2 Inch IR cut filter

gamewarden

Where should this filter be placed in the optical train? I have a 294 uncooled camera

Tech@ZWO

gamewarden The thread on the camera is M42, and the 2" filter is M48. You need to use an adapter to connect them, usually recommend close to the camera.

w7ay

gamewarden I have a 294 uncooled camera

Unless your OTA has very fast f-numbers, your sensor is small enough (23.5mm diagonal) that you might be able to use a 1.25" IR Cut Filter (26mm clear aperture, usually) without too much vignetting.

If you are willing to swap your 2" filter for a 1.25" filter, you can get something like this:

https://cloudbreakoptics.com/products/t2-1-25-filter-adapter

Thread the filter into the hole of the adapter. Then thread the combination into the M42 thread of your camera before threading any other M42 spacer into your camera.

BTW, the current adapter should not have four thru-holes in the image above. If it does, make sure to tape them off since they can leak light like nobody's business.

Chen

johnpd

My understanding is that it belongs directly in front of the camera.

JohnD

gamewarden

everybody.

Mark

johnpd

gamewarden

You might want to consider getting a filter drawer. It converts from M48 to M42 and you can swap various filters such as a dualband for the UV/IR filter if you want to do some narrowband imaging.

JohnD

gamewarden

Could you please recommend the correct adapter I need to make this happen,,

Thanks Mark

johnpd

You can get the filter drawer from here:

https://agenaastro.com/zwo-filter-drawer-with-m42-m48-threads-for-2-filters-fd-m42.html

JohnD

gamewarden

Thanks John for the reply but this will not do what I need it to. This setup will add extra lenght to my already extended back focus. I was hoping to find a M 42 female to screw onto camera and a M 48 female that the filter would screw into and then place directly into the 2 inch williams optic diagonal.

Mark

w7ay

gamewarden

Mark,

If the 1.25" filter creates too much vignetting for your taste, get an unmounted 36mm Luminence filter, and cement it to camera. If you do that, you can probably get rid of the existing D32 AR window too.

Also, what OTA are you using? Many of them have a way to insert a 2" filter into their existing metal backs.

Chen

johnpd

Someone else will have to help you. What you are apparently looking for is an M42 female to M48 female adapter. I don't see any. The only other option you have is to get a 1.25" filter. There is a ZWO adapter that screws into the camera and the 1.25" filter can screw into that.

JohnD

gamewarden

I may of solved my problem. Thanks for the 1.25 suggestion. I have already used this system and use it on my 224 camera but wish to use the 2 inch IR filter on my 294 camera. I am purchasing a M 42 to M 48 adapter to thred directly onto the 294 camera threads. I then found on Ali Express of all places a M 48 threaded adapter with female threads on both ends. So the filter with male m 48 threads will fit on one end and then thread the whole thing onto the camera, Hopefully. This will keep my back focus distance as short as possible.

Thanks all Mark