4" f/9 ED refractor vs 6" f/5 Newtonian

[enigma]

How much will I be able to see (if any) with a 6" f/5 Newtonian in comparison with a 4" f/9 ED refractor? I am more interested in deep sky wide field than in planetary views.

[Peter Drew]

The 6" F5 Newtonian will have around twice the light gathering  power of a 4" ED so should be a better bet for DSOs.  

[Kirscovitch]

I'd go with the bigger newt to suck in more photons.

[russ.will]

What is you current scope/mount/eyepiece collection?

[ronin]

Who makes a 4" F/9 ED ?

[YKSE]

I assume SW evovstar 100mm ED can be taken as 4" f9 ?

[ChrisLX200]

F/9 is faily slow optically, so rich field work wouldn't be possible. Nevertheless, I doubt there would be that much in it in terms of stuff you could see in one and not the other.

ChrisH

[John]

I used to run a 6" maksutov-newtonian alongside my Vixen ED102 which is F/6.5. The mak-newt showed deep sky objects better, though most were still smudges, resolved globular clusters deeper and would show fainter stars as you would expect. 

It's not an earth shattering difference but it's noticeable, especially under dark skies.

I love refractors though and really enjoy lunar, planetary and binary star observing so I'd have a 4" ED F/9 refractor over a 6" F/5 newtonian myself.

[enigma]

I already have a 4" f/9 ED which gives a 3 degrees TFOV, but sometimes I need more aperture. With a 6" f/5 I could have the same TFOV and objects should be brighter, but I am not sure if views would be better than the refractor.

[ollypenrice]

I think I'd take a bigger step up in aperture myself. Refractors do punch a little above their weight, maybe, so that's why I'd go to 8 inches or more. You really do not quite a lot to turn faint fuzzies into structured objects.

Olly

[StarryEyed]

The price difference is quite big.

But if its going to be six inches for not much more than an ed100 you could put a six newt in a goto mount. That could help finding them.

[Caldwell14]

I used to run a 6" maksutov-newtonian alongside my Vixen ED102 which is F/6.5. The mak-newt showed deep sky objects better, though most were still smudges, resolved globular clusters deeper and would show fainter stars as you would expect. 

It's not an earth shattering difference but it's noticeable, especially under dark skies.

I love refractors though and really enjoy lunar, planetary and binary star observing so I'd have a 4" ED F/9 refractor over a 6" F/5 newtonian myself.

I concur with all of that, no diffraction spikes to contend with and better contrast. That said a 6 inch Newtonian would be a hell of a lot cheaper than a ED100 unless you get a second-hand number 

[Moonshane]

My advice would be find someone locally to meet with that has a 6" f5 newt and compare directly. they are a very common scope. personally I found the views of fainter objects noticably better in the 6" newt compared with a 120mm f8 frac that I had previously (albeit an achro). double stars and clusters were a little tighter and neater in the frac though.

if you live near Stockport, you'd be welcome to have a look through mine sometime.

for what it's worth I'd also agree that a bigger step would make more sense. if you are not imaging then perhaps consider an 8" f6 dob although this would have a slightly narrower field, or of course an 8" f5 if you have the mount for it.

[LeeB]

I would concur with moonshane, find one (6 inch newt) to try, I have just sold my 120mm fract, as it saw little use,it compared well with a 6inch f5 newt , even on deep sky, but I would say for deep sky go to 8inch at least. The extra 2 inches over a six makes a hugh difference, if you need to keep the weight down go for an orion optics as although most are f6 and bigger they are far lighter than other scopes.

[The_PSY3NTIST]

Agree with the above. I had an 8" newt and swapped it for a 6" due to wanting to head down the ap road but for visual the 8" was much much better. I have my eyes on a 10 inch dob now because The 6" just doesn't quite do it for me.

[Naemeth]

From personal experience, and I can't stress this enough, light pollution (and being able to get away from it) makes a huge difference to deep sky observing. From a truly dark sky, a 70mm ED refractor rivals my 10" dob from home. Try handling a 6" F/5 and 8" Newtonian and see if you can manage it.

Alternatively you could get a dobsonian mount for whichever Newtonian you go for - cutting the cost and the space required to store it.

HTH

[F15Rules]

Some great advice here, as ever. I think 8" would make the difference you are looking for.

For a refractor I think apo or achro is usually irrelevant for faint star visiblity..a 120mm lens is a 120mm lens! But an apo or good long focal length achro will deliver better contrast and on a moonless night might show very faint stars more clearly and so give a more pleasing view.

Of course if you want to do imaging an apo or reflector well mounted is the way to go.

Good luck.

Dave

[Alkaid]

If you like Deep Sky - go with the 6" F5 Newt for a brighter and wider field view.

If you like the Moon and Planets, go with the 4" ED Refractor.

BR - Steve