ICEINSPACE
Most Read Articles
Moon Phase
CURRENT MOON Waxing Crescent
32.5%
The Sun Now
Time Zones
Sydney
12:27 am
Perth
10:27 pm
Auckland
2:27 am
New York*
10:27 am
Paris*
4:27 pm
GMT
2:27 pm




  #81  
Old 20-07-2018, 10:32 PM
Peter Ward's Avatar
Peter Ward
Registered User

Peter Ward is offline
 
Join Date: Dec 2007
Location: The Shire
Posts: 5,971
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!
Reply With Quote
  #82  
Old 21-07-2018, 07:45 AM
gregbradley's Avatar
gregbradley
Registered User

gregbradley is offline
 
Join Date: Feb 2006
Location: Sydney
Posts: 14,642
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.
Reply With Quote
  #83  
Old 21-07-2018, 07:47 AM
multiweb's Avatar
multiweb (Marc)
ze frogginator

multiweb is offline
 
Join Date: Oct 2007
Location: Hinchinbrook
Posts: 16,440
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.
Reply With Quote
  #84  
Old 21-07-2018, 02:59 PM
Paul Haese's Avatar
Paul Haese
Registered User

Paul Haese is offline
 
Join Date: Jan 2009
Location: Adelaide
Posts: 9,098
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.
Attached Thumbnails
Click for full-size image (Centre outside focus 20 July 2018.jpg)
5.2 KB52 views
Reply With Quote
  #85  
Old 21-07-2018, 03:31 PM
glend (Glen)
Registered User

glend is offline
 
Join Date: Jun 2013
Posts: 4,655
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.
Reply With Quote
  #86  
Old 21-07-2018, 03:59 PM
Paul Haese's Avatar
Paul Haese
Registered User

Paul Haese is offline
 
Join Date: Jan 2009
Location: Adelaide
Posts: 9,098
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.
Reply With Quote
  #87  
Old 21-07-2018, 04:13 PM
Slawomir's Avatar
Slawomir (Suavi)
PI cult member

Slawomir is offline
 
Join Date: Sep 2014
Location: Proserpine
Posts: 2,493
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.
Reply With Quote
  #88  
Old 22-07-2018, 08:18 AM
gregbradley's Avatar
gregbradley
Registered User

gregbradley is offline
 
Join Date: Feb 2006
Location: Sydney
Posts: 14,642
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.
Reply With Quote
  #89  
Old 22-07-2018, 09:00 AM
Slawomir's Avatar
Slawomir (Suavi)
PI cult member

Slawomir is offline
 
Join Date: Sep 2014
Location: Proserpine
Posts: 2,493
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.
Reply With Quote
  #90  
Old 22-07-2018, 09:21 AM
Atmos's Avatar
Atmos (Colin)
Ultimate Noob

Atmos is offline
 
Join Date: Aug 2011
Location: Melbourne
Posts: 5,439
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!
Reply With Quote
  #91  
Old 22-07-2018, 12:05 PM
luka's Avatar
luka
Unregistered User

luka is offline
 
Join Date: Apr 2007
Location: Perth, Australia
Posts: 1,005
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"
Reply With Quote
  #92  
Old 22-07-2018, 01:09 PM
LewisM's Avatar
LewisM
Novichok test rabbit

LewisM is offline
 
Join Date: Aug 2012
Location: Somewhere in the cosmos...
Posts: 8,036
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.
Reply With Quote
  #93  
Old 22-07-2018, 02:12 PM
ericwbenson (Eric)
Registered User

ericwbenson is offline
 
Join Date: Sep 2009
Location: Adelaide, Australia
Posts: 192
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
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 12:27 AM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.
Advertisement
OzScopes Authorised Dealer
Advertisement
Lunatico Astronomical
Advertisement
Interest Free Finance
Advertisement
FLI Cameras and Imaging Accessories
Advertisement
Atik Horizon
Advertisement
Bintel
Advertisement
SkyWatcher WiFi Adaptor
Advertisement
SkyWatcher 2018 Catalogue
Advertisement
NexDome Observatories
Advertisement
Astronomy and Electronics Centre
Advertisement