Results 1 to 5 of 5

Thread: 3X Barlow

  1. #1
    WileECoyote's Avatar
    WileECoyote is offline SUPER GIANT
    Points: 10,688, Level: 71
    Level completed: 46%, Points required for next Level: 162
    Overall activity: 0%
    Achievements:
    50 Posts Achievement!5 Threads Achievement!First 1000 Experience Points365 Days+ Registered Achievement!200+ Posts Achievement!
    Join Date
    Jul 2011
    Location
    West Bloomfield, Michigan
    Posts
    629
    Points
    10,688
    Level
    71
    Thanks
    126
    Thanked 161x 114 Posts

    Default 3X Barlow



    So last weekend I was able to get some good viewing and a chance to continue with my foray into Astrophotography. I was able to get some shots of Jupiter using my DLSR and my 2X Barlow. I tend to only use my Barlow for AP and not viewing. I am considering getting a 3X Barlow to add to my AP set-up. Is there one that’s better than the other? I don’t have a huge budget, but I want something that worth buying. I was looking at these two…

    Orion Tri-Mag 1.25" 3x Barlow Lens | Orion Telescopes: Barlows

    or

    Meade Instruments Corporation - Meade Series 4000 #128 3x Short-Focus Barlow Lens (1.25") #07278
    Steve
    Telescope:8" Zhumell Dobsonian
    Eyepiece: Zhumell 30mm 2", ES 82 Deg 8.8mm 1.25" & 18mm 2"
    Filters: Polarizing Filter, 2" DGM Optics OIII & Nebula filter
    Accessories: AstroZap Solar Filter, Rigel QuickFinder, Gibraltar Drum Throne
    Observing Partner: Teagan the Astro-Pooch
    “All civilizations become either space-faring or extinct.” – Carl Sagan

  2. #2
    MitchAlsup's Avatar
    MitchAlsup is offline SUPER GIANT
    Points: 5,847, Level: 52
    Level completed: 49%, Points required for next Level: 103
    Overall activity: 0%
    Achievements:
    200+ Posts Achievement!First 1000 Experience Points400+ Posts Achievement50 Posts Achievement!365 Days+ Registered Achievement!
    Join Date
    Sep 2011
    Location
    Austin Texas
    Posts
    1,066
    Points
    5,847
    Level
    52
    Thanks
    1
    Thanked 505x 381 Posts

    Default

    I think for AP work the long barlow will be better.

  3. The Following User Says Thank You to MitchAlsup For This Useful Post:

    WileECoyote (02-12-2012)

  4. #3
    sxinias's Avatar
    sxinias is offline Super Moderator
    Points: 321,571, Level: 100
    Level completed: 0%, Points required for next Level: 0
    Overall activity: 0%
    Achievements:
    Got three Friends20+ Friends Achievement!First 1000 Experience Points5+ Referrals Achievement!100+ Threads Achievement!
    Awards:
    Attachments Award
    Join Date
    Nov 2008
    Location
    Marathon Greece summer Tampa Florida winter
    Posts
    17,795
    Points
    321,571
    Level
    100
    Thanks
    4,581
    Thanked 10,187x 6,472 Posts
    Blog Entries
    4

    Default

    Steve,

    Using your DSLR you can calculate your image size by dividing the effective focal length of your telescope by the diagonal length of the camera sensor, which is approximately 26mmin a DSLR. The image size with your z8 with no barlow is 46x, 2x barlow is 92x, and a 3x barlow will be around 138x

    In astrophotography, its the focal ratio of a telescope (image brightness) that is important, not the telescope's aperture. The lower the focal ratio, the brighter the image and the shorter the exposure. When you add a barlow, you effectively increase the focal length of your telescope; thus, increase the image size as well as the telescope's focal ratio.

    Your Z8 has a focal ratio of f/6 ... with the 2x barlow it became f/12. The 3x barlow will make it f/18. As some point the image will be too dim for you to capture it in your DSRL unless you increase your exposure time to a point where you get star trails. When experimenting like you are doing... sometimes its best to keep expenses to a minimum. I know I do with my project using lightweight azimuth mounts for astrophotography.

    Another option is to get a web camera and going back to no barlow or the 2x barlow. The web camera's sensor is much smaller than that in the DSLR and will produce much larger images.

    Good luck with your project.
    SXINIAS

    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.
    ZEQ25 mount;
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    SynScan AZ
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    Mount;

    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    ST-80A 80mm Refractor (OTA); Meade
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    203mm SCT (OTA);
    Meade DS2090AT 90mm Refractor; Meade 2045LX3 102mm SCT;

    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    4 SE 102mm MAK; Celestron Advanced Series C6S (XLT) 150mm SCT
    with an iOptron GOTO Drive

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

  5. The Following 2 Users Say Thank You to sxinias For This Useful Post:

    Joe Lalumia (02-10-2012),WileECoyote (02-12-2012)

  6. #4
    WWPierre's Avatar
    WWPierre is offline HYPER GIANT
    Points: 64,445, Level: 100
    Level completed: 0%, Points required for next Level: 0
    Overall activity: 0%
    Achievements:
    10 Days registered3 Years + Achievement400+ Posts AchievementGhost Achievement! Averaging 5+ posts a day!1000 Days+ Registered Achievement!
    Join Date
    Jun 2009
    Location
    Squamish B.C.
    Posts
    6,948
    Points
    64,445
    Level
    100
    Thanks
    1,095
    Thanked 2,953x 1,808 Posts

    Default

    I have 2 3x barlows, I can't comment on their use with a camera, but I can comment on their relative quality. One is a plastic barrelled one that came with a used telescope I bought on Craigslist. It is probably worth about $20. The other is a Telvue bought on E-bay. These old eyes can see little or no difference in the views they produce.

    The lens cell in front is the element removed from a generic 2x short barlow so that I could use the body as a focuser spacer. I can drop it into the barrel of either barlow to make a 5x barlow. Used with my 30mm and 20mm EPs, I get 6mm and 4mm effective EPs with comfortable eye relief.
    Attached Images Attached Images
    Meade 16" LightBridge; Celestron G-8N Bird-Jones/motorized EQ5;
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    127 Mak/go-to EQ5; Burgess 127f8 refractor; Sky-Watcher 5" F/5 collapsible dob; 90mm Mak/motorized EQ2; Royal Astro 76/910-GEM; Meade 60x700 refractor/alt/az; Zhumell 25x100 Coin Ops; GalilleoScope. Celestron 8mm-24mm zoom; lots of fixed EPs,some good, some..not so much. A small collection of surveying instruments; a forest of tripods; Canon Rebel Xti. Confirmed gadget junkie; Custodian of the Magnetic North Pole (Send $1.00 to Pierre each time you use a compass.)
    49-41-37.03N 123-09-29.61W Calculated magnetic declination: 17° 39' East

    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.

    We have been broadcasting our presence to the Universe for 100 years now. If there is a detachment of Galactic Pest Control within 100 light years, they are already on the way.

  7. The Following User Says Thank You to WWPierre For This Useful Post:

    WileECoyote (02-12-2012)

  8. #5
    WileECoyote's Avatar
    WileECoyote is offline SUPER GIANT
    Points: 10,688, Level: 71
    Level completed: 46%, Points required for next Level: 162
    Overall activity: 0%
    Achievements:
    50 Posts Achievement!5 Threads Achievement!First 1000 Experience Points365 Days+ Registered Achievement!200+ Posts Achievement!
    Join Date
    Jul 2011
    Location
    West Bloomfield, Michigan
    Posts
    629
    Points
    10,688
    Level
    71
    Thanks
    126
    Thanked 161x 114 Posts

    Default

    ive been considering a web cam like the ones that Orion offer. I know it would be easier in the long run. thanks for the help everyone. lucky the weather in Michigan has gone back to normal...Cold and snowy...so i have a while to decide.
    Steve
    Telescope:8" Zhumell Dobsonian
    Eyepiece: Zhumell 30mm 2", ES 82 Deg 8.8mm 1.25" & 18mm 2"
    Filters: Polarizing Filter, 2" DGM Optics OIII & Nebula filter
    Accessories: AstroZap Solar Filter, Rigel QuickFinder, Gibraltar Drum Throne
    Observing Partner: Teagan the Astro-Pooch
    “All civilizations become either space-faring or extinct.” – Carl Sagan

 

 

Similar Threads

  1. Can't focus with Barlow& Barlow.
    By Astronewb in forum Astro Imaging Forum
    Replies: 4
    Last Post: 01-28-2012, 08:16 PM
  2. Replies: 1
    Last Post: 11-01-2011, 08:13 PM
  3. TeleVue 2" Big Barlow vs GSO 2" Barlow
    By mzu in forum Telescope Eyepieces Forum
    Replies: 14
    Last Post: 09-24-2011, 04:07 AM
  4. Celestron Ultima 2x Barlow and Parks Gold Series Barlow
    By botoole in forum Telescope Accessories Forum
    Replies: 1
    Last Post: 07-25-2011, 12:55 PM
  5. Barlow Selection - Celestron Ultima or GSO 2.5 Barlow?
    By PBalu in forum Telescope Accessories Forum
    Replies: 2
    Last Post: 02-05-2011, 02:02 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 12:36 PM.