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narrowbandpaul

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Everything posted by narrowbandpaul

  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 t
  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 imag
  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 co
  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
  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 an
  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 vi
  16. Hi Zak, Interesting choice of camera. Why the choice of the RS version over the 683? Are you planning on doing any kind of science with it? As for cooling the lower the better. I stick with the cooler at about 80% ish. I have never had any issues with this. The QSI is a good camera and the 8300 a good sensor. You'll enjoy working with it. Paul
  17. Hi all. Thanks for the responses, Dave is right with regards to how flats work. Each pixel in the flat is divided by the average. This creates a correction factor that then normalises the response of all pixels in the raw image. A high signal flat doesn't lead to large numbers for the correction factor, it leads to a high accuracy correction factor. As I said before the quality of a flat is signal per flat x no of flats. The issue of low signals used in the SX cameras is interesting. There could be a link there, although correlation doesn't always imply causation. I think it's possible for cam
  18. Hi Ivo, Thanks for your response. I will respond to your various points in order (replying in my post was a good idea, very easy to see what comment you were answering) 1. There might the odd user who doesn't know that the saturation ADU will be around 60-65000. They may only know that they want about 1/2 of max. Just a thought. Also what about DSLR users? They normally have 14bit raw files. Do you show these raw files on a 16bit scale, or on the native 14bit. If 14bit the camera will of course saturate near 16000. 2. Sounds good 3. Fair enough, although I do think there is some value in quoti
  19. Hi Ivo No worries. I would just say saturation ADU is about 60-65000 but I don't think there is much point in displaying it. What's important is the target ADU. Instead of quoting the absolute target ADU why not express it as a fraction of this fixed Saturation ADU. Ie specify the percentage of saturation you want rather than the actual value. What happens if the required exposure time for your target ADU falls outside the min or max exposure. I have used an EL for narrowband flats and the S2 filter was like 30s whilst the O3 was just a few. How does the software calculate the signal in the f
  20. Strange? Actually quite rude to you. Where there are the gullible you will find charlatans. Those that don't know any better buy in to it. If the guy tries to make money off of this then surely he is committing a crime. I hope the guy doesn't actually believe he is better than NASAs space probes, does he? I mean he must know its bogus. Surely.
  21. I watched that Canopus video. Was he trying to say that was the actual surface? Wow. I thought I wonder what point he is trying to make here about seeing conditions. I never even thought he was suggesting that a defocussed image of a star was actually it's surface. Wow. Just wow.
  22. I googled Hidden Micro Image retrieval also. Nothing. If this was a legit technique there would be papers and such like. Also 60s for Pluto is impressive. It's average mag is about 15. Need more than 60s to go as deep as that. Angular size of Pluto is, based on size an semi major axis 0.04". To even resolve Pluto he would need to better the diffraction limit of his 14" by a factor of 8. His "Pluto" images show surface details, so this factor must be even larger. Even the HST struggles with Pluto!
  23. Thanks Carole, Stephen. How do you determine what works best and what doesn't. How do you quantify it? Paul
  24. Hi All, I'm curious as to how bright your flats are and how you came to this decision. I see lots of different numbers being quoted and I'm interested as to how you came across these. The quality of a flat field can be expressed as Quality=Signal of single flat x Number of Flats. This quality term actually makes an appearance in the mathematics of flat fielding By using a low value for signal you only end up hurting yourself. You need a high quality flat to minimise the injection of random noise. Using 1/3rd of saturation and 10 flats just won't cut it really. You do want to keep your flats in
  25. Further information from Richard Crisps site. http://www.narrowbandimaging.com/images/Flat%20Fielding.pdf Cheers Paul
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