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QHY600 First Impression and Questions

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#1 rgsalinger

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Posted 21 January 2020 - 10:23 AM

I got a belated Xmas present - my QHY600 came in and I picked it up a week ago. I've had some challenges in getting it working, but overall I'm pretty pleased with it. I'm not seeing any amp glow at 5 minute exposures binned 2x2 which is as far as I plan to push it at this point. There's some large scale fixed pattern noise, though, but QHY says that this will calibrate out and I dither every frame anyway. In particular, I'm still (see below) confused about optimal settings as the documentation is still a little sketchy (IMHO) and not well written in places. There were two challenges that needed to be overcome when I first began using it to get it working as it should.

 

First, you have to take an initial exposure of over 1 second to get the cooling working properly. If you don't and you just connect the camera to the computer, then the cooling will cycle around forever . I found that I could never reach -10C where I planned to image. It would get to around -4 and then warm up! Just one 10 second exposure switches the camera into a normal cooling mode. This took me a while to figure out. QHY says that they will fix this in the next driver release in their response to my post on their forum. 

 

The second is strange behavior with regards to USB connections. At home it works properly on my desktop when connected to one USB 3 port but not to a second one on the same hub. When I connect to the "bad" port I get some skipped rows - zero values. What's even stranger (on my desktop computer) is that it works perfectly using USB 2.0 ports. I wonder if anyone else has seen this behavior. At the observatory, it would not work using the USB 3 port on my CEM120EC2, but did work when connected directly to the imaging computer and to a second computer of the same design at my desk out there. I've run my ASI1600 through the CEM120EC2 USB 3 port for quite some time with good results. So that was a surprise. Right now I have two free ports on the CEM120, it will be a shame if I can't get it to work properly without a dangling cable. 

 

(NB--- I also shot myself in the figurative foot with the CFW3 filter wheel setup. I connected the enclosed proprietary four pin connector between the camera and CFW3 filter wheel. I also connected the USB port on the camera to the USB hub on my mount. I could not get any reasonable looking pictures at all. Then the wheel failed on me after about 30 minutes. I have a new wheel (thanks to my local astronomy store) now and I carefully read the documentation this time. With the QHY600 you ONLY connect the 4 pin connector - you do not use the USB connection at all. I post this because I may not be the last person to make this mistake.)

 

Where it gets confusing to me is when I try to figure out the right settings for DSO long (5 minutes) exposures. The camera documentation refers to 3 modes. The setup ASCOM GUI calls these "Photographic DSO 16 Bit", "High Gain Mode 16V" and "Extend Full Well Mode". I decided to just use the Photographic DSO (Mode 0) and took the advice in the QHY online specification section (not the manual!) and set the Gain to 26. At that gain the camera switches into some mode that lowers the read noise down to around 3e. FWD is around 27K. However, in the online charts (in the specifications section) this is referred to as "Ultra High Full Well Readout" which seems to contradict what's in the written recommendation. Since I'm binning the camera 2x2, the effective FWD is around 110K which would seem more than adequate. I could go on about this, but I'd love to hear from someone who understands it better than I do (shouldn't be that hard).

 

I'm also completely confused about how to set the offset. I have that down to 12 at this point and built a dark library at Mode 0, Gain 26 and Offset 12 for exposures from 1 to 5 minutes. I can't imagine going longer than that but maybe narrow band will need different settings and a different library. I arrived at 12 offset by gradually lowering the offset until the bias frames gave values of between 150 and 200 but I really don't know if that's the right approach or not. I could (?) use Offset of 6 and get bias frames with readings between 50 and 70 but I worried about some pixels being negative so I kept to 12 out of fear/ignorance. 

 

Finally, there are two "read modes" reported in MaximDL for the camera. One is "Fast" and one is "Normal". My assumption is that Fast is just to be used for plate solving, focusing, etc and "Normal" is to be used for long exposure photography. I can't find any documentation online at the QHY site about exactly how (if at all) these relate to the modes described in the GUI. 

 

So, the camera seems pretty darn good. Tomorrow night looks clear and I'll give it another try out at the observatory but I'd love to hear from anyone who's farther along than I am with it about their experiences and what they've discovered about optimizing the performance. 

 

Rgrds-Ross


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#2 Madratter

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Posted 21 January 2020 - 11:06 AM

Typically with cameras that support a fast and normal mode, fast mode downloads faster but at the expense of higher noise. That higher noise is usually acceptable for things like focusing, pointing, etc. Normal (called default by some programs) is what you want for actual images you would stack. So it sounds to me like your understanding on that is correct.

 

At least on my camera, ROI is a much better way to speed up acquiring the data for things like focusing (if I'm doing single star). YMMV.



#3 FredOS

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Posted 21 January 2020 - 01:31 PM

I would have thought mode 1 « high gain » made the most sense :
- for LRGB at gain 0, you have full well of 50639 and read noise of 3.6.
- for narrowband at gain 56, full well of 21657 and read noise of 1.68.

In your mode at gain 26, full well is better at 27k but read noise is 2.7. For narrowband that will be less effective.

#4 TelescopeGreg

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Posted 21 January 2020 - 11:31 PM

FWD is around 27K. However, in the online charts (in the specifications section) this is referred to as "Ultra High Full Well Readout" which seems to contradict what's in the written recommendation. Since I'm binning the camera 2x2, the effective FWD is around 110K which would seem more than adequate. I could go on about this, but I'd love to hear from someone who understands it better than I do (shouldn't be that hard).

No expert here on FWD, but playing computer scientist, I would think it can't be any larger than the # of bits in the image.  110K is more than 16 bits worth of information (65535 is the max).  No?



#5 buckeyestargazer

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Posted 22 January 2020 - 09:05 AM

Hi Ross,

Are you using a QHY OAG with the QHY600 and CFW3?  If you are using an OAG with M54 opening I would really like to see a flat taken with your fastest scope to check on the vignetting with an M54 opening.  

 

Congrats on the camera!



#6 rgsalinger

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Posted 22 January 2020 - 09:13 AM

I have the medium OAG. Unfortunately, the only scope that I have to use with that camera is F8 so I don't think it will be a good test. Once I get it operating I'll send you a PM.

 

I bought some high quality USB 3 cables and connected them to both ports on my desktop. They work fine. I'm thinking that the cable that came with the camera may not have been of the highest quality. Even more interesting is that I found I can use a USB 2 cable. Downloads are under 10 seconds with the USB bandwidth set to 30. 

 

It's true that once you get about a full well depth of 64k, there's probably no point in worrying about that anymore. I was just pointing out that I'm now limited by the 16 bit A/D converter in terms of extracting signal values.

 

I'm still confused about the gain and modes though. I'm going to go with the 26 recommendation until I have a chance to run some numbers and see what's what. I'm also hoping that someone else has one of these (OPT had at least one other one) and is more au fait with how to tune it for best results.

 

My observatory skies are Bortle 2 on clear nights. I get about 1e per second of background (per CCD Inspector) per pixel with my old camera. With read noise of 3 that would mean that my exposures can be as short as 90 seconds and, if binned, maybe 45 seconds will be enough to get me 10x over the read noise squared. No more guiding if that's true. 

 

I found an article by Dr Qiu that shows how to set the offset and I used that to set it to 10 and that's how I made my dark library. 

 

Rgrds-Ross


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#7 EspacioProfundo

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Posted 24 January 2020 - 07:04 PM

Hi Ross,

 

I have the same camera. Did some tests with the SharpCap Sensor Analysis, as below

 

Captura de pantalla 2020-01-24 21.02.16.png

 

For RGB I suggest "Photo Mode", gain 26 (2,74e noise, 27000 full well). You can go higher at expense of lower full well. 

 

For narrowband use High Gain Mode, gain 56, (1,68e noise, 21700 full well) as a starting point. Going up with the gain in this mode is not worth. 

 

Regards

 


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#8 rgsalinger

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Posted 24 January 2020 - 10:44 PM

Thank you for the chart. I'm still struggling with the USB connections. I took it out to the observatory and I connected it with a short cable to the USB3 hub built into my mount. Then from there it went to my small PC at the foot of the mount. Got terrible results - connected but the download was way out of sync. Tried every USB bandwidth setting I could think of. Nothing worked. Then I just moved the cable to a different PC port and it worked perfectly all night long. Next night it would not connect no matter what I tried. I've powered it on/off. I've removed and reinserted the cables (which are new) to clear any corrosion. It just comes up with an error saying that it can't identify what's on the port (which worked for 12 hours the previous night). I've even disabled it, rebooted and enabled it ---- no go. Windows just does not see the device. I'll eventually get it working but I really hate USB3. This is the first time in years (really) that I've had a USB problem ---- years.

 

Rgrds-Ross



#9 smccully

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Posted 25 January 2020 - 12:40 AM

I had a ton of USB problems with this camera when I first got it. Nothing I tried was ever consistent, sometimes it would work and sometimes not. I finally found somebody saying they had a similar problem with another QHYCCD camera, and that it was because of a loose connection in the camera housing. There is a 3 pin cable from the camera board to the USB board it was loose. I unscrewed the top, and secured the cable. Haven't had a USB issue since. 



#10 Mert

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Posted 25 January 2020 - 03:38 AM

Sounds like a QA problem, quit a surprise for such an expensive toy! :thinking:



#11 smccully

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Posted 25 January 2020 - 04:15 AM

Sounds like a QA problem, quit a surprise for such an expensive toy! thinking1.gif

 

In all honesty i probably did something to it and knocked the cable out. It seemed to worked fine the first week, any one's guess when it actually started having problems.

 

Who knows, the cable is visible through the grating at the end of the camera though, so maybe placement isn't ideal or its there so you can access it easier.



#12 EspacioProfundo

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Posted 25 January 2020 - 09:41 AM

Thank you for the chart. I'm still struggling with the USB connections. I took it out to the observatory and I connected it with a short cable to the USB3 hub built into my mount. Then from there it went to my small PC at the foot of the mount. Got terrible results - connected but the download was way out of sync. Tried every USB bandwidth setting I could think of. Nothing worked. Then I just moved the cable to a different PC port and it worked perfectly all night long. Next night it would not connect no matter what I tried. I've powered it on/off. I've removed and reinserted the cables (which are new) to clear any corrosion. It just comes up with an error saying that it can't identify what's on the port (which worked for 12 hours the previous night). I've even disabled it, rebooted and enabled it ---- no go. Windows just does not see the device. I'll eventually get it working but I really hate USB3. This is the first time in years (really) that I've had a USB problem ---- years.

 

Rgrds-Ross

 

I have the QHY600, QHY290 for guiding, Sesto Senso electronic focuser, EQ8 thru USB to serial adapter all connected to a 8 port POWERED usb 3 hub. This hub have it's own 5 amp power supply, if you connect many devices to a hub it must be powered if you use cameras... Then the hub is connected thru a single USB 3 cable to the only usb 3 port I have on the intel nuc pc. Check the power of these built in usb ports on your mount, maybe it's not enough. 

In my case, I dont think that the 600 is transferring at full speed, a single usb 3 port is listening to 4 devices (to be honest 3, I disconnect the sesto senso usb cable). 

When focusing sometimes the image download have a little pause, maybe the port is busy but never had an issue regarding black lines or corrupted data. 

 

I've used several qhy cameras. QHY9, QHY16200, QHY5's, QHY290 and the 600. The drivers work as expected, never had a problem and now it seems that the cables are improved, the cable that connects the qhy FW to the 600 when plugged I hear a "click" and stays very firm without any wobble. 

 

I guess that the mounts with built in usb hubs must be powered with power supplies exceeding the mount requirements, for the EQ8 I have a 5 amp switching power supply, but if I had the new EQ8R with usb hub I'll power it with at least 10 amp to have room for connected devices.

 

Best regards



#13 rgsalinger

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Posted 25 January 2020 - 11:08 AM

I powered my ASI1600 through the CEM120's USB 3.0 port for a few months when my main camera (USB2) was being repaired so I figured it might work with the QHY600 as well. The port on the CEM120EC2 was upgratded soon after I got the mount to be "powered", but no one has said that it can provide "full" power. I'm running multiple devices off the same power port at this point as well. I'm going to replace the PS to one that's more appropriate and see if that fixes it. After that, it's shorter cables (move computer), USB 3 Startech Industrial Hub,  or long not through the mount cable. one of those is going to get it working. It's just hard to fathom how something can work flawlessly for 8 hours (8PM to 4AM) and then not work the next night sitting untouched in an observatory (mice?).

Rgrds-Ross 



#14 rgsalinger

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Posted 26 January 2020 - 12:16 AM

It turned out that the easiest way to connect it was to take a short USB 3 cable and connect it to the built in USB 2 hub on my mount. It then shares with the other components the same USB 2 connection quite happily. No idea of why this might work but it did and I'm imaging as I write this.

Rgds-Ross




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