Future-proof DS mod options for Lunt LS50 and Svbony 102mm

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Future-proof DS mod options for Lunt LS50 and Svbony 102mm

Post by CVABuck »

Greetings,

Since this is my first post in Solar Chat, I'll include some background information. To get to the meat and potatoes of my question, skip ahead to after the images.

I'm a photographer first and foremost. If I can't print it big, I don't want it. I've also had a lifelong interest in all things space, but aside from landscapes and occasionally strapping my Nikon onto a simple polar tracker (Ioptron Skyguider pro), I'm still relatively new to astro imaging. I recognize that there are no free lunches, particularly with solar imaging. I'm no stranger to modifying equipment, including OTAs and fabricating components, but I'm very new to Hydrogen A. Here's a couple shots of where I'm at so far: First is full disk, after the eclipse, second is an attempt to crop in on AR3664 in sub-optimal seeing before it rotated out of view.

Image

Image

The meat and potatoes:

I've been enamored with HA since I saw some images during the last solar maximum. I purchased a Lunt LS50THa last March, and due to a backordered feathertouch it wasn't delivered until a few weeks before this year's eclipse. It's been a fun little learning curve since then both visually and imaging. For imaging, I have an ASI2600mm, a QHY 585C, and I've been using a Televue Powermate 2.5x. Given the narrowband nature of HA, I've almost exclusively used the ASI, aside from a somewhat unsuccessful attempt to use the 585 on a very large prominence.

AR 3664 has given me detail fever, and now I find myself in a bit of a quandary as to my next step. My initial plan was to adapt my LS50 etalon to a Svbony SV503 (102mm doublet, f/7, 714mm Focal Length). The only thing that conversion is waiting on is a Baader 110mm D-ERF and the associated frame that I'm going to design and 3d print for it once I have it in hand, and then some final in-situ measurements, fabrication, and testing. Then, assuming a decent annual bonus next March, combined with a good fall/holiday art show season, I would hopefully be able to grab a LS80 Internal DS and fabricate the necessary parts to match the Svbony.

Now, I'm thinking I might want to explore options for double stacking before modifying the Svbony, and grabbing the TV Powermate 5x for a little extra reach in the meantime. The only downside to this is that I'm currently working with a budget of approximately $1400 after this coming pay period, and relatively little until next year's bonus so while I would be able to afford an LS50 DS etalon at the cost of holding off on the D-ERF, the LS50 DS wouldn't do me any favors once I started using the Svbony. I think I'd rather spend the money on more "future-proof" options. I'm also wondering if I wouldn't be better served with a smaller sensor, faster FPS unit, such as something with an IMX568 sensor. I'm going to do some experimentation at my next opportunity with various hardware binning and crop modes to see what kind of framerate I can squeeze out of my ASI2600mm in real-world situations. If my understanding of thumbrules is correct, adding the TV 5x to the LS50 will give me an effective F/35, and running bin2 on my ASI2600 will give me an effective pixel size of 7.5u, which should still be in the ballpark of optimum resolution vs resolving power.

Additionally, from lurking in this forum off and on over the years, I've seen it mentioned that as magnification increases, imaging FPS also needs to increase, with a nominal 100 FPS. So, this leads to:

Question 1: Why is 100FPS recommended for small surface details? My assumption is that at greater magnification, the volatile nature of the solar surface will noticeably change over the course of several seconds, so the greater FPS would allow for more images for stacking before artifacts are introduced. If my assumption is off base, I would appreciate a better understanding.

Question 2: In pursuit of better detail imaging, with an eye towards printing (2000x2500 pixel minimum), which of the following would those of you with more experience consider more or less important:
a) Longer focal length OTA
b) Upgrade TV Powermate 2.5x to TV Powermate 5x
c) Double stacking
d) Smaller/faster FPS sensor
e) Upgrade to a larger aperture single stack etalon (therefor larger Jacquinot spot)

Question 3: Based on my description of what I have and what my future plans are, care to share any advice or experience that might cover something I haven't thought to ask?


OTAs: iOptron RC8, Lunt LS50THa, Svbony SV503 102mm f/7, too many Nikon lenses to list
Mounts: iOptron SkyGuider Pro, iOptron CEM-40, too many static tripods/heads to list
Cameras: ZWO ASI2600MM, QHY QHY5III585C v2, too many Nikons to list
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Re: Future-proof DS mod options for Lunt LS50 and Svbony 102mm

Post by solarchat »

hi welcome to the forum!

You may not believe this but we get almost the exact same basic question about four times a month here. A person buys a small h alpha scope to start because they don’t know what they are getting into or for financial reasons and then starts adding every accessory on Earth and wants to doublestack the scope. (doublestacking any h alpha scope reduces the brightness by 40% which makes a really dim image in a 5mm scope this drastically increasing exposure times needed to image)
Generally it turns out that the newcomer will end up spending significantly more going this route then if they had simply purchased a 60 or 80 mm scope to begin with. it’s very similar to the way people get involved in DSLR photography.
How many times have people asked us what camera should they buy when they want to start doing wildlife photography or something similar? You tell them this, this and this and then they think they know better and go out and buy this and this which is a lot cheaper because they have “done their research” and think they know better. then a few months later they end up buying what you recommended in the first place once they learn how to use the equipment.
lol…
It’s just the way things go in every hobby.

to answer your questions:

1 Yes, you are right. The chromosphere of the sun is very dynamic and changes rapidly. The faster of the frame rate, the less blur in the finished product.

2 DEFINITELY E!!!!! I know you’re going to buy the double stack anyway :) I did, :)but you should stop spending money on this scope which is basically a visual use scope.. Just slow down a little bit until you have the money to get a 60 or 80 mm scope without all this modding stuff.

3: Slow down and learn how to tune the scope properly and how to take the best image you can with the current equipment that you have without adding anything else. Use this time to put away a little extra money to get a larger scope eventually.
You already have the stuff you need and more equipment is not going to gain you more experience which is what you could really use now.

Anyway, I’m glad you’re here and hope that you share your thoughts and images on your journey to solar imaging.

I’m sure other people will have different advice.


Stephen W. Ramsden
Atlanta, GA USA
Founder/Director Charlie Bates Solar Astronomy Project
http://www.solarastronomy.org
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Re: Future-proof DS mod options for Lunt LS50 and Svbony 102mm

Post by CVABuck »

That's great advice! And you're absolutely correct - no sooner than I had the scope in hand, I found myself wishing I'd started with the 60 or 80. C'est la vie. But it has been an incredibly fun experience thus far, both visually and with imaging.


OTAs: iOptron RC8, Lunt LS50THa, Svbony SV503 102mm f/7, too many Nikon lenses to list
Mounts: iOptron SkyGuider Pro, iOptron CEM-40, too many static tripods/heads to list
Cameras: ZWO ASI2600MM, QHY QHY5III585C v2, too many Nikons to list
http://www.buckphotography.com || https://www.printables.com/@CVABuck_862251 || http://www.instagram.com/photography_by_Buck

"Sometimes life has a way of knocking you down, just to force you to look up." - Random girl I knew in college
"For once you have tasted flight, you will walk the Earth with your eyes turned skyward, for there you have been, and there you long to return." - Leonardo da Vinci
"A library is like an island in the middle of a vast sea of ignorance..." - Lemony Snicket
"Give me a place to stand, and I'll move the world." - Archimedes of Syracuse
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Re: Future-proof DS mod options for Lunt LS50 and Svbony 102mm

Post by marktownley »

Welcome to the forum!

Stephen has excellent advice. Concentrate on getting the tuning right on the lunt50 first. With your camera (2600mm) a 2.5x is about as much magnification as you can use, don't bother with the 5x - that applies to the larger scope when modded. If you use 2x binning on the scope with a 5x the image size is half - it's exactly the same as not binning and using a 2.5x. You will find you need to use ROI on the camera when you use the mod else you will just get out of band sweet spot visible.

Mark


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Re: Future-proof DS mod options for Lunt LS50 and Svbony 102mm

Post by Ivan »

Hi! I am not a pro in this field, but I can tell you about my experience. 

I also have a Lunt50, and I started with it, then I modified my WO Megrez90 and added etalon Lunt50 to it. I did not use an external erf, instead I installed 2" cls in front of the red erf Lunt. I can't recommend doing this, but it's been working for me for 3 years now. I also know that I am not alone.

I have a x5 telextender and it doesn't match very well with the Lunt50 and WO mod. In both cases, there is a lack of lens resolution and seeing. I limited myself to x2 or even x1.5 Barlow.
As for fps, of course, the higher it is, the better, but even with a 100mm lens, values of 50 and even lower, I think you will have enough. The sun is certainly very dynamic, but not on this scale.
After shooting a year on mod WO, I realized that the photosphere that shines through upsets me so much that after processing a lot of information, I bought a second Lunt50 and doubled the stack. The double limb has disappeared, but the sweet spot has also decreased as expected. Overall, it was a success, because I have not heard that anyone doubled the stack in this way.

Then, after seeing the work done with SHG, I realized that my photos needed improvement. And I bought an aperture etalon Lunt50. My goal was originally a narrow band, not a scale, and I bought it based on the fact that I would only use it on the Lunt50.

In general, everything works and almost the entire disk is placed in the sweet spot. But the scale is too small, and then I turned out the adapter and began to use it on WO, i.e. I use a 50mm etalon on a 90mm lens. Again, the best solution would be to use the SM90, but it is very expensive and it is difficult to buy anything from us now.

However, it works and now I have a triplestack. But, as the focal length increases, the sweet spot decreases, so I take off the ROI and make mosaics.

Looking back, I probably wouldn't have changed anything. Yes, I could postpone the purchase of the Lunt50, save up money, and maybe buy the Lunt80 DS. It would have taken a couple of years, but after buying the Lunt50, I immediately started shooting.

I want to say that for me our hobby is a compromise, however, like everything in life. I'm sorry for writing so much.

Photo of the WO modification and an example image:
https://flic.kr/p/2pP1xGb
https://flic.kr/p/2pRB2S7

Ivan


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Re: Future-proof DS mod options for Lunt LS50 and Svbony 102mm

Post by CVABuck »

Thanks for the information Mark and Ivan - I agree, I definitely need to get more scope time in and practice, practice, practice, particularly with tuning.

The reason I was wanting the D-ERF for the 102 was because with that wide of an aperture, I'm concerned with internal heating without it, and I definitely don't want to burn up the etalon. My goal was to 3d print a frame to hold it - loose enough to allow for thermal expansion - in fiber-filled nylon for both the rigidity and heat resistance (In 3d printing engineering circles we joke that properly annealed fiber-filled nylon is plastic aluminum). I would then be able to make a series of adapters to use that with other optical tubes in the future.

Ivan, reading some of your build threads was part of my inspiration, and I can definitely understand some of the speed bumps and struggles you hit along the way.

I think I'm going to take a good bit of Stephen's advice and hold off on any purchases (unless I see a used 50 or larger come up for sale too cheap to pass up), for the time being while I continue to get shutter time. I do often find myself getting caught up in the excitement of things, and it's even moreso with this as I have a bunch of professional photographer friends that are all egging me on because they've never seen anything like this before.

If I look towards the medium-term, until I can afford a Lunt 100 (or heck, go big, take out a second mortgage, and go for the 300!), I might consider grabbing the 80/100 DS etalon to use with the Svbony, and possibly DSing the 50 with improvised adapters, until I can afford the Lunt 100, then I'll already have the DS in hand. My question there is physically and optically, what's the difference between the 100 internal DS and the 80/100 universal DS?


OTAs: iOptron RC8, Lunt LS50THa, Svbony SV503 102mm f/7, too many Nikon lenses to list
Mounts: iOptron SkyGuider Pro, iOptron CEM-40, too many static tripods/heads to list
Cameras: ZWO ASI2600MM, QHY QHY5III585C v2, too many Nikons to list
http://www.buckphotography.com || https://www.printables.com/@CVABuck_862251 || http://www.instagram.com/photography_by_Buck

"Sometimes life has a way of knocking you down, just to force you to look up." - Random girl I knew in college
"For once you have tasted flight, you will walk the Earth with your eyes turned skyward, for there you have been, and there you long to return." - Leonardo da Vinci
"A library is like an island in the middle of a vast sea of ignorance..." - Lemony Snicket
"Give me a place to stand, and I'll move the world." - Archimedes of Syracuse
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