SW M/N 190mm

[ollypenrice]

10 hours ago, DaveS said:

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.

He did, but he also ended up buying a TEC140 instead for this focal length...

(Slight difference in price, though!)

Olly

[Saj_37uk]

9 hours 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:

 

Reading the first link, the prospect of upgrading the focuser sounds very scary. Appreciate you sharing this, it has tempered my aspirations. Luckily the scope I have is reasonably well collimated - I think. When I rotate the Hotech SCA in the barrel, it moves suggesting that either the Hotech is off center or there's something off about the drawtube hole. Nonetheless, trying to KISS atm.

[Saj_37uk]

1 hour ago, alan potts said:

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

I'm in the OAG category, and have fitted the Orion TOAG. I think I'm going to have to inject a shim of somekind to tighten up the drawtube. Let's see how this goes. It's a shame the focuser replacement isn't a simple process.

[alan potts]

1 hour ago, Saj_37uk said:

Reading the first link, the prospect of upgrading the focuser sounds very scary. Appreciate you sharing this, it has tempered my aspirations. Luckily the scope I have is reasonably well collimated - I think. When I rotate the Hotech SCA in the barrel, it moves suggesting that either the Hotech is off center or there's something off about the drawtube hole. Nonetheless, trying to KISS atm.

My comment on the focuser there was at the time comparing it to the Feather Touch on my APO and the Moonlite on my Meade SC, I have had the scope longer than I thought.

[vlaiv]

Only thing that I object MN scopes for imaging is strange flare pattern on bright stars. I've mentioned this before in another thread on this scope (MN190) - not sure which one, but I was assured by other members that this is not universal thing and that images with other MN scopes don't suffer from this.

I guess it has to do with scatter on corrector plate, maybe even dirt (or rather greasy stains) or perhaps dew? For this reason, scope feels (to me) like not quite as sharp as it should be.

This is what I'm talking about:

[Gina]

I don't remember seeing anything like that with mine but it's been some time since I've used it.

[wimvb]

The MN190 has a central obstruction that will scatter/diffract some light, there's no way around that. But it doesn't suffer from diffraction spikes, and with the low focuser, no drawtube shadow in the light path.

[ollypenrice]

5 hours ago, vlaiv said:

Only thing that I object MN scopes for imaging is strange flare pattern on bright stars. I've mentioned this before in another thread on this scope (MN190) - not sure which one, but I was assured by other members that this is not universal thing and that images with other MN scopes don't suffer from this.

I guess it has to do with scatter on corrector plate, maybe even dirt (or rather greasy stains) or perhaps dew? For this reason, scope feels (to me) like not quite as sharp as it should be.

This is what I'm talking about:

I make it a rule not to put my bacon sandwiches on the corrector plates of catadioptrics while letting them cool down...

lly

Edited May 21, 2019 by ollypenrice
Typo

[JamesF]

1 hour ago, ollypenrice said:

I make it a rule not to put my bacon sandwiches on the corrector plates of catadioptrics while letting them cool down...

lly

And that hole in the lens cover isn't a cup holder, either.

James

[Gina]

Mine hasn't got a hole in it.  Maybe because it's an early version.

[alan potts]

I will look out for the defects on the stars as and when I get to use it, weather here is far from good at the moment, though 26 degrees yesterday mid afternoon we had a carpet of white hail covering the garden, thought the windows were coming in.

I no it was unguided work but I can't see any problems like that but maybe the exposure is not long enough, mine was and is such a good visual scope, almost APO good.

Alan

[wimvb]

11 hours ago, Gina said:

Mine hasn't got a hole in it.  Maybe because it's an early version.

Mine neither, and it's the latest version. I drilled a tiny hole in the centre of the cover to avoid a vacuum when removing it. It really is a tight fit.

[wimvb]

On 21/05/2019 at 13:13, vlaiv said:

Only thing that I object MN scopes for imaging is strange flare pattern on bright stars. I've mentioned this before in another thread on this scope (MN190) - not sure which one, but I was assured by other members that this is not universal thing and that images with other MN scopes don't suffer from this.

I guess it has to do with scatter on corrector plate, maybe even dirt (or rather greasy stains) or perhaps dew? For this reason, scope feels (to me) like not quite as sharp as it should be.

This is what I'm talking about:

Those look like diffraction from mirror clips.