John

Remove the lens cell containing the objective first. It unscrews from the scope tube. Careful when putting it back on that you don't cross the threading on the tube.

Once you have the objective cell with the objective in it off the scope, you can reach the inside surface of the objective which might be enough for your needs.

If you need to remove the objective from the cell, this photo illustrates the method. The lens retaining ring does need to be unscrewed to allow the objective cell to be lowered leaving the objective elements clear of it. The back surface of the lens rests on an optical cloth supported something that is a little smaller than the diameter of the objective - I think I used a sellotape roll in this instance:

It's a delicate job because you need to ensure that the elements are put back in the same alignment (hence the black marker) and the same orientation with any spacers used in exactly the same position.

With regard to Berlebach Uni tripods, I used to use the wooden tray but added the spreader stopper a while ago and just use that now. It's a bit quicker to deploy than the tray was.

I do wonder if the tray made the tripod a little more stable, by adding stiffness though. I'll need to dig the tray out and try it again. Has anyone else any experiences of spreader stopper vs wooden tray with the Uni tripods ?

41 minutes ago, Cosmic Geoff said:

I think you should have a good look at what a 12" scope looks like when mounted on your preferred mount.  I had a 8" f5 Newtonian on an EQ-5 and was not pleased to find that with the tripod legs fully extended the eyepiece was about 7 feet off the ground with the scope aimed near the zenith.

Thats just what I meant about turning the scope into a bit of a "monster" 😲

A well designed dobsonian mount can be compact, lightweight, observer friendly and vibration free even with a big OTA mounted on it.

My 12 inch F/5.3 dobsonian used an Orion Optics SPX optical tube - these went on to become the VX12's.

Mine was bought 2nd hand though so I have not had the pleasure of going through OO's customer service experience.

Mine was on a custom made dob mount and I would not personally have used it on an EQ mount because it would have moved from being a relatively easy to set up and handle 12 inch scope to a bit of a monster !

I prefer to stand while observing and my scope was tailored with that in mind. I reckon the F/4 version would be much better suited to the seated observer.

Plus I don't image (apart from the odd moon snapshot with an old mobile phone), I'm just a visual observer.

Quality wise I would say 9/10 optics in a 6/10 tube. But it only cost me £250 so I'm not complaining 😁 The VX series have probably raised the fit and finish standards, to be fair. The focuser in the pic below is the Moonlite which I replaced the stock single speed GSO one with.

All in all, not a lot of use to you but the scope was really good and I had loads of enjoyment from it during the decade or so that I owned it 😀

Gratuitous pic for old times sake:

I've owned lots of TV plossls and I've tried lots of the Vixen SLV's as well.

Optically they are pretty much in the same league I feel. For the glasses wearer (which I'm not) the SLV will be somewhat more comfortable.

I did find the 6mm SLV pretty indistinguishable from the 6mm Baader Genuine Ortho when I compared them - except that the SLV has a much larger eye lens, about 5 degrees more AFoV and much more eye relief.

1 hour ago, JeremyS said:

What’s the project, John? Or is it under wraps?

It's still in development but it will have a traditional look to it 🙂

Just now, Astrobits said:

You should have mentioned this to me on Friday. 🙂

I have a screw cutting lathe. The expensive bit is choosing Brass. Ally will be cheaper but that is, of course, your decision. I only have Brass rod to 35mm dia so would not be large enough. I do have larger dia. Ally so no problem/cost there. I am also hoping to do some anodising sometime so you might be able to choose your colour ( from those that I have available)😀

See you next time at BAS or pm me.

Nigel

Hi Nigel,

Thanks very much for that and for the Calotherm cloths. It was good to see you again on Friday 🙂

Since Friday my other half has OK'd the project so I've been able to think it through in more detail.

I will keep in touch with you as things develop 🙂

John

Thanks for these replies and suggestions folks 🙂

I have a measurement for the inside diameter of the drawtube (taken with a digital caliper) of 35.4mm. I'm wondering if the thread is one used by Tak and Vixen of 36.4mm but that might be a touch wide 🤔

Are thread diameters usually measured from the top edge of the thread or the valley between the threads ?

Thanks again 🙂

The message you don't want is "We've got it and we rather like it so we are going to keep it" 😁

4 minutes ago, dweller25 said:

Sounds like you may have bought a fancy brass scope toDAY ? 🙂

Still "kicking the tyres" David 😉

I may have the need to have a custom adapter made in the not too distant future. It is going to be 1.25 inch fit on one side and an as yet unknown male thread on the other. Brass would be my preference but alloy would also be OK.

Can folks suggest any places that I might approach when my specs are more certain to undertake such work ?

Many thanks 🙂

1 minute ago, bosun21 said:

 Setting up a 9.25" on a suitable mount won't be that quick to set up either especially if using an EQ mount with polar alignment etc which is crucial for imaging. I reckon I could wheel out a 12" dobsonian quicker.

My 12 inch dob was as quick as my 100mm refractor to setup. A little more time to cool though - useful after 20-30 minutes.

A pictorial history of some of mine. Yellow stars = I still own it, except for the 12 inch dob which I parted with last year. There have also been some duplicates over the years which are not pictured:

I rather optimistically had a bash as this one with my Tak 100mm tonight 🙄

The transparency is not too good so that did not help. I managed to get down to magnitude 12.6 stars near the location of 3C-273 but I really needed to be able to go half a magnitude fainter to be in with a chance of spotting the quasar.

It was good to remind myself of the star patterns in that part of Virgo though, for the next time I try. On a slightly better night with the 120mm refractor I think I'm in with a chance 🙂

Just now, Flame Nebula said:

Many years ago, I went to an astronomy evening in Alice springs. I had a look through their C11, and Saturn looked like a photograph! Fantastically sharp. But then I suspect it was fully eqilibrated and that the seeing was as good as it can get. It was my first time in the southern hemisphere, and I can remember seeing an upside down Orion. Couldn't quite get my head around Rigel and Betelgeuese swapping places. 🤪

We did a similar thing when we visited Alice Springs in 2018. Unfortunately it clouded over before we got to using scopes 🙄

It was odd seeing Orion rise "feet first" !

Seeing the Magellanic Clouds and the magnificent globular cluster 47 Tucanae with my 8x56 binoculars on another night was pretty special though 🙂

I've seen Saturn looking like that with a C8 many years back when it was high in the sky here in the UK. Almost like the Voyager 1 images !

3 minutes ago, Ags said:

I have bought my scopes to complement each other...

I suspect my scopes of being quite rude to one another, when I'm not around 🙄

Astro society meeting this evening so I didn't get the scope out until after 10:00 pm. So far I've been using my Tak 100mm to compare different high power eyepiece / eyepiece + barlow combinations on Iota Leonis, which is fun 🙂

Not proving much though - they are all providing very similar views tonight 🙄

Seeing is decent however - even a rather silly 450x is giving a quite nicely defined split of this uneven brightness pair. 300x is razor sharp with text-book looking airy disks. 

I picked up an old Parks 2x 3-element barlow a few days back. Nice Japanese glass in this one - same as the Celestron Ultima 2x I believe. These are supposedly 2.2x in reality. 

31 minutes ago, Nyctimene said:

Spotted Triton in September 2021 with the 12" f/5 Hofheim traveldob, using the hints I found in Phil Harrington's book "Cosmic Challenge" (No. 156), mainly, to observe during Neptune's opposition, and Triton in greatest elongation (max. 17"!). Mag 330x showed  the 13.6 mag moon clearly with averted vision.

Stephan

Yep - high magnifications certainly help. 

1 hour ago, Ratlet said:

I think the Megrez 90 has fpl-53 Vs fpl-51 in the long perng.

At least I hope that's the case lol.  

I don't even know if it'll make a difference for me with the glass as I don't think I'm massively sensitive to CA, it's just an abundance of caution because I've found with observing that once you can see something when observing it becomes easier.  I did have a long hard look at the LP90 and came close but at the time decided not to.  The main driver of the 102ed purchase was a good price in the classified and having some money to buy it.

I had a Megrez 90 for a while. I'm pretty sure the ED element was FPL-53, judging by the colour correction.

A Ceravolo 5.5 inch reflector always looked an interesting scope. They seem to be held in very high regard by those lucky enough to own one. Another that I could have bought about 20 years back, but that might have risked a divorce 🙄

I've always wanted to own an Astro Physics refractor. They are like hens teeth to find over here though and command high prices when they do come up.

I had the chance to buy an AP Star ED 120 around a decade back but I passed on it for one reason or another. I sometimes regret that decision 🤔

Right now I seem to be very attracted to an Ernie Elliot brass 3.1 inch F/15 refractor which is currently being sold. That desire is totally illogical though, given the other scopes that I already own. It's just such a wonderful looking instrument though ........ 

I find this tool for assessing Triton's position is useful but I generally consult it after having a go for it, to avoid averted imagination kicking in:

Neptune's Triton Tracker (skyandtelescope.org)

Stellarium and Cartes du Ciel seem to plot the position of these faint planetary moons quite accurately as well.

Sorry it's me again 🙄

I've seen Triton visually several times with my 12 inch dobsonian and a couple of times under very good conditions with my 130mm refractor. 

I was hoping to see it with my 120mm refractor at the last opposition but that didn't happen, or at least not conclusively, mostly due to poor weather. I still think it's possible with that scope though. Maybe even with a 100/102mm if things fall into place.

When I had the 12 inch dob I also managed to see Oberon and Titania, Uranus's brightest moons. I've not managed that with a smaller aperture as yet though.

Triton is quite magical to see visually. It's just a faint dot of course but it is the most distant rock and ice world that I've managed to see.

I seem to specialise in faint dots of light 🙄

It would probably be my 100mm refractor for me as well.  

1 hour ago, Rob said:

I have 5, but also have 2 more on my radar!.. not suggesting getting 2 more, but you never know!

I've tried to switch my radar off from time to time but it's just to hard too avoid peeking at UK Astro Buy & Sell and the classifieds on SGL a couple of times a day. It's a bad habit - I've just seen a C8 that I fancy but my other scopes are hardly getting used lately 🙄