Spacer for ZWO120

[michael8554]

Measure from the Moravian sensor to the front face where it attaches to the ota, call this dimension A

Measure from that front face to the prism B

Measure from the prism to the top of the guidecam tube C

Insert the guidecam and measure from the top of the guidecam tube to the front of the guidecam case D

The guidecam sensor is 12.5mm from the front face.

A needs to equal B+C+D+12.5.

To make them equal you add a spacer to the guidecam or the Moravian path.

You could make a full size drawing if it helps you visualise the problem.

Michael 

 

[Datalord]

9 minutes ago, michael8554 said:

Measure from the Moravian sensor to the front face where it attaches to the ota, call this dimension A

Measure from that front face to the prism B

Measure from the prism to the top of the guidecam tube C

Insert the guidecam and measure from the top of the guidecam tube to the front of the guidecam case D

The guidecam sensor is 12.5mm from the front face.

A needs to equal B+C+D+12.5.

To make them equal you add a spacer to the guidecam or the Moravian path.

You could make a full size drawing if it helps you visualise the problem.

Michael 

 

So, this makes total sense to me. This is what it really should be according to logic.

Moravian:

According to this, I should have 61.5mm backfocus. I can assure you I have tried absolutely everything, with every spacer known to mankind and absolutely nothing works.

The only kind of success I have had is with an eyepiece within 10mm of the prism. Otherwise, nothing.

[michael8554]

Well why don't you measure whether it's 61.5 or not !!!

Without measring the light paths you can't hope to know what size spacer is required !

If A=61.5 then B+C+D +12.5 needs to be 61.5 too, if it's less you add a spacer, if it's more then you add a spacer to the Moravian to make it the same length as the guidecam path.

Michael 

[Stub Mandrel]

Fit the 10mm spacer to the main camera and try again.

If it works then worry about why!

 

[Datalord]

Ok, I disassembled the entire thing. I thought I had an extra spacer for the g3, but it turns out to be a separate spacer for non-OAG mounting.

But, when I disassembled, I noticed that the the telescopes thread was protruding into the OAGs thread, which blocked the tiny eyepiece(camera)-holder from going fully into the OAG. Adding the holder first, I can insert it longer into the OAG, saving valuable mm at the cost of a very tight connection between camera and scope. This is a different problem I must handle somehow.

Anyways, with the new, low profile camera cap I bought, the new assembly, I got the following picture:

Btw, I thinkn the focus distance is about 40mm, which doesn't match any other calculations, but if it works...