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Piero

Lukehurst-Nichol classic dobsonian modifications

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The telescope has consistently been working very well for a while now. Stars don't show traces of astigmatism. 

Last night I had another nice session. The sky was rather steady and clear, with very low humidity. The telescope cooled with the fan on for about 2h and then collimated with my 2" Glatter laser (without tuBlug). Eyepieces: 30mm APM UFF (large targets), 12.5mm Docter (all targets), Zeiss zoom (all targets). 20mm Lunt was used for the galaxies, but didn't show anything more than the Docter. Lumicon OIII was used for the Eskimo PN.

Main targets were:

  • Monoceros: M50, NGC 2264 (Christmas tree cluster), Plaskett's star (giant O-type binary SE of 13 Mon)
  • Leo: Leo triplet, NGC 2903 (W from epsilon Leo)
  • Gemini: M35, NGC 2158 (interesting particularly above 250x), NGC 2129, NGC 2392 (Eskimo PN - what a sight at 400-500x!), Wasat (delta Gem)
  • Cancer: M44 (Beehive) M67 (King Cobra cluster)
  • Canes Venatici: M51 (faint spiral, but no connection due to LP) 

I must say that I was impressed with all the targets I've seen. The views were really rich in colour and intensity, with "star dust" visible in the background sky.

Beautiful.

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Posted (edited)

Yesterday I received 4 new pipe insulators for the truss poles. These reduce vibrations to nearly zero, are much more comfortable to touch in the cold, and minimise internal light scatter.

They are also rather cool! :headbang2:

 

IMG_20200318_140932.thumb.jpg.b5bf93f89b856969f18346270deecac2.jpg

 

IMG_20200318_143144.thumb.jpg.50d33f6e1250739f87e8a4d1b9d1c3c9.jpg

 

IMG_20200318_141000.thumb.jpg.8e3b92f9c7518c96eb497dcd9ca003e6.jpg

Edited by Piero
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Nice - looking good.  I've them on my truss poles too: they really are the job on a cold night especially when it comes to tear down!! Good for transport too - the poles just dont rattle and bang off each other.  Simple & effective ;)

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@niallk I agree! They make a substantial difference on a cold night. 

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Posted (edited)

This past weekend I took care of the telescope coatings. Certain parts were minimally coated, whereas others (e.g. UTA, wheelbarrow handles) didn't seem to be coated at all. Also, the internal was gray / black. After ordering the same products used by David from Rustins, I applied 4 coats of clear lacquer to the outside and 4 coats of matt black to the inside. Now the telescope looks so robust and protected from any kind of humidity! The parts in the light path are really black now. 

Also, before doing this work I removed the "button" screws used for attaching the light shroud to the UTA and mirror box. So many! Once removed the holes were all filled and the sanded. This was done a couple of weeks ago. I also removed the usual label that is attached to the UTA as the specs were wrong. 

in addition, I attached 4 X 2mm felt pads to each wheelbarrow handles so that there is a small gap between these and the rockerbox. This should have been done a long time ago, but for a reason or another I always forgot 🙁. Anyway, there are two advantages with this little mod: 1) the wood does not touch, therefore no scratches, cracks noises, etc; and 2) if the telescope is left out overnight or during a week of clear sky (I use a telegizmo cover when this happens), this gap allows the wet surfaces to dry properly.

I also decided to apply the matt black on top of the mirror box, to optimise contrast by reducing any stray lights or reflections. Will post a photo later! :)

Finally, Rob Teeter let me know that the Heather completed and just dispatched my new light shroud! It will arrive soon, hopefully. :)

This evening I will put back the primary mirror and re-collimate the telescope. Very happy with the results. Now I am confident that the telescope can really last for several years!

 

 

The first two external coats (..the UTA looked already so different!):

IMG-20200418-WA0000.thumb.jpeg.1645b37325994ab93d6ab1855b463364.jpeg

IMG-20200418-WA0002.thumb.jpeg.6e8f06bd80118a00ac90c96ff721eed5.jpeg

IMG-20200418-WA0003.thumb.jpeg.fd1359b5108f86d3a85815d9edf8b467.jpeg

IMG-20200418-WA0006.thumb.jpeg.4afd4c8b0d95af4b7b694aac11e31403.jpeg

IMG-20200418-WA0008.thumb.jpeg.1bbd70b8cf2a1e824ed70a131d98163d.jpeg

Edited by Piero
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Mounted! 

Just re-collimated the focuser and secondary. Therefore, I collimated the focuser and primary axial alignments and now it's ready!

Here are a few photos after painting:

IMG_20200420_131706.thumb.jpg.dabd940359a259cae8c13bbf34755fc1.jpg

IMG_20200420_131728.thumb.jpg.630392425b60593dc5c27aa05c9b8cc3.jpg

IMG_20200420_131741.thumb.jpg.6125e86cce367803b25ba2938e4a2c74.jpg

IMG_20200420_131800.thumb.jpg.97c103f561e918f1f7b40542a51df45c.jpg

IMG_20200420_131826.thumb.jpg.50c119f4fa52372ada8bfea78840e800.jpg

IMG_20200420_131912.thumb.jpg.41ef6306bf52e22d3ca5b1c48df23106.jpg

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Just returned from a session outside. Venus was superb, the best view I ever had. Faint white - grey patches were visible between 250x and 400x. Really good view!

I then moved to the classic open cluster in Auriga, Gemini, Cancer, and eventually ended up to the bright galaxies in Leo.

The new black paint certainly makes a difference. On Venus I believe the top of the mirror box now painted black also increased contrast, as the sky appeared noticeably darker than usual. 

Looking forward to use the new light shroud, which landed in Heathrow airport this morning! :)

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Looks great & glad to hear it's working well ;)

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43 minutes ago, niallk said:

Looks great & glad to hear it's working well ;)

Thank you! It is getting there! 

The positive thing of all this process is a good learning curve. There are a few things I would like to build..

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Posted (edited)
On 22/04/2020 at 02:19, Piero said:

Thank you! It is getting there! 

The inside of the rocker box also needs a coat of the black paint...stray light needs to be absorbed here. Espc the bottom.

Edited by jetstream

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34 minutes ago, jetstream said:

The inside of the rocker box also needs a coat of the black paint...stray light needs to be absorbed here. Espc the bottom.

 

Thanks for your feedback, Gerry. And yes I agree.

To do so, I would have had to sand it first, which was even more work. On the other hand, I recently built a wood panel to cover the opening on the lower part of the mirror box. This mod has given positive results, although there is still a bit of boundary layer that can be blown away. For this I will study the use of a fan gently blowing on top of the mirror surface. 

Anyway, because the opening is semi-permanently closed, I painted this wood bar instead. Therefore the is no chance to get stray light from the rocker box. 

And to be thoroughly, I would have preferred to stain and varnish the telescope rather than using lacquer on the outside. This would have required sanding the whole telescope enough so that the previous coat given by David did not interact with the stain and varnish.. I didn't want to risk, so I simply apply 4 coats of the same products.

All in all, another bit of leaning curve for my future project if it will ever come up to life! 

 

--------

The wood bar. It's light and attaches with 4 velcro stripes. Two side openings allow some air flow.

IMG_20200330_080540.thumb.jpg.7a63ee0270550a7f621ff78990bdf903.jpg

 

 

 

After lacquer and painting:

15876438585534429972092500876056.thumb.jpg.8e1985a5b7534b6838e72f5e312d72c9.jpg

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52 minutes ago, Piero said:

For this I will study the use of a fan gently blowing on top of the mirror surface. 

I would source Bryan Greers knowledge on fan ie micro blur.https://www.fpi-protostar.com/bgreer/sep2000st.htm

My very best views using the 15" are with no fan, it will go over 1000x on the moon using the barlowed 2.4mm HR. My fan reduces this ability considerably.

You might find a bit more opening on the bottom to be a benefit...

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