Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

sgl_imaging_challenge_banner_supernovae_remnants_winners.thumb.jpg.a13d54fa405efa94ed30e7abd590ee55.jpg

Darth Takahashi

Members
  • Content Count

    1,043
  • Joined

  • Last visited

Everything posted by Darth Takahashi

  1. My Neighbours are dutch so they don't care what I do so long as its in my garden Although I do try to be considerate when breaking down the kit at 04:00 in the morning..! Neil.
  2. To be fair I think there is a little more to it than these simple price comparison would lead you to believe. Such as the quality of the glass and the figuring / polishing of the lenses etc... However that said there is currently too much of a premium loaded on the top end APO's. It would be nice to see a few more images uploaded from the group demonstrating the qualities of the different refractors available today. Perhaps we could all agree on a particular target and exposure time etc... I know it quite subjective since the camera plays an important part, however there must be enough of us using a DSLR of one kind of another? What do you think? Neil.
  3. That's right, there are always going to be trade off made to achieve faster optics. F15 is fine for visual use on bright objects but its of limited use when imaging. Coming back to the point regarding focusing for each colour RGB or narrow band, I think you could only do that automatically. Its difficult enough to achieve the correct focus for one image so doing it 3 three times or more would be problematic at best? Here is another image taken with the Vixen Neo N120. (click to enlarge) Neil.
  4. Thanks Martin, I did learn something tonight (currently at GMT 9) I have never even thought about that, using a known G2V star at the zenith as a reference! I suppose that you really only need to carry out this procedure once for a known optical train and then its done, correct? Any minor variation from different declinations would be just that minor i suppose? I have the same problem as you in Holland, better things to do with my clear nights. The frustration for me is Japan must have at least 4x the clear night, especially in the winter but I have no telescope and the bright lights of Tokyo on my doorstep :? Neil
  5. I might be missing the point of this discussion or about to learn something myself! However, I thought that there are standard formula's for combining RGB and LRGB images? Well if you can call them formula's. I've seen that depending on the filters you are using you need to adjust the ratio's from 1:1:1 to 1.10:1:1 (RGB) etc... My understanding is that the cut off point of the filters are not exact and that this affects the R channel the most. Once you have a colour image I agree that its a matter of perception as to how the final image should look. Anyway I'm looking forward to receiving the groups feedback regarding the above point. Neil.
  6. I believe that the main point we agree on is that yes an Achromatic telescope can work well visual so long as the focal ratio is not faster than approx F9/10. Anything shorter than this needs a much higher degree of colour correction. Again, personally I believe it necessary to use ED glass for shorter focal ratio's such as F8/7 or lower etc... The Petzval design helps to flatten the field but it does nothing to improve the colour correction and at F6.7 these telescopes are just too fast for their own good. That's a real pity since these telescopes are obviously aimed at imaging. Perhaps a minus violet filter would have helped, in the end I went down another route. Neil.
  7. Whilst I'm current working overseas and have no opportunity to do any imaging at the moment I thought I'd organize my photos. I came across some older photos made with a Vixen 120N neo-achromatic telescope. This telescope is an achromatic type with a built in field flattener which is perfect for imaging, or so I thought. Unfortunately, it didn't live up to my expectations. You see a lot of discussion regarding the two different type of refractors, however, they say a picture is worth 1000 words so lets give it ago! Vixen 120 NEO-Achromtic Telescope (click to enlarge) TAK TOA130F Apochromatic Telescope (click to enlarge) Big difference! Yes the exposures are not the same and there is a tracking problem with the first photo. However, this still nicely demonstrates the difference between the two types. You don't need to buy a TAK to see the difference, any well correct doublet from Vixen, Borg, WO & others will do. Yes Vixen do make good telescopes its just that I personal wouldn't list this version amongst them! Chromatic aberration, the purple hazes that appears around the stars is unavoidable went imaging. The build up of the signal also means an equal build up of purple haze. Normally when discussing chromatic aberration people talk about viewing Venus or the limb of the moon because its only detectable by eye on the brighter objects. So the moral here is if you intent to take this hobby further and into imaging you might as well save a little more money for Apochromatic telescope. I move from this telescope to a WO Zenithstar 110 and was very satisfied. Its was only some years later when I started working in Japan that I had the opportunity to purchase my dream scope, the Takahashi TOA130F. I hope this helps which the most critical decision that you will make in this Hobby. Clear Skies, Neil.
  8. I agree with Paul, if the QE was 100% then every photon would result in an electron being kicked out of the CCD well. The area question is more interesting, yes more photons arrive on a larger pixel (photons / sec) but does this make any real difference? The reason I ask is because the photons arrive randomly? Therefore, to measure the rain falling on my roof I don't need to measure all of it just a representative sample of it. However, there is definitely a trade off in pixel size versus sensitivity and image resolution. Neil.
  9. To be fair to its an easy mistake to make and yes all the important elements in Earth Atmosphere are in Di-atomic pares but that's another interesting discussion. Neil.
  10. The simple answer is that nearby stars radiate their energy into a nearby gas cloud, the nebula. This then ionizes the gas in the nebula (Electrons gain energy). The nebula then re-emits the energy in the form of light (Photons) now at specific wavelengths determined by the ionized gas. Hydrogen being the most common. Interestingly, young blue stars that emit lots of ultraviolet light ionize gas the most efficiently. So depending on the gas and the amount of energy to ionize it, will all determine the emissions that we can detect. Narrow band filter are simply tuned to let a specific frequency / wavelength of light pass through them. OIII = Triple ionized oxygen Neil.
  11. Billy and Brendan, Thanks for your inputs, I'm listening, its just given all the variables of astrophotography its a difficult decision to make! Its interesting what you said about averaging 40 subs because I've being going in the opposite direction, striving to get the longest exposures possible. Perhaps the only thing I'm achieving is to raise the background signal. Its just with our weather we don't get many opportunities to gather our image data. Anyway, I've decided to try and pickup a second hand 450D in Japan and mod it. The only thing I'm still undecided about it whether or not to mod it myself Cheers Neil.
  12. I have followed the link, its very interesting, however wouldn't it be good to place three images side by side... STD DSLR, MOD DSLR & RGB CCD Your image of IC434 & B33 is better than mine since it definitely has more contrast. The question for me is does it contain more detail and if so how much more? Finally, how does that compare against a comparable CCD (large sensor) camera? I have seen a lot of these modified camera's on the internet for sale and I just wonder whether or not its appeal will last?
  13. Thanks for the replies and adjustments to the image so far. For the record, I don't mind anyone adjusting the images that I post so long as you let me know what you did of course. Thats why I'm here - to share and learn too. I'm not convinced that more subs will help me? The reason is that I'm sure that I'm running in to the limitation of my unmodified camera. The 1DMIII makes an excellent jobs of the brighter M42 but it doesn't seem to be able to cut it with IC434 & B33. I'm never going to mod the 1DMIII but buying a second hand 400D isn't out of scope. The question that I'm asking myself now is what would a modified camera bring to the table, just how much more detail could I expect to see? Especially with these predominately H alpha regions? Is anyone using a modified Canon and what would be your advise? Neil.
  14. WOW!!! Thats fantastic... There is something sureal about these monchrome images... The sensativity of the camera is amazing. Neil.
  15. I've struggled with this target for a long time now. It seem that a lot of things have conpired against me, including the weather. Anyway this is my best attempt so far at capturing the Flame and Horse Head Nebula. Telescope : TOA130F Camera : D1MIII Filter : Astronomik CLS Integration : 5x 20min subs (click to enlarge) I'm also sure that I'm running into my processing limitations... Most of this was processed using MaxIm DL5 (Calibration, Alignment & stacking) and then finished in PhotoShop (Curves & layers) I hope you like it, Neil
  16. I don't whether or not this is the right place for this, but the skies are clear! :hello1: Everything setup and running on M45! I hope it stay clear until Orion comes around to the SSW. Neil.
  17. If your going to be doing unguided exposures then for an 85mm lens and a target within the 30 - 60 degrees range 15 seconds will be your limit. A simple barn door tracker can be used to bring much longer exposures into range. Using a 300mm lens is definitely going to require tracking of some kind to be successful. A two arm barn door tracker is definitely the way to go with the 300mm lens. http://education.jlab.org/tracker/index.html Another PhotoShop trick is to use the FILTERS->NOISE->DUST / SCRATCHES option to remove the stars. For extended objects you may need to tidy up a bit with the clone stamp. I make all my flats this way. Last comment for now, all lens are equal at f8, therefore don't shoot wide open, the center will be OK but the corners will not impress! Stop down by at least 2 stops at first. Neil.
  18. I also have used a Canon 5D successfully for astrophotography, admittedly, with an APO which you still need to decide to purchase in the future. Regarding the camera and capture there are two mandatory points; 1. Only use up to ISO800 with BULB. higher ISO are too noisy in the RED channel. 2. Only shot in the RAW format, never shoot in the standard jpg format Regarding light pollution you can take some simple actions to try to beat it. First try to find a dark or shaded corner of your garden to shoot from. If there isn't any shade then try to introduce some with a simple cloth screen. Although this may sound stupid use a sun hood. This will prevent a lot of stray light from entering the lens and will narrow down the direction that the LP can enter from. Next take some test exposures of 15, 30, 45, 60 seconds and higher to find your local SKYGLOW limit. You should notice that the exposures will become increasingly more and more orange. Now the subjective point, pick the best exposure? Some orange SKYGLOW can be tolerated and even subtracted during your digital processing work flow. Use this exposure as your standard for all future imaging. A word of caution, the SKYGLOW limit will vary with your weather conditions and some days will be better than others. On thoughs day increase your exposure slowly. Finally, always shoot BIAS frames and DARK frames. DARKS most be shot with the same exposure as the LIGHTS or images only with the lens cap on. This records the thermal noise coming from the camera. BIAS frames are shot at the fastest exposure with the lens cap still on and these record the readout noise from the camera etc... Follow the normal image calibration or reduction procedures, there is a lot of information on the internet about this. And finally expect success, post your images here no matter how bad you may think they are. The people here can help you to analyse them and to improve them. I have substracted a lot of SKYGLOW using Photoshop and a difference layer after finding the offending orange colour using the eyedroper tool. Its not impossible, its just also not that easy, however, a lot of the techniques that you need will become second nature after a while. One book recommendation "Wide-Field Astrophotography by Robert Reeves" ISBN 0-943396-64-6. The book focuses on the use of film, however a lot of the information still applies to Digital. Good luck and I look forward to seeing some images. (click to enlarge) Here is an image of M13 taken with an unmodified Canon 5D, no filters just straight through an APO. Neil.
  19. Wow, great image with lots and lots of detail. I see you are using BORG's. I'm assuming the 77mm did the imaging? What do you think of these telescopes and which would you recommend? Neil.
  20. So what's the story can these DMK camera's see the UV light or not? Or is the jury still out! Neil.
  21. I'm one of many amateur astronomers in this hobby because of Patrick. I hope he gets well soon. I have been watching the Sky at Night since I was 13 years old, that's 30 years now and its the only program broadcast by the BBC that's never been dumb down. Still pushing back the frontiers of astronomy. Neil
  22. Attached you can find an image of the moon where I have pushed the colour / saturation as much as possible. The image was taken straight through my TOA130F with no filters or reducers etc. Just the canon 1DMIII on the back. You can really see the green and blue areas of the moons basins coming through. Does anyone know what are the different types of rocks that make these colours? (click to enlarge) Weather permitting I'll try again soon with the M250 and reducer since I don't want too many images to merge. Neil.
  23. :hello1: Very nicely done, you have set the bar really high, I'm going to try the full moon tonight if the weather holds... Not sure about merging 42 images!!! but you would never know from the final image. Neil.
  24. MartinB, I haven't needed to collimate the M250 yet. I brought it back from Japan myself and the star test went very well. The only real problem I can already see with collimation is that the weather here isn't really good enough to use a real star. I'm going to make an artificial star with some fibre optic cable, then the problem will be to get it in line of sight at some 60 meters distance!!! Anyway, the good news is that they hold collimation well. I have had a second hand M210 which I sold to fund the new M250. The reason is the the M250 focuses using the secondary, once focused it stay put which is great for imaging. Ron, Bert's own scope is a TAL200 which he has greatly improved, collimation and back focus. He already gets some great results with this scope so when I tolded him I was out with the M250 he came around to test it out! Actually, I wanted to borrow his IR pass filter etc... I'm going to try my web-cam when I can but its the colour version, no mods! Thanks for the comments, Neil.
×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.