Horsehead & Flame in LRGB

[Budgie1]

So, I got a chance to use my newly acquired L-eXtreme filter on my ASI294 MC Pro this week.

On Thursday night I got 29 x 120s usable subs of the Horsehead & Flame with a UV/IR cut filter on the camera.  Friday was also clear so I thought I'd try out the L-eXtreme filter to see what it would give me on the same target and got 23 x 120s subs with it. I stacked the first nights subs, then the L-eXtreme subs and finally stacked them all together. What came out of the full stack wasn't too bad after processing but Alnitak was blown out and I really didn't like it. So I did a bit of searching and figured out how to do a version of LRGB in PixInsight.

I took the stacked image from the first night and extracted the RGB channels, then did the same with the stacked image from the second night. I ditched the G & B channels from the second set to leave the R, which I used as a Luminance layer. Used StarAlignment tool on the luminance layer to correct a slight misalignment and cropped all four channels to the same size before using LRGBCombination to put them back together.

It worked quite well and reduced Alnitak nicely, as well as bringing out the detail in the Ha cloud in the Horsehead.

It's a bit noisy and using the luminance has reduced NGC2023 down quite a bit as well, but I can live with that for a first attempt at this process.  

The first image below is the LRGB version, the second is the first evening's subs with only the UV/IR cut filter.

C&C's very welcome on this one as it's a new way of processing for me, so happy to  learn.

[Padraig]

Their both great, the LRGB really makes nebulosity sand out. I’m trying to decide to get one of these asi294’s but there are a few horror stories with taking flats.
But after looking at your images , I think I take the plunge.
Have you tried the L extreme on moon lite nights, would be interesting to know how effective it is to get the most out of clear sky. 
Sorry , I can’t add any advice, but your images are great and thanks for sharing. 👌 Very inspiring. 

[Budgie1]

If, like me, you're changing from a DSLR to OSC then it will take time to get used to it because it's a different way of working, including making the flats and dark flats.

You will see amp glow in the subs, but they calibrate out with the darks and I don't use Bias calibration frames as I found they only added issues with the amp glow showing in the stacked images, so I just use Darks, Flats & Dark Flats (or flat darks, whichever way you want to say it ).

The more time you can put into the getting the subs, the cleaner the image and if/when you get an ASI294MC don't worry about the strong green cast on the stacked image. It's a trait of the camera sensor but does come out in post processing.

As for the L-eXtreme, this was it's first outing with me and I'm quite pleased with the results. I just have to wait for a fuller Moon to see what it can do, which is why I bought it. I live in a Bortle 2 area so the full Moon seems stronger with the low LP and I haven't bothered with nebula during a the full Moon period up to now, tending to go for galaxies instead as I can use shorter exposures.

Good luck if you decide to get an ASI294MC, let us know how you get on.

[Padraig]

Will do , thanks Martin 

 

[Paul M]

2 very nice Horses! I'd be super pleased with either.

TBH, I quite like Alnitak in all it's glory. In fact, before it's banned, I might organise a march on Downing St. to protest about overuse of star removal apps

Having said that, aesthetically, image 1 looks much nicer but image 2 just shows that star in the Horse's mane, which always scores points with me!

[Jamgood]

Very nice.

I've got the ASI294MC Pro arriving tomorrow. Looking forward to having a play around with it.  👍

[Padraig]

Hopefully you’ll get some clear sky’s, looking forward to seen some great images …no pressure 😀

[Budgie1]

17 minutes ago, Paul M said:

2 very nice Horses! I'd be super pleased with either.

TBH, I quite like Alnitak in all it's glory. In fact, before it's banned, I might organise a march on Downing St. to protest about overuse of star removal apps

Having said that, aesthetically, image 1 looks much nicer but image 2 just shows that star in the Horse's mane, which always scores points with me!

I know what you mean, Paul. I normally go with what the camera sees, with maybe a some star reduction if they over-power the intended target.

This was more of an experiment because I got the L-eXtreme filter so I could still image nebulas under a full or near full Moon, then use the Ha as a luminance layer to add to the unfiltered version. With some more playing with PixInsight, I may be able to produce a happy medium and keep the detail NGC2023 and the star in the mane.

[Budgie1]

7 minutes ago, Jamgood said:

Very nice.

I've got the ASI294MC Pro arriving tomorrow. Looking forward to having a play around with it.  👍

Nice, you'll enjoy it. The images are so much cleaner than the DSLR and the detail is clearer.

If it comes with clouds then use that time to create a Darks library. I set it up in APT to do 40 images at each of the exposure lengths I'm most likely to use and I just keep it at unity gain (120) and cooled to -10°C for everything. I now have a library of Master Darks for 45, 60, 90, 120, 180, 240, 300 and 360 seconds.

[Jamgood]

37 minutes ago, Budgie1 said:

Nice, you'll enjoy it. The images are so much cleaner than the DSLR and the detail is clearer.

If it comes with clouds then use that time to create a Darks library. I set it up in APT to do 40 images at each of the exposure lengths I'm most likely to use and I just keep it at unity gain (120) and cooled to -10°C for everything. I now have a library of Master Darks for 45, 60, 90, 120, 180, 240, 300 and 360 seconds.

Yeah, getting my dark library set up is on the list. (plenty of cloudy nights ahead to get them done, I'm sure.)  I've sorted my power box out today and I also have a Pegasus Power Box Advanced coming. So I have fixings, cable management, balancing, etc to sort out. Looking forward to having a play with some new toys.

[Jamgood]

@Budgie1 Can I pick your brains on taking Flats?

What ADU do you use? Do you use the white t-shirt/sky method?

Before with a DSLR I've just put a ipad thing over the scope with a white screen and shot in AV and it flats were fine. Tried this with the 294MC last night and no matter what settings I tried in APT the flats, although they looked OK, didn't work or over corrected and left me really bad vignetting in the stack. 

I'm stumped! Going to try the t-shirt/sky method later.

[Budgie1]

I think aimed at an ADU of 25000 (I found that figure on a thread on CloudyNights forum) with four layers of t-shirt over it and pointed at a blank Word document on my PC screen. 

The exposure was 0.03332s in the end but try a search for "ASI294MC Flats" and have a read of some of the forum results.

I need to do a new set of flats & dark-flats because I had it all apart last night to fit a new focuser, so I cleaned the lenses at the same time and fitted my flattener, instead of the SW reducer/flattener.

[Jamgood]

I started with ADU 25000 which I also read was optimal for this camera.  I tried very different scale of brightness and have been getting between 1s and 12s results. All the flats I've taken look fine but just don't seen to work. 

Stacking in DSS, the preview looks fine. Start stretching in Photoshop and there's just terrible vignetting. (There is some vignetting in the light frames but you would expect the flats to remove that) Not sure if it's a setting in DSS that's not right or what. I'm stumped.

[Budgie1]

So, I've done a bit more reading up on this tonight but won't be able to try it until I can get some subs because I need to focus the camera with the new focuser.

It seems an ADU of 25000 - 30000 is ideal for this camera, but I also saw someone was using 22000, and an exposure time of 3-4 seconds. So this may require the t-shirt and a couple of sheets of paper over the end of the scope so the image isn't saturated. The peak on the histogram should be about a 1/3 to 1/2 way from the left.

I normally take 40 flats and 40 darflats for stacking into a master of each.

Also, make sure these are not debayered when you stack them in DSS, they should be if you're loading them as flats or dark flats but worth mentioning.

It may also be worth posting something in the Discussion - Cameras section of SGL and see what others have done or can suggest. Like you, I'm still relatively new to the ASI294MC so experience is not on our side.

[Jamgood]

I've tried loads of different ADUs from 10000 to 35000. APT has produced Flats from 0.3s to 12s long with different methods from T-Shirt cover through to paper on an ipad. They all look the same and look like decent flats but I just can't get them to work, with DSS anyway. I've changed and tried every setting in DSS to see if it is something stupid I'm missing.

Going to try SiRiL and see if that fairs any better. 

After a couple of stretches I currently get this. Pants!

[Jamgood]

@Budgie1 Out of interest, are you using the Ascom or the native driver for the camera?

[Budgie1]

16 minutes ago, Jamgood said:

@Budgie1 Out of interest, are you using the Ascom or the native driver for the camera?

I'm using the ZWO drivers for it.

[Jamgood]

Hmmm. Maybe that has something to do with my issue then. I saw it recommend to use the ASCOM Driver and selecting Asi Camera 1 to connect but have just read about someone else having similar issues with ASCOM. 

I'll investigate further.

[Jamgood]

 

This was the interesting post about ASCOM vs Native Drivers.

http://forum.orpington-astronomy.org.uk/index.php?topic=11623.0

[Budgie1]

In APT I choose the ZWO Camera option, then choose camera 1 or 2 as I have a ZWO ASI120MM Mini as the guide camera.

I've also been looking at DSS tonight and discovered something I didn't try before. I've always had a green case over the stacked image, tonight I went into the Stacking Parameter settings > Lights tab > RGB Channels Background Calibration > Options > Calibration Method is set to "Rational" and RGB Background Calibration is set to "Minimum" (it was set to "None"). I then re-ran a stack and no green cast any more!

I don't know if it'll help with your issue, but maybe worth taking a look.

I'll have a read through that  now. 

[Budgie1]

I've had a read through.

I've always only used the ZWO drivers, so don't have a comparison with the ASCOM drivers.

The only other things I can add is that all my images are taken at 120 gain and an offset of 8. I have never touched the offset as I read somewhere that this is now fixed by the ZWO drivers and I've not found anywhere in APT to change it. The setting still shows in the APT progress log, along with the temperature, but I've not bothered with it apart form that.

[Jamgood]

Cheers. That gives me something to work with.

There is definitely some difference between the drivers at the same settings. Here's an example two darks, same temperature (-10) 120 Gain 30 Offset. The ASCOM Driver defaults to 30 Offset. Maybe that is part of my issue.

ASCOM

ZWO