Telescope Reviews: My 16" f7.2 Newt project code named "Grace"

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Sean Cunneen
Let Me Think

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

Post Extras:

Darren Drake
Carpal Tunnel

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.

Post Extras:

MessiToM
professor emeritus

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

Post Extras:

bremms
scholastic sledgehammer

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.

Post Extras:

magic612
Post Laureate

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?

Post Extras:

Jeff Morgan
Post Laureate

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 (104 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.

Post Extras:

MKV
Carpal Tunnel

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

Post Extras:

Sean Cunneen
Let Me Think

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.

Post Extras:

Sean Cunneen
Let Me Think

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.

Post Extras:

Jeff Morgan
Post Laureate

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.

Post Extras:

Jeff Morgan
Post Laureate

Reged: 09/28/03

Loc: Prescott, AZ

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.

Post Extras:

Darren Drake
Carpal Tunnel

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 (69 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)

Post Extras:

Sean Cunneen
Let Me Think

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.

Post Extras:

magic612
Post Laureate

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.

Post Extras:

StarryHost
member

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

Post Extras:

k9yr
super member

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.

Post Extras:

Sean Cunneen
Let Me Think

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 (65 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)

Post Extras:

Sean Cunneen
Let Me Think

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.

Post Extras:

Napersky
Carpal Tunnel

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

Post Extras:

bremms
scholastic sledgehammer

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.

Post Extras:

Napersky
Carpal Tunnel

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
Carpal Tunnel

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!

Post Extras:

Mike I. Jones
Carpal Tunnel

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
Carpal Tunnel

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!

Post Extras:

Jeff Morgan
Post Laureate

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.

Post Extras:

Sean Cunneen
Let Me Think

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 (68 downloads)

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

Post Extras:

Sean Cunneen
Let Me Think

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 (40 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...

Post Extras:

bremms
scholastic sledgehammer

Reged: 08/31/12

Loc: SC

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.

Post Extras:

Sean Cunneen
Let Me Think

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 (30 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...

Post Extras:

Sean Cunneen
Let Me Think

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 (34 downloads)

The poor donor:

Post Extras:

Sean Cunneen
Let Me Think

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 (28 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!

Post Extras:

Darren Drake
Carpal Tunnel

Reged: 10/09/02

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)

Post Extras:

magic612
Post Laureate

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.

Post Extras:

JohnH
Carpal Tunnel

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.

Post Extras:

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.

Post Extras:

niteskystargazer
Carpal Tunnel

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

Post Extras:

gatorengineer
Carpal Tunnel

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....

Post Extras:

Jeff Morgan
Post Laureate

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.

Post Extras:

Sean Cunneen
Let Me Think

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.

Post Extras:

gatorengineer
Carpal Tunnel

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.

Post Extras:

Sean Cunneen
Let Me Think

Reged: 08/01/07

Loc: Blue Island Illinois

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!

Post Extras:

Jeff Morgan
Post Laureate

Reged: 09/28/03

Loc: Prescott, AZ

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?

Post Extras:

gatorengineer
Carpal Tunnel

Reged: 02/28/05

Loc: Hellertown, PA

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.....

Post Extras:

Sean Cunneen
Let Me Think

Reged: 08/01/07

Loc: Blue Island Illinois

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)

Post Extras:

Sean Cunneen
Let Me Think

Reged: 08/01/07

Loc: Blue Island Illinois

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.

Post Extras:

Jeff Morgan
Post Laureate

Reged: 09/28/03

Loc: Prescott, AZ

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.

Post Extras:

Sean Cunneen
Let Me Think

Reged: 08/01/07

Loc: Blue Island Illinois

Re: My 16" f7.2 Newt project code named "Grace" new

[Re: Jeff Morgan]
#5620867 - 01/13/13 02:01 PM Attachment (24 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.

Post Extras:

Sean Cunneen
Let Me Think

Reged: 08/01/07

Loc: Blue Island Illinois

Re: My 16" f7.2 Newt project code named "Grace" new

[Re: Sean Cunneen]
#5620888 - 01/13/13 02:12 PM Attachment (22 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)

Post Extras:

droid
rocketman

Reged: 08/29/04

Loc: Conneaut, Ohio

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.

Post Extras:

Sean Cunneen
Let Me Think

Reged: 08/01/07

Loc: Blue Island Illinois

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!

Post Extras:

Sean Cunneen
Let Me Think

Reged: 08/01/07

Loc: Blue Island Illinois

Re: My 16" f7.2 Newt project code named "Grace" new

[Re: Sean Cunneen]
#5782393 - 04/06/13 06:45 PM Attachment (14 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)

Post Extras:

Sean Cunneen
Let Me Think

Reged: 08/01/07

Loc: Blue Island Illinois

Re: My 16" f7.2 Newt project code named "Grace" new

[Re: Sean Cunneen]
#5782401 - 04/06/13 06:49 PM Attachment (9 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)

Post Extras:

Sean Cunneen
Let Me Think

Reged: 08/01/07

Loc: Blue Island Illinois

Re: My 16" f7.2 Newt project code named "Grace" new

[Re: Sean Cunneen]
#5782415 - 04/06/13 06:52 PM Attachment (10 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...

Post Extras:

Sean Cunneen
Let Me Think

Reged: 08/01/07

Loc: Blue Island Illinois

Re: My 16" f7.2 Newt project code named "Grace" new

[Re: Sean Cunneen]
#5782417 - 04/06/13 06:56 PM Attachment (10 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...

Post Extras:

Sean Cunneen
Let Me Think

Reged: 08/01/07

Loc: Blue Island Illinois

Re: My 16" f7.2 Newt project code named "Grace" new

[Re: Sean Cunneen]
#5782418 - 04/06/13 06:58 PM Attachment (8 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!

Post Extras:

Sean Cunneen
Let Me Think

Reged: 08/01/07

Loc: Blue Island Illinois

Re: My 16" f7.2 Newt project code named "Grace" new

[Re: Sean Cunneen]
#5782421 - 04/06/13 07:00 PM Attachment (12 downloads)

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

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

Post Extras:

Sean Cunneen
Let Me Think

Reged: 08/01/07

Loc: Blue Island Illinois

Re: My 16" f7.2 Newt project code named "Grace" new

[Re: Sean Cunneen]
#5782664 - 04/06/13 09:38 PM Attachment (12 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!

Post Extras:

Sean Cunneen
Let Me Think

Reged: 08/01/07

Loc: Blue Island Illinois

Re: My 16" f7.2 Newt project code named "Grace" new

[Re: Sean Cunneen]
#5782667 - 04/06/13 09:38 PM Attachment (16 downloads)

and one more...

Post Extras:

jgraham
Postmaster

Reged: 12/02/04

Loc: Dayton, Ohio

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".

Post Extras:

Jeff Morgan
Post Laureate

Reged: 09/28/03

Loc: Prescott, AZ

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.

Post Extras:

Sean Cunneen
Let Me Think

Reged: 08/01/07

Loc: Blue Island Illinois

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!

Post Extras:

Sean Cunneen
Let Me Think

Reged: 08/01/07

Loc: Blue Island Illinois

Re: My 16" f7.2 Newt project code named "Grace" new

[Re: Sean Cunneen]
#5789261 - 04/09/13 10:26 PM Attachment (13 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)

Post Extras:

Sean Cunneen
Let Me Think

Reged: 08/01/07

Loc: Blue Island Illinois

Re: My 16" f7.2 Newt project code named "Grace" new

[Re: Sean Cunneen]
#5789269 - 04/09/13 10:34 PM Attachment (15 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!

Post Extras:

Sean Cunneen
Let Me Think

Reged: 08/01/07

Loc: Blue Island Illinois

Re: My 16" f7.2 Newt project code named "Grace" new

[Re: Sean Cunneen]
#5789273 - 04/09/13 10:36 PM Attachment (11 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...

Post Extras:

Scanning4Comets
Markus

Reged: 12/26/04

Loc: Deep Space!

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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