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narrowbandpaul

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About narrowbandpaul

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    Central Scotland
  1. Thanks for all the feedback. Invaluable as ever.
  2. Hi All What is the best way to run EQ8 in SkyX. The mount will operated remotely and autonomously using SkyX and ACP. Am I right in thinking that it is the EQDIR cable plus the EQMOD ascom driver? are there better ways to operate the EQ8? Thanks in advance! Paul
  3. I'm most of the way down the line to a remote setup at IK's site in Spain. Its shared with two friends which makes things bearable cost wise. We are all friends so deciding targets should be a gentlemanly affair. Several factors encouraged us to go down the remote route. The obvious one is weather. There are lots of nice imaging setups in the UK that cost lots of money and only see stars a couple times a month, maybe less is Scotland. With the promise of approx. 250 clear nights, 2500hrs of clear dark skies, running remote suddenly doesn't look so expensive. So far I have really enjoyed the process of getting stuff together. It began at astrofest last year. All great plans are hatched at astrofest. From looking at mounts, spacing the rights adapters, reading manuals, testing under the few clear nights we have its been a good way to keep the mind active and focused on a goal. What I've learned is that you need to very sure what setup you are going for, get it all configured before you actually buy things. Changing your mind half way through can lead to tears. You need to know that all the bits you want will work together and will fit in the back focus available. There seems to be an opinion that in order to do astroimaging properly you need to sit and watch every photon enter the tube and set up from scratch each time, like doing otherwise is dishonest. This is of course nonsense. you don't need to sit there watching it collect data. You can sleep and let it collect data. There is far more involved in setting up a remote telescope with internet connections, and remote power switches and so and getting it to run reliably from 1000s of miles away. It is in fact quite an achievement, unlikely to be mastered at the first or maybe even second attempt. For me, messing about in evenings that aren't quite ideal trying to grab one hour of data before the tree gets in the way, moon rises and clouds come in is just a waste. It takes a while to get everything going and these nights only bring frustration. If you want to get lots of data to make nice pictures or do science then remote is the only choice from the UK. Otherwise an object will take a season to do well. Its not fair that we live at 50N, the worst place on the planet for stable weather but you have to play the hand you're dealt. Yeah its not cheap, you need to spend the cash to get a reliable system, an unreliable system will cost lots more long term. That's my take on it. I'm obviously very for it. Sending it all out in a few months. Maybe it will be a nightmare. Who knows.
  4. and for RBI info, as Olly points out Richard Crisp is the guy for it.
  5. here is the cloudy nights thread about the ambient temp dependent bias frames for the QSI683. Cant help but think this should never have been an issue http://www.cloudynights.com/topic/498053-qsi-683-vertical-banding-issues-solutions/
  6. Regarding RBI, it is not an issue for interline sensors as pointed out. Only full frame KAF type sensors. In a nutshell, there are mini-potential wells at the epi-bulk interface which are handily placed to trap NIR photoelectrons (electrons generated by absorbing NIR light) during integration. Over time these trapped electrons will detrap just like dark current (as a result of their thermal energy). Point a KAF sensors (particulary the 16803 and 09000) at a bright star, then take a long dark....you'll see the star in your darks. This detrapping causes havoc for precise calibration of images, so the only way to deal with it is to fill all these traps prior to every exposure. Then all images start from the same condition and things calibrate nicely. The dark current is increased considerably as a result and deep cooling is essential. I have been testing a PL16803 that I have a share of and the rbi is significant, but its the only way. Some will say that a good work round is to run the sensor warmer than normal so that the traps empty faster, then continue imaging. How anyone thinks that is a hallmark of a good camera is beyond me. Its not solving the problem, its a work round that the manufacturer suggest because they cant be bothered to fix the problem. And these aren't small companies either..... Anyway, i've mentioned a wandering bias level as a possible cause of inaccuracy in the flat process. This has been observed with the QSI683 where the offset changed with ambient (not ccd) temp. I can only suppose that the electronics are to blame, maybe a lot of use has taken its toll. Maybe send it to terry. He turned round a camera for Uni of Glasgow pretty fast. Until the results are repeatable its impossible to say what is the cause
  7. Hi Glappkaeft Yes, f ratio only isn't enough. The problem is that everything is intertwined. Changing one whilst varying the other will affect the third. The etendue argument seems good and I remember from my days as an undergrad. I suppose 2 set ups are identical if the deliver the same etendue per pixel. I will check the derivation myself as every scientist should do! Cheers Paul
  8. Longer exposure with an uncooled sensor will significantly increase the noise in the image. It means an accurate calibration is much more essential which is hard to achieve when temp is unregulated. It's possible but it ain't easy!
  9. You need to be very careful with lasers obviously. I'm sure it goes without saying to never point them at aircraft. It's illegal in the UK not sure about the states. 5mW ought to do it. There are different classes of laser based on power and overall danger. There will be a limit to what you can obtain. My friend once had a 50mW and that was very bright! Green is best as it's near the peak response of the eye. They are frowned upon at star parties I believe. Paul
  10. Understanding how all these things work I find very beneficial in imaging. Doing something without understanding what it does is a no no for me. I'm not advocating becoming a scientist or anything but a little understanding will go a long way. Learning a little about how stellar spectra differ from nebula spectra will tell you why NB filters are good for nebulae but of less use for galaxies, except in the star forming regions. Understanding a little about how light becomes an image in your camera and what kinda of noise there is and how it's dealt with will improve your imaging. Fact. These concepts aren't too difficult to understand. The answers already exist on google and SGL so a simple search will answer the questions. Having a basic understanding of the imaging process, from polar alignment to telescope optics, from filters to camera, from image calibration to processing and from stars to nebula is, in my opinion, essential. Some say that it's not required. That you don't need to understand any of it, even at a basic level. That doesn't wash with me. It's nonsense. Look at the big guns. I don't know of many top imagers how don't have a reasonable understanding of what's going on either in space or in their telescope or camera. That's not to say that they know it all. Some imagers, including the top ones don't have a grasp on things that they probably should. I'm not saying that I do. I'm not as arrogant as that. In fact I know what I don't know. Some people don't know what they don't know. They are the dangerous ones. They say things that are unjustified and people swallow it up because if "he" said then they must be right. My original point is that most of the top guys know what's going on to some level. This is the common factor. Having the right tools for the job is not guarantee for success. A good set of golf clubs doesn't make you Tiger Woods. You need to know how to use the equipment to get the most out of it. So my advice is to keep asking questions and read up in things. The more you know the better your images will be. Fact. I'm not sure if I went off topic here, I lost track..... Cheers Paul
  11. You will often find excellent transparency associated with low pressure and especially with cold fronts. The lifting of the lower layers removes a lot of the pollutants and disperses them high far and wide. In summer during high pressure the descending air collects and traps pollutants in the lower levels making for very hazy days. A good test for transparency is to look at a distant object during the day. If it has high clarity the transparency will be good. If you can't see it it's bad. Seeing is caused by temp and pressure fluctuations in the atmosphere. This causes the refractive index of air to change on timescales of 10s of milliseconds up to a few seconds over patches a few cm across. Local affects count for much. Avoid looking over houses as others have mentioned. The heat given off will change the refractive index and disturb the path the photons travel. Concrete after a hot day is bad too as it retains heat for a while and then radiated it at night. Even your scope will have a residual heat if recently taken from indoors. You have control over a few things. In terms of the atmosphere, ideally you want little change in wind speed with altitude. Look at aviation forecasts for the winds aloft. The met office have a free subscription for general Aviation weather forecasting. They have a spot wind chart from surface to 24000 for the UK and Europe. To have such little change in wind speed you need high pressure where the isobars are widely spaced. This high pressure may trap pollutants though. Local conditions will determine the transparency. It depends in how high you are and how much crud is present in your local area. Low pressure is associated with tightly spaced isobars and generally high wind speeds. This doesn't lend itself to good seeing. Position of the "jet stream" also would be something to avoid. A jet stream is any wind over 60kts and it is generated BY the polar front depressions that hit the UK every couple of days. The weatherman never explains this correctly. The met office also forecast the jet stream position. So good seeing is normally encountered with high pressure and good transparency normally with low pressure or cold fronts. As with anything with so many variables only looking at the twinkling will tell you. Paul
  12. Hi Astroblagger I'm guessing you must be near auchterarder. I'm in the Stirling area. You will have some fairly dark skies up there. As for exact locations I can't help too much. Perhaps use google street view to get an idea of the horizon. The darkest skies would be to the N or NW, towards Muthill or Crieff. There is a road that goes from just north of Braco to Comrie. It's quite a good driving road but it feels pretty remote. Skies should be reasonable from there. Hope that helps Paul
  13. It's only the focal ratio that matters for determining the speed. Proven by both theory and experiment. Signal received per pixel depends only on the focal ratio. Aperture plays no part. The experiment is proved by DSOs requiring very long exposures at f10 and much shorter at f3. Time to reach a given SNR is shorter with the f3 scope. Perhaps it's counter intuitive but you shouldn't apply any prejudice you may have acquired from visual astronomy. The experiment and theory are in agreement. There is a reason people to mad for the latest ultra fast scope. If aperture was king, fast refractors and the Ricardi Honders would be overlooked in favour of an SCT or large newt. Aperture sets resolution, focal length sets image scale and focal ratio sets time to a given SNR. I don't suppose a large aperture and a fast f ratio will hurt things. Apart from your wallet. Paul
  14. You need high QE and low read noise. The KAF3200ME or the sony 674/694 fit the bill. Smaller pixels would allow for higher positional accuracy if that's what you are in to.
  15. Hi Ivo. 1. Normally the green would be brightest as the QE is higher. You could quote the average or max values in each channel, thought I'm not sure if it required. 2. Good point. With short subs the chance of saturation would be low I think. It should still be valid though to use the max. If an exposure shows that a pixel is overexposed then there is no way you can get a sensible value to correct the flat. The best thing to do would be reduce the exp time so that the brightest pixel is at an appropriate level. Hope that made sense. Alternatively you could show a histogram and the user can visually see where the peak is. Or you could median filter to remove the hot pixels. I don't really have any software know how. Just some thoughts as to how it might be improved. Perhaps some these suggestions are easy to describe but difficult to implement. Cheers Paul
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