luminance / flat problems

[Gerhard 44]

Hi all!

It's been a while since I wrote here, also because this year I've been less active in the field, unfortunately...

Anyway, I've now started to do autoguiding, with mixed results. I bought myself a laptop and guidescope, with CCD.

I'm able to do 10 minute exposures that come out fairly well most of the time. Guiding is mostly good. I tried PHD as well as Maxim, but lately Maxim seems to be doing better, or I just found the sweet spot for my setup.

The last 2 or 3 times however, I'm having difficulty in obtaining decent images. Even with no moon, the images I get are quite bright, with stars barely visible, and the stack is terrible: it's a light shade of grey, hiding all stars (let alone a nebula), and the histogram shows the peaks (in DSS) far to the right, so adjusting that is a nightmare, so much so that the last two times the result was not worth showing to anyone....

The site I go to is always the same, and I already obtained quite nice images, also with 10 minute exposures and the same ISO...

Apart from this, I'm having a very hard time getting my flats right... I've got a "flatbox" (EL panel with two sheets of white paper, 8 sec exposures at 800 ISO, the same ISO I use for the Light exposures) that I tried at home in the dark with the scope and camera, to get the right histogram, as I gather looking online: the peak should be at about a third of the histogram.

Problem is, which I discovered only last week, the histogram changes with the same setup, for the various "receivers" of the flat image: the camera, Maxim, or DSS. As shown in the photos below (the camera is a RAW picture, taken with the same settings as the FIT picture I used for the DSS and Maxim screen caps):

camera:

 

DSS:

 

MAxim:

 

Apart from the histograms, I also always get those very ugly red hue photos in Maxim.. Is this something of Maxim, or am I getting something wrong?? The image obviously is not red, but the grey shade of the DSS photo (the photo of the camera screen shows only white, but that's because of the phone cam)... This means I can never check in a decent way if the exposures are coming out right while I'm taking them with Maxim...

 

So, recapping, problems getting the flats right, and headscratching about the bright exposures I'm getting lately from a setup that already proved it doesn't have to be that way...

At the moment I don't have examples of the latter problem to attach (because I didn't finish any stack, seeing as they came out so horribly), but I can attach some, if needed.

 

Any suggestions? Somebody had the same problems? I'm getting a bit frustrated, I must say...

 

Clear skies!!

 

Gerhard.