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
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
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 Great guiding, awesome focus.. well processed... Cant ask for more than that!
Thanks Alex, I'll check out the FF/FR. Hope they aren't too pricey
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.
Quote:
Originally Posted by 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
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 Great guiding, awesome focus.. well processed... Cant ask for more than that!
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...
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.
Quote:
Originally Posted by 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...
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,
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
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..
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.
Quote:
Originally Posted by 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
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?
Quote:
Originally Posted by 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..
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?
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.
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.
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!
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.
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.
I used a touch of gaussian blur to try eliminate some noise in the processing.
Quote:
Originally Posted by 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.
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.
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!
I just need to work out what all that means. lol
I set the black point pretty strongly, but otherwise there was a bit of noise that stood out.
I did this on my laptop, so if its atrocious, let me know
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.
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.
Great guiding, awesome focus.. well processed... Cant ask for more than that! 
