JamesF

Whatever the light source is in my mini maglite it doesn't look like an LED, so I just wrapped red cellophane over the end and held it on with an elastic band. That worked nicely until a birthday offered me the opportunity to ask for a proper red light torch.

James

I'd pass on the beginner's set then. If you decide you need a barlow you can always pick up a decent one later.

James

I don't think the 10" would be significantly more difficult to use than the 8" as long as you can comfortably reach the eyepiece and there's no reason that should really be a deal-breaker. If you're happy with the weight and the increased size for storing and moving it then it shouldn't be a major problem. What comes in the beginner's pack besides a barlow?

James

This quote from Bob Piekiel will explain quite a bit on the subject.

That's excellent John. Thank you for posting it.

To summarise, assuming I've understood correctly, it pretty much means that "During assembly the corrector, primary and secondary are matched as a set if necessary by refiguring the secondary mirror and if the corrector is broken any replacement may well require the secondary altering to suit". Does that sound right?

James

I've read this a quite a few times now in various places, but never with an attribution and I got to wondering if it isn't actually urban legend. The best I can get out of google is this thread on CN:

http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/4784591/Main/4778676

suggesting that the corrector and primary are not matched, but may be sensitive to orientation and that the primary and secondary are likely to be sensitive to orientation, but it's hardly conclusive.

So, can anyone put their hand up to being told by someone who genuinely understands the optical design of the Celestron SCTs and would be familiar with the manufacturing process that the correctors and primaries (let's say in current production models) really are factory-matched?

I have an open mind on the subject, but it strikes me that if it's possible for a careful amateur to produce a mirror for a dob to an accuracy of a fraction of the wavelength of light then it should surely be possible, and more cost-effective, to produce optics sufficiently well-matched by machine without needing too much fiddling about with afterwards. On the other hand, it wouldn't surprise me either if, once the lens and mirrors have been fitted, they might be tested and re-orientated if necessary to pass QA nor if different production runs several years apart didn't match each other.

(Obviously if the primary and secondary orientation is sensitive to change then if you break the corrector you may well still be stuck if you can't put the secondary back the same way regardless of whether the corrector is matched or not.)

James

Thanks for the comments, now getting the thread back on track, there must be curved bricks on sale someplace, or it can't be that hard to make some moulds and make them out of cement with a colourer added...????

"radial brick" is what you need to feed google for this

James

Page 82, the gate is hung the wrong way, the Brace is bracing nothing...

So what are we saying? Don't let him build your pier *or* hang the door on your obsy?

James

*sigh* after typing all that I find this:

http://books.google....epage&q&f=false

James

I had a moment of enlightenment and discovered the passage in "Setting up a Small Observatory" by David Arditti. He says:

I previously tried making the telescope pier out of brick. This pier worked, but it was bulky and not so strong as the much narrower concrete and steel pier which replaced it. Laying bricks is time-consuming and needs to be done quite precisely, and brick structures are in fact surprisingly elastic, but with little impact shear strength. Overall, I do not recommend a brick pier, though it looks quite nice.

The picture of his shows it to be two bricks long on each side however and there's no indication of what filled the internal void, so his opinion of his won't necessarily apply to yours.

James

I read something a while back written by someone who had built a brick pier, then decided it didn't work and took it down to replace it with (I think) a steel tube. I can't recall what the reasons were, but obviously it doesn't mean brick piers don't work, just that his brick pier didn't work for him.

James

If you really want to do finder-guiding on the cheap it might be possible to fit the camera into the back of a binocular finder. I'm building a right-angle 8x50 finder at the moment from a broken binocular objective:

http://stargazerslounge.com/showthread.php?t=189521

Without the diagonal the camera could just go straight into the back. It would be interesting to see if the Xbox cam can pick up enough stars to be useful as a guider.

James

My next question is to work out how many shoes she'd have to buy before I can justify a Mesu friction mount.....

Is it called a friction mount because of the effect the purchase has on domestic harmony?

James

I'm really pleased with it. It now takes me about thirty seconds to align the mount whereas before it was so fiddly and I used to hate all the faff. I was contemplating adding a polar scope camera, but now it's so easy I can't see the point.

It may take a little fiddling to get the LED to a position where you have enough, but not too much, light illuminating the reticle. That may take some experimentation when you can see Polaris and depend on your local sky conditions. As I have mine it's probably the absolute minimum I could get away with, but I couldn't be bothered to saw a few mm off the ends of the tee and cap so it would go in further

What might have been neat to add would be a variable resistance inline with the LED to allow the brightness to be changed, but as it worked for me the first time I tested it wired up as it is, I didn't bother.

James

I checked with a meter

On my socket there was one prong for the centre pin, one for the sleeve and one that was connected to the second when the power plug was removed (so it can disconnect a battery with the power plug inserted and reconnect it when removed). With the socket prongs facing you, arranged left, top and right, the leftmost was the centre pin, top was the sleeve and right was the switched line. Looking at the image on the ebay page, I'd guess yours was the same.

If I recall correctly that means that the "long" leg of the LED goes to the left prong, and the shorter leg to the top. If you connect it the wrong way around it shouldn't hurt, but obviously it won't work.

James

Returning to the converstation late, I agree with the idea of a separate EQ3-2 thread, if only so it helps with search results.

James

Spurred on by other people's designs (mostly for EQ5s, I think) that have been posted here, I decided to make my own polar scope illuminator for my EQ3-2.

The polar scope "window" on my EQ3-2 is 35mm diameter. I couldn't find anything that would fit perfectly, but I had some 32mm waste pipe which is 36mm outside diameter so sanded the end of a piece down to a taper which would fit snugly into the window. I also bought (the horror!) a 32mm waste solvent weld tee and access plug:

I was planning on using a standard end cap, but the local builders merchants didn't have any in stock and actually the access plug probably worked out easier in the end.

To try to make the illuminator as short as possible I cut down the socket on the bottom of the tee to about 10mm and glued a section of the tapered pipe into it, having marked where it came to when inserted into the mount.

The access plug had a seal that I removed and some ridges on the top that I cut off with a hacksaw and sanded down. I then drilled a hole through the centre and fitted a power connector with a 5V LED (with a combined resistor) soldered directly onto the terminals. I planned to power the LED from a disused 3.7V Nokia phone charger, though I'd imagine it would work fine from three 1.5V batteries.

The plug body goes into the side of the tee, and the cap is screwed in so the LED just reaches the junction:

And here it is on the scope:

I went out this evening and set the tripod and mount up. There's enough light to see the reticle without making Polaris difficult to see and I have to say it's the easiest polar alignment I've ever done both in terms of accuracy and speed. It always used to be a real pain trying to adjust the mount one-handed whilst getting enough light from my torch down the tube to light the reticle without drowning out Polaris. Tonight it was almost a pleasure to do.

James

Ahhh, so there are two sets of firmware involved. The one for the handset (that we can change relatively easily) and one for the mount (to which we don't generally have access)?

James

Looks like the firmware may have been hacked to account for a change in the gear ratios. See the last sentence in the penultimate paragraph here:

Stepper Motor Replacement Parts EQ5 HEQ5 EQ6 Pro Atlas Sirius Telescope Mounts - Astronomy Forums | Telescope Forums & Reviews | Astronomy Community

I can't find any other reference to it being done on-line though.

James

Hmmm, well, it could just be too awkward to do without some information from Skywatcher. The firmware image is 1MB, and even taking out, say, eight bytes per item in the catalogue that still leaves a lot of code.

I can find the irritating solar viewing for dummies message though. I could be tempted to change that text to something along the lines of "This mount belongs to..." just to see if it would work.

James

James it will be in the firmware, using EQmod does away with the handset thereby doing away with the firmware.

Yes. But my thinking was that if the firmware could be suitably modified then the 4:1 change could be made *and* the handset would still function correctly.

James

I find myself idly wondering this evening if the knowledge of the gear ratio is built into the hardware or the firmware. If it's the latter (which would seem logical to me) then it might be possible to "hack" the firmware so it accounts for the changed gear ratio. Could be something of a slog to identify which bits need changing though.

James

I'm very happy with my 15x70s, but they really do need supporting on something to get a good view. Without a tripod or some other form of support I reckon 10x50s could well be a better bet.

James

Could be something to do with the size of the files? How big are they?

James

Oh, I don't know. Western Power did a load of work on the electrical supply for the area recently and replaced all the poles for the overhead supply. They were kind enough to leave me one. I reckon I could have an obsy a good 8m in the air now

James

I'd agree on the pricing. This is a tree house I built for the children a couple of years back (before it was quite finished):

It's not that different from an obsy build and was in the same sort of ballpark as regards cost.

James