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wesdon1

how safe is Solar Observing through foil like filters ?

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I'm still learning, and there's a question that's been in my mind from day1. How safe are foil like solar filters for solar observing? reason i ask is i'm scared the foil may have microscopic holes or cracks because it crumples/bends etc and some massively magnified light/heat radiation will seep through and fry my retina instantly! I'm not joking, it really frightens me! Would the experienced members recommend a solid state/glass/ceramic type filter instead of film, and can even these develop unforeseen faults and cause instant blindness!?? I really want to see the sun and it's amazing spots and other phenomena but this fear of harm is holding me back. Thanks in advance for any advice, and please forgive me if i sound dramatic or stupid.

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The Baader film might actually be safer because it is a double sided filter. Once it's delivered it should be fitted into a permananent ring the size of the scope's aperture so that it undergoes no further crumpling and it should be cared for properly, stored in a box etc. When fitted to the scope it should have permanent ties holding it in place against wind or knocks. It can be easily checked for pinholes and these can be blacked out. They won't show for the same reasons that a secondary mirror doesn't show.

Remember to block finderscopes, Telrads, etc., or you can get a nasty burn at the focal point!

If you really are worried you could try the projection method. Google solar projection and you'll find many ways of doing it.

Olly

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8 minutes ago, ollypenrice said:

The Baader film might actually be safer because it is a double sided filter. Once it's delivered it should be fitted into a permananent ring the size of the scope's aperture so that it undergoes no further crumpling and it should be cared for properly, stored in a box etc. When fitted to the scope it should have permanent ties holding it in place against wind or knocks. It can be easily checked for pinholes and these can be blacked out. They won't show for the same reasons that a secondary mirror doesn't show.

Remember to block finderscopes, Telrads, etc., or you can get a nasty burn at the focal point!

If you really are worried you could try the projection method. Google solar projection and you'll find many ways of doing it.

Olly

Hi, thank you so much for your advice. I will actually try out the solar proj. method initially, just to get used to pointing my equipment at the sun. Good job you told me to cover up Telrads, finders etc as i hadn't even considered that! See, that's why it's imperative that novices like myself ask the more experienced/expert Astronomers for advice! I will definitely buy Baader product(s) as they seem like they're of the highest quality? ( Please Correct me if i'm mistaken? ) Thank you for saving me a nasty burn/accident with finder scope/telrad! 

Many Thanks,

Wes.

SkyWatcher BK 1309 EQ2. 25mm/20mm super plossl/10mm/3.6mm/2 x Barlow/Laser Collimater/Tons of enthusiasm! lol

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As long as you check the filter for defects, i.e. pinholes, rips, securely attached to your OTA or 35mm/DSLR lens, etc., before each and every use, solar safety films are perfectly safe. Also worth mentioning that you should make a solar filter for your finderscope and/or RDF - better still, remove either or both before viewing and use the shadow for alignment. 

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Posted (edited)
23 minutes ago, Philip R said:

As long as you check the filter for defects, i.e. pinholes, rips, securely attached to your OTA or 35mm/DSLR lens, etc., before each and every use, solar safety films are perfectly safe. Also worth mentioning that you should make a solar filter for your finderscope and/or RDF - better still, remove either or both before viewing and use the shadow for alignment. 

Another neat idea is to make your own pinhole solar finder. There are some ideas further down this thread. 

Peter Drew's is a good method. Some people make their solar finders adjustable in angle to align with the viewing scope but the easiest way is to align it roughly, get the scope pointing at the sun, and then just mark the sun's central position on the finder screen you've made.

Olly

Edited by ollypenrice
Typo
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I agree with checking your filter every time. I hold mine up to the sun and check for pinholes by eye every time I put it on the scope.

Also, I check with my hand that it's on and solid every time I put my eye to the eyepiece.

I've also got a film filter for my finder scope which helps but a proper solar finder would be good.

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Good advice above. I think the biggest risk is of the filter falling or blowing off, if that happens then you get the full aperture hitting your retina with the sort if results you are worried about. Make sure it is held on tightly, belt and braces approach if you are really worried.

I have actually, unwittingly, viewed through a filter with some pinhole in it. The result? I'm not blind and didn't suffer any permanent affects. I just had little squiggles before my eyes for a while, much like after looked at a light bulb (although much much smaller) or other bright light source. I'm not recommending it obviously, but with sensible precautions the foil is very safe.

I would chose it over glass filters as it is optically superior. Glass filters are not made from optical glass so will not show detail as well at higher powers. The foil is pretty tough stuff and will last a long time if treated carefully.

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I would second all the advice given but would add that reflectors are not suitable for solar projection as too much heat will hit the secondary, most reflectors also have the option to use a filter over the whole aperture or just by covering the additional small hole in the endcap....

Alan

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@wesdon1you have received some positive and good advice. As Alien 13 stated above if you are using a reflector it is not suitable for solar projection.

Anyway this is my procedure when undertaking white light solar observing.

  1. I remove all items from the OTA - finders etc
  2. I inspect my solar filter each time - firstly by looking at a very bright LED light in my kitchen
  3. I then hand hold the filter looking at the Sun
  4. The filter is then secured to the OTA 
  5. I then find the Sun using a device like this - https://www.ebay.co.uk/itm/SVBONY-Solar-Finder-Scope-Fully-Metal-Mount-Dovetail-Slots-Mount-Dovetail-Slots/323318485106?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649
  6. I usually look into the eyepiece tube (no eyepiece fitted) to see if I can see any pin holes. If there are any pin holes you can cover them as Olly stated above

I have used Baader film, Glass filters (Orion and Thousand Oaks) and a Herschel Wedge and I happy to say no problems to date. You may decide to make your own - here is a video produced by Pete Lawrence for the Sky at Night - https://www.bbc.co.uk/programmes/p014hpkh

Finally, always check each time and don't rush. Have a procedure that you know works for you and stay with it.

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Solar projection works fine but you really want to use non achromatic eyepieces which don't use cemented lenses. The Huygens or Ramsdens are good because they are a simple design comprising of 2 singlet lenses. With solar projection the heat of the suns rays at focus passes through the eyepiece optics and the heat can melt the cement that holds lenses together.

 

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My first scope, a TAL Newtonian reflector, did come with a solar projection kit (including little clips to hold a card so you could copy the sunspot positions onto it.) I didn't use it a great deal but never had a problem. However, I'd err on the side of caution regarding heat build up at the primary.

Olly

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Posted (edited)

For me its not worth the risk even if tiny as the consequences of something going wrong are life changing. Hence I use a camera or project.

Edited by Adam J
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I feel that the Herschel Wedge is a pretty safe approach. Even if, in the most extreme circumstances, the wedge falls out of the scope, all the light and heat goes straight out of the back of the scope and not towards the eye at all.

 

 

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6 minutes ago, Adam J said:

For me its not worth the risk even if tiny as the consequences of something going wrong are life changing. Hence I use a camera or project.

That's a shame as you miss out on some amazing views.

Have you considered a Herschel Wedge with a refractor? As long as you follow a careful setup routine there is no risk of eye damage if the wedge breaks or falls out. Worst case just a hot leg. The views are amazing too.

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13 minutes ago, Stu said:

That's a shame as you miss out on some amazing views.

Have you considered a Herschel Wedge with a refractor? As long as you follow a careful setup routine there is no risk of eye damage if the wedge breaks or falls out. Worst case just a hot leg. The views are amazing too.

no my main interest by far is DSO imaging anyhow and so I would not want to invest any cash into solar observation just for transits. 

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47 minutes ago, Adam J said:

no my main interest by far is DSO imaging anyhow and so I would not want to invest any cash into solar observation just for transits. 

Fair enough. Plenty more to see than transits but if your interests lie elsewhere then not worth investing as you say.

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1 hour ago, Adam J said:

no my main interest by far is DSO imaging anyhow and so I would not want to invest any cash into solar observation just for transits. 

So it's more of a lack of interest in solar observing than concerns over the safety of the equipment available to do it ?

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Posted (edited)
9 minutes ago, John said:

So it's more of a lack of interest in solar observing than concerns over the safety of the equipment available to do it ?

No I am quite interested in seeing things like the transits or partial eclipses  but the sparsity of such events does not justify buying a solar wedge if i had a solar wedge for those events I am sure I would use it more frequently though, I simply prefare DSO imaging and that is expensive, my concerns over safety mean I dont want to use the cheap option in solar foil.

I have a masters degree in laser physics and people I know have been involved in laser related accidents resulting in eye damage, that is a very similar type of damage and so I am hyper aware of the consequences and it makes you take great care with your eyes. I dont need multiple things in my life that can potentially blind me even if it is unlikely.

Adam

Edited by Adam J

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2 minutes ago, Adam J said:

No I am quite interested in seeing things like the transits or partial eclipses  but the sparsity of such events does not justify buying a solar wedge and my concerns over safety mean I dont want to use solar foil.

I have a masters degree in laser physics and people I know have been involved in laser related accidents resulting in eye damage, that is a very similar type of damage and so I am hyper aware of the consequences and it makes you take great care with your eyes. I dont need multiple things in my life that can potentially blind me even if it is unlikely.

Adam

Fair enough. Would you look through someone elses Herschel Wedge setup ?

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2 minutes ago, John said:

Fair enough. Would you look through someone elses Herschel Wedge setup ?

If they were willing to look through it first lol

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23 minutes ago, Adam J said:

If they were willing to look through it first lol

Little point in owning one if you dont look through it, so I'm sure any owner would be happy to do that!

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21 minutes ago, Adam J said:

If they were willing to look through it first lol

On the occasions when I have had others wanting to have a look at the sun the last thing I do before they look through the eyepiece is that I look/check first.

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Posted (edited)
3 minutes ago, Stu said:

Little point in owning one if you dont look through it, so I'm sure any owner would be happy to do that!

I think its more to do with if I owned it myself I would know its condition and that it had been well looked after. :)

2 minutes ago, Paz said:

On the occasions when I have had others wanting to have a look at the sun the last thing I do before they look through the eyepiece is that I look/check first.

Sensible especially with kids. Although in that case I would also be concerned that I succeeded in getting across the message that you cant just do that with any telescope etc.

Edited by Adam J
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2 minutes ago, Adam J said:

 

Sensible especially with kids. Although in that case I would also be concerned that I succeeded in getting across the message that you cant just do that with any telescope etc.

That's a good point.

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I've used my Hershel Wedge for outreach events involving children quite a few times including most recently at a local junior school where over a period of 4 hours around 300 children and staff observed the Sun with it.

I do go to great lengths during these sessions to empasise that the equipment being used is specially designed to enable safe solar observing and on no account should anyone look at the Sun with any sort of optical device, including binoculars. We have posters up to this effect and also repeat the message as each group comes forward and again whenever it seems apt to repeat it.

It is a very responsible business that I take very seriously but the enjoyment that the children get from their solar views and the subsequent discussion we have on our nearest star are very rewarding from my point of view and theirs judging by the feedback :icon_biggrin:

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