Reflector or Refractor

[Paduan (Brett)]

HI i am a little new to this and i know that i am opening a big can of worms but i am looking for a new scope and co not know what to buy and really need help. i presently own an 8" sct and HEQ 5 mount as when i got involved in astronomy i was told that size is everything so the 8" was perfect cost/size however now i wish to see the fainter stuff out there and am confused as to whether to buy a large aperture refractor ie 120ish + or a large Dob ie 12-16 inch. have looked through many a dob but never through a refractor. a refractor will fit my mount but a dob has the BIG mirror, it sounds like bragging but cost is not really an option i have a couple of 'k' to spend. i have seen the images that are posted here and i know that they are blown and cropped but for ocular pleasure do i go for size or knowing how to use it,pardon the pun.

[RobF (Rob)]

Hi Brett. You're never going to see the colour and detail that a sensitive CCD (usually hours worth of data) shows. The human eye just isn't that sensitive. Most people are probably going to say you need a big dob, but what you have is no slouch either from a dark site. I would suggest you travel to a local site and hook up with local astronomers if possible next new moon and try to look through a larger dob to "see what you can see".

I loved the views through the 32" dob at the last South Pacific Star Party, but that doesn't mean I'm selling my trusty 8" reflector and Heq5 anytime soon!

[rmcconachy]

Brett, if you want to "see the fainter stuff out there" then a refractor is not the best tool for the job. Refractors have many fine properties and I like them very much for certain tasks but something that refractors do not do well is faint fuzzies. To see fainter stuff you need to capture more photons which requires more aperture and that means a larger SCT (which would require a substantially larger mount) or a (probably Dobsonian) reflector. How large a scope you should buy depends on how much you have to spend and also how easily you can use the telescope (it is no good having a scope that is so unwieldy that you never take it outside - unless you are going to build an observatory!). This last point also relates to how often you travel with your scope, an 8" scope under dark country skies will show more than a 12" scope in the middle of suburbia! If you can, I highly recommend going to a couple of astronomy gatherings (is their a club close to you?) and looking through a few scopes belonging to other people. That way you can get a feel for how big a 12", 16", etc, scope really is.

[Paduan (Brett)]

thanks guys i am a member of a club that has a 16" reflector but have never looked through a refractor. ALL of the images here seem to come from refractors ED 80's or TAK's so i believed that they were the norm for "fuzzies". cost is an option to a small extent but i would rather spend $2500 on the correct thing than $5000 and finding out that it was wrong and having to do the job twice. i have no interest in selling my trusty SCT as we go bush lots and the SCT is unbeatable as far as transportability for aperture (photon collecting) is concerned. just never looked through a refractor. i know i am never going to see the wonderful colours of Carina or Orion with my eye, however i would like to see Centarus A bigger than a smear of monochrome in my 4mm ep

[RobF (Rob)]

Originally Posted by Paduan

thanks guys i am a member of a club that has a 16" reflector but have never looked through a refractor. ALL of the images here seem to come from refractors ED 80's or TAK's so i believed that they were the norm for "fuzzies". cost is an option to a small extent but i would rather spend $2500 on the correct thing than $5000 and finding out that it was wrong and having to do the job twice. i have no interest in selling my trusty SCT as we go bush lots and the SCT is unbeatable as far as transportability for aperture (photon collecting) is concerned. just never looked through a refractor. i know i am never going to see the wonderful colours of Carina or Orion with my eye, however i would like to see Centarus A bigger than a smear of monochrome in my 4mm ep

Imagers like a Tak refractor because they can get a wonderful flat and relatively wide prime focus image covering their CCD chip. The focal length and shortish focal ratio is again great for a CCD. The human eye is much smaller of course so you don't need that wide flat circle of light. Getting as much light as possible is what counts, therefore a large dob is very hard to beat for View/$ spent. One possible exception is lunar or planetary work where there is already plenty of light to see, however then you need to consider the value of a big aperture with a central obstruction versus the crisp easy to focus clarify of a refractor. You usually need at least 1.5x the aperture in a reflector to match a quality refractor because of those obstruction issues.

You still really need to have a gander down some eyepieces as well as suss out the size of these beasts.

[kitsuna (Adam)]

your choices are:

refractor

dob based newtonian

or a bigger SCT.

I like refractors, but the fact is, they are not really suited to faint fuzzies. The sort of aperture you need to see faint fuzzies makes refractors prohibitively expensive, very difficult to mount/use (because you'll need a substantial equatorial system), and there aren't many manufacturers that can make a huge refractor of any worthwhile quality.

as far as a newtonian dob goes, this will be the cheapest way to get big aperture (especially if you get a non-goto verson). It's a big light bucket, for the least amount of money. For faint fuzzies, the amount of light you can catch is what counts. The trouble is, they will be big, heavy, and unless you spend a fair amount extra, will require manual movement.

SCTs can be bought in anything up to 16inches (meade and celestron both offer them up to 14 inches, and I'm reasonably certain meade still does a 16incher). Upside is that they can be mounted in a way to give you GOTO. However, it will be big. it will be very heavy. It will require a reasonable amount of setup, and it will cost a small fortune compared to a similar sized manual dob.

To put it into context for you;

A meade LX200ACF in 14inches costs $7000 on the meade website. It'll cost a lot more than that once you factor in the inevitable costs that come from either buying it in Australia, or getting it shipped to australia (assuming you can find a place that'll do it).

A meade lightbridge 160incher costs about $1900 on the meade website.

I know of absolutely no manufacturer that makes a refractor anywhere near as big. even if you accept that because a refractor is unobstructed, and therefore don't need as much clear aperture (which I don't, at least not to the extent that is commonly touted). I know takahashi and TEC have made some 8 inchers, but they cost way more than any other example I've given.

If it were me, I'd get the 16 inch lightbridge (or similar, if meade doesn't float your boat), and then get an argo navis for it.

This of course assumes that you have the time, space, inclincation to manage any one of these large scopes. No matter which way you go, at this kind of aperture, you're dealing with a big heavy scope.

Frankly, I'd rather stick with a smaller scope, and borrow a big one when I absolutely need to. that's what astro clubs are for.