Which is the 'easier' target

[eddy]

Hey guys, right so Orion dips below my house pretty early from my back garden, so thats out.

M31 is a target i want to image, but id really like to get a nebula. So, out of these 2 which is the 'easier' (' ' = by easier, i mean easier within reason as i know no targets are easy!)

Cone Nebula

Rosette Nebula

Both of these are easily viewable from my backgarden, hence why i chose those. I also want to concentrate on NGC884&869 which again, are good targets from my back garden

Any advice welcome

Many thanks!

[nmoushon]

I cast my vote for Rosette. Its huge and you can get good amount of data from relatively short subs. I havent tried cone nebula but I was able to get rosetta with just my 300mm lens on my Canon 450d. Here's a link to what I got with just my canon. Though I believe M31 is going to be gone soon too if I remember right. So don't push it off for too long.

[Shibby]

Is your camera modded? If not, how about the Pleiades early evening? It's a reflection nebula so you can get good results with an unmodded camera.

[jgs001]

Eddy, I don't think your 350d is gonna be able to do the nebs without really long exposures... 5 to 10 minutes or so.. as from memory you've not modded it yet. I've not even bothered trying as yet, for that very reason... although I might just have a go with the rosette with my 70-200 if it stays clear enough.

[eddy]

Yeah i dont feel confident enough yet to attempt and ruin a perfectly good camera that ive only used twice!LOL

But, ill see what i can do, i think my targets are going to be....

M31

M45

NGC884 & NGC 869

M42 - When i can get to my moms, she lives out in the sticks in the dark with lots of fields around, nice and dark!

Ill see what i can do with those!

[nmoushon]

If i was you Id try rosetta over M45. 1. Since your planning on trying M42 rosetta is relatively close by and plus with the dark skies you'll really be able to get great data. 2. M45's nebula is a lot more washed out by the bright stars so you have to get some long exposures to get really good nebula showing. OR you could just go for both Not trying to tell you not to try shooting an object just my opinion.

[eddy]

LOL rosette it is then!

Any suggestions on ISO settings/Sub length etc etc?

Aslo, so i read the best way to find it is the unmistakable shape/pattern of its core stars, right?

[nmoushon]

lol Sorry I really am not trying to push you one way or the other. Though I'm sure it sounds like it. Its just on the same night I shot rosetta I also shot M45 and I was kinda disappointed at how little nebulosity I got with data I got. Given it was only about 10-15min of data but I had to stretch the image so much to even get a hint of nebulosity that the stars were so blown out that I just gave up on processing that. I'm positive you could get M45 and good nebulosity if that was the only object you shot that night or maybe split the night between two objects. So go ahead and take a shot at M45 there's really only one way to find out what your going to get. But I was much happier and pleased with my 10-15min of data from rosetta than M45. So maybe you can split the night between the two because they are both great objects to capture.

Now onto actually answering your post lol. It really depends on how long of exposures you can achieve. The longer the better of course. If you can achieve longer exposures then go with ISO 800 but if you can only achieve 60-90sec subs I would go with ISO1600. Oh and of course your local LP always adds a helpful bit light so don't forget to adjust for that. And the best way to find it since I'm guessing you dont have goto is to do what you suggested. I wouldn't say its an unmistakable pattern of stars but you'll probably recognize it. Stellarium is a great program to reference off of if you have a computer available.

[Shibby]

Yes I agree at least that the seven sisters are very bright stars, making processing quite tricky. But this is the case regardless of the exposure length. In fact, if anything they should be easier to manage with short exposures, not long ones (as you could blow them out more).

You really should pick up more reflection nebulosity than emission given that your camera is unmodded. Here's what I took with an old, unmodded Nikon D70 with 2 minute subs:

[eddy]

Wow thats fantastic! How many subs did you take and flats/darks etc?

[Shibby]

Thanks, it was 38 subs at ISO-800. Don't think there were any calibration frames.

Compare it to my only attempt at an emission nebula with the same unmodded camera, which was 52x2mins:

[eddy]

So what was that an image of? (excuse my lack of knowing!) But most certainly can tell the difference!

So how would you bring out more data in the emission nebs? Other than modding, or is that the only way?

[narrowbandpaul]

Thats the pacman. NGC281 AFAIK.

2 things could be done. More data. Or modding the camera. Works especially well for nebula since they emit lots of red light (from Hydrogen), which the filter will attenuate in unmodded cameras.

as for ISO...generally for imaging I would say 800.

I did perform an experiment with my 300D, and the read noise fell with increasing ISO but the full well dropped also. For my camera ISO400 or 800 would be good. But newer cameras will have different sweet spots.

but bear in mind that just because an image at ISO1600 looks brighter than one at ISO800 doesnt mean that the ISO1600 contains more photons from the source. ISO is just amplification. Nothing else. Although the amplification does reduce read noise slightly....

[Shibby]

That was supposed to be the Pacman nebula (NGC 281).

Other than modding, there's not much you can do. Some people do manage reasonable results, but the response to the ha band of an unmodded camera is very poor, something like 30%, meaning you need at least 3x the amount of exposure. Even then, you'll find the trickle of ha to be washed out by all the other stuff causing a red response, such as thermal noise and light pollution.

[narrowbandpaul]

30% If its anywhere near this high, I will be shocked. 30% is a decent number considering the Ha coming from every nebula is reasonably high.

I am sure Christian Buil measured the response at less than 5%!!

paul

[Shibby]

Sorry, I meant 30% compared to the same camera modded

[narrowbandpaul]

M33 Salvatore Iovene

Graph on that page shows a Ha response of an unmodded 40D (656nm) to be approx 8%. With the IR filter removed you get roughly a 3x increase to 25% or so.

Typical CCD would be >40% at Ha. And many are around 50%.

paul

[narrowbandpaul]

yep, shibby, you are right. There is a 3x increase between unmodded and modded.

[RikM]

Give the Rosette a go. Here's what I got with an unmodded camera using 4 min subs at ISO800. I did take a load of them though. This is 4.5 hours worth.

[narrowbandpaul]

great image, especially from an unmodded camera

[eddy]

Thats given me a load of hope then Superb image, and 4.5 hours isnt too bad! lol dont think id manage 4 min subs on my EQ5 though, maybe 2mins max with a REALLY good polar alignment, but ill see what i can do anyway!

Thanks again guys for all your help