Choosing between IMX455 and IMX571 cameras.

[tooth_dr]

I have decided to buy a new CMOS camera to replace my KAF8300 CCD and was pretty much set on the QHY268M.

I now think the larger full frame might be a better option.

Whatever camera I get will be used with an Atik EFW3 7x2” mounted filters.  My telescope can illuminate a 44mm imaging circle.

ZWO / Atik / QHY?

QHY lite version?

The Atik looks like a really good quality product. The QHY600 claims some sort of K sensor? 
 

I have tried reading up but CN descends into excessive technical jargon.  
 

Any help much appreciated. 

Edited November 14, 2020 by tooth_dr

[Stuart1971]

Can I ask why you feel the need to replace the KAF8300, you have produced some excellent images with it, and it an excellent sensor, moving from CCD to CMOS....is a learning curve, and going from 16 bit to 12 or 14. May not be a good idea...

Just my twopeneth..👍😀

[tooth_dr]

20 minutes ago, Stuart1971 said:

Can I ask why you feel the need to replace the KAF8300, you have produced some excellent images with it, and it an excellent sensor, moving from CCD to CMOS....is a learning curve, and going from 16 bit to 12 or 14. May not be a good idea...

Just my twopeneth..👍😀

I suppose I'm trying to move with the technology, and make full use of the 44mm imaging circle in the Epsilon.  The smaller pixels will also bring me down from 2.2"/px to 1.55"/px which can only be beneficial and probably a closer match to the local seeing conditions.  I think the IMX455 is a 16bit sensor too.

 

[Stuart1971]

35 minutes ago, tooth_dr said:

I suppose I'm trying to move with the technology, and make full use of the 44mm imaging circle in the Epsilon.  The smaller pixels will also bring me down from 2.2"/px to 1.55"/px which can only be beneficial and probably a closer match to the local seeing conditions.  I think the IMX455 is a 16bit sensor too.

 

Yes it is 16 bit, looks like a very nice camera...👍

[Whirlwind]

4 hours ago, tooth_dr said:

I have decided to buy a new CMOS camera to replace my KAF8300 CCD and was pretty much set on the QHY268M.

I now think the larger full frame might be a better option.

The Atik looks like a really good quality product. The QHY600 claims some sort of K sensor? 

Based on what QHY state there are both consumer and industrial grade of sensors; and that QHY offer cameras with the industrial version.  They state that these are more robust, more stable and tend not to degrade as quickly.  However, without any empirical evidence then it is difficult to determine just what sort of difference this makes for astronomy.  If the degradation occurs with less number of activations in the consumer version then this might be less of an issue with deep sky astronomy (with longer and less exposures).  A difference of 1million vs 2 million exposures is relatively insignificant (and even more so in the UK!).  On the other hand if you are taking a lot of short exposures (lucky imaging / planetary imaging) then it might be more of an issue.  CMOS hasn't really been around long enough for user experience to really come into play here.  On the other hand you might be taking a risk that the consumer version degrades quite quickly (especially at the cost and a small extra outlay for the industrial version could be worth the risk).

In terms of moving up to larger CMOS do take into account the extra grunt you need in your PC to process the images.  Each image of the full frame CMOS at the moment are about 120MB so if you are taking lots of short frames then that is going to take time to calibrate, combine and process.

On an aside if you aren't happy with the resolution of the KAF8300 you can always drizzle the images.  With the fast telescope you have that would also mitigate the additional noise this introduces.

[Adam J]

7 hours ago, tooth_dr said:

I have decided to buy a new CMOS camera to replace my KAF8300 CCD and was pretty much set on the QHY268M.

I now think the larger full frame might be a better option.

Whatever camera I get will be used with an Atik EFW3 7x2” mounted filters.  My telescope can illuminate a 44mm imaging circle.

ZWO / Atik / QHY?

QHY lite version?

The Atik looks like a really good quality product. The QHY600 claims some sort of K sensor? 
 

I have tried reading up but CN descends into excessive technical jargon.  
 

Any help much appreciated. 

With the smaller pixels the new generation full frame mono cameras are challenging the flat field claims of established scopes like yours. I would stick to APS-C for that reason. 

[tooth_dr]

1 minute ago, Adam J said:

With the smaller pixels the new generation full frame mono cameras are challenging the flat field claims of established scopes like yours. I would stick to APS-C for that reason. 

Thanks. What scopes do you think will work well with this camera?  My 180mm lens designed for the FF Nikon sensor should work ok?  

[Laurin Dave]

Adam,  I'd have thought your Epsilon should be ok  ..  (assuming you have the focuser sorted).  Were you to get one you could always bin 2x2 in software to give better stars to the edge of the full frame and only use full res where the stars are good..  Who needs a 64mpixel image anyway? It'll nearly always be seen at reduced resolution..  

[tooth_dr]

32 minutes ago, Laurin Dave said:

Adam,  I'd have thought your Epsilon should be ok  ..  (assuming you have the focuser sorted).  Were you to get one you could always bin 2x2 in software to give better stars to the edge of the full frame and only use full res where the stars are good..  Who needs a 64mpixel image anyway? It'll nearly always be seen at reduced resolution..  

Thanks Dave. My new focuser is on its way back from Moonlite as we speak. It’s been set up / collimated by Ron so I can only hope it’ll work fine once fitted.

There are a few decent images out there at FF with 4.3um pixels on the epsilon 180ed (Nikon D850/810/800).

It’ll mean my dual rig will no longer be effective, but then perhaps I won’t need it, and I admit I’d enjoy the simplicity of just one telescope and camera. 

Edited November 14, 2020 by tooth_dr

[Adam J]

1 hour ago, tooth_dr said:

Thanks. What scopes do you think will work well with this camera?  My 180mm lens designed for the FF Nikon sensor should work ok?  

No idea what will work, just know that lots of people are struggling with the small pixels and full frame sensor. It is a big challenge optically. 

[tooth_dr]

2 minutes ago, Adam J said:

No idea what will work, just know that lots of people are struggling with the small pixels and full frame sensor. It is a big challenge optically. 

Is there much difference in the properties of the two sensors, or is it purely size?

[Adam J]

It's just the size and the field flatness in the corners. 

28 minutes ago, tooth_dr said:

Is there much difference in the properties of the two sensors, or is it purely size?

 

[tooth_dr]

1 minute ago, Adam J said:

It's just the size and the field flatness in the corners. 

 

Cheers Adam. I didn’t realise they had identical properties, so the 455 is just 2x as many pixels as the 571.  That does make some difference to my choice. I could do mosaics if needed.

Are there many targets out there that need the pure size FF sensor at 500mm?  I can see an advantage with a longer FL but I don’t know what scope will adequately illuminate the FF sensor (mono so FW needed)

[tooth_dr]

I could buy one colour and one mono of the 268?  That might be my best option given my current setup. 

Edited November 14, 2020 by tooth_dr

[DaveS]

Just be aware that, depending on the distance from filter to sensor, 2" mounted filters may vignette with IMX455 cameras, especially with something as fast as the Epsilon.

Also, as Olly found out with the FSQ85, Takahashi can be a bit optimistic in their image circles. Their "44mm" might not actually cover the sensor.

[Stuart1971]

9 minutes ago, DaveS said:

Just be aware that, depending on the distance from filter to sensor, 2" mounted filters may vignette with IMX455 cameras, especially with something as fast as the Epsilon.

Also, as Olly found out with the FSQ85, Takahashi can be a bit optimistic in their image circles. Their "44mm" might not actually cover the sensor.

I have the FSQ85 and no way will you get 44mm image circle, not without the new flattener for the 85 and a full frame sensor...

You will get 30mm at best with native FSQ85 scope....👍

[Adam J]

 

1 hour ago, Stuart1971 said:

I have the FSQ85 and no way will you get 44mm image circle, not without the new flattener for the 85 and a full frame sensor...

You will get 30mm at best with native FSQ85 scope....👍

Yes that is what I worry about. Its lost of cash unless you know can be sure its actually going to cover it.

I have been looking on astrobin through and found this:

https://www.astrobin.com/75ejog/0/

Its no so bad as I worried it might be. BUT and this is the thing, he is using 50mm square astrodon filters or maybe unmounted round, might be worth asking him?

Adam

[tooth_dr]

8 hours ago, DaveS said:

Their "44mm" might not actually cover the sensor.

The Sony IMX309 FF sensor seems to work well with the Epsilon (though I haven’t quite sussed the collimation), but the pixels are a little larger at 4.3 versus 3.8um

 

[tooth_dr]

Do the  SW esprit 120 and 150 provide flat fields at 44mm?

[Laurin Dave]

The specs say they do and my 150 certainly has one.. with 6 micron pixels in my Nikon D750..   with the new reducer they are flat to 36mm APSH ( ie 16200 sensor size) ..  field of view essentially the same as it is unreduced with FF chip..  but a bit squarer .. 

 

 

[tooth_dr]

3 minutes ago, Laurin Dave said:

The specs say they do and my 150 certainly has one.. with 6 micron pixels in my Nikon D750..   with the new reducer they are flat to 36mm APSH ( ie 16200 sensor size) ..  field of view essentially the same as it is unreduced with FF chip..  but a bit squarer .. 

 

 

Thanks Dave.  I feel like I have plenty of options now but not sure what to do.

 

Apologies in advance for over analysis - options:

1) 455 sensor - 6200 or 600 or APX60 -means an end to dual rig, may vignette excessively at F2.8 with 2” mounted filters, wont be effective on my 250px.  Increasingly this is looking like the least ideal option.

 

2) 571 sensor on the Epsilon - mono QHY268 - works with current EFW3, but also means dual rig (other scope ED80 + KAF8300) won’t have enough overlap to be effective at gathering lum in one scope and RGB in other.  
 

 

3) 571 sensor on the epsilon and change the ED80 to an Esprit 80, and continue to use KAK8300 mono

 

 

4) 571 mono sensor on the epsilon and change the KAF8300 on the ED80 to a colour 571 sensor.  I’m favouring this option currently.  I have a JTD saddle coming tomorrow from FLO so alignment shouldn’t be an issue.

 

5) ??

[Laurin Dave]

Dual mono will be quicker and more flexible for Narrowband so I'd suggest the KAF8300/Esprit80 route...  and KAF sensors may be old tech but they do work very well 

Dave

[gorann]

2 hours ago, tooth_dr said:

Do the  SW esprit 120 and 150 provide flat fields at 44mm?

I gave up waiting for a mono APS-C CMOS so I ended up going for an ASI6200MM. Is there a mono APS-C that can be bought now?

I expected that I would have to do quite a bit of cropping but I am happy to report that at least my Esprit 150 gives a flat enough field with that full frame sensor. This is what it looks like (with the Esprit flattener - no reducer):

Edited November 15, 2020 by gorann

[Allinthehead]

Hi Adam, you might find that the high signal from the Epsilon luminance will wash out the colour with the Ed 80. Dual Epsilon 180 i'd say🤣

[tooth_dr]

46 minutes ago, Allinthehead said:

Dual Epsilon 180 i'd say

That has been entirely considered except 1) I can’t fit two close enough to image between the dome slit 2) that would be my worst nightmare 😂