Lunt 60 Pressure tuning question(s)

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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marktownley
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Re: Lunt 60 Pressure tuning question(s)

Post by marktownley » Fri Nov 15, 2019 6:13 am

The sun really is totally blank at the moment, look for a day when there are some proms to aim at to get the tuning close to where it should be...
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Re: Lunt 60 Pressure tuning question(s)

Post by hopskipson » Fri Nov 22, 2019 5:32 pm

Thanks Mark for the assurance. I guess since I cut my teeth on the Quark which seems so easy to use and the higher magnification brings out more details ,I was expecting similar results. I also tried out a pst mod with a ST80 at f/10 and was able to tell when the sweet spot was on band. So I have some experience with what to expect.
I still haven’t had a chance to test it out but Faye is sending out some new O-rings. I’m keeping my fingers crossed!

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Re: Lunt 60 Pressure tuning question(s)

Post by Gert » Tue Dec 17, 2019 6:15 am

Hello All,

I would like to add my own method of setting / checking the tuner. I mostly work with a camera (ASI174) and a laptop where in the recording software I can see the histogram in real-time. Now we know the H-Alpha spectral line in the Sun is an absorption line. As the tuner sweeps the transmission of the etalon across the wavelength axis and we cross the H-Alpha line we will notice the image gets darker (as we enter the absorption line) reach a minimum (at center) and get brighter as we exit the line. This can be nicely seen in the histogram. So I twist the tuner knob until the histogram is at its lowest. That's the spot when the talon is centered to the middle of the H-Alpha line. Twisting the knob back/forth it is quite easy to find the best spot. Over time (>1hrs) there might be change. I.e. when I re-do the knob-twisting I find a better spot as guided by the histogram that is a little turn away. Once that is set I might run some images with the camera, and when I like later remove the camera for visual observation. If the contrast setting of the camera is high it becomes obvious that the filter is not homogeneous. There will be areas of different detail and contrast across the Sun's disk. The contrast of the camera can be very harsh, and I can make any tunable scope look bad with it. Visually the change is much less pronounced. Looking for a filtered solar-scope that does not have such variations would imply a 10x price uplift. So I'm OK to live with the quality I get.

Clear Skies,
Gert
Gert Gottschalk, Ph.D.

Tri-Valley Stargazers, Eastbay Astronomical Society, WFS Berlin

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hopskipson
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Re: Lunt 60 Pressure tuning question(s)

Post by hopskipson » Mon Dec 30, 2019 10:18 pm

Just an update, my brand new scope had a decontacted etalon that was replaced. It’s on its way back to me. I’m just a little concerned with shipping across the country again. Fingers crossed 🤞.

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Re: Lunt 60 Pressure tuning question(s)

Post by marktownley » Tue Dec 31, 2019 9:01 am

Fingers crossed indeed!
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Re: Lunt 60 Pressure tuning question(s)

Post by hopskipson » Sun Jan 05, 2020 7:07 pm

Here's the latest update on my LS60:

I received my scope last week and have it out now. The weather is not optimal 42*F and very windy with many clouds and only a few breaks of sun. I did wrap a dew strap around the blocking filter and a dish towel around that to try to keep it warm. The limited time out I can see a nice sized prom and some surface detail but nothing significant. Can't see the AR. Looked on Gong and the AR seems to be fading a bit. There doesn't seem to be much contrast with this scope. I would say that the scope is fixed but I'm hoping that the weather is inhibiting optimal performance. I find the pressure tuner to be kind of clumsy to get proper tuning. It seems to be really hard to get the entire disk on band. I know a lot of people knock the Quark, but I find the tuning to be much easier. Just find the proper setting and leave it alone. Also since I need a dew heater to keep the blocking filter warm, I need some external power source. Maybe it is my lack of experience with this system and the conditions that are making it extremely uncomfortable to be out today.


Does anyone have suggestions or comments on technique? I tried a ND filter but that didn't help. Does anyone use any other filters or polarizing filters to increase contrast?


Thanks

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Re: Lunt 60 Pressure tuning question(s)

Post by marktownley » Sun Jan 05, 2020 8:43 pm

Things sound fairly normal tbh - you're observing a quiet sun in the dead of winter. Give it a month or two, the sun will be higher and we should have a bit more activity fingers crossed. Call me a 'fair weather' solar astronomer but I only tend to head out when the weather is better. Really, the only proper way to increase contrast is to double stack, or, a blanket over the head to cut out extraneous light can help to.

Mark
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Re: Lunt 60 Pressure tuning question(s)

Post by hopskipson » Sun Jan 05, 2020 9:44 pm

Thanks Mark.
Brought the blocking filter inside and let it warm up with the dew heater on. About 2 hours later even with lousy seeing the contrast was much better. Was just able to make out the AR and a small filament. I wouldn't normally be out on a day like this, but with the scope just coming back from repair I wanted to put my mind at ease that it was working.

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Re: Lunt 60 Pressure tuning question(s)

Post by daslolo » Thu Feb 20, 2020 8:22 am

ForrestLockhart wrote:
Fri Jul 11, 2014 9:28 pm
I don't know what Brian did in the 30 minutes he had the scope, but the effect was dramatic... I think. Some friends say it was always good, others agree that something good happened in Tucson.
Call Brian and ask him! This knowledge is gold. Or they just put it in a machine that costs 1 million dollar :D
PST on its way to modding heaven
Quark + Orion 120mm + beloptik
LX65 8" ACF

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