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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
The Making of my 20" telescope for a Carl Z mirror
      #5755364 - 03/25/13 01:18 AM

So not sure how all this is going to turn out but we will see.

The Project: Make a telescope to hold a F4.5 20.03" by 1" thick 22lbs quartz mirror being made by Carl Z with a Lockwood 3.5" Flat.

Photos of work done to this point, will add as I get more done.

To help with weight I have used carbon fiber over balsa. Very light and very strong.

For the rings I am using a composit honeycomb board also very strong and very light. The stuf is used in aircraft.



[URL=http://s245.photobucket.com/user/ORduner/media/20130322_043449.jpg.html][IMG]


I hope when done the telescope with mirror will be under 40lbs

Edited by ctcables (03/26/13 12:43 AM)


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Daud
sage


Reged: 08/05/06

Loc: AZ, Scottsdale
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5755393 - 03/25/13 01:49 AM

Whoa, he is back, after 4 years...when can I get a 24" quartz blank form you, Chris ?

Edited by Daud (03/25/13 01:49 AM)


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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: Daud]
      #5755417 - 03/25/13 02:19 AM

So changing this post to a list of what people guess for the weight.
Marc 45.7LBS
kfrederick 51.0LBS
ausastronomer 47.4LBS


So NO prize as per CN, sorry wish I could give one out.

Edited by ctcables (03/28/13 12:58 AM)


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mark cowan
Vendor (Veritas Optics)
*****

Reged: 06/03/05

Loc: salem, OR
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5756422 - 03/25/13 03:27 PM

Quote:

I hope when done the telescope with mirror will be under 40lbs




That'd be amazing. I'm guessing 45.7, can you start a contest??

Best,
Mark


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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: mark cowan]
      #5757094 - 03/25/13 09:55 PM

Sounds like a good plan Mark, what do you think the prize shold be? Nice Quartz mirror blank? Say in the range of 6 to 12 inches? I will see what I have on hand, so start putting your guesses for the final weight.

To inclued telescope, mirror, foucser, finder, secondary,and eyepice. Anyother ideas would be great. Will post photos as I move along with this project.


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mark cowan
Vendor (Veritas Optics)
*****

Reged: 06/03/05

Loc: salem, OR
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5757230 - 03/25/13 11:26 PM

I'm including the weight of the SIPS Paracorr but no EP...

Best,
Mark


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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: mark cowan]
      #5757303 - 03/26/13 12:34 AM

Not sure on the paracorr but will be using a fethertouch light which is only .8 lbs. should I include the base with controler? may do a platform for tracking but not sure yet. Going to talk with Dan Gray about what system will work best with what I want to do. Anyway sounds like a fun give away, nice thing to do for all the people that have helped out over the years. So get the weight right and win a quartz mirror blank. Will post size tomarow. Plan on completing the telescope before OSP.

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GeneT
Ely Kid
*****

Reged: 11/07/08

Loc: South Texas
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5757328 - 03/26/13 12:57 AM

Very interesting project. Keep us updated on how things are progressing.

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tezster
scholastic sledgehammer
*****

Reged: 07/14/09

Loc: Missisauga, Canada
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: GeneT]
      #5757634 - 03/26/13 07:49 AM

Wow... that'll be an super light-weight scope for a 20" - my 10" DobStuff weighs just a shade under 40 pounds, and I already consider that fairly light.

This one will be fun to follow


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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: tezster]
      #5757645 - 03/26/13 08:06 AM

should this post be moved to ATM, Optics and DIY Forum? It is a reflector but might be better suited in the DIY area? if so how do I move it or should I just restart it? Anyway Lots to do yet but taking my time.

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kfrederick
Carpal Tunnel


Reged: 02/01/08

Re: The Making of my 20" telescope for a Carl Z mirror new [Re: tezster]
      #5757657 - 03/26/13 08:15 AM

Making things very strong and very light is not very easy . Chris Thanks for the glass I have gotten . I know your telescope will be very nice .A fast 20 is the perfect size . I say 51 lbs .[If no helium is used in the tubes] Ha Ha

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ausastronomerModerator
Carpal Tunnel
*****

Reged: 06/30/03

Loc: Kiama NSW (Australia)
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: kfrederick]
      #5758682 - 03/26/13 05:13 PM

Hi Chris,

I am guessing at 21.5kg which is 47.4lbs.

This is the exact weight of my 10"/F5.3 truss dob, which is designed to be rock solid and steady. It will be a tremendous effort to get a 20" down to that weight.

PS If I win I will pay the freight, after Carl Z turns it into another gem

Cheers,
John B


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Starman1
Vendor (EyepiecesEtc.com)
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Reged: 06/24/03

Loc: Los Angeles
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: mark cowan]
      #5758747 - 03/26/13 05:44 PM

Quote:

I'm including the weight of the SIPS Paracorr but no EP...

Best,
Mark



The SIPS does have the advantage of never having to guess about perfect coma correction, but there are advantages to the "slide-in" Paracorr:
--it parfocalizes all your eyepieces. If the truss poles are cut correctly, you may be able to achieve focus very close to the in-most position of the focuser. This has the advantage of minimizing the secondary-to-focal plane distance and reducing sag in the focuser due to the weight of heavy eyepieces. With the SIPS, your eyepieces will focus over a range.
--it is normally already removed when setting up, so collimation doesn't require removal, unlike the SIPS (some people do remove the SIPS lens when tearing down, but I don't think all do).
--it will never insert beyond the end of the focuser drawtube
--it is threaded for filters on the bottom end, standardizing filter diameter and making it possible to exchange eyepieces without changing the filter from eyepiece to eyepiece
--it can be removed easily and used in another scope so it can easily be shared with others or if you have more than one scope set up.
--Depending on your focuser cost, it might be cheaper in combination with the focuser than the SIPS focuser + Paracorr ensemble.
--it makes correction of an already existent scope easier than changing the focuser.

Obviously, this f/4.5 scope will need a coma corrector. If you build the scope assuming a 31 Nagler and Paracorr in the focuser, overall balance will be pretty good.


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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: Starman1]
      #5759307 - 03/26/13 10:21 PM

I have posted a photo of the 6" mirror blank that will be given to the winner. Also I have started a list of guesses and will keep it updated in the 3rd post, this should help people save time. So if you want to see what others have put for weight just go to the first page 3rd post. Good luck.

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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5759341 - 03/26/13 10:44 PM

So just got informed that Cloudy Nights needs to give the OK for me to give the blank away. should be ok but if things change very sorry. Will post when I find out.

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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5761612 - 03/28/13 12:48 AM

Good news I am allowed to give the 6" blank away to the winner or person that gets near the weight of the telescope.
My rules: Items to be included in weight of telescope!
1: Focuser
2: secondairy, wire spider and secondary cell.
3: 20 inch quartz mirror 1" thick
4: 18pt mirror cell with side support
5: main rotation bearing.
Not included in weight is drive system and telescope platform/stand.

6:deadline to get your guess in is April 30
7: winner of the free 6" quartz mirror blank will be contacted when the telescope is completed I hope before Oregon Star Party. Good luck



Edited by ctcables (03/31/13 12:33 AM)


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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror *DELETED* new [Re: ctcables]
      #5761616 - 03/28/13 12:55 AM

Post deleted by ctcables

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ausastronomerModerator
Carpal Tunnel
*****

Reged: 06/30/03

Loc: Kiama NSW (Australia)
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5763109 - 03/28/13 08:17 PM

Hi all,

This thread and giveaway by Chris is all good to go.

Please guess away as you wish.


We have untagged Chris as a vendor as he has wound his business down. There was never any question of Chris's generous intent with this giveaway, but as a tagged vendor it was against the rules and they have to be applied consistently for all vendors.

Good luck in the Giveaway.

Cheers,


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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ausastronomer]
      #5763186 - 03/28/13 09:02 PM

Hay thank you so much for doing this for me. Back on for the 6 inches blank give away. get the weight right and win this very nice 6" mirror blank including shipping with in the USA.







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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5763324 - 03/28/13 10:27 PM

Very cool delivery to day, just recived my 3.5" Lockwood quartz secondary mirror, wahooo. Around 1lbs.







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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5767952 - 03/31/13 12:33 AM

Good news I am allowed to give the 6" blank away to the winner or person that gets near the weight of the telescope.
My rules: Items to be included in weight of telescope!
1: Focuser
2: secondairy, wire spider and secondary cell.
3: 20 inch quartz mirror 1" thick
4: 18pt mirror cell with side support
5: main rotation bearing.

Not included in weight is drive system and telescope platform/stand.

6:deadline to get your guess in is April 30
7: winner of the free 6" quartz mirror blank will be contacted when the telescope is completed I hope before Oregon Star Party. Good luck


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gatorengineer
Carpal Tunnel
*****

Reged: 02/28/05

Loc: Hellertown, PA
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5768244 - 03/31/13 08:44 AM

Chris,

Good Luck, your goals are enviable, but if you are going to use any thing even vaguely approaching a widefield eyepiece (31 Nagler, etc). You wont come in under 70 lbs for the scope that goes to the field with the tailweights needed to balance, shroud, finder, telrad baffles... This is still great accomplishment as a commercial 20F4.5 would be over 100.

I understand the goals of fast cooling and thin mirrors, but that doesnt get away from the need for tailweights and crazy complex mirror supports to get a good image, as thin as your primary is.

Just looking at your sketch, a couple of other things jump out, I dont think your scope will swing through to Zenith (mirror box may be too short). You will need a significant light baffle opposite side the focuser, as you will have stray light issues (this also will add to the need for tail weights (You are around 5:1 distance to focuser versus distance to mirror), so every pound up top will be 5 pounds in the tail. Telrad, finder etc, to make the scope useable all add counterbalance (also the shroud)..... I am on my 5th or 6th large dob (currently a 25 F5 commercially built), but have built several of my own.... I applaud your ingenuity, and drive, and just want to give you a cuople of look outs....

Edited by gatorengineer (03/31/13 08:47 AM)


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kfrederick
Carpal Tunnel


Reged: 02/01/08

Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5768247 - 03/31/13 08:48 AM

How about Mark C be the judge as to if it is stiff enough .If Mark says it is stiff and you are under 40 lbs I send you a mirror . The X prize The first big telescope who weight is under twice the diameter . Now just get rid of the obstruction. All good fun

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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: kfrederick]
      #5768262 - 03/31/13 08:58 AM

My 14.5 inch scope is at 32LBS on the scale (no bearing stand just scope) photos can be seen at 2012 OSP. This one is going to be better in every way. I have given up some weight with the wood lam but it looks so nice. Still looking good on weight but we will see. Put your guess in.

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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5768267 - 03/31/13 09:10 AM

This is a photo of my 14.5, new telescope is not the same but a combo of it and others I have seen.


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mark cowan
Vendor (Veritas Optics)
*****

Reged: 06/03/05

Loc: salem, OR
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: kfrederick]
      #5769044 - 03/31/13 03:20 PM

Quote:

How about Mark C be the judge as to if it is stiff enough.




But I'm in the running for the contest, so I won't be impartial.

Chris does some amazing designs that work quite well - if you study the materials he's using and picture how large this will be you'll see where the balance point is going to be... OTOH I don't think it will actually end up looking exactly the design and still balance without weights. But I'm more than willing to be wrong.

Best,
Mark


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gatorengineer
Carpal Tunnel
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Reged: 02/28/05

Loc: Hellertown, PA
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: mark cowan]
      #5769127 - 03/31/13 04:26 PM

its clear that part of this interesting thread has been cut off the front when it was transferred. I think there is a segment about mirror support, which I would like to read. 18 pts is no way near enough in common thinking for a 20" F4.5...

Also I though the weight guess was for a finished functional scope? Is it just the ""OTA"" with no shroud baffles, eyepieces, counterweights etc


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mark cowan
Vendor (Veritas Optics)
*****

Reged: 06/03/05

Loc: salem, OR
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: gatorengineer]
      #5769364 - 03/31/13 05:53 PM

Page 1? It's all here...

Beg to differ, 18-points should be fine. 2.2nm RMS from PLOP 2D for fused silica, 1.8nm RMS from PLOP 3D. I'd go 27-point, but that's just me.

Yes, what are we guessing on? Mine was for push-to configuration including the base and paracorr and 1x finder.

It'll be interesting to see how my wire spider design works with a 3.5" secondary.

Best,
Mark


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gatorengineer
Carpal Tunnel
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Reged: 02/28/05

Loc: Hellertown, PA
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: mark cowan]
      #5769695 - 03/31/13 08:55 PM

mark, you are of course right, she calcs out just fine, using Plop with 18 points.... I keep remembering Krieg and Berry..... What the Cruxis program also shows is the criticality of the sling for this thin of a mirror.....

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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: gatorengineer]
      #5769905 - 03/31/13 11:36 PM

I have some more information to help with guesses.

Photo of 8foot by 4foot composit I am using.



and on the scale at 10LBS only a small % of a board is getting used.


I do have a couple of questions:
1 on the primary mirror support triangles can they have some flex and if so how much?

2: my secondary cage is 15" by 22"id with 25"od and will be lined with a wood varniear (yes my spelling sucks sorry) see photo below. how far from the top should the secondary mirror be for best light blocking. Was looking at 6" but not sure? Anyway thank you for the support.


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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5770192 - 04/01/13 06:21 AM

Ok this is about as good as I am going to get. .25 inch = 1" and I think this is very close to what the telescope without base is going to look like. Strut length and secondary placement may change slightly but this is the best information I can give at this time to help you guess the weight. Please comment good or bad, I think I have a very strong bearing / center core like a bike frame most cross members will be hollow light but strong. Anyway we will see how it turns out.



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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5771745 - 04/01/13 09:37 PM

Epoxy coat done just need Urethane top coat on light shrouds. Little bit at a time but going to be a long project.



Weight with shroud. will add another .5 pounds in hardware, 1lbs for secondary, .9lbs for fether touch, .5lbs for finder. and ?lbs for the rest.



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mark cowan
Vendor (Veritas Optics)
*****

Reged: 06/03/05

Loc: salem, OR
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5772050 - 04/02/13 12:50 AM

Your UC baffling isn't going to be adequate with the secondary that far forward, I suspect...

I'm sticking with my original guess as to the weight, but I'm not going out to buy lottery tickets.

Best,
Mark


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jpcannavo
scholastic sledgehammer
*****

Reged: 02/21/05

Loc: Long Island New York
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5772175 - 04/02/13 05:25 AM

Quote:


I do have a couple of questions:
1 on the primary mirror support triangles can they have some flex and if so how much?





As far as effectively "floating" your primary goes, some flexure in the triangles does not distort the mirror. It can however cause collimation shift. However, symmetry in the flotation system might allow this to cancel out.

I have never seen well quantified tolerances for this (although they are calculable) and I think the tendency therefore is to somewhat err on the side of overbuilding to avoid these issues, which is what I did with my cell.

Still, I have always suspected differential flexure/yielding etc. (i.e. asymmetric) to be an under reported source of collimation shift.
in mirror cells.


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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: jpcannavo]
      #5772187 - 04/02/13 05:54 AM

Thank You JP this is good info, going to use a thin alloy for the triangle and because it is floting with = preshure on all points I would hope they would flex the same amout at the same time. I may beff them up some.

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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5772202 - 04/02/13 06:24 AM

Some info on the Bubinga Wood I used.
Native Regions
There are nearly 20 different species of bubinga trees that grow throughout the world. At least a dozen of those species are found in the West Equatorial Africa Region, where it is warm and humid. They are primarily native to the Cameroon, Gabon, Ivory Coast, and Congo nations, although a few species are found in South America. They typically grow in tropical climates, along jungle waterways such as swamps, streams and lake shores. Bubinga is commercially known as African Rosewood.

Characteristics
Bubinga is a beautiful and interesting wood with colors ranging from pinkish-red to deep red with irregular purple and brown streaks throughout. Its grain pattern primarily varies from straight to interlocking, but can have a variety of other figures such as waterfall, pommel, and quilted. It has a fine texture with small pores. Also, if rotary cut, the patterns can show swirling and veining throughout. It is a very hard, dense, and heavy wood, weighting an average of 58 lbs/cu. ft. Also, it possesses an exceptional strength-to-weight ratio, bending strength, and shock resistance. Bubinga is a very durable wood due to its oily nature, which provides protection from insects, decay, and wet surroundings.


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droid
rocketman
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Reged: 08/29/04

Loc: Conneaut, Ohio
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5772242 - 04/02/13 07:13 AM

Id be interested in knowing how the carbon fiber over balsa works. As an amateur rocketeer, I've glassed balsa in the past, and the balsa gets extremely stiff. But no experience with carbon fiber...yet.

My guess would be somewhere in the 40 lb range.


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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: droid]
      #5772272 - 04/02/13 07:53 AM

Droid it is just outstanding at how strong and light it is. the 1" by 1/2" by 14"runners in my upper cage have almost no flex when 40lbs is put on them, have not found the breaking point yet. If I have extra I might test it, the only thing I have seen that is better is a nomex (nomax not sure) which is hexgonal core between carbon fiber sheets. It is used on the new Bowing plane and very very expensive.

some one is selling some at this link if you want to take a look.
http://www.ebay.com/itm/Carbon-Fiber-Balsa-Core-Sheet-6-x-18-1-2-Thick-glossy...


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tezster
scholastic sledgehammer
*****

Reged: 07/14/09

Loc: Missisauga, Canada
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5772370 - 04/02/13 09:02 AM

I'm going to throw in my guess at 48.5 lbs

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nevy
professor emeritus
*****

Reged: 02/07/12

Loc: UK
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: tezster]
      #5774251 - 04/02/13 09:56 PM

It will weigh 51.25 lb

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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: nevy]
      #5774274 - 04/02/13 10:02 PM

Marc Cowen 45.7LBS
kfrederick 51.0LBS
ausastronomer 47.4LBS
Tezster 48.5
Nevy 51.25

I am going to need a very accurate scale when this is done.


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Dave O
sage
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Reged: 12/21/11

Loc: Sri Lanka
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5775133 - 04/03/13 10:09 AM

I'll give you the benefit of doubt ... 39.9 lbs.

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VectorRoll
super member


Reged: 11/27/12

Re: The Making of my 20" telescope for a Carl Z mirror new [Re: nevy]
      #5775574 - 04/03/13 01:28 PM

Nice design. I really like the idea of Carbon Fiber Balsa Wood. I'll have to remember about that for some projects that I may do in the future.

I can't wait to see what it turns out like when you are finish.

On your contest.
I was going over your design to try and figure out the weight. I see you are hoping it would be under Forty Pounds. i think you can do it. If I had to guess, I would estimate it to be about 38.5 pounds. So that is my guess for your contest.

38.5 lb



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ctcables
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: VectorRoll]
      #5777292 - 04/04/13 10:16 AM

ok so need some more feedback? SIPS Paracorr which is better and with F4.5 is it going to make a noted change in the view? Spend 90% of time with 26mm to 3mm but who knows with this new mirror. Also I have moved the center of the secondary mirror 4" from the bottom of the cage, my thinking is I will get much less light behind the secondary but is this to low. My cage is 15" top to bottom and I do not want to add extenshions to block light but am happy to put a black wrap around the struts. Let me know what you think.

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ctcables
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5780350 - 04/05/13 07:04 PM

working on the balance problem trying to find out the right COG, any help with the difference between the paracore and the sips system would be great thanks.

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TxStars
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5781011 - 04/06/13 01:28 AM

How about 46.7lbs

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ctcables
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: TxStars]
      #5781141 - 04/06/13 04:29 AM

Hay Marc Cowen is this how you wired your spider, I just have it mounted temperly not center or anything but it feels solid.



Hiden hardware


Going to do some sanding to clean the mount up more and might paint the ss bolts black.




going to replace lock nut with banjo tenshiner, will look better and be much easer to set tenshion in wires with little added weight.


weight of secondary is 5lbs + focuser at .8lbs + secondary mirror at 1Lbs and ? 2lbs for sipps. total for secondary with sipps would be 8.8 lbs or 6.8 with out sips.
Anyway more updates latter.



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ctcables
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5781143 - 04/06/13 04:31 AM

Marc Cowen 45.7LBS
kfrederick 51.0LBS
ausastronomer 47.4LBS
Tezster 48.5
Nevy 51.25
Gatorengineer 70

Dave O 39.9
Vector Roll 38.5
TxStars 46.7
Nightstarker 44

Edited by ctcables (04/06/13 06:21 PM)


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nightstalker
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5781170 - 04/06/13 05:58 AM

44 pounds with a tak 6x30

Edited by nightstalker (04/06/13 06:02 AM)


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gatorengineer
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: nightstalker]
      #5782159 - 04/06/13 04:38 PM

you forget my 70 lbs... Which would still be amazing for a 20"...

The lightest usable large aperature scope I know of is here from a master builder who frequents this site at 63 lbs for an 18"..... one of the prettiest scopes I have ever seen as well...

http://www.stardazed.com/MoonsilverIV.html

Not trying to be a troll, just a realist....


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ctcables
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: gatorengineer]
      #5782359 - 04/06/13 06:26 PM

Gator that indeed is one very nice looking telescope I am counting on the lightness of my mirror to make up for the extra weight anof my components. 40lbs is going to be very hard and that is not including the base.

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mark cowan
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5782887 - 04/06/13 11:26 PM

Chris,

That looks OK to me. Just be careful not to crimp the wires with the through-holes on the secondary holder, you might want to radius those corners and only tighten it up once on any given set of strings - another reason to follow the design and use the flex plate and collimation screws for tweaks rather than messing with wire tension. I recommend using a jig to fix the secondary assembly in space before tightening down the wires (I updated my web site to say this a while ago) and also note the tension is not high at all - the spider gets its stability from the geometry, not from tension.

.008" might be on the light side for a 3.5" secondary but of course you can always change it as needed.

Best,
Mark


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gatorengineer
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5784538 - 04/07/13 07:00 PM

Chris, You have a great project going... The mirror will cool superbly no question, and optically your rig will be amongst the best 20"ers in existance. No question.

Quartz mirrors actually increase the need for counterbalance. I have well over 40's of lead shot in the tail of my obsession (with its massive rocker rocker box) 2" plus thick mirror, steel mirror cell, etc). Its all about the balance, and moment arms a 31 nagler is a bugger to balance.....

Great project and cant wait to see the end product.


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ctcables
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: gatorengineer]
      #5784879 - 04/07/13 10:00 PM

Yep COG is a bugger for sure gator; because of my very large bearing (effective 36" R) my COG is out there around 18 inches from face of mirror. Also I am working on making the bearing into what some might call a 2 strut system but the cage of the mirror replaces the lower struts and the bearings form the mid box making my top struts around 40". May not be a small system but because most of it is hollow it is much stronger and lighter. Will post some new photos along with my less than 1lbs upper strut.

This strut folds into a triangle that is 2.5" OD by 47" long and is less than one pound. Will cut down to size when complete, this is also going to get covered in carbon fiber.



Revised plans.


Looks like the added sips and extra epoxy to make it look nice is going to push me over the 40lb mark and then some, High hopes for supper light are not gone just revised in that I do want it to look nice as well. Anyway if you want to change your guess on the weight you can. After this I will not be posting any more updates on the weight so from this point everyone has = information. I think with the info I have posted we should get very close to a finished tube weight.


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ctcables
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5797523 - 04/13/13 09:40 PM

Well made some head way on the alt bearings, need to work on the carbon fiber lay up next.





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ctcables
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5801867 - 04/16/13 01:20 AM

Got started on the carbon fiber lay up. Lots of work left to do but it is going well.



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ctcables
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5814431 - 04/21/13 11:50 PM

Another week and a big part almost complete, this took lots and lots of time and checking but it looks to be turning out very well. So here are the photos.


This is how it will sit, cross bracing not showing in this photo as I still need to make them which is next.

inside of alt bearings showing the 4 cross bracing supports.




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mark cowan
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5815479 - 04/22/13 02:52 PM

Looking great Chris!

Best,
Mark


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ctcables
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: mark cowan]
      #5816770 - 04/23/13 02:34 AM

Thanks Mark, Getting things ready for it. Just put an order in for a ES 20mm 100 and found a great deal on an Ethos 13mm. Not sure if I should sell the 10mm and 4mm radian because I am not sure how they will work out with the SIPS system. Anyway going to make the COG bottom heavy. I have lots of room with the alt bearing location to shift the weight up top or to the bottom. I am thinking it is better to be bottom heavy so when the big eyepiece goes in it is just right.

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ctcables
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5833761 - 05/01/13 07:29 AM

getting things done but it seems like it is taking way longer than I expected. The bearings were not easy but they are turning out well.





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gatorengineer
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5834600 - 05/01/13 03:01 PM

Chris, looking good what diameter alt bearings are you using? Thanks

Mark


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ctcables
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: gatorengineer]
      #5835318 - 05/01/13 10:06 PM

36 inch. Alt will have a 6 to 8 inch from the bottom of the mirror cell to the bottom of the alt bearing putting the cog 21 to 22 from the mirror face.

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gatorengineer
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5838682 - 05/03/13 04:15 PM

are you eccentrically mounting the mirror box on the bearings? That will get you a little more to COG, look at what Spica eyes does, hard to explain...

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coinboy1
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: gatorengineer]
      #5838769 - 05/03/13 05:17 PM

Great telescope. 41.3lbs is my guess. Good luck and cant wait to see the updates!

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ctcables
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: coinboy1]
      #5877144 - 05/21/13 11:21 PM

Just got my carbon fiber trus tubes in to day, thay look very nice. I will post a photo later this week. It is looking to be in the 52 to 56lbs range for the ota depending on if I add finder and heater system. Not much done over the last 2 weeks as other things have taken up my time but will get back on it next week and start posting more photos. So the people in the 50+ lbs range are still in the running. Last update from Carl was the mirror was 70% complete and was lookiing good so we will see as it must pass his 5 tests.

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ctcables
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5884706 - 05/25/13 09:52 PM

This is a photo of the rocker mounted up to the mirror cage, still making the cross braces and will add the liner to the mirror cage after mounting hardware is added. The second photo is of the new carbon fiber struts that will attache the secondary cage to the rocker, will be 8 struts.




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ctcables
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5888347 - 05/28/13 05:05 AM

Ok need some help as this part is critical and just want someone to check my work. Using Newt for the web I have a 20.03 inch mirror at F4.5 using a 3.5 inch secondary. Inside ring is 22" and outside or (to focuser mount) is 23.25Diam or 11.684" from center of secondary to face of focuser mount. Newt shows 76.955 from face to secondary then the 11.684 to focuser. So my question is with a 1.5" feather touch with built in SIPS is this still the same? Dose my point of focus change with SIPS? If someone can confirm this for me that would be great, do not want to cut struts unless I am positive of the distance from mirror to secondary then secondary to where the focuser mounts. The outer diameter is fixed at 23.25” I hope this makes sense but if not let me know what I need to add for information.

Thank You


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ctcables
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5890357 - 05/29/13 09:00 AM

Ok let’s do something more simple, dose the SIPS change the focus point? Will I need to add or minus distance from secondary by adding the SIPS? Or am I correct in assuming the SIPS just moves it out so everything will come to focus as if the SIPS was not installed. Never had a paricor before or SIPS so I just do not know. Hope fethertouch sends info on this part if I get no answers here.

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gatorengineer
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5890562 - 05/29/13 11:34 AM

suggest that you just cut your truss poles long and trim them in as needed. There is a thread here on Fast Mikes Dob in which Mike Lockwood gave a marked up photo of a SIPS and the focal location. Hope this helps, thread was in the last month.

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mark cowan
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5890903 - 05/29/13 03:42 PM

Quote:

Ok let’s do something more simple, dose the SIPS change the focus point? Will I need to add or minus distance from secondary by adding the SIPS? Or am I correct in assuming the SIPS just moves it out so everything will come to focus as if the SIPS was not installed. Never had a paricor before or SIPS so I just do not know. Hope fethertouch sends info on this part if I get no answers here.




Yes, it changes it. Study that photo, it explains the geometry, it shows the original focal plane and the new one as well.

http://starlightinstruments.com/store/image/cache/data/coma%20correctors/SIPS...

In any case I wouldn't cut those struts shorter until you've installed the mirror and confirmed the focal plane of the entire OTA. You know, just to be sure.

Best,
Mark


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ctcables
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: mark cowan]
      #5891437 - 05/29/13 10:01 PM

Thanks for the information and the photo, just what I needed. I do appreciate your help with this.

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ctcables
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5912117 - 06/09/13 09:49 PM

Well I did not think the alt bearings were going to take so long, I think I over did it, lol. They are very strong and I think will work very well. I have completed the SS inlay for the drive motor contact along with putting in all the filler strips so the main part is done. I now need to laminate the wood then sand and recoat to clean it all up. Anyway hear is a photo, next steep drill mounting holes and make mirror cell which I have decided to go with a 27 point cell.





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ctcables
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5926942 - 06/18/13 07:46 AM

I am now starting to make the parts for the 27pt cell. I have Aluminum laminated to the honeycomb which makes it very light flat and stiff this is then attached to the solid aluminum triangle which is attached to a pivot ball joint connected to a Titanium valve which is supported by a brass valve guide. This makes a very strong accurate stiff anchor point while keeping every one of the 27 points floating. See photos.









Edited by ctcables (06/18/13 07:58 AM)


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jtpowers
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5927040 - 06/18/13 08:49 AM

Very inspiring project! I'll weigh in at 44.8lbs.

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ctcables
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: jtpowers]
      #5930109 - 06/19/13 09:36 PM

One more steep in the right direction. Custom Blue one of a kind.



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mark cowan
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5930149 - 06/19/13 09:59 PM



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ctcables
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: mark cowan]
      #5935419 - 06/22/13 09:49 PM

Mirror cell looking good, 27pt. There will be larg vent holes and a spot for small center fan if needed, with 1 inch thick quartz mirror I should not have much problems with mirror cool down.



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ctcables
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5958202 - 07/06/13 09:48 PM

Well been some time from my last update, Looks like I over did the alt bearings. They are very strong but weigh much more than I wanted. I know now that 5 lbs could have been saved on each one by using AL instead of stainless steel. So looks like the completed OTA weight is going to be. 69Lbs this includes mirror 22lbs, mirror cell 5lbs, ALT bearings 22lbs struts 3lbs, secondary cage with focuser and mirror 6lbs and primary cage 5lbs. So even cutting the alt bearings down looks like the best I could do would have been around 61 lbs and if I left it without any wood lamination this would have saved another 10 lbs as the epoxy turns out to be heavy as well. Anyway this way it looks much better and is very strong.








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ctcables
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5958209 - 07/06/13 09:55 PM

Looks like the clear winner is Gatorengineer at 70lbs great job. PM me as to location you want me to send your new blank to. I will post more photos as I get the mirror and rocker box completed.

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kfrederick
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5958225 - 07/06/13 10:12 PM



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mark cowan
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: kfrederick]
      #5959102 - 07/07/13 02:57 PM

70 lbs?

That looks extremely cool, BTW.

Best,
Mark


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ctcables
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: mark cowan]
      #5959648 - 07/07/13 09:36 PM

Mark no need to say it I am a looser LOL, I just could not stop adding things to the alt bearings. Because they will be part of the link between the primary and secondary I just wanted them to be very strong. Anyway instead of 6 lbs each they were 11 lbs each. I have some other great news, my mirror is off to OMI for coating and Carl told the mirror is one the best he has done. So if shipping is good and it gets turned around in good time I will have it for OSP. I need to get the rocker box done now.

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mark cowan
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5959923 - 07/08/13 01:11 AM

I tend to overbuild on prototypes too.

Mark


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seryddwr
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: mark cowan]
      #5960537 - 07/08/13 01:23 PM

I'm planning on making my 20" have direct drive motors. If I come in under 170, I'll be happy. 70 pounds is plenty light IMHO.

Greg


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seryddwr
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: seryddwr]
      #5960541 - 07/08/13 01:25 PM

PS. I have a dedicated 'scope trailer, so I'm not overly concerned about weight.

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ctcables
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: seryddwr]
      #5961265 - 07/08/13 09:47 PM

This is my trailer for the telescope so weight for me is no big deal but moving it from one spot to another. With the mirror and cell it is mounted in under 33lbs I know I can move it anyware with all other parts lighter than that. Anyway hope to have it complete and ready for first light by July 29th. OSP is AUG 7th so running out of time.



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ctcables
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5969443 - 07/13/13 06:46 PM

some more work done.
Mirror cell mounted.


Anchor points using Epoxy

27 point cell


Making Alt anchor plates.


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ctcables
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5973601 - 07/16/13 05:57 AM

some bearing for the telescope.




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ctcables
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5982105 - 07/20/13 10:05 PM

Rocker box is getting done, sure hope I make it for OSP, It is going to be close. I pick up my new mirror from Carl on the 26th. It has the OMI I-Bad 96% coating and I hear nothing but good things about how every aspect of the mirror turned out. I can not say enough good things about Carl at this point and all the work he put into making this get done so I could have it for OSP. On a side not I now have a Servo II controller with error checking encoders which I hope to have installed before OSP as well. Ed Johns is working on some platform parts so I will do what I can to get it all done. Will be nice to have a goto scope with Photo tracking as well. Time is my biggest road block at this point.



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Chriske
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5982843 - 07/21/13 11:40 AM

Looking great this 'monster' Chris...
Starting to read this thread I would have said 75 lbs.

Chris


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ctcables
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: Chriske]
      #5990720 - 07/26/13 03:59 AM

mirror cell almost done, will pick up mirror on friday. Just need to add cable support. I now have all stablizing pins in place and every point is fully floating.





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cpr1
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Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5990798 - 07/26/13 07:11 AM

Hi Chris, Interesting build with the cellular construction. Your very talented.

Do you plan on attaching a fan or fans on the mirror cell?


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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: cpr1]
      #5990965 - 07/26/13 09:49 AM

I have a fan for it that I can add if needed, currently the center of the cell is sold but It can be cut out to fit a verity of the different types of fans. With a 1 inch quartz mirror I am going to try it without it first.

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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5991955 - 07/26/13 08:42 PM

I have my new mirror and boy it sure looks grate.

uncovering


The polished back side. Mirror error? Carl did not find any, it is a very very good mirror. Can not wate for first light.


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mark cowan
Vendor (Veritas Optics)
*****

Reged: 06/03/05

Loc: salem, OR
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5993116 - 07/27/13 02:24 PM

Looking good, Chris. Polished back!

Best,
Mark


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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: mark cowan]
      #5993384 - 07/27/13 06:01 PM

Thank you mark, I will have it mounted in the cell this week. I have 3 days off next week to complete my telescope, I should get it done so it will work but not all the finish work will be done. Anyway I will do everything I can to get first light at OSP. May need to get someone to help me out with fine tune at OSP. One more photo with the velcro cable aligment system. I will be using the velcro to keep the cable centered at COG .434 inches.



all dressed up to keep it clean while working on it.



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mark cowan
Vendor (Veritas Optics)
*****

Reged: 06/03/05

Loc: salem, OR
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #5993781 - 07/27/13 10:33 PM

As much as I'd love to help fine tuning I won't be doing OSP this year - too much other stuff going on. But take lots of pics!

Best,
Mark


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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: mark cowan]
      #6005520 - 08/03/13 10:29 PM

looks like it is going to be very close for OSP. Secondary done, Rocker with ALT motor and encoder done, sling support for primary mirror done. Rotation bearing mounted not done, finish for rocker box not done but not needed to work, trus poles not mounted. I have 4 days left, hope I can find some one to help me out at OSP with tunning the servo controler II? Will do my best.

Cable support


With mirror


Drive motor with encoder and error corecting encoder mounted.


back to work


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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #6020080 - 08/12/13 01:15 AM

OSP was an outstanding success. Full report with photos to follow soon.

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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #6024218 - 08/13/13 11:49 PM

new 20" in action. Working on full report.


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mark cowan
Vendor (Veritas Optics)
*****

Reged: 06/03/05

Loc: salem, OR
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #6024293 - 08/14/13 12:35 AM

(Says something inappropriate for a family-oriented forum...)

Now that gives me a sense of the scale.

Best,
Mark


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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: mark cowan]
      #6024544 - 08/14/13 07:11 AM

Oregon Star Party 2013 Report
Back in December 2012 I had the rear opportunity to get a 1” by 20” quartz blank so I took the leap and got it. Now I had to build a telescope for it and get the mirror made so the work started. This report is in 2 parts starting with part 1 the build, part 2 first light at OSP.

After several days of haggling and trading I assembled my list of parts. My secondary mirror would be a quartz 3.5” by Mike Lockwood, the primary mirror would be a F4.5 done by Carl Zambuto optical, and the focuser would be a SIP system from Feather Touch and a Servo Controller II by Dan Gray. My goal was to have it completed for the Oregon Star Party Aug 7th 2013. I started with a drawing of what I wanted to create which changed several times during the build but stayed within the theme I was looking for. I wanted to make the OTA to be 40LBS with mirror, well that did not quite work out but at 69lbs with mirror focuser and all working parts it is still not too bad. As you look through the photos of the project from start to finish you will see that I used a honey comb fiber board for just about all the parts with some carbon fiber over balsa for key areas. The weight for one 4’ X 8’ by .25” is only 10lbs keeping things very light but strong. I found that the ALT bearings were harder to make and took me weeks and weeks to complete which was much longer than I expected. The mirror cell I must say turned out fantastic, 27 pt full flotation support with 180 degree cable support giving the mirror a very stable foundation to rest on. I was able to get the OTA completed but 3 days before the OSP I was still working on the drive system and base which I was able to patch a working system together at the last minute. I will need to complete this now that OSP is over.

Speaking of OSP how was first light? Well with all I had to do it turned out great, whether was not great on Thursday night and earlier when we arrived I found out that my telescope would not focus as my struts were to long so I packed it up for the night. Well around 3AM I stuck my head out and to my delight it was a very clear night so out came my back up telescope. Great views of M13, M31, Andromeda Galaxy, and many others. So the first night was not too bad after all. Friday I found a hack saw and some blocks with clamps (thank you Gary Kline) and was able to get my trusses shortened. Friday night and the sky were hazy to start but by 11:30PM were clearing up very nicely. I started off with some easy to find objects and was completely pleased at how much detail I could see. The 2 dust lanes in Andromeda were very clean and easy to see, The Ring nebula had a very nice shape and filled the eyepiece and M13 was just a stunning with my 9mm explore scientific + the Barlow. I felt like I was right there. Next stop contrast test, M101 pinwheel galaxy was well defined in the 20mm 100 degree EP. I was able to see each arm of the pinwheel with the central core and could not be more pleased about the optics. I enjoyed the rest of the night hopping from one area to another and everyone that stopped by was just as pleased as I was.






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kfrederick
Carpal Tunnel


Reged: 02/01/08

Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #6024556 - 08/14/13 07:28 AM

Well gone!! If you have another quartz blank might wont to try grinding one. You would have Carls to compare It to .

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mark cowan
Vendor (Veritas Optics)
*****

Reged: 06/03/05

Loc: salem, OR
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: kfrederick]
      #6025310 - 08/14/13 02:48 PM

Hey Chris,



There's the money shot! How many people can do that with a 20" OTA?

Best,
Mark


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Kretieg
member


Reged: 03/21/13

Loc: Louisiana
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #6025416 - 08/14/13 03:48 PM

What wood or veneer are you using?

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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: Kretieg]
      #6025654 - 08/14/13 05:39 PM

 Bubinga Wood more information on page 2

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johnnyha
Postmaster
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Reged: 11/12/06

Loc: Sherman Oaks, CA
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #6025897 - 08/14/13 08:09 PM

Awesome, fantastic job!

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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: mark cowan]
      #6035469 - 08/19/13 10:08 PM

Quote:

Hey Chris,



There's the money shot! How many people can do that with a 20" OTA?

Best,
Mark




Mark if that is the money shot where is the money? LOL
Wish you could have made it but there is always next year.


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mark cowan
Vendor (Veritas Optics)
*****

Reged: 06/03/05

Loc: salem, OR
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #6035668 - 08/20/13 12:18 AM

It's a metaphor in this case, on second thought I'd call it:

CALLING DOWN THE LIGHTNING!



Best,
Mark

PS those pics of that 16" Sudiball mount on the walkabout have got me doing sketches for the structure I need for the 14.7" meniscus mirror now...


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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: mark cowan]
      #6046141 - 08/25/13 10:44 PM

Was asked this question in the OSP walkabout so thought I would post it hear as well.
So to answer your question on carbon fiber layup I have added a photo (see below) along with this link
http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/5755364/page...

As you can see I am using the carbon fiber for outside support, strength, and damage protection, it also looks good. The best way I have found to work this is to use a sheet of glass on a flat surface then a Teflon release sheet (black plastic looking stuff in the photo), layer of epoxy on the release sheet slow setting then the carbon fiber then another thin layer over the carbon fiber to make sure it is soaked in. When this is done squeegee off the excess epoxy to be used on what you want to bond to it (for me it was a fiber glass nomax core ¼” board sanded with 120 grit for good bonding). Next is 2 options 1 bag the whole thing and vacuum it down or 2 if you have a flat board and lots of weight to put on it this works as well. It is like making a sandwich with a time limit based on the epoxy set time. No room for mistakes as this stuff is not cheap. Now you let this sit for 24 to 48 hours and when you are done you now have a nice carbon fiber bond. To finish you sand with 120, then 220, then 300 grit and recoat with thin layer of epoxy in dust free room. This will give you a nice finish. Last step is to sand with 600 grit and give a final over coat with UV protecting urethane spray. Simple lol


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careysub
Carpal Tunnel
*****

Reged: 02/18/11

Loc: Rancho Cucamonga, CA
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #6047187 - 08/26/13 03:15 PM

Great stuff! Thanks!

Where did you source your fiberglass Nomex panels from?

Making a polygonal UTA from prepared CF-honeycomb sheet using this cut-and-fold technique looks interesting:

http://www.acpsales.com/Cut-and-Fold.html

A variation on this would be to use those pre-scored end-grain balsa sheets, laminate it with CF, and then cut on the outside make them foldable. Applying a non-stick treatment to the pre-planned EGB joints would be needed so that they aren't glued together. After they are cut and bent, an patching compound would need to be troweled end (preferably also resin-based) and covered with CF tape.


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polaraligned
professor emeritus


Reged: 12/26/08

Re: The Making of my 20" telescope for a Carl Z mirror new [Re: careysub]
      #6047511 - 08/26/13 06:42 PM

The cut and fold technique has been used by the composite airplane builders for years. You can also pretty easily form a round tube by cutting a series of kerfs in the back of a single skinned panel. It will then roll into a nice tube. The inside then needs to get cloth covered.

CF certainly can enable the home builder to cut his weight to maybe 1/3 of that of a similarly stiff wooden structure. An advanced builder on a large scope can maybe achieve a weight of 1/5 that of a similar wood or metal scope. For advanced scopes the reduction of thermals and the nearly 'set and forget' focusing are huge. CF scopes even in tubes can perform superbly as demonstrated by the Dream Astrograph. There is a remote 16" Dream in AZ that discovered 6 comets in the last year. There is also a 24" scope (doing research) that used a lot of CF and is light enough to be mounted on a Paramount. This is in stark contrast to the metal monsters of days gone by. Plenty of 24" "professional" scopes are weighed by the ton...The 24" I referred to above is barely over 200# including mount!


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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: careysub]
      #6047772 - 08/26/13 09:38 PM

Quote:

Great stuff! Thanks!

Where did you source your fiberglass Nomex panels from?

Making a polygonal UTA from prepared CF-honeycomb sheet using this cut-and-fold technique looks interesting:

http://www.acpsales.com/Cut-and-Fold.html

A variation on this would be to use those pre-scored end-grain balsa sheets, laminate it with CF, and then cut on the outside make them foldable. Applying a non-stick treatment to the pre-planned EGB joints would be needed so that they aren't glued together. After they are cut and bent, an patching compound would need to be troweled end (preferably also resin-based) and covered with CF tape.




Yes this works great; I have used this folding system before. I find a 5 minute epoxy works great for this, if it is to thin it tends to not hold where you want it to stay. Set times are very important depending on what you want to glue together.


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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #6187724 - 11/10/13 10:44 PM

Just added a 5 to 1 gear box to my 2 drive motors now I will get about 10,000,000 counts per rev. Need some clear sky's so I can see ISON.

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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: The Making of my 20" telescope for a Carl Z mirror new [Re: ctcables]
      #6438588 - 03/30/14 10:33 PM

Just cleaned the mirror for the first time, very happy with how it turned out. Looking forward to some clear nights.

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