Request help with collimation

Forget the laser, you can easily answer the collimation question by looking at a defocused star image at the center of the field. If the rings are concentric, you are collimated.

I have the MN190, and it is trickier to collimate than a standard newtonian. In stead of springs pushing against the primary, there are two rubber rings on each collimation screw. It's a sign that the mirror cannot be pushed up into the tube. I use a cheshire and collimated laser for collimation. Be sure to NOT alter the position of the secondary down or up the tube. Only use the three collimation screws on the secondary. Use a cheshire to get the secondary correct. It should show the primary concentric. Then (I) use a laser to lign up the primary. Only small adjustments are allowed.
I agree that the focuser can be floppy. Several osers have replaced it by better ones. When you do, get a focuser that fits on the standard base plate.

cs,

Wim

The stock focuser can be used if you push the extension tube all the way in and tighten the thumbscrews as much as possible (by hand). In the long run it’s better to swap it. I replaced mine with a Omegon steel track Crayford focuser, which does not have an extension tube. Any low profile focuser with a 78mm base should fit in the stock base plate. There should be old posts on this forum that cover this.

cs,

Wim

By the way, if you own one of these, what is the point of the removable panel behind the primary? Is this to mount a cooling fan?

Yes. There are holes for screws that fit a 90mm brushless fan, I believe. Otoh, a cooling fan can introduce vibrations. If you set up your mount every session, it would make sense to have a fan on before the session, so the scope cools down faster. But I would turn the fan off during exposures. Also, if you decide to install a fan, add a filter. Otherwise you'll be sucking dust into the tube.
Btw, this thread may be of interest
https://www.iceinspace.com.au/forum/showthread.php?s=e0e283c39b33ccf68a50505b8d81e654&t=140193

Wim

Thanks for your thoughts Wim and, yes, lots of helpful information in that thread!

Anyway, I have no immediate plans to change the focuser. If I can correct the tilt (which I think is the problem) using the secondary, it will probably be fine as it is.

Hello-

I too just took ownership of a new 190MN. Optics are great, once you figure out collimation. I contacted SW Support and they sent me a copy of the manual that came with Orion version of the scope - apparently no one at SW has bothered to write a manual for one of their more expensive scopes....go figure. It explains the collimation process and mechanics CLEARLY. It is quite different from collimating a newt and I am sure some users have screwed up their scopes doing things the shouldn't, like moving the secondary position up or down the tube.

Ok, optically its fantastic. My first image was of the Perseus Double Cluster. The shape and color of the stars was better than any scope I have owned - small refractors, 8-13" newts, 8" cats, etc. IMO, its on par with large semi-premium APO refractors, but I am sure owners of WO and Stellarvue scopes in the 5-7" range would take issue with that statement.

The Bad - the focuser is trash. It reminds me of a cheep department store telescope focuser. The focusers on their Quattro scopes are far better, but I'm not a fan of those for heavy imaging trains either. I just dont get why they chose this focuser to put on a scope they market as an "imaging powerhouse." I have been forced to use a one-shot color camera b/c it won't support a mono setup with OAG and filter wheel without introducing a massive amount of tilt and thus throwing off that collimation you worked so hard to achieve. I just got delivery of Moonlite focuser. No motor (I will use a ZWO EAF), a rotating collar for framing. The tube is 68mm diameter, so I got a 68mm to 48mm adapter that threads into the drawtube and into the imaging train - no thumbscrews or compression rings holding things together. I plan to get it installed and tested in the coming days. My hope and expectation is that this will be the final puzzle piece that makes this a "premium" imaging solution (at least for my budget).

Matt, thank you. Very helpful.

I have had the same thoughts and experience.  The poor quality focuser seems to completely defeat the point of this design. I'd happily pay a few hundred dollars extra (on top of the $2k) to avoid all of this unnecessary frustration. Also, as you say, their other scopes are better from that point of view. I own a couple of S-W designs and they are essentially perfect given their price point. And no instructions?? 

But, otherwise, yes the optics seem great. 

I would be interested to hear if your solution has worked. In the meantime I have been experimenting with a ZWO tilter per Coenie's suggestion. 

Coenie, thanks so much for the additional info. Also for letting me know about tilters. I had no idea they even existed. Was able to buy one and have been experimenting. I think I'm making progress but this sill requires a lot of patience.  You can please take a look at an early iteration below. I think it is an improvement over the first image I posted (the intelligent thing would have been to do the same target, but of course I forgot to do that). Still has problems but hopefully I'm getting closer.  I only hope that the tilt does not have to be adjusted depending on the orientation of the scope, etc. If not, then I think I'll be ok with this solution. One thing which doesn't help is that I've also recently started to use the ASIAIR. It is very good for some things but not so convenient for online feedback and measurements. I assume to run the software you mention I'll have to dig out the laptop. Maybe I should do that and reduce the guesswork. 

Anyway thanks again both. 

Uncalibrated with a screen stretch:


I processed this image a little bit, BlurXTerminator being most relevant. That helps. Not sure if I should be satisfied at this point: carry on tinkering, or get back to actual imaging.