Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

sgl_imaging_challenge_banner_christmas_presents.thumb.jpg.587637e0d01baf4b6d21b73610610bbb.jpg

HiloDon

Lodestar Live User Guide

Recommended Posts

Hi All,

I am please to post a Lodestar Live user guide that I have been working on for the last several weeks.  The guide is version 1.0 and addresses version 0.12 of Paul’s brilliant software as it is used specifically with the Lodestar monochrome and color cameras.  The procedures outlined are ones that I have personally used and found to be successful.  I realize that there may be other ways to produce excellent results, but I tried to keep things simple and basic to help both new comers and others who may need some direction to achieving good results.

This is the first release of this guide, so there may be some erroneous or confusing statements present.  Please feel free to PM me if you think something needs to be corrected or clarified.  Paul has reviewed the guide draft and has given his OK, but as with anything, there is always room for improvement.  Any suggestions are welcome and would be appreciated.

Don

Lodestar Live User Guide.pdf

  • Like 18

Share this post


Link to post
Share on other sites

I've not tried my Loadstar for this type of use so far but this opens up possibilities. Excellent read full of information. Thanks to both you and Paul.

Derek

Share this post


Link to post
Share on other sites

Erm Moderators - isn't it time that VA had some sub folders marked for Guides,Tips etc UNDER VA. I know some exist else where but it would be nice to get to it quickly in the area of interest VA'a are most interested in. It would be a shame to loose this user manual amongst all the other waffling(albeit very good waffling). 

  • Like 4

Share this post


Link to post
Share on other sites

Erm Moderators - isn't it time that VA had some sub folders marked for Guides,Tips etc UNDER VA. I know some exist else where but it would be nice to get to it quickly in the area of interest VA'a are most interested in. It would be a shame to loose this user manual amongst all the other waffling(albeit very good waffling). 

Yes, a few spring to mind that would be useful to easily reference; Paul's LL downloads, Martin's Pretty Deep Maps, Don's LL Guide. I know there was also a useful guide to stacking in LL - apologies I don't know who wrote it as I can't find it (see, there is a need!)

Rob

  • Like 2

Share this post


Link to post
Share on other sites

Your instructions are much appreciated! I have had the x2c in use a couple times now, with spotty success... I can't wait to have another go at it using some of the info in hand now. 

cheers

Sean

Share this post


Link to post
Share on other sites

Erm Moderators - isn't it time that VA had some sub folders marked for Guides,Tips etc UNDER VA. I know some exist else where but it would be nice to get to it quickly in the area of interest VA'a are most interested in. It would be a shame to loose this user manual amongst all the other waffling(albeit very good waffling). 

Agree, I think this should happen especially as this is a developing area with many of us learning the ropes and others pioneering techniques.

  • Like 1

Share this post


Link to post
Share on other sites

Thanks, everyone, for the kind comments and likes. Agree that it would be helpful to have an EAA downloads section for programs, guides and references. If anyone has a suggestion on another location to post this, please let me know.

Don

Share this post


Link to post
Share on other sites

Great work Don, Thanks

Rob made note of Martin's Pretty Deep Maps. Where are these located?

Share this post


Link to post
Share on other sites

Great work Don, Thanks

Rob made note of Martin's Pretty Deep Maps. Where are these located?

I think they canbe found here.

  • Like 1

Share this post


Link to post
Share on other sites

Don,

Kudos for taking the initiative to do this. I look forward to reading and will provide any comments I can based on my so far fairly limited experience with the software.

Great contribution to the SX EAA community!

Alex

Share this post


Link to post
Share on other sites

Hello Mr/Mrs nice ,wonderful, hard working moderators any chance this can be "pinned" so that it stays at the top of the forum?

Not being sarcastic just trying to ask nicely as my mum said ask nicely and you might get what you want - never did get the Hornby Flying Scotsman. :grin:

  • Like 1

Share this post


Link to post
Share on other sites

I've made this a sticky  :grin:   If there are other threads that you think need the same treatment PM me and I'll have a look.  I wouldn't want too many pinned posts though as that makes regular posts drop too far down, so if there are a lot I suggest one pinned post which has links to useful posts.

Helen

  • Like 3

Share this post


Link to post
Share on other sites

I've made this a sticky  :grin:   If there are other threads that you think need the same treatment PM me and I'll have a look.  I wouldn't want too many pinned posts though as that makes regular posts drop too far down, so if there are a lot I suggest one pinned post which has links to useful posts.

Helen

You have made a man very happy - didn't get my Flying Scotchman but you pinned the guide - A very big thank you

  • Like 1

Share this post


Link to post
Share on other sites

This is a well written guide on how to use what is essentially a "black-box". It would be good to have as well some explanation of the stacking algorithm, which probably only Paul could write. 

Apparently each new image is fitted to the sum/mean/median of the previous images, and this "will reduce the amount of random noise generated by the sensor" but that "improvement is negligible after the first five stacks". Frankly I don't understand that. The signal is continuously summed within the CCD anyway, so it can't help to read it out at intermediate intervals and sum it externally. Indeed that would just add read noise. And so long as the signal doesn't overflow the file range, there can be no difference between mean and sum stacking. Without being told how SL actually works, this claimed noise reduction looks like magic :-)

But perhaps noise is reduced because the image is moving over the detector, due to imperfect tracking, so that it's sampled with different pixels? Indeed that sounds like a good idea - forget about mechanical tracking and just track using software. Can SL calculate the rotation of the sky around the pole, or does it just fit the new frame to the existing stack somehow ? 

I suppose that, provided you can track correctly, you can't produce better images with stacking than with equally long exposures. But the real interest of stacking is that you can simply "watch the image get brighter/better as it stacks". And stop when it's good enough.

Share this post


Link to post
Share on other sites

Hi Hibou,

You're correct, the stacking algorithms are beyond my knowledge, but I do know that stacking does improve the SNR by reducing random noise. Maybe reducing isn't the right word, but the signal is increased without increasing the random noise equally. Here's a reference written by Keith Wiley that does a good job of explaining how stacking works. He also explains how dynamic range is improved as well and why sum and mean stacking are really the same.

Hope this helps.

http://keithwiley.com/astroPhotography/imageStacking.shtml

Don

  • Like 1

Share this post


Link to post
Share on other sites

Here's a reference written by Keith Wiley that does a good job of explaining how stacking works. 

I like people who admit they don't know, because I don't know either :-) "Don't know" is the start to understanding.

I read Keith Wiley's explanation of why stacking works, and don't agree :-) He says "photons that entered the telescope and accumulated in the CCD" when actually it's electrons that accumulate. OK, semantics. Then he explains that by multiple sampling (stacking) the random noise fluctuations average out. That's right, but they also average out if you just accumulate the electrons in the CCD and read them out at the end of the period for which you would stack. There's no difference if you consider as he does a single pixel. Just the same as there's no difference in signal/noise if you average or sum, as he rightly explains. If sampling at short intervals could improve S/N then, reductio ad absurdum, you could improve S/N indefinitely by finer sampling.

I started low-light imaging 9 years ago with true video CCDs the Wat-120 and 120+. Then the image accumulated within the CCD, which also averaged out random electron noise, but it was sampled continuously at 50 Hz (PAL). Of course the dynamic range was limited to 8-bits, much less than with digital readout.

Then when I searched the forum I found a nice demonstration by Martin Meridith "To stack or not to Stack", which I think shows that there is indeed no difference. The only case where I suppose that stacking can help with noise is when the image is moving over the sensor. Apart from correcting for such movement, stacking might also reduce noise by sampling with different pixels.

I'm not asking anyone to justify stacking. Obviously it's practical, it works, and SL is a nice application. I would just like to know a little more about how stacking is implemented :-)

Share this post


Link to post
Share on other sites

Hibou,

Just another couple of thoughts. I think Keith is explaining why stacking works because it does. In practice I find that at least visually the image improves on a decreasing basis. It makes sense that the SNR improves. Longer exposure may do that too, but Keith also explains that you need to have a proper sub exposure to ensure the dynamic range of the camera matches that of the object. Too short and you can lose dimmer data. Too long and you can loose brighter data to saturation. That's why sensors with higher inherent sensitivity (higher SNR) and faster optics are better for EAA. That's my view as a practitioner.

This is a good discussion and an important one, too, especially with all the new cameras coming out. It probably would be better if we started a separate thread for further discussion.

Thanks,

Don

Share this post


Link to post
Share on other sites

I've never used a ccd camera before and I'd like to thank you Don for the idiots guide.  (This idiot would have been lost without it)  Also a huge thank you to Paul for the lodestar live program. 

  • Like 1

Share this post


Link to post
Share on other sites

Hibou,

Just another couple of thoughts. I think Keith is explaining why stacking works because it does. In practice I find that at least visually the image improves on a decreasing basis. It makes sense that the SNR improves. Longer exposure may do that too, but Keith also explains that you need to have a proper sub exposure to ensure the dynamic range of the camera matches that of the object. Too short and you can lose dimmer data. Too long and you can loose brighter data to saturation. That's why sensors with higher inherent sensitivity (higher SNR) and faster optics are better for EAA. That's my view as a practitioner.

This is a good discussion and an important one, too, especially with all the new cameras coming out. It probably would be better if we started a separate thread for further discussion.

Thanks,

Don

I like people who admit they don't know, because I don't know either :-) "Don't know" is the start to understanding.

I read Keith Wiley's explanation of why stacking works, and don't agree :-) He says "photons that entered the telescope and accumulated in the CCD" when actually it's electrons that accumulate. OK, semantics. Then he explains that by multiple sampling (stacking) the random noise fluctuations average out. That's right, but they also average out if you just accumulate the electrons in the CCD and read them out at the end of the period for which you would stack. There's no difference if you consider as he does a single pixel. Just the same as there's no difference in signal/noise if you average or sum, as he rightly explains. If sampling at short intervals could improve S/N then, reductio ad absurdum, you could improve S/N indefinitely by finer sampling.

I started low-light imaging 9 years ago with true video CCDs the Wat-120 and 120+. Then the image accumulated within the CCD, which also averaged out random electron noise, but it was sampled continuously at 50 Hz (PAL). Of course the dynamic range was limited to 8-bits, much less than with digital readout.

Then when I searched the forum I found a nice demonstration by Martin Meridith "To stack or not to Stack", which I think shows that there is indeed no difference. The only case where I suppose that stacking can help with noise is when the image is moving over the sensor. Apart from correcting for such movement, stacking might also reduce noise by sampling with different pixels.

I'm not asking anyone to justify stacking. Obviously it's practical, it works, and SL is a nice application. I would just like to know a little more about how stacking is implemented :-)

I agree that there is no difference in stacking vs. not stacking when we are talking about total photons collected as long as you are capturing sufficient dynamic range (less of an issue with low read noise cameras like the ASI224 or 187). But there are some other key differences. Stacking does reduce noise more quickly by averaging but the benefit disappears after a few subs. After stacking a few subs you are just focusing on collecting more photons (this is because the reduction in noise has a inverse square relationship to subs hence most of the gains are achieved with the first 5-7 subs).

I have written my own scripts in Python for stacking, image analysis and lucky imaging which clearly show a reduction in noise/artifacts when I average the subs vs. an equivalent single exposure. The effect disappears with meaningfully longer exposures as the SNR of the the single exposure catches-up. Also the way the math works you need to use floating point and sufficient bit depth for stacking otherwise you lose dynamic range.

But the real benefit of stacking is so obvious that it is easy to ignore. Stacking allows you to use lower quality mounts and achieve high quality results without doing a precise polar alignment or using guiding. Essentially it allows you to collect more photons than what your mount would permit were you not stacking.

I have been imaging for 15 years and even now going beyond 3-5min subs takes a lot of effort wrt to polar alignment, mount quality, guiding, PEC etc. In comparison by stacking short exposures I was able to do 15 min integrations on a Nexstar SE Alt Az mount.

  • Like 2

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.