almcl

Maybe that's something to try while the light nights are with us? I managed 3 minutes unguided with my 200 mm lens, so you might well be able to get past 60 sec. Of course the seeing, polar alignment, target altitude &c will all have a bearing, but certainly worth experimenting to see.

Had a play with your data and agree with what has been said above: it's very nice! Here's a crop of the central area just to show the detail that is present, well done! You can probably achieve something similar in APP?

Unfortunately most galaxies are fairly dim objects. Even mighty Andromeda (M31) is little more than a central blur from an urban or suburban location. All the usual advice applies, dark adaptation, not using phone, tablet or laptop screens so as to preserve night vision, use averted vision, scan the area, don't hold your breath, I have even resorted to 'black towel over the head' to help cut out street light pollution on occasions If you can get to a dark sky site, the situation gets better. Unfortunately, we are just about to loose astro darkness (which does make a difference) but before we do, and if you haven't already, try M81 and M82. They are almost overhead now as Astronomical darkness falls and are reasonably small and bright. What galaxies were you trying for?

Couple of other points which I don't think anyone has mentioned. Once you calibrate and before moving to target, carry out a guiding assistant run and accept its recommendations. This will account for changes in seeing and may make other suggestions. I can't see one in your log file? Second, and this may not be what you want to hear, but you appear to be imaging at around 0.5" per pixel (making assumptions about your DSLR and scope) but guiding at over 6 " per pixel, a ratio of 12 to 1. This is likely to be problematic, even if you can get the guiding down to a tenth of a pixel - which PHD developers suggest is the likely limit of possible accuracy. In the fullness of time you may need to consider an Off Axis Guider, although that too will not be without its challenges.

Can't you loosen the scope rings and slide the OTA down a bit?

This morning while sorting out a camera cooling issue with the ASI 2600, I tried an 'on-scope' dark. Normally the darks for the dark library are taken with the camera off scope. I was a bit shocked to see this 180sec 100 gain 30 offset image as a result. I have had a peer down the focuser tube with camera removed and although there is a bit of light right at the edge of the field of view (from the cut-out section of the Moonlight focuser) if I shine a light close to it, there's nothing that appears anywhere the long edge of the camera sensor. So could this be amp glow, I wonder? The ASI2600 mc is supposed to be free of this, so if it's not, how to find the source? (And I know there are some dust issues as well, but think those can be sorted.)

Han, please no criticism was intended of your software, it's free and it works, and that you do it for fun is wonderful. Rather I was trying to find out if my experience is the same as other people's and it clearly isn't. If you are ever able to consider a multi-threading version that would be marvellous, but even without, the performance others report is pretty good. Hope your clear skies work well!

So my i7 + ssd drive is no where near that - clearly I've got something mis-configured. Thanks for the comparison.

That's most interesting, Festoon, I suspected something was wrong with my set up or work flow and that pretty much confirms it. I'll have to start digging...

While many of the comments and Han's information are very interesting, could I, for a moment, drag the thread back to the original question, and ask if anyone else finds ASTAP taking over half an hour to stack 30 light frames with associated calibration frames?

That's interesting. Is the time taken of the six minute variety by both DSS and ASTAP or does it take a bit longer in both?

That's an idea I haven't tried yet! Thanks for the thought!

Thanks for the thoughts. I am not over bothered about speed, either, but this seems excessive just to stack the lights , flats and bias. I don't use darks; on the DSLR they didn't help at all and on the ASI 2600 they don't appear necessary, but I do dither every frame and always take more than 20 lights to allow Sigma Clip a good chance. So lights get loaded in the lights tab, flats in the flats tab and bias in the Dark Flats tab. Unfortunately this doesn't correct very well at the moment and I get much better vignetting removal in DSS but only if I use Flats, Dark Flats and Bias frames. ASTAP, of course doesn't allow for that. Slightly curious to know what advantage you get from calibrating flats by themselves?

I have been stacking my images in DSS and recently tried ASTAP as well having heard some positive comments about it. ASTAP seems to give slightly less noisy images and although I don't find the interface particularly intuitive, it does have some useful tools (CCD inspector, HFD contour diagram &c). One thing I have noticed is that it is SLOW. Yesterday as an experiment I stacked 40 lights, 30 flats and 30 bias frames from an ASI 2600 MC in DSS and timed it. It completed in just under 7 minutes. The same stack in ASTAP took in excess of 38 minutes to complete. Does anyone else find ASTAP similarly slow, or could I have got one or more of the settings wrong?

You might find this thread interesting: I haven't been brave enough to modify my kit lens (yet) but if I can find a cheap second hand one...

Fabulous images as always, Gorann. I do like your quest for the IFN, way beyond anything I could achieve. A question about settings on the ASI 2600, if I may? What offset are you using? I have had some difficulty with calibration recently and wonder what setting others are having success with?

It is possible, but I found it very fiddly and hard to get exact. The polar scope has to be unscrewed and then the three grub screws that hold the reticule slackened off and the reticule twisted round. The problem is that the reticule is tiny and quite hard to see. The polar scope then has to be re-aligned, of course. Better to go with Vlaiv's suggestion above?

Startools is easier to use with the defaults, but there is still a learning curve. You can download a fully functional version (with just 'Save' disabled) that has no expiry date, Ivo Jager its author gave a demo in Stargazine episode 41, it's available to watch in the Stargazine section.

That's a pretty good image! I've run your png through StarTools and got this result. Some processing artefacts (my fault for going too quickly) and two satellite trails but lots of detail! The satellites will disappear if you have more images and stack with a Sigma Clip. Or you could discard the subs with them on - but with only 10, that might not be a good idea? Pixinsight can probably do a very similar job. Are you using a light pollution filter?

I tried reducing the offset from 50 to 10 and I think it has reduced the rings a bit. It hasn't got rid of them and the test target (M42) is pretty forgiving, but I am going to experiment a bit more.

Ran the camera at -15°C for an hour with the window uncovered and couldn't see any signs of condensation or ice anywhere. Will have a close look at the rest of the imaging train tonight (corrector, secondary and main mirror). Just wondering now if the offset may have any effect. Using 50 at present but earlier on when the effect is less apparent it might have been lower. Not sure if the FITS header from APT records this. Must check.

It is unfortunately, Dave. Looking at shots from early February I can see slightly less pronounced signs of it , but over the last few sessions it's getting quite pronounced. I'll try a bench cooling test today (the %RH has dropped to an unseasonally low 53%) and see if I can find any misting on the sensor or its window...

Certainly a possibility, not at all sure how well the APT interface with the camera works - it is certainly at odds with ASI Image (the ZWO camera control software) over sensor temperature, so perhaps the anti dew device is mis-reported as well? Yes, indeed StarTools 1.7.458 - the synthetic flats in inverse vignetting mode doesn't help, but that may be because of a problem with the flats. I'll start a separate thread on that (!) but the two problems may well be linked. The OAG is quite new, it's the ASI one - do you think something in that could be causing an issue? The prism is fairly far out of the way The dew shield is doing quite a good job on stray light and the images were shot quite close to the zenith, but there is one of those pesky LED street lamps close by. It had a nice shield on until the council came and replaced it with an almost completely ineffectual one. At the moment I can just about tame things in StarTools but probably at the expense of some lost detail, and as you say dealing with the symptoms rather than the cause.

I have had the scope since last summer and initially used it with a Canon 700d, which doesn't/didn't display this phenomenon (at least as far as I can see). I've tried the ASI 2600 with a 200 mm Canon lens and that doesn't do it, either. Which has left me a bit stumped: the scope doesn't do it with a different camera and the camera doesn't do it with a different 'scope'. Perhaps, as you say, it's a reflection, although the 190 MN is quite well baffled, or some weird combination of the long dew shield/corrector plate/mirror is creating extra reflections around the 2ndry mirror? Thanks for the thought!

I've got some doughnut style artefacts in my images. Not the mini dust doughnuts, but whole image light and dark circles. They show up in individual lights and also in the stacked images, although different stacking programs react differently. Unfortunately they don't show up in the flats, which are also over correcting. I'll post separately about over correcting flats, but has anyone encountered anything like this? Unfortunately, it's not a one-off phenomenon. The equipment is a Skywatcher 190 MN attached via an ASI OAG to an ASI 2600 MC. The 2600 is running at -10°C, gain 100, offset 50 with the Anti-dew heater on. APT version 3.87.9 is managing the captures at 180 seconds. There is an Astrozap dew shield protecting the corrector plate. Here's a single, stretched, contrast enhanced sub to show the issue: Here's what the whole DSS stack looked like, again stretched and contrast enhanced but otherwise unmolested: