#1  
Old 11-08-2021, 01:45 PM
Emuhead (Andrew)
Registered User

Emuhead is offline
 
Join Date: Oct 2019
Location: Melbourne, Australia
Posts: 221
Paracorr 1 : Focuser travel 0

Hi guys,

So first time using a Televue Paracorr Type 2 with my 8" Quattro. Focuser is at max travel and even with a Baader clicklock collar that extends the focuser a bit i still can't reach focus when the Paracorr is all the way in.. i have to leave it out by 20mm.

Back focus is fine, I managed to get some data with it like this so i could leave it, but the OCD side says that's not going to fly. Question, I've had a look for M54 extension tubes but they're not easy to find, any ideas?

Thanks
Attached Thumbnails
Click for full-size image (PXL_20210811_010206947_resize_2~2.jpg)
56.1 KB40 views
Reply With Quote
  #2  
Old 11-08-2021, 02:15 PM
RyanJones
Registered User

RyanJones is offline
 
Join Date: Jun 2018
Location: Melbourne,Australia
Posts: 1,439
Hi Emuhead,

I think I read somewhere when I was looking at the parcorr that they extended the focal length by 20mm to allow for filter wheels etc. I have a similar issue with mine but I created my issue by redesigning my primary mirror holder. You can put cork spacers under your primary to lift it closer to the focuser but that will cause some extra vignetting because of the reduced distance to your secondary. You can also put extensions on your focuser but that will cause more focuser flex. I’m making a new OTA and my issues will be fixed with that but I agree it’s not a great situation to have to deal with.

Cheers

Ryan

Last edited by RyanJones; 11-08-2021 at 02:29 PM.
Reply With Quote
  #3  
Old 11-08-2021, 02:31 PM
AstroJunk's Avatar
AstroJunk (Jonathan)
Shadow Chaser

AstroJunk is offline
 
Join Date: Jan 2006
Location: Moonee Beach
Posts: 1,909
I think it looks fine as it is. The Paracorr has a pretty long tube so should still have plenty inside the focuser for it be true and stable.

BTW the space between your camera chip and the glass element should be as close to 55mm as possible for the best results. You may well be able to better attach your filter wheel to reduce the distance - ah the wonderful world of spacers, can never have enough!!!
Reply With Quote
  #4  
Old 11-08-2021, 07:49 PM
Emuhead (Andrew)
Registered User

Emuhead is offline
 
Join Date: Oct 2019
Location: Melbourne, Australia
Posts: 221
Thanks all, i think this might help, assuming the compression ring doesn't add tilt to my imaging train. Link here.

Agree, i could just leave it as is, as it's a long barrel. The data collected with it left like this is very usable. Yes its 55mm backfocus (+1mm for a filter) and the filter wheel is down the end next to the camera as one might expect.
Reply With Quote
  #5  
Old 11-08-2021, 08:00 PM
AstroJunk's Avatar
AstroJunk (Jonathan)
Shadow Chaser

AstroJunk is offline
 
Join Date: Jan 2006
Location: Moonee Beach
Posts: 1,909
Unfortunately, you won't be able to slide the paracorr more that 35mm into it before it stops. That will see you run out of in-focus. Any extender will have to be between the focuser draw tube and the Baader click lock. It can be done, but you may need to find a friendly machinist...
Reply With Quote
  #6  
Old 11-08-2021, 08:04 PM
Emuhead (Andrew)
Registered User

Emuhead is offline
 
Join Date: Oct 2019
Location: Melbourne, Australia
Posts: 221
Indeed, you're right there.. back on the hunt for a M54 extension tube.. or machinist, or settle for the Skywatcher Aplanatic Coma Corrector (which is very good also).
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 01:11 AM.

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