Page 1 of 2 12 LastLast
Results 1 to 10 of 13
Like Tree3Likes

Thread: Question about 2X Barlow

  1. #1
    birdmanGSP's Avatar
    birdmanGSP is offline White Dwarf
    Points: 1,695, Level: 24
    Level completed: 95%, Points required for next Level: 5
    Overall activity: 0%
    Achievements:
    2 Posts Achievement5 Threads Achievement!20 Posts Achievement!50 Posts Achievement!365 Days+ Registered Achievement!
    Join Date
    Jan 2015
    Location
    USA
    Posts
    31
    Points
    1,695
    Level
    24
    Thanks
    1
    Thanked 3x 3 Posts

    Default Question about 2X Barlow



    Hi guys .. i'm reading somewhere where someone posted quite simply that a Barlow 2x essentially doubles your eyepieces, by reducing their focal length. Is it really this "simple"? If I swap a 32mm and a 16mm, its the same as 32mm and a 32mm through the Barlow?

  2. #2
    mkettler's Avatar
    mkettler is offline Bright Giants
    Points: 5,532, Level: 50
    Level completed: 91%, Points required for next Level: 18
    Overall activity: 0%
    Achievements:
    2 Posts Achievement20 Posts Achievement!5 Threads Achievement!50 Posts Achievement!200+ Posts Achievement!
    Join Date
    Jan 2014
    Location
    Maryland, USA
    Posts
    489
    Points
    5,532
    Level
    50
    Thanks
    27
    Thanked 157x 140 Posts

    Default Re: Question about 2X Barlow

    Roughly, yes...

    Some subtle differences to think about;
    1) the barlowed 32mm eyepiece will have the same eye relief, even with the barlow on it. So for eyepieces like plossl where the eye relief gets shorter with shorter focal lengths, this can be beneficial.
    2) the barlowed will add more optical elements to the train, which will lower light transmission somewhat (assuming good quality, quite a lot if it is poor). That said, if your 32mm is a 4-element, and your 16mm is a 6-element this difference is moot.
    3) fast scopes often benefit from barlowing, as it reduces the angle of the light cone entering the eyepiece, resulting in fewer aberrations in the eyepiece.
    4) the barlow isn't going to be ideally optimized for the eyepiece you are mounting, so a barlow +eyepiece generally won't perform as well as a modern negative-positive eyepiece design that has a barlow-type element built in.
    5) the barlow is going to add physical length to your eyepiece setup, which may or may not be an issue.

    Some of these subtle differences are why some folks absolutely hate barlows... I think they're handy but I generally try to keep my primary viewing magnifications as single eyepieces, then use the barlow to diversify for less common scenarios.

    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    130ST f/5 reflector, 10x50 binoculars
    5mm Zhumell z, 9mm Orion Expanse, 25/12mm Xcel-LX, 25/10mm Orion plossl,
    Meade 8-24 zoom, Orion 2x shorty barlow
    filters: Astronomik UHC, Orion Skyglow, ND 13%, #25, #80A
    back yard:
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    7

  3. #3
    UrbanArmitage's Avatar
    UrbanArmitage is offline SUPER GIANT
    Points: 10,464, Level: 70
    Level completed: 72%, Points required for next Level: 86
    Overall activity: 0%
    Achievements:
    2 Posts Achievement20 Posts Achievement!50 Posts Achievement!Ghost Achievement! Averaging 5+ posts a day!200+ Posts Achievement!
    Join Date
    Jan 2013
    Location
    South Africa
    Posts
    907
    Points
    10,464
    Level
    70
    Thanks
    441
    Thanked 316x 223 Posts

    Default Re: Question about 2X Barlow

    A 2x barlow will double the magnification of your eyepiece, and in order to do that it will make your 32mm perform like a 16mm eyepiece, so you are quite correct. You can use a barlow to reduce the number of eyepieces you need this way. For example if you have a 25mm and a 2x barlow, there is no need to buy a 12mm eyepiece because your 25mm will perform like a 12.5mm eyepiece. This reduces the amount of money you need to spend on eyepieces.

    Wayne
    Lowjiber and bill_reed like this.
    East London, South Africa - 32°57' S 27°56' E

    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    8SE 8" SCT, Celestron 80LCM 3.15" Refractor,
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    9x50 RACI finder, Celestron Upclose G2 10x50 Binoculars, Celestron OMNI 40mm Plossl, Orion
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    32mm Plossl, Celestron ELUX 25mm, Orion Expanse 20mm, 15mm, 9mm and 6mm, Orion Shorty 2x Barlow, Orion Variable Polarizer filter, Orion Ultrablock filter, Celestron 7aH power tank


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

  4. #4
    birdmanGSP's Avatar
    birdmanGSP is offline White Dwarf
    Points: 1,695, Level: 24
    Level completed: 95%, Points required for next Level: 5
    Overall activity: 0%
    Achievements:
    2 Posts Achievement5 Threads Achievement!20 Posts Achievement!50 Posts Achievement!365 Days+ Registered Achievement!
    Join Date
    Jan 2015
    Location
    USA
    Posts
    31
    Points
    1,695
    Level
    24
    Thanks
    1
    Thanked 3x 3 Posts

    Default Re: Question about 2X Barlow

    Thanks for the responses, guys, I got a Celestron eyepiece kit with a NexStar 8Se which included some varying EP's and the barlow

  5. #5
    PhilipLangley's Avatar
    PhilipLangley is offline SUPER GIANT
    Points: 15,459, Level: 85
    Level completed: 74%, Points required for next Level: 91
    Overall activity: 0%
    Achievements:
    2 Posts Achievement20 Posts Achievement!5 Threads Achievement!50 Posts Achievement!200+ Posts Achievement!
    Join Date
    Jul 2014
    Location
    Western Canada
    Posts
    1,451
    Points
    15,459
    Level
    85
    Thanks
    39
    Thanked 630x 456 Posts

    Default Re: Question about 2X Barlow

    And if you are using a laser collimator tool to collimate your telescope, you can use the Barlow together with the laser when adjusting the primary mirror.

    A really neat trick!

    Read up on the Barlowed-laser method of primary mirror collimation.

  6. #6
    birdmanGSP's Avatar
    birdmanGSP is offline White Dwarf
    Points: 1,695, Level: 24
    Level completed: 95%, Points required for next Level: 5
    Overall activity: 0%
    Achievements:
    2 Posts Achievement5 Threads Achievement!20 Posts Achievement!50 Posts Achievement!365 Days+ Registered Achievement!
    Join Date
    Jan 2015
    Location
    USA
    Posts
    31
    Points
    1,695
    Level
    24
    Thanks
    1
    Thanked 3x 3 Posts

    Default Re: Question about 2X Barlow

    Is there a need for collimation straight away with a new scope, or should it be tested" to see if its needs it?

  7. #7
    MoosBros's Avatar
    MoosBros is offline HYPER GIANT
    Points: 15,876, Level: 86
    Level completed: 94%, Points required for next Level: 24
    Overall activity: 0%
    Achievements:
    2 Posts Achievement20 Posts Achievement!5 Threads Achievement!50 Posts Achievement!200+ Posts Achievement!
    Join Date
    Dec 2013
    Location
    South Carolina
    Posts
    2,990
    Points
    15,876
    Level
    86
    Thanks
    408
    Thanked 464x 426 Posts

    Default Re: Question about 2X Barlow

    Quote Originally Posted by birdmanGSP View Post
    Is there a need for collimation straight away with a new scope, or should it be tested" to see if its needs it?
    generally speaking, the collimation should atleast be checked every time just prior to use... It may or not need a slight adjustment....it's a normal expectation....
    Lowjiber likes this.

    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    6-7 Bob--aka--<> urban guerrilla star gazer <> YURT Urban Mobile Observatory
    Zhumell Tachyon 25x100, Celestron Comet Hunter 11x80, Zhumell z12 f/4.92 w/HALO--StellarVue F80M2 80mm f/4--Vixen R130Sf
    Zhumell 2" 2x ED
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    , TeleVue 2x Big Barlow
    Explore Scientific 100* Series-----5.5mm, 9mm, 14mm, 20mm, ES 82* Series-----30mm
    Thousand Oaks 2" O-III , DGM 2" NPB

  8. #8
    bladekeeper's Avatar
    bladekeeper is offline Super Moderator
    Points: 306,678, Level: 100
    Level completed: 0%, Points required for next Level: 0
    Overall activity: 100.0%
    Achievements:
    2 Posts Achievement20 Posts Achievement!5 Threads Achievement!50 Posts Achievement!200+ Posts Achievement!
    Awards:
    Activity Award
    Join Date
    Aug 2014
    Location
    Lowell, Arkansas, USA
    Posts
    39,010
    Points
    306,678
    Level
    100
    Thanks
    29,135
    Thanked 17,683x 12,109 Posts

    Default Re: Question about 2X Barlow

    I always equate it to playing a stringed instrument. Always to good to check the tuning prior to playing. Guitars are generally good about holding tune. Banjos, not so much. Someone could break wind and you'd need to re-tune.

    Moving the scope about can require a slight adjustment. Always good to verify collimation. When you get practiced, just a quick tweak or verfication before you start viewing is all it takes. Takes longer to get all your stuff together that collimating.
    Bryan

    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.
    f/5; Celestron C6-R f/8; ES AR127 f/6.4; ES AR127 f/9.4; Stellarvue SV102T f/7; ES AR102 f/9.8;
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    MC90 f/13.3;
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    ST80A f/5; Celestron Premium 80 f/11.4; Celestron C80 f/11.4; Unitron Model 142 f/16; Meade NG60 f/10
    Mounts: Celestron AVX; Bresser EXOS-2; ES Twilight I; ES Twilight II; iOptron Cube-G; AZ3/wood tripod; Vixen
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.

    Eyepieces: GSO Super Plössl 40mm, 32mm, 15mm, 9mm; ES 82° Series; GSO Superview 30mm; Celestron Plössl 26mm, 20mm; ES 70° 25mm; ES Plössl 25mm; Vite Aspheric 23mm, 10mm, 4mm; Orion Expanse 20mm, 9mm; KK Ortho 18mm, 12.5mm; Bresser 70° 15mm; Coulter Optical 12.5mm; BCO 10mm; ES 62° 9mm; Zhumell Z Series 5mm
    Binoculars: Pentax PCF WP II 10×50, Bresser Corvette 10×50, Bresser Hunter 16×50 and 8×40, Garrett
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    12×60 LW, Gordon 10×50, Apogee 20×100

    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.

    Galaxy Hunter's Creed - When you play whack-a-mole, sometimes you hit 'em on the head, sometimes you miss 'em. But its always fun to play, and if you don't play, you ain't gettin no moles! - KT4HX

  9. #9
    PhilipLangley's Avatar
    PhilipLangley is offline SUPER GIANT
    Points: 15,459, Level: 85
    Level completed: 74%, Points required for next Level: 91
    Overall activity: 0%
    Achievements:
    2 Posts Achievement20 Posts Achievement!5 Threads Achievement!50 Posts Achievement!200+ Posts Achievement!
    Join Date
    Jul 2014
    Location
    Western Canada
    Posts
    1,451
    Points
    15,459
    Level
    85
    Thanks
    39
    Thanked 630x 456 Posts

    Default Re: Question about 2X Barlow

    Quote Originally Posted by birdmanGSP View Post
    Is there a need for collimation straight away with a new scope, or should it be tested to see if its needs it?
    All good advice up ahead of me here. May I add however that, when initially checking the collimation of the scope for the very first time, or at the beginning of each observing session, and you find that it appears to need tweaking, you restrict your adjustments to the primary mirror only.

    Promise yourself that you will resist all urges to tweak the secondary.

    Adjusting the collimation of the primary mirror, by manipulation of those three pairs of screws at the back-end, is the easiest aspect of the whole collimation process. It is unlikely that the secondary mirror will be significantly out unless you're using a telescoping truss-type Dobsonian.

    Do yourself a BIG favour and do not touch the secondary's screws until you have a really good idea of what to expect after having done a whole lot of reading, learning and/or watching the process demonstrated. Doing so, will only lead to tears and heartbreak if you're ill-prepared for task. In the end of the matter it will be for you, like a walk in the park, like riding a bicycle, like falling off a log...but for now, please leave the secondary alone.

    It is after all, the alignment of the optical axis of the primary mirror with the optical centre of the focal plane (as modelled by a peep-hole, Cheshire ring or a laser target) that is the most critical for image performance...yet it is the easiest to do and to get right. And this is what you're doing when you collimate the primary from the back-end.

    Adjusting the secondary, important of course, but not so critical and definitely a whole lot more difficult for newcomers at the job.

  10. #10
    mkettler's Avatar
    mkettler is offline Bright Giants
    Points: 5,532, Level: 50
    Level completed: 91%, Points required for next Level: 18
    Overall activity: 0%
    Achievements:
    2 Posts Achievement20 Posts Achievement!5 Threads Achievement!50 Posts Achievement!200+ Posts Achievement!
    Join Date
    Jan 2014
    Location
    Maryland, USA
    Posts
    489
    Points
    5,532
    Level
    50
    Thanks
    27
    Thanked 157x 140 Posts

    Default Re: Question about 2X Barlow

    Quote Originally Posted by birdmanGSP View Post
    Is there a need for collimation straight away with a new scope, or should it be tested" to see if its needs it?
    Unless your telescope has been very gently hand carried from the time the factory adjusted it until it got to your home, checking the collimation is required.

    Generally speaking mild bumps, mild bangs, and thermal cycling are what tend to cause your scope to slip out of collimation. A normal pass through shipping (ie: from factory to distributor, distributor to your home or local store) will generally include all of these, and probably be some of the roughest treatment your scope ever endures....

    It might be in collimation, it might not, but checking at this point is very worthwhile...

    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    130ST f/5 reflector, 10x50 binoculars
    5mm Zhumell z, 9mm Orion Expanse, 25/12mm Xcel-LX, 25/10mm Orion plossl,
    Meade 8-24 zoom, Orion 2x shorty barlow
    filters: Astronomik UHC, Orion Skyglow, ND 13%, #25, #80A
    back yard:
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    7

 

 
Page 1 of 2 12 LastLast

Similar Threads

  1. Another Barlow question
    By JD215 in forum Astronomy Beginners Forum
    Replies: 9
    Last Post: 03-19-2014, 08:02 AM
  2. Barlow Question
    By jbanks in forum Telescope Accessories Forum
    Replies: 1
    Last Post: 03-10-2013, 07:48 AM
  3. Budget Barlow Shootout - GSO 2x Achromatic Barlow vs Orion Shorty Barlow!
    By MyNighttimeJacket in forum Telescope Accessories Forum
    Replies: 2
    Last Post: 12-27-2012, 02:46 AM
  4. To Barlow, or not to Barlow...that is the question?
    By Telstar in forum Astronomy Beginners Forum
    Replies: 26
    Last Post: 10-10-2012, 09:17 PM
  5. To Barlow or Not to Barlow That is the Question
    By sportsmed in forum Telescope Eyepieces Forum
    Replies: 14
    Last Post: 06-29-2012, 09:59 PM

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 12:29 PM.