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Posts posted by almcl

  1. Not sure about the 10m cable, or the unpowered hub, but I connect my mount, DSLR (when I used it) and guide camera via a home made powered hub and a 2m cable and PHD2, APT and the planetarium program all run very happily on my 2nd hand refurbed Toughbook, so the answer maybe try and see but be prepared to invest in a plastic box to put the laptop closer to the mount?

  2. Coming rather late to this, but it appears just possible that the artefact is a reflection in some part of the imaging train from the bright star alpha Tri.

    Here's the final image with the artefact image overlayed superimposed on the neighbouring starfield:


    It does seem rather a long way for a diffraction spike, perhaps try a similar exposure with a longer dew shield to see if it goes away?  Or maybe not, given the lack of clear skies at present.

    • Like 1
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  3. Can't help with your focus issues beyond saying that I use a click lock holder that allows the guide camera to slide in and out without moving the stalk (see below), but your 'cosmic ray effects' are walking noise, hot pixels.  You are practically guaranteed to get these with a guidescope and a Newtonian and are a very good reason to persevere with the OAG.  Dithering between the shots (I think you stacked 15, from counting the hot pixels) can help together with a Sigma clip stacking algorithm, but you need at least 20 lights and more would be better. 


  4. 2 hours ago, Pryce said:

    Should I then calculate the median temperature of my subs and use the dark frames that are closest in temperature to that.  Or should II just deslect the outliers?

    It might be worth reading the EXIF temperature data for your subs.  

    If you don't already have an AP to do that, this one maybe of use:


    You can see what temp is recorded for the lights and darks and if they match, try stacking both with and without darks and seeing which result you prefer?


    If you want to go into it a bit more there's Dark Master which will automatically generate stacking lists of matched darks and lights, I tried using it but my subs were too variable for it to be much use.  Once I started using an external cooler on my 700d it wasn't really necessary.


    1 hour ago, SteveBz said:

     I might try StarTools again and see what I can do,

    Since you mentioned StarTools, I ran your .fits file through version 1.7.455 and (binning to 35% and cropping pretty heavily) got this:



    I am sure that with a bit less haste and more attention to detail a much better result would be possible.

    • Like 1

  6. Cooling a DSLR can help with noise, although how to achieve this is not always simple. 

    But without a stable temperature on both lights and darks, calibrating with mis-matched dark frames can actually make matters worse.  Especially so when the temperatures don't match. 

    Processing software too, can help with noise.  I've used a couple of modules from StarTools on your screenshot to quickly get this result:


  7. I have got tilt with my ASI 2600, but at the moment it appears to be caused more by focuser and connector sag so am playing around with different adapters &c. 

    Be interested to hear how you get on with the tilt plate?  The instructions in the ASI manual (adjust one of the sets of screws and see if it gets worse or better) don't seem particularly helpful.

    Here's what two of the free analysers have to say about one of my recent subs taken with the SW 190 MN:




  8. 3 minutes ago, Davey-T said:

    A lot of advice seems to be from heresay and just repeated by folk without any personal experience 😄


    Thanks, Dave.  Ain't that the truth though?  I notice several of our more expert contributors don't always agree with the much repeated 'wisdom'.  Trial and error is still valuable!

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  9. Not silly questions at all Steve!

    I haven't done a dark library yet is one reason but my experience of darks with a DSLR was that they didn't help, even when my home made cooler stabilised the temperature and allowed darks at the same reported EXIF temp as the lights. I've yet to experiment with the bias frames to see if they make a difference either way but at least they were quick and easy to do.  

    Then there's also the issue of gain and offset settings.  These were shot at a gain of 100 but opinions vary as to whether this works better than gain 0.  Then there's sub length - haven't got my head around the histogram display in APT's CCD camera screen.  At the moment I can't interpret it! 

    So quite a bit of learning still required.

    Meantime here's a version with less emphasis on stars (not sure if it improve things though)


    • Like 2

  10. I've given up trying to mount my newly acquired ASI 2600 squarely on the MN190's stock focuser and instead decided to screw it to my Canon 200 mm lens.

    As luck would have it a clear night came along, so plonking the modded EQ5 mount down on the sopping wet grass and going through the usual set-up rituals, I managed a couple of hours of images at M31 (unimaginative, or what?)

    Given that I am still 'learning' both the camera and APT in CCD mode,  I was moderately surprised at how the subs turned out, although am also having to try different workflows in StarTools and haven't got the stars properly under control yet.  Cropped result below.

    Comments and observations welcomed.

    48 x 3 minute lights
    30 flats
    35 bias


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  11. Thanks, Wim.  I'll try that.

    I have noticed that when tightening the individual single screw on the extension or the focuser,  there is a massive amount of movement before things get tight enough to hold the ASI2600 and OAG in place.  And tightening the focus lock moves things about quite a bit, too. 

    Ideally I would like to use my Baader 2" click lock but can't see a way to screw it on.  

  12. Just measured the dust doughnut size on a full sized image and it's ~540 pixels.  Taking that with an f5 scope and 3.76 um camera pixel size suggests a distance-to-sensor of ~ 10.1 mm which is pretty close to the distance from the front of the protective screen to sensor distance for the ASI 2600.  

    Need to improve my flat panel arrangement, I think!

  13. Thanks for responding, Vlaiv.

    Don't think anything moved in the imaging train - I moved the scope to horizontal to take the flats, but that was all.

    But, now you mention it, I've looked again at an individual stretched + binned flat and yes, there are rings (see below).  The off-centre vignetting (and the pretty awful tilt) are down to the stock focuser on the MN 190 not being up to the job, particularly with the single screw clamping arrangements.  That's another thing to address!



  14. Saturday night was the first chance to try out my newly acquired ASI 2600 mc.

    Below is a stretched stack of the first target I pointed it at after getting the OAG and main camera para-focalised.

    I was a little concerned to see the 'rings', some of which are indicated in the image below.  At first I though they were dust bunnies, but I can't see them in the flats and they look more like an out-of-focus star as seen before focusing.

    The imaging scope is the SW 190 MN, so the light path consists of corrector plate, main mirror, secondary mirror, OAG (which should be out of the light path)  and then camera.  No filters (at the moment).

    While I can get rid  of these in post processing, does anyone have a suggestion on the cause or how to reduce them?



  15. 48 minutes ago, woodblock said:

    My idea is to use plate solving to get the scope pointing dead on to the astronomical north pole at the home position. APT has an add on which I think can be used to automatically plate solve and make corrections until it's very accurate. I haven't tried this yet.

    APT has three possibilities with plate solving: All Sky Plate Solver (ASPS), PlateSolve 2 (PS2) and ASTAP.  Once downloaded and installed with correct index files PS2 is very quick to solve provided you are fairly close to the target.  ASPS will solve almost anywhere but takes a little longer in my experience.

    However, why bother refining the home position?  Instead, set up as normal, goto your target (or a nearby bright star for focusing purposes) and plate solve that.  Sync and then ask CduC to goto the target.  In my experience it is then almost always dead center in the frame and has taken under two minutes to achieve.  A good home position is not to be sniffed at, but it's probably not worth wasting valuable imaging time over.  Of course if you can do this before Astro Dark, it helps while away the time?

    • Like 1

  16. In my case it wasn't a Windows 10 update (don't usually have any trouble with Win 10 ones) but an ASI Studio one.

    A couple of weeks ago I downloaded ASI studio from the ASI website.  It worked fine but was a bit limited in function.  Today when I fired it up, it offered an update (which took ages to download).  Once installed it wouldn't run.  I am going to have a search and see if I've still got the older version's installation files.


    Just had a look at the ASI forum where several people have reported the same issue but noted that the individual programs (ASICap, ASIFitsView, ASIImg and ASILive) can be run from within the ASI studio folder.  The conclusion is that there's a bug in the menu program.

    • Like 2
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