Takahashi Mewlon 210 - getting going

[kerrylewis]

I’ve

I’ve long coveted a Takahashi Mewlon for a number of reasons:

having owned one Tak I am impressed with the quality and performance, and having read lots of  reviews the performance of the 210 seemed to be just what I wanted  - more aperture than the 100DL but still light enough for my Ioptron mount. I also liked the slightly quirky look of them .

So now I have a Mewlon 210 courtesy of the SGL classifieds but it’s  been a slightly stop/go start.

The scope didn’t have a dovetail but one was easily obtainable from FLO but with no fixing bolts. The manual and all the retail information said that two M6 bolts were needed - not so, the two fixing holes are in fact different sizes; M6 and M5 as it turned out and isn’t it always the case that however many bolts and washers and things you accumulate you never have the right ones? However I eventually got the two bolts of the right size and length (short) and the scope was mounted. It’s in great condition by the way - not a mark.

All I needed now was clear skies and an hour away from comet Neowise.

This eventually happened but the views were disappointing. It was immediately obvious the scope was out of collimation -presumably due to being shipped. Stars showed that characteristic comet-like appearance and when defocussed the central doughnut hole was clearly displaced. In all the comments that I had read concerning the Mewlon design everyone was agreed that collimation could be really problematic but once achieved it would stick.

I tried the daytime collimation method recommended on a couple of forums. This involved looking down the tube and seeing if the reflections of the spider vanes and the vanes themselves line up. They do appear to line up so I am assuming that any adjustment required is fairly small and this is again backed up by the various reports that I’ve read.

So now I’ve got a cheap artificial star (FLO again) and the next step is to try that. The three screws to adjust the secondary do seem very tight but should be easier to tackle in the daytime. Bob’s Knobs are available but a few sites do not recommend them for the Mewlon - at least one in very strong terms so I’ll try the existing ones. I’m not sure if I can achieve the necessary distance in my garden that is needed to use the artificial star but there’s only one way to find out!

Even with less than perfect collimation the views of some old favourites at lower magnification, like the Double Cluster, showed the promise of the scope.  So here goes...

Meanwhile if anyone has experience of collimating this scope I would be glad to see any comments or suggestions.

I’m not sure that I have the distance in my garden that is needed to use the artificial star but there’s only one way to find out!

 

Meanwhile  if anyone has experience of collimating this scope I would be glad to see any comments or suggestions.

 

Edited July 24, 2020 by kerrylewis

[garryblueboy]

Hi Kerry very surprised it’s out of collimation they usually are super tough on travelling did you allow plenty of cool down the Mewlon does require more than most  avoid bobs knobs at all cost the collimation screws are very tight and only require a very small tweak 

[kerrylewis]

Hello Garry

The scope had been out for a while but lack of cooling shouldn’t cause the effects of non collimation should it?

Given all I’ve read I was surprised too but to me if an out of focus star shows an asymmetrical image it means the scope needs collimating 

[garryblueboy]

It does make the coma reports like what your describing when you say a while what are we talking 

Edited July 24, 2020 by garryblueboy

[kerrylewis]

8 minutes ago, garryblueboy said:

It does make the coma reports like what your describing when you say a while what are we talking 

Most of the day - but the weather has been warm of course . But then it was a few hours into the evening before I tried it. If they are that sensitive to temperature then perhaps I’m making the wrong diagnosis 

[garryblueboy]

I found with the two I owned it needed several hours to cool and not to leave it out if it’s warm outside they are sensitive to heat and cool down 

Edited July 24, 2020 by garryblueboy

[kerrylewis]

2 minutes ago, garryblueboy said:

I found with the two I owned it needed several hours to cool and not to leave it out if it’s warm outside they are sensitive to heat and cool down 

That’s very interesting Garry. Obviously I’d rather not mess about with the collimation If it’s not necessary. Now if I had a bigger fridge... 
I will do as you suggest and not leave it out during the day and see how we go.

Thanks 

[garryblueboy]

I put mine out early evening and left the cap off for a couple hours 

[kerrylewis]

Had to break off for dinner or I would lose even more brownie points 😀

So if cooling is such an issue then checking things with an artificial star in the summer daytime seems to be a complete non-starter. 

Before I do anything else it seems clear that I have to try another night's viewing after following the suggested cool down protocol - don't leave the scope out during the day; take the cap off and leave for a while and perhaps use a fan?

Thanks Garry  - I'm learning more about these Mewlons every day!