From: Mark Gaffney <markgaffney@me.com>

Date: January 8, 2010 8:48:57 PM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] solar beginnings...


Good warning! I shut it down & covered up before it got too hot....Hope I haven`t done any real damage?! I`ll try making a couple of masks...You have a good sleep!


Mark.

On 09/01/2010, at 12:33 PM, Ray Byrne wrote:

Hi Mark,


I wouldn't let the Sun's light travel through your scopes optics with being filtered. The focussed light from the sun is very hot indeed and will damage your scope. As soon as I'm finished observing the Sun I turn it away from the Sun before taking the filter off. SCTs are particularly susceptible to damage being enclosed tubes and having adhesives in them and an glass near the focus will crack from the heat in all probability or plastic caps catch fire. 


SOLAR OBSERVING IS BLOODY DANGEROUS BEWARE!


 

On 8 Jan 2010, at 21:47, Mark Gaffney wrote:

Here it is...

<Picture 5.png>


Mark.

On 09/01/2010, at 7:54 AM, Ray Byrne wrote:

Hi Mark,


Happy New Year to you.


I'd be inclined to have an off-axis aperture to fit your Baader film into. Measure the largest area of the corrector plate that is free of any obstruction and cut a hole in some card that will fit in you cake making spring that will avoid the secondary mirror and the ring that holds the edge of the corrector (probably 3" or so). That way you will have no secondary obstruction to interfere with the light path, effectively like a refractor, and being that seeing is nearly always poor during the day a smaller aperture will help combat the poor seeing. Also the Sun is obviously extremely bright and you don't want or need all that light so a sub-aperture mask will help there too. Do a Google on secondary obstructions and also smaller aperture in poor seeing and you'll see what I mean.


IHTH


ATB


Ray



On 8 Jan 2010, at 04:19, Mark Gaffney wrote:

Hi Alan, Ray & others,
My Baader solar film (1 foot square) is I believe in the mail
somewhere & I now have a 280mm cake making spring form as per the
following site & some cardboard. Here`s the site I`m using for advice
on the construction of my filter; http://www.backyard-astro.com/equipment/filters/baader.html
I can`t find an email link to the author so am asking here. How much
of the aperture of my C9.25 can I use i.e. how big a circle should I
be cutting in the cardboard? The spring form does seems to fit the
scope & & I`d be using a reducer...

Mark.