Recommended ZWO camera for CaK

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Recommended ZWO camera for CaK

Post by Jordan Konisky »

I just received a Lunt B1800 CaK star diagonal filter module that I will pair with my SW ED100 refractor. What would be the recommended ZWO model to match with my set-up? Thank you for suggestions and advice.

Jordan


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Re: Recommended ZWO camera for CaK

Post by marktownley »

What f-ratio are you thinking of using?


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Re: Recommended ZWO camera for CaK

Post by MalVeauX »

Jordan Konisky wrote: Sun Feb 28, 2021 7:22 pm I just received a Lunt B1800 CaK star diagonal filter module that I will pair with my SW ED100 refractor. What would be the recommended ZWO model to match with my set-up? Thank you for suggestions and advice.

Jordan
Hi Jordan,

A full disc can be done with any sensor larger than 9mm for yourself, so the 1" class sensors will do this. Smaller pixels will sample it more appropriately. You could do this with an IMX183 sensor (2.4um pixels), IMX253 sensor (3.45um pixels), M34320 sensor (3.8um pixels).

Moderate resolution partial discs can be done with smaller, faster FPS sensors to beat the seeing and go for critical sampling, as small as 2.9um pixels which would critically sample 393nm at F18 (so 2x amplifier), but take great care with the amplifiers/barlows you use to avoid problems with correction in near UV. The IMX290 sensor does well for this at 2.9um pixels and is fast.

100mm at 393nm requires significantly excellent seeing conditions to critically sample (around 0.9 arc-seconds!). So I recommend you be prepared to maybe make a 60mm or 80mm aperture mask for your refractor for this reason if your seeing is not superb.

Very best,
Last edited by MalVeauX on Sun Feb 28, 2021 8:21 pm, edited 1 time in total.


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Re: Recommended ZWO camera for CaK

Post by Jordan Konisky »

My ratio is F9


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Re: Recommended ZWO camera for CaK

Post by marktownley »

MalVeauX wrote: Sun Feb 28, 2021 7:53 pm 100mm at 393nm requires significantly excellent seeing conditions to critically sample (around 0.9 arc-seconds!). So I recommend you be prepared to maybe make a 60mm or 80mm aperture mask for your refractor for this reason if your seeing is not superb.
I can't stress how important this is.


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Re: Recommended ZWO camera for CaK

Post by MalVeauX »

marktownley wrote: Sun Feb 28, 2021 8:24 pm
MalVeauX wrote: Sun Feb 28, 2021 7:53 pm 100mm at 393nm requires significantly excellent seeing conditions to critically sample (around 0.9 arc-seconds!). So I recommend you be prepared to maybe make a 60mm or 80mm aperture mask for your refractor for this reason if your seeing is not superb.
I can't stress how important this is.
To illustrate with recent images why seeing is 100% the limit of this, not the gear...
Click image for full size image in Flickr to appreciate the resolution (and hit the +, + to see full scale)

60mm F16.7 refractor with an IMX253 (3.45um pixel) with fair seeing conditions (1.5 arc-seconds roughly):

Image

100mm F10 refractor with 290MM (2.9um pixels) with poor seeing for image scale and aperture, seeing was 1.6 arc-seconds, not good enough for 100mm in 393nm at all, so the image is soft and barely more resolution than my 60mm option, just barely a bit more maybe, due to being limited by seeing conditions.

Image

120mm F10 refractor with 290MM (2.9um pixels) with excellent seeing, sub-arc-second to 1 arc-second seeing, and this was not critically sampled at all at only F10, shoulda be F18 to critically sample, and seeing wasn't good enough for that even, so I just under-sampled with 1 arc second seeing to get this with the 120mm aperture.

Image

393nm and 395nm, near UV, is heavily influenced by atmospheric seeing. It requires sub-arc-second seeing to use even 80~100mm apertures at critical sampling limits. A 150mm aperture needs around 0.3 arc-seconds in reality to truly see and record the resolution. 100mm needs superb, 0.9~1 arc-second seeing conditions to record the resolution, ideally a bit better, closer to 0.8 arc-seconds really and really fast FPS.

Seeing is always the limit unless you have adaptive optics! :)

Very best,


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Re: Recommended ZWO camera for CaK

Post by Jordan Konisky »

Mark,

What ZWO would you recommend?

Jordan


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Re: Recommended ZWO camera for CaK

Post by Merlin66 »

I’m currently using an ASI1600MM for all my solar imaging, CaK, Ha and WL.
I usually can get around f15 to f18 with my average to poor seeing conditions.
Using an ED80 with TV or Baader Barlow’s. Stopped down to 60mm for CaK.
Frame rates for ROI are very. Good.
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Re: Recommended ZWO camera for CaK

Post by marktownley »

Jordan Konisky wrote: Sun Feb 28, 2021 8:55 pm Mark,

What ZWO would you recommend?

Jordan
Hi Jordan

I think the ASI1600 like Ken is using would work well. You could make a 50mm aperture mask for the ED100 to get your full disks, and then barlow up when using full aperture to get the sampling, When you're barlowing up you would use ROI and get the benefits of an increase in frame rate.

Mark


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Re: Recommended ZWO camera for CaK

Post by Alto »

I know I'm getting old when I, now, struggle to understand these restrictions - no matter what I read!


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Re: Recommended ZWO camera for CaK

Post by Jordan Konisky »

Thanks so much everyone for your comments and advice. I find that each time I interact with this forum, I gain a quantum leap in understanding. The dust cover of my SW ED100 converts to a 50mm aperture mask, so it becomes trivial for me to reach F18. Ken et al, how do you achieve a color image with a ASI 1600MM? Adding color to your image or using a filter system?

Thanks everyone for continuing this stream. I am close to getting where I need to be.

Jordan


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Re: Recommended ZWO camera for CaK

Post by Alto »

Jordan Konisky wrote: Mon Mar 01, 2021 3:06 pm Thanks so much everyone for your comments and advice. I find that each time I interact with this forum, I gain a quantum leap in understanding. The dust cover of my SW ED100 converts to a 50mm aperture mask, so it becomes trivial for me to reach F18. Ken et al, how do you achieve a color image with a ASI 1600MM? Adding color to your image or using a filter system?

Thanks everyone for continuing this stream. I am close to getting where I need to be.

Jordan
Hi Jordan, faux colour is added at the final processing stage, photoshop or similar ( I use Affinity Photo ). Enjoy!

Geoff


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Re: Recommended ZWO camera for CaK

Post by Jordan Konisky »

Folks, one final question. Zwo AIS 1600MM is what I want, not AIS 1600MM Pro or cooled. Right? Not going to do any deep sky imaging with this camera.

Jordan


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Re: Recommended ZWO camera for CaK

Post by Alto »

Cooled not necessary unless you're in a hot climate. ( though I use a cooled 174mm as a dual summer/winter purpose ).


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Re: Recommended ZWO camera for CaK

Post by Merlin66 »

Here in Australia I just use the uncooled ASI 1600MM (and the ASI 174MM). No issues so far.
I cheat a bit with the colouring....
I use Irfanview (freeware) "Image/ colour corrections" and set up a colour scheme for Ha, WL, CaK etc.
The CaK is RGB = 25/-5/105
WL is RGB = 75/38/22
Ha surface 84/-14/-114
and Proms 165/32/55
Hope this helps.


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Re: Recommended ZWO camera for CaK

Post by EGRAY_OBSERVATORY »

Thanks Ken for adding the IrfanView link - which looks interesting and downloaded here..

Cheers
Terry


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