Five galaxies

Well done Dave. I'm wondering why you used the focal reducer? To get as much data into the short exposures? I assumed these were single exposures or have I missed something? I'd be looking to stack 15-20 of those 2 min exposures. However for SN detection I suppose its not a pretty picture were looking for as an end result.

Dave G - I just couldn't be bothered to remove it

Actually, some of those galaxies (especially image 2) wouldn;t fit in the native FOV of the DSI/C8 combo. So a reducer will be needed a lot of the time. Also, it *does* help shorten exposure time. The second image (the grainy one Seanie) is a single exposure - hence the poor look to it. It would be nice to get a good looking image of it - as you say, 15-20 stacked 2 minute expsores would make it look really well. Ah well, yet another project I'll give it a lash when I bag the other five.

Seanie - the two blobby images are not as a result of exposure, just over processing to show you there really was a galaxy there! Like M42 though, to show fine detail can result in washout in cores... A trade off as ever...

Thanks for the comments lads - appreciate them. I'll try and get the other five before heading to Galway.
Cheers

Dave

I guess the real question is,
How good an image does it need to be for SN detection, do we need to get the spiral arms someway visible, or is it good enough to know they are there and any SN in that area will easily outshine them?
I look forward to trying some of these galaxies and seeing what comes out.

Good question Dave but I see the the fundamental question as - how bright will the SN be... You'll never know that.

Presumably, for a mag 12, 13, 14 galaxy, the spiral arms are going to be much dimmer than that (if the galaxies magnitude is based on the core).

I'd say, that if you can image somewhere between say mags 12 and 18, you'll get the SN no matter what the galaxy's mag is.

In the case of SN20005EP, presumably that has spiral arms that we just can't see - but the SN is very clear - and also clearly 'outside' the galaxy. Although it must be within the galaxy to be a SN - we just can't see the arms that its exploded in...

In short, no, you don't need your image to clearly show spiral arms - just the core will do - only so you know you are imaging the right galaxy

Now we have initial images, every subsequent image set just be compared to these 'masters'. A SN will show up clearly (well as long as its bright enough) as a rogue star. OF course, if we get better quality images of these galaxies, then *they* become the masters.

Just as a matter of interest, I shot the five in about 30 minutes. So it needn't take up a whole night's observing. You can still go for Saturn!

Cheers

Dave

:lol:
fair enough. The next good night I'll try those five galaxies with differing exposures and see whats best, and also get dark and bias frames, and will try and get good flats if possible, all those will be raw origs from the canon, it should prove to be a nice challenge given the light pollution, I'll also try with and without the IDAS filter, its mainly for nebula. Its effectiveness on galaxies is somewhat reduced, but we'll give it a go all the same.

Nice one Dave - look forward to seeing them.

As a matter of interest, any idea how you'll take the flats? I use two white t-shirts over the scope and point it at a dark area in shadow (a wall or even the grass). To be strictly correct, you also need to shoot darks for your flats... Same temp and duration.

To be honest though, I'll just be sticking with lights and darks and forgetting about bias and flat frames for now. Maybe later on in the new year I'll refine the process. I think serious image reduction (lights, darks flats, flat-darks and bias frames) is pretty tough going. Well, tough enough when I'm still struggling with really twealkking the mount to get it to its optimum level

Cheers and good luck - keep us posted.

Dave