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New Mewlon 180C ?

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#51 plyscope

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Posted 03 November 2016 - 12:09 AM

The scopes maximum field of view will be determined by the focal length. In this case the aperture 180mm multiplied by the focal ratio of f/d 12 equals a focal length of 2160mm.

 

Now if you use a 2" eyepiece with the max field stop value generally available of 46mm (55 plossl or 41 Panoptic etc.) then the actual field of view will be 46/2160 multiplied by 57.3 equals 1.22 degrees.

 

For a 1.25" eyepiece the maximum field stop is about 27mm (32 plossl or 24 Panoptic etc) so the calculation becomes 27/2160 multiplied by 57.3 equals 0.71 degrees.

 

With regards to the restriction of the baffle tube this will not affect the FOV other than possible slight light loss (vignetting) at the edges of the FOV. This minor loss of light at the edges is generally not visible to the human eye and will not be a problem for visual use.

 

The Mewlon is designed for high magnification but will still serve well at lower mags. Takahashi are releasing a new 40mm LE eyepiece which will give a magnification of 54x with an exit pupil of 3.33mm and a field of view of approx. 0.95 degrees.


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#52 vkx86

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Posted 03 November 2016 - 12:27 AM

Thanks for explanation, plyscope!
I mistakenly thinked that rear baffle opening will act as field stop.

#53 Marcsabb

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Posted 03 November 2016 - 03:24 AM

 

...from a quick visual inspection, the rear port in the primary cell is a bit larger than a 2" barrel...

...I can confirm that the fully illuminated image circle is 16mm for the 180...

Larger than 2"? You maybe mean larger than 1.25"?

From that Mewlon-180C photo (I don't think that was changed from your Mewlon-180B) it looks like it is maybe a bit larger than 1.25" but smaller than 2":

 

m180cb.jpg

 

I don't know how to convert fully illuminated circle to scope's max FOV (is that possible?). I want to calculate scope's max FOV by restricting barrel - looks that in Mewlon's case it's primary mirror baffle rear opening (if it larger than 1.25").

 

The opening is larger that it seems in picture. The Mewlon visual back is also quite large compared to those commonly employed for 6-8-10" SCTs. When I go home I'll try to post a comparison pic.

 

At any rate, there is a formula that correlates focal length and the image circle with FOV; it's commonly employed for telephoto lenses to  calculate FOV in relation also to the crop factor (full frame=43mm image circle). The formula is:

 

FOV = 2 arctan (D / (2 FL)) where D is the image circle (or diagonal, in case of sensor/film) and FL is the focal length.

 

Please also note that the documentation I have speaks of 'fully illuminated image circle', so possibly the circle is actually larger than stated, but with some obvious illumination fall off and vignetting. I never bothered to check as I use the Mewlon for planetary work, with small sensor devices or with high magnification eyepieces, so I'm actually using only the center portion of the image circle. 


Edited by Marcsabb, 03 November 2016 - 03:34 AM.

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#54 Marcsabb

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Posted 03 November 2016 - 02:49 PM

As promised, here's a picture of the Mewlon 180 visual back compared to Celestron 1.25" visual back for 5" - 11" SCTs. I believe it's a bit oversized for the 180 but it is shared with its larger brothers which have larger image circles.

Attached Thumbnails

  • _DSC0096 copy.jpg

Edited by Marcsabb, 03 November 2016 - 02:53 PM.

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#55 The Ardent

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Posted 03 November 2016 - 03:02 PM

Some thoughts:
The finder is not an issue since this will be a 95% a Jupiter/ Moon binoviewing scope. The finder has more utility as a carry handle. For deep sky star hopping I prefer a RACI finder.

A Telrad will be added , perhaps two bases 120 degrees apart for dual alt-az/ GEM utility, to be determined by length of viewing session.

The Baader Clicklock and Mewlon adapter will be ordered.

Bobs Knobs ordered already.

Biggest question, will the Mewlon 180 outperform the FC-100D for binoviewing planets/ moon? On paper yes, in real life ???
The refractor wins for low power rich field viewing, I know this already.

The waiting .....ouch!
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#56 bottlecrusher

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Posted 03 November 2016 - 03:23 PM

Some thoughts:
The finder is not an issue since this will be a 95% a Jupiter/ Moon binoviewing scope. The finder has more utility as a carry handle. For deep sky star hopping I prefer a RACI finder.

A Telrad will be added , perhaps two bases 120 degrees apart for dual alt-az/ GEM utility, to be determined by length of viewing session.

The Baader Clicklock and Mewlon adapter will be ordered.

Bobs Knobs ordered already.

Biggest question, will the Mewlon 180 outperform the FC-100D for binoviewing planets/ moon? On paper yes, in real life ???
The refractor wins for low power rich field viewing, I know this already.

The waiting .....ouch!

I think it would be a big mistake to put Bob's Knobs on this scope.  Tak knows what they are doing and this scope will arrive close to collimation and will not lose collimation easily.  


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#57 The Ardent

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Posted 03 November 2016 - 03:31 PM

Thanks for the advise. Pleas post a pic of your Mewlons's collimation screws so I have an idea of what I'm dealing with.
Thanks![/quote]
I think it would be a big mistake to put Bob's Knobs on this scope. Tak knows what they are doing and this scope will arrive close to collimation and will not lose collimation easily. [/quote]
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#58 ryderc1

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Posted 03 November 2016 - 03:31 PM

Some thoughts:
The finder is not an issue since this will be a 95% a Jupiter/ Moon binoviewing scope. The finder has more utility as a carry handle. For deep sky star hopping I prefer a RACI finder.

A Telrad will be added , perhaps two bases 120 degrees apart for dual alt-az/ GEM utility, to be determined by length of viewing session.

The Baader Clicklock and Mewlon adapter will be ordered.

Bobs Knobs ordered already.

Biggest question, will the Mewlon 180 outperform the FC-100D for binoviewing planets/ moon? On paper yes, in real life ???
The refractor wins for low power rich field viewing, I know this already.

The waiting .....ouch!

You may want to re-think the Bob's Knobs. The Tak's secondary collimation screws are very tight and the Bob's Knobs tend to loosen, with a resulting loss of collimation. I found that my M-180 held collimation extremely well once I removed the Bob's Knobs and replaced them with the original Tak screws.

 

As for the planets and the Moon, the M-180 left my FS-102 (a terrific scope) in the dust on nights of good seeing.


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#59 The Ardent

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Posted 03 November 2016 - 03:41 PM

The former Mr Takahashi here had a Mewlon 210 that did the same thing to his TSA102. That is why I'm assuming the mantle of Mr Tak in my area. Imitation is the sincerest form of flattery.

Thanks for the counsel.
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#60 Traveler

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Posted 17 November 2016 - 03:34 PM

Nice. Congrats!...and we will see your first light report (of course) in while... :grin:


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#61 Bill Barlow

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Posted 17 November 2016 - 08:41 PM

Some thoughts:
The finder is not an issue since this will be a 95% a Jupiter/ Moon binoviewing scope. The finder has more utility as a carry handle. For deep sky star hopping I prefer a RACI finder.

A Telrad will be added , perhaps two bases 120 degrees apart for dual alt-az/ GEM utility, to be determined by length of viewing session.

The Baader Clicklock and Mewlon adapter will be ordered.

Bobs Knobs ordered already.

Biggest question, will the Mewlon 180 outperform the FC-100D for binoviewing planets/ moon? On paper yes, in real life ???
The refractor wins for low power rich field viewing, I know this already.

The waiting .....ouch!

I would be curious on how the FC100D performs against the Mewlon 180.   I would think the Mewlon should be the obvious winner, but seeing is believing.

 

Bill


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#62 vkx86

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Posted 18 November 2016 - 01:48 AM

Baby-Mewlon first-light report

 

I'm approximately 10 years into hobby, I'm 99% Lunar and planetary (Jupiter and Saturn) "balcony-type" urban observer.
I started the hobby with SW mini-dob 130mm, swapped it to SW ED80 on AZ-4 about half a year ago.
ED80 with stock dielectric diagonal + Baader Hyperion zoom with Hyperion zoom barlow serves my observing needs very well.

 

My motivation for Mewlon-180 is a desire for more resolving power in compact package with sharp optics on those nights of stable seeing – there are quite a lot of them at my location, especially starting from late spring till late autumn.

 

Scope arrived from Japan intact and in pristine condition, to my mental tranquility :)

 

I put it on AZ-4 with aluminum tripod – for my biggest surprise, that combo carries Baby-Mewlon quite well - I planned mount/tripod upgrade later, after confirming that scope survived the shipping and is problems-free.

 

Finder was aligned spot-on from the box.
It's surprisingly bright, pain-in-the-neck little one, that does its job of pointing the scope on the Moon/planets in the city very well. My SW 7x50 RA finder goes deeper, but for my intended scope's usage, I will not bother with alternate solutions. Flashing the light into scope's tube towards the main mirror I can see 2 screws that fix the finder leg to the cast ring from inside.

 

Tested the collimation on distant street lamp - it appeared spot-on, to be confirmed later on Rigel at up to 607X power. Yes, the scope had traveled half a globe, passed customs and courier's handling and kept the collimation - I'm impressed, since I was mentally ready to start the night from collimating the scope, spending unknown amount of time on that, since I never collimated Cassegrain scope.

 

I ran focus knob couple of times all way in/out to distribute the grease evenly.
Focus shift in my specimen appears to be very small, but I think I need more stable mount to fully evaluate it.

 

I used SW dielectric 2" diagonal that came with ED80 and Baader Hyperion zoom Mk3 with Hyperion Zoom barlow.
The seeing was above average, with moments of very stable seeing, main target was the Moon.
I was concerned that 180mm aperture will be affected by the seeing too much, but that wasn't true – quick-swapping 2 scopes, at comparable magnifications (~90X to ~150X) ED80 rendered more stable image, yet Mewlon left the little frac in dust for details, especially in moments when turbulence was at minimum – a jaw-dropping experience. The whole new level of Moon's surface details was opened for me – I had observed that night Rimae Atlas and other small details not visible in 80mm frac, that I need to dig into Virtual Moon Atlas a lot deeper to name the features I saw with Mewlon.
I pushed the scope up to 607X on Atlas and in numbered moments of stable seeing it delivered sharp image. That's 0.3mm exit pupil, I didn't expected such results at all.

 

I had long ago re-greased my AZ-4 it with bike grease on aluminum axels with couple of drops of Joe's Eco-Nano bike chain lube on Teflon-to-aluminum/Teflon-to-ebony star surfaces. That combo appears to be usable with Mewlon for altitude range of 30-65 degrees (my observing place limits) and mags up to 270X same way as I use it with ED80 for mags up to 169X, both for manual tracking and for focusing. Altitude axis is a bit stiff, but I intend to tinker with grease choice on alt axis a bit more (I will get EQ5 a bit later).

 

I wish to thank all respectable members of that forum, who shared the info on that scope with me.


Edited by vkx86, 18 November 2016 - 02:22 AM.

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#63 Marcsabb

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Posted 18 November 2016 - 03:33 AM

So I take you're happy with your new purchase?  :)

 

'Spacewalks' on the moon with the Mewlon are worth alone the price of the scope. The edges of the craters, the contrast of the shadows projected on the surface: maybe I'm exaggerating but I think the small 180 can be in the same league of any other brand 10" reflector/compound scope despite the mirror size difference.

 

I'm surprised the Az-4 can handle the 180 so well. With accessories it should be around 6.5-7kg. Is the tripod stable enough?


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#64 vkx86

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Posted 18 November 2016 - 06:46 AM

Yes, I'm happy with my Baby-Mu, despite I went against your recommendations ;)

- I have to drive couple of hours into the desert for dark skies, also the turbulence there is usually quite strong, so it's not a place for high-power planetary observing. Add to that logistics - you will not go to the desert alone...so my destiny as amateur observer is the Moon and the planets in my very LP skies.

 

The Moon in Mewlon definitely worth the scope's price, I'm still digesting the views from last night.

 

Baby-Mu on AZ-4 is a big surprise, I confess.
I was ready to be surprised by Mewlon's premium mirrors, but regrading AZ-4 I planned to use it for basic checks/collimation on distant street lamps only.

 

I have some explanations for that surprising AZ-4 behavior:
Baby-Mu is very well balanced scope, it's better balanced than my ED80.
The total weight of Baby-Mu with diagonal and Hyperion zoom is around 7050 grams.
Baby-Mu is very close to ED80 size-wise, just heavier (my ED80 fully equipped is ~4450 grams).
Tripod legs are extended to less than half of their extension range.

Vibration damping for 30-45 degrees altitude at 200X was around a second.
50-60 degrees around 2 seconds.

At 300X-400X around 3-4 seconds.
Holding the AZ-4 panning handle gently in 3 fingers while tracking/focusing cuts vibration time in half.

Also, I had half a year to practice tracking/focusing on AZ-4 with ED80 at 169X :)


Edited by vkx86, 18 November 2016 - 07:04 AM.

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#65 Marcsabb

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Posted 18 November 2016 - 07:35 AM

(...)

Baby-Mu is very well balanced scope, it's better balanced than my ED80.

 

Despite the size the tube is very light. The secondary is also small, there is no front lens like SCT or MAKs, so most of the weight is concentrated around the primary cell which is placed directly over the short dovetail rail. This reduces unwanted torques when slewing and of course it reduces the inertia and vibrations. 

Attached Thumbnails

  • AzProMewlon.jpg

Edited by Marcsabb, 18 November 2016 - 07:36 AM.

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#66 vkx86

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Posted 18 November 2016 - 10:32 AM

...concentrated around the primary cell which is placed directly over the short dovetail rail. This reduces unwanted torques when slewing and of course it reduces the inertia and vibrations. 

Makes sense.

 

In hope for a good weather and seeing tonight I'd put thick copper grease into AZ-4 altitude aluminium shaft. 

Looks promising - now alt axis movement is as smooth as az axis movement. 

The convenience of manual alt-az is great, I can move that setup with left hand holding tripod's head from below and holding the scope with right hand from it's "parking place" - it's around 14 kg.

 

BTW, where is your Baby-Mu number plate? Is that legal at your skies to use it without? :confused:  ;)


Edited by vkx86, 18 November 2016 - 10:35 AM.

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#67 Marcsabb

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Posted 18 November 2016 - 03:25 PM

 

(...)

BTW, where is your Baby-Mu number plate? Is that legal at your skies to use it without? :confused:  ;)

 

in a plastig bag. :p I wrote earlier that it's a second hand purchase; I recently disassembled it for a complete cleanup (while I waited for the new mount to arrive) and that picture was the first light after I reassembled it. Some non essential parts are not yet in place. Mewlon serial no. 005013 is still kicking ****! (but a recoating in a year or two wouldn't hurt...)


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#68 vkx86

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Posted 18 November 2016 - 08:09 PM

Baby-Mu second observing session

 

That night the turbulence was a bit lower, despite occasional high-alt clouds.

 

The only target was the Moon, the perfect source of infinite fine details for any scope, seeing allowing.

 

Gentlemen, I ask you to filter out my excitement of new toy purchase and my total lack of previous experience in premium optics, but I have to say that Baby-Mu had blown my socks off, my brain is still "in re-wiring phase" to adapt to the details that Baby-Mu pumps into my retina, even at 90X…that scope is razor-sharp. Hyperion Zoom Mk.3 compliment Baby-Mu's mirror very well with with it's focal range to adjust quickly to seeing conditions. It's appears to be a killer scope for medium-high power Lunar work, in my opinion.

 

Attempted again to evaluate focus shift in my specimen – to my eye it appears to be approximately as big a Grove crater diameter at 270X.

 

Copper grease in AZ-4 alt shaft was quite a good choice – alt movement is a lot better now.
I put my right-hand elbow on the table for support and can attest that the Baby-Mu on tweak-greased AZ-4 is a good-working combo for mags up to 400X, see the shot of my observing place.
I'm not sure I'll get the EQ5 to put my Baby-Mu on it…

 

 

 

Attached Thumbnails

  • b-mu-in-work-1.jpg

Edited by vkx86, 18 November 2016 - 08:10 PM.

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#69 bobhen

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Posted 19 November 2016 - 09:03 AM

Here is a quote about my Mewlon 210 and lunar observing from my post number 14 over on the “Information on the Takahashi Mewlon 210 and Mewlon 250” thread.

 

“Here in PA seeing limits high power viewing (that’s why I also have the TSA 120) but on above average nights the Mewlon 210 just kills on the moon delivering a view that is solid and sharply defined and unlike the view compared to SCTs, which have more light spray that can soften very fine details.”

 

The deep sky views will also delight you with the Mewlon’s sharp stars and high contrast optics.

 

Enjoy.

 

Bob


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#70 plyscope

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Posted 21 November 2016 - 08:15 PM

It looks like the Mewlon 180C is going to be relatively popular. The Australian Takahashi agent has pre-orders for 10 of them already. It is not available here until January. 

 

http://www.astronomy..._mewlon180c.htm



#71 pwd

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Posted 19 December 2016 - 11:48 PM

I was in TNR/LandSea&Sky this afternoon picking up an older Mewlon 180 that I had asked Fred Garcia
to go over. I noticed that they had a new Mewlon 180C on the showroom floor, mounted and ready for
sale at $2,350.

 

pwd


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#72 vkx86

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Posted 22 December 2016 - 12:50 AM

Got Baader T2 prism diagonal with helical micro-focuser eyepiece clamp (Baader #2456005, (#2458105 & #2458125)

On bright stars and especially Jupiter there is noticeably less light scatter than SW mirror diagonal, diffraction spikes on Jupiter are less visible than in SW mirror diagonal (now they are barely visible), Moon looks a bit sharper too.

Helical micro-focuser (although quite stiff one) is very handy too.

That prism diagonal is a very good match to the scope, in my opinion.


Edited by vkx86, 22 December 2016 - 01:00 AM.


#73 Marcsabb

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Posted 22 December 2016 - 02:35 AM

Got Baader T2 prism diagonal with helical micro-focuser eyepiece clamp (Baader #2456005, (#2458105 & #2458125)

On bright stars and especially Jupiter there is noticeably less light scatter than SW mirror diagonal, diffraction spikes on Jupiter are less visible than in SW mirror diagonal (now they are barely visible), Moon looks a bit sharper too.

Helical micro-focuser (although quite stiff one) is very handy too.

That prism diagonal is a very good match to the scope, in my opinion.

I've had that kit too. The helical focuser is really smooth and excellent for fine tuning. I sold the diagonal and got me the one with the Zeiss prism (#2456095). It's even better than the #2456005 and it also has the advantage of having a slightly larger unobstructed image circle (35mm) so it can be used with 2" or T2 accessories despite being no larger than a typical 1.25" prism diagonal. 


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#74 vkx86

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Posted 22 December 2016 - 10:07 AM

 

It's even better than the #2456005 and it also has the advantage of having a slightly larger unobstructed image circle (35mm) so it can be used with 2" or T2 accessories despite being no larger than a typical 1.25" prism diagonal. 

 

I considered that Zeiss glass too, but based on comparison between these two I read online and my experience with Hi-Fi gear (there is some similarity between astro and Hi-Fi gear price levels), concluded that it's not worth for me that more than 2X price difference, so I went for "regular" #2456005 prism + Fujuyama ortho 12.5mm.

Now, since I had put Baby-Mu on EQ5 SynScan, I can investigate how ortho compares to Hyperion zoom in 1mm exit pupil range.


Edited by vkx86, 22 December 2016 - 11:03 AM.

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#75 The Ardent

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Posted 19 January 2017 - 06:13 PM

Still waiting......


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