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JohnSadlerAstro

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About JohnSadlerAstro

  • Rank
    Sub Dwarf

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  • Gender
    Male
  • Interests
    Aerospace, Aviation Gaming, RC Aviation, Electro Swing, Technology
  • Location
    Chippenham, Wiltshire
  1. JohnSadlerAstro

    Imaging with the 130pds

    Thanks! Yeah, those are well written and explained. I wouldn't recommend trying my method for now, it needs some more work to 100% prove that it works and to sort out some miscalculations etc which cropped up! John
  2. JohnSadlerAstro

    Imaging with the 130pds

    Hi, 1. The collimation was "correct" according to the Cheshire on all of the images, with the secondary centred and the primary dot lined up etc. However, it has been around 8 months since I collimated last, and I think things have drifted a little, theres a tad more coma than usual in some parts of my latest subs. 2. I'm planning to re-collimate next week in time for the new moon using this method so I will post up some shots once its properly done, but here's what it looks like atm. John
  3. JohnSadlerAstro

    Imaging with the 130pds

    Hi, As far as I know it isn't a standard method of collimation, I had to develop it after my Cheshire showed the scope as collimated but my subs showed severe coma and distortion across the upper right hand third of the fov. This drawing sort of explains the idea, sorry about the quality! The main concept is that coma and *secondary* light-cone misalignment are related when primary misalignment is removed. Image coma and vignette are in the same places as each other, when the primary is collimated relative to the secondary. In other words, the method can only adjust the secondary and therefore requires use of a Cheshire to keep the primary constantly aligned with the secondary throughout the process. To get a flat, I simply take a quick shot through the scope with my laptop screen open in Notepad, and then take the result into GIMP or StarTools to do a full desaturation and a savage clip/stretch. This was the result from the scope before any secondary adjustments, bear in mind that at this point it was "perfectly" collimated according to the Cheshire *and was rotated/centred almost perfectly, too*. The dark gradients were indeed in the same place as the bad coma, and they fell in the position I had predicted. As shown on the diagram, I then worked out which direction on the photo was which direction for the secondary, then started to adjust. Throughout the process the corrections were perfectly logical and followed my 'hypothesis'. Note that the same stretch has not been applied to each flat, I altered the black point etc to optimise each one for the section I was trying to clean up. Shots 1-3 below show me getting the vertical (horizontal for the secondary) axis correct, then numbers 4-5 show me rotating the secondary into place. After a bit of work I got this ^. Most of the adjustment I had to make was rotation on the secondary, (up is to the right on the photos, so it was drooping a bit) and a little bit of centring with the vanes; I made sure that the primary was correctly adjusted after each movement of the secondary before I took the flat to estimate mis-collimation. I was then able to get almost entirely coma-free images. Hope this helps John
  4. JohnSadlerAstro

    Imaging with the 130pds

    Hi, That's looking really good. Secondary collimation is a pain with the PDS, I used flats to get the rotation right in the end, and it worked quite well. John
  5. JohnSadlerAstro

    Where are the Canali?

    Hi, Thats really interesting! I knew someone on the forum must have "seen" them at some point, but perhaps was too embarrassed to say! John
  6. JohnSadlerAstro

    Where are the Canali?

    Hi, So there are a lot of theories about what they actually were. Possibly the "sightings" were from a combination of those? It would be really interesting to actually look at Mars through those great refractors and see what it looked like, I think the Lowell one is still in existence? It is rather disappointing though. A river cruise on martian waterways would be quite a nice holiday. John
  7. JohnSadlerAstro

    Where are the Canali?

    Hi, I was reading W E Johns' sci-fi book Kings of Space, which pre-dates space flight and is very over-optimistic about life on other worlds etc. One part left me rather confused: the Martian Canali. In the book one of the characters explains how they were spotted by Schiaparelli and mapped by several astronomers (and are later discovered by Johns' explorers to be inhabited by giant swarms of killer mosquitos). It's now known that these do not exist, and the standard explanation is that they were simply an optical, visual, or mental aberration that was mistakenly identified as an actual surface feature. However, although many astronomers were really certain that the canali existed back then, I've never heard of anyone seeing them more recently? As they were an aberration of some sort, surely certain types of scope will still show them, perhaps the scopes that were actually used to map them? Or should Schiaparelli just have gone to Specsavers? John
  8. JohnSadlerAstro

    Imaging with the 130pds

    Thanks! I'll keep a look out for that, I'm interested to see what it will look like with more resolution! Eyy, its about time the galaxy gets some attention, searches suggest its not a common target! A word of warning--you'll need long subs, as it does have a low surface brightness--mine were too short really and found that teasing out the arms was quite a challenge. Thanks for the likes, kind words and encouragement! John
  9. JohnSadlerAstro

    Imaging with the 130pds

    Hi, I hope you get on well with your choice! One thing I will say about the EQ5-It looks waay better than any other EQ mount on the market! John
  10. JohnSadlerAstro

    Imaging with the 130pds

    Hi, Yes, for size and weight those two are very nicely matched. However, I would just warn you about using the EQ5 for guiding--I tried it and it was quite frustrating, I ended up upgrading to a used NEQ6. It might be worth considering an HEQ5, which is really designed for astrophotography--it is also a bit sturdier so it will be able to hold the 130 really steady. Hope this helps, John
  11. JohnSadlerAstro

    Imaging with the 130pds

    Hi, My first data this year! I cant believe its been so long, but finally I'm back to imaging again! The NEQ6 worked a dream, an average of around 1" total RMS over the night, for 4 hours! I was able to keep around 80% of the frames, too. NGC2403, A difficult target that's probably a NASA copy-paste of M33. 130PDS on NEQ6, Guided with ASI120MC and 50mm finder 1000d, 200sec subs at ISO 800, 3hr 30mins DSS, PHD2, GIMP Star Tools It's a really exciting area of the sky, loads of galaxies and some beautiful colour contrasting binaries. The processing is pretty awful, but there was a really large gradient on each side of the image that was a big pain to remove and took most of the colour with it. I put picture alongside some 100x100 crops to highlight all the little fuzzies. And then compiled them into a table, because the weather was bad. (Square brackets are my data, SIMBAD and the NED are disappointingly incomplete) It's a testament to the miraculous abilities of the 130PDS that I could catch a magnitude 19.4 active galaxy with very newbish processing, a bad camera and a complete lack of experience over the 12 months. Clear skies! John
  12. JohnSadlerAstro

    NGC2403 & An Experiment

    Hi, My official first light with the second hand NEQ6! I'm really pleased with its performance in all aspects, it's enabling me to get some good FWHMs on long subs and take advantage clear skies to the full. Sadly my camera, a modded 1000d is not so happy these days--ive noticed that noise is increasingly becoming an issue. Either this is because im imaging fainter objects or theres something about to break, Im not sure. I decided to try something a bit different this time, as the image itself isn't amazing from the aesthetic point of view. NGC2403 is almost a clone of M33 the Triangulum Galaxy, but is a tiny bit dimmer in surface magnitude so its an awkward one. There was baad gradient at the top and bottom from who knows what, and the colour just wouldn't work as a result. But then I noticed there were a lot of fuzzies in the background and thought it was time to give them some attention. 130PDS on NEQ6 Guided with PHD2, ASI120MC & 50mm guider EOS 1000D at ISO 800, 200sec subs ~ 3hr 30 mins Stacked DSS, Processed Star Tools & GIMP Tables in Word, compiled in GIMP Identification from SIMBAD & NASA NED The crops are all 100x100 pixels, so thats around 181 x 181 arc sec. Some of these are quite faint, like the NVSS which shows up as a really odd blue dot contrasted against the LP. I compiled the results from SIMBAD and NED searches into a table. 9 of the galaxies I cant identify so I just recorded their estimated magnitudes and exact positions along with some notes. Perhaps someone will be able to help out with these? Data was very incomplete even for the identifiable ones, so I added some extra data of my own, which appears in the table in [square brackets]. (I used SDSS data from SIMBAD quite a bit to get the galaxy types.) There's a lot of interesting stuff in this part of the sky, some blue dwarfs, lots more galaxies and galaxy clusters that I missed, and several beautiful colour-contrasting binaries. I could have started identifying some of the objects within 2403 itself, as well but ran out of time (and patience)! This is the original, theres a particularly notable blue dwarf about one 2403 diameter above the main galaxy, it shows up as something looking a lot like a hot pixel. I'm aware that attempting to identify all the galaxies in images and cataloguing them isn't standard practice (probably because its *very* tedious ), but it would be interesting to hear people's views on this, and what the strangest objects that you've found are? Clear skies! John
  13. JohnSadlerAstro

    StarTools problems

    Hi, That should sort the issue out, the other thing you could check is that STar Tools is in 64 bit for your system. John
  14. JohnSadlerAstro

    StarTools problems

    Hi, That is a pretty massive FITS file, mine are normally around 59MB. Are you drizzling the image in DSS, by any chance? John
  15. Magnitude 19.5 radio source? No problem for a 130PDS! :D All will be revealed later....

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