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

[teoria_del_big_bang]

41 minutes ago, scotty38 said:

Those mists have impacted my Jellyfish.....

Pretty much the same here now, you could have kept them down there a bit longer 😞

Still taking images as it will flip in an hour and want to check it all works okay as I think it failed last time. But when I go out and look how cloudy it is I cant believe it is still guiding. I think all but a few of the early images will not be of any use but might as well achieve something before I lug all the gear back in.
You never know it may clear up again ?

Steve

Edited January 20, 2022 by teoria_del_big_bang

[Stuart1971]

Me too clouds stopped play….☹️

[Stuart1971]

1 hour ago, teoria_del_big_bang said:

Okay, so far so good, clouds have not yet appeared so doing some Ha and SII on Jellyfish, not bothering with OII as there is so little there and giving massive halos on the two bright stars.
So I have come down in exposure time big time from my usual 10 minutes to 4.
Looking at the statistics in EKOS I am getting a mean  of 475, so that is pretty much in line with what @Xiga suggested was correct for this gain and offset, but the maximum is 65534. When I look in Pixinsight the two bright stars are maximum ADU before any stretching, so I take it there is nothing I can do about the brightest of stars in the data itself and I will have to take care of that in the processing, because even a slightly shorter exposure time is not going to significantly reduce those two stars, if at all. I guess some stars you just cannot stop from being over blown when imaging dim targets and have to deal with them later.
 

Steve

That sub says 400 seconds….or is that that wrong…if that is the data you get with a narrowband filter, in 4 mins, then I have something wrong with my camera….☹️

Edited January 20, 2022 by Stuart1971

[Stuart1971]

This is all I get in a 5 min sub….mode 1 gain 56

 

[tomato]

But @teoria_del_big_bang has a mono camera?

[Stuart1971]

23 minutes ago, tomato said:

But @teoria_del_big_bang has a mono camera?

Ok, so stupid question…..is that the difference…..really…..?? 

[teoria_del_big_bang]

12 minutes ago, Stuart1971 said:

Ok, so stupid question…..is that the difference…..really…..?? 

Well yes I would say so because to get a colour image I have to take 3 of these images and combine so really the intergration time for one colour image is actually 12 minutes.
Okay this is NB but some checks I did earlier on using RGB looks like I need to be around 120 seconds for RGB images so for one frame of RGB would be 6 minutes.

Steve 

[Xiga]

3 hours ago, teoria_del_big_bang said:

Okay, so far so good, clouds have not yet appeared so doing some Ha and SII on Jellyfish, not bothering with OII as there is so little there and giving massive halos on the two bright stars.
So I have come down in exposure time big time from my usual 10 minutes to 4.
Looking at the statistics in EKOS I am getting a mean  of 475, so that is pretty much in line with what @Xiga suggested was correct for this gain and offset, but the maximum is 65534. When I look in Pixinsight the two bright stars are maximum ADU before any stretching, so I take it there is nothing I can do about the brightest of stars in the data itself and I will have to take care of that in the processing, because even a slightly shorter exposure time is not going to significantly reduce those two stars, if at all. I guess some stars you just cannot stop from being over blown when imaging dim targets and have to deal with them later.
 

Steve

Hi Steve

There will always be some stars that clip (it's unavoidable to some extent) so it's just about making sure the number that do isn't excessive. Those 2 stars are Very bright, so it's to be expected really. 

ps - don't give up on the Oiii either. A few years back i shot the Jellyfish in Ha and Oiii, using just a Nikon D5300, and found there to be plenty of Oiii, so you should have no difficulty with your mono CMOS. https://www.astrobin.com/384884/

[teoria_del_big_bang]

24 minutes ago, Xiga said:

Hi Steve

There will always be some stars that clip (it's unavoidable to some extent) so it's just about making sure the number that do isn't excessive. Those 2 stars are Very bright, so it's to be expected really. 

ps - don't give up on the Oiii either. A few years back i shot the Jellyfish in Ha and Oiii, using just a Nikon D5300, and found there to be plenty of Oiii, so you should have no difficulty with your mono CMOS. https://www.astrobin.com/384884/

I thought that was the case.

It was more the horrible halos that made me give up.
I will try another nights, whether it would be any better with less moon up or not I do not know ????

Your image on Astrobin is really nice, you have captured that OIII really well. I guess on mine there are some signs on the outer edges, maybe a bit longer exposure on OIII and more frames would add some nice detail so I must r=try at a later date (hopefully not too much later). I can deal with the halos in processing, a pain but would be worth it.

 

Steve

Edited January 21, 2022 by teoria_del_big_bang

[Xiga]

1 hour ago, teoria_del_big_bang said:

I thought that was the case.

It was more the horrible halos that made me give up.
I will try another nights, whether it would be any better with less moon up or not I do not know ????

Your image on Astrobin is really nice, you have captured that OIII really well. I guess on mine there are some signs on the outer edges, maybe a bit longer exposure on OIII and more frames would add some nice detail so I must r=try at a later date (hopefully not too much later). I can deal with the halos in processing, a pain but would be worth it.

 

Steve

From my comment on AB, it seems that I shot my Oiii with a very bright moon up, so you should still do ok. I agree, I can see some showing at the outer edges on yours, and that's just a single 400s sub. Capture a few hrs and it will really show up. 

[Stuart1971]

Ok, this is just 3 hours of 5 min subs, no calibration at all, just stacked lights to see what I had…

‘Does it look ok for 3 hours…Mode 1 gain 56…bortle 6 and with Idas P2 LP filter, it’s certainly better…Or should I expect more for 3 hours of data…..🤔

 

Edited January 21, 2022 by Stuart1971

[teoria_del_big_bang]

I think for 3 hours, Bortle 6 and a near full moon that's about what I would expect.
With some calibration and work on the background it will probably pop out some more.

Steve

Edited January 21, 2022 by teoria_del_big_bang

[Stuart1971]

23 minutes ago, teoria_del_big_bang said:

I think for 3 hours, Bortle 6 and a near full moon that's about what I would expect.
With some calibration and work on the background it will probably pop out some more.

Steve

Thanks,

The moon was not out at this point…also I forgot to add I use an f5.3 scope, 450mm

I have  done the darks now, and will do the flats and dark flats tomorrow, but think I will get at least another 3 or 4 hours before I fully process….

I just wonder how much useable light the Idas P2 filter blocks, also i do get some vignetting and think it’s from the filter…🤔

[Xiga]

9 minutes ago, Stuart1971 said:

Thanks,

The moon was not out at this point…also I forgot to add I use an f5.3 scope, 450mm

I have  done the darks now, and will do the flats and dark flats tomorrow, but think I will get at least another 3 or 4 hours before I fully process….

I just wonder how much useable light the Idas P2 filter blocks, also i do get some vignetting and think it’s from the filter…🤔

Hi Stuart,

it's a very nice image indeed, and will look even better once you get the calibration frames done. 

If you're wondering why the nebulosity isn't popping more, it's entirely down to the Idas filter. It's certainly a very nice LP filter (i have a D1 one myself), but when it comes to shooting a narrowband target like the Heart Nebula, you would see a big improvement with one of the many Dual-band filters (such as the L-Extreme) that are popular right now. Then you will get a lot more contrast between the nebulosity and the sky background. 

[Stuart1971]

1 minute ago, Xiga said:

Hi Stuart,

it's a very nice image indeed, and will look even better once you get the calibration frames done. 

If you're wondering why the nebulosity isn't popping more, it's entirely down to the Idas filter. It's certainly a very nice LP filter (i have a D1 one myself), but when it comes to shooting a narrowband target like the Heart Nebula, you would see a big improvement with one of the many Dual-band filters (such as the L-Extreme) that are popular right now. Then you will get a lot more contrast between the nebulosity and the sky background. 

Thanks very much for that, much appreciated, I did wonder about the filter, I think this has been much more of a hinderance, as my last two images have been the Pac-Man and this Heart Nebula and both seem to have shown less data per 5 min sub than I though they would, so have treated myself to the Optolong L-Xtreme should be here soon…. 👍🏼

[Richard_]

18 hours ago, teoria_del_big_bang said:

I thought that was the case.

It was more the horrible halos that made me give up.
I will try another nights, whether it would be any better with less moon up or not I do not know ????

Your image on Astrobin is really nice, you have captured that OIII really well. I guess on mine there are some signs on the outer edges, maybe a bit longer exposure on OIII and more frames would add some nice detail so I must r=try at a later date (hopefully not too much later). I can deal with the halos in processing, a pain but would be worth it.

 

Steve

Hi Steve. Let me preface this with saying that I have no experience with narrowband imaging. I'd recommend checking out this video from Adam Block which may help in the removal of halos from your OIII data. In his video, Adam explains how you can replace signal from one channel into another with the use of masks, linear fit and pixel math. 

I tried this approach for my above issue on reflections, but unfortunately it didn't fix the issue as the signal was present in all three RGB channels so there was no clean data for me to replace. 

I wonder if this would be useful for the halos you saw in the OIII channel,  perhaps substituting with data from the HA or SII channels could reduce or eliminate them? 

 

[teoria_del_big_bang]

15 minutes ago, Richard_ said:

Hi Steve. Let me preface this with saying that I have no experience with narrowband imaging. I'd recommend checking out this video from Adam Block which may help in the removal of halos from your OIII data. In his video, Adam explains how you can replace signal from one channel into another with the use of masks, linear fit and pixel math. 

I tried this approach for my above issue on reflections, but unfortunately it didn't fix the issue as the signal was present in all three RGB channels so there was no clean data for me to replace. 

I wonder if this would be useful for the halos you saw in the OIII channel,  perhaps substituting with data from the HA or SII channels could reduce or eliminate them? 

 

Cheers, thats is exactly what I intended to do using Pixelmath but this will mean I don't have to work out the maths ha ha , cheers 🙂 

[teoria_del_big_bang]

On another note regarding the humidty the camera reports what sort of figures are people getting both when idle at room temperature and when inaging whith cooling on (They should be different).

I forgot to fit the desecant tube and only just ft it a few weeks ago as when imaging it was up to 73%, and was 60% when at room temperature (well garage so probably 7 C or so) so have just fit it and slowly coming down.

Steve

[Stuart1971]

Ok, to stir up a bit of a discussion regards these cameras….

I have been reading on the NINA discord forum that the new IMX571 family of cameras are so clean that there is only a need for Flat frames and bias frames, with your lights,  and not to bother with Darks or Dark flats, now I have been using Flats, Darks and Dark flats with my images and seem to work ok,  but are we wasting time with darks and dark flats as they only really contain the bias signal so may as well just use bias frames…..🤔🤔🤔

Something to ponder….

[tomato]

Are there not hot and cold pixels on these sensors, they don’t normally put premium grade chips in commercial astro cameras? 
 

If so don’t you need the calibration frames to produce a bad pixel map?
 

 

[Stuart1971]

7 minutes ago, tomato said:

Are there not hot and cold pixels on these sensors, they don’t normally put premium grade chips in commercial astro cameras? 
 

If so don’t you need the calibration frames to produce a bad pixel map?
 

 

Very good point, I have lots of hot and cold pixels on mine….🤔

Dithering….? Rejection when stacking….?….would that sort them…

Edited January 29, 2022 by Stuart1971

[tomato]

True, although I struggle with making dithering work on a dual rig, even with NINA. In APP I know Mabula extolled the virtues of creating a Bad Pixel Map so I have stuck to that mantra.

[scotty38]

1 hour ago, tomato said:

True, although I struggle with making dithering work on a dual rig, even with NINA. In APP I know Mabula extolled the virtues of creating a Bad Pixel Map so I have stuck to that mantra.

Have you tried the Synchronisation plugin that's designed for this? I've no idea what it's like but maybe worth a go?

[Stuart1971]

2 hours ago, tomato said:

True, although I struggle with making dithering work on a dual rig, even with NINA. In APP I know Mabula extolled the virtues of creating a Bad Pixel Map so I have stuck to that mantra.

So you use BPM, flats and bias..?  but I guess you need the darks initially to create the BPM…?

[tomato]

Yes with CMOS cameras I use darks, flats and   flat darks. The darks are essential with the ASI 178s I use for small object imaging as they have a healthy amp glow, and I just stick to the same regime for the IMX 571  cameras.