ASI224MC and ASI178MC comparison

[Averton]

When we started planetary imaging a few years ago we were using a ToupTek camera that had the Sony IMX224 sensor in it but only operated at USB 2. A year ago we purchased an ASI224MC with USB 3 hoping that faster capture rate would be of benefit. We found that both cameras suffer from colour balance issues. Basically everything is greenish. Our starting point to fix this in processing is to use RGB balance in Registax (having already RGB aligned in AS!3). This helps to some extent but we still have to try additional correction in GIMP.

Serendipitously, when we recently started to use an ADC we found that there was no convenient point to attach the IR cut filter needed by the 224. This resulted in us changing to using our ASI178MC which has an IR cut window fitted instead of the AR window on the 224. We don't touch any colour settings other than the RGB align in AS!3 with the 178MC and have been very happy with the results.

The other day a simple solution to the fitting of the IR cut filter occurred. We are attaching the cameras to the ADC via the M42 thread on the front of the camera. We noticed that the M42 thread adapter only had 4mm of thread on it whereas the thread on the front of the camera is 7.5mm deep. So we 3D printed a 3mm thick adapter to go from M42 to 1.25" filter thread. The filter now sits snugly in the front of the camera. This could be really useful for anyone attaching the camera not via the 1.25" nose piece.

With this new arrangement we decided to try the ASI224 with the ADC and make a comparison with the ASI178 images which we did on Sunday night (9 Oct). Also attached is a wider view of Jupiter with 3 moons taken with the 224.

[evltoy]

Very interesting you had to make a 1.25 to T2 (M42) adaptor when zwo have always made these
https://www.bintel.com.au/product/zwo-t2-to-1-25-inch-adapter-3mm/

I was using this (came with my 294MCpro) as an interim before I got a filter wheel.

Not sure which ADC you have, but with the zwo you can screw a 1.25 filter to the front of it before inserting into a barlow or focuser. I never used that option as I use a T2 nose with the filter screwed to the end before going into the ADC.

[Averton]

Thanks Wayne.
We actually had not seen this adapter in the ZWO accessories list but it wasn't the issue of the availability of the adapter, it was the idea that the thread which was being used to hold the camera still had adequate length to also have the filter adapter in the same thread. BTW it took less time to design and print the adapter than it would to have ordered it :)

Yes we do use the ZWO ADC, but the thread on the front is already being used to hold the barlow lens which unfortunately doesn't have a filter thread on the front of it.

[Dave882]

Interesting comparison shots and good job getting the imaging train together. I know what you mean about the colour balance - it always needs some adjustment. Great results on both shots tho!

I’m lucky to have one of those old aluminium eyepiece cases chock full of random adaptors and pieces that I don’t even remember where they came from anymore but wow it’s invaluable when you’ve just gotta fit stuff together. I use exactly the same solution to you with my uv/ir with Asi224mc and my new Asi462mc but with the asi290mm I’ve got a filter drawer in the train and a rotator for good measure.

[evltoy]

I'm I missing something?

I'm getting the feeling that the preferred method is to have the filter installed as close to the sensor as possible.

P&C - Is this a little tip in the book you recommend?

[Averton]

Thanks David.
We thought that it was an idea to just do a comparison as we are happy with the current results from the ASI178 but wanted to just check against the camera we were last using.

We have accumulated some adapters but obviously not enough. Never get rid of anything, it might be useful one day :)

[Averton]

Hi Wayne,
We don't believe there is any particular advantage to where the filter is fitted in the image train. We have had the IR cut filter in several locations and all seemed to perform the same. The only issue is if there is a long optical train at the 1.25" diameter, you'll eventually be obstructing the edges of the FOV and creating vignetting. So if you're using a 1.25" IR cut filter a long way from the sensor, this could be an issue. Having said this, with planetary we are often only using the very centre of the optics anyway.

No this isn't a tip from the book.