Page 1 of 2 12 LastLast
Results 1 to 10 of 15
Like Tree26Likes

Thread: "Resolving" Globs

  1. #1
    stoest219's Avatar
    stoest219 is offline Main Sequence
    Points: 3,562, Level: 39
    Level completed: 42%, Points required for next Level: 88
    Overall activity: 0%
    Achievements:
    2 Posts Achievement5 Threads Achievement!20 Posts Achievement!50 Posts Achievement!365 Days+ Registered Achievement!
    Join Date
    Dec 2015
    Location
    Dallas burbs
    Posts
    128
    Points
    3,562
    Level
    39
    Thanks
    0
    Thanked 33x 27 Posts

    Default "Resolving" Globs



    I'm a little confused by the way different people use the term resolved when referring to globular clusters. When I first saw this I thought that meant they were seeing only individual stars for the entire cluster and was disappointed when I could see some individual stars on clusters like M13, but the core remained a gray fuzzy. The more I read reports though it seems like what some people mean by resolved is that they were able to see some stars but the core remained solid.

    Is there a generally accepted view of what resolving a glob is? Even in great photos most globs have a core that becomes a mostly solid wash of stars that can't be seen individually. Not worried about how other people use the term I'd just like to be able to use the term correctly myself when reporting and talking to other astronomers.

    To me in dark skies most globs look like they have a "twinkling diamond dust" halo around the gray fuzzy. If I try to look straight at a single twinkle it usually disappears but with averted vision the number of twinkles can be amazing. I'm assuming this is about what should be expected with a 9.25 CAT in good conditions.
    Celestron Evolution 9.25, .63 Focal Reducer, 2" Williams Dielectric Dura Bright diagonal
    18" Dob, Lockwood mirrir, Paracor SIPS, Nexus 2
    ES 30, 24, 14, 11 and 6.7 82° eyepieces

  2. #2
    Johnny J.'s Avatar
    Johnny J. is offline SUPER GIANT
    Points: 17,769, Level: 92
    Level completed: 18%, Points required for next Level: 331
    Overall activity: 0%
    Achievements:
    2 Posts Achievement20 Posts Achievement!5 Threads Achievement!50 Posts Achievement!First 1000 Experience Points
    Join Date
    May 2015
    Location
    South Dakota
    Posts
    979
    Points
    17,769
    Level
    92
    Thanks
    280
    Thanked 408x 334 Posts

    Default Re: "Resolving" Globs

    You pretty much nailed it. The cores are so dense in most globular clusters that the individual stars start to blend in to form a dense white core. Resolving the outer stars are what most people are describing. In binoculars and small aperture telescopes globular clusters just appear as a wispy spot of smoke or a cotton ball.

    JJ
    mandomom likes this.
    Telescopes: Assorted brands and designs from 60mm up to 203mm (9). Eyepieces: Two 6mm BO's (Brown Organics - Eye Balls). Mounts: Celestron, Meade, Orion, Vixen, Skywatcher. Cameras: Canons, Logitech, Orion, QHYs.

  3. #3
    Lola Bruce's Avatar
    Lola Bruce is offline SUPER GIANT
    Points: 9,010, Level: 65
    Level completed: 87%, Points required for next Level: 40
    Overall activity: 6.0%
    Achievements:
    365 Days+ Registered Achievement!2 Posts Achievement20 Posts Achievement!50 Posts Achievement!5 Threads Achievement!
    Join Date
    Jul 2012
    Location
    So cal
    Posts
    1,192
    Points
    9,010
    Level
    65
    Thanks
    48
    Thanked 268x 226 Posts

    Default Re: "Resolving" Globs

    After five or so years observing only twice have I experienced the thousands of tiny diamonds cast onto black velvet. Most good nights a fuzz ball with some resolved stars is the norm. I am fortunate to have tried with a CPC800XLT, Takahashi TSA 102, C11, ES 127 CF Triplet, and Mewlon 250 corrected. I now know that these rare events are much more seeing dependent than equipment related. So in my experience as a duffer the needed prerequisites in order are first you have to be out observing, second the seeing gods need to be in a good mood, and finally the optics need to be up to the task. My best nights so far have been spring in the high desert with CPC 800 XLT, second spring in the central valley California with a TSA 102, and third last night with my corrected Mewlon 250.
    Bruce
    j.gardavsky likes this.
    CPC 800XLT, Takahashi 102 TSA, Takahashi Mewlon 250s,
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.

    Losmandy G11, Losmandy GM8, AP Mach1 GTO,
    (Nagler 3-6, 7,13,22, Panoptic 35,41, Delos 6,14, Powermate 2"x2), Pentax 10 Televue 8 Plossl
    DBK41, Atik Infinity, Horizon

  4. #4
    My 2 Stars's Avatar
    My 2 Stars is offline HYPER GIANT
    Points: 18,008, Level: 92
    Level completed: 77%, Points required for next Level: 92
    Overall activity: 0%
    Achievements:
    2 Posts Achievement5 Threads Achievement!20 Posts Achievement!50 Posts Achievement!Monthly Activity Achievement!
    Join Date
    Nov 2015
    Location
    SE Penna.
    Posts
    1,729
    Points
    18,008
    Level
    92
    Thanks
    222
    Thanked 402x 323 Posts

    Default Re: "Resolving" Globs

    It all depends on scope and EP's. A 6" scope will resolve some stars in a particular glob while a 10" will resolve more and a 12" even more. AND it also depends on your LP in your viewing site.
    Even with using the same scope and EP, if you go to a darker site, you will resolve more stars than a LP site.
    musiclucho likes this.
    John...... Listentothestars.net

    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    :
    ES AR152
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    , SW 80mm ED APO/SW NEQ6 Pro Mount,
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.
    XT10i
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.

    Cameras: ASI1600mm-c, ASI120mc (guide), Canon T2i (550D)
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.

    Filters: Astrodon Ha 5nm, ZWO LRGB, LPS D-1,
    EP's: ES 2" 82* 18mm, 24mm & 30mm, ES 8.8mm, 11mm.
    BINS: Garrett 12x60, Nikon 9x25
    Processing: SGP, BYEOS, DSS, As!2, Reg6, Star Tools, PS, PHD2, Stellarium, CdC, PIPP

  5. #5
    musiclucho's Avatar
    musiclucho is offline HYPER GIANT
    Points: 23,911, Level: 100
    Level completed: 0%, Points required for next Level: 0
    Overall activity: 12.0%
    Achievements:
    2 Posts Achievement365 Days+ Registered Achievement!20 Posts Achievement!5 Threads Achievement!750 Days+ Registered Achievement!
    Join Date
    Sep 2012
    Location
    Boulder Creek, CA
    Posts
    3,246
    Points
    23,911
    Level
    100
    Thanks
    713
    Thanked 1,095x 830 Posts

    Default Re: "Resolving" Globs

    I really like the term you used to describe the stars inside the cores. They certainly look like magic sparkles. You should tried M22 where the core is not as compact as M13 or M5. With a bigger size scope you can dig on those clusters more and more. There is more than just stars on them, but you need a big telescope and dark skies for that.
    路易斯 LG
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.

    Skymaster 15x70, Up-close 10x50, SCT 6" on a CG4 EQ mount
    8x50 RACI and RDF. 9mm X-Cel LX, 15mm Luminos and 40mm Omni.
    My astro-adventures and sketches: http://pollutedskiesstargazing.blogspot.com/

    "A full appreciation of the universe cannot come without developing the skills to find things in the sky and understanding how the sky works." Alan Dyer

  6. #6
    mental4astro's Avatar
    mental4astro is offline SUPER GIANT
    Points: 13,855, Level: 81
    Level completed: 16%, Points required for next Level: 295
    Overall activity: 0%
    Achievements:
    First 1000 Experience Points365 Days+ Registered Achievement!750 Days+ Registered Achievement!2 Posts Achievement50 Posts Achievement!
    Join Date
    Jun 2009
    Location
    Sydney, Australia
    Posts
    1,071
    Points
    13,855
    Level
    81
    Thanks
    173
    Thanked 947x 447 Posts

    Default Re: "Resolving" Globs

    I can assist with this.

    Below are two sketches I've done of the same globular cluster, Omega Centauri. These two images show how aperture affects the ability to resolve globular clusters.

    The first was done using a 4" refractor from a dark site using low magnification. While some stars do show resolution, the core of the GC is essentially nebulous in appearance.

    Attachment 135793

    The second image was done using a 17.5" scope from suburban Sydney. Stars are resolved a whole lot more extensively, though the core still has a glow to it. This is not unusual as the variation in star size/shine varies, and the fainter stars still resist being resolved.

    Attachment 135794

    The 'hollow' that is seen in the centre of this sketch is called "The eye of Omega", and is the one key signature pattern of Omega Centauri. It is a line of sight coincidence of fewer bright stars in this area. This is very much a visual artefact as photographs always burn out this feature.

    Of course, this is an extreme example. All other globular clusters are smaller than Omega Centauri, and even a 17.5" scope has its resolution limits, and the smaller GC's still do only appear as round, nebulous spots.

    Alex.

  7. #7
    Wingsfan81's Avatar
    Wingsfan81 is offline HYPER GIANT
    Points: 24,014, Level: 100
    Level completed: 0%, Points required for next Level: 0
    Overall activity: 0%
    Achievements:
    2 Posts Achievement20 Posts Achievement!5 Threads Achievement!Gallery Achievement!Album Achievement!
    Join Date
    Apr 2015
    Location
    Jackson, Michigan
    Posts
    3,018
    Points
    24,014
    Level
    100
    Thanks
    1,377
    Thanked 1,202x 872 Posts

    Default Re: "Resolving" Globs

    Back when I had two scopes (4.5" Newt and 11" SCT) it was interesting to compare the two on resolving globs. My 4.5" scope is capable of resolving the bigger, brighter globs such as M13, M3, M22, and a couple others. My 11" scope could resolve many more. Comparing the two on M13 was fun, obviously the view was much brighter and the resolution of the core more complete in the big scope. However, the small scope can also resolve the core of M13 at higher magnifications, just not to the level the big SCT was capable of (you can see core stars in the small scope, but a substantial percentage remains unresolved). Averted vision helps very much when trying to resolve globs with limited aperture, even in the big scope I'd use averted vision to try and coax out those extra fine details. I had a few memorable nights with good conditions where I stared at M13 for a good 45 minutes at 311x magnification with a 9mm EP in the C11, just an awesome view!
    frazmataz likes this.
    Celestron Powerseeker 114az "Little Tyke", CPC 1100 GPS “Big Daddy 2.0”
    ES82 30mm, 6.7mm, 4.7mm; Tele Vue Delos 17.3mm, 12mm; Tele Vue DeLite 9mm; Meade UWA 14mm; Assorted Budget EPs
    ES 2" 99% Dielectric Diagonal

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

  8. #8
    Bigzmey's Avatar
    Bigzmey is offline HYPER GIANT
    Points: 40,753, Level: 100
    Level completed: 0%, Points required for next Level: 0
    Overall activity: 59.0%
    Achievements:
    2 Posts Achievement20 Posts Achievement!5 Threads Achievement!50 Posts Achievement!200+ Posts Achievement!
    Join Date
    Sep 2015
    Location
    Planet Earth
    Posts
    7,545
    Points
    40,753
    Level
    100
    Thanks
    1,801
    Thanked 3,185x 2,291 Posts

    Default Re: "Resolving" Globs

    I think most of the time it means to see at least some stars in the core.

  9. #9
    KT4HX's Avatar
    KT4HX is offline HYPER GIANT
    Points: 102,795, Level: 100
    Level completed: 0%, Points required for next Level: 0
    Overall activity: 0%
    Achievements:
    365 Days+ Registered Achievement!First 1000 Experience Points750 Days+ Registered Achievement!1000 Days+ Registered Achievement!200+ Posts Achievement!
    Join Date
    Dec 2008
    Location
    Virginia
    Posts
    11,786
    Points
    102,795
    Level
    100
    Thanks
    1,443
    Thanked 8,098x 4,361 Posts
    Blog Entries
    200

    Default Re: "Resolving" Globs

    If one wants to quantify globular resolution, you could use the five level ranking system employed by experienced and noted observer Don Pensack. Of course, resolution can be affected by aperture and magnification. Here is Don's system:

    5. Unresolved: looks like a nebula with no stars.
    4. Grainy: incipient resolution, with a few brighter stars occasionally winking in and out.
    3. Partially resolved: most of the outer stars are seen and averted vision shows some brighter members of the core winking in and out. Some core background still nebulous.
    2. Nominally resolved: stars seen across the cluster but stars are still a little soft and unresolved dead center.
    1. Fully resolved: pinpoint tiny stars seen all the way to the center, no nebulous haze of background stars. If you see this, chances are it's in a 12" or larger scope in superb seeing.
    Alan || My DSO Blog:
    To view links or images in signatures your post count must be 5 or greater. You currently have 0 signatures.

    ---------------------------------------------------------------------------
    Astro Sky 17.5 f/4.5 Dob ||
    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 Dob || Zhumell Z10 f/4.9 Dob
    ES AR127 f/6.5 and ES ED80 f/6 on Twilight-II Mount
    ES 82° 24mm, 18mm; Pentax XW 10mm, 7mm, 5mm
    ---------------------------------------------------------------------------
    Astronomers: We look into the past to see our future.

  10. The Following User Says Thank You to KT4HX For This Useful Post:

    helicon64 (06-11-2016)

  11. #10
    stoest219's Avatar
    stoest219 is offline Main Sequence
    Points: 3,562, Level: 39
    Level completed: 42%, Points required for next Level: 88
    Overall activity: 0%
    Achievements:
    2 Posts Achievement5 Threads Achievement!20 Posts Achievement!50 Posts Achievement!365 Days+ Registered Achievement!
    Join Date
    Dec 2015
    Location
    Dallas burbs
    Posts
    128
    Points
    3,562
    Level
    39
    Thanks
    0
    Thanked 33x 27 Posts

    Default Re: "Resolving" Globs

    Allen, I really like that system. That will really help me take notes when observing. I have to confess that when I first started I kinda had the "all globs look alike" mindset but as my skills have improved globs have become really interesting. I could not stop looking at M13 the other night, and I would have rated my view as a 3 on this scale.
    Celestron Evolution 9.25, .63 Focal Reducer, 2" Williams Dielectric Dura Bright diagonal
    18" Dob, Lockwood mirrir, Paracor SIPS, Nexus 2
    ES 30, 24, 14, 11 and 6.7 82° eyepieces

 

 
Page 1 of 2 12 LastLast

Similar Threads

  1. Replies: 4
    Last Post: 01-19-2013, 08:25 PM
  2. Replies: 27
    Last Post: 03-24-2011, 12:40 PM
  3. "Science" Lightweight Addresses "Global Warming" (and Chinese Food)
    By John Steinberg in forum Amateur Astronomy Forum
    Replies: 3
    Last Post: 06-21-2006, 09:33 PM
  4. need email addresses of "Emil Bonnano" and "Perry Remaklus" (MEGASTAR)
    By Michael Feiler in forum General Astronomy Forum
    Replies: 0
    Last Post: 12-14-2004, 07:23 PM
  5. MEBAY: "Space Frontiers," "Shuttle/Comet," "Secrets of Space"
    By Scott Lowther in forum Space Exploration History Forum
    Replies: 8
    Last Post: 11-15-2003, 09:41 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 08:48 AM.