Tapered dew shield?

[binofied]

I am putting a 450mm long dew shield onto my 10" Meade F10 OTA. It is actually running at F6.3 or 1600mm with a celestron focal reducer.

What size should the open end be?

The normal tubes from Meade are 300mm and parallel. However this is for F10.

Also i am going to make it like a baffled tube with rings about 20mm wide and 300mm ID then covering the outside with balsa sheet. There will be three rings bottom mid and end of tube. This way there will be less reflection from the sides as they will be in the shade of the rings.

So is 300mm wide enough at the open end? Or does it need to be a tapered tube?

Dave Moorhouse
Auckland NZ

[marki]

Originally Posted by binofied

I am putting a 450mm long dew shield onto my 10" Meade F10 OTA. It is actually running at F6.3 or 1600mm with a celestron focal reducer.

What size should the open end be?

The normal tubes from Meade are 300mm and parallel. However this is for F10.

Also i am going to make it like a baffled tube with rings about 20mm wide and 300mm ID then covering the outside with balsa sheet. There will be three rings bottom mid and end of tube. This way there will be less reflection from the sides as they will be in the shade of the rings.

So is 300mm wide enough at the open end? Or does it need to be a tapered tube?

Dave Moorhouse
Auckland NZ

Hi Dave

I use a astrozap flexible dew shield on my LX200 10" and this also runs parrallel to the tube. I use my scope at F10, F6.3 and F3.3. The dewsheild does not interfear in any way so tapering is not necessary. Why would you bother to baffle the dew shield??? Mine does a great job of keeping stray light out and you really do not want to add any extra weight to the tube espeacially if there is little or no gain optically. The OTA is well baffled in anycase.

Ciao Mark

[binofied]

The reason for the baffle idea is that the existing Meade shield if you look down it at an oblique angle there is a lot of reflection off the black painted inside. The paint is not very matt. I want to use it mainly to stop stray light entering the system. I am often using it during almost full moon with the moon only 15 deg away to take measurements for gravitational microlensing science work to find extra solar planets.

[marki]

Fair enough. You might like to try the astro zap shield as it has no reflection from the inside surface and is much lighter then the meade dew shield. You could always use felt inside the meade version which would stop the reflection and is nice and flat so there is no extra obstruction.

Ciao Mark

[Shawn]

I made one out of acetate sheet...was very light and you can get it laminated with film the same blue as your OTA.....