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PostPosted: Thu Mar 15, 2012 3:55 pm 
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Hi folks,

I thought I'd share the new imaging setup. I don't have the luxury of a garden large enough to host a dedicated observatory so the solution I started planning a year ago had to at least look presentable during daylight.

    Image
The pier was made in two stages with a deep foundation poured using regular cement plus a plasticiser with 2 metre stainless steel rebar protruding about a metre above ground level. Once that had cured I then poured the top half into a mold and also poured the detachable top upon which rests the armillary. I used the same recipe for the cement with the addition of a dye to give a stone effect. To give an idea of scale the pier without the top stands just under 1.3 metres (50 inches) tall. When I poured the pier I embedded four stainless steel eye-bolts. This was done using the same stainless steel circular plate you can see in the top right image to get the positioning absolutely precise. The two circular plates were made for me to my design by a laser cutting company so I was able to specify a tight tolerance between the width of the various bolts and the holes they fit through.

Assembly is pretty straightforward. There is still a very slight (small fraction of a millimetre) play when the two plates are attached but I always make sure I rotate each one fully clockwise before tightening up the nuts. The aim was to get a totally repeatable set-up each time and indications are that I actually see an accuracy of about 1 minute of arc (1/60th of a degree). The heaviest detachable item by far is the mounting itself but I've avoided any hernias so far!

Here's a closer view of the telescope where you can just about see the four bolts holding down the bottom plate and the bolts fastening the top plate to the bottom one. The mounting is bolted to the top plate but you can't see that in the image.

    Image
The equipment list is:
  • TEC 140 telescope: 140mm objective and a field flattener at the other end giving f/7
  • Kendrick Dew Heater: It's the black strap around the dew shield - essential in the UK
  • ASA DDM60 Pro: The Pro version includes a USB hub
  • Starlight Instruments motorised focuser
  • A power distribution/switch box
  • An FLI CenterLine filter wheel
  • An FLI ML16803 astronomical CCD
The USB hub in the DDM60 Pro mount means that all I need is a single 12V power line and a USB connection running to the mounting. Both power and USB are routed internally and are available by the telescope which means no tangled cables. The focuser, filter wheel and camera are all controlled via USB as, indeed, is the mounting itself. As a result, although I need a micro-ATX sized computer relatively close to the telescope together with a 12V power supply, I can take advantage of a long HDMI cable and a wireless mouse and keyboard to control the whole shebang from inside my conservatory which is just out of shot on the left. Luxury!

Testing has gone really well and I've already demonstrated an ability to take 1,000 second exposures unguided. That's down to some remarkable technology in the ASA mounting, although I'll take credit for doing the calibration work.

Bob.

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Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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PostPosted: Wed Mar 28, 2012 2:57 pm 
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Drool......very nice.

Maybe we should have a sticky where people can post images of their setup?

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PostPosted: Wed Mar 28, 2012 4:36 pm 
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Thanks Lee. I guess it depends on demand. :?

I've just upgraded the software that runs the mounting. Normally I prefer to leave software that works well alone, especially as the computer concerned is never connected to the Net, but the latest Autoslew version promises an upgrade to the pointing modelisation so after having synced to around forty stars tonight I'm hoping for even better accuracy. The downside is that I have to do that pointing/syncing as the old pointing file will no longer be valid. At least I don't have to wait for it to be particularly dark to get started.

Bob.

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Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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PostPosted: Wed Mar 28, 2012 4:44 pm 
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40 sync stars, that sounds like a PITA to complete, but worth it for improved accuracy.

I know what you mean about leaving things that work nicely! The next step for me will be to look at EQMOD to control my scope from my laptop, although there are a few other things I want to get first like an electric focuser etc....

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PostPosted: Thu Mar 29, 2012 11:59 pm 
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Hi Lee,

Well the software upgrade didn't work out too well on Wednesday night. To be fair it was something that ASA had flagged as a possible outcome and I was one of the unlucky ones. The more I did the worse pointing and tracking became. So eventually I bit the bullet and did a full factory reset. That meant configuring everything from scratch again and despite packing up at 6:35 on Thursday morning I had by no means finished. But I had done enough to let me rattle through nearly 600 exposures pointing at and fine tuning and recording the pointing for some 82 stars this evening. The proof of the pudding will be in the eating and this evening the Moon was clearly indicating a thin and persistent layer of cirrus so I thought I'd call it a night, eschew my planned sequence of green exposures of the M81 group and get some much needed sleep. But just before I packed up I idly wondered if my astro CCD's shutter could work quickly enough to capture the Moon and the answer was Yes. Not what the imaging train is designed for and without extra magnification the level of detail doesn't begin to approach the eyepiece view but I thought I'd share. Nighty night everyone!

    Image
Bob.

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Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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PostPosted: Sat Mar 31, 2012 5:26 pm 
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Works well on the moon!

Hopefully you can finish your calibration soon and will beip and running. I'm looking at getting a CCD this year, not sure if I've mentioned it before, and will be looking at a mono so I can try narrowband. One thing I need to resolve is the best way to align subs on different nights as I have no pier and have to setup/strip down each session. Then of course there's getting my head around PEC and whether this is worth doing with a guided setup.....always a learning curve.

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PostPosted: Sat Mar 31, 2012 7:44 pm 
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Thanks Lee. I think calibration went well and I'm hoping to put it to the test tonight with the start of a four frame mosaic. This project may run for a few months as I'd like to add SII and OIII as well as H-alpha and RGB. PixInsight does all my alignment and stacking.

Bob.

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Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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PostPosted: Sun Apr 01, 2012 11:37 am 
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Hi folks,

Last night I got to test the two nights of calibration work I spent on the mounting earlier in the week. Put simply, the mounting knows what angle it is pointing at with incredible precision due to some very clever encoders embedded in the works but that doesn't mean on its own that the mounting can point at and track any star you care to name because of mechanical misalignments, most commonly in the way the telescope is attached, mechanical flexure of the telescope and atmospheric refraction which bends the position of a star the closer it gets to the horizon. To calibrate the ASA mounting I told it to point where it thought a star should be, I then fine tuned that pointing using my camera and, with the star centered exactly on the electronic crosshairs, I then told the mounting's software that that was where the star actually was. Repeat many times (I went over the top and repeated 82 times) with stars scattered all over the sky and then tell the software to build a pointing file so that in future it can compensate automatically for all those repeatable errors.

All fine and dandy and it's very nice to have a star appear where you expect when you tell the mounting to point the telescope at it but, of course, the real purpose is to allow the mounting to track the stars with high precision. How high? Well this is a 400% crop of a few stars with an unguided exposure time of 1,000 seconds (16 minutes 40 seconds). The scale is 0.475 seconds of arc per screen pixel.

    Image

Photoshop smoothed out the pixels during the 4x enlargement but it didn't make the shape any rounder. This was cropped from pretty near the corner of a single 4096 x 4096 pixel Hα sub (the ML16803 sensor has a diagonal of 52.1 mm) in the Gulf of Mexico region of the North America nebula so it will show up tracking errors, image rotation caused by polar misalignment and optical flaws in the TEC 140 'scope and field flattener. The only processing done was image calibration (bias, dark and flat frames applied) and a histogram stretch to show the stars at reasonable brightness while de-emphasising the nebulosity as all I wanted to test was star roundness. For context here is a 100% crop of the region taken from a stack of eight 1,000 second Hα subs with a more normal histogram stretch and a little contrast enhancement and noise reduction applied.

    Image

For this image the scale is 1.9 seconds of arc per pixel. Quick and dirty processing done just for the purpose of this post. The data will eventually be combined into a four panel mosaic of the area which I'll be working on this summer with, I hope, the addition of SII and OIII narrowband data as well as Hα and RGB. Based on what I'm seeing I think the mounting will comfortably be able to run 1,500 second exposures for the SII and OIII subs so I'd better order those filters! 8)

Bob.

P.S. Please note that this is not some April fool's joke - no deconvolution was applied to either image!

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Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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PostPosted: Thu Apr 12, 2012 4:09 am 
Wow!

I'm so jealous of you right now. I've always wanted a telescope but I never had the chance to have one.

Can I use your take on the moon as a desktop wallpaper? It looks remarkable. The details on it are amazing.


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PostPosted: Thu Apr 12, 2012 11:07 am 
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Hi hunterstella,

I'm glad you like it and you are welcome to use it. The terminator doesn't show too well, largely because the shot was taken through cirrus cloud. I am delighted with the scope but if you are able to get a scope see if you can get one with a GoTo mount. They really do help you get more value from the optical bits.

Bob.

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Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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PostPosted: Thu Apr 12, 2012 1:23 pm 
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When I saw the ASA logo, the first thing I thought of was NASA. Maybe they could borrow some off your telescope with all the budget cuts going on over there. :oops:


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PostPosted: Fri Jun 07, 2013 12:39 am 
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Hi folks,

A little over a year on and I've finally summoned up the courage to update the software controlling the mounting. That also provided a good excuse to do a new polar alignment (now just 1.6 minutes of arc away from perfect), recalibrate the high precision encoders which allow the mounting to know exactly where (it thinks) it is pointing and build a new pointing file. That is done by telling the mounting to point the 'scope at a selection of stars all over the sky (I used 51) and then fine tuning the pointing for each one in turn using the camera. The difference between where the mounting thinks it is pointing and where you tell it is pointing allows the software to build an error map which is used to aid unguided tracking. MaximDL is my tool of choice to control the camera and its crosshair display gets each star close to the center of the field and then the Information Window can be used to determine the exact position of the star (to sub-pixel accuracy) in the frame.

It looks like it has gone really well over the two nights it took to do all this but the proof of the pudding will be over the coming weeks as I start imaging again. Fingers crossed that the unguided tracking accuracy will be even better on those 1,000 second exposures!

Bob.

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Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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PostPosted: Fri Jun 07, 2013 2:24 am 
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wow Bob, first time I read this thread, good setup. Hope you get good weather with clear night time skys.

:D How does it go shooting down V2 rockets? :D

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PostPosted: Fri Jun 07, 2013 8:16 am 
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I really should even start to configure the software for my setup. Still been running it semi-manually. My thought is, does it really get dark enough now to do serious deep sky? Then again, if my memory is right Bob did get some rather nice filters not that long ago... :)

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PostPosted: Fri Jun 07, 2013 8:50 am 
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Hi Max, Hi popo,

Nope, no rockets shot down yet. The mounting should be capable of following the ISS but I've not found a way to command that yet.

The nights maybe short but there are still enough hours of darkness to do some imaging - and I'm currently eyeing up NGC 7822 as a target for those new filters as it rises above my northern horizon around about dusk right now. I finished off last night by doing a single 1,000 second unguided exposure through my H-alpha filter, not with any particular object in mind but to have a first look at the tracking. Just one spot on the sky so surprises may still lurk if I've made a mistake identifying a star as I built the pointing file but here's the result at 400% (0.475 seconds of arc per screen pixel), stretched to give the maximum detail within the stars rather than to show any nebulosity:

    Image

There was some thin cloud around last night which didn't help but ignoring the hot pixel and just considering the roundness of the stars this looks very encouraging - slightly better than before, I think. Another benefit I've noticed is that the mount now does a much better job of pointing accurately after a meridian flip. I'd still re-sync the pointing before imaging as I like to start off with the best possible accuracy. That way even after dithering each sub to allow the stacking process to remove any remaining hot pixels I can still just crop a 48 pixel border safe in the knowledge that all the remaining pixels are derived from a full set of subs.

Bob.

_________________
Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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