DSS Help

[drumsolo]

Hi I am trying to stack several subs using DSS. first attempt worked fine and succesfully stack 20 subs.

I then tried stacking a different set of pics but I keep getting the message only 1 frame out of 18 will be stackes try adjusting the star threshold. What does this mean and are these subs no good?

Thanks

Stuart

[Jannis]

My first thought is that you have the stars too much out of focuse, or you have startrails. With either of these, DSS refuse to stack them.

If they are only slightly out of focuse, but tracking is good, you can resize the images to fool DSS into beliving they are in focuse and stack them properly.

Can you upload an example of the sub you're unable to stack at full resolution (or full crop at least), then we can more easy answer why it doesn't work, and what you need to do/adjust to get it working.

[old_eyes]

First step is to look at all the subs and reject any that have obvious problems; star-trailing, aircraft lights etc. Using a DSLR I capture both RAW and jpg files, becuase it is easier to quicly look at a jpg to see what is going on.

If weeding out your obviously defective subs doesn't work, you can force DSS to use all the subs and then see what it looks like. Set % stacked to 100%. You can play around with the star threshold to see if it can find more stars. If it can't find stars it can't register.

[drumsolo]

I have attached 1 of the subs, this is a 1 min exp at 800 iso of the triangulam galaxy. Well its supposed to be in there somewhere!

[Jannis]

It's out of focuse, that's why it wonh't stack.

To be honest, it looks like it so much out of focuse i'd probably just delete the files, and give it anotehr go. Even if you can stack it after resizing the files it's not going to be much more then a blurry dot that comes out, not a nice clear galaxy.

if it's clouded and you have nothing better to do anyway you coudl give it a try at a very low resolution though, but it won't look detailed in any way.

Sorry for being a joy-killer though, but without perfect focuse, your pictures won't turn out very good in the end

[drumsolo]

Thanks for your comments so here is why I am confused. Before this attempt I took 20 subs of Pinwheel galaxy and stacked them no problem and its in focus. I kept the focus the same before I slewed to this object so why would the focus be so out if i didn't change anything?

[Jannis]

Focus change with temperature. So for example, if it's cold outside, and you have everything stored inside, when you go out and focus and start shooting, things will be in focus. But as things cool down, the focus will change a little (more notisable on a fast scope like we have), and if i'ts very cold, it will change more as it cools down even more.

Also possible the focus wasn't locked properly with the screw, and therefore, when you slewed around (as it's quite a bit of distance between the two targets), the weight of the camera itself changed the focus a little.

[old_eyes]

Jannis is right. You always need to check focus if you have moved any distance.

For example, when I have had to do a meridian flip I find the focus sometimes changes. Even though the scope is pointing in pretty much the same direction the different orientation of OTA and camera, and the long slew round to the other side of the mount, can shift things (especially in a sloppy rig like mine!).

old_eyes