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AndyUK

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AndyUK last won the day on May 19 2013

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About AndyUK

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  1. Brian - As Carole's noted the "secret" behind hubble palette is using selective colour - I always found THIS link pretty useful in getting something close, and you can then tweak the colour further, either by repeating some of the changes and/or amending the layer transparency to taste... ... But back to Carole's image... Very nice indeed, Carole! . (I'm hoping I might even be able to capture some data myself sometime - maybe this year?)
  2. AndyUK

    Hello again

    Great to have you back, John... .
  3. Thanks Dave - It looks as though my error is trying to use the ball-head for framing rather than relying on the "fine tuning mount assembly"...
  4. Hi Dave, I do have a hot-shoe mounted RDF and of course once calibrated that makes it easy to get to the closest high mag/named star (which I can just about manage using my phone to help :))... it’s just that hop from that star to the DSO I struggle with, especially when I’ve been trying to use the ball-head (ie not RA buttons / DEC knob on the adjuster)...
  5. I'm fairly new to my Adventurer - I bought it last October/November so that I can take it abroad but I've been monitoring this thread for some time and have to say I'm very enthused about the prospects . With a mate's assistance, we took mine out for a test last weekend - The transparency was atrocious, but we went through the process of setting it up and all seemed to perform pretty much in line with what I expect to be using it for... However, as I've always used a goto mount (and/or platesolve), I knew that was one thing I was going to miss badly when trying to find DSO's at longer FL - To my shame, starhopping doesn't come naturally to me . However, we thought we'd see how a 70-200/f2.8 would perform - No problem getting Arcturus in the frame and again, tracking / focus looked promising, so we thought we'd see if we could get M3 on the sensor @ 200mm... and failed miserably... even when zoomed out to 70mm! Unfortunately using setting circles was / is also beyond us both (again, FAR too used to the simplicity of goto / EQMOD / platesolving!), but I did find an interesting article for manual goto using dead reckoning on DPReview, so thought I'd post it here in case anyone else is in the same boat as me. A “Manual Goto” method for use with the Star Adventurer mount When using a simple mount like the Skywatcher Star Adventurer with a telephoto lens to photograph faint deep sky objects, the problem arises of how to locate the target. This is a manual GoTo method that allows the mount to be moved from a known position to a desired new target position using dead reckoning. It only works if the camera is mounted on the Star Adventurer “Fine Tuning Mounting Assembly”: the necessary control is lost if the camera is mounted on a ballhead. The method makes use of the fact that object coordinates in the RA/Dec system are readily available (ie Stellarium app) so that a move from one place to another can be easily described in terms of a change in RA and a change in Dec coordinates. The key is that the motor on the mount only moves the imaging camera in RA, and the control knob on the Dec bracket only moves the camera in Dec. Thus, the necessary RA correction is made with the motor (and the N/S direction slider) and then the necessary Dec correction is made by turning the control knob on the Dec bracket. The detailed procedure is as follows. · Find the coordinates (RA in hours / minutes / seconds; Dec in degrees / arcminutes / arcseconds) of an “easily identifiable star” near the target · Find the coordinates (RA, Dec) of the target. · Work out how many minutes RA must change to move from the initial star to the target and how many degrees Dec must change to move from the initial star to the target · Calculate the direction (S or N on the mount three position slider) and time that the mount needs to run at 12x speed to make the necessary RA correction: · Observers in Northern Hemisphere: For every minute increase in RA coordinate, the SA has to run [S, 12x] for 4.62 seconds. For every minute decrease in RA coordinate, the SA has to run [N, 12x] for 5.45 seconds NOTE: Opposite for Southern Hemisphere · Calculate the number of rotations of the Dec adjustment knob that are needed to make the Dec correction, given that I measured one full rotation of the knob to be equivalent to 2.95 degrees. The knob has 10 ridges on it, so it’s easy to make 1/10 of a turn, or about 0.3 degrees. If Dec needs to increase, the knob must be turned so that the camera turns towards the N celestial pole. If Dec needs to decrease, the knob must be turned so that camera turns away from the N celestial pole · Get the mount polar aligned and turn tracking on at the normal 1x rate and direction · Centre the camera on the “easily identifiable star” · Make the RA adjustment [turn tracker off; set N-S slider appropriately; set speed to 12x; wait the required time; turn tracker off, set N-S slider appropriately for normal tracking; turn normal tracking back on] · Make the Dec adjustment I’ve tested the procedure (Northern hemisphere settings) by moving from Elnach to a point between the Jellyfish nebula and the Shoe-buckle cluster. · The overall angle between Elnach and the target was 11 degrees and 45 minutes Initial star (Elnath) is at: RA 5h 27m 31s Dec 28 degrees 37’ 15” The target was at: RA 6h 14m 56s Dec 23 degrees 28’ 19” Difference: RA + 47.5m Dec - 5 degrees 9 m · Location after the GoTo move: RA 6h 11m 25s, Dec 23 degrees 40’ 15” Error: RA – 3.5m Dec + 12m Overall, these errors mean that the image centre was about 50 arcminutes from the desired target. A 300mm lens on an APS-C camera has an angle of view of about 5 degrees so an error of less than a degree means, with this sensor size and focal length, that the target will be within the field of view after the GoTo move. Has anyone used a process such as this (or something similar?). If anyone has any experience/tips on framing at longer FL, please pile in .
  6. For focusing, I know many simply open the lens up, ISO 25,600, zoom in 10x, centre a nice bright star and then bring it in and out of focus until happy that it's as good (small) as they can get it. However, I'm a great fan of bahtinov masks... There are 2 main types - Those that clip into the lens filter thread, and etched filters that slide into square filter holders. The clip in masks are a lot cheaper, but when I tried one I found the view using a 24mm lens (even f1.4 / ISO 25,600, live view 10x zoom) was too dim for me. There are also Y masks which might be brighter (but I've not tried one of those with a lens - Maybe someone else can comment?). I use an etched filter - There are two I know of - Lonely speck and Kase. Not cheap, and I have to admit I do struggle seeing the "whiskers" at 24mm, but it works pretty well at 70mm . (For framing I also have a hot-shoe mounted red-dot finder, but I've not used mine yet as I've only used 24mm and 70mm lenses so far...)
  7. AndyUK

    Moravian 8300

  8. Very nice indeed... and very good considering it was virtually full moon - You've got to love Astrodon NB filters for cutting through it! (I'm not sure what process you used for the Hubble Palette process, but I've always found this link quite a useful starting point...)
  9. The ED72 certainly does indeed seem to be an excellent little scope, and I'm sure it'll be perfect for its originally intended use (visual / solar on the SW Adventurer) but I've only managed to get it on the mount once since I've had it (just to give it a basic test - The intra / extra focus airey disks looked very good ). Unfortunately my skies aren't that great at all (my SQM reading is c. 17.9 ) and when I had a modded 40D I definitely had to use an LP filter, but I'm still encouraged to give it a go...
  10. Very nice indeed Mick . (I personally wouldn't have spotted the vignetting though....) I recently bought an ED72 myself for a "mobile" / SW adventurer setup, and am also getting a DSLR modded for milky way/night landscapes etc, but the more I see images like this the more I think it might be interesting to combine the OTA and the camera, put it on my AZ/EQ6 at home and see what comes out... . Do you use any kind of LP filter?
  11. I agree - These are seriously impressive results!
  12. It should do... 1. Select the imaging mode tab 2. Select a target [ie Messier - M31] 3. Select your telescope from the drop-down list (or custom scope and manually enter it - Focal length / aperture) 4. Select your camera from the drop-down list (or custom camera and manually enter it - Resolution / pixel size) 5. If you want to add a barlow or reducer, put that in the barlow option [Binning I usually leave at 1x1, ditto angle] 6. Click "add to view"... and M31 should be displayed (and you get all the calculations for focal ratio, resolution, field of view and Dawes limit) If you then go back and enter different values for step 3-5 and add that to view, you get 2 boxes showing the difference in field (and you can add more if you want :)) Here's an example of what you get:
  13. I had a similar problem... I first tried connecting my powered USB hub into a different laptop port (my laptop has 3 ports, although 2 share the same bus) but when that didn't work I plugged the camera directly into the laptop... and the images then completed downloading. (Unfortunately that wasn't the final solution for me as my USB hub was connected to my laptop inside the house via a 3m long active USB cable - I eventually bought a new powered hub, and that resolved the problem... Hopefully you won't have that problem!)
  14. Very informative indeed, Steve - I've learnt a lot from that (I'd better go and lie down now!). And a stunning image too - Thanks for the inspiration .
  15. I'll let you know... I can't say I can recall ever having seen a value of 0.00 when using Bahtinov Grabber (maybe it happened but I wasn't looking?!). I used to be very happy if I could achieve a focus error of +/- 10 microns (I'm not sure how that calculates but that would definitely be sub-pixel). It'll obviously be much easier with better transparency, and admittedly it's a little more difficult with narrowband filters. (I now have 3nm filters - that was the reason I decided to go for an auto-focuser!). If you wanted to practice with Bahtinov Grabber (to see if you like it), maybe try Luminance filter instead - The "whiskers" are MUCH easier to see and you can use shorter exposures .
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