ZWO ASI294mc pro

[Stephane]

Hi all,

Yesterday, I received my first dedicated astro camera, the ZWO ASI294mc pro. I've been reading up on settings and processing for this camera. Can't wait to use it.

I heard that optimal temperature is -15 degrees (apparently no point going any lower, even in Winter), unity gain at 120 or 121 and offset of 30 are ideal, that bias frames should be avoided at all costs because of something being non-linear, and that dark flats are an absolute must. Apparently amp glow won't be an issue when calibrated with lots of darks, so I am aiming to create a dark library with 50 darks each at fixed temperature and settings, but varying exposure times; so 50 darks at 60", 50 darks at 120", etc.

Any further tips specifically for this camera?

Clear skies,
Stéphane

[Startrek (Martin)]

Stephane,
Congratulations on your new cooled OSC camera , you didn’t take long to transition from the DSLR ( took me 2.5 years to go from DSLR to OSC )

There’s some good information on this camera on the ZWO site , I’d recommend to read up on it
In particular the charts which show Gain , Read noise , dark current etc... Also some good information on amp glow
As far as cooling goes -10C should be fine
I’m sure folk who have this camera will provide some practical advice as to settings etc ... ( my 2600MC is a different beast )
For filters , in particular narrowband you can’t really go past the Optolong L Extreme

https://astronomy-imaging-camera.com...94mc-pro-color

Good luck and enjoy !!

Martin

[Stephane]

Thanks for those tips Martin. In an ideal world, I would love to spend 2.5 years with my Nikon, but the lure of an astro camera was just too great.

-10? Good to know. I was wondering what a good temperature would be, as I think the camera would struggle to get to -15 on some Summer nights. I'll definitely read up on the website. So much to learn on the never-ending astro learning curve.

[The_bluester (Paul)]

To chip in as I used to have a 294MC Pro.

Gain 120 is where the high gain conversion mode kicks in and significantly reduces the read noise and offset 30 was what I used with mine.

And yes, bias frames are not useful with that camera, I would not bother shooting any. Apparently the built in circuitry on the chip times exposures under several seconds and over that (I don't know where the specific change over is) the ZWO designed external circuitry takes over. The best approach to flats is to use a dimmable flat panel and set up to use say 5 second exposures for flats, then you can shoot 5 second darks and create a master dark-flat to use with your 5 second flats. If you end up using a duo band filter you need to look at the histogram to see where the peaks are and adjust your target ADC upwards (And probably the panel brightness as well to keep to the same exposure time) as the average will probably be skewed downwards by the filter.

As for sensor temp I started with -15 and stuck with it as long as I had the camera, but dark current is still very low at -10 so I would probably go with that if I had one now as it makes the coolers job easier. Just like an aircon, the power required to cool is not linear per degree of cooling, -15 takes substantially more power than -10. Noise wise, even at -5 it is still less than 1 electron per pixel per minute so even a very long exposure for the camera (Say 10 minutes) is only going to add up to about 10 ADC across the image at 120 gain and a master dark should subtract it away nicely anyway.

[Stephane]

Originally Posted by The_bluester

If you end up using a duo band filter you need to look at the histogram to see where the peaks are and adjust your target ADC upwards (And probably the panel brightness as well to keep to the same exposure time) as the average will probably be skewed downwards by the filter.

[…]

Noise wise, even at -5 it is still less than 1 electron per pixel per minute so even a very long exposure for the camera (Say 10 minutes) is only going to add up to about 10 ADC across the image at 120 gain and a master dark should subtract it away nicely anyway.

This is great info Paul, thanks. I have an Optolong L-Extreme duoband. I assume I need to keep it on when taking flats? I’m not sure I understand what you mean about targeting ADC upwards according to the duoband peaks. I guess having a filter means that exposure time will be a little longer than without a filter? Speaking of flats though, I have an LED tracing board I can use (See third image https://www.ebay.com.au/itm/165175229351). However, it’s not perfectly white like paper, in that there is a small network of LED lights in a grid-like formation. Would that adversely affect the flats? Would a white t-shirt fix this?

The temperature tip is much appreciated. I was getting a little ambitious in wanting the coolest temperature possible, but treating the camera well will result in it treating me well. I’ll stick to -5 & -10 so as not to put too much strain on the camera.

[AdamJL]

Originally Posted by Stephane

This is great info, thanks. I have an Optolong L-Extreme duoband. I assume I need to keep it on when taking flats? I’m not sure I understand what you mean about targeting ADC upwards according to the duoband peaks. Speaking of flats though, I have an LED drawing panel I can use. However, it’s not perfectly white like paper, in that there is a small network of LED lights in a grid-like formation. Would that adversely affect the flats?

The temperature tip is much appreciated. I was getting a little ambitious in wanting the coolest temperature possible, but treating the camera well will result in it treating me well. I’ll stick to -5 & -10 so as not to put too much strain on the camera.

You can put one (or multiple) layers of paper between the tracing panel and the scope as it can diffuse the LEDs over a broader area. Or even add a t-shirt or pillowcase. I do the same thing

And yes, keep your filter on when taking flats. Everything stays the same as your lights.

[Nikolas (Nik)]

Flats at average adu between 25000 and 30000 taken at 3-5 seconds. Dark flats at the same exposure as the flats. Also make a darks library of 10 and 30 seconds for objects like the Orion nebula.

[Stephane]

Thanks so much Adam and Nik. All this information is really helping me.

Nik, I will add those exposures to my library. They don't take too long to do.

Adam, I heard that for this camera flats need to be rather long, around 3-5 seconds. So I guess if ADU goes too high, I just add sheets of paper? Does it matter if I place 2 sheets of paper side by side? Or will the overlay create a line straight through my image? I might buy some A3 paper, and problem solved

[AdamJL]

ha, yeah try not to have two pieces side by side or overlapped. They should be stacked so you can't see anything besides the paper.. no edges!
I also use A3 paper to ensure coverage. And yes just keep adding layers of paper or t-shirt until you hit 3-5 seconds.

[Startrek (Martin)]

Taking flats, calibrating them and integrating them successfully to produce an even clean flat field is a tough task which has taken me 3 to 4 months with my Newts and 2600MC camera.Many posts and replies on IIS , ZWO forum , DSS forum and ADT forum plus many nights taking calibration frames.
It’s definitely not “one shoe fits all” for various scope and camera combos plus different software can give different results too
For instance folk on another forum who used my camera ( 2600MC ) in a 120mm refractor with NINA and same T shirt method find that Dark flats calibrate Flats better than Bias. With my newts I’ve proven over and over with and without the L Extreme filter that Bias frames calibrate Flats the best ( Dark Flats and Dark are a disaster )
I use a White T shirt and a Huion LED tracing dimmable panel
Target ADU is set at 22,000 in ADT and Flats end up 1/3 to 1/2 on histogram ( ADU range of approx 8500 to 32,000 ) and exposure time of 0.4 to 0.5 sec . With an L Extreme filter exposure time is around 5 to 7 sec.
My only advice to spend time experimenting with your Flats and calibration frames to get the best outcomes
There’s no straightforward manual or handbook on taking good Flats that work well. Although I’m sure medium to larger newts are more difficult than the smaller aperture 80mm or 120mm refractors.
One bit of advice I was given on DSS was to ensure the back end of the newt was covered and not allowing any light seeping in. I bought a $2 shower cap from Woolies , sprayed it Matt black and it just fits over the back end , works a treat ( fits up to a 10” newt )
Good Luck with your Flats and Calibration
Martin

[Nikolas (Nik)]

Different camera mate the 294mc is specific when it comes to flats and darkflats

[Stephane]

Thanks Adam, Martin, and Nik.

Adam, I’ll get the A3 sheets.

Martin, the shower cap is a great idea. $2 must make it the cheapest accessory in the Astro world! I’m glad you have highlighted that flats are not easy to get right. I find them harder to get right than the lights . I’m still learning and still have a long way to go.

Nik, agreed. This is what I’ve read over and over for this camera.

[floyd_2 (Dean)]

I was trying out an A3 led tracing panel for my C9.25 recently and noticed that the illumination from the panel wasn't completely even. Using A3 against the tracing panel still showed the illumination to be uneven, but better. I then tried placing an A3 sheet cut to a 9.25" circle just near the corrector plate to diffuse the light after it had travelled a little way from the tracing panel and it was heaps better. A3 paper seems a little flimsy in terms of its ability to withstand humidity etc, so I'm going to try a custom cut piece of flat acrylic light diffuser near to the objective of my C9.25 instead (probably with a small handle or something on it to make it easy to put on / remove). I have some on order from eBay and will cut it to size on my scroll saw if it ever arrives I'm hoping that it'll diffuse the led panel light nice and evenly, and be long lasting. Fingers crossed! It's an ongoing experiment

[AdamJL]

Originally Posted by floyd_2

I was trying out an A3 led tracing panel for my C9.25 recently and noticed that the illumination from the panel wasn't completely even. Using A3 against the tracing panel still showed the illumination to be uneven, but better. I then tried placing an A3 sheet cut to a 9.25" circle just near the corrector plate to diffuse the light after it had travelled a little way from the tracing panel and it was heaps better. A3 paper seems a little flimsy in terms of its ability to withstand humidity etc, so I'm going to try a custom cut piece of flat acrylic light diffuser near to the objective of my C9.25 instead (probably with a small handle or something on it to make it easy to put on / remove). I have some on order from eBay and will cut it to size on my scroll saw if it ever arrives I'm hoping that it'll diffuse the led panel light nice and evenly, and be long lasting. Fingers crossed! It's an ongoing experiment

that's a great idea and the same thought crossed my mind about using acrylic after some of the paper I had got wet due to dew.

You can also get ND gel film that video folks use in their movie making. 0.9 or 1.2 is fine.
That's a wonderful diffuser.