bobro

Great to see you getting flats to work now - really makes a big difference to your images! I wonder if your scope is a litttle out of collimation? A stretched version of the flat should be fairly symmetrical in brightness, whereas yours is offset. This can be seen in coma in the stars in the darker regions of the first image without flats. For comparison here are stretched flats for our scopes. No big deal though...

Hi Peter, You did much better than my attempt on the Veil last night - reflections inside my scope due to the Moon I think. Perhaps a cowl will help. Clouds too! If you're not already doing this, before saving the image in DSS set the Saturation shift (Saturation tab) to about 20% before aligning the RGB histogram peaks (RGB/K Levels tab). Bob

Probably depends on how an image is subsequently processed e.g. I normally use Kappa Sigma clipping in DSS which (I understand) needs a consistent background level in order to operate correctly. Hopefully someone will be able to explain a bit more about Background Calibration......

Probably a good idea to ensure DSS stacking has 'Per Channel Background Calibration' set to 'Yes' to ensure a consistent sky background level before stacking.

Just my sort of image! Sometimes images can seem to be a bit over processed (easy to do) but this one has a lovely natural colour progression to it that is easy on the eye. Lovely and well done!

Another Stub sub challenge to us all?

Here's Mr Pelican looking a bit less blue - tried out (in GIMP) decomposing an image to separate RGB layers for the first time, allowing the blue haze to be adjusted out. Quite a useful feature.

Peter's flat shows as taken at ISO3200 and 1/4096 sec exposure. I guess the speed is as fast as the camera will go. Perhaps the shutter is a bit sticky at this fast speed. In any case it looks a bit overexposed - a good plan is to have the histogram around the mid point. Flats don't need to be taken at the same ISO as images (I previously thought flats needed to be taken at the same ISO as images but was corrected by someone with more knowledge and did some tests that showed flats worked irrespective of the ISO used). So I suggest reducing the shutter speed and ISO if necessary in order to obtain flats with roughly a mid point on the histogram.

Thanks guys for the images of the Crescent Nebula. It's certainly not the easiest subject! If I try it I think a test with a good long exposure is called for - perhaps 10-12 minutes and preferably with a darker sky.

Neil - could you post the standard DSLR image for comparison? Thanks. Bob

I like the sharpness and clarity of the image Mikey. Can you tell me what subs were taken? (It helps me evaluate the image/target and also decide if I should have a go at it.) Thanks Bob

Better positioning this time on the Pelican Nebula. Longest exposure I've given so far to any image - 20 subs @ 480 secs. As you can see, still not a great result. The blue gaseous 'haze' got in the way of the red pelican, reducing contrast. Will need to practice processing on this one.

Ah! Thanks Art. Makes sense now as the Dumbbell is smaller than the Cocoon. I must find a good source of surface brightness values for potential targets. Must admit, I didn't expect to find the summer nights quite so interesting in terms of targets - but there are plenty around!

According to Wikipedia, the apparent magnitudes of the Dumbbell Nebula and Cocoon Nebula are very similar. I know this isn't an exact science but, even with 240 second exposures for the Cocoon (compared to 60 sec for the Dumbbell), the nebula was still quite faint. The sky was perhaps a bit less clear. Can anyone comment on this difference? Here is the Cocoon 'final' image - needs a lot more input. 23 subs @ 240 sec.

Fascinating objects these planetary nebulae. M27 Dumbbell Nebula : 35 subs @ 60secs. Good clear sky - could just make out the Milky Way - must try and capture some of it.

Another attempt at M57 - as suggested by Neil: more subs + drizzling. Plus better focus and used the centre of the scope's image without the CC in place in case the CC degraded the image. I think that's about the best I can manage at the moment. 32 subs @ 60 sec.

It's certainly made a worthwhile improvement to the earlier image. What's the plan for imaging with the Ha filter - B&W, false colour, other filters, improving earlier images? Now I'm typing this I wonder if the answer is 'yes' to everything!

I liked Peter's M57, so had to have a go too, stretching my setup perhaps a bit too far...19 subs @ 120sec.

Here is a comparison of images taken with and without the (DIY) Coma Corrector on my Meade 130EQ scope. There doesn't seem to be too much light loss (though this is subjective) due to the addition of the CC. Commercial CCs are usually 2" aperture, where my DIY CC is 1.25". I don't know if that aperture difference will make any difference in light loss - possibly the light loss is mainly down to the CC lens glass in the optical path.