Focal Reducer Questions

[cuivenion]

I've got a couple of questions about focal reducers. When using a webcam with my Explorer 130p I'm unable to achieve focus without using a barlow lens, does this mean that a focal reducer is unlikely to work with my set up?

Also, I've recently purchased an Astro Engineering AC333 2x barlow that I'm very happy with. It's a three element lens system and pretty reasonably priced. I'm looking for a focal reducer of similar quality but all the budget options seem to be two lens designs. As someone who's only been in the hobby a year or so I'd appreciate some advice, thanks for your help.

[Tinker1947]

Focal Reducers are normally designed for a particular type of scope a Refractor uses a Focal Reducer, they don't all work with different scopes, most are designed for a particular model....

[cuivenion]

Thanks for the reply. So I need to look for one that works with Newtonians then? Or the 130p in particular?

[Tinker1947]

Thanks for the reply. So I need to look for one that works with Newtonians then? Or the 130p in particular?

They don't work with Newts, full stop, you might need a Coma Corrector but from memory the 130p might not come to focus with a Camera, a 130P-DS is the correct type....

[alan potts]

To some extent I am only guessing here but I would have thought the issue was to do with focal lengths of scopes more than type as they are designed to change the light path to shorten the F/L of the scope.

I have a Meade F6.3 reducer which is designed for in my case F10 but I believe it also works in F8 versions that Meade made. Many refractor ones are for scopes from F9 to F5, I don't know if this would work on say an F 6 Newtonian. I know the same Meade reducer will not work on my F15 Mak but only because it vignettes badly, it shows an image when tested in daylight.

Maybe someone will put us all right, it would be nice to know.

[cuivenion]

Would be nice to get the whole moon in the webcams view.

[jambouk]

What camera are you using in the 130 scope?

I think you'll struggle to get the whole moon on the sensor of a webcam. Plug your kit into here and have a play around with options:

http://www.12dstring.me.uk/fov.htm

Making a mosaic is very easy to do using freeware.

James

[cuivenion]

What camera are you using in the 130 scope?

I think you'll struggle to get the whole moon on the sensor of a webcam. Plug your kit into here and have a play around with options:

http://www.12dstring.me.uk/fov.htm

Making a mosaic is very easy to do using freeware.

James

I've got a PS3 Eye and a Logitech Pro 4000. I used the beta software because the other one didn't let you select the moon. Using the specs for the PS3 eye with a 0.5 focal reducer the moon just fits in the Fov. If this would work in reality and how well is another thing entirely.

Doing a mosaic sounds like a fun project, I'll try that while I'm making my way through the Messiers.

[jambouk]

A mosaic would be far cheaper and probably offer better resolution.

[Dave In Vermont]

Though this document has to do with use of FR's with video-cameras, it provides some very useful information regardless of one's intended use:

http://www.mallincam.net/uploads/2/6/9/1/26913006/focal_reduction_for_dummies.pdf

Download a copy and enjoy!

Dave

[riklaunim]

Newtonians have short backfocus and at 0.5x reduction you won't be able to focus. I tried lesser reduction with f/5 Newtonian and got really bad image quality with DMK21 - the coma/reducer curvature were clearly visible on the small frame.