How hard is it to build a telescope?

[Peter Drew]

You have the choice between a useable mirror with an eyepatch or a glass blank, no brainer. Don't try and stick the chip back on unless you can align it to a fraction of the wavelength of light!, keep it as a momento. 

[gooseholla]

Tonight was a bit too misty even for my liking so I packed the scope up early and brought the secondary cage upstairs. I decided that enough was enough and that I really should align the focuser properly, as it has just been in the same guess work position since I installed it. It wasn't miles off the optical axis, but following the tips in the K + B book, I shimmed it left and right and up and down so it was aligned, then put a small dot on my secondary mirror and got a shock - this was miles off where I thought it was! It needed to come quite a bit up the cage. Hopefully this will cure the annoyance I get when viewing, a kind of sense that I am looking over the light cone rather than at it directly.

I also had enough with my 26mm Panaview. The view through it is tiny central part sharp then spiralling out it goes seagull shape then elongated fuzzy blobs. Most annoying in a telescope of this calibre. So I took the plunge and ordered a Maxvision 24mm 82 degree. Hopefully this will give me the lower power views I desire. Also, it will let me test the mirror more fairly for my review. Not fair to say "probably gives good views of the Double cluster, but I can't tell for sure!".

John
 

[gooseholla]

Well since this build is now completely done and we're just lamenting a chipped mirror and what affects have or haven't occured.... Tonight I was measuring up the size of my wardrobe for something and opened one of the doors... low and behold I forgot I owned a massive 12" solid tube telescope that I was going to turn into a dobsonian... I guess a second build thread might be coming up soon! Might try my hand at one of those ultra light, ultra compact versions!

John

 

[gooseholla]

Hey all,

Today I made the new mirror posts to repair the broken ones from the incident. Now bring on clear nights so I can use it!
 

I invite everyone to head over to http://stargazerslounge.com/topic/254246-12-compact-goosescope-build for my new scope build where we can continue the banter, laughs, and mutual learning opportunities.

John

 

[gooseholla]

Well the new mirror posts are in and the aligning of the focuser has ended all my elongated milky tubes. I think I'll call this scope a success. Thanks for the help guys, support and for following. I promise to get back to the mirror review now the chunk missing issue is solved. I guess my next update will be to let you all know what John says about the mirror in November. Remember to head over to my new scope build.

John

[mapstar]

Great stuff John we will be following it with interest

Damian

[gooseholla]

Review is now up

http://stargazerslounge.com/topic/254589-nichol-optical-18-f4-18th-wave-mirror/

John

[gooseholla]

Not a scope update as such but I think I have come up with a nifty solution for running a dew heater into my shed. Installing a vent has certainly helped, the scope no longer sits in heavy dew but there are times when it sits in a light film of moisture. I cannot run a power supply out permanently but found a way to utilize my 12v 70AH leisure battery.

I purchased one of these 12v programmable timers off of ebay for £5.99. they are cheaper if you don't mind waiting for one from Hong Kong. It has 17 programs you can set.

I connected this up to a 12v 10w bulb, in this case stolen from the boot of a car I sold...

It uses 0.8 amps but produces a lot of heat and clears the mirror in a few minutes. I place it under the back of the telescope when it is in storage, make sure the telescope is locked at a slight angle to let air flow and place it on a brick so it cannot heat anything like the wood of the rocker base. It is set to come on at night 3 times. Two programs are for an hour each and the middle of the night is set for 2 hours. This means it produces just 3.2 amps per night. This gives up to 3 weeks of use off a single charge of battery, but I want to keep it charged nicely, so I'm going to do it every 10 or so days.

Seems to be effective so far!

John

[starman345]

. It wasn't miles off the optical axis, but following the tips in the K + B book, I shimmed it left and right and up and down so it was aligned, then put a small dot on my secondary mirror and got a shock - this was miles off where I thought it was! It needed to come quite a bit up the cage. Hopefully this will cure the annoyance I get when viewing, a kind of sense that I am looking over the light cone rather than at it directly.

Hi  John,

I've enjoyed your journey through the build, and appreciate you documenting it here, lots to learn for all of us. Just a note to try and save you some headaches...I too built a scope using the K&B book as a guide and also found my secondary was too low according to their  method. After much cursing, and head scratching  I posted here   for help and well, you can read it yourself.  There is also another thread here that might be of some interest. 

Sorry to hear about your mirror mishap, that is discouraging but hopefully the views won't be affected.

[mapstar]

Hope that heat shrink is good stuff John as I've just laid out for some. Cheers for the link.

Damian

[gooseholla]

Did the job for me no problems. I don't know what heat shrink is like but it was quite thick to the touch and smooth once shrunk on. Nice black colour to it. No horrible writing on the heat shrink.

John

[mapstar]

Did the job for me no problems. I don't know what heat shrink is like but it was quite thick to the touch and smooth once shrunk on. Nice black colour to it. No horrible writing on the heat shrink.

John

Great stuff I was concerned about the writing but you wouldn't see it with the shroud and in the dark.

[gooseholla]

Great stuff I was concerned about the writing but you wouldn't see it with the shroud and in the dark.

I noticed a lot of them had writing on but this one - as long as it was that decohome seller - didn't seem to have it on. Hopefully yours won't too.

[mapstar]

I noticed a lot of them had writing on but this one - as long as it was that decohome seller - didn't seem to have it on. Hopefully yours won't too.

Got the heat shrink yesterday and it has writing on it. Won't really matter but it wasn't in the pic!

[Soupy]

That's a nightmare Damian, will it work if you turn it inside out?

[mapstar]

That's a nightmare Damian, will it work if you turn it inside out?

Doesn't really matter only for aesthetics

[gooseholla]

Hmmmmm. All I know is mine definitely didn't have it on! What a shame. Perhaps they have random sources for the stuff? Might be worth contacting them and seeing If they would swap it for a non-writing one?

John

 

[gooseholla]

Well I thought I was done on this build. As you may know I am slowly building a 12" portable scope. But before I move on one thing was bugging me - the pole blocks on this scope. The current ones were quick oak jobs to last me a while so I could use it. But I wasn't really happy with them. Today I reopened the K + B book and decided to have a go at the complex split blocks. Here is the result...

Works great! So my job tomorrow is to make 8 of them out of this hunk of beech offcut. If you're wondering why not today, well I knocked over a pot of black paint and had no white spirit to clean up so I reached for the nearest substitute... well a can of air intake cleaner later and I've evacuated the area for a day

John

[gooseholla]

So let me talk you through the new blocks. I know the K + B book describes how to make them but there are some things to make it easier.

Plan ahead and make the recess in the back for all the left and all the right before cutting them down into little blocks! It is easier to clamp and run the router along a 15" bit of wood than a little block. I made the slits using a battery powered jigsaw. The book suggests a handsaw... well, if you've made the hole for the pole you can use that to clamp and run a jigsaw along one side then flip it and then clamp the block itself and run along to make the other. Takes seconds.

The blocks are Beech again. The originals were beech and held up well for the time they were in use. The knobs have been upgraded to slightly larger ones.

The only problem I have is the bolts through the mirror box were set by the smaller ones. I think I will need to move them and fill the old holes with plywood plugs.

Anyone like to guess what this solid lump of ali is for?!

John

[gooseholla]

Well this beauty just came from an engineering company my neighbour took me to yesterday. They did it between jobs and well all I can say is wow!

It has four flat surfaces for the vanes to attach to. 3 x 6mm tapped holes 120 degrees apart for the collimation bolts. The hole in the centre allows the bottom part to pivot slightly.

It is a beauty and shame it is going to have to be painted black! There will be nichrome wire attached to the stalk to provide heat to the back of the mirror.

John

[mapstar]

Nice work John and these refinements come along after thought and use.

That aluminium billet looks to have had a lot of machining done on it. Machining ally is very satisfying.

Will it affect the balance of the scope John as it is going to be heavier than the old set up?

Damian

[gooseholla]

Because the pole blocks at the bottom are going to be double the weight than now there seems to be no net increase in the weight. But we'll see. If there is I'll just have to take a bit of steel bar and bolt it to the tailgate.

Yes I don't know what they did but it is lovely!
 

John

[gooseholla]

just an update on primary mirror chip. John Nichol has tested it and there is no stress or problems with it so that is great news. Can't wait to get observing again!

[mapstar]

Just arrived home and it was great to meet you today John.Hope it was an Interesting and informative day.

The mirror looked good under test despite the chip. Hopefully we will get some good weather this winter for you to get some memorable observing sessions in.

Damian

[gooseholla]

Yes I really enjoyed it and was nice to meet you, John et al. I was sitting there when John was on about a long focal ratio 8" planetary mirror thinking I really need one of those in my life   Maybe one day ill attempt to grind one when everything else is out of the way! Aye hoping for some good nights in the next three months. Also hoping my mirror goes back in the mirror box without being damaged more!!!