TS Optics Herschel Wedge Filter Options

[Littleguy80]

I’ve taken my first steps into the world of Solar observing and am thoroughly enjoying it. I’m currently using the TS Optics Herschel Wedge with my SW Equinox 80. Details of the Wedge here:

https://www.teleskop-express.de/shop/product_info.php/language/en/info/p9409_TS-Optics-1-25--Solar-Prism-with-Polarizing-and-Narrowband-Filter.html

One benefit of the TS Optics Herschel Wedge is that it includes a Narrowband filter which seems to be much the same as the Baader Solar Continuum Filter. This gives the Sun a green appearance but improves detail. I’d quite like to do some observing with a more natural colour. I’m wondering if I can remove the narrowband filter and replace it with an ND3.0 filter? The obvious concern is whether this will filter enough light to be safe?

The narrowband filter looks to be screwed into the bottom of the eyepiece holder which unscrews from the main body of the wedge as shown below. 

Any thoughts or advice would be greatly appreciated. I’m very aware of the risks of solar observing so don’t want to take any chances!

[Ags]

An affordable Herschel Wedge? Darn it! Another thing to add to my very long astro wish list!

[johninderby]

Glad to see you’re enjoying using the wedge. 👍🏻

The narrowband filter is just for enhancing contrast so removing it should be OK unless it’s a combined filter. Are there two filter elements stacked together?

If you hold the filter up to the light does it look dark tinted?

Might be wise to play it safe and screw in an ND3.0 filter and try it.

Edited May 12, 2019 by johninderby

[John]

I use a Lunt 1.25 inch Herschel Wedge with an integral ND 3.0 filter and a single polarising filter on the eyepiece which gives adjustable brightness (by twisting the eypeiece). I have heard that replacing the single polarising filter with a Baader Continuam Filter might increase contrast of features but the reported green colour tint puts me off going for that.

 

[Stu]

It's a little unclear to me exactly how this wedge is functioning Neil. Standard theory goes that the wedge itself removes 95% of the heat and light, sending this up towards the eyepiece. You then use an ND3.0 filter to reduce this further by a factor of 1000, and then use either a polarising or continuum filter to moderate the light a little more and/or to enhance the detail.

I can't work out exactly what is happening with your wedge, it appears not to use an ND3.0, which to me implies that all the additional reduction is being done by your version of the Continuum. The Tech Spec does not say that it has a built-in ND3.0 aswell.

So, it would be worth asking TS to confirm, but I believe you should be fine using an ND3.0 plus a Polarising filter which will also allow you to adjust the brightness by rotating the eyepiece.

[Littleguy80]

Thank you, all. I just had a further play. The filter installed in the eyepiece holder is, as suggested by John, stacked. The bottom part is the narrowband/continuum filter. On top of it is, I assume, an ND3.0 filter. I can remove the whole thing and it leaves a standard 1.25” filter thread. Looks good for replacing it was an ND3.0 filter. I’d quite like to figure out what the thread is where the eyepiece holder screws into the the wedge. It has a T2 thread on top of the holder but has a small diameter where it screws into the wedge. If I could get a second eyepiece holder with a filter thread then I can install the ND3.0 in that. I would then be able to change eyepiece holders depending on whether I wanted the additional narrowband filter or not. 

[johninderby]

Good that you have discovered that the filters are stacked. 👍🏻

Wonder if the eyepiece barrel from a diagonal would fit or maybe TS could supply a spare barrel from the wedge. Worth asking them. 🤔

[Littleguy80]

16 minutes ago, johninderby said:

Good that you have discovered that the filters are stacked. 👍🏻

Wonder if the eyepiece barrel from a diagonal would fit or maybe TS could supply a spare barrel from the wedge. Worth asking them. 🤔

Good shout. I’ll drop them an email and see if they can supply one

[Stu]

Sounds promising Neil, but I would just double check with TS that it is indeed an ND3.0. Not worth risking really.

[Littleguy80]

18 minutes ago, Stu said:

Sounds promising Neil, but I would just double check with TS that it is indeed an ND3.0. Not worth risking really.

That’s a good point. I will ask that as well to be safe. Thank you!

[johninderby]

Ask them for a price on the barrel and the correct filter and get it sorted in one go. 

[Littleguy80]

Email sent. I’ll report back on their response for those that are interested. Thank you once again for the replies  

[Ags]

9 hours ago, johninderby said:

The narrowband filter is just for enhancing contrast so removing it should be OK unless it’s a combined filter.

Surely the narrowband filter is blocking most of the light, thereby acting as an ND3 filter... Be careful before removing it!

[Littleguy80]

6 minutes ago, Ags said:

Surely the narrowband filter is blocking most of the light, thereby acting as an ND3 filter... Be careful before removing it!

It looks like it’s stacked with an ND3.0 in a single filter cell. I’ve emailed TS Optics for confirmation 

[Littleguy80]

Heard back from TS today and they confirmed an ND filter is used though didn't specify ND3.0. They made, what seemed to me, an odd suggestion of using a filter to switch between the existing filter and an ND3.0 filter. Feels like that's asking for trouble if you click into a sot with no filter. I think I'll pick up an ND3.0 filter and try that. I suspect after trying both, I'll find that I have a preference one way or the other and that will be the filter that stays in the wedge most of the time.

[Paz]

I had thought what has been said above, that the wedge takes out about 95% then and nd3.0 takes it down by another 1/1000, and then a polarising filter tunes the brightness.

I always have a nd3.0 and polarising filter in the train then may add another filter sometimes. If I add a solar continuum filter which dims the view the using the polarising filter I'll increase the brightness to compensate but I've not tried observing without the polarising filter.

[Piero]

On 12/05/2019 at 01:51, John said:

I use a Lunt 1.25 inch Herschel Wedge with an integral ND 3.0 filter and a single polarising filter on the eyepiece which gives adjustable brightness (by twisting the eypeiece). I have heard that replacing the single polarising filter with a Baader Continuam Filter might increase contrast of features but the reported green colour tint puts me off going for that.

I guess it is personal. I tried both the polarising and the solar continuum, and I prefer the latter, particularly on granulation. The green sun does not bother me though. 

[John]

41 minutes ago, Piero said:

I guess it is personal. I tried both the polarising and the solar continuum, and I prefer the latter, particularly on granulation. The green sun does not bother me though. 

The green tint would not be my preference but that is, as you say, personal. 

 

 

 

[Paul73]

5 hours ago, John said:

The green tint would not be my preference but that is, as you say, personal. 

You get used to it! It does feel really odd to start with.

Paul

[johninderby]

Yellow filters help with contrast. Not as good as a green continuum filter but not bad and do give a more acceptable colour.for many observers.

[Stu]

6 hours ago, Piero said:

I guess it is personal. I tried both the polarising and the solar continuum, and I prefer the latter, particularly on granulation. The green sun does not bother me though. 

After experimenting quite a bit I'm the same Piero, I just use the Continuum on its own (plus ND3.0 of course!). It can be quite bright still but I enjoy the vividness of the views. I don't even notice that they are green any more, it just seems perfectly natural to me. I get a surprise if someone else looks through and asks why the sun is green!

[Littleguy80]

I’ve only ever seen the Sun through the TS Wedge so a green Sun is all I know. I quite like the white light images taken without a continuum filter through the eyepiece. Once I’ve tried it, I’ll have a better feel of what I’m losing through not using the continuum filter. 

Edited May 18, 2019 by Littleguy80

[michael.h.f.wilkinson]

I always use the Baader Solar Continuum filter. The added contrast is worth the green colour. When imaging, you do need to add an IR-blocking filter of some kind, as the continuum filter had quite an IR leak. No problem for visual, but an issue when using a camera.

[John]

1 hour ago, Paul73 said:

You get used to it! It does feel really odd to start with.

Paul

I hardly do much solar observing myself - mostly then it's outreach. I'd get fed up of explaining why the sun was green I think !

 

[johninderby]

Another irelevant and useless fact. 😁

When kids in America were asked to draw the sun they coloured it yellow but in Japan they coloured it red.