Go Back   IceInSpace > Equipment > Equipment Discussions

Reply
 
Thread Tools Rate Thread
  #1  
Old 24-03-2015, 07:33 AM
gregbradley's Avatar
gregbradley
Registered User

gregbradley is offline
 
Join Date: Feb 2006
Location: Sydney
Posts: 17,877
Are GSO Truss RCs OK now?

I see a number of members have one but only Paul who has posted an image using one.

If you have a GSO truss RC - how are you finding?

Are the issues resolved now or would it be buying a project to get it operational?

Greg.
Reply With Quote
  #2  
Old 14-04-2015, 03:00 PM
baileys2611's Avatar
baileys2611 (Simon Bailey)
I like biscuits

baileys2611 is offline
 
Join Date: May 2012
Location: Murrumbateman
Posts: 337
I'm about to put a deposit on one but before I do that I'd be interested in this also. I see there's a plethora of forums on this and some people have had problems with the mirrors flopping.

...but, is there a better alternative for about $4k for DSO photography? I like taking shots of DSO and nebula, generally using a QHY8.
Reply With Quote
  #3  
Old 14-04-2015, 04:00 PM
baileys2611's Avatar
baileys2611 (Simon Bailey)
I like biscuits

baileys2611 is offline
 
Join Date: May 2012
Location: Murrumbateman
Posts: 337
Actually there's a few discussions on this already. Horses for courses, summary from what I've read so far: It's a long life, get in and experience them all if you can.
Reply With Quote
  #4  
Old 14-04-2015, 04:21 PM
Logieberra's Avatar
Logieberra (Logan)
Registered User

Logieberra is offline
 
Join Date: Mar 2010
Location: Canberra
Posts: 1,635
Does this count?
http://www.iceinspace.com.au/forum/s...d.php?t=132933
12 x 5min and 10 x 5min exposures for these, respectively.
Reply With Quote
  #5  
Old 14-04-2015, 05:14 PM
baileys2611's Avatar
baileys2611 (Simon Bailey)
I like biscuits

baileys2611 is offline
 
Join Date: May 2012
Location: Murrumbateman
Posts: 337
Yeah, I saws those earlier today Logan. Damn fine images, I know that the Sombrero holds a special place for you and is an excellent shot but the other picture is fantastic!
Reply With Quote
  #6  
Old 14-04-2015, 05:47 PM
Logieberra's Avatar
Logieberra (Logan)
Registered User

Logieberra is offline
 
Join Date: Mar 2010
Location: Canberra
Posts: 1,635
Quote:
Originally Posted by gregbradley View Post
... If you have a GSO truss RC - how are you finding?
Greg. I really love mine. Wonderful scopes for the price. Mirror coating was pristine out of factory, as it should be. The CF trusses are a beautiful thing. Mirror is as good as fixed. They use some kind of black compound to retain the primary. Secondary housing and bolts are solid as. Holds colimation beautifully. All joints, connections and bolts etc - very rigid. GSO got it right, for the price.
Reply With Quote
  #7  
Old 14-04-2015, 05:49 PM
Paul Haese's Avatar
Paul Haese
Registered User

Paul Haese is offline
 
Join Date: Jan 2009
Location: Adelaide
Posts: 9,937
Yes the scopes have reached a level of maturity now. The 12-16" models should have the new back plate which has the collimation ring incorporated. If it does not ask for one that does. The new back plate is designed to remove loads placed on the mirror cell.

Some things you will need to do though.

  • The focusor is garbage and no good for lifting heavy loads. A good focusor is a must. The FLI Atlas is perfect as a suggestion.
  • The secondary can be prone to dewing up in areas with heavy dew. I have installed a dew heater into the secondary and that has removed that problem. If you like I can dig up some photos of how I did the install.

Other than these minor issues these scopes are good.

Careful collimation is a must though. You cannot do a good job without a Takahashi collimation scope. I cannot stress this enough. It is next to impossible to get the primary aligned without one. The primary will move during transport and will need adjusting. A laser will not work properly. The Glatter one is not going to work for you at all and gives inconclusive results. Anyone considering buying one of these scopes needs to take my advice on this.
Reply With Quote
  #8  
Old 14-04-2015, 06:36 PM
niharika
Registered User

niharika is offline
 
Join Date: Jun 2012
Location: melbourne
Posts: 216
What flattener options are available for medium to large format CCDs?
Reply With Quote
  #9  
Old 14-04-2015, 07:36 PM
baileys2611's Avatar
baileys2611 (Simon Bailey)
I like biscuits

baileys2611 is offline
 
Join Date: May 2012
Location: Murrumbateman
Posts: 337
Fair enough on the colimation & focuser. I've got a moonlite I was going to use and will obviously need to invest in a colimator and shroud, but I use a QHY8 which is large format so will also need to look at a flattener I think.
Reply With Quote
  #10  
Old 14-04-2015, 07:51 PM
Paul Haese's Avatar
Paul Haese
Registered User

Paul Haese is offline
 
Join Date: Jan 2009
Location: Adelaide
Posts: 9,937
Quote:
Originally Posted by niharika View Post
What flattener options are available for medium to large format CCDs?
I've been working on using a TS Optical 3" flattener suited for RC's Getting the right spacing has proven to be a pain. I hope that TS have given me the right spacing this time.
Reply With Quote
  #11  
Old 15-04-2015, 06:49 PM
Logieberra's Avatar
Logieberra (Logan)
Registered User

Logieberra is offline
 
Join Date: Mar 2010
Location: Canberra
Posts: 1,635
Quote:
Originally Posted by niharika View Post
What flattener options are available for medium to large format CCDs?
Paul, I found your flattener post: http://www.iceinspace.com.au/forum/s...d.php?t=125409

If you're having to buy multiple PreciseParts adapters - I feel for you. They cost a fortune! I hope TS compensates you in some fashion, for the incorrect spacing advertised...
Reply With Quote
  #12  
Old 15-04-2015, 07:07 PM
Paul Haese's Avatar
Paul Haese
Registered User

Paul Haese is offline
 
Join Date: Jan 2009
Location: Adelaide
Posts: 9,937
After testing last night I can confirm that the spacing is still a little off. It is certainly better than it was but it is still not 100%. I have attached crops at 100% of the corners. Not a lot in it but enough to irk me. I have requested a response from TS Optical. So far I have had two adapters for this part of the imaging train. Though that is nothing compared to the 6 adapters I have had made up for the rest of the train because GSO don't have specs on their back focus from the back plate. I had to request back focus specs but got ones from the sagitta of the mirror. Not very useful. I think Ashley from Precise Parts loves it every time I order yet another adapter.
Attached Thumbnails
Click for full-size image (bottom left.jpg)
166.1 KB39 views
Click for full-size image (bottom right.jpg)
17.5 KB40 views
Click for full-size image (Top left.jpg)
19.7 KB38 views
Click for full-size image (Top right.jpg)
16.3 KB39 views
Reply With Quote
  #13  
Old 15-04-2015, 07:39 PM
Howie Glatter
Registered User

Howie Glatter is offline
 
Join Date: Nov 2011
Location: Bronx, New York, USA
Posts: 11
Paul Haese said: "The Glatter one is not going to work for you at all and gives inconclusive results."

Can you detail why ?
Reply With Quote
  #14  
Old 15-04-2015, 08:04 PM
Paul Haese's Avatar
Paul Haese
Registered User

Paul Haese is offline
 
Join Date: Jan 2009
Location: Adelaide
Posts: 9,937
Quote:
Originally Posted by Howie Glatter View Post
Paul Haese said: "The Glatter one is not going to work for you at all and gives inconclusive results."

Can you detail why ?
In all the tests I have done with the laser and adapter for making concentric circles I have noted that little if any difference could be seen in the concentric rings and yet the collimation would be wildly out from the results using a Takahashi collimation scope. I followed your instructions to the letter and I got the same result each time.

Now I am happy to have it wrong and use the collimator rather than it become a counter weight and would welcome any tips you might have on how to get a very accurate result. I need to warn you, I am really a stickler when it comes to collimation.

In the end this is only my opinion, and I have found that using a Takahashi scope works best at solving collimation on these scopes. And then a final tweak on a out of focus star.
Reply With Quote
  #15  
Old 15-04-2015, 08:21 PM
gregbradley's Avatar
gregbradley
Registered User

gregbradley is offline
 
Join Date: Feb 2006
Location: Sydney
Posts: 17,877
Sounds like you need a variable length adapter and then you fine tune it by trial and error.

I think there are some like this stock from some suppliers but Ashley may be able to make a variable one that suits your setup. If it has a range of say 20mm you should be able to nail it.

If its getting better as you go shorter then I suppose you need to go even shorter.

Of course you are assuming the corrector works perfectly at a certain distance. We aren't talking Takahashi, AP or APM quality here so there is a chance the corrector is not up to the job. Full frame is pretty demanding on the optics in my experience. But if changing the distance is getting an improvement then the variable approach is the way to go (2 adapters one that slides into the other and can be locked down).

Looking at your corners at an educated guess that looks like more than 3mm error in the spacing. More like 5-10mm.

What percentage did it change when you reduced the spacing by 3mm?

Greg.
Reply With Quote
  #16  
Old 15-04-2015, 08:50 PM
Paul Haese's Avatar
Paul Haese
Registered User

Paul Haese is offline
 
Join Date: Jan 2009
Location: Adelaide
Posts: 9,937
Quote:
Originally Posted by gregbradley View Post
Sounds like you need a variable length adapter and then you fine tune it by trial and error.

I think there are some like this stock from some suppliers but Ashley may be able to make a variable one that suits your setup. If it has a range of say 20mm you should be able to nail it.

If its getting better as you go shorter then I suppose you need to go even shorter.

Of course you are assuming the corrector works perfectly at a certain distance. We aren't talking Takahashi, AP or APM quality here so there is a chance the corrector is not up to the job. Full frame is pretty demanding on the optics in my experience. But if changing the distance is getting an improvement then the variable approach is the way to go (2 adapters one that slides into the other and can be locked down).

Looking at your corners at an educated guess that looks like more than 3mm error in the spacing. More like 5-10mm.

What percentage did it change when you reduced the spacing by 3mm?

Greg.

TS Optical did some measurements and came up with the last back focus length. Apparently some optical tech said it would be right this time.

You could be right about it being more. The improvement over the field has been about 94% looking corrected rather than about 50%.

You could be right, the flattener might not be up to what is being stated on their website but I have seen an image taken with a STL11K and this flattener on a GSO RC12 and it looked really good.

Yes a sliding adapter might be ok, but I have put the ball in their court for the moment and I have an acceptable level of correction at present.

I am with you 100% about sensor size. This camera is not for this scope long term, but now this scope has to fill my wants.
Reply With Quote
  #17  
Old 15-04-2015, 09:00 PM
Logieberra's Avatar
Logieberra (Logan)
Registered User

Logieberra is offline
 
Join Date: Mar 2010
Location: Canberra
Posts: 1,635
Quote:
Originally Posted by Howie Glatter View Post
Paul Haese said: "The Glatter one is not going to work for you at all and gives inconclusive results."

Can you detail why ?
With the RCOS guys swearing by the Tak Collimation Scope, I didn't think to look elsewhere. Where I have found the Glatter comes in handy (I borrow a mate's on occasion), is aligning the focuser to the factory applied seconday 'spot'. The small laser 'dot' of the Glatter works well there.
Reply With Quote
  #18  
Old 15-04-2015, 09:04 PM
gregbradley's Avatar
gregbradley
Registered User

gregbradley is offline
 
Join Date: Feb 2006
Location: Sydney
Posts: 17,877
If you can see examples where it is fully corrected then that gives you confidence it can be done.

Funnily with my experience in flatteners they have not been this sensitive to a few mm being exact. But that's with refractors and so its a different optical configuration.

If you got 94% it sounds like a few more mm should do it.

I presume you are confident the focus is spot on as I do notice with sensitive spacing correctors the stars can look off and then when you are in focus the stars all come good.

Did you allow to add 1mm for the filters and 1mm for the CCD window to the backfocus to get optical back focus as per the Astrodon site advice?

Greg.
Reply With Quote
  #19  
Old 15-04-2015, 09:10 PM
Eden's Avatar
Eden (Brett)
Registered Rambler

Eden is offline
 
Join Date: Jan 2014
Location: Melbourne, Australia
Posts: 399
Quote:
Originally Posted by Paul Haese View Post
Careful collimation is a must though. You cannot do a good job without a Takahashi collimation scope.
I'm looking at a GSO truss as my next purchase. I'd expect that it would need collimation after purchase but ~$300USD for a Takahashi collimation scope is laughable. Are you suggesting that the many GSO truss owners out there who opted not to collimate with said scope haven't done a good job?
Reply With Quote
  #20  
Old 15-04-2015, 09:21 PM
Paul Haese's Avatar
Paul Haese
Registered User

Paul Haese is offline
 
Join Date: Jan 2009
Location: Adelaide
Posts: 9,937
Quote:
Originally Posted by gregbradley View Post

I presume you are confident the focus is spot on as I do notice with sensitive spacing correctors the stars can look off and then when you are in focus the stars all come good.

Did you allow to add 1mm for the filters and 1mm for the CCD window to the backfocus to get optical back focus as per the Astrodon site advice?

Greg.
Focus is with focusmax at HFD so it is about as close to perfect as you can get and you have seen my images with this scope. Though I take your point being slightly out of focus will present differing results for both the corners and centre of image.

Yes I allowed for the optical effect. Though it should not be as finicky to get it within 12%. My experience has been about 12-16% has the appearance of being flat. So 1mm for filters is not really going to make a huge impact. Right now I would be happy with 16% curvature.
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 07:45 AM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Advertisement
Testar
Advertisement
Bintel
Advertisement