Splitting hairs - Mewlon 210 vs OO 200mm f8

[Stu]

Best title I could think of 😉

As some of you may know, I have a Tak Mewlon 210, which I use on a Vixen GP-DX mount, and have more recently acquired/assembled an 8" Orion Optic f8 dobsonian.

There is a valid question to be asked about whether I need both of these, but I suspect both will stay with me unless that cruel goddess called 'Finance' intervenes.

In the blue corner we have the dob. In terms of setup, it is quite easy, although carrying it down to the bottom of the garden strains my back more than I would like. I tend to use it on my EQ platform so it is a few trips up and down and then a fairly simple alignment before I'm up and running. I have a Rigel Quickfinder and a 60mm RACI on it, so finding things is fairly easy, although I'm not a natural dob user; fracs are much more intuitive to me!

In the red corner is the Mewlon. This is easy to get onto the mount, with just the Skysensor 2000PC controller to connect, plus the SkyFi unit if I want Skysafari for goto. The finder is a rock solid straight through unit, attached to the scope so firmly that you can use it as a carry handle and not affect the alignment! Last night I aligned it using three stars, Vega, Mizar and Arcturus, and it was very accurate all night. The beauty of the setup is that, because the mount is permanently set, I don't need to align each time I can just power up and crack on. The negative here is that the mount is permanently in one place, and the hedge has grown quite high, blocking my views to the East and South East. Hedge trimmers need to be wielded I think!

Collimation is a different story on each scope. The Tak is pretty much set and forget. I did adjust it when I first got it, as case of very small adjustments to the secondary, keeping everything really tightened up so it stays put afterwards. It is pretty good now, but there remains some mirror shift which affects collimation quite a bit. I need to get this looked at, but for now I just set the primary focus where the collimation is accurate and use the Feathertouch focuser from then on. Last night this worked very well and collimation was bang on. 

The Orion f8 is much simpler. Normal story, the secondary once adjusted stays pretty close, just the odd tweak if needed, but normally it's just the primary that needs doing. I have a hotech laser and find this works well, and quickly. Last night I didn't touch it at all as it looked good on a star test.

Usage wise, I tend to favour the dob for quick sessions on one or two targets, and the Mewlon if I want a more varied list using Goto. My skies are pretty average, not great, so I don't really enjoy star hopping from here.

Anyway, back to the title. I do intend to do some more comparisons between the two scopes, and over the last two nights managed to do a little of this. The dob has been very successful so far on the doubles front, delivering Zeta Herc to me finally. It does seem to give nice clean stars (for a dob ) and on Wednesday night I split 16 Vulpeculae after it was highlighted to me by Mr Spock elsewhere. This is a fairly even double with 0.8" separation. I can't totally recall which eyepiece I used, but I think it was the nag zoom, putting me at x266 or more, most likely I was over x300. The seeing wasn't that great, but it was a clear split although with quite alot of glare around the stars. Not sure if this is the mirror which probably needs a clean.

Last night in the Mewlon, I got it first at x403 (NZ at 6mm), but then also at x345 and x268 with 7 and 9mm BGOs, getting tighter obviously. The view seemed cleaner in the Mewlon, much less scatter and very nicely defined airy disk and diffraction ring when the seeing settled.

I also got Delta Cygni which I've not done for a while. The primary was quite flary, but the secondary was very clearly there, good separation between them. They are not crazy close, at 2.8".

When I defocused, I saw what looked like heat flumes still affecting the defocused star. This surprised me after so long, and I'm sure my results would be better if I can get this under control. Will try again tonight, giving a longer cool down time.

As said in the title, splitting hairs really. Both scopes are very capable and very different. The dob was relatively cheap compared with the Tak, but still runs it close, and likely betters it in some areas ie Zeta Herculis has eluded me in the Tak so far.

I will re-visit this thread with any further comparisons I make. Tonight is looking clear and the jet stream is not overhead so should be another good doubles night. Need a list!!

 

[Rob]

Interesting read Stu. I've had similar situations with scope comparisons over the years. It usually ends up with weather/atmosphere conditions presenting a further strength/weakness between them.

I'm sure as time continues you will see this!. Nice read thanks.. added some value to my lunch break

Rob

[Geoff Barnes]

I've been looking forward to this battle ever since you got the OO Dob Stu. There was never going to be much between them in terms of quality of view, both top bracket scopes. Eager to hear more reports to come.  

[John]

Great comparison report Stu

16 Vulpeculae is a great split to get with a 200mm aperture. I believe it's right at the very limit of a top end 6 inch refractor.

 

[Moonshane]

Really well written Stu - I felt I was there with you! 🙂

Looking forward to gazing again once my obs is operational. Might be sort of usable with a dob by Sunday (albeit not finished).

[johninderby]

I was allways impressed with the OO 200 f8 when I had one. A great performer indeed. Saw off my C11 most nights. Why oh why did I ever sell it. 🤦🏻‍♂️

[Moonshane]

This is one reason I have never thought about selling my 1/10PV 6" f11 even though I hardly every use it now I have the 120mm Equinox. It's not worth much and is a great option to have.

[Stu]

8 minutes ago, Moonshane said:

This is one reason I have never thought about selling my 1/10PV 6" f11 even though I hardly every use it now I have the 120mm Equinox. It's not worth much and is a great option to have.

That's very true Shane. The Mewlon is more at risk in some ways if ever the financial wheels fall off (again 🤣🤣) because it's worth more! The dob, being relatively cheap wouldn't gain me much so will hopefully be with me for the long term. Fingers crossed the Mewlon is too though.

[Stu]

1 hour ago, John said:

Great comparison report Stu

16 Vulpeculae is a great split to get with a 200mm aperture. I believe it's right at the very limit of a top end 6 inch refractor.

 

Thanks John. Yes, I was pleased to get it. I think I'm getting more used to chucking higher powers at these doubles! Certainly having tracking helps to steady the view so you don't miss the moments of good seeing.

I think I need to play around with my dob mount. It is quite stiff, particularly when up at higher altitudes, towards the dob hole I guess. It makes centering the target a bit challenging at times.

[Stu]

1 hour ago, Geoff Barnes said:

I've been looking forward to this battle ever since you got the OO Dob Stu. There was never going to be much between them in terms of quality of view, both top bracket scopes. Eager to hear more reports to come.  

Thanks Geoff. Perhaps I will put them both out tonight for a few more comparisons. I guess it will only be the tougher targets where the differences really show up.

[Davey-T]

Good stuff Stu, got a policy of never sell anything here, there was a Mewlon for sale locally to me recently but " luckily " someone beat me to it 😂

Dave