MN190 - Owners feedback

[ribuck]

Hi all,

i recently purchased a 8" RC with a focal reducer and i've fought with it a fair bit to try and get it collimated, until i found out that there is an issue with the secondary mirror holder due to the previous owner stripping the stripping the head on one of the screws.

i'm going to source a new secondary holder, but i'm considering selling it and buying a MN190, as i think deep down it's scope i've always wanted but i've always been worried about the stock focuser.

i've read so many different conflicting reports about the stock focuser being unusable and others say it's fine for for imaging. lot of post's have talked about replacing the focuser, with some saying it's straight forward and others saying that they haven't been able to achieve proper collimation.

i really want to give this scope a try would really appreciate some honest feedback about the scope and it's focuser from people using it for imaging.

Rich.

[glend]

Richard, I have a Skywatcher MN190 and say it is without any issues at all and a great all round scope at its medium focal length and relatively fast optics. If I could only have one scope it would be the MN190. Visually it gives performance close to a large APO at 1/3 the cost, and true colour rendition, undectable coma, and great contrast. It is great for both visual and imaging use and I have not had any problems with the focuser. I'd be cautious about reading people complaining about the focuser and trying to change to Moonlights etc - there were a string of problems tha emerged on some forums when people tried to 'upgrade' the focuser; due to the need to get the focuser near the front of the scope and most of the 'upgrades' don't have suitable adaptors for the MN190. I'd forget about a focuser upgrade unless you can prove it's going to be better, the stock one is that good. Importantly, if you buy one make sure it is the recent model with the dual speed focuser. Early MN190s and it's Orion clone had single speed focusers. Also avoid the early Orions as they had a larger secondary which created a larger central obstruction and reduced contrast compared to the MN190. Imaging wise it is good with a DSLR using the APS-C sensor size and there is no issue with the corners. The focuser easly handled my cold finger Canon 450D with its big heatsink and fan and never slipped. The focuser come with a sliding internal extension tube, so it's unique in that regard I believe, and this comes in really handy for visual use as you don't need to carry an extension tube - the one in the focuser can slide out exactly the length you need for any EP. For imaging you just slide the extension in fully and it's out of the way, and your DSLR or other camrera will focus with some spare intravel.
Remember that any Mak-Newt is going to be heavy compared to say an equivalent sized plain newt, and the MN190 is on the heavy side. Not so heavy that it can't be managed but you will need at least a NEQ6 mount if your planning on imaging with it.

Now to the RC08, which I also have, they are scopes that always need some setup tuning and collimation is a drama unless you have the right tools (like the TAK Collimation Scope) to help. At f8 they require a good mount and usually guiding to get the best out of them. Even though they are lighter than the MN190 I'd still prefer a NEQ6 for imaging with the RC08.

Hope that helps. I will PM you a link to some images that i have taken with both scopes.

Cheers

[pluto]

That's great info Glen.
I don't mean to hijack this thread but I'd be really interested to hear if anyone's imaging with this and a heavy camera and whether the stock focuser is up for lifting over 3kgs (In my case STT8300+FW8G+AO-8T).
This scope has been on my wishlist for ages but I wouldn't want to change the focuser, due to the bad stories which Glen referred to and which I've read also - unless Moonlite or someone has come up with a better way of fitting a new focuser (I haven't googled it in a while)?

[glend]

Hugh, wow that's a heavy rig. My DSLR with cooling system weighs 1.5kg and I've been thinking that was heavy. What size is your sensor? You may have issues if It's is 'full size'. I know the scope is fine with APS-C sensor size but the secondary might be an issue with full-size. vignetting.

[ribuck]

High glen,

Many thanks for your reply and private message. I have the QSI 683 WSG camera with the built in OAG & FilterWheel and i just weighed it, and it's about 1.7kg, so a little heavier than your camera setup, but not by much.

As far as i'm aware the Kaf 8300 chips are fine with the MN190 in terms of imaging circle, it's more the back focus i'm not sure about as i need 50mm which i'm sure will also be fine.

My mount is the EQ8, so no problems with weight, but i am curious how easy these things are to balance.

Also do you know if there is an easy way to motorise the stock focuser ? I do have a spare Lakeside Astro motor and control unit, so might look to see if there is a bracket available.

Rich.

[pluto]

It's a kaf8300, the same as Richard's, so vignetting wouldn't be a problem.
My camera is an SBIG STT8300 with self guiding filterwheel and adaptive optics. I'm surprised how much lighter the QSI 683 combo is than mine (even without the AO) - though I haven't weighed it, I'm just using the manufacturers data - I'll weigh it when I have a chance. I guess SBIG don't do lightweight ;)

[ribuck]

yeah nearly twice the weight at 3kg is a lot of weight, and here was me thinking that my wsg 683 was a bit heavy.

The 2 things that i really can't get my head around are :

1) With this scope being so popular, why haven't they released a new carbon version with a high quality focuser,

2) This scope has been out for a long time now, so why hasn't any of the focuser manufacturers made a specific focuser for this wonderful scope.

I might just bite the bullet and buy one, but i really need to figure out a way to motorise the stock focuser.

Rich.

[glend]

Why not a carbon tube and high quality focuser? Cost! This is not a cheap scope as it stands now. It has a rather unique optical architecture and the only production Mak-Newts in the same ball park are the Intes ones and they are more expensive. If the demand was there then it would be done. There is nothing wrong with the current tube, it does the job. The Intes Mak-Newts are heavier. Yes a carbon tube may save some weight, but in this design cool down won't necessarily be improved, and with widely spaced tube rings the stiffness if fine. I would suggest you buy an Orion fan that fit onto the rear fan mount perfectly, this aids cooldown times (no more than 30 minutes required, and remove the focuser plug so you get flow through).

Contact Ron at Moonlight and ask about an adaptor for the MN190. He is aware of the issue and I believe he may have one by now. The problem with the regular adaptors is that they did not provide enough fore and aft adjustment to allow the focuser to be centred over the corrector moutned secondary. Traditional newt secondaries sit on a spider which has some setback from the front ring, but with the MN190 secondary being mounted on the corrrector there is no spider or setback, so the focuser has to be centered further forward. The secondary also has a centre spot on it which is used to align it at the factory. The secondary centre spot is useful for collimation by the owner as well as your laser and the primary donut spot should be aligned with the secondary centre spot for perfect collimation. Don't ever touch the secondary offset on a MN190, it is factory set and I've found it to be perfect on mine.

PS I know Ron (Moonlight) has an adaptor for the Intes Micro Mak-Newts so the issues would be the same for those. It's worth asking the question. I don't have an issue with the stock focuser, so don't anticipate changing in the near future. I'll let someone else do the developement and testing, and proving it works for imaging before I change mine.:shrug:

[ribuck]

Hi Glen,

I just thought skywatcher might follow the same process they have with their other scopes, where they have upgraded their standard scopes and released them as a new premium model.

Good to know about the secondary, having a donut for centring with a laser if i did want to upgrade.

I'll get the RC repaired by re-tapping the collimation screw holes and give it a fair try and if i still struggle then i'll get the MN190 and accept the shorter focal length.

Rich.

[SkyWatcherMike]

The first MN190's from SkyWatcher had the single speed crayford, which was not great for imaging.
This is still available from the factory, however Tasco import the version with what SkyWatcher call the Linear Power Focuser, this is an improved dual speed crayford.
Same design as the focusers on the F4 Carbon Fibre newts.

[Shiraz]

if that's the case, then it will be OK for imaging with a light load. I fitted the SW focuser on my F4CF Newtonian with one of the original SharpSky kit stepper drives and it worked perfectly for a couple of years with a 1kg imaging train load. The main bearing eventually became a bit "gritty" ( I guess from dirt) so I swapped it out for a Moonlite as a preventative measure. Was still working OK though.

If it is the same design, never unscrew the top ring and then loosen the tension screw - I did and found that there was nothing to stop the draw tube from falling into the OTA. Mine did just that and hit the secondary on the way down - leaving a small ding in the mirror coating :mad2:

[SkyWatcherMike]

Ouch, I'll check that out.
If that's still the case (they've been through a couple revisions) I'll inform the factory.

[glend]

If your talking to the factory better point out the need to improve cleaning and final inspection. The MN190 I bought was absolutely filthy inside the tube, metal shards from screw tapping on the inside of the corrector, some sort of blue stain on the primary, and other issues. It' had obviously not been vacuumed out prior to assembly. I had to take it apart and clean it , something I should not have had to do with a new scope.

[SkyWatcherMike]

That's disappointing to hear.
Glad to pass on feedback.
When did you purchase the scope?

[ribuck]

Hi Mike,

Tell them that people want a Pro + version of the scope with nice carbon tube and a decent focuser :-)

Rich.

[egoleonard]

The MN190 Is an astrograph, and designed for Astrophotography.

One aspect of that configuration, is the secondary mirror is oversize compared to a normal Newtonian. The reason for that, is to ensure all of the light cone returning from the main mirror, is intercepted, and diverted to the focuser, without any vignetting, which simply means no light is lost due to passing by the edge of the secondary mirror. It may well appear odd as you look at the various elements in the system as reflected back to your eye.

Whatever method used to collimate a telescope, the star test is the only one that will reveal anything amiss with the optical alignments.

Try upgrading the focuser, I would expect you also fitted a set of Bobs Knobs to aid easier collimation. If not, it is a desirable thing to do.

[glend]

Do you own a MN190? The secondary is relatively small at 26% central obstruction, the Orion version had a larger secondary. It's fully illuminates APS-C sized sensors without vignetting. Do not try to uograde the focuser as attempts usually fail due to the lack of a suitable adaptor that allows for positioning the focuser tube directly over the secondary centre spot.

[ribuck]

Glen,

The focuser is the bit that worries me and puts me off from buying a MN190. from all of my reading online i have heard conflicting reports, some say they have no issue and others report a complete nightmare due to not being able to align the focuser properly due to limitations in movement.

Rich

[glend]

Well that is correct, in part, the stock focuser has sufficient range of movement, and honestly you should not tamper with the setup as it is aligned at the factory - the problem arises if you bought a Moonlight - the available standard tube adaptor did not provide enough adjustment up and down tube to centre the focuser tube over the secondary centre spot. The stock focuser base has that up and down tube adjustability already. The people that rushed out and bought a Moonlight could not centre it, so then they tried to move the secondary instead which messed everything up.

On behalf of all the people that have asked me about this subject (a Moonlight focuser replacement) I have emailed Ron at Moonlight to ask them to look into making a proper adaptor plate for the MN190.

He has a similiar one already for the Intes Micro Mak-Newts so he should be able to make them easily enough. The difference is the MN190 requires four adjustment holes to slide and the Intes Micro only needs two. You can find photos of the Intes Micro adaptor on the Moonlight website. Below I have attached photos of the Skywatcher MN190 stock focuser that shows the slide hole arrangment.
So when Ron gets back to me I will post up his response here.

[Camelopardalis]

Not owner feedback, so take this with a handful of salt...

...but given the cost of the scope (in UK or Australia) plus any focuser improvements and you have to question how much more you're really going to get out of this scope over a 4" or 5" apo. I understand how the theory works, but in practice...:shrug:

If you want aperture and speed, have you looked at an f/5 imaging newt? (slippery slope, I know, when you factor in coma corrector, etc)

[glend]

Well Dunk, you know I have a 10" f5 imaging newt, and it weighs about the same as the MN190. Even with the Baader Coma Corrector I prefer the images and contrast of the MN190, for it's tack sharp stars and blacker sky - don't ask me why that is technically. Yes a plain 8" f5 newt will be cheaper, and field of view similiar. Mak-Newts have their devotees and I think it comes down to the fact that they are great both visually and imaging, something that an imaging newt can't match in my opinion.

[Camelopardalis]

Hey, I'm sold Glen, if it wasn't for my current kit embargo :lol:

Ease of use is worth paying for IMO

[glend]

Ha ha 'embargo'! I am so glad I am not accountable for justifying my gear. I am held back by $$$.

[Camelopardalis]

Oh me too!!! If I don't sell something, nothing else makes it past the beady eye ;) :lol:

[ribuck]

Hi dunk,

I had considered a 130mm APO, but the sticking point is that they are twice the price, Slower @F7 and have a shorter focal length.

The only way you would get anywhere close to a MN190 is with a 150-180mm apo with a reducer and you are generally look at 5x the cost at a minimum.

Cheers,
Rich.

[Camelopardalis]

For sure you don't get something for nothing :shrug:

Something like a SW Esprit 120 (here (http://www.firstlightoptics.com/esprit-professional-refractors/skywatcher-esprit-120-ed-pro-triplet.html)) is "only" 2x the price of the MN190 and head-to-head I'd be _very_ surprised if the MN could put clean dark pixels between stars where the 120 couldn't.

Speed...yeah you got me :D but it's a little less than an f/stop...

As for focal length, careful choice of pixel sizes and sensitivities should be able to claw that back under most sky conditions, shy of excellent nights. But when was the last time you had one of those? ;)

[ribuck]

Hi Dunk,

I've read some comments from one user who is a very well respected imager who has a TEC140, and he said that the MN190 outperformed it, but the difference was that the TEC just worked without any faffing all the time, i.e no messing with focusers / collimation etc.

In contrast, I have had a second hand GSO 8" RC for about 2 month which hasn't had proper 1st light imaging wise, as i'm still trying to tame the beast collimaiton wise.

So there is a lot to be said for scopes that just work straight out of the box like most APO's.

Rich.

[glend]

I have had a reply from Ron at Moonlight to my email regarding an adaptor for the MN190 that might actually allow a Moonlight focuser to properly align. It was a fairly long reply but I am inserting here the main points Ron made:

"I think the best bet is to add slots to the CR model universal install kit for the MN190. Getting bolts in to the slots may still be accessible even with the focuser mounted on the plate, it is going to be close? So at least with the CR 2" format focuser- it should be possible to slot it, but not the big CRL model.

I would need some measurements ( hole/ slot spacing) just to confirm it. Let me know and I'll machine them."

So it appears that A: he now knows about and recognises that there is a problem with the stock install kit for the CR focuser, B: That there is not a current adaptor that is made specifically for the MN190, and C: He is prepared to modify the stock tube adaptor to allow the focuser to be moved to align but that will only work for the CR focuser and not the larger CRL.

I am considering my next step. Given that Moonlight has not done anything to address this yet, I am inclined to keep going with the stock focuser (which I don't have a problem with, other than some slop in the slide out extension tube - which is not used for imaging anyway).

I may send Ron the hole measurements from my focuser but I don't think I want to lead the development and testing of the Moonlight solution. For those that want to see the focuser slide arrangment just look back at the photos in post #19 below.

[Camelopardalis]

It's all a matter of perspective. You have to consider where the respected imager images from and the average conditions and correlate that with when/where you will practice your art. TEC 140 have a less than stellar reputation for imaging (search for blue halos), pun intended.

IMO there's little to be gained from a scope that can theoretically show you more and to experience that on one or two nights a year. Most of us don't live in the desert but the more temperate coastal fringes where conditions for high resolution astro imaging are less than ideal.

I'm not trying to discourage you from the MN190 btw, as I said I'd like one myself if my circumstances were different :D but there's a lot to be said for ease of use, even if you need to take a few extra subs to compensate.

What you really need is a spread of scopes to test, in parallel, on a bunch of randomly selected nights through the year. Since you list your location as UK, most of those would probably be cloudy anyway ;)

[glend]

Ouch! You got me thinking of Skyfall - what a miserable location. Not everyone is lucky enough to live in Australia hehehe.

[ribuck]

well dunk, you have unwittingly hit the nail on the head. Imaging time is very precious in the uk due to the sucky weather, so having a faster scope F5 scope Vs F7 will make quite a difference.

I'm not so much bothered about the resolution, simply having a nice flat field and decent speed is what i crave.


Glen, i dont have a MN190 so can you send your measurements to Ron at Moonlite at least to get the ball rolling.

Regard,
Rich.

[glend]

Yeah, I guess I'll have to. I will post the measurements up in this thread.

[ribuck]

glen,

if you dont want to, then it's fine, dont worry about it. i'll probably buy the MN190 at some point after xmas, so i can just email Ron with the measurements then.


Rich

[Camelopardalis]

Well, if opportunistic imaging is the name of the game, then yeah that extra stop can make a difference.

If the weather is that much trouble, then it's rare/doubtful you'd benefit from the theoretical resolution of larger aperture. A 5" or _even_ 4" apo should suffice. Fast 4" apos of f/5 or so are not uncommon or outrageously expensive.

Of course, what I'm suggesting is turning the traditional paradigm on its head...angular resolution is achieved by a combination of the telescope's theoretical resolving capabilities and the size of the pixels being suitably matched to discern details. So for wide field for example, relatively large fields of view can be achieved using a full frame DSLR. For smaller objects, one of the new Sony sensors with small pixels but high QE and low read noise would be a really interesting proposal :question:

[ribuck]

unfortunately, opportunistic imaging is all i have available most of the time living in the uk.

[rkayakr]

glen
The Skywatcher sale + Thanksgiving sale was too much for me. I just ordered an MN190. Two questions:
Any tips about cooling? Did you put a fan on yours?
Would you please measure the dovetail bar length? I plan to order some aluminum and make a Losmany D type dovetail befitting this beast. I'll put the Vixen bar on top and attach the guide scope to it.
Bob

[glend]

Hello Bob, Yes I did put a fan on mine. The back fan port is tapped for a standard 92mm fan - I used the Orion one it fits perfectly. I mounted it with nylon screws (M3 I think they were) to minimise vibration - but this has not been a problem. It's good for cool down but really it does not take long to cool down anyway. I put the scope out maybe 30 minutes prior to start and it's equalised by the end of that time. Take the focuser plug out to get airflow through the tube and setup the fan to pull air out of the tube. You can put some filter material in the focuser if your obsessive about dust getting inside. The scope is actually pretty easy to take apart and clean anyway. I don't run the fan while imaging, it has not been necessary and would not be very effective as the focuser is blocked with the camera anyway.
As the the bar length, the long Vixen dovetail is 335mm and I have the same on the top as well, this has proved to work just fine. The cast rings have a flat section (40mm) for the Vixen bar to sit on and are tapped for the screw. I don't know how you would attach a Losmandy style bar (some of which are tube curved, some flat) but you would need to attach it on the 40mm tube ring flat. I would think making a Losmandy style bar would be fairly difficult. Certainly I have never felt I needed one.
Re guidescope attachment, I hate the screw adjuster rings used on many guidescope rings, and I use a Skywatcher Guidescope Mount on my larger scopes because it is wonderful in X & Y axis control with a single knob -but it is heavy and would need the additional Puck to attach it to the top Vixen bar. I have been using a ZWO guidescope (yes with those pesky ring adjusters) mounted to the top bar with a standard camera tripod screw adjuster. It's not the optimal solution but it works and is light.

I have attached some photos for you.

[rkayakr]

Thanks Glen
The dovetail bar is just a piece of bar stock with 30 degree tapered sides and a few holes drilled in it. Thanks for the dimension. I have a piece of 14" x 4" bar so It should be fine.
I also have the ZWO guide scope that I plan to mount to the Vixen bar.
I see from the pix that the bar has cone adjustment. I'll have to add that to mine.
Given your comments I'll wait on the fan.
Bob

[rkayakr]

A post on CN indicates that Starlight Instruments is selling a FeatherTouch adapter for the MN190.

http://www.cloudynights.com/topic/520597-new-sky-watcher-mn190-counter-weight-requirement-others/

Still haven't seen mine and I'm getting conflicting emails from the vender - never a good sign.

[glend]

It's is actually a custom adaptor they made after he had sent them the stock focuser base - Moonlight has offered to do the same if provided with the base hole dimensions. And no I have not done that yet, with Christmas holidays looming and the need to complete my mono dslr project I won't get back to Ron until January. I will try to send him an email but he won't take action without an order for a focuser to justify it and I can't afford that just yet. If someone wants photos and measurements for a Moonlight order I can probably get that to you and you can then email Ron to get It's started.

[glend]

I have attached a series of photos to this post that show the focuser, the adaptor plate, and a drawing with all the measurements that Moonlight, Starlight, etc would need to build an adaptor to correctly position their focuser over the corrector mounted secondary centre spot. Anyone who wants to get an adaptor made is welcome to use these figures, they are as precise as I can make them.

I have emailed all of this information and photos to Ron at Moonlight. When I hear back from him I will report his response here.

[rkayakr]

Last night was mostly clear and it was up to -5C so I gave the MN190 a try with my Canon T3i using the supplied skinny 2" to T2 adapter. I had previously collimated the scope and an initial star test looked good. When I closely examined the first images I freaked out. The stars that were nice, small points in the center were donuts at the edges. I tore everything down and rechecked the collimation that looked still good.
On reattaching the camera I noticed that the camera wobbled slightly in the direction perpendicular to the set screw no matter how much I tightened it. I suspected that the doughnut stars were out of focus due to camera tilt.
I found an old 1 1/4" nosepiece to T2 adapter and put my T2/EOS/camera on that. I inserted the nosepiece into an Antares centering twist lock 1 1/4" to 2" adapter. This time the images had good stars out to the edge.
The next day I found a reference to the issue in Craig Stark's Orion MN190 review.
http://www.stark-labs.com/help/blog/files/OrionMN190.php

[glend]

Bob thanks for the link to Craig Stark's old review. It reviews the old Orion version of this scope, which had the single speed focused and the larger secondary. The Skywatcher MN190, as it is sold today, has a dual speed focused and a smaller secondary. The smaller secondary improves visual contrast and still will fully illuminate an APS-C size sensor. Issues with focuser slop can usually be traced to too much back focus requirement in some camera setups which flex the focuser extension. Most Canon DSLRs will reach focus with just 10mm of back focus and thus the slide out extension is not required, just wind back the knob to adjust focus. Starlight and Moonlight will eventually provide the right adaptor. Re tube flex itself, I have none, but maybe this is because I run a top mounted dovetail bar on the rings to mount my guidescope. If you use a long top and bottom mounted dovetail it seems to adequately support the ota. Being a scope with a corrector and a mirror it is heavy for its size but pretty easy to balance, however as with many mounts having it slightly east side heavy helps with gear engagement and reduce over correction.

[rkayakr]

Glen
My take away was that the 2" to T2 adapter that Skywatcher provides didn't fit well and caused a problem for me. After I replaced it my images had sharp stars out to the corners. I didn't see any problem with the rails, rings or focuser.
I included the Stark article because it also mentioned issues with that adapter.
BTW - I too have a top dovetail rail with a Stellarvue SV60EDS mounted in Stellarvue guide scope adjustable rings as a finder, guide scope and wide field imager mounted on mine.
Bob

[glend]

I did not use that Skywatcher T2 adaptor it is useless, I use the Bintel T-adaptor on my EOS bayonet. It's rock solid.

[rkayakr]

After the usual issues I finally captured some images last night. It was cold and on looking into the scope after imaging I saw a patch of material opposite the focuser. Anyone else have this? Any clue to what it is?

[glend]

Yes, that patch of material is an anti-reflection material (like a flocking), to keep light from reflecting off the side of the tube into the focuser tube and thus into the camera or eye piece. Mine has one as well.
Does your DSLR have a filter mod for full spectrum? You have pretty good 'curtain' capture behind the Horsehead, which is normally mostly Ha. Nice first shot. What are the details of that shot: number of subs, stacking, duration, etc? Or is it a single test sub?

[rkayakr]

Thanks Glen
I'm glad to hear that patch in normal. I'd hate to have to send it back.

The camera is a Gary Honis Baader mod Canon T3i. I was using an Astronomik CLS filter.

60 x 120s shots stacked and simply stretched in ImagesPlus. I'll reprocess later.