Lacerta solar wedge (2"/M54) for white light observing

[Victor Boesen]

This thread will consist of my impressions of the 2" (M54) Lacerta solar wedge with the Brewster angle prism. This includes observing through it, build quality and other aspects I find important

Build quality
I received the bare prism so the final verdict may vary for different units/combinations of accessories, but I'll try to focus on the wedge only.

The metal construction of the wedge feels very solid, and the large heatsinks on the rear end of the wedge don't feel too large, nor too small to the point where they would essentially be unnecessary. The angle of the Herschel prism itself can be adjusted with screws on the side of the wedge, and these don't seem to go loose or move the slightest when shaking the wedge.

The wedge clearly shows its infamous "Brewster angle" which I will eventually add a comment on later in the post.

I went for Baader equipment for the threads, for which I purchased an M54 to 2" clicklock clamp and an M48 to 2" nosepiece with safety kerfs*.
Furthermore I also use a 2" to 1.25" eyepiece adapter in which I have a Baader ND3.0 filter permanently mounted.

The entire wedge with the chosen accessories is quite large compared to a regular night time 2" diagonal!

The entire body including accessories ends up being quite large, but the feeling is very sturdy!

*The nosepiece is quite short, but I haven't had any problems with it and it feels secure in the focuser of my telescope.

Observing with the prism
The prism was used together with a 4 inch F7 apochromatic refractor and Explore Scientific 82 degree eyepieces.

I have only done a small amount of white light observing before including brief looks in SCT's, Cat's and my own Evostar 72ED with Baader white light film. It has never really caught my interest properly, but after getting hooked on solar with a Daystar Quark I couldn't help it, when an offer on a Lacerta wedge came up. After I had overcome the fear of pointing my 4" apo towards the sun, verifying the prism was in place together with the ND3.0 filter, I immediately noticed how bright the view was by just looking at the glass of the eyepiece and not through it!

You may notice my eyepiece is not all the way into the focuser. This is because the polarizing filter would otherwise hit the ND3.0 filter in the 2"-1.25" adapter. This is not a problem without the polarizing filter.

I placed a variable polarizing filter in the eyepiece and rotated the 2" to 1.25" adapter by simply loosening the clicklock slightly until the view was comfortable. This rotating mechanism works surprisingly well. Focusing on the solar limb I noticed a small active region in the center of the disk, which looked like a small colony of islands consisting of small umbras with faint gray penumbras. Limb darkening was also visible and some faculae towards the edge of the limb. I added a 2" OIII filter to the ND3.0 filter (acting as a solar continuum filter) and this reduced the brightness noticeably and faculae across the disk became visible. Adjusting the brightness with the polarizing filter in my 14mm eyepiece (51X) I could begin to see more faculae and granulation was also visible.

Two small sunspots visible on the 8th of July 2021 together with faculae just below the left sunspot

I found that low magnifications made it easier to observer the low contrast faculae, which I assume is due to a larger exit pupil. This meant I preferred keeping the magnification at around 50-80X, although I have yet to observer larger sunspots, so that might change my preference. I do see a zoom eyepiece coming in handy for white light, but funds are currently limited

I really enjoy the wedge and the view is very sharp with granulation, faculae and small sunspots easily observable at low magnifications. I really like being able to rotate the 2"-1.25" adapter to dim/brighten the view, and my OIII filter helps a bunch. Can't see myself observing without it, but I still think a 2" solar continuum filter is quite pricey for a single filter which may not perform much better than my OIII filter. I look forward to observer larger sunspots as I just barely missed AR2835

Final notes

The thing I'm most skeptical about is the open bottom of the wedge. I know this cools the prism a lot more efficient, but I have a slight OCD towards dust and speckles on optical equipment Another thing about the open bottom is the risk of burning yourself. I haven't done this yet, but I usually grab the diagonal, when nudging my scope to follow a target, and I could definitely see myself sticking my fingers too far into the prism housing at some point.
Together with the heat sink on the back, however, the prism stays nice and cool when observing with my 4" refractor. I even have difficulty feeling the slightest heat from the heat sink, which I find very reassuring!

Need a lighter? The Lacerta wedge got you covered!

The Brewster angle of the prims means that this might not be for everyone. If you're living far north/south - no problem! But, due to the angle of the prism you can risk having the need to observe with the eyepiece pointing towards the ground. Not only can this be uncomfortable, you would likely also need a taller tripod/mount. This feature is something that should not be overlooked since it can result in some uncomfortable yoga positions at the eyepiece.

If you're not looking into getting special adapters or not good with/don't want to worry about thread dimensions and adapters the naked Lacerta wedge body might not me for you. Instead I'd get the complete "set" which includes all the necessary adapters, or you can get something like the Lunt or more pricey yet highly coveted Baader wedge.

As the final note I'd like you to take my opinion with a grain of salt. As I briefly mentioned, I have never been a keen white light solar observer, and I can't compare the Lacerta wedge to any other wedges out there. I can only say that I'm very satisfied with mine, and I'm a huge fan of the build quality and ability to use this wedge in many other scopes of larger apertures due to its great dispersion of heat. I am definitely not disappointed with my purchase and I must confess I really like white light observing as well as H-alpha since the granulation and faculae are quite interesting features to observe together with sunspots of course!

Thanks for reading!

Victor

[johninderby]

Actually the open bottom is no problem heat wise. No heat escapes out the bottom and even when accidentally sticking a finger inside nothing happened. Maybe if you held your finger inside for a while? 🤔

You don’t have to worry about dust or dirt getting on the back of the prism as the rear surface of the prism isn’t a part of the light path you look through. 

You might want to read this review.

https://fullerscopes.blogspot.com/2019/02/lacerta-lac2s-2-50mm-herschel-prism.html

https://fullerscopes.blogspot.com/2019/02/lacerta-lacs2-brewster-angle-herschel.html

Edited July 8, 2021 by johninderby

[Rusted]

Thanks for the excellent review. I find myself in general agreement.
I have had a Lacerta 2" wedge for quite a while and used it on my 7" f/12 iStar refractor.
Now occasionally on my 6" f/10.
The heat sink gets hot with these larger apertures.
Optical quality seems fine.

The Brewster Angle is insignificant if you have a camera attached.
Not so good visually in high summer with high solar altitudes.

The Lacerta rotating adapter system is valuable for a polarizing filter and works really well.
The downside is the available, internal depth for multiple filters. The Solar Continuum plus polarizing plus ND. 
The downside is the darkness when you forget to turn the polarizer to match your brightness needs.
You can find yourself winding up the gain in SharpCap until you realise your error.
[Probably an age related error when WL isn't a major interest.]

The open bottom is valuable for centring the sun. I often tilt the prism so I can see inside when first setting up.
The inside of the heat sink gets quite a tan after many hours of tracking the sun.
But then many black anodized surfaces do.

[Victor Boesen]

17 minutes ago, johninderby said:

Actually the open bottom is no problem heat wise. No heat escapes out the bottom and even when accidentally sticking a finger inside nothing happened. Maybe if you held your finger inside for a while? 🤔

You don’t have to worry about dust or dirt getting on the back of the prism as the rear surface of the prism isn’t a part of the light path you look through. 

Haven't had my finger in there yet So perhaps I would feel it in time before things get too serious, but I think it'd be too stupid to even try it out "for fun"😅 I'm aware the backside of the prism doesn't really mattere as far as performance and dust goes, dust and fine surfaces aren't my thing anyways. Good thing I don't wear glasses!

[johninderby]

I have the stock rotator on the top with the ND3 and variable polarising 2” filters screwed to the bottom and a ZWO T2 to 1.25” filter adaptor screwed into the bottom of the T2 adaptor for the continuum filter.

Edited July 8, 2021 by johninderby

[Victor Boesen]

11 minutes ago, Rusted said:

I have had a Lacerta 2" wedge for quite a while and used it on my 7" f/12 iStar refractor.
Now occasionally on my 6" f/10.

Would love to have a look through such apertures! Must be quite a view under good seeing

[Victor Boesen]

1 minute ago, johninderby said:

I have the stock rotator on the top with the ND3 and variable polarising 2” filters screwed to the bottom and a ZWO T2 to 1.25” filter adaptor screwed into the bottom of the T2 adaptor. 

That's quite a long optical length! I could imagine you'd have trouble reaching focus in some telescopes? It's a really nice solution for keeping filters permanently in the wedge though;)

[johninderby]

1 hour ago, Victor Boesen said:

That's quite a long optical length! I could imagine you'd have trouble reaching focus in some telescopes? It's a really nice solution for keeping filters permanently in the wedge though;)

Fortunately in my Tecnosky 125 infocus travel is no problem even with the 2” extender still mounted on the focuser. Wish more scopes would come with a removable focuser extension for those using a wedge or binoviewer. 

Edited July 8, 2021 by johninderby

[Rusted]

Here is the Lacerta 2" wedge on my 7" f/12 with the 6" f/8 [H-alpha.]
Together on my home made mounting in my home made two storey observatory. A couple of years ago.

Larger instruments need very steady seeing to maximise their usefulness.
My Vixen 90mm f/11 with Lunt 1.25" wedge can give the illusion of a sharper image.
Until I need far more reach [power] to make a small detail visible. 

Yesterday there were a few small spots on a disturbed area in the far NW. AR12840[?]
So I used the 2" Lacerta, ASI174 and 2x Barlow on my 6" f/10 to show it.
The seeing was poor so 3m of focal length wasn't going to be razor sharp.
The curvature of the solar limb shows the scale of the image.
The 7" is waiting to be remounted on a home made cross-axis. under a new dome.

Edited July 8, 2021 by Rusted
added image

[Stu]

Great report @Victor Boesen, glad you are pleased with the wedge. I must say I do love white light observing. The contrast, sharpness and fine detail visible can be amazing when conditions allow. Don’t rule out (I know you haven’t) using higher powers. When conditions allow, there is plenty to be seen at x150 or even x200, bringing out the detail in large ARs and the granulation.

Somewhere in my garage I have an old 6” f10 scope which I intend to use for both Ha and white light solar observing when I get around to it.

[Victor Boesen]

54 minutes ago, Stu said:

Somewhere in my garage I have an old 6” f10 scope which I intend to use for both Ha and white light solar observing when I get around to it.

Thanks Stu! Wow 6" will be nice Will you be using it with a quark for H-alpha or the PST mod?

[Stu]

7 minutes ago, Victor Boesen said:

Thanks Stu! Wow 6" will be nice Will you be using it with a quark for H-alpha or the PST mod?

The intention is to use it as a big PST primarily, but I would like to be able to pop the Wedge in it too to see what it’s like. It was a somewhat irrational eBay purchase a while back, no idea how good it is optically but hopefully will be ok.

[Victor Boesen]

1 hour ago, Stu said:

The intention is to use it as a big PST primarily, but I would like to be able to pop the Wedge in it too to see what it’s like. It was a somewhat irrational eBay purchase a while back, no idea how good it is optically but hopefully will be ok.

Sounds interesting! Look forward seeing more about it in the future. Perhaps in the following summer days?

[Victor Boesen]

Reaching focus with the Skywatcher Evostar 72ED and the 2" Lacerta wedge

A couple days ago I began to worry I wouldn't be able to reach focus with my Evostar 72ED and a quick experiment confirmed that I couldn't reach focus and I needed inward focus. I then remembered I had purchased an M54 to M48 adapter a while ago for my OVL field flattener to be mounted directly onto the focuser tube of the Evostar. I replaced my baader click lock with the adapter and it threaded perfectly in the thread of the Lacerta wedge.

With my eyepiece that requires the least outward focus I'm then left with 0.55mm of spare inwards travel subtracting the 5mm optical length of the adapter. Call that a close call

This is by no means an ideal solution to this, but since I'm mostly going to use the wedge with my 102mm F7 refractor I'm not in a rush buying adapters to decrease the optical path length of the wedge/system. I figured I'd share this solution as some may find it good to know that this specific adapter can be useful with the Lacerta wedge.

Victor

Edited July 15, 2021 by Victor Boesen

[johninderby]

Infocus travel is a headache with a wedge with many scopes. Wish all scopes had a removable focuser extension for when you need more infocus.

 

[Rusted]

My focuser extension is called a hacksaw. 

[johninderby]

Been there with a couple of scopes. 🙄

[Victor Boesen]

4 minutes ago, johninderby said:

Wish all scopes had a removable focuser extension for when you need more infocus.

 

That would be great! But I guess I really can't ask for more in a scope I got for 269£

4 minutes ago, Rusted said:

My focuser extension is called a hacksaw. 

Don't even make me consider

[Highburymark]

Great report Victor. I had the 1.25” Lacerta wedge and thought it was excellent. If you have access to any Plossls or orthos you might find them slightly sharper than widefield eyepieces, although some widefields do work well. 

[Victor Boesen]

46 minutes ago, Highburymark said:

If you have access to any Plossls or orthos you might find them slightly sharper than widefield eyepieces

Thanks Mark! I find my ES 82 degrees work quite well but haven't tried anything else so can't tell for sure I consider buying a Baader Hyperion zoom with the 2.25X Barlow for white light and some night time observing, and my impression is that it's highly coveted among white light- and H-alpha observers and for binoviewers.

And who knows, perhaps I can get a pair of them in the future and stick them in a binoviewer