PST flocking

[moriniboy]

Has anyone flocked the inside of the gold tube between the front blue lens and the Etalon?

I'm thinking that it would reduce scattered light bouncing down the tube and improve contrast.

Will be going stage 1 PST mod sometime in the future and would not hesitate flocking the donor tube so why not the PST one?

Any thoughts?

[iwatkins]

It can't hurt can it?

Whether it will improve anything, I really don't know being such a narrowband.

But if you do, do report back if it improves the image at all.

Cheers

Ian

[Odd Thomas]

I'm by no means an solar expert, but is it not the etalon that does the narrowband filtering, so whatever happens before that, in the optical tube, won't matter?

[moriniboy]

PST tube flocked, attached are photos before and after.

Before (OE paint is not that bad)

After

Not a massive increase in contrast but at least I know that scattered light is less of an issue

[Cath]

I think scattered light is the main reason for contrast loss in all telescopes, whether it's wide band or narrow band I don't think makes any difference, it's still light at the desired frequency.

Reducing internal scattered light can do nothing but help improve contrast as I see it - for any type of telescope.

[JamesF]

In my limited experience (ie. with my own PST) light scattering does seem to be quite a problem, so this looks like a good idea.

James

[Cath]

Their are some interesting articles on scattered/stray light problems in telescopes.

Here's one, although this one doesn't really show the light path bouncing off the inside tube walls ..

http://minimaestro.a...light_paper.pdf

This one shows the problem with scattered reflections off the tube inside wall ..

http://www.bro.com/r...calculation.pdf

[moriniboy]

By the way I did not stick the flocking to the tube, I cut some black card to the exact dimensions then flocked the card.

This way the card can just be removed as it is a friction fit within the tube.

[Peter Drew]

The majority of light scatter during solar Ha observation comes from external atmospheric scatter. A murky yet clear day will show up as a pink haze round the Sun whereas a day of excellent transparency will show a nice black background. On a couple of PST mods we have removed the baffles in the donor telescope as forward reflections from the etalon lit up the rear of the baffles like red glowing rings, even when they were flocked. The main tube was still flocked.