M27 - and first light Atik 460EX mono

[LDUNN1]

Lots of 'firsts' for me on this one:-

first time with the Atik 460EX

first time with a dedicated astro CCD

first time with a mono CCD

first time processing LRGB

.......I started astro in 2011, using DSLR's & for the first 8 months, just camera lenses.

I tell you all this so you don't judge the camera too harshly due to its inexperienced operator ;-)

Imaged with an f9 refractor

L: 4x300s+2x600s

RGB: 4x300s

Dark Frames: none

Flat Lights: 12x0.5s (I think!) via each filter

Stacked in DSS, post processed in PS CS5. I've only cropped the very edge to remove the registration marks, so this is pretty much the field of view I got & the resolution - albeit, I've saved in jpg to upload here.

I am content with the processing on the nebula, I'm sure someone with better skills can do a superior job, but for me I was happy enough with it, BUT I have some kind of optical defect which is giving horrible spikes to the larger brighter stars. If anyone can advise how to best process these out, or point me to a tutorial or PS plugin that would be great - I don't feel like doing it one star at a time manually. I'll be investigating the cause of these spikes, but the optics are old & contaminated, so that maybe the cause, I just have not been brave enough to remove the lens cell to give it a good clean.

[Keiran]

Looks pretty good laurence, quite impressive. Is this with your AP scope? Only thing i can see (like you spotted) is them strange strickes through the stars. Does this occur in all of your subs?

[shaunster]

Hope you can get the problem sorted ASAP, apart from that its a brilliant start to CCD imaging IMO

[Looking Up]

Very nice for a first on several fronts, I had the same line on the bright stars on a few pics I did, on the same orientation, I never found out what it was but I put it down to a reflection or a small amount of dew on the objective, I am probably wrong though!!!

[Gina]

Great first - lovely image

[RikM]

Wonderful first CCD image. I love the translucent effect of the neb. Well done.

If shorter subs gets rid of the spikes on the brighter stars, you could take a set and drop them in as a separate layer.

[LDUNN1]

Keiran, 'yeap' & 'yeap'!!!!

I also had those spikes with my Canon's & Noticed Simon (SCAG member you may not have met) also had it with his Canon - so I 'assumed' that it was Canon sensor related....BUT now the Atik has it too, the finger has gone back to the optics, which are know are old & tired.

Shaun - me too! I'll have to take a brave pill & remove the lens cell I think & give it a good clean & check the internals of the scope for anything that may be causing the issue. That's going to be a fun day when I attempt this ;-) ........I may be imaging with a C102 next time you see me ;-)

Gina, I saw your M27 with a DSLR - like you it's daunting posting M27 after Olly's ;-)

Rik, I only have 300s & 600s subs to compare & they both have the spikes, so I don't think dropping the sub duration is going to overly help me, but thanks for the suggestion.

It has been suggested that I may have a spider (a real one) that has got inside my scope at some point & added a thread inside which could cause the diffraction, it's a 1988 scope, so it's possible! Other suggestions I've had so far are dew stains that have run down the optics causing a faint line & a lens spacer intruding into the light path. I'll be looking out for these in due course (no pun intended).

[ollypenrice]

That's a great first go and the camera is seriously sensitive! When you make your flats be sure to stack them and calibrate them as you do so using a master bias as a dark frame. If you don't use a dark-for-flats (and a master bias is fine for this) they will mess with the image.

One processing thing; somewhere you've introduced dark haloes round the stars. Usually this comes from deconvolution or sharpening. Always exclude the stars from any sharpening. (See Martin B's Star Layer tutorial on here or use Noels Actions.)

Fancy adding a bit of Ha? Go on!!!

Olly

[LDUNN1]

That is ace feedback Olly - much appreciated.

Not sure I totally follow you mind! ;-)

There were no dark flats. The only flats I took & used were light flats. I loaded these up into DSS with the light subs for each filter run. ie:-

first stack in Dss was for L so 4x300s & 2x600s & 12x0.5s flat lights taken via L filter - saved gray scale L-image

second stak in Dss was for R so 4x300s & 12x0.5s flat lights taken via R filter - saved gray scale R-image

3rd for green as per red, but light flats via Green filter

4th for blue as per red, but light flats via Blue filter.

Combined all 4 gray scale images in PS - the colours being pasted into teh RGB channels & the L being a layer on the background.

I high pass filtered for sharpening, plus some USM later too - almost certainly over done it - I agree........I did not exclude stars during this process......I'll look for that Star Layer tutorial - thanks for that. Think I've been so focused on the neb & the lines through the stars that I missed the over shapening, so really good that a fresh pair of eyes have pointed that out. Thx.

I don't own an Ha filter yet.......maybe one day......;-)

[dmahon]

I had similar spikes which turned out to be down to a light pollution filter - swapped it for a new one and they were gone.

Do you use one?

If not, are they present on all your LRGB images or just on one filter?

Try rotating things individually (camera, flattener, telescope, filterwheel) and see which one makes the spike change.

[ollypenrice]

What I meant about the flats was this; flats normally need to be calibrated, ie have their own individual darks applied. In reality a master bias (a stack of the shortest darks you camera can take) will do this job.

However, I'd totally forgotten that you are using an almost noise-free camera so you probably don't need to bother! Ignore me, I'm getting on a bit these days...

Olly

[LDUNN1]

ahhhhhh - now that makes sense to me ;-) I had not thought about applying calibration to a calibration file before, that is why I did not 'get it' the first time.

I also agree with you though, that as the camera appears to be exceptionally low in noise on 5 & 10 minute exposures, that the sub 1 second exposures probably don't require a calibration for the sort of use I am putting teh files to.

I really appreciate you taking the time to post your thoughts & advice Olly. Last year you posted on a thread with me on short tube large aperture 'travel' scopes - we were posting about Tak FSQ-106 & you also mentioned told me to seriously consider the FSQ-85. Just over a week ago I had the opportunity to see an FSQ-106 close up & personal (day time) and a Sky 90 along side it. I came away from it thinking 'wow that 106 is huge & heavy' - I'm not sure it's 'travel friendly' enough for me now, & I am coming round to the FSQ-85 (which I have yet to see in the flesh!)......or of course the Sky90 which impressed.

[LDUNN1]

Dmahon - I was not using an LP filter - just LRGB. I've just checked a sub of each & they all have it.

Thanks for your post & a good suggestion, someone else had mentioned this to me, but it had escaped my mind to check, good catch, thanks, that is another potential ruled out I think - plus I also saw it on a Canon DSLR with no additional filters.......think it is all pointing one was towards the optics.

[ollypenrice]

For imaging the FSQ85 literally eats the Sky 90 for breakfast. It has far better colour correction, controls bloat on hot blue stars, needs no flattener, has a larger flat field, is better made and is not prone to needing re-collimation. Only a conservative firm like Takahashi would still be producing a scope so far past its sell-by date as the Sky 90. I do love the firm but sometimes they don't do themselves any favours. Doublet versus quadruplet Petzval? Not in the same league.

Olly

[LDUNN1]

.....not a Sky90 fan then? ;-)

We're getting a tad off topic here now, but the trouble is that this would now be taking the 'ideal' largest aperture travel scope available (just about) 106mm then dropping to the 90mm of the sky90.....& now dropping to 85mm. Not an issue if you are imaging, but if you want it fro occassional visuals too as a 'grab n go', that loss of aperture from 106->90->85 may start to becoem apparent.......

Still glowing endorsement of the FSQ-85!

[x6gas]

Looks good. I'm impressed and jealous that you got any imaging time at all. I'm an hour up the road and haven't captured anything for months :-(

[Spikey]

Looks like the 460 is a winner and a great FOV, similar to my 16HR.

I don't think you're going to be needing any darks

[badgers]

Great first light on the 460ex!

Mine is sat in polythene waiting for it's first night out....

I just hope I can get something as pleasing as you've got there. Lovely Image.

[LDUNN1]

X6gas - opportunities have been very thin on the ground for getting out the astro gear recently. I wouldn't normally contemplate going out on a Sunday night mid summer as I am usually in work before 6.30am......but I was getting desperate ;-) so I set up & went through from 11.30pm through to 3.30am, got to bed about 4.15am & back up at 7am & went into work a bit later than normal.

Badgers - I don't know what camera you are coming from, but the 460EX is my first steps into dedicated astro CCD imaging/ mono / LRGB. I can only tell you how it compares to Canon DSLR's. The field of View is very limited compared to what I am used to, & resolution is a tad low too which limits cropping opportunities (compared to DSLR's) so you have to be more accurate with your framing to start with. No big deal really. The noise is impressively well controlled, & that means I cam saving loads of time vs taking dark frames with the Canon's. That is a big plus. I've dialled in -7.5 degs cooling - my logic is that this should be a consistently achievable temp throughout the year regardless of ambient night time temps......I appreciate that I could dial in a lower temp but -7.5 degs seemed fine for noise control anyway. Light Flats seem more critical to take than they did on the Canon's - I noticed many out of focus dust bunnies on the subs, which I am assuming is dust on the filter wheel - whcih you don't have on teh Canon's.

Simon - I guess teh FoV is something you get used to - it seems a little narrow to me coming from full frame DSLR's. .......& its great not having to waste time taking darks! Flat lights I can cope with! ;-)

Cheers all for your responses.

[badgers]

I'm coming from a Canon 40D Ldunn, so yes, I know what you mean.

The Canon was great for framing and resolution with its large sensor. But I was never happy with the colour I was getting and trying to image at 20C ambient really convinced me to go cooled CCD.

I'm extremely impressed already.

[shaunster]

I think its safe to say all my banging on about a CCD paid off then

[Gina]

The Canon was great for framing and resolution with its large sensor. But I was never happy with the colour I was getting and trying to image at 20C ambient really convinced me to go cooled CCD.

I'm in the process of adding cooling to my second Canon DSLR (1100D) to use with lenses for wide DSOs. I agree that 20C sensor temperature is decidedly NOT good and -15C is an enormous improvement!

[LDUNN1]

Gina, I know someone else who is converting his tupperware lunch box into a DSLR cooler ;-)

;-) @ Shaun - I never doubted that a dedicated astro CCD would be better than a Canon DSLR for astro Shaun, my posts in SCAG defending the use of DSLR's for astro still stands - they can be used & decent results had - they are a great way for many to get into astro imaging. My posts in SCAG were directed at a comment that you can't use DSLR's for astro. Like Gina, I suspect that I'll still use my Canon's for wider field work. I'm still not entirely convinced yet btw Shaun - look at Gina's m27 with a fraction of the expsoure I had with the 460 - I shot about 1hr 40mins on the 460 - if Gina had shot 50 mins lights & 50mins darks, & then we compared results, there may not be such a difference - & that would reinforce the DSLR argument somewhat. I am however, looking forward to the 460's increased sensitivity to Ha & I do like not having to shoot darks ;-)

Badger, for info, I have been primarily using a 5dmk2 (unmodded) for most of my astro imaging to date. Earlier this year I added a modded 40D. The 40D is noticeably noiser than the 5d2, but that could be part of the impact of a modded camera, but when you were imaging a target rich in Ha - like the Horsehead, then the modded 40D was the camera of choirce between the two. I'd love to see what a modded 5d2 could do.

[rfdesigner]

A very nice start, and a very nice camera, a great choice for shorter focal lenghts.

Re the spikes.

I've had them on my setup: 12" newt + Atik 383L+. In my case I've been assuming (with some good reason) that the problem is soemthing interfering with a perfectly clear circular aperture. In my case I've got a single small streak of dirt on the window and I'm assuming that is causing a very slight diffraction spike effect.

perhaps there's a small hair or fleck somewhere in your OTA.

Derek

[Coco]

Very nice indeed...

I have the OSC 428 and it knock my old 40D modded DSLR into a cocked hat..