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About vince1976

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    Colchester, Essex
  1. Clearly I was too tired when looking at the horizons site last night to notice the Table Settings link, which changes the data properties the site returns and allowed me to select just the target angular diameter. I now have 10 years worth of daily data for all the planets in a format that can easily be converted to JSON for use in Javascript without any need for trigonometry. I'll be using the Horizons site a lot more now I realise what it's capable of.
  2. Thanks - Solex looks an interesting tool but sadly doesn't seem to allow me to export the data I need directly. The average values on that page unfortunately don't help me as it's the variation I'm interested in. Looking at wikipedia (Angular diameter - Wikipedia, the free encyclopedia) I see there's a lot of variation between the minimum and maximum angular diameter and it's this change I'm hoping to plot over time. I get the feeling my best option will be to import the raw data from JPL's Horizons website into mysql and then use SQL to perform trig to determine the angular diameter based on the each planet's distance per day and the average of the polar radius and equatorial radius of each planet. Accuracy isn't essential here as I'm concerned only with the relative change per day for my needs.
  3. I've been trying and thus far failing to find a reliable source of data showing the angular diameters of planets (specifically Venus, Mars, Jupiter and Saturn) as viewed from Earth for each day of the year. I'm aiming to produce a visualisation of these values using the D3 Javascript library but am unfortunately stuck at the first hurdle. I've found the JPL Horizons web interface (HORIZONS Web-Interface) that shows ephemerides for a given planet. This gives me the distance (delta, in AU) and thus allow me to determine the angular diameter via trigonometry. Aside from that the data is in fixed-width format embedded between text, making automated parsing annoying. Is that the best option I have or does anyone know of any other data sources that might provide me with the information in a more usable form?
  4. Wow, thanks. That's an excellent page that I'll certainly be keeping an eye on. I can think of half a dozen things worth buying already.
  5. Reading up seems to confirm that its the mount itself that will be overloaded, not the legs. Not to worry, I'll carry on enjoying my GOTO AZ and maybe manage to pick up a 2nd hand EQ3 sometime. Thanks again for the advice.
  6. A very good point Do you think that the weak point would be the mount itself or the aluminium telescopic tripod legs? If it's the tripod I'm sure I could replace the legs with something a lot sturdier, especially as I don't envisage moving it further than my back yard so portability can certainly be sacrificed. If it's the mount itself though, the required structural changes would certainly exceed my metalworking skills and budget.
  7. I've currently got a SkyWatcher 130P on a GOTO AZ mount. I'm very happy with the OTA and the GOTO mount is great fun once aligned but want a cheap manual EQ mount to play with, largely because I feel the GOTO mount just provides so much hand-holding that I don't feel like I'm learning enough about the sky when using it. Without a pressing requirement for this though it's hard to justify shelling out too much cash on a whim. I notice that my OTA is often also supplied on an EQ2 mount. Although I can buy an EQ2 for £112, I can buy a small refractor on an EQ1 for £90 or less (for example, this). Obviously this suggests value for money to me as I get a cheap equatorial mount, refractor, star diagonal, red dot finder and a couple of spare eyepieces for less than the cost of the EQ2 mount alone. Comparing the EQ1 and EQ2 via Google shows what looks like only a very slight increase in sturdiness (compared to the EQ3 which is a much more sturdy but expensive setup). My query really is what the practical difference between the EQ1 and EQ2 is and whether I would stand any chance of success in buying an EQ1 and manually hacking it to be at least as sturdy as an EQ2? I don't imagine any issue in mounting my tube as I'm sure I can butcher together a mounting using stuff lurking around the shed but I don't want to go down that route without some degree of confidence that the stability of the EQ1 mount can be improved on via a strip down and rebuild. I was hoping to find guides or YouTube videos of such mount modifications but the the scarcity of results for EQ1 mount mods worries me that there may be some practical limitation that prevents enough improvement being made. Any suggestions are appreciated (apart from shelling out hundreds on an EQ3 - my other half would surely kill me).
  8. Drat - I don't have registax on this PC but I have the raw video so uploaded to Youtube here but unfortunately even at 480p their compression removes most of the detail. I've linked to a reasonable section 50% of the way through - change quality to 480p then press the keyboard shortcut '5' whilst playing to return to that point. That said, what I have is the same colour, just a good deal sharper. Registax didn't manage to improve at all on the colour information either, just the sharpness. I should add that a 2x barlow was also used. Again, the non-barlowed image was smaller and sharper but with no colour at all. With the lens on used as a webcam (or with it removed but pointing at a sodium streetlamp) colour shows up fine so I don't think it's a dud camera.
  9. I must be doing something wrong as my camera mod is really only working for lunar images. Jupiter's colours are so washed out as to be greyscale. The sharpness is fine but I'm getting almost no colour at all. Could it be that my SkyWatcher 130p simply doesn't have a large enough aperture to capture the colours? I've tried with and without a 2x barlow and captured several videos of about 1500 frames each at differing exposures to try and get more than the merest hint of colour with no joy. I'm thinking of shelling out for either an MS LifeCam Cinema HD or a Logitech Pro 9000 HD (comparative recommendations appreciated ) as many people seem to get good colour images with them both despite them having CMOS sensors. Before I relegate the Xbox camera to the finderscope though, has anyone any ideas where I might be going wrong?
  10. That pretty much echoes my results from the first time I tried to set up the GOTO last week (I'd just been slewing manually prior to that). It took me ages to find stars on the list that were actually viewable from my back yard and not obscured by fences, sheds, street light pollution or my house. I was trying to track Mars at the time and simply couldn't get it to track for more than a few minutes without minor manual adjustment. The 2nd time though I looked through the star list first and located the familiar sounding stars in stellarium. I knew I always had a decent view of Orion so decided Rigel or Betelgeuse would be an easy star to start with. Regretably Polaris is hidden behind my house (that'll cause me issues later if I ever get an EQ mount) so I settled on either Castor or Pollux for the 2nd star as both are easily located from Orion. Using two stars so close together did seem to leave the tracking slightly innaccurate so I then slewed to some planets (easiest of all to find in the eyepeice) and used the PAE option (Pointing Accuracy Enhancement - found in the Utility menu) to to re-centre them. This seemed to leave me with excellent tracking over the few hours I needed to observe and image. Each time I inserted a higher powered eyepeice, barlow or webcam I re-centered using the slowest slew and then used PAE again to lock it at increased accuracy. Another lesson learned is that there seems to be the tiniest bit of give in the motor gearing at the slowest slew meaning that it might take a second or two to respond to you telling it to move one way after you've just told it to move in the opposite direction. If I centered the star/planet by moving the scope in a direction opposite to the motion of the celestial sphere then tracking was bad as the scope's motors would have to go through that small "dead zone" first. I solved this my simply ensuring I centered the object by manually tracking close to its direction of motion. This way the scope responds instantly to movement requests and thus held the alignment perfectly after I'd used the PAE option. That's my experience of the two times so far I've done the alignment. After a few more clear nights practicing I'm sure it'll be second nature to me but for now suffice to say GOTO sadly doesn't work by magic but the 2nd time is a lot easier than the 1st time. To give me something to do until the skies clear again, Intend to take a 360 degree panoramic photo of my back garden and import that as a stellarium landscape to make it easier for me to see what will be obscured from view. I have a lot of obscructions and light pollution leaving me a restricted window to observe in so I'm sure this will prove a valuable use of my time. Oh and as got the location co-ordinates, I used the excellent Android app GPS Status, which serves both to give accurate location coordinates and as a handy compass.
  11. Well I couldn't catch Jupiter tonight but managed to get mars in a position where it I wasn't blinded by streetlights so dragged out the scope and webcam. Tonight's taught me an awful lot of things I need to research: 1. Practice aligning the GOTO mount. I kept having to use the PAE feature to correct for drift every few minutes. 2. I really need to take several AVIs with more varied exposure settings. All my captures seem either under or over exposed. 3. Wow, registax 6 has a lot of options. I just went with the defaults but I certainly need to take some time to learn it properly. 4. I may need to get hold of something a little better than my Xbox Live vision camera. 5. Don't bother with Mars in a skywatcher 130P. The results aren't entirely rewarding. Well, I did say my first go at stacking was likely to be an embarassment but at least future results can only be an improvement.
  12. Belated thanks for all the hearty welcomes. I can see I'm going to enjoy my time here.
  13. Thanks very much for all the advice. It's great to know what to expect from this scope. I luckily managed to catch a break in the clouds tonight and get a decent view of Jupiter before the skies swiftly closed in again. The moons were pin sharp and I could see two blurry dark bands with the slightest hint of colour through my new 4mm EP, which I was very happy with given the far from perfect conditions. It seems not too far off what John describes above. 10mm showed a sharper image but it was too small to distinguish the bands without a 2x barlow. Unfortunately the skies remained clear only for a short while so I wasn't able to get my webcam fitted in time but I'm content I'll be able to get some initial footage once the weather improves for long enough to align the GOTO mount and keep Jupiter in shot. I'll be sure to post a youtube video once I finally manage it. I'm eager to have my first (no doubt embarassing) attempt at producing a stacked image. In case any other beginners happen across this thread looking for an answer to my 2nd question (what to view and when in a small scope with light pollution), I can't stress how highly I recommend the truly excellent book Turn Left At Orion, which I am working my way through an old copy of at the moment. It answers pretty much all my questions about what to expect in light polluted areas, what to see with a small scope and where and when to find it. There's a chapter list and preview available on Google Books.
  14. Thanks - I've got a Skywatcher LP filter on the way so it's good to know I may be able to see a good selection. There's relatively little visible to the naked eye here so I thought I'd be quite restricted.
  15. Thanks John - that's very useful to know. I've been wondering if I should be seeing more from my setup. I've only tried Jupiter twice so far. First time was in good conditions at 65x in a 10mm EP, because my barlows hadn't arrived yet. Moons pin sharp and Jupiter was a tiny disk what looked creamy white but it was too small and bright to see any belts. The edge of the disk wasn't perfictly crisp though, despite the moons seeming so. 2nd time was poor seeing - I could focus it to a disk but the moons weren't pin sharp like the first time and air currents kept shimmering the image hence it seeming more like a blob than a disk.
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