Webcam focus

[Pete D]

I am having trouble getting focus using my webcam SPC900 on a Skywatcher 200p unless I use a barlow lens. Does anyone know if a 1.25 diameter extention tube will work and can anyone reccomend one.

[ronin]

I think that the problem is that you cannot get the webcam in close enough to where the prime focus is. The barlow will have it's object plane on this prime focus and in order to magnify the image will create the second image further out, so this image will be far enough out from the barlow to fall on the web cam.

An extension tube would not therefore be of much use.

Sorry I cannot draw the optics to show what I mean.

I would suggest that you ask somewhere like FLO concerning what you are finding and ask what they suggest. However I think that an extension tube is not what is required. A shorter focusser is what I suspect is wanted.

Why not use a good barlow and simply have a magnified image on the webcam?

[todd8137]

a would think its the other way round i could not get focus with a rack and pinion focuser theres not enough inwards travel well thats was the prob on my sw300p

[Mr TamiyaCowboy]

had the same problem with a converted webcam. could not get close enough to the focal plane.

took me about 5 mins to work out that the eyepiece holder was the problem. removing this gave the camera the added few mm drop to focus perfect. was the most effective way to get camera and telescope to focus.

[pritc]

I purchased one of these for my 200P:

Orion Precision Centering Adapter - SCS Astro

Slots into the 2" adaptor.Never get an issue achieving focus now with my SPC900 webcam or DSLR Canon 1100D.

Wayne

[tiredboy]

I have the same problem with my Meade ETX80. I can use the webcam with the barlow flipped in but not with it flipped out.

...the eyepiece holder was the problem. removing this gave the camera the added few mm drop to focus perfect. was the most effective way to get camera and telescope to focus.

Might have to look into this. Any other solutions greatly received.

[Stephen]

The only other solution to lack of inward focus is to move the mirror up the tube.

You can do this by either chopping some off (bad idea) or using spacers, springs and / or longer bolts between the mirror cell sections.