Another imaging test M42

[leinad]

5 x 5min ISO400
5 x 5min ISO800

Another test imaging session of M42.
Pushed a couple of 10min exposures, but didnt have enough to process. Tried 15mins, but it came out all white!? Maybe camera psuhed to far, or ISO too high.
I need to find an easy way to take flats, dust and noise is atrocious in the final processing.. Also need to take equal exp. darks.

Also noticed trailing round the corners, possibly need a focal reducer?
Was up till 5am; and back out again tonight ;)

:)

[AlexN]

Looks good mate... The stars at the outer edge of frame are a little stretched, this indicates field curvature, and a field flattener/focal reducer is the way to go to fix this... The William Optics FF/FR v2 or v3 is what you want.. They both work well with the ED80...

Are you stacking with Deep Sky Stacker? If so, then throw the couple of 10 min subs in the mix, it will stack them all together and you'll get a bit more of the nebulous extension...

Heres a link you should have a read of, I think you'll find it useful :)

http://www.astropix.com/HTML/J_DIGIT/LAYMASK.HTM

If you have **ANY light pollution, 15min at ISO800 is going to wash out pretty harshly, if you want to run longer subs for better Signal to Noise Ratios (SNR) then you should go to 20min ISO400 (equal to 10min ISO800) it will have equal data to a 10min ISO800 shot, but much less noise..

Simple flats. Put a white T shirt or a white plastic bag over the end of the scope, and take 10 to 20 short exposures, enough to show the vignetting on the image.

Best of luck with all that, And for your 2nd image :thumbsup: Great guiding, awesome focus.. well processed... Cant ask for more than that! :)

[leinad]

Thanks Alex, I'll check out the FF/FR. Hope they aren't too pricey :sadeyes:

Great link, thanks!

I assume with the white t-shirt, placcy bag trick you need to do this under light, Facing near a light bulb few feet away?

Should I take equal amount of flats to darks. Therefore roughly 5 darks and 5 flats per light. Im thinking if finding an LCD to pull the screen off and use the backlight as a lightbox.

Moon is causing lots of washed out noise tonite and killing my chances of finding guidestars. Hopefully in an hour or so, Orion will be near Meridian and moon will be lower.

[AlexN]

The V2 of the flattener was about $250 and the V3 around $280 last I checked.. Which is better? Depends who you ask. T-shirt/plastic bag flats should be taken pointing at a diffuse light source. A white/pale colored wall illuminated by a light should work ok.. A lot of people take them just pointing the scope to the eastern area of sky just on sunset, this provides good light, with minimal gradient due to the sun...

[prokyon]

Hi,

I like it! Especially the running man.

cheers

werner

[leinad]

Would a white laptop wallpaper work given the scope was covered with a shirt and close to the screen? I'll try something out shortly.

[Tandum]

Leinad,
I knocked up a light box for under $40. You can get that foam board stuff from office works which is easy to chop up. White LEDS from Dick Smiths and a bit of wire via a resistor to a battery and that's it. Done.

Next step, use the refractor as a guide scope instead of an imaging scope. That will fix the blue halos :)

I like the image though .. Colours are ok except the core is burnt out. You have to layer mutiple exposures to get a good image of M42. Here's mine, and it still needs work :(

[leinad]

Brilliant, thanks! ..and that is one nice nebula. :D


Blue halos are a chromatic problem?

[AlexN]

The blue halos are CA, however, being on the outside edge of the frame, its not due to an optical error, its due to the field not being flat, hence, those stars are slightly out of focus..

More often than not, a decent refractor with a field flattener will not show this problem.

You could, as robin said, use the refractor for guiding, and use your newt for imaging...


Yep. A white background on the LCD + a white t-shirt over the scope should work fine for flats..

[leinad]

Took 2hrs worth of exposures last night, darks, bias and flats. flats didnt come out too well.

[leinad]

Attached 2hrs worth of processed exposures taken last night, darks, bias and flats. Flats didnt come out too well, though processing was much better than without.




Thanks, I'll head over to dick smiths tommorow pick up the materials. Is there an easy to follow wiring readme for making the lightbox?



I ended up using a white booklet with lamp shone onto it. Didnt have the desired effect though.

I'll have to get a side-by-side bar shortly to mount refractor and newtonian, so I can not worry about undoing rings and bars if piggybacking between scopes.

Cheers :)

P.S Not sure if the final result colors are correct, but it looks more natural in the first image ?... How do you know what the natural color should be without over saturating in color?

[Bassnut]

I disagree with Alex on this one, id try 1600ASA at shorter exposures (and more of them) and some 1 min and less for the core to stop blow outs (OK, for the core, lower ISOs perhaps). If your having trouble with darks, use ICNR. 20 min exposures with an EQ6 and DSLR just wont work.

Anyway, I think this image is pretty good, the noise doesnt look that bad.

[Bassnut]

wow, those last 2 look very nice, I like the colour balance, top work.

[AlexN]

You need to expose your flats for a very specific amount of time. Just enough to get the histogram peaking between 1/3 and 1/2 of the way across. They should only need a maximum of 1sec exposure using an LCD to do them... I'll do a test with my 350D tonight and see how long it takes to expose right on my (rather dim) laptop LCD, and on my bright as hell desktop monitor.

[AlexN]

I just opened those 2 M42's in photoshop, and the histogram is heavily black-clipped. Theres a lot more nebula that can be pulled out with more stretching... Theres plenty of good data in there!

[leinad]

1600ASA, ISO?

The darks even though not all at same exp. lengths as lights reduced the noise in DSS better than without. Its a great learning experience seeing the results when stacking, then processing. :D

I used a touch of gaussian blur to try eliminate some noise in the processing.



I thought flats should be the same length as darks and lights? Or is this applies in different scenarios? The latop birghtness on my laptop wasnt bright enough.

I read that you take takes flats and darks at other times, when the weather isnt too good for instance, and then create master flats and darks and use these for most processing, so that you can just focus on lights during imaging sessions and not the rest. Would definitely save time, as I learnt the hard way last night.

Thanks for the feedback guys :thumbsup:

[leinad]

I just need to work out what all that means. lol :D

I set the black point pretty strongly, but otherwise there was a bit of noise that stood out. :sadeyes:

[Bassnut]

OK, smart bum :D, ISO (im old) Yes, the black is heavily clipped, but then that hides the lack of flats ;)

[AlexN]

I did this on my laptop, so if its atrocious, let me know :D

Even if its bad, it shows the data is in there, you just need to use photoshop, and keep working the image to bring it out..

I'll download your shots from the other day (that I forgot to do until now) and see whats in there...

Be careful when working with levels, as its easy to clip the black in search of a dark, smooth background in your image... better to have a bit of a gradient, and a bit of noise, than to clip the black and lose valuable data.

[Bassnut]

No, no, flats have nothing to do with the image exposure time. Its just another image (with its own appropriate dark of the same time) as Alex says, of 1/3 to 1/2 across the histogram. With a small apature (ED80), an LCD display is a neat idea, and can be done anytime.

[AlexN]

Ok, you can create a darks library, Ie, take 15x15min/15x10min/15x5min at ISO400, ISO800 and ISO1600, save these somewhere on your hard drive, and use them for your darks in your images you take from then on, although, temperature affects darks too.. So essentially you would need darks for every 5 degree difference in temperature... so, all the above images, for 5/10/15/20 degrees C... Thats a hell of a lot of darks to have, but it would make life fantastically easy from then on.

Now, Flats.... You can't make a flats library, becaues your flats will almost always be different.. you could get more dust on your scope, or clean dust off your scope, get dust in your camera sensor, or have your sensor cleaned, your focus position could change slightly, you could rotate your camera to more than 360 different angles in the focuser, all of these things would make a flats library useless. Flats need to be taken without having moved the focuser or camera....

Flats dont need to be at the same temperature as the lights/darks, so they can be done the next day... their exposure time varies on the brightness of the source.. it does not have to be the same length (nor should it ever be) the length of your lights.

[leinad]

:)



I tried to bring out more, but it just got noisier. Oh well, practice, practice. Might start from orig stacked and try again.

Is there ever a quick art to processing, or do even the pro's battle for hours on end tweaking images to try and get it just right? lol

I have the 'New Astro - Zone System for Astro Imaging' book, Im going to get stuck into.

Thanks again for the feedback :thumbsup:

[leinad]

Thanks alex. :thumbsup:

[AlexN]

No worries mate... And I know for a fact some data takes me months to get it right...

My recent Eta Carina ha:ha+R:G:B shot took me 39 days between capture, and final process... I worked on it a couple of hours nearly every day...

I almost always to a quick rough edit to get a feel for what data is in the images, then attack it again, more gentle, to slowly pull the data out without generating tons of noise.. sometimes I'll produce 4 or 5 images from one set of data, all processed differently and just pick the one that looks best, and then make the final tweaks to that image to post on the forums/web..

It takes tons and tons of practice.. Im still learning myself, as I think everyone is...

[leinad]

I was able to pull a little more nebulosity out after a few hrs fine adjusting.
Final result I'm happy with . :)

[spearo]

Looks good
might want to try some very short exposures too like 1 min at ISO 400 to mask over the core to better reveal he Trapazium.
The field curvature is quite minimal really, I'd just crop it slightly personally (and save a few dollars).
cheers
frank

[Tandum]

Here's a webpage for calculating the resistor but you'll need the data sheet from the LEDs to get the figures for the calculator. The data sheet should come with them. I used 4 LEDs in parrallel in mine, one in each corner, pointing to the back so reflections light up the diffuser.

http://www.hebeiltd.com.cn/?p=zz.led.resistor.calculator

I was only jocking with the refractor crack :)

[edit]
I put 2 sheets of foam board on the front so it just pushes onto the scope and I hot glued the round cutouts together so they push back into the diffuser as a cover when not in use.

[multiweb]

It looks very good mate. well done. :thumbsup:

[leinad]

Thanks Tandum, I found quite a number of light box tutorials/projects online to give me further ideas.

Tonight I'll read more into lightbox design and construction. I'm thinking of using a variable resistor so I can adjust the brightness if this will work ?
Joke? I just went and sold my ED80 today :scared: J.k:whistle: