First stacking attempt

[bishbosh]

Hi,

This is Andromeda comprised of five 5 minute exposures. Unguided and stacked in Rot n stack. I had tried Registax but it kept crashing with many different errors.

I expect I could have done better with more but shorter exposures. Anyway, I haven't a clue how to process any of the images.

I did a better attempt at the Orion nebula too, this is a single exposure of 2 minutes

Any hints/tips greatly appreciated!

[cjdawson]

Great starting point on Andromeda.

Try stacking in Deep Sky Stacker and see what you get at the end.  Looking at that image, I'm wondering if it's over exposed, or if that's as a result of post processing.  The middle looks pure white to me - which means any stretching has gone too far.

I'd not try processing those images any further than you already have, they're telling me a great story of your imaging, which can give some things to try to improve next time.

First here's what the Orion image is telling me.

1. More frames needed so that you can stack.

2. Focus is spot on. I'm seeing defraction spikes on one of the stars, so that's perfect.

3. you've caught the middle ground of the exposure time.....

Shorten the exposure to get the Trapesium and central region of the nebula.

Lengthen the exposure to get the huge amount of nebulosity.

4. Frame the Nebula lower in the image next time.  As you capture more data, you'll see that the nebula is flowing to the top of the image, and the really faint stuff might be just out of the frame.  I'd hate to see you get a wonderful set of exposures, then have the top cut off.

Here's what Andromeda is telling me.

1. Consider trying to get a guiding setup of some kind.

The stacked image shows that the stars are not points, but as lines.  Would be interesting to see what DSS makes of your sub frames though.

2. Overexposed.

As you said, take more frames, but shorter exposure time.  This might help with 1 above as a freebie.

3. Rotate your camera for next time.  Andromeda is huge, it's poking out of both the top and bottom of the frame.

4. Glow on the right of the image.

I'm not sure what this is, it's on the right but not the left, so I don't think it's light pollution, that would tend to present as an even cast on the image.

It might be Amp glow, but I doubt it as that tends to present as a spot in a corner of the image.

It might be an LED that's leaking light into the camera.  This would present as a glow over part of the image.  That's my best bet, but with a DSLR, I've never seen that.  Had that problem with my old Film SLR, turned out the light meter in the viewfinder was leaking light onto every image, do I removed the battery to solve that problem.

It might be cloud.  Clouds can have weird effects on the image.  If it's light reflecting off a thing cloud that could easily cause this issue.

I know that it looks like I've been really critical there.  My intention is to give you some hints and tips for things to look out for next time.   I really do think they are great pair of images.  So keep them!

[bishbosh]

Thanks for that detailed feedback. On the contrary this criticism really helps, you've mentioned things that I hadn't considered at all at the time, such as ensuring my camera is at least at the correct orientation to capture large objects. I shall try DSS and see what that makes of them. I really don't have a clue about post-processing so I expect that will be a steep learning curve.

The glow possibly could have come from the neighbour who had a bright light on during my observing session, I had to stand in between the scope and the light otherwise the light would hit the top few inches of the tube, I expect this is where the glow came from. There weren't any clouds at least none I could see.

I'm not sure what you mean by I've caught the middle ground of the exposure time, do you mean that 2 minutes is a fair amount of time per exposure?

Anyway, I hope I'll remember these points for next time
Cheers

[wimvb]

Nice images, which have some nice possibilites. You captured the blue nebulosity in Andromeda very nicely.

After cjdawsons fine comments, I would only add this:

The first image seems overstretched. As the left side is very dark, you probably pushed the histogram too far to the left. The glow to the right of the galaxy may be due to a natural gradient in your frames. The reason the right corners are darker is then due to vignetting.

Remedy: stretch less, such that the background never loses detail. The dust lanes should reach into the central core of the galaxy.

Remove the vignetting by using flat frames.

Remove the gradient by using background extraction. (can be done in both Photoshop or PixInsight, don't know how other apps handle this kind of processing.)

Crop the bottom of the image a little.

Good luck

[Feral Rabbit]

Great attempt bishbosh. I'd be happy with those as a starter.

cjdawson lovely constructive criticism.

Regards

[Craig20264]

As a photographer first and astronomer second, this may sound a basic question to you guys and girls, you mention the shots were unguided,but how on earth did the stars not trail in the Orion shot with a 2 minute exposure.

They're very good by the way. 

[bishbosh]

I'm not sure either really. The Synscan hand controller shows the coordinates of the target in the sky and these seem to constantly update. The mount also makes a faint swish-swish-swish sound so maybe it is tracking the object on the R.A axis.

I haven't studied the manual too much so if anyone could clarify if that's the case it would be appreciated. If it is indeed tracking I presume it's ok but not good enough for long long exposures in which case you'd need to autoguide.

[Starlight 1]

Two mins on a Heq5 is not hard  I have done 5 mins unguided with a SW 120  on a still night , or so thay say it once in blue Moon every thing works .

[wimvb]

Unguided means that you didn't use an extra camera that images a star and moves the mount so that that star stays in the same Place on the cameras sensor.

If you have a motorised mount witha goto handcontroller, this means that the mounts motor will constantly rotate the scope to counteract the rotation of the Earth. this is called tracking.

Tracking is done by dead reckoning and only works perfectly if you carefully setup the scope and align it perfectly to Polaris.

Guiding is more forgiving in setup as it is an Active method.

[RSM]

Hi. For a first attempt, these are really good. Especially the steadiness of the images and lack of star trails. Having just begun processing a couple of months ago my recommendation would be to choose which software you are going to use then hunt around for tutorials on you tube. After having similar crashing issues with deep sky stacker I chose Pixinsight. You can get a 45 day free trial to see if it's good for you. After that it's quite expensive but it does wonders on my 30-60 second exposures. It's quite daunting at first but with the aid of two tutorials from a fellow PI user called Richard Bloch (search for his name and pixinsight in you tube) I got the basics of stacking and processing. Once you've been through them a few times, you may then find the need to do more and again there are some excellent walk through tutorials which show you exactly what to do. Couple that with excellent friendly advice here on SGL and you'll be up and running in no time Your andromeda looks better than my first attempt!

Good luck!

[cjdawson]

Thanks for that detailed feedback. On the contrary this criticism really helps, you've mentioned things that I hadn't considered at all at the time, such as ensuring my camera is at least at the correct orientation to capture large objects. I shall try DSS and see what that makes of them. I really don't have a clue about post-processing so I expect that will be a steep learning curve.

The glow possibly could have come from the neighbour who had a bright light on during my observing session, I had to stand in between the scope and the light otherwise the light would hit the top few inches of the tube, I expect this is where the glow came from. There weren't any clouds at least none I could see.

I'm not sure what you mean by I've caught the middle ground of the exposure time, do you mean that 2 minutes is a fair amount of time per exposure?

Anyway, I hope I'll remember these points for next time

Cheers

What I meant was that for M42, you need to different exposure times.  Once for the Trapesiam (The central stars) and another for the much larger nebulosity. A 2 min exposure is too long for the stars, and too short to capture enough detail from the nebulosity.  Actually, it might be plenty with enough frames to stack, I'm not sure.

For the trapesium try shorter shots - 60 seconds, 30 seconds etc.  The idea of these frames are to capture the central stars and see them distinctly.

For the rest, try longer shots.  2 mins, is what you saw above.  More sub frames might be enough to get more data from the image.  3 mins would be better.  4 better still, etc.  This where alot of experimentation could be useful.  Capture a set of images something like 16 frames or more and stack them.  More the merrier.

As a photographer first and astronomer second, this may sound a basic question to you guys and girls, you mention the shots were unguided,but how on earth did the stars not trail in the Orion shot with a 2 minute exposure.

They're very good by the way. 

Unguided means that the shots were taken without the use of an autoguider.  That's all.  With a goto mount, it will still track, however it's a guess rather than observed and corrected.