ASI1600mm cool

[Guest]

10 hours ago, Andyb90 said:

Can I just check what mean ADU is about right for taking flats? I've used the flats wizard in SGPro. I got a reading of approx 22,000 ADU with the ASI1600.

Is this okay for flats or a bit on the high side?

Andy.

Hi Andy - I've been using 22-24k, moving the histogram as near the middle as I can without going out of this range - the histogram usually winds up just under  midway.

Seems to work ok :-)

David

[Guest]

7 hours ago, Andyb90 said:

Here's a second attempt at the Rosette this time with gain 200, Ha 30 x 90s, -25c. I wanted 50+ subs, but had to throw many away due to bad guiding. I think I prefer this version to my attempt at gain 300. I'll try gain 139 next. 

 

 

Andy.

Excellent results Andy - now try it at 139 gain and 5 minute exposure :-) .....go on - give it a shot, just make sure to take darks :-)

David

[IanL]

Here's a Rosette from Boxing Day.  Skywatcher 80ED with 0.85x reducer, so about f/6.6.  20 x 300s each of Ha, OIII, SII, Bias x 300 frames, Darks 100 x 300s.  Gain and offset were at the default unity settings (139/21).  Cooler was set at -15C as I can reliably produce matching darks in the house at that temperature.  I'm getting about -39C below ambient so if I move the camera somewhere colder to create a dark library I can go for a lower set point in future.

Observations:

1.  This is my first ever NB image, so processing is a bit rough and ready - needs more work and have definitely pushed the background beyond what the data will support.  Deconvolution wasn't spot on either so there is a bit of ringing still around the bigger stars.  The colour palette needs a bit of tweaking as it is too green for my liking.

2. I need more data full stop, especially for the SII which was very noisy.

3. I thought I had the spacing issues to the FR spot on.  On closer inspection I think it's slightly too long - plate solving tells me I am getting a reduction of 0.86x rather than 0.85x so probably needs a mm or two less - had similar issues with my DSLR when the spacing was too long.  I also didn't refocus between filters which won't have helped the stars

4. The bias looks fairly normal to me - there is no amp glow to respond to a question asked above.

5. Dark subtraction work fine - the amp glow increases proportionately with increasing exposure times so nothing weird going on there.  What I have found (for PixInsight users) is that you need to turn off dark frame optimisation when calibrating.  If you leave it on then temperature and time-matched darks will under-correct the amp-glow, but turn it off and you will eliminate it completely with matched darks.  This isn't surprising since PixInisight's optimisation looks to minimise the residual noise in the whole frame and doesn't look at localised effects.

6. I just went with what the SGPro flats wizard suggested for each filter for the flats and they worked out fine.

[Guest]

10 minutes ago, IanL said:

Here's a Rosette from Boxing Day.  Skywatcher 80ED with 0.85x reducer, so about f/6.6.  20 x 300s each of Ha, OIII, SII, Bias x 300 frames, Darks 100 x 300s.  Gain and offset were at the default unity settings (139/21).  Cooler was set at -15C as I can reliably produce matching darks in the house at that temperature.  I'm getting about -39C below ambient so if I move the camera somewhere colder to create a dark library I can go for a lower set point in future.

Observations:

1.  This is my first ever NB image, so processing is a bit rough and ready - needs more work and have definitely pushed the background beyond what the data will support.  Deconvolution wasn't spot on either so there is a bit of ringing still around the bigger stars.  The colour palette needs a bit of tweaking as it is too green for my liking.

2. I need more data full stop, especially for the SII which was very noisy.

3. I thought I had the spacing issues to the FR spot on.  On closer inspection I think it's slightly too long - plate solving tells me I am getting a reduction of 0.86x rather than 0.85x so probably needs a mm or two less - had similar issues with my DSLR when the spacing was too long.  I also didn't refocus between filters which won't have helped the stars

4. The bias looks fairly normal to me - there is no amp glow to respond to a question asked above.

5. Dark subtraction work fine - the amp glow increases proportionately with increasing exposure times so nothing weird going on there.  What I have found (for PixInsight users) is that you need to turn off dark frame optimisation when calibrating.  If you leave it on then temperature and time-matched darks will under-correct the amp-glow, but turn it off and you will eliminate it completely with matched darks.  This isn't surprising since PixInisight's optimisation looks to minimise the residual noise in the whole frame and doesn't look at localised effects.

6. I just went with what the SGPro flats wizard suggested for each filter for the flats and they worked out fine.

 

Excellent feedback and great results on the image! ....and with 5min exposures - cool.

 

 

[Gina]

9 hours ago, sharkmelley said:

I see numerous references and examples of amp glow in this thread.

Does this amp glow exist in a master bias?  For instance what happens if a master bias is created from, say, 100 bias frames?

If the edge glow exists in the master bias, then it isn't "traditional" amp glow with an underlying thermal cause but it could well be the same kind of edge glow effect seen in other Sony sensors:  https://stargazerslounge.com/topic/283484-edge-glow-on-master-bias/

Just curious ...

Mark

No, amp glow doesn't show in bias frames, even at a gain of 600 (the maximum).  It shows in the darks.

[Gina]

1 hour ago, IanL said:

5. Dark subtraction work fine - the amp glow increases proportionately with increasing exposure times so nothing weird going on there.  What I have found (for PixInsight users) is that you need to turn off dark frame optimisation when calibrating.  If you leave it on then temperature and time-matched darks will under-correct the amp-glow, but turn it off and you will eliminate it completely with matched darks.  This isn't surprising since PixInisight's optimisation looks to minimise the residual noise in the whole frame and doesn't look at localised effects.

Thank you for that   Maybe that's why my amp glow isn't being properly subtracted.  I'll have another go.  I used BPP last time but I think I'll use separate processing steps for more control.

[Gina]

Examined some of my calibrated subs and while much of the amp glow has been subtracted, when I apply STF quite heavily I can see the gradient and particularly a bit of amp glow at the bottom of the frame.  I shall now apply calibration separately.

[Gina]

Yes, that was it - strong STF on calibrated frames shows no sign of amp glow - thank you very much Ian

[IanL]

1 hour ago, Gina said:

Yes, that was it - strong STF on calibrated frames shows no sign of amp glow - thank you very much Ian

No problem Gina. I spotted it on the OIII master. The subs were taken 50:50 before and after the meridian flip so I had residual amp glow on both sides of the master. Checking the logs I could see that a dark scaling of about 0.45 was being used despite matched frames. Lesson is to build a dark library for the common exposure and gain settings you will use.

Also since optimisation needs to be off in PI, probably no need to use bias subtraction, except perhaps in lieu of a dark for short exposure flats.

Another tip is to use the DefectMap process to deal with hot and cold pixels.

- Just take an existing master dark (maybe 120s exposures or thereabouts).

- Clone it and Use Binarize with a high threshold to isolate hot pixels. Invert this clone (Bad pixels need to be black).

- Use Binarize with a low threshold on a second clone of the master dark to isolate cold pixels (only found a handful of these). Bad pixels should already be black in this one.

- Use Pixel math  and put Image1 * Image2 in the RGB/K box (replace Image1 and 2 with the identifiers of the Binarized maps).  Execute it outputting the result to a new image.

- You should now have a mostly white image with a scattering of black pixels (hard to see, so invert if you need to check but remember to re-invert afterwards). Save the defect map in your calibration library.

You can then use it with the (documented) DefectMap process immediately after calibration and before StarAlignment, with an ImageContainer of the calibrated subs. If you have lots of well dithered subs it may not be necessary to do this but it's a quick and easy step and may help where you have few subs. I was only dithering every fourth frame to save time in the example above.

 

[Gina]

Thank you Ian   I'll check that out   I do have a library of master biases and darks.  And flats too for each filter and lens combination.

[Filroden]

3 hours ago, IanL said:

Also since optimisation needs to be off in PI, probably no need to use bias subtraction, except perhaps in lieu of a dark for short exposure flats.

I've stopped using bias for my lights as I'm using matching darks with no optimisation. However, for my flats, which vary from just under 1s to just over 3s exposures, I'm optimising a 5s dark and calibrating with a bias. I'm not sure what's best for flats as I can't build a matching dark library for them as they change in length each time (though only by fractions of a second).

[trev27]

20 minutes ago, Filroden said:

I've stopped using bias for my lights as I'm using matching darks with no optimisation. However, for my flats, which vary from just under 1s to just over 3s exposures, I'm optimising a 5s dark and calibrating with a bias. I'm not sure what's best for flats as I can't build a matching dark library for them as they change in length each time (though only by fractions of a second).

Hi Ken, I believe that the darks are scaled when calibrated to the flats. e.g. I've actually been using a 30 second master dark (bias calibrated) on all of my flats as that was the shortest dark frame I had captured. The results seemed pretty good.

Trev

[Filroden]

3 minutes ago, trev27 said:

Hi Ken, I believe that the darks are scaled when calibrated to the flats. e.g. I've actually been using a 30 second master dark (bias calibrated) on all of my flats as that was the shortest dark frame I had captured. The results seemed pretty good.

Trev

Indeed they are. I have a library of 1s, 5s, 15s darks for these but I'm not sure if the flats need dark correcting or just be calibrated with a bias. I don't see any amp glow in my darks, even at 60s, so it's only hot/cold pixels I would be correcting.

[trev27]

Easy target I know but I'm pretty surprised again by how much detail can be pulled in so quickly. The ASI1600 was set to a gain of 200 and offset of 35. 

30x60s in each HA and OIII

30x10s in each for the trap area.

Nebulas was hovering around 30 degrees over the city lights. Bright target so I got to use short exposures this time.

Megrez 90 doublet and ASI1600MM

Trev

[trev27]

2 minutes ago, Filroden said:

Indeed they are. I have a library of 1s, 5s, 15s darks for these but I'm not sure if the flats need dark correcting or just be calibrated with a bias. I don't see any amp glow in my darks, even at 60s, so it's only hot/cold pixels I would be correcting.

I was wondering that also. It seems like a bit of overkill to be sure. I'll try my next set without dark on the flats.

[imballinger]

Would this camera take good pictures with a Celestron Nexstar 8?

[Andyb90]

15 hours ago, David_L said:

Excellent results Andy - now try it at 139 gain and 5 minute exposure :-) .....go on - give it a shot, just make sure to take darks :-)

Would like to try longer, but my guiding is rubbish. Here's just one example. Its a scary graph!

But I'm sure things will improve when I get a new mount. I don't think they can get much worse!

Andy.

[piprees]

On ‎1‎/‎5‎/‎2017 at 16:37, trev27 said:

Easy target I know but I'm pretty surprised again by how much detail can be pulled in so quickly. The ASI1600 was set to a gain of 200 and offset of 35. 

30x60s in each HA and OIII

30x10s in each for the trap area.

Nebulas was hovering around 30 degrees over the city lights. Bright target so I got to use short exposures this time.

Megrez 90 doublet and ASI1600MM

Trev

Absolutely brilliant, puts mine to total shame. In my defence, I'm not too sure, (don't laugh), what I'm actually doing.

Going to get Pixinsight shortly and follow the tutorials and all the advice that I can find.

orion nebula.tiff

[Guest]

13 hours ago, piprees said:

Absolutely brilliant, puts mine to total shame. In my defence, I'm not too sure, (don't laugh), what I'm actually doing.

Going to get Pixinsight shortly and follow the tutorials and all the advice that I can find.

orion nebula.tiff

Here's my goto list of PixInsight.....insight :-)

http://www.harrysastroshed.com/

http://www.lightvortexastronomy.com/

 

[Gina]

Great tutorial sites - thoroughly recommended   And Harry is a member here

[halli]

Hi All

Had a go at IC443 (Jellyfish) with the 1600 and a TS71 imaging star refractor - see below:-

Gain 300, offsett 10

140xHa @ 120s -30C

30x each of R,G and B @ 120s -30C

using Darks , flats and bias

This is a cropped image as I introduced a bit of camera rotation between 2 nights accidentally, so unfortunately lost some of the FOV

I also took some frames of OIII , SII and HB   but not had a chance to try these with the Ha  yet 

It was processed as Ha RGB using PI introducing the Ha as if it was LUM using LRGB combination

 

[Gina]

Ah yes, reminds me I've only done Ha on the Jellyfish must do OIII and SII.  That's whenever we get some clear night sky and goodness knows when that will be!!  Nice shot BTW

[halli]

Thanks for the comment Gina - OIII and SII is a new venture for me so it will be interesting to see what comes out !

[Magnus_e]

Hi.

I got my new camera last week and have been playing with taking biases, darks and installing filters.

I took around 200 bias, and darks of 30sec to 600sec. They do look good to me, but I have no experience with a mono camera, and I'm not sure I have translated the settings correctly. I use INDI and there is no unity and offset, only gamma and brightness.

All darks with links to originals are in this thread.

Filters installed

 

Just noticed as I'm posting that i can see rgb trough the L filter (1), that seams a little strange.

 

Eagerly waiting for a chance of first light

[Gina]

I think that's just colour fringing on the sensor.