core
super member
Reged: 02/23/08
Posts: 116
Loc: Mostly in Norman, OK
|
|
Just picked up my 6SE yesterday, while I'm not expecting too much optics-wise, I've had some concerns during my quick test last night (ample cool-down time, steady seeing). OTA was out of collimation and I fixed it the best I could for the moment.
First off, there's a distinct flare when using medium fl eyepiece (tried supplied ep, 26mm silver-top vixen/celestron Plossl, 22mm vixen LVW, TV 40mmPL) and I put a bright star (~mag1) starting ~2/3 from center. The star circumscribes a ring of light towards the center. When I switch to a 13mm ep (TV PL), there is no flare all the way to the edge.
Here's a picture I took to try and get the flare (just look past the horrid noise as I tweaked the curve - prime, 6 sec @ 1600iso; fyi EXIF is intact) - keep in mind this is taken with a 4/3 sensor which has a 2x crop factor (vs. ~1.5 for APC)
--------------------
~Peter~
|
core
super member
Reged: 02/23/08
Posts: 116
Loc: Mostly in Norman, OK
|
|
And another shot with Vega in the corner (15 sec exp.) Note that in actual observation the ring of light is very bright, and I can trace out an entire elliptical.
I also had a C8 out for comparison, and from my suburban backyard I have to admit though the the handful of bright DSO's I had a peek at were quite comparable (M13, 27, 57, 92) brightness and resolution wise - perfect for my intention as a large-aperture grab-and-go (C6 will double-duty on a Porta/Voyager).
Now, in comparison the C8 did not exhibit any flare at all. iirc, I had a C5+ OTA from a decade back that did not have this flare issue as well.
--------------------
~Peter~
|
core
super member
Reged: 02/23/08
Posts: 116
Loc: Mostly in Norman, OK
|
|
I inspected the OTA this morning, and found a small spot 1/2 way down the main baffle that was not entirely painted (will try and get a picture) - this is not the cause as the flare is symmetrical (ie, any off-axis position I put the star at produces the flare). Looking down the rear opening off-axis as much as I can, it looks to me like the ring of light is coming from the baffle in the secondary. Either there is some painting issue in the secondary baffle, or the design is inadequate - any thots?
fwiw here's some in/out-of-focus Vega images (100% crop); I'm no expert at decoding diffraction rings (let alone take them, I think I racked in/out the focuser a tad too much), but to looks to me like some zone issues?
--------------------
~Peter~
|
core
super member
Reged: 02/23/08
Posts: 116
Loc: Mostly in Norman, OK
|
|
And a final shot (for now  ) with focus the other way. Both are 1600 iso @ 1/4 sec.
--------------------
~Peter~
|
bcuddihee
scholastic sledgehammer
Reged: 11/04/06
Posts: 919
Loc: Cincinnati Ohio
|
|
The star test image looks pretty good to my with the exeption of collimation being off a bit.
--------------------
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
|
Eddgie
Carpal Tunnel
Reged: 02/01/06
Posts: 1723
|
|
I think you are looking in the right spot. Look for any glossy surface in the light path. Inside the central baffle sould be DEAD BLACK.. Take off the visual back or diagonal and aim the scope at the moon or other bright target, If you spot ANY glinting, something is wrong.
Next, check the front of the diagonal. Make sure that there are no glossy surfaces.. Or just swap the diagonal with another one.
If you don't have a second diagonal, get the scope in position were the arc is present and try viewing straight through and with the diagonal to see if the problem comes and goes. If you are using the stock diagonal maybe there is a problem.
It is unlikey that there is a problem with the DESIGN of the baffle. More likely some problem in your sample.
But if it is new and you can't find the problem, My advice is to send it back immediatly. These things NEVER heal themselves..
Regards.
--------------------
Celestron C14, CGE (Big Al)
Astro-Physics 6" f/8 (Buffy)
Televue 101 (No name, but I call it my Widescreen HD Space TV)
The night sky is my mistress. She seduces me away from all other lovers.
|
doug76
Carpal Tunnel
Reged: 12/05/07
Posts: 2554
Loc: SE Louisiana
|
|
I'm with Eddgie on this one. I own the black tube version of this OTA, the C6S, and it doesn't have that flare, and it's optics are outstanding. You should expect great optics with this scope, and if you don't have it, then that's another reason to return it.
Doug
--------------------
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
---------------------
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
|
core
super member
Reged: 02/23/08
Posts: 116
Loc: Mostly in Norman, OK
|
|
Thanks for the input; looks like I will have to get an exchange on the scope from where I got it from (locally), and hopefully I don't get the run-around to contact Celestron directly ...
fwiw I get the ring with 2 different diagonals, and even just straight-thru viewing. Now here's a couple more shots ... this is the smudge on the main baffle, looking from the rear cell:
--------------------
~Peter~
|
core
super member
Reged: 02/23/08
Posts: 116
Loc: Mostly in Norman, OK
|
|
And from the font end ... surprise, it's a rust spot! 
--------------------
~Peter~
|
core
super member
Reged: 02/23/08
Posts: 116
Loc: Mostly in Norman, OK
|
|
And some shots directly (almost) down the rear cell - this one is focused on the secondary cell:
--------------------
~Peter~
|
core
super member
Reged: 02/23/08
Posts: 116
Loc: Mostly in Norman, OK
|
|
This shot is focused on the edge of the main baffle tube.
--------------------
~Peter~
|
core
super member
Reged: 02/23/08
Posts: 116
Loc: Mostly in Norman, OK
|
|
And same shot with +3EV from camera's chosen exposure; I was trying to detect how much of the inside end of the baffle is illuminated.
I'm going to star test again tonight.
--------------------
~Peter~
|
rmollise
Carpal Tunnel
Reged: 07/06/07
Posts: 1564
|
|
Quote:
Just picked up my 6SE yesterday, while I'm not expecting too much optics-wise, I've had some concerns during my quick test last night (ample cool-down time, steady seeing). OTA was out of collimation and I fixed it the best I could for the moment.
First off, there's a distinct flare when using medium fl eyepiece (tried supplied ep, 26mm silver-top vixen/celestron Plossl, 22mm vixen LVW, TV 40mmPL) and I put a bright star (~mag1) starting ~2/3 from center. The star circumscribes a ring of light towards the center. When I switch to a 13mm ep (TV PL), there is no flare all the way to the edge.
Here's a picture I took to try and get the flare (just look past the horrid noise as I tweaked the curve - prime, 6 sec @ 1600iso; fyi EXIF is intact) - keep in mind this is taken with a 4/3 sensor which has a 2x crop factor (vs. ~1.5 for APC)
Your star test/blur circle images look good correction wise, so you are off to a good start. I didn't notice anything but MAYBE a small amount of over or undercorrection (not sure which photo was inside and which was out). Again, looks good. Collimation is the main problem I see. As far as the reflection, the place to start looking is the rear cell stuff: eyepieces, diagonals, visual backs etc.
--------------------
Uncle Rod
Watch for Rod's New Book:
Choosing and Using the New CATs--coming soon!
Edited by rmollise (08/06/08 06:00 PM)
|
core
super member
Reged: 02/23/08
Posts: 116
Loc: Mostly in Norman, OK
|
|
Okay, it's over a month - I should at the very least wrap up this issue with a quick update.
Long story short, Astronomics swapped out the OTA for a new one (the rust spot was enough of a reason), new shots of Vega no longer show any flare, and it is not present in eyepiece - I'm a happy camper! 
The one thing I forgot was to note down the s/n of that particular OTA. For some reason though, the new OTA was a real pain to collimate properly, even with video assist - I've not really had a chance to put the scope thru its paces, but I like the visuals that I've seen so far (albeit not quite the C5+ from years ago that I should not have sold ... then again, it's probably just regret kicking in )
--------------------
~Peter~
|
yg1968
Carpal Tunnel
Reged: 01/26/04
Posts: 1714
|
|
Seems like you weren't the only one with this issue. See these threads:
Other thread
One more thread
|
yg1968
Carpal Tunnel
Reged: 01/26/04
Posts: 1714
|
|
Some people are suggesting that this is normal for an SCT because of the light hitting the corrector plate. I am starting to wonder if this is really a problem or if it is normal:
DSLR Forum thread
|
CHASLX200
professor emeritus
Reged: 09/29/07
Posts: 689
|
|
Quote:
Some people are suggesting that this is normal for an SCT because of the light hitting the corrector plate. I am starting to wonder if this is really a problem or if it is normal:
DSLR Forum thread [/quote
I have owned over 60 SCT's over the years and it was never normal. I never noticed anything like that in any of my SCT's.
Chas
|
Dubboy
Carpal Tunnel
Reged: 07/05/05
Posts: 2145
Loc: Northern Michigan
|
|
After following this thread, and a couple of others, I decided to check my C6 on Jupiter and Vega last night.
Holy *bleep*...a terrible flare/ring when the bright target was moved off axis. I changed eyepieces and diagonal, as someone suggested, with no change. I then inspected the main baffle with a flashlight and found that the first inch or so (corrector end) had what looked like high gloss paint or shiny glue smeared on it.
Tonight, I took the corrector off (marked it first, of course) and lined the shiny portion in the baffle with black felt.
I then took it out for another test...
No more flare/ring and the background seemed to be darker.
A definite improvement!!
This is one nice little scope and is an absolute joy to use on my Vixen PortaMount.
Thanks to all for contributing to this thread and bringing the (possible) problem to my attention.
--------------------
Don
"Don't worry about what telescope you own, or its quality. Just get out under the night sky and enjoy God's wondrous universe" Thomas Back.
|
yg1968
Carpal Tunnel
Reged: 01/26/04
Posts: 1714
|
|
Here is the flare showing up in an image I took. I will be returning my C6 to Celestron. I am not handy enough to fix it myself.
|
Dubboy
Carpal Tunnel
Reged: 07/05/05
Posts: 2145
Loc: Northern Michigan
|
|
That's about what mine looked like.
--------------------
Don
"Don't worry about what telescope you own, or its quality. Just get out under the night sky and enjoy God's wondrous universe" Thomas Back.
|
Previous
Index
Next
Threaded
Edit
Reply
Quote
[Re: 