DERF for TSA120

[Fedele]

hi

 

I want to adapt a 135mm DERF to both my TSA120 and a 159/900 acrho. any idea?

[Altocumulus]

Create a new housing for each 'scope size, that the 135 can fit in- on- to.

I use the "keep cool" styrofoam (?) sheets that we got with some frozen food a long while ago. It's flexible whilst being strong enough when used with gorilla tape. Doesn't tend to look pretty, but it's functional. I have one as a baader film derf on my 180 mak.

[Rusted]

If you use the 135mm D-ERF on a 159mm it will reduce the aperture.

You could insert the D-ERF inside the 159mm but it is not an easy task.
It will almost certainly interfere with the telescope's baffles.
Requiring their removal or being moved further away. Making them pointless.

The 159mm objective could be removed to allow easier access for this work.

The reflected energy from the face of the D-ERF will exit the objective in a fiercely hot, focused beam.

The objective effectively doubles up on refocusing the original f/5.6 to a much shorter beam without ANY loss of solar energy!
The D-ERF reflects 99% of the sun's heat without ANY filtration.

The danger is extreme for anyone looking closely into the dewshield unless they manage to block all the sunlight with their head.
I set fire to a temporary cardboard aperture stop in the dewshield before I realized the very real danger from the reflected beam.

[Merlin66]

I agree with Geoff.

make a couple of masks/ holders for the D-ERF one for each scope.

unless you have phenomenal seeing conditions a 135mm aperture for solar is pretty good.