7 replies to this topic

[sHighlander]

I started imaging with Canon 600D/T3i  a couple of months ago from a dark site about 20 minutes drive away, with some good results. Recently I purchased a CLS CCD filter and tried a few shots at NGC 281 Pacman from my bortle 6 home location but after processing in DSS resulting stacked tif image is saturated in green colour which I found very hard to remove. 

 

Is there a good tutorial/book about post processing images taken in heavy LP.  Thank you in advance

[bobzeq25]

I started imaging with Canon 600D/T3i  a couple of months ago from a dark site about 20 minutes drive away, with some good results. Recently I purchased a CLS CCD filter and tried a few shots at NGC 281 Pacman from my bortle 6 home location but after processing in DSS resulting stacked tif image is saturated in green colour which I found very hard to remove. 

 

Is there a good tutorial/book about post processing images taken in heavy LP.  Thank you in advance

The CLS is notorious for doing this.  The underlying reason is that it removes a large chunk of the spectrum, which _really_ makes getting good color difficult.  I gave up on it, one gathers dust on my shelf.

 

People like instruction manuals.  Unfortunately, DSO astrophotography does not lend itself to that.  Too complex, one has to adapt to many situations, different equipment.

 

Tips on processing/imaging in light polluted skies.  Mine are Red Zone, Bortle 7, mag per arc sec squared.  My astrobin shows what I've done there, all but 2 DSO images came from my backyard.

 

General thing.  More data is better.  Longer total imaging times.  More photons.  Faster optics help a lot, consider getting a reducer if you don't have one, consider faster optics in your next scope.

 

Specific.  Learn how to use gradient reduction well.  Light pollution is a gradient, more at the horizon, less overhead.  Astro Pixel Processor has an excellent gradient reduction tool that's relatively easy to use.  There are others.

 

If your DSLR is modified.  Imaging emission nebulae with a duoband filter works well.  If the DSLR is not modified, the filter is useless.  Consider getting an astro specific camera.

 

I try to never image below 45 degrees altitude.

 

Imaging from light polluted skies is neither easy nor cheap (both time and money).  I get a great deal of satisfaction impressing my friends with what I can do from there.  I spend a lot of time and some money (not a fortune, not just a little) to do that.  The time is spent on research, learning, experimenting, and imaging.

 

The pretty pictures do not come easy.  <smile>

Edited by bobzeq25, 24 January 2023 - 10:17 AM.

[jml79]

Download Siril (free), load your stack, use the "background extraction" tool, "photometric colour calibration" and then "remove green noise". It should help get you started. When using BGE, make sure there are no stars in any of the little squares and often less is more as in fewer well placed squares (truly dark sections of the photo) can be better. Check youtube and the wiki for instructions on each tool. Then export the tif and treat it to star removal or whatever your normal process is.

 

The heavy green tint isn't always from light pollution but it can be. Just using a filter can cause the heavy green tint and there are lots of ways to remove it. I have found processing to be a bigger learning curve than capture. To me, getting the data feels easy but each image presents a processing challenge. Bortle 6 isn't to bad. I have even shot images without any filters from my B 5/6 backyard and they have turned out well (Andromeda in my gallery) but took a lot of learning to process. 

Edited by jml79, 24 January 2023 - 10:46 AM.

[sHighlander]

Thank you guys. I will download Siril and test it tonight. I like the challenge. There is a lot to learn, so I'll keep reading and experimenting. I have one Canon 600D and one T3i. I bought T3i with the intention of modifying it.

 

I am thinking of buying a dedicated astro colour camera. I guess it will pick up more signal, but the noise will be amplified in equal measure?

[bobzeq25]

Thank you guys. I will download Siril and test it tonight. I like the challenge. There is a lot to learn, so I'll keep reading and experimenting. I have one Canon 600D and one T3i. I bought T3i with the intention of modifying it.

 

I am thinking of buying a dedicated astro colour camera. I guess it will pick up more signal, but the noise will be amplified in equal measure?

No.  One factor is the cooling (getting uncooled to save a few hundred dollars is a bad idea).  Another is that, if you choose properly, the sensor will be far newer, with significantly better technology.  Add in the fact that it won't need to be modified, and you can see why CMOS cameras have pretty much taken over, with DSLRs only for people with low budgets, or who want to use a camera lens easily (though there are adapters to mate a Canon or Nikon camera lens to the 533, below.

 

An obvious choice is that 533MC.  Cooled, modern sensor.  $800.  People find them really easy to use (as opposed to older cameras like the 294).

 

https://astronomy-im...533mc-pro-color

 

Somewhat smaller chip than a DSLR, less field of view.  But the equivalent camera with an APS-c chip, the 2600 (I have both of those, great cameras) is $1800.

 

Other point.  Filters can work really well on emission nebulae (which I use them for), but not so good on other targets.

Edited by bobzeq25, 25 January 2023 - 12:10 AM.

[sHighlander]

Excellent Bob, thank you. That will be my next investment. @jml79 Siril looks awesome, I watched a really good tutorial how to use it plus refine in Photoshop. I am going to run the process on some imaging data I gathered.

 

Thank you guys.

Edited by sHighlander, 25 January 2023 - 05:53 AM.

[jml79]

I can't wait to see the result. Like I said, processing has been the hard part to learn for me. It has taken months to get slightly competent and then I am constantly reminded how much I have left to learn. Keep at it.

[sHighlander]

I can't wait to see the result. Like I said, processing has been the hard part to learn for me. It has taken months to get slightly competent and then I am constantly reminded how much I have left to learn. Keep at it.

The images are in my galery, for basic processing, Pleiades
 

There is one image  processed by Deep Sky Stacker  + Photoshop

 

The second is processed by Siril - stretching, photometric colour calibration  and background darkened in Photoshop

 

 

Siril wins for me hands down. It can render true colours by looking up photometric data, which is a big deal for me.

Altair Astro Starwave 80 ED, 1 hour total, 60 subs.

Canon 600D unmodified, from Bortle 3 No filters

SW EQM 35, SynScan 3 star alignment and SynScan Polar alignment no guiding