John

My DL was the same as yours - no extension section but it did have a 72mm black Tak extension tube (which I don't use).

These are the details of the tripod and head that I am currently using: http://www.slik.com/PS-MASTER_CLASSIC.html Looking around, without sacrificing stability, I suspect the best I'm going to be able to do is to save around 500g and at some expense. Not sure that's worth the bother given that the current tripod/head are doing rather well

Thats the tripod and the panning head Mike.

Thanks ! The tripod (which is very stable even at 150x) is 2.5kg of that. If I could save 1kg and get similar stability I'd be interested

Don't think I've posted this one in this thread Tele Vue Ranger 70mm F/6.8 ED + Slick Master Classic tripod. My travel eyepiece set is a 26mm BST Starguider, 21.5-7.2mm zoom, 2.25x Q-Turret Barlow (covers from a touch over a 3 degree TFoV up to 150x) and a UHC filter. Can also take along the Lunt 1.25" wedge which works nicely with this scope. Weight of scope, finder, diagonal, eyepiece and tripod is 4kg in total. A pleasure to use at home as well as away - a real "one hand grab and go" outfit

Thanks Mike

I don't want to put you to any trouble Mike. When you get home from your trip will fine. The weight of the setup as pictured would be interesting to me. Many thanks

Great setup Mike May I ask, what is the total weight of the scope + mount (including tripod) ? Thanks

Some planetary observers, when observing in darkness, shine a white light on a piece of white card and stare at it for a short while to provoke the opposite of dark adaptation, and improve the contrast and colour of their intended targets. If they are observing next to deep sky enthusiasts, there might be some "discussion" about this technique I reckon

Vixen ED102SS get it's turn this evening. Examining the Moon at 200x-250x. Theophilis lovely and and sharp !

I've owned quite a few products from both brands and I'd say that the quality was about equal. Back in the 1980's and 1990's Celestron used manufacturers such as Vixen and back then I'd say that Celestron would have been the better products. It's wrong to generalise though becuase Skywatcher can and do produce really top end products when they want to.

You can put Losmandy type clamps on most "T" style alt-azimuth mounts as long as the clamps have the mounting holes in the right places - usually 35mm apart. You don't usually see Losmandy clamps on the top mounting point of the Skytee II because, as I've mentioned a number of times in threads, it's not the best mounting point to use for heavy, long scopes. I hope that you never need to find out but I wonder if the 4 rings and long DT bar that you are using with your Tak might actually increase the risk of damage to the tube in the case of a fall onto a hard surface As I say, I hope you don't get a chance to find out ! Perhaps just encase the scope in plaster, and remove the risk of damage altogether ?

Tele Vue Ranger 70mm ED and, at another extreme, TMB/LZOS 130mm F/9.2 triplet

The Vixen R&P focusers that I've used (the one above and the original on my Vixen ED102SS) were very good. They needed adjusting now and then but once done were smooth and positive even with monsters such as my 31mm Nagler. YMMV of course. Here is how to adjust them, if it's of any interest: http://miltonhill.us/Tele/Vixen_Focuser.html

Here's one from my dim and distant past. Circa 1985, Astro Systems (Bedford) 6 inch F/6 (David Hinds primary mirror) on a Fullerscopes Mk II equatorial built for me by Dud Fuller. Saw Halleys Comet with this one

Before the premature clouds arrived this evening I was observing the Moon with my TMB/LZOS 130mm F/9.2 tripet. Really lovely views at 270x.

I think a 6" achromat needs to be f/15 at least to reduce the CA to levels that are not really visible in the eyepiece. My Istar 6" F/12 had a very nice objective (ie: nice, smooth figure) but the CA was quite obvious around the brightest targets I thought. The 6" F/8 achromats I've owned showed more, until the Chromacor was installed and then it was controlled to ED doublet levels. Sir Patrick Moore's 5" Cooke refractor is one of my very favourite telescopes It was part of the motivation behind my decision to buy the 5.1" TMB / LZOS F/9.2 - the latter being a touch easier on the mount than an F/12 but having roughly similar lines and proportions perhaps ?:

I've not seen one. It would have to take into account the various ED glass types, mating elements glass types, and combinations thereof, so lots and lots of options and a very complex chart ! The achromat one just needs to take account of the standard flint and crown glass achromat doublet and apply the Dawes and Conrady standard formula to the various apertures and focal ratios. I've seen figures that indcate the potential CA reduction that certain types ED glass elements can deliver but there are a number of other factors that influence the end result that the observer actually sees. I'm sure there are threads on other forums such as Cloudynights on this topic - many of them !

I've not used one but here is a German optical test of the AX103S which seems very positive (might want to run it through Google translate or similar): http://astro-foren.de/index.php?thread/13357-refraktor-als-fotomaschine/&postID=57253&l=2

Many chinese achromats have a noticable degree of SA as I discovered when I was playing around with Chromacor's a few years back. I think the chart is accurate from my experiences with various achromats but I agree that terming the CA as "unnacceptable" is not helpful. Thats down to personal preference I think. Personally I prefer as little CA and SA as possible which is why I was exploring Chromacor's back then. The difference in performance, particularly at higher magnifications, of a chinese 6" F/8, when the CA and SA were reduced around 80% was quite dramatic !

Interesting link. The table below is quite a useful guide to the relative amounts of chromatic aberration that achromats of different specifications should show. It's a normal feature of the optical design though, in the same way that coma is to the newtonian design so we should not be overly concerned by it. Spherical aberration is present in many refractors and has more of an impact on performance than CA does.

I found the Radian's and Nagler T4's quite straightforward to use without needing to use the pupil guide. The 22mm T4 was a lovely eyepiece - my favourite Nagler I think. I'd steer clear of Tele Vue eyepeices if they don't suit you though. There are other decent options around

But they do provide pupil guides with the models that are most sensitive to this.

I think it's a standard F/5 achromat. Similar performance to the Skywatcher ST80 probably (which are not too bad for CA) but a more individual looking scope. Vixen also produced some small refractors for Tasco during that era. Good Tasco's to watch out for