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_imaging_challenge_banner_widefield.jpg.36065d79cb2625eb299137a5b4432c96.jpg

Martin Meredith

Advanced Members
  • Content count

    1,200
  • Joined

  • Last visited

Community Reputation

1,470 Excellent

3 Followers

About Martin Meredith

  • Rank
    Sub Dwarf

Profile Information

  • Gender
    Male
  • Interests
    Mountains, cycling, growing stuff
  • Location
    Northern Spain
  1. Seeing Red

    The reddest-orangest star I've observed (with a camera) is V CrB, a Mira-type variable with a range of mag 5.7 to 12.6 over almost exactly a year. Funnily enough I haven't checked it out visually so if anyone can report on its appearance I'd be interested to know.
  2. Intel compute stick on mount...

    I haven't but you might find some useful info in this thread: https://www.cloudynights.com/topic/563964-evolution-8-intel-compute-stick-i-think-i-am-in-eaa-heaven/ Martin
  3. Crab Nebula with Lodestar guide cam

    Lovely image for 5 mins. The Lodestar is a real gem isn't it? Could you say more about the processing? Was it LRGB? The brighter filaments certainly look nice and sharp, something I struggle for when combining pure RGB (live) at short exposure lengths. Martin
  4. Star Catalogues

    For free online resources with customisable downloading options check out the catalogues available at CDS e.g. this one is an extended catalogue of the Hipparcos mission stars and contains information on spectral class, colour etc. http://vizier.u-strasbg.fr/viz-bin/VizieR-2 If it's any use to you, here's the same data I made into a PDF ordered by descending magnitude. Clicking on a constellation code restricts to just that constellation. BSMagI.pdf There are more detailed catalogues of stellar classes too (check out Skiff's Catalogue of Stellar Spectral Classifications, also available at CDS). It depends how deep you want to go. cheers Martin
  5. Astronomers and flight...

    Per ardua ad astra could equally well be the motto of the amateur astronomer... Personally, I've never flown anything. I do love reaching the tops of mountains though, so maybe the common factor is a subconscious desire to get above the clouds? Martin
  6. This is what Pillow v4.3 has Agree, OpenCV worth a look too. (BTW it is pretty straightforward to treat Pillow images as NumPy too with a relatively minor overhead https://stackoverflow.com/questions/384759/pil-and-numpy) Martin
  7. I thought the same (and speaking as a daily Matlab user for the last 20 years) but I really regret not switching completely to Python 5 years ago. I work in signal processing, and to my surprise I found Python to be a little faster than Matlab too even for areas where you'd expect Matlab to have the edge (e.g. filtering). I find my Python code to be about a third as long as the equivalent Matlab code. Matlab will linger on for a while longer but I really doubt there will be much serious new development in that language. The area where Python appears at first glance deficient wrt Matlab is the ease of building interfaces, but I've recently started to use Kivy in anger, and the GUIs are far superior to what it possible in Matlab (+platform-independent). Martin
  8. Assuming you haven't already done so, the best starting point is to download your python + data science packages from https://www.anaconda.com. Using Jupyter notebooks is highly recommended. Then there is Jake's handbook online here https://jakevdp.github.io/PythonDataScienceHandbook/ For image processing, check out Pillow https://pillow.readthedocs.io/en/4.3.x/ There's much more out there but these might be useful (not sure how far into Python you are yet!). Martin
  9. The stacking happens automatically if the 'Enable Live Stacking' is checked (which it may be by default), so it could be happening regardless and hence could be the cause of a lack of image.
  10. Hi Does the Stacked count change? If the Max FWHM setting on the Stacking tab is set too low it might be rejecting frames due to poor seeing/tracking. Change to say 6 or more just to check. I've noticed that when I use two screens the image disappears when I move from one to the other, but I don't suppose that is your issue if you're seeing focus screen images. Martin
  11. Nice video. I relatively recently (in the scheme of things) converted from Matlab to Python and never looked back. I also use his book extensively for teaching Python Data Science (also freely available as a bunch of Jupyter Notebooks on the web). Definitely the way to go for developing astronomy apps. Martin
  12. Multispectral Captures with StarlightLive and NB Filters

    Hi Bruce Re the Modify All/Auto Align, with respect to the current question it doesn't matter whether you check them or not. Most of the time auto-align does the right thing but occasionally the colour channels need to be adjusted manually and independently. In this case I uncheck Auto Align and uncheck Modify All, select each channel one by one, and alter their individual brightness and contrast values in order that their histogram contributions line up well. Re 'this is when combined'. Yes, to get the combination you must have 'Display Selected' unchecked, since the 'selected' in this case corresponds to the R, G or B that is checked in the row below. (It really means, display selected *only*). The semantics would be clearer if the logical were to be reversed and the checkbox said 'Combine channels'. Filter order doesn't matter and you can go round several times topping up the data. For RGB imaging I find the blue channel typically weakest so I tend to start with R, then G, then B, which also corresponds to the order I have those filters in my filter wheel (so it doesn't have to go all round the loop each time). Starting with a weak channel might lead in some cases to insufficient stars to align on I guess. The same would apply to narrowband -- best in my opinion to start with the strongest signal, usually H-alpha. If you have Sulphur it tends to be very weak, although the likes of the Crab (as well as M27) do have some. Martin
  13. Multispectral Captures with StarlightLive and NB Filters

    Exposure Channel Mask defines which logical channels receive the signal from the sensor. If you collect H-alpha with 'all' (in Exposure Channel Mask) checked, you get H-alpha on all channels and when you display it combined it appears as monochrome. If you collect with just 'red' selected, then when you 'combine' it it only contains information on the red logical channel, and so when examine it with the 'Display Selected' unchecked (this displays the combined channels), you will see a red signal as there is nothing in the G and B. However, if you were to look at your red-only signal with 'Red' checked and 'Display Selected' checked, you should see a mono signal. For maximum clarity, by 'red' selected, I mean 'red' in the 'Channel Selection' part of the 'Display Processing' pane, and not 'red' in the Exposure Control' pane... This is M27 in H-alpha, O-III and S-II separately (i.e. looking at the red only, green only, blue only respectively), with 'Display Selected' checked And this is when combined (with 'Display Selected' unchecked) HTH Martin
  14. Pretty Deep Maps v0.2

    Current version is v0.3. I recently moved them from Dropbox so they're now accessible from here. The place to start is the technical guide.
  15. Cloudy, with a touch of Florence

    Nice animation and good to see the reality yet at the same time the impotence of the clouds i this case. What is Florence's magnitude in these shots? Martin
×