At last, O' dear, at last!

Visionary (David) · #1 26-10-2015, 10:47 PM

my Meade SCT LX90 8" has been the recipient of much of my attention and money. I have adapted the scope for low vision, low vision is another way of saying blind. So, the telescope is fairly much one of a kind.
Today after one final tweek to the Red Dot finder atop the scope I discovered that aluminium filings had fallen through the screw hole and fallen to rest beside the collect plate, inside the scope. If I remove the plate I am going to completely blow collimation.
I don't know exactly what to do, what are your suggestions? Should I attempt to remove the p,ate myself of put through an emergency call to the guys at Bintel?
Cheers

casstony · #2 26-10-2015, 11:08 PM

A few filings inside the scope are unlikely to cause any problems, they're just unsightly.
If you do remove the corrector make sure it goes back in the same rotational orientation and replace any spacers around the edge of the plate. You'll need to fine tune the collimation after removing the plate.

Visionary (David) · #3 26-10-2015, 11:59 PM

Quote:

Originally Posted by casstony

A few filings inside the scope are unlikely to cause any problems, they're just unsightly.
If you do remove the corrector make sure it goes back in the same rotational orientation and replace any spacers around the edge of the plate. You'll need to fine tune the collimation after removing the plate.

Tony, many thanks I really don't trust myself with the plate. If it's not a high risks then I will continue to use it but I think I will "phone a friend".
I am genuinely jumping out of my skin. I have worked on the thing for so long, now to have it 100% complete is just a huge thrill... I havent been this excited in a long time.

Shiraz (Ray) · #4 27-10-2015, 12:00 AM

Take Tony's advice, shrug your shoulders and ignore them if you can. A few filings are unlikely to degrade the view by a noticeable amount and could only cause problems (possibly) if they got into the focusing mechanism. Then you would have something to fix, whereas at this stage it sounds like a cosmetic issue.
For perspective, my Newtonian spends all night in the open on most clear nights. It has been assaulted by insects, wind blown dust and grass debris, heavy dew, salty aerosols and rain. It has survived and still works as well as it ever did - even though it only gets a clean out when the mirror starts looking dirty.

Visionary (David) · #5 27-10-2015, 12:48 AM

Shiraz, that makes sense but I cannot help but feel my "baby" is injured. Seriously I have worked so long on the thing it could qualify as a dependant.

ab1963 (Andrew) · #6 27-10-2015, 11:26 AM

As we all know with telescope equipment if something isn't just quite right it plays on the mind until we either get or fix whatever will remove the doubt ,my advice to you is to have it professionally removed so you have piece of mind ,especially with the scope being so important to you I think it would be money well spent IMO

Robert9 (Robert) · #7 28-10-2015, 11:54 AM

David,
I agree with Andrew. For the few dollars you will need to spend, after apparently spending quite a bit on the scope already, the peace of mind will be well worth it. I certainly would not want to leave the filings in there for fear that they might get caught in the focussing mechanism. Have it done professionally and sleep well.
Robert

Visionary (David) · #8 28-10-2015, 12:40 PM

Quote:

Originally Posted by Robert9

David,
I agree with Andrew. For the few dollars you will need to spend, after apparently spending quite a bit on the scope already, the peace of mind will be well worth it. I certainly would not want to leave the filings in there for fear that they might get caught in the focussing mechanism. Have it done professionally and sleep well.
Robert

Robert, I steeled myself and removed the corrector plate. I took many precautions. Once the corrector plate was off, I tilted the OTA slightly downwards then proceed to vacuum out the aluminium debris. Again with utmost care and observing the taped markings I made prior to removal, placed the collector plate back onto the OTA.
From my yard I have a horizontal view of some 4km. Observing with the corrector plate returned, focus was as sharp as a tack over the entire 4km. Given that the air was unstable I could push focus out beyond 4km.
It seems the mission was a success! Many thanks for the guidance it's much appreciated I obviously hadn't removed a corrector plate before.
If the focus is sharp to 4km, would this mean collimation is still OK? In any case if the clouds clear tonight I am going to test collimation on some stars.

jenchris (Jennifer) · #9 28-10-2015, 04:55 PM

I was going to suggest just removing the secondary mirror and using some flexible tube attached to a vacuum cleaner to suck the bits out but I am too late.

Visionary (David) · #10 28-10-2015, 05:06 PM

Quote:

Originally Posted by jenchris

I was going to suggest just removing the secondary mirror and using some flexible tube attached to a vacuum cleaner to suck the bits out but I am too late.

I don't know for certain as I have never removed the secondary mirror. Once I had all the necessary precautions in place, it was surprisingly easy to remove and replace the corrector plate.
Meade was exceeding helpful they had marked the correction position of the corrector plate. It looked like liquid paper with a pen marking running through both the plate and it's correct position on the rim of the OTA.
If it hadn't sort of opened easily moving through the hole created by the secondary would have been the neatest solution.

casstony · #11 28-10-2015, 05:32 PM

Quote:

Originally Posted by Visionary

If the focus is sharp to 4km, would this mean collimation is still OK? .

Low daytime magnifications won't tell you much about the collimation; it's likely to need a slight tweek on a star, but not until after the tube is cooled to ambient temperature.

casstony · #12 28-10-2015, 05:36 PM

Quote:

Originally Posted by jenchris

I was going to suggest just removing the secondary mirror and using some flexible tube attached to a vacuum cleaner to suck the bits out but I am too late.

Removing the secondary can only be done on fastar capable scopes such as the Celestron Edge HD. Unless they've been retrofitted it's necessary to removed the corrector on a Meade before removing a secondary assembly.

jenchris (Jennifer) · #13 28-10-2015, 06:58 PM

I actually did it with mine, so that's not exactly a 100% correct.

casstony · #14 28-10-2015, 07:21 PM

Quote:

Originally Posted by jenchris

I actually did it with mine, so that's not exactly a 100% correct.

Please explain how it's done. Perhaps the newer Meade secondary holders are different to what I had.

Robert9 (Robert) · #15 31-10-2015, 06:50 PM

Quote:

Originally Posted by Visionary

Robert, I steeled myself and removed the corrector plate. I took many precautions. Once the corrector plate was off, I tilted the OTA slightly downwards then proceed to vacuum out the aluminium debris. Again with utmost care and observing the taped markings I made prior to removal, placed the collector plate back onto the OTA.

David, you're a braver man than I. Well done, I'm glad to hear that the operation was successful. Check your collimation by focussing on a star, then defocus and the blurred donut image should be perfectly symmetrical with the shadow (and diffraction circles if visible) of the secondary mirror absolutely central.
Robert