View Full Version here: : Solar Scope idea ...
20-12-2011, 10:55 AM
With the upcoming Venus transit in June and just the general cloud issues I was looking into building a solar scope as another viewing option.
I've got an 4" f12 mirror from a old newt that the silvering has been mostly gone and wondered if using it as a low reflective surface ( silver all gone ) how it would work either as a projector setup or whatever.
Anyone ever played with this setup or am I re-inventing the wheel badly ?
I have plenty of other lenses and the old 60mm Refractor which could become a 'sacrificial' projector scope. If it melts it ain't a big loss so to speak.
Come to think of it I have another wee scope that could be a guinea pig with no loss incurred.
Add it to the project list .. could be fun :P
20-12-2011, 08:32 PM
There are quite a few posts floating around online about this .
Important to remember BOTH the primary and secondarys coatings are completely removed.
20-12-2011, 08:45 PM
I reckon it's a good idea, and like Graham suggested, have the secondary uncounted as well.
You still may need an ND filter, but it will be less than if they were coated.
21-12-2011, 04:32 AM
Yes, It works.
Stripthe coatings from the drimary and secondary mirrors; you may have to paint the rear of the secondary to prevent ghost images...
You'll definately need a ND3 at the focuser.
21-12-2011, 09:50 AM
Thanks for the warnings guys. I had thought about the secondary but not about the filter. I have some optical flats that can become a secondary, the bonus of being a collector of oddball bits.
Very cagey about frying my eyeballs, may go with a webcam test first or a bit of projection viewing.
01-01-2012, 05:14 PM
Hi all, I also would remove the silvering from Primary and Secondary. I have also had this plan in mind for a 3-inch I had. I would sugest using non direct ways of testing. Why fry a video, when a piece of paper across the eye piece would tell how hot it gets, then projection viewing.
Y/O (YogieOne) :thumbsup:
09-01-2012, 10:14 PM
Sun was shining today. most unusual, clouds had gaps in them.
Setup my wee 60/700 refractor with a cheap binoc EP and .965 diag and pointed it at the sun. What the heck if it all fries.
Waved a piece of paper in front of the EP and had an image. A wee tweak with the focusser and I could see sunspots !! Who knew it was so easy !!
I switched the paper for a piece of frosted plastic screen from an old LCD screen I'd pulled to bits and had a projection screen image of about 150mm with sunspots as clear as a bell.
I've been dead scared to point anything at the sun but it worked better than I expected by far. Roll on the Venus Transit in June, I'm ready !!
And I have something to play with whenever the sun comes out to play, probably about April or May ... :shrug:
:D new toy ...
10-01-2012, 02:38 AM
For such a small refractor, get a piece of solar film for the front. It will cost almost nothing and be far less fry-ey.
10-01-2012, 06:38 AM
During my student days, I was using Herschel prism for Sun observing (it was made by Zeiss) see some info here:
Due to it's construction (total reflection of light + polarisation), it was possible to adjust the amount of light (white - there was no filtering) that reaches the eye.
However, today Baader Planetarium foil filter is much more practical, inherently safer and way cheaper solution.
10-01-2012, 08:18 AM
Cheers Peter & Bojan,
I've spotted Solar film on local trademe, only about $15 for a piece more than big enough to work.
I guess I've just been a bit over cautious about the safety aspect of solar viewing. I've only got one 'good' eye these days and also wasn't sure about the heat effects on a scopes internals. The wee 60/700 was a no loss test that was more successful than I'd imagined. I even set it up on the old GEM mount and was able to track it by slowly turning the drive shaft.
Just another astro-option to play with. Don't think I'll ever spend the large $$$ for a solar scope with all the fancy doodahs but I'll spend a few $$ for film and some sort of screen mounting system for future experiments.
It's just another star .. right ? :D
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