Lunt LS50THa b400 first light- a frustrating event

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Lunt LS50THa b400 first light- a frustrating event

Post by T McVicar » Thu Apr 07, 2016 1:52 am

Hello all, I just wanted to say again how much I love your images and I need your help big time. I don't know any other solar imagers. I imaged nighttime stuff just to get experience with software to one day solar image, and am obsessed with the sun in general.

I was finally able to recently pull the trigger on a preowned lunt 50 b400 (purchased in 2015 but barely used) for a decent price. I am not new to imaging, but this was my first time out during the day with my AZEQ6 and using it to track the sun.

I brought out all of my imaging gear for a standard session. I wasn't sure where Polaris was, my snycscanegps said hour angle 1154 but I obviously had no idea where that was but I put the mount roughly in the right spot in the sky, my latitude adjustment basically the same from when I went out imaging last at 55 degrees.

I did a 1 star align, chose alkaid I think and it slewed to it roughly and i just hit enter. It said alignment successful to my big surprise. I went to object list, solar system, and found out they don't have any option for the sun. No worries, I slewed over to it manually and selected solar tracking rate speed. The mount stayed on the sun from that point on in the TV solar finder that I had mounted to the lunt, even with questionable polar alignment.

I had the hardest time trying to see anything at all. With a 25mm plossl, I simply could not focus the sun. It was dim, fuzzy, devoid of detail. The only time I could say for sure I was still looking at the sun, was with the 32mm plossl. Again, small red disk. Probably too far away mag to see anything. But as soon as I switch out the EP's, I basically couldnt find it. I tried barlowing the 32mm, nothing. I tried using various extension tubes (barlows with the len taken out) for visual. There seems to be a number scale on the scope that itself is an extender of sorts. I racked that in and out. Nothing. I spent two hours trying to figure out how to use the scope. I cant even tell you if I was looking at a ghost reflection of the sun or not, thats how bad it was. I put it my TV 13mm nagler, with a wide FOV- nothing. Barlowed it , nothing. barlow with extender. nothing.

It was not all bad. For one brief fleeting moment, with the 25mm and the TV 2x barlow, I was able to get just under a quarter of a disk limb shot. it was bright red and looked great. I thought I was seeing a big sun spot, but I couldnt be sure it wasnt a dust mote. The view was like nothing else I saw previously, almost where I would want to be and how the scope is suppose to work, but I simply could not keep it in the view. and it bounced around. Maybe my polar alignment was the cause, and maybe the sol finder doesnt line up great with the 4mm blocking filter? I dont know.

I tried using the entire sensor of my ASI cam like I do for lunar imaging and cranking up the exposure time and gain , and back down again and scrolling around to see if I could see the sun on the screen. couldnt find it. I tried using all of my barlows and extenders, couldnt find it as well. I forgot my box that covers the laptop, but I brought a dark towel to put over my head to help try and use my computer during the day

I think I have to buy the 6mm blocking filter just to try and use the scope visually. I am also ditching my tracking mount and am going to try using the skyview pro manually next time out to rule out the polar alignment, as I do not have a permanent set up to measure my PA at night and try to remember or mark on the ground to high accuracy for daytime use.

But does anyone have any pointers at all on how to enjoy my scope to get a decent view? Or have experience using the b400 BF successfully for visual?

In regards to the pressure tuner, the graduated scale extender on the tube itself? I found that the eye relief/exit pupil whatever it is, made my eye right to the ep, and the FOV was so tiny the small red sphere was barely in it entirely as easily lost. I was always able to find the sun going back down to the 32mm because of my tracking, but whenever I tried to get closer, the sun vanished or couldnt not fit into the fov at all with the blocking filter. It was very weird, nothing like my 100mm equinox using a 1.25 diagonal when I had it

Thanks for your time and suggestions. Here are some pics of my set up at various times
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Re: Lunt LS50THa b400 first light- a frustrating event

Post by T McVicar » Thu Apr 07, 2016 2:01 am

Basically the FOV was ridiculously small.

Also, despite completely unscrewing the pressure tuner I didnt hear any air come out. It built up pressure in the tube when I screwed it in though......maybe the seal is gone?


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Re: Lunt LS50THa b400 first light- a frustrating event

Post by T McVicar » Thu Apr 07, 2016 2:22 am

I am guessing that is a built in, numeric etched extender in the OTA by the focuser to roughly find the sun, and the pressure tuner to draw out the details. But if my pressure tuner is gone because of a seal, then that may explain why I wasnt able to see anything or much of a view at all beside a fuzzy red blob


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Re: Lunt LS50THa b400 first light- a frustrating event

Post by Davidm » Thu Apr 07, 2016 2:49 am

Sorry to hear about your dramas. I don't have a simple answer, but a few thoughts on some of the peripheral issues, so you can focus on the main one.

For your polar alignment, a rough alignment to north is good enough, particularly at fairly low magnifications. I just do a visual line-up with a compass, which I find good enough for fairly high-resolution imaging. I then just select solar tracking speed and it only needs the occasional correction by hand to keep things rolling.

I would think your solar finder should be pretty well aligned, and if you are seeing the bright spot somewhere near centre, you should be in the right area to find the sun with a low mag eyepiece. I am thinking stay with plossls at the moment to keep things simple in terms of reaching focus. You shouldn't need any extenders for visual work with these, as far as I know (I haven't used this scope myself). It would be good to do a systematic sweep around the area where you get an image to make sure you aren't looking at ghost images. I don't think you will need a larger blocking filter to help you with the view. You should be able to get a good image with what you have.

If you are totally unable to get a focussed image, there might be a problem with the scope itself, perhaps a de-contacted etalon for example. The pressure tuner sounds like it is OK if you are feeling resistance, even though there might not be a pop when you take it off. Hard to say. Before asking Lunt for advice on this aspect, it would be important to make sure you are happy you are viewing the primary sun image correctly, though.

Not sure if this helps much, but hopefully next time out you get a good view.

David


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Re: Lunt LS50THa b400 first light- a frustrating event

Post by T McVicar » Thu Apr 07, 2016 2:53 am

Thanks a bunch for your suggestions. I will go out with my Skyview pro tomorrow weather permitting. It will be easier to scan around and play with the plossl's and built in extender. from there I will find the sun with the 25mm plossl or 10mm plossl and possibly the barlow on the 25mm and see if I can get that good image again- and then see if I can focus that. The Nagler may not work because of its design, like you said.


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Re: Lunt LS50THa b400 first light- a frustrating event

Post by T McVicar » Thu Apr 07, 2016 2:55 am

The scope was shipped from the states, preowned. If It cannot focus it perhaps it was damaged somehow in shipping.


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Re: Lunt LS50THa b400 first light- a frustrating event

Post by Merlin66 » Thu Apr 07, 2016 5:45 am

Tyson,
There are two aspects to your "problem"
1. Obtaining a reasonable focus on the solar disk - the helical focuser should get you close - the solar edge should appear tight and crisp.
2. The tuning of the etalon to provide the central wavelength needs to show the surface detail and the proms around the edge of the sun.
This takes trial and error - gentle use of the pressure knob/ring and look for improved contrast on the surface.
Get these two right and you're well on your way to success.


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Re: Lunt LS50THa b400 first light- a frustrating event

Post by GreatAttractor » Thu Apr 07, 2016 7:36 am

Davidm wrote:I would think your solar finder should be pretty well aligned
My finder was way off (scope straight from the store), so don't rely on it until you have found the Sun in the FOV and then readjusted the finder.

Tips for pointing at the Sun: 1) hold something flat behind the scope and observe the shadow; try to make it look completely "in line" with the Sun. 2) Then, with EP removed, look down (from some distance) into the diagonal and wiggle the scope around the minimum shadow position. You should be able to get the disc into view; once done, replace the EP.

As mentioned, even with the etalon not tuned you should at least see a sharp red disc equivalent to white light view.

I also remember that with the stock focuser I lacked in-focus to use a Barlow with one of my eyepieces.


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Re: Lunt LS50THa b400 first light- a frustrating event

Post by Davidm » Thu Apr 07, 2016 7:44 am

Good point about the finder. I had assumed the screws on the mounting ring would ensure that things were pretty well aligned, but you do need to ensure proper alignment.


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Re: Lunt LS50THa b400 first light- a frustrating event

Post by GreatAttractor » Thu Apr 07, 2016 8:18 am

And regarding the laptop – using it will be much more convenient with some sort of shield (which will also help keep the temperature down). Check out this thread for ideas and pictures (I use a packaging box).


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Re: Lunt LS50THa b400 first light- a frustrating event

Post by Montana » Thu Apr 07, 2016 10:01 am

I know exactly what it is like first getting a Halpha scope, I couldn't find anything for an hour either and it is most frustrating.

Here is how I polar align during the day https://www.flickr.com/photos/alexandra ... 535593245/
Using this method I can track for 5 minutes+ at hires, hours at low res.

Start simple, forget about imaging yet, concentrate on getting a good view in the eyepiece. Use a low power eyepiece to start and forget about the solarfinder (take advice from above first as it might not be aligned) try and find the Sun. I wonder whether you couldn't get focus because you were actually looking at a ghost, I spent 45 minutes on one once and just could not get focus. The simplest way to tell is to move the etalon to change the band, if it is a ghost it will zip out of view. If it is the real Sun then it will stay rock steady in the centre and gradually change band. This is the one which will give you focus.

Now focus to get a crisp edge, then change the band with the pressure tuner until you see maximum contrast on the filaments and proms are visible on the edge.

Once this is done only then worry about imaging. It is much easier to find the Sun through an eyepiece than through a camera. Start with that first.
Alexandra



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Re: Lunt LS50THa b400 first light- a frustrating event

Post by michael.h.f.wilkinson » Thu Apr 07, 2016 11:20 am

I wonder if the ghost will zip out of the way with a pressure tuned system (with a tilt-tuned system certainly!)


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Re: Lunt LS50THa b400 first light- a frustrating event

Post by aaube » Thu Apr 07, 2016 4:51 pm

michael.h.f.wilkinson wrote:I wonder if the ghost will zip out of the way with a pressure tuned system (with a tilt-tuned system certainly!)
I was wondering too but i now think on a 4mm blocking filter it would.

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Re: Lunt LS50THa b400 first light- a frustrating event

Post by robert » Thu Apr 07, 2016 7:15 pm

The sharp edge to the disc is a key part of getting setup, before you consider tuning at all. The LS60 has a draw tube that needs to be extended a bit with many eyepieces and cameras and often prevents new users from getting to focus at first. I don't know if the LS50 has this but it might? Looking at your photo it looks similar to the 60 and the blocking filter can slide in or out of the 2" focuser and needs to be set about right before you can get any image. 10-12mm eyepiece is good, no barlow to start with. Get focus and then try tuning.

It is always hard to find the sun surprisingly. It is very bright but only 1/2 a degree across and easily missed.

Keep at it, it gets easier!
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Re: Lunt LS50THa b400 first light- a frustrating event

Post by T McVicar » Fri Apr 08, 2016 12:40 am

Update: got some sun again today. I am thankful for the advice I received here. I made considerable improvements today!

The Good:

I found out my sol finder is completely off, best used a rough guide at best. No matter what allen keys I loosened, it couldnt get it bang on. I found the bright red disk- analogous to the WL filter looking sun. Many times yesterday I was looking at a ghost image.

Speaking about loosen allen keys- I found my key problem to yesterdays set up: I was too stressed to realize at the time but my actual clamshell was a tad loose. I have always used tube rings, but this is why my view bounced around so much trying to torque down the pressure tuner. I noted this at the time, trying to figure out why my mount was loose but i was looking at the dovetail when it was the clam, i did notice the loose clam after but didnt think it mattered either way at the time. It did, big time.

After finding the sun manually with my manual controlled mount, the rest was easy. All of my ep's worked. My barlows, I dont think so, except my only powermate (parfocal) My 5 x powermate that I bought for my 100mm frac for imaging which was a bit too much mag for Jupiter turned out perfect for my little lunt. I used the 5x powermate with the 25mm plossl, and my 13mm nagler as well. There was a large sunspot on the limb, I used this to realize my helical focuser works. It is a bit hard to be precise, but it works. Focusing this sunspot gave me hope of my purchase.

The Bad:

The jury is still out on my pressure tuner. I am not convinced im seeing much if any of a difference. I was delighted to focus the disk with the helical focuser but that is where my improvements stopped. I played with this, putting in all the way in, and taking it out. Trying to see proms. I could not. GONG showed several targets that were absent in the ep.

Either this is because it is a single stack, the seeing was 2/5 or 3/5 average as per Clear sky chart and the time of day was probably the worst you can have at approx 4-6pm local time. I am going to go out at the crack of dawn on the weekend to see an improvement with the pressure tuner and see my first prom. I have heard reports of seal problems with these scopes PT, and if there is no air releasing from the PT being slacked off, that may be the cause. Either way im more hopeful


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Re: Lunt LS50THa b400 first light- a frustrating event

Post by T McVicar » Fri Apr 08, 2016 12:48 am

I thought i was seeing faint waves of red stream off from time to time, almost like the corona-like gas come and go, but I doubted that is what I was seeing was because of a possible defocused sweet spot on the limb or seeing conditions or something, and you cant see the corona with Ha, on the chromosphere I think.


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Re: Lunt LS50THa b400 first light- a frustrating event

Post by robert » Fri Apr 08, 2016 3:54 pm

You should feel a small increase in resistance as you screw in the pressure tuner if it is holding the air. It may need to be screwed in almost fully to get tuned. If there is no increase in torque needed to turn the knob it is leaking.
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Re: Lunt LS50THa b400 first light- a frustrating event

Post by Gordon Ewen » Fri Apr 08, 2016 7:49 pm

Hello Tyson, glad you have made some progress with the LS50. I have had one for a year and it is an excellent scope. I have a couple of comments that might help.
I have had no trouble with the pressure tuner on the 50 but I did have a leaky one on my 152. I simply took the pressure tuner apart, cleaned it and regreased it with Molykote grease and it has been perfect ever since. It might be worth taking yours off and checking the state of the grease. The mechanics are dead simple so it may just be a dry seal.
When you get to imaging with your ZWO you won't be able to reach focus using the 1 1/4" eyepiece holder that sits on the diagonal; it pits the chip too far from the focal point. To use my ASI120MM I remove the eyepiece holder from the diagonal and fit a 10mm T extension tube and then screw the ASI camera onto the adapter (after removing the eyepiece adapter from the ASI) - picture attached. YOu should then be able to image.
Good luck
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Re: Lunt LS50THa b400 first light- a frustrating event

Post by nebulabru » Tue Jan 14, 2020 8:43 pm

Hello,
But the B400 model for visual can be acceptable?
Regards,
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Re: Lunt LS50THa b400 first light- a frustrating event

Post by nebulabru » Tue Apr 28, 2020 3:04 pm

But, if I put one 8mm ploss(50º afov) in this Lunt 50 B400, is the same like if I put one 8mm Ethos(100º) in the same solar telescope ?
Only one example...
thanks



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Re: Lunt LS50THa b400 first light- a frustrating event

Post by marktownley » Wed Apr 29, 2020 8:11 am

nebulabru wrote:
Tue Apr 28, 2020 3:04 pm
But, if I put one 8mm ploss(50º afov) in this Lunt 50 B400, is the same like if I put one 8mm Ethos(100º) in the same solar telescope ?
Only one example...
thanks
An 8mm ethos with a b400 isn't going to work the way the ethos was intended. The B400 means the largest effective field stop is 4mm, the Ethos field stop has a near 14mm field stop. Lots of that 100deg field of view would be vignetted, which defeats the object really. I would suggest you may have big issues getting the Ethos to focus on the Lunt50, maybe?


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Re: Lunt LS50THa b400 first light- a frustrating event

Post by nebulabru » Wed Apr 29, 2020 3:37 pm

Thanks for your kind reply!
Cheers.



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Re: Lunt LS50THa b400 first light- a frustrating event

Post by nebulabru » Thu Apr 30, 2020 10:00 am

One last question, then would no eyepiece with a field stop greater than 4mm benefit from a great AFOV? vignetting?
Best,



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Re: Lunt LS50THa b400 first light- a frustrating event

Post by marktownley » Thu Apr 30, 2020 10:56 am

I just used a FOV calculator to see what different eyepieces give with the Lunt 50. One of my regular for full disks is the TeleVue 15mm plossl. I plumbed in the 8mm Ethos too, a lot of space and not much sun for the £££. 8mm Plossl looks like a good one if the eye relief isn't an issue.
astronomy_tools_fov (1).png
astronomy_tools_fov (1).png (97.17 KiB) Viewed 1343 times
https://astronomy.tools/calculators/field_of_view/


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