To Double Stack or Not To Double Stack...?!

[PhotoGav]

Not sure if this is really in the right section, but I thought the right people would see my question in here...

I have a Lunt LS50THa and am wondering whether the expense of a Double Stack unit is really worth it? I use the scope for both visual (mainly outreach) and for imaging. I am pretty happy with my imaging results, but am always keen for better! I have considered the Quark route as I have an Esprit 100, but have really decided that is not best for me as it would be tricky when the Esprit is set up for DSO duties, as it is now for example. I like the full disk capabilities of the Lunt with my Chameleon 3 and I use a 2.5x Powermate to get in a bit closer.

So, what do you reckon - should I go for the Double Stack unit?

Thanks in advance. 

[laudropb]

Hi Gav. I was in much the same position as you last year. I am purely visual and wondered if the outlay for a double stack for  the LS 50 could be justified. I read in some reports that it dimmed the image too much and rendered the views of proms less detailed, while others said it was a great improvement. I finally bit the bullet and ordered a DS unit from FLO. It has turned out to be one of the best decisions I have made. The difference in the surface detail is night and day. Yes it did dim the image but not to any great detriment. As for the proms, it certainly does not make them any worse and on certain occasions I think it improves them. I also find that it enlarges the sweet spot and greatly improves low mag, whole disk views. Definitely one of my best decisions.

Edited April 6, 2021 by laudropb

[PhotoGav]

As an example, here is my image of the Sun in Ha yesterday (2021-04-05). What would a Double Stack do to improve this image, if anything?! Or do I need a completely different set up to make a difference?!

[PhotoGav]

1 minute ago, laudropb said:

Hi Gav. I was in much the same position as you last year. I am purely visual and wondered if the outlay for a double stack for  the LS 50 could be justified. I read in some reports that it dimmed the image too much and rendered the views of proms less detailed, while others said it was a great improvement. I finally bit the bullet and ordered a DS unit from FLO. It has turned out to be one of the best decisions I have made. The difference in the surface detail is night and day. Yes it did s the image but not to any great detriment. As for the proms, it certainly does not make them any worse and on certain occasions I think it improves them. I also find that it enlarges the sweet spot and greatly improves low mag, whole disk views. Definitely one of my best decisions.

Ah ha, thank you, that is a very interesting and helpful reply. It looks like you may have pushed me over the edge!!

[laudropb]

Nice image. I don’t image myself but visually the double stack brings out surface details which I just do t see with the single stack.

[PhotoGav]

3 minutes ago, laudropb said:

Nice image. I don’t image myself but visually the double stack brings out surface details which I just do t see with the single stack.

Thank you. It is good to hear that the DS does add a significant enhancement.

[Highburymark]

5 hours ago, PhotoGav said:

As an example, here is my image of the Sun in Ha yesterday (2021-04-05). What would a Double Stack do to improve this image, if anything?! Or do I need a completely different set up to make a difference?!

Looks like you’re picking up some nice detail in single stack Gavin. And as the Sun is pretty blank at the moment, you wouldn’t really appreciate the full benefits of a second filter right now.
But when activity increases, double stacking transforms views of surface features like filaments. Instead of just being perceptible, they become dark and detailed, in sharp contrast to the brightness of the background chromosphere. This provides a real sense of 3D, particularly if they also arch over the solar limb, into a so-called ‘filaprom’. The mottling across the rest of the disc becomes more defined, and you get a clearer appreciation of the swirling detail around active regions and sunspots. As John says, views are slightly dimmer, but certainly not enough to diminish views in any way. 

[PhotoGav]

2 hours ago, Highburymark said:

Looks like you’re picking up some nice detail in single stack Gavin. And as the Sun is pretty blank at the moment, you wouldn’t really appreciate the full benefits of a second filter right now.
But when activity increases, double stacking transforms views of surface features like filaments. Instead of just being perceptible, they become dark and detailed, in sharp contrast to the brightness of the background chromosphere. This provides a real sense of 3D, particularly if they also arch over the solar limb, into a so-called ‘filaprom’. The mottling across the rest of the disc becomes more defined, and you get a clearer appreciation of the swirling detail around active regions and sunspots. As John says, views are slightly dimmer, but certainly not enough to diminish views in any way. 

Thank you, that’s good to hear. It certainly sounds like it would be a worthwhile addition. I have an opportunity to pick up a second hand DS ‘in perfect condition’ at a sensible price. I think it is rapidly becoming too good an opportunity to turn away. At least I would then be ready for the increase in activity due as we move back towards maximum, eventually!

[PhotoGav]

So, I took the plunge and acquired a Double Stack for the Lunt 50. I gave it a test drive today. Here are the results...

Single Stack:

 

Double Stack:

 

Conditions were reasonable, but not perfect - it was quite hazy by the time I was up and running.

I think the DS definitely has great potential, but I'm not convinced that I have found the best tune for it yet. The bright area of the image is quite narrow and I found it difficult to get it in the correct place. I felt as though it either showed one side or the other in best contrast, but never the two together. Any advice on tuning and that sort of thing would be most welcome, please!

 

[JeremyS]

Looks very good to me @PhotoGav 👍🏻

[JeremyS]

I have a related q. 
I have a Lunt 50 and it’s wonderful. I’m using it visual only.

Would the next step up in image quality be:

1. adding a Lunt 50 double stack filter to the existing Lunt

or

2. Going for a Lunt 60 single stack scope

?

I’m sure @Nigella Bryantwouks say Lunt 60 plus double stack 🤣

[PhotoGav]

4 minutes ago, JeremyS said:

Looks very good to me @PhotoGav 👍🏻

Thanks Jeremy. 

Here's a close up that I took as well (with a 2.5x PowerMate):

[PhotoGav]

1 minute ago, JeremyS said:

I have a related q. 
I have a Lunt 50 and it’s wonderful. I’m using it visual only.

Would the next step up in image quality be:

1. adding a Lunt 50 double stack filter to the existing Lunt

or

2. Going for a Lunt 60 single stack scope

?

I’m sure @Nigella Bryantwouks say Lunt 60 plus double stack 🤣

Good question (and yes, Lunt 60 with DS would be ideal! Hey, why not the 80?!!?). I will be interested to hear what people say.

I think that there is a significant increase in contrast with the DS on the 50, though I have only used it with the camera so far, not with an eyepiece.

Certainly the cheapest next step would be a DS for the 50 (though not exactly cheap!).

[Nigella Bryant]

7 minutes ago, JeremyS said:

I have a related q. 
I have a Lunt 50 and it’s wonderful. I’m using it visual only.

Would the next step up in image quality be:

1. adding a Lunt 50 double stack filter to the existing Lunt

or

2. Going for a Lunt 60 single stack scope

?

I’m sure @Nigella Bryantwouks say Lunt 60 plus double stack 🤣

Hi Jeremy, the problem visually will be quite a significant decrease in light visually. It'd be ok imaging as you can adjust the settings. 

Of course I'd say go for a double stacked 60mm, without question, lol 🤣🤣🤣

[AdeKing]

I'm using a LS60 visually but with a 50mm DS attached.

Yes I am getting a significantly dimmer view than single stacked, but the boost in contrast on surface detail is also significant and I get what I think are amazing views.

Sometimes I use an R-Sky observing hood to cut down external light but not all the time.

I've never really struggled visually with the brightness when the DS is attached and as the 50mm DS is reducing my 60mm aperture to 50mm anyway, the brightness that I'm getting must be equivalent to a LS50 with 50mm DS attached anyway.

I'd love a 60mm DS but ££££ prevents me from taking the plunge.

Edited April 18, 2021 by AdeKing

[Highburymark]

12 hours ago, JeremyS said:

I have a related q. 
I have a Lunt 50 and it’s wonderful. I’m using it visual only.

Would the next step up in image quality be:

1. adding a Lunt 50 double stack filter to the existing Lunt

or

2. Going for a Lunt 60 single stack scope

?

I’m sure @Nigella Bryantwouks say Lunt 60 plus double stack 🤣

I’d definitely prefer a 50DS over a single stack 60 Jeremy. No contest (unless you’re one of lucky few who gets a top performing LS60 single stack - maybe a one in twenty chance?). The dimming is not a problem in my view - even with binoviewers. But to really appreciate the extra detail, I block out any external light with a huge silver observing duvet.

[Luke]

On 17/04/2021 at 20:48, JeremyS said:

I have a related q. 
I have a Lunt 50 and it’s wonderful. I’m using it visual only.

Would the next step up in image quality be:

1. adding a Lunt 50 double stack filter to the existing Lunt

or

2. Going for a Lunt 60 single stack scope

?

I’m sure @Nigella Bryantwouks say Lunt 60 plus double stack 🤣

My thoughts are, get the largest aperture funds allow / you can live with single stack, then double stack it at a later date once you have recovered! I think that means I'd go for the 60 single stack. To be double stacked at a later date! Two lovely options anyway!