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Received my QHY268M

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#1 2ghouls

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Posted 28 January 2021 - 09:19 PM

I received my QHY268M, and am happy to answer any questions. 

 

It comes with a great assortment of M54 spacers (not threaded) and M48 spacers (female threads) and M3 bolts (23.5mm and 27.5mm long). 

 

qhySpacers.jpg

 

The front of the camera has no threads, just a smooth front plate for bolting on the spacers or a filter wheel. Edit: This plate can be shimmed with copper tape to adjust tilt ( https://www.qhyccd.c...catid=30&id=317 ) don't have a filter wheel for this camera yet, so I'm just trying some stuff out with a generic 2" filter drawer and the spacers it comes with.

 

qhyFront.jpg

 

No first light yet, as it's cloudy (of course), but I have generated calibration frames at gain 0 and gain 56 (both with an offset of 25) in the high gain readout mode (mode #1). All the specs matched up extremely well with what QHY has published for this sensor. See below:

 

gain0.jpg

gain56.jpg

 

I used a 99 and 999 sec. dark to get the dark current measurement to work in BasicCCDParameters script. With 30 and 300 sec. as is often used, the dark current measurement was way off. 

FITS files: https://drive.google...X6c?usp=sharing

 

Also happy to answer any questions or perform more tests as I know there is a lot of interest in this camera!

 

Cheers, Nico


Edited by 2ghouls, 29 January 2021 - 01:13 PM.

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#2 lucam

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Posted 28 January 2021 - 09:21 PM

That’s exciting, Nico! Is this a test pre-production unit or did you receive it from a QHY dealer? I have one on order and it’s great to hear they are starting to be seen in the wild.


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#3 2ghouls

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Posted 28 January 2021 - 09:54 PM

It's a production unit, but I was able to get mine a bit faster (DHL Express 2 day) straight from the source because I am a QHY tester. The first batch should be arriving at dealers very soon though.

 

Also should mention, I downloaded the latest beta system package from here: https://www.qhyccd.com/download.html Have only tested the ASCOM driver in SGP, but had no issues at all so far.


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#4 Sponge

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Posted 29 January 2021 - 04:47 AM

Great results!

 

Could you please show a photo of the tilt adjuster that you mentioned in the OP?

 

I'd also be interested in the FITS files if you could upload them!

 

Cheers


Edited by Sponge, 29 January 2021 - 05:00 AM.


#5 xiga

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Posted 29 January 2021 - 05:34 AM

Thanks Nico!

I'll be picking one of these up too, I think. Im still on SGP 2.9, I presume I will now have to upgrade to the latest version to get it to work with the camera?

Ps - can you weigh it and measure how long it is for us, pretty please? 🙏

#6 OnTheArrow

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Posted 29 January 2021 - 07:46 AM

Thank you for the review. I'm also waiting for the camera to arrive, so every piece of information is valuable and so exciting))
By the way the numbers you've posted which were taken at gain 56 correspond to gain 60 on the graph published at qhyccd page. According to it gain 60 triggers this super low read noise and at 56 you must be still at around 3,5e.

#7 SilverLitz

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Posted 29 January 2021 - 09:10 AM

Does the tilt adjuster have M54 Female threads?



#8 OhmEye

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Posted 29 January 2021 - 10:51 AM

Thank you for the review. I'm also waiting for the camera to arrive, so every piece of information is valuable and so exciting))
By the way the numbers you've posted which were taken at gain 56 correspond to gain 60 on the graph published at qhyccd page. According to it gain 60 triggers this super low read noise and at 56 you must be still at around 3,5e.

The graph likely is, er, not quite on the mark.

 

By watching the noise and increasing gain you can clearly see it switch from LCG to HCG at gain 56, which is where minimal readout noise is for mode #1. I had this process demonstrated to me by dghent using Sharpcap, watching the Histogram SD as the noise increases until the gain value where HCG kicks in and the noise drops off the cliff to minimal then rises with gain as it's increased. I don't have my 268m yet to test myself but my understanding is the HCG happens at gain 56 as with the 268c and 600m, not at 60 as the graph implies. I'm expecting mode #1 with gain 56 and offset 25 may become the defacto popular settings for the 268m for DSO imaging.

 

Don't trust graphs. Test. smile.gif


Edited by OhmEye, 29 January 2021 - 10:58 AM.

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#9 dghent

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Posted 29 January 2021 - 11:15 AM

Yeah the way to find the actual LCG->HCG transition point where read noise drops and DR recovers is simple. It's better than reading graphs where the actual value is visually ambiguous due to the resolution of the graph.

 

  1. Cap the camera to prevent external light from reaching the sensor
  2. Open up SharpCap or your favorite app that provides standard deviation in its frame stats. I prefer SharpCap because it's quick and easy.
  3. If using SharpCap, open the Histogram window and look for the SD ("Standard Deviation") on the right side. If you're doing this with a color cam, make sure you're in MONO16, no debayering. You want a mono representation in the histogram. 
  4. Set exposure time to the minimum allowed
  5. Set gain to 0. You can ignore offset for this exercise

One you have the above set up, you will want to verify which readout mode the 268M is in. Set it to the one you want to find the transition value for (Photo DSO, High Gain, etc) 

 

Increase the gain while watching the Standard Deviation (SD stat in SharpCap's histogram) and you will witness the value increasing as you increase the gain. Since the standard deviation is a representation of noise, this is expected, and since the camera is capped to prevent external light, the deviation being measured should just be readout noise.

At some point, you will notice that the standard deviation suddenly drops once you increment the gain to a certain value. How much of a drop depends on the camera and its sensor type of course, but once you enter the HCG realm, there will be a drop none the less. If you then go back one point of gain, you ought to see the SD return to its previous higher value, indicating that you are in the upper end of the low conversion gain realm. At any rate, that gain value where you witness the sudden drop in SD marks the point where you've entered the high conversion gain realm. After you have found that, you can then determine the offset which you should operate at.


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#10 2ghouls

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Posted 29 January 2021 - 11:25 AM

Great results!

 

Could you please show a photo of the tilt adjuster that you mentioned in the OP?

smooth.jpg

smooth2.jpg

 

Does the tilt adjuster have M54 Female threads?

No threads. Comes with a generic 55mm lens cap; see photos above.



#11 2ghouls

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Posted 29 January 2021 - 11:29 AM

Thanks Nico!

I'll be picking one of these up too, I think. Im still on SGP 2.9, I presume I will now have to upgrade to the latest version to get it to work with the camera?

Ps - can you weigh it and measure how long it is for us, pretty please? 🙏

I might have a laptop that still has 2.9 installed. I could try to check later. I did these tests on whatever the latest version of SGP3 is.

 

Weight: 812 grams. Length: 107mm Width: 90mm

 

weight.jpg

length1.jpg

width.jpg


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#12 2ghouls

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Posted 29 January 2021 - 11:37 AM

Thank you for the review. I'm also waiting for the camera to arrive, so every piece of information is valuable and so exciting))
By the way the numbers you've posted which were taken at gain 56 correspond to gain 60 on the graph published at qhyccd page. According to it gain 60 triggers this super low read noise and at 56 you must be still at around 3,5e.

You can see the posts by OhmEye and dghent on testing. I will just point out that the graph published on the QHYCCD page here is accurate, but could be misleading. If you look closely at the plotted line, you can see the actual samples are spaced every 5 increments of gain (0,5,10...55,60) For this reason, it looks like LCG->HCG kicks in at 30 in readout mode 0 and at 60 in readout mode 1, when in reality the high gain kicks in at 26 and 56 respectively. Rough visual example of what I mean:

chart.jpg



#13 2ghouls

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Posted 29 January 2021 - 11:43 AM

I'd also be interested in the FITS files if you could upload them!

Here we go: https://drive.google...X6c?usp=sharing

Also added the link to the original post. I may add more files to the same link later.



#14 bigeastro

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Posted 29 January 2021 - 12:14 PM

This should be interesting.  If you bolt it on to a filter wheel, how do you dynamically adjust the tilt with it bolted on?


Edited by bigeastro, 29 January 2021 - 12:16 PM.


#15 Peter in Reno

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Posted 29 January 2021 - 12:20 PM

This should be interesting.  If you bolt it on to a filter wheel, how do you dynamically adjust the tilt with it bolted on?

Tilt? Do you mean rotating to frame DSO?

 

Peter 



#16 bigeastro

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Posted 29 January 2021 - 12:24 PM

No, I mean adjusting the camera so the light cone is perpendicular to the chip.  The larger the chip the more the tilt issue can arise.



#17 bigeastro

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Posted 29 January 2021 - 12:25 PM

The graph likely is, er, not quite on the mark.

 

By watching the noise and increasing gain you can clearly see it switch from LCG to HCG at gain 56, which is where minimal readout noise is for mode #1. I had this process demonstrated to me by dghent using Sharpcap, watching the Histogram SD as the noise increases until the gain value where HCG kicks in and the noise drops off the cliff to minimal then rises with gain as it's increased. I don't have my 268m yet to test myself but my understanding is the HCG happens at gain 56 as with the 268c and 600m, not at 60 as the graph implies. I'm expecting mode #1 with gain 56 and offset 25 may become the defacto popular settings for the 268m for DSO imaging.

 

Don't trust graphs. Test. smile.gif

We should be able to trust graphs.  We are not paid to test.   We pay to enjoy.


Edited by bigeastro, 29 January 2021 - 12:28 PM.


#18 Peter in Reno

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Posted 29 January 2021 - 12:28 PM

No, I mean adjusting the camera so the light cone is perpendicular to the chip.  The larger the chip the more the tilt issue can arise.

Ok. I was referring to bad English translation from QHY web site about how they use the words "tilt adjuster". I wish they get rid of these words and replace them with something like dovetail. 

 

Peter 



#19 xiga

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Posted 29 January 2021 - 12:32 PM

I might have a laptop that still has 2.9 installed. I could try to check later. I did these tests on whatever the latest version of SGP3 is.

 

Weight: 812 grams. Length: 107mm Width: 90mm

 

attachicon.gifweight.jpg

attachicon.giflength1.jpg

attachicon.gifwidth.jpg

Absolute legend, thanks Nico!



#20 2ghouls

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Posted 29 January 2021 - 12:40 PM

This should be interesting.  If you bolt it on to a filter wheel, how do you dynamically adjust the tilt with it bolted on?

Right, you can't with a filter wheel on. I possibly could with my current setup, where I am using some spacers, than a filter drawer, then more spacers. But maybe this piece isn't meant to adjust tilt, but just for attachment (dovetail would be the correct word as Peter correctly points out above). I had assumed based on documentation that these exposed screws (circled in red) could be used to adjust tilt, but that might not be their purpose.

tilt.jpg



#21 bigeastro

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Posted 29 January 2021 - 12:49 PM

Are there set screws adjacent to them?  Three of them have what appear to be set screws adjacent to them.  If so, then their purpose may be tilt adjustment.  However, as is the case with the ZWO unit, they are near worthless as tilt adjusters because having to take the entire filter wheel apart is a non starter.  Actually having the ability to unscrew the camera would be a better design for sure.



#22 bigeastro

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Posted 29 January 2021 - 12:51 PM

I am looking to purchase this camera, and re-purchase the 294.  However, the manufacturers have to issue a product worth purchasing.  No hype in the world is going to get me to purchase anything new without a critical analysis of what is being offered.  Not even pretty pictures is going to do it for me.  This time, things are different for me and I urge everyone to behave similarly.  Let's see what has been produced.  Thank you Nico for disclosing you are a QHY tester and as a result have a relationship with the company.   This disclosure adds to your credibility. 


Edited by bigeastro, 29 January 2021 - 12:56 PM.


#23 2ghouls

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Posted 29 January 2021 - 01:02 PM

Are there set screws adjacent to them?  Three of them have what appear to be set screws adjacent to them.  If so, then their purpose may be tilt adjustment.  However, as is the case with the ZWO unit, they are near worthless as tilt adjusters because having to take the entire filter wheel apart is a non starter.  Actually having the ability to unscrew the camera would be a better design for sure.

Ok. I was referring to bad English translation from QHY web site about how they use the words "tilt adjuster". I wish they get rid of these words and replace them with something like dovetail. 

 

Peter 

There are threaded holes on either side of three of the screws, but no set screws installed inside the threaded holes. I just looked through the packaging again and nothing was provided that fits in these threaded holes, so :confused:  All I can tell you is the thread is not M3 as the M3 bolts are just a bit too big to fit, maybe M2.5. I think Peter is right that it's just a poor translation. I've updated my original post, and will pass this on to QHY.



#24 bigeastro

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Posted 29 January 2021 - 01:04 PM

Actually better that the plate is simply a dovetail plate.   They should just indicate the holes were for aeration.



#25 Shannon Foye

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Posted 29 January 2021 - 01:08 PM

Tilt can be adjusted by placing copper tape shims between the camera and the plate.

See Note1 at the bottom of this page:
https://www.qhyccd.c...catid=30&id=317

And this PDF for a picture of the copper tape:
https://www.qhyccd.c...22052913161.pdf
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