Firstly, hi all... only posted here a couple of times but have always received tons of great advice, so
End of last year I decided to get a GSO 12" Dob thanks to responses to my previous thread. I'm really happy with it and looking forward to next new moon to make it worth the drive to a dark site again.
As suggested would be the case (and part of the reason I got one) some modifications would be in order. Well I've only used it a few times so far but I've done a bunch of stuff to make it more enjoyable/easy to use and transport. Some were my own ideas, some came from here and other forums, but for anyone else looking for same I thought I'd document them. Almost everything I did was from bits and pieces I had lying around, or acquired very cheaply.
First... for those who haven't seen or handled a 12" solid tube Dob, they are BIG. Well they look big the first time you see one! It's much less daunting now. I'm a big unit myself so carrying the OTA and base separately requires little effort, for a quick plonk down and look I prefer it to carting my 130SLT on a tripod outside and going through the goto alignment process. Each to their own though and to some the storage and transportation considerations would rule out a scope this big.
First thing I realised was that the rocker box/base (which is 630mm diameter and 700mm high) will not fit in my ute with hard lid and allow the lid to close. So the day it arrived I took to it with the jigsaw, which I was planning on doing anyway to cut away for an Azimuth setting circle. I cut the back of the base flat and made a curved cutout at the front which is where I view the setting circle. The height when laying on its back like so is around 430mm so I can shut my ute lid. I remove the circular base and bearing for transport obviously, takes 5sec to put the rocker box back on and screw the bolt in:
The black rubber edging I removed and kept intact. On completion of the cutting I simply cut the spine off and siliconed it all back around the newly cut edges making sure to seal any gaps, it's just exposed chipboard after all. Did it in a few separate sections to clamp it each time but the end result is as good as I would have hoped after taking a jigsaw to melamine covered chipboard! The marker for Az I made out of a fishing sinker and clock hand, it just rests on the base and can be positioned exactly provided I aim the base roughly North.
First time I used the setting circle I was scratching my head why, after doing a precise Azimuth alignment, the next star was off by up to a degree or two. Well, obviously the base needs to be level! I was on the camber of a road, I thought it would be "level enough" but no. I just wedged some small rocks under the feet to get it close and accurate viewing coordinates all started to come together. So next I built a triangular levelling base that you can see below. Just some 16mm MDF cut to a triangle and bits of pine for the feet, sanded and slapped with plenty of black paint for protection. I'm waiting for some screw-in 50mm leveling feet to arrive ($15). The (flat) top of the triangle that you can't see has three 32mm holes recessed into it with a spade bit for the plastic feet of the dob base to sit in. Overall the triangle is the exact diameter of the circle with nothing sharp sticking out to trip over or stub toes on, which is something I thought would be a problem on some of the other solutions I saw.
The graduated degree circle came from this Cloudy Nights post:
http://www.cloudynights.com/topic/51...tting-circles/
The 12" just happened to be the exact size (630mm) for my base. I had it printed on heavy poster paper at Officeworks for $8 and glued it very lightly to the base with craft glue to allow positioning right to the edges without wrinkling. Once positioned I painted multiple coats of Mod Podge (basically PVA glue mixed with water) to build up a nice thick layer, brushing under all the edges to glue and seal, and protect what is after all a piece of printed paper. I then sprayed clear acrylic lacquer over everything till the can was empty and replaced the black rubber edging again. I'm 100% confident that it's impervious to moisture and is protected enough from minor scratching.
With the base and Azimuth setting circle taken care of I then bought a Wixey digital angle gauge. These things are amazing and very thoroughly discussed especially on the UK Astronomy forums. I don't know where to get one here but it was about $35 delivered from the UK. It simply attaches magnetically to the top of the tube and reads out inclination angle in 0.1 degree increments. So far I've no reason to doubt its claimed accuracy. One point to note : there is a backlit version available, but the backlight is bright green, and also shuts off after a short time. So I got the non-backlit one and made a tiny red LED lamp for it. $3 AAA battery holder incl. switch from Jaycar, plus a red LED and resistor worth a few cents. I just glued the battery pack on the back of the gauge, bent some wire around the front and made a little bezel for the LED. Works perfectly! Stays on unless you switch it off and is just enough to view the display at night:
Oh and speaking of red LEDs, Bunnings sell Energiser 60 Lumen head lamps with red mode for $10 each that you can see in the first pic. They have mounting holes on the backplate so I just screwed a couple to the side of the rocker box to illuminate the azimuth pointer and eyepiece tray. The head pivots so is a handy solution for getting some dim red light around the place, lets you see the surrounding ground as well. As a tip - I run on two AAA's not three which makes it much dimmer and more suitable for our needs. Just bridge the missing battery with some wire.
Also while I was at it with the jigsaw I knocked out a couple of other bits and pieces... small tray for the base near the eyepiece holder, for lens caps and other loose items. I also had an old telescoping broom handle lying around, and those $3 mini tripods I've gotten for free with every camera I've ever bought over the years. I took the pivoting head off, epoxied it to the telescoping handle, and made a thin recessed MDF tray to hold my 7" tablet. I use Sky Safari Pro and having it sitting just where you want without having to hold or pick it up, is great. I still need another 2" eyepiece tray though!
After a few times carrying the OTA everywhere by holding it at the top and bottom I thought it'd be more convenient to add a handle about 2/3 up the tube. It's now a piece of the proverbial to drop the tube into the rocker box using the handle to guide it in. Handle was under $2, you can just see it in the pic above.
I also had an old Red Dot finder lying around that stopped working but which I resurrected rather than buy a new one for $20
I cable tied and taped it to the top of my finder, which I find helpful in aiming to the rough spot when using the RACI finder for a quick look at planets etc.
Finally.. after a couple of most-of-the-night viewing sessions, I realise why most people say how important a good observing chair is! Especially when you are bent over looking at anything that isn't at the zenith. So I picked up what is actually a 2nd hand guitarist/musician stool for $50. Height is adjustable up and down from lower than normal chair height to bar stool height, I've yet to use it, but thought I'd include a pic for the sake of it
I've got a few other things I'll get around to.. I want to enclose the mirror cell to make the fan more effective and blow across the mirror. I also got a much stiffer spring to cut up and replace the collimation springs with but in all honesty, I think the current ones supplied by GSO have been beefed up and are more than adequate. I've seen pics of what were previously deemed to be inferior, thin springs but the ones on mine look much heavier. In any case I've not had any issues with maintaining collimation, I use a laser and a cheshire.
At one stage I was going to put a Nexus with encoders on this.. for the very minimal outlay to get surprisingly accurate Push-To functionality I'm glad I held off. Maybe one day I will but the thought of wires, controllers, and encoders hanging all over the place making disassembly just that much more of an effort irks me. Besides I really enjoy hunting for objects through the eyepiece, even if an app on a tablet tells me where to look!
That's about it.. hope this helps someone down the track with some info, like I was able to be
