21 replies to this topic

[DonBoy]

I've had the ASI071MC-Cool for a few weeks and have had several extended sessions with it in conjunction with my 152mm f4.8 Mak-Newt + IDAS LPS D1 filter.   The conditions have not been the most favorable due to clouds, but we have gotten some very nice live images despite the clouds .   I image using the latest Sharp Cap Beta and AstroToaster software programs.  The camera specifics can be had from the ZWO website:  

 

https://astronomy-im.../asi071mc-cool/

 

Running this camera or any other for EAA takes a totally different approach than running it for long exposure Astrophotography.  Not that the EAA exposures are necessarily shorter, they could actually be longer, but that the image quality just needs to be at a reasonable level so that it takes the minimal amount of stacks to present a respectable image.   All my EAA imaging is primarily done for broadcasting on Nightskiesnetwork.com.  So my goal is to put up images quickly and not extend the stacking times to perfect the image, just enough to get by.  Now it's not to say I haven't spent some time on air exploring the results from extended stacks but that's not my norm.  

 

So what is my approach for EAA broadcasting.  Well it boils down to working at higher gain settings than would be used for AP where one would use zero or unity gain.  For EAA I have been exploring the 300 to 400 level for gain.  I'm finding that the exposure for a 400 gain can be in the 30sec to 60 sec range and yield reasonable results.  But I've been actually favoring 250g - 300g at a longer exposure say 120sec to 180sec to be more pleasing to my eye.  Part of the problem with what is pleasing to my eye comes from my evaluating the acceptable noise level in the images on my capture screen that shows more noise than what the viewer sees and I need to take that into account when I choose the working gain settings.  If there were a noise reduction function in SC or AT then higher gain settings would be more useable.

 

I use SC 2.10 and set the camera to the native driver, Raw 16, Bin1, Auto WB, cooling set to -20C and gain set to what I'm testing for that evening.  I don't use SCs stacking feature because I like the image controls in AT better.  I use the built in histogram function in SC and set the exposure so that the peak of the histogram is somewhere between 15% - 25% from the left stop.  The images captured in SC are sent to a shared folder with AT in fits format.  I then stack, stretch and tweak the image in AT live while the stacks one by one are being broadcast.  Generally I run 5 - 15 stacks.  The total time for each image should come down once I find the combination that works best for my skies (red zone) and equipment.

 

Having used the ASI1600MC-Cool for several months I felt very comfortable using the ASI071.  My initial impression has been that it is more sensitive than the ASI1600MC but also a little more noise at the same high gain settings.  The ASI071 actually can achieve a lower noise level than the ASI1600 when at -15C or greater when used at unity or zero gain.  The ASI071 has twice the full well, more dynamic range, 14 bit A/D output vs. 12 bit of the ASI1600.  This makes the ASI071 an overall better choice for AP imaging.   For EAA imaging you may not notice that much difference to warrant the higher cost.  With my limited use of the ASI071 I  feel that it provides higher quality images that I can see and if I want in the future to make pretty post processed images this camera is definitely a better choice.  I always have felt that my modded T3i provided more detailed images than the ASI1600 but had more noise and thus required more stacks, not the most ideal for broadcasting.  With the ASI071 I feel I have the same level of detail with way less noise that the T3i and will probably retire the Canon.  

 

Here is a link to CN Image Gallery for some recent unprocessed images from my broadcasts:

http://www.cloudynig...01#entry7673699

 

and a link to my ASI071 Flickr album, some images have had noise reduction applied:

https://www.flickr.c...157679587372466

 

For comparison you could view the ASI1600 and T3i albums also found thru this link:

https://www.flickr.c...5399@N04/albums

 

ASI071

 

ASI1600

 

ASI1600

Edited by DonBoy, 06 February 2017 - 06:31 PM.

[petert913]

Great shots, nice equipment, and you live in a very beautiful area !

[A. Viegas]

wow Don   I am so envious of your relatively clear open expanse of sky!      

Al

[DonBoy]

Great shots, nice equipment, and you live in a very beautiful area !

Thanks Peter

[ChrisFC]

That's a beautiful spot. And thanks for the tips. I've been using a gain of 300-350 and exposure of 30-60sec. But haven't had the weather to really give it a go. Are you using the flat/dark adjustment in sharpcap. Or are you doing that in AT.

Thanks Chris

[DonBoy]

That's a beautiful spot. And thanks for the tips. I've been using a gain of 300-350 and exposure of 30-60sec. But haven't had the weather to really give it a go. Are you using the flat/dark adjustment in sharpcap. Or are you doing that in AT.

Thanks Chris

Chris I'm using flats only in AT no darks.  I tried flats in SC 2.10 and got weird red circular concentric artifacts.

[Relativist]

Don, I'm curious if maybe using darks in AT would allow you to use higher gain settings. Also if you've tested other % for the histo in SC, maybe 50% and 75%?

[Dwight J]

Good to see that MN fired up.  Thanks for testing this camera out.  I lurked as a guest on a couple of broadcasts and it looked like a keeper.  

[A. Viegas]

Don

Have you tried the new ASI 071 with you C8 and reducer?  I am wondering if your image circle there is enough to not see significant vignetting?   I would assume that it should be ok unless you are using filters, in which case you would probably need 2"  or at the very least 36mm filters to avoid vignetting with 1.25" filters

 

 

Al

[Astrojedi]

Beautiful captures Don. The camera is producing some excellent results.

 

I did notice quite a bit of noise in many of the captures. It looks like "noise" I see when there is a mismatch (temp, duration etc.) between calibration frames and light frames. Did you try the camera without any calibration frames i.e. no flats or darks?

[WhitezonePrisoner]

So what is my approach for EAA broadcasting.  Well it boils down to working at higher gain settings than would be used for AP where one would use zero or unity gain.  For EAA I have been exploring the 300 to 400 level for gain.  I'm finding that the exposure for a 400 gain can be in the 30sec to 60 sec range and yield reasonable results.  But I've been actually favoring 250g - 300g at a longer exposure say 120sec to 180sec to be more pleasing to my eye.  Part of the problem with what is pleasing to my eye comes from my evaluating the acceptable noise level in the images on my capture screen that shows more noise than what the viewer sees and I need to take that into account when I choose the working gain settings.  If there were a noise reduction function in SC or AT then higher gain settings would be more useable.

 

DonBoy, I like the results you're getting with this camera, but I'm kind of a new kid on the block in regard to EAA, so can you or others help me with answers to a few questions?

 

1) I think I understand your issue with running 120sec to 180sec subs to get acceptable noise levels at your 250 -300 gain levels. No offense, but man,  if I have to wait 3mins for a sub to appear it would seems to me to be semi-dead rather near live viewing . My question here is, if you are doing AP length subs, isn't this really just another form of AP, but with semi-automated  live processing? Other than the fact that you got AstroToaster to do some "real-time" processing rather than post processing, what's the difference between this and  AP?

 

2) I'm also confused by the need for 2-3min subs at these gain levels. Someone else in another thread (maybe Astrojedi?) is talking about needing no more than 10-15sec subs to stack with another ZWO camera(the ASI290) because of the low readnoise, and says you can use a lesser quality mount for such short subs. So I don't understand how he can get away with low noise using 10-15sec subs with an ASI290, but you need 2-3mins subs. Are the two cameras that different in terms of read noise to warrant this? I doubt it, but I haven't used either. I'm kind of interested in this issue, as I would like to get away with short subs using a lower quality mount and no-guiding, which leads to my last question:

 

3) Do you need to guide if you are doing 2-3minute subs, or even the 60s subs with the approx 750mm focal length scope you are using ?

 

Sorry if I seem a bit rough in my 1st question, but this near real time viewing has me a bit confused if we are talking about 180sec subs.

[DonBoy]

Don

Have you tried the new ASI 071 with you C8 and reducer?  I am wondering if your image circle there is enough to not see significant vignetting?   I would assume that it should be ok unless you are using filters, in which case you would probably need 2"  or at the very least 36mm filters to avoid vignetting with 1.25" filters

 

 

Al

Al,  I haven't tried the camera with any other scope.  I would suspect that the C8 with a .63FR will yield a larger image circle but  with more coma than the 6" Mak-Newt.  I think one would experience vignetting with 1.25" filters.  I'm not even thinking anything but larger size filters these days.  I'll leave the 1.25" filters for the smaller chip sensors: 224, 290, 825.

[jimthompson]

Hi Don,

 

I am wondering how you are finding it working with such large MP cameras?  Any issues with CPU usage, memory, video display, etc.?

 

Thanks,

 

Jim T.

[DonBoy]

Beautiful captures Don. The camera is producing some excellent results.

 

I did notice quite a bit of noise in many of the captures. It looks like "noise" I see when there is a mismatch (temp, duration etc.) between calibration frames and light frames. Did you try the camera without any calibration frames i.e. no flats or darks?

Thanks Hiten.  I have not used darks.  I have tried to use the camera without flats with the 6" Mak-Newt but the image circle is too small so flats are a must.  So to answer your question I have not tried imaging without calibration frames.

 

I was on last night with the same combination 6" Mak-Newt and this camera and tried a gain of 400.  The initial images are noisy but eventually things improve.   Working with a lower gain, say 300, makes me more comfortable event though it requires more exposure.  It just feels better not to see so much of that initial noise and the longer exposure does yield a higher SNR.  I may try bin 2 to see if that helps with noise;  it should yield a 2 x SNR.

[DonBoy]

 

 

DonBoy, I like the results you're getting with this camera, but I'm kind of a new kid on the block in regard to EAA, so can you or others help me with answers to a few questions?

1) I think I understand your issue with running 120sec to 180sec subs to get acceptable noise levels at your 250 -300 gain levels. No offense, but man,  if I have to wait 3mins for a sub to appear it would seems to me to be semi-dead rather near live viewing . My question here is, if you are doing AP length subs, isn't this really just another form of AP, but with semi-automated  live processing? Other than the fact that you got AstroToaster to do some "real-time" processing rather than post processing, what's the difference between this and  AP?

Ed, capturing images for broadcasting and capturing images for viewing at a later time have different requirements.  When broadcasting I'm trying to put up a reasonably finished image as quick as possible.   The camera outputs the same file size and resolution whether I use a 1 sec exposure or a 120sec exposure.  So 120 x 1sec or 1 x 120sec moves 120 times faster and consumes 120 times less hard drive space.  So I try and set a level of exposure that just gets the signal on the histogram to move off the left side so that the peak of the graph is around 10%-25%.  This will generally yield an image that will show enough of the object to get started.  If the gain is set too high then this initial image is noisier than one using a lower gain setting.  For me I try and find what puts up  respectable initial image that cleans up quickly.  Right now I'm trying to work through that testing process with this camera.  

 

Now if I were doing captures for AP the gain would need to be set at unity gain.  The exposure then would be set so as to minimize star saturation.  Then one would capture hours worth of frames.   Now one may in this process be using 120sec to 600sec exposures, depending on FR, but it is at unity gain and if you tried to broadcast what you're capturing it wouldn't work for broadcasting.   

 

 

2) I'm also confused by the need for 2-3min subs at these gain levels. Someone else in another thread (maybe Astrojedi?) is talking about needing no more than 10-15sec subs to stack with another ZWO camera(the ASI290) because of the low readnoise, and says you can use a lesser quality mount for such short subs. So I don't understand how he can get away with low noise using 10-15sec subs with an ASI290, but you need 2-3mins subs. Are the two cameras that different in terms of read noise to warrant this? I doubt it, but I haven't used either. I'm kind of interested in this issue, as I would like to get away with short subs using a lower quality mount and no-guiding, which leads to my last question:

Low noise cameras will work with short 10-15sec exposures stacked 100's of times and yield an image, but not for broadcasting.  This method works best in a non live mode, although it could be done live.  The problem doing it live is that it requires X amount of time to process each stack.  So it would take X times 100's of stacks or X*100's in a live mode.  Doing a 60sec exposure would require 6 times less stacks and thus 6 times less stacking time and would provide initially a cleaner more vibrant image.  This type of capturing procedure works much better with a camera like the ASI224 or ASI290 which typically are 1.4 - 2mega pixel cameras, where as a ASI071 is a 16mp camera.  A big difference in data to be processed.  Also the 224 and 290 I believe are lower noise cameras than the ASI071.

 

So using a Alt/Az mount or an unguided EQ mount would work well with these smaller lower noise CMOS sensors in a very short exposure x high stacked frame mode.  Some AP guys have run the higher resolution cameras at very short exposure with 100s of stacks which require large storage space and an extremely long time to process the stacks.  The smaller size sensor works better for this type of imaging.

 

 

3) Do you need to guide if you are doing 2-3minute subs, or even the 60s subs with the approx 750mm focal length scope you are using ?

Sorry if I seem a bit rough in my 1st question, but this near real time viewing has me a bit confused if we are talking about 180sec subs.

Yes you need to guide only if your mount can't handle that long of an exposure.  If using shorter FLs of say 400mm you could probably get away with it using a good stacking program.

 

Ed, one could get much closer to near real time viewing by using very fast scopes in the f2 to f3 or faster with sensors that have larger pixels for increased sensitivity.  Cameras that would work more closely in this fashion are actually available and they are the older lower resolution designs that are still out there.  Cameras like Mallincams, and Lodestars, Stellacams, etc.  With the advent of higher resolution sensors and the desire to use them in a live format have created challenges that have yet to be overcome in matching the speed of presentation that the older lower resolution so called video cameras.   

[DonBoy]

Hi Don,

 

I am wondering how you are finding it working with such large MP cameras?  Any issues with CPU usage, memory, video display, etc.?

 

Thanks,

 

Jim T.

Hi Jim, working with these larger MP cameras the ASI1600, ASI071 and DSLRs is challenging, and they chew up a lot of disk space, take much longer to process, some require USB 3.0 to function efficiently.   So in general it puts a burden on the computer for memory, CPU, graphics, monitor resolution, etc.  It took some tuning to get everything working together.  Example, sorting through USB 3.0 cables, changing monitors to handle the higher resolution, using ethernet cable instead of Wi-Fi, working with USB hubs, adding new more useful software, etc.

[WhitezonePrisoner]

Thanks for addressing my questions, Don. Your explanation on how processing time for a big sensor camera impacted your broadcasting decision to use long subs makes a lot of sense, and is something that would not have occurred to me. I am real grateful to you for sharing this insight, and again, please excuse my somewhat irreverent comment with regard to near live viewing.

 

 As for using a standard resolution camera, I did get a Lodestar X2 recently and agree with you that the camera is amazingly sensitive in my limited experience. Next camera for me will probably be one of the ZWOs with low read noise and higher resolution/smaller pixels.

[Relativist]

Jim, what I've found key is the use of Astrotoaster, which is written to handle larger megapixel DSLRs and gives the user tools to lower the compute burden, like superpixels and cropping.

Compute resources at that level are a commodity now, but it does require planning to make sure they are above a minimum threshold. Where I had a problem was my use of a dual core Mac and parallels with only one core assigned, so AT had to fight for resources. This was on my 7 year old MacBook (2010). I found that if I have windows at least two cores then AT worked fine, a 2011 MacBook Pro with 4 cores did just fine in comparison. For those on windows this is probably less of an issue.

P.S. I left out that the DSLR in question was my A7s which is 12 megapixels.

[Ain Soph Aur]

Awesome images Don. It looks like you got the Comet Hunter collimation sorted out nicely, grats!

 

I have a tax refund incoming, looking hard at the ASI071-MC now!

[Astrojedi]

Thanks Don. Look forward to more results. I am definitely watching this one. Should be a good fit for the Hyperstar as well.

[DonBoy]

Awesome images Don. It looks like you got the Comet Hunter collimation sorted out nicely, grats!

 

I have a tax refund incoming, looking hard at the ASI071-MC now!

Thanks Brandon.  Yes the scope is working as it should.  The ASI071 has a lot of potential and I'm sure you'll like it.

[DonBoy]

Thanks Don. Look forward to more results. I am definitely watching this one. Should be a good fit for the Hyperstar as well.

Hyperstar would be a great choice.