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_2019_sp_banner.thumb.jpg.a0ff260c05b90dead5c594e9b4ee9fd0.jpg

prusling

Members
  • Content Count

    140
  • Joined

  • Last visited

Community Reputation

70 Excellent

1 Follower

About prusling

  • Rank
    Star Forming

Profile Information

  • Gender
    Male
  • Location
    Poole
  1. Hi Matt, welcome to the group. Others will contribute suggestions I'm sure, but here go mine: As you say, Durlston and Badbury Rings are favourite spots along with Hyde Common near Fordingbridge and Steeple ridge near Wareham. There are also various sites with interesting foreground features - St Aldhelms Head, Durdle Door, Knowlton Church, etc. Cranborne Chase AONB is applying for International Dark Sky status and there are various sites within that area. One option is to join one or more astro clubs who hold sessions at these venues - Wessex Astronomical Society meets in Wimborne on the first Tuesday each month and has an observatory at Durlston with regular public/member sessions, and Fordingbridge Astronomers at St Ives near Ringwood on the 3rd Tuesday also holds sessions at Hyde Common and other locations. We also have informal get togethers with members of this SGL club. What are your preferences - visual and/or imaging? DSO/planetary/solar/lunar/widefield? Hope to see you at one of the meet ups.
  2. StarTools is one tool that can interpolate green from Ha (as red) and Oiii (as blue) giving images where the Ha comes out a rich golden colour. I sometimes process using the Ha as Luminance as well but that doesn't seem to make much difference. I also have an Sii filter but struggle to capture enough with it to avoid Hubble SHO coming out over-green.
  3. Article on 1:1 pixel resolution by Jerry Lodriguss
  4. I have a 550d and it has been superb. It and only one other (60d) have a special movie crop mode where the middle of the sensor is used to record 640x480 1:1 video for e.g. planets. With all Canon cameras they can develop a degree of banding but this can be removed using Fitswork4 or other tools.
  5. Hi, I saw this old topic referenced in a current thread and wanted to ask how you conduct a Roddier test. I also have a TS 80/480 - of 2011 vintage - and I seem to get a spread of colours within stars - with red more prominent in one segment. I'd like to determine whether it's the scope or another part of the optical train.
  6. I now also read that binning the guide camera 2x2 can help in such circumstances - is this recommended? Thanks for any guidance.
  7. Hi, I have read a number of articles about appropriate ratios for image scale between guider and imager but I have a potential setup where the ratio will be less than 1:1 and would like to know whether this could cause image problems. If my thinking is right I can see that the guiding could look good but the error would be multiplied at the imager. I'm considering switching from a guidescope to an OAG - the main scope is an 80/480mm f6, the guide camera is a ZWO ASI224MC with 3.75 micron pixels and the imaging camera in question is an Atik 314L+ with 6.45 micron pixels. With all else being equal in this setup the scale ratio is that of the pixel sizes (i.e. 0.58x) whereas general wisdom seems to indicate that less than 4x is OK but nowhere seems to mention how low you can go. More generally is the OAG approach sensible in this setup? I've been using a guidescope but want to free up its space and weight to mount a Raspberry Pi and powerblock on the scope.
  8. The better-calibrated the image (darks, flats, etc) the more you can stretch it to obtain fine detail; my crib sheet for calibration frames is below (any comments very welcome). Darks are pretty well essential with a DSLR, especially at this time of the year; also it is best to turn off LiveView when imaging as that adds to the noise. I also cover the optical viewfinder to avoid stray light entering. I judge the exposure time and ISO according to the darkness of the skies and the camera. I have a Canon 550d (precursor to your 600d) and use 1-minute subs with ISO800 in dark skies and the same exposure with ISO400 in light pollution at home. This means that you can afford to discard poor images and use a sigma clipping algorithm when stacking to eliminate outlier pixels giving a cleaner image. Lights Darks Flats Dark Flats Bias/Offset When Before/after or can use a dark library Ideally every session; can be next day Optional if using Bias Occasional Number The more the better 20+ 25 20+ 50++ (> Darks) Format RAW RAW RAW RAW RAW Optical Setup Capped Exactly the same as lights Capped Capped Temperature As close to lights as poss any As close to flats as poss any ISO 400 (LP) or 800 (dark sky) Same as lights Same as lights Same as lights Same as lights Exposure time Can vary with tracking / guiding, I normally use 1 min when tracking but not guiding Same as lights AV mode until 50-70% histogram then set manually Same as flats Shortest e.g. 1/4000 sec Lens F Stop Widest / 1 click or more back any As used for lights any n/a Lens Focus LiveView x 10 on a bright star / distant target any As used for lights any n/a Stacking algorithm Kappa-Sigma if >15 frames otherwise Average Median Median Median Median
  9. This is the workflow I use for DSLR; for other cameras I adjust the Wipe params (e.g. Aggressiveness 83%, Drop-off Point 50%). I don't think your result is caused by 'Canon banding' but if so, there are ways of fixing this. STARTOOLS EXAMPLE WORKFLOW Command Action Params Notes (for DSLR imaging) Open Open the stacked image from DSS (ideally from fits format) Use left option on opening - DSS actually does some white balancing which can't be disabled Bin Scales down pixels and noise and reduces subsequent processing time 50% (default) 50% converts each 2x2 pixels to 1 pixel AutoDev 'Digitally develops' the image - stretches it to show faint signal and issues to be addressed Drag RoI around target Will probably look horrible but this shows you the worst of the image that the processing will fix Crop Discards unwanted border around target (and stacking artefacts) Drag area to be left Best to eliminate worst of gradients, vignetting, etc around the edges Wipe Removes light pollution, gradients, vignetting and colour casts Drop off point 0% Say Yes to Temporary AutoDev as well and maybe a few pixels of dark anomaly filter Dev 'Digitally develops' the image - stretches and applies curves Re-do global stretch Use "Home in" or manual % to stretch until best compromise achieved (detail vs. noise) (Decon) Compensates for atmospheric distortion (e.g. tightens stars) 2 pixels Optional - set Mask manually first using Clear, Auto, Stars, Do, Shrinkx2, Invert, Keep (Sharp) Sharpens the image using wavelets Optional (Contrast) Increases local contrast Clear mask from Decon beforehand (Mask, Clear, Inverse, Keep) (HDR) Optimises dynamic range - replaces manual curve manipulation Choose algorithm Optional - apply algorithm to suit the target - e.g. Tame, Reveal, Optimize, etc (Life) Brings back life into an image by remodelling uniform light diffraction Moderate Optional - not sure how natural this action is - may border on artistic licence! Colour Adjusts the colours of the image (e.g. compensates for modded DSLR) Fill mask if not already Can adjust to suit - presets for scientifically accurate or artistic (latter can seem more natural!) Filter Modifies features in the image on the basis of their colour e.g. Ha Can boost nebulae Track Switch off tracking in top menu to reduce noise and finish image 10 pixels? Initial example screen makes it look as though everything will end up fuzzy, but it is selective Save Save resulting image to storage Need to put type e.g. TIF Not supported in trial version Key commands are in bold N.B. Can re-do the AutoDev (or manual Digital Dev) any time before tracking is switched off and it reapplies the other changes made
  10. Resurrecting an old thread, I rarely use my Star Discovery but tonight I thought I'd have one more go at dialling out the 'backlash' in Az. I've found the cause and fixed it so I thought I'd pass it on to anyone who may be suffering with this. It's not backlash after all! The Az drive assembly is held in position by two pairs of screws on either side (one pair is shown on the left of Slightly Brown's first photo above) and I noticed that the movement I had was because these were not fully bearing on the assembly and so were allowing it to move a little from side to side. I carefully tightened these down evenly on both sides using a flat head screwdriver and that eliminated the movement completely. I notice that there is a similar setup on the Alt drive assembly but I had no movement there. I've tested this in the house and the motors seem to operate fine. When it's clear I'll test it outside and report any issues. Hopefully this will improve performance significantly - I hope so as these mounts are well engineered and streets ahead of the old Az Goto. They seem to have ended up as an under-utilised stop-gap between that and the Az Gti but with a wifi adaptor they are equally competent.
  11. Despite the cloud some great views last evening - a stunning sunset, gas giants and their moons, M57, and a lovely low-down orange crescent moon. A pesky cloud bank did its best to mark the ecliptic which made imaging difficult, but it was worth trying. Not sure what caused the blueness below though... Thanks AdeKing and kev100 for your company. Look forward to the next time.
  12. Hi, I'm keen as well but the forecast for Friday is not great. Fingers crossed it will improve. Cheers, Peter
  13. Amazing skies - went on an excursion called Teide by Night run by local astronomers; even lent us tripods. Highly recommended.
×
×
  • Create New...

Important Information

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