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

Long slow Newtonians

equipment mirror making observing planet reflector
  • Please log in to reply
186 replies to this topic

#176 SandyHouTex

SandyHouTex

    Soyuz

  • *****
  • Posts: 3987
  • Joined: 02 Jun 2009
  • Loc: Houston, Texas, USA

Posted 13 February 2019 - 10:07 AM

I finally had first light with a Celestron 114eq Power Seeker last night.  4.5 inch mirror and f/7.89.  The optics are wonderful, but the provided eyepieces and mount suck.  With a 18mm BGO though, the moon was razor sharp and M45 was awesome.


  • Deep13, Astrojensen, happylimpet and 2 others like this

#177 Philler

Philler

    Surveyor 1

  • *****
  • Posts: 1512
  • Joined: 15 Jul 2013
  • Loc: Olathe, Ks. USA

Posted 24 February 2019 - 03:23 PM

When I was a beginner in the 1980's with my first scope I read that if you are using a Barlow like say a 2x or 3x, you are not only doubling or tripling your magnification but the Barlow negative lens is actually increasing the focal length of your scope and focal ratio, by changing the steepness of the angle to you eyepiece. (hope I explained this right).. So, if I used like a 2x Barlow, Tele Negative, or Power Mate with an f/4.5 reflector, would that end up making the f/4.5 Dob something like an f/6 or f/7 reflector?   But, on the other hand, the mirror itself is still an f/4.5, and that doesn't change. 

Something else: with more complicated, multi lens group eyepieces like Nagler's, etc. that use a kind of built in Barlow in their shorter focal lengths for higher powers, greater eye relief, and wide fields;  are they not also increasing the focal length and thus focal ratios also?


Edited by Philler, 24 February 2019 - 08:28 PM.


#178 Astrojensen

Astrojensen

    Voyager 1

  • *****
  • Posts: 12117
  • Joined: 05 Oct 2008
  • Loc: Bornholm, Denmark

Posted 25 February 2019 - 10:04 AM

 

Something else: with more complicated, multi lens group eyepieces like Nagler's, etc. that use a kind of built in Barlow in their shorter focal lengths for higher powers, greater eye relief, and wide fields;  are they not also increasing the focal length and thus focal ratios also?

They do indeed increase the focal length, as seen from the perspective of the rear elements in the eyepiece. 

 

But since the main mirror is still f/4.5, you still have the coma, very tight focus tolerances, etc., of the fast primary. 

 

 

Clear skies!
Thomas, Denmark


  • Jeff Morgan, starcanoe and Earthbound1 like this

#179 Deep13

Deep13

    Skylab

  • *****
  • Posts: 4404
  • Joined: 25 Jan 2005
  • Loc: NE Ohio

Posted 25 February 2019 - 01:45 PM

***  The optics are wonderful, but the provided eyepieces and mount suck. ***

That's a common lament.



#180 mic1970

mic1970

    Viking 1

  • -----
  • Posts: 718
  • Joined: 09 Aug 2018
  • Loc: St. Louis Metro Area

Posted 25 February 2019 - 02:06 PM

Oh man... I can't wait to see this when complete.

Had this little project sitting around for a few years...12 inch F/20.

 

Orion Optics UK ground this and another one for the BBC for a Herschel Telescope doco  they were making.

 

I'm going to start the mirror box soon as per image from the Smithsonian Museum with the same mirror holder and access panel.

 

Three 7foot sections....1/ .Mirror box...2/ .carbon fibre rods....3/.carbon fibre rods with secondary holder.

 



#181 Astrojensen

Astrojensen

    Voyager 1

  • *****
  • Posts: 12117
  • Joined: 05 Oct 2008
  • Loc: Bornholm, Denmark

Posted 25 February 2019 - 03:20 PM

That's a common lament.

Sadly, yes.

 

 

Clear skies!
Thomas, Denmark


  • Deep13 likes this

#182 SandyHouTex

SandyHouTex

    Soyuz

  • *****
  • Posts: 3987
  • Joined: 02 Jun 2009
  • Loc: Houston, Texas, USA

Posted 26 February 2019 - 10:42 PM

At least I finally have an anwere for someone who wants to buy their kids a scope for $100.  The Celestron 114eq Power Seeker fits the bill.  Just make sure you recommend a reasonably priced Symmetrical.  Maybe a 12 mm for 72X.

 

Whatever you do don’t get the 127mm Power Seeker.  It’s a Bird-Jones and hard to collimate.

 

I also finally got the 6 inch solid tube Skywatcher Dob f/8.  I tried it out Saturday night.  Excellent optics and a pretty nice mount.  I didn’t try the eyepieces.



#183 John Fitzgerald

John Fitzgerald

    In Focus

  • *****
  • Posts: 6328
  • Joined: 04 Jan 2004
  • Loc: ROR Obs. near Pettigrew, AR

Posted 27 February 2019 - 12:11 AM

  This is the 8 inch f/8.6 I ground and made back about 1988.  It was a good scope, on an old Edmund mount.  I had a 6" Byers gear on it.  That fence is an L shaped light and wind block.  I had a pier in the yard, with the mount under a trash can and bags.  I would carry that big aluminum OTA out about 100 feet.  It had a redwood plate that attached the tube rings to the mount.  I had the tube and rings fabricated locally, bought the focuser, mirror cell, secondary, and spider mail order.  I cut / bored all the holes and did all the mounting myself.  It worked well with the simple eyepieces we had back then.   Sold it about 1999 or 2000 on "Starry Messenger" ads.

Attached Thumbnails

  • 8 eq refl2.jpg
  • 8 eq refl.jpg

Edited by John Fitzgerald, 27 February 2019 - 12:14 AM.

  • Deep13, Astrojensen, SandyHouTex and 5 others like this

#184 CHASLX200

CHASLX200

    Hubble

  • *****
  • Posts: 18366
  • Joined: 29 Sep 2007
  • Loc: Tampa area Florida

Posted 27 February 2019 - 06:13 AM

  This is the 8 inch f/8.6 I ground and made back about 1988.  It was a good scope, on an old Edmund mount.  I had a 6" Byers gear on it.  That fence is an L shaped light and wind block.  I had a pier in the yard, with the mount under a trash can and bags.  I would carry that big aluminum OTA out about 100 feet.  It had a redwood plate that attached the tube rings to the mount.  I had the tube and rings fabricated locally, bought the focuser, mirror cell, secondary, and spider mail order.  I cut / bored all the holes and did all the mounting myself.  It worked well with the simple eyepieces we had back then.   Sold it about 1999 or 2000 on "Starry Messenger" ads.

Just what i would love.



#185 Earthbound1

Earthbound1

    Viking 1

  • -----
  • Posts: 906
  • Joined: 19 Sep 2018
  • Loc: Gordo, Alabama

Posted 27 February 2019 - 06:34 AM

It's a real shame how many telescope review sites out there recommend that Powerseeker 127, Space.com as well as SEVERAL others. I had my heart set on one for months!!! Got the chance to buy one used for $50 on CL but it was not to be... Then I discovered CN and all you guys set me straight! Thanks for saving me lots of frustration and headaches as well as buyer's remorse! I finally got the parts to make a REAL 4.75" f/8.3 back around October 2018 and have been happy ever since (except for the weather!!! Grrr!!!). Too bad those review sites don't recommend CN as a pre-buyers guide! Anyway, been in love with my medium-long moderately slow f/8.3 since first light!

Attached Thumbnails

  • image.jpeg

Edited by Earthbound1, 27 February 2019 - 06:38 AM.

  • Inkswitch, Deep13, SandyHouTex and 3 others like this

#186 Deep13

Deep13

    Skylab

  • *****
  • Posts: 4404
  • Joined: 25 Jan 2005
  • Loc: NE Ohio

Posted 27 February 2019 - 03:05 PM

  This is the 8 inch f/8.6 I ground and made back about 1988. 

Awesome!



#187 John Fitzgerald

John Fitzgerald

    In Focus

  • *****
  • Posts: 6328
  • Joined: 04 Jan 2004
  • Loc: ROR Obs. near Pettigrew, AR

Posted 27 February 2019 - 04:18 PM

Awesome!

Thank you!  Gotta love that 6x30 finder and the yellow setup "bug" light hanging on the fence.smile.gif


  • Deep13 and Earthbound1 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





Also tagged with one or more of these keywords: equipment, mirror making, observing, planet, reflector



Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics