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how to view the whole sun with camea?

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5 replies to this topic

#1
Cartron81

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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

#2
Macavity

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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.firstligh...al-reducer.html

Edited by Macavity, 07 May 2012 - 12:15 AM.


#3
Cartron81

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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

#4
Macavity

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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! :eek:

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?

Edited by Macavity, 07 May 2012 - 01:34 AM.


#5
Merlin66

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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....
"Astronomical Spectroscopy-The Final Frontier" -to boldly go where few amateurs have gone before.

C11, NEQ6pro, DMK41AF04, ATik314L+, 1000D modded, SM60DS/BF15, 102mmPST, Spectra-L200 and other Spectroscope(s).
"Astronomical Spectroscopy for Amateurs", "Grating Spectroscopes -How to use them" - Springer
http://tech.groups.y...l_spectroscopy/

#6
Macavity

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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. :eek:
The operative word being easily?

In the UK, a couple of "fun things", I have around, to experiment (at reasonable cost):
http://www.rotherval...ucer_d1952.html
http://www.rotherval...ucer_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. :mad:

Edited by Macavity, 07 May 2012 - 08:14 AM.





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