Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Am I nuts to think of Mewlon 180 when I already have a 4” Tak APO (and a bigger SCT)?

  • Please log in to reply
94 replies to this topic

#76 dr.who

dr.who

    Voyager 1

  • *****
  • Administrators
  • Posts: 13757
  • Joined: 05 Jan 2012

Posted 19 April 2019 - 10:50 PM

But what do I do with the HD145??
I would hate to sell it but .....


No one is saying you have to. Why not keep all of them?

#77 NHRob

NHRob

    Cosmos

  • *****
  • Posts: 7977
  • Joined: 27 Aug 2004
  • Loc: Southern Cloud-Hampshire

Posted 20 April 2019 - 06:04 AM

Let me know if you do.

Hi Phil,

  I actually have no plan to sell it.  That was just a thought experiment.

In fact as grow older into an old geezer I could easily see the HD145 being my lone keeper scope.


  • Phil Cowell likes this

#78 bdg

bdg

    Viking 1

  • *****
  • Posts: 737
  • Joined: 31 Oct 2013

Posted 01 June 2019 - 11:56 PM

OP -  what did you decide? 



#79 Axunator

Axunator

    Viking 1

  • *****
  • topic starter
  • Posts: 594
  • Joined: 23 May 2015
  • Loc: Helsinki, Finland

Posted 02 June 2019 - 12:40 AM

OP - what did you decide?


To get the M180, but it will have to wait until the summer has passed - getting a new scope and not being able to properly test and use it for months due to the lack of darkness (I live at 60 deg north) would drive me nuts.

Edited by Axunator, 02 June 2019 - 01:02 AM.

  • bdg likes this

#80 jgraham

jgraham

    ISS

  • *****
  • Posts: 20175
  • Joined: 02 Dec 2004
  • Loc: Miami Valley Astronomical Society

Posted 02 June 2019 - 07:52 AM

+1

I have found that a refractor compares well with a Cat that is 2" larger, so adding a quality 8" Cat to a 4" Apo should make for a nice companion scope.

Enjoy!
  • terraclarke and Axunator like this

#81 Auburn80

Auburn80

    Viking 1

  • *****
  • Posts: 886
  • Joined: 01 Apr 2013

Posted 04 June 2019 - 09:54 AM

+1

I have found that a refractor compares well with a Cat that is 2" larger, so adding a quality 8" Cat to a 4" Apo should make for a nice companion scope.

Enjoy!

I've read this many times and at first glance, makes sense. But upon further review . . . .
If the primary purpose of the 4" is for nice wide fields, wouldn't at 6" f4.5 newt be just about as wide and go much deeper than the 4"? And with an 8" sct, given the long FL, one would want best planetary performance in good seeing right? Of course, it IS 8" so should have good DS performance.
Sorry if this goes a bit OT. Delve a little deeper here if you please.
Also, I have been thinking about an M180 to replace my C8 and AT115 and maybe C6. Except for the difference in quality (a major factor for sure) would the C8 be a good approximation to the 180?

Thanks!

Clark

Edited by Auburn80, 04 June 2019 - 09:58 AM.


#82 Axunator

Axunator

    Viking 1

  • *****
  • topic starter
  • Posts: 594
  • Joined: 23 May 2015
  • Loc: Helsinki, Finland

Posted 04 June 2019 - 10:26 AM

I've read this many times and at first glance, makes sense. But upon further review . . . .
If the primary purpose of the 4" is for nice wide fields, wouldn't at 6" f4.5 newt be just about as wide and go much deeper than the 4"? And with an 8" sct, given the long FL, one would want best planetary performance in good seeing right? Of course, it IS 8" so should have good DS performance.
Sorry if this goes a bit OT. Delve a little deeper here if you please.
Also, I have been thinking about an M180 to replace my C8 and AT115 and maybe C6. Except for the difference in quality (a major factor for sure) would the C8 be a good approximation to the 180?

Thanks!

Clark

I very, very much doubt that 6” f4.5 Newt would do anything better than an excellent 4” f7.4 APO. It *might* resolve slightly tighter doubles, provided the optical quality is excellent, but that’s it.

Reasons:
- Secondary in a small, fast Newt must be relatively large to provide reasonably wide illuminated field, robbing contrast (relevant for high-mag planetary observing) and decreasing light throughput (compared to an unobstructed scope)
-The secondary would have to be really large to illuminate well as wide a field as APO does (4” f7.4 has a 3.6 degree true field with 41 Pan)

As for M180 vs C8 comparison, I don’t want to bash SCTs (hey, I’m a happy user of C9.25 myself, used mainly for DSOs), but let’s just say that I consider my chances of getting really good on-axis optical performance better with a random sample of Mewlon 180 than with a random sample of C8. Whether it’s worth the price differential is a personal matter.

The chances for excellent optical quality in a compact scope would probably be best with a high-end 7”-8” Mak, but weight, price and poor availability make that a much less desirable option for my intended purpose.

High-end 8-10” longer-focus (f6-7) Newt would undoubtedly be excellent lunar/planetary scope, but, alas, way too large for my current circumstances.

Edited by Axunator, 04 June 2019 - 10:37 AM.


#83 bdg

bdg

    Viking 1

  • *****
  • Posts: 737
  • Joined: 31 Oct 2013

Posted 04 June 2019 - 10:47 AM

I very, very much doubt that 6” f4.5 Newt would do anything better than an excellent 4” f7.4 APO. It *might* resolve slightly tighter doubles, provided the optical quality is excellent, but that’s it.

Reasons:
- Secondary in a small, fast Newt must be relatively large to provide reasonably wide illuminated field, robbing contrast (relevant for high-mag planetary observing) and decreasing light throughput (compared to an unobstructed scope)
-The secondary would have to be really large to illuminate well as wide a field as APO does (4” f7.4 has a 3.6 degree true field with 41 Pan)

As for M180 vs C8 comparison, I don’t want to bash SCTs (hey, I’m a happy user of C9.25 myself, used mainly for DSOs), but let’s just say that I consider my chances of getting really good on-axis optical performance better with a random sample of Mewlon 180 than with a random sample of C8. Whether it’s worth the price differential is a personal matter.

The chances for excellent optical quality in a compact scope would probably be best with a high-end 7”-8” Mak, but weight, price and poor availability make that a much less desirable option for my intended purpose.

High-end 8-10” longer-focus (f6-7) Newt would undoubtedly be excellent lunar/planetary scope, but, alas, way too large for my current circumstances.

how do you plan to outfit your 180C? e.g. Binoviewer, reducer etc.



#84 Auburn80

Auburn80

    Viking 1

  • *****
  • Posts: 886
  • Joined: 01 Apr 2013

Posted 04 June 2019 - 11:00 AM

Thanks Axunator. I love a good debate!
Re: the 6"; its forte would be wide field, not planetary. That's what the Mewlon would be for. Now if ones priority is sharp optics in a small package then the frac wins no doubt. It can do planetary nicely for its aperture but would it out do the Mewlon? Probably not. So that narrows it to size and wide fields. Agreed, the 6" newt probably couldn't go as low/wide as the frac without getting messy. Go too low and the central obstruction messes things up. And a 6" f4.5 would be more cumbersome and inconvenient to use. A 4" frac and 7-8" Mewlon would be my choice too, I just wanted to go a little deeper into the "whys".
  • Axunator likes this

#85 Axunator

Axunator

    Viking 1

  • *****
  • topic starter
  • Posts: 594
  • Joined: 23 May 2015
  • Loc: Helsinki, Finland

Posted 04 June 2019 - 12:50 PM

how do you plan to outfit your 180C? e.g. Binoviewer, reducer etc.


Probably just a 1.25” prism or BBHS diagonal for cyclops viewing. My left eye is pretty bad, so I’m not quite sure binos would be worth the added expense for me personally.
  • bdg likes this

#86 salico

salico

    Viking 1

  • -----
  • Posts: 582
  • Joined: 12 Jul 2016
  • Loc: Germany

Posted 06 June 2019 - 02:50 PM

I recommend the Televue Everbrite 2" Diagonal. Use it on my M180C.


Edited by salico, 06 June 2019 - 02:50 PM.


#87 plyscope

plyscope

    Surveyor 1

  • -----
  • Posts: 1839
  • Joined: 23 Nov 2006
  • Loc: Perth, West Australia

Posted 06 June 2019 - 03:41 PM

I find the Baader prism diagonal with 1.25" focusing eyepiece holder very useful for fine focusing at high power. It eliminates the small image shift that occurs with the primary focuser. I rarely use 2" eyepieces with this scope. To be honest I have not used the Mewlon as much as I would have liked. But that is due mainly to weather and lack of opportunity.


  • terraclarke likes this

#88 Axunator

Axunator

    Viking 1

  • *****
  • topic starter
  • Posts: 594
  • Joined: 23 May 2015
  • Loc: Helsinki, Finland

Posted 06 June 2019 - 10:57 PM

To be honest I have not used the __________ as much as I would have liked. But that is due mainly to weather and lack of opportunity.


Insert any scope into that sentence and you get the story of my life. LOL.
  • GlenM likes this

#89 Axunator

Axunator

    Viking 1

  • *****
  • topic starter
  • Posts: 594
  • Joined: 23 May 2015
  • Loc: Helsinki, Finland

Posted 07 June 2019 - 05:07 AM

I’m really not that keen on using 2” gear on M180, despite having a decent collection of 2” wide-fields and a couple of nice 2” diagonals (including 2” Baader BBHS mirror). Of course, I don’t even have the scope yet, so never say never and I’ll probably give it a try just for the heck of it (and probably gasp at the amount of coma - but then again, I’d be happy to be proven wrong). But c’mon, this is really not a wide-field scope, so I have no need to try to make it one.

On a related note, does anybody know the optimal design back focus of Mewlon 180? I’d presume asking for too much back focus will result in vignetting and spherical aberration. This is also relevant point for the choice of diagonal.

#90 salico

salico

    Viking 1

  • -----
  • Posts: 582
  • Joined: 12 Jul 2016
  • Loc: Germany

Posted 07 June 2019 - 06:02 AM

I found coma to be very little in my 2" N22 EP, and very small image shift with the Everbrite. M13 just stunning in the N22 and N12.


  • Axunator likes this

#91 plyscope

plyscope

    Surveyor 1

  • -----
  • Posts: 1839
  • Joined: 23 Nov 2006
  • Loc: Perth, West Australia

Posted 07 June 2019 - 06:41 AM

This image came from the internet, sorry I can't remember where I found it.

 

image013.jpg


  • Axunator likes this

#92 Axunator

Axunator

    Viking 1

  • *****
  • topic starter
  • Posts: 594
  • Joined: 23 May 2015
  • Loc: Helsinki, Finland

Posted 07 June 2019 - 07:39 AM

This image came from the internet, sorry I can't remember where I found it.


Great, thanks! So looks like the shortest possible light path is in order for critical viewing.
  • Kunama likes this

#93 plyscope

plyscope

    Surveyor 1

  • -----
  • Posts: 1839
  • Joined: 23 Nov 2006
  • Loc: Perth, West Australia

Posted 07 June 2019 - 03:39 PM

It probably doesn't make a huge difference, however it is most likely the designer had 1,25" diagonals in mind or even just straight through with no diagonal at all. The dimensions in the image certainly allow for most 2" diagonals. 



#94 BGazing

BGazing

    Apollo

  • -----
  • Posts: 1148
  • Joined: 25 Feb 2016
  • Loc: Belgrade, Serbia

Posted 11 June 2019 - 11:45 AM

Someone else's 2c...re pairing up with 100mm Tak

https://www.cloudyni...-210/?p=8517333


Edited by BGazing, 11 June 2019 - 11:45 AM.

  • Axunator likes this

#95 nicoledoula

nicoledoula

    Viking 1

  • *****
  • Posts: 950
  • Joined: 31 Jan 2018

Posted 19 June 2019 - 04:08 PM

Yup.




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics