QHY268M & QHY268C Users Thread (Please share your knowledge and tips)

[Richard_]

I don't use SGP or Nebulosity (I use NINA and Pixinsight respectively), so I can only go by my experience. Yeah, I remember having a buggy temperature readout too (it kept reading a static temperature like 25°C or something) which I think was happening when I used the ASCOM driver. The temperature readout would not change when I turned cooling on. I use the native driver for the camera and it works fine now! 

I've not had images as bad as yours, but every now and then I have a sub where maybe the top third has downloaded whilst the bottom two thirds haven't. It happens at a rate of no more than 1 sub a night so I'm not able to replicate the issue. The rate is low enough that I'm not too bothered about it right now (perhaps over winter with longer sessions I see more issues?). My camera is connected to my Pegasus Powerbox Advance which is then connected to my mini-pc via 0.5m Lindy Chromo USB cable. I've tried both the provided 1m USB cable which came with the camera and also an 0.5m Lindy Chromo USB cable between camera and PPBA, but I still drop the odd file with either cable. I used this exact setup but with an ASI533MC and never dropped a file, so I suspect this is an issue with the camera firmware/driver. 

Within NINA my USB traffic is set at default value of 0 which I have not tried changing. For troubleshooting, if possible it might be a good idea to do some testing when the camera is connected directly to your computer/laptop and to bypass the PPBA altogether. Which port on your Pegasus is it plugged into, as there is one port which are USB3 only and cannot communicate with USB2. 

Edited September 16, 2022 by Richard_
Spelling

[AMcD]

27 minutes ago, Richard_ said:

My camera is connected to my Pegasus Powerbox Advance which is then connected to my mini-pc via 0.5m Lindy Chromo USB cable

Many thanks Richard.  In light of the description of your set up, I suspect one of my issues might be that I run a long USB3 cable from my PBA to my server cabinet in the observatory.  It never caused a problem with the QHY8, but it may be that the firmware / increased data with the QHY268M is too much for it.

I have just done a quick test with the camera attached to the computer directly and it worked perfectly, including no buggy temperature readings.  I will continue to test tomorrow to see if I can bring the PBA back into the picture.  At least I know I do not have to send the camera back!

Many thanks for your extremely helpful advice.

A

[teoria_del_big_bang]

5 hours ago, AMcD said:

Many thanks @Rob_Jn.  I have just finished trying it with a direct connection to the computer and it works fine!  Should have tried that before posting 😃  It looks like the Pegasus PBA USB hub is corrupting the communication as I have plugged it into the PC with a relatively long USB3 cable.

Many thanks for your help, I am most grateful.

Hi, Just woke up to check how the imaging went and seen this.
I am glad the camera is good and works at least.
Just so you know I too have my camera going via my Pegasus PBA the USB from the PPBA to PC is 2M and it has worked fine. I normally like to connect ccd directly to computer to stop any issues like this but to save runnung a 2nd usb3 cable from rig to PC when I got the PPBA I ran it via a USB3 port on that and it seemed to work okay so used it that way the past 2 years or so.

Steve

[AMcD]

5 hours ago, teoria_del_big_bang said:

Hi, Just woke up to check how the imaging went and seen this.
I am glad the camera is good and works at least.
Just so you know I too have my camera going via my Pegasus PBA the USB from the PPBA to PC is 2M and it has worked fine. I normally like to connect ccd directly to computer to stop any issues like this but to save runnung a 2nd usb3 cable from rig to PC when I got the PPBA I ran it via a USB3 port on that and it seemed to work okay so used it that way the past 2 years or so.

Steve

Many thanks Steve.  I think the problem is almost certainly my USB3 cable from the PPBA to the computer.  In particular, and looking at in the cold light of day, it is clear I have done two silly things.  

First, I bundled the USB cable with the power cable to the PBBA, which probably does not help.  Second, having now looked at the USB3 cable during daylight I have remembered it is a high speed USB3 cable but one that is 5 metres long!  This caused no issues with the QHY8 but I strongly suspect the drop off in speed inevitably caused by a 5m long cable is far more significant for the QHY268M.  

I need some slack in the cable to avoid it cable snagging but God knows why I thought I needed a 5m cable when the server cabinet is only a metre from the mount 😳. The fact I have had to partly coil it because it is so long probably makes matters worse.  

Anyway, I have a ordered a 3m Lindy Chromo USB3 cable and I will see if that solves the issue. It will give me the slack I need, will not have to be coiled and is within the tolerance limit for USB3.  It is coming tomorrow - by which time the clouds will no doubt be back!

Thanks again to everyone for the advice and assistance.

[Richard_]

Pegasus have written up some good information and advice regarding cable management per the below link. 

For USB3, they say that 3m is the longest you should use so hopofully you will see an improvement with your new 3m cable! 

https://pegasusastro.com/cable-management-recommendations/

[Starflyer]

QHY also discuss the USB frame corruption problem here, look for this section in the FAQs;

USB data corruption can also be caused by voltage/ earth leaks between equipment, this is discussed in the same FAQ, and has the potential (pun intended) to destroy your camera, mount or something else. It's easily tested for and you probably should before just putting the problem down to a USB cable problem.

Before you start probing with a meter make sure you take note of their warning to do it with the camera, and probably everything else USB, disconnected first.  You do this at your own risk, I've seen a mount mainboard destroyed by earth leakage.

[AMcD]

Thanks @Starflyer  I have this afternoon unbundled the USB3.0 cable from the power cables to eradicate noise / interference.  The image misalignment remained.  I then checked each of the USB connections for looseness and contact problems.  It would appear increasingly likely that the culprit is the patch panel USB3.0 connector where the USB cable enters the server cabinet, and another short cable goes then from the connector to the computer.  The patch panel connector connection was very loose.  If I bypass the patch panel connector by plugging the cable from the PPBA directly into the computer I get consistently good data transmission from the camera and I get this even over the 5-meter long USB3.0 cable.  This suggests to me it was the patch panel connector that is in fact the culprit.   I will try for first light tonight and if that goes well will forego the voltmeter.  Thanks again for your kind assistance.

[Starflyer]

You're very welcome, looking forward to your first light, they're great cameras.

[AMcD]

12 hours ago, Starflyer said:

You're very welcome, looking forward to your first light, they're great cameras.

Well, here is first light on the QHY268M with the Antlia 3n Ha filter.  I managed 1 hour of 360s integrations under high cloud, before the clouds moved in completely.  I have stacked it in DSS with dark frames and stretched the result in PS.  Compared to the QHY8 I am blown away 😃.  I used the 5m USB3.0 cable last night but the 3m Lindy Chromo USB3.0 cable is coming today.

It is clear from the stars in the corners that my back-focus is off considerably. I have set the back-focus to 55mm per the QHY recommendation. However, the information for my TS 2.5” Field Flattener states as follows:

“The 2.5" flattener offers generous back focus:
Like the smaller 2" version, we have designed this flattener with a long back focus distance.  So it is not a problem to add Off-Axis-Guiders, filter wheels etc. The recommended distance between the flattener's M69 thread and the focal plane is 91.5 mm for lenses with f/7 and slower. For f/6, we recommend a distance of 106 mm. For f/5.5, we recommend a distance of 111 mm”

Within this context, I note the following extract from the OPT guide to setting back-focus:

“My Camera Says I Need 55mm Back Focus. Is This Correct?
Let’s get one thing out of the way: back focus is a property of optics, not cameras. That being said, 55mm is an industry-standard length of back focus for many optical correctors and focal reducers. So, while 55mm is usually correct for most setups, we always recommend double checking the manuals and diagrams for your corrector/reducer or telescope (if it has a corrector built in) to be sure. These can usually be found on the manufacturer's product page. If it's not listed, contact the manufacturer.”

Having regard to the above, with the field flattener I had the back-focus for my QHY8 set at 106mm for my f5.9 TS152 and had round stars to the edges. I am wondering whether I should do the same for the QHY268M?

Many thanks again for all your assistance @Rob_Jn, @Richard_, @teoria_del_big_bang and @Starflyer

[Richard_]

Wow, we must be on the same wavelength as I also shot NGC 6888 last night! I'm using a 120mm refractor and the 4.5nm Antlia edge filters 😊 See screenshot of the master lights below. The camera is still new to me, so I was blown away when the first H-alpha sub came in, so imagine my surprise when I stacked them together! 

H-alpha (1h 40m total at 300s exposures) 

OIII (3h total at 300s exposures) 

Regarding back focus, you're off to a good start. Your star shapes in the corners suggest the camera is too close to the flattener so you could increase the distance slightly. When a filter is introduced, you typically increase back focus by one third of the thickness of the filter. I think the 36mm Antlia filters are 2mm thick so add 0.6mm to 106mm bringing you to 106.6mm. 

Luckily, I'm using a William Optics adjustable flattener so I can increase back focus up to +15mm in fine steps instead of using spacers. Even when I hit the correct back focus stated for the falttener (taking into account filter thickness), I still needed an extra 1mm of back focus to get rounder stars at the edges. They're still not perfectly round, but it's good enough for me! Maybe give that a try? 

Edited September 18, 2022 by Richard_

[AMcD]

1 hour ago, Richard_ said:

Wow, we must be on the same wavelength as I also shot NGC 6888 last night!

Many thanks, I will add in 1mm to account for the filter as the 2" Antlia 3nm Ha is 3mm thick I believe.  There is a lot to learn with mono imaging.  Looking at your images I realised I had left the OSC settings on in DSS, so was producing an RGB Tiff file 😳.  Now corrected...

[Starflyer]

5 hours ago, Richard_ said:

Wow, we must be on the same wavelength as I also shot NGC 6888 last night! I'm using a 120mm refractor and the 4.5nm Antlia edge filters 😊 See screenshot of the master lights below. The camera is still new to me, so I was blown away when the first H-alpha sub came in, so imagine my surprise when I stacked them together! 

H-alpha (1h 40m total at 300s exposures) 

OIII (3h total at 300s exposures) 

Regarding back focus, you're off to a good start. Your star shapes in the corners suggest the camera is too close to the flattener so you could increase the distance slightly. When a filter is introduced, you typically increase back focus by one third of the thickness of the filter. I think the 36mm Antlia filters are 2mm thick so add 0.6mm to 106mm bringing you to 106.6mm. 

Luckily, I'm using a William Optics adjustable flattener so I can increase back focus up to +15mm in fine steps instead of using spacers. Even when I hit the correct back focus stated for the falttener (taking into account filter thickness), I still needed an extra 1mm of back focus to get rounder stars at the edges. They're still not perfectly round, but it's good enough for me! Maybe give that a try? 

Nice images, I can see the soap bubble quite clearly in both images, something I hope to get this season.

[Richard_]

5 hours ago, AMcD said:

Many thanks, I will add in 1mm to account for the filter as the 2" Antlia 3nm Ha is 3mm thick I believe.  There is a lot to learn with mono imaging.  Looking at your images I realised I had left the OSC settings on in DSS, so was producing an RGB Tiff file 😳.  Now corrected...

Yeah this is my first mono camera so we're learning together! However, compared with my OSC camera (ASI533) the master lights from this camera are so easy to process which I'm sure you'll enjoy. 

That looks like a good detailed image, especially as you had high cloud cover too. Do you have the full SHO filters or are you collecting H-alpha for now? 

[Richard_]

4 hours ago, Starflyer said:

Nice images, I can see the soap bubble quite clearly in both images, something I hope to get this season.

You have better eyes than me! I could swear blind I missed it, but looking at another person's photo, I can see where the soap bubble is meant to be. Perhaps it'll appear during processing? 

[Starflyer]

1 hour ago, Richard_ said:

You have better eyes than me! I could swear blind I missed it, but looking at another person's photo, I can see where the soap bubble is meant to be. Perhaps it'll appear during processing? 

Bottom edge at 5 o'clock

[AMcD]

4 hours ago, Richard_ said:

Yeah this is my first mono camera so we're learning together! However, compared with my OSC camera (ASI533) the master lights from this camera are so easy to process which I'm sure you'll enjoy. 

That looks like a good detailed image, especially as you had high cloud cover too. Do you have the full SHO filters or are you collecting H-alpha for now? 

It is certainly a learning curve!  But what I love about this hobby is the willingness of its adherents to give their time and help to others.   

I want to get full SHO filters eventually but will stick with HaLRGB for now (or at least until my bank balance recovers!)

I am still having trouble dialing in the back-focus.   Having been plainly in error in using the generic 55mm figure without regard to the requirements of my field flattener, I went to 106mm per the TS recommended back focus for the flattener.  However, I now appear to be too far from the first optical element having regard to the star pattern, although I only managed 15 minutes between the clouds:

So, I guess that back-focus is somewhere between the 55mm I incorrectly commenced with and the 106mm that TS says it is, and which worked with the QHY8.  I will just have to achieve it by trial and error - unless @vlaiv knows some Ninga maths for this 😂

[AMcD]

6 minutes ago, AMcD said:

So, I guess that back-focus is somewhere between the 55mm I incorrectly commenced with and the 106mm that TS says it is, and which worked with the QHY8.  I will just have to achieve it by trial and error - unless @vlaiv knows some Ninga maths for this 😂

Hold the phone!  I have just found this on the TS website:

Connecting a camera to the TSFLAT 2,5:
For best results, a correct distance to the camera sensor is necessary. This distance is measured from the female M69 thread of the corrector. The thread itself does not count.

♦ Focal length up to 500 mm ... 106 mm
♦ Focal length 510-600 mm ... 101 mm
♦ Focal length 610-700 mm ... 96 mm
♦ Focal length 710-800 mm ... 91 mm
♦ Focal length 810-950 mm ... 88 mm

I could have sworn I read somewhere that for the f5.9 TS 152 the correct back focus was 106mm.  But the TS152 has a 900mm focal length, which the table equates to a back focus of 88mm.  

I'll get my coat 😂

[vlaiv]

10 hours ago, AMcD said:

unless @vlaiv knows some Ninga maths for this 😂

North of lake Tanganyika in Burundi, there is little village called Ninga.

There they teach this special math needed to determine back focus distance for flatteners. People of TS went there to study, but I was not fortunate enough to get the chance to spend some time in village Ninga and learn this sacred math of backfocus calculations

 

[AMcD]

On 19/09/2022 at 10:10, vlaiv said:

There they teach this special math needed to determine back focus distance for flatteners. People of TS went there to study

It turns out the people of TS were taught well.  This 10-minute subframe suggests that 88mm (plus 1mm to account for the filter) seems about right.  Now, if I can just solve the DEC backlash that is playing havoc with my guiding...

[teoria_del_big_bang]

Something I have noticed since I started using NINA is that when I first power everything up and connect everything NINA reports the camera temperature as very low, usually around 0 to 1 degrees yet the ambient temperature is in the low teens so this seemed unlikely to be true as I had not asked it to cool.
So then disconnected from NINA and started EZCap and connected to camera and that said around 1 degree to start with but then the temperature gradually started to rise and after a minute or two got to 14 C so i am happy the cammera is reporting the correct temperture but have no idea why it seems to set temperature to around zero as soon as I connect.
And then when I reconnected the camera in NINA that also reported it to be 14C and it stayed there.

Any ideas ?

Steve
 

[scotty38]

The QHY cameras will start to cool as soon as 12v is applied. Also NINA will not show the % cooling until asked to cool and then it fetches the information from the camera. With regard to the temp being low from the get go then I'm not sure. My 294 will warm up as soon as the USB is connected and NINA seems to show that temp just fine. Of course as soon as 12v is applied the temp drops to about 0 degrees until I ask it to cool and then it will go to the -5 degrees that I have set in the config.

[Richard_]

Scotty is on the money. Camera will automatically cool to 0°C when you connect 12V power with no way to disable. If you start cooling, then hit warm, the sensor should then return to ambient temperature instead of holding at 0°C.

Edited September 22, 2022 by Richard_

[teoria_del_big_bang]

Cheers guys, that confirms what I was suspecting, as 12V goes to the camera as sopon as I power up the rig but it takes a few minutes to get NINA poered up and everything connected.
Steve

[AMcD]

On 20/01/2022 at 16:29, Richard_ said:

Circled on the right of each panel is some condensation (which disappeared on second night when I heated the front of my camera with a dew strap).

I had one of those astrophotography nights last night that seems to be an endless exercise in problem solving.  First, the battery in my Gemini I was low, causing strange slewing behaviour, and had to be replaced.  Second, as the autumn temperatures decrease the focuser tensioner on the TS152 became looser, causing slippage when pointed at the Zenith, and had to be tightened.  Finally, following the heavy rain, and with humidity at 98%, it would appear that the heater for the window in front of the CMOS chip on the QHY268M was overwhelmed, as condensation formed on the outside of the window (presumably once the temperature gradient between the inside and outside of the window became too acute) ruining my red frames...

I suspect this may be consistent issue for me as the camera / filter wheel are kept permanently in the observatory, which is dry but unheated; at least when there are very high levels of humidity and I attempt to go for a low CMOS temperature (last night -20C).  Does the dew strap solution work consistently @Richard_?  I also wondered about purging the filter wheel and remainder of the imaging train in front of the CMOS window with argon.  I have also read that keeping the camera temperature at parity with the ambient temperature resolves the issue but, of course, at the price of increased noise.

Edited October 1, 2022 by AMcD

[teoria_del_big_bang]

@AMcD Oh Dear, we all have these nights from time to time, sometimes feels like you would be better off in bed 🙂 

Maybe you need to replace the desiccant in the tube ?
I had a slight issue with this when I first had the camera because I did not fit the tube and desiccant and when I used the supplied software for the camera (EZCap I think)  it reported 90% humidity in the camera. After the tube and desicant were added it gradually came down (took a couple of days to get really down) and has remained low ever since, worth checking on EZCap now and again to see what level is.

Steve
 

Edited October 1, 2022 by teoria_del_big_bang