Baader Solar Film vs Baader Zeiss Herschel Wedge

[Stu]

I can't remember how I started down this route, but here we are, so let's go! First off, the title is misleading.... This is not a controlled test to show the differences between solar film and a wedge with no other variables. It is more a comparison between two different setups, one good and one great!

In the blue corner, a nice Burgess Optical 91mm f6.6 fpl-53 triplet fitted with a home made Baader Solar ND5.0 filter. Very easy to make, just used a cereal packet, double sided tape and insulating tape to finish it off nicely. Actually that reminds me how I started on all this. I decided to make a filter for my 50mm finder which I acquired recently, and having seen how easy it was, thought I would do the same for the BO, which being oil-spaced is not suitable to use with a wedge. Back on topic, I used a good quality Baader Maxbright diagonal, AP Barcon and a Meade 10.5mm RG Ortho plus a green filter. This represented my good setup.

In the red corner, we have the Takahashi FC-100D, with Baader Zeiss Herschel Wedge, 2" Continuum filter, Zeiss Abbe Barlow and Leica ASPH Zoom. This represents a great setup in my experience.

Both scopes were mounted on an Ercole mount with dual clamps, and a Skywatcher guidescope mount to bring the two into line.

I started this during the early afternoon and there was high level cloud passing quickly over the sun so that the views were very poor initially. In general the seeing has not been great, but I had a few clear spells this afternoon to start the comparison.

I will try to take some pictures through the eyepiece to show the differences but it's not easy to keep consistent exposure etc using an iPhone.

So, although the outcome of this was never in doubt, I thought it would be interesting to see just how much difference there was.

The first thing that struck me was the level of brightness out of the Wedge. Quite significantly higher than the film, even taking into account the aperture difference. The Continuum filter gives a dramatically vivid green image whilst the green filter in the BO looked fairly washed out by comparison. I guess this is a combination of the broader band pass of the filter, a green #56 and lower brightness of the setup.

The higher brightness and narrow band pass gave the views much more contrast in the Wedge. Faculae were significant easier to see, around AR12532 but particularly on the opposite limb where they were less pronounced. The seeing was poor, so the granulation was not visible in the film, and only subtly visible in the Wedge.

In general, the wedge setup allow higher mag to be used, and during good seeing the detail in AR12533 was very nice. The umbra showed fine detail around its edge, and the penumbra showed petal like structure as well as the edge detail. This level of detail just wasn't there with the film setup, I could only catch some waviness around the edge of each structure, and only hints of the penumbral detail.

In terms of Spot detail, the wedge clearly showed 4 spots in AR12532 in all but the worst of the seeing. They were sharp and crisply defined. In the film setup, they were just about visible in the best of the seeing, but were generally quite hard to see.

AR12535 in the wedge showed complex detail, individual pores and nicely separated structures. In the film setup, these tended to blend into coarser structures and I was unable to separate the finer details.

I know from experience that in good to excellent seeing, the Wedge in the Tak is capable of delivering image like quality which is quite staggering to see. At high power, the individual granulation cells can be seen, although this does require the best of the seeing, and the detail in ARs is incredible. 

I need to give the film more of a chance under better conditions. From what I have experienced already, the light throughput is lower, as is the contrast and it cannot sustain magnifications as high as the wedge. That said, in the few periods of better seeing I could tell that it was capable of showing very nice views. I suspect that because the contrast is lower, it suffers more in poor seeing than the wedge so I expect the views to be much better under good conditions.

More to come on this one, but all in all an interesting comparison. Like I said, more of a total setup comparison than a Film vs Wedge, but the best I could do under the circumstances. I may try changing eyepieces around to see what effect these have.

Fingers crossed for clear skies and good seeing on May 9th!!

Stu

[Floater]

Good stuff, Stu.

As you wrote, the outcome was never really going to be in any doubt but nice to see it laid out before you, I'm sure. I have had a couple of short sessions with film and wedge on the go at the same time but never had (made?) the chance to get a long run at comparing the views. I will do, though ... ??

All part of the fun and building the experience. 

[Moonshane]

Nice comparison mate. I rarely use more than about 100x on the sun but perhaps I should try!

[Stu]

7 minutes ago, Moonshane said:

Nice comparison mate. I rarely use more than about 100x on the sun but perhaps I should try!

It's definitely worth it when the seeing can take it Shane. I learned from Ken (Merlin66) that the actual granulation cells are tiny (a couple of arc seconds across I think) so to actually see them you need high power. Most of the time we are seeing a larger scale version of it rather than the cells themselves.

That's one area where I think the Zeiss Wedge beats the Lunt, the accuracy of the prism does maintain image quality at higher powers. Still worth trying with the Lunt though, they are quite capable of showing it I'm sure.

[laudropb]

Very good report Stu. I recently purchased a Lunt Herschel wedge. I use this on a ST 102 , for which I also have an Astrozap filter. I have done a quick comparison using both on the scope with the same eyepieces and a Baader solar continuum filter. I found that the the image using the wedge was much crisper and certainly showed a good deal more contrast. Umbral and penumral details were enhanced using the wedge. Faculae were also much easier to spot. I only went up to a magnification of 100x but the wedge certainly out performed the solar filter

[LukeSkywatcher]

Colour me confused. I may have missed the whole point of this thread. In my eyes what you have done is compared 2 different scopes (with 2 different solar WL set ups). 

Lets eliminate the scopes. Any scope suitable for Solar observing is good enough (even my 70mm Refrac). So as far as i can see what you are comparing is Baader solar film to a Hershel wedge with ND filter etc.

I may be wrong and sure i have missed something. I love my HW.

 

[Stu]

3 minutes ago, laudropb said:

Very good report Stu. Having recently purchased a Lunt Herschel wedge. I use this on a ST 102 , for which I also have an Astrozap filter. I have done a quick comparison using both on the scope with the same eyepieces and a Baader solar continuum filter. I found that the the image using the wedge was much crisper and certainly showed a good deal more contrast. Umbral and penumral details were enhanced using the wedge. Faculae were also much easier to spot. I only went up to a magnification of 100x but the wedge certainly out performed the solar filter

Thanks John, I'm glad you are finding a quality increase in your new wedge over the film. I've seen comments I in the past that the difference is not that great, but in my experience the difference is significant, and well worth the investment.

[Stu]

10 minutes ago, LukeSkywatcher said:

Colour me confused. I may have missed the whole point of this thread. In my eyes what you have done is compared 2 different scopes (with 2 different solar WL set ups). 

Lets eliminate the scopes. Any scope suitable for Solar observing is good enough (even my 70mm Refrac). So as far as i can see what you are comparing is Baader solar film to a Hershel wedge with ND filter etc.

I may be wrong and sure i have missed something. I love my HW.

 

Well.... As said, what I did was try to compare two different setups which you might typically find yourself using. It was by no means scientific as there are two many variables between the setups, so it's not a straight comparison.

To answer your question, or rather your statement that any scope suitable for solar observing is good enough, I don't agree. Put your 70mm alongside my Tak and you would get a significantly better image in the Tak, particularly at high power due to the figure and accuracy of the optics. A 120ED with a wedge will also show much better views due to the increased resolution and brightness over a 70mm.

So the comparison is of the complete setup, not just the Wedge vs Film. I could, and perhaps should make a filter for the Tak to do a direct comparison although it won't be 'side by side' as I don't have the luxury of two Taks ??

EDIT If it wasn't clear, I love my HW too!

As an aside, I was able to spot AR 12533 and 12535 in the 50mm finder with film. Tiny but there!! ??

[Merlin66]

Resolving the granulation cells (rather than the larger supercells) takes at least a 100mm aperture, very steady seeing and magnification >x100 (probably closer to x150, depending on your eyesight)

I've seen fantastic images of granulation and detailed sunspot fibrils with both the Baader Solar film and various Herschel wedges. IMHO if the above conditions are observed, the significant factor comes down to seeing conditions.

[Stu]

1 hour ago, Merlin66 said:

Resolving the granulation cells (rather than the larger supercells) takes at least a 100mm aperture, very steady seeing and magnification >x100 (probably closer to x150, depending on your eyesight)

I've seen fantastic images of granulation and detailed sunspot fibrils with both the Baader Solar film and various Herschel wedges. IMHO if the above conditions are observed, the significant factor comes down to seeing conditions.

Thanks Ken! Yes, I tend to see them at probably around x150 but only when the seeing is excellent. Good seeing is not enough, it needs to be really cracking.

I'm sure that for imaging the Film, particularly the ND3.8 version can produce excellent results as the contrast differences can be adjusted for. For visual though I'm sure the wedge is better.

[Stu]

The sun has been shining this morning, and I've engaged my brain a little to make some adjustments.

I tried the Meade RG/Barlow in the Tak and it gave excellent views, not dissimilar to the Leica so that is not a factor in this. The only other variable is the scope, and I don't think all the difference can be down to that. To be fair though, I really should make a filter for my Tak. Need to eat some more cereal for that though ??. Watch this space.

In the meantime, I removed the Barlow from the BO setup, and added my ES OIII filter. That has sharpened things up no end and I am now getting a very nice full disk view with nice space around it, with crisp ARs and nice faculae showing around 12532. I tried the UHC but think the OIII is better.

I then added the Barlow plus the Binoviewers to the Tak, so I'm getting lovely high powered views in that. The film setup just doesn't seem to take the power, but at x60 ish it is very nice. I'll do the rest with film on the Tak just to remove the scope as the variable; even though that wasn't my original intention, I feel I owe it to the film to give it a fair crack! ??

[JB80]

At times I can get quite good granulation in my images using ND3.8 and x2 barlow, that said I do use a full 6" filter and totally agree that seeing is the most important followed by in the case of using a reflector, collimation.

Still even though I can get for me an excellent image out of it there is always a look that something is missing it's a bit dull or a lack of vibrance if you can call it that and I am sure that I can get better with a wedge although I have never tried one. Maybe it's a reflector thing and a frac would give a better end result?
I don't think it is the processing but can't rule it out.

 

Guess I'll just have to get a refractor and wedge and sort it out.

[Stu]

45 minutes ago, JB80 said:

At times I can get quite good granulation in my images using ND3.8 and x2 barlow, that said I do use a full 6" filter and totally agree that seeing is the most important followed by in the case of using a reflector, collimation.

Still even though I can get for me an excellent image out of it there is always a look that something is missing it's a bit dull or a lack of vibrance if you can call it that and I am sure that I can get better with a wedge although I have never tried one. Maybe it's a reflector thing and a frac would give a better end result?
I don't think it is the processing but can't rule it out.

 

Guess I'll just have to get a refractor and wedge and sort it out.

Definitely worth a go with a wedge and a frac I reckon. The 1.25" Lunt is cheap and pretty good.

[Paul73]

46 minutes ago, Stu said:

Definitely worth a go with a wedge and a frac I reckon. The 1.25" Lunt is cheap and pretty good.

I'll second that. Although, the £20 that the Baader film will set you back, is outragously good value!

The wedge is a lot better.

Stu - How does your Tal f10 work with the wedge? 

Paul

[Stu]

1 hour ago, Paul73 said:

I'll second that. Although, the £20 that the Baader film will set you back, is outragously good value!

The wedge is a lot better.

Stu - How does your Tal f10 work with the wedge? 

Paul

Just waiting for a replacement bearing for my TAL focuser and will give it a go Paul.

[Stu]

Well, Blue Peter would be proud of me. I've made a filter for the Tak and just given it a go. Seeing conditions not great, but I used it with both the binoviewers and the Leica to see how it went.

EDIT It's a good job I had a pizza last night, the box came in handy, no need for more cereal!!

The basic findings still stand, although the view through the Tak is significantly better than the Triplet. Detail is sharper, the faculae are better defined and I'm seeing some signs of surface granulation. The brightness is significantly lower than with the Wedge, and the fine detail just doesn't seem to be there in quite the same way, but all in all its a pretty good performance from the film. If you keep the mag under control and the seeing is good, it is a very good and economical option still. It's surprisingly easy to make a filter which fits securely with no chance of falling off.

I didn't start this little adventure off aiming to do a straight comparison, but that's where I've ended up. It's very interesting and has been fun to do.

One thing I have learnt is that an optical finder with film over it is quicker and easier to locate the sun with than a projection finder because of the larger field of view. Fun seeing the tiny spots through the finder too.

[jetstream]

Great write up Stu!

Seeing that granulation and their little "lanes" is amazing. Another amazing thing is the ability to get photo like visual views of the sun under VG seeing.

[Peter Drew]

Interesting comparisons and observations. I have film and HW options and agree that the HW offers the better performance, despite the undeniable great value of the film in financial  terms, the entry level HW's are not particularly expensive by astronomical accessory comparisons and should have a long lifetime of safe useage. One thing about HW's still puzzles me, in other telescopic applications great fuss is made of the avoidance of tube currents and the maintenance of thermal equilibrium yet a HW letting into the telescope heat that is sufficient to potentially damage some optical designs seems to give the better results!

This is one reason why I am happy to use sub diameter internal ERF's in Ha PST mods, in my experience, certainly for visual use, seeing conditions have always been the overriding factor.

[Piero]

Nice reading!  

Do you reckon your solar continuum filter is noticeably better than your green filter #56?

[Stu]

1 hour ago, Piero said:

Nice reading!  

Do you reckon your solar continuum filter is noticeably better than your green filter #56?

Piero, I haven't directly compared them in a like for like yet as the Continuum is currently fitted to my Herschel Wedge and is a 2", vs 1.25" for the green. Now I have a filter for the Tak this is something I can do though.

From what I've seen so far my ranking of the 'quality' order (for solar WL) goes like this, from High to low:

Continuum > UHC > OIII > #56 Green

The UHC shows less colour fringing (red) than the OIII and definitely sharpens up the detail, particularly in faculae vs the #56. I will try same conditions and kit vs continuum next time I see the sun!

[jetstream]

Seeing as were talking about green filters, does anyone else have the green turn to yellow when observing? The Baader Continuum goes yellow to my eye almost immediately now.

[Stu]

11 minutes ago, jetstream said:

Seeing as were talking about green filters, does anyone else have the green turn to yellow when observing? The Baader Continuum goes yellow to my eye almost immediately now.

I can't say that happens to me Gerry. I don't really notice the green now though, I'm always surprised when someone new looks through it and asks why the sun is green ?.

The UHC gave quite a nice colour I must admit, sort of blue green I guess.

[jetstream]

It is just me then lol! I asked a couple of years ago and no one else see's this then either. I also notice that when I look at things immediately after the Continuum that the reds and browns really stand out...

[Stu]

17 minutes ago, jetstream said:

It is just me then lol! I asked a couple of years ago and no one else see's this then either. I also notice that when I look at things immediately after the Continuum that the reds and browns really stand out...

Now that is something I do get, the Reds and particularly Browns....

[Piero]

Interesting. With my Lunt, the green filter #58 I have is better than my UHC or OIII.

I guess we are comparing too many variables to make reliable conclusions in here though..

Different types of filters, different telescopes, different eyes, different sky conditions and possibly different tastes?