Tweedledee Posted February 24, 2018 Share Posted February 24, 2018 Got a new accessory for the big 3" eyepiece - 6" frac! It is the very same one as pictured in the top left corner of the EMS webpage and is the now discontinued version of the Bresser Messier AR152S. This is a cut above the average 6" F5 achromat as it has a 6" doublet focusing at F10 plus a 4" Pretzval lens just before the focuser doing a bit of correction and reducing the overall ratio to F5. It came with a 4" wide focuser with an adapter to 2"/1.25". I needed a 4" to 3" adapter in order to use the 3" diagonal and eyepiece, but nobody seems to do these off-the-shelf. Graham made one perfectly turned out of a solid billet of aluminium. Cheers Graham. The ES 3" 100 degree 30mm eyepiece will provide a massive 4 degree FOV on the 6" refractor! Here is the 4" to 3" adaptor expertly made by Graham, it threads on to the outside of the focuser drawtube. The three thumb screws are bigger than most at M5, because it needs to have a firm grip as the diagonal and eyepiece weigh a whopping 3.3 kg... This shows the size of the eyepiece compared to my next largest, the ES 9mm 120 degree and ES 25mm 100 degree... Scope out cooling ready for a squint through the eyepiece tonight. On the left is the 120mm F5 with 9mm 120 2" ep... Comparison between ES 30mm 3" and TV 20mm 1.25"... tuckstar, philjay, +Bino-viewer and 1 other 4 Link to comment Share on other sites More sharing options...
Smithysteve Posted February 24, 2018 Share Posted February 24, 2018 Wow! Still not sure which end you look down though! Glad it is all coming together now! ? i hope the mk1 eyeball is delighted with the view tonight! Try it on the Perseus double cluster if you can, and the Pleiades- with that whopping TFOV they should be stunning! Tweedledee 1 Link to comment Share on other sites More sharing options...
BAZ Posted February 24, 2018 Share Posted February 24, 2018 Just wow. You have had to buy a scope to fit the eyepiece? Those AR's are a nice bit of kit as well, I like my AR127mm. I am happy with 2" but would love a look through your 3". Tweedledee 1 Link to comment Share on other sites More sharing options...
Tweedledee Posted February 24, 2018 Author Share Posted February 24, 2018 Cheers, it finally all came together after getting a bit from here and a bit from there, including the bargain $50 ep and diagonal from South Korea! Well, the mk1 eyeball was thoroughly engrossed in watching our wedding video and reminiscing over others showing the kids as babies etc. as we had borrowed a VHS player and hadn't watched VHS for years. Forgot all about the kit outside till about 9.00pm and, of course, it was completely overcast by then. So will have to do all that cooling down of the heavy metal and glass another night. But nevermind, because I now feel 23 years younger and could marry my lovely wife all over again. So it was a real good night anyway. BAZ and tuckstar 2 Link to comment Share on other sites More sharing options...
+Bino-viewer Posted February 25, 2018 Share Posted February 25, 2018 Spectacular looking setup Pete. 4º fov is something else.......thats approaching my 15x50 binocs ! Tweedledee 1 Link to comment Share on other sites More sharing options...
Doc Posted February 25, 2018 Share Posted February 25, 2018 11 hours ago, Tweedledee said: Cheers, it finally all came together after getting a bit from here and a bit from there, including the bargain $50 ep and diagonal from South Korea! Well, the mk1 eyeball was thoroughly engrossed in watching our wedding video and reminiscing over others showing the kids as babies etc. as we had borrowed a VHS player and hadn't watched VHS for years. Forgot all about the kit outside till about 9.00pm and, of course, it was completely overcast by then. So will have to do all that cooling down of the heavy metal and glass another night. But nevermind, because I now feel 23 years younger and could marry my lovely wife all over again. So it was a real good night anyway. You big softie Pete Tweedledee 1 Link to comment Share on other sites More sharing options...
Tweedledee Posted February 25, 2018 Author Share Posted February 25, 2018 18 hours ago, Bino-viewer said: Spectacular looking setup Pete. 4º fov is something else.......thats approaching my 15x50 binocs ! Yes, it should make a nice rich field telescope at 25 x 150. +Bino-viewer 1 Link to comment Share on other sites More sharing options...
Tweedledee Posted February 28, 2018 Author Share Posted February 28, 2018 (edited) Oh Well, first trials were unsuccessful. I knew it would be close, but the big ep would not quite get focus in the 6". The 3" diagonal adds a massive 147mm onto the light path. Fully racked in, the eyepiece very nearly achieved focus, but I just needed a few more millimetres. I was going to put the eyepiece straight into the 3" adapter without the diagonal and take some accurate measurements of the focus position and calculate precisely where it needs to focus with the diagonal and establish if the adapter could be reduced in size to accommodate this. The adapter was a bit tight and I couldn't get it off the diagonal. I'd asked Graham to make it a tight fit with all the weight hanging off it, but with temperature changes it just wouldn't budge, so I didn't manage to try it that way. Graham is going to adapt the adapter for me. Hopefully when he's slimmed it down a bit more, I will have another 8 to 10mm of in-travel. It may or may not be enough. I managed to get a short visual session with 2" eps in the 6" refractor. Despite the bright moon in the milky way, I was surprised and pleased with the views in the 6". Edited February 28, 2018 by Tweedledee BAZ and Smithysteve 2 Link to comment Share on other sites More sharing options...
Doc Posted February 28, 2018 Share Posted February 28, 2018 You don't have many options Pete. Firstly I would see if you can reach focus without the diagonal. Then your only options are to shorten the tube or add a barlow into the mix. Tweedledee 1 Link to comment Share on other sites More sharing options...
Tweedledee Posted February 28, 2018 Author Share Posted February 28, 2018 5 hours ago, Doc said: You don't have many options Pete. Firstly I would see if you can reach focus without the diagonal. Then your only options are to shorten the tube or add a barlow into the mix. A Barlow would defeat the object slightly, and have you seen the price of a 3" barlow? Shortening the tube could easily cause problems with the collimation between the objective at one end and Pretzval lens at the other, so that might not be a good option. If the modified adapter still doesn't allow focus I will be a little disappointed, but I'm still very pleased to have a big refractor to use with my other eps. In any case using the 3" eyepiece with a refractor was never in my original plan. It only became an option when I found the 3" eyepiece for sale with a 3" diagonal thrown in. The main idea was always to use it in the dob. Link to comment Share on other sites More sharing options...
BAZ Posted February 28, 2018 Share Posted February 28, 2018 Sorry it didn't work out for you Pete, well not yet anyway, here's hoping the adapter works out. Tweedledee 1 Link to comment Share on other sites More sharing options...
Tweedledee Posted February 28, 2018 Author Share Posted February 28, 2018 I think that reaching focus without the diagonal would also be a problem without an extension tube. Fully racked in with the adapter as it was and diagonal pushes the eyepiece out 23mm for the adapter plus 147mm for the diagonal, which is 170mm. I reckon that is only a tad too far by just several millimetres. The drawtube fully racked out adds 120mm which wouldn't be enough without an extension. So if the new slimline adapter is not slim enough, I'm between a rock and a hard place. But it's all good fun anyway. Link to comment Share on other sites More sharing options...
BAZ Posted February 28, 2018 Share Posted February 28, 2018 Good luck, it will be a belter if it works. Tweedledee 1 Link to comment Share on other sites More sharing options...
Tweedledee Posted February 28, 2018 Author Share Posted February 28, 2018 Thanks Martyn. And thanks for your suggestions Mick. Of course, I might also be able to get a few extra millimetres machined off the diagonal, but that's really grasping at straws. Link to comment Share on other sites More sharing options...
+Graham Posted March 1, 2018 Share Posted March 1, 2018 16 hours ago, Doc said: You don't have many options Pete. Firstly I would see if you can reach focus without the diagonal. Then your only options are to shorten the tube or add a barlow into the mix. There is another option. I will make it today if I get the time. I won't explain it on here so it will be a surprise for you. Tweedledee 1 Link to comment Share on other sites More sharing options...
Bottletopburly Posted March 1, 2018 Share Posted March 1, 2018 Lovely kit , bet you can get both eyeballs in that eyepiece lols Tweedledee 1 Link to comment Share on other sites More sharing options...
Tweedledee Posted March 1, 2018 Author Share Posted March 1, 2018 2 hours ago, Graham said: There is another option. I will make it today if I get the time. I won't explain it on here so it will be a surprise for you. You've really got me scratching my head now Graham. Link to comment Share on other sites More sharing options...
+Graham Posted March 1, 2018 Share Posted March 1, 2018 Scratch no more. It took a bit of working but it is all done. I will anodise it tonight /tomorrow. Once you see it all will become clear. I have managed to gain you another 20mm back focus. I have also reduced the original adapter to your specifications. Smithysteve, Bottletopburly, BAZ and 1 other 3 1 Link to comment Share on other sites More sharing options...
Tweedledee Posted March 1, 2018 Author Share Posted March 1, 2018 Marvellous thanks Graham, you've obviously done some engineering magic there. Looking forward to seeing how you managed to get 20mm. Still racking brains but suspecting hidden grub screws might have something to do with it. Will put some pics up when I get it. Link to comment Share on other sites More sharing options...
philjay Posted March 1, 2018 Share Posted March 1, 2018 looking good there Pete. Those scopes are a doddle to cut the tube down, just remove tge three screws holding the focuser and get the hacksaw and drill out. Done it many times Tweedledee 1 Link to comment Share on other sites More sharing options...
Tweedledee Posted March 1, 2018 Author Share Posted March 1, 2018 44 minutes ago, philjay said: looking good there Pete. Those scopes are a doddle to cut the tube down, just remove tge three screws holding the focuser and get the hacksaw and drill out. Done it many times Thanks Phil, hopefully I won't need to resort to cutting the tube, but it's another option if all else fails. Link to comment Share on other sites More sharing options...
philjay Posted March 2, 2018 Share Posted March 2, 2018 (edited) Its the simplest way. It also gives you the opportunity to beef up the focuser fixing method. If you are putting a load like that on the back end I would recommend it even if you didnt cut the tube down. The focuser body will sag because the 3 fixing screws do not fix directly to the tube the focuser just nips the tube and relies on friction, Martyns 127 had that if I remember rightly. My fix is to undo the screws, rotate the focuser slightly so there is fresh tube showing, then drill and tap the tube. This way the focuser body cant sag unless you drop it and bend the tube Edited March 2, 2018 by philjay BAZ and Tweedledee 2 Link to comment Share on other sites More sharing options...
Tweedledee Posted March 2, 2018 Author Share Posted March 2, 2018 Good advice, Thanks for alerting me to that Phil. As you say it sounds like a much needed mod in my case even if I don't need to cut the tube. Link to comment Share on other sites More sharing options...
BAZ Posted March 2, 2018 Share Posted March 2, 2018 (edited) I didn't have to cut mine down, but the objective end wasn't cut square and that was what threw the collimation out. You're right though, the focuser was moved and retapped so it didn't move. It's Bob on now. Edited March 2, 2018 by BAZ philjay 1 Link to comment Share on other sites More sharing options...
Tweedledee Posted April 22, 2018 Author Share Posted April 22, 2018 (edited) On 01/03/2018 at 10:17, Graham said: Scratch no more. It took a bit of working but it is all done. I will anodise it tonight /tomorrow. Once you see it all will become clear. I have managed to gain you another 20mm back focus. I have also reduced the original adapter to your specifications. Grahams special 4" to 3" adapter with the secret hidden grub screws allows focus on the 3" diagonal and ES 3" 30mm 100 degree monster with just 8.5mm of in-focus to spare. Fantastic job Graham thanks. ? I've noticed that the big focuser on the 6" frac does have a tiny bit of play in it where it fits to the tube, so will be taking it off and refixing it as per Phil's suggestion. Edited April 22, 2018 by Tweedledee tuckstar and +Graham 2 Link to comment Share on other sites More sharing options...
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