QHYCCD

First evaluation of QHY5III 174 monochrome (uncoled)

ajs

Re: First evaluation of QHY5III 174 monochrome (uncoled)
« Reply #15 on: August 09, 2016, 05:45:48 am »
Hello,
I have tested the QHY5III 174C for deepsky and my results are sometimes good and sometimes the pictures has a lot of aleatory stripes like in the attachment picture. I don't know why this happens.

Does anybody know the reason of those stripes?

This picture is the result of 400 lights, 400 darks a 400 bias at 10 sec, 100 offset, 70 gain, adquired with Sharpcap and stacked with DeepSkyStacker. Stacking with Pixinsight gives the same result.

Thank you in advance,

Andres

Re: First evaluation of QHY5III 174 monochrome (uncoled)
« Reply #16 on: August 09, 2016, 02:48:07 pm »
Andres, Was this taken with a guided mount ?

Steve.

ajs

Re: First evaluation of QHY5III 174 monochrome (uncoled)
« Reply #17 on: August 10, 2016, 04:54:55 am »
No Steve, but I made tests with autoguide and there is no difference.
But the fabolous pictures posted below weren't adquired with guiding, isn't it. This is the advantage of this technique.

The tests I did were taked from my house and I can't see Polaris from here, but I made aligment to Polaris with an option in the mount software. This aligment is not as good as the true polar aligment, so I think this can be the reason.

Yesterday I can go out and I made several tests with true Polar aligment using the Polemaster and without guiding, and now I am procesing them, but I have seen that there is drifting between the individual frames because periodical error, so it can be possible that the effect happen again.


When I process the new tests I'll put the results here.

Re: First evaluation of QHY5III 174 monochrome (uncoled)
« Reply #18 on: August 10, 2016, 06:12:28 am »
Andres,

The stripes are typically caused by errors in calibration, eg if a dark frame is used that was at a different temperature, gain or exposure length to the light frame.

Terry

ajs

Re: First evaluation of QHY5III 174 monochrome (uncoled)
« Reply #19 on: August 10, 2016, 06:55:16 am »
Thank you Terry.

Logical thinking goes to you said about error in calibration, but I always make darks and bias in the same session after making all the light frames and with the same gain, offset and exposition time that light frames.


Could be another possibility the calibration error?

« Last Edit: August 10, 2016, 12:54:44 pm by ajs »

ajs

Re: First evaluation of QHY5III 174 monochrome (uncoled)
« Reply #20 on: August 10, 2016, 01:02:04 pm »
Here are the result of yesterday session.
As you can see, the stripes are there. >:(

I'm sure that darks and bias are made in the same conditions that lights. I am disappointed, I bought this camera for applying the technique described in this topic, but I can't get good results.

I'm afraid that I have only a very expensive camera for autoguiding and planetary.  :'(
« Last Edit: August 10, 2016, 07:07:52 pm by ajs »

Re: First evaluation of QHY5III 174 monochrome (uncoled)
« Reply #21 on: August 11, 2016, 02:13:36 am »
If it is uncooled camera then dark temperature can change during imaging session making darks uncorrect.
You could try leaving darks out of calibration - see if that helps.

ajs

Re: First evaluation of QHY5III 174 monochrome (uncoled)
« Reply #22 on: August 11, 2016, 03:12:54 am »
Sorry, but my english is not very good. I don't understand the phrase "You could try leaving darks out of calibration".
Do you mean that try process the images without darks?

Re: First evaluation of QHY5III 174 monochrome (uncoled)
« Reply #23 on: August 11, 2016, 04:17:33 am »
Yes.
Then you can see hot pixels unless you use suitable stacking method - median or better some sigma rejection (= clipping).
If you are using DeepskyStacker there's a hot pixel removal option (Stacking - Cosmetic):
http://deepskystacker.free.fr/english/userguide.htm
« Last Edit: August 11, 2016, 04:23:31 am by einari »

ajs

Re: First evaluation of QHY5III 174 monochrome (uncoled)
« Reply #24 on: August 11, 2016, 11:27:32 am »
I have attempted with the Stacking-comsetic option and the result is that the stripes smooth a little, but the image too, and the result is worst.

I have substrated one light with one dark and one bias, and results an image without hotpixels, but I suppose that the hotpixels are not fully eliminated.

I can't found what is the problem. The camera was working for three hours, it's possible that in the first captured frames the temperature was lower, but after a time I suppose that the temperatura stabilized itself and some of the objects captured would be ok.

I am thinking that my camera is not able to do the described technique in this topic. I would like Albéric see my results and tell me why I can't captured images as good as his fabulous galaxies.




easybob95

Re: First evaluation of QHY5III 174 monochrome (uncoled)
« Reply #25 on: August 12, 2016, 01:51:54 am »
Hello ajs,

maybe your camera have a problem ... or not.

The problem happens some time with very good beta tester is that they have very good results with very heavy treatments and it is hard to have the same results.

So, it is quite dangerous to choose a camera only considering the results very good testers have.

Alberic is very very good and i know he made very heavy treatments with IMX174 uncooled camera because of the strippes and the ampglow.

Standart astrophotographer will have difficulties to gain such results.

Alain

ajs

Re: First evaluation of QHY5III 174 monochrome (uncoled)
« Reply #26 on: August 12, 2016, 03:41:37 am »
I have got acceptable results, at least without stripes in two or three times, but the conditions are quite diferent. The exposition time 20 s, and gain less than 60. You can see tehm in the attachement files. (Ignore the processing of the images, are the first images I process with Pixinsight)

Alain, you can are right and that is because I am asking in this forum and I am grateful to all you for your help.

« Last Edit: August 12, 2016, 07:48:43 am by ajs »

easybob95

Re: First evaluation of QHY5III 174 monochrome (uncoled)
« Reply #27 on: August 12, 2016, 04:37:09 am »
IMX174 uncooled cameras are quite hard to manage. IMX174 is a very interesting sensor but it may needs heavy treatments.

Alberic had some big difficulties to manage the uncool version and despite his great experience of treatments, he did not always succed to get very good results.

The cooled version of IMX174 is easier to manage but it is also complicated to manage stripes.

As for me, i did not buy an IMX174 sensor based camera because this sensor is to difficult to manage (i don't talk about planetary imaging). I had the miniCAM5F experience which was already quite hard to manage (but much easier then IMX174 camera).

When Sony will bring us a new IMX174 sensor with IMX290 quality, it will be very good for us.

Alain


Re: First evaluation of QHY5III 174 monochrome (uncoled)
« Reply #28 on: August 12, 2016, 04:41:31 pm »
The appearance of the noise in the Eagle Neb is a consequence of unguided imaging with an alignment error. The noise itself is from the things you know about (thermal noise, gain, etc) but the pattern indicates drift over the total imaging time.
Each sub doesn't have any noticeable drift that would make the stars oval but over the total time, the stars have drifted relative to the absolute position on the sensor. When the stacking program aligns the frames on the stars, it effectively moves the noise by the drift amount.
Obviously, you'll get the the greatest benefit from reducing the noise in the first place but better polar alignment will remove the pattern which is hard to remove with noise reduction techniques.

Steve.