harlequin2902 wrote:Not sure if this is relevant, but sounds like what I faced when I tried to take photos using my Nexstar 8 as the lens for my camera.
What I did to achieve focus was to first go to a very bright star and try to get it into focus into a point on the camera's LCD.
After that, I rely on the GOTO's accuracy to center the object, which is usually invisible on the camera's LCD, and trigger the shutter. Not sure if you have seen my shot of NGC 4755. This is a single frame 4 or 6s exposure, around ISO 1600 through the Nexstar 8. I do not know how to stack images since I'm not so much into astrophotography, but I'm wondering how it will really look when stacked.
Harlequin2902
What you're describing is the same method I'm using for the above Omega Cent, prime astrophotography where the camera is directly connected to the scope, using the scope as the lens through a T-adapter.
Eyepiece Projection is where I use a T-adapter to connect an eyepiece to the camera, then the eyepiece is connected to the scope, magnifying the image from the scope, through the eyepiece and into the camera - still figuring this out lol.
For achieving sharp focus on stars using Prime AP, I use a home-made Bahtinov Mask and find a bright star. My process is usually:
- Start from rough point on the focuser that I know is close to focus
- Hook my camera to my PC or tablet running EOS Utility (from Canon)
- If its very clear and the star is bright (e.g. Arcturus, Mimosa, Gacrux etc), I might be able to see the star on the Live View
- If not, then I take a 5-sec ISO800 shot of the star
- Adjust focus accordingly until the Bahtinov Mask shows a sharp and aligned 6 pointed star image (beautiful, btw
)
From there, I turn on my motor to start the tracking and take two sample 15 - 30 sec shot to see if there's any drift and adjust accordingly.
After that, shooting begins.
Because it's unguided and I'm doing rough polar alignment inside a HDB flat, it can take about 10 - 15 minutes before I'm happy enough to start shooting, which means I need to anticipate what I want to shoot and plan accordingly - thank god for Stellarium!
If your mount has a tracking motor, you may want to consider extending the exposure to above 10-secs and, depending on your camera, stopping down to ISO800. Since you're not stacking, you would benefit from less noise from ISO1600. It's a bit of trial and error but rough polar alignment should do fine.
Maybe I'll attempt Eyepiece again, but on Omega Cent since it seems to be directly in front of me from 10pm these next few nights!
