Hotech Reveals More than Simple Collimation Required.

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a100171
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Hotech Reveals More than Simple Collimation Required.

#1

Post by a100171 » Fri Aug 09, 2019 11:19 pm

So, now that I got my mount adapter all constructed, and I had a nice stable platform for giving everything the once-over, I setup the Hotech Advanced SCT Collimator to give the Meade f/6.3 a top-to-bottom checkup.
It took a bit of figuring things out, as far as how to use this thing and what it is telling me each step along the way. It was not long before I started figuring out why the images are not as good as they should be.

It is obviously a used scope, but who knows how many hands it has been through in its life.

Getting the scope and collimator all squared-up took some time. Watching the YouTube video sure helped. But it became clear rather quickly (kind of a reverse pun there I guess!) that there were at least a few things wrong. The video says that setup is 90% of the work...Not!!!
The secondary/holder was definitely not centered in the optical path. Unfortunately, this older LX200 OTA does not have a removable secondary; the entire corrector has to come off. The secondary holder was actually rather loose, as it could move from side-to-side a bit (almost like the corrector hole was too large). I carefully marked the corrector orientation on the scope, and started removing the outer ring.
With the ring removed, I could see various pieces of spacer material on the outer corrector edge. It looks like someone tried to center the corrector plate using paper-like material. This was not going to be fun using this method. There had to be a better way. I put everyting back together to let the brain think about things a bit.

The secondary centering in the corrector plate: I am thinking about applying some sort of rigid material around the assembly so that it fits more snugly in the corrector lens. It almost seems like some sort of spacer is missing. There is simply too much play right now. Once I get this tighter, I will tighten the assembly on the corrector so that it will not come loose.
In the Hotech video, they mention how the EdgeHD scopes have screws to adjust secondary positioning (by shifting the corrector plate in the tube). Certainly nothing like this on this old Meade, but makes me wonder if I should drill and tap three holes and put in a set-screw/locking screw in each. That way I can adjust the secondary position without using the Paper method. Maybe not.

I am hoping things will be easier once the secondary holder and corrector are rigid. Wondering what others may have done to get corrector centering accomplished.

As far as corrector orientation, I will put it in the position that it was in, but who knows if this is actually the right position (e.g. have previous owners rotated the plate). Not sure how I could check to see if the orientation is in fact correct.

I was just about ready to flip a coin and order a new 10" OTA ,and leave this one to a blizzard /snowed-in and at-home time this winter instead.
Meade 6", 8", and 10" SN, Meade 10" f/6.3 Lx200, ES ES-102, Meade 90mm DS-2000, Celestron CPC-800 HD, Celestron 11" EdgeHD, Meade ETX-90, AVX, CGEM, CGEM-DX, Twilight I mounts. Omegon 2.1x 41mm Binocs.
Hyperstar for EdgeHD, ZWO and Celestron Nightscape CCD. And now: a fully-functional Meade 12" RCX-400. And now: a Vaonis Stellina!
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#2

Post by smeyer8015 » Sat Aug 10, 2019 4:35 am

On Celestron scopes the corrector and secondary have indicators for orientation. The corrector plate has a serial number etched into the edge and the secondary has a sharpie mark on the back of it. These two marks are 180 from the focuser knob. Don't know for sure if Mead does the same or not.......


Scott
Celestron Classic 8, Old Sears 60mm f/15 refractor, Old Edmund Scientific 6 inch F/8 newt, GSO 2" Diag, ES 30mm/70, ES 25mm/70, Orion 32 Super Plossl, Mead 24mm MA,
X-Cel LX 18mm, Luminos 15mm, F/6.3 reducer, Luminos 2.5x barlow, Telrad, Celestron 9x50 RACI, DIY Baader Solar Filter, Celestron Skymaster 20x80, Bresser EXOS-2 Goto, Revolution Imager R1

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#3

Post by a100171 » Fri Aug 30, 2019 2:47 am

Well after messing around with the collimation with the Hotech, and then re-starting the whole procedure again to "verify" that I had done this correctly, it looked like I had this thing set rather well.
The secondary was not quite centered, but I was able to get this just about spot-on by loosening most of the corrector plate screws, keeping two of themjust a tiny-bit loose,and sliding the whole plate by moving it by holding the whole thing by the secondary.

The other night, I carried the whole thing outside and covered it up with the Telegizmos cover (I was dead after getting it mounted and pseudo polar aligned). Tonight I removed the cover to see how she looked. And I must say, I was rather impressed how it looked.

I put in a low-power eyepiece and tried to check the finder alignment. After messing around, I was able to get it right on the money using Vega. But all the while looking around, I never even noticed any sort of coma at all, even at the edges. I can remember how much coma that my ancient 2080 showed. This was not at all the same. I had not even messed-around with fine-tuning the secondary with a star-test yet. And I am not inclined to do so yet. maybe after I get this thing fully polar aligned, so I can do a high-magnification run. Given how much I had this apart, I was rather impressed with myself.

Took a quick peek at The Ring, which had its normal smoke-ring appearance. I popped-in an 8.8 UWA, but it was darker than I would have thought. Andromeda was just over the trees, and was quite bright. Then the mosquitoes found me, as I had not sprayed myself down.

I have got to get into work early tomorrow, so I left it all uncovered (with the scope caps on) so maybe I can take a peek at our Winter Friends before dawn.

At least I don't have to take this thing down! Very handy living in the country!
Meade 6", 8", and 10" SN, Meade 10" f/6.3 Lx200, ES ES-102, Meade 90mm DS-2000, Celestron CPC-800 HD, Celestron 11" EdgeHD, Meade ETX-90, AVX, CGEM, CGEM-DX, Twilight I mounts. Omegon 2.1x 41mm Binocs.
Hyperstar for EdgeHD, ZWO and Celestron Nightscape CCD. And now: a fully-functional Meade 12" RCX-400. And now: a Vaonis Stellina!
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