Very Amateur Astronomy

It’s late so this is short, I had another go at the whirlpool with my now carefully adjusted mount. I think the photo says quite a lot about what having a correctly tensioned and balanced mount does for your imaging.

And now with added colour!

More time on M51 after making adjustments to the mount, it didn’t work quite as I had hoped as there is still some jitter in RA resulting in reduced exposure times from my expected target, but I was able to collect some data.

I took 50 frames plus 10 dark frames, and Deep Sky Stacker threw most of those out leaving me with 13 usable images. The problem as ever is drift leading to extended stars, but at least I have some noticeable progress.

13 x 1 minute exposures,10 dark frames, ISO 1600, unmodified Canon EOS 1000D, Skywatcher light pollution filter.

I’ve no idea why DSS decided these were black and white images, that’s another thing to look into, they are definitely colour when viewed individually.

Lessons learned

1. My adjustments to the mount were not perfect, mostly due to inexperience and incorrect technique. I had another look last night after reading up on the process and I’m happier with the result, the mount sounds and feels better. Still trying to balance between to tight and to loose is a matter of trial and error.
2. Balancing is really important. I was able to reduce the streaking by moving the counter weight further down the shaft, producing more drag. It looks like I may have had it balanced to much on the scope side, the general rule of thumb is that the motor should be lifting up slightly rather than slowing down, I had things the wrong way round. The Vixen Sphinx is a pig to balance.
3. Before turning off the lights in the shed check which plug your hand is on. Turning off the main power to the scope just when you started imaging is really annoying.

There have been few updates here recently, as to be honest not much has been going on. The few clear nights we have had have been dedicated to testing and correcting the alignment of the mount via the drift alignment method. I won’t write up exactly what that is all about right now though it would certainly help my understanding of the process to do so, but last night I was finally ready to go.

I decided to take a look at imaging the whirlpool galaxy M51, a nice bright target high up in the night sky. A quick 20 minute alignment check on two stars proved good, and a run through the PEC (periodic error correction) routine worked ok. I got the mount aligned to 5 stars for goto, focused the camera and locked it on a nice bright star with the bahtinov mask, a home made focusing aid which is a life saver. I then sent the scope to whirlpool and took a quick image to confirm it had landed where I wanted it.

So that’s a big yes, I’m really very happy with that, the goto on the Vixen is excellent once it is aligned, that’s pretty much bang on where I want it to be so I decide to start imaging. I run a few more test images first, testing for maximum exposure time before trailing starts to appear and looking at ISO speeds. The maximum exposure time is about 3 minutes, I’d like to run more but I’ll need an autoguider for that unless I decide to manually guide which sounds like a pretty tedious job.

Anyway, I’m happy and I’m ready to go. So I setup the laptop to take 50 2.5 minute exposures, hit the start button and head in to find a cup of tea. ten minutes later I login to the desktop inside to take a look at my images and they all look like this :

Well that’s not right at  all. Star trails in this case are showing me that something is up with the tracking, for some reason it’s slipping in Right Ascension. Somethings not happy but I’m unsure what, maybe it’s the balance? The scope needs to be balanced on both axis to make sure the motor can move it cleanly but this was carefully checked before I started I’m suspecting at this point that there may be an issue when tracking objects near the zenith, the scope is pointing pretty much strait up to see M51.

Not being entirely sure what the issue is I reset the scope and recheck with my alignment stars to check the tracking.

Well that’s not right at all, it’s now entirely failing to track, but I can still slew in RA so clearly the motor is attached, though it does seem slow. I’m going to have to assume that something has come loose on the RA axis so I guess that’s what I’ll be looking at today. I had previously loosened off a few bits on the advice of the Vixen owners group as that come from the factory severely over-tensioned, maybe I’ve done to much? Well I shall go see and report back once the weather allows.