Orion XX14 Solar Filter?

[Terrorfex]

Good Evening,

 

I've recently gotten the exclusive use of an Orion XX14 Dobsonian, and would like to make use of it for the Solar Transit of Mercury on the 9th. Unfortunately, there's no solar filter made for a telescope of this size (16.2" outside diameter of tube) and despite my efforts, I can't seem to locate any DIY filter material sold in sheets larger than 12 x 12. Does anyone have any suggestions about where I could go next? Was genuinely surprised the manufacturer didn't have their own range of filters.

Thank you for any help,

[Davey-T]

You don't need the whole aperture, you could buy a sheet of Baader Solar Film and make one that fits between the spider arms.

Dave

[Terrorfex]

1 minute ago, Davey-T said:

You don't need the whole aperture, you could buy a sheet of Baader Solar Film and make one that fits between the spider arms.

Dave

Wouldn't it be more difficult to get a perfect seal internal to the casing, and to make sure it was absolutely parallel to the mirror? 

[michael.h.f.wilkinson]

You do not have to. Solar film should not be perfectly flat, so getting it parallel isn't an issue. If you really want a big sheet, you can get them here:

http://www.teleskop-express.de/shop/product_info.php/language/en/info/p545_Baader-Astro-Solar-Filter-Film--visual-ND-5-0---50-cm-x-49-cm.html

[Davey-T]

If you make a circle with a return on it that fits over the end of the scope like a normal cap, then cut a circular hole in it that fits between the spiders you can cover that hole with the Baader Solar Film.

Don't worry about it being parallel to the mirror the film will be all wrinkly anyway.

Do a search for instructions.

BTW welcome to SGL, someone else will no doubt notice this thread in a minute and may have a picture.

[michael.h.f.wilkinson]

BTW, the Orion XX14 is a truss-tube design, I see. Do not forget to use a shroud!

[Terrorfex]

28 minutes ago, Davey-T said:

If you make a circle with a return on it that fits over the end of the scope like a normal cap, then cut a circular hole in it that fits between the spiders you can cover that hole with the Baader Solar Film.

Don't worry about it being parallel to the mirror the film will be all wrinkly anyway.

Do a search for instructions.

BTW welcome to SGL, someone else will no doubt notice this thread in a minute and may have a picture.

 

Thanks for that. Found a few helpful tutorials ... Any idea about ratio of size of the "circular film hole" to the overall aperture or size of the primary/secondary mirror? I suppose I could just guess one quadrant in size ...

[Stu]

1 minute ago, Terrorfex said:

 

Thanks for that. Found a few helpful tutorials ... Any idea about ratio of size of the "circular film hole" to the overall aperture or size of the primary/secondary mirror? I suppose I could just guess one quadrant in size ...

Just make it so it is the biggest possible whilst still fitting between the vanes of the secondary spider, in one of the quarters as you say.

[Terrorfex]

Just now, Stu said:

Just make it so it is the biggest possible whilst still fitting between the vanes of the secondary spider, in one of the quarters as you say.

Thanks. Will do!

[John]

Whats the largest hole that you can fit between your spider vanes and without obstruction by a segment of the secondary / secondary support ?. I found with my 12" dobsonian that I could get just over a 102mm aperture. It might be a little larger for a 14" aperture dob ?

 

[Davey-T]

As Michael said fit the shroud and cap the finder if it's got one.

Dave

[Dave In Vermont]

This is why I opted to use an ST80 F/5 refractor for my solar adventures. Inexpensive to outfit with a filter, and no central obstruction. I use film for this. But I also have a full aperture glass solar-filter for my 200mm F/4 Newt. But a shroud around your truss-tube 14" and a 1/4-aperture should work very nicely. I'd suggest a white-coloured shroud to reflect away the light, and thereby keep the internal temperature of the scope, and optics, low.

Enjoy the transit!

Dave