Jump to content

NLCbanner2024.jpg.2478be509670e60c2d6efd04834b8b47.jpg

ts-quattro coma corrector woes

alacant

By alacant
in Getting Started With Imaging

Recommended Posts

alacant

alacant

Posted
Posted

Just a warning. TS Germany told me that the focus point for this cc is more or less the same as focus without it. It isn't. It needs a whopping 8cm of forward focus away from the tube. An extension tube. With a dslr. On a newtonian.  The working distance is 70mm. I tried various combinations of spacer rings either side of this thinking it was critical. Nada. It renders the flex and imbalance on the focuser impossible with a dslr hung on the end. OTOH it may be great news for those without the back focus needed. HTH.

IMG_20161209_191002300.jpgIMG_20161209_191445133.jpg

Link to comment
Share on other sites
D4N

D4N

Posted
Posted
17 minutes ago, alacant said:

Hi. No. It's this one. No one has the GSO or Altair versions in stock.

Have you got the 15mm spacer between it and the camera?

That does seem a long way out considering it is designed for newts.

Link to comment
Share on other sites
Thalestris24

Thalestris24

Posted
Posted
1 hour ago, alacant said:

Hi. No. It's this one. No one has the GSO or Altair versions in stock.

Ah, ok. I think anything which has a largish back focus also increases focal length. I seem to recall that the gso increased focal length of my 130pds by ~10% so +65mm for the 130pds, +75mm for a 150pds. etc I was a bit perplexed about it too and posted at the time. You can't trust advertising blurb or salespeople!

Louise

ps a visual user on CN has also posted about it

Link to comment
Share on other sites
alacant

alacant

Posted
  • Author
Posted

Thanks Louise. My reflector is 750mm so the 14% from your calculation in your link gives me 855mm. It's increased the fl so taken the focus away from the tube. Anyway, as I see it, with the focuser racked out almost to its limit, there's no way it's gonna be stable enough for ap. It's not the the focuser is sloppy. It's that over that distance, the walls of the tube flex visibly with even slight pressure on the camera. 

May I ask where your Baader focus position comes relative to focus position without? Maybe I should pay the difference and get that one instead? Is it any good? Cheers, clear skies, sorry about all the questions and TIA. 

Link to comment
Share on other sites
Pompey Monkey

Pompey Monkey

Posted
Posted
25 minutes ago, Thalestris24 said:

Ah, ok. I think anything which has a largish back focus also increases focal length. I seem to recall that the gso increased focal length of my 130pds by ~10% so +65mm for the 130pds, +75mm for a 150pds. etc I was a bit perplexed about it too and posted at the time. You can't trust advertising blurb or salespeople!

Louise

ps a visual user on CN has also posted about it

 

10 minutes ago, alacant said:

Thanks Louise. My reflector is 750mm so the 14% from your calculation in your link gives me 855mm. It's increased the fl so taken the focus away from the tube. Anyway, as I see it, with the focuser racked out almost to its limit, there's no way it's gonna be stable enough for ap. It's not the the focuser is sloppy. It's that over that distance, the walls of the tube flex visibly with even slight pressure on the camera. 

May I ask where your Baader focus position comes relative to focus position without? Maybe I should pay the difference and get that one instead? Is it any good? Cheers, clear skies, sorry about all the questions and TIA. 

A coma corrector changes the F-ratio and effective focal length of the scope. This does not necessarily mean that the focal-point is any closer or further from the primary than without it.

Link to comment
Share on other sites
Thalestris24

Thalestris24

Posted
Posted
13 minutes ago, alacant said:

Thanks Louise. My reflector is 750mm so the 14% from your calculation in your link gives me 855mm. It's increased the fl so taken the focus away from the tube. Anyway, as I see it, with the focuser racked out almost to its limit, there's no way it's gonna be stable enough for ap. It's not the the focuser is sloppy. It's that over that distance, the walls of the tube flex visibly with even slight pressure on the camera. 

May I ask where your Baader focus position comes relative to focus position without? Maybe I should pay the difference and get that one instead? Is it any good? Cheers, clear skies, sorry about all the questions and TIA. 

Ah yes, it was 14%! The Baader MPCC Mkiii is very good and doesn't change focal length. On th other hand, it's spacing is critical and it only has a ' standard' back focus. The reason I got the gso was to accommodate a filter wheel or quick changer. I vaguely recall that you can use the gso at less than the 70mm and so reduce the focal length, but I'm not sure. I didn't have any problems imaging with the gso.

Link to comment
Share on other sites
Thalestris24

Thalestris24

Posted
Posted
1 minute ago, alacant said:

NP. It's not workable as it is. I've a dslr. It looks like the Baader screws straight into it with a m48 adaptor to give the 55mm required. Is this the spacing you mention?

Yes, I think it's 55mm +/- 1mm Have you tried using the Quattro cc at less than 70mm?

Link to comment
Share on other sites
Thalestris24

Thalestris24

Posted
Posted
Just now, alacant said:

Yeah. It looks like the worse of the bunch he tested. Makes the stars worse. Oh dear! Maybe the guy got the spacing wrong or a bad example?

Maybe! As I say, it worked fine for me and I'm pretty sure lots of people on here are happy with it. 

Link to comment
Share on other sites
Thalestris24

Thalestris24

Posted
Posted
3 minutes ago, alacant said:

I currently have a cheepo unbranded cc. It seems better then the Baader in the review. The main problem with it is reflections. Dunno. Maybe the Baader could handle this better, in particular the bright patch next to the horsehead?

 

PS could probably sort that! Lovely image :) Ask around re other Baader mkiii users?

Link to comment
Share on other sites
alacant

alacant

Posted
  • Author
Posted

Thanks for taking a look. I appreciate your time. With Altinak being just about as bad as it can get and as you very wisely say, nothing that PS (or Gimp for me) couldn't fix, I may just ask for a refund on this ts mess and keep my AliExpress special; it's the reflections that got me looking for an alternative in the first place.

26 minutes ago, Thalestris24 said:

Ask around re other Baader mkiii users

OK. Will do.

** done

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.