Anyone used Lunt LS80 for imaging using B1200?

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SimonM
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Anyone used Lunt LS80 for imaging using B1200?

Post by SimonM »

The good folks at Lunt recommend a B600 filter for Visual and a B1200 filter for Visual and Imaging with an LS60. Also using a B1200 for Visual and B1800 for Visual and Imaging with an LS80. The argument given is that the target (The Sun) is 4.2mm and the filter is 6mm with a B600 with an LS60.

They say this works because the scope forms an image e.g. at 420mm and the EP must be placed to align with the image e.g. 16mm behind it to achieve focus. With a camera, the CMOS sensor is placed at 420mm and they estimate it can be up to 50mm closer than using an EP.

The reason given is the cone of light that gets wider as you move away from the image plane. With a MINI camera (I have a QHY5III178M) the guide camera allows it to be placed further into the 1.25" barrel and if necessary outside of the barrel using a 20mm extension. A pancake-style camera can be directly attached to the T2 of a Lunt BXXX Blocking Filter - so not so effective.

So, I get it for the B1200 with the LS60. But the target with an LS80 is also 4.2mm, so the cone is roughly the same shape. If it's a near-miss with the B600 but the B1200 is plenty for an LS60, then why not a B1200 with the LS80? The kind folks at Lunt also say that the Etalon in the LS60MT is not the same as the one in the LS80MT. This means you can't easily upgrade a modular setup with a new LS80 refractor (which they sell) - or can you?

Simon - 50 posts on and I'm still rambling. One day I will get this sorted (promise)! :bow2


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Re: Anyone used Lunt LS80 for imaging using B1200?

Post by marktownley »

:lol: What question are you asking???


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Re: Anyone used Lunt LS80 for imaging using B1200?

Post by SimonM »

marktownley wrote: Thu Feb 04, 2021 8:58 pm :lol: What question are you asking???
Can you use a Lunt LS80 for imaging using a B1200 Block Filter e.g. without needing to get the B1800 for Visual and Imaging? The usual advice for Visual and Imaging is to get the larger Blocking Filter, not sure why this applies with LS80 being not dissimilar to LS60.


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Re: Anyone used Lunt LS80 for imaging using B1200?

Post by marktownley »

Yes you can.

The rule with blocking filters is the smaller the number the more vignetting you will get. Remember chips are getting ever larger on cameras, gone are the days of 640x480 pixel chips where this sort of thing was never a consideration. Remember with eyepieces if the field stop diameter of an eyepiece is greater than the blocking filter size you will get vignetting.

With my Coronado scopes I found I used 12, 15 and 18mm focal lengths the most which worked with the BF18 (the 18mm eyepiece has black space around the sun so the vignetting doesn't matter.

It makes no difference with the blocking filters with the 60mm or 80mm scopes as both are f7, so the light cone is the same diameter for the same distance from either the camera chip or the eyepiece focal plane.


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Re: Anyone used Lunt LS80 for imaging using B1200?

Post by SimonM »

marktownley wrote: Thu Feb 04, 2021 9:38 pm Yes, you can.

The rule with blocking filters is the smaller the number the more vignetting you will get. Remember chips are getting ever larger on cameras, gone are the days of 640x480 pixel chips where this sort of thing was never a consideration. Remember with eyepieces if the field stop diameter of an eyepiece is greater than the blocking filter size you will get vignetting.

With my Coronado scopes, I found I used 12, 15, and 18mm focal lengths the most which worked with the BF18 (the 18mm eyepiece has black space around the sun so the vignetting doesn't matter.

It makes no difference with the blocking filters with the 60mm or 80mm scopes as both are f7, so the light cone is the same diameter for the same distance from either the camera chip or the eyepiece focal plane.
Total agreement, except, you are using your Coronado scopes for Visual?

Agreed. Great to know that the B1200 would be OK for Visual and Imaging, for both LS60 (as recommended) but also for the LS80 (where the good folks at Lunt recommend B1800)!

Understood. I intend to use the QHY5III178M that I have as a guide camera. It is 4.92mm x 7.37mm (and 2048 x 3072, with the 2.4 μm pixels). By chance, I already have a smallish sensor and so not the best and not the biggest. Alexandra gets good results with the QHY 178 version and not the ZWO 178 version. I assume (for now) that it will perform badly e.g. with Newton Rings) and will require some kind of tilt correction (as used on her pancake ZWO 178).

Except with your Coronado scopes, you were using them only for Visual and with an 18mm Blocking Filter? The Coronado SolarMax III 70mm BF15 Double Stack Solar, is also available with a BF10, but not a BF18 Blocking Filter. Would it be a good choice for Visual and Imaging? They are a lot cheaper in the UK than a Lunt LS60 or LS80 double-stacked (if that is a reasonable comparison to make). My take is that SolarMax is primarily for Visual and appears to show a good 3D like quality. Also suitable for Imaging?

Agreed. Common sense says that the light cone is the same for an f/7 scope. Both the LS60MT and LS80MT are f/7 for h-alpha. For WL the LS60MT is f/6. So the same blocking filters can be used for Visual and Imaging.

I'm 99% certain to get the LS60MT. In weaker moments, I look at the Coronado SolarMax III 70mm BF15 Double Stack Solar as a potential Visual and Imaging h-alpha scope, but I'm also 50% (undecided) if it is suitable for imaging. I contemplated an LS80MT with only a B1200, but I'm also 99% sure it is too expensive (for me).

A wildcard thought, would my 550mm f/5.5 Refractor be a good match for the "modular" LS60MT Etelon. Perhaps if I stopped it down to f/7, it might (just) work as well as an LS80MT that is 560mm and f/7 for single-stack? For double-stack, the front-mounted Etalon would make it f/9 and offer no advantage over using it with the LS60MT. Mix 'n match was never going to be a good idea.

Simon


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Re: Anyone used Lunt LS80 for imaging using B1200?

Post by Highbury Mark »

Am sure you’re aware but the Coronado 70 actually uses a 60mm etalon. And the parent scope is a basic achro, rather than Lunt’s ED.


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Re: Anyone used Lunt LS80 for imaging using B1200?

Post by SimonM »

Highbury Mark wrote: Fri Feb 05, 2021 1:27 pm Am sure you’re aware but the Coronado 70 actually uses a 60mm etalon. And the parent scope is a basic achro, rather than Lunt’s ED.
Yes, I'm familiar with the description of the product. The Meade website seems open enough about it:
The SolarMax III is a 70mm F/5.7 refractor equipped with 60mm external hydrogen-alpha (H-a) filters. This model is a double-stacked (<0.5 Angstrom) bandpass with a 15mm blocking filter.

Additionally, the SM3 70mm includes only external "True" H-a etalon filters giving higher contrast views and sharper features compared with models using smaller internal H-a etalon designs. Experience darker backgrounds, sharper features, and higher contrast with the SolarMax III series telescope.

Day and night
Whether you are focusing on the solar edge or surface features in the chromosphere, the SolarMax III 70mm is the solar scope for you. Since both etalon filters are now external to the telescope, you can easily remove both filters and rear blocking filter diagonal to use the scope as a normal refractor for night time astronomy. It’s like having two scopes in one!
I have also seen images looking into a distant orchard. The edge definition looked more like a child's kaleidoscope than anything you would want to see through a modest telescope or cheap pair of binoculars. A traditional achromat has two lenses (flint and crown glass) and this is not one of those. There appear to be three controls for the Etalons. Rich and tilt on the first one and tilt on the second (that is a bit confusing for me). The front Etalon also has a central obstruction to try to maintain a separation between the components of the etalons. Aside from the fact that it looks like something from a Set from Starwars, is it any good for h-alpha for Visual and Imaging - it seems to have a loyal following...

Using fewer lenses for a one target/one wavelength scope isn't that uncommon in Solar scopes. The Lunt LS60THa also has a single front objective, but with a second lens before the Etalon (one is positive and one is negative). For true multi-use, the newer LS60MT is an ED doublet - one is FPL51, LS80MT is also an ED doublet - one is FPL53 and only the LS100MT is a true 3 element APO with one FPL53 element. The LS60MT also has a bigger front element and is 70mm. So that scope is f/7 for h-alpha and f/6 for nighttime use. All the Lunt scopes have an internal SS Etalon. The LS80MT and LS100MT also use a smaller DS Etalon.

Simon


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Re: Anyone used Lunt LS80 for imaging using B1200?

Post by marktownley »

Just my thoughts on both the Lunt modular scopes and the Coronado SMIII series, both are going to be using the bottom of the range optics they can get to keep costs down. While they will be fine with Ha, a bit like you say, it will be looking through a kaleidoscope if you try and use these poly-chromatically for night time stuff.

Sorry, the bf18 I talk about with my Coronados is a BF15 (coronado blocker) - typo from me! Yes, I use the eyepieces I talked about visually with these scopes.


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Re: Anyone used Lunt LS80 for imaging using B1200?

Post by MapleRidge »

Hi Simon...

I have both the B1200Ha and B1800Ha blockers and have had no issues with the smaller BF while imaging. The B1200Ha was the only one I had for several years, and added the B1800Ha to match a longer focal length scope.

I generally use the B1800Ha now days as I have the tilt adjuster threaded to it and just swap it between the LS80 and my modded 150mm scope, to make life easy . I would recommend getting the largest blocker you can afford...leaves the option to use it with future scopes, but the B1200Ha has no faults in it as a default.

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Re: Anyone used Lunt LS80 for imaging using B1200?

Post by Carbon60 »

...... as Brian and Mark say....

Personally I use a BF1200 (12mm) with my Lunt 60 for imaging and visual and a 15mm blocking filter with my modded scope.

Stu.


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