ollypenrice

I've no experience of the flattener you mention but the standard Baby Q does not come close to covering full frame. We've experience of two instances of the 'scope here and both produced heavy coma on the long ends of the chip. Have you seen evidence that this flattener lets the Baby Q cover full frame? I wouldn't take someone's word for it without proof. You might be lucky to catch the whole of Andromeda in any refractor setup. I needed a 2-panel with full frame at 530mm. M31 tends to be bigger than you think! (Note the left hand side in this orientation...) Olly

'Damn, all those images make me feel even worse for wasting such a trip 😆. At least I learnt a bunch of things. ' That's a contradiction in terms! You learned a lot. There will always be an element of, 'Two steps forward, one step back,' in this game. I know little about camera lenses, I'm afraid, but the Samyangs have a big following. My lens Orion was with the Samyang 85. (6 panel mosaic on a small CCD chip with some bits enhanced by telescopic data.) A B mask ought to help. Telescope Service also do a crafty gadget to help with fine focus. I used to use this at the time. Olly

You'd have picked up the Ha if the camera were capable of doing it. I'm pretty sure of that. Looking up the 550 I see that it is between 10 and 8 years old. At that time the filters used on DSLRs to exclude light either side of the visible spectrum excluded the Ha emission line far more severely than they do now. That's why a whole industry of camera-modding grew up. One of our guests tried the North America Nebula with an unmodded camera and we could extract almost nothing from the stack. By the following year he'd modded the camera and the NAN stood old boldly. So I think your camera's in-built filter is the culprit. The shuttlecock stars are almost certainly from the lens but further experimenting just from your home site would confirm or deny this. How do you focus? I'm not a DSLR imager but I've read that one way is to aim into some starry sky, zoom right in, and look at the very faintest stars on screen. Only when focus is bang on will they be visible. The slightest displacement either side will make them disappear. The Nifty Fifty has a proven record. This is by Stéphane Guisard and Rob Gendler. (So quite serious!!!😁) http://sguisard.astrosurf.com/Pagim/Orion_constellation-HRVB-50mm.html Olly

It's a pleasure. There is an arc of increased stellar density on the left of your image, annotated here: Although it's interesting (and I have never seen it before) this isn't Barnard's loop. To help you decide whether or not you're seeing the Loop in your image I've superimposed a camera lens image in HaRGB over yours to show exactly where it is... (This was a six panel HaRGB CCD image with 80 hours of exposure so don't beat yourself up.) Olly

Much of the year, yes, but certainly not all of the year! Olly

Stellar cores will usually be saturated in any exposure long enough to get the faint stuff. The solution lies in post-processing. You can still have attractive stars if you pull their colour into the core from the outside. How do you do that? Buy Noel's Actions for Photoshop! (Now called Pro-Digital Astronomy Tools, I think.) You can do it longhand by using Ps Layers but I just leave it to Noel! My advice would simply be to experiment. My own conclusions disagree with most of the published advice... Olly

Well you guys are doing better than we are! Terminal clag and soggy cloud here, the goopy kind you think you might be able to tow away behind a big bulldozer... 🤣lly

The F ratio is already F4.9. Taking it down to half that, F2.45, is simply unrealistic. Systems as fast as that do exist but they are complex and involve optical elements designed to work together. Even if you raised the primary mirror in the tube to get more back focus I think you'd find all sorts of aberrations in the image. Olly

A characteristically excellent response from FLO. Best of luck to all. Olly

No, in my view the spikes cannot be explained by any problem associated with the mount. That imaging train would have produced those spikes on that night on any mount, however perfect. Nor are they connected with dithering. Some of the CMOS cameras are sensitive to internal reflections and I wonder if dew close to the chip or high haze might exaggerate this. However, the main suspect remains a physical obstruction in the light path. Could the filter drawer or filters, or some part of the fixations, be intruding into the light path? Take a good look down the OTA from the top with a clear view to the chip. This really is a likely explanation but they may be hard to spot. Olly

Hi, I've worked through the raw files using Pixinsight's Dynamic Background Extraction and then an assortment of techniques in Photoshop. I'm afraid that your camera really is blocking Ha to a remarkable degree and there is very little signal from it in the data. I have one trick which is particularly good at extracting Ha but even that found almost no sign of Barnard's loop. If you want to image emission nebulae you're going to need either a camera mod or a different camera. There is another issue: your stars are showing a well-known aberration which makes them look like shuttlecocks. This is resampled upwards for clarity. In my view this is not a tracking issue because the stars fan out wards and upwards, they don't trail into parallel sided streaks. We see this quite often and it arises from miscollimated optics. In daytime images the lens may seem fine because stars are very exacting tests for any optics. The effect might be mitigated by tighter focus but my guess is that it won't go away entirely. There is a Photoshop 'dodgy bodge' for oval stars but it did more harm than good in this case. It does work on trailed stars which confirms that these are not trailed but optically distorted. So much for the bad news. The good news is that you do, after all, have your picture of the constellation and, if kept in a smaller format, the stars look OK. Your tracking also seems up to the task. The image was easy to flatten and had little residual gradient, meaning a good background sky is possible from your location. These are important positives to take away from your trip. I think you've come close to what is possible with a camera and lens less than ideally suited to this task. Olly

Strange! You weren't shooting with a clothes line or power cable in the line of sight? Or a spider's web in the dewsheild? We've seen both before now on here. Rather than posting a link to a file, just post a large JPEG here, not of a stack but of a single sub. That will contain all the info that's useful. The spikes are unrelated to wind or polar alignment. Olly

There is another option for Dec, by the way. You can put the full payload on the kitchen table with a length of thin tubing (or a pencil...) under the dovetail and find the point of balance. Just be sure the pivot is square to the dovetail. Mark this mid point and put it at the centre point of the saddle plate. I've never bothered but I did use this method on a review mount I once had. Olly

There are now five Mesus based at my place, three of them carrying complex multiple scope payloads, and all have been balanced simply by 'feel' as I guess you did yours. None of them shows the slightest sign of a problem. I wouldn't worry about it. Olly

There's theory and there's IC342! What do you need to capture IC342? Exposure time. Squared and then squared again. It is a delightful but very demanding target. The two problems are that 1) it is very faint and 2) the field is infested with stars. Optimizing the altitude and transparency at capture will help control the stars but, in the real world, what you need first is signal. Personally I would get all the signal you can and, while doing that, bone up on how to control stars. I'd look at Starnet++ for removing them and then at some way of putting them back. I do so by pasting the linear image over the de-starred one in Photoshop in blend mode lighten and then gently stretching it till the stars appear. When I did this target I didn't have Starnet so I don't knw how it would have played out. https://www.astrobin.com/327910/?image_list_page=2&nc=&nce= Olly

Next time I have a visit from my optical engineering guru, Ralf Ottow, I'll ask him for a tutorial on spot diagrams. I can't contribute anything sensible to the discussion before then... Olly

A good point! If the star were Polaris one would end up very cold and looking (unsuccessfully) for an igloo. If it were close to the celestial equator, each nightly wandering would describe an arc curving to the south west. You'd end up in need not only of a house but of a mosquito net. It is, however, possible to have too few walls... I once moved into a loft-converted bungalow with lots of wonderful french windows. Then I realized that bookshelves need vertical walls! Olly

It isn't at all difficult to image because its shape is defined by the background Ha cloud it obscures. The eye is not sensitive to Ha light, unlike the right camera which is highly sensitive to it. Since H Beta generally traces the same gasses as Ha, but in a wavelength they eye sees easily, that's probably the best filter for the observer. I visualize it as a hole in the pale coloured grey-ish gasses through which a crooked finger emerges, standing out against the much redder hydrogen emission behind it. A similar feature exists directly below it, doubtless created by the same physical processes, but the lower 'hole' is more blurred and the equivalent of the 'finger' much larger and more diffuse. We must remember that, in reality, the Trapezium is far brighter, relatively, than it appears in my image. Multiple exposure lengths have been combined to compress the dynamic range into what the screen will allow. That means that the brightness at the eyepice is already falling off dramatically as you get down to the first 'hole.' By the second there is little to see - at least with my eyesight. Olly

I've seen it at the EP a couple of times but it just appeared as an oblong of darkness (larger than expected) against slightly lesser darkness. One SGL member said he'd seen it like the chess piece but most just describe an oblong notch. It certainly isn't the most tantalizing ultra-faint target in my personal canon of obscurities. My own ultra-faint obsession is the 'beckoning finger' feature in M42. I can just - just - get it with the right exit pupil. Olly

Worth remembering: nobody called it the Horsehead Nebula before astrophotography... Olly

NIce. (It looks as if you processed the image without edge-cropping it first, since the unaligned borders are visible. I don't know how APP's algorithms work but in PI things like gradient removal would be badly confused by the uneven borders. Just a thought.) Olly

They are, it's true, and a fast one does make processing even more enjoyable. Olly

Indeed. I met this issue processing Yves' 32 panel full frame Cepheus/Cygnus mosaic. Fortunately I have a fast machine. (Not my Royal Enfield...🤣) Olly

Honestly, these things are best dealt with by experiment, which is very quick in the case of short exposures. See what works for you. I have read endless discussions about how long I should expose for with my kit and the majority of theorists come up with something like 10 to 15 minutes. I've been bombarded, in the past, by assertions that 30 minutes is a waste of time. These assertions are wrong. On certain targets 10 x 30 minutes beats 20 x15 minutes. I've compared both. I believe my own results. Olly

That might, indeed, be a key factor. Olly