LS50 mod questions from a beginner

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Vinch
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LS50 mod questions from a beginner

Post by Vinch »

Hello,

I am looking into buying a solar telescope and, to guide my choice, I do not want to close the door on possible future modifications, especially given the high prices of large diameters and the fact that finding a good etalon seems to be a lottery.
  • To make a modification on the Lunt LS50, is it easy to unscrew the etalon from the original scope? I saw HERE that the red part of the etalon has an M68 threading, but is it enough to simply unscrew it from the original scope or is there a "safety" feature to prevent easy unscrewing? I saw on some PST posts that glue is used to prevent opening. How does it work on the LS50? I also understand that it is easier to modify an LS50 than an LS60?
  • Does unscrewing the etalon from the original scope void the warranty?
  • I mainly want to do visual observation. Is an LS50 modification suitable for visual use without any issues? Is there any danger to the eyes?
  • Once the etalon is unscrewed from the original scope, I assume that it can be used in the same way as a Quark? I could screw it onto other larger scopes but also screw it back onto the original scope and continue using it in its original configuration?
  • The LS50 is sold with a B600 but not a B1200 (while the LS40 is available with a B1200?). If I buy the LS50 with a B600, does that limit the possible modifications later? I saw in this post that for a "good mod", a B1200 is preferable. Would a B600 limit the possible diameter of scopes I could combine with the etalon?
  • If I use a 100mm scope for example, I read that an ERF must be placed at the beginning of the scope to reflect a good part of the energy. But isn't an ERF already integrated into the LS50 etalon module? If so, should it be removed and is it easy to do?
  • In the case of modification to a 100mm scope for example, is it still useful and feasible to use a double stack?


Thank you in advance!


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Ivan
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Re: LS50 mod questions from a beginner

Post by Ivan »

Hello and welcome!

Yes, etalon is easy to unscrew, there is no glue (I have two Lunt 50).

Modern modular LS60 are also easy to modify, they have more etalon, but they also cost more.

For visual and photo it is better to have an ERF. Some, including me, don't use it, but I use 2" CLS before etalon. This is not the best solution.

To get out of etalon, you will be able to use it effectively on f7 lenses and so on. Then you can screw it back on.

The more BF the better, but it all depends on the camera. To begin with, the B600 is what you need. In addition, remember that by increasing the focal length (by moving etalon to a large telescope), the size of the sweet spot will decrease and you most likely will not need a large BF.

A double stack is much better than one in all cases.

Ivan


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Re: LS50 mod questions from a beginner

Post by Vinch »

Thanks a lot for these answers!
  • So, if I understand correctly, can we say that we can use the LS50 etalon module a bit like a Quark on scopes with different apertures? The only difference I see is that LS50 etalon must be used with f/7 scopes while Quark is more flexible as it can be used with f/4 to f/9 scopes? Or are there other differences? Is there a notion of sweet spot as well with Quark?
  • If I have an LS50 etalon mounted on a 100mm scope equipped with a Baader D-ERF filter on the top, how will I be able to double stack it? Do I have to use a front Lunt LS100FHa Solar Filter (see HERE, quite expensive), but then how will it work with the ERF filter? How can we combine both in front of the scope? Or do we have to use an internal DSII module (see HERE)? But will it adapt with this mod?
Thanks!


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Re: LS50 mod questions from a beginner

Post by Ivan »

To the first question, yes. The internal etalon Lunt 50 is better used on the f7 lens.

I don't have a Quark. If we talk about the possibility of using Quark with different lenses, then, yes, it is more versatile. But it's not easy to get a good Quark, you may be unlucky and the band will be too wide, but if you're lucky, you'll have a great copy.
You can search the forum for owner reviews and photos, among them there will be copies of exceptional quality, but there will also be disappointments. However, you may not be lucky with any etalon.

I think that any commercial etalon has a sweet spot, which is the cost of low-volume, but still in-line production.

The best solution to double the stack is to buy an aperture filter, for example the Solormax90. 100mm Lunt filter is so expensive that its price is scary to look at. All aperture filters have a red erf on the front, so it doesn't seem to make sense to buy another one.

The second option is to buy an internal module, the link to which you sent, or buy a second Lunt50 as I did: viewtopic.php?t=33541

Or buy a pst and make a modification of Lunt50 + pst https://youtu.be/J_604nzl6Cg?si=5T8A1uflPV8tKyqr (in Russian).
Note that in this scheme, the etalon pst is the first, so you will need an f10 lens. But you can use SCT, for example 8". This is already a really high resolution. Do not forget about erf, it is strictly mandatory here.

Ivan


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Re: LS50 mod questions from a beginner

Post by Ivan »

I also recommend you to study these topics.

You will understand how to correctly find the distance at which etalon should be located on the new telescope:
viewtopic.php?t=19238

Mod of two ds Lunt 80 modules:
viewtopic.php?t=32743

Ivan


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Re: LS50 mod questions from a beginner

Post by Vinch »

Hello!

Your mod with two LS50 is very smart! It's great that you don't have internal reflection and red glow as mentioned here. As you have 2 Lunt LS50, did you notice a difference in terms of quality between them? From what I have read, it seems that you have to be lucky to get an etalon of good quality.

Thanks!


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Re: LS50 mod questions from a beginner

Post by Ivan »

Vinch wrote: Sat May 25, 2024 1:02 pm Hello!

Your mod with two LS50 is very smart! It's great that you don't have internal reflection and red glow as mentioned here. As you have 2 Lunt LS50, did you notice a difference in terms of quality between them? From what I have read, it seems that you have to be lucky to get an etalon of good quality.

Thanks!
Hi, I didn't see your message, so I didn't reply for a long time.

In fact, during the subsequent operation, I discovered a ghost. It just doesn't overlap with the Sun's disk. Nevertheless, it gives a slight illumination of the disk on one side. However, this does not interfere, because you can always reduce the exposure a little.

As for the quality of the etalons, they are about the same for me and their sweet spot is not in the center, but a little closer to the edge. I was lucky in this, although it is not difficult to make an adapter that allows you to rotate etalons. If the location of the spot sweet on etalons were different, for example, one in the center and the other on the edge, it would be more difficult.

But even in this case, I think the sweet spots would still overlap. The quality of all etalons is of course different, some are better, some are worse, but in general the level is good, it seems to me that quark has a greater spread in quality, and the risk of getting not exactly what you want is higher.

Ivan


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