Ongoing Mods on my Orion Optics UK 6" f11 Planetary Dobsonian

[Moonshane]

as an eternal fiddler I decided a while back to change the secondary adjusters for a tool free option. my problem was that I could not find anything with a head small enough to be hidden by the secondary mirror. everything I tried was too wide and I could see it when collimating.

my last option was a standard M4 stainless cap head bolt. this has a small head (approx 6mm) and could be obtained in the correct length 40mm, threaded all the way. ideally they would have had a knurled ring around the top but alas the ones I could source did not.

as the secondary bolts only need to be lightly finger tight, I thought I may get away without the knurled top and it seems that I was right. they can be done and undone by hand no problem. at the same time I added a washer which is again hidden behind the secondary and allows more accurate positioning as the bolts were digging into the back of the secondary holder otherwise.

in the pic you can see the mods, the small size of the secondary holder bear in mind the bolt shafts are 4mm!) and the black edges to the secondary.

flocking is definitely a future job!

[Moonshane]

hi all

more minor mods to update on - yes, I cannot help myself.

the first is the fitting of my 'proper' friction brake. the first effort (see start of thread) worked well enough but this new version looks much better and is a lot sturdier. I may paint it black eventually.

the second is a larger fan. the 40mm fan was dinky and cute but really didn't shift enough air and although very quiet, seems to have rid itself of the energy by being creating a lot of vibration when run at 12v. so I ordered a 60mm fan from Shiny Hardware Limited who are highly recommended for fans and also liquids in bulk such as acetone and 99.9% Isopropyl Alcohol etc. this is much better at shifting air and also creates less vibration even at full tilt.

although I have a variable voltage mains adapter which I use for the initial cooldown, I tend to then run my fans at half speed to observe. this reduces any vibration to pretty much nil but means that I still have wires trailing and a mains connection. this annoyed me sometimes as the freedom of 'the dob' was affected. therefore I rigged up some AA batteries (four for each scope to give 6v) in a battery carrier from Maplins and with a bit of quick soldering had a dual power source connection. it works really well and means I can go anywhere. I also created a long multi-connection cigar lighter lead for initial cooldown in the field.

I added a further mod to this which was a quick and cheap plastic cover as the dew gets to the connections if not. might make this a little more aesthetic and better fitting in due course but made it from what I have for now. the pack and cover held on by tabs of velcro for easy removal.

all works a treat!

here's some pics.

[Moonshane]

hi all

First update on this scope for a while; the dreaded flocking. I bought some 'Scopestuff' flocking at a good price (£25 for enough to do the scope) and yesterday was the day. Did a complete strip down (although left the tube in the secure cradle as it was easier this way. Wiped all the inside surface with alcohol and then measured up. Two hours and a lot of swearing later and it was done.

The process went reasonably smoothly but as the tube is 175mm in diameter and five feet long it's a challenge to do the flocking all the way down. OK I know I could have just done around the primary and behind the focuser but as I had enough to do the whole thing I thought I may as well.

I started at the bottom with a full piece two feet wide. This went on OK. The next piece (in the middle section) did not and I ended up stripping this out again and removing the reside with lighter fluid.

I then worked in smaller one foot wide pieces and this was a lot more manageable - recommended.

Eventually it was all finished and I trimmed off the excess and holes etc and fitted everything back on / collimated etc.

The effect is very good and well worth it I think. Not used the scope yet but if it increases the contrast even by a smidge on planets then it's worth it.

Here's some pics which kind of represent the differences, the flash does not really represent how dark it is down there but the other non flash image gives an impression of what it will be like when observing - pretty dark.

[Gina]

Looking good

[Moonshane]

cheers Gina

it would certainly have been a lot easier with either a larger or a shorter tube (or both).

[gliderpilot]

She's looking good, you can see the effect of the flocking in the photo. Is there any chance of fibres coming loose & being shed onto the primary?

By the way there's an interesting article in this months astronomy now about the diffraction spikes caused by the spider. Have you any plans to make or buy a curved spider to alleviate the spikes?

Mark

[Moonshane]

hi Mark

It's not a woven product so I don't think it will shed but time will tell.

Re the spider, I don't get major spikes now to be honest (the flocking for some reason seems to have reduced this too) and I am quite happy with the one one there. As an experiment though I may try and make one in the future and see how it goes.

[Moonshane]

one thing that was winding me up a while back on this dob was the size of the primary clips. they were MASSIVE!!

see the first pic below.

I am not sure that there was a dramatic effect but the spider diffraction spikes were very noticeable on Jupiter when it was last on show.

So while I was in fiddling mode, I took out the primary, cut off the bulk of the clips and then cleaned up and ground down the edges to a rounder profile, being just big enough to hold the mirror if it lifts a bit in transport. I had some flocking material scraps left over and covered them with this too.

I then re-centred the mirror and took up any vertical slack (but left enough space for the mirror to just be able to move about 1mm) in the clips through the plastic bolts through the cell which support the mirror and then re-collimated.

it all makes a big difference to the look of the mirror in the tube and will hopefully make a difference (albeit slight) to the contrast etc.

I also added some teflon washers (bought on Ebay) to the collimation nuts and this has made a massive difference to the ease at which they can be turned.

cheers

Shane

[johninderby]

And the nomination for the worlds biggest mirror clips goes to.................

The clips are a bit OTT aren't they. With the CNC cell on my 150 f/8 silicone is used to secure the mirror so no clips at all and it does seem to help a little bit.

John

[Moonshane]

ha ha cheers John

I thought about silicone but I like the mirror to be 'free and easy'

might try it one day though and see how it is.

dobs are great for fiddlers like me.

[johninderby]

I was a bit concerned about using silicone, but the manufacturer of the cell designed it that way. Silicone is only used on the side of the mirror at the three "arms" that stick up (about 3mm thick) and felt like pads are used underneath the mirror at the contact points.

John

[Moonshane]

seems good to me. I expect that silicone blobs underneath the mirror would create more problems at least potentially.

[John]

Those clips did look a bit on the large side Shane. Thanks for posting the pics, it's prompted me to have a look at improvements to the mirror cell on my OO 10" F/4.8. I'm going to "neaten and blacken" the mirror clips and I'm considering perforating the backplate to allow more air circulation around the mirror. I'd also like to replace the secondary adjustment screws with Bob's Knob's or similar - I seem to recall that you found an alternative ?.

With the lack of darkness, now seems a good time to tune up my modest light bucket so it's sorted for the Autumn galaxies

[rabbithutch]

Howdy Shane,

I don't recall having read this thread before, but it is a jewel. Thank you for posting your experiences here.

I'm new to gazing upward only having got a scope last February. It's an older Orion 8" f6 Newt on a Dobson mount. I bought a kit that had been well used and well kept by its former owner giving me a set of ep's, a telrad, and filters. Because it's an older scope, there are things about it that I would like to change but don't know how and don't know if upgrades make as much sense as would putting those pennies into a new dob. I would greatly value your opinions and those of all SGL scope mavens.

First, my focuser is not of the Crayford type - can't recall the name for its type but focusing is done by moving the ep up and down the focusing tube to get close, screwing it down, then making fine adjustments by twisting the tube. I would like to replace it with a well makde Crayford type with a barrel for both 2" and 1.25" eps. Does this sound a reasonable goal?

Secondly, the secondary mirror is attached with a single vane connection. All I read tells me that the best are 4 vane models. Is it reasonable to expect to be able to replace the secondary mirror supports and improve the scope.

I'm also thinking about building a triangular shaped sub-base with all-thread posts at the corners to be used to level the scope on set up so that I can then use a digital angle finder and compass as aids to finding targets.

I would very much appreciate comments, criticisms, suggestions from all re these mods.

ps. If the mods here feel that this is an inappropriate place for my questions, please be assured that I would welcome your moving to wherever you think appropriate. It is not my intent to hijack Shane's great thread, but it was his inspiration that motivated my post.

[Moonshane]

Those clips did look a bit on the large side Shane. Thanks for posting the pics, it's prompted me to have a look at improvements to the mirror cell on my OO 10" F/4.8. I'm going to "neaten and blacken" the mirror clips and I'm considering perforating the backplate to allow more air circulation around the mirror. I'd also like to replace the secondary adjustment screws with Bob's Knob's or similar - I seem to recall that you found an alternative ?.

With the lack of darkness, now seems a good time to tune up my modest light bucket so it's sorted for the Autumn galaxies

hi John

for this 6", the secondary central section is so small that I could not find any knurled nuts small enough to be hidden from view. If I can find someone able to put a knurled pattern on these stainless M4 cap head bolts then I'll do so in future and they will do.

For my 16" I have found these

10 M4 FINE KNURL METAL THREADED NUTS BLACK | eBay UK

which when glued onto the end of an M4 bolt (with the head removed of course) make perfect 'Shane's Knobs' and for almost no cost. The threads on my 16" secondary adjusters are M4 and therefore your 10" may be too?

Here's a pic from the 16". The 'head' is 14mm diameter approx.

Funny you should mention widening the hole in your primary cell plate. I thought about this last night too and is something I'll be doing in the future too.

My cell is constructed from a single plate of 10mm ali with a 10mm hole in the middle so may also put a larger hole here (and possibly go mad and make some triangles for the cell to make it a 9 point). Then again, I'd like to get my 16" ready for the same reasons you state!

[Moonshane]

Howdy Shane,

I don't recall having read this thread before, but it is a jewel. Thank you for posting your experiences here.

I'm new to gazing upward only having got a scope last February. It's an older Orion 8" f6 Newt on a Dobson mount. I bought a kit that had been well used and well kept by its former owner giving me a set of ep's, a telrad, and filters. Because it's an older scope, there are things about it that I would like to change but don't know how and don't know if upgrades make as much sense as would putting those pennies into a new dob. I would greatly value your opinions and those of all SGL scope mavens.

First, my focuser is not of the Crayford type - can't recall the name for its type but focusing is done by moving the ep up and down the focusing tube to get close, screwing it down, then making fine adjustments by twisting the tube. I would like to replace it with a well makde Crayford type with a barrel for both 2" and 1.25" eps. Does this sound a reasonable goal?

Secondly, the secondary mirror is attached with a single vane connection. All I read tells me that the best are 4 vane models. Is it reasonable to expect to be able to replace the secondary mirror supports and improve the scope.

I'm also thinking about building a triangular shaped sub-base with all-thread posts at the corners to be used to level the scope on set up so that I can then use a digital angle finder and compass as aids to finding targets.

I would very much appreciate comments, criticisms, suggestions from all re these mods.

ps. If the mods here feel that this is an inappropriate place for my questions, please be assured that I would welcome your moving to wherever you think appropriate. It is not my intent to hijack Shane's great thread, but it was his inspiration that motivated my post.

hi Bob

No worries on posting here as it will certainly help others too.

I am certainly no expert but like most if you think about something for long enough, take your time and know your limitations, it usually goes (kinda) OK.

Your point about cost of changes/upgrades vs buying another scope are well made and need to be considered before going ahead for sure. My 6" f11 is a scarce scope on the used market and even by the manufacturer was described as a 'collector's item' as they made so few and don't intend to make any more (or that's the impression I gained when speaking with them).

Furthermore I got it quite cheaply too so for me it's certainly worth the cost of the minimal changes I have made.

You can often offset some of the costs of changes by selling what's on the scope. E.g. when I bought this it had a single speed Crayford and I wanted a dual speed. I sold the one on there for £45 and then bought another dual speed for £70 so net cost £25.

I mention this as your focuser (I think you describe a helical focuser) is quite unusual and they are quite light more often than not. This lack of weight can be an advantage to a smaller dob especially as they create less balancing issues. My dual speed Crayford weighs about 2lbs so is quite a heavy chunk to add on at the top end where weight is effectively increased by a factor of 5 in an f5 scope.

You could sell the focuser and buy another and I like dual speed Crayfords but you really do need to consider the weight. Perhaps one thing you could do is take off the focuser, weight it then replace it and add the difference in weight to 2lbs and see how your balance is. If it's likely to cause a problem then at least you know before you sell/swap.

The secondary would definitely be improved with a four vane and collimation would hold better. But if you cannot make one, they are not cheap in the after sales market.

The base sounds a great idea and I am sure would work well. That said, why not just replace the feet that are on already with adjustable ones?

I'd look at the costs of changing (include the costs of all the changes you wish to make) and then the cost of replacing the scope (new price minus sale of existing scope) and then make a judgment. I think when they come back in stock, the new Skywatcher 8" f6 dob will have a dual speed focuser and be around £300. Not sure of prices/availability in USA though. If you got say £150 equivalent for your own scope and prices are about the same in USA then the difference to me is maybe not worth all the work involved.

Hope this rambling reply helps a bit

[rabbithutch]

Thank you, Shane!

That is great information. Thank you for sharing your experience and observations about my ruminations. You are very kind!

[Moonshane]

No worries at all Bob

We are all on the same ship, trying to find the best way to do everything

[FairviewSteve]

And the nomination for the worlds biggest mirror clips goes to.................

The clips are a bit OTT aren't they. With the CNC cell on my 150 f/8 silicone is used to secure the mirror so no clips at all and it does seem to help a little bit.

John

This is a great thread. I have the 8" version of this scope and have been interested in what the primary looks like. I have been longing for the CNC cell so that I can have the fan built into it. Unfortunately I cannot afford it ATM, but great to see what it all looks like inside. I've also been put off by the fact that I'd need to drill the tube to fix it and then also buy a tube end to cover the sharp edge of the steel.

I iwll watch this thread for more interesting mods!

BTW - I have the actual OO friction brake available to buy if you're interested?

Steve

[johninderby]

On my 150PL OTA I bolted the CNC cell to the existing tube end so no need for a new tube end ring. It's not an OO CNC cell as hey don't do a 6" one.

John

[Telrad]

Moonshane, I like your mods. I've been looking into ways to 'upgrade' my dobsonian too. I especially like your counterweights with velcro. I used the lunch-box idea posted on this forum previously, which works. I like your rigel and fan too. Thanks for posting!

[Moonshane]

This is a great thread. I have the 8" version of this scope and have been interested in what the primary looks like. I have been longing for the CNC cell so that I can have the fan built into it. Unfortunately I cannot afford it ATM, but great to see what it all looks like inside. I've also been put off by the fact that I'd need to drill the tube to fix it and then also buy a tube end to cover the sharp edge of the steel.

I iwll watch this thread for more interesting mods!

BTW - I have the actual OO friction brake available to buy if you're interested?

Steve

cheers Steve

as you probably saw, you can easily add a fan without drilling anything (other than a small hole for the wire. in truth I am not sure my fan does that much although I can just feel air blowing up the tube when it's on so it must be doing something. I tend to use it for cooldown speed mainly but I have never done any objective testing to confirm it works - makes me feel better though.

my friction brake works pretty well to be honest and once I get some black paint it will be identical almost anyway to the OO unit.

one possible future mod is to make the primary end heavier as I'd really like to use this scope without the friction brake but I fear I'd need to add a fair bit of weight.

re the end trim, you could always cut a circle out of the one that's on it and hey presto.

the CNC cells are very nice from OO and John, they do a 6" one now (I think £70 plus VAT). but I may just adapt the one I have on it for the time being. Might tap some holes in the plate, paint it black and then have the back end open which might help. I'll probably buy an end trim if I do so I can revert it back to standard in the VERY unlikely event I ever sell this scope.

One reason for this being e.g. http://stargazerslounge.com/observing-discussion/144803-double-stars-dont-afraid-use-ludicrous-magnification.html

[Moonshane]

Moonshane, I like your mods. I've been looking into ways to 'upgrade' my dobsonian too. I especially like your counterweights with velcro. I used the lunch-box idea posted on this forum previously, which works. I like your rigel and fan too. Thanks for posting!

cheers Telrad!

I have actually drilled a small hole now for the counterweight as the velcro was PK but I prefer things not to have a chance of dropping on my toes! also I have a new finder too - a Telrad!

[FairviewSteve]

Herein lies the quandary. Do I upgrade the mirror cell and reap the benefits that it provides for cooling and colimation for £120. Or do I save my cash and buy an upgrade to the crayford focuser witht he 10:1 reduction drive. . It's probably a moot point either way as I've just spent what my wife would describe as a considerable sum on the go-to upgrade for my EQ5.

[Moonshane]

personally, I am not 100% convinced that a mirror 10" and below benefits from a 9 point cell so on this basis I'd go for the 10:1 Crayford. The Revelation one at Telescope House is excellent, I have two.