Stub Mandrel

What @Stu says... I've really gained loads form joining our club, it's a big, active one and we are soon to commission our observatory, we have courses, talks and informal events. It was a clear night last time we had our 'informal' meeting and there were 20-25 of us imaging and observing at about -2, some of us until well after midnight. But the best thing about it is regularly meeting up with a great bunch of people who enjoy discussing our very peculiar hobby! It's very friendly (it's not cliquey) and new (and longstanding) people get help and encouragement , lost of us put in time as volunteers etc. We meet up to go to shows, observing/imaging etc. its not just club meetings. Many of us have even been sharing photos of Christmas presents etc. today.

The Ikea box came, and it's a perfect fit for the 15" screen laptop. I need to add some sort of front cover, probably just a piece of fabric. Hopefully the heat from the computer will create a slightly warmer micro-climate inside.

Could be, but I've been using this setup for three years with a DSLR and haven't had the same issue (I have had nights when the subs have been too poor to get anything though).

Here we go, comparison of flats from 9th and 17th of December - you can see I got rid of the dust bunnies for the second run... both auto stretched. The one on the left was used for the heart nebula image above. This makes me pretty confident it is something about my subs, rather than a problem with the flats.

I think its a bit misleading to use the histogram from DSS, it looks skinnier in other programmes. I suspect it's either something to do with SharpCap settings OR an issue with my subs. I lean towards the second as I didn't have this issue the first time I use the ASI1600. The big difference is thAt this is narrowband, the images with the dark spot are with an L filter. Ironically the flats for both sessions were taken with the L filter, so the problem session should be better matched! See - no problem I can see here (aside from framing and slightly soft focus):

It seems all subs are affected equally. All I can conclude is that, for some reason, the flats just aren't matching the subs.

Bought a new W10 laptop with an SSD in it... boots so fast it even impressed my daughter who has a Macbook 🙂

Looks like the process is OK, allowing for the fact my LED flat screen probably has a gradient (I rotate it to eliminate this) the result is pretty even, certainly no big dark (or light) spot in the upper middle: Linearly stretched to show the very smooth residual gradient, this is just because the LED panel is brighter on one side - bear in mind that it's always worked fine for my other camera (and last week with this one!)

Yep, everything is 16 bit. (12 bit really).

I'm not 100% sure, but I suspect the problem is that my image has virtually no detail (conditions were far from good) and that I'm just stretching it far beyond what the data will allow.

Hi David, still set up. I've taken another set as FITS. Also, I've done them without the dewshield - previously I've always done them without it. Fingers crossed.

I'm having trouble with flats over correcting in DSS. This hasn't been a problem for me with DSLR images unless I made silly mistakes. I'm using an ASI1600MM, all frames (lights, darks, flast, dark flats taken at -20C), flats are taken using a flat panel with an extra layer of diffuser, rotated between frames (24 of them). I've greatly reduced the sample images in size and these are 8 bit too. Here's the unstretched master flat, clearly not over or under exposed (I checked the histogram): Here's a stretched master flat which looks sensible enough: Here's the result of a stack, with a quick stretch in DSS, note the over darkened centre: I can't help noticing that the dark area looks suspiciously 'square'... For completeness, stack without flats: I've tried stacking with and without darks and with and without dark flats, and with and without checking 'set the black point to zero'. The only things I can think of are that: 1 - I used TIFF this time for Lights, Flats and Bias, I didn't have this issue when I used FITS (sharpcap generates a master dark that's a FITS). 2 - Dark subtraction may have been switched on when taking the lights.. but if this was the problem not using a dark should surely have solved the issue? Has anyone got any suggestions?

Very nice 🙂

This reminds me of a conversation I had with a friend many years ago. We were sat in a room with a black and white TV that wasn't tuned properly. those of us of a certain age will remember the appearance of a screen of 'static', which is a pretty balanced random image as the automatic gain control averages it out to a mid grey. We noted that it was possible to stare at the screen form much longer than, say, a plain painted wall or a blank sheet of paper. We surmised this was because the ever changing, but essentially information less image didn't 'bore' the retina or the brain as the nerve cells were receiving constantly changing input. You can try this experiment with @vlaiv's two simulations. It's a pain to stare at the static one for more than a few seconds but the moving one has a wierd fascination. Obviously something with a longer cycle would be better as this short animation has some detectable repeating patterns.

I must say my fairly small apo scope (66mm f.6) which is probably helped by not being super fast, a which i use for AP and it doesn't really show any chromatic aberration.

Not the best skies, but excellent pics! (I'll never complain about light pollution again...)

I'll try the Ikea box first, I've ordered one along with some smelly candles for christmas presents...

Wow, some really good ideas - I like the way Carole's box closes up, but I've put an Ikea one in my 'bag (has anyone else noticed that all of a sudden shopping carts have become bags? Must be some 'nudge' psychology going on there...

That is rather nice! Funnily one of my best moon images was through an Ha filter in the same circumstances probably because red light is less scattered and dispersed? It's a bit close to full to show nice relief, but plenty of 'crater rays'.

Has anyone made a good example of a 'laptop protector/box' for keeping the dew off etc. while allowing it to be used for imaging. I imagine something that shields it a bit to stop dazzling and dew while enclosed to help keep it warm to max battery life. I could do with some inspiration...

Like a thrusting, masculine Battlebus Logo?

This is far from perfect, virtually everything except the scope and mount was different to what I'm used to... ASI1600, EFW, EAF... There wasn't much OIII about, conditions were poor with thin cloud passing through, guiding was off. Here's a comparison between the HOO and an L-enhance version on my DSLR on a better night.

Thanks Ivo.

And the same bit depth... I've just spent and age generating cooled flats and darks but in MONO8 so DSS hast just thrown them all back in my face 😞

Surely an LP filter will be useful for luminance under poorer condtions?