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

Did I completely ruin my old 9.25 inch SCT?

  • Please log in to reply
11 replies to this topic

#1 revans

revans

    Surveyor 1

  • *****
  • topic starter
  • Posts: 1701
  • Joined: 26 Sep 2005
  • Loc: Fitchburg, MA

Posted 20 October 2019 - 04:04 PM

In the summer of 2006 I had a nearly perfect 9.25 inch Celestron SCT on a Meade LXD75 mount.  I was a star test collimation freak at the time and decided to install something called Bob's knobs to make collimation to the nth degree possible using star testing.  Unfortunately, I must have been all thumbs that day and although exactly what I did eludes me after all these years, the corrector plate somehow became detached/loose and moved but didn't damage anything else in the optical train.  I was unaware that the corrector plate had alignment numbers on the edge so when I put it back in place the scope didn't behave very well.  I couldn't understand what the problem was for three years during which time I had fuzzy images of the moon etc., then I realized that I'd put the 3 o'clock number where the 1 o'clock number should be.  I rectified that in 2009 and made a note at the time that the scope behaved much better.  I still had the impression that the scope wasn't quite as precise as it had been before my debacle though.  I switched more and more to using my Mewlon which is a shame as I considered both scopes to be essential equal optically even if the Mewlon 250 was a lot more expensive.

 

Now I want to use the 9.25 inch again.  It produces very sharp images at low power.  I'm not as sure how great it is on detail at very high power though compared to the old days. I've just got its old LXD75 mount working again.... found the hand paddle controller and bought a new power supply.  It seems to work although the AutoStar Suite by Meade that goes with the mount isn't fit for modern computers.  But if I remember right, the had paddle had a lot of inherent capability on its own.   Any thoughts?



#2 DLuders

DLuders

    Gemini

  • *****
  • Posts: 3332
  • Joined: 10 Apr 2017
  • Loc: Spokane, WA

Posted 20 October 2019 - 04:40 PM

You could send it in to Celestron, and have them determine the best optical alignment of the corrector plate --  https://www.celestro...chnical-support



#3 Jeff Lee

Jeff Lee

    Surveyor 1

  • *****
  • Posts: 1674
  • Joined: 17 Sep 2006

Posted 20 October 2019 - 04:47 PM

Or you could try and do an alignment -  tighten all of the knobs and then slowly on a bright star loosen one and then the others them until the star image is correct. Take care not to over loosen and move the knobs out of the screw holes.



#4 macdonjh

macdonjh

    Aurora

  • *****
  • Posts: 4568
  • Joined: 06 Mar 2006

Posted 20 October 2019 - 07:23 PM

Just to be sure: you rotated the corrector plate?

 

Unless you send it back to Celestron, the only way I know to fix the problem is trial and error.  Start by doing what you did: put the corrector back in your scope with the alignment marks oriented correctly.  Collimate and see how you do.  Then try a slightly different orientation, and recollimate.  Repeat until it's right.

 

Since you have the factory orientation marks on your corrector it shouldn't take too many iterations, and I'll bet collimation won't be far off when you rotate your corrector.


Edited by macdonjh, 20 October 2019 - 08:02 PM.

  • revans and Augustus like this

#5 MitchAlsup

MitchAlsup

    Skylab

  • -----
  • Posts: 4010
  • Joined: 31 Aug 2009

Posted 20 October 2019 - 07:59 PM

Basically, you either have to have a keen understanding of how the centering of the optics and how the rotation of the optics influences the image, or you have to send it back to Celestron, or send it to someone who has an optical bench of appropriate size.



#6 Augustus

Augustus

    Fly Me To The Moon

  • *****
  • Posts: 8157
  • Joined: 26 Dec 2015
  • Loc: Connecticut

Posted 20 October 2019 - 08:19 PM

As someone who lives relatively nearby and has worked on these sorts of things I'd be happy to take a look in person sometime. Cheaper than sending to Celestron......


  • eros312, Joe1950 and Stevegeo like this

#7 macdonjh

macdonjh

    Aurora

  • *****
  • Posts: 4568
  • Joined: 06 Mar 2006

Posted 21 October 2019 - 07:31 AM

Basically, you either have to have a keen understanding of how the centering of the optics and how the rotation of the optics influences the image, or you have to send it back to Celestron, or send it to someone who has an optical bench of appropriate size.

 To me, that's akin to saying an amateur can't collimate a scope by eye (star test).  I get your point: perfection my require optical tools, but it is certainly possible to home in on good-better-best by eye and with trial and error.



#8 revans

revans

    Surveyor 1

  • *****
  • topic starter
  • Posts: 1701
  • Joined: 26 Sep 2005
  • Loc: Fitchburg, MA

Posted 21 October 2019 - 07:33 AM

As someone who lives relatively nearby and has worked on these sorts of things I'd be happy to take a look in person sometime. Cheaper than sending to Celestron......

You are very kind to offer and perhaps I could take a drive out to where you are and show you the scope if I'm still not happy with its performance.  I've been completely out of amateur astronomy for a decade or so.  Prior to that I was very active and had my small list of accomplishments and contributions that I'm still proud of.  As I got older (mid 60s now) my attention was taken up by parental care and house repairs and transitioning to part time work etc.  I've only very recently opened up my old telescope shed which houses some real beauties including losmandy, takahashi, meade and celestron mounts and a Mewlon 250 (admittedly I put I bing in the end cap banding the end of the scope if that is what it is called and could have thrown out the collimation in the process.... but eventually I'll send it back to Texas Nautical for repair when the time is right), and a pristine Gladius, and a costly pristine British SCT 12" (I think) planetary scope I haven't thought about in years.  I've chucked out an old 14 inch Celestron orange SCT obtained years ago from a high school observatory and a 16 inch long tube Newtonian on a heavy nuy very primitive mount because they took up too much space and didn't turn out to be very good for astrophotography or add anything much to visual either in my light polluted skies.  I've also got a couple of nice refractors in the 5 inch range.... short and long focus. 

 

I'm looking at winter approaching and in addition to my low tech 5" F5 achro I wanted another scope or two to use on a second floor trex decking porch (vibration and all) with good views.  The simplest two would fit on my simple LXD75 mount that I now have working again.... the 9.25" SCT and a 5" F9 semi-apo (ED glass doublet). They are easily interchangeable on the mount.  I thought I could at least take some moon photos.  All my old expensive cameras are outdated (firewire or software not compatible with the new Windows) and I'll have to probably  start off buying one of the new Meade LIP type imagers (although I think it is monochrome and I'd prefer color.... using 3 filters is a drag).  Maybe even a Meade DSI imager if they are still made.  I wish the Meade autostar suite program would work on Windows 10 because with that I could avoid star hopping which while interesting takes more time.  But no matter, I'll starhop and still know the layout of the sky pretty well.  I've also had good luck on deep sky in the past just stacking 1 minute photos taken on my old Canon Rebel camera.

 

If I can't get reasonable performance out of the 9.25 inch SCT I'll likely PM you at some point but I'm hopeful things won't be as bad as a seem to remember after nearly a decade.  I remember great low power views but less contrasty high power views than before my debacle with the scope.  I am all thumbs... even to my eternal regret drop the Mewlon 250 about 7 years ago denting the endcap.... the drop was only about 1 ft though and the scope still works, or seems to.  But someday as I say it is off to Texas Nautical for repair.

 

Thanks again,

 

Rick


  • eros312 and Augustus like this

#9 Chuck Hards

Chuck Hards

    You don't know Swift from Astrola

  • *****
  • Administrators
  • Posts: 25619
  • Joined: 03 May 2010

Posted 21 October 2019 - 08:27 AM

Not ruined at all, no worries.

 

Relatively easy indoors with DPAC, at least you can make adjustments on the bench and know immediately if you are working in the right direction.  Can be frustratingly slow to get everything adjusted using outdoor star-testing only.

 

First step is to collimate as close as possible using a laser, once that is done then you can start rotating elements if needed.  

 

Take it to Zane (Augustus) and at the very least, he can point you in the right direction if not solve your problem completely.


  • PrestonE and Augustus like this

#10 revans

revans

    Surveyor 1

  • *****
  • topic starter
  • Posts: 1701
  • Joined: 26 Sep 2005
  • Loc: Fitchburg, MA

Posted 22 October 2019 - 07:55 PM

Finally getting the mount and drive working, I took the C 9.25" F10 SCT out last night which was clear and dark for my city area.  I hadn't used the scope at night in some 9 years or so and had it carefully packed away.  I had a note in my journal from the summer of 2009 saying that I'd appeared to resolve the corrector plate issue and done a good collimation of the optics and noted that the moon looked sharp and had good contrast with good detail visible at 300x. 

 

Last night there was no moon when I was out with the scope.  I had my choice of a couple of deep sky objects and a very bright star, Vega.  I did a quick star test on Vega and apart from the effects of some atmospheric turbulence I didn't notice any dramatic abnormalities.... no coma, good collimation, no astigmatism, no pinching, and no tube effects.  I found that a wide field eyepiece providing 52x seemed to be the best power for deep sky and looked at M31 and M57 which were brighter and much better seen than in the 5 inch F5 achromat I had set up next to it.  The ring nebula had a greenish tinge to the usual grey I see with my smaller refractors.  All the minor stars were pinpoint and sharp.  So maybe the scope is OK. Higher powers on these two objects didn't provide any real advantage visually.  As the night went on things were a bit misty in the eyepiece and I had to remember to wipe away the dew that had formed on the plate :)  Hadn't done that in nearly a decade and almost didn't think about dew as an issue at all after all those years of hibernation.  Anyway, to my surprise the old LXD75 mount drive behaved as well as ever I remembered in the past.  So I have a possible photographic scope of medium aperture to use later this fall and winter.  Rick


  • Augustus likes this

#11 Don H

Don H

    Viking 1

  • -----
  • Posts: 975
  • Joined: 28 Dec 2006
  • Loc: Desert SW

Posted 25 October 2019 - 03:06 PM

You could use Saturn or some close doubles to evaluate collimation and performance. I usually think Jupiter is the best for that, but it is now too low to be helpful. Star test sounds very encouraging...


  • revans likes this

#12 revans

revans

    Surveyor 1

  • *****
  • topic starter
  • Posts: 1701
  • Joined: 26 Sep 2005
  • Loc: Fitchburg, MA

Posted 25 October 2019 - 04:53 PM

You could use Saturn or some close doubles to evaluate collimation and performance. I usually think Jupiter is the best for that, but it is now too low to be helpful. Star test sounds very encouraging...

I think Jupiter is in my tress this season.  If I get up early.... like 4:30 am or so, I get a good view of Orion and Taurus.  The Orion nebula M42 is just fabulous in the 9.25" SCT.  The F6.3 focal reducer doesn't really do it any favors so I left it off as it is such an easy object to find.  It was glorious at 52x at F10.  So large and greenish grey.  Almost reminds me of a great bird of prey. I imagine I see the head and the wings, but the nebulosity extends beyond the wings even in my city skies in this scope.  

 

I am nearly in a position to do photography of it again now that my old Meade LXD75 mount and drive are working just fine.... almost because.....  The deck vibrates so I'll need to use the long cord method and use delayed shutter release.  Maybe the best try I'd start off with is a stack of about ten, 30 sec. photos in my ancient Canon Rebel DSLR using the scope as a lens with the focal reducer in place.   Problem is that Polaris is in a pine tree at the moment so I can only get a near Polar alignment accurate to within a few degrees only :)  But I can keep a star NEARLY but not exactly centered for about 3 minutes at 52x and maybe 4 minutes at 30 x now in this scope.  Maybe I get a 10% drift in the field over that time period.  I'm hoping maybe the new Autostakkert program can deal with that, but I don't know... haven't tried yet.

 

Rick




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