Carina, 2nd attempt: help required!

[thegableguy]

I took 40 x 2-min subs, went through them and hand-picked the best 25. Not sure why some were blurry and others razor-sharp; it wasn't windy, I didn't walk anywhere near the tripod, I had all cables / straps tied back... weird.

Anyway very happy with the data collection - the resolution is wonderful and the detail is great. However, I'm still not happy with the processing & editing. It's a lot better than my first attempt but it's got some VERY intense editing to make it look like this. As a photographer I know that the more you push the editing the less natural it looks, and this doesn't look natural to me.

I used 10 flats, 20 darks and 10 bias. Noise & vignetting levels are fine by me so I don't feel adding more would solve anything. I messed with the luminance curves in DSS to put RGB spikes all overlapping at the inflection point.

I'd like to put all RAW images (lights, flats, darks, bias) into a Dropbox folder and see what other people come up with; is that sort of thing done here?

[rustigsmed]

looks good to me Chris, what don't you like about the photo?
re: sharp vs soft frames, its possible that you had focus drift over the night as temperature changed or perhaps some dew.
you can definitely put the files up in drop box, if I get time I might have a crack.

[Atmos]

On the surface it is looking pretty good! Difficult to see a lot in a 200kb version though ;)

What is causing those errors is more than like to be mechanical. The NEQ6 has a worm period of about 7.5 minutes, are the poorer subs randomly distributed or it is every 1/3 or 1/4?

You are always more than welcome to give out your data if you wish, Dropbox is good for that sort of thing.
I'd give them a look over but I currently have unstable Internet and no laptop :P

[thegableguy]

Nah, the focus was perfect (I wasn't going to make that mistake twice in a row!). Some stars were elongated, or doubled like the mount had been very gently bumped. But I think Atmos has nailed it - it's almost exactly every 3rd/4th image.

As for what I don't like, well I dunno exactly. I'm fairly happy with it I guess. Maybe I'm comparing it to Ha images, or differently edited & filtered mono cameras, or vastly longer total exposures, but other shots I've seen don't look so... worked on, for want of a better term. But maybe it just looks that way to me because I know how far from the original TIF it is.

I'll put the necessary files in a Dropbox folder and will post the link here when they're all uploaded (will likely take a while, they're big files).

[thegableguy]

I think you just worked it out! Of the 40 shots I took, these are the ones I deleted:

4
8
11
12
16
20
21
23
27
30
31
35

So where does that leave me, is there anything that can be done about it?

[Atmos]

It could be something as simple as a little bit of grit in the worm gear. Did you buy it new?

I would suggest a strip down and clean/regresse if it has been around for a while. I personally found it really good just to understand what was going under the hood of my EQ6 :)

[thegableguy]

For anyone interested, here's the link to a Dropbox folder with 25 x lights, 20 x darks, 10 x flats and 10 x bias.

It's still uploading but almost done - maybe give it 10 mins from when this is posted.

https://www.dropbox.com/sh/xrk77cpoik3jnja/AADvb6wUgxqb0Rn_Q39wYZdVa?dl=0

Would love to see what you all come up with. I just have this feeling it could be done a lot better.

[thegableguy]

I like taking stuff apart and learning about it, but I'd be slightly nervous with this thing! I bought it from Somnium (Aidan), who struck me as a guy who both knew about his gear and looked after it - but I believe it was sitting in storage for a while before I bought it, so it's possible.

Do you know of any good videos for guiding one through the process of stripping it down?

[Somnium]

i had considered greasing the gears before i sold it but never got around to it. seems like a good idea. you could also train the periodic error, i never did it on that mount so you could gain some tracking accuracy that way.

[glend]

I believe therevis enough data there to improve the image. What did you do with the levels and curves post DSS. DSS alone is not much of a processing engine. Are you using Photoshop or something else?

[thegableguy]

I just used Lightroom, which is the program I'm most familiar with for portrait photography; I'm okay in Photoshop but I generally avoid it whenever I can. Thinking that maybe I'll have to start using it again.

[raymo]

Just google astrobaby, or alternatively just enter "how to strip EQ6" and
you'll see several very good tutorials on how to overhaul and adjust the
various SW mounts. Many people never use the PEC routine on their
mounts [including me], don't think for a minute that Aidan would sell you
anything faulty.
raymo

[raymo]

You have a nice image there. I think you are expecting too much from
shortish subs with a small scope. Obviously your processing skills will
only improve with experience.
I would go through the PEC routine before considering stripping the mount;
it is probably absolutely fine.
raymo

[thegableguy]

Thanks Ray.

It could be simply comparing this to shots with vastly superior setups, as you say... but I just think my editing isn't great. The post editing is done in Lightroom, which is vastly easier to use but a lot less powerful than Photoshop. I'm just being lazy and using the program with which I'm most familiar as a portrait photographer - since getting LR a few years ago I barely touch Photoshop anymore, except for stuff like cloning / stretching / warping etc.

However, before I start down that path I'd like to see someone who knows what they're doing have a crack with this data so I can see how much difference it makes.

[thegableguy]

I'm certainly not accusing Aidan of selling me anything dodgy! But all mechanical devices need maintenance; as Aidan himself said, he was planning to service it but never got around to it. The dud frames every 7-8 minutes suggest that it could be of help, and I don't have a guider with which to program the PEC anyway. I'll strip it down, grease it up and learn a bit more about how it works, and perhaps when it's back together it will track a little more smoothly. It'll be a fun cloudy night project.

[raymo]

Fair enough.
raymo

[Somnium]

But when will you ever have a cloudy night ... Haha jk

Good luck

[Atmos]

As raymo mentioned, look at the Astro Baby website for full instructions on stripping and regreasing. It is very comprehensive and goes step by step.

The EQ6 that I bought off of here last year developed some tracking errors a few months after I bought it. Was it faulty? By no means, worked very nicely BUT it hasn't been regreased for about two years and had been sitting in storage for the 12 months prior.

As for working on a NEQ6, give yourself the better part of a day for it. Take it slowly and you should be fine :)

[thegableguy]

Sounds like a good way to spend a rainy day to me. It's like a nerdy version of the guy across the road who works on his muscle cars on the weekend. I'll get the tools out, put on some old torn jeans, blast some Chisel at the neighbourhood and take a look under the hood of me fully sick equatorial mount maaaate.

[thegableguy]

REMINDER TO ANYONE INTERESTED:

Here's the link to all the RAW files. 25 lights, 20 darks, 10 flats, 10 bias.

https://www.dropbox.com/sh/xrk77cpoik3jnja/AADvb6wUgxqb0Rn_Q39wYZdVa?dl=0

Would really love to see what other people manage with them.

[Atmos]

Give me 8 days haha

[rustigsmed]

just lights and flats, no darks or bias.

stretched the crap out of this :lol: i had a feeling you wanted something with a bit more oomph? this is going a bit too far but why not.
is the dslr stock? i think your version maybe a tad red for the brighter areas.

also unless it was my DSS setting there is either some sky glow or over exposure perhaps on the flats? there was alot of gradient going on in the background to the left of frame which i cropped out (and i think you might have too).

cheers

russ

edit: added something a little less nitro :thumbsup:

[thegableguy]

Wow!

Love them both but probably prefer the second one. I never even considered not using darks or bias but the difference is enormous. I often wondered how others got their amazing blanket of stars; now I know. Darks sure do take out a lot of the data.

Yep camera is stock. It's the cheapest Nikon DSLR they make, but we've got some vastly better bodies I want to try one day. I bought this with the suspicion I'll mod it one day. Did you use a lot of noise reduction, or was it not really necessary at ISO 800? It's pretty noisy at ISO 1600.

Agreed re the red; I kinda forced it in that direction because that's what most other images I could find of it looked like.

Thanks for doing that - really appreciate seeing what someone else does with the same data.

[rustigsmed]

no worries. its been months since i've taken any shots myself

yes definitely the first one is way too stretched ignore that one.
i read somewhere ages ago that you don't require bias frames for dslrs so i have never bothered (when using a dslr). Flats in my opinion are the most important one to get right (along with the lights :lol: )

if you've got darks go for it, i was in a rush so didn't bother downloading them (no nbn here) the extra stars are mostly from stretching the data further (rather than from not applying darks). saying that i stopped using darks even when using a dslr (most would disagree with me) but instead aimed for dithering between subs and a minimum of 16 light subs to further reduced noise (getting a library of darks at the right temp and lengths for a dslr was too time consuming for me). I didn't use any noise reduction mostly simple levels and curves (took a lot of iterations). i made a duplicate converted it to LAB mode, then extracted the luminance layer and put it over the original and blended via luminance. the bottom layer (colour) you can crank the saturation before blending the luminance layer in it seems to help with colour noise.

modding will help a lot with sensitivity and picking up the Ha.

cheers

[Atmos]

I personally would recommend making a Master Bias of maybe 200 exposures. Takes maybe a minute to get them and having a good bias is great to have for both the flats and lights. Russell is correct that flats are the most important of the calibration frames, this is why I would suggest hitting these with a master bias along with the lights, can remove a fair bit of noise.

You can largely get away without darks by dithering between each frame as Russell suggests. Darks are mostly for removing hot pixels and slow dark current build up, with one 120s subs the build up is not too bad anyway.

It looks like you have some good data there. Realistically, it is going to take you a good year or so to start to get the hang of image processing. I've been slowly muddling my way through it for the last 9ish months and what I have most learned is just how much further I have to go haha

[Luke.]

Alright I had a go at it. I am only just starting to learn processing now.
I have no idea how to control the colours and I lost a lot of detail towards the center but its a start!

[thegableguy]

This is all great. There's stuff I really like about that last one Luke - the fainter stuff really punches, but yeah somewhat at the expense of the finer details and brighter areas.

It would be a lengthy process to overlay two or more versions in Photoshop and layer them that way, but I'm guessing that's the best way to get the full dynamic range of everything you want to see. RAW images have great dynamic range for daytime photography, but I'm realising this is a whole other level.

Having said that, this is a pretty cheap nasty DSLR. Next time I take a shot at Carina I'll try with a better DSLR and see if there's any significant benefit.

Mostly the different versions are showing me that there's way more than one way to skin a cat and that there's no one right answer.

I'll keep slogging away! Thanks all who had a crack at it. I'm trying for the Leo Triplet tonight but I think the alignment is off; just went "meh - good enough" after an hour of fiddling around. Fingers crossed. Lovely clear skies we're enjoying at the moment.

[rcheshire]

It's a nice image and you may be expecting too much of the data given the total exposure time.

As it's a DSLR image the camera has applied a human eye response curve to the data which can make calibration a bit tricky at times.

The bias and flat frames are likely more nearly linear than the longer lights and darks.

The darks should improve the image. So rather than following the conventional method of calibration in which the bias is subtracted from the lights and darks you could try this as an alternative.

1. Subtract the master bias from the flats as normal. Don't subtract the master bias from the lights or the darks.

2. Subtract the master dark (which still has the bias in it) from the lights and divide by the master flat (with the bias removed)

That way you 'largely' avoid a problem that sometimes creeps in with DSLR data where the whole set of images may not be taken at the same temperature, further complicated by the corrections applied to the data by the camera software.

Colour calibration is much easier with a properly calibrated set.

I wrote a little utility for performing the task above but unless you are a Linux user it's not much use.

Hope this is helpful.

EDIT: had a go at processing on a laptop. My monitor has been seconded. Colours might be a bit off. Ignoring that because it's fixable, the image set calibrated well using the method above and stacked easily in Pixinsight, which is a good sign with DSLR data and usually means calibration didn't leave too many zeros. Finished off in StarTools.

The image has retained its nebulosity and a lot of small fine detail and the stars have colour.

You've done a good job of acquisition and more bias and dark frames would be good but overall there is a lot of detail.

If the camera is not modified attempting to increase red saturation will throw the image off. Best thing is to go for detail and then worry about colour.

Here's a dropbox link (https://www.dropbox.com/s/jrfdu5fk0y5pnch/etacarinachris.tiff?dl=0)to the preprocessed 16bit tiff file