rotatux

I don't know your equipment and capture settings (how many subs / overall minutes etc), but it's beautiful. Sadly my FoV is even narrower with the MFT sensor, but I'm planning to take about the same framing (which should just fit in the diagonal) with the help of my now stabilized mount and CC-reducer.

@ neil : in your first one it was color-less and quite difficult to distinguish fuzzies from stars, so I much prefer your 2nd for its color and easiness to read. @ nigel : in fact I prefer your first one, which despite less natural (but still good) colors I find more constrasty. You catched nice structure. Still annoyed by that mottling effect (of your processing software?) when zooming in. /Myself must wait for another try at this target with my new cam (since last year) and tightened mount... you lucky, I yet have to find the right cloud-dispersing magic wand Edit @ neil : strangely your 2nd image shows the same mottling effect on the background than Nigel's... same software ?

Thanks for kind comments. Yes I quite like the edge-to-edge consistency of this lens (no coma!), as much as I hate its color-diffraction pattern (BTW no tool for this yet under Linux, I tried generic deconvolution as a wild guess but I must still learn how to use it). For reference, here's the page about tightening this mount: http://nexstarsite.com/Reviews/NexStar102SLT.htm#AltAxis (the last paragraph especially helped IMO).

Here's first output from my session of sept. 22. I got out nearly all night with my Alt-Az mount and a bunch of lenses to test. It's also first light since I tried to fix my mount by tightening hardly the altitude gear as advised by some page on the net; Hopefully on this one it managed 40s exposures with a high keep rate, which it had never achieved yet (whatever the focal). This one is not really a test any more, as I now know what to get of this lens. I let it uncropped so you can appreciate the FoV given by this setup. Thanks for watching. M31 - Andromeda Galaxy Details: Gear: Olympus E-PL6 with OM-Zuiko 200mm/4 at F/5.4 and TS-Dydimium filter on Celestron NexStar SLT Capture: 60 lights (/80% keep) x 40s x 3200 ISO, 13 darks Sky: average (didn't get any SQM, was prb 18-19), 50km from Paris, France Processing: Regim, Fotoxx

You don't tell about capture conditions, so as I wild guess, your star elongation looks approx. perpendicular to the direction of image center. To me this looks more like field rotation, maybe mixed with a bit of coma in angles. About tilt checking during the day with the cam train on, just a rough idea: maybe focus on a the vertical face of a far building, and check focus along a vertical line on live view ?

Don't be discouraged, I too face a mount that doesn't want to be stable enough more then 20-30s (more often 20). My keep rates vary from 22 to 80%, so you're pretty up the score I think if you would read back this thread it would be somewhat the same for others. You're on your way. Nice image, you caught much nebula. However I find it's strangely too noisy given the high number of frames you stacked. Maybe you had to stretch very aggressively ? What ISO were your subs ? Did you shoot low on horizon ?

Here's a last-half moon from last month (this one fullsize, contrary to my gallery). First try at video-like stacking with a proper burst shots sequence. Auto white balance then added some contrast and color saturation. To my surprise some color differenciation appeared, so quite happy with it This was without Barlow, now I'm just wondering for next try whether I should do 130PDS+barlow or 127MAK ? Optically I prefer the MAK, but the focuser and camera coupling is much better on the 130...

Here's some planetary for a change: 2 sample shots of Saturn taken on 2017-06-11. Details: ~120s FullHD @ 30p movie crop mode, Olympus E-PL6 with Celestron 127MAK/1500mm and x3/x2 APO Barlows on NexStar SLT, processed with cvastroalign. (indulgence requested, I'm still learning how to process planetary footage and use cvastroalign) Edit much later: realized this is not in the thread's subject (not DSO), I should not have posted here. Oops :-/

I rather suspect our browsers to be the culprit... Some of them try to be smart and alter color profiles (for the sake of cohesion I presume). To check, you could try to open your local image in a browser tab, rather than going through SGL submission, and compare with external viewer of even PS. BTW nice image, I like star colors too (a bit too cyan?). Interestingly the version I prefer is your last one without darks (less contrasty mottles), but it's maybe just a matter of black point.

At your current keep rate, you may also improve it dramatically by dropping your sub exposure time a little, say from 30s to 25s or 20s. BTW you don't tell how long your subs are. Nice pic however, it has depth and colors; Details and your processing skill will improve with time and practice (and yet more subs as always :-P)

Not enough: you have to rotate the polar scope to either 1/ match your local longitude + date + hour, or 2/ match other constellations around NCP (such as Ursa Minor/Major and Cassiopeia). Otherwise you may be up to 2x40' (1.33°) offset from NCP, and that might explain your trouble.

No need to ask and welcome to altaz imagers. That's a very nice image, with crips stars and beautiful colors (stars and nebula). The blue background is nice too, after all. Did you have any experience with astro imaging before ? if that's your first it's a very good one.

It appears your CC introduces more vignetting as there was initially. Meaning you will *need* flats to correct your images taken with it The global level is also very different : 202 vs 217 (on the full-width bottom area below the label) which is about 7%. This is difficult to see (and hereforth quantify) with the eye+screen, so I used Gimp to measure (though I wanted the median, it only offered the mean, but that's another story). I think that result is not bad per itself (90-95% Tx factor is usual with good glass assemblies), but if you're comparing brightness variations between apertures, you should remember to apply that value as transmission factor of the CC. Such an interesting subject that I'm now planning myself to check exposure levels from all my lenses/scopes x apertures, just to try to clarify whether focal+transmission ratio play a role alone, or must be combined with focal (have seen both theories defendable). Just need to build a DIY light lab to keep things constant :-P

Very interesting. Though, for the sake of comparison, I'd like to see the scope's result without CC, to account for just the mirrors' transmission, and starting the lens at f/4.0. Given that I've heard pixel individual illumination should be proportional to F ratio (all other conditions being equal), it's quite strange to observe your scope's F:5 result to be between the lens F:8 and F:11. That's a kind of flat images you made, but was your light source for them constant in intensity and distance ? BTW I don't believe in the T-stop explanation, as that would make the result even worse, i.e. the lens results around the scope's would not be F:8 and F:11 but more something like F:9 and F:12 (assuming 80% transmission). Don't forget that your 2 newton's mirrors each have typically 95% reflectivity so overall ~90% transmission.