NEW SCOPE

[barry f]

I am looking to get another new scope and wondering if anyone can help with this

Bresser Messier AR-15W2S/760  Refractor with EXOS-2 goto mount

i am going to use it mainly for observing but want to also do somke astro photography with it too i do already have a zwo caera to go with it so has any one got any ideas as to what this is like ?

[Alan64]

The refractor is a fast achromat, an f/5.  There will be considerable false-colour(chromatic aberration) when it's pointed at brighter objects, like the planets and brighter stars.  It's quite suitable for deep-sky observing however, the dimmer of celestial sights and wonders, and its forte.  In that there are far more deep-sky objects, the performance of an unobstructed 6" aperture should prove quite satisfactory.

Imaging with a fast achromat is certainly doable, but not as well-suited as a Newtonian or apochromatic refractor would be.  But by all means, give it a whirl.

Know that a fast, f/5 achromat is more of a specialty telescope than a do-it-all.  A 6" f/5 Newtonian would be more versatile, for visual and imaging. 

[ronin]

That is a large fast achro, as above expect an amount of CCA on it but also I would expect to find other aberrations, SA being one and that likely will manifest as a never quite sharp image - the edges of the lens will focus the same wavelength at a slightly different position so not a specific sharp focus.

A lot will depend on how you take CA as some people do not like it's presence at all, others wonder what all the fuss is about and don't care.

If you do not mind the visual side of using a fairly large achro then I would half suffect that you get the 152+EXOS and later pick up a small ED for astrophotography with the ZWO. It is getting easier these days to suggest people seperate the 2 aspects by having a scope for one and a scope for the other.

Doesn't stop you presently attaching the ZWO and trying things out as knowing the setting needed and processing side is all to beb learnt. But CA and AP do not produce a good result, just be aware of that, and accept it if it is present.

Should be a good scope for things like comets.

[Louis D]

Hopefully you've read this review of a similar scope on CN.  It echos what others have been saying about what to expect from it.  I've always wanted to look through one, but I've never seen one at our local star parties.  Lots of Dobs, SCTs, and APOs, but no short tube achromats at these events.  Personally, I have an ST80 and couldn't stand the haziness of the views compared to a Dob, so it has sat mostly unused over the years.  I recently picked up an AT72ED and love it.  It looks nearly APO except on bright objects at high powers, and even then only modestly achro.  Surprisingly, I don't miss the aperture that much because I really enjoy the pin-sharp wide field views so much at low to medium powers.

For a photographic comparison, I tried a 500mm f8 mirror lens and couldn't stand the daytime haziness of the views in it compared to a modest 500mm f8 refractor lens.  I gave the lens away to a friend who had nothing longer than 200mm, and he really likes it.  If you are picky about visual or photographic perfection, you might not care for a short tube achromatic refractor or a short tube CAT with a large central obstruction.  Both noticeably decrease contrast, but in different ways.