Dso help

[Starcrazzy]

Hi,
I have an eq mounted f6 8" newt..I recently got the meade dsi..I fell in love with it the first time out,it really is a cool thing..I first tried the orion neb of course, and then tried the tarenula neb..Because of my rough polar allign ment i was only able to use exposures of 9 seconds..Should i be trying to get this longer or is the stacking method accounting for that??Also, my images seem to have a lot of information but don't really look much good, i have photoshop, any tips on some enhancment tecniques would be greatly appreciated...
Thanks Guys

[ving (David)]

people doing DSOs generally do long exposures...
keep up the good work

[Starcrazzy]

Thanx ving,don't the rest of you all reply at once hey...just go steady

[janoskiss (Steve H)]

I donno bout astrophotography 1st hand but yes align better, and yes go for longer and yes stack more of them. use specialised filters for DSOs for best results.
stacking very many frames is not necessary like with planets, because seeing won't be as much of an issue in the much wider angle DSO shots.

[Chrissyo (Chris)]

I don't know squat all about dso imaging. However, I might suggest you darken the image a tad in photoshop, as there seems to be just a little too much red. (then again, I don't know much about the tarenula neb so if its supposed to look like that, my bad ).

[[1ponders] (Paul)]

Hi Starcrazzy.

Couple of things to think about.

1. Mount issues
- polar alignment
- polar alignment
- what sort of tracking are you using? Motorised or slowmotion manual
-polar alignment

2. Image capture
- the dimmer the object the longer the exposure - within reason. At some point the electronic noise will overpower the signal. Often multiple exposures for multiple exposure lengths then layer masking in PS after stacking is the way to go for objects with large differences in brightness across the object eg Orion Nebula and to a certain degree the Tarantula
- for the DSI (pro or standard?) lots of images stacked will give you much better signal to noise ratio
- make sure you take dark frames for subtracting the electronic noise. DSI will do this almost automatically. Check the manual for this process it's pretty straight forward.
- focus
- focus
- focus
- Oh and did I say - focus. Yes it is that important. If you have good focus then you can often pull something out of even the most disappointing image. But if your focus is off you may as well chuck it as you are not going to get nice sharp stars or a really pleasing image no matter what you do. Take your time with the focusing. Even if you spend half an hour to an hour (yes if you have to). Just think, spend 5 minutes focusing and 2 hours image capturing and get a so so image (or a lousy image) which is really a waste of 2 hours and 5 mins or spend half an hour (it will get quicker as you get used to your equipment) and take your 2 hours of capture and get an image your going to be able to work with and be happy with. It is that important.
- large differentials between ambient air temp and mirror/internal tube temps will lead to poor images. Let your system cool down. Also let your DSI have power running through it for a while so that any images you take will have a similar amount of noise in them so the darks will work better. Same applies when you take your darks. In fact, start the DSI, let it run for 15-20 min and then take the darks you need. Then take your images. (assuming everything has reached equilibrium)

3. Processing
- in PS use your curves and levels in Image>adjustment. Keep your adjustments small and use multiple adjustments. Don't try to do it all in one or two goes. Use your curves to increase the amount of detail and brightness visible and then after a couple of curve adjustment go back into levels and reset your black point (not too heavily initially) What you don't want to do is "clip" your information. Clipping in your histogram looks like the graph is chopped off at one end. The stars in your image are clips as the white point has been too agressively set by the look of it.

See how you go with that to start with.

[[1ponders] (Paul)]

Here's is an image of the levels histogram of your image on the left. See how at both ends the black graph looks like its been chopped off. A more even curve may give a better result. Like the other example on the right, though if you look closely you will see that I've clipped that one just a bit on each end.

btw the second hist is of one of my images, not an adjustment of yours. Once your histo is clipped the clipped off information is lost and can't be reclaimed (unless you know how to use the PS history pallete)

Also something I didn't mention in my previous post, when saving your initial DSI image see if it is possible to save it as a 16 bit image (TIF, FITS or BMP not jpeg) rather than an 8 bit image. You will have more information to play with that way. I can't remember if you can save DSI images as 16 bit

[Starcrazzy]

Exellent, thanks ponders..Some good tips to go on with there..i do use dark subtract but i havnt been letting the unit cool for 15-20 mins..mistake number 1..yes, focussing is a problem but after i took this image i made a hartman mask which seems to make things much easier and am getting use to parafocalising an eyepiece...but its all a very steep learning curve...Thanx again for the tips..I shall endevour to better polar llign tonight mabye??weather has been crap here lately..