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.

  • Announcements

    SGL 2017 SP


Advanced Members
  • Content count

  • Joined

  • Last visited

Community Reputation

16,541 Excellent

About ollypenrice

Contact Methods

  • MSN
  • Website URL
  • Yahoo

Profile Information

  • Gender
  • Interests
    Imaging, Cycling, Thinking, Literature, French culture, Mountains...
  • Location
    South east France, Lat 44.19N.

Recent Profile Visitors

9,319 profile views
  1. Do you have a jinxed target?

    Mine too.
  2. Do you have a jinxed target?

    Good lord, I really wouldn't know!
  3. excessive noise after stacking

    We need all the information. Camera, optics, mount, guide trace if applicable, sample images... Olly
  4. This is a very good image indeed. Since it embraces, just, the target it sets out to capture I'm not sure that I'd call it a 'widefield.' With more data M31 would entirely fill the diagonal. The background sky is not flat and it would be a top starting point to deal with that. To my eye, if you take a diagonal top left to bottom right, you see that, close to the galaxy, the sky is a bit dark and a bit green. I do think that Pixinsight's DBE, working on the linear data, would easiy deal with that. Olly
  5. Another NGC7000

    I haven't tried using star masks in PI but it's a routine procedure there. In Ps: Open the linear image and make a copy of it as a layer. Use Ctrl A and Ctrl C to select and copy the image and... Put the cursor on the mask symbol in the Layers palette and Alt click to make a full size blank mask. Ctrl V will paste a greyscale version of the image onto the mask. You now want to stretch the stars on the mask and clip out all the nebulosity just leaving the stars. You can do this in levels or you can use the contrast and brightness tool (to extremes) but the idea is to black clip out anythng but the stars and get the stars up to larger size than you'd want them in the image. Invert the greyscale mask so the stars are dark. Apply a considerable blur so the dark mask stars are soft. (It's impossible to say how big a blur you need because it varies with pixel scale so just experiment.) At this point you can give the image itself a very gentle stretch in Levels. Zoom in to the stars to make sure they look natural and don't go too far. For me, I stop there, flatten and stretch as normal. I have never found a way to stretch hard under a star mask, but the little initial stretch under the mask is a significant help in star control. Regardng the lower right artefacts I'd first look at the individual subs. If it's a camera issue they will show at this first stage. After that just try one calibration routine at a time, first just darks, then just flats, then darks and flats. Olly
  6. What causes these weird shadows - first light help!

    The upshot of the other thread was that it was not the mirror clips but the absence of the mirror clips which was the problem! The mirror clips were the solution and just needed extending right round the mirror, so to speak. Olly
  7. Do you have a jinxed target?

    Delicately put, Gina. Olly
  8. Do you have a jinxed target?

    My jinx on this target was that I lost my high res image and all its files. However, I just found them again after over a year. Somehow I'd mis-clicked them into a meaningless folder and I'd failed to find them in a search because of a typo in the title. Doh. Olly
  9. Another NGC7000

    Perhaps an initial soft stretch under a star mask might then allow a more aggressive one afterwards, allowing for a contrasty nebula with smaller stars. That's a strange business in the lower right. Good to see you back. Lots to like in this image. Olly
  10. To bin or not to bin

    My TEC/460 numbers are very similar to yours, John, so next time out I'll give binned colour a go. To be honest it's so long since I did any binning that I'd forgotten about it. We would have binned Yves' data from the 14 inch back in the day but the camera wouldn't do it. Olly
  11. Do you have a jinxed target?

    So lust, though to a radiant angel linked, Will sate itself in a celestial bed. But soft, methinks I scent the morning air! Brief let me be... (We can mention anything at all so long as we do it by quoting Shakespeare... Then we're being highbrow.) Olly PS, Sara, I actually call it the Member's Nebula. This is a very tenuous nod towards Brooklands race track and 'The Members' Banking.' As well as a nod in a different direction!
  12. To bin or not to bin

    On some targets, even with heavy luminance contribution, I prefer to make my stars from RGB only. For this to work they need to be good (that's the whole point) so unbinned. Like Martin I don't think binning is detrimental to the object but it is to the stars. It also depends on pixel scale. At 0.9"PP I think I will try binning (which I haven't done for years) because I'm finding the colour 'thin' on the Atik 460. But at 3.5"PP in the Taks I won't be binning. I think you have Registar (?) so simply register your RGB to the L in that and it will resize for you in a trice. Olly PS It cannot be guaranteed that your camera will bin successfully. We've had three here which wouldn't, though most do.
  13. Mount recommendations.

    Another vote for the EQ6 (or Atlas, is it, in the USA?) Strong, simple, proven and well supported by suppliers and users on the net. Polar alignment on it is dead easy. Once you've checked that the polarscope is correctly parallel with the RA axis, which you need to check on any mount anyway, you can get a workable PA simply by rotating the reticle so that the Plough and Cassiopeia are orientated as they are in the sky. You then centre Polaris in its little hole and you're off. If you want to refine the PA for imaging then the DARV method is very quick and intuitive, even performed in haste. https://www.cloudynights.com/articles/cat/articles/darv-drift-alignment-by-robert-vice-r2760 I'm not much impressed by software-based PA routines. They're fine if they work but, if they don't, how do you interact with them? (In my case probably with a hammer!) Olly
  14. M27

    Really nice M27. The main object, the background sky and the stars (apart from a minor shape issue) are super. The stars are small and colourful which is also important. Olly
  15. Excellent advice. The quality of the EP won't have any effect on whether or not you can see the object. It will just refine the quality of the view. It really does help to have a very widefield EP with a Dob though. A long focal length 2 inch ultra wide is a huge asset for finding things. A Telred reflex sight is also a boon. Its large red circle provides a sense of scale. You first place a 'virtual Telred over the target on the chart/planeatrium and then note its position relative to adjacent stars. You then replicate that position on the sky with the Telrad itself. Olly