Help needed with a 1.25" accessory

[RobertI]

I'm hoping someone can help with a question about an imaging accessory. I use my Lodestar camera for EAA and the 1.25" adaptor I use is poor quality (one screw and no compression ring - see image below) and results in a very poor fit. I think it may be the cause of coma in one corner of the image. Does anyone know of an alternative adaptor which would provide a more solid fit (eg: two to three screws and compression ring) and ideally allow adjustment in the plane of the sensor?

I have considered directly screwing the camera to the filter wheel with a threaded adaptor, but the spacing needs to be millimetre perfect to get right F ratio and not sure I can achieve it.

Any help much appreciated.

 

[kens]

Reading between the lines you have a focal reducer between the FW and focuser so you need to get the spacing right. I would (and I do) thread the camera directly to the FW and use T2 or M48 spacers between the FW and FR to get the spacing right. For fine tuning I use shim washers between 0.1 and 0.5 mm thickness although that’s more for orientation.

Less chance of vignetting,, tilt etc

Edit: the FR looks like a 2” so probably M48 thread

[RobertI]

1 hour ago, kens said:

Reading between the lines you have a focal reducer between the FW and focuser so you need to get the spacing right. I would (and I do) thread the camera directly to the FW and use T2 or M48 spacers between the FW and FR to get the spacing right. For fine tuning I use shim washers between 0.1 and 0.5 mm thickness although that’s more for orientation.

Less chance of vignetting,, tilt etc

Edit: the FR looks like a 2” so probably M48 thread

Many thanks for the reply Ken. It's a Meade x0.33 SCT reducer, so I have an SCT to T-thread (same as T2?) adaptor, so reckon your suggestion of T2 will work well - I had not considered this. My only concern is that this provides no ability to adjust laterally in the event that the imaging train is not perfectly aligned, but I guess with good quality connectors everything should be aligned? 

[kens]

I’d trust threaded connections for alignment more than a slide in. And yes T2 and T-thread mean the same thing for your purposes and are shorthand for M42 x 0.75

[RobertI]

10 minutes ago, kens said:

I’d trust threaded connections for alignment more than a slide in. And yes T2 and T-thread mean the same thing for your purposes and are shorthand for M42 x 0.75

Thanks Ken.