Finally... A first image with 314L+

[AndyUK]

Wow, Thanks again guys - I have a lot of things to try out for a rework on this (Steve - That's a great tip for aligning in DSS - Trying to nudge things about in PS wasn't exactly a great way of trying to do it!)

@ Paul - I didn't realise that globs weren't that easy with a CCD - I thought it would be easier as it was easy to "see"! Still, it's turned out to be a good test for the camera... and I've certainly learnt a helluva LOT from the exercise (cheers again all!)

@ Sara - There's no doubt that CCD imaging is quite a bit different from using a DSLR (especially mono) but the difference in noise and sensitivity is quite amazing. Please don't rule it out just because of me - I'm that person who will always make every mistake or hit the button that shouldn't be pressed (like that bl**dy pre option!) and then fumbles around with not quite the right software... and I'm sure I'm going to come across some more hurdles (probably very soon!). However, I'm hoping that I'll be able to get to grips with most of it over the summer months and I'll then be more ready when the nights start getting darker...

I won't stop using the DSLR though (certainly for widefield and it may get used a bit more in the Autumn / winter), but the narrower FOV, lower noise and increased sensitivity has opened up a lot more possibilities. I can now begin to see though why some people also have an APS-C OSC CCD - I dithered quite a bit about going down the mono route before buying this camera, but I'm sure I'll be able to cope with the additional steps of aligning/combining in order to gain the additional sensitivity that mono provides.

@ Dennis - Thanks again... I'll skip the L filter next time out and take unbinned RGB. I'll also have a crack at getting those tif files to you as soon as I can. As the camera is pretty noise-free, I'll probably stick with bias and flats only in future.

@ Tony - Thanks very much for those links on Blue stragglers - That explains those blue stars in clusters... (cheers!)

@Rob

you must have noticed how much more sensitive the 285 chip is compared to a DSLR

Oh yes...! Taking me out of the equation (and my previous "adventures" with that bl**dy "pre" option) I'm very impressed with what the camera can do. I must admit I found processing the binned subs even more of a PITA as of course they also had to be resized, and together with not having to use the L filter will simplify things even more (we like simplification!)

Thanks Catanonia - And I agree, some great tips in here! I'm going to have to review it all and make some notes I think...

(Uranium - I'll await your nod on M16!)

[shaunster]

Glad your on the road to taking some great images Andy, its been a tough time getting there..

[ollypenrice]

Although Dennis talks of one careful stretch - and he may well be right - I increasingly do different stretches of the same data and then use layers. I feel I get the greatest control over dynamic range that way. I don't always create proper layer masks, I just lay a shorter one over a deeper one and then erase, very well feathered, what I don't want to keep. Adjust opacity and flatten.

Olly

[RobH]

That's exactly what I do too Olly.

[AndyUK]

Hi Dennis - I'll upload the seperate stacked L,R,G and B tiff files as soon as I can (my dongle internet connection is awful where I am!). These will be straight out of DSS (no processing whatsoever). The L frames will have had bias subtracted, but RGB will be "as is" (I haven't taken any binned callibration files yet and I'll be nowhere near the camera until next Thursday)

@ Shaunster - Well, the battle became personal a little while back - I hate it when technology threatens to defeat... I know I didn't / haven't mastered post-processing DSLR images, but I (and more importantly my wife) was happy with the results. The thing is, I have to make this work otherwise I'll never hear the end of it

Cheers again Olly / Rob - Re: post-processing there seems to be loads of ways of achieving a similar end result (at least, way beyond my eyesight to tell the difference!). However, I must admit I tend to do EVERYTHING in layers as if I screw it up I can always very easily delete it (and as you say, if you go a bit over the top, then you can sometimes pull it back with opacity)

[AndyUK]

Hi Dennis - Here's the files...

20110524 M13 L Embed.zip

20110524 M13 RGB Embed.zip

[antimorris]

Andy -

I hope you don't mind I had a quick stab at your tiffs this evening.

Here is what I got on my first run-through. I might play with them more tomorrow or Tuesday (as I think we are planning a hike for tomorrow)

[ncjunk]

Andy,

Great to see you got it all sorted! Nice first pic :-)

[roundycat]

Olly and others, I hope I didn't give the impression that I just use Curves the once - do a stretch and that is it. Nothing could be further from the truth. A recent cluster (belonging to someone else) took me a total of seven Curves to get it somewhere near right.

My point was that it is not usually necessary to go to great lengths to get the overall picture looking right unless there are significant differences in brightness across the field.

I wouldn't say anything against what you are suggesting, just that I have hardly ever found it necessary.

Dennis

[Deneb]

Andy, can you send me the whole stack please.

Nadeem.

[AndyUK]

Hi Anna - Of course I don't mind... It's nice to see what someone else can get out of these who knows what they're doing - You've brought out a lot more stars in there than I managed! I had another go myself this afternoon (without being able to access the tutorial I used before) and not even managed to get anywhere close to my first version, let alone the 2nd (or yours!) . (I don't suppose you have a summary workflow on how you got to this???)

Also, whilst about it, can I ask your opinion on the look of these stacks? They seem grossly overexposed to me (and the RGB's maybe not quite in focus?)

(Thanks ncjunk - Yes, I seem to have got the technology sorted (), but I certainly wouldn't say I've got it ALL sorted...! However, it's just me now (oh, and probably getting the right software... and then learning how to use it )

Nadeem - No worries... I'll upload the raw fits files in my dropbox as soon as I can (but again, not from where I am - Uploading over dongle is about 2Kb/s, and the link times out )

[roundycat]

Andy, the main reason I wanted a peep at the TIFFs was to measure some of the stars. Of course, as they were binned they looked to be very undersampled until re-sized. Then the sampling looked ok but the stars all gain in FWHM due to the re-sizing. Two of the brighter stars measured 3.457 and 3.677 and when re-sized they went to 6.639 and 6.833. It was finding this out for the first time that put me off binning. Very little increase in gain and most stars twice as fat. Same thing happens with resolution of fine detail, it is only half as good.

Interestingly, none of your stars managed to reach 65,536 ADU although it wasn't far short. Perhaps the result of gain changes in the camera when binning. Having said that, many of them were around 65,280 which seems to indicate much over exposure.

I think for best results you should take one or two test exposures and examine some of the brighter stars for max pixel. Bearing in mind you will get differences between R, G and B it might help to measure the pixel values in each channel and then expose so as to limit the brightest channel to no more than 60,000ADU. That should help to keep the FWHM down and keeping away from saturation will more or less guarantee better star colour.

Focus may have been lacking but it is not possible to pass useful comment on this with binned exposures. FWIW I usually manage to get focus FW of between 1 and 1.5 pixels with focus mode binned x3 and a (usually) 1 second exposure. As often as not that translates to about 2.5 to 3.5 with ten minute un-binned subs.

Dennis

[AndyUK]

Thanks again Dennis. You've certainly confirmed that these were (as I thought) all but over-exposed - As you mentioned previously, 2-3 minutes would have probably been ample! I've learnt my lesson that I need to check the ADU values before firing away...

In addition, I'll also be putting binning back on the shelf - I never did like the idea that it would be sacrificing resolution/detail, but as some others seemed to use it (some of whom write articles in well known magazines (not members here I hasten to add!)), I thought it must be the done thing. As has been mentioned on this thread though, it would seem that there is a time / place for it, but obviously not on naked eye objects when trying to capture star colour!

With regards to focus, I did use a B mask with the L filter, but then forgot that I can also call up FWHM in Artemis Capture by clicking on a star to get it in even closer - This is something else I now won't forget in a hurry. However, I was actually quite pleased to see the FW values down at c. 3.5-4 as previously, with the 40D, I've usually been in the 4.5-5 range - I'll be EXTREMELY happy to see them down around the 3 mark with 10 min 1x1 subs!

The weather forecast is still saying it might be clear tonight (although pretty wet at the moment), but I'm hoping I might be able to put everyone's guidance/advice into practice soon.

Cheers again