A Flaming Star, A Pacman & Unwanted Eggs

When stuff works fine this hobby can be wonderfully relaxing. When stuff doesn’t work fine, it tends to feel more like a job at times!

I’ve had issues with my last two consecutive nights of imaging. The first night I was attempting to build a mosaic of one of my favourite deep sky targets, The Rosette Nebula. Unfortunately, I ended up aborting the session before the first panel was completed due to horrible star shapes. I put the tracking issues down to a loose clutch, and setup again last night.

For the first three hours everything ran perfectly, I was taking 5 minute subframes, my guiding system was reporting nice steady guiding, and most importantly my stars were night and round.

Until they weren’t :/


How my stars looked in a 5 minute sub at the start

What my stars looked like in a 5 min sub 3 hours later


I started to see some horrid egg shaped stars, indicative of a tracking error – and yet my tracking was still looking fine according to the data.

I made a couple of changes, reduced the subframe length and switched targets and the rest of the evening went without a hiccup.

However, having switched a couple of things, I’m now not entirely sure which of them cured the problem!

I think it’s a power issue – the nights have been cold here recently (down to -5c) overnight, so i’ve been running my dewheaters harder than usual to keep the scopes from icing. My theory is that the extra current draw to do that was meaning the mount didn’t quite have enough juice to track accurately.

Dropping the dew heaters to less agressive settings and reducing the sub length to 3 minutes meant I was able to carry on imaging right through until I got clouded out at 5am – but was it the sub length change, or the power change that cured things?

It’s looking like a clear night tonight again, so to test I’ll run the mount from a seperate power supply and see what happens with another run of 5min subs.

I did manage to complete a couple of images. The top images is The Pacman Nebula (41*5min subs) and the bottom is The Flaming Star Nebula (128*3min subs).

If the eggy star issues are cracked, I’m hoping to finish the Rosette Nebula mosaic this evening.