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Martin Meredith

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Everything posted by Martin Meredith

  1. You can indeed use the return value without having to call the function again. Does a statement of the form print ("The temperature on" ,date_now() ,"at" ,time_now() ,"was" ,temperature ,"Deg C") not work? A Python function's return statement returns a value rather than placing it in a memory location. It is perfectly legal not to use the return value, in which case it is lost (not placed anywhere in memory). The only way to use the value is either to use it directly (as you've done in the print statement), or assign it to a variable such as 'temperature'. I would avoid thinking in terms of memory locations. Python is not like C, for example. Everything in Python is an object, which is roughly equivalent to the value of the object as well as its type, and the concept doesn't map on to memory locations in a way that it might do in a more primitive language like C. cheers Martin
  2. Just to add since you were asking for general help with Python, if you've done a bit of programming in other languages, many people recommend this 'Whirlwind Tour of Python' which is also written by an astronomer... It used to be available as a free pdf but is still available in the notebooks in the link. Martin
  3. I agree with Mike. All function calls need parentheses.This means that the earlier statements in the while loop need parentheses too. To make things more explicit you might say temp = get_temp() humidity = get_humidity() dew_point = calc_dew_point(temp, humidity) BTW The reason you need the parentheses is to distinguish the act of calling the function (which is what you want and what is the most normal case), from the use of the function name itself. Python allows functions as entities in themselves e.g. in a generalised sort algorithm you can pass the name of the function used to compare pairs of elements, allowing any kind of sorting to be implemented easily. cheers Martin
  4. The 'N' might mean 'nuclear ring' defined as a ring of intense star formation close to the nucleus. The image I'm looking at right now in de Vaucouleurs for NGC 1097 is somewhat similar to your PGC 606 in that it has a bright ring close in with several knots and gaps. There are also images of other 'peanut' galaxies like NGC 128 but I have to say that your image beats them all! To better see the x-shape they use unsharp masking in the Atlas. Sounds like it might be worth implementing. The x-shape is also visible in some non-edge-on galaxies using this techique. The examples shown are for NGCs 7020, 1527, 4429 and IC 5240 which is pretty spectacular with unsharp masking. Martin
  5. What a marvellous collection! I'll have a go at NGC 7428 as soon as I get a clear night. The one that stands out for pure interest is the last shot. The curve on NGC 128 looks like a gravitational lens (though obvs. isn't). Can't wait to take a closer look at this field myself -- so much to see here. I've no idea what the N means either but will dig out the de Vaucouleurs Atlas later to see if I can spot anything. Thanks for posting such an interesting collection. Martin
  6. If you have a scope/camera combination with a relatively small FOV and type M24 into your goto controller, chances are you'll see something like the left hand image here (or indeed the right): Messier 24 is around 2 square degrees so for my 0.45 x 0.35 degree FOV I'm only seeing a small part of it, and it is fortunate that the M24 goto in my case lands pretty much on the open cluster NGC 6603, seen here, located in the direction of the galactic centre within the Small Sagittarius Star Cloud (ie M24). NGC 6603 contains mainly mag 14 and fainter stars. A 1998 study by Sagar & Griffiths analysed just over 3500 stars in the region and found around 54% members and a further 13% probable members, so 2000-2400 stars are likely to make up this grouping, the bulk of them with apparent mags 17-20. The same study suggests an age of half a billion years. The bright star is BD-18 4895, a mag 7.4 M2 type with a colour index of about 2. Why two images? It turns out I looked at this almost exactly 2 years ago. I've observed a lot of OCs in the intervening time but this one stood out for its diagonal line of slightly-brighter stars. I reloaded the older version and adjusted it to match the new one as closely as I could. They're remarkably consistent. For instance, the subtle pale yellow, peach and orange colours at the top end of the star diagonal are preserved in the two images. I did a crude blink comparison but couldn't spot any interlopers -- unfortunately, Pluto is at the other end of Sagittarius. The main difference I think is slightly worse collimation in 2021 than 2019... The older image was taken with 5s subs while the newer one used 15s subs. What I find quite interesting is that very little colour data is required for the moderately-bright open clusters. The 2021 image on the left has a single 15s red filter and 45s in each of G and B (these were not deliberate mismatches but came from randomly-shuffling the subs to match the overall exposure in 2019). The only effect of using different exposures in the colour channels is a different quantity of colour noise in each, and for sufficiently bright subjects this isn't really of much concern, making OCs ideal subjects for EEVA-style observation. cheers Martin
  7. Thanks Rob and Mark. Mike, I looked at a few other sky surveys via Aladin and also could find no hint of the arm. Nice work on the double! Very clear separation. I might add a position angle/separation measure tool at some point. Martin
  8. Alerted to this by a post by Steve Gottlieb, I had a quick look last night at this fairly bright SN in Hercules. The SN is the bright object more or less equidistant from the two galaxies and just off a line joining their cores. Compare with the DSS shot and the SN is obvious. It seems to be of a similar magnitude to one of the companion stars listed as GAIA g-mag 14.6. Here's the discovery info (23 Aug). NGC 6500 is a type Sab spiral while NGC 6501 is type S0-a. They lie at 150 +/- 3 MLyrs. As Steve points out, it isn't clear which galaxy this should be assigned to. With the stretch turned up (lower right inset) NGC 6500 appears to have a spiral arm curving upwards and clockwise, with the SN lying near the tip (or perhaps this is just a visual suggestion -- there is an arm there as the DSS image shows, but whether it continues upwards is open to question). The bright star at the left of the image is the double Struve 2245 with a sep of 2.7". The position angle is 116 which is manifest in my shot by a slight ellipsoid bulge in the ENE direction and a hint of a kidney shape (2.7" is less than 1.5 pixels on my sensor...). The companion star is also pretty bright, at mag 7.5. There is a strange piece of galactic? fluff due north of the double star. It isn't an artefact of the bright star as it also appears in the same location on the DSS image. Apart from being very blue, I haven't been able to find out more about it -- perhaps an irregular galaxy? Martin
  9. Here's a quick capture from a couple of hours ago. N up. Live LRGB combination of 2s subs. This is with saturation at minimum (otherwise the red was at the unbelievable end of garish...). Martin
  10. You can get this information from the Washington Double Star catalog, available e.g. here: http://vizier.u-strasbg.fr/viz-bin/VizieR-3?-source=B/wds/wds Enter STF (discovery code for Struve) in the discoverer field (Disc), click submit and you'll get just the Struve data (just the first 50 rows -- select max rows in the menu to the left to see more, and to choose a different format more useful for further processing). The pa1 and sep1 columns provide the data you're looking for at the time of discovery while the pa2/sep2 columns contain the most recent data. Discovery codes are in this separate table: http://vizier.u-strasbg.fr/viz-bin/VizieR-3?-source=B/wds/refs I plot this data in tabular and graphic form in the charts in my sig but unfortunately I don't show the original PA and Sep. cheers Martin
  11. Good idea to start a thread on these. When I first looked at your LBN 438 I imagined there was a dark nebula in there somewhere but I think it is just the contrast with the swirls of the bright nebula. That's a great object with its back-to-front S-shape. I've added a few in Scutum to my observing list for tonight, though 40% cloudiness is predicted... Unfortunately I don't have any data on the apparent size of these nebulae so it is a bit hit and miss as to whether things will fit in a narrow FOV. Still, many of them appear to be in dense star fields, which I find lend a beauty all of their own. Martin
  12. Hi Robert Apologies. The documentation is a little out of sync with the versions. For v0.4.5 I removed the rebuild observations option because I'm introducing a cleaner way to do this in the next version and 0.4.5 was a step on the way to that. For the moment, if you delete previous_observations.json in your JocularData directory it will automatically rebuild. The directory structure you show above ought to work but if not I suggest clearing out the captures directory and generating a structure like this: There will be a completely new version with improvements to the installation side amongst others coming soon but I need to find the time to finalise it. cheers Martin
  13. Sorry -- I use the white background theme (default simple theme) so it looks OK at my end....
  14. I believe the incantation is pip install --upgrade jocular==0.4.7.dev2 cheers Martin
  15. Last update was c 3 months ago after a lengthy diversion fighting a largely losing battle with ASCOM integration.... No major release ready just yet though there is a dev release (0.4.7.dev2) for the daring available via pip (features a more polished interface and configuration system and more watched folder options). Version does indeed appear (in title bar). Will return to the fray in early October once I've got a bunch of new lectures out of the way... Martin
  16. What's more, there's a beautiful line of stars in that last one (lower left) Martin
  17. Very nice "double double" of galaxy pairs. Gives a great sense of perspective. Looking at the DSS image on Aladin I see you've caught the semicircular loop joining the VV 102 pair. Martin
  18. This shot of NGC 7008, also known as the Foetus Nebula, was captured and processed 'live' in EEVA mode on 6th June using Jocular. It consists of 8 x 10s each of L, R, G and B taken with a Lodestar X2 mono guide camera attached to a Quattro 8" f4 scope mounted in alt-az mode on an AzEQ6 mount. The nebula appears to consist of two shells which might be due to both members of a binary star expelling material one after the other. The nebula lies in a star-rich region in Northern Cygnus close to a colour-contrasting visual triple. cheers Martin
  19. I always see a diagonal pattern in my master bias frames (also from a SX camera, the Lodestar X2 mono ). This is heavily stretched of course (min val ~ 1.6% of 16-bit range, max val ~ 1.7%). This is a mean stack of 23 frames but I see the same with longer stacks. I've been regarding it as normal... Martin
  20. In case anyone missed it, the Willmann-Bell catalogue has been acquired by the American Astronomical Society https://aas.org/press/aas-acquires-willmann-bell-titles who plan to make the bulk of them available indefinitely. Phew! Martin
  21. Agreed, an excellent intro that will be very useful to anyone starting out in EE(V)A. Martin
  22. That's a lovely grouping. The surrounding star field seems to have formed a circular window thru which to view SHK 361.
  23. Glad you reminded us of the Hickson 93 designation as I couldn't find it under my Arp collection... What I find fascinating about NGC 7549 is the appearance of a sudden drop in intensity along the upper arm as if there's a discontinuity of some kind. I also recall thinking when I looked that the lower arm looked somewhat 'frayed' but I suspect these are artefacts. Here's a close-up from last year (which doesn't add much if anything to your shot, where your better resolution shows up in the various 'knots' along the bright arm) Martin
  24. I agree, a wonderful write-up and a lot of links I'd like to follow up when I have more time. It goes to show how much fascinating stuff there is in some fields. As an aside, I've often found myself wondering about why sometimes in EAA we spend so little time on each field (trying to differentiate EAA from AP, I suppose). Even with my small FOV there are too many objects to properly appreciate in a short time, and with the larger FOVs that are becoming more widely-used in EAA one could easily spend an hour or more on each field. Martin
  25. I found that I had to update the drivers (for the cable) to get my AZ EQ6 to talk to my laptop using EQMod. This is with the Lynx Astro cable. Martin
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