Making a start on M83

[Dave882 (David)]

After doing a full strip and re alignment of the c14 last week it was great to see some clear sky last night to collimate and test things out. Having some weird dramas with the oag for some unknown reason but persisted anyway with the eq8 guiding getting better as things progressed (0.7 down to 0.4 by the end). 180sec subs and no filters.

I decided to live stack for the first 1.5hrs until i hit the meridian and went to bed with the rig continuing on ASIAIR autorun. All subs saved and ready for another go at startools in the coming days. But in the meantime I was pretty happy with what was coming out on the iPhone with only a bit of a push of the contrast and saturation. So excited to get under the stars again so thought I’d share how it’s going.

[atalas]

Hey great effort there Dave a bit of background colour bias balance and you've got one for the pool room.

What camera did you use?

when you shoot Live Stack what format does It save files in?

Also, what programs do you use for pre processing and post processing?

C14 eh.....that will be testing your skills!

I was out last night too shooting M104, and although the seeing wasn't great It was still good to be under the stars again for a few of hours.

[Dave882 (David)]

Hey thanks Louie- yeah thanks for pointing that out just realised how bad that colour balance was and did a v2 with another tweak. I’m using the asi2600mc but still struggling to get my flats right so having to crop quite a bit. The c14 is certainly a challenge but I’m really loving the long fl stuff so hoping to get some more galaxies over the next months.

I’m doing all the capture and stacking in the ASIAIR pro and while it is saving individual subs as FITS the live stack is just saved as a JPEG to the phone. I just do some simple edits in photoshop express on the phone while the process continues or I move to another target - It’s just a bit of fun a as love watching and playing with the image as it builds. My version of eaa I guess.

Since that live stack was finished I’ve got another 3-4hrs of data when I went to bed I haven’t even had time to look at yet. I’m hoping it’s ok and will add to this image for some proper post processing.

Cheers mate

[atalas]

Ah ok, just looked up the specs on your camera and they are impressive and full 16 bit with 80% QE coming from a OSC! maybe you'd expect that from back illuminated I would imagine.

The long focal length and narrow field should help with the LP skies that we have here in Padstow for sure but I must say that those small pixels aren't ideal for this focal length......but hey rules are made to be broken.

With your flats try about a 20,000-25,000 adu (max value not average)and make sure you didn't get a focus shift through the session or, there's no stray light getting to your sensor.

Also with a low noise OSC try just using bias frames and no darks and also a defect map.....ie, subtract a bias from your flat master, and a bias from your stacked lights instead of the dark and see how that goes.

To get a balanced background look at your histogram on the left hand side and just line up the RGB black points.

For best results work on raw files but I'm sure your aware of that anyway.....like you said....just having some fun.

Anyway all good Dave just have fun

[Anth10 (Anthony M)]

Looking the goods Dave.
You must be super excited with this taking shape. Nice rich colours and plenty of detail to work with.
Great stuff.
Anthony

[Dave882 (David)]

Thanks Anthony- yes while it’s a bit of a beast that I’m still learning to tame I’m a real fan of the long fl captures and super keen to hone my skills. Even with 8 & 10” scts I’ve never seen such colour revealed on the live stack even before any processing is completed. Can’t wait for planet season!

Louie- I really appreciate your insights there mate. It’s been a bit of a process trying to get the calibration frames right and now it seems to be over correcting in the corners so definitely need to keep try some different values. I had it pretty much perfect when I had the asi294mc but now it’s like I’m learning all over again!!
It’s REALLY hard to prevent focus shift during the session with the c14. This is a huge difference I’ve noticed between this and my 8”. I’ve got mirror locks installed but the drop in temperature is what I’ve noticed can really shift things. I’ve now insulated the tube that has made things much better but I think about every 45-60min it still needs a tweak.

[Dave882 (David)]

Well… it’s been a bit of a while but following on from the initial 1.5hr livestacked data I still had an additional 3.5 hrs of data while the rig ran into the night () There was definitely some focus shift into the wee hours and some weird thing must have happened for some unknown reason ASIAIR shifted the entire image fov off centre with about an hour to go…

Anyways- after having many frustrations with dss I managed some success stacking in APP with the added bonus of gradient reduction and a cool little feature called star colour correction. I’m actually really stoked with how this is turning out and will try run the linear fit file through startools to see if I can get any better result.

So here’s where it’s up to now- with a total of 4hrs data (was aggressive on the quality rating to try and mitigate bad frames but in hindsight probably not warranted). I’m actually pretty happy with just a 10% stretch & very slight push on the saturation/sharp slider and of course a crop due to the random fov change.

Would appreciate any comments or areas for improvement! Cheers

Here's the larger image

[sil (Steve)]

Thats a beaut. Only suggestion is the stars are a little soft, but then they always are of course. Nothing here to be disappointed about mate.

[Dave882 (David)]

Thanks Steve. Yes I agree- I didn’t do any masking or advanced processing yet so still a little soft and a bit eggy here and there. I think there may be some tools in APP and also Startools to help with this and will be my next step if I can work it out. But without an eaf a bit of softness may be unavoidable I suspect but for galaxy work perhaps not as bad as if I were capturing vast star fields. Very much appreciate your comments. Thanks

[atalas]

Good work Dave......nice detail in the core revealed, some faint galaxies in the background popping through, good colour, and well a balanced background....quite a feat in Padstow skies

One small critique..... bit darker background would be better for contrast I think.

[Dave882 (David)]

Originally Posted by atalas

Good work Dave......nice detail in the core revealed, some faint galaxies in the background popping through, good colour, and well a balanced background....quite a feat in Padstow skies

One small critique..... bit darker background would be better for contrast I think.

Thanks Louie- yes I agree with you the background could be a bit darker and have since made a few tweaks in PS which bring a bit of improvement. APP makes it extremely difficult to finetune these details so was only doing very rough adjustment. I find it very difficult to settle on a background darkness as every screen I look at it displays a bit different.

Regarding the Padstow skies- while it’s B6/7, looking SE TO NW is a bit darker so can still get some results. With the c14 I’ve found it near impossible to image any galaxies to the NE due to the Sydney light dome so I’m just learning to pick my targets.

[Startrek (Martin)]

Dave
Excellent M83
Detail and colour spot on
You’ve got that big scope dialed in well
After exhaustive testing with my 2600MC I found Bias frames calibrated with my Flats works best
I’ve tried Dark flats , Darks you name it and Bias works best with and without filters and under different sky conditions
I use an ADU target of 21,000 in APT to get my histogram up to 1/2 way ( not overexposed ) ADU read out range is around 8,500 to 31,500
Without filters Flats are usually 0.2 to 0.5 sec
With an L Extreme filter Flats are usually 7 sec to 13 sec
Bias frames are taken with an exposure of 0.000032 , the lowest setting for this camera
I take 40 to 50 Flats and 50 to 70
Bias
I don’t use Master Flats or Master Bias

Well done !!
Martin

[Dave882 (David)]

Hi Martin thanks for your reply. I actually learned a lot from your previous thread on asi2600mc calibrations and yes although I’m not sure I’ve got it fully “dialed in” yet but it’s getting much better! I very much appreciate the trial and error you did on this.