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payner
sage
Reged: 03/22/07
Posts: 230
Loc: Bluegrass Region, Kentucky
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Well, after star testing/observing with my recently purchased FS-128 I realized stars were not nearly as pinpoint in my C14. Visual observations of Saturn and Jupiter have proven very fruitful in seeing bands, ring divisions (Cassini) even given the poor angular orientation of them now and the gossamer, festoons, etc. The stars tell the story of need for fine collimation, especially when splitting doubles.
Last night I felt I had the time and inclination to begin this simple, yet too often avoided, tune-up. It took maybe 15 minutes and ever so slight tweaking of Bob's knobs, to get tight, concentric diffraction rings and stars that are nice points.
I posted this not because it is a great feat, but to encourage all who have been avoiding this task to get it done. Your precious time spent at the scope will be handsomely rewarded.
Randy
--------------------
CGE1400 w/XLT & FT MicroFocuser
Russian-Intes MK 91 Rumak
Takahashi FS-128
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w orchid
professor emeritus
Reged: 04/23/07
Posts: 662
Loc: Tampa, Fl
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Roger that.
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Celestron C8 orange tube circa 1982
Stellarvue SV102ED
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skybsd
sage
Reged: 02/01/08
Posts: 274
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Hi payner..,
Quote:
Well, after star testing/observing with my recently purchased FS-128 I realized stars were not nearly as pinpoint in my C14.
This is the very same sinking feeling I have when comparing my NextStar 6SE to my (sometimes, less than impressive) c-9.25 XLT 
Quote:
Last night I felt I had the time and inclination to begin this simple, yet too often avoided, tune-up. It took maybe 15 minutes and ever so slight tweaking of Bob's knobs, to get tight, concentric diffraction rings and stars that are nice points.
Good show! 
Glad to hear it worked out great for you..,
Quote:
I posted this not because it is a great feat, but to encourage all who have been avoiding this task to get it done. Your precious time spent at the scope will be handsomely rewarded.
Well done!
I know to myself that deep down, I do harbour fears that I'll really mess things up and make my borderline good experience with my c-9.25 even worse - hence my literal, and open scardiness (silly, I know) of touching the thing. See I've got Bob's Knobs installed as well, but somehow I got to thinking that if Bob's Knobs make it so easy to make adjustments, then conversely, Bob's Knob's also make it lethally easy to lay waste to all in its path 
I'll take heart in your (and others!) success and REALLY TRY to pluck up the courage to collimate my c-9.25.
Thanks for the post!
Regards,
skybsd
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doug76
Carpal Tunnel
Reged: 12/05/07
Posts: 2554
Loc: SE Louisiana
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Did the same on my newest acquisition, an Omni XLT127 (C5 really). Did it at 60x on Arcturus when I first got it, then a week later finished the process at much higher power on a fainter star. Really looking sharp now.
Doug
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Doug
The Truckstop Astronomer
Meade 12" Lightbridge/Dob Driver II
Celestron C6 SCT
Celestron C6R/Moonlight focuser
Celestron XLT150
Astro-Tech AT80EDT
Celestron CG5-ASGT, CG-4
Celestron Nexstar SE (large)
Meade SWA 34mm
Televue Panoptic 24mm
Pentax XW 10mm, 7mm
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Astro-Tech AT66ED
Celestron Nexstar SE (small)
Televue Plossl 32mm
Smart Astronomy Solar System 14.5mm
BO/TMB Planetary 9mm, 7mm, 5mm, 4mm, 3.2mm, 2.5mm
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rmollise
Carpal Tunnel
Reged: 07/06/07
Posts: 1558
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Quote:
I'll take heart in your (and others!) success and REALLY TRY to pluck up the courage to collimate my c-9.25.
That's good. If it is NOT precisely collimated and collimated correctly, you are NOT getting the performance your scope is capable of giving you. It can, in fact, be like the difference between night and day. Tips?
--The only way you can "lay waste" to anything is by removing/loosening all three screws at the same time. That makes your secondary go KER PLUNK.
--Always collimate on the just slightly out of focus image of a star. Only defocus until you can see rings. If you have a big "donut" you are way too much out of focus. Collimate until the rings are concentric. Not squished on any side.
--Normally you ONLY collimate by tightening knobs/screws. Only when a screw is snug should you loosen an opposite number(s). When they are loosened, go back to the original screw and tighten some more. This ensures your scope will MAINTAIN collimation once collimated.
--Always recenter the star between tweaks.
That's all there is to it.
--------------------
Uncle Rod
Watch for Rod's New Book:
Choosing and Using the New CATs--coming soon!
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payner
sage
Reged: 03/22/07
Posts: 230
Loc: Bluegrass Region, Kentucky
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Skybsd: Don't worry about it, it is not the "Oh my I'll break it doing this" for sure. Heck, installing Bob's knobs, then re-collimating the scope, is a bigger feat than collimating the scope only.
Remember, it takes very slight twist of the knob(s) to perfect collimation in a scope you are already basically happy with the views you're getting (that's where I was, but it showed it was slightly out of collimation on double stars). Whether one has a Celestron or other brand, go to their website and download their CGE series owner's manual. You'll find very good step-wise directions there.
Randy
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skybsd
sage
Reged: 02/01/08
Posts: 274
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Hi,
Great to hear from you..,
Quote:
That's good. If it is NOT precisely collimated and collimated correctly, you are NOT getting the performance your scope is capable of giving you. It can, in fact, be like the difference between night and day.
Yeah, I know that I need to get this done. I'm in fact, more motivated today (on reading this post) that ever in the past, so will put collimating the OTA before observing next time I go out - weather permitting.
Quote:
Tips?
--The only way you can "lay waste" to anything is by removing/loosening all three screws at the same time. That makes your secondary go KER PLUNK.
Check!
Quote:
--Always collimate on the just slightly out of focus image of a star. Only defocus until you can see rings. If you have a big "donut" you are way too much out of focus. Collimate until the rings are concentric. Not squished on any side.
See., from what I recall reading on this, isn't the "donut" what you need to work with? The other bear-trap I've been afraid of is when using my diagonal to do, this, that I end up turning the wrong screw, the wrong way 
Quote:
--Normally you ONLY collimate by tightening knobs/screws. Only when a screw is snug should you loosen an opposite number(s). When they are loosened, go back to the original screw and tighten some more. This ensures your scope will MAINTAIN collimation once collimated.
--Always recenter the star between tweaks.
Ahh., okay. Will see how it goes. Hopefully will get it done okay.
Thanks a lot!
Regards,
skybsd
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rmollise
Carpal Tunnel
Reged: 07/06/07
Posts: 1558
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Quote:
See., from what I recall reading on this, isn't the "donut" what you need to work with? The other bear-trap I've been afraid of is when using my diagonal to do, this, that I end up turning the wrong screw, the wrong way
No. Using the donut is ONLY good for achievin', at best, rough collimation. You need to use the diffraction rings to do a good job.
There is nothing to be afraid of vis-a-vis a diagonal. A trick? Move the scope to place the squished side of the diffraction pattern on the edge of the field and turn the appropriate collimation screw(s) to move the star/diffraction pattern/bullseye to the center of the field. Keep doing that until it is unsquished. Do not be afraid of turning screws experimentally _by small amounts_...
That's the other secret to SCT collimation: turn the screws/knobs by small amounts, center the star, check image, tweak, repeat as needed.
My suggestion? Since you sound very tentative about this, why not enlist the aid of a fellow club member the first time out? You DO belong to your local astronomy club, doncha? Good, I knew you did!
--------------------
Uncle Rod
Watch for Rod's New Book:
Choosing and Using the New CATs--coming soon!
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skybsd
sage
Reged: 02/01/08
Posts: 274
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Hi Rod,
Quote:
No. Using the donut is ONLY good for achievin', at best, rough collimation. You need to use the diffraction rings to do a good job.
I see - okay that makes sense then. Excellent!
Quote:
There is nothing to be afraid of vis-a-vis a diagonal. A trick? Move the scope to place the squished side of the diffraction pattern on the edge of the field and turn the appropriate collimation screw(s) to move the star/diffraction pattern/bullseye to the center of the field. Keep doing that until it is unsquished. Do not be afraid of turning screws experimentally _by small amounts_...
Ahh.., Cool, I like the logic involved in that..,
Quote:
My suggestion? Since you sound very tentative about this, why not enlist the aid of a fellow club member the first time out? You DO belong to your local astronomy club, doncha? Good, I knew you did!
I don't actually - due to that fact that.., well.., there isn't really a local anything as far as astronomy goes. I am aware of clubs in other towns in (the county of) Surrey where I am though..,
However, I do take your point - so I can post a request for assistance in a UK-based online forum to see who's around, close and willing to help.
That said though., confidence is high on my part, so I'm keen to try it for myself first, anyways 
Thanks again for the pointers!
Regards,
skybsd
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bcuddihee
scholastic sledgehammer
Reged: 11/04/06
Posts: 919
Loc: Cincinnati Ohio
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Always keep track of which screw you turned and which way. You can put a colored piece of vinyl tape by each screw to help you keep track. I have not used Bob's Knobs, and I'm sure they work well but..they are not necessary for collimating your scope. I find I can get those pesky little screws pretty darned snug with a small Phillips head.
bc
--------------------
B Cuddihee
On the quest to find the best for the least!
--------------------------
1968 Jason Empire 60X700mm refractor (my buddy from way back)
Celestron Nexstar8SE(a remarkable 8" grab and go)
Feathertouch Microfocuser
Stellarvue 50mm "Sparrowhawk" finder
Denk bino's with Power x switch
Pair of Smart Astronomy 25mm Sterling Plossls
Pair of Smart Astronomy 19 EF's
Pair of 15 Garrett SWA's
7mm UO HD Orthoscopic
Agena 38 SWA
Agena 26 SWA
Garrett 2" 2x ED Barlow
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skybsd
sage
Reged: 02/01/08
Posts: 274
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Hi All,
Quick question on this, please..,
If I were to (at the start, but really at any point) turn the wrong screw such that the concentricity of the defocussed star becomes even more out-of-whack, do I: -
a] Slacken the wrongly turned screw then tighten the opposite (as much as it is opposite) screw to compensate for the initial wrong screw being turned?
OR
b] Go straight to the opposing screw and tighten so as to get back to where I started from
Thanks.
Regards,
skybsd
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bcuddihee
scholastic sledgehammer
Reged: 11/04/06
Posts: 919
Loc: Cincinnati Ohio
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I guess it would depend on whether the opposing screw was too tight to allow it to turn enough to get you back to where you began..but that is how would approach it. If after tightening the opposing screw it still does not get you back, then start by slowly backing off the initial screw. Hope that makes sense.
BC
--------------------
B Cuddihee
On the quest to find the best for the least!
--------------------------
1968 Jason Empire 60X700mm refractor (my buddy from way back)
Celestron Nexstar8SE(a remarkable 8" grab and go)
Feathertouch Microfocuser
Stellarvue 50mm "Sparrowhawk" finder
Denk bino's with Power x switch
Pair of Smart Astronomy 25mm Sterling Plossls
Pair of Smart Astronomy 19 EF's
Pair of 15 Garrett SWA's
7mm UO HD Orthoscopic
Agena 38 SWA
Agena 26 SWA
Garrett 2" 2x ED Barlow
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payner
sage
Reged: 03/22/07
Posts: 230
Loc: Bluegrass Region, Kentucky
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Quote:
I have not used Bob's Knobs, and I'm sure they work well but..they are not necessary for collimating your scope. I find I can get those pesky little screws pretty darned snug with a small Phillips head.
bc
No, Bob's knobs are not necessary; I just rather not get a screwdriver near my correct plate and absolutely ruin my evening (and many more to come).
Randy
--------------------
CGE1400 w/XLT & FT MicroFocuser
Russian-Intes MK 91 Rumak
Takahashi FS-128
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Rick Woods
Post Laureate
Reged: 01/27/05
Posts: 4262
Loc: Inner Solar System
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One last thing to remember:
Whatever you do, do NOT turn the screws!
(Kidding! It's easy, just like everyone says. Just go slow).
--------------------
- Rick
14" LX200GPS
8" Meade 826C
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skybsd
sage
Reged: 02/01/08
Posts: 274
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Hi,
Shaping up to be a good night tonight, so will have a go - twiddling my thumbs waiting for Polaris to show up so I can align the mount..,
Regards,
skybsd
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payner
sage
Reged: 03/22/07
Posts: 230
Loc: Bluegrass Region, Kentucky
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Go for the gusto! Just keep in mind the worst thing you may do is have a less collimated scope, but I think that is unlikely. Follow advice given here and the Celestron instructions on collimation, you'll do fine.
Randy
--------------------
CGE1400 w/XLT & FT MicroFocuser
Russian-Intes MK 91 Rumak
Takahashi FS-128
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skybsd
sage
Reged: 02/01/08
Posts: 274
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Hi Payner!
Quote:
Go for the gusto!
Thanks!
However, not really a success tonight, I'm afraid 
Pretty much as soon as I had set up the mount, scope, etc.., the &*%$£*?%% clouds came out of nowhere!
Quote:
Just keep in mind the worst thing you may do is have a less collimated scope, but I think that is unlikely. Follow advice given here and the Celestron instructions on collimation, you'll do fine.
Yeah, I had actually started - used the 15 Panoptic to get the Mizar double-stars (easily resolvable, by the way) centered, then swapped in the 9T6 to begin.
Following Uncle Rod's advice, I centered the brigter of the two and defocussed (I checked forward and backward focus just to see what that looked like) and found that my target looked a_little like the image on the left .
So, confidence high, but not really knowing which of the screws I needed to turn, I decided to try tightening the screw on the same side as where the shadow of the secondary appeared closer to the edge.
So using the example of the left image (above), through the eyepiece, the secondary's shadow appears shifted to the right, so went round to the front to face the corrector and tried tightening the screw on my left a little.
I did this a couple of times, but I honestly can't say if this was improving anything as going back to center the target the second time, I noticed that my image was distinctly dimmer. Thinking the worst - I thought I messed up somewhere! 
Looking up to the heavens in despair though, I saw that the clouds had rolled up on me. A quick glance round the sky confirmed that in the few minutes of my fiddling around, it had gone completely overcast 
So.., not entirely successful, but no disaster - so all good.
So here's my BIG QUESTION :
Was I turning the right screw, anyway??????
Thanks again for (all of you!) the help and encouragement. One night of some visibility is what I figure I need - confidence is still high, you see 
Regards,
skybsd
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amys
Carpal Tunnel
Reged: 06/12/06
Posts: 1763
Loc: Groton, CT
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Did the star move out of the center of the FOV in the direction of the flare of the rings (wider rings)? If so, then yes. If not, then no.
--------------------
Amy
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skybsd
sage
Reged: 02/01/08
Posts: 274
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Hi,
GOT IT!
Gosh - lets hope I don't have to do THAT again soon. Got there in the end, folks.
Took me 2.5 hours of dodging clouds and three targets, but with the view I could get with my 9T6, I finally got evenly concentric rings. Verified by double-checking against a fourth target, but by the time I had returned from my celebratory cigarette, it had gone completely overcast.
Will be anxiously awaiting the next time out with the C-9.25, I tell you!
Thanks so much to all of you, not in the least, Uncle Rod - TOP MAN!
Regards,
skybsd
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