First images with 120mc

[don4l]

The world of CMOS imaging is a complete mystery to me.  I've had a 120mc since the summer.  It works great as an autoguider with PHD2, but I have really struggled to capture anything other than a guide star.

Last Thursday there was cloud about, and the moon was almost full.  So I decided to have a proper play with it.  I'm very impressed!

I've photographed the moon through the same OTA before, but I have never achieved anything like this.

I used Sharpcap to capture.  I did 50 frame AVI's for the moon.  I used "Live Stack" for the other images.  I didn't use any darks or flats.  As far as I can see, this didn't affect the moon, but it had a huge effect on the other shots.

 

I would appreciate advice on what settings to use for the camera.  For the Moon I used a gain of 10.  For the deep sky stuff it was 40.  Anything higher than 60 seemed to produce a saturated background.  This might have been moon glow???

 

The deep sky exposures are about 10 minutes each.   The images are Moon, M42, M82 and NGC869.

 

 

 

[CedricTheBrave]

all good but the moon for me is fantastic 

which OTA?

[Sunshine]

One heck of a sharp moon shot!

[don4l]

7 minutes ago, CedricTheBrave said:

all good but the moon for me is fantastic 

which OTA?

Thank you!  The OTA is a Tak FSQ106ED at F5. (FL=530mm)

I have taken a couple of shots of the moon in the past, but they didn't come out anything like this.  Previous shots were mono or R, G and B combinations.  I was very surprised when I saw this, but I don't know if I caught a moment of good seeing, or if stacking frames produces a much sharper result.  The individual frames in the AVI did look almost as good as the final result.  The pixel size in this camera is only 3.75um and my usual camera is 9um.  My gut feel is that the smaller pixels made a big difference.

I've since had a go at M42 with my normal camera and very short exposures, but I cannot get

I should have said that the moon shot is a 4 frame mosaic.

 

 

[Stub Mandrel]

2 hours ago, don4l said:

I would appreciate advice on what settings to use for the camera.  For the Moon I used a gain of 10.  For the deep sky stuff it was 40.  Anything higher than 60 seemed to produce a saturated background.  This might have been moon glow???

You need to use dark subtraction in Sharpcap. That coloured background will disappear like magic.

[don4l]

7 minutes ago, Stub Mandrel said:

You need to use dark subtraction in Sharpcap. That coloured background will disappear like magic.

I was wondering about this. 

If I use "Live Stack", then I suppose that I must have the darks before I start imaging.  The alternative is to have dozens, or even hundreds of raw files which sounds like a pain to process????

[Stub Mandrel]

1 hour ago, don4l said:

If I use "Live Stack", then I suppose that I must have the darks before I start imaging. 

Yes, past a few seconds they make big difference with the ASI120MC. This is  a Sharpcap stack of 16 second exposures, the raw stack and processed.

The final frame is the 16-second dark so you can see how much noise it is getting rid of:

.

[Thalestris24]

Hi Don

Yes, do make a dark library in SharpCap! Make sets of common exposures and gains you're likely to use. SharpCap will create Master Darks and Master Flats for you (see under Capture). It's a good idea to take about 30 of each gain/exposure setting for darks and 30 flats as per 40% of histogram. It's obviously much better to be able to use set point cooling but sometimes you just have to make do! In terms of exposure lengths you could do 15s, 30s, 60s, 120s depending on how long you can expose for with your sky, plus corresponding darks. Gains of 4 and 8 are probably ok for lights and darks but you'll have to see how your camera performs. SharpCap does have a built-in tool for measuring sensor performance which is useful.

Louise

Edit: Just to mention, I based the above exposures on my qhy5l-ii mono/Gpcam v1 mono and Minican5s mono - your colour cam may need longer exposures e.g. 20s/40s/90s/150s - you'll have to try and see. The sensor analysis will show how your bit depth varies with gain. I set my mono cameras to 12-bit and 1280 x 960. Hth.

[don4l]

1 hour ago, Thalestris24 said:

Hi Don

Yes, do make a dark library in SharpCap! Make sets of common exposures and gains you're likely to use. SharpCap will create Master Darks and Master Flats for you (see under Capture). It's a good idea to take about 30 of each gain/exposure setting for darks and 30 flats as per 40% of histogram. It's obviously much better to be able to use set point cooling but sometimes you just have to make do! In terms of exposure lengths you could do 15s, 30s, 60s, 120s depending on how long you can expose for with your sky, plus corresponding darks. Gains of 4 and 8 are probably ok for lights and darks but you'll have to see how your camera performs. SharpCap does have a built-in tool for measuring sensor performance which is useful.

Louise

Edit: Just to mention, I based the above exposures on my qhy5l-ii mono/Gpcam v1 mono and Minican5s mono - your colour cam may need longer exposures e.g. 20s/40s/90s/150s - you'll have to try and see. The sensor analysis will show how your bit depth varies with gain. I set my mono cameras to 12-bit and 1280 x 960. Hth.

Thanks for that advice.  I wasn't aware of the sensor analysis, but I've just run it.  It does show very clearly the trade off between gain and dynamic range.

I will lower the gain next time and try 40s exposures.

 

[Stub Mandrel]

Do you have to wait for dark to do a sensor analysis or can you do it with a capped camera?

[Thalestris24]

33 minutes ago, Stub Mandrel said:

Do you have to wait for dark to do a sensor analysis or can you do it with a capped camera?

No - you want a good, tight lens cap with no light leaks and even illumination - https://docs.sharpcap.co.uk/3.2/19_SensorAnalysis.htm

Louise

[Stub Mandrel]

Great, thanks Louise.

Something to do this (cloudy) evening!

[Thalestris24]

Oh, there is a bit which asks you to point at the sky to measure your sky glow. I've not actually done that yet since it varies a lot. Early evening I get a lot of lp from nearby artificial pitch, and it can also vary a lot according to humidity. I'll get around to trying to do it one of these days...

Louise 

[don4l]

I just ran it indoors last night.  When it analysed the darks I  wrapped it up in a jumper and switched off the lights.  I had some horizontal bands during the illumunated tests, so I didn't do a perfect test by any means.  However, the results really helped to give me a feel for what gain and other settings were doing.

It helped to lift some of the fog that surrounds CMOS technology inside my head.

 

[Unklewhale]

This is a really useful forum topic. Info here I knew nothing about. I am sure it will save me a lot of time in the future.

[don4l]

I'm currently capturing darks with the 120mc. 

Does anyone know what the "Brightness" control does in Sharpcap?

 

I thought that it only affected the display, but I've had a quick look at some of the FITS files that I've captured and they are greatly affected by the Brightness control.

What setting should I be using?

Edit:  I had it at 18 for the first captures, I've now set it to 9.

[Thalestris24]

3 hours ago, don4l said:

I'm currently capturing darks with the 120mc. 

Does anyone know what the "Brightness" control does in Sharpcap?

 

I thought that it only affected the display, but I've had a quick look at some of the FITS files that I've captured and they are greatly affected by the Brightness control.

What setting should I be using?

Edit:  I had it at 18 for the first captures, I've now set it to 9.

I'm not sure (have never adjusted it) but I know you choose how frames are saved. I just use exposure time and gain to control how a frame looks on the screen, plus histogram, of course.

Louise

[don4l]

16 hours ago, Thalestris24 said:

I'm not sure (have never adjusted it) but I know you choose how frames are saved. I just use exposure time and gain to control how a frame looks on the screen, plus histogram, of course.

Louise

Thanks for the answer.

I'm not even sure that every camera will have the option shown on screen.  As far as I can see, it is performing a similar function to the Gain setting. 

 

I can see from my FITS darks that the Brightness setting has a huge impact.  Hot pixels went from about 500 ADUs to 4000.  That wouldn't be any good at all using the processing methods that I understand.

 

Still,  I'm making good progress.  I'm able to get an image out of it.  If conditions look right, then I'll have a proper go at M82.

[Thalestris24]

I think there are 'display controls' which don't affect how an image is saved and 'image controls' which do. There are also options to save with and without adjustments. It's worth ploughing through the documentation https://docs.sharpcap.co.uk/2.9/#!2!Display Controls The latest version has a number of other options. It's been getting more and more complicated! I really only use it for the mono live stacking with flats and darks, for a kind of hybrid eaa/imaging.

Louise

[Thalestris24]

Here are some snips of the settings available to my qhy5l-ii mono with SharpCapPro 3.2:

Live Stacking:

And a clip from the document re saving:

Hope that helps

Louise

[Stub Mandrel]

I always save as RAW.

[JamesF]

I've not used SharpCap for a while, but in the case of the ASI120, as the camera itself has a brightness control I'd guess that's what you're changing if you play with it.

My understanding is that the brightness control adds some fixed value to each pixel, so if your brightness setting was, say, 10, then what the camera registered as absolute black with a value of 0 would actually be returned to you with a value of 10 and something with an actual value of 200 would be return as 210.  I'm not sure I can see any value in that for astro imaging.  I've just plugged my 120MM-S in and the default value for the brightness setting appears to be 0, so I'd be inclined to leave it there.

James

[don4l]

21 hours ago, Thalestris24 said:

Here are some snips of the settings available to my qhy5l-ii mono with SharpCapPro 3.2:

 

 

Live Stacking:

 

And a clip from the document re saving:

 

Hope that helps

Louise

 

Thank you very much Louise.  I don't recognise a lot of the screenshots that you have posted, so I will have a play this evening at home.

Also, thanks for the link in your previous post.  For the ZWO cameras there are TWO sliders marked "Brightness"!!  I hadn't noticed this and I must have used the wrong one.

[don4l]

17 hours ago, JamesF said:

I've not used SharpCap for a while, but in the case of the ASI120, as the camera itself has a brightness control I'd guess that's what you're changing if you play with it.

My understanding is that the brightness control adds some fixed value to each pixel, so if your brightness setting was, say, 10, then what the camera registered as absolute black with a value of 0 would actually be returned to you with a value of 10 and something with an actual value of 200 would be return as 210.  I'm not sure I can see any value in that for astro imaging.  I've just plugged my 120MM-S in and the default value for the brightness setting appears to be 0, so I'd be inclined to leave it there.

James

Thank you!

I'll have a play to see if there is a fixed figure added on to each pixel.  This will be easy to test.  It would also mean that the dark frames that I have already taken can be corrected.

 

[Thalestris24]

20 minutes ago, don4l said:

 

Thank you very much Louise.  I don't recognise a lot of the screenshots that you have posted, so I will have a play this evening at home.

Also, thanks for the link in your previous post.  For the ZWO cameras there are TWO sliders marked "Brightness"!!  I hadn't noticed this and I must have used the wrong one.

Hi

You may have some different options as you have a colour cam which is zwo, so different driver. You have to setup hardware such as mount in File -> SharpCap settings. I find it very useful to be able to control the mount (via eqmod in my case) and use blind plate solving (need to be within 15 deg) to get on target  You obviously have to download and configure the relevant plate solving tools - I use Astrotortilla..

Louise