helpwanted
Carpal Tunnel
Reged: 07/04/07
Posts: 2585
Loc: Phoenix, AZ
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i'm looking for everyone's choice between these two RACI finders. i will use my Rigel, but also want one of these for my 6" f5 refractor. i am leaning to the 6x30, even though it's the smaller of the two, it has a nice 7 degreee fov.
the 9x50 would have a 5.5 degree fov, but more light.
so even though i am leaning to the 6x30, i am looking for everyone elses thoughts... which one and why?
thanks,
david
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Charles Laird
super member
Reged: 08/24/07
Posts: 145
Loc: Kerrville, Texas
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I have a 7x50 and am happy with that combination on my 8" dob. My opinion on your question is that it depends a lot on what you are trying to view and your experience level. If you have quite a bit of experience, are comfortable finding your way around looking through a finder scope and are seeking some of the more obscure deep space objects you probably know you want a powerful finder scope. An experienced observer can cope with a narrow field of view. The 6x30 has a wide field of view which makes finding your way around much easier. You can see more stars to help you keep your bearings. Using a Rigel finder is easy because you can see all around it. Using a finder scope is like trying to find your way around in the woods at night looking trough a toilet paper tube. It takes a little getting used to at first. But my Telrad is actually sitting in a drawer right now, I like using the finder scope better. My old 6x30 binoculars will give me more visible stars than my sky atlas has recorded and would provide plenty of magnification for basic telescope use such as completing the Messier list. The 9x50 is much bigger and heavier than the 6x30 which is another consideration. Believe me, the 6x30 will be much easier to use if you are just learning to use a finder scope.
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"Nothing is too wonderful to be true."
Michael Faraday
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Zebra24601
Postmaster
Reged: 10/09/05
Posts: 11405
Loc: San Gabriel Valley, CA 91770
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Given you already have the Rigel to get you in the neighborhood, I would absolutely prefer a 50mm finder. It's big enough to help you narrow down on to most of the Messier objects. The 30mm wouldn't be nearly as useful in that respect.
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Zebra24601
Meade 8" SCT w/UHTC * Celestron 100ED * Celestron C11 * Celestron Firstscope 80EQ
Meade LXD55 mount * Orion Sirius goto mount
Bushnell Voyager 4.5" Compact Reflector * Barska 15x70 binoculars * Galileoscope * Really cheap Tasco spotting scope
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RalphK
member
Reged: 02/07/08
Posts: 51
Loc: Outside Philly
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I asked this very same question about a year ago for my 4.7" refractor. The consensus was go for the 9x50 and I'm glad I did. The Rigel should get you to your target area so the ability to go deeper with the 9x50 is much more useful than the greater FOV of the 6x30.
Just one guys' opinion.
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Celestron Omni XLT 120
Orion ST80
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KWB
Postmaster
Reged: 09/30/06
Posts: 9268
Loc: Westminster,Co Elev.1646Meters
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Your scope is large and designed to take in all the FOV it can get. With a magnified finder a 50mm finder is the way to go.
A 6 X 30 has it's place and that is with a really small OTA like a 90mm Mak that wasn't intended to seek out the Cosmos on a small mount like an EQ1.
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Kenny
"Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe." - Albert Einstein
Edited by KWB (07/02/09 02:48 AM)
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revans
Carpal Tunnel
Reged: 09/26/05
Posts: 1501
Loc: Fitchburg, MA
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The 50mm finder for sure...
Rick
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Rick Evans
http://www.freewebs.com/revans_01420/
"The universe is there for us to see, but it cannot be understood without learning its language -- mathematics." Galileo Galilei
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denodan
professor emeritus
Reged: 10/06/04
Posts: 609
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The 50mm for 2 reasons. More light gathering power means easier to find those faint objects, and if you have some light pollution, then a 50mm is really a must, with light pollution a 30mm is to small.
I have a 9X50mm and never looked back. One my old scope it had a 6X30mm and quickly changed it to 9X50, a hugh improvment and found it a lot easier to find to use.
A 30mm finder I feel is to small, get the 50mm.
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Luigi
Post Laureate
Reged: 07/03/07
Posts: 4890
Loc: Massachusetts
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A 6" f/5 is a nice finder in it's own right. Just add a Telrad/red-dot.
If you're looking for faint objects (faint in the scope) then you're not going to see them in a finder. A finder is used to position the scope between stars easily visible in the finder such that it is centered very near the faint object you hope to see in the scope. A wide true field of view often makes this easier.
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Discovery 17.5" f/5. IM 7" f/15 MCT. Eon-120ED
Lunt 60mm Ha on Nexstar mount.
CG5ASGT, Orion Skyview AZ
9 Nag. 35&19,Pans. 24.5 4kSWA. 14&4.7 5kUWA Meades
6, 9, 12.5 UO-AO. 3mm Edge-on. 7mm BO-TMB
Zeiss, Leupold, Bushnell spotters
Zeiss, Leica, Fujinon, Nikon, Pentax, Bushnell binos
One each generic rescue Greyhound
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 14613
Loc: Cumberland, R I , USA42N71.4W
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Quite often the scope itself cannot be used as a finder, in whch case a 9x50 is a huge plus. For instance, when double star observing at very high power, once the eyepiece of choice is precisely focused, I would never take it out to use a low power eyepiece in the scope as a finder. In this instance I'm dependant on my finder to help star hop and find my ultimate target.
BTW, not all 9x50 finders are really 9x50. My Celestron 9x50 finder has a 7mm exit pupil. That ain't 9x.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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Astraforce Paul
Carpal Tunnel
Reged: 04/05/05
Posts: 1875
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I've been there, owned both, would recommend the 9x50...
With a Rigel, you'll get in the general vicinity such that the 7 degree fov of the 6x30 won't be that great an advantage (if you didn't have any red-circle pointer, then there might be more reason to get it).
OTOH, the 9x50 will show you many DSOs directly (they may look like tiny fuzzies, but at least you'll know you're in the right place!). That's particularly true of brighter objects, especially brighter globulars.
I've not found the 5 degree fov to be a problem as the Rigel gets me so close that the finder can help from there (although often, if I'm using good star charts, I don't even need the finder).
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Midnight Dan
Carpal Tunnel
Reged: 01/23/08
Posts: 2644
Loc: Brockport, NY
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If you ONLY have the finderscope in use, the 6x30 is the better choice. I like my 9x50, but I find that I have to sight along the outside to get my target into it's view to start with. Not very convenient.
However, if you use it in conjunction with a unit power finder like the rigel or a GLP, then I'd definitely go for the 9x50. The unity power finder is much easier to get a quick alignment with the target. Then the magnified finder becomes more like a permanently affixed low power eyepiece. In this case, you DO want some magnification and aperture to help you pick out those dimmer stars for star hopping to your final destination.
-Dan
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Scopes: Celestron NexStar 8SE, Orion EON 72mm ED/APO, Orion ShortTube 80
Mounts: NexStar Alt/Az GoTo, Orion Astroview (EQ3) w/single axis drive
Eyepieces: Baader Hyperion 36mm (Aspheric), 21mm 13mm, 8mm, 5mm;
Other: 2x & 3x Barlow, 0.63x Focal Reducer, Dew-not strips, DewBuster controller, SQM Meter
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helpwanted
Carpal Tunnel
Reged: 07/04/07
Posts: 2585
Loc: Phoenix, AZ
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Edz reminded me of two follow up questions... what are the exit pupils for these two finders, and what are the limiting magnitudes for them?
IIRC, the 50mm = mag 11.0 ???
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 14613
Loc: Cumberland, R I , USA42N71.4W
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a 9x50 scope under mag 6 skies might reach mag 10
a 7x50 under mag 6 skies might reach mag 9.8
a 6x30 under mag 6 skies might reach mag 9.5
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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bbasiaga
professor emeritus
Reged: 05/10/06
Posts: 723
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You could go nuts and get the Stellarvue 80mm F3.75.  That'll find some stuff...
I vote 9x50, like many others have said, because you have a rigel. Its not so much the extra mag on the finder, but the extra aperture. Helps a lot, IMO.
-Brian
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Vixen 80EDSF
Stellarvue 102ED2
Orion Atlas 11 EQ-G
15" Astrosystems Telekit w/ Discovery Optics
Lust for something Larger
Lust for something Larger than that
Past Lovelies:
Oberwerk 20x100 binocs
Meade AR5
Meade LX10 8" SCT
All sold to a good home
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helpwanted
Carpal Tunnel
Reged: 07/04/07
Posts: 2585
Loc: Phoenix, AZ
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1/2 magniture difference...??? i might defy the group and stick with the 6x30... i kind of forgot about weight... i am trying to stay light... the 6x30 is almost half the weight of the 9x50
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astro744
member
Reged: 09/22/07
Posts: 68
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Have a look at Stellarvue F50 (19 ounce) or the F60M (23 ounce). Even with finders there is no substitute for aperture since 30mm will just not have the capacity to show faint fuzzies, (magnification helps too).
I had a 6 x 30 finder on my 6" short f ratio Newt for many years and then switched to a Telrad + wide field low power eyepiece combo on the telescope. I found the 6 x 30 very limited in what it would show (stars mainly plus only the biggest/brightest globulars and open clusters). The extra aperture helps in barren star fields where there aren't too many bright stars to use as guide posts.
I have now added a Stellarvue F80M that I also use on another telescope. Now that one can pull in galaxies!
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Astraforce Paul
Carpal Tunnel
Reged: 04/05/05
Posts: 1875
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Don't know about the only 1/2 mag difference, but in real world observing experience, the 50mm can bring in many DSOs whereas the 30mm brings in few. It's the difference between knowing the object is there vs. guessing that you've found the right asterism around the DSO.
The light-gathering area is almost 3x as much in the 50mm --wouldn't that make the visual magnitude difference be over a full mag? Or is that not how that works?
Weight is another matter; the 30mm are much lighter. I used to be a staunch advocate of 6x30mm finders, especially because of their wider fov... until I started using a 9 x50mm finder! Under dark skies 6 x 30 might work fine, but in semi light polluted suburban skies, it's a different matter as the 50mm show you much more.
Dan summarized this well-- with a red dot or red circle pointer, go 9 x 50. In fact, given how lightweight red dot pointers are, and how versatile they are in use, they're highly recommended.
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 14613
Loc: Cumberland, R I , USA42N71.4W
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Quote:
The light-gathering area is almost 3x as much in the 50mm --wouldn't that make the visual magnitude difference be over a full mag? Or is that not how that works?
Don't work that way at low powers, only at optimum magnification that could utilize all that aperture, and that would be, OH somewhere's around an exit pupil of 1mm.
Finder scopes are sort of like binoculars, except you only get one eye, so they allow you to see a bit less than binoculars. A 10x50 binocular under a mag6 sky can only see to about mag 10.5. Well an 8x40, under same conditions, can see almost to mag 10. Same with a 7x50.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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KWB
Postmaster
Reged: 09/30/06
Posts: 9268
Loc: Westminster,Co Elev.1646Meters
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Quote:
Quite often the scope itself cannot be used as a finder, in whch case a 9x50 is a huge plus. For instance, when double star observing at very high power, once the eyepiece of choice is precisely focused, I would never take it out to use a low power eyepiece in the scope as a finder. In this instance I'm dependant on my finder to help star hop and find my ultimate target.
BTW, not all 9x50 finders are really 9x50. My Celestron 9x50 finder has a 7mm exit pupil. That ain't 9x.
edz
100% agreed! My sentiments exactly as this is also how I use a finderscope. 
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Kenny
"Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe." - Albert Einstein
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b1gred
Enginerd
Reged: 04/01/04
Posts: 15667
Loc: Castle Rock, CO 6677' MSL
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I go with the "bigger is better" school of thought on this one, grab as much light as you can.
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"Dark Skies & Great Viewing"
RandyR / W0RDR
GPS 9.25 XLT/Sky Align /FeatherTouch
TV85 w/FeatherTouch
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