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ATIK 460EX - Beginners questions


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Dithering. Is it needed or do I just do a darks library? Dithering eats into a lot imaging time, especially if using CMOS and hundreds of short subs. Whereas I can do a darks library during the day. I get i will be taking longer subs with this and not a deal breaker if I should still dither but if its not needed its less hassle with PHD trying to recentre each time.

Bias frames. Do I include these in my post processing again? Do I just set the exposre to 0 or do I need to be specific ie. 0.001 or whatever the lowest setting is?

Darks. I have seen some people mention you dont need darks at all. Is it worth the time creating a library anyway?

Flats. I assume I'm still looking for an ADU value of 21k or there abouts, a third to a half the histogram? These are calibrated with just a master bias?

Software for capturing calibration frames. Atik has its own capture software. Is this software free to download or is it licensed based and offered when bought from new? Is there any benefit to using Atiks software compared to say, APT, NINA, Sharpcap etc

Cooling. What is a nice happy medium for this camera here in the UK? It has a conservative cooling delta though I got it down to -5°C indoors last night at 80% power. -10/-15 most of the year round when imaging in anger?

This is my first CCD camera so beginners learning curve again for me. 🙂

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This is important regardless of other factors - if you can, dither, no question about it. If you don't plan on using dark frame optimization or calibrating with different length of darks than d

Vlaiv tells you how to do it by the book, which is fine. However, this is how I actually do it: - I don't dither because mine is a dual rig and I take different exposure lengths on each scope. If

I had an ASI1600 and sold it to go back to a DSLR. I grew a bit tired of half finished LRGB projects. The modded 6D I have is great and you can get a decent image in 1 night as long as you can get a f

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16 minutes ago, david_taurus83 said:

Dithering. Is it needed or do I just do a darks library? Dithering eats into a lot imaging time, especially if using CMOS and hundreds of short subs. Whereas I can do a darks library during the day. I get i will be taking longer subs with this and not a deal breaker if I should still dither but if its not needed its less hassle with PHD trying to recentre each time.

This is important regardless of other factors - if you can, dither, no question about it.

16 minutes ago, david_taurus83 said:

Bias frames. Do I include these in my post processing again? Do I just set the exposre to 0 or do I need to be specific ie. 0.001 or whatever the lowest setting is?

If you don't plan on using dark frame optimization or calibrating with different length of darks than don't bother with bias subs. If you are going to use them - just set lower exposure value allowed by software.

17 minutes ago, david_taurus83 said:

Darks. I have seen some people mention you dont need darks at all. Is it worth the time creating a library anyway?

Only way to do proper calibration is to use darks. Maybe some people don't need darks, but then they don't need proper calibration. Simple as that. Use darks.

18 minutes ago, david_taurus83 said:

Flats. I assume I'm still looking for an ADU value of 21k or there abouts, a third to a half the histogram? These are calibrated with just a master bias?

Half to 2/3 of histogram would be my choice. These are calibrated with flat darks. You can use master bias if you have low dark current and strong flat panel and no mechanical shutter - meaning short flat exposures. Using bias will introduce very small error in your flats which in most cases won't show in your image. If it shows - use flat darks, or if you want to do it properly from the start - use flat darks

 

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As an Atik 460EX user i will try to answer what i can.

Dithering. I dither between frames. The 460 does not need a darks library (according to Atik) so i have not bothered. I dont understand where you think it eats into a lot of imaging time (i have not noticed it). The 460 is a CCD not CMOS and i find it needs a reasonable sub length (i tend to use 5 minutes-depending on how bright the target is). PHD uses the same star and  and knows it is a dither so it does not re centre every time AFAIK.

Bias. I have never bothered in the past but recently made a library which took next to no time.

Darks never bothered see above

flats again never bothered however i have noticed a couple of dust bunnies recently so will do some eventually. Your assumption about the ADU and histogram are right. 

Software. I use SGP which works for me. Others use APT and more recently the free NINA. I could not get away with the Atik supplied software. It all comes down to personal preference. SGP also has a wizard (the others probably do also) for setting up a library of flats ETC.

Cooling I use -10 as my standard setting however i am not sure if it needs to go that low. Again it works for me so i leave it alone.

Like everything these work for me in my Bortle 8 location. Once something is working i tend to leave it alone.

Here are a few low resolution images that are currently work in progress but show you the quality of the 460

 

1497479549_EasternVeil.thumb.jpg.8ccae8bc5a2260114da0d0ded631cfb7.jpg1271551603_TulipNebulaSH2-101.jpg.1d94480b9439e8c07b64d9397cc8d648.jpg1807122193_FishHeadnebula18_09_2020.thumb.jpg.37c457893f2030adf52aacd26f0eeed1.jpg

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I have only had a (second hand) 460EX since spring this year so am also just starting out with it. 

I'm now dithering between each shot as I've only used 300s / 600s so far.

I've used the camera with Apt and Voyager without any troubles.  I've used Apt to create Dark libraries and Bias frames.  As above, Atik states minimum shutter speed of 1/1000 (0.001) seconds, so I used that for Bias.

I also use -10 on the cooling due to the mentioned conservative delta and the listed low dark current at -10 (from Atik's tech specs).  

With the very limited imaging I've done with it, I plan to experiment with the darks / no darks etc.

For what it's worth, here's a recent 600s Ha sub @250mm (just STF stretch in PI, 50% resample)

Lobster_Bubble_M52_single600s.thumb.jpg.c5415e03e83389af03a47d61306a971e.jpg

 

Edited by geeklee
Added example sub.
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Thats some contrasting opinions there @m.tweedy& @vlaiv

Regarding dithering, I should be more clear. When I say recentring I mean settling. Also, my mount can overshoot due to backlash so the settle time can be quite a bit. Up to 60s some times. If I'm doing 60s subs (CMOS) and dither after every 3 frames that's 15 minutes per hour. I would say that's significantly eating into image time. I suppose I could simply try without to start with.

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40 minutes ago, m.tweedy said:

flats again never bothered however i have noticed a couple of dust bunnies recently so will do some eventually. Your assumption about the ADU and histogram are right. 

 

 

1497479549_EasternVeil.thumb.jpg.8ccae8bc5a2260114da0d0ded631cfb7.jpg1271551603_TulipNebulaSH2-101.jpg.1d94480b9439e8c07b64d9397cc8d648.jpg1807122193_FishHeadnebula18_09_2020.thumb.jpg.37c457893f2030adf52aacd26f0eeed1.jpg

You know, I never even considered not using flats! I've had an ASI1600, Canon 600D and 6D so medium to large sensors and flats were always necessary. I have a an SX filterwheel with 1.25" filters. Perhaps i won't have vignetting?

Great pics BTW!

Edited by david_taurus83
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My filters are 1.25 and i dont have any vignetting. If i did i would just crop it anyway. I dont even bother with a field flatner or reducer. As you may have guessed i am not a pixel peeper. I want to get better at what i am doing and when i finally get round to picking up my MN190 (i currently use a GT81) i may then set up a flats library and (god forbid) clean my sensor and filters (which have not been touched in over 4 years)

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23 minutes ago, david_taurus83 said:

Thats some contrasting opinions there @m.tweedy& @vlaiv

Regarding dithering, I should be more clear. When I say recentring I mean settling. Also, my mount can overshoot due to backlash so the settle time can be quite a bit. Up to 60s some times. If I'm doing 60s subs (CMOS) and dither after every 3 frames that's 15 minutes per hour. I would say that's significantly eating into image time. I suppose I could simply try without to start with.

I would ALWAYS listen to vlaiv as i respect his input and experience. Mine is just a case of what i tried and works for me. Maybe further down the line I may understand and then adopt other iterations. 

Have you tried the PHD2 wizard that measures backlash and sets appropriate values to compensate. My CEM120 has a lot of backlash in Dec (again i may adjust the mesh someday if the stars stop being round). I could (and have) had 10 minute subs-however the core of the Tulip and Fishhead were getting blown out so reduced them to 5 minutes.

CCD imaging is not quite the same as CMOS. I have never had a CMOS camera and am pleased i do not have things to fiddle with such as offset and gain otherwise i would not get any imaging done.

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6 hours ago, david_taurus83 said:

Thats some contrasting opinions there @m.tweedy& @vlaiv

I still maintain that it is best to take darks, however, Atik is right to recommend that darks are not really necessary for certain sensors.

This does not mean that taking darks is wrong approach or should not be done - it means that you are highly unlikely to notice the difference. Let me show you why is that:

On this page

https://www.atik-cameras.com/specification-tables/

you will find specs for different models of their cameras, and this is important bit:

image.png.fc5037db7cc1c6986e6c762024505a50.png

I outlined 460Ex model. It has dark current of about 0.0004e/s/px.

That is very, very low current, and if you look, next few models also has very low dark current. These are Sony ICX series of CCDs.

But not all CCDs have that low current and that low current is at -10C. Someone working at 0C will not have that low current.

Just to understand how low current is that, let's do single exposure at 5 minutes at -10C

This will add 300s * 0.0004 = 0.12e of dark current to your image. That is very low dark current indeed and I've seen cameras that have more variation between main value of dark subs than that.

However, in some cases, that might not be negligible. Take for example 30 minutes exposure at 2C (and we assume doubling temperature is 6C).

In that case we would have 1800 * 0.0004 * 2 * 2 = 2.88e of dark current.

Now it is not negligible any more.

I agree that not taking darks and instead using bias sometimes can give same results as taking darks - but I would only "allow" it when one knows what sort of impact to expect given camera parameters.

However, try doing that with Kodak sensor - any one from last three to see what will happen. It is again Atik camera - does it mean it is so good as to not need darks? Most certainly not with those dark current rates.

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@vlaiv As I said I respect your input greatly and knew it was best to take darks (and flats and bias) but was happy with the results at my current experience level. When i get the new scope i fully intend to take a full library of them all. So David if you can take them then do so. I do think the 460 is a very good camera. Curious question-why did you move from the CMOS to the smaller sensor ATIK

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43 minutes ago, m.tweedy said:

@vlaiv As I said I respect your input greatly and knew it was best to take darks (and flats and bias) but was happy with the results at my current experience level. When i get the new scope i fully intend to take a full library of them all. So David if you can take them then do so. I do think the 460 is a very good camera. Curious question-why did you move from the CMOS to the smaller sensor ATIK

I agree with you - in this case, as long as you don't have any issues with flats (or don't use them if you don't have any dust or vignetting in your system), since this camera has such low dark current - one can use bias instead of darks. I just wanted to show why is that the case here, and under which circumstances it holds. After all, we are not doing rigorous scientific work and as long as there is no impact on final result - one can certainly choose one approach over another.

 

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Vlaiv tells you how to do it by the book, which is fine. However, this is how I actually do it:

- I don't dither because mine is a dual rig and I take different exposure lengths on each scope. If I could easily dither I would but, quite honestly, it doesn't matter. Slight polar misalignment, reframing after the flip, reframing on different nights, etc, builds in natural dither anyway.

- I do shoot bias at 0.0001  0.001 second and I do use them as darks for for flats. If there is a difference, on this camera, between dedicated flat darks and a master bias it will be imperceptible and the tedium of shooting dedicated flat darks is absolutely not worth it. The same applies to my much noisier Atik 11000 as well. I don't know anybody who uses dedicated flat darks with CCD. There is no point since bias does the job, but it is necessary with CMOS.  And, yes, you do need flats. Even with my TEC 140, which has a flat, well illuminated field the size of Hampshire, I need them even when there are no bunnies - though there always are.

- I've tried using a bias as a dark instead of full length darks with this camera and it works fine if you're at -10C or less but, if you're running warmer than that, it is worth using darks. This is just what I've found with my own 460. Interestingly, and contrary to what one might expect, I find a bias-as-dark and bad pixel map works better than darks on my Atik 11000. This is where experiment leads me to disagree with Vlaiv. When I stopped using darks on the 11000 and used bias and BPM I got significantly cleaner stacks and with a lot less trouble. Plenty of other imagers have stopped using full length darks as well, finding they get better real world results with bias and bad pixel map. Theory and practice do not always agree.

- Atik software is free to download from their website. I'm using the older Artemis Capture, which I love, and am rather dreading having to learn my way around the new software. I had some advice from Ian King many years ago: If you're having trouble with a product, run it in its own software.  That's the argument in favour. However, the old Artemis won't communicate with PHD so, to dither, you'd need a capture software which did. That's the argument against. (I don't know where the new Atik software stands on this. Anybody?)

- Finally a 460 quirk (on my example, at least.)  I get clean stacks with good signal. However, when I begin stretching process I find that the background sky values remain very low. If I use a conventional log stretch in Ps Curves I'll find the brighter signal is reaching the upper limit before the background sky has come up to the kind of value I like (which is around 23 in Photoshop.) In the end I usually have to settle for a darker background than I'd really like. I can't explain this and it might not happen at a site with LP. My skies are very dark. 

Essentially it's an easy camera to use and does the business. Have fun!

482836587_M101HSTcolour30Hr.thumb.jpg.715e74a37ba708d80f35d71cb6c8971d.jpg

 

Olly

PS Anyone interested in a 460 should know that SGL member Gorann has an unused one for sale.

 

Edited by ollypenrice
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2 hours ago, ollypenrice said:

However, the old Artemis won't communicate with PHD so, to dither, you'd need a capture software which did. That's the argument against. (I don't know where the new Atik software stands on this. Anybody?)

You can dither using PHD and Artemis by using a script set in Artemis.

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If you are running a dual scope rig, you can't dither.  If you are running a single scope then you might as well dither and spread the image over adjacent pixels.  To be honest, theory aside, I am not sure that in the real world with amateur gear it makes that much difference in my experience, FWIW.

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27 minutes ago, kirkster501 said:

If you are running a dual scope rig, you can't dither.  If you are running a single scope then you might as well dither and spread the image over adjacent pixels.  To be honest, theory aside, I am not sure that in the real world with amateur gear it makes that much difference in my experience, FWIW.

With N.I.N.A. one can use dual scope and dither. Synchronized Dithering with PHD2

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Thanks all for the advice. I think I'll just do a darks library anyway. 5, 10 and 15 minutes to start with. No harm just having them to hand. I will try without dithering to start with seeing as I'll have darks. I could use Pixinsights CosmeticCorrection to clean up any hot pixels left in the calibrated subs. Looking forward to doing mono and narrowband again. Just need a scope now. And guide scope, guide camera etc. Pretty much everything I sold a few months ago! 🙃🙂🙃🙂🤔

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28 minutes ago, ollypenrice said:

Does this require an ASCOM compatible mount?

Olly

I am experimenting at the moment Olly. But it works with my Mesu 200. 

Have the ZWO 183MM on the TS65Q, Atik4120EX on C11 with ZWO OAG and Lodestar X2. All on Mesu200.

Have the SiTech selected in NINA as the scope mount.  Works well so far.

Plate solving using ASTAP is very fast, even using the ATIK 4120EX at 2800mm FL.

https://nighttime-imaging.eu/docs/master/site/requirements/

 

I will start a new thread with my setup and any snags if anyone is interested.

Edited by Star101
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13 hours ago, m.tweedy said:

Curious question-why did you move from the CMOS to the smaller sensor ATIK

I had an ASI1600 and sold it to go back to a DSLR. I grew a bit tired of half finished LRGB projects. The modded 6D I have is great and you can get a decent image in 1 night as long as you can get a few hours of data but I almost instantly missed the crutch of narrowband data for when the moons about. IMO the Atik seems to produce cleaner images than CMOS. Going by other peoples images that is. Smaller sensor yes, but easier to get a flatter field hopefully. Most of my imaging to date has been wide field stuff at 330mm focal length so its time for a change now to get a bit closer to smaller regions of targets at 450/550mm.

I'm still keeping my 6D BTW. Dont think I could sell it as it served me very well over lockdown.

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1 hour ago, Star101 said:

I am experimenting at the moment Olly. But it works with my Mesu 200. 

Have the ZWO 183MM on the TS65Q, Atik4120EX on C11 with ZWO OAG and Lodestar X2. All on Mesu200.

Have the SiTech selected in NINA as the scope mount.  Works well so far.

Plate solving using ASTAP is very fast, even using the ATIK 4120EX at 2800mm FL.

https://nighttime-imaging.eu/docs/master/site/requirements/

 

I will start a new thread with my setup and any snags if anyone is interested.

My Mesus are pre-Sitech, using the non-ASCOM Stellarcat-Argonavis combination so I don't suppose they will work as yours do. Not the end of the world. I love the simplicity of the old system.

Olly

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