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Old 23-12-2014, 07:12 PM
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Regulus (Trevor)
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1.25 Solar filter

Q. I have seen some solar filters that fit on a 1.25 ep filter thread, and look like an insanely dark neutral density filter.
Has anyone used one of these, and are they ok?
Someone suggested the focused heat from the sun would perhaps crack the glass, and I have to allow that possibility.
The brand is Bosma, the item is made in China so the brand may have been 'borrowed'.
Trevor
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Old 23-12-2014, 07:27 PM
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Merlin66 (Ken)
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Trevor,
DON"T USE THESE FILTERS!!
We have extensive documentation on the failure (heat cracking) of this type of filter.
They are unsafe and should be banned from distribution.
The best thing you can do is to go to the beach, hold the filter in your right hand and throw them as far as possible into the sea.
Seriously, they are dangerous.

There are some very safe ways of observing the sun - Baader solar film or a good Herschel wedge.
The specialised Ha etc. type filters are very expensive and complex (optically) and designed to function safely with most refractors.
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Old 23-12-2014, 09:37 PM
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RB (Andrew)
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There's a "Sticky" warning thread in the Eyepieces, Barlows and Filters warning everyone about the dangers of these filters.

Click here ->>> http://www.iceinspace.com.au/forum/showthread.php?t=934

Don't use these filters at all, destroy and throw them away.


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Old 23-12-2014, 10:50 PM
Tony_ (Tony)
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Here's the seller's warning I once found for these type of filters sold on e-bay (from China):

Note:
Solar filter can only see the sunrise and sunset
Viewing time from 30 seconds to 60 seconds for the gifted
Not long look
Otherwise there is a risk of explosion lenses


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Old 24-12-2014, 09:54 AM
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dannat (Daniel)
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there is a baader solar continuum filter which is 1.25" thread on -it must be used with a front solar filter -it enhances detail around sunspots & granulation
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Old 24-12-2014, 12:00 PM
issdaol (Phil)
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If you wish to do visual observation of the sun with an existing telescope the best option is the Baader Cool Ceramic Hershel Wedge.

This is used for direct solar observation instead of your normal diagonal adaptor.

It has all the necessary inbuilt protection and filters to allow this to happen safely using your normal telescope and eyepieces.

I have attached some images so you can see what this looks like.

Please note that these can only be used with refractors.
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Old 24-12-2014, 07:49 PM
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Regulus (Trevor)
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Thanks folks.
It confirms my paranoia about the product.
Think I will go with a front mounted glass solar filter for the 6" Mak.

Cheers - Trev
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Old 25-12-2014, 12:38 PM
Renato1 (Renato)
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Quote:
Originally Posted by Regulus View Post
Thanks folks.
It confirms my paranoia about the product.
Think I will go with a front mounted glass solar filter for the 6" Mak.

Cheers - Trev
Just make sure that the front mounted filter is a tight fit so that wind doesn't blow it away. If it's not that tight, either add more material to the inner lining to make it tight or don't hesitate to use a bit of tape to make sure it is securely attached to the telescope.
Regards,
Renato
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Old 26-12-2014, 05:11 PM
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OzStarGazer
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Quote:
Originally Posted by Renato1 View Post
Just make sure that the front mounted filter is a tight fit so that wind doesn't blow it away. If it's not that tight, either add more material to the inner lining to make it tight or don't hesitate to use a bit of tape to make sure it is securely attached to the telescope.
Regards,
Renato
Indeed. I bought a cheap one from China and it works fine (I posted an image in the NexImage thread some time ago), but it was a bit loose, so I wrapped a bit of black tape around it and now it fits perfectly.
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