SharpCap Live Stacking

[rwg]

Hi folks,

thought I'd post here as more people here seem to be using the Live Stacking feature of SharpCap now.

SharpCap - if you haven't encountered it before - is a free Astro-focused capture application for Windows.

SharpCap includes support for a wide range of cameras - including QHY, ZWO, Basler, QHY, Webcams, Frame Grabbers, ASCOM and others. Any camera that SharpCap supports can be used in live stacking mode, although to get decent results you will need to be able to set exposure lengths of about 1s or more.

Live Stacking includes an alignment option (on by default) that will correct for drift and field rotation in each new frame as it is stacked. Alignment depends on being able to detect at least 3 stars in each frame. Additionally you can filter incoming frames based on a FWHM measurement of the stars detected, allowing frames with better seeing conditions to be stacked and worse frames discarded.

There are simple functions allowing the histogram of the stacked image to be stretched for display and the stack can be saved either 'as seen' with the stretch applied in PNG format or in FITS format with no stretch applied for later post-processing.

SharpCap also has an embedded scripting language which allows simple programs to be written that will automate a capture session - some users over on Cloudy Nights have been using this facility to automatically stack a target for say 30 minutes then move the mount to point at a new target and start stacking that.

SharpCap 2.9 is currently in beta and will contain improvements to the live stacking features including an easier-to-use histogram stretch function, more star detection options for alignment and automatically remembering most stack related options. However, if you prefer to avoid beta software, feel free to use SharpCap 2.8 instead.

Just as a taster, here is an M81 I produced in 30 minutes of 4s exposures with the ASI1600MM-Cool.  This was really just a test stack -  taken on first-light with the camera, testing a new version of SharpCap and with a whole bunch of other things in my setup changed - I'm sure it's possible to do better when hurrying a little less!

I'd love to hear any feedback people have on how to improve the live stacking feature - and see any images you capture with it!

cheers,

Robin

PS. For about the first 10 minutes of stacking I had left the mount accidentally on Lunar tracking rate having used the moon earlier to sort out focus and align the finder scope. The alignment feature took care of this quite happily and I didn't even notice until I spotted a little line of hot pixels building up due to the drift.

[baggywrinkle]

Been looking at that feature. I use SC all the time.

I see you are in Vale of the White Horse. Lovely area often used to visit Uffington to see the Horse.

[PeterCPC]

Very impressive Robin for 4 secs exposures. Do you think the stacking would be ok with longer exposures e.g. 10 secs? I am going to be trying this with my ASI224MC (uncooled) with a UHC-E filter to reduce LP.

Peter

[Dragon_Astro]

Having just started in my EAA journey, I've only used the live stacking a couple of imaging sessions.

ive been impressed with it so far though  one thing I dont understand is why after saving a stack in the designated folder, it also creates lots of empty folders with random numbers as names?

[rwg]

@PeterCPC

yep, should be fine with 10s exposures - your limit will be determined by your mount tracking - once the stars start getting badly mis-shapen the alignment won't spot them.

@Dragon_Astro

the problem of empty folders is much improved (probably fixed completely) in 2.9

@baggywrinkle

Unfortunately VOWH only by district council rather than by actual physical location. Shame really, the skies are a lot darker in Uffington...

cheers,

Robin

 

 

 

[DoctorD]

Hi Robin

Nice to see you in this neck of the woods - great work on Sharpcap, any chance of an OSx version

CS

Paul

[rwg]

35 minutes ago, DoctorD said:

Hi Robin

Nice to see you in this neck of the woods - great work on Sharpcap, any chance of an OSx version

CS

Paul

Unfortunately an OSX version would involve pretty much re-writing from scratch. And to be honest, I don't much like OSX or Apple for that matter

I guess the starting point for something equivalent on OSX would be a program like OACapture and then to add the alignment/stacking code to that as it already has good support for lots of different cameras.

cheers,

Robin

 

[alphatripleplus]

Recently I had a chance to try out the new Digital Gain switch, which is a new feature that Robin has added in the  live stacking options of the latest SharpCap 2.9 beta. For anyone having difficulty with stacking in a field with faint stars and a mount that can track well for only a few seconds, I think this feature is going to be much appreciated. The Digital Gain, as I understand it, aids in star detection by boosting the contrast for stars in the field by 2x, 4x or 8x so that more or fainter stars can meet the threshold for use by the alignment algorithm. (Hopefully, Robin will correct me if I am wrong here).

Anyway, when I last used this feature, I was using a C8 @f3.4, stacking 5s exposures with an uncooled ASI224 camera @350gain on M51 the Whirlpool Galaxy. I had what I thought was my Lumicon Deep Sky filter in the optical train, but noticed the image was exceedingly dim and I needed to push the Digital  Gain to 4x to stack at  5s sub exposures. What I didn't realize until after removing the filter was that I actually had mistakenly put a Lumicon O-III narrowband filter in place, not the Deep Sky filter! It still amazes me that SharpCap could stack 5s subs through an  O-III filter with a narrow band 11nm bandpass around the O-III lines and (for the Lumicon version) limited band pass in the infrared (unlike some other versions of the O-III). The Lumicon 0-III was clearly the WRONG filter for galaxy viewing, but here is the 5minute exposure (60 x5s) that I mistakenly took through the O-III filter. It is obviously not a great picture, but the point is to demonstrate that SharpCap has fairly robust live stacking capability. (I desaturated the brownish color that resulted from using the O-III filter).

 

[ramdom]

Regarding the Windows version, while I currently only own SX cameras for which Starlight Live works for live stacking, I exclusively use Unix systems, which means Mac OS X or Linux and not Windows. However, I have been using Registax and AutoStakkert with Wineskin Winery which takes Windows software and puts them in a container so they can run on the Mac. These programs work as well as they would on Windows (clunky Windows interface and all) and I've been impressed so far. From what I understand, the process to "bottle" any Windows program is fairly straight forward and if it's done once,  others can just install the container like they would any other Mac OS program. Here's someone who has listed the instructions to get DSS to work on the Mac (along with the prepackaged versions of DSS and Registax and if you Google, you can find others who've done it as well):

http://blog.tom-goetz.org/2013/01/running-deepskystacker-for-windows-on.html

If I purchased a non-SX camera, I'd give it a go but anyways, this is just a suggestion for those who want to get this going on a Mac.

--Ram

 

[aparker]

On 5/30/2016 at 14:47, ramdom said:

Regarding the Windows version, while I currently only own SX cameras for which Starlight Live works for live stacking, I exclusively use Unix systems, which means Mac OS X or Linux and not Windows. However, I have been using Registax and AutoStakkert with Wineskin Winery which takes Windows software and puts them in a container so they can run on the Mac. These programs work as well as they would on Windows (clunky Windows interface and all) and I've been impressed so far. From what I understand, the process to "bottle" any Windows program is fairly straight forward and if it's done once,  others can just install the container like they would any other Mac OS program. Here's someone who has listed the instructions to get DSS to work on the Mac (along with the prepackaged versions of DSS and Registax and if you Google, you can find others who've done it as well):

http://blog.tom-goetz.org/2013/01/running-deepskystacker-for-windows-on.html

If I purchased a non-SX camera, I'd give it a go but anyways, this is just a suggestion for those who want to get this going on a Mac.

--Ram

 

That's very helpful.  I am toying with getting a ZWO camera but would like to stay on OSX as completely as possible, so this will definitely be worth looking into.