Hello, I would like to ask for some advice re. polar alignment and tracking orientation. Below is an SLR picture of M42 taken straight through an 80mm refractor so according to things I have read, it should be orientated with North down and West to the left etc. Is this right?
Looking at a series of these taken in the same orientation, same set up/night- the target drifts down (North?) and to the right (East?) over a number of frames.
M42 was in the North Western sky when I took it so when I read the article about drift it suggests because it drifts North my altitude needs lowering. Am I on the right track?
Equally so, as there is some Eastwards movement then I probably have some RA speed?PEC issues as well?
There are some complicating issues as Orion was above the ecliptic so not strictly near celestial equator. My problem is most of my Southern and Eastern sky and horizons all around to about 30' are obscured by trees.
Any tips gratefully recieved
Graham
Sorry having difficulty loading small file, suffice to say pic is orientated so M43 points to bottom right hand corner. Will try and postit soon.
oops sorry about quality of picture, must have compressed it way too much. Suffice to say oreintation and movement of target is as described in previous message.
Drift alignment is a pain. I don't have an illuminated reticule, and use camera live pre/view instead. Once basic alignment has been completed with the mounts polar scope., I take a series of images adjusting in Altitude and Azimuth until drift is minimized/eliminated
Star trails LEFT adjust azimuth RIGHT - vice versa.
Star trails UP adjust altitude DOWN - vice versa.
If star trails get longer adjustment was in the wrong direction - adjust back, plus some.
Thats one of the issues -I can't use the mounts polar scope as I can't see SCP from my back garden. I will try the star trails though- sounds simple, this is assuming up is North in scope and camera ? I was working on a refractor having up down reflections which inverted image unless you used a 45' diagonal
Additional point- does it matter if you are pointing West or North for your adjustments? I was sort of thinking that the corrections are opposite directions if you take a guide star in the East or West?
Baffled Graham!
Hi Graham. It seems you've done quite well already.
I had the same problem from my place to begin with - couldn't see the SCP. No polar scope either. Sometimes weather obscures half the sky to the south anyway.
Don't worry too much about which way the camera is pointing, but if you can, do the alignment on the piece of sky you intend imaging, preferably the target. I go for the comfortable option and pick something near the ecliptic that isn't going to strain my neck looking.
Importantly make sure the live view screen is horizontal - otherwise it is more difficult to interpret the drift. Think left/right, up/down.
I start with 30 second shots, then as the error reduces increase the exposure time and make finer corrections.
Give yourself some time to practice.
(The other method which I find more difficult is to correct for drift by keeping a bright star like Sirius in the same place on the live view screen. A reticule of some sort helps, or just place tracing paper over the live view with a hole in the middle - keep the star in the hole. Through the tracing paper you can see which way it's drifting. With the canon using 5x live view would be ideal).
Something I've been playing with when doing my initial polar alignment as I can't see the SCP from my yard either - Google Sky on my phone.
I place the back of my phone on the polar scope eyepiece and then adjust until the SCP is in the centre of the screen on my phone. It seems to work OK for an initial alignment!!
Mario
PS My phone is an Android one but I know that the iPhone has a similar app.
Hi Mario. Technologically, I'm in the dark ages. That's a novel idea- even if you don't have a polar scope, that method would work aligned with the RA axis.
