Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

3X Barlow vs. 2X Plus Extension Tube

  • Please log in to reply
4 replies to this topic

#1 Frisky

Frisky

    Ranger 4

  • -----
  • topic starter
  • Posts: 392
  • Joined: 08 Feb 2019
  • Loc: Austin, Minnesota

Posted 08 December 2019 - 04:05 AM

I’ve been pleased with eyepiece performance out of my f8.3 scope. I always have several eyepieces that put up a good view of whatever Im looking at. I really don’t need another eyepiece. Still, I’m growing restless, lol! I’m particularly impressed with my low power eyepieces. I thought if I barlowed them at 3X, I would have additional high power planetary views. However, I read that 3X shorties, like Meade’s 128, will vignette with long focal length eyepieces like those around 25-26mm. Not sure if the Celestron X-CEL 3X would vignette. I want to barlow my Meade HD-60 25mm to high power and also my Russell 19mm 70 degree and maybe even my 28mm RKE. I tried all three of them with my 2.2X Celestron barlow and a 1.25” extension tube and got nice views! I don’t remember seeing vignetting, but I didn’t look for it. The extension tube does increase stack height a little. Do you think I should just stick with my extension tube and 2X barlows or maybe get a 3X shorty?

 

Joe



#2 MitchAlsup

MitchAlsup

    Skylab

  • -----
  • Posts: 4,135
  • Joined: 31 Aug 2009

Posted 08 December 2019 - 07:35 PM

A 3× longie will have lower aberrations than a 3× shortie.

 

And will vignette less (or not at all).


Edited by MitchAlsup, 08 December 2019 - 07:35 PM.


#3 Frisky

Frisky

    Ranger 4

  • -----
  • topic starter
  • Posts: 392
  • Joined: 08 Feb 2019
  • Loc: Austin, Minnesota

Posted 08 December 2019 - 07:40 PM

I shy away from long barrel barlows, as I'm concerned it might contact the diagonal mirror. 

 

Joe



#4 BillP

BillP

    Hubble

  • *****
  • Posts: 19,062
  • Joined: 26 Nov 2006
  • Loc: Spotsylvania, VA

Posted 09 December 2019 - 10:40 AM

I shy away from long barrel barlows, as I'm concerned it might contact the diagonal mirror. 

 

Joe

The TV 3x is excellent.  The 2.5x TV Telecentric is also excellent, will preserve your FOV and ER but can't increase power with extension.  The TV2x with a 65mm extension gets you 3x.  If you want 3x I'd say go with the TV and get parfocal rings to ensure it will not contact your diagonal mirror.

 

https://www.telescop...ur/p/100280.uts


  • Frisky likes this

#5 Frisky

Frisky

    Ranger 4

  • -----
  • topic starter
  • Posts: 392
  • Joined: 08 Feb 2019
  • Loc: Austin, Minnesota

Posted 09 December 2019 - 01:09 PM

Thanks Bill! I'll look into this.

 

Joe




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics