short focus APO refractors

[ian_d]

Hi all

What are people's views on the best value short focus APO refractors for <i>visual</i> observing (vice astrophotography)? Which scopes provide the best views at the best price point? Around 4" aperture is where I've been looking (beyond that the prices do get silly!)

I've been idly Googling such things for a while now and haven't really been able to decide for myself, so wondered if there's any "received wisdom" out there!

For background, I already own a 6" Celestron SCT (f/10) and have been wondering about getting something much faster to complement this scope (which is great, by the way!)

cheers

Ian

[NickH]

The Meade 5000 80mm is excellent as are the WO Megrez series at around F5-6 range.. all for under £400

[brianb]

I already own a 6" Celestron SCT (f/10) and have been wondering about getting something much faster to complement this scope

The focal ratio of the scope has not much to do with its visual performance, and a 4" frac will not show faint obects as well as a 6" SCT. The resolution will be less too.

If you want a short focus scope for wide fields, I'd reccomend dropping to 3". The reason for this is that a 3" f/6 scope will give a wider field than a 4" f/6, the cost is less, the bulk & weight are a lot less .... Or decent binoculars in the 20x80 / 20x90 class.

Wouldn't reccomend dropping below f/6 as the cost of the eyepieces needed to work properly at f/5 starts to dwarf that of the tube.

[ian_d]

Yes, it's all about getting a good wide field instrument....really useful tips, thanks both.

[michael.h.f.wilkinson]

I use a short focus newt for wide field work (4.5" F/4.4), which gives me 2.6 deg true FOV. I also got a very cheap 70 mm F/5, which gives me 3.7 deg. More FOV but less light, that's the eternal trade-off.

[brianb]

More FOV but less light, that's the eternal trade-off.

If you can't afford a Takahashi Epsilon....

[michael.h.f.wilkinson]

If you can't afford a Takahashi Epsilon....

Many of us cannot , and you still have the exit-pupil size to contend with: at X mm aperture, I have to use X/5 as minimum magnification; youngsters (sound old don't I) could achieve X/8 as minimum. Then there is the AFOV of the eyepieces to contend with (100 deg if we are going to go expensive). Hence, the trade-off stands firm.

[brianb]

If you can't afford a Takahashi Epsilon....

Many of us cannot ... the trade-off stands firm.

Indeed - and at the lower end of the price range, the common or garden 10x50 binocular is a good compromise.

I was just pointing out that medium aperture, short focus instruments of very high optical quality do exist.

For imaging - but not for visual - the Hyperstar conversion available for Meade & Celestron SCTs is another medium aperture, short focus, wide field option.

[michael.h.f.wilkinson]

Indeed - and at the lower end of the price range, the common or garden 10x50 binocular is a good compromise.

I was just pointing out that medium aperture, short focus instruments of very high optical quality do exist.

For imaging - but not for visual - the Hyperstar conversion available for Meade & Celestron SCTs is another medium aperture, short focus, wide field option.

Absolutely! However, at low magnification, you might not require the top quality, and expensive systems for visual work. When imaging, things are different