Altair Capture Tutorial 2
Updated: Dec 31, 2020
THE FIRST 5 SECONDS.
At the top of the Altair Capture screen navigate to the Options menu. This is where we will set up where your exposures will be saved. This contains just one option called Preferences. Click on it, and it opens a submenu with lots of options. For our needs there is only one that requires attention. Click on the Autocapture tab. This opens more options. Now click in the file prefix box and enter your target name, such as M57 or whatever you will recognize later. Make sure file type FITS is selected. Moving down select Capture every frame. Now tick total images. An arbitrary number can be used here so just enter 100. Leave everything else as it is, but MAKE SURE you click APPLY and then OK. This will take us back to the main screen.
Ok, we are almost ready to start capturing and this involves getting the exposure time and gain settings right. Obviously, these 2 settings are the most important and quite possibly the most difficult to get right if the questions and confusion on the internet are any guide, so I am going to try and explain this for you, as these settings caused me so many problems and failures that at times I was ready to pack it in and go back to visual observing only. Checking the internet always resulted in the same outcome ie: no one knows what is best. Just keep fiddling about and carry on until you lose your mind and then decide it's not for you. Oh, and then the final insult, ditch the CMOS and go for a DSLR. What!!!
Then I suddenly had a thought, idea, revelation! I realized that all the forums and so called advice was being given by users with DSLR/CCD cameras and most of it based on out dated camera information. I know these users mean well, but if you have not used a CMOS camera then you have no advice to give. Just telling people you would be better off with a DSLR blah, blah, blah, is of no use whatsoever. This is why there is hardly any advice on gain settings and exposure times to be used available on the internet. But with a lot of “impatient” trial and error, I finally got it right.
So, let's go back to the main screen having set up as above 2 paragraphs. One thing I cannot help with is how long your mount will keep the object in the centre of the screen without trailing the stars. You alone should know what your mount is roughly capable of when you have used it for visual study. So for now we will try 5 second exposures. In the Capture & Resolution menu, make sure Video Mode is selected. Now simply pull the Gain slider to the left until it says around 17.00. This will dim the object you are viewing and this is quite normal. Pull the Exposure Time slider to the full 5 seconds. In Video Mode you are limited to 5 seconds anyway. With those settings in, navigate to the top menu where it says Capture. Left click on this and it opens a small menu. Left click on Auto Capture. You have now started the capture process and at the bottom of the screen you will see an exposure box filling up by moving to the right exposing each capture for 5 seconds. Great, you are now taking your first shots! You will also notice that after every 5 seconds is up, a frame counter is counting the frames taken. After about 25 frames, left click on the Capture menu at the top and left click on the Auto Capture again and this will stop the capture. At this point you can now check the framing of the object to see if there is any drift. Pull the Gain setting all the way to the right to 50.00. You will now be able to see your object again. If it has moved from the centre by a great deal then you will now use your hand controller to re-centre the object. Once centred restart the capture again as above and go for another 25 frames. Keep repeating this method until you have about 500 frames. You can check this by going into the Altair Capture folder usually in Documents and you will see all your frames in FITS file format.
The next thing to do is take some dark frames. Do not alter any settings within the Altair Capture main screen. At the top of the Altair Capture screen navigate to the Options menu again. Click on Preferences again. Click on the Autocapture tab again. In the file prefix box where you entered your target name, just enter the word dark. This will now add the word dark to your frame names, so you will now know which frames are dark which is very handy when it comes to processing them. Make sure file type FITS is selected. Moving down select Capture every frame. Now tick total images. This number is up to you, but for now just enter 50. Leave everything else as it is, but make sure you click APPLY and then OK. This will take us back to the main screen. Now put your telescope cap back on the scope. The screen should now be black. There is no need to change any of the settings to take the darks. Click on the Capture menu again. Left click on Auto Capture. You have now started the dark capture process and at the bottom of the screen you will see as before the exposure box filling up by moving to the right exposing each capture for 5 seconds. You do not need to do anything but wait until the frame counter reaches 50. It will now stop automatically because you changed the frame capture to 50 in the box as above. Your capture process is now complete using 5 second exposures.