Evostar 80ED and QHY 8L

[Sabalias]

Hi all,

Just a quick question. I currently use a DSLR with my 80ED as my default rig and I'm thinking about getting a dedicated astrophotography camera. I realise that there are a number of cameras out there that will work well with the scope but I could purchase a second hand QHY 8L; however, I have looked at the Astronomy Tools website and it seems that the camera/scope combination are not at all optimal. Does anyone have any experience of this combination before I decide on whether to make an offer or not? 

Many thanks,

Stu

[MKR]

I'm thinking of upgrading my DSRL to a dedicated camera too. I wonder - why would you choose QHY 8L instead of a similarly priced ASI 294MC for example? Is it because it's a CCD? It's a genuine question, I hadn't even considered QHY 8L mainly because of its age, I just keep thinking about 294MC.

Edited January 31, 2022 by MKR

[vlaiv]

Depends what you mean by optimal.

That is very decent combination that will give you good results.

It can be considered low resolution / wide field setup that is very suitable for a range of targets - but not so much for other targets.

Here is an example - if you attempt to image say M51 galaxy - it will be very small in the FOV:

and if you zoom to 100% on the galaxy - it will look something like this:

It will be small. Similarly - this is what will M13 look like when zoomed in to 100% - in the FOV it will be equally small:

But objects like M31 - will be nicely framed

So will be other larger objects - mostly nebulae.

[vlaiv]

3 minutes ago, MKR said:

I'm thinking of upgrading my DSRL to a dedicated camera too. I wonder - why would you choose QHY 8L instead of a similarly priced ASI 294MC for example? Is it because it's a CCD? It's a genuine question, I hadn't even considered QHY 8L mainly because of its age, I just keep thinking about 294MC.

Because of sensor size. Sensor size is equal to speed (if properly handled and paired with right optics).

8L is APS-C sized sensor - it has 442.764mm2 of surface while ASI294 is 4/3 sensor and has only 248.3mm2 - that is only what? 60% or so of the size.

If you have idea of what sort of FOV you want to image - 8L can be paired with bigger scope (and hence bigger aperture that lets in more light) for same FOV.

[Sabalias]

21 minutes ago, vlaiv said:

Depends what you mean by optimal.

That is very decent combination that will give you good results.

It can be considered low resolution / wide field setup that is very suitable for a range of targets - but not so much for other targets.

 

Thanks Vlaiv. Very helpful as always! The CCD suitability tool seems to indicate that I'll be looking at considerable under-sampling with this combination (which is why I was suggesting the combination would not be optimal).

Cheers,

Stu

[Sabalias]

30 minutes ago, MKR said:

I'm thinking of upgrading my DSRL to a dedicated camera too. I wonder - why would you choose QHY 8L instead of a similarly priced ASI 294MC for example? Is it because it's a CCD? It's a genuine question, I hadn't even considered QHY 8L mainly because of its age, I just keep thinking about 294MC.

I was also thinking of the 294 but found a second hand 8L so thought it was worth checking with the experts 😉

Stu

[Lee_P]

I actually used a QHY8L and 80ED back in 2017. I found them a decent enough pairing, especially coming from the Nikon D700 DSLR I used prior. The camera definitely shows its age when compared to the modern CMOS cameras we have now though.

In case it's useful, I've fished out some images I took. My processing skills were in their infancy, so perhaps take these as a kind of lower limit of what you could achieve?

 

 

 

Edited January 31, 2022 by Lee_P

[vlaiv]

9 minutes ago, Sabalias said:

Thanks Vlaiv. Very helpful as always! The CCD suitability tool seems to indicate that I'll be looking at considerable under-sampling with this combination (which is why I was suggesting the combination would not be optimal).

Cheers,

Stu

One of the features of wide field setup is under sampling - but that should really not bother you that much.

If you say go for 4° field of view with say 4000is pixels - then it must lead to 4 * 60 * 60 = 14400 covered by 4000is pixels - or 3.6"/px. That might be under sampling - but in context of FOV is perfectly fine (and high pixel count image for that matter).

You should not worry about "square" stars - that is just a myth and never happens, even when under sampling.

Under sampling in itself is not as bad as over sampling.

With under sampling you possibly don't record the finest detail available but have no other ill effects. With over sampling you don't record detail as none is available and suffer SNR loss over regular sampling. That is why over sampling is bad - you loose SNR over nothing.

[Rustang]

I've been using the WO Z73 and QHY-9, so I'm under sampling too but its really not been an issue. This is the last image I took with that set up. 

Edited January 31, 2022 by Rustang

[Sabalias]

4 minutes ago, vlaiv said:

One of the features of wide field setup is under sampling - but that should really not bother you that much.

If you say go for 4° field of view with say 4000is pixels - then it must lead to 4 * 60 * 60 = 14400 covered by 4000is pixels - or 3.6"/px. That might be under sampling - but in context of FOV is perfectly fine (and high pixel count image for that matter).

You should not worry about "square" stars - that is just a myth and never happens, even when under sampling.

Under sampling in itself is not as bad as over sampling.

With under sampling you possibly don't record the finest detail available but have no other ill effects. With over sampling you don't record detail as none is available and suffer SNR loss over regular sampling. That is why over sampling is bad - you loose SNR over nothing.

Again - really helpful, thanks. Given that the framing for my EOS600D is I very similar to the 8L I imagine that the only real advantage to buying it would be better quality images - is that a safe assumption? Sorry about all the questions, just want to make sure I'm not making a mistake.

Stu 

[Rustang]

1 minute ago, Sabalias said:

Again - really helpful, thanks. Given that the framing for my EOS600D is I very similar to the 8L I imagine that the only real advantage to buying it would be better quality images - is that a safe assumption? Sorry about all the questions, just want to make sure I'm not making a mistake.

Stu 

A dedicated camera is a big upgrade in quality from a DSLR, I have no regrets in doing so myself and I also upgraded from a 600D

Edited January 31, 2022 by Rustang

[Lee_P]

2 minutes ago, Rustang said:

I've been using the WO Z73 and QHY-9, so I'm under sampling too but its really not been an issue. This is the last image I took with that set up. 

That's a really fantastic image!

[Rustang]

Just now, Lee_P said:

That's a really fantastic image!

Cheers, its the only image Ive taken so far with the new scope, its been packed away now for a while. Had issues with focusing the Z73 properly so I'm pleased I managed to get this image but I'm hoping to get back on it later in the year when our house renovation is nearly complete and I can use the garden properly again. 

[Sabalias]

19 minutes ago, Lee_P said:

I actually used a QHY8L and 80ED back in 2017. I found them a decent enough pairing, especially coming from the Nikon D700 DSLR I used prior. The camera definitely shows its age when compared to the modern CMOS cameras we have now though.

In case it's useful, I've fished out some images I took. My processing skills were in their infancy, so perhaps take these as a kind of lower limit of what you could achieve?

 

Thanks Lee, really nice pics there. It sounds like I might be better off saving up longer and getting a newer CMOS camera though?

Stu

[Sabalias]

12 minutes ago, Rustang said:

I've been using the WO Z73 and QHY-9, so I'm under sampling too but its really not been an issue. This is the last image I took with that set up. 

 

Fantastic image there!

[Lee_P]

1 minute ago, Sabalias said:

Thanks Lee, really nice pics there. It sounds like I might be better off saving up longer and getting a newer CMOS camera though?

Stu

That's the question! Depends on your finances and how much you want to put into the hobby, I guess. @Rustang's photo is very impressive, and certainly shows that the QHY8L is capable of good results when in the right hands. 

[Rustang]

Noise has been my only gripe and that's a small gripe as its been a great camera, it just gets on with things with out fault (touch wood!). It needs pushing harder, longer subs etc than compared to the CMOS cameras. I will probably upgrad to something like the 294mm when I can but for now I've been more than happy with the QHY-9. As Lee has said, budget normally helps decisions, I managed to step into the dedicated camera world after buying a complete set up, camera, filter wheel and filters for a great price so took the jump. Future proofing yourself is something to consider aswell, if your doing this long term, buy right first time round if you can!.

Edited January 31, 2022 by Rustang

[Lee_P]

3 minutes ago, Rustang said:

Noise has been my only gripe and that's a small gripe as its been a great camera, it just gets on with things with out fault (touch wood!). It needs pushing harder, longer subs etc than compared to the CMOS cameras. I will probably upgrad to something like the 294mm when I can but for now I've been more than happy with the QHY-9. As Lee has said, budget normally helps decisions, I managed to step into the dedicated camera world after buying a complete set up, camera, filter wheel and filters for a great price so took the jump. Future proofing yourself is something to consider aswell, if your doing this long term, buy right first time round if you can!.

Ah, so your QHY9 is mono? That would make a difference considering the QHY8L Sabalias is considering is OSC. A whole other can of worms to be opened..!

[Sabalias]

1 minute ago, Lee_P said:

Ah, so your QHY9 is mono? That would make a difference considering the QHY8L Sabalias is considering is OSC. A whole other can of worms to be opened..!

On the event horizon and about to be sucked into the black hole 🤣

[Rustang]

4 minutes ago, Lee_P said:

Ah, so your QHY9 is mono? That would make a difference considering the QHY8L Sabalias is considering is OSC. A whole other can of worms to be opened..!

Yeah sorry its mono, I was only really trying to state that with my combo its also under sampling so not to worry about it. Keep the worms firmly in the can if your not ready for it or don't have the extra time and dedication! 😁

Edited January 31, 2022 by Rustang

[vlaiv]

30 minutes ago, Sabalias said:

Again - really helpful, thanks. Given that the framing for my EOS600D is I very similar to the 8L I imagine that the only real advantage to buying it would be better quality images - is that a safe assumption? Sorry about all the questions, just want to make sure I'm not making a mistake.

Stu 

As others have already mentioned - yes, moving to a dedicated camera usually brings significant improvements for DSLR users.

Cooling and set point temperature really helps as well as absence of different filters present on DSLR (like anti alias filters and UV/IR cut filters with slope that seriously hamper Ha performance).

[Sabalias]

Thanks all for your excellent insights and help. Before I finally shell out I thought I’d bung a few images on here from my 600D - not massively long exposure times and I think there is a bit of a problem with the image train but wondering what kind of improvement I might expect?

 

Thanks again,

Stu