Possible dangers of observing with a Lunt Herschel Wedge

[Guest]

I have just taken delivery of a Lunt 1 1/4 inch Herschel wedge and will have a single polarising and a Baader ND 3.0 filters. Now that I have it in my possession,it has given me sobering thoughts on how safe is it to the eye?

We are never to look at the sun with the naked eye due to the UV and IR.So what does reach the eye when observing with a wedge and filters?Any harmful rays?Should I also get a UV/IR filter aswell.The image of the sun would be magnified .I'm worried.Have I done the right thing buying a Herschel Wedge?Or am I just being a drama queen? (oops,can I say that these days?)

[Stu]

Being a drama ....royal I'm afraid Martin.  

Of course, you must always be extremely careful to follow the instructions and make sure the correct filters are fitted, but assuming that, you are perfectly safe.

I believe the Wedge removes around 95% of the light and heat into the heat sink. That means without the ND3.0 filter it is still dangerous to look through, but the 3.0 means a factor of 1000 so only 1000th of that 5% is passed through the ND3.0 filter so it then becomes just dazzling rather than dangerous. Further dimming with a Continuum or Polarising filter makes it comfortable for viewing over an observing session.

So, always make sure you have the two filters fitted (mine are permanently fitted in the Wedge so I can't forget them) and all will be well.

If the Wedge should fall out of the scope, the risk is a hot leg (or worse!), but your eye will be fine.

[John]

I've used the same setup that you have with 100mm, 102mm and 120mm refractors and I feel quite safe with it. I have not felt the need to add any further filtering. The single polarising filter on the end of the eyepiece controls the brightness of the image but even at it's brightest it is not uncomfortable.

I understand your caution - we have all been bought up not to view the sun through optical instruments so I did take a little gulp before putting my eye to the eyepiece for the 1st time with the Herschel Wedge. It has worked fine though and does show more detail than the Baader Film filter that I used before I had it.

Make sure your finder is either removed or firmly capped though. Don't want any accidents with that !

 

 

[Pete Presland]

I know exactly what you mean  but they are widely used and completely safe. I think we have all been brought up on never look at the sun direct and it is deeply bedded in our psyche!

[Moonshane]

As above. Used correctly=no risk.

[xtreemchaos]

if I can use one safely anyone can, and I dash around like ive got worms in me brain at the slightest hint of sun.  goodluck and clear skys charl.

[Chris]

I personally feel safer with a wedge plus ND3 & polarising filter, rather than using solar film which could potentially fall off or get ripped. If you get the chance, try the wedge with a binoviewer, it's one of the best uses for BV's I've found, fantastic views   

[ronin]

By rights everything is reduced to 0.00001 but I agree the question of IR and UV has crossed my mind, also thinking of one for a summer event. Even at 0.00001 I suppose that is still more then usually impacts the retina as we are collecting say 100mm diameters worth and directing it at the retina. Lets face it they sort of demand you buy UV blocking sunglasses for when on the beach. If you buy glasses now they are also coated to block UV.

Think the eye will block some IR, but not exactly sure how much and which wavelengths.

Would be interested to know if you (I) could add a filter that passes say 700nm to 400nm and block the IR+UV outside these. The Baader UV/IR Block looks ideal. If one can be added suitably then I suspect that when I get round to it I will try. Levels may be low but when my eyes are concerned 0 is level I would prefer.

Personally I think you have asked a good question. My take on it follows your thoughts.

EDIT:

Just had another thought somewhat against what I said - I think that glass as a material tends to block UV, so at the reduction to 0.00001 then the glass in the eyepieces may act as a sufficent UV blocker for what remains.

[Merlin66]

Don't worry.

The Herschel wedge when used with the ND filters is completely safe.

The attenuation across all visible wavelengths is well within the recognized world safety standards.

Just enjoy!!

 

[Guest]

(Drama Queen ! Now become a normal subject of the realm)

Thanks for all your advice.I shall use the wedge at the weekend.Good point about glass blocking UV. My reactolite spectacles donot darken in the car when driving.I beleive that they react with UV.

[Peter Drew]

Don't catch hold of the Lunt wedge version whilst in use or immediately aftrwards, the back face of the diagonal gets pretty hot!. The Baader ceramic version doesn't as far as I know. 

[John]

1 hour ago, Peter Drew said:

Don't catch hold of the Lunt wedge version whilst in use or immediately aftrwards, the back face of the diagonal gets pretty hot!. The Baader ceramic version doesn't as far as I know. 

My Lunt 1.25" gets warm with my 4" fracs and pretty warm with my ED120 but I've never known the heatsink to get so hot that it could scald or anything like that

It cools down very quickly once the Sun is no longer shining down the scope.

Both of which are what it's designed to do of course

[Moonshane]

If you remain concerned about the dangers it's one of the many reasons to buy one of these

 

[Peter Drew]

8 hours ago, John said:

My Lunt 1.25" gets warm with my 4" fracs and pretty warm with my ED120 but I've never known the heatsink to get so hot that it could scald or anything like that

It cools down very quickly once the Sun is no longer shining down the scope.

Both of which are what it's designed to do of course

I have to admit the wedge was on a 150mm. 

[Paul73]

2 hours ago, Moonshane said:

If you remain concerned about the dangers it's one of the many reasons to buy one of these

 

+1 for the Comtinuum filter. Mostly for quality of view rather than safety (mine is permanently screwed into a short extension tube so that I can swap eyepieces without the tedious screwing / unscrewing filters with every change).

On the safety side. I wasn't 100% comfortable using Solar film due to the risk of damage to the film. But, the Lunt is as safe as houses! And it gives cracking views.???

Paul

[michael.h.f.wilkinson]

As others have said, the wedge is safe with the correct filters in place. I do notice the Baader Solar Continuum Filter transmits quite some near IR, but that is only noticeable in imaging; the amount of heat transmitted is negligible. In my case I generally put a Beloptik triple-band ERF in front of the scope (which transmits only narrow bands centred on Ca-K, 540nm (solar continuum) and H-alpha). I use this mainly to cut back potential tube currents. These are rare beasts, however, and not for sale anywhere any more.