I don't find my Mewlon 180 C difficult to collimate. I collimate without a diagonal and follow the instructions in the owners manual. If I'm observing on a night with good seeing and the scope is acclimated stars are textbook airy disks at high power and planet and lunar detail is excellent.
Information on the Takahashi Mewlon 210 and Mewlon 250
Posted 27 July 2021 - 08:09 PM
I have a µ210 also and have wondered the same thing as you, is my Mewlon perfectly collimated?
Teashea, who posted just above you on this thread, has discussed this issue on other posts about his Mewlon and learned from his own trail and error, that sometimes the diagonal is not perfectly aligned perpendicularly to the light cone. It is best to collimate your Mewlon without the diagonal in place, because sometimes the diagonal does not seat perfectly.
I find where I live that atmospheric seeing can be a problem when trying to attain that ultimate perfection in collimation. Ultimately, I decided that my collimation must be pretty good, because I can split the A and B components of Xi Scorpii, which are separated by 0.76" using my 2" star diagonal inside a Moonlite focuser. I have not tried to change the collimation of my µ210. I used to have a µ180c, but could never get the collimation right and I asked TNR, from whom I purchased it, to please check the collimation of my 180c before they shipped it to my door. It arrived mis-collimated and remained that way. Jupiter's moons were little footballs and the planet surface was blurry. I had to send it back within the return time limits, so maybe it would have eventually been fixable if I had more time available to tweak it, but I couldn't take the chance. Ed Ting had a similar problem with his µ180.
I think that if you can split a tight double star close to the predicted Rayleigh limit, which I believe for a 210 mm scope is around 0.67 arcseconds, that your collimation would have to be excellent.
Larry, that was someone else with the Mewlon collimation issue. My Mewlong 180C arrived from Japan in perfect collimation.
Posted 28 July 2021 - 01:53 PM
I found this for a RA eyepiece for polar scope. probably will work with straight through finder.
I have seen this, a company in Germany sells it, but they don't respond to emails. Now Orion Telescopes also sells it. The problem (as I see it) is the inside diameter of the part that goes onto the finder is 30mm. The outside diameter of the finder eyepiece is about 36mm. I'd need some form of adapter from 30mm id to minimum 36mm od to make it work. I was thinking maybe this company could cobble an adapter for me. I don't have experience with them. Has anyone dealt with them?
Posted 28 July 2021 - 04:33 PM
I though there were two versions. A small and a large. As far as I can tell these are repurposed camera right angle viewers.
Posted 11 August 2021 - 05:06 PM
Thanks for the input Larry and Apollo. Between post LASIK spikes and cataracts my vision does not allow me to do any fine visual observations, so I have been relying on camera work for my use and star tests. This has not been a good summer in my area for observations so I am still waiting to move to a better site when time and weather allow. I think that the collimation is reasonable, but when I use a laser collimator there seems to be some opportunity to improve, but not clear how much of an opportunity. Just trying to focus with a computer screen seems to create more variability in results than the collimation may. I have added an electronic focuser which seems to help a lot, and maybe more experience with the software to aid focus may give me some confidence in the collimation.
Posted 24 September 2021 - 08:15 AM
I wanted to contribute to the mother thread. For Mewlon 210 probably 180 regarding the Takahashi Female Dovetail Saddle.
I'm not sure if anyone else feels the same way but when I mount my 210 into the universal saddle on my AZ Mount Pro the whole thing always feels a little...iffy, so I did the following.
If you want to use the Mewlon 210 Takahashi female dovetail saddle (https://takahashi-eu...-for-mewlon-210) the DUP7T- D Series Universal Dovetail Bar. 7″ Long, Takahashi works perfectly and the dovetail saddle slots right into the circle and is very stable so far (although the whole thing is new to me).
Advantages are the telescope can now sit upright on a table and would require some effort to roll over and the female saddle has security screws that work with the stock dovetail.
Disadvantages are its purpose built for Takahashi stuff, and the dovetail + saddle adds some weight and also moves the scope away from the mounts center of gravity a little compared to right into the saddle.
Edited by nva, 24 September 2021 - 03:53 PM.
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