MillHey Nebula

Looking at the images, given the size, not moving as you rotate the camera and (lack of) sharpness, I would suspect that the dust spots are on the surface of the camera window. They are certainly not sharp or small enough to be on the sensor itself . I would guess that they are on the outer surface of the window. The number you have is actually not that bad. I know it is always nice to have a pristine optical train, but that is sometimes just to hard and cleaning only results in a different set of dust spots. From thta image, I would expect that they will calibrate out very easily with a good set of flats and flat darks.

I read somewhere a while ago that when the relative humidity climbs above 92%, it is time to pack up and go to bed.

Wow, that is old - it is the Mk 1 version. I used to use the Mk 2 and that was 38 years ago!

Strange - it worked for me about 40 minutes ago. The link was in the website and the email as a button labelled "View Content"

Place adjacent to the front lens. You want the surface of the glass above the dew point of the humid air. If you just heat the air, its dewpoint will not be changed as the water content is fixed and so if it meets glass below this temperature, the condensation will form.

What Offset /Black level did you use for your exposures? This behaviour seems normal. When you have stacked uncalibrated frames, the offset will still be included and so the histogram will have that additional "separation" from the left. However, when you use calibration frames, the offset will has also been applied to the dark frames so when you do the subtraction, the offset will effectively be removed. At this stage, this is absolutely fine and should not lead to any actual clipping of the data.

Why not start your DSO journey by imaging galaxies? Those such as M51 and M101 will fit quite nicely in your 100mm f10 / Zwo ASI224 field of view. This will enable you to get up to speed with the image capture, stacking an processing techniques as these are quite differenet to lunar and planetary. If from this, you do indeed get the DSO bug, then you could start the upgrade route with your camera. Moving to something like a Hypercam 269 would give you a good increase in field of view. It should be quite acceptable to go for a non-cooled version as modern CMOS cameras are pretty low noise and as long as you use a good set of calibration frames (darks, flats, dark flats) you should be able to start to move on to some of the smaller nebuale. This camera would then still be very comaptible when you feel able to upgrade to a wider faster scope such as an 80mm f6.

Nice example Louis D. Do the ADC and software methods only work with small objects in the centre of the field like planets or will they also work with larger objects such as galaxies and clusters?

How do you distinguish between CA and atmospheric dispersion?

I am thinking of upgrdaing my camera. I currently use a GPCAM 290c. It has been great for imaging galaxies and things of a similar relatively small size. I now want to get something that has a sensor size more appropriate for photographing nebula etc. At present I do not want to go down a monochrome route so OSC it will have to be. My scope is a Starwave 80mm F6 triplet. For a long time I had been leaning towards the 183c, but I am now begining to think that maybe the larger pixels of the 269c would be a better bet. Does anybody have any experience and / or view on these two cameras?

If nothing changes when you rotate the camera, then the sensor chip is not off centre. Are you sure that there is not tilt somewhere? It is difficult to tell from the screen shots but I am not convinced that you have uniform focus across the image

So this was my first DSO - M42. It has got me hooked and started me on an upgrade path to rapidly deplete my bank account. This was taken through my wife's Orion StarBlast 4.5 - £180 for scope and mount with another £40 for a tracking motor, where the tracking speed is set manually by twiddling a knob until the star trails don't look too bad! I will confess, I had treated myself to an Altair Astro GPCAM2 290c camera. I had also read "Astrophotography is easy" so I knew to take a number of lights (100 @15s) and even did the corresponding darks. I soon realised that TIFs were not a good way to go (I had come from a background of over 20 years of conventional digital photography) if I wanted an easy life without using PIPP. I recorded these as FITS and stacked and processed them using Affinity Photo, which I had already been using for a couple of years for landscape photography. So now I have a decent mount (CEM26) and have just set up autoguiding and that seems to have jinxed the whole thing - no astronomical darkness for another three months or so and continual clouds and rain!

Certainly got the right movements, although it sounds as though it is really for a finder scope. I wonder whether it would introduce too much possibility of flexure if used with the main scope.

I am trying to adjust the alignment of my OTA to reduce the cone angle in the hope that I will get better goto performance without having to do a star alignment. Does anybody know of a dovetail and / or ring space blocks that allow the necessary adjustment to be made with the scope sat on the mount. Or is my only option to shim the rings and "wiggle" the position of the rings on the dovetail? This latter would seem to be a bit of a pain requiring a lot of demounting and trial and error compared to being able to adjust a couple of screws while aligning the scope to a target that is centred in the polar scope. I have had a look at a few dealers on the internet but cannot seem to see anything suitable