JAC51

You will have no problem with white light solar at least with the telescope itself. I have the longer f9.2 130mm LZOS version of your telescope which I use with a Baader 2” Herschel prism. After an hour of use the prism body is merely warm. I asked Markus Lundy at APM about this when I first bought the prism and he told me has used the same prism with an 8” triplet. Also a little UV light down the tube can be good for reducing the risk of any fungal growth. still day or night you have an excellent telescope, among the best of it’s aperture, all the best. John

I have tried a friends SLV 2.5mm and the precursor to the SLV10mm with his LV10mm and have to agree they are very good and excellent value.

I think this for mount and all is remarkably compact. EasyJets extra legroom overhead storage is 56cm x 45cm x 25cm for example , give or take 4mm, this can go with you in the cabin.

Great great picture, very impressive.

Here is another picture of a big Konus in orange and in a case nearby what I think is early? Celestron orange. Both pictures taken in a optical museum in Madeira, I should add with the owners permission. John

Good picture for how low Saturn is to the horizon. I had to wait until 1am before Saturn cleared the neighbors house. Visually with a 5” frac I saw a bleached out version of your image. I could just make out the “wider” parts of Cassini division as in the left and right side of your image. On the disk itself I could make out clearly the darker band below the rings in your image, just make out the fainter thin band below that and just a hint of darker shading around the pole. Thank you for posting the image. John

I have a 2” Maxbright Baader diagonal and I have no problem with the nose hitting the mirror. In fact I often use them in 2” mode with my 48mm Brandon as the focus positions are similar, within a few mm. I did very carefully check the clearance of them in the diagonal on the kitchen table before I used them in the telescope.

I have the 9mm and the 17.5mm and have to agree with all the posts above. Sharp on axis and sharp almost to the edge of the field of view and comfortable on the eye. They are now my general go to eyepieces. John

I remember a clean split, just, of both pairs some years ago under a very steady sky. Tak FS60CB with Tak 5mm LE eyepiece for x71. The split was also seen, with the above, by a friend observing with me.

Thank you for the excellent video which I have enjoyed watching.

I would agree with the above statement from my experience of a Borg 76mm achromat with the 80mm draw tube system at least when compared to the Tak FS60 I own. The Tak is more robust but also heavier. The Borg draw tube I found sagging a little with 2” eyepieces , one of the two screws holding the draw tube in place lost its threads . In the tube itself I discovered Jupiter had rings around it one night. The tube had one plastic baffle at the rear which had come loose and rotated to cut across the inside of the tube, this was pulled out to fix the problem. All of the above though is over a 20year period and I still like my flat back telescope for camping. Though the Tak has been camping as well, also easy to pack. Though the model you are looking at does not seem to have the draw tube, has a better focuser? than the Tak and I assume the fluorite lens like the Taks is also made by Canon-Optron? Does the Borg tube have an attachment for a finder scope if needed? Good luck with you choice John

I have bought the 17.5 mm at the start of 2020 which impressed me so much that within a month I also had the 9mm. The 17.5mm has become my goto low magnification eyepiece with my 1200mm focal length telescope.Then I switch to the 9mm for targets like globular clusters with still having plenty of space around the target. I also really like the fact that you can use them as 2" or 1.25" which for a long refractor has proved to be a great help with finding a comfortable sitting position. When I first tried out the 9mm on M5 I thought very nice on axis but at the edge of the field of view I'm star I'm seeing stars as a double image. The double image of course turned out to be an actual double star (5 Serpens) which I was amazed look so good almost up to the field stop. John

Thank you for the link John, very interesting link. I looked up the Abbe numbers (google) of FPL-51 ( 82 ), FPL-52 (90,) OK-4 ( 92 ) and FPL-53 ( 95 ) (rounded to whole numbers) Though of course as you say the mating elements are just as important. Then the figuring and polishing. Then the steel lens cell. John

I will indeed Steve, I have been just been trying to figure out how to add detail to my profile, which I will shortly. In the meantime I and currently prefer visual astronomy and have begun to try and sketch what I see, very crudely so far. So far I tend to Double stars, planets, Lunar, open star clusters and now white light solar (5" refractor). John

They are indeed excellent telescopes. I have aTMB 130/1200LW version from 2005, lens number 005. It has a draw tube and 2" Feather light focusser which I think is to make it bino friendly. The contrast as already said is superb , the tube dews up but the lens at the business end never has so far in 10 years of ownership and it seem to have very little in the way of tube currents when cooling. The f9+ focal length is very forgiving of any eyepieces used and the cool time down is no where near as bad as I feared (45min?+) perhaps due to thinner glass in the more gently curved lenses compared to shorter focal lengths. Below is things that I have read online and perhaps half remembered , if I'm wrong I apologise and please contact me.. OK4 glass by accounts I have read is very close to FPL53. Now I wish I had the link to this but here goes.. Years go I remember reading, I think on APM website that their 6" ED F8 doublet using FPL51 glass was equivalent to an achromat of F30. They also produced for a short while a 6" LZOS F8 doublet using OK-4 which was equivalent to a F45 achromat. I think my memory is accurate in which case the above would suggest that OK-4 is optically superior to FPL51, though of course the mating elements matter a great deal as well. Now for complete speculation from me. It is possible that FPL51 and OK4 might be equivalent in how easy they are to work . FPL53 is I believe said to quite soft and difficult to work with, something I have not heard about OK-4. This by the way is my first post after saying hello, please forgive any typos. John

I have been reading some of the excellent threads on here for years. Thank you for that now it's about time I took part. John