Freddie

Bit slow processing my captures from the 6th but here is one from about lunch time. Processed with AS!3, ImPPG and CS5.

Don’t get confused by points being moved left or right. All that matters is where a point ends up. If the point ends up above the original diagonal line it means all pixels with the particular brightness as defined by the bottom scale have been made brighter. If the point ends up below, they are darker. Height above (or below) the original line indicates by how much the pixels have brightened (or darkened). This is why the line is at the very bottom on the left (represents pure black, so you can only brighten, lift the point, from there) and at the top on the right (represents pure white, so you can only darken, lower the point, from there) Some histograms show input and output numbers when you select a point. Input being the original brightness value, output being the new brightness value.

Just to expand on this a bit, if you think about it, you already know the answer to your question. As you say, the black part of the histo is on the left and white on the right. If you look at the original image, the sky is dark (left part of histo) and the disk is lighter (right part of histo) The curve that Nigella has applied lifts the left part of the histo to the top i.e. telling it to turn the darkest parts of the image to pure white as seen in the next picture. Care however is needed as the curve is basically turning the darkest ~20% of the image to pure white so if not careful you could turn some very faint part of a prom i.e. a dark part, pure white and therefore lose it in the pure white background. The same is true for the right part of the histo. Yes, most of it applies to the disk but any very dark parts are in the left side of the histo so again, care is needed when adjusting the curve that you consider this. So as you know which parts of the histo represent which parts of the image, you can adjust the curve to brighten the dark parts or darken the bright parts to give you the contrast you need to bring out the detail you want.

You are correct. Immediately in front of the cam.

No need for darks or flats with lunar shots. You say they are stacked. How many in each? No mention of sharpening which would improve the results of the stacked images. Amount of sharpening you can use will depend to some degree on the number of images in the stack.

No need for fancy optics with Ha imaging. Why not an ST102( or ST120) with a 0.5 focal reducer to give you two options on FL. If you don’t get on with the std focuser (it’s not great) then get the SW upgrade for ~£140. All for less than an ED80.

Just let us know if you want any thoughts/help with the adaptive settings.

A Skywatcher ST80 is the same scope. I think they are just under £100.

Thanks. It was specifically the threshold and trans. width settings I was referring to as you make no mention of those in your process flow and you have left them as default on your screen shots. Without setting them to appropriate levels for your particular image, there is no point in using adaptive.

That’s an interesting tutorial. Although you use “adaptive” you don’t adjust the settings to control how the sharpening is applied across the image. Any reason for that given that using them would give you better control over how your two settings are being applied?

Thanks Pete. This was with my usual WL setup of CPC9.25, 2x Barlow and ASI120mm-s.

Nice. Flats have made such a difference to your images.

I think you need to do a bit of research into what guide scopes are used for as you appear to be a bit confused on that.

Have you thought about getting a copy of the book “making every photon count” (or something similar) as it will help you with the basics.

If you are using a Barlow as shown in the calculator then best to remove that. Also you have it setup for an eyepiece so you should change that over to be your specific camera to get the proper FOV for your setup

If it only happens when you use your flats, obviously the problem must be with the flats. What does your master flat look like?

Ah ok, I see the problem now. That must cause real issues though as focusing must be a bit of a guessing game and hitting critical focus must be down to pure luck! It’s hard enough to focus with your head under a dark towel staring at a screen 30cm away especially as focus will keep changing as the scope heats up/cools etc. Have you thought about moving your monitor? I still think defocusing once during your image run will be worth it to get a decent flat. Just rotate the focuser one turn (check it is truly out of focus, rotate one more turn if not) and when done, rotate it back the same number of turns. It doesn’t matter how out of focus it is, as long as it is out of focus.

Nice. I would still come back a touch on gain or exposure as you are burnt out at the base of the prom.

Are they the flats? I assume not as they shouldn’t look anything like that. Go on, give defocusing a go. Surely it can’t be that difficult to refocus afterwards.

Can you post the flat and the image where the flat was used and maybe we can see what went wrong.

Yes, if the ROI moves to a different position on the sensor, that new position may have dust specks that the original position does not have. The flat is used to both even out illumination across the FOV as well as remove dust specks from the image. I was aware that you can change the size of the ROI but I wasn’t aware that you could move a given ROI to a different position on the chip.

You only need to do it once. So maybe get set up, set your gain and exposure to roughly what you will be using in your imaging session, defocus, take your flat and you are done.

For a flat, just defocus on an area of the surface with no features. No need to mess about with all that other stuff.

You are a bit off on this. As there is no light getting to the cam for bias and darks there is no need to do them for each filter. For flats they are not determined by light sub duration but are determined by exposure length to get the correct histogram so you only need one for each filter. Should be done for each filter but depending on your setup you may get away with using a flat from the L filter for everything. Edit: I should have typed faster!!!

A couple of ms off exposure may help then. Flats are well worth doing for surface shots. Just find a section of the surface with no features (easy enough these days!!!) defocus and grab an AVI with a couple of hundred frames. The AVI can then be processed and flat applied in AS!3.