MN190 - Owners feedback - Page 3

glend (Glen) · #41 08-12-2015, 10:33 AM

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 (Bob) · #42 31-01-2016, 03:05 AM

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/...OrionMN190.php

glend (Glen) · #43 31-01-2016, 07:09 AM

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 (Bob) · #44 31-01-2016, 10:41 AM

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 (Glen) · #45 31-01-2016, 10:58 AM

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 (Bob) · #46 03-02-2016, 08:08 AM

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 (Glen) · #47 03-02-2016, 08:18 AM

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 (Bob) · #48 04-02-2016, 01:43 AM

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.