alan potts

This is something that cropped up before over a year ago and I am not sure we ever got to the bottom of the question. I have a Televue 41mm and that has a 68 degree FOV, now TV being who they are have always pushed the limit of the envelope. Myself I find it hard to accept that a company albeit a very good one can out Tele-vue Tele-vue, with 1 more millimeter and 4 more degrees, without vignette issues. The 41mm in fact show a mild vignette when used in my LX 12 inch scope with a diagonal, the one it was bought for. The limit of what can be seen as you probably know is governed by the size of the field stop of the eyepiece, this must be within a very tiny amount identical on both eyepieces in order to fit the telescopes. If the Vixen is 72 degrees and 42mm I struggle to understand how they do it. I am not saying this is not the case but personally I do not believe it. I have even considered buying one to see for myself. If there are like eyepieces (65) from your supplier and you ordered 72 degrees based on a picture then I for one would not be happy with what you have received, my advice is send it back and make sure they pay for the postage, it's their mistake. Alan

Some good ones there Nick, sadly I have to wait a while for these to be in the right place. I either have to knock the house down or cut a walnut tree down, now where is that chainsaw. Only other problem is the weather, terrible now for 11 days. Alan.

Lovely collection you have there, though Televue cases is one expense I will not stretch to. Alan

Taliking about the rare BGO's I got the 6mm 7mm & 9mm without much fuss but I have never seen a 12.5mm at all. I got the Hutech which is fine for me, that too seems optically pretty spot on. I have the Kasai in at number 18mm and that is very good too, I am not sure but I wonder if these are all the same just dressed differently. Anyway Stu a very nice set of eyepieces just to get back on thread.

Good luck, years ago I made a 12.5 inch and didn't quite get it right but after correction by Hinds, I think it was called, it was still in use back in 2005 and recoated twice now. I think it was 1976 it was made. You though at 22 inches would laugh at 12 inches I am sure. I hope it all goes well as 100 hours is a lot of work, bet you have arms like Arnold. Alan

The most important thing with eyepieces is that you are happy with them, that is a nice collection and as Stu says cover all bases, it don't matter what everyone elae has, if I was more like you my pockets would be more full than they are. Alan

Stu, No Delos, shock horror!!!! this means a visit from the Tele-Vue inquisition, prepare yourself for the cuffy chair.

James, I like a man with taste. Beautiful collection, thinking of adding a 5mm Nagler myself even though I have the XW, I've run out of things to write about at the moment.

Shane, Bulgaria as well, I still have his 7mm Nagler. Sorry Stu I missed that from you, yes I still have it but have you still got my 10mm Delos or did I buy it back from Mike? Alan

Agreed but I would still like to try a Nikon 100, a ZO ll and XO 5mm which is of course Pentax. Alan

The T4 range look lovely, I had the 12mm and though it is a very good eyepiece and only got evicted from the case by a Delos, I did find it a little difficult with eye placement. The Delos is easier to use but this could of course be different for other people. That 30mm Pentax is a size, almost the same size as the 41mm Panoptic and I am looking at mine now. Alan.

Qualia, I am a little lost for words after reading these few short notes you have put together, can I just say excellent! Alan

Why don't you post this fine report on in Review or Eyepiece section, sadly it will be missed by many here. Well done very nice write-up. I had the 10mm Radian and as our first poster say they are very under-rated, under-rated indeed as far as I am concerned. I have read a good deal of posts on USA sites where they talk of a colour caste, well unless it becomes more obvious in a massive scope I would say it is somewhat overstated. Try M22 if you can get on it. Fabulaous! Alan

Sort of wish I had not read this, it's got me wanting agian. Congratulations on the new scope and I hope you get some better sky conditions to really get the best from it.. Alan

Derek, How could you, I haven't even got my 11mm & 15mm yet and you have a whole set. I think treatment is required. Alan

Avtar, I spy with my little eye an eyepiece that used to live with me. Caldwell 14, Still quality though

As always an excellent piece of work and a very good early morning read, 4.30 am your time. It may be tempting to pick one of these up next time I am in England as I don't appear to be able to get them here without a lot of messing with different currency. Alan

Derek, I have that one on my to get list, the 11mm and maybe the 8mm. I read an interesting report by someone on SGL about the TV Plossl and thought I must see this myself, reported the colours come across better on Planets like Jupiter. I will have to wait a while as it is not best placed now. Alan.

Derek, Nice collection there, I rather like the T4's from Televue though I only have one, the 12mm and that may well go soon. There is not much between the 13mm T6 and the 12mm in cost but with the 12mm you feel you are getting your money's worth. Now all we need to do is spend some more of your money to fill the holes, 3 of them you say? Alan

Tinker, Yes one of the other Moderators told me about this as with larger scopes it makes it easier, with mine my arms need to be a few inches longer but I have done it so many times now I could almost do it in my sleep. Know what you mean about clear skies though. Alan

John, The WO goes to 11. One of the all time great films, I love it. :grin: Alan

Aaron, I have never seen most of the Pentax range but I would not make the mistake of buying one if I were you it could end up costing a pile of money. The 30mm and 40mm I believe have been discontinued but the others are still available I think, I always fancied the 40mm for the LX but could never get one, I have the 41mm Panoptic but I am not over the Moon with it, in fact now I regret selling the 40mm Meade SWA at F10 it is a great piece of glass in every sense of the word. Alan.

Collimation of a SCT. The collimation or alignment of a telescope is very important if you are going to get the best from your equipment, at first it may well look very difficult and many can be worried about touching anything which is normally no bad thing. Basically all SC telescopes have three screw adjusters located on the outer surface of the secondary mirror which sits on the other side of a housing in the middle of the collector plate. Some people fit a system known as Bob’s Knobs which is just an extension replacement screw system that makes the job easier. Most adjustment is done with the use of an Allen key and some with Philips type screw heads, if this is the case great care must be taken when performing the task. The good thing about this type of scope is that they hold their collimation very well indeed so this will only need to be done occasionally. It is a good idea to perform this with the use of a torch until such time you are comfortable with the job, night vision is not important to carry this out and it is always better to be safe than sorry. Choice of star. I always select a star that is not too high up in the sky, select something of at least 2nd magnitude that is about 45 degrees above the horizon, this will make it easier to view the star and to easily adjust the screws. On larger scopes you will always find your arms are just a few inches too short making it essential to make journeys to the front of the scope. First steps. You have selected a star and placed it in the center of the field of view, on driven scopes there is no problem of the motors holding this position. I do not know of an un-driven SC telescope but if there is one out there then select Polaris as all stars appear to revolve around it. I use an eyepiece giving a power of between X80-X100, a bit little more or less will not matter. I also collimate without the diagonal fitted but some people do it with it in place, the choice is yours Once the star in the centre then de-focus it so that you see a large starlight circle with a blacker circle somewhere within, this is the shadow of the secondary mirror assembly, if it appears in the centre then the scope is fine. I always go for a fairly large star circle as I find it easier. Let’s say the scope needs adjustment. Whilst looking at the defocused star take note of where the shadow is offset within the light circle, now place your finger on one of the screws at the front if you can and see where the shadow falls, be careful not to touch the glass collector plate, you will see you fingers shadow on the light circle. You need to locate the screw that needs to be adjusted first, move the finger around until you see the shadow at the thinnest part of the off centered circle, once you have located this you know the first screw to adjust. Using the drive motors at a very slow slewing speed move the de-focused star to the edge of the field, this needs to be in the same direction that the darker shadow of the mirror is off-set within the brighter star circle. Careful place your Allen key or screwdriver in the selected screw head and turn it a little, then check the image, if it has disappeared from view you have moved it the screw the wrong way, so turn it back the opposite direction . Correct action at this point will bring the star back to the centre and will have moved the shadow of the secondary to a point nearer the middle. Never turn the screw more than one full turn, it will never be required to turn this far for normal alignment. If you can do this whilst looking through the scope it is so much easier, however on larger scope it is a process of elimination to find the correct screw at first. In most cases the screws will only require a quarter of a turn or less. It must be noted that on some occasions small movements of two of the screws will be required to achieve this. Once you are getting the shadow closer to the centre of the starlight disc you may find you need to adjust other screws, the same applies very small movements until you have the star as close to the middle as you can see. If it is near or in the middle you will start to see a number of small thin concentric rings of light around the shadow at the centre. Increase of power. I normally increase the power using an eyepiece to give X150-X200, then repeat the process using very small adjustments of 1/10 of a turn or less, until the shadow looks exactly in the centre of the light from the de-focused star. Check the image after every action and if a mistake has been made undo that action. Look for the concentric light rings again. I often repeat the process using an even higher power of over X300 but this is not always necessary, if you are happy with what you have done focus the star and have a look at the diffraction rings, the scope should now be in good collimation and ready for use. A good final check is select a star of around 4th magnitude and check for a clean point of light, this is known as the Ariy disc and offen has concentric diffrations rings around it on brigher stars. Any adjustments made at this stage will need only the very tiniest of screw movements, be careful not to undo the work you have done. This seems very worrying and difficult at first but once you have done this a few times you really will wonder what all the fuss was about. The scope should now be in good collimation for a night of astronomy. Clear skies to all, Alan.

I will try and borrow the 14mm as well as something else, I had the lions share of the set as my first eyepiecs so they are not new to me, it was only the 40mm that I didn't bother with. I remember the first target with these eyepieces, Mercury with the 14mm and the 12 inch, out the window of the apartment in town, I was still building the house at the time. I have never seen Mercury since, there is always a tree in the way, or treed out as the Great Man would have said. Alan

I have got to go to see Dani in Sofia at the end of the month as he had a couple of Televues I was selling and the buyer has let me and him down, I was thinking of doing the 14mm S Plossl against the 14mm Delos and maybe the 26mm against the Panoptic 24mm, I will see what he will lend me, he is a bit red faced, he don't like to upset his best customer. Alan