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drjolo

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Posts posted by drjolo

  1. I used to have ZEQ25 and CEM26 and found them a bit troublesome. These spring loaded worms are a nice way to get rid of play in the worm gear, but in the same time the worm gear is not rock solid. These type of mounts require real good balancing in three (yes - three) axes - so both RA and Dec, but also the tube must be symmetrically loaded along its optical axis. If you have for example finder scope at the side or heavy focusing motor it needs to be balanced on the other side of the telescope. 

    I also do not know what type of motors are in GEM28, but in CEM26 stepper motors are pretty much downsized, and the microstepping torque is very susceptible for the actual worm gear spring loaded force. If you put there too much force, you will end up with backlash in Dec due to the fact that the torque at 1/128 microstepping is not enough to actually rotate the worm till the moment some amount od Dec corrections accumulate and the actual correction movement is done. But it often overshoots then. My friend that has CEM40 observed the same phenomenon, but in less extent. 

    But eventually I balanced CEM26 well and adjusted worm gears spring load, then I was able to get RMS error below 1" when guided. ZEQ25 I had before had DC motors with encoders, and it was a bit crappy, because it was just loosing the encoder pulses. Pointing and guiding were problematic, and it never got back to the home position accurately. 

    On the other hand my ten years old EQ6 does not have problem to get 0.6-0.8" RMS error even badly unbalanced. HEQ5 that I had before as well. There is some play in worm gears, but such static play is not a problem to guide with PHD2 for example, since the software can measure and handle backlash in Dec, and RA backlash is not an issue. 

  2. The amount of the dark (thermal) signal  depends on the total integration time. It does not matter if you collect 1000x15s or 15x1000s of frames - you will collect the same amount of thermal noise. The only way to limit it is to cool the chip. So you may use the same temperature preset as before. Each 6-7C of temperature difference doubles the thermal signal. Thermal noise in modern cameras is not a big issue, unless you reach some larger positive values (like +10C or more), or you capture data with narrowband filters. 

    As for 2-4 seconds subframes it was probably calculated for light polluted sky, so for your specific case the read noise amount becomes not significant when you use 2-4s subframes, or longer. You can make subframes longer, and then you need to consider the pixel capacity (so they will be saturated) and your tracking/guiding capabilities.  Collecting few hours of frames in 2-4s subframes probably is not reasonable, unless you would like to do a kind of lucky imaging and then select best frames to stack this selection into better resolved final image. 

    PS - offset is as far as I remember called "black level" in SharpCap currently

    • Thanks 1
  3. Since the weather is a joke here (as usual in January) I decided to test Xterminators on my old stacks, and probably I will invest to this tool. All the comparisons below were made by applying BlurXTerminator and then NoiseXTerminator. All data was collected under my suburban LP sky with average brightness 19.50, sometimes close to 20.00 mag/arcsec2. Left image is raw calibrated stack, sometimes with DBE applied to remove gradient. Right is the same with terminators applied.

    M16 fragment with 90mm refractor and QHY268M camera:

    01-M16.thumb.png.5212b01f977486e0f960202b8ed58188.png

    NGC7380 fragment with 90mm refractor and QHY268M camera02-N7380.jpg.9cba45621ec8b9ea5ec59e5290243800.jpg

    NGC7380 with Meade ACF 10" telescope and QHY163M camera

    03-N7380.thumb.jpg.afa8a50998be6370462be4f8fb91382d.jpg

    Sh2-132 with 90mm refractor and QHY268M camera - HSO palette

    06-sh132.thumb.jpg.eee7a58343b18f69772fcf86c9703c4d.jpg

    Sh2-171 with 90mm refractor and QHY268M camera - HSO palette

    07-sh2-171.thumb.jpg.2d82dded27e0e3a2bc3ed6d2f8c13911.jpg

    Tadpoles with 90mm refractor and QHY247C camera

    09-tadpoles.jpg.6b3e766fc86eafab9ae695a00628b830.jpg

    NGC1333 with Samyang 135 lens and QHY247C camera

    08-N1333.thumb.jpg.5f47e8f0098f0e9c2dfa33f959f63cc4.jpg

    M63 with Meade ACF 10" and QHY163M camera

    14-M63.thumb.jpg.648defbaed40704c6e6f3fdbc1edcc16.jpg

    NGC3718 with Meade ACF 10" telescope and QHY163M camera:

    15-NGC3718.thumb.jpg.8155dd2ab8de2b78c48580afe13a7aef.jpg

    Abell 1185 cluster with Meade ACF 10" and QHY163M camera:

    17-A1185.thumb.jpg.986495735a6db68cf60e08b2d401dc4a.jpg

     

    I am quite impressed with the results 🤩

    • Like 7
  4. What scope and flattener/reducer do you use? I can see some slightly elongated stars in some corners, not quite symmetric, so it may indicate some tilt or miscollimation. But in my opinion it is really minimal and hard to notice unless at 100-200%. You could provide raw FIT file to estimate it more accurate. 

    When you analyze an image with CCDInspector there should be no nebulosity in the frame, so it is better to capture some star field alone. 

    • Like 1
  5. During yesterday's tests of live stacking in SharpCap I have captured this comet just before the clouds came. Not a very pretty image, just a souvenir from the space. It is only about 7 minutes of exposure (100x4s), but the comet has already moved a little during this time (actually over 5000km in the space relative to us :)

    100x4s with Player One Saturn C camera, TecnoSky 90/540 0.8x FF/FR on EQ6, cropped a bit (533 sensor is square). NGC6463 open cluster is visible in top left corner. 

    2023-01-12-V2-ZTF.thumb.jpg.fb331ce97ecc3bba7460b867bbe61f13.jpg

    • Like 2
  6. Yesterday I had a chance for the first light. I plan to use Saturn C camera with my Celestron SCT 8" for EAA (and maybe with Samyang 135 as travel setup), but for testing I have attached the camera to 90/540 refractor with 0.8x FF/FR. It was quite windy and some high clouds were present, but first live stacks are already in my hard drive :)

    The very first one was M45 - it is 60x4s stack. I have started stacking too early when the mount haven't finished goto, so some stars are elongated :(

    2023-01-13-M45.thumb.jpg.e3d38234f6808a0177ff3dee68aee578.jpg

    Another one is M33 galaxy - 100x4s:

    2023-01-13-M33.thumb.jpg.b192c426fd96fb4f4f7b73f66ec724ce.jpg

    and NGC891 galaxy with Abell 347 cluster - 150x4s

    2023-01-13-N891.thumb.jpg.83bbdf9750307f381530132cfe560d93.jpg

    Camera settings: mode RAW16, gain 150, offset 100, live stack in SharpCap with master flat, but without master dark yet (so I needed to remove a few hot pixels manually), algorithm: Average (I need to test sigma clipping next time). Raw stacks were shortly processed in Pixinsight: stretching, color balance and noise reduction.

    • Like 3
  7. I did a small test some time ago, and that is very true that at a grazing angle many black paints shines like crazy diamond.

    Looking at 90 degrees

    spacer.png

    at 45 degrees

    spacer.png

    at 15 degrees

    spacer.png

    The numbers are mean level read with sampler.

    Starting from the left there are:

    • flock (velor)
    • bottom: black acrylic mat paint with talcum powder, top: the same plus black mat spray (Boll)
    • bottom: black acrylic mat paint without talcum, top: the same plus black mat spray (Boll)
    • black mat spray plus talcum powder
    • black mat spray
    • nothing (aluminium) 
    • Like 6
    • Thanks 2
  8. I was quite surprised how big is 533 sensor placed in the planetary camera housing - looks like a muscle camera :)  ASI290 at the right for comparison.

    DSC01600.thumb.JPG.072efc65cb9b78f810b8afd814bf7daf.JPG

    I ordered mine (color version) for EAA and lucky imaging tasks, because I have never done that before. Internal passive cooling (additional fan can be attached to the camera back) seems to be a nice feature. When shooting 4s frames (typical EAA probably) sensor reached 32*C, while enclosure was 30*C, so heat transfer seems to work fine (in 21*C room temperature). 

    Do you have already any experience with that cameras? I have done sensor analysis with SharpCap so far and waiting for clear skies - though it may take a days or weeks at my location :( 

    image.png.fa0271e1f16022d770c682cee5206b65.png

    I also tested the transfer and it reached promised 42fps - good, good. 

    https://player-one-astronomy.com/product/saturn-c-sqr-usb3-0-color-camera-imx533/

    https://player-one-astronomy.com/product/saturn-m-sqr-usb3-0-mono-camera-imx533/

     

  9. These are quite a similar filters:

     - L(uminance) or UV/IR cut filters just passes the visible part 400 to 700 nm

     - IR cut filter only cuts part longer than 700nm and leaves UV part, however cameras sensitivity in UV part usually quickly decrease, so IR cut is a cheaper replacement for UV/IR cut filter

     - sometimes UV/IR cut filters passes narrower part to even more tighten the transmission band and get rid of some remaining chromatic aberrations of the optics. Like for example Astronomik L1-L3 filters https://www.astronomik.com/en/uv-und-ir-block-filter/luminance-filter-l-1-l-2-l-3.html 

    So you can use luminance filter as UV/IR cut. 

    • Thanks 1
  10. Recently I have found some frames collected in the middle of the last year. These frames contain a well-known target - the M16 Eagle nebula imaged with H alpha narrowband filter. In the left part of the image there are a few faint blobs as well - these are Sharpless Sh2-48, 50 and 53. Sharpless Sh2-49 is actually the M16 itself :) 

    The image below is 70 frames, 3 minutes exposure each captured with a 90mm TecnoSky Owl refractor, QHY268M camera, EQ6 mount and Baader hydrogen alpha narrowband filter. This target is somehow difficult to catch at my location because it never gets high in the sky, and this part of horizon is heavily obscured. So M16 is a project that needs to be continued this year.

    2022-09-30-M16Ha.thumb.jpg.c31507c16102307a1d4b93a9816dae4c.jpg

    2022-09-30-M16Ha-crop.thumb.jpg.93414e84d14191c88bcfc3b7eddb3585.jpg

    • Like 7
  11. On 09/12/2022 at 10:53, tooth_dr said:

    I tried out a new to me Pegasus hub last night and there was quite noticeable banding when the dew heaters were turned on.  I was using a Hitec Astro MHP V3 prior to this and there was no banding with the same dew heaters.  I have a Nevada 25-30A power supply, and use Lindy USB cables, and branded dew heater cables.  I havent tried accessing the PC remotely to see if it's visible, or havent tried if it affects subs as it was late last night when I got it setup.

    Any suggestions?

    https://streamable.com/4urgkc

    I assume it is a hardware issue - the PWM frequency used for heaters outputs in Pegasus interfere somehow with your monitor. It may be okay with different monitor. If Pegasus allow to change PWM frequency you may check different ones. 

    Cable management is important, but PWM outputs with simple rectangle signal and high load are often a pain. 

    • Like 1
  12. At the beginning of these year during the tests of TecnoSky 90/540 Owl refractor I have captured several frames with different targets. Actual field of view of this setup (with APSC camera) is 3 by 2 degrees, but I was wondering how the smaller targets will look like in that modest aperture telescope. Then I have prepared a mosaic of them and here it is below. 

    Each single frame is about 0.5 degree, and each image is 1-2 hours of total exposure with Baader L filter and QHY268M camera under suburban sky (NELM about 5mag). Mosaic panels are resized down 50% (click to enlarge).

    spacer.png

    Here is example 1:1 crop on NGC4214:

    2022-05-04-Owl-mosaic-NGC4214.jpg.1b5ece8e40cb8912a535f2a86ddd6e1e.jpg

    and example full frame resized down 50% with NGC4088 galaxy and others:

    N4088L-50.thumb.jpg.5636809257dbbd2aceaf6215ee800c3e.jpg

    More images from this refractor here https://stargazerslounge.com/topic/394454-tecnosky-owl-90540-first-images/ 

    • Like 10
  13. I probably should not even introduce these two targets, as I am pointing my telescope there almost every winter. This season I have already did it in November, so I feel free now for other winter gems :)

    60 frames, 3 minutes each captured with TecnoSky 90/540 Owl refractor, 0.8x FF/FR, QHY268M camera, EQ6 mount and old Baader Ha filter. Conditions were not great, transparency was medium and under my suburban sky LP was significant. But Ha and SII bands are somehow resistant to that, so I decided to catch these low altitude targets. 

     

    spacer.png

    • Like 27
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