FrenchyArnaud

Ok, I can't help but share with you this preview...


The blocks are glued with CT1 (brand C-Tec) and the local jewson's reliably informs me that after 24H it will be easier to break the blocks than to unbond them. I hope it is true.

The mount is actually screwed on as I drilled the block BEFORE installing it (I was unsure how hard it would be) Drilling the main axis was not especially difficult but drilling at the right place was. So I drilled 3 times on 2 blocks before one of the centering was correct - this centering now sits on top of the column. Drilling the brake disc holders will be much easier because I will just clamp the disc in place and use it as a guide. Of course this is just a temporary fixing for the sake of the picture, the mount will be put on a proper adapter. 

So now I am only waiting for the brake disc to be delivered 😇

The GF is hunting for the correct colour of concrete paint to match the fences and is looking into hanging small flower pots to decorate the column; I will supervise the weight distribution but I am confident it should be ok. The thing is solid as a rock - litterally. 

9 hours ago, M40 said:

A great start 👌 and as for a dampener, how about installing some wood around the existing slabs and slab base, pour your concrete, remove the wood when dry and then just back fill it with pea shingle.

Yes I could have done that but I read your idea AFTER  I poured, plus, it woukd have added too many steps for my taste (even though objectively that would have been better)

I keep the idea though because if it turns out I can detect foot steps on the guiding graph, I think I can dislodge the adjascent tiles, cut the slab base underneath the middle of the tiles and fill this fracture line with sand or sthg, in effect isolating the square where the pier is and the ones directly around it from the rest of the walking zone, while still having the benefit of a 3x3 tiles surface to fight gravity sinking of the foundation. 

I'll do it if it proves needed.

Ok, Day 2! 
Went to Jewsons, bought all I needed : 5bags of quick concrete "postfix", 4 hollow blocks and masonery glue. Because my garden is accessible only from behind/around the house, I had to carry all of it around and that's no fun. Fortunately I was able to recruit my trusty assistant Mocha for help. Well, for moral support at least; well, he has a knack for being exactly where it is the most irritating but hey ho, he's trying. That must count for something. 

I threw a couple of liters of gravel stolen from the flower bed at the bottom to provide a support for the first block, which will act as my anchor. 

That allowed me to present this first block/anchor and set it stable and, after a lot of fiddling and jiggling, to get it nicely aligned and level.

This Postfix aka Blue Circle aka Postcrete does not require mixing. The way it works, you fill the hole 1/3 to 1/2 with clear water, pour the dry mix on top of it, paddle with a stick to eliminate bubbles (and in my case, make sure the mix gets inside the lower hollow), until the water surface is reached, and repeat until you are at the desired level, at which point you just cover the top of the mix, still dry, with more water. You have 5 to ten minutes for the whole operation so you really want to make sure you have everything at hand. After 15minutes it is mostly set and pretty much impossible to move. I dedicated 2 minutes half way through to making sure the block had not moved and was still perfectly level.

Once you reach top level you can, if you wish, smooth the surface - I did not bother. Here is the result. 

 Because I added tons of water, it took about 1 hour to really set, but right now, about 2 hours in, it is pretty much rock hard. I will not try to walk there or do more out of precaution but I am confident I could stand on the block and it would not break a sweat. 

Only I did. That's some serious exercise for old me. 

Next stage: glueing the 3 other blocks on the anchor - that at least in theory should be child's play as my support is dead level and rock solid. 

46 minutes ago, edarter said:

I've been pondering the relative merits of cutting my focus tube vs trying to move the primary up

I am a bit puzzled here. Why do you need eithet? the pds are already adapted to get prime focus (shorter tube than the P)

I tell you what, I have spent 2hours asking myself exactly that when I realized I needed a new plan. It is actually 2 questions: is it needed? How to do it? 

I could not decide if it was needed but i sure as **** was not able to come up with  simple way to do it, so I decided that no there will be no dampener. The downside is, I will need to avoid walking there during sessions but I usually don't anyway. I just wonder if the temperature change will make the tiles oscillate 😞

Thread pursued here : 

Hi guys, 

so, following the thread here: 

I have begun the construction of the pier. I am opening this thread to document the progression; as I have been reading countless threads and watched countless videos before begining, I assume this will, at some point, be of interest to someone (and allow me to keep track as well)

So, for starters, the quick photoshop of what the GF agreed to: 

I understand it's a classic design called a Tordmorden Pier. 

That was the original plan but it went south from the get-go. My idea was to screw/glue the bottom brick to the tile, which is solid and encased on a concrete slate, avoiding the need to build a foundation. However! Just for peace of mind I probed, pried the tile with a crowbar... And it popped right out without any resistance. The material underneath felt and sounded like concrete indeed, but I was able to mark it with the crowbar, and it turned out to be some sort of hard, but brittle grout. So I drilled into it to have a better feel of what I was facing and the drill went rigt through it in seconds. 

Totally unsuitable to rest the pier... So, plan B. I need a foundation and for that, no two ways about it, I need to cut away this slate of whatever it is and dig underneath it. Brittle but pretty sturdy and a good 3" thick, I tried brute force but no way. So I did the obvious: drilled all around to cut it..

.

From there I was able to fracture it with the crow bar and pry this part of the slate open without disturbing the other tiles. (GF would NOT have been impressed!) 

From there is has been much more straight forward but back breaking: break the ground with the crow bar, dig out, rince, repeat. I am now left with a neat 1.5ft * 1.5ft * 1.5ft deep hole where there once was the tile. I cannot go deeper as I have hit what looks like either the bed rock or a massive boulder. Either ways, I am confident this will be ok. 

The plan is to fill it with concrete with one of the hollow bricks 3/4 submerged in it, exposing only the side surface (21cm*21cm) about 1" above the level of the adjacent tiles. And this, will be my foundation... 
Half way through digging:

Next stage : pouring concrete and inserting the underground block to create the leveled anchor plane the rest will be glued on
To be followed! 
 

14 minutes ago, StevieDvd said:

make sure you allow access for the central M10 bolt holding the mount in place. There are a few advocates of the block pier here on SGL so worth a search for tips and do's/don'ts.

Yes. My reasoning is that I can drill bang central of the very top, use a long bolt with a washer from inside the last hollow, so by conception it's the most simple with the least parts and alignment errors possible. Also, rapid maths tell me that the whole assembly can be just under 100kg, so, considering it will be centered on the tile and, by definition, perfectly balanced, there will also be the least stress on the cement underneath. A poured pillar would weight several times that and potentially could fracture the cement underneath. So to me, this has the merit of a ridiculously low cost (in the region of £50 all inclusive), a light structure, easy to design / align / realise, and likely durable because the thing would not put more stress than me just standing there.

EDIT : and no need to break the tile, dig a hole, mix and pour concrete, cut rebars etc... because no reinforced foundation is needed.

So after a lot of debate, I settled on a pillar made of 3 concrete hollow blocks, possibly 4. These tiles are on a concrete base so I am thinking, drilling-screwing-glueing the bottom one, glueing above that with one big bolt in between the blocks, one brake disc on to suspended by M10s to be able to set perfect level. 

Quick and dirty photoshop to show the GF what she agreed to (the telescope here is facing east but it's unimportant)

2 hours ago, Graeme said:

So my spare brake disc (they come in pairs) is still available to a good home of a diy observatory builder for a fiver, if you think you might need it Arnaud.

Check DMs 👍

15 minutes ago, Budgie1 said:

I followed the disc brake method using the same parts listed in THIS THREAD.

My build thread is HERE and the only difference between my pier and the original is that I only used 3x 16mm threaded studs instead of 4. For drilling the holes, I used a neighbours pillar drill and it wasn't that difficult (as long as the drill is sharp!). 

Ok I am officially jaleous 😇 That is top notch!

1 hour ago, Franklin said:

MoreBlue do this one which could be fitted to a pillar via the 6 bolt holes. It is designed for the old 60mm GP base which is the same as CG5/EQ5, ordered direct from Japan it would set you back around £70 or maybe FLO could get one for you?

 

Do you have a link? I can't seem to find it.

8 minutes ago, StevieDvd said:

In this older thread there is a diagram of the pier adapter types used showing the measurements of the eq5 & eq6. It would seem the eq5 size is what you'd need.

Not sure what older thread you nean but I will forage the forums

9 minutes ago, StevieDvd said:

The north pin/peg/bolt or Azimuth pin is a better term for the locating lug.

Duly noted 😅 Sorry, I am french - been 10years in the uk but sometimes I come up short 😅

11 minutes ago, StevieDvd said:

Have you yet to start or have you a pier column ready for an adapter?

Nothing is done, it's ground zero for now. I did not want to do anything before I have a completely defined plan for everything. I know how and where to do the foundation and the column, insert threaded studs etc, and make an electric box to set everything safe. I struggle purely on the assembly concrete column / mount. But at this point I already have a much better global vision of this part too, thanks to you guys 👍

Nice set up, by the way, very neat!

3 minutes ago, Franklin said:

CG5 has the same profile base as the SW EQ5.

Good to know!

19 minutes ago, StevieDvd said:

A quick google shows the pier adapters are available see RVO adapters FLO also do one which is a multi-fit

Actually this multi fit one looks like a nice option and lists the cg5 as compatible ! great find 😃👍

2 minutes ago, StevieDvd said:

A quick google shows the pier adapters are available see RVO adapters FLO also do one which is a multi-fit

You could contact them to make sure it will fit your mount. I could not find the dimensions for your exact mount so not sure if it's an EQ5 or EQ6 equivalent. If you go for a diy job or a local company to fabricate something you'll need the dimensions.

What's the diameter & depth of the hole the mount fits in, that'll be a great help to know when seeking the adapter.

 

Hi, yes I have seen these ones. Not sure it fits the cg5, I will contact them. The central hub is 58mm (so need a 60mm hole) and 18.5mm deep (so need  20mm depth) and the north tit (sorry there is surely a correct name for that in english but i don't know it) is 40mm away from the central main bolt. 

I am looking for the possibility of having someone manufacturing it from a brake disk or from scratch, not as straight forward as i thought

3 minutes ago, Carbon Brush said:

When building my concrete pier, I didn't know what sort of mounts I would use over the years.

A soltuion presented itself when I replaced the brake discs on my car.
I embedded studs into the pier in a circle, a reasonable fit for the friction part of the disc.
The hole in the disc centre takes various mounts, sometimes adding washers as required.

My permanent setup has the alter D6 on there. A bit ugly looking and I meant to sort some nicer looking spacers.
That was in 2008 but it still works so nothing got done.

Some car parts suppliers even include dimensioned drawings on the web pages, allowing to you use a new shiny disc with predictable size.
If you shop around, discs are not that much money. Maybe treat your car to a new set?

HTH, David.

 

Yes I have seen this sort of thing on youtube. I am actually looking seriously into it, but my only concern is that I would need to drill through the disks (to place the studs and the north tit) and drilling this seems like an endeavour requiring some serious diy equipment. Besides, it would require some plate or stopper to prevent the mount to just pop out the central hub and the whole thing would need to be suspended up to be able to access the main central bolt. Do you have any pictures by any chance?

Hi guys!

I have decided to build a pier to set up my antique CG5-GT permanently. However I am struggling a bit with the design: the concrete column and cabling etc are not a problem but I cannot for the life of me find a part, an adapting head that could be screwed on top of the column and receive the mount itself. I have found old forum references to orion / sirius pier heads but I could not get much further than that.  Not a problem if you have a SW or even ioptron mount but it seems much more difficult to source for the celestron cg5.

Can anyone point me in the right direction or have relevant remarks? Thanks in advance.

I love this little scope. Best investment so far. Super capable little thing.
Currently working on my first mosaic, Heart Nebula + Fishhead Nebula. 2 panels, 45x300s & 55x300s, (calib : 20B, 12D, 20F) total about 2x 4H.

That is still a work in progress as I hope to add 2h+ on each panel tonight if all goes well, and later to add 4h of RGB when I have received my mutiband filter and the moon allows, to create a coloured HaRGB.

Shot from backyard in UK/Bournemouth, Borttle 6/7 the past 2 nights, with a self modded and cooled to 5C canon 450D, SWx0.9 Field Flattener, Baader 7nm Ha, SW 130PDS, CG5-GT, guided with Altair 60mm+ZWO ASI120MM mini. (Nina, Gimp) 

It's a cooled box "with a twist". Here it is : 

Red : current temperature of the heat shield, blue, target temperature, 22.2C = cold heat sink temperature and 23.6C = ambient air temperature. With these and looking at the current local dew point it is possible to set the ideal target temperature, as cold as possible while avoiding condensation/fogging/frost. And because it can be set, it is straight forward to make libraries of darks that are perfectly calibrated. The excellent freeware ExifLog also helps a lot to check temps variations over a series (and was critical during tests to put the shield probe EXACTLY at the right place so that the set temperature = sensor temperature) 

And here it is on  the telescope : 
 

The 4 cables coming out are : cold cell PSU, DSLR usb connexion, DSLR PSU, ambient air temperature probe

The twist is that the box itself is separated in 2 compartments, the cooled box itself and a separate zone where the electronics are (because along with the wiring they also give off quite some heat) The partition is made of wood because it is easy to work and is a very good thermal insulant.  Beside, it decreases the volume of the cooled zone as much as possible. 

You can also see in the middle of the back of the box (flipped over) the temp probe of the thermostat, placed so that it presses against the heat shield of the sensor. The bubble padding adds insulation and acts as a spring to ensure intimate contact. 

The cable that goes inside the cold heat sink is another temp probe that measures the temp of the cold side of the peltier cell (to judge how fast it is cooling / warming up and make sure it is not far below 0C) 

The back of the camera is gone permanently, the fan on the cold heatsink ensure the air circulates straignt within the electronics. Under the heat sink where the USB is connected, and under the cell PSU cable I pack silica gel (2x 20G). As the box is pretty much air tight it prevent condensation very well. 

The camera in its original state heats the sensor up to Ambient +10C. In this config the sensor can be Ambient - 9C. That's -19C and is actually too much as I learned the hard way yesterday (frost on the outer side of the field flattener when the air temp fell to 10C and the cold cell went down to -8.5C, sensor just above freezing) The thermostat allows to maintain a safety temperature without fogging or frost (sensor around 8C) as the field flattener is in effect wormed up by the metal focuser. So the trick will be to set the proper temperature which is 1) above freezing 2) just under the dew point (the sensore being 1 or 2 degrees above the set temperature) Yesterday I f**** up because I just forgot that the temp would drop at night... and I left the thermostat to -50C, forcing the cell full blast for 3 hours.

The current PSU is 12V3A but the peltier is rated for 6A so another psu is on its way. Also, I will ad 8mm neopren foam on the front side to limit heat exchange (the insulation is thiner there to ensure proper square contact of the ring against the front). It's not about getting cold faster but about preventing fast warming when the peltier cuts off at the target temperature: this will allow a more constant temp. It seems that with this specific sensor my ideal target temperature is around 6-8C which should be safe in most situations, except maybe in heatwaves where I'll need 10-15C; but even at 15C, the image is so much cleaner than uncooled that I can absolutely live with whatever little noise is left.  

Out of boredom (mount out of commission for a while), curiosity (I like to make my own opinion), necessity (I don't have uber money) I endeavoured to DIY a cooled box for modded canon DSLR (I sacrificied a 450D) .  With a few specific things that would decide if it was a success or a waste of time; namely, I wanted to be able to

• set a specific temperature for the sensor, so as to be able to calibrate my darks (that is one of the most often quoted argument AGAINST cooling boxes) 
• cool the sensor 10/12C under functional temperature (as the thermal noise is reduced by half for every 5C of cooling)
• keep under 1.5kg
• be able to SEE the difference on my lights without pixel peeping. 

I am not going to get into the build itself and all the tests I have conducted for the past 2 or 3 weeks, because it would be long and boring, but simply jump to the final result. 
This are two unprocessed, 100% crops. Canon 450D modded on SW130PDS/CG5GT, guided, 600s, ISO800, taken about 1 hour apart.  One is not cooled (ambient temp: 20C, sensor temp: 28C) one is cooled (ambient temp:18C, sensor temp: 8C) 
No points for figuring out which is which. 

It was not a total success because there are a few details that did not pan out as planned (and because I proved to be an imbecile who did not consider that the ambient temp would fall later during the night!) and therefore, more dev is left to undertake BUT I think it is fair to say that for an investment under £150 including the camera, the work in my opinion is totally worth it. 

One of the things I have come to realise during the design/build is that, while everyone seems to consider the temperature of the sensor vs ambient temperature, this is actually irrelevant; what counts is the temperature the sensor reaches when cooled vs when uncooled, regardless of ambient temperature, because uncooled the sensor will get much warmer than the air (typically for this specific dslr, 10C).  And this difference does not have to be massive to see a real improvement : in fact, other comparisons and tests I have made convinced me that cooling by just 6 to 10C make an absolutely massive difference in the "cleanliness" or level of detail of the light frames.  In this case, uncooled : a very noisy image purely due to thermal noise and the infamous ""canon banding" is very visible; cooled by 20C, the light frame is virtually noise free with a very smooth background. 

I hope this will inspire others  

Well, after last month's catastrophe with my CG5-GT, tonight will be, if ClearOutside is correct, my first night bacj in business. And my first night with my new guider (ASI120MM mini). And my first night with my latest project, a cooled astromod 450D. 

It took me almost 2 weeks to get it to work as I wanted (being able to calibrate the sensor temps) and the long series of tests indicates that it allows to shoot consistently at 9°C below ambient (instead of 6°C above - that's quite a difference! )

So... yeps. Wish me luck. Surely it can't go wrong on me every single time for ever. 

Sorry guys, that cloudy spell is on me : ASI120MM-mini. 

I used to have a touptek gpcam GP0130Mono but following the self destruction of my mount, after which I thought I had avoided any major damage, it turns out it actually did not survive and needed a replacement. Shoutout to @FLO for the great deal, superb com (Thanks Chris) and super fast delivery - also known as a normal  Tuesday for FLO. 


 

On 14/08/2022 at 20:15, Clarkey said:

Why does focal length dictate the FOV of a scope? 

Well, mostly because it does not. The focal length defines... the focal length. The field of view is defined by the ratio between the size of the image projection and the focal length. For instance, if you use a full frame capteur, you will enlarge your apparent field of view compared to if you use a webcam with a 5mm*4mm sensor. 

There is no mathematical limits (only practical/optical limits) to the FoV you can get with any given FL. It is mathematically possible (but practically impossible) to design a fish-eye with a 1200mm FL. It is also mathematically possible to have a .5arcsec FoV with a 20mm FL. 

FoV and FL are often mentioned interchangeably or to give an indication of the other simply because in practice there is a limit to the size of the image projection, from a few mm to a few centimeters - say, roughly 5mm to 5 cm, the vast majority of practical applications being around the 20/25mm mark.  But that's just a practical constraint, not really a physics/optics law.

Mt turn I guess... 

Taken yesterday under a 88% moon from my backyard in Bournemouth UK, borttle 6. 

3.5 hours in 6mins subs for Ha (baader 7nm) + 2.5hours in RGB (Svbony CLS) taken a week ago.

CG5-GT + Canon 50D modified with my very own sausage fingers, 130PDS+skywatcher coma corrector
Nina + Gimp.

Considering that my gear is mostly strings, duck tape and second hand cheap stuff, and that my mount has LITTERALLY fallen apart two days ago and was fixed (I mean botched) in conditions I don't even want to begin to describe, I am pretty satisfied. Very capable little thing, this 130PDS...