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Everything posted by narrowbandpaul

  1. Hi Fraser Yes, I was going to mention the photon transfer method. Its certainly the way I would do it, but it is slightly more involved. Spent a good year doing this at Sheffield Uni (or trying to!) with some CMOS sensors. Paul
  2. Well understood fact about dark current faling with falling temperture. When the camera is cooled, it only takes around 4-5C lower to halve the dark current...ie even a 5C change will have quite an effect on the current and hence noise. Have used the QSI583 at -32C so far (80% cooling) fraserclarke has summed up the difference in sensor design very well. The KAF sensors are well known for being noisier than the KAI and especially the sony chips. as for measuring dark current: very easy to do. Set the temp to the value you use at night (if you can). Take a variety of long exposures say, 1s, 30s
  3. Hi Les Nice image, especially image 2. If you dont mind an observation....I would say that devoting 4.5hrs on Ha and 1.25hrs on S2 and O3 is not the most effective break up of the time. The O3 and S2 are far weaker and hence require most time spent on them. Perhaps something like 2:2:3 (Ha:O3:S2) or 1.5:2.5:3 would allow for more stretching of the weaker lines. Nevertheless you do have a good deal of S2 and O3 showing up. Its just an observation. And as for your setup: Wow! Very nice! paul
  4. Nice image olly! I would be VERY keen to hear your opinions on the ODK as an astrograph. This scope promises alot and is significantly cheaper than its planewave cousin! paul
  5. great image, especially from an unmodded camera
  6. yep, shibby, you are right. There is a 3x increase between unmodded and modded.
  7. M33 Salvatore Iovene Graph on that page shows a Ha response of an unmodded 40D (656nm) to be approx 8%. With the IR filter removed you get roughly a 3x increase to 25% or so. Typical CCD would be >40% at Ha. And many are around 50%. paul
  8. 30% If its anywhere near this high, I will be shocked. 30% is a decent number considering the Ha coming from every nebula is reasonably high. I am sure Christian Buil measured the response at less than 5%!! paul
  9. With good alignment one minute should be possible, with good quality drives, maybe more. The only way of knowing is experimentation. If one minute is easily and regularly achievable, then try 90s and so on. As for the serial-USB cable, PC world or maplins will do these. The remote cable...jessops or a camera store like that should have them. I am trying to remember where I bought mine?? The only goal in imaging is to maximise signal, and minimise noise. We just need to think how to do these things...
  10. Thats the pacman. NGC281 AFAIK. 2 things could be done. More data. Or modding the camera. Works especially well for nebula since they emit lots of red light (from Hydrogen), which the filter will attenuate in unmodded cameras. as for ISO...generally for imaging I would say 800. I did perform an experiment with my 300D, and the read noise fell with increasing ISO but the full well dropped also. For my camera ISO400 or 800 would be good. But newer cameras will have different sweet spots. but bear in mind that just because an image at ISO1600 looks brighter than one at ISO800 doesnt mean that th
  11. the things you could do to improve your situation would be: 1) Ensure polar alignment is as good as you can get it. The better the alignment the longer your subs can be. 2) Take loads of data. I would be aiming for at least an hour. If you use 60s subs then that equates to 60 images. In astronomy there is NO substitute for data. If you can:get more. The fainter the object, the more critical this is. 3) Image reduction: That is, the use of darks and flats. Your uncooled DSLR will have a reasonably high dark current, that is to say, electrons will be generated in the absence of light, creating n
  12. rosette should be quite do-able. Also IC405 the flaming star nebula in Auriga might be possible too. IC405 should be imageable for a good few hours in the evening.... paul
  13. The sensor size solely sets the FOV. The pixel size sets the resolution, ie the arcsec/pix. Whilst it may be nice to have a very high resolution you will be limited by the atmosphere. I estimate that there would be little resolution increase for a sampling of less than 1"/pix the following equations are useful "/pix= 206.265*p(um)/f(mm) where p is the size of the pixel in microns and f is the focal length in mm and FOV(')=3438*L(mm)/f(mm) where FOV(') is the FOV in one dimension in arcminutes, L is the sensor length in mm. Small pixels gather less light but have higher resolution...but too muc
  14. excellent article on the effect of mis-collimation. Thierry Legault - The collimation the hotech laser works quite well, but cannot fully collimate a newtonian. I have used the catseye system, and although confusing initially it was quite easy to get the hang of. very good discussion on cloudy nights as well regarding various collimation errors and techniques. a laser collimator is fine for visual I imagine, but imaging is more demanding of precise collimation. http://www.cloudynights.com/item.php?item_id=2677 paul
  15. that is pretty much the right colour. It is quite blue, because its very hot.
  16. Hi Nick, just for clarification as to the nomenclature used in emission line imaging. The number after the element referes to the state of ionisation. For O[iII], the oxygen atom is missing 2 electrons. In S[iI], the sulphur atom is missing just one electron. The square brackets denote a forbidden line. This is a state which is very long lived, which can only exist in low pressure/density environments like space. The Ha line for example is an allowed transition (from the 3rd energy level to the second). Cheers
  17. the obvious one, is the virgo cluster, at the tail end of leo...
  18. I have imaged from central scotland (56N) at solstice and full moon. You will need a really tight filter <10nm ideally. Baader to a 7nm which is good value. But DSLR's even modded ones dont respond to Ha anywhere close to that of most CCD's, so your options are limited. Even from 56N we only had one hour for narrowband useful darkness. Stick to the brightest objects. The north american nebula is a good one. maybe also the dumbell. Star clusters and planets are of course easier. So you can do stuff, but its difficult. Good luck paul
  19. really quite impressive Luke. You have given me an idea well done. paul
  20. i have used the iEQ45..... its pretty good, though quite noisy when slewing. Certainly looks like an AP, not its not up to the same standard. This could be a very good mount with just a few small tweaks. paul
  21. those are slightly more than rocks.... Brodgar is a neolithic henge and stone circle dating back to around 2500BC. It is a UNESCO world heritage site...according to wikipedia paul
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