Preliminary data on Abell 2218 lensing 167 hours

[dan_adi]

I've manage to capture some RGB data for the Abell 2218 project. The R was replaced with NIR because I already had the data from last year.

Specs:

• Scope: CFF 8 inch refractor 
• Mount: Mesu 200
• Astrodon L filter: 100 hours, bin 1, -10C, 300 sec
• Astrodon B filter: 20 hours, bin 1, -10C, 300 sec
• Astrodon G filter:20 hours, bin 1, -10C, 300 sec
• Astrodon NIR filter:27 hours, bin 1, -10C, 900 sec
• Original image scale: 0.93"/pixel
• Data was drizzled 2x
• Software: Prism Observatory Control v.11. Pixinsight 1.8.9-1

Total exposure time: 167 hours during 2021,2022,2023.

This is my first astro LRGB image so my processing skills are at sub - newb level. I think are need more color data, probably because luminance has 100 hours vs 20 hours per RGB .... 

I added 3 images:

1. The whole wide field shot. 
2. Center crop
3. Magnitude vs log10(SNR) chart, to see how deep I could go.

Identifiable arcs: ARC 359 (R mag = 21.4), ARC 384 (R mag=21.68), ARC 289 (R mag = 21.67), ARC 730 (R mag =21.93)

Quick reference source: The system of arcs in the cluster of galaxies Abell 2218

Magnitude reach at 167 hours: object with mag=25.148 SNR=3.482

Some overall impressions:

• I think I need more colour data. Probably the amount of hours in Luminance washes out the colours ... 
• Definitely need to take my time to learn processing!
• Probably the longest exposure done with an 8 inch scope of this region?

the best image with a 12 inch scope I found on Astrobin by Morten C. : Abell2218 - 67 hours

Thanks for looking!

Final_LRGB-2.tif Final_LRGB.tif

[Elp]

Maybe better if you post it as a jpeg or PNG?

[dan_adi]

7 minutes ago, Elp said:

Maybe better if you post it as a jpeg or PNG?

Sure

[WolfieGlos]

How many hours? That’s dedication, and a great result!

[dan_adi]

16 minutes ago, WolfieGlos said:

How many hours? That’s dedication, and a great result!

Thanks, I still need to practice processing ... the image can be improved

[ONIKKINEN]

Superb, just love deep fields like this.

[dan_adi]

I played around with PI and got a little bit better result. This is a crop at native resolution without drizzle.

[windjammer]

That is competitive with Morten!  A heroic crop from the full frame!  Very interesting pic.  If you have PI it would be worth trying the plate  solver (scripts->image analysis->image solver) and annotate (scripts->render->annotate image) scripts. The image solved image has data embedded into it that enables 'annotate' to label all the galaxies in the field, draw the RA/Dec grid etc.  Side by side with the original pic it can be very interesting.

Simon

[dan_adi]

On 15/07/2023 at 22:14, windjammer said:

That is competitive with Morten!  A heroic crop from the full frame!  Very interesting pic.  If you have PI it would be worth trying the plate  solver (scripts->image analysis->image solver) and annotate (scripts->render->annotate image) scripts. The image solved image has data embedded into it that enables 'annotate' to label all the galaxies in the field, draw the RA/Dec grid etc.  Side by side with the original pic it can be very interesting.

Simon

Thank you for the kind words. Indeed my inspiration was from Mortens work. He did it with a slightly bigger scope and better skies, but after doing the math I saw it was possible with an 8 inch scope too.

I continued gathering data these last few days, and I am at 130-ish hours in Luminance. So I am approaching the 200 h total time. 

I have refined the calibration process and got rid of some residual dust motes and other artefacts. As a first step I sorted the bias and dark frames according to year, by introducing another keyword for WBPP (I didn't know I can use multiple keywords for WBPP). This way each set of darks and biases can be assigned for the specific season.

The resulting Luminance master is much cleaner now. For the colour masters, making a synthetic flat did a wonderful job. Once I introduced a new keyword, I had to rename all fits files, around 3000 of them :)) and that was no fun, but necessary.

Another hiccup was that StarXterminator was removing the arcs and small galaxies in the centre, so I couldn't process the cluster core separately from the stars. I've found I can spare the centre region by applying the GAME script mask and invert it.

It is still a work in progress, most likely I will finish next galaxy season, depending on how the weather cooperates. I am aiming at 200 hours for the Luminance and maybe a bit more colour wouldn't hurt either. Overall, I'll end up with a 300 hour exposure time picture, kind of an amateur deep field of that region :).

I am confident the image can be much improved as I learn more and more about processing in PI.

 

Edited July 20, 2023 by dan_adi