The Filters We Need With Digital...

Started Oct 5, 2008 | Discussions thread
Henrik Andersson Senior Member • Posts: 2,454
Re: Don't point it at the sun!

Joseph S Wisniewski wrote:

Henrik Andersson wrote:

Now the light path look like:
Maybe a weather proofed housing
IR/UV-blocking. Maybe this should be in front of the telescope ...

I like those kind of things at the low density part of the optical
path. How big was this scope again?

10" to 20". I'm aiming for dual FoV, so a 10" for wide and a 14", 16" or 20" for the details.

I hoped they had a 8" in the LX400 series but they don't.

"variable-ND"-servo solution
Servo board with three settings 0.63x focal reducer, none and 2x tele

Now, that should be interesting. Getting all that to be parfocal
should be fun.

I don't need it to be par focal if I use some sort of focus table or faster servo board. I guess that's easier then making all focal lengths being parfocal. What's the easiest way to do that?

Traditionally, focal reducers eat back focus,
extenders increase it. If you're using off-the-shelf reducers and
extenders, the distance your focus shifts is going to be very great.

I assumed that but it's good to know.

You might want to consider a system that racks the camera back and
forth automatically by large fixed distances quickly, in order to
accommodate that.

That's what I'm aiming for.

If you wait for a standard motorized


Camera on a focus table

Are you sure? What's the focusing range of the scope's focuser? Is it
internal or external?

Good question, I assumed I needed to adjust focus externally. Anyway I need to move the camera depending on the reducer/extender. I'll have to check if it's more straight forward to control the internal focus remotely then building an external.

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