Yep. Their relative rotational positions to one another.
I've got a strong feeling, and it's been backed by a few folk who've looked through my scope, that perhaps the corrector is not optically aligned for peak performance.
I dropped it off today to be checked and fixed, if needed.
Merlin - a Ronchi test will definitely pick up optical misalignment???
Thanks guys.
I appreciate you taking the time to post ideas/suggestions
I think, Yes! The distortion of the Ronchi bands shows the nett effect of the optical train, whether the error is coming from the secondary, primary of any other optic between you and the reference star ie correctors, atmosphere, etc etc.
I guess you also have to be confident that whoever you take it to can
a) perform the tests accurately
b) analyse the results accurately
c) Give you honest and accurate recommendations
Finding someone to carry out the first 2 is particularly troublesome if not impossible and the third? Nigh on impossible if you're dealing with anyone remotely connected to the product (ie where you bought it from, dealers etc).
Thanks for that link John, although from my initial reading of that page it looks like it's intended for assessing the "figure" of the optical components and not their alignment/ orientation???
I fear the problem with my scope is the corrector has rotated/moved out of alignment.
Could be a worthwhile investment though.
I'm just about at the point of giving up, to be honest.
No-one seems willing or capable of testing and/or offering a guarantee it will be ok, even if the problem is correctable.
I could go into more detail but that would just depress me more, and I'd need to pass negative comment on a few astro industry "sacred cows".
I just don't need the grief
Bottom line (for me, anyway)... unless you can get a replacement, you are on your own kid.
Doesn't Celestron have a service agent in Australia who could pull the corrector out and check the index marks? This is a very simple and quick proceedure for someone who is practiced at doing it, well worth it for Celestron to ease the minds of forum members who may be considering a purchase. I've seen enough bad reports on Meade and Celestron recently that I wouldn't purchase either right now without going through a dealer who would check the instrument up front.
One of the big problems I'm facing is finding anyone who can actually
a) Check to see if the corrector has moved relative to the index marks
b) If it hasn't moved, test if that orientation is the correct (optimal) rotation for the corrector
On the face of it these seem like simple enough jobs, for which I'm willing to pay a fee.
But so far all I'm able to find are so-called "experts" whose big idea of optically checking my scope is to stick it in front of an artifical star and tell me whether or not my scope is collimated.
BIG DEAL!!!!!!!!
I can collimate a telescope and I don't need to spend $170 for the privilige of someone telling me my collimation is OK.
I'll say this one more time: It's not the collimation!!!
An SCT with misaligned optics can still produce perfect in and out of focus star tests.
It's the OPTICAL ALIGNMENT which i want tested and if necessary... corrected
I can assure you 100% that testing the telescope complete against a reference star ( or real star) with the Ronchi test will show the effect of ALL the optical surfaces and the impact of any misalignment, poor optical quality ( ie surface accuracy) of both the corrector ( in a SCT) secondary, and primary. If the system is 100% then the bands will be ABSOLUTELY straight and equally spaced and equal widths with no tapering ( mis-aligned optics) or waviness ( poor optics).
I base this on almost 35 years experience!
Tapered means the lines appear wider apart at one side of the image than the other. A perfect image/ system will show perfectly straight and equally spaced ( all over ) lines.
Try it, you'll quickly see what I mean. A 120 line grating would be a good starting point.
If you have concerns regarding the optical alignment or configuration of your telescope, and its still under warranty, why not just take it back to the original supplier for service or replacement? Then you wouldn't need to worry about cost, as nothing comes from your pocket. Worst case scenario, you get a brand new scope! As soon as you have someone else work on it, you have voided your warranty.
Just out of curiosity (coz I believe there's no such thing as a stupid question), what level of magnification are you using?
That's exactly what I'm doing in talking with Extravision.
Gotta be careful of voiding that warranty.
Re: magnifications?
All sorts. Depends on seeing etc
I have (on occasions) checked it with the ToUcam in the barlow...watching the image on the laptop screen. Otherwise various eyepieces offering a wide variety of magnifications.
Just a thought. You mention the corrector might not be "optically alligned". If this is the case then you have one of two problems, 1. The corrector has rotated (in which case the alignment markers are going to be misalighed. or 2. The corrector was always out of alignment and the alignment markers are not going to indicate anything.
I would suggest that 2 is probably extremly rare, and probably not an issue.
1. However can be checked by simply taking off the corrector locking ring and checking if the markers line up. Another handy approach is if you still arent satisfied, to loosen the locking ring, line up the scope and by hand turn the corrector until you are happy with the results (mark the new position) and then tighten it all down.
Anyway if Extravision cant help (and hence the warrenty is not an issue) then I would ask Don at Bintel to do this as he suggested this to me for mine.
