Changing camera to smaller pixels.

[tooth_dr]

If I wanted to get the most out of my current scopes, I was thinking that I may need to change my current camera - Kodak KAF8300 with a 5.4um pixel size.

 

Scopes: Tak Epsilon 180ED - 500mm F2.8 + SW 250px - 1200mm F4.7

With the 180ed this gives me a resolution of 2.23"/px, and the 250px I get 0.93"/px

 

If I changed to a camera with 3.69um pixels I would get a resolution with the Tak of 1.52"/px, and if I binned 2x2 with the 250px I would be on 1.26"/px

 

What do you think about this?  Are there other factors to consider?  Would it be worth it overall?

 

Thanks

Adam.

 

[WanderingEye]

I don’t see anything wrong with your current set up to be honest, they are both more than doable with those pixel scales...one thing to consider is the slight loss in sensitivity if you change...would it be to a CMOS or CCD camera of you change...? . 👍😀

Edited January 20, 2020 by WanderingEye

[vlaiv]

2.23"/px is very good working resolution for wide field setup.

0.93"/px is indeed too high resolution, even for 10" scope.

I would say that you need to find a sensor that will keep current FOV or expand it and improve things on read noise and QE "front" in order for that to be viable swap.

Alternative would be to just fix newtonian in terms of sampling rate to make it better suited. This could probably be less costly affair than going for different camera.

You have mentioned 3.69um pixels, are you looking at ICX814 sensor? You will be loosing too much of FOV with 16mm diagonal.

Do have a look at this instead:

https://www.teleskop-express.de/shop/product_info.php/info/p4685_ASA-2-inch-Newton-Coma-Corrector-and-0-73x-Reducer-for-Astrophotography.html

that would make 1.28"/px - much better sampling rate for high resolution work.

 

[tooth_dr]

9 minutes ago, WanderingEye said:

I don’t see anything wrong with your current set up to be honest, they are both more than doable with those pixel scales...one thing to consider is the slight loss in sensitivity if you change...would it be to a CMOS or CCD camera of you change...? . 👍😀

I really think I want to go CCD again, adding gain settings isnt something I can be bothered with, nor the ampglow or calibration issues, nor the large number of files captured per night!

My current camera has a quantum efficiency as follows - Red 33% Green 40%, Blue 33%.  The sony chips seem double that.

 

[tooth_dr]

5 minutes ago, vlaiv said:

2.23"/px is very good working resolution for wide field setup.

0.93"/px is indeed too high resolution, even for 10" scope.

I would say that you need to find a sensor that will keep current FOV or expand it and improve things on read noise and QE "front" in order for that to be viable swap.

Alternative would be to just fix newtonian in terms of sampling rate to make it better suited. This could probably be less costly affair than going for different camera.

You have mentioned 3.69um pixels, are you looking at ICX814 sensor? You will be loosing too much of FOV with 16mm diagonal.

Do have a look at this instead:

https://www.teleskop-express.de/shop/product_info.php/info/p4685_ASA-2-inch-Newton-Coma-Corrector-and-0-73x-Reducer-for-Astrophotography.html

that would make 1.28"/px - much better sampling rate for high resolution work.

 

See I thought that 2.23 was in the realm over oversampling and I wanted to aim for half of that?

[vlaiv]

11 minutes ago, tooth_dr said:

See I thought that 2.23 was in the realm over oversampling and I wanted to aim for half of that?

Depends really on telescope that you are using. Something like 70-80mm of aperture in regular seeing - and you are right where you want to be with ~2"/px.

2.23"/px is ideal sampling rate for FWHM of about 3.5". 80mm of aperture has airy disk diameter of 3.21" - add to that a bit of guiding error and a bit of seeing and you can easily get to 3.5" FWHM (FWHM corresponding to airy disk diameter of 3.21" is less than 2" but again - add those influences and you are easily back over 3").

Don't know what sort of spot diagram has TAK Epsilon180 - I would not be surprised that it is perfect given that it is TAK after all, but that scope is fast wide field astrograph and less than perfect spot diagram will certainly be acceptable as such scope is used for wide field and inherently low sampling rate.

When you think about it, what would you say that you would consider to be wide field image? I would put it somewhere above 2-3 degrees of FOV, right? Now couple that with modern sensor that has 4000-5000 pixels in width - what sort of resolution can you expect with such combination?

2-3 degrees = 120-180 arc minutes = 7200" - 10800" now we divide that with 4000-5000 pixels and we get 7200/4000 = 1.8" and 10800/5000 = 2.16"

So you see 2"/px is start of wide field one way or another (meaning FOV larger than 2" and sensor in 4/3 and upward size and decent pixel count).

For that reason I would say that 2.23" is very decent wide field sampling rate - even on lower side of things - if you want really wide field, like to fit whole m31 or similar, you need at least 3-4 degrees and that means almost double what we've calculated to be feasible sampling rate - 3"-4"/px is perfectly fine in those cases (that or use of APS-C / full frame sensors with enormous pixel counts - 6000-8000px in width).

[tooth_dr]

Thanks Vlad! No need to upgrade my cameras 👍🏼👍🏼👍🏼

[tooth_dr]

57 minutes ago, WanderingEye said:

I don’t see anything wrong with your current set up to be honest, they are both more than doable with those pixel scales...one thing to consider is the slight loss in sensitivity if you change...would it be to a CMOS or CCD camera of you change...? . 👍😀

Thanks! No point in changing for the sake of it!

[WanderingEye]

8 minutes ago, tooth_dr said:

Thanks! No point in changing for the sake of it!

Absolutely....the KAF8300 is a very capable sensor and with a good pixel size... I have the SX version of the camera the H18... 👍😀