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

Lunt 50mm HA focus issues

  • Please log in to reply
8 replies to this topic

#1 shaesavage

shaesavage

    Vostok 1

  • *****
  • topic starter
  • Posts: 183
  • Joined: 06 Jun 2009
  • Loc: Saskatchewan, Canada

Posted 30 March 2020 - 07:26 PM

I recently acquired a used Lunt 50mm HA telescope with the Feathertouch focuser. I am having problems achieving focus with almost all of my eyepieces. The focuser does not enough inward travel. I have tried my Leica Asph zoom, Nikon zoom, various Pentax SMC ortho focal lengths, and various Takahashi 0.965 ortho focal lengths.

 

Any suggestions how I can resolve this issue? I am really hoping to avoid buying solar specific eyepieces.



#2 bigdob24

bigdob24

    Apollo

  • *****
  • Posts: 1,002
  • Joined: 19 Apr 2008
  • Loc: Central Illinois

Posted 30 March 2020 - 07:30 PM

Have you tried moving the Blocking Filter and change the focus point?

When I set up Ive got a piece of tape on my BF and move it out to that position and everything reaches focus.

BD 


  • Gray likes this

#3 james7ca

james7ca

    Cosmos

  • *****
  • Posts: 8,269
  • Joined: 21 May 2011
  • Loc: San Diego, CA

Posted 30 March 2020 - 08:27 PM

The Lunt LS50 doesn't have a lot of backfocus so are you sure that the Feather Touch focuser is the correct model for that scope? The blocking filter (diagonal) should be all the way forward/inserted into the focuser and you sould avoid using any type of adapter for you eyepieces (they should also be inserted directly into the diagonal).

 

Also, it might help if you used a weak barlow. Are these all 1.25" eyepieces, as I notice that you mentioned 0.965 Taks?

 

I have a Lunt LS50 with a Feather Touch focuser that I use mainly for astrophotography (and the backfocus is tight with that setup), but I've never had any problems with my Tele Vue 1.25" eyepieces (probably my Radian models, although I haven't tried all of my eyepieces on that setup).



#4 shaesavage

shaesavage

    Vostok 1

  • *****
  • topic starter
  • Posts: 183
  • Joined: 06 Jun 2009
  • Loc: Saskatchewan, Canada

Posted 31 March 2020 - 10:38 PM

Thanks for the replies. The FT focuser is the correct one. The blocking filter is inserted all of the way. The Leica is 1.25" but the rest are 0.965". I think this is a result of my eyepieces simply require a lot of inward travel to reach focus. I have a Lunt 35mm HA and all of my eyepieces reach focus in it. I purchased the Lunt 50mm for a little more aperture, but sadly I think I will end up selling it because I do not want an extra set of eyepieces for HA viewing.



#5 sunnyday

sunnyday

    Fly Me to the Moon

  • *****
  • Posts: 6,829
  • Joined: 23 Sep 2019
  • Loc: Ottawa,Canada

Posted 31 March 2020 - 10:44 PM

Thanks for the replies. The FT focuser is the correct one. The blocking filter is inserted all of the way. The Leica is 1.25" but the rest are 0.965". I think this is a result of my eyepieces simply require a lot of inward travel to reach focus. I have a Lunt 35mm HA and all of my eyepieces reach focus in it. I purchased the Lunt 50mm for a little more aperture, but sadly I think I will end up selling it because I do not want an extra set of eyepieces for HA viewing.

hi
did you talk to faye at lunt's.
she is very nice is very helpful.



#6 sunnyday

sunnyday

    Fly Me to the Moon

  • *****
  • Posts: 6,829
  • Joined: 23 Sep 2019
  • Loc: Ottawa,Canada

Posted 31 March 2020 - 10:48 PM

The blocking filter is inserted all of the way.

 

 

mine is out about 2 inches to have a good focus precisely.

 

if it's all the way in it doesn't work with mine I have to take it out 2 inches
i have a lunt 60 with ft too



#7 shaesavage

shaesavage

    Vostok 1

  • *****
  • topic starter
  • Posts: 183
  • Joined: 06 Jun 2009
  • Loc: Saskatchewan, Canada

Posted 01 April 2020 - 05:40 PM

The blocking filter is inserted all of the way.

 

 

mine is out about 2 inches to have a good focus precisely.

 

if it's all the way in it doesn't work with mine I have to take it out 2 inches
i have a lunt 60 with ft too

My problem is I need the blocking filter 0.25”-0.5” closer to the objective. My focus problem is the opposite direction of yours. Thanks for the suggestion to call Faye, I will give that a try. 


  • ToxMan and sunnyday like this

#8 ToxMan

ToxMan

    Skylab

  • *****
  • Posts: 4,126
  • Joined: 23 Jan 2011
  • Loc: Tucson, Arizona, USA

Posted 03 April 2020 - 12:13 PM

How does increasing focal length (pulling some out) help when there is not enough "inward travel"? If you have the original stock helical focuser, did your eyepieces come to focus with it? If not, then your new focuser is not the problem...



#9 shaesavage

shaesavage

    Vostok 1

  • *****
  • topic starter
  • Posts: 183
  • Joined: 06 Jun 2009
  • Loc: Saskatchewan, Canada

Posted 04 April 2020 - 06:42 AM

How does increasing focal length (pulling some out) help when there is not enough "inward travel"? If you have the original stock helical focuser, did your eyepieces come to focus with it? If not, then your new focuser is not the problem...

Increasing the focal length does not help, it makes my problem worse. The original focuser has the same problem. 




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