Revisiting M81 & M82

Well, to start off, I’m breaking my statement from the end of my last post. I’m doing a target in one night and then moving on, and not spending an entire month on it. I have already shot this target way back in July when I first got my telescope, so I already have it crossed off on my list of targets. However, I wanted to capture it again using my modified camera to try and get the beautiful red Hydrogen Alpha emission jets of the Cigar Galaxy.

M81 & M82 are located in the constellation Ursa Major. This target is quite difficult at this time of year for myself, as Ursa Major dips quite low in the sky behind my neighbours house. Fortunately, it doesn’t drop that low that it goes below my fence line, allowing me to get a full nights imaging on these two galaxies. However, I did have to do my first meridian flip, as the counterweight started to go above the telescope at around 1AM. I ended up having to manually reposition it though with the camera upside down, which was quite awkward looking at the screen.

M81 & M82 can be found if you follow a direct line formed by the two stars in the tail of the big bear, Alkaid and Mizar.

Lowest Point From My Back Garden

Messier 81 is a large spiral galaxy, and one of the brightest that can be seen from Earth. Its characteristic two spiral arms, exiting the core at near 180º opposition from one another, make it one of the most stunning galaxies to observe.

In contrast, Messier 82 is classed as a starburst galaxy. From Earth, we see this galaxy edge-on, which is why it took until 2005 to find that it had two symmetrical trailing arms, which could only be seen when being imaged at near-infrared.

My tiny 130PDS won’t be able to image it in that much detail, but it can still produce a stunning image of this galaxy pair!

This time round, I pushed my mount to its limits with unguided exposures. Taking 83x 120-second exposures at ISO800. To get this length of exposure, I have had to up my polar alignment game, making a new routine for myself.

To start with, I leave the right-ascension axis at its home position. I then place Polaris in the centre of the crosshairs of the polar scope using the azimuth and elevation bolts. Then, by only using the silver elevation bolts, I move Polaris up until it hits the surrounding circle. Only at this point do I release the RA clutch, and rotate my right-ascension axis round until the 0 position is perfectly over Polaris.

This makes sure that the polarscope reticule is in the correct position, and not slightly off from being perfectly vertical, therefore reducing any polar alignment errors to a minimum. From this point, I still use my PolarAlign app on my phone to give the correct position of Polaris.

I’ve been using this technique since the middle of last month, and I have been getting repeatable errors that are less than 30 arc-seconds. This has allowed me to push up my exposure lengths.

This imaging session wasn’t completely plain sailing though, as I kept having to battle passing clouds. This becomes even more of a problem when you start to use longer and longer exposures, as you can lose a full 2 minute exposure, instead of only losing one lasting 30-seconds. In the end, I lost about 20 or so exposures, which would have pushed me up above 3 hours total exposure, which is a little disappointing.

Even so, I managed to get a solid 2h46m on M81 and M82, which I’m really happy with. Compared with my previous attempt, I have kept the natural colours of M81 when taken with a full-spectrum camera, and not tried to over-process the colours too much.

Even so, the amount of detail that I have managed to capture in such a short time is quite remarkable, especially in M82. You can just start to see the red Hydrogen Alpha jets coming out of the top and bottom. So I have accomplished my goal that I set out on this little single-night session.

I don’t know what September holds in store for me weather wise, I hope it brings more clear nights, as it’s still been quite cloudy in the evenings. Also, I don’t want to embark on larger imaging sessions before I can purchase a coma corrector. It’s got to a point where it’s becoming unbearable, to me at any rate. Hopefully, I can rectify that this month all being well!

Til next time, I wish you all clear skies!

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s