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.
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.
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)?
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.
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.
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.
Quote:
Originally Posted by ribuck
High glen,
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.
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
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.
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.
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.
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.
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
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
Ouch, I'll check that out.
If that's still the case (they've been through a couple revisions) I'll inform the factory.
Ouch, I'll check that out.
If that's still the case (they've been through a couple revisions) I'll inform the factory.
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.
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.
That's disappointing to hear.
Glad to pass on feedback.
When did you purchase the scope?
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.
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.
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.
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.
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.
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...
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)
