Stub Mandrel

Not me, but that's a good idea.

I've been quiet for a while. It's ggod to see lots of great new images with teh 120P-DS Here are some of my latest images with mine.

🙂 Equally true of imaging - if not more so!

RGB image of Mare Crisium.

My first pair of planets using an ASI178MM.

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I've seen it low down with atmospheric dispersion, each short 'tick' is a spectrum from red to blue. You can actually use it to adjust an atmospheric dispersion corrector, as when it's set right the pattern becomes straight. I might also he caused by chromatic aberration with a frac.

Hmm. I 'tuned' my HEQ5 rather than 'modding' it and have got as low as 0.6". I've since fitted a Rowan kit but have only used it for planetary since. To be honest, I think the biggest issue is getting the worm gear engagement right.

I'm late to the party, but Ii found I had to do a fair bit of editing to get my image right. I cropped away the top while adjusting maptex_top and cropping away the bottom of the image until it was properly aligned AND in proportion. I also had to be very careful to match the view to the exact spot where I put my scope.

Can you swing the camera around by its strap? But seriously the correct answer is the longest exposure possible, so the fewest subs you can get away with to give your cronky laptop a chance to stack them before the zomb...

I think the limit on resolution is mostly down to my scope, it's only 6" aperture, which give a theoretical resolution one 1 arc-0second, about 1/20th of the diameter. Stacking and drizzle improve that a bit, but I think I need at least an 11" scope to get much more.

It's been so frustrating waiting for a cloudless night, I've had a few aborted tries and last night I only managed Saturn, I saw about ten seconds of Jupiter on screen.

Not bad for a newbie 🤣 Actually, that's smashing especially for a single sub, you should be proud of that!

It's a wonderful time for anyone seeking a cheap set of 7nm Baader nb filters... I have a filter wheel that will take 31mm filters, not a lot extra.

This will finally let me put a Pentax lens on my SP1000 after 38 years 🙂 Plus should be good for wide field, apparently they are sharp all over stopped down to f2.8.

It is rarely mentioned, but a shorter focal length scope of the same aperture used with a smaller sensor with smaller pixels can be cheaper than going for large sensor and big filters.

Excellent, well done!

Update: excessive noise reveals Ii need to rotate the darks too, of course, and my dark flats. I've found Irfan view can do this and save as a TIFF, which will do BUT it insists on stretching some FITS files - making them useless for calibration (but not others?)

Last night I was imaging with the scope flipped for only the second time ever (I have a new location biased west). I thought I would be clever and rotate the image in Sharpcap so everything would be the right way up. What I didn't realise is this would mean my flats (taken without rotation) would be the wrong way up resulting in uneven results and a gradient. I can't see a way to tell Deep Sky Stacker to rotate the master flat or a way to save a rotated but otherwise unedited flat in FITS liberator. Can anyone offer a solution?

Tadpoles, Ha from last year, rather puny Oiii and Sii from the 4 April with poor transparency. Rather over-processed, needs more/better data to get less noise.

I think that sums up my typical imaging session quite well, I always end up chanting "BBBB, GGGG, RRRR! BBBB, GGGG, RRRR! BBBB, GGGG, RRRR!"

If you look at the contents page of the manual it says that Menu operations and Settings are on page 38: This explains how to get to the settings I've listed below better than I can explain it. If you can't follow those instructions, I suggest you either look for a video tutorial or try and find someone who can show you once lockdown ends.

I agree with this and am glad that I progress very much incrementally,m ironing out the snags at each stage. My next leaps in the dark (arf!) are autofocus and platesolving...

Indubitably!

Now I have just over a year's experience of using a mono camera, I have to conclude that @ollypenrice is mistaken about the efficiency of Mono versus one-shot colour. He is significantly underestimating the relative efficiency of mono cameras! Despite my initial scepticism I've found my ASI1600MM requires much shorter overall exposure times than my DSLR. They are both cooled and the DLR is astro modded so two sources of 'inefficiency' in the OSC are effectively eliminated or at least greatly reduced. But I find that 45-60 minutes of RGB data knocks the spots off an hour's OSC data by far more than the 6:4 ratio Olly suggests. I think this is because my RGB filters have 'square' passbands while OSC cameras more closely mimic the eye's response - sacrificing efficiency for more accurate colour rendition. Here's the curves for my filters (actually the 2"v versions I have the 1.25" ones) you have to imagine these normalised to the QE curve to be strictly comparable, so efficiency drops slightly at far blue and far red) : This is the ASI1600MC Pro OSC version (curiously FLO have this graph on their page for the mono version): The key points are: Both the green and blue RGB filters are highly sensitive to an Oiii signal, giving a stronger response to that band of nebulosity and causing it to render as turquoise (aqua as we now call it...). The RGB filters have a gap at the sodium lines, increasing contract under many light-polluted skies. The RGB filters have more sensitivity into the near infra-red including at Ha and Sii wavelengths. My estimate of the 'area under the curves' even allowing for the QE of the sensor suggest only marginally more sensitivity for the RGB filters than the OSC, but the shape of the curves gives stronger colour contrasts with our typical targets which probably means we can get expected results with gentler processing = better s/n ratio and smoother results.