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Solar filters.

Pitsmoor Col

By Pitsmoor Col
in Discussions - Eyepieces

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Pitsmoor Col

Pitsmoor Col

Posted
Posted

Hello,

I am thinking about doing some solar observing, One reason being I think the scope is not being used as much as it could be, ie. why just use it at night, it performs just as well in the day. Looking at some filters I notice some are glass and some are film. I can see why the glass ones are more expensive, but don't the film ones perform just as well? Has anyone on here had any experience with both types of filter?

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johninderby

johninderby

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The Baader film is actually better than the glass type that you can buy nowadays, and surprising safer, as they don't shatter like glass if hit. It's actually very expensive to make an optically flat piece of glass and there is no way you are going to able to make a really good one for £100.00 to £200.00.

The very best glass solar filters were the ones that Zeiss used to make, but they can sell now for a few thousand even though they are second hand. :p

John

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ismangil

ismangil

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Use the Baader film. If you have a 150mm refractor then you can stop it down to, say, 100mm for the Sun. One advantage of that is you can cut two filters from a single sheet of Baader film!!

How do you determine how much to stop down? Say for 200mm?

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sungazer

sungazer

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Hi, If you can make the diameter of the stop to equal approx F25 to F30, you will get very good views with an eyepiece of about 20-25mm and reduce the heat in the tube. This applies equally to a reflector or refractor, in my opinion.

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Bizibilder

Bizibilder

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The reason I suggested stopping down was due to the Baader Solar film being too small to make a full aparture filter for a 200mm scope. It is 200x290mm (A4 is 210 x 297) so is a little smaller.

This leaves no "edge" over your 200mm aparture for holding/sticking the filter sheet.

You have a 150mm scope so if you stop down to, say, 125mm you can make two filters from one sheet! The only problem here is that the central obstruction of the secondary may start to cause problems - hence the reason some folk make the filter holder "off axis" - so you only use light entering the tube away from the secondary and between the secondary spider legs. However this leads to filter apartures of around 75mm or less. For the Sun this will reduce resolution a bit but at least you don't have to worry about getting enough light to your camera or eye!

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Gina

Gina

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I thought of taking the small cap off the full size cap and making a Baader Film filter to fit that. I made a full size filter for my Celestron newt and have some left over that will make a stopped down filter for the ED80. Does this sound sensible?

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Pitsmoor Col

Pitsmoor Col

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This is a common PST;

Coronado Personal Solar Telescope - 40mm PST

This may give an idea of Ha;

GONG H Alpha Network Monitor

Where as this is a more normal coloured white light image;

http://sohowww.nascom.nasa.gov/data/realtime/mdi_igr/1024/latest.jpg

Ha yes I have seen one of those scopes, but my financial dept. i.e. the pocket, says no.

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Kwizxi

Kwizxi

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I'm about to order some Baader film. This may be a silly question, but does it come with instructions for making up a filter? Obviously this isn't something I can get wrong, I like my eyes.

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PreludeToADream

PreludeToADream

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I thought of taking the small cap off the full size cap and making a Baader Film filter to fit that. I made a full size filter for my Celestron newt and have some left over that will make a stopped down filter for the ED80. Does this sound sensible?

That's what was suggested to me, and what I've done. Haven't tested it out yet (today might be the day if the sky clears).

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