#41  
Old 07-10-2015, 04:17 PM
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Great looking scope Peter,

How big is your dome and how much clearance does the scope leave you with?

John K.
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  #42  
Old 07-10-2015, 04:20 PM
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Originally Posted by Peter Ward View Post
I had Alluna custom machine some bolt holes on the side of the scope so
I could mount a pair of Losmandy universal plates...hence the AP slung on the west side which counterbalanced on the east.

The north south balance was for two reasons....firstly to get the OTA lower
down to better fit in the dome, and second to allow for different camera weights. This simply a standard d-plate extending from the PME saddle
with a sliding counterweight...hence no load is being applied to the carbon truss.

Nicely planned out. If I change the camera on the CDK I have to move the scope in its large Planewave dovetail which has 3 very large tightening handles. Its not that hard but I worry about loosening the dovetail to move it. If I undo them too much it would be probably impossible for me to hold the scope up as it weighs too much. So I use a lot of caution, although I have done it many times now.

Greg.
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  #43  
Old 07-10-2015, 05:21 PM
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Peter, what are those doughnuts around Fomalhaut? There's three overlaid on top of each other, each getting bigger?

H
I suspect off axis reflections from the field corrector..or possibly the CCD window/filters.

In time I'll try out all configurations (eg mirrors only, reducer/corrector) to see whether there is a difference.

I'm not fussed as I've seen similar in my other 'scopes...plus I don't normally take images of 1st Magnitude stars.
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  #44  
Old 07-10-2015, 05:23 PM
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Originally Posted by gregbradley View Post
Nicely planned out. If I change the camera on the CDK I have to move the scope in its large Planewave dovetail which has 3 very large tightening handles. Its not that hard but I worry about loosening the dovetail to move it. If I undo them too much it would be probably impossible for me to hold the scope up as it weighs too much. So I use a lot of caution, although I have done it many times now.

Greg.
The thought worth 60kg worth of telescopes sliding off the saddle I find a little scary....hence the sliding lateral weights!
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  #45  
Old 07-10-2015, 05:32 PM
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Great looking scope Peter,

How big is your dome and how much clearance does the scope leave you with?

John K.

Bog standard Sirius 2.3 metre.... that said, I have to limit southerly slews
to about 15 degrees above the horizon, as the OTA won't quite clear the dome at very low southern altitudes.

The pier really needs to be about 20cm further north. It would then have full and free clearance.....but I didn't foresee a 16" RC when I set it up 20 years ago! (my C11 at the time, had heaps of room )
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  #46  
Old 08-10-2015, 01:19 PM
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Originally Posted by Peter Ward View Post
I suspect off axis reflections from the field corrector..or possibly the CCD window/filters.

In time I'll try out all configurations (eg mirrors only, reducer/corrector) to see whether there is a difference.

I'm not fussed as I've seen similar in my other 'scopes...plus I don't normally take images of 1st Magnitude stars.
Yep see them on my scope too on really bright stars. Those are a product of bright stars and getting reflections back from all the optical surfaces. I doubt there would be anything to worry about.
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  #47  
Old 08-10-2015, 01:24 PM
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Beautifully pinpoint stars. A very encouraging first light.

I wouldn't worry about those minor rings. I am sure you will track it down. The corrector is the most likely culprit.

Greg.
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  #48  
Old 08-10-2015, 04:53 PM
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Stars look great across the entire image - looking forward to the "2nd light"
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  #49  
Old 08-10-2015, 06:41 PM
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Looks stunning on the mount and first very brief light seems good indeed.

Guiding with an AP130 Starfire... Thats they type of excess only Mr. Ward can muster I think.

Bung an old st10xme in there as a guide camera and I reckon you could guide on 13th magnitude stars.
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  #50  
Old 08-10-2015, 08:33 PM
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Looks stunning on the mount and first very brief light seems good indeed.

Guiding with an AP130 Starfire... Thats they type of excess only Mr. Ward can muster I think.

Bung an old st10xme in there as a guide camera and I reckon you could guide on 13th magnitude stars.
Actually the Starfire won't be used as a guidescope (self-guide cameras
make them redundant) but it will be my new Solar (H-alpha) scope....so glad I didn't sell it!
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  #51  
Old 08-10-2015, 08:43 PM
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but it will be my new Solar (H-alpha) scope....so glad I didn't sell it!
Now that will make a nice solar scope
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  #52  
Old 08-10-2015, 08:54 PM
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Beautifully pinpoint stars. A very encouraging first light.

I wouldn't worry about those minor rings. I am sure you will track it down. The corrector is the most likely culprit.

Greg.
Ta...the only adjustment I had to make was a slight primary collimation tweak....the secondary was dead-nuts on. Not bad considering it was shipped from Europe.

The field corrector spacing won't be optimal until the precise parts adapter shows....that said, looking at the off-axis stars the correction looks pretty awesome already.

Alluna have a few more software tweaks in the pipeline..eg: focus tracking

The attention to engineering detail has blown me away, it makes my old RCOS look clunky.

From the pin-point secondary collimation spot to oversize stainless bolts, collar locked electronics connectors, sequenced robotic mirror cover flaps that fully overlap when closed, 18 point mirror cell, carbon fibre shroud etc.

The interferogram shows a Strehl of around 95% with not even a hint of a turned edge.

I'm really looking forward to getting some serious data with this puppy
(actually more of a Rottweiler )
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  #53  
Old 09-10-2015, 08:07 AM
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That's really good. It sounds amazing. Looking forward to first light. I think 16/17 inches is a good size. 20 inch is a big jump in cost and weight and whilst it may capture a bit of extra detail the bang for your buck gain from the extra aperture seems not so great.

Whereas the jump from 12 inches to 16/17 is a large one. A bit like the jump from 4 to 6 inch APOs.

Greg.
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  #54  
Old 10-10-2015, 01:33 AM
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I finally got to taking a little data tonight....sans some decent flat-fields due overcast early in the evening (I like to use sky flats)

Looks like there are a few small tweaks needed. The camera system needs a little shimming...and without the correct spacing field flattener
is a tad off its optimum distance from the CCD....

So! A couple more test images.....warts and all.

M42...of course .... 2 minutes unguided

NGC1365 had a mere 30 minutes of exposure, self guide mode. There is a weird stray reflection/arc lower left that I suspect is from the obs' PC screen....

Both are straight luminance, un-cropped 16803 fields. Darks, a dodgy flat and some scaling was the limit of the processing.

Seeing was just OK, but as the focal length is around 3340mm I'm pretty pleased with stellar footprints so far.
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  #55  
Old 10-10-2015, 07:28 AM
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That looks very good. I used to see some reflection arcs like that occasionally on the CDK. What seemed to stop it was the baffle they supplied that went around the primary mirror baffle and is about 15mm wide. Also they supplied baffles that went on both sides of the corrector. Only one is still in the other needs to be reglued but I don't see any reflections now so it must not do much.

Greg.
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  #56  
Old 10-10-2015, 09:38 AM
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Detail looks good Peter, the halo is most likely a very bright star just outside the field of view. Most likely mirror distance is slightly out from the null point. Might be worth checking.

Would be good to have the scope in a dark sky though.
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  #57  
Old 10-10-2015, 12:36 PM
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Detail looks good Peter, the halo is most likely a very bright star just outside the field of view. Most likely mirror distance is slightly out from the null point. Might be worth checking.

Would be good to have the scope in a dark sky though.
Well...so far so good.

Alluna's TCS focus software graphically shows where you are relative to the optimal spacing...it's not optimum yet (the required part should turn up soon), but I suspect it needs a further collimation tweak and squaring on of the camera.

I've uploaded a more detailed web page here
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  #58  
Old 10-10-2015, 07:27 PM
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The attention to engineering detail has blown me away, it makes my old RCOS look clunky.
Glad to see that we are comparing older manufacturing to current manufacturing.

Making statements like this is simply ridiculous.
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  #59  
Old 10-10-2015, 08:10 PM
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Glad to see that we are comparing older manufacturing to current manufacturing.

Making statements like this is simply ridiculous.
Whoa there Mr Echo, your ripping into a guy with nearly 5000 posts, compared to your 5! You don't know him or the context of his statement.

Much to learn, you still have.
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  #60  
Old 10-10-2015, 08:23 PM
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Mmm. That 1365 looks amazingly good for just 30min Peter.

Once you get that alignment and collimation seer sorted this will be producing some ripper images in no time.
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