Exposure lengths for unguided DSO images

[pel]

Afternoon gents ,

I'm just getting into AP and managed to get around 20 20 second exposures of M42 last Friday 800 ISO and 1 dark on an un-modded Canon 350d. The images were pretty clear but lacked detail in the dust. My polar alignment is getting quite accurate.

Is 30 seconds about the max I should be aiming at with good polar allignment ?

The are lots of conflicting advice on ISO settings, is 800 ok?

I'm averagely light poluted what other DSO's would be easy to find and image. The ring neb or dumbell ?

Thanks, Perry

[eddy]

My polar alignment is awful and i can manage 70sec, which for me, is quite my limit now and every now and then i have to tweak it as the session goes on.

But id be happy doing 60secs all evening without adjustment, again thats quite my personal limit, although there are people on here that do 90sec unguided

So within reason, 45-60sec should be managable.

With ISO settings, im always on 1600 as my skies are pretty dark and not much LP. Wouldnt know where to start at other places mind, sorry i cant help with that!

[Black Knight]

With good polar alignment and a 200P on an EQ5 you should be able to routinely get 60 seconds, perhaps more. I managed 2 minutes unguided once, although I never managed it again!

[Ags]

Hi, I just posted this thread which has useful info for you:

http://stargazerslounge.com/imaging-tips-tricks-techniques/182261-bdget-dso-imaging-links.html#post2224960

By the way, there is no point at all in shooting asingle dark. The dark will introduce more noise than it removes unless you reduce the noise in the dark by shooting lots of darks.

[pel]

Thanks guys. Great advice, I will experiment between 30-90secs.

Thanks Agnes, I was thinking about a pollution filter and good advice on the darks.

Perry.

[Bizibilder]

I would go for it with 90-120 sec subs and just be prepared to throw away maybe 40-60% of them. With short subs like these the odd few in the bin is a small price to pay. Take maybe an hour or two's worth (invest in a remote timer!) and go from there. Take your darks on a cloudy night (so as not to waste good imaging time) and save them with a note of the exposure length and temperature - you soon build up a library of them that you can use over and over. Try and get a set every 5 or so degrees and use the nearest for processing.

[Ags]

A library of darks is a good idea - I keep meaning to make such a library, but never get round to it. Shooting on a cloudy night is a good idea - then you can shoot a crazy number of darks, 50 or more. Am I right in thinking I do not need to store all the raw darks just the master dark made by DSS? Hard drive space is severely limited on my laptop.

[perfrej]

According to tests made, the 1000D performs best at ISO 800 (most bang for the buck, so to speak). My guess that the 350D is similar in that respect.

[Nadeem Shah]

Polar Alignment & Balance is key here, I use to unguide with a MN190 for 2mins...

Nadeem

[Quatermass]

I once managed 3 full minutes unguided but never again most times your looking at just over a minute before they kak on you. I use a modded 350d and most times it 800 iso for bright targets and 1600 for fainter stuff. For M42 try 60x60seconds at 800 with a few shorter ones saved to fix the core. Best one I ever did was 30x30seconds at iso 800 and then 30x30sec at iso 1600 I then added 40 darks and flats to that and stacked them all and had great results. It was also a very dark clear sky that really helps a great deal. Make sure your scope is well balanced before you start and work hard to get your focus spot on as well.

[pel]

Thanks QM. Wow 40 darks and flats, I never thought I'd need that many.

Cheers, Perry.

PS Hope the new scope is producing some good stuff.

[Quatermass]

Yep 40 is about average for most of my pics at the moment I take them on a cloudy night making a note of the temp and use them as stock darks for a week then do another batch a week later. I take my flats just before I start during the evening as the light fades with a pillow case over my scope. The key to good flats is keeping an eye on the histogram and not moving the camera. Looks like another great clear night tonight too

Sent from my GT-S5670 using Tapatalk

[pel]

Thanks for the tips. I'm sure Suffolk is a lot darker than Wokingham though. I'm too near Reading.

I've pointed a lot of newbies at your guiding thread lately, everyone wants to do AP but only has the money for a 200p/eq5.

Perry.