Partial Solar Eclipse-West Sydney-Projection Method

circumpolar (Matt) · #1 07-02-2008, 04:50 PM

Here is my attemptwhen the clouds cleared at about 4pm.

kljucd1 (Daniel) · #2 07-02-2008, 04:53 PM

Hi,

I have never seen/done this, what equipment did you use?

Looks really cool by the way!!

Thanks

Daniel...

circumpolar (Matt) · #3 07-02-2008, 05:06 PM

This is what I used. 12" LB and a white board. That's it.
Great for sunspots as well.

h0ughy (David) · #4 07-02-2008, 05:08 PM

well done - storms and still raining in newcastle

kljucd1 (Daniel) · #5 07-02-2008, 05:08 PM

Hi,

So, this method doesn't cause any risk of damage to the equipment/user?

Daniel...

citivolus (Ric) · #6 07-02-2008, 05:14 PM

Well, I wouldn't want dust on the eyepiece!

I've heard of people melting the reticle in their finder by forgetting to cover it

But seriously, you're putting a lot of energy through the optics, and a lot of heat can build up. If you insist on using projection, you'd better stop down your optics significantly. Better yet, solar film is cheap cheap cheap.

I was doing solar filter projection on my neighbour's fence 40m away. A 60mm aperture filter was giving a very nice eclipse shaped reflection, with no risk to my equipment

Matty P (Matt) · #7 07-02-2008, 05:15 PM

Great idea Matt! Nice work.

circumpolar (Matt) · #8 07-02-2008, 05:21 PM

Quote:

Originally Posted by kljucd1

Hi,

So, this method doesn't cause any risk of damage to the equipment/user?

Daniel...

You can't look down or into the eyepiece!!
Depending on how the scope is focused, the focal point is beyond the EP by maybe 20mm. Beyound this point the image expands and expands depending on how far away the board is held. The further away the larger and dimmer the image (inverse square law). The focus has to be adjusted again if you change the distance again.

This method will not damage youe scope.

sheeny (Al) · #9 07-02-2008, 05:23 PM

Quote:

Originally Posted by kljucd1

Hi,

So, this method doesn't cause any risk of damage to the equipment/user?

Daniel...

It's best done with a newtonian scope (because they are well ventilated and have less inside them that an be burned) and maybe even go to an old eyepiece just in case. I used to do it with my old 8" newt, and a 2-2.5" off axis objective mask to knock down the heat a bit.

You just don't want to get the focal point inside the EP while your focussing, or focussed on part of the insides of the scope while you're pointing it at the sun...

I used to focus on something as far away as possible, then fit the off axis mask, and place the tube cap over that. Then aim at the sun and use the shadow of the tube to get it aimed (it's pretty close when the tube shadow is circular

), and then remove the objective cap and fine tune the focus.

Al.

sheeny (Al) · #10 07-02-2008, 05:25 PM

Quote:

Originally Posted by circumpolar

You can't look down or into the eyepiece!!

Good point, Matt! Important technical tip...

Al.

circumpolar (Matt) · #11 07-02-2008, 05:26 PM

Quote:

Originally Posted by citivolus

If you insist on using projection, you'd better stop down your optics significantly.

Good point!
I had a 12"GSO click on cover handy in case the clouds parted for a long period. This has a offset 50mm hole. As it turned out, I could only see the sun for about 2mins at a time every 10-15min intervels!

So I didn't use it.

But hey, I saw it!