SW M/N 190mm

[alan potts]

I have yet to have a play with this scope now I have guiding working but it is on my list to try out. I had reasonable results from it unguided as is it a fair bit faster than other scopes I have at F5.26. I was wondering, is there any type of focal reducer available for these scopes or are we stuck at 1000mm. The only reducers I have are flatteners as well and too large.

Alan

[Gina]

I haven't used mine unguided - I use an OAG.  Never considered a focal reducer - I have other scopes with shorter focal length and wider FOV.

Edited May 20, 2019 by Gina

[alan potts]

20 minutes ago, Gina said:

I haven't used mine unguided - I use an OAG.  Never considered a focal reducer - I have other scopes with shorter focal length and wider FOV.

I have too, 800mm apo with a reducer down to 640mm and a couple 420mm 70mm ED, I was just wondering because it is faster than my others.

Alan

[ollypenrice]

It's already F5 and has a front lens. Would it like to be pushed much faster even if you found a reducer? Not sure.

This scope seems to have gone quiet of late but I always thought it a very interesting one with huge potential. They do need to be very well set up but I remember Steve Loughran getting great results with his a good few years ago. I remain surprised that nobody, so far as I know, has made a more mechanically up-market version using the stock optics.

F5's good. Fast but not silly-fussy on depth of field for focus.

Olly

[Saj_37uk]

13 minutes ago, ollypenrice said:

I remain surprised that nobody, so far as I know, has made a more mechanically up-market version using the stock optics

Hey Olly,

I just got my hands on this scope, and am in the process of setting up. Can you elaborate on this statement? What do you mean?

Thanks

[vlaiv]

Just a slight off topic, I wonder how does ES Comet hunter fare in imaging role? Again MN type scope, but 6" F/4.8 with 730mm it is very interesting on paper.

[gorann]

Wim @wimvb just had his first season with MN190. He may have an opinion....

[ollypenrice]

3 hours ago, Saj_37uk said:

Hey Olly,

I just got my hands on this scope, and am in the process of setting up. Can you elaborate on this statement? What do you mean?

Thanks

I was thinking of an improved primary cell, a stiffer and lighter tube, maybe an improved secondary holder and better focuser. People do get the standard ones into good shape but given the number of people marketing improved GSO RCs I'm surprised that the 190 hasn't had the same attention.

Olly

[wimvb]

34 minutes ago, gorann said:

Wim @wimvb just had his first season with MN190. He may have an opinion....

He has.

It's a great scope, but not a newbie item. When I got mine, collimation was off by a mile and a half. And collimating it is a bit harder than an equally fast standard newtonian. But once tamed, it can produce extraordinary results. No CA for one. And unlike a frac + flattener, there are no critical distances behind the focuser. For me, that are two reasons not to add more glass to it. As @Gina wrote, for a shorter fl it's better to use a frac.

I've used mine with a finder guider, an ST80 as guide scope, and an oag. The oag adds weight to the stock focuser, which atm is Skywatchers low profile Crayford. It may bring the load outside the focusers comfort zone (2 kg according to Teleskop Service). I'm still considering swapping the stock focuser for a Baader Steeltrack, but I don't like the prospect of having to drill holes in the OTA. Before I make that decision, I'll try to tighten the focuser draw tube.

Some (potential) users complain about its weight, but it's not heavier than a frac of comparable size.

Regarding Olly's comment about the mechanics, the scope would probably gain more attention if it were made of carbon fibre, and not steel. But as far as I know, the carbon tube would need to be very thick in order to make it stiff enough. And that would necessitate swapping the corrector cell and the primary mirror cell, making the scope more expensive.

It's the corrector plate and the mirror that make up most of the ota's 10 kg.

[Gina]

I've found it to be a great scope - my flagship - though the Esprit 80ED Pro is also truly magnificent for a frac with shorter FL.

[alan potts]

10 minutes ago, wimvb said:

He has.

It's a great scope, but not a newbie item. When I got mine, collimation was off by a mile and a half. And collimating it is a bit harder than an equally fast standard newtonian. But once tamed, it can produce extraordinary results. No CA for one. And unlike a frac + flattener, there are no critical distances behind the focuser. For me, that are two reasons not to add more glass to it. As @Gina wrote, for a shorter fl it's better to use a frac.

I've used mine with a finder guider, an ST80 as guide scope, and an oag. The oag adds weight to the stock focuser, which atm is Skywatchers low profile Crayford. It may bring the load outside the focusers comfort zone (2 kg according to Teleskop Service). I'm still considering swapping the stock focuser for a Baader Steeltrack, but I don't like the prospect of having to drill holes in the OTA. Before I make that decision, I'll try to tighten the focuser draw tube.

Some (potential) users complain about its weight, but it's not heavier than a frac of comparable size.

Regarding Olly's comment about the mechanics, the scope would probably gain more attention if it were made of carbon fibre, and not steel. But as far as I know, the carbon tube would need to be very thick in order to make it stiff enough. And that would necessitate swapping the corrector cell and the primary mirror cell, making the scope more expensive.

It's the corrector plate and the mirror that make up most of the ota's 10 kg.

It is a scope that I saw a very interesting thread on where I a member from either your country or Norway put a Moonlite onto one, I recall reading it was difficult to get the second at the correct angle square on to the draw tube. I can't recall who posted it sadly but it was a very well written thread. I rather get the impression that there is no reducer for this scope but I enjoy it and I would say of all I have it is a favourite even if the focuser is a bit of a weak link.

Alan

[vlaiv]

Out of all available reducers, I think best to try out, but not necessarily purchase straight away (I have no clue how good it will work) - if you have a chance to borrow, that would be the best option - would be CCDT67.

That is based on what I've read about that reducer - it works best with flat field telescopes, or ones with minimal field curvature. I guess MN190 qualifies in this regard. Don't know how good it will work given fast light cone - but that is what trial is for.

Just make sure you have reasonable expectations and do a bit of math - check fully corrected imaging circle of MN190 and account for x0.67 reduction factor. You probably won't be able to use very large sensor with this combination. APS-C when reduced by x0.67 covers diagonal of about 40mm and that is full frame territory. Don't know if MN190 has such a large fully corrected field.

Probably better to try it with sensors up to ~22mm which will cover about 33mm of original circle, or vary spacing of reducer to get smaller reduction factor.

[wimvb]

24 minutes ago, alan potts said:

It is a scope that I saw a very interesting thread on where I a member from either your country or Norway put a Moonlite onto one, I recall reading it was difficult to get the second at the correct angle square on to the draw tube. I can't recall who posted it sadly but it was a very well written thread. I rather get the impression that there is no reducer for this scope but I enjoy it and I would say of all I have it is a favourite even if the focuser is a bit of a weak link.

Alan

That may have been either Jonas Grinde or the late Per Frejvall. Per bought this scope and replaced the focuser, but afaIk, he had trouble collimating the scope afterwards. But since then, Skywatcher have replaced the stock focuser. What I've also learned is that the distance from the corrector plate to the center of the secondary is rather critical. If you remove the focuser, you need to first make sure the scope is collimated. Then you replace the focuser, and align that to the secondary, rather than the other way around.

Last saturday (see the Eurovision thread in the Lounge), I recollimated my scope, making sure to center the seconday under the focuser. Cheshire, laser and barlowed laser now tell me that collimation is perfect. But the proof will be in the pudding. And that won't be served until late August.

[DaveS]

As I recall, Per started a long thread on fettling the 190 mak so the mirror wouldn't slop about, plus some other tweeks. The motivating reason being that mirror slop was affecting his modeling with the 10micron mount.

[wimvb]

2 hours ago, alan potts said:

It is a scope that I saw a very interesting thread on where I a member from either your country or Norway put a Moonlite onto one, I recall reading it was difficult to get the second at the correct angle square on to the draw tube. I can't recall who posted it sadly but it was a very well written thread. I rather get the impression that there is no reducer for this scope but I enjoy it and I would say of all I have it is a favourite even if the focuser is a bit of a weak link.

Alan

This thread from down under may be of interest.

http://www.iceinspace.com.au/forum/showthread.php?t=140193

[JamesF]

And a few threads from the archives that might be worth reading, though I don't know if this includes the one Olly was thinking of:

 

[Gina]

I serviced the stock focuser on my MN190 as it was shot when I bought it secondhand.  That was several years ago and it's been fine since.  I use remote focussing with a stepper motor and timing belt drive.  The focuser is a simple single speed Crawford.  I needed to replace all the bearings and generally clean it up.  I think there's a thread detailing what I did somewhere on here.

[Saj_37uk]

1 hour ago, JamesF said:

And a few threads from the archives that might be worth reading, though I don't know if this includes the one Olly was thinking of:

 

Thank you for this! 😍

[JamesF]

Just now, Saj_37uk said:

Thank you for this! 😍

You're very welcome.  I have an MN190 to set up myself now my observatory is progressing, so it's useful information for me, too.  Mine already has a Moonlight focuser (came that way when I bought it used), so I shall be checking it all out when I'm ready to mount it up.

James

[alan potts]

It was a shock to read Per had passed away, my condolences to all his family and friends, I always found what he had to interesting and believe he was doing some great imaging from less than perfect locations.

It was the thread by Gunnar that I have read at least a couple of times. As for the focuser, mine has the duel speed version and was bought about 5 years ago, the focuser always seemed fine with extension tube and heavy TeleVue eyepieces like the 31mm Nagler and 21mm Ethos, it was also pretty much OK with the Canon DSLR 40D. There was a problem which was in fact grub screws missing from the adapter ring, how 2 of them came out I will never know, maybe not there to start. These missing the weight of the camera cause a tilt.

As for colimation I Hotect laser and found that to be fine, however being unguided images it was hardly put to a severe test of all's well.

I see this scope is rated by many, I have always liked it alot for its visual ability and have split Sirius with is many times, also Antares.

Alan

[Miguel1983]

Interesting stuff here, i've had my eye on the SW and ES Mak Newton scopes for a while now, but there aren't that many around you can read about.

At least on paper these scopes look like they offer the best of two worlds.

Choices choices, there so many great scopes out there 🙈

[alan potts]

18 minutes ago, Miguel1983 said:

Interesting stuff here, i've had my eye on the SW and ES Mak Newton scopes for a while now, but there aren't that many around you can read about.

At least on paper these scopes look like they offer the best of two worlds.

Choices choices, there so many great scopes out there 🙈

From my point of view it is one of the most complete scopes on the market. If visual you can get good wide field views with the right eyepieces and whilst a bit over the top for exit pupil I always use a 35mm Panoptic giving wide view and low magnification. At the over end it handles a 3.5mm Delos of even a bit shorter with magnification of over X300, gives first rate planetary views of Mars when it's close to us. Also judging by what I have seen it is more than capable for imaging in the right hands, not sure those hands belong to me yet though.

Alan

[Saj_37uk]

1 hour ago, alan potts said:

From my point of view it is one of the most complete scopes on the market. If visual you can get good wide field views with the right eyepieces and whilst a bit over the top for exit pupil I always use a 35mm Panoptic giving wide view and low magnification. At the over end it handles a 3.5mm Delos of even a bit shorter with magnification of over X300, gives first rate planetary views of Mars when it's close to us. Also judging by what I have seen it is more than capable for imaging in the right hands, not sure those hands belong to me yet though.

Alan

Haha.. I hope I'm so fortunate to be able to image with it. It's my first scope, but I've almost accumulated everything I need for AP. I do wish it came with a better focuser, the stock focuser really does feel rubbish. 

[Saj_37uk]

13 hours ago, vlaiv said:

Just a slight off topic, I wonder how does ES Comet hunter fare in imaging role? Again MN type scope, but 6" F/4.8 with 730mm it is very interesting on paper.

From my reading around the subject, I read that the ES MN takes a long time to cool down because it's carbon fiber. Not sure how big of a problem that is in the U.K., but certainly in the summer it could be an issue.

[alan potts]

22 minutes ago, Saj_37uk said:

Haha.. I hope I'm so fortunate to be able to image with it. It's my first scope, but I've almost accumulated everything I need for AP. I do wish it came with a better focuser, the stock focuser really does feel rubbish. 

I have a couple of SW scopes and just got the ED finder for guiding, that works nicely. I have always thought SW scopes are nice in the optics department without being Lzos quality, though they seem to let themselves down somewhere on most things. The Mak180mm which I got a few years back has the old style Mak thread and had the most awful visual back I have ever seen, so cheap I binned it then bought a SC thread converter and put my Meade visual back on it. Whilst the focuser on the M/N 190mm is not the worlds best I do feel it sort of does the job for many smaller cameras. It doesn't stop there though with some, as many people want large chip CMOS and CCD's as well as filter wheels and other bolt ons like OAG's, here I could see the wheels coming off