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Getting back into imaging after a long break


Gina

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OK I'll give it a try.  Been looking on Amazon UK and there are lots of these panels at various prices but some seem to have grid lines or dots so I guess it's best to get the same brand, at over twice the price of cheaper ones. 

A4 Tracing Light Box - LitEnergy 9x12 Inch Light Pad Ultra-Thin Only 5mm USB Power Light Table for Artists, Drawing, Sketching, Animation

If the unit uses LEDs with a phosphor that glows white with UV illumination, I guess it's wideband rather than discrete wavelengths.

Edited by Gina
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Ordered it.  Due for delivery tomorrow.  If this works it will save me a lot of work.

That lovely clear blue sky is gaining more and more clouds - getting ready for tonight - marvellous!!!  Typical!!!

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Carefully watching a cloud bank as it comes and goes.  There's a bank of cloud more or less above and extending westwards.  To the east there's just odd little bits of cloud.  Using No.1 eyeball to watch the cloud ATM - I could do with my ASC but it's not working yet.  This bank of cloud has been moving eastwards then westwards and back again all evening.  It's very slowly moving eastwards ATM and it looks very dark in places so I've closed the observatory roof just in case there's rain in that cloud.

Edited by Gina
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Couldn't get Load and Slew to work so went out and moved the mount by hand to the right area of sky.  Got that about right but seems I've knocked the focus out slightly and no longer getting those nice tight stars I was getting.  I need to alter the focuser driver to get the remote focussing working correctly.  I'd forgotten that - the manual focussing I had done on the distant hill in daylight had worked really well so didn't bother.  My focuser system uses relative positioning whereas the KStars auto-focus uses absolute positioning.

103479816_Screenshotfrom2019-07-0900-19-53.png.89264ba2968250eb5eb74fea772a9160.png

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Having got the focus as good as I could I set about capturing Light subs.  26x45s Ha (1170s=19.5m), 13x120s OIII (2600s=43.3m), 8x240s SII (1920s=32m) before daylight swamped the rest.  Selected with Blink in PI.  I was hoping to capture more SII but time ran out.

Edited by Gina
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Now I'm trying to remember what I'm supposed to be doing today 😁

  1. I was going to add my own focuser INDI driver but the auto-focus seems to be working quite well.
  2. The flat panel is arriving later today and I have some flats that need taking - better avoid touching the rig until I've taken Flats to match the latest Lights.
  3. There's Darks and Biases to be taken when it's dark tonight (unless I can manage to exclude all light but may not be able to cool enough to match the -20°C Lights).
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The light panel has arrived (and opal acrylic sheet too, which I may not need).  Plugged it into a USB port on my desktop PC and it works.  I'll check that it works with the Astrodon 3nm NB filters before opening the back and making a direct connection to the LEDs.

Edited by Gina
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I think for initial testing I'll set the rig pointing straight up and place the panel on top of the dew shield and plug the USB into a spare port on the RPi (if there's enough power).  Then I can try taking Flats with each of the 3 NB filters.  If all's well with that I'll arrange something more permanent.  KStars has controls for remote operation of flat panels.

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Panel is working well.  With the gain turned right down to zero, the exposures are around 1-2s for a corrected ADU of 32000.  I've set camera cooling to 0°C.  There is little sign of noise and Bias subtraction should be sufficient, I think.  Now capturing 30 frames of each filter.  I think that should do the trick - unless anyone has any comments.

A couple of screenshots, one from KStars FITS Viewer and the other from PI with CurvesTransformation.

560090766_Screenshotfrom2019-07-0914-08-58.png.dd6f8414e60f983da22f915b4c96870a.png

793404640_Screenshotfrom2019-07-0914-09-29.thumb.png.0c6903bbc56ec1aa9e8e3a30e40304c1.png

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On 07/07/2019 at 12:40, Skipper Billy said:

Just ordered one of these.

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Been looking out my selection of lenses.

  1. 28mm f3.5
  2. 35mm f3.5
  3. 55mm f1.8
  4. 105mm f2.8
  5. 135mm f2.5

I also have 200mm f4 and 300mm f5.6 lenses somewhere I think. 

After that come telescopes.

  1. Esprit 80ED 400mm f5
  2. Evostar 80ED 600mm f7.5 or with 0.85 reducer/flattener, 510mm f6.4
  3. MN190 f5.1 1000mm f5.3

I think I can say that I've got almost every FOV covered 😄

Edited by Gina
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3 hours ago, Gina said:

There is little sign of noise and Bias subtraction should be sufficient, I think.  Now capturing 30 frames of each filter.  I think that should do the trick - unless anyone has any comments.

For short exposures Bias subtraction should be ok. But if you see any hint of amp glow, dark flats can replace bias files. You don't really need bias with cooled cmos.

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I get amp glow with long exposures (>30s) but Darks should take care of that.  No sign of amp glow on the Flats.

Edited by Gina
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No sign of light getting in with 120s and gain of 600 as used for OIII - temperature set to -20°C as for the last set of Lights.  No problem reaching that even with ambient of 25°C.  The light patches on the left are amp glow and shot in the Lights.  The band along the top is also in the Lights.

294646782_Screenshotfrom2019-07-0917-54-09.png.0ce33cfe3431aa8a3329b4a61795df56.png

1921082027_Screenshotfrom2019-07-0917-58-17.thumb.png.371f733a483b1a044ddaf1539ba2c42e.png

 

 

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I found out the hard way that plastic lenscaps can be remarkably transparent. I never trust them. One way to avoid light getting in is to wrap the lens (with lenscap on) in two layers of aluminium foil.

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47 minutes ago, wimvb said:

I found out the hard way that plastic lenscaps can be remarkably transparent. I never trust them. One way to avoid light getting in is to wrap the lens (with lenscap on) in two layers of aluminium foil.

I certainly do that with my bias & dark frames.

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