Apo refractor or skywatcher 190mn

[Hitesh]

Well I'm having a tough time choosing n imaging scope and can't decide between the 190mn or a good apo frac, the frac I had in mind was 120ed or possibly WO megrez 90.

With the 190mn collimating and weight is the major con for me

Major con for frac is cost (not so much for 120ed, but other brands and scopes seem to be very pricy)

Thoughts gents and ladies

[stevepeverall]

There is a WO Megrez 90 for sale at the moment on AB&S.

http://www.astrobuysell.com/uk/propview.php?view=72464

[Herrman]

Hi,

The type of mount you have will help you decide: I have both a EQ120 & MN190, the 120 sits comfortably on a HEQ5, but the 190 needs a NEQ6 or similar.

Hope this helps,

Herrman

[paulastro]

I've used many Mak-Newts over the years and they really are superb image wise if well made, The main dowside for me (I'm happy to collimate one if I must, though they are rather fiddly) is the size and weight. The other thing of course is that in the long run a Mak-Newt will need attention for something at some time. Well mae apos should never need attention of course - unless the oil leaks out of an oil-filled one .

Coindicentaly, I have used and owned several SW 120EDs, and a couple of Megrez 90s! The 120s really are excellent, though a tad (and it really is a small amount) of colour can be found if you really want to look for it, they are unbeatalbe value and as good or better than some refractors costing much more. A friend of mine currently has one and considers it compares very favourably with the Tak FS128 he used to own.

I had a Megrez 90, sold it when I was short of funds and really regretted it. I have another one now, and it's staying put! They really are lovely scope, sharp image and no objectional CA at all. I've used a feew different WO refractors, and consider the 90 one of their best scopes.

[Hitesh]

Well the mount I'm defiantly getting is neq6. I reckon it should be sufficient for all those scopes mentioned.

Is there a massive difference in picture quality between megrez90, 120ED, and the 190MN. Also what's their ability like when used visually?

[Hitesh]

Forgot to mention all imaging will be done on my Canon 650d, the CFO won't allow me to get a Ccd just yet. Lol

[swag72]

Interesting this, as I think that there are a few people who are divided by telescope type alone. For example I would go with the refractor every time as the thought of collimation scares me to death!!! There'll be no reflectors in my obs!

When you start asking about which scope will produce a better quality image, I would say that all things being equal they are pretty much a muchness. As long as you have the necessary flatteners required to produce a flat field on the refractors then quality per se will be very similar I would expect.

Where you will see a difference is with regards to speed of capture as the MN190 is rather quick and so you'll get your data quicker. The devil for me is in the processing. As good as your data is from which ever scope you choose, if you can't master the processing then the images won't show their potential. While you can not make a silk purse out of a sows ear, there are some guys on here who can make stuff sing with their processing expertise. In my opinion this is where the biggest improvement lies, not in three scopes.

Also, another big improvement would be in your camera. The general though is that the mount is the most important, camera next and scope last. Based on that, you are worrying about the least important part of the setup. A CCD will, again in my opinion, produce better results than a DSLR. Saying that though there are some DSLR imagers producing good results. You normally have people moving from a DSLR to a CCD, and not often vice versa. That should tell you about the quality of CCD data.

Have you looked at the field of view calculators on the net? They will give you a good feel for each combo of scope and your camera. Pick one your happiest with, I feel that image quality difference really is quite insignificant in comparison to other things.

Of course, all just my opinion and I am probably going to be contradicted!!! Such is life!!

[Hitesh]

Well I just went down to wide screen centre in London and had a lovely chat with a fella called Simon, he has convinced me to go with the evostar 120ed, but has also got me intrigued with the new az eq6 mount. Hmmmm this is getting interesting now!!!

[damnut]

Or get both!!. Terrible choice to make, just make sure that your mout will take both. One of my friends has a skyteeII with a Meade 10"sn on one arm and my old 152mm frac on the other to balance it!!

[Donkeiller]

If you are thinking of getting a Megrez 90- check the focuser for functionality.I had two focusers- both U/S. Eventually sent the whole system back to WO and got a refund.

[ollypenrice]

If a SW190 Mak Newt is in perfect fettle it will beat our TEC140, never mind a Skywatcher doublet. But that can be a big 'if.' People who are good with optics and mechanicals get them into perfect fettle but less competent technical people never do and would be better with the 120. The 190 is a big boy, too. The NEQ6 is OK but certainly not overkill for the 190. In the wind it is a real sail.

Personally I wouldn't let myself be seduced by the prettiness of WO scopes. WO have made some of the worst focusers in history. I'd be very hard nosed and go by the optics. The SW 120 will show some blue bloat in imaging. Indeed so will almost any refractor including TEC and Takahashi, but it won't be much.

I would take advice only from practising imagers or people close to practising imagers.

Like Sara I would take the road of greatest probable success since there is already a lot to go wrong in DS imaging. But if you are good technically then the 190 will slightly out perform the refractors and will be faster.

Have you given much thought to focal length? I find a metre to be slightly 'between two stools,' neither wide not yet close up. It sees less action here than shorter and longer. Shorter makes guiding much easier.

Olly

[Hitesh]

Thanks for that olly you make some very good points. I think I'm going to settle for the SW120ed just deciding between the new az eq6 mount or the older neq6 mount. The reason why I opted for this focal length was so that it would be a decent visual setup for when I don't want to do AP.

Thoughts am I going down the wrong path?

[Moonshane]

would something like this with a cf tube be worth thinking about? http://www.firstlightoptics.com/reflectors/skywatcher-quattro-f4-imaging-newtonian.html

obviously you'd need a coma corrector too.

[MartinB]

I have had a SW ED120 for a few years and used it very happily for imaging. Although it can be used with focal reducers I found it performed best at it's native f/l. SW make a good flattener for it but you do have to get the spacing between the reducer and the chip spot on, not as easy as it sounds.

I got a SW MN190 2 or 3 years ago and now wouldn't dream of going back to using the ED120 for imaging. It is so much faster and in my subjective opinion gives better results in terms of contrast, star tightness and absence of halos. I've never compared them side by side and star tightness is very dependent on seeing conditions at the imaging scale. As far as collimation goes, it is possible to go to extraordinary lengths in an attempt to achieve the ultimate in precision. I have to admit I haven't really bothered to get into precision adjustment of the draw tube or the secondary and so on. I use a hotech laser to adjust the primary mirror and this 5 minute job seems to give an excellent out of focus star pattern. Once done it holds it's collimation very well. The field is beautifully flat across an APS size chip unlike an ED120 which definitely needs a flattener. I never did get a field flatness to match the MN190 (as measured by CCDinspector).

The downside of the MN190 is that it is heavy and bulky. For precision imaging it is at the limit on an NEQ6 if there is any breeze about. I use mine inside a dome which gives terrific shelter and my EM200 copes without a problem.

I still use my ED120 for observing, often sticking it on a little Vixen Super Polaris. It is quick and easy to set up and a joy to use. I've only ever once bothered to use the MN190 for observing, it gave great views but give me a refractor every time for ease of set up and use when chasing a quick gap in the clouds. Again though, the MN190's aperture will nearly always reveal more than the ED120.

[ollypenrice]

I take Martin's points without a doubt. What I would really like to see would be a de luxe MN190. Even at twice the price it would be an almighty instrument if it wre really tight on QC. The optical system has to be right. Why we don't see more of this design is a mystery.

Olly

[Jessun]

Have a look in my gallery here on SGL if you like. Almost exclusively reduced SW120ED picures. Spacing seemed easy enough to achieve with my OSC (more options I suppose in combining little extenders than being 'locked in' by what's left over after a filter wheel)

Blue halos do pop out of bright stars, but none too bad.

It covers the APS size CCD nicely with the aid of flats. I did however replace the focuser. At f6.4 it has left the 'slow' segment by a notch but still keeps things easy focus/tilt wise - ie not annoyingly sensitive. (I often leave the focus for several nights).

/Jesper