how to view the whole sun with camea?

[Cartron81]

I have a celestron se8 with a F10 , and I also have a meade DSI II When I look at the sun I can only see a partial view. would a focal reducer help if so which one should i use. I also have a solar filter so I dont go blind any advice would help. thanks

[Macavity]

In truth, with a chip of that size, not easy? You would get some way towards this objective with the Celestron f3.3 reducer. But, with a Maksutov of ~similar focal length, I still had to use an additional 0.5x reducer on the nose of the camera! The in-focus required was also significant and doubtless there were distortions? But the Celestron-appropriate f3.3 field reducer / flattener would doubtless be a start.

I see Meade make such things too:

http://www.firstlightoptics.com/reducersflatteners/meade-f33-focal-reducer.html

[Cartron81]

im not looking for great detail. I want to catch the venus transit on a picture I would like to see the whole sun while it happens

[Macavity]

Lemme think... your focal length is about 2000mm. A half inch chip has a diagonal of 8mm (6.5x4.5)

Your current field with no reducer would be:

(inv tan)(2000 / 8) ~ 0.2 degrees - So, WITH the 0.33 reducer ~ 0.6 deg

But that's the diagonal field... so the rectangle is actually ~0.3 x ~0.5 deg

Probably why I remember the Sun's disk not fitting on the short axis!

IN THEORY, you could obtain greater reductions by increasing the reducer to chip separation, but you may get problems with vignetting or lack of in-focus. Probably why I added an Atik 0.5x reducer to the camera nose-piece as well, as the f3.3, to image the full disk.

<shrug> Basically it's *just about* possible to image the whole solar disk (much as I remember!) but you'd still get nice (more guarantee-able!) images with the standard f/3.3 setup?

VISUALLY, you should be able to see the whole disk with a 24mm ... 32mm Plossl or better / wider?

[Merlin66]

The size of the solar disk is approx 1/100 the focal length.

So at 2000mm it will be about 20mm diameter.

If your camera is only 4.5mm clear, then you'd need a focal length around 450mm.

I don't see how you could easily achieve that on a stock SCT.

A small scope would be better/ easier....

[Macavity]

The size of the solar disk is approx 1/100 the focal length.

So at 2000mm it will be about 20mm diameter.

If your camera is only 4.5mm clear, then you'd need a focal length around 450mm.

I don't see how you could easily achieve that on a stock SCT.

A small scope would be better/ easier....

I sense, "within errors", we're in no fundamental disagreement on any of that.

The operative word being easily?

In the UK, a couple of "fun things", I have around, to experiment (at reasonable cost):

http://www.rothervalleyoptics.co.uk/antares-2-inch-0-5x-focal-reducer_d1952.html

http://www.rothervalleyoptics.co.uk/antares-1-25-inch-0-5x-focal-reducer_d1921.html

Fitting the filter threads of 2" & 1.25" eyepieces.

Try these things before or after diagonals, in combination even. Get some filter thread extension tubes? Who knows? <G> Personally - Aesthetically, I'd be trying for a PART solar disk, with some evidence of Venus being a small disk, rather than a "black dot"? My betting is on clouds or a neighbours roof intervening.