6 inch ED doublet or SW BD 180mm MAK

astro1965 (Nick) · #1 31-01-2018, 09:55 AM

Hi all,have been considering for a while now to purchase a 180mm mak cass,but now with all the hype of this new SW 150mm ED due for release soon,its got me thinking.My question is,which would be better for contrast and sharpness?And lets assume the MAK is flocked and cooled as well,to make things interesting.
Has anyone with these scopes or similar types of scopes done a side by side comparison?Would be very interested to know peoples views and opinions on sharpness and contrast for the above scopes.,thanks Nick.

glend (Glen) · #2 31-01-2018, 10:48 AM

There should be some preliminary reports on the ED150 by the end of February.

AstroJunk (Jonathan) · #3 31-01-2018, 12:26 PM

Very different beasts - the Mac will be at a long focal length and quite specialised as a result. It will give gorgeous solar system views though so it depends what you are after in your viewing.

bigjoe (JOSEPH) · #4 31-01-2018, 02:25 PM

Quote:

Originally Posted by astro1965

Hi all,have been considering for a while now to purchase a 180mm mak cass,but now with all the hype of this new SW 150mm ED due for release soon,its got me thinking.My question is,which would be better for contrast and sharpness?And lets assume the MAK is flocked and cooled as well,to make things interesting.
Has anyone with these scopes or similar types of scopes done a side by side comparison?Would be very interested to know peoples views and opinions on sharpness and contrast for the above scopes.,thanks Nick.

Nick ..the 180 SW BD Maksutov I had, boasted superb optics ..one night in May 2 yrs ago popped in A 4.5 mm Delos , and bang.. MARS TACK SHARP..or should that be Tak sharp.. at about 600x near Zenith....yes there are clouds on Mars.

FOV very limited , at F15..though you can use a 2 " 40mm EP to telling effect ..with a bit of vignetting of course.
Great on any showpiece Globular ,Planets or Planetaries , M77, M 83 etc.

If you like Open Clusters and nebulae ..this is not the tool.

A 6 ED Refractor would do all of the above...but not quite as bright or resolved as 7.1 inch Mak and have a big FOV.

The Maksutov has less Moment Arm, and weight at 7.8kg, and thus need a lesser mount capacity...something to think about as HEq5/ AVX would probably be the min for 6 ED APO...

Steffen has a superb 6 inch Russian Maksutov in the Classifieds ..at F12 for more FOV than 180 , and v solid mount ... just another to consider.

bigjoe.

Wavytone · #5 31-01-2018, 03:00 PM

I’d take the mak. I’ve had one of those that was as near perfect as you could wish - and a 130 ED triplet APO. With the two side by side the mak was the one that was used most.

netwolf · #6 31-01-2018, 03:01 PM

I love my 180 Mak, I also know have the ETX-125 both are super scopes to use. Both have converted me to be a more visual observer now hunting for variable stars etc.

astro1965 (Nick) · #7 31-01-2018, 03:40 PM

thanks guys for the info,I am strictly a visual observer and tend to view lunar/planets more,but I also like to look at globs and nebulae from time to time.I have read that the f15 ratio on these SW 180 make them sharper and have more contrast for lunar/planets,than refractors.Read that on cloudynights somewhere,any experiences or thoughts on that?

AG Hybrid (Adrian) · #8 31-01-2018, 03:57 PM

Quote:

Originally Posted by astro1965

thanks guys for the info,I am strictly a visual observer and tend to view lunar/planets more,but I also like to look at globs and nebulae from time to time.I have read that the f15 ratio on these SW 180 make them sharper and have more contrast for lunar/planets,than refractors.Read that on cloudynights somewhere,any experiences or thoughts on that?

There is truth to those statements. The 180mm Mak tends to have more resolving power then most refractors as very few are above >152mm in diameter. The long focal length makes getting high magnification easier with your eyepieces (assuming the atmosphere supports it). Not the ideal nebula telescope however. You want large exit pupils for nebula's but my 150mm Mak does alright. Planets,luna,bright globs, double stars, star clusters, possibly planetary nebula. Anything thing with a high concentration of its light in a small area is ideal for the Maks.

On thing you need to think about is mounting either device. 6" refractors are large long things. The 180 Mak by comparison is compact and relatively easy to mount. That being said the 6" refractor would probably be a lighter instrument - especially being only a doublet.

Also no chromatic aberration with the Mak - or at least nothing visually appreciable. There will certainly be some in the 6" since we now know its a FPL-51 objective and not FPL-53 like its little brother the 120ED.

Of course the price difference is substantial too. Refractors are pretty much the "worst"(lack of a better word) value for money per inch of any telescope design.

Here's the kicker though. If price was not a consideration, despite everything I said. Id get the refractor.

xelasnave · #9 31-01-2018, 04:31 PM

Could you photograph any thing with the mak with a dslr or even narrow band...or is it really only for visual.
Probably good for Moon and planets but what about deep sky objects given you can track and stack making long exposure less of a worry?
I like the idea but the focal length is it too long for photos?
Alex

bigjoe (JOSEPH) · #10 31-01-2018, 04:44 PM

Quote:

Originally Posted by netwolf

I love my 180 Mak, I also know have the ETX-125 both are super scopes to use. Both have converted me to be a more visual observer now hunting for variable stars etc.

Good to hear Fahim..and some doubles as well I hope.
bigjoe

bigjoe (JOSEPH) · #11 31-01-2018, 04:59 PM

Quote:

Originally Posted by xelasnave

Could you photograph any thing with the mak with a dslr or even narrow band...or is it really only for visual.
Probably good for Moon and planets but what about deep sky objects given you can track and stack making long exposure less of a worry?
I like the idea but the focal length is it too long for photos?
Alex

Thats the problem Alex ..too long a focal length at F15, restricted field, and the mount you would need , and guiding, would have to be top shelf for long exposures ....and you would need them , though with stacking software these days..

Here are some images taken with the older model without the Schott Glass used today
https://www.myastroshop.com.au/guides/promak180.asp
bigjoe.

Wavytone · #12 31-01-2018, 05:44 PM

Regarding eyepieces - you’ll probably find the range 40 downto 10mm useful, and with the SW 180mm mak there’s a sweet spot with eyepieces around 13mm focal length. Occasionally you could go as far as an 8mm on very still nights.

Photography through the mak cassegrains is limited to moon and planets and you may even want to double or triple the focal length for that.

For photographing DSOs though there are several options depending on the aperture, focal length (and f/ratio) and the image scale (microns per pixel) desired.

For small scopes say 80-130mm aperture a refractor is hard to beat.

From 150mm aperture / 750mm focal length though you’re better off with a newtonian or Maksutov Newtonian (much overlooked IMHO).

Tropo-Bob (Bob) · #13 31-01-2018, 06:44 PM

I am a refractor guy and the idea of an affordable 6" well-correct scope is pretty heady stuff.

However, when I calmed down, I thought that an edge or coma corrected 8" SCT is a better option for most people. It collects more light, as well as being cheaper, lighter and 100% colour corrected. The SCT's 2000mm focal length is more comparable with the refractors than the 2700mm of the F15 Mak, which may be too specialised with its narrow field for those who may be considering the refractor.