Imaging with Celestron C8 and ZWO ASI533MC

[PeterCPC]

I will be using a 0.63 reducer but this combination is not ideal and could show oversampling. Is there a 0.5 reducer out there that works with the C8? This would be more suited to the 533.

[vlaiv]

https://www.teleskop-express.de/shop/product_info.php/info/p11425_Starizona-Night-Owl-2--0-4x-Focal-Reducer---Corrector-for-SC-Telescopes.html

(or from somewhere where you don't need to wait 1/3 of a year for delivery ) 

[PeterCPC]

Thanks @vlaiv but I was thinking of 0.5 reducer and somewhat less money.

[vlaiv]

I don't think there is one that will work well with 1" sensor.

At that sensor size - you want dedicated / optimized x0.5. Regular ones that you can find won't work well.

For example - https://www.firstlightoptics.com/reducersflatteners/astro-essentials-05x-2-focal-reducer.html

will work only for very small sensors.

If think about it - 533 sensor has 16mm diagonal. Using x0.5 reducer will compress 32mm field into 16mm diagonal. 32mm field of SCT is going to be very curved and coma will be evident. You need reducer that will also correct for these aberrations as well.

Maybe you could try this one and see how it works:

https://www.firstlightoptics.com/reducersflatteners/stellamira-2-06x-reducer-field-flattener-with-m42-adapter.html

but that is meant for F/5-F/7 refractors. Not sure how it will work on SCT.

[PeterCPC]

@vlaiv Thanks. Perhaps I will just try with the 0.63 reducer and see how it goes.

[vlaiv]

Just now, PeterCPC said:

@vlaiv Thanks. Perhaps I will just try with the 0.63 reducer and see how it goes.

You can always control over sampling with binning and field of view with mosaics.

That is the cheapest option - you don't have to get any new hardware to do it.

You'll probably want to aim at x3 binning in most conditions. That will produce 1000x1000 image per mosaic tile (or single image if you don't want to do mosaics) and about 1.8"/px.

[PeterCPC]

1 minute ago, vlaiv said:

You can always control over sampling with binning and field of view with mosaics.

That is the cheapest option - you don't have to get any new hardware to do it.

You'll probably want to aim at x3 binning in most conditions. That will produce 1000x1000 image per mosaic tile (or single image if you don't want to do mosaics) and about 1.8"/px.

But I am using a 533 MC colour camera so, as far as I know, I would lose the colour.

[vlaiv]

1 minute ago, PeterCPC said:

But I am using a 533 MC colour camera so, as far as I know, I would lose the colour.

Depends on how you do it.

Here is easiest way to do it without loosing color information.

Record, calibrate, stack your image as you normally would - to get 32bit per channel RGB image.

While still linear prior to any processing - you bin your data x3 and then proceed to process as you normally would.

This will have almost the same effect as using larger pixels (not quite as you are using color camera and there is bayer matrix and actual resolution of your data is not what is commonly believed - not the same as equivalent mono camera, so improvement from binning won't be the same - but it is best way to do it with color data in your case).