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  #81  
Old 20-07-2018, 09:32 PM
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Peter Ward
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Quote:
Originally Posted by glend View Post
According to the website the AP 305mm is shipped on a pallet, which normally you would expect to be handled by a forklift, not thrown into cargo holds. And the pallet and shipping is on top of the $22k USD price. It's way over the Orion price point.
Yes, Yes. and Yes. Shipping 5 years ago was $AUD 1400

So the AP is indeed now about twice the price...but it simply works and is a little more complex to make than a Newtonian with a Wynne Corrector.

But I would expect for..best guess.. $AUD 17k...should I'd be getting the bee's knees in corrected Newts that I did not have to "rebuild" to make functional.

Secondary spacing should be absolutely nailed at the factory and is not something that would made amiss by shipping from A to B.

As I said..a gutsy effort from Paul.

But to quote one R. Benaud on Orion Optics: pi$$ poor effort that!
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  #82  
Old 21-07-2018, 06:45 AM
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Also keep in mind to retail a product in Australia by law it must be fit for purpose.

Nobody rebuilds a poorly mounted engine in their new Toyota Corolla. That's a budget but high quality car.

Greg.
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  #83  
Old 21-07-2018, 06:47 AM
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Quote:
Originally Posted by gregbradley View Post
Also keep in mind to retail a product in Australia by law it must be fit for purpose.

Nobody rebuilds a poorly mounted engine in their new Toyota Corolla. That's a budget but high quality car.

Greg.
That about says it all.
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  #84  
Old 21-07-2018, 01:59 PM
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Well I managed to get down to the observatory for quick visit last night to do final collimation. I think that is achieved now, but will need a closer to focus test in better seeing. Perhaps the secondary is still a tweak out of circular. With the storm that has passed though in the last day or so the seeing has been fairly average, so it will have to wait.

I also now need to find out what the correct distance of the corrector should be. OOUK site says the correct distance is 79mm +/- 1mm from the lens to the sensor. The adapter that was made for me by them is 32mm screwed all the way down. The back focus of the QSI is 50.4mm from the T adapter to sensor, then I need to subtract 1mm for Astrodon filters and that equals 49.4mm. 79-49.4 = 29.6mm. At the suggestion of the manufacturer I moved the corrector further away by 4mm and took images. This has made things slightly worse general (although the centre is now sharp with the better collimation), which comes as no surprise. So I have ordered a new adapter from Precise Parts of 28mm. OOUK have supplied a locking ring which will help me set the correct distance I hope. I hope their information about the corrector is accurate. It's a $400 adapter.
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  #85  
Old 21-07-2018, 02:31 PM
glend (Glen)
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Doesn't the filter act to push the focus further away from the camera sensor so to reach precise focus you need to add backspacing, using the Rule of One Third. So 3mm of filter thickness, or combinations of filter, cover glass etc that add up to 3mm, require an addition of 1mm of focal distance, thus adding to the backspacing by 1mm. I have been using this rule for years.
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  #86  
Old 21-07-2018, 02:59 PM
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Quote:
Originally Posted by glend View Post
Doesn't the filter act to push the focus further away from the camera sensor so to reach precise focus you need to add backspacing, using the Rule of One Third. So 3mm of filter thickness, or combinations of filter, cover glass etc that add up to 3mm, require an addition of 1mm of focal distance, thus adding to the backspacing by 1mm. I have been using this rule for years.
Click here and see Backfocus adjustment with filters. It says -1mm. Maybe I am reading it incorrectly.
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  #87  
Old 21-07-2018, 03:13 PM
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Glad too see that you managed to adjust the telescope nearly perfectly Paul. I have been tempted by the idea of having a fast Newtonian myself.

You are correct Paul that 1mm needs to be subtracted for Astrodons - the camera needs to be brought closer to the corrector.
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  #88  
Old 22-07-2018, 07:18 AM
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I don't think that is correct. Here is a quote from the Astrodon site:

Please note that camera manufactures often specify the MECHANICAL back focus of their products. 3 mm thick filters will ADD 1 mm (0.04") to that mechanical backfocus as measured from the telescope or from the MonsterMOAG prism. The camera window, often 3 mm thick will add another 1 mm (0.04"). So, You may have to add 2 mm (0.09") to the mechanical backfocus.
There may be some confusion as camera manufacturers measure backfocus from the focal plane of the CCD to the outer surface of the camera. When they account for the thickness of the filters, the SUBTRACT the 0.04", which is correct as measured from the CCD. However, most people measure backfocus from the back of their scope of from a corrector, and then add/subtract spacers to arrive at the correct backfocus. In this case, as measured from the scope, the 0.04" must be ADDED. A subtle point, but does get people in trouble from time to time.


There also is a thread on Cloudynights that discussed this QSI note.

Clearly the definition of optical backfocus has been misunderstood by QSI. They must be measuring mechanical backfocus.

I would research this point more before you order to satisfy yourself what is the correct spacing.

There is a thread that shows a ray diagram where the filters cause the light to bend less in extending the focus point of the light a bit further out.


Greg.
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  #89  
Old 22-07-2018, 08:00 AM
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Thank you for clarifying that Greg - it makes perfect sense now. I stand corrected. Itís a happy day - I learnt something new

I think what reinforced my mistake was trying to fine-tune a spacing for my Riccardi reducer. I am getting better results when I reduced recommended by APM for my telescopeís focal length physical distance between the Riccardi and the camera by about 1.5mm, and when I added a 1mm spacer correction was clearly worse.
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  #90  
Old 22-07-2018, 08:21 AM
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I've always worked from whatever the optical back focus requirement is from one point +1.

I have 53mm of working distance from my M68 to M48 adapter, the calculation would be:
54-23.8(current spacer I have)-15(filter wheel)-10.5(QHY163M)= 4.7mm

So if I want to put my QHY163M on my Sky Rover I need to add another 4.7mm of spacing which I will do but need some new screws

Unless someone tells me I'm doing it wrong!
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  #91  
Old 22-07-2018, 11:05 AM
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Quote:
Originally Posted by Paul Haese View Post
Click here and see Backfocus adjustment with filters. It says -1mm. Maybe I am reading it incorrectly.
It also says "Back focus reduced by". Maybe they meant "reduced by -1mm" which means "extended by 1mm"
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  #92  
Old 22-07-2018, 12:09 PM
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I am glad this is starting to coalesce into a decent scope Paul. As others have said though, this amount of adjustment and tinkering out of the box for a semi-premium scope (that should have been premium) shouldn't have to be done AT ALL. It's a damning shame against OOUK yet again. I'd be having harsh words with them.
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  #93  
Old 22-07-2018, 01:12 PM
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Quote:
Originally Posted by gregbradley View Post
There is a thread that shows a ray diagram where the filters cause the light to bend less in extending the focus point of the light a bit further out.

Greg.

Here is a link to the focus shift diagram on my website:


http://www.faintgalaxy.com/focusshift.htm


I think the confusion of the +1/-1 thing is because from QSI's point of view the filters are internal to the camera, hence making the 'camera unit' use less back focus out of the total available than what the mechanics would measure.


I always see the filters as 'helping' in the usually limited backfocus situation by lengthening the path available.


So be my calc:

79 - 50.4 + 1 = 29.6mm


or alternatively by QSI interpretation:
79 - (50.4 - 1) = 29.6



So Paul has it correct.


EB
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  #94  
Old 17-08-2018, 08:52 AM
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Well I finally got the new adapter. I installed that yesterday and took some images last night. The corrector is 79.4mm from the sensor but it looks like this is still a tiny bit too far away. So Orion Optics Website is yet again incorrect. Collimation needs some work and that might be contributing to this problem. I also note that using nylon screws to hold the corrector in place does need particular attention not to tighten one side more than the other; this being because there is just the tiniest amount of slop between the adapter which holds the corrector and the OD of the corrector and tightening one way or the other affects the correction. However, I think I am getting very close to having a working system. See attached image. The resolution looks pretty good overall.
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  #95  
Old 17-08-2018, 09:25 AM
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Just by way of comparison I have included a full resolution image taken on the 18th of July which shows the corners and centre.
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  #96  
Old 18-08-2018, 09:22 AM
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Quote:
Originally Posted by Paul Haese View Post
Well I finally got the new adapter. I installed that yesterday and took some images last night. The corrector is 79.4mm from the sensor but it looks like this is still a tiny bit too far away. So Orion Optics Website is yet again incorrect. Collimation needs some work and that might be contributing to this problem. I also note that using nylon screws to hold the corrector in place does need particular attention not to tighten one side more than the other; this being because there is just the tiniest amount of slop between the adapter which holds the corrector and the OD of the corrector and tightening one way or the other affects the correction. However, I think I am getting very close to having a working system. See attached image. The resolution looks pretty good overall.



Hi Paul,

Still not perfect but it's damn close.
What does CCD inspector show?


cheers
Allan
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  #97  
Old 01-10-2018, 04:19 PM
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Bit of a report on the scope.

I have been having all sorts of trouble trying to eliminate flex and star shape problems. My general motto in the past has been to use screw fittings on all the adapters I use (unless there is a dovetail zero tilt connection). I went with the adapters supplied by OOUK. The adapter from the Atlas that holds the corrector is a reasonably tight fit but has some movement which is supposed to be supported by nylon screws. This system cannot be used reliably to prevent flex or even get the star shapes right in every corner. At least that is the case in my experience. If you move the screws one way the stars go haywire in another corner.

Then the screw threaded adapter made by OOUK from the corrector to the QSI, was firstly too long, secondly the screw threads were not centred to each other, and then each set of threads were not parallel ( a friend of mine who is a machinist said that the each axis was out by over five thou. This means that each time you screw the adapter around by as little as an eighth of a turn the adapter will produce a slanting projection of the correction and that means stars will be not corrected properly and produce poor star shapes.

So I have had two more adapters made up by Precise Parts. One I am waiting on and the other I have already received but needed the thread depth adjusted due to OOUK drawing suggesting that correction is 79mm from the centre of the external rear element and that is level with the outside of the corrector housing. It is not level and in fact almost 1.5mm lower than the housing edge. I am now near the correct position for correction. The other adapter is to replace the adapter which holds the corrector. It will screw thread into the back of the corrector. With any luck this will be the end of these issues and allow me to get on with imaging.

A frustrating experience so far. If anyone asks me if I would recommend a Newtonian, I will certainly caution them about the issues I have faced with both Newt's I have owned in recent years.
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  #98  
Old 01-10-2018, 04:50 PM
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Thank you for sharing your journey with the scope Paul and I'm keeping fingers crossed that the new adapters will fix the last remaining issue.

By looking at the photo, the QSI is dwarfed by the Atlas and adapters!
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  #99  
Old 01-10-2018, 06:19 PM
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Good to hear you are still making progress, Paul. I have been struggling at f/2 and feel very sympathetic
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  #100  
Old 02-10-2018, 11:25 PM
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Certainly a frustrating experience Paul, in future if things go awall, you will know how to fix em'
It is not acceptable that parts, which need to be precise, are simply not up to standard. There are enough challenges without having to fix up the basics which should have been done properly from the factory!
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