Test run on the Redcat51

[Adam1234]

My first test run on the Redcat51 (with Canon R6, Optolong L-Pro and EQ6-R Pro). Certainly nothing to write home about by a long shot. Only about half hour of 60s images. I did have about 2 hours, but culled half hours worth because of tracking issues (no guiding), and another hour because of the local power lines through the image. 

At 250mm, I don't think I'll be using this in my garden, way too much light pollution (bortle 8-ish + street lights as my garden faces out into the road), and the short focal length means I can't escape the power lines like I can with my deep sky set up. With my usual deep sky gear, the pixel rejection during stacking sorts out the shadows from the power lines, but I had them in most of the images in this case so it simply didn't work well.

This is one scope I shall be reserving as a travel scope for darker skies. That was always the plan anyway, but I had to test it out at home before going out in the field. Luckily I live close to the New Forest national park anyway. 

With 6.58um pixel size, the Canon R6 probably isn't the ideal camera either as I'm under sampling by quite a bit at about 5.43"/pixel according to astronomy tools so I drizzled 2x which did seem to help with the blocky stars. I do plan on getting another dedicated astro cam with smaller pixel size sometime in the future. 

I do think I need to nail the focus, as stars were more or less ok in the centre but looked a bit pointy around the corners. The direction of the stars I think indicates the back focus wasn't quite right, but I've read that due to the design of the optics, as long as you are in focus, you have the correct back focus, which suggests my focus is slightly off. I find it reasonably difficult to get exact focus with very small movements of the focuser making a huge difference to the focus. 

Anyway. here is said test image, of the Sadr region, with a quick process in PI.  At least I can make out a bit of nebulosity, can even see the crescent nebula in the lower right.

 

 

Adam

Edited July 22, 2022 by Adam1234

[symmetal]

For a full frame sensor I'd say those stars are very good indeed. Being a posted jpg it's hard to say but the slight corner spikeyness is most likely very slight coma It's certainly better than my redcat which has noticeable coma in one corner on an APS-C sensor.

As you mentioned there is no required back focus distance with the redcat, the quoted figure just makes the distance scale on the focus ring read correct, but as long as you are able to go through focus you're fine. 😊

Alan

[Uranium235]

Just a question, have you tired removing that verical banding in the image? (does it calibrate out?) I had a bash at it with noels actions, but it wont shift.

Its one reason why ive avioded the new generation of sensors that have dual pixels for focusing (which this camera has), as they are the cause of this (seemingly unfixable) banding.

[Adam1234]

20 minutes ago, symmetal said:

For a full frame sensor I'd say those stars are very good indeed. Being a posted jpg it's hard to say but the slight corner spikeyness is most likely very slight coma It's certainly better than my redcat which has noticeable coma in one corner on an APS-C sensor.

As you mentioned there is no required back focus distance with the redcat, the quoted figure just makes the distance scale on the focus ring read correct, but as long as you are able to go through focus you're fine. 😊

Alan

That's reassuring,  thanks

[Adam1234]

14 minutes ago, Uranium235 said:

Just a question, have you tired removing that verical banding in the image? (does it calibrate out?) I had a bash at it with noels actions, but it wont shift.

Its one reason why ive avioded the new generation of sensors that have dual pixels for focusing (which this camera has), as they are the cause of this (seemingly unfixable) banding.

No I've not tried to remove it - I'm not entirely sure where it's come from, I need to investigate that. 

I calibrated with bias and flats (flats done an amazing job at getting rid of heavy vignetting which was present without the flats).

[Uranium235]

8 minutes ago, Adam1234 said:

No I've not tried to remove it - I'm not entirely sure where it's come from, I need to investigate that. 

I calibrated with bias and flats (flats done an amazing job at getting rid of heavy vignetting which was present without the flats).

Hmmm yeah you will need to take a look at it at some point. But I dont think it might be the AF pixels now (unles theyre different on your camera) as your banding is different (heaviest in red channel), I found an image that demonstrates the DP issue (from a 750d):

Hope you get it sorted 👍

[Adam1234]

11 hours ago, Uranium235 said:

Its one reason why ive avioded the new generation of sensors that have dual pixels for focusing (which this camera has), as they are the cause of this (seemingly unfixable) banding.

I'm a bit unsure what you mean by dual pixels, how does this work?

[Uranium235]

9 hours ago, Adam1234 said:

I'm a bit unsure what you mean by dual pixels, how does this work?

The auto focus sensor for newer models is located on pixels that serve as imaging and focusing pixels.

https://www.usa.canon.com/internet/portal/us/home/learn/education/topics/article/2018/July/Canon-Autofocus-Series-Dual-Pixel-CMOS-AF-Explained/Canon-Autofocus-Series-Dual-Pixel-CMOS-AF-Explained

The below list is not exhaustive, but the consensus ive read elsewere says they should be avoided for AP in general. Sure, theres a chance you can fix it in processing, but its better that it isnt there in the first place surely?

 

Canon mirrorless cameras with dual pixel autofocus:

1. Canon EOS M100
2. Canon EOS M200
3. Canon EOS M50
4. Canon EOS M6
5. Canon EOS M6 Mark II
6. Canon EOS M5
7. Canon EOS RP (full-frame sensor)
8. Canon EOS R (full-frame sensor)
9. Canon EOS Ra (full-frame sensor)

Canon DSLR cameras with dual pixel autofocus:

1. Canon EOS Rebel SL3 aka Canon EOS 250D aka Canon EOS Kiss X10
2. Canon EOS Rebel SL2 aka Canon EOS 200D aka Canon EOS Kiss X9
3. Canon EOS Rebel T7i aka Canon EOS 800D aka Canon EOS Kiss X9i
4. Canon EOS 77D aka Canon EOS 9000D
5. Canon EOS 70D
6. Canon EOS 80D
7. Canon EOS 90D
8. Canon EOS 7D Mark II
9. Canon EOS 6D Mark II (full-frame sensor)
10. Canon EOS 5D Mark IV (full-frame sensor)
11. Canon EOS-1D X Mark II (full-frame sensor)
12. Canon EOS-1D X Mark III (full-frame sensor)

 

[Ratlet]

The autofocus pixel thing is horizontal lines.  Not sure what that red banding is. 

[Adam1234]

46 minutes ago, Ratlet said:

The autofocus pixel thing is horizontal lines.  Not sure what that red banding is. 

Is it possible it's some effect of light pollution? It probably isn't, but I do have at least 3 streetlights facing into my garden.

I'll try and investigate the raw the images tomorrow and see if it's present in those 

Edited July 23, 2022 by Adam1234