M66 - Leo triplet - first go

[LouisJB]

Nice night last night. Spent most of it capturing some data on M82 supernova and M81/M82 and some of M1 Crab nebula which I've yet to process. Unfortunately work commitments meant having to pack up early otherwise I'd have been out there for many more hours.

Just at the end of the evening I pointed towards Leo and got 3 x 3 min subs of the Leo triplet. This is my first go at this area, it was still very low in the sky also so there was light pollution around. I appreciate this is no award winner, it's pretty bad and I'm not sure anything can be done to improve the image given the lack of data but as a test shot it raises some questions;

Can I remove the gradient in the background (horizontal) without losing the limited detail there is in the galaxies.

What sort of sub-length would you normally take for this sort of image, 5mins?

I'm not sure I could push about 3-4mins with the objects so low in the sky, would just raise light pollution in the background, but armed with information from this test shot I hope to give it a proper go and collect 1hour + data in the coming weeks (weather permitting).

Any advice etc always appreciated.

[Russe]

Very nice! Maybe a gradient in the background (brighter left than right). Have you tried gradient exterminator?

[wookie1965]

Well i am very envious i have been trying for two years just to see these so your image is an inspiration to me to go to a dark site and get it in the bag nice one.

[LouisJB]

thanks everyone. I know it's not great, but that anything showed up was a bit of a surprise, first time I've seen anything like that and that I've pointed to that part of the sky.

I realised after that the tube wasn't colminated. I think I knocked one of the locking nuts, after noticing I pinched it up thinking it was be back to the same position - however I double--checked it today and was fairly far out :s Re-colminated now, lesson learnt too...

Still you have to go through this sort of process of mistakes to learn how to do it properly. I don't suppose many people go straight to perfection with their imaging.

Next time it's clear I'm going to try capturing this area for as long as possible, loving the shapes of these galaxies, absolutely fascinating!

As for gradient exterminator, no I've never tried it. It looks like a paid-for photoshop plugin, is there a free equivalent?

[Russe]

The free version would be explained in one of Doug German's YouTube videos. Google his name, they're great!!

[CraigSavery]

Well done on capturing these galaxies for the first time. Nicely framed too.

Gradient Xterminator is a paid-for plugin but I think you can have a free 30 (ish) day trial to try it out. It works a treat for light polluted skies.

Sent from Android Mobile.

[Physicist13]

very good! the obvious statement is that more data will help..no need for longer subs just lots more of them to get a better signal to noise.

[Russe]

[Pete Presland]

nice start louis. i do like this grouping 3 nice galaxies for the price of one exposure, what a nice "value for money" target!

[Eddy_]

Very nice!

[whizzbang]

Good effort, love the framing, if you can repeat that then it's looking good.

me, and I'm no expert, but do live in sunny Brixton, would probably try 20 * 3 min subs, the reason is I think longer subs my over saturate the stars. Also the stas are a little eggy in one direction, so maybe tweek your guiding.

Good first try. I love scoping out the low horizon and sizing your target up.

[whizzbang]

Btw you couldn't post up the plate solved image as we'll could you?

[Ags]

I'd like to feed this through my prototype no options, no adjusting, no thinking, does it all for you gradient extractor. I'll PM you. :-)

[LouisJB]

hi, thanks for all the great replies. If you'd have asked me about the plate solved image I'd have had no idea what you meant until a few days ago when I signed up astro bin!

Here's the image there. http://www.astrobin.com/76634/ which was solved. I'm not sure how to get a copy of a solved plate.

I think the framing was a happy accident. I pointed the tube, took a test shot, saw "stuff" was there (much to my surprise) and so took shots for the remaining 10 mins I had left.

Hopefully I'll be able to repeat that again, I know roughly how the camera was orientated. It certainly helps once you know what is there already. First shots for me are usually a process of discovery and either, wow that's amazing (like M81, this triplet, M27 etc) or wow that's difficult, like my recent 1st experience at trying M1.

As for the stars, yes I think there was a bit of a guiding failure. The settings I used to use with the smaller 130 tube don't seem to quite cut it, also the tube wasn't really balanced much at all so that probably made the mount struggle. And there was a problem with dew on the guider tube! All part of the learning curve.

So sounds like lots of 3 or 4 min subs when it's higher in the sky and the weather clears, attempting the same orientation/framing might be something worth attempting at the next opportunity.

It's difficult when you don't have clear weather for weeks and the only time you do either there's an early start for work the next day and/or the Moon is full :s all part of the challenge though isn't it, we don't like it to be too easy do we.

I'll dig out the tiff and send, be interested in what gradient removal can do!

[Ags]

Well, i fed the tiff through my crude code. This is the gradient it found:

Here is the image with gradient straight subtracted:

And here it is after a bit of a stretch:

[Ags]

Looks like my prog over-corrects the gradient. But I think it is noise speckles that get skimmed off on the left but still show up on the right (probably something to do with the curved-ness of the gradient).

[Russe]

If you remove a gradient, a good idea is to deselect the galaxies first, so that no data gets deleted.

[LouisJB]

wow that's really neutralised the gradient effectively. The lack of data captured probably means there's not enough to distinguish background gradient from image, but I could see this working well with stronger data.

Will you make it slightly adjustable so it can be tweaked, perhaps there's a compromise between ensuring no data is lost and having a slight background gradient in cases like this.

Good work anyway, do keep us posted on updates etc

[Ags]

If you remove a gradient, a good idea is to deselect the galaxies first, so that no data gets deleted.

My gradient extractor designed to deselect the areas of interest automatically, with the downside that it thinks large areas are gradient. If you look at the gradient image the areas where the galaxies are does not get brighter so I think I did correctly deselect them.

If you are saying that I should not have subtracted the gradient from the galaxies, I disagree. The gradient occurs over the galaxy too and is not part of the signal.

[Russe]

I'm not saying anything about your gradient extractor at all. Sorry if it came across this way. It was meant as a general statement about gradient "extermination". If you have a tool that confidently leaves areas of interest alone w/o any further user input, that's great.

[Ags]

Ah... sorry :-)