MN190 factory setup for collimation - help needed

[mattias]

Is there anyone out there that knows what factory and/or correct setup distance it is between the secondary mirror and the correction lens, or between the secondary lens holder and it's counterpart that holds the adjuster screws?

As well as the height of the primary mirror measured towards its holder?

I would like to do a base setup for the scope before I can do a proper collimation, due to the scope has been wrongfully adjusted before I bought it.

[alan potts]

There is I believe one of your countrymen that put a very good thread together on how to change over the focuser to a Moonlite, it was very in depth, I am sure he would know but I can't recall his name, try searching for threads on scope and Moonlite focuser, In the mean time I will try to think of his name.

Alan

[AndyUK]

(Good memory Alan - I thought it was Grinde... but it wasn't - It was Gunnar)

Here's the thread - http://stargazerslounge.com/topic/141012-skywatcher-190mn-fitting-of-a-moonlite-focuser/?hl=%20grinde%20%20moonlite%20%20focuser

[mattias]

Thanks! I will check this with him!

[perfrej]

It is a fantastic scope and a total bummer to collimate. Once there it will give refractor-like images with very high quality, and it does keep collimation rather well.

The thread referenced above is long and I believe there are a few more...

/per

[alan potts]

Per.

Really I find it very easy. I use the very cheap and nasty 2inch to 1.25 inch reducer that came with it and Hoteck laser.

The reducer has slots in it and using the laser in its 1.25 inch outfit slot the laser into place. Place into the focuser and then look through the slots at the seconary, you can see the laser hitting the small circle on the secondary (rather assuming it is in the centre of course), you can view the circle on the main mirror through the front glass plate, mine is spot on for visual I stress but I am sure it would work with a camera as the star test is excellent and cheaper than the catseye system though that is very good too I believe.

Alan

[DaveS]

Having read through Gunnar's thread I'm seriously wondering if the MN190 is the 'scope I want to buy. Not just now, but I may be looking for something with ~1m FL in the near-ish future.

It would appear that ex-works it's a bit of a dog and needs a complete strip-down and rebuild with modifications in order to perform as it should, something that shouldn't have to be done, and another example of Synta's lack of attention to detail.

Aside, I wonder if there would be a market for any firm that took ex-works MN190s and fettled them so they are fit for purpose? Or offered this as a service?

[perfrej]

Alan, it is a total b*tch, let me tell you! But once there it is very good. Of course, my attempts are with a Moonlite focuser (which is so-so) which doesn't really fit the secondary mirror distance.

Dave, this baby needs some tender care, especially if you want to use it with a mount that is modeled. I have changed a bunch of things in the main mirror cell and thrown away the stock focuser (not that the moonlite is that big of an improvement, but still). 

One of the most difficult things to get right is squaring of the focuser. It is really difficult to get right, and then comes the secondary. The mirror placement in the holder varies between examples and there are no published figures for mirror displacement with this particular type of maksutov newton design.

All things considered, I'll take the 190MN over most available reflectors because of its excellent optical quality and the refractor-like style. Not to mention the absence of spike...

/per

[alan potts]

Per,

There is no doubt that without the cheap slotted reducer it would be impossible without something like a Cheshire tool, which I do now have, not that I really know what to do with it on the big Dob. If I were to place one of my Televue reducers in the focuser or try using the 2 inch fitting on the Hotech, no chance. It works for me though but fully understand for what you do it really needs to be right.

Alan