133 replies to this topic

[erik]

in comparing my modified 8-inch orion newt, i've yet to come across a refractor,APO or otherwise, that shows a crisper more detailed view of the planets.i'm curious why,aside from portability and cooldown issues, anyone would spend thousands of dollars on a 4-inch telescope.(is it just asthetics?)my newt has no false color,doesn't have a front lens to dew up, and since i installed a 3 vane curved secondary support,there are no longer any diffraction spikes. the scope is f/6,and the secondary mirror is only 1.83",so contrast isn't an issue.i've looked through many refractors, some of them high end,and while they do look nice, i've never been overly impressed with the views,considering what they cost.i also have a 120 mm short tube refractor.it's great for traveling, but i ALWAYS choose the newt when i go to my dark sky site.the views,planets and obviously deep sky are that much better. so i guess my question is, what advantages do refractors have besides being more portable and taking less time to reach outside temperature? am i missing something ? erik wilcox

[DenisY]

Warpd
That's one hell of a reply, there absolutly nothing i can add. It even get's me to want an APO now.

[jrcrilly]

I dunno; I can see the charm of the APO's for portability and for esthetically pleasing widefield views. For those of us who don't value portability above all else, though, the smaller ones just seem too much of a compromise. I can't visualize any conditions under which a less than 7" APO would begin to approach the planet or one degree deepsky performance of my 12.5" F/8 Newt. I know the 4" APO I had wasn't close. It was great for BIG starfields and brighter extended objects but there's only so much four inches can do.

I think we need to compare apples to apples - I'd rather have a 4" APO than a 4" Newt or Cat, but if I can have aperture I'll take that first.

[erik]

thanks for all the replies.you guys make some good points.in comparing apples to apples, i agree, a high end refractor of the same aperature as the newt will beat it every time because it suffers no light loss from the secondary obstruction. in fact, in my experiences, i think a 6 to 7 inch refractor equals a 8 inch newt or a 9 inch SCT. however, we all know what a 7 inch APO costs, and i think that if price is any consideration, the newt wins out.an 8 inch newt also weighs much less than a 7 inch refractor.and if were talking about a 4 inch APO ,as john said, theres only so much 4 inches can do.on deep sky, the newt will obliterate it, and in my opinion, it wins out on the planets as well.even when the seeing is bad,you can stop the newt down for a more pleasing view.(you can even eliminate diffraction spikes from straight vanes in this way) i think every telescope can serve a purpose, and if i had an unlimited amount of cash(and a lot of time to spend on a waiting list),i'd probably buy a nice astrophysics APO.but it wouldn't be my only scope, and i bet i'd still use the newt quite a bit.i think that a newt is just a more versatile instrument, capable of doing everything well, wheras the 4 inch refractor is more or less designed for planetary work(due to its limited aperature).having said that though, its true that newts need more maintanance and cant be banged around as much(although i dont think i'd want to bang around a $8000 refractor!)anyway, i'm sure the debate will continue. just my 2 cents.- erik wilcox

[pete]

I recently went for a refractor aside form all the reasons mentioned above. They look less threatening and more like a telescope. I was vacationing on a mountain overlooking a vally sometime ago with my 6" on a Dob mount. When a concerned patriot call for security becuase, they thought I was a terrorist about to fire a cannon into a town down in the vally. Bundled up in a black trench coat along with a ski mask for warmth, I was lucky not to get shot while observ. Pete

[eric moerman]

Dude(and al others)

the problem here is that we are not really comparing appels with appels.We are comparing 4000$+ apo with newtons around 800$.
Ofcorse the apo wil perform bether.
I think that if you take a newton that is build to the same high quality standart that al the apo's are build to it will always be as good or bether.
What we are doing now is comparing a JVC amplifier costing 150$ with a high-end amplifier costing 10000$.
The difference in sound is also big.
I dissagree that you dont need light gathering power to look at moon and planets because it comes with more aparture and you need aparture to resolve smaller details.
Ofcorse again the quality of the objectief and the rest of the telescope has to be very good to so that you can use the high powers you need to see the smal details and if seeing conditions lets you use them.
We al know that there always be refractor and reflector people and this tread can go on and on buth there is nothing else to do with al this rain anyway.
Greatings,Eric

[DenisY]

I recently went for a refractor aside form all the reasons mentioned above. They look less threatening and more like a telescope. I was vacationing on a mountain overlooking a vally sometime ago with my 6" on a Dob mount. When a concerned patriot call for security becuase, they thought I was a terrorist about to fire a cannon into a town down in the vally. Bundled up in a black trench coat along with a ski mask for warmth, I was lucky not to get shot while observ. Pete

Pete that happen to me once, i was in a public park, i somehow wanted to show the stars to the people passing by, then people started to sit near me, 1,2,5,10 person were sitting there looking at me, i found this pretty weird and after a while someone approched and asked me when would the firework start!!!

[matt]

What also happens with multi-k$ refractors is where you place your priorities, and all of you hinted towards that.
When you place, say, $3,000 for an FS102 (2,000 naked ota + 1,000 to get pointed upwards), you are not only paying for performance, you are paying for the best performance available in a 4" scope, and the comfort of not worrying about anything: no miscollimated optics or optics that cannot be collimated in case of a fall, no under- or over-greased focuser, no flexing in the focuser drawtube, etc.

You will notice there are plenty websites devoted to getting your Autostar to work or your synta mount to track, but none about tuning up (meaning: getting it to work properly) a Takahashi refractor.

It's available only to the deep-pocketed, and even the deep-pocketed might not choose to put their money there, but it makes sense, provided you are not give the bad excuses for owning one (such as saying that it would beat a $3,000 8" reflector).

[jrcrilly]

When you place, say, $3,000 for an FS102 (2,000 naked ota + 1,000 to get pointed upwards), you are not only paying for performance, you are paying for the best performance available in a 4" scope, and the comfort of not worrying about anything

Hi, Matt!

Sure thing - aperture for aperture the Taks (and most of the other APO's) will give great, no-fuss performance. They'll even outperform a somewhat larger scope. I do question whether a $1000 mount will do the same; at that price level you are still firmly into the Synta and Synta clones or limited to altitude/azimuth mounts and will still have mount issues. I used to use an LXD55 mount for my 4".

I'm not against small refractors; I had a very nice 4" APO myself and will soon have one again. It's just that, like every other instrument out there, it'll be a compromise. There are times when giving up that much aperture won't make sense to me. There are also times when it's a good tradeoff in exchange for wonderful visual performance on brighter objects.

Besides, they make great finderscopes!

[erik]

wow, you guys have brought up a lot more good points. money does matter, and its not just about where your priorities lie.even though, in stock form, an 8 inch tube will set you back only a few hundred dollars, it literally can take many times your initial investment to get it to perform the way that you want it to. this is especially true with dobs, most of which are a work in progress.however, i think that modifying and customizing a scope is half the fun! because i wanted a 8 inch steel tube that was f/6(which nobody sold by itself), i bought an orion XT8 dob just to get the tube.then i bought an 8 inch meade LXD55 for the autostar, promptly sold the meade tube and realized that the tripod sucked too, so i bought an orion equatorial pier.after installing a 3 vane curved secondary support, pyrex primary and secondary mirrors, aluminum oversize focus knobs, a cooling fan, better tube rings, flocking the tube, modifying the focuser drawtube and much more i finally have a scope on a rock solid mount that shows more planetary and deep sky detail than any refractor or 8 inch SCT or mak that i've ever looked through.and i still spent MUCH less than a large APO would cost.and as far as it being an open tube, i've never had any problems with air swirling smearing details.and i dont think that a closed tube is immune from problems either. not only do they tend to dew up,but in light polluted areas, glare can be more of a problem, due to stray light reflecting off the lens (i've noticed this even on high end fully multi coated apo refractors)there are several articles on cloudy nights that talk about what you can see in newts compared to refractors. there is one article about making a multi aperature mask and the writer describes how he couln't even look through his 4 inch apo after the $10 modification to his newt. theres also an interesting article on the effects of central obstructions, and how the human eye can't detect anything less then 30%.it's true that mirrors do eventually need to be recoated and collimated regularly, but refractors aren't maintanance free, especially ones that use exotic flourite lens, which can be unstable and deteriorate in cold damp weather. i think that refractors advantages are portability, cooldown time and in the high end models, beauty and craftsmanship. newts advantages are more bang for the buck, easier to modify, having the eyepiece in a more comfortable location(in most cases) and being more versatile instruments.SCTs advantages are........well i guess they're more portable than newts, but they have a lot of downsides as well, including hefty cooldown times, lowest performance per inch(due to light loss from the folded light path and larger secondary obstruction) and higher cost per inch than a newt. (now i probably just **** off everyone that owns an SCT) anyway, to summarize, the differences are usually small, and i can appreciate any fine optical instrument, but , in my opinion, NEWTS RULE! - -erik wilcox - erokkarma@hotmail.com - orion 8 inch newtonian,orion 120 mm short tube refractor

[jrcrilly]

SCTs advantages are........well i guess they're more portable than newts, but they have a lot of downsides as well,

Yes, SCT's are a compromise - but the size and weight difference is quite substantial. I can't fit a 14" F/10 Newt (or my 10" F/7.5 or the 12.5" F/8) in my observatory and certainly don't want to pay for a german EQ mount that would handle either one but the 14" SCT sits in there very nicely on a compact mount. I do like Newts also but to keep the size reasonable many folks choose faster ones - and there's a compromise inherent there as well. One must choose what features to give up and what to keep.

[erik]

john, you're right about SCT's being portable, and i've looked through some with very good optics, but i always feel a little boxed in with the narrow FOV. also, i think there's more variance in optical quality with SCT's- like i said, i've looked through some good ones, but i've seen some, especially older models that weren't very good.it's probably because they're more difficult to make, which is one of the reasons they cost more than a newt.i haven't seen a bad one in a while though, so maybe they're getting more consistent in quality.i'm sure your LX200 is awesome, but in the smaller sizes the image always appears dim, less contrasty and not as "alive" looking as a newt with the same aperature and magnifacation. if i had the $$$ though, i probably would own an C-14 or an LX200 for what they have to offer. -erik wilcox

[Barry Fernelius]

When I owned an 8" Mag1 Portaball with a Zambuto mirror, I used to compare the views of the planets through my telescope with refractors. Over a two year period, there were a few refractors that came close to providing better views on a few exceptional nights, but I didn't find a refractor that could compete head-to-head with my reflector. (The best refractor, the one that came the closest, was an AP 155, if I recall correctly.)

I now own a 12.5" Mag1 Portaball (also with Zambuto mirror.) I'm still waiting for the night where the refractors demonstrate their clear superiority. I'm not holding my breath. Under crappy seeing conditions, I've seen the phenomena of a refractor providing what its owner called 'a more aesthetically pleasing view.' This is another way of saying when the seeing is bad, smaller aperture scopes don't see the bad seeing as well as large aperture scope. (In this type of condition, one can 'stop down' the larger scope and see the same sort of views that are seen by the refractor.)

When the seeing is good to excellent and when optical quality is excellent, aperture wins every single time. And dollar for dollar, high quality reflectors rule.

But don't take my word for it. Check out Gary Seronik's article "Four Infamous Telescope Myths" in the February 2002 issue of Sky and Telescope. You can also go to star parties and try a few experiments. Under good seeing conditions, take a look at the planetary views through a correctly collimated reflector equipped with a Zambuto, Royce, Swayze, Hall, etc. mirror. Then take a look at the views through a 6" refractor that's many times more expensive. I think that the results might surprise you.

Finally, consider this Mars image, made by Wes Higgins with a 14.5" Starmaster. In the past, when the optics in most large reflectors were mediocre at best, I believe that high quality refractors provided the best views. Now, with high quality optics readily available in large reflectors, I believe the situation has changed.

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[erik]

barry, i agree.while i've seen a more "pleasing"view from a refractor or a large stopped down newt, i've never once seen more DETAIL in a smaller aperature. i think it's easy to perceive that you're seeing more detail if the view is less affected by the seeing, but if you were to critically compare them side by side, i would bet that the larger scope would show more or at least the same amount of detail as the smaller scope. - -erik wilcox

[Relativist]

There's no way I'd ever buy an expensive refractor, part of it is an irrational fear due to my experience with the old tasco refractor, but mostly it's the great views I've gotten from relatively inexpensive reflectors. Sorry to all you refractor fans, as long as you get more photons right?


.....Curtis

[erik]

and due to simpler and easier to make design of a newt, there are less inherent things to go wrong. ther are a lot more things that refractors can suffer from(chromatic abberation, false color, glare from poorly coated lens,etc.), wheras reflectors normally provide a crisp color free view. you have to pay much more for that same view in a refractor.newts can suffer problems, like coma in faster focal ratios, and they need to be collimated regularly, but these issues are a lot easier to correct, or in the case of coma, to live with.i'd rather notice a little coma on the edge of the FOV,than a bright purple halo that fuses double stars together.you can spend another $75 on a filter that blocks some of that, but they genarally introduce an annoying greenish tint.and all refractors, except the very top of the line models, suffer from chromatic abberation to some extent.an inexpensive, well collimated newt will provide nice views right out of the box, and with a few modifications, it's easy to make them even better. just my take on things. -erik wilcox