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Lunt Question: Which is better - pressure or tilt tuning?

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#1 solarviewer

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Posted 14 August 2014 - 06:02 PM

Which is the better option for the Lunt 60mm LS60Tha - pressure-tunning or tilt-tuning? What are the advantages and disadvantages?



#2 rigel123

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Posted 14 August 2014 - 06:41 PM

I don't know.  I have the Tilt Tune model, I tuned it once and haven't touched it since.  Others claim the pressure tuned is better, but having never looked through one I have no opinion.  My views are great, it works great for imaging, but some swear by the pressure tuned.  You can see my images on my Astrobin site in my signature.


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#3 BYoesle

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Posted 14 August 2014 - 07:33 PM

On a theoretical basis, pressure tuning is far superior (as is mechanical pressure tuning used by Coronado -- "rich view" tuning).  In some instances, tilting can result in causing the filter to go off-band opposite the axis of tilt, and creating a band of good performance, and the filter falling off-band outside this "sweet band."

 

SEE:

 

http://luntsolarsyst...ift-part-1.html

http://luntsolarsyst...ift-part-2.html

http://luntsolarsyst...m-has-been.html


Edited by BYoesle, 15 August 2014 - 03:22 AM.

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#4 Doc Willie

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Posted 14 August 2014 - 07:51 PM

I had the tilt -tuned, and upgraded to a pressure tuned. The tilt-tuned had a gradient where one side was darker than the other, and you could tune it to put the sweet spot wherever you wanted. The pressure tuned has not gradient - the entire field is evenly illuminated. Worth the upgrade. 


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#5 solarviewer

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Posted 14 August 2014 - 07:58 PM

Thank you so much, this information has been exceptionally helpful!



#6 dpreneta

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Posted 15 August 2014 - 10:35 AM

I have a Lunt 60 with pressure tuner.  This tuning to me appears more precise and I can really get the details looking sharper as compared to a Lunt 60 tilt tuner.  I find that to work properly the pressure tuner barrel needs to be unscrewed off then screwed back on to balance the pressure inside the unit.  Also, the O-rings can deteriorate and allow air leaks...this happened to me and I could not tune it to get good images.  I called Lunt and was sent two replacement O-rings along with a small packet of grease for lubrication.  After replacement all is better now. 



#7 solarviewer

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Posted 15 August 2014 - 11:50 AM

How much of a problem are temperature extremes for the pressure-tuner? For example, observing under really hot or freezing cold weather conditions? About how long does it take to reach thermal equilibrium and how does it perform while waiting? Does it need a "heating up" period or something similar?



#8 dpreneta

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Posted 15 August 2014 - 02:36 PM

Honestly I only use my Lunt from late spring through early fall so its never experienced cold weather...I'm in Buffalo NY.  I've never noticed any issues with temperature affecting the pressure tuning or optical performance either.   I use it as soon as I set it up.   My Lunt also has the double stack unit, it is a great scope.


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#9 GUS.K

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Posted 15 August 2014 - 07:43 PM

I have the LS60PT, and a couple of tilt tuned  coronado scopes, and I much prefer the view through the PT.Proms and surface features are visible together, its nice to see the rim surrounded by proms and surface features across the disk at the same time. The PT  view does have a sweet spot, roughly 70%, and if the sun is centered, detail is visible across the whole disc.Regards temperature,I haven't noticed any issues in the nearly 3 years I've owned the scope.and that's in the temp range of  -5 to 40 plus degrees C.

 

GUS.K


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#10 GooglyEyes

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Posted 15 August 2014 - 08:05 PM

How much of a problem are temperature extremes for the pressure-tuner? For example, observing under really hot or freezing cold weather conditions? About how long does it take to reach thermal equilibrium and how does it perform while waiting? Does it need a "heating up" period or something similar?

 

I've never used mine in temperature extremes, so I can't really answer that(typically I image between 40F and 90F). The tunning does change with temperature changes (or as the 'scope heats up), so I usually find myself having to re-adjust the pressure tuner at least once during an imaging session. No heating up period is required ( sometimes you may need to unscrew the tunning knob and equalize the pressure), but irregardless of the temperature you just turn the tuning knob until the Ha image snaps into place.

 

 

Mar


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#11 solarviewer

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Posted 20 August 2014 - 01:16 PM

Just wanted to post a quick follow-up. I found a used Lunt 60mm LS60Tha with the pressure-tuner, B1200CPT, Lunt eyepiece, motorized focuser attachment, and the Sol-Searcher finder. I am so excited and can't wait to start taking and posting photos of the sun.

 

I wanted to say thank you to everyone who has taken time out of their busy schedules to answer my questions and provide helpful information, you all are totally awesome! :-)

 

Bob



#12 rigel123

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Posted 20 August 2014 - 01:56 PM

Sounds great, enjoy!



#13 Eddgie

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Posted 25 August 2014 - 10:00 AM

I had the tilt -tuned, and upgraded to a pressure tuned. The tilt-tuned had a gradient where one side was darker than the other, and you could tune it to put the sweet spot wherever you wanted. The pressure tuned has not gradient - the entire field is evenly illuminated. Worth the upgrade. 

 

You may have been lucky.

 

I have some of the same issues with the Pressure Tuned Lunt as I had with the PST.  Sometimes the field will not be evenly in tune.

 

I had expected this not to be the case, so I talked to the people at Lunt and they explained to me that it is not at all a guarantee that you won't have this kind of issue with a pressure tuned scope.

 

They offered to take it back to try to improve it, but they said that this condition could still be present.



#14 Eddgie

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Posted 25 August 2014 - 10:11 AM

Which is the better option for the Lunt 60mm LS60Tha - pressure-tunning or tilt-tuning? What are the advantages and disadvantages?

 

I have not had the tilt tuned, but here are my reservations about the pressure tuning.

First, as I noted in my previous post, I still have tuning positions where the field is not equally in the same bad.  The people at Lunt told me that this is indeed common to both types and they try to set up the scopes to minimize the condition (in both tilt and pressure tuned instruments) but that it may not have the exact same tuning across the field at all settings.

 

As much as I had hoped to leave this behind from the PST, in my case at least, there is still some of this condition.

 

Next, the scope is very heavy (for its size) and the position of the tuner is not easily adjustable with respect to the plane of the focuser knobs.  This means that mounting on some Alt-Az mounts can cause problems with position and balance.   In one case, I could not get the solar finder (mounted in the grove in the clamshell) to clear the tuner and still provide a sufficient balance point so that the focuser knob cleared the back of the mount saddle.   This was very frustrating to me.  The scope balances very tail heavy.  The model I have does not have a rotating focuser and this might have improved some things...

 

And last, the pressure needed to tune is so much that on a light mount, the entire mount will shake badly when increasing the pressure.  The tilt tuning on my PST was light enough that even on a photo tripod, I could tune with less shaking.

 

Now, I have not used the tilt tuned, so I can't tell you how much difference there is in detail.  I am sure that some will say that you can see more but I can't either confirm or deny this

 

I  have since went to a heaver GEM mount to deal with the shaking imposed by the force required to pressure tune and this negated any balance/clearance/obstruction issues I was having on the Alt Az mount.

 

I am not "Disappointed" with my scope, but it is not as "Perfect" as I was expecting it to be either. 

 

I think I could have been just as happy (and maybe a bit happier) with the Tilt tuned.


Edited by Eddgie, 25 August 2014 - 10:12 AM.


#15 BYoesle

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Posted 25 August 2014 - 01:55 PM

 

I think I could have been just as happy (and maybe a bit happier) with the Tilt tuned.

 

Hi Eddgie.

 

Maybe, but likely not if you are looking for better field contrast uniformity (and irrespective of the mechanical issues you cited).  For this you would need to use a front mounted etalon system, where the field angles are at a minimum.

 

Most internally mounted etalons used with a collimator lens system will have some degree of field angle magnification, whereby the acceptance angle of the etalon is exceed in the outer portions of the field of view.  This will produce a "sweet spot" regardless of tuning method.  The size of the sweet spot will vary depending on the amount of field angle magnification provided by the collimator lens configuration.  This sweet spot may be slightly displaced off-center due to internal component tilts and other mechanical factors.

 

However, tilting an internal etalon can produce an additional contrast anomaly known as banding, as the acceptance angle of the etalon is exceeded along the tilt axis (i.e. parallel to and along both sides) with increased amounts of tilt.  In an internal etalon system, tilting can "add insult to injury."  This also occurs also with telecentric based filter systems, and why DayStar has likely abandoned the older tilt-tuned "T-scanner" model.


Edited by BYoesle, 25 August 2014 - 03:24 PM.







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