Sct f3.3 reducer query

[PeterW]

What's the usable focal plane diameter usable with the f3.3 reducer. It's ok with little sensors and vignettes a lot with big sensors.... What is the actual usable diameter before the vignetting kicks in?

Thanks

PEterW

[HiloDon]

Hi Peter,

The Optec NexGen F3.3 FR has a maximum corrected diameter of 9mm as stated on their website. I was never able to find specific information on the Meade F3.3, but I own both and get some vignetting with the Meade and my Lodestars. This article comparing the two supports my experience:

http://homepage.isomedia.com/~cvedeler/scope/focal_reducers.htm

It's apparent that both are designed for small sensors less than 9mm on the diagonal. The Optec appears to be better, but costs more, too.

Hope this helps.

Don

[Dave In Vermont]

Though written for MallinCam owners, this .pdf contains excellent information on focal-reducer combos to achieve different F/ ranges for SCT's as well as other scopes. And at what point the image begins to degrade/vignetting. Worth downloading and printing IMHO:

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

Clear Skies,

Dave

[PeterW]

Great stuff, cheers. Was hoping the answer was more like 18mm, but not to worry, there is always other things I can try.

Cheers

PEter

[Merlin66]

AFAIK the original x0.33 reducer was specifically designed for webcam sized chips. Around 3-4mm.

[Dave In Vermont]

Hi Peter,

The Optec NexGen F3.3 FR has a maximum corrected diameter of 9mm as stated on their website. I was never able to find specific information on the Meade F3.3, but I own both and get some vignetting with the Meade and my Lodestars. This article comparing the two supports my experience:

http://homepage.isomedia.com/~cvedeler/scope/focal_reducers.htm

It's apparent that both are designed for small sensors less than 9mm on the diagonal. The Optec appears to be better, but costs more, too.

Hope this helps.

Don

It was due to complaints about vignetting that Meade discontinued their F/3.3 focal-reducer. Some folks use them set up in different configurations - extension rings and other spacers, etc. - and report very favorable results. I have one I purchased new just before they vanished from the market. They can now be found occasionally on the used markets such as Astromart:

http://www.astromart.com/news/

Clear Skies,

Dave