Galaxies with 585MC Pro - Forums

Hi everyone,

I’m at the point of maximum confusion. My new ASI585MC Pro is a great piece of technology. But when it comes to the right settings, I’m getting lost.
Clear skies are rare at the moment, so I’m doing a lot of theory. I use the camera on my Skywatcher 200PDS/1000. When shooting, I usually get around Bortle 4.2-4.8 in my area.
My first multi-session project is M81. After 3 Nights I was able to get this result:

It’s about 175 Minutes broadband (175x60s) and 100 Minutes Narrowband (50x120s). All subs were taken at Gain 252, Offset 15.
I can’t go out and do test sessions, so that’s why I ask you, the more experienced users. With my setting I’m slightly oversampling. I don’t have a reducer, so should I do 2x2 binning? But if I do so, I loose my pixel color values, don’t I?
What about the gain and exposure time? Wouldn’t it be better to use Gain 100? Some say that for this kind of galaxy I should to 200-300s exposure with gain 100 rather than taking 60s at 252?
I know, the best way to find out is to take pictures and compare results. I might start a session, but as i said, CS is rare here.

Thank you for reading and any advice in advance!

Sven

Hi there,

There is no material binning available on that kind of camera so that i) you won't loose color but ii) the interest is very limited as you don't expend the material photosites exposure area.

Honestly, this is an excellent result given the limited exposure time you have. For galaxies, the broadband signal is the most important. 175 minutes is not that much. I would focus on getting more exposure time. Playing with gain is nice, but improvement are to my experience limited except if you have an extensive experience of your camera. With my 294mc pro, I always shot at 121 gain and now with my ATR2600m, I shoot at 100 in HGC except for very very bright targets such as M42. And that's it. Many people here do the same.

Finally, I note that your skipe are not aligned. You may want to avoir removing your camera between session or ensuring that the orientation is the same. Alternatively, you may add the NB signal after having removed the stars (but in that case be carefull not to remove the Ha pocket with the stars…).

Clear skies,

Patrice

Thank you Patrice!

That helps. Yes, unfortunately I’ve noticed after shooting that I didn’t had the same orientation. For the broadband I thought, siril will do the alignment. But I really messed up the narrowband. I don’t know how to let siril do the alignment, so I did the combination of these two in photoshop manually. Not perfect of course. Still learning 😉
So you would recommend to use the HGC at Gain 252 like I did so far?

I would just stick to 252 to enable HCG mode. There is no need to complicate things any further as far as I'm concerned. I shoot my cameras at HCG gain as well, no matter the target.

As far as sampling goes look at the image at full size, which everyone should always do while editing. If its not very soft/blurry/bloated (call it what you will) you don't need to downsample it. This should always be done in post processing with these cameras anyway so it won't affect your shooting settings at all.

I am very oversampled with my 8" SCT due to my guiding RMS on that setup. I downsample all of those images x2 because of the reasons mentioned above. If you need to resample you will know, it will be very apparent.

I have been shooting with a 585 for two years now and your basic settings sound just fine. I wouldn't worry about over sampling, I certainly wouldn't bin a relatively small sensor like this, that's for sure. For your broadband subs you night want to shorten your exp. time. I would typically use 15 sec. To my eye the image is a little soft and the stars a bit bloated and a shorter exp. time, especially with some effective culling will sharpen that up.

With the ZWO 585 cameras, set the gain to 252 and suffer the short exposures. 60s-90s is likely about right for your PDS. I use 60S but my newt is a little faster at f/3.8. Ignore advice from others with 294 and 571/2600 cameras and even those with other 585 cameras like the QHY or Player One. ZWO setup all of their 585 cameras for EAA and planetary and as a result you must use short subs to avoid blowing the stars apart. Even other versions of the 585 sensor are setup totally different and can use longer subs.

PS, nice image. If it's working for you , do what you're doing.

Well, the picture look great to me, but of course I can also spot many things that went wrong in it. The stars are not so good, but that can also be the result of bad stretching. I chose the 60s exposure for the light frames cause that sounds like a good compromise. M81 is quite bright, so the core part tends to burn out. Still get a lot of noise, but I try to compensate with more exposures. Of course I can do better, and sure it will be better in the future.
But it’s good to hear that all of you recommend to stick with the HCG settings. Depending on how good my guiding is, I will stay with the 60s or maybe less. When I did the NB I couldn’t get the 60s frames stacked. It was just too dark for siril to recognize enough stars. So I went with the 120s.

Hello,

I have the same camera as you, and today I made a thread on the forum looking for help with exposure times. I got a lot of useful replies, some from people who also commented on this post. I recommend checking out the replies under my post, there is useful information there.

Btw, amazing image! Looks like whatever you are already doing is great.

Link to the post: https://www.astrobin.com/forum/c/astrophotography/deep-sky/exposure-time-recommendations-for-my-setup/

Clear Skies!

Sven Frei:
Well, the picture look great to me, but of course I can also spot many things that went wrong in it. The stars are not so good, but that can also be the result of bad stretching. I chose the 60s exposure for the light frames cause that sounds like a good compromise. M81 is quite bright, so the core part tends to burn out. Still get a lot of noise, but I try to compensate with more exposures. Of course I can do better, and sure it will be better in the future.
But it’s good to hear that all of you recommend to stick with the HCG settings. Depending on how good my guiding is, I will stay with the 60s or maybe less. When I did the NB I couldn’t get the 60s frames stacked. It was just too dark for siril to recognize enough stars. So I went with the 120s.

If that happens again, run whatever script your using and let it fail at star registration. Change the working directory to your process folder, search for the pp_light_sequence, then go to the registration tab and you'll have all kinds of options. Normally Siril uses minimum of 10 star pairs for registration but you can reduce that down to 4 if you need to. That that won't get it then you can try the 3 star option where you pick the stars. I'm sure you'll have at least that many to work with.

I used to own a 585, it was a great camera. I am not an expert and feel a bit underqualified to give much feed back but here is what I think.

First, this image is great, my comments below dont suggest otherwise, I am just trying to share what I have learned.

1. Your image seems great and any issues you are experiencing likely unrelated to being oversampled. With newer CMOS sensors I feel like the worry of "exact" sampling is a bit overblown. The pixel size of 2.9 on that camera is ideal for up to 900mm, but the difference between 900 and 1000 is negligible, I wouldnt worry about it.

2. Binning any OSC only really helps with 2 things in my opinion. Making File Size Smaller, and Collect Light faster for EAA, I sometimes bin the asi2600MC just to lower the file size, (basically because my wifi extender is 2.4ghz and the smaller files transfer faster. I would suggest you NOT bin the 585 if you are shooting for image quality.

3. I looked at your image close up and see a few things, I see a fair amount of noise, this is expected and can be resolved with more integration time. I also see what I would consider "over processing" and a lot of gradients. Suggestions, to try in processing
Crop out the stacking artifacts and some of the gradient on the edges. This will help background extractions and gradient removal work better
Be careful when you stretch, dont get so caught up in trying to make the background jet black. This often pulls galaxy details out and you get the strange "dots/spots"

Gain 252 was the sweet spot for my camera, I basically left it there all the time, instead I would change exposure times based on the targets and surrounding light

I was never able to really get good data from any subs longer than 60 seconds, and I actually found 45 seconds to be my sweet spot with the 585

Question for you, did you take Calibration Frames? I have used some tools to try and avoid it in Photoshop and PixInsight but it is never as good as the real thing.

Just my thoughts.

Last year I bought a Player One 585 specifically for galaxies. I used a 122mm triplet refractor. I had the results I expected.
I would only use HCG Mode;
Bin 1 is a must. You don't want to use bin2 with this chip. If you do you'll end up with a 2.1mp image which is way to poor on details.
If you're used to a 294 or 533/2600 you might struggle a bit with color balance. I did when I was using IMX585, just a bit.

CS

Wow, a lot of great tips, thank you!
Yes, I did calibration frames. Darks, Bias, Flats. I maybe ran into problems with my flats, that’s why there are some gradients too much I think. But cropping before background extraction is a good hint. Never did that in this order.
Also, I tried the Generalized Hyperbolic Stretch for the first time on this picture. So I guess that’s why there is some over-processing.
I will try the 45s next time. Probably not useful on the M81 project cause I can’t mix the different exposures then.
Correct me if I’m doing wrong, but I ran the OSC Preprocessing Script in Siril on each nights frames. I then took the calibrated (pp_light) from each nights and added them to a new sequence. Then I ran registration on them and finally stacked them. Tried Sirilic as well, but I was overwhelmed by the options, so I went with the regular Siril scripts.

Sven Frei:
Wow, a lot of great tips, thank you!
Yes, I did calibration frames. Darks, Bias, Flats. I maybe ran into problems with my flats, that’s why there are some gradients too much I think. But cropping before background extraction is a good hint. Never did that in this order.
Also, I tried the Generalized Hyperbolic Stretch for the first time on this picture. So I guess that’s why there is some over-processing.
I will try the 45s next time. Probably not useful on the M81 project cause I can’t mix the different exposures then.
Correct me if I’m doing wrong, but I ran the OSC Preprocessing Script in Siril on each nights frames. I then took the calibrated (pp_light) from each nights and added them to a new sequence. Then I ran registration on them and finally stacked them. Tried Sirilic as well, but I was overwhelmed by the options, so I went with the regular Siril scripts.

If nothing changes you can just combine all of the lights from multiple nights just fine. The only limitation is if you end up with more than 2000 frames because you'll hit the limit there unless you edit the script. Unless the nights were radically different from each other this usually works a treat.

If nothing changes you can just combine all of the lights from multiple nights just fine. The only limitation is if you end up with more than 2000 frames because you'll hit the limit there unless you edit the script. Unless the nights were radically different from each other this usually works a treat

Ah, good to know. Thanks, I’ll keep that in mind. But right now I’m far away from 2000 frames! 😂

I would learn to preprocess without the scripts. There are excellent tutorials out there to do that. You just go through one of them once and you're done with learning. It is easy. That way, you will immediately learn how to use SIRIL to align the Ha or DNB layer with the RGB layer (i.e. prepare a sequence with both stacks and align them).

The spikes miss alignment is not related to star alighment. You can align the stars and yet, if your camera was rotated between the different session, or when you changed filter, the spikes wont' align even if all stars overlap perfectly. Spikes are diffraction pattern projection from the spider onto the sensor. If you rotate the sensor, you get other projection from the same spider.

I completely agree with all what was said about sampling and gain. Sampling does not need to be ideal. Concerning gain, I ignore academic debate about fine tuning of gain to minimize background noise based on sky background luminosity. This is way too advanced for my tast and some of greatest image published here are produced without caring. Gain is a useful tool to manage read noise and to get the histogram where you want it to be. I tend to like 300s exposures to minimize the number of files. But bright object need much shorter exposures.

Cheers,

Patrice

If the spikes starting to annoy me I will try Starnet++ on some of the lights and see how it works.
These files are great for learning. I didn’t trust my skills using Siril without Scripts, but you’re right. It really helps to understand what’s going on.

I have been using the 585MC Pro since Dec 2024 and I use Gain 252, 30s for broadband, 90s for IR pass, 180s for narrowband. Tried Gain 0 and Gain 100 but the noise is too much. I am thinking of going for 300s for narrowband as I am not clipping any data at 180s but am sticking with 30s exposures since was getting clipped stars at 60s for broadband.

IR pass is new since May. Might try 120s and see if FWHM suffers too much on my WO GT81. Should be fine with longer IR pass subs on my SQA70 and on your Newt. The advantage of using IR pass is I can get better data in the miserable seeing we have on the east coast of USA. I plan to use it for luminance on nebulosity after removing stars and add luminance from stars from broadband and continuum subtracted narrowband data.

AstroÅmazer:
I have been using the 585MC Pro since Dec 2024 and I use Gain 252, 30s for broadband, 90s for IR pass, 180s for narrowband. Tried Gain 0 and Gain 100 but the noise is too much. I am thinking of going for 300s for narrowband as I am not clipping any data at 180s but am sticking with 30s exposures since was getting clipped stars at 60s for broadband.

IR pass is new since May. Might try 120s and see if FWHM suffers too much on my WO GT81. Should be fine with longer IR pass subs on my SQA70 and on your Newt. The advantage of using IR pass is I can get better data in the miserable seeing we have on the east coast of USA. I plan to use it for luminance on nebulosity after removing stars and add luminance from stars from broadband and continuum subtracted narrowband data.

So far I haven’t tried IR Pass on Deepsky. Actually I don’t own a 2” pass filter. Just a 1.25” that I tried on Jupiter and Saturn. Seeing is average here in southern Germany. There are really good nights, but clouds and rain are unpredictable.
I think I have to optimize my guiding for longer exposures than 120s. Some nights I end ip spending 1hr for polar alignment and guiding setup. But my HEQ-5 is not a high precision mount. You have to make compromises.

If you're trying to beat the seeing I would recommend shorter subs, not longer.

Tony Gondola:
If you're trying to beat the seeing I would recommend shorter subs, not longer.

Agreed. All I was saying is the ProPlanet 742 I am using is more resistant to seeing related issues. If FWHM with it is not too bad (because refractor isn't well corrected in IR etc), might try longer subs. But sticking to 30s subs with my Luminance filter.

Edit: Picked up the IR pass because in Feb/Mar was throwing out a lot of subs due to high level clouds too. This winter have had 8 nights total of astrophotography. IR pass helps with light clouds and I can start 30 mins earlier and stop 30 mins later without the sky background getting brighter.

Sven Frei:
AstroÅmazer:
I have been using the 585MC Pro since Dec 2024 and I use Gain 252, 30s for broadband, 90s for IR pass, 180s for narrowband. Tried Gain 0 and Gain 100 but the noise is too much. I am thinking of going for 300s for narrowband as I am not clipping any data at 180s but am sticking with 30s exposures since was getting clipped stars at 60s for broadband.

IR pass is new since May. Might try 120s and see if FWHM suffers too much on my WO GT81. Should be fine with longer IR pass subs on my SQA70 and on your Newt. The advantage of using IR pass is I can get better data in the miserable seeing we have on the east coast of USA. I plan to use it for luminance on nebulosity after removing stars and add luminance from stars from broadband and continuum subtracted narrowband data.

So far I haven’t tried IR Pass on Deepsky. Actually I don’t own a 2” pass filter. Just a 1.25” that I tried on Jupiter and Saturn. Seeing is average here in southern Germany. There are really good nights, but clouds and rain are unpredictable.
I think I have to optimize my guiding for longer exposures than 120s. Some nights I end ip spending 1hr for polar alignment and guiding setup. But my HEQ-5 is not a high precision mount. You have to make compromises.

I have a SW SA GTi and a ZWO AM3. Polar alignment with the AM3 is so much better. Also using the ASIAir for Polar alignment has cut down my setup time to < 10 mins including an EAF run. Guiding is around 0.7".

The GTi is still 15-20 mins. Guiding is ~1"-1.2" on good days. 1.5"-1.7" on bad. Mostly use it for unguided camera lens sessions. Focusing with a bahtinov on a camera lens adds to the setup time.

AstroÅmazer:
Tony Gondola:
If you're trying to beat the seeing I would recommend shorter subs, not longer.

Agreed. All I was saying is the ProPlanet 742 I am using is more resistant to seeing related issues. If FWHM with it is not too bad (because refractor isn't well corrected in IR etc), might try longer subs. But sticking to 30s subs with my Luminance filter.

Edit: Picked up the IR pass because in Feb/Mar was throwing out a lot of subs due to high level clouds too. This winter have had 8 nights total of astrophotography. IR pass helps with light clouds and I can start 30 mins earlier and stop 30 mins later without the sky background getting brighter.

I feel your pain. It's been a horrible spring here in Oklahoma. Tons of rain and endless clouds. I may as well be in the UK!