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Quote:The TV Paracorr does one useful thing that the Baader MPCC does not; namely, to increase the focal length by about 20%
Quote:If you want to do wide field viewing or imaging with a Newtonian / Dobsonian faster than about f/6 I would suggest that the Paracorr or MPCC are more or less essential.
First and foremost observing love: naked eye.
Last but not least, telescopes.
And I sometimes dabble with cameras.
Quote:Quote:The TV Paracorr does one useful thing that the Baader MPCC does not; namely, to increase the focal length by about 20%I actually view that as a downside, not a benefit. Paracorrs mostly seem useful for widefield viewing, and when I want a wide field, I generally want the shortest focal length possible.Quote:If you want to do wide field viewing or imaging with a Newtonian / Dobsonian faster than about f/6 I would suggest that the Paracorr or MPCC are more or less essential.I'm quite happy without a Paracorr at f/5. Not sure I would be so happy at f/4. Coma is proportional to the inverse cube of the focal ratio, so f/4 is much, much more problematic than f/5.I wouldn't even consider a Paracorr at f/6.
Quote: 'm quite happy without a Paracorr at f/5. Not sure I would be so happy at f/4. Coma is proportional to the inverse cube of the focal ratio, so f/4 is much, much more problematic than f/5. I wouldn't even consider a Paracorr at f/6.
Happy owner of-- A Mag 1, 12.5 inch Porta Ball A Dual Axis Equatorial Platform A PST Double Stack
Teeter STS 11 f/4.3 Zambuto | XT8i | XT8g | XLT 150 | C90 | EON 80mmAT Voyager and Nexstar SLT mountsEyepieces: Mostly TeleVue and PentaxDenk II BV'er, Earthwin PFS-SE, Pentax 10x50 PCF WP II
Quote:I don't know about refractors and using a Paracorr. All my experience is with reflectors. Refractor owners--does a Paracorr fit in with your viewing experience, and if so, what parameters for the optics?
Zhumell Z10 34 ES 68° 24 ES 68° 13 T6 8.8 ES 82° 6.7 ES 82° 4.7 ES 82° 8-24 MkIII Baader Zoom (plus Zoom Barlow) (35 Ultrascopic, 28 RKE, 26 TV Plossl, 20 Sterling, 18 Paradigm, 3.8 Parks Gold, Celestron 8-24 zoom2.5x (~2.2x) GSO Barlow, . Hardin DSO6, Orion 90 Mak, Astroscan, Celestron 90AZ) *GONE* [for now?] Bigger Dobs, refractors, Naglers, XWs, UWANs, etc, etc
One 'scope at a time... "Onward! Ever forward, never straight!" - T. McMahon
The TV Paracorr does one useful thing that the Baader MPCC does not; namely, to increase the focal length by about 20%
I actually view that as a downside, not a benefit. Paracorrs mostly seem useful for widefield viewing, and when I want a wide field, I generally want the shortest focal length possible.
David W. Knisely . . . . . . "If you aren't having fun in this hobby, you aren't doing it right." Hyde Memorial Observatory http://www.hydeobservatory.info Prairie Astronomy Club http://www.prairieastronomyclub.org
woody a parsec farther out...
12.5" f/4.8 custom truss dob, EQ platform
Quote:It is a $500 accessory but if it brings a cleaner and sharper image and also reveals stars and objects that you don't see without it I would think all dob owners should have one?
4.5", 6", and 10" Newtonian astrographs.
2 ST80s; ED80; 3 CCD cameras; 5 EQ mounts: all polished, tuned, and modified.
The rule of telescope features: aperture; equatorial tracking; or low cost. Pick any two.
Nothing would be done at all if one waited until they could do it so well that nobody could find fault with it.
Present gear: 16-inch f/4.5 Dobsonian 50mm straight through-finder Green laser pointer 26mm, 32mm, and 38mm 70 degree field EPs 4.7mm, 14mm and 18mm 82 degree field EPs 8mm, 17mm, 21mm 68 degree field EPs 2X 2" Barlow Tirion star atlas (white stars, black background) hand-laminated Megastar Editor & co-founder Las Vegas Astronomical Society Observer's Challenge To nudge or not to nudge, that is the question www.fredrayworth.com
Quote:I am tempted to get a Paracorr/Coma Corrector for a 6" f/5 I have. One issue? My focusser is 1.25" and companies do not make these devices in 1.25" barrel size.
My eyepieces are made from the waste product of exploding stars. 10XTi 102XLT ST80A(2" Focuser) XW: All; XO: 2.58 Televue: Naglers-T1 Smoothside-full set, 17T4,12T4,Ethos 17,4.7; plossels-40,32,20,17,&7.4mm; Pans-22,24mm; Delos-6,8,12,17.3mm ES100: 5.5,9*,14,20 ES82: full set ES68: 16,20,24,34 NLV: 5,9,10,15 Ortho: HD-7,9; OPS-9,12 Meade RG 7mm Other: Pentax 12.5K(.965), 10mm Parks Zoom: Nag3-6 *=on b/o DAS Dark Site
Dr. Willie K. Yee President Mid-Hudson Astronomical Assn.Member RAC, AOSNY, IDA, Astronomers Without Borders, Charlie Bates Solar Astronomy Project
NexStar 50 Expert, Lunar 50 Expert; AL Outreach, Messier, and Sunspotters AwardsCommander Prius Class Shuttlecraft Zhang HengTeeter 13.1" f/4.5 Custom Dob, NexStar8 SE, Meade 80mm f/6 ED Apo, Meade 363 f/10 80 mm, Lunt LS60THa, PST dbl stk
Quote:Quote:I am tempted to get a Paracorr/Coma Corrector for a 6" f/5 I have. One issue? My focusser is 1.25" and companies do not make these devices in 1.25" barrel size. Sorry to hear that, but considering that the largest actually "useable" 1.25" eyepiece is a 32mm plossl(the 40 if you like soda straws), or the 24mm 68* or shorter f/l eyepieces are better corrected and the coma may not be as noticible. The other option is to upgrade to a 2" focuser, but that could get expensive as you may have to replace the secondary mirror as well. The paracorr really was designed for the large f/l widefield eyepieces, which you really aren't going to get into much with a 1.25" focuser.Was there ever a 1.25" Paracorr??? Doubtful, but they do include a 1.25" adapter with it. Maybe BillP might know if Televue ever put one out (if they did, it would be a rare collector's item indeed).
Quote:I use my 18" Obsession at f4.5 without a paracorr with ES82 eyepieces. I personally don't find an issue with it.
-- Matt -observing since fall 2012 16" F/4.5 truss DOB / EON 120mm ED / 10" F/5 strut DOB Paracorr (T1 tunable),telrad, RACI finders, AltAz Tripod mount ES 82° 4.7,6.7,8.8,30mm AT Paradigm 60° 25,18,12mm Pentax XW 70° 20,14mm , Baader zoom observing list/notes.. beginning dslr astrophotos (moon/widefields)
Quote: As far as a "must have"; that depends entirely on the person viewing.
DJ Eastern Missouri, USA Bushnell 8x42's, SV80ed, Nexstar 130SLT, C5+, 8" LX200 Classic, 10" f/7 Cave, Orion XT10 w/Moonlite focuser
Quote: - My least favorite quality is that I recently discovered it dims the light transmission. Makes sense since more glass = less light. That said I'm also viewing in a light polluted area 90% of the time.- It feeds the monster.
Quote:The coma free region of an F/5 Newtonian is small, it can be calculated using the formula:Dcf = 0.022 x F^3 mm.For an F/5 Newtonian, this is 2.75mm, in a 10 inch F/5, this corresponds to 0.125 degrees... At 200x this corresponds to an AFoV of about 25 degrees.
Quote: How did you determine that it dims the light transmission? The 15% Barlow effect results in a more magnified as well as dimmer image but this is not the light loss or transmission loss, it is just what happens when the magnification is increased by 15%.
12" Harden Optical "Bubba"
16" Meade Lightbridge "Beached Whale"
70mm ETX-AT "Peashooter"
& a slew of EPs
...It is better to know the value of your equipment than the price of your equipment.
Quote: I am not a scientist, and may have used the term "transmission" incorrectly, but what I meant was what you said, that the image is dimmer. Is that different?
Quote:That formula is a little misleading; it gives the region within which coma is less than diffraction. One would conclude from it that the coma-free AFOV at 50X is just 6 degrees.
Quote:Myself, I am not one who confines my observations to the center of the field, I tend to look at the entire field of view, sharp stars across the field are nice.