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Herschel Wedge on SCT?

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#1 James Cunningham

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Posted 24 March 2013 - 01:45 PM

Can you use a Herschel Wedge on an SCT? Thanks

#2 zippeee


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Posted 24 March 2013 - 02:30 PM


As I understand it, unfiltered sunlight (especially the amount that can be collected with 11") is not intended to be focused on internal mirrors. There would be too much heat build-up on the secondary, apart from other things I'm sure.

#3 Peter in Reno

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Posted 24 March 2013 - 02:41 PM

Look at this:


It says that it cannot be used for reflecting scopes and an SCT is a reflecting (mirrors) scope. It's best for refractors.


#4 HeyJP


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Posted 24 March 2013 - 09:32 PM

Not a good idea for a lot of reasons. On SCT or reflector I would always use a big-*BLEEP* solar filter in front of everything. I like my eyes.


#5 rmollise



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Posted 25 March 2013 - 02:24 PM

Can you use a Herschel Wedge on an SCT? Thanks

Nope, not if you are smart. You will likely damage the scope--and badly. Stick to full aperture solar filters.

Oh, and Mr. Jim means "big @ss" solar filter... :lol:

#6 HeyJP


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Posted 26 March 2013 - 01:49 AM

Uncle Rod,

That's exactly what I meant. Takes another southerner to interpret what gets lost in translation.

Jim (originally from Tennessee)

#7 btieman


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Posted 13 April 2013 - 09:47 AM

Hmm...I wonder if a full aperture solar filter as a pre-filter to knock down the heat would allow it to be safe? Or are there reasons beyond heat why a wedge won't work with a reflector...

#8 Starhawk


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Posted 13 April 2013 - 12:39 PM

Do not attempt this. Lots of awful things can go wrong.

First, the wedges aren't made for giant scopes, so you'll risk destroying your eyesight forever on that first peek. There would seem to be countermeasures to this, but they are flawed.

Specifically, if you put a full opaque cover over the entire front of the telescope with a cutout within the stated safe diameter range for the wedge, then that could appear to be safe for the wedge. However, things like the baffles, lubricants, paints, mirrors, and optical coatings aren't intended for this and can outgas and fog items, crack, melt, or flake off.

Now, there is a dirty little secret: the Baader safety film sold by Astro-Physics in sheets or Kendrick in ready to use filters is safe, inexpensive, and produces absolutely fantastic images. I made a filter for my C5 out of a round cardboard box I found at Michael's craft supply and made an off axis filter for my C8 out of a round gift box I found at Big Lots (and some people here accuse me of being elitist).

Paint your filter cover gloss white wherever the sun can hit it and make sure it goes on very snug and secure (you can use art foam sheets to decrease the diameter so your filter has no chance if being knocked off, blown off, or otherwise being removed by a deliberate effort which can't happen without being noticed by the observer before it's too late).


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