Saturday, 13 March 2010

Shared observing and M3

I've not had time to write this up till now. But there we go...

Last weekend, we had four clear nights in a row, but my back has not been good and I didn't get the rig out for the first couple of nights as it's quite heavy. On the Saturday, a friend and his daughter joined me in the garden for a short visual session. I set up the C80ED on my redsnapper and got out the eyepieces... it's been a while since I did that. We also took out the 10x50 and 15x70's.

We just had a short tour of the more visually interesting targets. I used the 24mm Hyperion on the C80ED and kept it at that. We started with M45, the sisters looking as stunning as ever in the dark sky. I pointed out the obvious difference, and lets be honest M45 is a very obvious choice for this, between looking without optics and what even something like a pair of 10x50 binoculars reveals of the sheer number of stars up there.

From there onto M42 (before it got to low, and the wings of the nebula were clear in the eyepice. M44, another stunning display of stars, we also spent some time looking at the Mirfak association and the double cluster.

I should have taken notes, but I didn't and now of course I can't remember... There were more targets we looked at.

Sunday was also clear, and after watching the early evening ISS pass and failing to capture it spearing Orion, I should have known then what the evening foretold, but having been over a month since actually getting any imaging done, I decided I'd go for it and suffer the consequences.

I carted the rig out, and setup. Polar alignment was as simple as normal, as was balancing, I still can't believe I was put off this at one point, and after debating what target to go for... should I choose M101 or M3... I started the goto alignment. All was going well, until after slewing to the third star, and getting ready for the final tweaks, I caught the power cable to the mount and knocked it out. Ok, thought I, start again. So off I went... now though the slews were going in completely the wrong direction. I don't know why. After trying to sort that out, I gave up, powered down, reset everything and tried again.

This time, the goto alignment went as I expected, and I was locked onto my target of choice within 5 minutes. Then my next problem... I couldn't find a guide star. I couldn't work it out, this was just odd... I slewed back to a bright star and had a short hunt around... nothing, then it occurred to me, that the focus might be out. So I started tweaking, and finally up came a star on screen. I must have knocked the focuser at some point. I slewed back to my target, fired a test frame (30s at ISO1600) and my target was pretty much in the middle of the frame. I kicked off PHD, chose a star and started calibration. This went well and once calibrated, went to setup my timer remote. That's when the next problem hit.

As I was programming the timer, it started blinking and that was that. Now what I thought. I took the timer remote in, removed the battery, cleaned it, reseated it, put it back. Nothing... Tried again, it came back to life. Phew... I plugged it back into the camera, went to check it, press the light button and again, it started blinking... I repeated the process. After 3 minutes of fiddling, I still wasn't getting anywhere. I checked for spare batteries, none of course. I was thinking I was going to end up having to keep track of the exposures on a timer. But at that moment, it sprang back to life. I was able to setup the remote for my exposure sequence, plugged it in, pressed go, and went off to get on with the things I needed to do.

Whereas, I'm normally up and running in under 30 minutes, it had taken me 90 minutes to get going. Ho hum... talk about a way of cutting the session short.

Anyway, I stopped capturing data a couple of hours later, and after the initial problems, everything had worked exactly as I'd expected it to.

After stacking and processing, here's the result..

A Widefield M3

Canon 450d on C80ED. 59 x 2 minutes @ISO200, with 15 darks and 22 flats.
QHY5v on Konus Vista 80s guiding with PHD
Mounted on an HEQ5

But there was something odd with this, I've had it before with M3, a green/cyan tint to the cluster. I don't know why. Anyway, with some additional tweaks in processing, I got

Which I'm much happier with. I've come to the conclusion, that ISO200 works great for subs of at least 5 minutes, but below that, such as with these 2 minute subs, I probably ought to be using ISO400. There was a little more noise than I was expecting showing up. Still it's all good information.