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Lunt 230mm honest opinions.

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#1 RAC

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Posted 17 November 2017 - 04:24 PM

Hi, I have a friend that has had a pre Meade SM90 Double stack for about 13 years. He's thinking about upgrading it to a larger Lunt scope. He was looking at the 152 in DS but has now sent Lunt and email asking for info about the 230mm, their reply says it's an internal double stack with a .5 Angstrom bandpass. I can only find info on the net of them being single stack?

 

He is visual only and likes to be able to see the full disk but also wants good detail when zoomed in. I'll be the only one doing imaging with the scope but I can see him getting a camera at some stage.

 

The money is of no concern but we really need some honest opinions of how much better it would be over the current SM90DS. He's not wanting to keep both scopes as he wants to give me the SM90 when the new one arrives so the Lunt has to be good at everything.

 

Thanks, I'd like to hear your thoughts.


Edited by RAC, 17 November 2017 - 09:32 PM.


#2 junomike

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Posted 17 November 2017 - 04:29 PM

Lunt 230mm DS........jawdrop.gif


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#3 George9

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Posted 17 November 2017 - 09:07 PM

I remember looking through what I thought was a 200mm Lunt SS at NEAF a few years ago. We had a spectacular prom. I remember the sky background was very red but the prom was incredibly detailed. It looked like it was raining onto the sun.

 

George


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#4 BYoesle

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Posted 17 November 2017 - 09:48 PM

Here's the info on the LS230 double stack:

 

https://luntsolarsys...om/limited-run/

 

 

He's not wanting to keep both scopes as he wants to give me the SM90 when the new one arrives so the Lunt has to be good at everything. (Emphasis added).

 

That's impossible, so he's likely to be disappointed, as Andy Lunt stated for even the single stacked LS152 the design purpose is not to provide optimum full-disc views, but optimum high-resolution close up views:

 

"It is my opinion that the smaller systems require a larger sweetspot at the slight compromise of bandpass. Given that the smaller aperture results in a minimal effect by seeing conditions and air turbulance, I like to see a fairly bright image that provides an nice overall Full solar image with a balance of proms and surface (typcial to <0.7Angstroms).

However, as the aperture increases we are faced with a few more decisions.
Increased aperture, in my opinion, allows the user the advantage of light due to image scale. It allows the use of higher magnifications under ideal conditions to see within the details of the Sun without significant loss of brightness.
Increase in aperture has the disadvantage of being effected by poor seeing conditions.. However, I would prefer to know that while my system may not have ultimate performance under less than average conditions, it will provide the best resolution and contrast under ideal conditions, AT HIGH MAGNIFICATION. If it is not your intent to use the systems at high magnification, you do not need a large aperture scope.
Under low magnification the user will note a sweetspot in the eyepiece. If the Sun is placed in the center and an eyepiece is chosen that allows the Sun to be about 40% of the field of view, you should see uniform detail around the entire disk. In some cases the sweetspot maybe slightly off center. This is an unavoidable result of tilted optics and mechanical tolerance holding those optics.
With the Sun at about 40% of view, you will have an dark area around the Sun equal to about a Sun radius..
Moving the Sun around in the field of view you will note that the proms will drop off quickly as the image moves to the edge of the field of view. This is due to the off axis rays becoming greater than the acceptance angle of the Etalon. This is NOT the result of a poorly tuned Etalon (however, you can re-tune to get this detail back at the loss of the center (basically de-tuning the Etalon to match that angle)), or the result of mis-aligned optics.

Note that when you magnify the image you are using a much smaller area of the field of view and will note that the sweetspot quickly disappears as the heart of the system is utilized.

Note: the narrower the bandpass of the Etalon (higher R for narrower bandpass) the faster, or more pronounced the sweetspot.

 

sweetspot.jpg

 

The image at top (had to get there eventually smile.gif represents the ideal internal system. We try to provide what we refer to as a slight “bird” shape. The Sun would sit within this area provided that the magnifiaction was set such that the Sun was 40-50% the field of view. The center comes down very slighly in order “push” out the sweetspot.
The narrower the bandpass of the Etalon, the narrower it’s acceptance angle. Therefore, lower bandpass systems will deteriorate faster at the edges.
The above deterioration can be offset by placing a wider bandpass Etalon in the system. ie: if we placed a <.08A Etalon in the 152T, we could increase the sweetspot to 70-80%. Hmmmm, I designed the 152T for high resolution, high magnification viewing. Research of the active areas, and NOT for a quick overview of the entire Sun. That can be done with a 60/PT or a 100/PT. I believe that I would be doing a dis-service to the customer if I provided a systems that worked okay at low mag by simply showing a uniform, if less contrasty Sun, but showed very little detail close up. There’s a reason the University of Hawaii moved the 152T to the top of the volcano and typically use it at 100-200X."

 

For the 230, the field angel magnification for the first etalon in series is roughly the aperture divided by the etalon diameter 230 / 80 = 2.9, quite high for full disc contrast uniformity to be maintained (actually it can't be), especially because it has a narrower FWHM of 0.5 A. Therefore if he likes to have good full-disc views, he should not give away the SM90 DS, and use the LS230 (or LS152) for times when seeing allows good close up views, which likely will be fewer unless he lives near the coast with a stable marine layer nearby to preserve better than average daytime seeing.

 

Most of the time he'll likely be using the 90...


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#5 RAC

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Posted 17 November 2017 - 10:21 PM

Thanks. That's the perfect response I'm looking for.

#6 petert913

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Posted 17 November 2017 - 11:29 PM

I wonder who is making the objective for this beast?



#7 BYoesle

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Posted 18 November 2017 - 04:59 AM

Lunt has a very strong association with Markus Ludes of APM Telescopes in Germany, and it may be one of their optical sub-contractors, such as LZOS, etc., but that's just a guess.



#8 BYoesle

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Posted 23 November 2017 - 09:55 AM

The objective was designed by Riccardi and is IR blocked:

 

Lunt-LS230-4.jpg

 

APM Telescopes (Markus Ludes).

 

 


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#9 contrailmaker

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Posted 23 November 2017 - 09:31 PM

I agree that the challenging part will be finding good atmospheric conditions to take advantage of the large aperture. I owned a SM90 when I lived in Arizona and when the conditions allowed the high power views were breathtaking. Can only imagine how 230mm will perform. What a great dilemma to have....

CM

#10 LarryAlvarez

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Posted 26 November 2017 - 09:42 AM

I was told that Lunt does make a double stack for the 230 system.  I have not seen them advertised but did get word from their sales folks that he does make them when I inquired.  The newer 230's have the pressure regulated by a separate pressure system.  So unlike a 90DS you'll have to have a power plug for it to regulate the pressure if you get a new one.  The first 230's did not require the pressure regulator and had the standard pressure tune cap that is on the 60-152mm scopes.  The 230 and 152 are much more heavy than the 90 also so you might also take that into consideration as an updated tripod may be necessary as well.

Visually the 152 or 230 are going to be much better for close up viewing or imaging.  I have only used both for imaging at <.65 so I can't speak to how they work as doublestacks.  I can say that the single stack view is awesome.  Neither is as easy to use as a 90 for full disks.  On full disks you see a sort of concentric ring artifact of varying detail density consistent to what Bob described in his post.  On a 152 telescope you can stop it down in the front to 90mm and get a good full disk.  Both scopes are heavy to setup and take down so think "permanent mount" like a pier for either.  For me the details you can see make it worth it but at the same time I also bought a Lunt 60 for full disks.

 

Below is what you can expect from a 152 single stack as far as the concentric ring artifact goes:

 

Attached Thumbnails

  • odd_donut_sm.jpg
  • Lunt_152_review_map1sm.jpg

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#11 LarryAlvarez

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Posted 26 November 2017 - 09:56 AM

I forgot to mention that if he gets the 152, be sure to also get the whitelight attachment for it or Cak attachment. It think either of these will give you a normal visual back that you can then use when collimating the scope with a star.  The 230 does not have a WL visual back although the front lens does have collimation screws.  I had to build one for mine to collimate it. 

 

If you are looking for convenience, ease of setup, and awesome full disk and great close ups then the 90DS already fills that bill but if you are going for an ultra zoomed in close up then the 152 or 230 is great for that.  :)



#12 Holltim4103

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Posted 26 November 2017 - 03:16 PM

On a 152 telescope you can stop it down in the front to 90mm and get a good full disk.  

Great post and details Larry. I noticed the same concentric ring artifact on my Lunt 152 with full disk images, but the high resolution images are amazing.  I agree, my Lunt 60 has a more pleasing full disk image than the 152. I never thought to stop the aperture down. I will give it a shot! I also just got an internal doublestack for the 152 which I will try imaging with and post some pictures. 



#13 RAC

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Posted 26 November 2017 - 11:36 PM

Thanks everyone. We're looking at making a little compromise by getting a double stack Lunt 152.

 

Thanks for the concentric ring effects image, it shows it very well.




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