Quote:
Originally Posted by sheeny
Yep. The scope focuses the light (i.e. intensifies it) so it can do damage inside the scope before it gets to filter, or the filter or EP can be subject to extreme temperatures and fail.
If you have an old EP that you wouldn't mind destroying, you can use it in a Newtonian scope for solar projection into a screen or card, but never look though a scope without a on objective solar filter!
There are also Hershel wedges which dump 95% of the light energy out the back and only allow 5% through. These perform very well for solar imaging, but I don't think they are considered safe these days for visual work (I'll stand corrected by someone more up to speed with a Hershel).
Having seen the damage done to an uncovered finder scope from the sun as it passed over (the finderscope looked like an oxy torch had cut across the back and up the side of the finderscope and the cross hairs were of course gone!), I wouldn't recommend solar work without an objective filter without extreme care, and especially never for visual work.
Al.
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Good points Al. You can't be too careful with our nearest star.
I use the Baader wedge, SC+ OD3.0ND and LVW 13, 22, & 42 eps.
I initially used the wedge without the SC filter, but have reinstalled ( it gives a lime green image) & have found even in my apo the SC reveals more detail than the white image only. It also has the benefit of reducing the 'seeing' induced degradation as it passes only the green light around 540 nm.
I find its easier to remove the finderscope from the OTA altogether, no nasty surprises. My mate wraps alfoil over his finder (not a quickrelease base) and puts an elastic band around it.
I tried the LVW42mm on the Sun for the first time today ( Is it wrong to be in love with an eyepiece
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Hi Ken, Good to know that, the Baader Manual cautions about the rear element designs but I guess the actual point of focused light is quite far from the last element.