Quanity or Quality

[Caldwell 14]

I have a 4 inch short tube frac and I am considering an up-grade (well who isn't?) Do I go up the way to a 5 or 6 inch frac (again short tube as wide field views of clusters float my boat) or do I go for the ED option and go down to 80mm, most likely a Skywatcher ED80. The ED is fl 7.5 as I'm sure you all know, the 5 (Orion Astroview) and 6 inch (Skywatcher Startravel) are both fl 5.

[swamp thing]

Speaking from a visual point of view.

I guess it would depend on why I wanted to upgrade.

If it's to acquire more targets, aperture wins, but if it's to improve the view. An Apo is as good as it gets.

I imagine your 4" will have shown you most of the wide field wonders of the sky.

A 5" or 6" RFT Achro is only going to show them the same. Only an Apo will improve the view.

If more targets is your requirement this is where aperture rules.

Although TBH a 5" or 6" isn't going to show much more than a 4"

To get more targets I would consider a 10" or bigger Newt.

Regards Steve

[John]

Assuming that we are talking visual here, an 80mm ED is not going to show more of DSO's than a 102mm achro, less if anything, so you want to increase your aperture I reckon. As an alternative to another short tube achromat you could consider a 6" F/5 newtonian. They don't need a lot of mount and don't suffer from CA as the achros do (more so in larger apertures). An SGL colleague and I spent a great night with 6" scopes at the SGL6 star party earlier this year and managed to pick up an impressive array of deep sky objects including some pretty faint ones. His Skywatcher 6" newtonian was mounted on a simple alt-az mount and worked excellently.

[Caldwell 14]

Assuming that we are talking visual here, an 80mm ED is not going to show more of DSO's than a 102mm achro, less if anything, so you want to increase your aperture I reckon. As an alternative to another short tube achromat you could consider a 6" F/5 newtonian. They don't need a lot of mount and don't suffer from CA as the achros do (more so in larger apertures). An SGL colleague and I spent a great night with 6" scopes at the SGL6 star party earlier this year and managed to pick up an impressive array of deep sky objects including some pretty faint ones. His Skywatcher 6" newtonian was mounted on a simple alt-az mount and worked excellently.

Uuummmm.... a fl 5 Newtonian you say, I hadn't thought of that. I am a little nervious of mirrors and love the nice sharp images you get with a refractor. Would one go on a AZ4?