PRESTON
super member
Reged: 10/28/04
Posts: 147
Loc: Haldimand, Ontario, Canada
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Hi,
This is my first post, I have been observing with a borrowed 4” Newtonian for the past month or so, and have read cover to cover a handful of magazines, and the book “The Backyard Astronomer's Guide”.
I am considering purchasing my own telescope, and have a burning question that I can’t seem to find the answer to, so here goes:
What telescope will be better suited for Lunar viewing, an 8” Dobsonian, or a 3 ½” refractor?
To me the knee-jerk answer is the 3 ½” refractor, but I have also read that a larger aperture telescope will give better high power views regardless of the fact that its mirror based, and obstructed by the secondary.
Is this true? Is aperture king regardless of style?
For the sake of this argument, please disregard cool-down time and portability.
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15x70 Binocular & Tripod
114/900 EQ Newtonian
150/1200 Dob Newtonian
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BluewaterObserva
Post Laureate
Reged: 05/18/04
Posts: 4763
Loc: Zuni Mtns, NM
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With lunar observing in particular. Two things become important. Size isn't one of the bigger ones.
a 3.5" APO high quality Refractor will at least equal if not better an average 8" reflector in all likely
hood.
A high quality 8" Dobsonian (with extremely high quality optics) will slay the 3.5" APO.
An average 8" Dob, will slay an average 3.5"....
Optical quality and decent long focal length are the ticket on Lunar, Planet, and double star observing. In my opinion as always, others may feel somewhat different on it.
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MMICKELS
Aluminum Knight
Reged: 01/20/04
Posts: 25071
Loc: The Land of Shake and Bake
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A larger scope will be able to see finer detail regardless of scope type reflector or refractor as long as the optics are of similar quality. I hope this answers your question. Welcome to Cloudy Nights.
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Mark
"The only thing wrong with immortality is that it tends to go on forever."
Herb Caen
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PRESTON
super member
Reged: 10/28/04
Posts: 147
Loc: Haldimand, Ontario, Canada
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Thankyou, Both replies do answer my question indeed. My choices for my first telescope have been as follows:
Synta brand 8" Dobsonian OR Synta brand 90mm achromatic refractor on an EQ 3 or 4 mount.
Obviously the 8" Dob will cost me quite a bit less, it will let me see DSO's as well, and apparently, show greater lunar detail than the 90mm, so for me its the 8" Dob!
Thanks!
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15x70 Binocular & Tripod
114/900 EQ Newtonian
150/1200 Dob Newtonian
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Tom L
Reged: 01/07/04
Posts: 29811
Loc: Sunny Oregon
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I had an 80mm Stellarvue 80/9d which is a very fine achro refractor. I still prefered the view through my 8" Dob.
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Tom 
Tele Vue 102mm f/8.6 on an EzTouch
Vixen 80mm f/5 A80SSWT on a grab-n-go mount
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NewAstronomer
Carpal Tunnel
Reged: 09/03/04
Posts: 2690
Loc: Scranton, PA U.S.A
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I have a 90mm Orion, I am regretting purchasing it over a large Dob. The views are great, but I now realize that I'll need a bigger scope to get detail out of a DSO cluster etc. The views the 90mm are good, but all DSO's so far are faint grey smudges.
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Chris
AT66ED f/6
C80ED f/7.5
10" GSO Dob f/5
SVP w/ autoguide mod
Oly E-500 DSLR, DSI-P, DSI-C, NexImage
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lighttrap
Reged: 02/06/04
Posts: 3833
Loc: cloudy, foggy, humid NC, US
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Welcome to CN.
Between the Synta 8" reflector and Synta 90mm achromatic refractor, I'd pick the 8" reflector every time. You'll get larger image scale and more detail in the eyepiece. Also, you'll have lots of other objects available to you when you decide to branch out and look at other celestial wonders.
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18" Starsplitter II f/4.5
8" Hardin Dob f/6
C5 workhorse mini SCT f/10 or f/6.3
70mm TV Ranger dual purpose birding/astro
77mm Leica Televid APO
16x70 Fujinons on UA Deluxe Mt.
12x50 Nikon SE
8x30 Nikon E2s
and many others
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Jarad
Post Laureate
Reged: 04/28/03
Posts: 3850
Loc: Atlanta, GA
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I would also take the dob over the achro. The moon is one of the hardest targets on achromatic refractors. There is so much light that the chromatic abberation becomes quite bright, and costs you contrast on lunar features. If you were considering an APO, it might be closer, but between these 2 the dob will win by a lot.
Jarad
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David Knisely
Postmaster
Reged: 04/19/04
Posts: 6758
Loc: Beatrice, Nebraska
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Quote:
With lunar observing in particular. Two things become important. Size isn't one of the bigger ones.
a 3.5" APO high quality Refractor will at least equal if not better an average 8" reflector in all likely
hood.
A high quality 8" Dobsonian (with extremely high quality optics) will slay the 3.5" APO.
An average 8" Dob, will slay an average 3.5"....
Optical quality and decent long focal length are the ticket on Lunar, Planet, and double star observing. In my opinion as always, others may feel somewhat different on it.
You aren't alone on that feeling. Too many people get suckered into liking the quick sharp low-power view in a small refractor, but never get to see some of the fine high-power detail an 8 inch will show on the moon. However, unless the 8 inch is a *really* bad instrument, even one of average quality will still outdo the 3.5 inch by quite a margin. The refractor might be more portable, but the 8 inch will "clean the 3.5"'s clock". Clear skies to you.
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David W. Knisely
Hyde Memorial Observatory
http://www.hydeobservatory.info
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desertstars
Deja moo
Reged: 11/05/03
Posts: 29956
Loc: Tucson, AZ
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Also consider that you will be tempted to observe fainter stuff, as well. I went with an 8" newt (eq mount in my case) because as fond as I am of the Moon, there are times when the Moon isn't up these to view. Gotta look at something!  An 8" newt, whatever the style of mount, comes pretty close to an all-purpose scope (in my opinion). You won't be sorry if you go that route.
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Tom W.
SVP8 'She turned me into a 3-legged Newt' EQ
Ralph, the All-Purpose 102mm Refractor
Under the Desert Stars
"If we don't change direction soon, we'll end up where we're going." Professor Irwin Corey
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Jon Isaacs
Postmaster
Reged: 06/16/04
Posts: 12070
Loc: San Diego, California
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In my experience there is no doubt about it, the 8 inch Newtonian will out perform the 3.5 inch Achromat. Its bigger, it takes time to cool and it needs collimation every so often. At 200X the Newtonian can provide nice bright and stunningly sharp views while the 90mm scope is getting quite dim and at the limit.
jon
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John M
professor emeritus
Reged: 12/01/03
Posts: 570
Loc: Phoenix, AZ
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Preston,
I am another supporting the 8" newt. It seems to be that right in the middle scope that isn't to large/expensive for the beginner and is large enough that it could be the last one you buy. I have had a GEM mounted 8" for almost 2 years and have not been disappointed in the views. Basically it sees better then my observing skills. OK so it doesn't compare to the 18" Dob I looked through but I also don't have the size and costs to deal with. Views of the moon are spectacular. It will be years before I see all of the DSO's I want to see with the 8".
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John M
Mesa/Tucson, AZ
8" Sky View Pro Newt
90mm Meade 386D Refractor
60 mm Monlux Refractor
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John M
professor emeritus
Reged: 12/01/03
Posts: 570
Loc: Phoenix, AZ
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Quote:
I have a 90mm Orion, I am regretting purchasing it over a large Dob...
New Astronomer,
Although I have an 8" now my first purchase was a 90mm 1000mm focal length refractor and I had some of the same feelings about the 90mm when I bought the 8". Over time I have really learned to appreciate the 90mm and I use it almost exclusivly for the moon and very often on Saturn and Jupiter. I can seldom get to the maximum magnification of 200x and it is so much easier to set up. It offers very good "contrasty" views of the planets. Very few of us have one scope and a mix of scopes is a good thing. knowing what I know now, if I had it all to do over again I would probably end up with exactly what I have now.
I'm not sure what your site is like, but I have had some really good views of DSO's from dark sites with my 90mm.
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John M
Mesa/Tucson, AZ
8" Sky View Pro Newt
90mm Meade 386D Refractor
60 mm Monlux Refractor
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Yaquina
sage
Reged: 09/07/04
Posts: 358
Loc: Newport, OR
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Dob, Dob, did I mention Dob? Just my opinion, but my preference is DSO's. I have used small refractors that amazed me with there performance, but for an all around scope, go with a Dob.
Clear skies, Y
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Orion ED80
Orion XT10 Classic (many mods)
8x50 Nikon binoculars
14"-18" Dob in my future!(
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werewolf6977
Lord High Smasher
Reged: 12/15/03
Posts: 7407
Loc: Hanover, Ohio
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Aperture rules - all things being equal.
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Pete
6" Apogee/LXD55 - "The Beast"
Starhopper 6" Dob - "Shiva"
Spaceprobe 130 EQ - "Spacey"
Bushnell Fatboy
The Abomination
Sun Pak Pro 7500 Platinum Edition
10X25 Bushnell Camo Roofies
7X35 Tasco Classic Plastic (good views though)
7X42 Tasco Rare Bird
10X50 Nikon Actions (Type 7)
15X70 Skymasters - "DroolMeisters"
One ratty old IBM 600E LapTop
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jdickson
professor emeritus
Reged: 04/26/04
Posts: 685
Loc: Desert Hot Springs, Ca
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The 8" dobs are a real bargain for the instrument you get.
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Joe
10" f5 ATM dob, 20x80 p-mount binos.
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Anonymous
Unregistered
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When looking at the moon with a 8" telescope, I recommend some sort of filter on the eyepiece. When I trotted out my Meade 8" CAT a few years ago and pointed it moonward, the resulting image was bright enough to project on a piece of paper! It was almost painful to look at (the moon was near full at the time).
Probably a variable polarizing filter would be best, and they aren't all that pricey.
-- Tom
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dgs©
Postmaster
Reged: 03/29/04
Posts: 13835
Loc: West Monroe, Louisiana
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Tom has a good suggestion on that variable polarizer. It's just about a neccesity with an 8"Ø scope. Looking at the moon with out it is kind of like shining a Mag-Lite™ directly in your eye. 
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- david
8"Ø Newtonian on SVP, Moonlite CR2, Telrad
PST Oberwerk Ultra 15x70 Orion Ultraview 10×50
Hand-me-down Sears Refractor (Discoverer) 60mm×900mm
"What we have done for ourselves alone dies with us; what we have done for others and the world, remains and is immortal." --Albert Pike
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MMICKELS
Aluminum Knight
Reged: 01/20/04
Posts: 25071
Loc: The Land of Shake and Bake
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If you can't afford a filter, wear sunglasses!
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Mark
"The only thing wrong with immortality is that it tends to go on forever."
Herb Caen
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RandyR
Enginerd
Reged: 04/01/04
Posts: 14031
Loc: Castle Rock, CO 6677' MSL
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Mark's suggestion is very good. During the eclips party the other night and at the recent star party in Denver, I suggested to several people that they use their sunglasses, it worked very well.
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"Dark Skies & Great Viewing"
RandyR / NQ0R
GPS 9.25 XLT/Sky Align /FeatherTouch
TV85 w/FeatherTouch
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