Creating a hot pixel map

[Petergoodhew]

I'm probably totally insane but I'm converting my remote rig in Spain to become a triple rig - dual long-focal length scopes (1200mm) plus one short focal length scope (350mm) - all sitting atop a 10microm GM2000 mount.  This means that I can no longer dither, and thus need to make and use a hot pixel map. I use CCDStack for calibration and stacking.  Can anyone advise me on how to create and use a hot pixel map? 

[Davey-T]

Hi Peter, I've been trying to set up a triple rig on my GM1000 using 3 WO Star71s so look forward to your effort.

I'm using Maxim ATM but trying to get SGP working, the biggest problem I've had is with autofocus, I can open 3 instances of Maxim but whichever one loads first loads the Lakeside driver then the next instance reuses the same driver, still trying to get it working.

I've used the hot pixel map in Maxim but can't remember exactly how, I do remember the instructions were rubbish, I think it runs a Median filter maybe anyway running a median filter has the same effect.

Jessun had a triple setup working so may be able to help if he's still around.

Dave

[ollypenrice]

Hi Peter, the system in AstroArt is this: open a long exposure master dark and, in the Arithmetic section, go to Clip and clip 2000 ADU off the black point. This takes out the bias and read noise, as I understand it, and just leaves the hot pixels. The Defect Map then goes into a slot in the stacking page dedicated to that purpose. This may put you on the right lines in other programmes but I can't be sure. To be honest I don't know if the Defect Map brings much more to the table than AstroArt's singles and multiples hot pixel filter, which is also very good.

Olly

[alan4908]

On 02/10/2018 at 12:02, Petergoodhew said:

I'm probably totally insane but I'm converting my remote rig in Spain to become a triple rig - dual long-focal length scopes (1200mm) plus one short focal length scope (350mm) - all sitting atop a 10microm GM2000 mount.  This means that I can no longer dither, and thus need to make and use a hot pixel map. I use CCDStack for calibration and stacking.  Can anyone advise me on how to create and use a hot pixel map? 

Hi Peter

I also use CCDstack for calibration and stacking. I follow Adam Block's advice for hot pixel removal (the details can be found here: https://adamblockstudios.com/categories/CCDStack). I've found this to be highly effective. After calibration but before stacking run the CCDstack hot pixel filter:

1. Go to Process->Data Reject-> select reject hot pixels from the drop down menu. Set the strength to be 2 (which is a mild rejection). 

2. Apply to all the images.

3. Have a look at the rejected pixels and see if the strength is adequate or not.

4. When you are happy with the rejected result go to Process->Data Reject->interpolate rejected pixels. Apply to all images.

I'd also suggest that you experiment with the cold pixel filter. Whether you need this really depends on your camera but it follows the same procedure as above. 

Alan

[Petergoodhew]

1 hour ago, alan4908 said:

Hi Peter

I also use CCDstack for calibration and stacking. I follow Adam Block's advice for hot pixel removal (the details can be found here: https://adamblockstudios.com/categories/CCDStack). I've found this to be highly effective. After calibration but before stacking run the CCDstack hot pixel filter:

1. Go to Process->Data Reject-> select reject hot pixels from the drop down menu. Set the strength to be 2 (which is a mild rejection). 

2. Apply to all the images.

3. Have a look at the rejected pixels and see if the strength is adequate or not.

4. When you are happy with the rejected result go to Process->Data Reject->interpolate rejected pixels. Apply to all images.

I'd also suggest that you experiment with the cold pixel filter. Whether you need this really depends on your camera but it follows the same procedure as above. 

Alan

Thanks Alan, will do.  Would you recommend subscribing to the Adam Block CCDStack videos?

[alan4908]

1 hour ago, Petergoodhew said:

Thanks Alan, will do.  Would you recommend subscribing to the Adam Block CCDStack videos?

Hi Peter

Yes I would. It is not cheap but the amount of quality information that you will obtain will be huge.

I would also recommend his PS and Pixinsight tutorials. 

Alan