teoria_del_big_bang

Gains, Offset and modes being used

Currently I am using Mode 1, Gain 56, offset 25. I will try to populate this section with other users info so you can see what people are using at a glance.

User Settings.xlsx

Useful Links

QHY268 Manual

As this is still a relatively new camera I though I would start a thread for users to share their knowledge on it.
Of particular interest would be what Gains and modes people are using and why they settled on these settings, also any links to other websites with useful information would be good, and also to report any issue you have had.

If there are useful links or particularly useful info I can update this first post so the info is ready available.

Steve

Fantastic, and so well deserved for your perseverance, well done and many thanks for sharing the wonderful experience 🙂 

Steve 

13 hours ago, Dunk76 said:

I've been a total lurker on this board to date.  I've never thought my images were good enough to post 😂

Always worth posting early images, I have not yet seen a post where anybodies images have been berated, I know some SGL members have such fantastic images it is rather intimidating to put what you think is not worthy, but think about it any image, whether not so well focussed, or not so clear is a triumph when you think what you have managed to do.

You can often learn so much from constructive comments it is invaluable, often if you post the raw stacked image others will take the data and make it look so much better and also explain you are missing a trick in bringing the full image out in the processing, so don't be afraid to post 🙂 

And also don't worry all these issues are sent to try us, and we all have been there, but some nights it will all just go right and when you get a half decent image it all seems worth it 🙂 
From the thread title sounds like you still have a sense of humour and believe me that helps in this game 🙂 

Steve

9 hours ago, Stuart1971 said:

Would you say gain 56 or 60, (in mode 1) as the start of the drop is 56, so would it not be best at 60 where it’s the lowest read noise….or don’t you think it matters….?

Sorry I left the conversation, had early night.
I admit since revisiting all this and looking at the graphs I would say yes but I think even QHY say 56 is the sweet spot that's why I chose it, whether its just the graph that looks that way I am not sure.

I am afraid the thread has drifted a little bit from the OP's original post - sorry @centroid

Steve
 

9 minutes ago, Stuart1971 said:

So excuse my ignorance, but does that mean upping the gain will help, with shorter exposures and so using mode 1 and gain 56 would be a good idea….?

You have told me before that you use these settings to good effect, so will give them a try, I tried mode 1 gain 0 last time out with 5 min subs, but still noisy, but I guess that maybe somewhat down to the almost full moon….🤔🤔

That.s how I read it but this and other threads you have also seen lead me to think I may not know as much as I though I did.
Unfortunately my biggest enemy is the weather, especially since getting the new camera as good imaging time was very limited last year and so just did not want to waste time experimenting with different modes, gains exposure times, just wanted some data to play with.
Given endless clear dark nights I would love to do all sorts of trials to fine all these optimal values, but I read a few other threads, on SGL and other web sites when the camera first came out and many were using mode 1 gain 56 or mode 0 gain 28 (or there abouts) both where the traces step down on the noise to gain graphs and so basically stuck to those values, they seemed to work well so didn't want to fix what seemed to be working, so ne real science from my side anyway.

Steve

8 minutes ago, MartinB said:

Robin Glover explains that there is minimum exposure time required to neutralise the effect of read noise.  He also points out that there is no benefit in increasing sub exposures beyond this for achieving a desired ultimate SNR of the final stacked image.  I have no argument with this at all.  When I got my QSI 532 CCD back in 2010 I used the CCDware sub exposure calculator to work out my minimum sub exposure, it was invaluable.  However, Robin Glover isn't saying that longer exposures are detrimental.  Craig Stark has done a lot of work with CCD cameras examining exposure times and SNR in the real world.   SNR continues to increase beyond minimum optimal sub exposure time.  The limiting factor is the point where pixel response becomes significantly non linear of brighter parts of the image such as bright stars are becoming saturated.  Yes, gusts of wind and rogue clouds give a bigger hit when they ruin a longer sub.  Satellites less of an issue for me since I rarely have less than 30 subs per channel.  One other issue with short subs is time lost through dithering.  You certainly need to be avoiding dithering after every sub otherwise the loss of exposure time becomes substantial.  

 

I have seen this video sometime ago now but think I need to revisit it and work out some optimal sub lengths.
Due to lack of actual imaging time due to weather last year I did seem to come to a conclusion that with very narrow band filters I needed at least around 5 minutes and generally just put it up to 10 minutes and just left it at that as it seemed to work.
Because of LP I tend not to do LRGB unless the moon is almost non existent and seeing is good, so not so often but have just stuck with 5 minutes for these as well.

Now possibly because of the bandwidth of the ND filters I do need 5 minutes, but possibly not 10 ?? and from what has been mentioned on this thread, and others, I should be far less than 5 minutes on the non NB stuff.

Steve

1 hour ago, Stuart1971 said:

Looking at the graphs above, mode 1 gain 60 seems the best to me…rather than unity ...but I may well be reading it wrong

In the manual for this camera it does state the following:-

Steve

5 minutes ago, Lee_P said:

I use an ASI2600MC Pro -- same sensor as your camera I believe. I always shoot 120s subs, regardless of target or whether I'm using an L-eXtreme or no filter at all. Always 120s. Bortle 8 skies, to make things even harder. Check my gallery and you'll see it can work well

 

Certainly does work well, I know the drivers for these cameras may be different so gains and modes may differ to the QHY version but what gain(s) are you using ?

Steve

10 minutes ago, Stuart1971 said:

This is my point, they are not, I get an image full of stars and nothing else until it’s mega stretched…..which brings out all the noise, I would expect after stacking even with very little stretch so see the DSO….but no….🤔🤔

I too am still a little perplexed at the issues you are having with this camera, and the frustration it is causing.
I know mine is the mono version so not easy to make a direct comparison but if you want to send ,me some of the subs to compare them to some I have taken you are welcome, I may not see anything significant, but if I can help at all.

I still intend to try gain 0 on mine next clear night and CO does say Wednesday is and with the full moon it will be NB so I can take some at gain 0 and my usual gain 56 so see if there is a noticeable difference.
But it will be with significantly longer suns I know that with my ultra NB filters I get nothing worthwhile on most targets below 5 mins and usually go to at least 10 mins, but as we said before because the nature of your NB filter is different then you should not need longer than 5 min subs.

I guess there could be an issue with the camera itself, very difficult for you to determine this I guess.

Steve
 

Wow, "The Beast" indeed, what a beautiful scope 🙂 

Steve

That really is a cracking image Adrian 🙂 

Steve

Power in remote areas is a bit of a mine field, generally doesn't come cheap and even worse if you need differing voltages and not just 12V.

You pretty much have two options, some sort of car or leisure battery or the more modern Lithium ion batteries.
On top of that you can either buy a ready made power pack of various types, some made specifically for astro gear or some for camping or similar pursuits, or build your own.
If you are not that savvy with electrical gear, even 12V then you may prefer the first option.  

Which ever option you pick you need to work out how much power you need (not in volts or amps but in ampere hours) and bear in mind that you will probably not get the amount of power out of any battery that is stated and generally it is not a good idea to run them til they are totally flat anyway (lithium ion not such an issue but the lead acid batteries should not be run till totally flat it will permanently damage them).
So you need to buy a higher capacity than you work out you require and I would recommend getting at least 50% more power.

Working the power out is also a bit of a guessing game but your setup

•  CEM26 mount 0.5A tracking and 0.8A goto, so say average 0.7 A.
•  Beelink mini PC, so take the 2A stated, it probably is less but to be safe.
•  ZWO camera, very much depends on what type and mostly whether it is cooled. a non cooled camera will be maximum 1A but a cooled camera could be up to 4A., but again cooler will not draw maximum current continuously unless in hot climate so again this will be less than the maximum 4A.
•  dew strap or two, again depends on the size of dew strap and how hard they have to work but generally 0.5A to 1A each.

So if camera is cooled you are looking at maximum draw of around  5 to 7 A, if camera does not have cooling then more like 4A.

So to run at 5A for 4 hours you need at least a 20 Ampere/hour source and ideally a bit more to be safe so the one you are looking at at 26 A/h would just about do for 4 hours, and a bit longer if you currently do not have dew straps.

You really do not need the invertor so they may be other things out there  without the inverter a bit cheaper but try to get something with a lithium ion battery, they are lighter to carry and you do not have to be so careful about charging them periodically and running them down. Car batteries can easily be damaged by running them right down and when in storage you need to keep topping the charge up as they will naturally start to run down if left. If these are not well maintained they may still work but the available power will deteriorate and will not deliver the current for as ong as when it was new, sometimes by a lot.

Steve

19 minutes ago, Ian McCallum said:

I've heard of the Raspberry PI and Arduino, but have never used one.  I know that they are a small, standalone computer, but little else.  At the moment, I'm reading this article below...

https://stargazerslounge.com/topic/344913-getting-started-with-astroberry-for-the-raspberry-pi-beginners-guide/

I'm not sure what specs I need or even want. Can the RPi act as a standalone image and video gatherer, if connected to a suitable ZWO camera or similar?🤔

Absolutely it can. I think Ideally needs to be a version 3 or better still 4 pi and the amount of images it can store is just down to the size of the memory, either SD card or SSD.
I actually have mine booting up from a SSD so everything runs fast and plenty of memory available.

You could then, if you were happy to do so, sit next to the scope with a USN keyboard, mouse and a HDI monitor and run the whole setup from there (although when running you can just leave it to do its thing) or as most do connect to it over your network from a remote computer or laptop, that laptop does not have to be anything special.

And to transfer your images from the night either download to a portable harddrive or SSD card or with a bit of messing about transfer them over the network to another computer or Laptop.

Just get it all working in the daytime first rather than leaving it to a night as you might need to play about a bit to get used to it all but generally pretty easy (must be I did it).
 

Just one thing to note the RPi obviously needs some sort of case and often these are metal which does tend to limit the wifi capability of the RPi but there are wifi doingles that work a treat and get your wifi range and speed to something useable, or use a LAN cable.

Steve

I have seen this video but (and its only what I have noticed in my imaging so maybe does not relate to all setups) is that yes this works for broadband but for NB I get poor results below 5 minute exposures no matter how many frames I take and generally will go for 10 minutes for NB. 

Now maybe because I am using Ultra NB filters this is why and maybe the bandwith of a Optolong L-eNhance is not so narrow and that will work with shorter subs.

Steve

14 minutes ago, smr said:

Slightly OT but the skies may be clear tonight, and I'm wondering whether I should image with my l enhance filter or not (re the Moon) what would you suggest? It's 80 percent Moon and sort of close to the Horsehead.

The only issue is that I have to unscrew the Camera to add the filter inside the field flattener so when I screw the Camera back on it's going to be at a different angle to the previous sessions. ie. The 6 hour stack was two sessions (with and without filter) hence the differing angles and required cropping.

Personally with that moon I would add the filter and go for 10 (or longer if guiding is up to it) min subs. 
Regarding angle, before I got my rotator (which is a great help)  if I had to remove camera , or anything in the optics, I would put a small piece of masking tape on somewhere where I could draw a line across the gap between them so I could line them back up when re-assembling.
OK not accurate to seconds but usually got me back to within a degree so minimal cropping required.

Steve 

8 hours ago, Budgie1 said:

I took your 5h57m stack and put it through my normal workflow in PI. After stretching, I removed the stars and processed the background & nebula separate to the stars, then put the background through Topaz AI Gigapixel to further reduce the noise and sharpen, before adding the slightly reduced stars back into the image.

When you remove the stars (I assume in PI with Starnet) do you still have the big ones like Alnitak to contend with ?

I had never heard of Topaz AI Gigapixel, just looked at their website now, does it really do what they say it can, and can this not be done with other software ?

Steve

Brilliant, thanks for letting us know, it's so good when something goes right isn't it 🙂 
Personally I am not so experienced so can't help with many aspects but if I can I am so happy to do so because that's what others on here did for me, and still do 🙂 , and thats how it should be and one of the main aims of a forum like this.

Steve

I really do like these images you do with the local landscape in the foreground 🙂 

Steve

17 minutes ago, Ian McCallum said:

The telescope is a SW Evostar 120 achromatic refractor and the mount is an EQ5 Deluxe with the Enhanced dual axis motor drive with ST-4 guiding.

In my limited knowledge as still a relative newbie, for serious AP probably not the first choice of scope or mount, but they will be members on SGL who have given it a go so maybe others can give better advise.

But as you state you are just dipping your toe into imaging so I would not spend a fortune until you have a go, perhaps a good way to try it without spending a fortune is to get a 2nd hand DSLR (unless you already own one), and do some lunar stuff and also there will be some DSO targets that suit the FOV you get.
Use the FOV calculator in astronomy tools menu on SGL to see what you would get.

FOV calculator

Steve

9 minutes ago, Ian McCallum said:

Perhaps I should look into DSO subjects, instead of lunar and planetary work?🤔

Have a good think.
What I wouldn't do is try for both to begin with.
The techniques and much of the equipment is totally different, and trying to have a stab at both with same gear will not yield good results and you will get very frustrated and more than likely give it up.

I do DSO and tried a bit of lunar early days but not any planetary so cannot really comment on the planetary side but for sure enough DSO stuff out there to keep you interested for a lifetime.

But in a way you are maybe looking at it the wrong way in trying to get your laptop to work with either DSO or planetary, what you maybe should look at is what scope you have, if intending to use a scope you already own, or what scope you intend to buy, and maybe even more important than the scope is what mount you have or intend to buy.
These are more likely to suggest DSO or planetary than your laptop and whichever way you go you will easily find a pretty cheap laptop that will do for either 2nd hand whereas the other gear may not come so cheaply.

Steve

Personally I would just try it first before splashing out on a new laptop.

Funnily enough lunar and planetary work probably more demanding on the computer than DSO work because (I think - not done any planetary stuff) planetary uses either video of a lot of short exposures whereas DSO is usually a much smaller number of frames but each frame a longish exposure (typically 2 to 10 mins). So the planetary stuff I would think needs more memory (but could be a USB hard drive or memory stick of some sort) and will have more USB traffic to contend with.

Also even new state of the art laptops rarely have enough USB ports for Atrophotography and so most people end up looking for reliable USB hubs of which there are plenty of threads about as these need to be reliable (usually powered) and people do have issues with cheap ones.

So try your current laptop and see what issues, if any you have, you can try in daylight so not to waste a valuable clear night 🙂 

Steve 

6 minutes ago, aramitsharma said:

regarding the cigarette power connectors, I've used them inside a plastic box with small vent holes for ventilation. never saw condensation cause a problem.

Although I used tracer and skywatcher batteries, I don't know if this caused erratic guiding or it was just me...

I am sure many use them as so much Astro gear comes with them, maybe I just had some dodgy ones in the early days that just put me off them as I had a few sessions where my gear kept getting power losses.
But like anything if it isn't broke then don't fix it, so if it works for you that's what counts 🙂 

I hope you get it all sorted soon and most important you get some clear skies soon 🙂 

Steve

56 minutes ago, AstroKeith said:

I suspect its output may not be very 'clean' and may not even be regulated.

It has a fan and so is open to the atmosphere. Not good in dew conditions.

Those cigarette lighter plugs and  sockets are trouble waiting to happen.

Make sure you use an RCCD protected mains supply!

All very good points with 240V outdoors in cold damp conditions (usually the case in UK unfortunately 😞 ).

Whilst most 12V stuff for Astro use these cigarette sockets for the life of me I am not sure why, not from a danger point of view really (although I have heard of cheap switch mode supplies have been known to put high voltages on low voltage side if they go wrong) but just reliability wise, I find often some makes just do not make good connections and can get intermittent loss of power during a session, obviously not great in an unattended imaging session. If its worked for you so far even on battery power then carry on but I did have issues with some of them early days, maybe worked okay some nights but not others.

And very important is to use an RCCD, if you can I would get a qualified electrician to install a proper outdoor 240V socket that will go to a RCCD in your CB or Fuse box that way also you do not have long extension cables you have to get through a window or crack in the door that are just waiting to get trapped when somebody forgets the cable is there and shuts the window or door, or trips over the cable.

Steve