M27 First 'Proper' Deep Sky Picture

[TakMan]

Hi...

Thought I'd share with you my first 'proper' deep sky image of the Dumbbell Nebula...

I say 'first', as the last time I took a 'deep sky' image was in January (this year) of M42 (single 2-3 minute unguided exposures), to make sure that the second hand gear that I had purchased in November/December 2008 was all OK.

Since then, as some of you will have seen I've been occupying myself with taking some lunar shots with my Nikon D3 attached to the TSA102s and enjoying the 'visual side' of this great hobby - I always promised myself that I would try and learn my way around the night sky before I got too involved in the photography side...

After some frustrating nights trying to manually achieve a decent focus and get the damn auto-guide to work - in which my confidence took a considerable knock (along with time it takes to set up a portable system - especially after a long commute home - and then having to dodge the clouds!)

To help with my focusing woes I purchased a Bahtinov mask from: Stay Focused Bahtinov masks from £9 (Powered by CubeCart) and I have to say for around £25 it's far better than what I tried to make myself - and wont go soggy either!

I took the attached shot last Saturday and is my first auto-guided image of any significant length, and from the results below, appears to have gone remarkably well....!

In fact, from what I can tell from the FITS (Raw file) headers that Equinox Image logs (my Mac acquiring software, I achieved a Root Mean Square 'guiding pixel error log' of around 0.39-1.19 pixels (across the 6 sub frames), which I'm told is excellent (for our atmosphere) as less than 1 pixel is usually only achievable with an Adaptive Optics unit and between 1 and 2 pixels of guide error is more than enough (especially imaging at my short focal length), to achieve nice round stars in the final image.

At last I'm now able to capture enhanced target signal over my moderate light pollution signal - to be able to stretch the data and get something half decent! Sounds like I know what I'm talking about!!!!

Although small in the frame (probably not the best target for my scope, which is more of a specialist widefield instrument), I chose to stay with M27 as it was the same target as I had tried the previous week (after viewing), and wasting hours trying to calibrate and auto guide, eventually giving up and taking just a single 2 minute exposure (to have something to show for hours sitting outside), but at least I now had a comparison shot....

This new one is a composite of 6 x 12 minute exposures with 6 x 12 minute dark frames. All pre-processed, aligned and stacked in my newly purchased software: Stark-Labs Nebulosity 2 (so also a first go at learning my way around this too!!!!) Then finished in Adobe Photoshop CS3 with the added help of 'Noel's Actions' and my own 'messing!'

Tonight I'm going to learn how to take additional correction frames (Bias Exposures and Flat Frames), to hopefully further enhance this and future images..... as there is still plenty of noise in this..... I'll probably then have a few goes re-processing

this shot again....

In fact, I've emailed two poor forum members with an essay of questions (they know who they are!) to try and get some additional help.... sorry guys!

Anyway, hope you like the picture, any advice please forward!

At least my confidence is heading the right way now!

Lets hope it's clear for the weekend....?

Clear skies to you all....

Damian

Equipment details (sorry, nearly forgot!): Takahashi EM400 mount, FSQ106-ED at f5 (530mm), SBIG ST-4000XCM on shot colour (self guiding and regulated to -20C). Apple 17" G4 PowerBook with MicroProjects Equinox 6 (planetarium) and Image (camera control), with Nebulosity 2 and CS3.

[Beyond_Vision]

Tracking and focus looks spot on with lovely crisp stars to the corners. It would be worth running the increase star colour action from Noel's tools to lift the star colour a bit.

Regards

Kevin

[ashenlight]

Brilliant work, Damian. The colour is great, the star field is so rich and crammed and the wispy nebulosity just looks stunning.

I am really pleased to hear you are taking your time when getting into this, learning the sky first was an excellent idea. Just shows what kind of results taking your time can achieve You've done a cracking job on one of my favourite deep sky objects

[Tim]

Really nice picture Damian, the Tak, as expected, does a lovely job on those stars, and the software package you have will ensure a simple relaxed approach to imaging

Get the hang of Bias and Flats as soon as you can. It is important to get the flats with the camera and everything aligned EXACTLY as it is for the light frames. The flats will get rid of those two teensy dust spots for you.

There is a gradient that runs from one corner to another, and divides the image in half, it looks like the effects of light pollution, but I would have thought M27 would be high enough to avoid the worst of that at the moment. If LP does prove to be the problem, then it may be worth considering a LP filter, either CLS or IDAS. Noels tools has a gradient thingy, but it would be better to eliminate at source where possible.

I wish my first go at a DSO had been this good Well done.

TJ

[TakMan]

Thanks for all the kind comments!

Kevin; I will be having another go at re-processing, I was just chuffed to finally have some decent data to play with when it's cloudy.... I think there's more to be gained and I'll certainly try to add more star colour....

Amanda; thanks for the thumbs-up..... your looking very sexy in your new avatar! How was the holiday...?

TJ; Thanks for all the useful info! I'm sure you're right with regards to the light pollution issue (picture on my calibrated screen at work looks far better), but seeing it so light on here does show it up - I think it's more down to the next door neighbours back light being on all through my imaging session... I'll have to go and ask nicely for them to turn it off - or perhaps it'll be an air rifle rather than a 21mm Ethos for Christmas!!!

As I mentioned above, I'll have another go re-processing as I've got plenty to learn now with Nebulosity 2 - only had it 3 days!

I took your advice and took 30 Bias frames, 30 Flats and 30 Dark Flats... Flats are another 'Dark Art' it would appear (after guiding) I've got something half decent I think - around 21,000 average signal strength and 'only' a 500 difference in reading between the upper and lower portions of the image - don't frown, I did the best I could....!

I could see from the results coming in why everyone rave about the Sony chip based cameras.... mine (Kodak 4021) looked like dandruff on a black desk! Not that I have any - H&S man myself:D (Not that I can complain as I only paid £1700 for it - virtually unused - and it's in-built guide chip at least means I don't need another scope/camera/rings, etc to guide with!)

Now for these LP filters you mentioned (I'll PM you to make sure you see this!), any chance you could reply with a post of URL's so that I don't look at the wrong ones....?

A couple of questions though...

1) Do they impact significantly on light transmissions and exposure times...? I ask, because you sort of implied that in your post with that fantastic Horse Head capture from kelling...

2) Would this interfere with light balance on a colour camera - although yours is a one shot, isn't it...?

3) Any idea how I would fit such an item into my light-train (all screw-threaded), as I don't have a filter wheel.... I could forward a pic if needed....

4) What about Russel Croman's GradientXTerminator as another option....

That's it apart from I felt it was a good idea to throw in two extra pics of how I image (TJ - I think you may be right... eventually about my software - it's the operator that needs updating!) and another of my first go (when it all went wrong), of M27 with a single 2 minute exposure with automatic dark frame subtraction....

LASTLY - any idea what this dark curve is (top right) from my flats...? Now I've got all my correction frames in the bag, I've taken the back off the scope off - got rid of the two specs of dust that I could see on the rear lens element, and I could not see anything that would encroach like this, unless it's shadow from the CCD housing.... HELP!

I know TJ - I'll have to do my flats again (better next time!)

Question though - do I need to re do the Bias frames after I've rotated the camera...?

Those that understand such things will see that my guiding graph was far from perfect. The chap who writes the software has been helping and explained how I need to do 'Drift Trend' so that I can get better results.... - MY BRAIN IS STARTING TO HURT!!!!

Thanks again!

Dame

[Beyond_Vision]

The shadow may be something to do with the built in guider. If it is uses a pick off prism like an off axis guider this cause the effect.

Regards

Kevin

[Tim]

I think the sbig has a seperate chip for guiding built in Kevin.

Damian, i'll have a proper look at your questions later on. For now, you can do away with dark flats if you capture the flats properly, the bias frames will do the job that you need. They are all about taking away noise and irrelevant "signal" from the lights, so that just the proper data remains.

Getting drift aligned early in the session will really help, especially if you later go for closer in shots.

[TakMan]

Thanks for the reply TJ - and you to Kevin....

You're right though about the SBIG's guide chip TJ - It's flat (on the same plane) under the imaging sensor.

An LP filter won't hinder the in-built guide chip will it?????

Good thought though Kevin, have since spoken to Nick at True Tech and there's a chance that I don't have my spacers sorted up to the camera - it could just be one of the flanges clipping the light cone..... we'll see...! (blumming Tak spacers!!!££££££?????)

Also contacted Ian King with regards to LP filters (as he's UK SBIG man), for my moderate light polluted skies he suggested the IDAS version (without a UV/IR cut as my camera already has that) - Astronomic one as I understand it, is 'more aggressive'. Any thoughts...?

One last thing - just thinking ahead..... I was looking to fix a LP filter into the insides of the light-train.... If I spent the extra and went for a filter wheel, could I use in the future Narrow Band filters with my one shot colour unit.....

Thanks again!

Damian

[Taff]

Hi Damian' Neb looks nice with the stars in the backround nice one.Mark

[TakMan]

Hi again....

Finally got around to having a second go at processing that first shot again... using the Drizzle stack function in Nebulosity 2 - along with Noel's Action's in CS3.

This time, instead of standard Dark Frame Subtraction of the lights, I used the Bad Pixel Mapping function 'BMP' and then Bias subtracted...

I'm amazed at the difference of this compared to the first go - this time with the help of all those flat frames (also dark/bias dark subtracted), I'd tried to sort in the garage on Thursday night! I think the 'other half' is starting to get worried about me...

To keep 'BeyondVision'/Kevin happy, I also gave it a good going over with the 'Increase Star Function' too!!!

Any extra help welcome!

Regards

Damian

[Beyond_Vision]

Now thats a great improvement the flats have got rid of the dust bunnies and the star colour looks much more vibrant. Excellent rework Damian

Regards

Kevin

[RobH]

That's looking really good now Damian, a big improvement.

My first image is leagues beneath this in quality

With regard to calibration frames, you don't really need to worry about dark subtracting your flats. Just make sure that both your lights and your fllats are bias subtracted.

The Hutech IDAS filter should be fine for you. It adds a slight bluish cast, but this is easily dealt with in processing.

Ha filters can be used with colour cameras, but are better suited to mono cameras, due to the increased sensitivity and resolution of the chip.

OIII, SII and H beta filters would be pushing it a bit with a colour camera I would think.

Cheers

Rob

[TakMan]

Rob

Thanks for the info and positive comments! That's a real boost to my confidence coming from such a great imager like yourself - your fantastic collection of deep sky art (and hard work) is an inspiration to us mere mortals!

Regards and clear skies to you...

Damian

[TakMan]

Are SCS Astro the best place to get an IDAS filter from...? And it's the V2 version (without the UV/IR), one I need (not V3).... Ian King said "The Standard One"....

Damian

[SteveL]

The V2 (or P2 as its labelled on the filter) is a "allow everything through, but block the light pollution", whereas the V3 is more like a UHC "block everything and only allow in the interesting wavelengths"... or at least thats what I vaguely remember.

For OSC RGB, its the V2/P2 LPS filter you are after

[Ant]

What a lovely image, especially for a first proper one...?

The second process has improved things quite a bit!

I think that the IDAS would be better than the CLS, the CLS is rather brutal.

Cheers

Ant

[ollypenrice]

Boy, you are going great guns!

As regards the painless taking of flats, I have just bought a luminescent A4 sheet. It is just a self-illuminating plasticky sheet like a document wallet that glows in the dark. I placed it between a sheet of hardboard and a sheet of translucid perspex and taped the lot together round the edge. It's dead easy to use; you just put the scope to the zenith, sit the sheet on top and shoot away. It was about 80 euros but really is the business. I was plagued by light getting in through the filter wheel in the daytime or by my big light box being antisocial to other imagers at night.

It came from a French firm called Selectronic but is no doubt available in the UK.

Gradient Xterminator is very good, though I rarely need it here. A trick I picked up, though, is not to run it over the whole image but to select the dark sky background in Select-Colour Range and run it only over that.

All good fun!

Olly

[TakMan]

Thanks Olly for that - will take a look...

Also been looking at your place for a holiday break at some time..... I could get some useful tips on how to use the gear - and process all the data afterwards....!

Julie speaks French (teacher of Modern languages), so that should help out in the daytime when we go 'adventuring'....

Regards

Damian