Page 1 of 3 123 LastLast
Results 1 to 10 of 26
Like Tree35Likes

Thread: Rehabing an old handmade telescope

  1. #1
    djameson's Avatar
    djameson is offline White Dwarf
    Points: 509, Level: 10
    Level completed: 18%, Points required for next Level: 41
    Overall activity: 0%
    Achievements:
    2 Posts Achievement365 Days+ Registered Achievement!
    Join Date
    Dec 2017
    Location
    Dallas
    Posts
    3
    Points
    509
    Level
    10
    Thanks
    0
    Thanked 0x 0 Posts

    Default Rehabing an old handmade telescope



    Hi everyone,
    I am brand new here but I need some help. My dad was really into astronomy and when he passed away a couple of years ago I got his prized telescope he built in 1947. I have taken it apart and re-painted the interior and the exterior. I just got a few new eyepieces for it for Christmas but the primary mirror is in very bad shape. I know I can have it re-silvered but I am thinking that it might be better to get a new modern mirror (my dad hand ground his).

    This is an 8 inch reflector and when I measure from the primary mirror the secondary and then to the lens I get about 47 inches (or 1200mm). Not sure I did that right but if so I think from a calculator I found online it should be about an f/6.

    Can anyone confirm that I did that right and can I just replace the primary and re-culminate or do I need to replace the secondary as well? I don't know if this is odd but my dad made the secondary out of a prism.

    Thanks for the help in advance,
    Dave

  2. #2
    Ozman13's Avatar
    Ozman13 is online now HYPER GIANT
    Points: 29,186, Level: 100
    Level completed: 0%, Points required for next Level: 0
    Overall activity: 46.0%
    Achievements:
    2 Posts Achievement5 Threads Achievement!20 Posts Achievement!365 Days+ Registered Achievement!50 Posts Achievement!
    Join Date
    Jun 2013
    Location
    Hopkinsville Kentucky
    Posts
    8,430
    Points
    29,186
    Level
    100
    Thanks
    170
    Thanked 2,237x 2,010 Posts

    Default Re: Rehabing an old handmade telescope

    I couldn't confirm that without measuring it myself, but you probably have that right. You can replace both or only the primary.

    https://agenaastro.com/gso-parabolic...f-6-ad082.html
    DeanD and DirtyOptix like this.

    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    ACF 8"SCT,
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.

    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    ,
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    120, ES 102CF Apo triplet, ES AR102, ST100, ST90, Apex 90mm Mak, ST80, ETX60,
    Oberwerk BT-82XL-ED, 25x100s, 15x70s, 8x56s, Kasai 2.3x40s, Celestron AVX, CG4, SLT, LCM, Obie HD Parallel Bino mount
    Explore Scientific 82 degree and 68 degree EPs, Baader 9mm Ortho, Meade 5000 SWA EP set, many more various EPs, Baader
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    &SkyGlow, FringeKiller, SemiApo filters, Celestron UHC, Meade 4000 Nebular Filter, Kson OIII, DGM NPB and lots of astro stuff.

  3. #3
    Macrob1's Avatar
    Macrob1 is offline SUPER GIANT
    Points: 6,018, Level: 53
    Level completed: 34%, Points required for next Level: 132
    Overall activity: 0%
    Achievements:
    2 Posts Achievement20 Posts Achievement!50 Posts Achievement!5 Threads Achievement!200+ Posts Achievement!
    Join Date
    Feb 2017
    Location
    Melbourne, Australia
    Posts
    1,140
    Points
    6,018
    Level
    53
    Thanks
    411
    Thanked 258x 239 Posts

    Default Re: Rehabing an old handmade telescope

    Hello Dave and welcome to the forum.

    Cheers
    Bob


    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    :
    Skywatcher Star Discovery Mak 127 + SW 9x50 RACI on SynScan alt/az go-to mount; Saxon ST80; Bintel (GSO) 8" dob Eyepieces: SW kit 25mm, Starguider Dual ED 8mm and 15mm, SW 19mm flat field, SW 32mm Plossl, Vixen NLV 20mm, Svbony 12.5 mm illuminated reticle Barlows: SW 2x, Celestron Omni 2x Binoculars: Acuter 15x70, Olympus 10x50 DPSI

  4. #4
    DeanD's Avatar
    DeanD is offline HYPER GIANT
    Points: 16,477, Level: 88
    Level completed: 65%, Points required for next Level: 123
    Overall activity: 17.0%
    Achievements:
    365 Days+ Registered Achievement!2 Posts Achievement20 Posts Achievement!50 Posts Achievement!750 Days+ Registered Achievement!
    Join Date
    Apr 2012
    Location
    South Australia
    Posts
    2,373
    Points
    16,477
    Level
    88
    Thanks
    278
    Thanked 733x 597 Posts

    Default Re: Rehabing an old handmade telescope

    Hi Dave, and welcome! It certainly sounds like an f6 mirror. You could have it re-aluminised, but it will depend on how well your Dad made it in the first place: unless you can test it before spending the money getting it re-aluminised then it is a bit off a lottery! I don't know what the costs for re-aluminising are in the US, but the GSO mirror that Ozman pointed you to is a pretty good bet! GSO are making very nice mirrors now.

    Regarding your secondary: it is unusual to use a prism, and again it depends how good and how big it is! A 40-50mm secondary mirror will not be very expensive though. Here is a site you may find useful before you commit yourself: Sizing Up the Newtonian Secondary – Gary Seronik

    All the best, and good luck,

    Dean
    Ozman13 likes this.

    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.


    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    :
    12" home-made dob, Celestron 150 f5, Tak TSA102, TV 76, Celestron 800CPC, ETX 125
    Mounts:
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    MiniTower, HEQ5Pro
    Binos: 25x100FB, Carton 11x80, Vanguard Endeavour 1045, Takahashi 22x60, Swarovski Habicht 8x30
    Eyepieces: My favourites are my Televue 32mm plossl, Nagler 13mm T6, Nagler 3-6mm

  5. #5
    not_Fritz_Argelander's Avatar
    not_Fritz_Argelander is online now HYPER GIANT
    Points: 182,949, Level: 100
    Level completed: 0%, Points required for next Level: 0
    Overall activity: 36.0%
    Achievements:
    365 Days+ Registered Achievement!2 Posts Achievement20 Posts Achievement!750 Days+ Registered Achievement!First 1000 Experience Points
    Awards:
    Thread Award
    Join Date
    Jul 2011
    Location
    US
    Posts
    22,040
    Points
    182,949
    Level
    100
    Thanks
    7,254
    Thanked 46,396x 14,954 Posts
    Blog Entries
    59

    Default Re: Rehabing an old handmade telescope

    Yes, the prism is unusual but it was more common to see in reflectors made in the 1950s and earlier. Silver coatings rather than aluminum were more popular since the coating could be applied by an amateur. Silver coatings can be applied in a chemical bath and don't need vacuum vapor deposition technology.
    j.gardavsky likes this.
    Scopes: Refractors:
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    ST80 (mods for white light solar), SV ED80 f7 Newtonians: Z12 f5 Catadioptrics: VMC110L, Intes MK66 EPs: KK Fujiyama Orthoscopics, 2x Vixen NPLs (40-6mm) and BCOs, Baader Mark IV zooms, TV Panoptics, Delos, Plossl 32-8mm. Mixed brand Masuyama/Astroplans Binocular Nikon Aculon 10x50, Celestron 15x70, Baader Maxbright. Mounts: Star Seeker III, Vixen Porta II, Celestron CG5, Orion
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    EQG

  6. #6
    frazier's Avatar
    frazier is offline Main Sequence
    Points: 1,597, Level: 23
    Level completed: 97%, Points required for next Level: 3
    Overall activity: 0%
    Achievements:
    2 Posts Achievement20 Posts Achievement!Gallery Achievement!50 Posts Achievement!365 Days+ Registered Achievement!
    Join Date
    Dec 2017
    Location
    Richmond, Illinois
    Posts
    157
    Points
    1,597
    Level
    23
    Thanks
    6
    Thanked 29x 20 Posts

    Default Re: Rehabing an old handmade telescope

    Hello Dave, a few thoughts for what it's worth:

    Back in the day, 6" kits were much more common. An 8" would have been a definite step up, which speaks to a certain level of dedication on your father's part. In other words, he may well have made a very good mirror. I would never think of replacing it without at least testing it first (I would definitely replace the secondary though).

    I would see if there are any astronomy clubs in your area. If you replaced the secondary (to eliminate that as a possible source of error), and brought the scope into usable condition, you could take it to an observing session and have someone do a star test or otherwise render an opinion on the mirror. This can be done even with an uncoated mirror. At that point you can decide whether to recoat or replace the mirror.

    Cheers,

    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    : Homemade 8" f/7
    In process: 10" f/5; 12" f/7
    "It's good to be Kzin"

  7. #7
    not_Fritz_Argelander's Avatar
    not_Fritz_Argelander is online now HYPER GIANT
    Points: 182,949, Level: 100
    Level completed: 0%, Points required for next Level: 0
    Overall activity: 36.0%
    Achievements:
    365 Days+ Registered Achievement!2 Posts Achievement20 Posts Achievement!750 Days+ Registered Achievement!First 1000 Experience Points
    Awards:
    Thread Award
    Join Date
    Jul 2011
    Location
    US
    Posts
    22,040
    Points
    182,949
    Level
    100
    Thanks
    7,254
    Thanked 46,396x 14,954 Posts
    Blog Entries
    59

    Default Re: Rehabing an old handmade telescope

    Quote Originally Posted by frazier View Post
    Hello Dave, a few thoughts for what it's worth:

    Back in the day, 6" kits were much more common. An 8" would have been a definite step up, which speaks to a certain level of dedication on your father's part. In other words, he may well have made a very good mirror. I would never think of replacing it without at least testing it first (I would definitely replace the secondary though).

    I would see if there are any astronomy clubs in your area. If you replaced the secondary (to eliminate that as a possible source of error), and brought the scope into usable condition, you could take it to an observing session and have someone do a star test or otherwise render an opinion on the mirror. This can be done even with an uncoated mirror. At that point you can decide whether to recoat or replace the mirror.

    Cheers,
    I really like this advice. The GSO mirrors are very nice and high quality but a well made amateur optics set can rival the work of premium mirrors. Find some help to assess the quality of the optics, that is the heart of your legacy not the tube.
    DeanD likes this.
    Scopes: Refractors:
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    ST80 (mods for white light solar), SV ED80 f7 Newtonians: Z12 f5 Catadioptrics: VMC110L, Intes MK66 EPs: KK Fujiyama Orthoscopics, 2x Vixen NPLs (40-6mm) and BCOs, Baader Mark IV zooms, TV Panoptics, Delos, Plossl 32-8mm. Mixed brand Masuyama/Astroplans Binocular Nikon Aculon 10x50, Celestron 15x70, Baader Maxbright. Mounts: Star Seeker III, Vixen Porta II, Celestron CG5, Orion
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    EQG

  8. #8
    frazier's Avatar
    frazier is offline Main Sequence
    Points: 1,597, Level: 23
    Level completed: 97%, Points required for next Level: 3
    Overall activity: 0%
    Achievements:
    2 Posts Achievement20 Posts Achievement!Gallery Achievement!50 Posts Achievement!365 Days+ Registered Achievement!
    Join Date
    Dec 2017
    Location
    Richmond, Illinois
    Posts
    157
    Points
    1,597
    Level
    23
    Thanks
    6
    Thanked 29x 20 Posts

    Default Re: Rehabing an old handmade telescope

    Dave -

    Also, you could consider starting a thread on your project in the "DIY" forum. I, for one, would be interested in seeing "before, during, and after" photos.

    Cheers!

    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    : Homemade 8" f/7
    In process: 10" f/5; 12" f/7
    "It's good to be Kzin"

  9. #9
    not_Fritz_Argelander's Avatar
    not_Fritz_Argelander is online now HYPER GIANT
    Points: 182,949, Level: 100
    Level completed: 0%, Points required for next Level: 0
    Overall activity: 36.0%
    Achievements:
    365 Days+ Registered Achievement!2 Posts Achievement20 Posts Achievement!750 Days+ Registered Achievement!First 1000 Experience Points
    Awards:
    Thread Award
    Join Date
    Jul 2011
    Location
    US
    Posts
    22,040
    Points
    182,949
    Level
    100
    Thanks
    7,254
    Thanked 46,396x 14,954 Posts
    Blog Entries
    59

    Default Re: Rehabing an old handmade telescope

    Here are some resources that can do both coating and testing:

    H. L. Clausing Inc. ----- Testing

    NOVA Optical Systems



    For coating only

    Majestic Thin Film Optical Coatings - Telescope Lense Coating

    https://www.spectrum-coatings.com/prices

    It may well be worth making an $80-$150 investment to coat and test a mirror rather than jump to a replacement strategy. If it was your Dad's pride and joy it could well be an excellent optic that deserves ordinary maintenance rather than getting trashed.
    CamelHat, DeanD and Ozman13 like this.
    Scopes: Refractors:
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    ST80 (mods for white light solar), SV ED80 f7 Newtonians: Z12 f5 Catadioptrics: VMC110L, Intes MK66 EPs: KK Fujiyama Orthoscopics, 2x Vixen NPLs (40-6mm) and BCOs, Baader Mark IV zooms, TV Panoptics, Delos, Plossl 32-8mm. Mixed brand Masuyama/Astroplans Binocular Nikon Aculon 10x50, Celestron 15x70, Baader Maxbright. Mounts: Star Seeker III, Vixen Porta II, Celestron CG5, Orion
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    EQG

  10. The Following User Says Thank You to not_Fritz_Argelander For This Useful Post:

    Hillrat (12-26-2017)

  11. #10
    CamelHat's Avatar
    CamelHat is offline Bronze Supporter
    Points: 51,951, Level: 100
    Level completed: 0%, Points required for next Level: 0
    Overall activity: 0%
    Achievements:
    50 Posts Achievement!5 Threads Achievement!First 1000 Experience Points2 Posts Achievement20 Posts Achievement!
    Join Date
    Dec 2011
    Location
    Santa Barbara, CA
    Posts
    5,806
    Points
    51,951
    Level
    100
    Thanks
    1,170
    Thanked 1,719x 1,387 Posts

    Default Re: Rehabing an old handmade telescope

    Hi and welcome to the forum!

    I would also advocate trying to fix the mirror if it can be done. Otherwise, with the primary and prism removed, the most authentic parts are gone and you might as well have bought a new one and preserve your dad's scope as is. For that matter, ES has a nice looking 8" Dob on sale for $350, or why not the 10".
    DirtyOptix likes this.
    ... Henk. Telescopes: 6" Mak-Newt (Comet Hunter), ES ED127CF, ES ED80, Zhumell Z12, Coulter Odyssey 10, AT6RC, Venture RX-7, Celestron Skymaster 20x80, Mounts and tripod: Losmandy G11S, AVX, LXD55, Tiltall, Cameras: Fuji X-a1, Canon SX40, Xt, XSi, T6, ELPH 100HS, DIY: Dob and camera barndoor trackers, afocal adapter, Dob with foldable base and Az/Alt setting circles, Accessories: SSAG, Plossls, Barlows, Telrad, laser collimators (Seben LK1, Z12, Howie Glatter), Cheshire, 2 Orion RACIs 8x50, Software: DSS, ImageMagick, PHD, Nebulosity, Photo Gallery, Gimp, CHDK

    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.

 

 
Page 1 of 3 123 LastLast

Similar Threads

  1. My handmade 10" f/ 6.4 dobsonian
    By Koopyetz in forum ATM DIY Telescope Making Forum
    Replies: 10
    Last Post: 02-24-2011, 12:54 PM
  2. Double images on handmade Dobsonian telescope?
    By reggieana in forum Dobsonian Telescopes Forum
    Replies: 4
    Last Post: 11-23-2008, 05:57 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Powered by vBulletin® Version 4.2.0
Powered by vBulletin®
All times are GMT. The time now is 09:07 PM.