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Steve Clay

Herschel wedge do I need one

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After seeing the mercury transit last week with my 150pds and solar film filter. Im considering a wedge for my newly acquired ED80.  Would this give me significant gains over the newt with filter?

Steve

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Not a significant gain but a worthwhile one and a more long lasting accessory.       😀

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I moved from a Baader solar film filter to a herschel wedge and found the difference subtle but noticable especially if the observing conditions are calm and the scope optics very good.

I also feel that the wedge is a safer way to observe the Sun. If it falls off the back of the scope the eyepiece goes with it and the damage that the heat and light could do is restricted to possibly scorching your trousers. If an over the front type filter falls off or is knocked off (eg: at an outreach event) the 1st you will know of it if observing would be rather catastrophic.

 

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The reason that I went for a wedge is that it is rather more robust than a solar film filter. 

I'm of a rather clumsy persuasion and figured that in my case the more robust the better.

Ade

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Tricky one given the difference in aperture. I love my Herschel Wedge, used in a 4" scope. For me, it is about the finer detail that you get to see, generally at higher powers that is, I think, more accessible with a Wedge.

It's an investment which will remain useful, even more so actually if you move up to say a 100mm or 120mm refractor in future. The 80mm is obviously much more portable an easier to use than the 150pds too.

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When it comes to white light the Baader solar film is very high quality, cheap and does the job just fine - especially at the moment while we're peaking somewhere within the solar minimum. As with many things astro related, most gains are relatively small. As such, the Herschel wedge was purchased for very much the same reasons as the gentlemen above. Slight increment in finer detail, more robust, safer to use, easier to store and travel with and longer lasting.

Installed in an eyepiece when using the Wedge is a Solar Continuum filter which isolates the 540nm bandwidth and helps a tad with contrast and a polarizing filter which rotates via the eyepiece and adjusts the overall brightness. If you do purchase a Wedge make sure it has an ND 3 filter already built-in the actual unit and if not, you must have this. The continuum and polarizing filters are optional the ND 3 is not. Finally, I know you know this already but the Herschel Wedge is only suitable for refractors. It cannot be used on any type of reflecting scope.

Whether you feel it's worth forking out so much more money for a wedge in these times of solar minimum I cannot say. NASA have made very tentative predictions that we'll pull a little out of this solar minimum cycle around 2020 before dropping in again around 2025. Some research suggests that post-2025 might even be the advent of another Dalton Minimum.

Needless to say, when the Sun was more active the views with the wedge were spectacular. Good crisp detail which often showed different solar tones within the umbra itself. Granulation was nearly always apparent and faculae bright and twisting. In short, a visual experience no less equal to and often better than the white light images you see in the solar section. Hand on heart, I'd rather view the Sun through the 80ED with Herschel Wedge than a 6" newt with solar film.

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Which solar prism?

I bought the 2" Lacerta which as an odd 67° Brewster angled eyepiece.
This works fine in winter. Or in the early mornings and evenings.
But, it means you are looking upwards in summer when the sun is high.
Looking upwards demands a higher tripod, or pier, unless you are going to sit on the ground.
Most solar prisms are 90 degree. You may find this more comfortable at all times of the year.

Some prisms have an exposed heat sink which gets very hot.
This could burn curious, little fingers. Never leave a solar telescope unattended!

While other prisms throw a hot beam of light out of the bottom.
More rarely these days, but  once commonplace.
You don't want a hot beam on a telescope anywhere near children.
It places them at the perfect height to look upwards into the blinding beam!

Hopefully you will keep your prism for a very long time.
They are rather too expensive to buy several, just to try.
So choose your prism carefully. :wink2:

 

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Always used a Baader solar film made into a tight fitting holder. Fine for several years . I always check the filter before use and was very surprised to find several small areas where the light came straight through.the filter was keep in a plastic box when not in use and never touched or dropped .

I decided that a Herschel wedge would work well in a 4" frac. Wonderfully surprised at the results. Much finer resolution and much safer to use .

Although at a minimum the odd small AR has woken up and it's always a pleasure to observe anything , under clear skies !

Nick.

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12 hours ago, Steve Clay said:

After seeing the mercury transit last week with my 150pds and solar film filter. Im considering a wedge for my newly acquired ED80.  Would this give me significant gains over the newt with filter?

Steve

Short answer from me, yes.
I have had both scopes and WL solar observe when I can.

A refractor with a Wedge, I have the Lunt One give a stunning view when things are active.
It's what I used on the Mercury transit last week, but on a ED103 scope.

A film on a Newtonian does work ok, but to me the refractor view was and is more detailed.
A solar wedge is the maker of the differnce in my opinion.
Money well spent.

And observing in the warm (relative) day is a nice bonus too.
 

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I made a really strong cardboard holder for my solar film into this I added properly formed metal small 'eyes' (cheap kit off ebay).  Into these I place a number of the really small bungee hook ended cords that you can buy, and use these to hook the filter onto various locations around the telescope.  I think this is a useful precaution to help prevent them falling off accidentally - that's why I've mentioned it.  As above I also keep mine in a old plastic cake box by itself and inspect it prior to use.   I don't have a wedge, but one with a home-made filter might want to consider the bungee route to fastening it to the telescope if losing it accidentally is concerning.

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They are an improvement but in their basic form still "white". For a step up you need the continium filter. And they add to the cost. Have used an ED80 with a Herschel Wedge and will say very good experience. They are a solid lump so no concernes about damage to the film filters.

Have read of the Lacetera being at the Brewster angle, not sure what extra that adds.

Bought the TS wedge for the transit and after some confusion it is fine. It comes with a continium filter AND they have an ND3 filter stacked with the continium. Slight problem is no real mention of the ND3 so I bought a seperate ND3 then found 2 days before the transit that I did not require it. Works well as it comes and I suppose I can now swap the TS combination for a simple and single ND3, so have White, not Green.

I also purchased a UV/IR cut, bit additional safety but never fitted it on the day.

Suppose the answer would be you do not "need" one, but they are a very nice addition to the equipment armoury. You will use it and I would expect use it more.

Edited by PEMS

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18 minutes ago, PEMS said:

They are an improvement but in their basic form still "white". For a step up you need the continium filter. And they add to the cost. Have used an ED80 with a Herschel Wedge and will say very good experience. They are a solid lump so no concernes about damage to the film filters.

Have read of the Lacetera being at the Brewster angle, not sure what extra that adds.

Bought the TS wedge for the transit and after some confusion it is fine. It comes with a continium filter AND they have an ND3 filter stacked with the continium. Slight problem is no real mention of the ND3 so I bought a seperate ND3 then found 2 days before the transit that I did not require it. Works well as it comes and I suppose I can now swap the TS combination for a simple and single ND3, so have White, not Green.

I also purchased a UV/IR cut, bit additional safety but never fitted it on the day.

Suppose the answer would be you do not "need" one, but they are a very nice addition to the equipment armoury. You will use it and I would expect use it more.

This TS wedge seems the cheapest of them all. Can the continuum filter be removed so that the image is white and not green and does the back get very hot?

Thanks

Steve

Steve

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The continuum filter is stacked with the ND3 filter in a single screw in filter housing so it can be removed and be replaced by a standard plain ND3 filter. You must never use a wedge without an ND3 filter fitted.

The housing gets warm but not too hot.

Performance is the same as the Lunt wedge so I’d only ever buy a second hand Lunt wedge.

Edited by johninderby

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2 minutes ago, johninderby said:

The continuum filter is stacked with the ND3 filter in a single screw in filter housing so it can be removed and be replaced by a standard plain ND3 filter. You must never use a wedge without an ND3 filter fitted.

The housing gets warm but not too hot.

Great thanks for that John.

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My own impression of the Solar Continuum green filter is that it removes glare.

It is much more comfortable to view with than dealing with a bright, white solar disk.

I have always found the TS accessories to be of good quality and nicely finished.

Their 1.25" star diagonal is rather posh. No doubt their solar prism will be rather posh too. :biggrin:

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I think I'll go with the TS optics wedge and get an additional ND3 filter so I have green and white options. I'm guessing the supplied filter stack can be screwed into the bottom of the eyepiece holder so it's still there when swapping eyepieces.

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yes just unscrew the eyepiece holder from the body and the filter is screwed into the bottom of the holder. 

Here’s a pic from someone elses thread that shows it.

D802DAE9-9A53-413B-842B-0374F486C6D0.jpeg

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22 minutes ago, johninderby said:

yes just unscrew the eyepiece holder from the body and the filter is screwed into the bottom of the holder. 

Here’s a pic from someone elses thread that shows it.

D802DAE9-9A53-413B-842B-0374F486C6D0.jpeg

Once again cheers John.

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Are wedges really safe to use with compound refractors?  All that energy is pouring down the tube and must surely be warming things up, especially if there is another set of lenses back from the objective, as in a Petzval.  I thought I once read somewhere that Herschel wedges couldn’t be used on Petzval-type refractors for just that reason?

Just a thought, I kno knothing....

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33 minutes ago, Hallingskies said:

Are wedges really safe to use with compound refractors?  All that energy is pouring down the tube and must surely be warming things up, especially if there is another set of lenses back from the objective, as in a Petzval.  I thought I once read somewhere that Herschel wedges couldn’t be used on Petzval-type refractors for just that reason?

Just a thought, I kno knothing....

I believe they are, but @Merlin66 knows alot more than me and has, I think, obtained assurances about their use with petzval designs. Hopefully Ken will comment on this thread.

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I think Tele Vue has said that it is safe to use their Petzval design refractors with a herschel wedge. On their website under the Lunt HW, First Light Optics advise against using it with Petzvals though so maybe it varies depending on the particular Petzval design ?:

https://www.firstlightoptics.com/lunt-solar-white-light-systems/lunt-white-light-herschelsolar-wedge.html

 

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13 minutes ago, johnturley said:

Would you be able to use H alpha filter such as the one below in conjunction with the Hershel Wedge to view further details of the chromosphere, and possibly also prominences

https://www.firstlightoptics.com/narrowband/baader-ultra-narrowband-35nm-h-alpha-filter.html

John 

No, I'm afraid not. An etalong filter plus other filtration is required to view in h-alpha light.

 

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Re: Solar viewing & Petzval fracs....(@Hallingskies)

I also find it quite confusing.

On the one hand, it's acknowledged from experienced observers on sites like Solar Chat, SGL and Cloudy Nights that using Petzval fracs and a wedge is fine. On the other hand, we get warnings from the wedge manufactures like Baader and Lunt categorically stating that they're not suitable for such scopes.

Similar kind of thing happens with Quark's solar eyepieces. Quark makes no mention but again, experienced observers argue that either a) it makes no difference, b) it only becomes a concern if you're tracking for a long time, c) they canot be used in oil-spaced Petzval's d) but can be used in air spaced Petzval's.

Icing for proverbial cake comes in the form of using Fluorite fracs for white light. Again, experienced observers argue that either a) it makes no difference, b) the risk of cracking a €2.5 - 6k scope is just not worth even contemplating, and c) thermal expansion, fracturing and shock of the lens is augmented in Fluorite.

In my own case solar viewing is important. I'm not out everyday but I reckon we get an average of around 300 clear days a year. For white light I finally settled on a portable TV-76 + Wedge. A Lunt 60mm for H-alpha (ease of use, no cables, no faff) and a fluorite strictly for those delicate and tender photons of the night :smiley:.   

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