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  1. 20, 25 and 30 minutes (added above as well): Full-sized versions here - http://www.omaroo.net/albums/album47/20_min.jpg http://www.omaroo.net/albums/album47/25_min.jpg http://www.omaroo.net/albums/album47/30_min.jpg Really starting to get some glow going now, although nowhere near as much as I was expecting still. Starting to also get quite a number of hot pixels. Each of these frames were taken and then the camera turned off for 10 minutes to cool - the idea being that there would be a stable reference point to start from each time.
  2. Arthur - I think I see where you're trying to go. The order looks "out" because some frames exhibit less glow than the previous. What I probably really need to do was to take a frame and then turn OFF the camera to let it cool down COMPLETELY between shots. I've realised that what I've done is take some of the shorter frames here, waited a minute or two while I reset my countdown timer and then exposed the next one. The longer frames (up beyond 10-11 minutes) I did make sure to turn off the camera between shots to cool down to a constant. Hmm.. re-do time?
  3. Just found this: http://www.takegreatpictures.com/HOME/Columns/Digital_Photography/Details/Dark_Frame_Subtraction_using_Adobe_Photoshopby_Chris_Limone.fci Seems pretty simple! Cheers Chris
  4. Hi Arthur I suspect that it's a graduated effect as a function of time rather than heat. It couldn't be light leakage because I had the body cap on snugly and the camera was placed in a dark cupboard while the exposures were running. Cheers Chris
  5. Not as far as i understand. Amp glow is an electroluminescent effect caused by the IR noise emitted from the readout amplifiers situated at the corners of the chip, and is not caused by heat. Pixel noise or "hot pixels" are caused by heat.
  6. Thanks fellas Now - given that I use Photoshop CS3, how do I "subtract" a dark? As a difference layer? Cheers Chris
  7. Hi all Just wondering what the best way might be to be able to judge how long an exposure I could take before amp glow got the better of me. Given that summer is coming on, I've done a few dark tests on the D40 at ISO400 and ambient temperature of 22 degrees C. I've taken frames from 1 to 15 minutes long at one minute intervals and can't see hugely appreciable difference in glow - but a few noisy pixels start to creep in after 9 minutes. How do you guys achieve this? Is 15 minutes too short for a meaningful test? Should I push the next set up to ISO1600 or even 3200 if I'm going to shoot most at 400 or 800? Cheers Chris All images have noise reduction set to "off". "Mode 3" has been used (camera turned off prior to median NR taking place automatically) such that the frame is flushed & written to storage before the NR algorithms can remove noisy pixels. More or less a true RAW in Nikon parlance. A higher resolution version can be found here: http://www.omaroo.net/index.php?set_albumName=album47&option=com_gallery&Itemid=40&include=view_album.php Here are direct links to the full-sized images: http://www.omaroo.net/albums/album47/1_min.jpg http://www.omaroo.net/albums/album47/2_min.jpg http://www.omaroo.net/albums/album47/3_min.jpg http://www.omaroo.net/albums/album47/4_min.jpg http://www.omaroo.net/albums/album47/5_min.jpg http://www.omaroo.net/albums/album47/6_min.jpg http://www.omaroo.net/albums/album47/7_min.jpg http://www.omaroo.net/albums/album47/8_min.jpg http://www.omaroo.net/albums/album47/9_min.jpg http://www.omaroo.net/albums/album47/10_min.jpg http://www.omaroo.net/albums/album47/11_min.jpg http://www.omaroo.net/albums/album47/12_min.jpg http://www.omaroo.net/albums/album47/13_min.jpg http://www.omaroo.net/albums/album47/14_min.jpg http://www.omaroo.net/albums/album47/15_min.jpg http://www.omaroo.net/albums/album47/20_min.jpg http://www.omaroo.net/albums/album47/25_min.jpg http://www.omaroo.net/albums/album47/30_min.jpg Dark frames - 1-30 minutes: 1 minute 2 minutes 3 minutes 4 minutes 5 minutes 6 minutes 7 minutes 8 minutes 9 minutes 10 minutes 11 minutes 12 minutes 13 minutes 14 minutes 15 minute 20 minutes 25 minutes 30 minutes
  8. Thanks Ron & Cap'n Yep - It's a keeper :shock: I've just ordered replacement parts for the scope I took (more ratted) the visual back off. Cheers - and thanks for the interest! Chris
  9. I have to say - I wish I'd had this scope for the recent lunar eclipse now! Not bad at all - and given that the seeing is good tonight, it even rivals the better shots I've taken through the Megrez. Cheers Chris
  10. OK all - here's a quick moon shot through this cheapie home-built. Nikon D40 at 160th sec ISO400 Actually surprised me! Cheers Chris
  11. Rocker Box - Two long rails are 755mm inside edge to edge, two short are 420mm. Aluminium rail will form frame under the sides which will hold the two separate mirror cell assemblies. Edges are rebated so that the finish is nice and neat. Jeez this jarrah wood is tough - it's like steel to cut. Stainless screws will hold it together - and the corners of the frame will be either tigged or bolted. Mirror templates are 395mm between centres.
  12. Well, I suppose that the biggest plus in this design, for me, is the fact that you can roll down just the one side you want to observe through. You can leave the other up, which affords you dew shelter and a nice comfy undercover spot to sit for the night. From what I've seen so far of roll-off designs, you have to pretty-well have the whole thing open.
  13. LOL Helen No worries. It's all related in the end! I'm not sure why people are assuming that the counterweights are a problem. What is shown..well.. works! The roof sections are quite light, and all the counerweights need to do is assist you to move them. According to the article I took this from, the owner states that raising and lowering the roof sections is a one-handed job. Cheers Chris
  14. Yes indeedy! The cages rotate on teflon pads just like the alt and az bearings. Liquid smooth and easy to get just right for each observer in the line. The cages are physically restrained in place vertically by roller bearings. See image: Cheers Chris
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