#1  
Old 25-11-2008, 10:52 AM
erick's Avatar
erick (Eric)
Starcatcher

erick is offline
 
Join Date: Dec 2006
Location: Shoalhaven Heads
Posts: 8,469
New T-adapter

I know little about astrophotography, but I do have a HoTech laser collimator, purchased mainly because of the clever way of mounting in the focusser - their so-called SCA ("Self-Centering Adapter").

The HoTech have developed a T-adapter based on that technology:-

http://www.hotechusa.com/SCA%20T-Adapter.html

What do you imaging folks make of that?
Reply With Quote
  #2  
Old 25-11-2008, 02:34 PM
bojan's Avatar
bojan
amateur

bojan is offline
 
Join Date: Jul 2006
Location: Mt Waverley, VIC
Posts: 5,884
It uses expandable rubber rings to obtain grip around barrel (they probably expand because of axial pressure).
It might not be as repeatable and as rigid as claimed.. possible temperature issues? therefore too expensive...
But perhaps it is worth checking..

Last edited by bojan; 25-11-2008 at 02:52 PM.
Reply With Quote
  #3  
Old 26-11-2008, 06:39 AM
celstark (Craig)
Registered User

celstark is offline
 
Join Date: Nov 2008
Location: Irvine, CA
Posts: 17
I've had a chance to use them a bit and posted a blog entry here:
http://www.stark-labs.com/blog/blog.php

They're very solid and I've not noticed anything changing with temperature. Once clamped on there, they're going nowhere...

Craig
Reply With Quote
  #4  
Old 26-11-2008, 07:38 AM
erick's Avatar
erick (Eric)
Starcatcher

erick is offline
 
Join Date: Dec 2006
Location: Shoalhaven Heads
Posts: 8,469
Hi Craig

Your blog suggests you are a happy customer!
Reply With Quote
  #5  
Old 28-11-2008, 09:32 AM
multiweb's Avatar
multiweb (Marc)
ze frogginator

multiweb is offline
 
Join Date: Oct 2007
Location: Hinchinbrook
Posts: 18,138
The best solutions are always the simplest ones. Such a clever design.
Reply With Quote
  #6  
Old 28-11-2008, 09:38 AM
multiweb's Avatar
multiweb (Marc)
ze frogginator

multiweb is offline
 
Join Date: Oct 2007
Location: Hinchinbrook
Posts: 18,138
Quote:
Originally Posted by bojan View Post
It uses expandable rubber rings to obtain grip around barrel (they probably expand because of axial pressure).
It might not be as repeatable and as rigid as claimed.. possible temperature issues? therefore too expensive...
But perhaps it is worth checking..
All hydraulic [oil] technology works at high pressure and high temperatures mostly. I remember in my short time working with Liebherr and Klem Hydraulic hammers that everything that had a moving piston had those centering groves and series of O'rings and composite material rings ... and these hammer drills used to hit at 2000 hits per minutes with pressures exceeding 400 bars so it was critical everything was aligned with very tight tolerances. So I recon the focuser grip with 3 O'rings will stay centered no matter what once it's "clamped in"
Reply With Quote
  #7  
Old 28-11-2008, 01:01 PM
DeanoNZL (Adrian)
Seize The Night

DeanoNZL is offline
 
Join Date: Sep 2006
Location: Rodney, New Zealand
Posts: 310
Hi Craig.
Welcome to IIS.

For those unaware, Craig is the author of PHD guiding & Nebulosity.
Reply With Quote
  #8  
Old 28-11-2008, 07:57 PM
Dennis
Dazzled by the Cosmos.

Dennis is offline
 
Join Date: May 2005
Location: Brisbane
Posts: 10,866
Quote:
Originally Posted by DeanoNZL View Post
Hi Craig.
Welcome to IIS.

For those unaware, Craig is the author of PHD guiding & Nebulosity.
Thanks for the heads up Deano, itís nice to know when an international luminary drops by, a name to be remembered and respected indeed. With the introduction of PHD Guiding, Craig irrevocably changed the landscape of auto guiding overnight!

Thanks Craig, for a terrific set of applications. Your prodigious output never ceases to amaze me, Iím sure there are at least 2 or 3 of you, or is it that you simply donít require sleep!

Welcome to Ice In Space.

Cheers

Dennis
Reply With Quote
  #9  
Old 29-11-2008, 06:24 AM
[1ponders]'s Avatar
[1ponders] (Paul)
Retired, damn no pension

[1ponders] is offline
 
Join Date: Nov 2004
Location: Obi Obi, Qld
Posts: 18,778
to IIS Craig. If you've given it the then I'd guess it definitely one to look into then.

BTW Thanks for some great astro applications, I know I'd be lost without them.
Reply With Quote
  #10  
Old 02-12-2008, 04:14 AM
celstark (Craig)
Registered User

celstark is offline
 
Join Date: Nov 2008
Location: Irvine, CA
Posts: 17
Thank you all, but "luminary" is a bit much, IMHO, unless you're referring to the effect of the bright Southern California sun bouncing off my bald head, temporarily blinding those around me

Anyway, it's hard for those getting their guiding rigs going to underestimate the role that flex can play in making us tear our hair out (did I mention I was bald?). A few weeks ago, I was looking at a new-to-me 8" f/5 Antares (Synta) Newt and the new "wsg" off-axis guide setup for my QSI camera. I ran some tests using my current guide rig (the Borg XY setup -- great, great setup) and the onboard "wsg", looking at the post-guiding error (what Nebulosity reports it had to do to align the frames).

With the "wsg", I averaged 0.14 pixels of error across a 25 minute run (this is error in the main image, so where it really counts). I could stack without any alignment and have no issues at all (using whole-pixel alignment, no frames were shifted at all).

Without and using a separate guide scope, the error was horrible. I was drifting at almost 2 pixels per minute!

Why? Does my guide scope suck? Nope, the Borg is a rock (previously tested as equal to at least 0.95 rocks). The focuser and the main tube itself flex a good bit under the load of this heavy camera. Move the camera around and you can watch the tube flex. Think that'll have an effect on your collimation and your guiding accuracy? You bet...

Anyway, that's why I like this HoTech setup. The coupling of the scope to the focuser is one place I've had to fight this (I had a really bad time of it on a TMB 105-LW I used to have). It's such a simple idea and it just plain works. That source of flex is just taken out of the equation (and you're left to fight the other sources...)

Craig
Reply With Quote
  #11  
Old 02-12-2008, 06:55 AM
Dennis
Dazzled by the Cosmos.

Dennis is offline
 
Join Date: May 2005
Location: Brisbane
Posts: 10,866
Hi Craig

Thanks for the details on the flexure investigation – I am gradually taming my rig having iteratively minimised various contributing factors. I reckon the next step is to try one of Ho’s adapters – a Xmas present to myself!

Cheers

Dennis
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 04:13 PM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Advertisement
Bintel
Advertisement
SkyWatcher Australia
Advertisement
OzScopes Authorised Dealer
Advertisement
Lunatico Astronomical
Advertisement
NexDome Observatories
Advertisement
Celestron Australia
Advertisement
Meade Australia
Advertisement
Astronomy and Electronics Centre
Advertisement