ASI 585MC PRO offset value

w7ay

Tech@ZWO The default value is 3.

The ASIAIR default for this camera is total garbage.

This is a subframe captured on ASIAIR from a few hours ago with the ASI585MC cooled to -10ºC. Gain is set to +25.2 dB, and exposure duration is 20 seconds (this is where the read noise and ther dark current noise balances out -- the ASI585 is a very noisy camera) with the IDAS NBZ-II filter on a Takahashi FSQ-85 at f/4.5.

In case you do not see what is wrong, take a look at the Min ADU.

For those of you who are stuck with using the ASIAIR, do not buy this camera, since the ZWO default offset is too small, and ZWO does not allow you to change the ADC offset in ASIAIR.

For those of you who are using some other image capture software, increase the default offset so that the MIn ADU is solidly off from 0 (at least 99.7% -- 3 sigma for Gaussian distribution -- of the time). A Min ADU of 0 means that a stack of images will not reduce the noise variance by half each time you double the number of subframes. The noise will remain high even if you stack more subframes.

Chen

Tech@ZWO

w7ay Thank you for your feedback, i forwarded to our team, they will look into this

My-Stars

w7ay This is kind of bummer info. I did a quite a bit of research before i purchased mine. I guess I didn't do enough. It was touted to be a pretty much noise free. And pretty much plug and play. I have had my share of difficulties with it. I think I'm slowly getting them ironed out. Right now I'm getting only black and white photos. not sure what the problem is.

danielfelix

w7ay I don't have your experience, I need you to guide me on what values to use. They say about increasing the offset, by how much? 9? Another value?
What gain do I use to get the most out of it, 252 or lower it to 100?
Are you going to update the firmware? How do I find out?
It's a shame to have spent money on a product with little development.

Tech@ZWO

My-Stars If the histogram was cut off in the dark frames, you can increase the offset in NINA to make sure no cut. we will also fix the default offset problem as soon as possible. sorry for the problem.

w7ay

My-Stars Right now I'm getting only black and white photos. not sure what the problem is.

Looks like ZWO gave the usual non-sequiter.

Regarding your problem, is it completely monochrome, or is it washed out color (sort of brownish in daytime pictures)?

If it is the latter, be sure to install a good UV-IR cut filter (not ZWO brand -- they do not cut UV worth a damn; money wasted). The windows that are used in the ASI585MC "pro" are AR glass, and the Sony CMOS sensor has very strong responds both below 400 nm and above 700 nm.

Without a IR cut filter, the colors would appear very washed out because the R, G and B components are all equally strong (thus monochrome) in the near IR.

Without a UV cut filter, you could experience severe "blue bloat" on your stars. Even at 400nm, the response of the blue component of the sensor has only fallen 25% from its maximum at 450nm. And many cheaper OTA are not very "APO" at and below 400nm.

Now, if you do not get any color at all, what software are you using to process the raw data? You might be missing the part in the documentation where you need to ask to software to demosiac the Bayer pattern (it needs "RGGB").

Color is not the problem with this camera. It can be fixed by using the proper filters. Dark current noise is the problem, and the problem is multiplied by the fact that the HGC level is set too high at 25.2 dB (about 18x linear gain, what ZWO calls "252"). So, by the time you can start benefiting from HCG taming the read noise, the dark current noise has been multipled by another factor of 18.

I have given up using this as a DSO camera, and permanently shelved my ASI585MC "pro."

Chen

My-Stars

Is that also a partial reply to my problem with black and white verses color. I will say I wish I would’ve gotten one with a larger sensor. And that would’ve also had the ability for live viewing.

w7ay

My-Stars I will say I wish I would’ve gotten one with a larger sensor.

I have the QHY533M and the ASI2600 (both a color and a monochrome), and all of them are leaps and bounds better than the ASI585MC "pro" that I played with in the past couple of weeks.

Chen

Tech@ZWO

My-Stars Are images in color when viewed in ASIStudio-ASIFitsview? the raw fits images are all black and white, need to debayer to convert it to color. our software ASIStudio-ASIFitsview will auto debayer in view.
If the images still are black and white could you share some here? thanks.

My-Stars

w7ay As far as software. I’m using Siri and or deep sky and N.I.N.A. My cut filter is ZWO. So pretty much what I’m getting from your post is. I’ve waisted $600+ on this camera. Not to mention the time I’ve put into it. I’ll give your other suggestions before giving up on the camera.
Do you have any suggestions on why live viewing doesn’t work.

My-Stars

Tech@Zwo, I’ll give that a try and get back with you.

w7ay

My-Stars Do you have any suggestions on why live viewing doesn’t work.

No idea. What in LiveView does not work? You simply mentioned it didn't work, but not what you were getting.

Chen

w7ay

My-Stars I’m using Siri and or deep sky and N.I.N.A.

Are you sending FITS files to the other software? They should be able to tell if your camera needs to be debayered from the FITS headers.

But in Siril (I assume it is Siril and not Siri), check this anyway to make sure you are debayering and also using the correct Bayer pattern:

https://siril.readthedocs.io/en/stable/preferences/preferences_gui.html#fits-ser-debayer

Use RGGB as the Bayer pattern.

There is no such thing as a CMOS color sensor (other than the sensor from Foveon which has very low blue sensitivity). The CMOS sensors in use today are monochrome sensors with a mosaic (grid) of RGB filters placed on top of them. The raw data you get is just the data from the filtered array. To synthesize a colorimage from the monochrome data, you need to deBayer or demosiac the raw monochrome data to create a (lower resolution) color image.

https://en.wikipedia.org/wiki/Bayer_filter

An RGGB pattern is a repeated 2x2 pattern that looks like

RG
GB

repeated over the 2 dimensional surface of the sensor.

Chen

My-Stars

w7ay live view, meaning I don't need to take single photos to try and center a star/image. If I use my DSLR I would pick the video camera button and can pan an area outside the initial viewing area. When I use my astro camera that button does not even appear.
you're right. My bad on spelling Siril.
I had a late night last night, so I likely won't get outside tonight. But I plan to try your ideas asap.

My-Stars

w7ay Chen, since my last communication with you. I have learned how to obtain live view. I knew it had to be something simple, and it was. It was just a matter of turning the loop switch to "0n". now all i have to do is figure out how to get color pics from a so called "One Shot Color camera". Any ideas other than purchasing a filter drawer with filters.

w7ay

danielfelix I need you to guide me on what values to use.

The need to apply a DC bias ("offset") to the input of the A/D converter is to make sure the bilevel noise from the camera sensor does not cause the A/D converter input to go negative, since the A/D converter input is assumed to be an intensity (therefore, always positive).

Not only is the camera output an intensity, it is a countable (vs continuous) value, since it is directly related to the count of the number of electrophotons (scaled by the quantum efficientcy).

Once you understand the above, bias (offset) setting is easily done by looking at the histogram of the ADU, and increase the ADC offset (for a given camera gain) to make sure that the minimum ADU is solidly above zero.

I don't have your experience

There are some astrophotography books that explains it. I highly recommend buying a few books, and study them before taking pictures. For the price of a camera, you can obtain knowledge that lasts you a lifetime.

Chen

My-Stars

danielfelix Danielfelix, I am also pretty new at astrophotography. And have had the same issue. I have recently discovered a fix for it. As soon as I locate the YouTube posting I’ll send you the link. But until then. For me I’m useing an offset of 5 and iso 400 binning at 2x2. It seems to work. The telescope I’m using is a celestron evolution 9.25. Nothing real fancy.

danielfelix

My-Stars
Ok

My-Stars

danielfelix Daniel, I have not seen the video that Cuiv's is refering to but here is the link I mentioned to you
https://www.youtube.com/watch?v=mCYQoVSuEaI&t=22s
Take a look . I hope it helps.

danielfelix

https://youtu.be/zibS7JyKdw8?si=ungTXeEpJAfJnh3H
Here's Cuiv's video

zwo2_jacky

@ Tech@ZWO
Is there already a solution for the offset-problem in connection with the ASIAIR Plus (computer)?
The camera does not seem to work properly with the standard offset of 3.

Or:
When can we expect a solution?
Will the firmware of the ASIAIR or the camera be changed or will nothing change?

Tech@ZWO

zwo2_jacky Do you refer to the offset problem on ASI585MC? we have fixed this problem in the new version SDK files and should be released on the next version ASIAIR app as well.