Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

sgl_imaging_challenge_celestial_motion.thumb.jpg.a9e9349c45f96ed7928eb32f1baf76ed.jpg

ollypenrice

Members
  • Content Count

    32,595
  • Joined

  • Last visited

  • Days Won

    229

Everything posted by ollypenrice

  1. Two thoughts: 1) if you're going to swap to a 106 much of the extra cost will go into giving you a corrected circle your new camera cannot exploit. Surely this would be a waste, though there is no way past it if you sstick with 1.25 filters which are on their limit with the APSc chip anyway. So what would you hope to gain with the 106? With the small pixels of a CMOS camera you won't be short of resolution in the 85, you'll have a wider FOV and a better telescope. See point 2. 2) The ED 106 can be a bit of a devil, quite apart from the QC issues which have plagued all FSQ modelss of late. It is terribly prone to temperature-induced focus drift. Your 85 and our 106N Fluorites are better in this respect. I would only change to a 106, myself, if I were also going to go to full frame or larger, like the 35x35 Kodak, but then you need even bigger filters, the square ones. An APSc CMOS in the Baby Q would be great, I suspect and, for me, preferable to the same camera in a 106ED. We already know that the QSI683 works sweetly in the Baby Q. Olly
  2. I entirely agree about the quality of Rob's imaging and with this image in particular. He's gone for a more contrasty curve than I did in the stretch, making the dust lane and filaments much darker. This is something I could do with our data as well but I'm going through a period of conservative stretching at the moment! I felt my images were developing a hard look so I'm trying to keep things softer. Maybe I overdid it this time. There's a close double in the right hand end of the galaxy which gives another interesting point of comparison between large refractor and larger reflector. I suspect we miss Rob more than any other retired imager. I certainly do. Olly
  3. You need to know the Bayer pattern of your camera. Each pixel has either a red, green or blue filter over it but which is which? Is the top left pixel, for instance, red or green or blue? Using a stellar image is not the easiest way to find out. Maybe the camera manual tells you? If so you need to set the debayerig pattern in your software to match and you should get the right colour. In my rare forays into one shot colour imaging I've done an exposure of a multi coloured terrestrial target and simply tried all the bayer patterns (there are not that many) till I got credible colour and noted then applied that Bayer pattern. Olly
  4. I was aware of something wrong with the Mk1 version of this image and, indeed, my previous 891 renditions: somewhere along the line I seem to damage the little dark threads rising from around the core roughly at right angles to the plane of the disk. I parked this problem in my copious To Do bin and would have ignored it but from an email from Laurin Dave pointing it out. This gave me the guilts so I pulled my socks up and reworked the core of the luminance. Dave then suggested dropping the saturation to improve the little threads some more. Another excellent critique, which helped. Thanks, Dave. The little filaments now connect with the core. Olly
  5. The charm of PNs in widefield is imagining a time lapse in which all the medium mass stars produce their own. What a sight that would be but I'll happily settle for this one. What's your pixel scale, Gorann? I did this at about a metre and 0.9"PP. Like you, I used shorts for the core. Olly
  6. Quality all the way in. Olly
  7. That's a very polished bit of imaging. Top quality all the way. Olly
  8. This is very nice. I have it in a NAN widefield mosaic but, because it is significantly fainter than the NAN, I didn't feel I could stretch it too far without making it dishonestly bright relative to its neighbour. Doing it on its own like this gives you more freedom to bring it on! Olly
  9. I found little to choose between data taken at 2.4 metres/0.6"PP and data taken at 1 metre and 0.9"PP. I do think it's resolution which matters and to be inclusive I'd have thought that something around 2"PP would find lots of takers. Olly
  10. I guess I'd be inclined to try an alternative scope. It's the only way to know for sure, unless you know you don't have a problem (as in the case of a system guiding with an RMS in arcseconds which is reliably less than half the imaging scale. Olly
  11. There have been SGL collaborations before and I like the idea. I think the target should be a very faint one, or have very faint components, to maximise the benefit. Rather than settling on focal length it would be better to set an approximate image scale in arcseconds per pixel. Olly
  12. The main thing is to ensure that everything in and around the guide scope is rigid. I have some parts of mine held solid by epoxy resin (slightly extreme but they are cheap ST80 scopes). The focuser, the guide rings, all the attachments, need to be treble checked for rigidity. Soft stars don't matter, within reason, and PHD prefers them to be in imperfect focus according to its author. If the little guide scope is really rigid it should be OK. I guide a pair of parallel 140 refractors working at 0.9 arcsecs per pixel with an ST80. As ever, the only way to be sure you're guiding to the mount's capacity is to try one modification at once and see if it helps. Olly
  13. I don't object to Go To at all, per se, but I do object to the amount it eats up in a £350 budget. 8 inch Dob, red light, star charts, just as Steve said earlier. Olly
  14. Dave, those really are good! You've used a number of techniques I don't know at all, here. You have the holy grail of natural colour in tiny narrowband stars and the narrowband structure and depth in the gas with close to natural RGB colour. The images are not just gorgeous and informative but are also original. I've never seen the Veil rendered in this way. Chapeau! Olly.
  15. My pleasure. Want to fix that very slight star elongation top to bottom in Ps? - Create a copy layer. - Set blend mode to darken. - Go to Filter - Other - Offset and, in this case, offset vertically by 1 pixel or maybe 2. Slightly too much is best. - Then go to Edit - Fade and fade the offset till you have perfectly round stars. (This one is very well known and not one of mine.) Olly
  16. If you have APP I'm not sure that AstroArt will add much. Does APP have a 'repair line' feature? This is very good for getting rid of satellite trails and is a big help with planes, though not infallible. Olly
  17. It was the big gap in AstroArt's stacking features. I don't know why it doesn't default to a max of 180 degrees since I'm sure most users would want this. More people will be doing meridian flips than getting their camera orientation out by a mile - surely! Olly
  18. I thought you did. It's dead easy from (I think) AA5 onwards. Go to the second page of the Pre-processing window and 1) choose auto alignment, then 2) Star pattern, translation and rotation and then 3) type in 180 for the max rotation. The screen grab is from AA6 but AA5 is almost the same. The third step is easy to identify, it just requires the maximum permitted rotation to be 180 degrees. This will save you an awful lot of faffing about. A note on terminology: a meridian flip, confusingly, makes a rotated image and not a flipped one. A flipped image is a mirrored one. Some capture software does produce flipped output files, which is rather silly! Olly PS Correction: It seems you have to uncheck 'Automatic Settings' to make the third step. I always do so anyway because I prefer to up the number of alignment stars to the maximum allowed.
  19. 'The TEC180 represents a small increase in resolution for a large increase in spending.' This came from a reliable source - TEC's own website! In truth they've now changed it but I'm all but sure it used to say this because it always made me laugh. However, it remains perfectly true. 0.66 arcsecs for the 180 against 0.8 arcsecs for the 140 and a threefold increase in cost. Will this affect resolution in imaging? Hard to say. On nights of very good seeing it might, just. On most of the nights I experience I don't think it would. However, my friend not far away has an AP175 and just looking at this scope, let alone through it, would entertain me for hours! Refractors in this class just look fabulous. Olly
  20. This isn't a beginner image. It's tightly focused, well guided and has a flat background sky. Whatever your 6 inch optics are, they are very good. Personally I use nothing larger than 5.5 inches to get 0.9"PP. Before getting too gung-ho with the blue it's worth a look at the astrophysical data to find the colour index of selected stars. It's available from many planetarium packages (I use SkyMap Pro) and can be compared quickly with a B-V colour index chart like this one. https://www.researchgate.net/figure/Dependence-of-color-index-V-t-mdinstTH-from-color-index-Bt-V-t-for-different-spectral_fig1_275388313 Blue stars have negative or low B-V values, red stars have high ones, as the chart shows. Clearly there's no need to check all the stars in your image but checking a few gives you an idea of your colour calibration. Olly
  21. 'Rotate 180' in Artemis does require rotated calibration files. A meridian flip doesn't. On the other hand a meridian flip does require the stacking software to know that a rotation of the calibrated image is necessary. Mine, Astro Art, needs to be told to support rotation up to 180 degrees. Some just do it without being asked. Because of the danger of forgetting, I never use 'rotate 180' in Artemis. Instead I open the earlier image I'm using as a framing reference in another package and rotate that so it matches the incoming images. Olly
  22. Agree with Francis - nailed! Super. I often end up blending two separate processings. Why not? Olly
×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.