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Captain Magenta

Intes M603 Tear-Down Refurb & Re-Collimation

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I had a more extended session observing on Saturday night. Star testing showed vastly better patterns than before, and stars were more or less points, though there's plenty of room for final improvement.

To demonstrate how much better the first rough collimation was, I took a couple of terrestrial photos, "before" and "after" of a pipe about 50m away. The "before" pic is really the very best focus I could achieve at the time. The "after" pic is of the same pipe a few inches down.

 

_S7A4449.jpg

_S7A4456.jpg

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I decided to re-test the primary-mirror axis and Baffle/focus-tube collimation with the external focuser attached, as the external focuser likely has its own axis. Sure enough, it was slightly off (the laser in the focuser pointed at a point 2-3mm different from my artificial star and its coincident reflection from the primary). I shimmed the meeting-face of the Revelation focuser on its rotatable dovetail-ring, and established that there is one position where all three dots coincide. I set it there, and locked it down.

To do that, though, I had to remove again the secondary-mirror boss to create a hole for the laser to get through. In the process of doing that, THE SECONDARY MIRROR FELL OFF!!! Wow. As the picture shows, the glue was very old with almost no "stick" left. I'm glad it did, as it would otherwise likely have happened at night in the cold while the scope was pointed up. And would therefore have landed on the primary.

_DSF0595.thumb.jpg.e51f87da9b4aa4cc3865dcd7556d6a9d.jpg

I also removed the not-especially useful central pin the the middle of the secondary front-plate, and will keep it removed to allow a permanent hole for a laser to be able to shine through. I'll keep it covered with some sort of plug or tape though.

I re-glued the secondary to its plate, and it's now curing:

_DSF0600.thumb.jpg.5a376f1416d0676508eb58108743436f.jpg

I had planned to start fine-collimating the scope today with an artificial star at the bottom of my garden, but this episode put paid to that.

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2 hours ago, Captain Magenta said:

I decided to re-test the primary-mirror axis and Baffle/focus-tube collimation with the external focuser attached, as the external focuser likely has its own axis. Sure enough, it was slightly off (the laser in the focuser pointed at a point 2-3mm different from my artificial star and its coincident reflection from the primary). I shimmed the meeting-face of the Revelation focuser on its rotatable dovetail-ring, and established that there is one position where all three dots coincide. I set it there, and locked it down.

To do that, though, I had to remove again the secondary-mirror boss to create a hole for the laser to get through. In the process of doing that, THE SECONDARY MIRROR FELL OFF!!! Wow. As the picture shows, the glue was very old with almost no "stick" left. I'm glad it did, as it would otherwise likely have happened at night in the cold while the scope was pointed up. And would therefore have landed on the primary.

_DSF0595.thumb.jpg.e51f87da9b4aa4cc3865dcd7556d6a9d.jpg

I also removed the not-especially useful central pin the the middle of the secondary front-plate, and will keep it removed to allow a permanent hole for a laser to be able to shine through. I'll keep it covered with some sort of plug or tape though.

I re-glued the secondary to its plate, and it's now curing:

_DSF0600.thumb.jpg.5a376f1416d0676508eb58108743436f.jpg

I had planned to start fine-collimating the scope today with an artificial star at the bottom of my garden, but this episode put paid to that.

 

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Phewww least you saved the secondary!

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Posted (edited)
15 minutes ago, lnlarxg said:

Phewww least you saved the secondary!

Yes probably a bit difficult to replace! Phew is right.

Edited by Captain Magenta

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Hows the collimation going ?? 😀

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52 minutes ago, stuy said:

Hows the collimation going ?? 😀

Having satisfied myself the primary is collimated properly, I worked out another way of achieving first-order collimation of the secondary indoors, without looking at difficult-to-compare concentric circles on a target through a collimation cap, or via the hall-of-mirrors from the front of the scope, which I have found to be a very rough guide. Rather, if I put a laser in the focuser eyepiece, and look through the front of the scope, I can see the reflection of the facing-plate of the laser, reflected in the secondary and the primary. Which means I can see both the laser source and its returning dot reflected off the secondary. I just need to adjust the secondary until that dot coincides with the source. I did that, and now await a clear night for some real stars. Or the delivery of my tactical high-intensity torch to shine at a ball-bearing.

Tonight is clear, tomorrow I'm WFH, so I'll have a go tonight...

Cheers, Magnus

 

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Having once again "indoor-collimated" using my new technique, Monday night was just too temptingly clear to resist using Polaris to try to fine-tune, in spite of being a School Night. I'm now WFH anyway for the foreseeable future, so an extra hour in the morning would compensate.

Using the indoor-collimated setup, stars were, as expected, more or less points (unlike my horrid smear from a week or so ago), but nonethelss even at 43x wide-field obviously highly aberrated diffracted-comet-shaped horrors. Confirmation that indoor collimation is really a very rough starting point.

The high-magnfication defocused diffraction ring for Polaris was, at 250x, a bright outer nearly-circle with a bright point and squashed rings bottom left. I worked out which of the three secondary collimation screws was appropriate for that position, and adjusted it a small amount in a random direction. The pattern seemed to get worse and it certainly was worse when I had a look at best focus. So I'd adjusted the wrong way. At least now I knew which way I needed to go.

After a very slow process of adjusting screws, re-locating and centering Polaris as it moved away due to the adjustments, sometimes out of field in which case I had to change "down" eyepiece to find it again and change magnifcation back up, I finally managed the spot into more or less centre of the now-circular rings. By now the direction of the much-reduced aberration was slightly different so I switched collimation screws, and suddenly, bang, I found myself looking at textbook defocused diffraction rings, or something very close.

With not a little trepidation, I moved the focus-knob to actual focus, and my goodness! Nice Airy disc around Polaris, and symmetrical.

I changed from 250x back to my Panoptic 35mm to get a wide-field 43x, and suddenly I seemed to be looking through a high-quality refractor, lovely sweet pinpoint stars everywhere, lots of different star colours, it reminded me of the view I'd had through @Stu's Tak a while ago. It was after 11pm by now, I needed to look at something definite before I went to bed so I eventually found Castor (no finder so was hunting around a bit) and beautifully evident pair even at 43x.

I went to bed well pleased I'd finally got this little Intes performing. I don't really count this as First Light, so I'll round off before long with a First Light and some pics of its restored state.

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