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About bobro

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  1. Yes, not a certainty but a possible step forward in understanding (and hopefully a bit of fun!). Could be an issue with PHD2 perhaps, but this didn't work with my webcam until recenltly, so changes are happening. If you are more ready for a bit of hardware testing send me a pm with a paypal email address (or similar) and I will happily contribute £20 towards the purchase of a module. Other suggestions equally welcome. Tonight the sky looks clearer - so off outside to see if I can understand a bit more about how the DIY Coma Corrector works.
  2. Probably down to the implementation and driver - I was hoping someone else would do all of the work and I could then copy it! Seriously though, I'm thinking along similar lines, but somehow just purchasing a QHY.... or similar seems too easy. I have an Arduino Nano that happily will drive an ST4 (or the peculiar interface on my setup) so just need a sensitive guidecam. A collaborative test/venture? Count on 50% from me.
  3. Images look fine for 30 second exposures. The lack of flats can probably be got round with processing for images with small galaxies, but could be an issue for nebulae or single galaxies. Flats aren't really that difficult : keep the scope/camera config unchanged, put a piece of paper across the scope, point to an even source of light at least a couple of meters away (don't point a source of light at the scope) and take flats at the same ISO so that a mid-point grey image is the result. For me the single biggest (and easiest) improvement to imaging was flats - really worth doing! I hope this makes sense/helps? Bob
  4. Great to see the work going into making the EQ3 tripod more stable. Of course, perhaps the main way to show the result is to make a before/after comparison. I've been occupied with imaging using a 130mm reflector scope on a Meade EQ2 mount. This has tubular steel legs - an improvement on an EQ3? So far guiding has kept me occupied enough not to fill the legs with sand, but overall stability has an obvious effect on guiding, but not too much on imaging as my scope has a relatively short focal length of 650mm. I've tried putting weight on the tripod shelf - no obvious effect. Still wondering about sand in the legs - would be useful to see how much an EQ3 tripod can be improved as a reference. Keep up the good work!
  5. On the DIY front, could a module using the AR0130 sensor be suitable? US$39 (including shipping). No ST4 of course.
  6. Yes, I found it slightly tricky trying to find a suitable guide star when imaging the Virgo galaxies - my thoughts also turned to a proper guide-cam. QHY5-II perhaps. Glad you have your Arduino guider working - a great little device! Must admit I don't find using an online telescope too interesting - a bit like downloading someone else's images. DIYing is more fun for me!
  7. Previously I posted my efforts at a DIY autoguiding setup This setup used a Raspberry PI and Lin_guider for guiding, driving DC Economy RA motors for RA and DEC and works well. As an alternative (and simpler/lower cost setup) the PI/Lin_guider combination has been replaced by PHD2 running on the laptop and an Arduino Nano acting as an Ascom interface to drive the Economy RA motors in a similar (though not identical) way to an ST4 interface. This is a potential, and very low cost, way for someone with a basic reflector scope without Goto to upgrade to a single or dual-axis guided system. It does require some DIY skills though. Note the motors cost about £30 each and are simple DC - not stepper motors. Some scopes come with a single RA motor. Only 3 batteries in the setup : PC, RA motor (PP3), and camera. The DEC motor is driven by the Arduino output and hence the PCs USB output. Code for the Arduino is at : Testing so far has shown the setup produces a similar guided result to the PI/Lin_guider config. Having PHD2 on the laptop provides a very good set of utilities for polar alignment etc. Although Astro Photography Tool is used on the PC, any image capture method could be employed. There's not a great deal in the sky other than small galaxies I can image at present, so apologies for the lack of images. Galaxies images are composed of 300 second subs. If there's interest I can post more details.
  8. I checked on the lenses I ordered from Eskma - they are 25.4mm dia. Part numbers 111-0222E (bi-convex) and 112-0227E (plano-concave). HTH
  9. Certainly I do wish to test out the CC more, but clouds are doing their best to prevent this! In particular bringing the lenses closer together. I'm also testing out a guiding setup of an Arduino Nano driving simple DC RA/DEC Economy Motors (not steppers), with PHD2 controlling this. Seems to work, but perhaps I need to move to where there are clearer skies - living on a small island means sea mist can scupper efforts even if there are no clouds!
  10. First attempt at a 'proper' image with the new config of Arduino/PHD2 driving the Economy RA/DEC motors. Of course clouds did their best to thwart this : only 6 subs at 5 minutes. Trouble finding guide star so this was a bit away from the image - result was trailing (tried to fix in processing) due to polar alignment not being good enough. Still good to see M58 and the Siamese Twins in the image, plus a few other smaller galaxies.
  11. Curious halos around the galaxy - a misty night perhaps, or flats not included in processing?
  12. Yes, there are many questions when deciding on a guiding setup! Each setup is different, so that means there isn't a single correct answer. Anyway, possible responses as follows: Pixel ratios guider:imager - Orion suggest their 50mm guide scope is good for scopes up to 1500mm focal length. Of course that doesn't mean a lot on its own, therefore the pixel ratios make for a good comparison. With a very good guiding setup, a ratio of 10:1 could be possible, with 4:1 being conservative. So both of your suggested image scopes look ok. Flexure - haven't noticed this to be problem (I'm imaging with the Orion 50mm at 650mm fl), though my EQ2 is way below any required stability requirements for imaging. Assuming you are imaging up to 750mm focal length and everything is well tightened, flexure shouldn't be too big an issue. Added weight - best to keep weight down so that the mount is in control and not the scope. Aperture/guide star brightness - depends on the guiding camera. in my case a simple webcam, so a low f ratio means more/brighter stars. If a purpose made CCD camera is used then not so important. Weight & stability - the mount is trying to keep the scope/guide camera under control, so best to keep scope/guide camera weight down. With a good solid mount, such as an EQ5, that will track well (assuming appropriate polar alignment) for many minutes, a guiding system only need gently nudge the mount in the correct direction from time to time. Mount periodic error is perhaps the real issue that guiding is trying to deal with as PE can suddenly appear from nowhere and needs to be corrected quickly. It would be great to see an 'equation' covering the many parameters of a guiding setup. A PhD thesis perhaps? Would be good to hear a few more responses on this often discussed topic!
  13. As light from the panel is not focussed, if the cloth is left on the scope and the panel moved away from the scope (say 12 inches), the banding should reduce if not disappear.
  14. Anyone know why the global Sky-Watcher site shows the EQ3 with a steel tube tripod , yet (in the UK at least), it is sold with the aluminium tripod that doesn't seem great for stability?
  15. The ratio based simply on focal length is a rough starting point. However, a guiding setup works by monitoring pixels on the guide camera and will try and guide to this. The movement between the guide camera's and the imaging camera's images is based on focal length and pixel size - this is measured in arcseconds per pixel (aps). Your imaging scope has a focal length of 750mm and the imaging camera a pixel size of 4.3um. aps_imaging = pixelsize * 206 / focal_length = 4.3 * 206 / 750 = 1.18 arcseconds per pixel (each pixel of the imaging camera covers 1.18 arcseconds of the sky) An Orion mini guide scope has a focal length of 162mm. Although the guide camera has not been specified, assuming a QHY5-II Mono with a 3.75um pixel size : aps_guiding = 3.75 * 206 / 162 = 4.77 arcseconds per pixel For good guiding, a maximim ratio of around 4:1 between aps_guiding and aps_imaging is often suggested. This is based on modern guiding software being able to guide to sub-pixel accuracy. The above guiding/imaging setup gives : aps_guiding / aps_imaging = 4.77 / 1.18 = 4.04 So the above system is at the bounds of the typical match between the guiding and imaging parts of the setup and should be ok to go ahead with (other factors such as mount stability and seeing can make for much bigger variation). HTH.