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Drizzle function in DSS


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I use an 18mp Canon 650D DSLR for my imaging and stack images using DSS.

I have no issues stacking my images in DSS usually.  However, recently I have tried to stack using the x2 and x3 drizzle function.  DSS takes a while longer to process with these drizzle options and stacks all of my subs.  However, when the program moves to autosave the stacked result, DSS shows a yellow exclamation mark in a triangle and goes no further.  It gives no error message.

Has anyone else had this issue and how did you resolve it?   Is the18mega pixel image too much for DSS to stack in drizzle mode?

Hope you guys can help, thanks

Julian

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Drizzle greatly increases the size of the image so using it on an 18mp image is likely to cause you to run out of addressable memory. DSS is a 32 bit program so is limited in this respect.

What can work is if you use the red region of interest box to stack only the part of the image you actually want.

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Been a while since I used DSS so forgive me if this doesn't make sense.

When you have loaded you images select one of the light subs and let it load into the preview screen. On the right of the image there should be four icons and the top one will resemble a red box with a cursor.

Select this and draw a box around the part of the image you are interested in.

Now under stacking parameters the custom rectangle button should be available, click this.

Now stack as normal.

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Hi Julian, D4N has sorted you there, but I just thought I would add that I have just found that option myself and find that selecting the rectangle allows me to stack an area of interest pretty quickly even with x2 Drizzle applied - whether that does any good, I have no idea! But it is really handy with "small" galaxies on a large sensor as you can focus in on the particular area you are interested in.

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Hi Marky1973, thanks hopefully it will work and will have to try x2 & x3 to see what difference it makes to a normal stack?.

Don't really know what the drizzle function really does?  I thought that it improved the area of interest but don't really know why or how??

Hopefully someone can shed some light on the benefits of drizzle??

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I use an 18mp Canon 650D DSLR for my imaging and stack images using DSS.

I have no issues stacking my images in DSS usually.  However, recently I have tried to stack using the x2 and x3 drizzle function.  DSS takes a while longer to process with these drizzle options and stacks all of my subs.  However, when the program moves to autosave the stacked result, DSS shows a yellow exclamation mark in a triangle and goes no further.  It gives no error message.

Has anyone else had this issue and how did you resolve it?   Is the18mega pixel image too much for DSS to stack in drizzle mode?

Hope you guys can help, thanks

Julian

DSS is still a 32 bit software and therefore its use of memory is rather limited. It was never really designed to handle huge DSLR file sizes so if the size of the file to drizzle is huge it will hang. The effective use of drizzle is also subject to certain conditions with regards to the scale and the number of subs. If these conditions are not met it only acts as a very laborious and inefficient resampling algorithm rather than fulfilling its function to recover detail in which case  one is better off using PS or other resampling software. If you have to use drizzle in DSS for whatever reason on a very large DSLR files then try and draw a ROI rectangle around the target ( the red rectangle  lines in the DSS ) and may just work.

A.G

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Thanks AG.  You say that the effective use of drizzle is subject to certain conditions re scale and subs.  What are those conditions so I know if they can be met or not?  Is it not right that If I am dithering my subs that I need to drizzle??

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Thanks AG.  You say that the effective use of drizzle is subject to certain conditions re scale and subs.  What are those conditions so I know if they can be met or not?  Is it not right that If I am dithering my subs that I need to drizzle??

As it was mentioned earlier effective drizzle is mandatory. Set the guide software to extreme dither ( you need this for a DSLR ) and give it a long settle time before exposure begins so the guiding settles to the normal rhythm. If the pixel sixes of your sensor are on the small size the drizzle may not be as effective as you are probably reaching the theoretical resolution limit of your scope and camera combination. The number of the subs need to be rather large, I 'd say upwards of 30 . In theory a minimum of 4 subs should be enough if the dithering could be absolutely repeatable from sub to sub  but this is beyond the mechanics of most hobby or even pro equipment, I believe Hubble space telescope is capable of doing this but I would not go to court with this one. In practical terms set your dithering to extreme and go for many subs as you could get. Hope this helps.

Regards,

A.G

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As it was mentioned earlier effective drizzle is mandatory. Set the guide software to extreme dither ( you need this for a DSLR ) and give it a long settle time before exposure begins so the guiding settles to the normal rhythm. If the pixel sixes of your sensor are on the small size the drizzle may not be as effective as you are probably reaching the theoretical resolution limit of your scope and camera combination. The number of the subs need to be rather large, I 'd say upwards of 30 . In theory a minimum of 4 subs should be enough if the dithering could be absolutely repeatable from sub to sub  but this is beyond the mechanics of most hobby or even pro equipment, I believe Hubble space telescope is capable of doing this but I would not go to court with this one. In practical terms set your dithering to extreme and go for many subs as you could get. Hope this helps.

Regards,

A.G

Thanks AG.  I have my dither set to 5, so I would assume that would be classed as extreme.  I usually set the delay to 5 seconds but may now increase that to 45s for the guiding to settle down??  I am not too sure of the theoretical resolution limit of my scope and camera combi though, Explore Scientific 102mm 714 FL APO and Canon 650D. 

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Thanks AG.  I have my dither set to 5, so I would assume that would be classed as extreme.  I usually set the delay to 5 seconds but may now increase that to 45s for the guiding to settle down??  I am not too sure of the theoretical resolution limit of my scope and camera combi though, Explore Scientific 102mm 714 FL APO and Canon 650D. 

I believe the pixel dimension is about 3.2micron so at 714mm of FL you'd be imaging at approximately 0.9 arcsec/pixel, this itself is a slight oversampling and well over the UK seeing which restricts imaging to about 2 arcsec/pixel, however even if you do not get any benefit from drizzling on the resolution front it will do wonders for noise reduction and with a robust Sigma clipping algorithm during stacking a lot of the nasties will be removed. The ES 102 is a fine scope BTW.

Regards,

A.G

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Thanks to all of your advice.

Leo Triplet in Leo

Explore Scientific APO 102mm, Canon 650 D Unmodded camera on a SW HEQ5 mount. These subs were dithered to minimise noise.
This result is 10 x 600 second guided subs with associated calibration frames, 3 darks, 25 flats & 25 bias.
Shot at ISO 400
Has been stacked in DSS with x2 drizzle function and then been processed in PS CS6 using Noel Carboni's tools.
This is my best attempt to date of this target and probably the last this year.

triplet%20drizzle%2012%20frames%20HLVG%2

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  • 4 years later...

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