Jump to content


Photo

Polar Finder for Old Style HD Wedge

  • Please log in to reply
9 replies to this topic

#1 yepimanerd

yepimanerd

    Sputnik

  • -----
  • Posts: 46
  • Joined: 10 Jun 2012
  • Loc: Tomball, TX

Posted 22 August 2013 - 09:31 AM

Hey all,
I picked up an old style (#93655) HD wedge for my CPC 9.25 on the cheap, and am looking for either a direct purchase or some sort of kludge to allow me to mount a polar alignment scope on the wedge.

Any thoughts???

- Glen

#2 mclewis1

mclewis1

    Thread Killer

  • ****-
  • Posts: 10892
  • Joined: 25 Feb 2006
  • Loc: New Brunswick, Canada

Posted 22 August 2013 - 12:41 PM

Glen,

There's no polar alignment scope for either the CPCs or the older NexStar GPS scopes. Instead they rely on the software based polar alignment routines. You'll often hear folks referring to the ASPA (all star polar alignment), this is the software polar alignment routine.

I have seen home brew wedge setups where a polar alignment scope was incorporated but for the Celestron scopes the firmware based polar alignment routines are very accurate and very convenient.

#3 yepimanerd

yepimanerd

    Sputnik

  • -----
  • Posts: 46
  • Joined: 10 Jun 2012
  • Loc: Tomball, TX

Posted 23 August 2013 - 10:57 AM

Mark,

Thanks for your reply. What I'm really looking for is a tool to aid in getting the wedge & tripod accurately aligned with polar north prior to mounting the scope on the wedge.

I would think that regardless of the firmware alignment routine, having the wedge accurately aligned both for azimuth & latitude would be extremely important. Given that the latitude markers on the HD wedge are less than precise, I would prefer to get the latitude settings tweaked as necessary before adding the more significant mass of the scope & fork mount, that just strikes me as an exercise in futility.

#4 mclewis1

mclewis1

    Thread Killer

  • ****-
  • Posts: 10892
  • Joined: 25 Feb 2006
  • Loc: New Brunswick, Canada

Posted 23 August 2013 - 11:58 AM

Glen,

I've only been around a few guys who've used wedges in the field. You're right that some sort of aid in roughly aligning the wedge helps so you don't have to wind the adjustments on the wedge too much.

What I remember was guys putting marks on their wedges and doing a rough by eyeball alignment on Polaris of the wedge/tripod setup.

If you're not imaging though you'll be surprised about how far off you can be in polar alignment and still be able to perform a good initial alignment and get good gotos for visual work (but still lousy tracking for imaging).

Perhaps a few folks who are still using a wedge in the field will chime in with specific ideas.

#5 rmollise

rmollise

    Hubble

  • *****
  • Posts: 15567
  • Joined: 06 Jul 2007

Posted 24 August 2013 - 08:08 AM

Glen,

There's no polar alignment scope for either the CPCs or the older NexStar GPS scopes. Instead they rely on the software based polar alignment routines. You'll often hear folks referring to the ASPA (all star polar alignment), this is the software polar alignment routine.

I have seen home brew wedge setups where a polar alignment scope was incorporated but for the Celestron scopes the firmware based polar alignment routines are very accurate and very convenient.


Yes and no. Quite a few of the GPS finder, anyway, came with polar alignment reticles. ;)

#6 Brian Risley

Brian Risley

    Mercury-Atlas

  • *****
  • Moderators
  • Posts: 2865
  • Joined: 04 Sep 2006
  • Loc: SW Florida

Posted 24 August 2013 - 03:02 PM

Tuthill made a polar scope for wedges back in the 80's. Not sure how accurate it is, but it was built with a rifle scope that allowed adjustment of the crosshair and had a ring to determine how to rotate it. Some were meant to go inside the old C wedge with the round hole, others were made in a metal bracket that could be attached so that it could be left on the wedge or in the case of the Tuthill Isostatic Mount, mounted on one of its legs.
Brian

Attached Files



#7 Brian Risley

Brian Risley

    Mercury-Atlas

  • *****
  • Moderators
  • Posts: 2865
  • Joined: 04 Sep 2006
  • Loc: SW Florida

Posted 24 August 2013 - 03:03 PM

Another Pic from other side.

Attached Files



#8 Mr Greybush

Mr Greybush

    Viking 1

  • *****
  • Moderators
  • Posts: 900
  • Joined: 16 May 2013
  • Loc: Virginia

Posted 13 September 2013 - 11:36 AM

The Tuthill is a rare bird I found one on Fleabay yesterday and if it doesn't work out it will be up for sale.

#9 iam1ru12

iam1ru12

    Mariner 2

  • *****
  • Posts: 225
  • Joined: 25 Feb 2006
  • Loc: Raleigh/Durham, NC

Posted 15 September 2013 - 09:32 PM

Having had a Celestar 8 as my main scope for 5 years, I got quite used to polar alignment on a wedge.

1. Set up tripod so that if you were to take your arm and poke it thru the hole in wedge base from the back, you,'d be roughly pointing at polaris
2. Level the scope/tripod and attach the OTA
3. Align your finder scope
4. Make sure your OTA is parrallel with the fork arms (if you had setting circles on your scope it would read 90 degrees in declination).
5. Make sure the fork arms are parallel with each other, I.e. - one arm should not be higher than another

From here on out do not adjust the Dec (alt when not on a wedge) or RA (azm when not on a wedge), all adjustments must be made to the wedge or tripod.

Using your finder or a very low power EP giving a degree or more field of view you'll want to use the wedge's altitude adjustment and azmuth adjustments to get polaris in the correct spot in your finder or EP.

It is worth noting that Polaris is actually 0.8 degrees away from the true celestial pole. Therefore you'll need to figure out in which direction to adjust your wedge in order to get correct polar alignment. I really like the Kochab method (click here for more details) . However for long exposure astrophotography, you may wish to try the drift alignment method, it is much more precise.

-Mike

#10 Mr Greybush

Mr Greybush

    Viking 1

  • *****
  • Moderators
  • Posts: 900
  • Joined: 16 May 2013
  • Loc: Virginia

Posted 15 September 2013 - 11:25 PM

I found this company that uses a Polar alignment scope for their wedges but the price is way to out of my range to even think of getting one but that's up to you http://www.orbit-eng....com/index.html






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics