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.

  • Announcements

    sgl_imaging_challenge_banner_lunar_winner.thumb.jpg.e75de1ff1128e51a02fe7b63e48dbc51.jpg

symmetal

Advanced Members
  • Content count

    212
  • Joined

  • Last visited

Community Reputation

135 Excellent

About symmetal

  • Rank
    Star Forming

Profile Information

  • Location
    North Cornwall
  1. My EQ3-Pro GOTO had exactly the same issue with the RA setting circle. It had been tightened up too much when I got it as I had to use some pliers to release it. When tightened up there is a grinding noise at some spots when rotating the scope in RA. I assume the screw has punched through what it tightens against and is fouling something inside. I just leave it undone and there is no problem. The DEC setting circle does seem to have been set wrongly on yours. With my scope at the home position the arrow does point to 90. You can easily alter it by loosening the hex headed grub screw in the side of the DEC circle and resetting it. That's the only thing I use the DEC circle for, setting the home position, so it makes sense to have it reading 90 at the home position and be useful. The setting circles don't have any other use on a GOTO and they're not much use on a non-goto either. Alan
  2. 12v Power Board

    Gina's right, though I think Kaliska was referring to a current surge rather that a voltage surge. Modern mains powered 12V supplies should be reasonably protected against over voltage. The power wiring to the mini pc would probably be quite thin and be about 3A rating anyway so a 3A fuse also seems sensible. If in your working with your PC you accidentally shorted something out and blew the 3A fuse there's a reasonable chance your PC will survive. If the fuse was 10A it's most likely something in the PC including some PCB tracks would start smoking long before the fuse even considered blowing. If the fuse is only supplying power to one item it's reasonable to fuse it according to the rating of that item rather than just the wiring going to it. The 3A is the best fuse to use in this situation Kaliska . Alan
  3. A/D offset value used on Atik CCD?

    Ah! That makes sense. I'll have a read through the link you've given. I can do some tests too on the ASI1600 at different gains and offset and see how the noise is affected. Don't need clear skies for that. Thanks Ken. Alan
  4. A/D offset value used on Atik CCD?

    Thanks Ken. In the absence of the offset of 322 the median value out of the A/D would then be 0 which is the ideal result, but as there will be noise generated in the pre-amp and A/D, I'd have thought the median value would in that case be some value above 0. Maybe not enough to have much effect, but I was just trying to get a better understanding of the noise distribution. Yes, I was doing the conversion between ADU and e-, and the x16 multiplication factor between the 12bit ASI and 16bit Atik OK I think. As the noise distribution on the Atik is around 64 ADU the lowest 5 bits don't really hold much signal information. Alan
  5. I've been reading about the calculations for determining the optimum sky background level for various gain and offset values on the ASI1600 to swamp the read noise by a certain factor and it was stated that the same calculations can be done for CCDs too. I have the Atik One 6 which is the same sensor as the 460ex. The gain is fixed at 0.27e-/ADU but the offset used isn't mentioned anywhere. That the offset value is correct can be checked by looking at a master bias and ensuring that the minimum ADU value is between around 100 to 500. Here's the Fits Liberator display of the master bias which shows the min and max values are 297 and 360. I cropped off the first column on the image as that is 0 and ruins the minimum value. This implies that the offset value is good but does anyone have an idea of what it might be. Would 300 ADU be a reasonable offset value looking at this or is there a reason it would be higher or lower than that? Hopefully the noisy knowledgeable members could help me out. The other reason I wanted to know was to determine the sky flux I have here without having to buy a Sky Quality Meter, as well as what it was over the past few years. You need the offset value used on your CCD to calculate this. It's just something to do really on these long windy rainy days. Alan
  6. Is this power supply ok for the HEQ5

    Yes, I had a check on the web and nowhere stated what type it was. A reviewer for the next size up (200W) did say it was a switch-mode. A common use for these supplies seems to be charging banks of batteries for modellers so they would be running near max output for long periods. Switch-modes will run hot at maximum output which is what defines their maximum load, similar to a linear. They just do it in a smaller, lighter package and are more efficient. A fan would enable the max rating to be higher, or let it run cooler. On ebay they are available from £18 to £20. Alan
  7. Is this power supply ok for the HEQ5

    By the size and the price it would be a switch-mode, which isn't a problem. Alan
  8. Aurora Flatfield Panel help !!!

    ADU means 'Analog Digital Unit' (US spelling of analogue is the norm in this context) and refers to the smallest digital division that your analog signal voltage (as read from the CCD pixel 'well') can be converted into. The 460ex is a 16bit camera so the digital value of each pixel can be one of 2^16 or 65,536 states (actually 0 to 65,535). They used to be called 'bits' or 'LSB' (Least Significant Bits), but that was confusing so ADU is now commonly used. So 20,000 to 30,000 ADU is roughly one third to one half 65,535. 100 bias and flats is certainly a good number to take, the more the better, although the actual improvement in signal to noise gets less and less the more you take until it's not really worth taking any more. I've found that 40 flats is sufficient though other people will have different opinions. As the bias images can be taken very quickly 100 is no problem. I'm sure you know but when taking the flats ensure all the elements in your imaging train haven't moved since you took you 'lights'. Camera still in the exact same position and focus still at infinity so that your vignetting areas appear in the same position as your 'lights'. The darker outer ring has quite a distinct outline, so the vignetting source causing it is fairly close to your sensor so the Reducer is a good bet. And yes the flats you take should remove that no problem. Good luck with your processing Dan. Your image even without flats or bias looks pretty good. Alan
  9. Aurora Flatfield Panel help !!!

    For the bias you want as short an exposure as possible so that there is no time for any 'dark' noise to build up and you're only getting the 'readout' noise from the camera, I believe 0.001s is the shortest you can go on the 460ex. For the flats you want the histogram peak to be about 1/3 to 1/2 way across, about 20000 - 30000 ADU. It's not critical, you just want the edges of the histogram peak to be well away from the top or bottom clipping point. You want the exposure to be short enough that 'dark' noise is insignificant but long enough that any flicker or other effects on your light panel don't cause a problem. Aim for around 0.5 seconds or so. If your image is overexposed at that exposure put some sheets of white paper in front of the light panel to reduce its intensity. You might think that when putting sheets of paper in front, it's no longer an 'even illumination' light source as the grain of the paper is visible, but at that distance the paper is so out of focus on the sensor it's not a problem. You're right in that it's not necessary to take darks for the 460EX. Use your 'bias' as a 'dark' when calibrating your images. Alan
  10. Like Dave and John I drilled holes in my pier after it had set and fixed 3 lengths of 300mm M20 studding (A4 Stainless) using Anchorset Red 300 2 part resin. It fits a standard sealant gun with 2 bags in the tube which mix when they flow down the supplied helical cored applicator tube. It lets you fit them exactly where you want them without the risk of dropping them in wet cement. Alan
  11. That's true, but I believe Steve was looking at the already bent bolts to take the hard work out of it. Alan
  12. The zinc coated ones I saw only had a 3 micron coating and were recommended for indoor use only. If the coating gets scratched or worn rust will set in quickly. Stainless steel is resistant through its whole thickness and not just the surface. A4 grade stainless is better than A2. I would go for the largest bolts that would fit the pier and mounting plate just to add more rigidity. Mine uses M20 A4 bolts using a 300mm diameter concrete pier. I believe they were about 300mm long. The extra price of the stainless over the zinc is not much compared to the cost of the equipment it will be used with. Once set in concrete they can't be replaced if they go rusty. Well not without a great deal of hassle. Alan
  13. Quadruplet - Flat Field

    Hi Aidan, it's easy to spend too much time chasing imperfections than actually taking images and CCDI can be responsible for this. I've had a similar time with my ZS61 and ASI1600 and apart from the last few days there has only been the odd few minutes of stars visible since October so test images were all I could do. Coincidentally, I did post yesterday, an image very similar to yours enquiring how collimation was measured in CCDI particularly with a refractor, as it was always reported as spot on even when the image was slightly off centre. It was concluded (with Ray's help ) that there's not much to measure with a refractor in the way of collimation error. I noticed with your image that apart from the focus being a bit out, the corner stars tented to smear towards the centre (like back to front coma) rather than the usual elongated corner stars you get with spacing errors. I did run your image through CCDI to check and apart from some tilt it reports the collimation as being noticeably out. I don't know if that is enough to cause the star shapes you're getting and maybe difficulty in attaining a good flat field. Alan
  14. Yes, you're probably right Ray. It would be nice to be able to look at the tilt error and say which location on the camera needs to move closer or further away. I'm sure it is but the orientation of the camera, and image flips makes my head hurt. Alan
  15. Canon 600d usb cable

    I have a 700D which seems identical to the 600D in the USB connection. I use any mini USB cable to connect to the PC. I'm not sure if Canon Utilities needs to be installed on the PC to see the camera. The mini USB connector on the camera doubles up as A/V out as well. I assume it looks for 5V on pin 1 to determine which mode it should work in. Alan
×