Quick question re looking at the sun

[justme]

Hi all,

My family have an 8 inch dob which we don't use as often as we'd like to for various reasons. For christmas I plan to get us a goto upgrade to make viewing a little easier for us.

I was also considering a solar filter and there seem to be some good deals on at the moment with the eclipse coming. Now the sun being a big old ball of blinding ferocity, I just wanted to check that I know what I'm doing.

I'm thinking of getting this filter: http://www.ozscopes.com.au/skywatcher-200mm-solar-filter-for-reflector-telescopes.html

Is that the right one for an 8" dob?

Also, is it correct that you don't need any additional filters for eyepieces and such? Wouldn't want to burn out the old retinas. And on that note, is there a limit on how long you can observe for? I don't imagine any of us will be peering at the sun for hours on end or anything but I'd hate to spend 15 minutes looking only to find we should have only looked for 5 minutes at a time or something.

All advice appreciated. Thanks.

[Merlin66]

Cathy,
The good news is that the Solar filter you're looking at, when fitted securely is 100% safe and can be used for unlimited solar viewing.
If your dobbie is a truss type you'll need to add a shroud to stop the unwanted reflections and ambient light.
Enjoy!

[justme]

Thanks Ken.

My son is quite keen to have a look at the sun so I think I'll add it to the christmas list. Luckily it's a solid tube dob so I won't have to spring for a shroud as well. :)

[alocky]

Make sure you leave the finderscope front lens cover on- may seem obvious, but the crosshairs can burn away pretty quickly!
Cheers,
Andrew.

[lacad01]

Or even remove the finder scope completely just in case...

[h0ughy]

you can look here for some moe info as well http://xjubier.free.fr/en/site_pages/solar_eclipses/SolarEclipse_EyeSafety.html

[justme]

Thanks so much guys. Cheers for the tip on the finderscope as well. It's obvious now you mention it but I probably wouldn't have thought of it.

[barx1963]

The main safety tips with these style of filters are:
1. check they are securely in place, especially if there is any wind
2. make sure no one removes the filter from the scope while it is in use
3.check it before use for any pinholes, rips and tears. Even if they are tiny they can be dangerous

Malcolm

[alocky]

Pinholes are generally fine within reason. They act as a point source, and since they're so close to the mirror the light doesn't come to focus. Obviously there is a point where they will start to degrade the contrast, and you don't want too many. Many of the glass front filters have pinholes, you can cover them up with a marker pen. If in doubt, send a query off to the manufacturer.
Cheers,
Andrew.

[RAJAH235]

Cathy,
#4. Do not leave the t'scope un-attended.