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Lunt 80 internal double stack questions

Use this section to discuss "standard" Baader/Coronado/ Lunt SolarView/ Daystar, etc… filters, cameras and scopes. No mods, just questions/ answers and reviews.
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Carson B
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Lunt 80 internal double stack questions

Post by Carson B » Mon Nov 25, 2019 8:36 pm

Hello everyone

I have been a lurker here for quite some time. I do a lot of Solar outreach and use a 92mm APO with a Herschel wedge for white light and a Lunt 80mm PT SS for Ha. I have some funds available soon and I was looking at the possibility of adding the internal double stack option to my 80mm Lunt. After banging around Google it seems my Google Fu is inadequate and I haven't been able to find much on it. Thus my first post here. I am only a visual observer and as I mentioned I do outreach as well. So this will only be used for visual. I will not be imaging with it at all. My Lunt is I guess like the newer one. It has the red on the tube where the PT is. It is like the one in the picture here:

https://luntsolarsystems.com/wp-content ... escope.jpg

Is this a viable option? Meaning does it work and does it work well?
Will I get good detail without ghosting? I want to see more detail on proms and granulation on the surface.
How hard is it to install myself on my existing Lunt?
What can I do with the old system I assume I would be removing?

Thanks!

Carson

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marktownley
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Re: Lunt 80 internal double stack questions

Post by marktownley » Tue Nov 26, 2019 6:03 am

Hi Carson.

Welcome to the forum! If you already have a Lunt80 and double stack it, at the moment, with a blank sun there won't be a huge amount of difference visually, but, as we progress more through cycle 25 and disk features become more abundant, the difference between SS and DS will be huge and you'll find the DS very beneficial and very pleasing. I love DS, both visually and for imaging.

Mark
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MapleRidge
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Re: Lunt 80 internal double stack questions

Post by MapleRidge » Wed Nov 27, 2019 3:57 am

Hi Carson...

I have been a DSII user with the LS80T for many years, and have little poor to say about the system.

On its own the SS version is a very capable scope and add in the DSII really boosts its performance, especially on the chromospheric details. Double stacking does reduce the image brightness, so this really is the only real drawback to me...though it is to be expected. The current solar minimum is not offering many bright disk features or large/bright proms, so the lower brightness has the biggest effect on viewing faint proms. With more activity the DS system offers great views.

There really isn't anything that is being removed that you don't need to keep. There is a spacer between the etalon and focuser that you swap out for the DSII module, but it is a fast, simple procedure. A suggestion of you plan to switch between SS/DS on a regular basis would be to get the thumb-screw set and install them on the primary etalon and the DSII module to allow an easy removal and attachment of the DSII/focuser so you don't have to use the small allen key set screws.

You may have to experiment on the rotation of the DSII on the back of the primary etalon to reduce ghosts, and rotate the blocker as well to get the stray light/reflections to a minimum. I suspect each scope will have its own ideal configuration. The is a red background 'glow' in the DS system which I find minimal visually but it does show more in images. Lunt has a filter that installs between the two etalons to reduce the effect. I have had mine in so long I forget what is was like without it.

It so a good system and does work well. As a purely visual system it provides great views, though keep in mind that for outreach the dimmer views may be more of a challenge for inexperienced observers, but it should still provide excellent views.

I hope I covered the primary questions, and more than happy to answer any others you may have. Others may offer their thoughts as well...this is just my take on the system.

Brian
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george9
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Re: Lunt 80 internal double stack questions

Post by george9 » Thu Nov 28, 2019 5:15 am

Hi, Carson.

I also own the LS80 DSII. The double stack unit will show you details that will be missed single stack during the solar minimum. Subtle active regions, small, dim filaments, small fila-proms, fibrils on the surface, etc. Spicules and prominences will be a little dimmer though.

Great advice to get the thumb set screws. Lunt supplies them.

I leave the spacer on the scope so that I don't have to pull the blocking filter so far out. If you do that, just make sure it is not between the two etalons. It has to go behind the DSII unit before the focuser if it is on at all.

Most people find that placing the two pressure tuners 180 degrees apart works best, and Lunt reports that's what they hear from customers. But you can experiment.

It definitely results in a glow around the Sun. My approach at first was to create a shim that perfectly aligned the two etalons. That put the glow mostly on the Sun, which sounds bad but looked the best. It was too dim to hurt the surface view, but that moved it off the prominences.

Then I got the Lunt high resolution glass (HRG) filter that really drops the glow, but dims the view further.

And then I got a circular polarizer and stuck it in an HRG cell. It pretty much eliminates the glow, but again dims it further.

With the two etalons plus the HRG or circ pol, you will likely use a cloth cloak to block outside light and view better.

If you could make the blocking filter brighter, then that would be a perfect solution.

I forget if you have a binoviewer, but that is essential SS or DS.

George

Carson B
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Re: Lunt 80 internal double stack questions

Post by Carson B » Thu Nov 28, 2019 7:05 am

Thank you guys! This is great information and I will get the internal DS.

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