I've only used dss once. Normally I use Neb 2 to do the stacking. So, I have no clue as to settings but would like to use this during imaging to stack live by having it monitor the Neb 2 folder. Not sure if I can do that. I've set Register and Stacking settings, but don't have a clue what they should be.

hey i had dss for a year with no luck when i turned the drizzle off it worked like a charm i guess my computer could not keep up with it or some thing so if anyone out there is haveing a problem with it not completeing the job this might b the problem it would go just about to the final product and bam something about memory would pop up and it would stop hope this helps someone

I use DSS for all of my stacking. Unfortunately, anything I try to stack exposures in 6nm Ha... DSS says it can't find any stars. I changed the star threshhold and moved the slider all the way to the left, but no joy.

John, how long is your exposure time? Cam.modified? I stack 9mn exps. w/a 12nmHa clip filter on a modded Can1000d. Star detection set at 10% and noise reduc unchecked. I do use dark calibration w/these. Marc

Hi Mark,
The exposure info is 6 minutes @ ISO800. There are 15 subs. The camera is a Canon 50D Hutech modified. I'm using a 6nm HA clip-in filter from Astronomik. It looks like I error and moved the star detection threshhold the wrong way. Once I moved it to you setting of 10%, DSS found plenty of starts. I'm stacking right now.
Thank you so much for your suggestion and solving my dumb mistake.

John, I hear you on that slider, I did the same thing w/it, it's counterintuitive. Marc

I know how to do a flat(white sheet over the scope 15" at 800 during the afternoon) and dark flats into the lens cover (ie 15" at Iso 800 if that is what I am going to do) plus a bias (1/4000th into the lens cap) but what and how do you do a DARK?

Thanks Starhopper, If I don't take a flat during the daytime can I use one from another day or is it temperature sensitive?

Al, DSS has a good explanation on shooting the calibration stuff under FAQ. If you can't take flat frames every time you shoot, the flat frames you have usually work ok. Providing the camera orientation and the imaging train is the same the flat frames will clean up the vignetting. Dust motes-no- they will move around, but a clone tool can usually fix that. The bias will take care of the temp thing. You are not going to see a ton of difference w/temp changes (some) so maybe take seasonal bias frames to get a rough ambient temp. Marc

Thanks Marc, So I can put a small library of flats together and use you when I need them. When I was shooting M 42 the other night I shot 12 light frames at 5" at 1600 ISO and I set the star threshold at 300 and it was the first time I had ever had more than 1 frame stacked as it did all 12. I think that using the flat gave me a bit of colour so I was happy. I would have done longer exposures but I was having a bit of trouble tracking and the star trails were abviously too great for the program but I am having a good time working out one problem at a time. I just switched from a refractor to the C8 SCT and there is lots to learn. Thanks Al

Thanks Starhopper, I have a reducer but I nor the dealer knows what it is, he thinks between a 5 and a 6. All the box said was Telecompressor Made in Japan. It was in the back of a cabinet at the dealer's and was stock from the previous owner. It fits inside my camera adapter and it seems to work. Jerome and I have been working on some other problems like proper polar scope alignment, balance, finder scope and mount adjustment. I didn't realize I had tighten the bolt that holds the head on the tripod too much so I used to move the tripod legs when it was out. Jerome loosened the bolt and now the movements are like butter. Now if we can just get rid of this blasted snow storm I can try out all these items.

I shot some images of m 42 tonight with my DSLR set at 24" at ISO 800, also 2 dark flats (24" at 800) plus one bias 1/1000 at 800. When I try to set the star threshold at 300 the pictures dark flats and bias all uncheck. Does that mean perhaps there was a bit of star trailing in those images?

I wondered if an images had NC under Star in the headings but I stacked them anyway and there was a star count as the images were being processed so maybe NC doesn't mean No Count.

Could someone please explain to me the difference between a DARK and a Dark-flat. I prepare the Dark-flat by taking an exposure with the lens cap on for the same length of time that I will be taking individual images. I take a bias by shooting 1/1000th image of the lens cap and I take a white sheet of paper and put it over the scope during the day for the same length of time I will be imaging at night when possible. Thanks in Advance Al

I'm pretty sure a google search or even a read of the DSS site will answer that but a dark flat is a dark with the same exposure and temperature as your flat.

Say I shoot two dark flats ie 15" at iso 1600 and then I can designate one of them as a dark. I don't see the difference.

A dark is an exposure with the same length and temperature (iso) as your lights except no light is allowed on the sensor. If your lights and flats have the same exposure length then the darks will be the same.

Sander Check out this site, now it is for CCDs but it is very interesting http://www.lefevre.darkhorizons.org/articles/proctutorialchap2.htm

That looks interesting Al. Before I bought my first real CCD camera I bought and read HAIP (Handbook of Astronomical Image Processing) so I'd know what I was getting into before handing over my money. It explains signal to noise ratio and image calibration in great detail.

I am using a DSLR and subtracting a dark frame from each light image I can do with the camera as I shoot but it takes an equal length of time for each shot. The one thing I realize is that I have to shoot more than one or two shots for the dark stuff but now I kind of understand why. I can actually just shoot with the ordinary lens and put a cap over the lens. Your are right that is a good site and I book marked it and I will try all of it if we ever have any good weather.

Al, it's also a good to take the dark frames at another time so you can take full advantage of a clear sky. Marc PS save them and make a library (they're good for a year or 2+) and reuse them.

Thanks I thought they were temperature sensitive?

They are (time, temp, iso, sensitive), but a 5mn 32* 1600 dark frame is going to be close enough to use w/a 5mn 36* 1600 light frame for calibration purposes. Most people I've seen use 10*F increments (some use 5*). Myself I used 10* incr. picked the lowest/closest temp for calibration. Then I would check the resulting pic close up and look for little black dots (holes) if they were there (most times not) I'd go back and adjust the multiplication factor (under dark frames) down to say .75 and stack again (a bit of trial and error). So a library can go as (lets assume all is iso1600 if 800 make an additional libr. for that)-
Dk 5mn 30*F master
Dk 5mn 40*F mas
Dk 6mn 40*F mas
Dk 6mn 50*F raws (might want to save these too if you switch stacking sftwre)
Dk 6mn 50*F mas
etc. Marc

Great, that makes sense because you would end up spending the whole night doing everything but the lights. I kept getting confusing info while reading up on each, one would say you don't need to worry about temperature and the next article would say you have to keep them the same. Making a library of lens cap on and flats sounds great but what about moving the camera is it a minor problem?

Hey Al,
Making a library of Darks and Bias/DarkFlats is good but not for Flats. The optical problems change with each setup so you need to take fresh flats for every session - before moving the camera or changing the focus or anything.

Russ is right, flats should be taken for each session. Flats reverse imperfections 1) in your optical light path (tunnel vision) and 2) dust shadows on your glass. Once the cam is moved these things are in different orientations. When you're starting out you shouldn't get too fired up about flats (that will come later). So for a 1/2 right way first read FAQ in DSS on how to take flats. Then decide on a imaging setup you are going to use say; 2" focuser,-lt poll filt,-2" nosepiece,-t ring,- camera-or whatever. Once you decide a good orientation for the camera stay w/it and mark it w/a piece of tape so that the camera always goes back pretty close to the same spot. This will get you close (not exact, this is also good if you shoot the same target over 2 nts). If you take a flat master w/this setup you can keep reusing it w/all your light frames (of the same setup) and it will at least clean up the tunnel vision. This will not remove the dust motes (can make them a little worse, PShp clone tool for that) and if you change your imaging train say an extension or FR, anything. you will need new flats. Again this is just a get in to it method that will help your pics for now. Disclaimer: the above written is Marc's opinion - ask 10 people about flats get 10 different answers. Known to cause much civil unrest amongst APers.

Thanks Marc and Russ apparently we are not supposed to have good weather until Saturday but if we have some breaks I may be able to get out during the day and catch a range of temperatures as Marc suggested to make a library.

Marc I did read the DSS info on flats and darks and Dark flats plus other sources, it made for an interesting afternoon since it was raining anyhow.

Hey Al, what better time to catch some dark frames than on a rainy day/night. Here's a trick or two you can try. Get yourself a good thermometer and check the temp in your refrigerator. Place your camera in a ziploc w/o battery and place it in the fridge for an hour. Take out and place battery back in - set up your timer to take your duration, set ISO and then place it back in the fridge. The camera will warm up after the first couple of shots and then the rest should be pretty even in temp. Then do the same thing out in your garage or any other place it gets cool. Over several days, weeks or months you can build a dark library. The thermometer is so you have an idea where the temp is when you start. The data in the images should tell you the temp of the sensor - if you have a camera that records that. I use BarkyardEOS for Frame/focus and Capture which records all of this data. The bad thing - a cable running out of the fridge,,, oh and trying to explain it to the wife LOL

Thanks Russ that is a great idea, I will wait until my wife is not around. During the winter I had a bag with a heating pad plugged into my extension cord and it solved the problem of the little AAA batteries in the timer from getting cold and now the whole process is reversed as the timer will be outside the fridge. The big surprise will be for the camera it thought summer was coming.

Russ, I started my collection at 55°F with 20 Darks at 1600 and 30" and then I took 20 Bias also at 1600 and 1/4000th same temp. It was raining a bit so I followed your procedure except I put the camera in the BBQ for protection and acclimatization. I can do the cold one in the fridge later as the battery is low

Al, I like it. You tend to get pretty resourceful (and get weird looks) when taking darks. Marc

In regards to my library of Darks, Dark Flats and Bias files, maybe Marc or Russ can answer this because I read somewhere "at the same focus as your lights". As Marc mentioned if you move the camera you can use photoshop to get rid of the dust mites so I have marked the camera position and my question is,"Am I OK with the focus bit?"