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StamosP

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Posts posted by StamosP

  1. On 26/10/2020 at 23:02, Spaced Out said:

    Last night I used the TS GPU CC for the first time with narrowband filters. Unfortunately I had a terminal issue with my autoguiding, I managed just 3 subs before spending 3 hours failing to diagnose a PHD2 problem ! 

    Anyway here's one of the subs with a quick and dirty process. Pacman neb Ha.

     

    Very, very  good! I'm starting to suspect there is something wrong with the optics of my pds...

    Is it possible to share a single unprocessed-uncalibrated sub? (the best one in terms of fwhm...)

  2. 18 hours ago, Uranium235 said:

    @StamosP wow.... newtons rings.... ive never seen that before in a reflector!

    https://en.wikipedia.org/wiki/Newton's_rings

    http://www.365telescopes.com/how-to-deal-with-newtons-rings-in-cmos-imaging/

    It only usually affects solar H-alpha images, so Im a bit clueless as to why its appearing in a DSO image. Remove the corrector and try imaging again, if it disappears - youve found the culprit.

    I actually think it is the classic Airy diffraction pattern Rob. 

    But it shouldn't happen. I wonder if there is someone else who has also used the GPU coma corrector with 130pds and what the results were...

     

    18 hours ago, Adam J said:

    Maybe a reflection within the corrector. Have seen it before with a TS branded corrector, its possible you have a missing coating.

    In the smaller stars  its like a reflection of the out of focue airy disk overlayed on the star.

    Adam

    I will perform some tests with a different corrector this weekend and see if this is a corrector problem.

     

    11 hours ago, kaelig said:

    Problem of collimation or the eyepiece holder moves in extra-focalisation state (like Airy) or reflection effect (filter, corrector). 

    Could you give us the results of your investigations, thank you.

    Of course i will post the results, it is a very interesting phenomenon (but very, very annoying...)

  3. Has anyone else encountered this issue?

    Autosave001.jpg

    This is a crop of 45image stack (450s in Ha @unity gain) taken with my 130pds, TS GPU coma corrector, Qhy183m and Baader Ha filter.

    Oiii looks approximately the same...

    Here is another crop of the stack:

    Autosave001-clone.jpg

    And an aberration inspector mosaic of a single 450s frame:

    CTB1-Light-450sec-Ha-0010-mosaic.jpg

  4. Hello all

    Is it possible for someone to measure accurately the outside diameter (or perimeter) of the white ring in front of the tube (where a dew shield is going to seat ) and the inside diameter of the tube?

    After 3 years i purchased again this magnificent scope, its vfm is simply unbeatable, and i want to have the parts for the modification i'm planning (aperture mask, dew shield etc) ready before the scope arrives...

    Thanks in advance!

  5. On 25/07/2020 at 17:09, geordie85 said:

    That shouldn't be a problem as long as you can eliminate all of the tilt.

    This is a 2 pane mosaic I did. I still have slight tilt on the left which I need to eliminate

    1789196767_2paneorionredo2.jpg.db3506888086258d2c8bfcd370909115.jpg

    I'm using the Samyang to t2 adapter from flo and all the connections are screwed (qhy183-qhycfw3s-qhyoags).

    The adapter could be better manufactured though...

    The problem is that usually i get different aberrations in the corners (for example in one corner the stars are seagull shaped, in another triangles, in the third coma etc).

    I don't know if this is a tilt related problem...

    • Like 1
  6. Hello all!

    Has anyone tried combining the lens with an 183 camera?

    I've tried 5 samples so far and i haven't found one performing as i would like. I know that this specific chip is very demanding due to the very small pixels (even though the chip's size is small) and it would be very helpful to know if i'm expecting too much...

  7. Yes, this banding has to do with some kind of flickering and the camera's shutter, i rarely see it and i didn't bother to recapture the frame as i was only interested in the vignetting.

    I had the suspicion that the ring will cause vignetting but i had not performed any back to back tests until now.

    There is indeed a significant amount of vignetting when the lens is stopped down by using the step down ring so i think the best approach is to close it by using the internal diaphragm (even though this will cause diffraction spikes).

     

  8. On 20/04/2020 at 20:25, Adreneline said:

    Yes, but the greatest improvement was in the peripheral stars in the extreme corners of the image - there was no real discernible difference for stars in the central region. As you are finding even tiny changes in spacing make a huge difference to the focus position. It is worth the effort in the end.

    Good luck.

    Adrian

    I hope i will see that improvement too, thanks a lot Adrian!

     

    I have performed some tests to see what happens to the field illumination when the lens is stopped down.

    The first pic is with the lens wide open, the mean adus were about 30.000. The second one is with the lens stopped down at f2.8 by using the internal diaphragm and the last one by using a 48mm step down ring (equivalent to ~f2.8) in front of the lens. Both of these images have a ~18.000 mean adu value. 

    F2.jpg

    F2-8diaphragm.jpg

    F2-8ring.jpg

    All the images have been autostretched in pi, the last two have exactly the same stretch to make them comparable

  9. 6 hours ago, Adreneline said:

    I can't help but feel that if this is your infinity focus position then the spacing is incorrect - probably by a fraction of a millmetre. When my stars are in focus the centre mark is right in the middle of the base of the 'L' mark which in my understanding is where it should be. Modern lenses will focus "beyond infinity" so you should not be looking to align the centre mark beyond the 'L' toward the infinity mark either. It took lots of trial and error for me to find the correct spacing and even then inserting/removing a 0.15mm spacer would throw the whole thing out.

    Even once I achieved the correct spacing the star shapes in the extreme corners were not perfect compared with the centre of the image; I guess it all comes down to just how good the optics are in your particular lens. Astrophotography makes demands on focussing that are never/rarely required in regular everyday photography.

    Good luck.

     

    Thank you very much, this was indeed my infinity focus position during testing

    Did you notice any significant improvement when you nailed down the distance?

    Yesterday i did some experimentation from my balcony to see whats wrong with the distance, no mount at all, i just held the lens-camera in my hands as steady as i could.

    Thankfully Venus made the process very easy and in 5 minutes i found that i had to add exactly a 0.5mm spacer (i also tried 0.2-0.4-0.6mm) to achieve infinity focus exactly at the vertical line of L.

     

  10. Hello everyone

     

    I finally managed to setup my rig and i would like to hear your inputs about the aberrations i see.

    First of all, i have a qhy183m directly attached to a qhycfw3s-sr and an Astro Essentials Samyang to m48 adapter.

    I have carefully set up the distance to 44.67mm (taking into account the optical thickness of the filters) and everything seems to be fine mechanically.

    I have also made a support ring for the camera, the screws simply touch the camera, i don't want to induce tilt myself by tightening them.

    Below there are some pictures of the rig, the focus point and two aberration inspector pics...

     

    20200326-104327.jpg

    IMG-20200419-120544.jpg

    east-stack-mosaic.jpg

    west-stack-mosaic.jpg

     

    What are your thoughts?

  11. Hello all!

    I discoverd this thread after a very very long time so here is my widefield setup:

     

    IMG-20180827-204254.jpg

    IMG-20180827-204411.jpg

     

    And here are some photos taken with this setup and with my old Canon 600d:

     

    get.jpg?insecure

    get.jpg?insecure

    get.jpg?insecure

     

    I had tilt problems too (well maybe a little lens miscollimation too, very difficult and time consuming to find out what exactly is wrong) plus the smallish imx183 pixels are not forgiving, with my dslr the results were much better.

    During last month i tried to find a solution to modify the bayonette to a t2 male thread (i have a few ideas) but today i saw Rob's (i remember you from the legendary 130pds thread!) solution, very good indeed.

    Any info about this?

    • Like 3
  12. On 19/4/2017 at 16:01, mAnKiNd said:

    However, since I use a IDAS LPS-D1 filter, which has a glass thickness of 2.2mm, then if I understand correctly, I can subtract that value from the total distance, giving me a "true" distance of 52.8mm, which is not a far cry from the recommended 52.5mm.

    Hello Minos,

    this is the answer i got some time ago from Ted Ishikawa of Hutech regarding the thickness of clip EOS filter:

    "Hi Stamatis,
    Current D1-EOS is 0.5mm thick.
    Ted"

    • Like 1
  13. Hello!

    I finally decided to reprocess my first astrophoto (and the 130pds' first light). After a year i believe my processing skills got a lot better, and i managed to find a 20x20s stack to "save" the core.

    The first edition following just the basic steps is here.

    The collimation wasn't good enough (i was a rookie) and the ca coming from the SW CC is rather obvious. But i think the final result is good...

    get.jpg

    • Like 5
  14. When i took my 130pds to pieces i discovered that the vanes were not screwed properly to the cylindrical central "thing", two of the vanes hadn't their plane parallel to the axis of this "thing" (i cannot describe it better...).

    So i unscrewed them and with careful measurements and the help of a digital caliper i managed to align them perfectly.

    I cannot tell if this is the case here but i have the impression that the 3 o'clock vane is slightly bent-twisted (as happy-kat mentioned.)

    Furthermore i think that the secondary has to be slightly rotated clockwise...

  15. It was a SW Esprit 80.

    A thread regarding my little adventure: http://www.cloudynights.com/topic/551425-star-testing-the-esprit80/

    I also believe that the optics are very good but something was out of alignment (the cell, the focuser, the flattener, who knows...). And unfortunately it isn't an easy job to collimate a refractor.

    The overall build quality was impressive (especially the focuser) but i wanted something to work straight out of the box, i think this is the primary reason to buy a refractor...

  16. Hello all!

    A little story i want to share with you:

    I selled both my 130pds and my 200pds (plus the sw coma corrector) a couple of months ago since i wanted to try something different.

    So i bought a refractor costing 5-6 times more than the 130...

    The results were disappointing (distorted stars) and so i returned the scope to the online store i bought it from, i couldn't accept the fact that my refractor was worse than my cheap newtonian... 

    [I already regret that i didn't buy it from FLO (excellent communication plus they offer a checking service)]

    I haven't decided yet what i'll do next but there is a big possibilty to buy a 130pds again...

    The vfm of this telescope is simply astonishing.

    Of course if i will finally proceed i will definitely buy the Baader coma corrector and not the sw one...

  17. IC 1318-Sadr region 

    I had some issues while capturing this image, pretty bad guiding, an obvious collimation issue (or most likely a camera tilting issue since my laser showed that the collimation was very good) and i did a major mistake while shooting flats and i had to reshoot them the next day.

    Image details:

    Location: Attica, Greece

    Telescope: SW 130pds mod + SW x0.9 CC

    Mount: SW HEQ5pro

    Camera: Canon 600d Baader mod

    Filter: Hutech IDAS LPS D1 2inch

    Guiding: 9x50 Finder-Guider + ZWO asi120mc

    Lights: 33x240s (2h, 12min) iso1600

    Flats: 30, Darks: 20, Bias: 80

    get.jpg

    • Like 4
  18. You're right, there shouldn't be chromatic aberration with a Newtonian but this is a fact when the system is all reflective.

    When you use a coma corrector there is refraction also and if the corrector isn't well made (like apo refractors) there will be aberration due to dispersion.

    If you give a close look at the M51 image i posted you will notice that away from the picture's center middle-small sized stars have red-blue edges, blue the side closer to the center of the image, red the opposite one.

    This is chromatic aberration... The main suspect is skywatcher's coma corrector i'm using but i have not tried shooting without it.

    I have talked about this with Rob (Uranium) and came to the conclusion that Baader shouldn't create this problem but then i saw some pics in Astrobin where ca was evident even with Baader mpcc...

    The phenomenon is more obvious when you boost saturation a lot. Have you noticed something like this with mpcc?

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