Preliminary data on ABELL 2218 lensing ~ 100h exposure time

[dan_adi]

Two years ago I wanted to see if I can confirm gravitational lensing in the cluster ABELL 2218 using a small aperture 8 inch apochromatic refractor.

This is a preliminary result, composed of luminance and near infrared data.

As a side project I wrote a little webapp for computing exposure time, since I had no idea how much I should expose for such faint targets, especially in my backyard. To make matters worse, I live at sea level  

 

Next summer, I will add an estimated 20hours per RGB channel, for a total exposure time of 160 hours.

I was pleasantly surprised to capture some of the arcs, so all the work paid off.

The image is a widefield view with lots of other interesting galaxies. You will have to zoom in to reach the cluster. I also attached the hubble image for comparison and easier arc identification. 

 

Specs:

•  Telescope: CFF 8 inch apochromatic refractor
•  Mount: Mesu 200 MK1
• Camera: Moravian G3 16200 mono CCD
• Filters: Astrodon Luminance, Astrodon Ic (NiR)
• Luminance: 81 hours
• NIR: 27 hours
• Data was drizzled

I only made minimal processing PI: Crop,  automatic background extraction, noise reduction and blur exterminator (works awesome).

Data on some ARCs using Planck 2018 cosmology:

The whole cluster is located at 2.3 Glyrs, with a redshift of 0.1704

ARC A

•  Redshift = 2.515
•  Proper distance (at light emission  or  “then”) = 5.553 Glyr (Billion light years)
•  Proper distance (at light arrival or “now”) = 19.520 Glyr (Billion light years)
•  Light travel time = 11.191 Gyr (Billion years)
•  Velocity = 434267.523 km/sec or 1.448 x c
•  Currently the galaxy is outside the event horizon, so light emitted now will never reach us again
• Vmag = 22.35

ARC L

• Redshift = 1.033
• Proper distance (at light emission  or  “then”) = 5.578 Glyr (Billion light years)
• Proper distance (at light arrival or “now”) = 11.340 Glyr (Billion light years)
• Light travel time = 8.067 Gyr (Billion years)
• Velocity = 210330.975km/sec or 0.701 x c
• Vmag = 20.25

ARC H

• Redshift = 0.702
• Proper distance (at light emission  or  “then”) = 4.954 Glyr (Billion light years)
• Proper distance (at light arrival or “now”) = 8.432 Glyr (Billion light years)
• Light travel time = 6.501 Gyr (Billion years)
• Velocity = 153231.638km/sec or 0.551 x c

[vlaiv]

15 minutes ago, dan_adi said:

Two years ago I wanted to see if I can confirm gravitational lensing in the cluster ABELL 2218 using a small aperture 8 inch apochromatic refractor.

Oh, I just love this part (note my emphasis in bold)

 

[dan_adi]

4 minutes ago, vlaiv said:

Oh, I just love this part (note my emphasis in bold)

 

😃  it's small and big at the same time, depends on your perspective ... but it does take 2 people to safely mount it

[tomato]

Brilliant result, I admire your dedication, clearly I was being hopelessly optimistic trying to capture the gravitational lenses on Abell 370 with 6 hrs on a 6” refractor.

Alas, an 8” CFF APO would seriously distort my wallet.☺️

[SiriusDoggy]

Wow! 100hrs. That's dedication.

[dan_adi]

1 hour ago, tomato said:

Brilliant result, I admire your dedication, clearly I was being hopelessly optimistic trying to capture the gravitational lenses on Abell 370 with 6 hrs on a 6” refractor.

Alas, an 8” CFF APO would seriously distort my wallet.☺️

Thank you! Abell 370 seems to be about twice as far as Abell 2218, with z = 0.375. But the main arc seems rather big compared to the ones in 2218. So it might be doable ... if I can find some info on the magnitude of the arc, I can crunch the numbers. 

I am anxiously waiting for next galaxy season  to add the RGB data!

My inspiration was the effort of Morten here https://www.astrobin.com/344564/?q=Astrodon E-series 2 B , and the image from Mauna Kea http://sky.esa.int/?target=248.9765671854323766.1993560685588&hips=DSS2+color&fov=0.20099604102438107&cooframe=J2000&sci=false&lang=en&hst_image=heic0404c

He used a 12 inch scope, with better seeing, and 65 hours. But I think I am very close to his performance.

Edited December 21, 2022 by dan_adi

[dan_adi]

55 minutes ago, SiriusDoggy said:

Wow! 100hrs. That's dedication.

Thanks. Still not done yet ... need the RGB data, and to learn more about processing 🙂

[tomato]

Thank you for the link to Morten’s marvellous image on Astrobin, I will certainly have a go at this object in the coming galaxy season.

[dan_adi]

9 hours ago, tomato said:

Thank you for the link to Morten’s marvellous image on Astrobin, I will certainly have a go at this object in the coming galaxy season.

You're welcome, 

In my search of an amateur shot of this object, Morten's image was the best. He benefited greatly from better seeing and a bigger scope. His image contains subs with fwhm <2.5, but in my case I had to go with  subs  <3fwhm otherwise too much data would have been tossed. In my Luminance image, PI reports a median fwhm of 2.6 and an eccentricity of 0.43. 

Edited December 22, 2022 by dan_adi

[dan_adi]

Thanks for all the likes, happy holidays everyone!

[ollypenrice]

Super project - and successful.

Olly

[Adam J]

On 21/12/2022 at 18:06, dan_adi said:

Two years ago I wanted to see if I can confirm gravitational lensing in the cluster ABELL 2218 using a small aperture 8 inch apochromatic refractor.

This is a preliminary result, composed of luminance and near infrared data.

As a side project I wrote a little webapp for computing exposure time, since I had no idea how much I should expose for such faint targets, especially in my backyard. To make matters worse, I live at sea level  

 

Next summer, I will add an estimated 20hours per RGB channel, for a total exposure time of 160 hours.

I was pleasantly surprised to capture some of the arcs, so all the work paid off.

The image is a widefield view with lots of other interesting galaxies. You will have to zoom in to reach the cluster. I also attached the hubble image for comparison and easier arc identification. 

 

Specs:

•  Telescope: CFF 8 inch apochromatic refractor
•  Mount: Mesu 200 MK1
• Camera: Moravian G3 16200 mono CCD
• Filters: Astrodon Luminance, Astrodon Ic (NiR)
• Luminance: 81 hours
• NIR: 27 hours
• Data was drizzled

I only made minimal processing PI: Crop,  automatic background extraction, noise reduction and blur exterminator (works awesome).

Data on some ARCs using Planck 2018 cosmology:

The whole cluster is located at 2.3 Glyrs, with a redshift of 0.1704

ARC A

•  Redshift = 2.515
•  Proper distance (at light emission  or  “then”) = 5.553 Glyr (Billion light years)
•  Proper distance (at light arrival or “now”) = 19.520 Glyr (Billion light years)
•  Light travel time = 11.191 Gyr (Billion years)
•  Velocity = 434267.523 km/sec or 1.448 x c
•  Currently the galaxy is outside the event horizon, so light emitted now will never reach us again
• Vmag = 22.35

ARC L

• Redshift = 1.033
• Proper distance (at light emission  or  “then”) = 5.578 Glyr (Billion light years)
• Proper distance (at light arrival or “now”) = 11.340 Glyr (Billion light years)
• Light travel time = 8.067 Gyr (Billion years)
• Velocity = 210330.975km/sec or 0.701 x c
• Vmag = 20.25

ARC H

• Redshift = 0.702
• Proper distance (at light emission  or  “then”) = 4.954 Glyr (Billion light years)
• Proper distance (at light arrival or “now”) = 8.432 Glyr (Billion light years)
• Light travel time = 6.501 Gyr (Billion years)
• Velocity = 153231.638km/sec or 0.551 x c

impressive dedication to a facinating project.