Newtonian Secondary Mirror Mod

A modification to the secondary mirror of my newtonian telescope to assist in more accurate collimation

[@nordmende73]

I can't thank you enough sir. I had huge difficulties collimating my secundairy mirror because of the tiny holes you mentioned. Your spacer makes an enormous difference.

[@astronomyshed]

Thanks for the feedback

[@brettlaniosh6262]

Centring the secondary by adjusting the vanes...I use a pair of compasses with the point sitting in the centre of the screw. I open the pencil end until hits the edge of the OTA and then check the other two vanes to ensure that the spider is central.

[@Daftruck2001]

Awesome idea. I had a bit of a hard time adjusting the rotation of my secondary and this will deffinitelly come in handy. It might be a good idea to wet the sandpaper when you flatten the back of the secondary holder so no loose metal dust accidentaly gets on the mirror

[@oliveoilsjim]

VERY useful information, I never noticed how much my secondary mirror holder was marked by the screws! No wonder when adjusting the screws ,one or two would seem to hang up and not move right! Think I’m going to see if I can find replacement screws for these cheap Chinese ones! Not as easy in this backward Country (USA) that’s the last place but a few microscopic countries still using the Kings arm to size things! Love your very practical approach to telescope repair!

[@moeshickenyay]

I have the same Crocks, excellent tutorial, Thanks.

[@qwertyu2387]

Secondary mirror centering tool is absolutely killer of this video. I've just did one using Perspex plastic leftovers. It's turns out that my secondary mirror was way out of place where it's should be. Mate I'm not being funny I owe you good beer. Thanks !!!

[@astronomyshed]

Jerzy Paluch Thanks for the feedback.

[@Bass-guitarist]

Great vid, you made it very informative and easy to follow, thank you 👍

[@Aircurve]

Thankyou for all your vid's. Many times whilst watching the various ones I have thought to myself 'Now that's a good idea' :)

[@vargaferenc4687]

On the other hand big thank you, for this, and other very useful videos! I just complain on subtitles, because I am not really good in listening English and would have been happy with text too.

[@akacagen]

Fantastic as per usual!

[@ChristopherKovacsw0anm]

Great idea, good video presentation!

[@dantyler6907]

Sandwich a large stainless washer BETWEEN the secondary and the spider. Should minimize erosion due to alignment bolts. My suggestion showed up as I heard the same comint from the poster...

[@astronomyshed]

?

[@astronomyshed]

You could, but the indents stop the washer rotating and force any rotation to take place between the mirror boss and the opposite side of the washer via the teflon. Both ways would work, this is just my own take on it.

[@bigwheelsturning]

Finally a video that shows how the secondary mirror is put together and is mounted on the spider. From Newcastle?

[@astronomyshed]

It was a rub with very fine wet or dry paper, used wet with a little washing up liquid, and then finished with metal polish ;) DVD's, you aren't the first to suggest it, just don't know if I have the time.

[@AlmightyAddman]

Fantastic guide, thanks very much

[@oalithgow]

Excelent mod thanks for the tips mate!!

[@astronomyshed]

@hollywdd Thanks for the feedback, works a treat for that very precise colli adjustment.

[@glennsubawalla9884]

very good it was really helpful

[@onefortherazorbacksjenkins6731]

Excellent mods, nicely done. Worth doing in order to give yourself finer granularity on collimation adjustments. Google really need to work on the auto-subtitles. I use them because I'm hearing impaired but they're absolutely brutal on that lovely Yorkshiresque accent. "book directly down and not a little mama"? :-)

[@bear5016]

10:18 incidentally thats called lapping.

[@brumster01]

How long was the counter sunk screw that you replaced the old one with?.

[@bmw540i]

Two things, Dion, How did you get your washer so shiny and if you made these tutorials into DVD'S, you could make a good few quid, plus it would be you insentive to make more... As already said, your tutorials have made my life sooooo much easier, many, many thanks

[@adimeshort]

Great idea

[@mossy1s]

Thank you! Great info.

[@honoriosergio5454]

Nice job! tank you

[@grahamalgeo3867]

Your videos are extremely informative, and will aid me along the road to collimation of my Skywatcher 200P. The grub screws for the spider are 4 X 16 mm. what are the dimensions for the spider's central bolt?

[@JaySott]

Love all your videos.. :-) Recently acquires the 10" Quattro, which the previous owner did "some" of the mods here. A couple of questions if I can.. I need to "square" up the vanes vertically. There are two screws at the base where the vanes attach to the central hub. Have you ever tried to loosen those to make sure the vanes are not twisted in any way? The other question was from the "mods" you did. Did the neoprene extension (dew shield) ever seem to absorb the moisture and being to become mis-shapen? Again, I enjoy all your videos on the Quattros.. Thanks!

[@hollywdd]

That is a great video thanks for the upgrade hint, suscribed

[@hypersphereengineering6015]

Why not just make a circular template with a hole in the middle?

[@gianniformica8235]

Off topic... Why not replace the secodary with a camera sensor?

[@NFawc]

Nice tip - But why not omit the three indentations? Especially as these are obviously the hardest piece of the mod?

[@astronomyshed]

@Aircurve Many thanks for your comments, feedback is always appreciated, I just need to find a way to earn a living at it now lol

[@shaunozs1ra92]

Thanks for your really good videos. I always find them hands on and practical. I have a question, I am considering purchasing a 1000mm f/5 Newtonian and modifying it to a 500mm Newtonian. My thinking is that I will have to fit a larger secondary mirror when I cut the tube. I am sure there is more to it than this and I am probably missing some important detail. Can you please advise if there are any pitfalls I should consider befor cutting. TIA

[@pilotguy1983]

Not an expert, but cutting the tube won’t change the focal length of the primary mirror. What are you hoping to achieve?

[@shaunozs1ra92]

pilotguy1983 Thanks, you are right I had a brain fart. I realized afterwards that I’ll need a new objective mirror to reduce the focal length and simply moving the diagonal wouldn’t do a thing except give me blurry views 😃

[@sparkyuiop]

I bought a brand new Celestron Astromaster 130MD and the mirror was filthy and the colomation was way out. I know this telescope is a budget model but I managed to clean the mirror following another of your videos and it went really well. I also bought a LASER but no matter how much I try I just can't get it right. Any hope for this scope or am I just doing it wrong.

[@dionheap7786]

sparkyuiop Your probably doing it wrong, but if scope had arrived new in that state it should have been returned. Best option is to ask advise on the forums of my site at www.astronomyshed.co.uk

[@sparkyuiop]

Dion Heap Thank you, I'll do that.

[@TwoPancakes]

hello! where did you find this mod? because i have a tri spike which doesnt look good and i want to change it into a 4 spike

[@mariavon22]

By adding the washer aren't you moving the secondary slightly closer to the primary? I'm assuming the distance, probably 1 or 2mm is so small that it is of no consequence?

[@astronomyshed]

mariavon22 My other videos cover focuser and mirror alignments in detail

[@mariavon22]

Thank you very much for that. I will have a look at it.

[@vargaferenc4687]

Jesus, what the machine made the subtitles? Horror ...

[@Misho89vn]

What type of painting you use for blacked the secondary? brush, roller or something else?

[@astronomyshed]

Misho89vn Just a small brush and a little care.

[@Misho89vn]

Thank you!

[@patterdalezipsuzilil]

I wold rather have my adjusting screws biting into the aluminium the washer makes it all slippy

[@astronomyshed]

It was a rub with very fine wet or dry paper, used wet with a little washing up liquid, and then finished with metal polish ;) DVD's, you aren't the first to suggest it, just don't know if I have the time.