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Thommy

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About Thommy

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    Nebula

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    Stenloese, Denmark
  1. CSX-249 would be sensitive due to the pixels size. With regard to dynamic behavior it is not optimal. With a full well depth of 33k and, say 2 e read noise (should be lower according to preliminary specifications), it has a dynamic range of 1:16500 which is very good, BUT since dataformat is 12 bit, you only have 4096 stops. For this camera a data format of 14 bit would be more appropriate to take advantage of its dynamic range. For CSX-304 the dynamic range is 1:5500 which is consistent with 12 bit.
  2. Excellent! I think the colour is right where it should be. Regarding Ha, this object doesn't really give any Ha signal. For some reason that I'm not aware of, there are no prominent HII regions in NGC 3718. I've never seen a photo of NGC 3718 with visible HII regions. This is a bit surprising - the close encounter with NGC 3729 should initiate a lot of star formation, and certainly there is plenty of young star clusters. So why don't we see any HII regions? That said, it could add a bit to NGC 3729, but probably not much. For other interacting galaxies, e.g. the cocoon galaxy, a Ha exposure is definitely adding a lot to an image.
  3. I currently use a SX MX7 but with a retrofitted Sony 829 chip in combo with a MN190. The large pixels (not square!) gives me a resolution of around 1.9 "/px which is just too low. CSX 249 would increase the resolution to 1.3 "/px and increase the field size a bit as well. That´s fine with me as I normally image galaxies spanning no more than 15-20'. Actually I consider the new SX Trius 825 or 694 Pro or as well, should I decide to continue with CCD's. Anyway, the discussion in this thread brings some interesting information...
  4. Steve, as I seriously consider the CSX249, I wonder if you have some more information by now from SX?
  5. Yeah, children can be like that! For the last few years I had to reduce my imaging to a minimum due to those beasts. Indeed, a very interesting presentation. I think the right way to look at it is to use the theory as a starting point for all the tweaking. The span of trial and error component is very reduced when you have an idea where to start.
  6. That's a good question, James! Perhaps we will have some opinions on this. Glover does a good presentation - just a shame that he had to skip the gain part. Nonetheless a difficult choice. With my suburban sky, I would probably be better off with a cmos, but I would have to add a new laptop to cope with the extensive number of subs. The low read noise of the new SX trius pro series may be a good compromise
  7. Thanks a lot for the detailed explanation. I can see that I need to study the CMOS technology to understand this better. If I understand you correctly, getting the most out of a CMOS based camera nails down to finding the optimal gain, where read noise is low. This also reduces dynamic range, so using short exposures (not to fill the well) but take lots of subs would be the way forward. This would result in a similar S/N and dynamic range as a CCD with similar total integration time but using longer subs. Is that about right? So the advantage of the CMOS would be lower price of course, but also that the shorter subs are more forgiving to accuracy of mounts but the downside would be generating more GB data. So there's no particular advantage in choosing a CCD when only imaging faint stuff and not like M31 or M42?
  8. I'm planning an upgrade from my current mono CCD. Apparently a lot of people go the CMOS way these days, so I consider whether I should follow the trend or stick with the CCD. I'm primarily interested in imaging faint far-away galaxies. I noted the new CMOS cameras from SX, but one thing worries me: They are 12 bit whereas CCD cameras are 16 bit. I know that you gain contrast when processing the images, so does it matter?
  9. Very nice! I prefer those "unknown" galaxies as well. I gave up imaging until it starts to darken again - I'm amazed how much you catch with such a short exposure. Definitely worth the effort. /Thommy
  10. I don't have any experience with PEC. But I've considered using it on my EQ8 to prevent some rapid movements in the gears. So just some general observations: If you use PEC you would probably set the aggresivity of the guiding much lower, as rapid movements should be removed by the PEC - otherwise you would overshoot leading to a higher RMS figure. If your gears are of good quality, and the grease is clean and free from debris, you would probably not expect much of a difference. Just some thoughts ... /Thommy
  11. IF you want to keep your handset (which I do), you don't actually need EQMOD (I don't). In CdC you just have to synchronise first, e.g. using a bright star, then you can slew to your object directly from CdC. Probably the same for Stellarium.
  12. You can disable guide outputs in phd guide. As far as I remember it's in the menu and not in the brain, but I might be wrong. Should be fairly easy to find though. With this option ticked you can still follow the guide curves. /Thommy
  13. Nice catch! The Mesu should do better than 1" RMS so if you don't guide you'll probably be better off.
  14. Very nice, Wim, and congratulations with your new toy! I wonder what your impression is with the focuser. I'm very pleased with my MN190 as well, with the exception of the focuser and in particular the built-in extender. However the optical quality is exceptional. Also nice to see a not so often imaged target. By the way, the Pegasus cubefocus looks interesting .... /Thommy
  15. Really nice - and wide? My field is so much smaller - currently have a go at IC 417, but clouds, a flu and crying babies effectively put that to a stop! Something wrong with the colour - particularly evident in the lower left where it looks pinkish? /Thommy
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