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

Questar Finder Mod Andromeda Image

  • Please log in to reply
4 replies to this topic

#1 mtr1

mtr1

    Mariner 2

  • -----
  • topic starter
  • Posts: 226
  • Joined: 02 Nov 2013
  • Loc: Westchester Co. NY

Posted 28 September 2021 - 02:34 PM

When I brought my Questar in for servicing, I had spoken to Jim Perkins about my wish for a few additional millimeters of focusing room in the EP so that I could experiment more with a filtered camera.  I was thinking mostly about having an easy way to spot nebulae using a color camera and dual narrowband filter (like my IDAS LPS-V4 which is more permissive than the Optolong L-Extreme or OPT Triband).  Jim explained that I could try a different finder lens (sourced from TeleVue) which would increase the finder focal length and leave enough room for a filtered eyepiece format camera, like the QHY 5iii-178 color cam I acquired with this use in mind.

 

The modification changes the EP so that I can't focus my Brandons if I screw them down, but I can still use the Brandons by using the two little screws on the universal 1.25" EP port (my scope is 2012 vintage).  Not much of a sacrifice, and now I can set other EP's -- e.g. TV 20mm Plossl -- to focus with the finder and that long ignored Plossl is now getting lots of use.

 

The finder is not much in terms of aperture, I confirmed with Jim that the lens is 15mm of clear aperture, and the focal length is 112.5 per PixInsight.  I am finding that the f/7.5 optics are not really fast enough for real EAA, and I've shot a few so-so wide nebula images with it.  But after a little experimentation I decided to make a serious attempt at M31 which fits very nicely in the finder FOV.  My PG3 tracked well for 4 hours under very good skies for me (SQM-L 18.7) on Sunday night, requiring 1 rechargeable battery change, but otherwise needing just a few adjustments, and I got this:

 

M31losatwmsm.jpg

 

In this case the filter is an Astronomik CLS and the capture was done using 8 second exposures collected in SharpCap LiveStacks.  I did a lot of PixInsight and ACDSee processing to get this as clean as it looks.  The simple finder optics generate a lot of coma once you move from the center of the lens so this is not the best way to go after wider targets with a Q (piggybacking a better camera/lens combo for instance could work considerably better).   But it did seem to work, and it's yet another way of taking advantage of the nice format of the Q sitting on a very capable fork mount drive.

 

Regards,

Mauri


  • cbwerner, Mike Allen, Astrojensen and 8 others like this

#2 JamesMStephens

JamesMStephens

    Apollo

  • *****
  • Posts: 1,294
  • Joined: 25 Jan 2015
  • Loc: Hattiesburg, Mississippi

Posted 28 September 2021 - 04:14 PM

Mauri,

 

Does the e/p adapter look noticeably different with this mod?  Would we see the difference in a picture of your scope?

 

Jim

 

PS: Not that I'm dropping a hint or anything like that....:-)



#3 munirocks

munirocks

    Viking 1

  • *****
  • Posts: 665
  • Joined: 21 Oct 2013
  • Loc: Bourne End, UK

Posted 28 September 2021 - 04:16 PM

If you want more focus range in the finder, you could try using a B&L 12.7, 18, or 30mm ASP (Achromatic Symmetrical Plossl) eyepiece. You can push or pull these eyepieces in or out of the eyepiece holder to achieve first focus in finder mode and then fine-tune it with the helical focuser on the same holder.

The focus range of the push-pull fit of the B&L eyepieces is huge in both directions, I estimate -10 to +10 diopters, maybe more.


  • JamesMStephens likes this

#4 RobertPettengill

RobertPettengill

    Viking 1

  • -----
  • Posts: 514
  • Joined: 06 Jan 2013
  • Loc: Austin, Texas

Posted 28 September 2021 - 05:35 PM

Great shot. Years ago I used the finder for a wide FOV composite with closeup views of the moon and Mars from the main scope. This setup sounds cool. 
 

I’ve been thinking about guiding with my finder while imaging through the axial port.  Can you post images of your EP setup. 
 

;Rob


  • JamesMStephens likes this

#5 mtr1

mtr1

    Mariner 2

  • -----
  • topic starter
  • Posts: 226
  • Joined: 02 Nov 2013
  • Loc: Westchester Co. NY

Posted 28 September 2021 - 09:15 PM

Hi, thanks for the kind words.  To be clear the only change is the lens in the finder portion of the control box -- there's no difference visible externally.  Since I was surprised to learn this, maybe it will help others:  the finder mirror is a flat mirror, no curve/no magnification.  There's a small (15 mm) lens in the finder (which gets covered by the solar finder filter when engaged) between the mirror and eyepieces.  This small piece of glass is the only change in this modification. 

I've posted this before, but this is what the scope looks like with an EP format cam in the EP port.  It's that simple.  But again, to be clear, while the physical configuration is simple, focusing the camera, getting proper exposures for an image like this, and processing into a decent form are more intermediate than beginner AP skills. 

 

Q with EP cam sm.JPG

 

Regards,

Mauri


  • JamesMStephens and Spikey131 like this


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