Took this last night, several 10m subs with the QHY8 stacked. My flats are still very far from perfect, but they are getting better, and with everything happening in the middle of the frame, this is probably the worse object image to see if my flats are ok! I am also having problems with stray light causing reflections on the colimation marker on the primary, probably off the back of the MPCC, as can be seen radiating from any bright object, the whole image is also a little clipped, and it looks kinda dark (Again, processed on a laptop screen) its also the very first time i have used Nebulosity (LOADS easier than Maxim) to stack and process etc.
So there you go, its small, amateurish, and not very good! but after a hiatus of a few months, i wanted to post something, no matter how iffy it is, that said, its a nice colour, and the composition of the image is probably its best feature.
While i am here, a HUGE thanks to all the help i have recieved from forum members wanting to help, you have all been a massive help, in public and in private, and if your reading this, then you know who you are!
Mate !!!Considering the problems you have had that's an awesome shot.
Nice colours. Once the reflection problem is solved the images will be excellent. two thumbs up from me.
Mate !!!Considering the problems you have had that's an awesome shot.
Nice colours. Once the reflection problem is solved the images will be excellent. two thumbs up from me.
You are getting there. Nice shot and colours. A little cliped at the black level but 95% there. Well done, you just need to sort out the reflection issue but the rest is there.
You are getting there. Nice shot and colours. A little cliped at the black level but 95% there. Well done, you just need to sort out the reflection issue but the rest is there.
Yeah Allan, its a work in progress. i quite literally couldnt have done it without you.
Here's what I do with flats (and sometimes I don't use them as occassionally I get a flat that worsens an image for some reason).
1. White T-shirt over the end of the scope.
2. Point towards the west about 15-20 degrees up.
3. At dusk I take a flat for each filter. Usually I go for at least 3 seconds
(not so long if using an SBig but FLI and Apogee with a shutter requires that long otherwise you see the blades of the shutter in the flats).
I go for an exposure around 20-23,000 ADU.
You have to be fast and efficient as it is amazing how fast dark encroaches on you. You'll see the ADU number drop with each flat.
Make sure the camera is at the same temp you will be imaging at.
I take:
Luminance 1x1
RGB each 2x2 and one for Ha 1x1 if I am shooting Ha.
Don't change the position of the camera when you go to image it has to line up with the flats or they are useless.
Telescope should also be in focus even though its a flat as that also would be a difference between the flat and the light.
Use median combine, I usually take 3 flats.
I also take a bias at the same temp. I take 3 and median combine them.
These are subtracted when making the master flat.
I use CCDstack where its all very easy and I use CCDsoft to control the camera.
You don't want a flat that is too bright like 50,000 ADU. That'll degrade the image. Go for about a 1/3rd of total exposure ability of the camera - ie 22,000 ADU (fully exposed is 65,535).
Duncan, it's looking pretty good (apart from those round thingies that need to be cloned out). The processing looks damn fine to me . Good luck with the reflection hunt.
Perhaps its time to reflect on how far you've come Duncan...Looking good and heading in the right direction. Keep at it.
Quote:
Originally Posted by gregbradley
Go for about a 1/3rd of total exposure ability of the camera - ie 22,000 ADU (fully exposed is 65,535).
Greg, I think you're making the assumption that all cameras saturate at 65,535. While this is indeed the upper limit of a 16bit ADU, the correct value should be the chip's pixel well depth, not the 16bit ADU limit.
Formula:
FullWell / ADU Gain * ~30% = target saturation value of your flats.
Nice work! Deep vivid colour and enough nebulosity to demonstrate the majesty of this target! I posted this target a couple of days ago. It didnt show the amount of nebuloisty you captured. Its the same reasons as Trevor mentioned, too low and away from Zenith sitting in the LP soup!
Nice work! Deep vivid colour and enough nebulosity to demonstrate the majesty of this target! I posted this target a couple of days ago. It didnt show the amount of nebuloisty you captured. Its the same reasons as Trevor mentioned, too low and away from Zenith sitting in the LP soup!
Hi Jo, TBH its even lower here in Canberra!
And take heart, i only imaged this as i seen your pic from a few days ago, and liked it so much i thought i would try!
love dohnuts
