things look pretty rough, but you'll get the idea soon enough!

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5789273 - 04/09/13 10:36 PM Attachment (31 downloads)

Here is the underside to show some structure. The mirror is pretty hefty, so the pieces are all stiff and thick. I'm not going to go into any detail about what the next few posts will show...

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5790629 - 04/10/13 04:09 PM



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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Scanning4Comets]
      #5885741 - 05/26/13 03:05 PM Attachment (24 downloads)

Another update! Starting to feel the progress coming along. Worked through some mistakes and some miscalulations. I found some others but I'll keep those to myself

The mirror cell is now roughed in and glued up... The Mirror supports have been reinforced, everything sanded and plenty of holes drilled.


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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5885747 - 05/26/13 03:08 PM Attachment (14 downloads)

Here is the shot of the underside. I am looking for a third clamp knob, turns out the two I have are a weird size so the search is on for that one! I had to make a couple of trips to the hardware store to find stiff enough springs. The three I have now will provide a nice cushion for that big mirror!

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5885753 - 05/26/13 03:13 PM Attachment (15 downloads)

Next up is the framing of the lower OTA. Each pine panel is trimmed with 3/4' rounded red oak. I started with gluing in reinforcing strips of 2x2.

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5885756 - 05/26/13 03:15 PM Attachment (15 downloads)

Then the first baffle is glued in with a partial assembly of the rest of the components to make sure the clearances are nice and tight. My daughter thought I was building her the castle she always wanted. I'll let her down easy when she turns 5.

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5885759 - 05/26/13 03:16 PM Attachment (22 downloads)

A final shot of everything coming together.

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5885858 - 05/26/13 04:34 PM

It is really a joy watching you build this scope. Congrats on the progress, looks great. I will definitely follow your build progress. Thanks for posting.

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: cpr1]
      #5902852 - 06/04/13 10:47 PM

Thanks Christopher! It has been a fun build with some interesting challenges. Things are starting to work themselves out, so the build should progres fairly quickly in the next few weeks.

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5902855 - 06/04/13 10:51 PM Attachment (15 downloads)

My youngest stayed home sick today so I snuck away for 20 minutes here and there to make some more progress. One gimmick I wanted to try out was a hinged mirror cell so that I can easily install the mirror when traveling. The mechanism is very simple, two carriage bolts through the side of the mirror box straight to the cell rails to act as hinges. Two small clamping knobs to hold the cell rails in the box. Here is the rail assembly getting the holes marked and drilled.

Edited by Sean Cunneen (06/04/13 10:52 PM)


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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5902860 - 06/04/13 10:53 PM Attachment (13 downloads)

Test fit...

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5902863 - 06/04/13 10:54 PM Attachment (11 downloads)

I made folding hangers for each side to hold the cell rails out of thin aluminum strips.

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5902867 - 06/04/13 10:57 PM Attachment (14 downloads)

Each end was rounded and holes drilled. It took me a couple of iterations to figure out where the hangers would be mounted so they could move freely and fold up and out of the way. They ended up working out really well! I thought these would be much more finicky... Here the back end is just you know; hanging out...

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5902878 - 06/04/13 11:01 PM Attachment (13 downloads)

Another thing I wanted to try was to make the clamping knobs for the rails captive. I rummaged through the parts bin at the hardware store to find a couple of "E" clips that fit the 1/4-20 shaft(tip, they were NOT the 1/4' ones, go figure). I mounted a cutting wheel in my drill, slipped a washer on the knob shaft and ground down one turn of thread.

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5902887 - 06/04/13 11:06 PM Attachment (18 downloads)

Whaddya'know, worked like a charm! The trick is to drill the hole for the shaft a size larger, in this case 5/16" so that the knob has plenty of wiggle room.

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5902891 - 06/04/13 11:08 PM Attachment (18 downloads)

Here is a beauty shot right down the OTA

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5902901 - 06/04/13 11:12 PM Attachment (18 downloads)

I made one panel removeable via screws, the other three sides are glued in. That way I can get good access to add fans or anything else I need to do inside.

My last step of the night was to add some trim to the top. I'll use the coping saw to rough the corners and finish up with the belt sander.

Edited by Sean Cunneen (06/04/13 11:13 PM)


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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5995454 - 07/28/13 08:51 PM

I've had a couple of weeks to put some more hours into this project. Originally I wanted this thing together Aug 1st, that is not going to be the case, Perhaps Sept 1st!

Once the box was put together I took a fair amount of time working on the altitude bearings. I thought maybe I should use some cast aluminum tube caps from a 60's fiberglass newt tube I had salvaged. The rings are 11" dia but I was having fitting and mounting issues. The rings were no more than 1/2" wide and tapered immediately to 1/4". The problem that I couldn't get my head around was how to drill through the sides of the box and hit the rings to an accuracy of 1/16" inch or so. After a week or so I went back to my original idea of a 24" wooden disk cut in half and glued directly to the sides.

Then I got tricky. I figured with a scope this big, at some point I'd like to have both axis driven. Also, if it's on an eq platform, I would need to be able to lock things down to change eyepieces(that is going to be a process!) or check out the charts. When thinking about movements and big things, the magic of materials gets kinda hard to figure out ahead of time. One thing I learned building my Eq mount is that you have to build things to move nice and easy, then you build a brake. Thinking about materials that will do both can be a roll of the dice and when things get big and heavy, everything moves nice and easy!


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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5995461 - 07/28/13 08:56 PM Attachment (33 downloads)

So I roughed out the sides and bottom of my base out of my chair sides and nice hunk of wood. I figured with my skinny wood bearing disks, I could have each side bearing just inside of each chair side. I sourced a handful of nice sealed captive bearings. I cut 4 pieces of 1/2" threaded rod and tapped straight into the oak sides...

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5995501 - 07/28/13 09:15 PM Attachment (24 downloads)

The brake took a fair amount of figuring. I figured that if I mounted one bearing away from the side of the LTA, I could use a bar and clamping knob to provide a good braking action. I put the brake on the same side as the focuser to minimize any torquing action from moving the scope around by the UTA.

I used a hole saw to cut out some disks of UHMW Polyethylene and mounted three on the inside of the oak chair side as well as 3 in a piece of strong ply. I had to cut out some material and countersink the UHMW pads for clearance.


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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5995522 - 07/28/13 09:21 PM Attachment (23 downloads)

After a lot of roughing, measuring and mocking up, the dimensions and construction fell into place. Sometimes I hate my brilliant ideas as it can take an hour to find the right bearing or bolt to fit the design I come up. This time it went together pretty smooth and the clearances were all right where they should be. With some spacers and a carriage bolt with a clamping knob and there you go, a brake.

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Sean Cunneen
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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5995527 - 07/28/13 09:22 PM Attachment (21 downloads)

The outside view...

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5995542 - 07/28/13 09:34 PM Attachment (21 downloads)

I used a spring with the clamping knob to allow the braking bar to adjust to the wood bearing. It would be nice to have a perfectly straight and smooth side bearing, but this being the real world, a spring will keep the brake assembly from binding on any high-spot on the side bearing.

Next up is a little bit of beautification. I glued up the UTA out of my plywood rings and some plywood planks...

I picked up some red oak iron-on veneer tape and spent a night taping over all of the exposed ply on the UTA. It's a nice light assembly and kinda purty too...


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Sean Cunneen
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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5995546 - 07/28/13 09:35 PM Attachment (25 downloads)

Here is where I'm at now: a mocked up LTA. I will have to figure out a way to ensure the side bearings are parallel before gluing...

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #5995786 - 07/28/13 11:44 PM

Quote:

Here is where I'm at now: a mocked up LTA. I will have to figure out a way to ensure the side bearings are parallel before gluing...




Thanks for the update Sean!

As for the parallelisms:

1) Not too critical for non-DSC scopes. In understand well it is a point of pride, but don't go crazy on it.

2) Parallelism starts from the Inside Out. If you have not already glued the mirror box, cut a series of spacers to maintain equal widths of the mirror box interior. Clamp it tight until the walls meet the spacers and do not use the edge cuts of the mirror box for guidance! Any excess edge(s) on the mirror box can be sanded down.

If the MB is already glued, you can use a spacer cut to the same width as the back edge of the mirror box and place it at the front edge of the alt bearings, shimming as needed any gaps in the mirror box.

Good luck!


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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Jeff Morgan]
      #6033820 - 08/19/13 12:11 AM Attachment (23 downloads)

I made a bit of progress this weekend, I am at that great point where the end is far off, but in sight.

I have spent most of the last 2 weeks figuring out how I was going to attach the poles. So what did I do? something else.

First, the mundane. I glued up some oak floor board scraps and glued them to a sheet of 3/4 birch ply for a stiff base. Another problem had been working on was how to brake the azimuth axis. I was very please with my alt-brake and was looking for the same magic for the az-axis. The complication was I did not have the space on the bottom as I did on the sides. I needed a brake that was going to fit in 3/4 of space. I also wanted to use a lazy-susan bearing for easy movement. After digging through my parts pile I settled on a train-wheel style brake. I guess one of the benefits of building a bunch of scopes is that I have assorted circles and arcs left over from other builds and sure enough, this time my parts bin came through!

I started by finding a nice round and centered 12" disk of plywood left over from the interior of routing out disks for the UTA.

I spent some time truing the circle and sanding it smooth. I then centered it on the base board via center screw and after lots of careful measurement, attached the lazy susan bearing:


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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #6033837 - 08/19/13 12:24 AM Attachment (17 downloads)

The brake is installed on the LTA side so that I can have tensioning knobs for both axis on the same side of the LTA. I figured I could use some leverage, so I roughed out where the parts should lay. One thing to think about is that unless you have access to a lathe, a shoe-brake has to be able to travel, you can't just use a screw to push against the brake disk as any out-of-round imperfections will cause binding. What I want is not binding but a consistent resistance of movement. That means, much like my alt-brake, there has to be a spring involved which means I have to have a pulling action instead of a simple push type action. Now there is a penalty for getting to complicated in one's setup as well, but then what is life but a roll of the dice?


So here is what I came up with: a clamping shoe actuated by a simple lever:


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Sean Cunneen
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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #6033847 - 08/19/13 12:34 AM Attachment (22 downloads)

Here is everything finished up with a nice clamping knob, spring, etc. The wooden lever is actuated by a 1/4-20 eye-bolt which is tensioned by a spring and clamped by the knob. After reassembly, the clamping action is noticeable so we'll call that effective for now. If the clamp needs some help, we can always clamp down via the center bolt. We'll see how it goes though....

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #6034465 - 08/19/13 12:16 PM

Pretty clever - it looks like a drum brake with the mechanism on the outside instead of the inside.

I would think that humidity changes will raise the grain on the wood parts, changing the feel the of action. Are you going to attempt to seal that, or just retune with each observing session?


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Sean Cunneen
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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Jeff Morgan]
      #6034562 - 08/19/13 01:09 PM

Thanks Jeff,

I've contemplated gluing a bit of sandpaper to facilitate everything wearing down. After a while, a bit of clearance will wear in and I can line each with a bit of plastic or aluminum strip. Or asbestos, whatever...


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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #6034606 - 08/19/13 01:41 PM

asbestos, lol Very nice work.

May I ask where your lazy susan bearing came from, its weight limit, and dimensions?


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Sean Cunneen
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Re: My 16" f7.2 Newt project code named "Grace" new [Re: MessiToM]
      #6040029 - 08/22/13 12:22 PM

I bought that lazy susan at our local Menards(big box store). It is a little larger than 12" in diameter, about 1/4" thick and has a listed capacity of 250lbs, though I haven't seen one sweat yet. Usually they are too smooth with zero stiction, hence the need for the brake.

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #6095753 - 09/22/13 08:58 PM

My deadline for first-light is the Illinois Dark Sky Star Party Oct 6th-ish. Hopefully a deadline will help! I have been working on all the little parts. What you gain in portability with truss construction, you pay for in complexity.

I began this project with lofty ambitions about how to handle the tube connections. I considered buying ball-connectors but I had second thoughts about having so much visible machinery, this being mostly wooden construction. I then talked to another ATM who had made wooden clamping blocks and was telling me about how expensive they were, since they had to be cut from one piece of wood. I must have gone back to the drawing board a dozen times!

I finally decided on a simple bolt at either end. For that I needed 6' tubes(technically 5'-6"L) So I went to my local box store and the only conduit lengths were 5' or 12'! Oh brother. Nothing like a mid-aisle redesign. So I could spend $8.60 and figure out something new or $120 on proper sized aluminum. Guess which direction I picked? Yep. $10.45 total with the bag of M&Ms.

That's okay, trying to figure out how to stretch 5' of tubing to 5'-6" of tube ended up fixing another issue, that of inevitable trimming of tubes. Having 8 tubes, I was not looking forward to that part. I have found ways with my other builds to have some adjustability for accessories like filter slides, binoviewers, etc.


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Sean Cunneen
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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #6095769 - 09/22/13 09:07 PM Attachment (10 downloads)

The answer came to me in the form of plywood tube anchors that would allow the tube to slide in and out. If I made them 6"l on the bottom and 3" long on top, I would give myself the extension I needed and it would fit in with the rest of the construction. The downside is all of the sawdust. My gosh, the sawdust from all the routing and sanding was not-to-be-believed!

Construction is simple, I routed a channel for 5" down a 7"l block. I then cut a back-plate that will clamp down on the tube end via screws.

Easy, huh. Now make 8 of them. Still have 10 fingers (whew!)


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Sean Cunneen
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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #6095787 - 09/22/13 09:15 PM Attachment (4 downloads)

For the other end, I followed the same methodology for construction with the channels and such however I opted to make each union whole rather than individual mountings. This is one area I often question both from a field-assembly point of view as well as a stability issue. For a stiff union, the forces from each tube should meet at the same point to form triangles throughout. Often with ball connectors you end up with a clunky assembly which makes trapezoids. They also take two people to assemble. I opted to make the tubing connectors one piece.

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #6095793 - 09/22/13 09:19 PM

I routed the channels the same way and cut the slight 5deg angle to each side. I glued each side together with a channel in the center for further adjustment. A cam lever will provide quick assembly/adjustment, They are on order.

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #6095798 - 09/22/13 09:22 PM Attachment (5 downloads)

The base of each tube mounts via corner blocks and machine screw anchors/clamping knobs. The top baffle/corner blocks will also unbolt from the LTA so I can completely disassemble the trusses or if I want to be up and going quick, I can unbolt the assembled trusses and UTA from the LTA.

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #6095805 - 09/22/13 09:25 PM Attachment (37 downloads)

I added mounting tabs to the bottom of the UTA. I wanted to make sure that the trusses were angled in one axis only. I got pretty close!

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #6095831 - 09/22/13 09:34 PM

The secondary holder was constructed from parts I had laying around. One part was pretty crazy, I had a magnesium base from a Monfrotto tripod head that was reversible for 3/8" or 1/4-20. That became the top mounting disk. 4 8/32 threaded rods, some thumbwheels and some springs from every click-pen we had in the house. The mirror holder is cut from a piece of PVC tubing on my chopsaw. All in all, everything made for a nice secondary holder! I don't know that I could make another like it in my lifetime though!

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #6095850 - 09/22/13 09:49 PM Attachment (27 downloads)

Last for this weekend is the construction of a three curbed-vane spider. I wasn't going to do a curved vane spider originally, but I was going through my scrap shelf and found a 2" thick section of 7" diameter tube from my refractor build. The thing i hate most about curved vane spiders is forming the curve and for a span as long as 17", any excess curvature beyond the main curve will affect the final image. My last curved vane spider had one vane torqued a bit which caused a flare in dark skies.

I figured if I could cut the section into two 1" rings and cut each ring in half, I could have three vanes with curves that I know maintain their parallelism with each other.

My favorite way to cut tubing is using a hacksaw, using hoseclamp as guide. I get perfectly square cuts. Then each ring is cut in half...


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Sean Cunneen
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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #6095860 - 09/22/13 09:53 PM Attachment (23 downloads)

For the hub I had a 1" dia 1/8" wall aluminum tube that was originally a roller for some piece of manufacturing equipment. I had a couple of aluminum washers that I press-fit into each end(again, pure luck that they fit!) and I drilled the center to fit a 3/8" shaft. I marked the 120deg sections and started drilling and tapping...

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Sean Cunneen
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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #6095864 - 09/22/13 09:55 PM Attachment (35 downloads)

Another view...


It turned out well. Stiff enough (you can see the secondary holder in the background). If it doesn't work, I might end up buying a 4 vaned straight spider and commercial secondary holder.


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Jeff Morgan
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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #6096063 - 09/22/13 11:59 PM

Quote:

My deadline for first-light is the Illinois Dark Sky Star Party Oct 6th-ish. Hopefully a deadline will help! I have been working on all the little parts. What you gain in portability with truss construction, you pay for in complexity.




October 6th is coming up pretty fast ...

Good luck on the truss connectors. After my third failure at making my own, I vowed to buy that part commercial in all future scopes. I burned up a lot of days in the shop trying to get a functional and attractive solution - to no avail. I hope your experience is better.


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Sean Cunneen
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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Jeff Morgan]
      #6097961 - 09/24/13 08:29 AM

I was up pretty late last night(or early this morning) trying to mock up the OTA. My truss connectors aren't going to do the trick, at least not how I had intended. There is too much force for the clamping action to handle and the tubes slide and twist too easily. Fixing that is going to require pinning each tube into either bracket end Not the end of the world, but not the super cool adjustability I was shooting for. Oh well, I make the mistakes so you don't have to!

Edited by Sean Cunneen (09/24/13 01:12 PM)


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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #6098334 - 09/24/13 11:54 AM

Don't feel too bad. I recall Dave Kriege at AstroFest 20 years ago saying that it took him three prototypes on the Obsession design.

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Jeff Morgan]
      #6098466 - 09/24/13 01:15 PM

The fix isn't too bad. I was thinking almost solely in terms of compression and standing straight up the assembly was a piece of cake and the OTA looked great! As I moved it to horizontal so I could find the balance point, everything turned into limp spaghetti and I had tubes coming apart all over. All I could hear was the Benny Hill theme as I tried to wrangle 3 poles with two hands!

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #6132236 - 10/11/13 11:36 PM Attachment (24 downloads)

Okay, I admit it, this post jumps the gun a bit, but at least you see it is a scope!

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Sean Cunneen
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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #6132237 - 10/11/13 11:36 PM Attachment (22 downloads)

Doesn't look quite so huge in this pic...

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #6132248 - 10/11/13 11:42 PM

Sean. like I said on Facebook: Ladder.

Or should I say: TALL LADDER!!


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Re: My 16" f7.2 Newt project code named "Grace" new [Re: magic612]
      #6132265 - 10/11/13 11:55 PM Attachment (19 downloads)

Quote:

Sean. like I said on Facebook: Ladder.

Or should I say: TALL LADDER!!






Congrats Sean!

Here is a ladder worthy of such a scope. The tape measure I am holding is set to 110", the original planned eyepiece height of my 16" f/7 scope Stripe.


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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Jeff Morgan]
      #6132308 - 10/12/13 12:29 AM

I tried grabbing one of those Home Depot stocking ladders but the guards caught me before I could get it in the car.

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #6132588 - 10/12/13 08:35 AM

Holy elevator shoes Batman!

JimC


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Re: My 16" f7.2 Newt project code named "Grace" new [Re: magic612]
      #6132633 - 10/12/13 09:14 AM

Quote:

Sean. like I said on Facebook: Ladder.

Or should I say: TALL LADDER!!




facebook is for oldtimers

kids say hashtag #tall ladders.


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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Pinbout]
      #6132880 - 10/12/13 11:38 AM

Looking forward to looking through it very soon!

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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Darren Drake]
      #6133967 - 10/12/13 10:24 PM

These 16" f/7s are my dream scopes - it was the largest I thought Id go if I were to go in that direction. As it is Ive been too busy and honestly, happy with the 8" F/9 bit I do envy you guys with those awesome systems. Great work on both 16s.

Pete


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Re: My 16" f7.2 Newt project code named "Grace" new [Re: azure1961p]
      #6134095 - 10/12/13 11:59 PM

Quote:

These 16" f/7s are my dream scopes - it was the largest I thought Id go if I were to go in that direction. As it is Ive been too busy and honestly, happy with the 8" F/9 bit I do envy you guys with those awesome systems. Great work on both 16s.

Pete




Thats so funny ... we have a sloped property, and the limited flat spots are just too small for Stripe (and the accompanying ladder). So Stripe is strictly a remote session telescope.

But I often wake up in the early morning and need a scope for quick yard sessions. I have been sketching out a solution to this problem over the past couple of weeks. No ladder is one requirement, the other is fast and easy set -up. The solution I am closing in on is a 8" f/9 scope!

At some point, I will become too old and frail to use my 16" f/7, at which point it will come up for sale. But since Clyde Tombaugh used his long focus 16" well into his 80's .... don't hold your breath.


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Sean Cunneen
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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Jeff Morgan]
      #6340830 - 01/28/14 12:11 PM Attachment (15 downloads)

I have spent a good month working on this project however I had a catastrophic Update with my computer which deleted all pictures of the finishing steps Here is a photo of the UTA and LTA together...

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Sean Cunneen
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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #6340842 - 01/28/14 12:16 PM

The OTA is finished in red-oak stain and the oak base is finished in Ebony. My atrocious basement lighting doesn't do the contrast justice, but until our "Polar Vortex" calms down, my basement lighting is all you get! This is by far the largest and most complex wood project I have ever undertaken. I thought painting would take a couple of days, but it took many days over a month to sand and paint everything to a proper amateur standard (thank goodness for soft-focus!)

Some features like the Azimuth-brake and lazy-susan bearing have been removed in favor of a Berry&Kriege-like ball-bearing assembly. I'll revisit that concept in an inevitable re-fitting prior to the Equatorial table-build. For now movements are smooth enough in AZ and fantastic in altitude!

I'll take some photos of the completed interior tonight and post them soon.


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Re: My 16" f7.2 Newt project code named "Grace" new [Re: Sean Cunneen]
      #6342041 - 01/28/14 10:43 PM

Quote:

The OTA is finished in red-oak stain and the oak base is finished in Ebony. My atrocious basement lighting doesn't do the contrast justice, but until our "Polar Vortex" calms down, my basement lighting is all you get!




It already looks great even under that light!

Any sightings of glaciers crossing the Wisconsin border yet?


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