nicoscy

Quick addition: F4 Vs F5: Means that the trusses are 300mm longer at f5, meaning greater torque on the bungee cords...

Hi Bill, I had a 12" f4 Sumerian but not the Alkaid (it was its slightly beefier cousin) in the past. Some feedback: 1. More bungee cords will definitely be required and the best thing is to actually email Michael of Sumerian with the weight measurement of your Binos with eyepieces and corrector so that he can inform you as to the best way to go about it. 2. There is no difference in where focusing will take place either in f4 or f5 in terms of using the scope, as depending on what you order, the trusses will be cut to the right length to facilitate focusing an eyepiece at either ratio. The decision you need to make is if you want to use the binoviewers natively or not. Using them without a corrector means that you need to let Michael know the lightpath of your binoviewers to shorten the trusses accordingly, be it f4 or f5. Binoviewers need significantly more in-travel than eyepieces due to the internal folding of light from the prisms inside. You need to keep in mind though, that using binoviewers in native configuration and regular eyepieces, means also getting a focuser extension tube as your eyepieces will focus further away as a result. Another option is to get in touch with Harry Siebert and get one of his binoviewer zero or 1.3x OCS units for your binos. 3. F4 Vs f5. Coma becomes an annoyance for most people at anything below f5, resulting in the purchase of a Paracorr. It is up to personal preference, but I for one, always used a Paracorr with my dobs to make sure I get the best image fidelity and quality. Since you will be travelling with the scope, a Paracorr is extra weight. However, going from f4 to f5 results in longer trusses by about 30cm - so something to consider. Hopes this helps a bit

I asked a friend who sells astrogear and the thread after you remove the green bit is M53. This whole situation is ridiculous! SW comes out with a very attractively priced, good looking, FPL53 50mm scope and they couldn't just shave off 30mm from the tube and have a longer extension at the back. Had they done so, these things would fly off the shelf like hotcakes! I applaud all those who are fighting the good fight to adapt this thing for visual but I think I'll stick to reading this thread and give up on the idea of the SW as a mini grab n' go

Derek, By any chance, do you have calipers at home? I'd be most interested in a measurement of the ID of the OTA once the entire back assembly is removed. The OD is 56mm according to FLO so I suppose the ID is probably M54 or so. In any case, it would be relatively easy to find an adapter from whatever thread to a T2 connection and then just shove a T2 non rotating short helical focuser and then a Baader T2 to 1.25" short adapter and use any regular diagonal. If the threading is "reasonable" here's what I am thinking (it's your fault for pursuing this and making this finderscope so interesting!): Say it's M54: https://www.teleskop-express.de/shop/product_info.php/info/p203_TS-Optics-M54x1-to-T2-Adapter-fo-Skywatcher-Crayford-focusers.html (2.5mm) Then this focuser: https://www.teleskop-express.de/shop/product_info.php/info/p4591_TS-Optics-short-T2-Helical-Focuser---Adapter---camera-does-not-twist.html (18mm) Then this T2 to 1.25" adapter: https://www.teleskop-express.de/shop/product_info.php/info/p9743_Baader-2458121-Ultrashort-1-25----T2-Clamp.html (12mm) I would really appreciate it if you could measure it and let me know. As things stand, I have a wonderful Borg 55FL as a finderscope on my FS-128. I wouldn't mind selling the Borg and getting this one to use, and money to spare for further astronomical purchases The quality of the optics is of interest of course and I really look forward to reading your detailed observations later on EDIT: The pitch of the thread is also important

Sigh... very disappointing that SW didn’t make it as a split tube model... Thanks for the photos - puts the whole thing into perspective.

If I am reading you correctly, you removed the extension, installed this and there is still not enough in travel to reach focus with a 1.25” 90 degree Prism?

The point is to remove the extension after the focuser which is quite long and use this one which only eats 12mm...

Possibly removing the extension tube, replacing with the below and using a 1.25” 90 degreee Baader T2 prism or a Tak Prism is the only way to reach focus... https://www.teleskop-express.de/shop/product_info.php/info/p9743_Baader-2458121-Ultrashort-1-25----T2-Clamp.html

I wonder what the threading on the back of the OTA is.. if it’s something “sensible”, possibly a Borg helical focuser could go there and really reduce the length of the finderscope, permitting the use of a diagonal without a Barlow....

Thanks Slomoe, Looks like I will soon pay a visit to a shop that sells fishing gear!

And suddenly it is tempting again!

Was tempted till I saw the M10 connection

Which extension is that by the way? Love the scope - got the same myself

Nice! And where would one find such lovely repurposed filter cases?

Paul, I'd promised Tom Peters of DiscMounts some cameo shots of the mount and well, I went wild with my DSLR

Takahashi FC76DC with 2"FTF and Borg Series 80mm rings, mounted on a Discmount DM-4 and a Sirui R-5214X tripod

Here's my 1.25" kit eyepiece bag. Celestron 40mm Kellner for maximum exit pupil in 1.25" format, a Pan 24mm, 13mm and 7mm Nagler T6 and a Nagler Zoom 3-6mm. The finderscope is a 50mm with interchangeable eyepieces and the finderstalk is the only one in the market available for these type of finderscopes (sold under the Teleskop Service, William Optics and Stellarvue names among many) - a Vixen finderstalk. I wanted to avoid using rings for this. Comes with a 23mm cross hair eyepiece. Also a Baader 1.25" Sital BBHS diagonal (I LOVE the click lock mechanism) and a Celestron Starsense RDF. The top of the camera bag houses an anti-dew heater that runs on a 9V battery (Tech2000 brand) and UHC, O III, Hb, #21, #80A, Tele Vue Planetary Filter, Baader Moon & Skyglow, Baader Solar Continuum and Lumicon Comet Filter, as well as a single prism ADC. Only upgrade left to this kit is getting Lumicon UHC and OIII filters - on the list of things to get in the next month or so. All very compact and easy to carry. On the side of the bag there is a led light torch as well

Photos of the adapter. The SM II 40 has a 52mm thread at the back.

All Beat Kohler would need would be the thread at the back of your filter and the outside diameter of any refractor you will use. I will upload a photo of mine later this evening.

Helen, Do you have a separate Etalon and BF? In that case Beat Kohler of AOK Swiss (also sells Borg scopes) can make any adapter you want. For €59 he made me an adapter for my Coronado SM II 40mm for my Borg 71FL.

Any time you are in Cyprus...

Chris, You are right about the Tak dissassebly. And also about the Tak 60 + 76 module. Kill two birds with one stone and I have heard great things about the small 60mm Taks... Not only that, but you can make the Tak a 76mm binofriendly scope in that configuration... Helen , The main concern would be to protect the lens assembly though, but one can get a plastic dustcap from eBay or Amazon for that. A shower cap would protect the back of the OTA from dust getting in, but you still end up with the OTA @ 19", a focuser and a dew shield to pack, so not very portable considering you want to take other accessories with you...

@ both Chris & Helen, Now for the dilemma!!! I must admit I am at crossroads. Just to explain, when I received the Tak, I found shortly afterwards a very small blem (like 1x1mm) on the coatings. But despite the guarantee, I did not return the scope. Why one might ask? After going through about 20 refractors with apertures ranging 50mm to 152mm, achro, ED and FPL-53 triplets, it was hands down a win for the Tak. Nothing I have touched (including the 20 scopes I mentioned as well as other scopes of friends) has come close to the color fidelity, the superb contrast, the super tight stars, the zero chromatic aberration, the lovely intra and exrtra focal pattern of the scope, the lovely depth of field - well, I could go on forever. BUT (yes, here it comes) it is long. Light, but long. I am considering (and will consider for some time), whether to actually sell it or maybe send the lens assembly to Mark of Moonraker Telescopes and ask him to make me something ultralight with a retractable dew shield and stick a FTF focuser at the back. I could make the Tak binoviewer friendly for example (have Mark make a shorter tube) and use an extension for mono viewing. I don't know really. All I know is that I have no need to sell the scope but I feel a certain pain at not using it.

Helen, These photos are for you. I misaligned the Tak relative to the measuring tape so take off 2 centimeters off its length as measured. There is no size comparison here - the Tak loses big time. The Borg should also ride very well on the Skywatcher Adventurer and I can even reduce its weight further by 100 - 120 grams by removing one of the findershoes and the extra securing screws on the rings. The Borg 71FL produces images like a very good ED scope of focal ratio of say 7 - 8. Considering that it is f5.6, I consider that most satisfactory. The Borg is mostly geared to the AP folk as when you mate it to its dedicated field flattener, it can become a f3.6 flatfield 5 element scope. In Japan it is also widely used for imaging birds e.t.c. The intra-focal pattern indicates no serious abberations, however the extra-focal pattern is a different story. I need to sit down one evening with my Suiter book and decide on the optics, as well as use my Ronchi eyepiece to assess the optics, but offhand, there is virtually zero color on the moon (a very slight yellowish tint at the rim of the moon), stars are nice and tight, contrast is excellent and Mars and Saturn are looking good for the aperture. Lacks depth of field due to short focal length and needs very good eyepieces to tame field curvature. I use Naglers and Pans - anything else and the result is not satisfactory.

Chris, I have 4 observing sites within a 50 minute drive with SQM readings between 21.1 and 21.3 which I try to frequent twice a month, so I consider myself blessed. Paradoxically, I find it more difficult to drag my very tired rear end out the door to observe from my back yard than it is to pack a 12" dobsonian and various accouterments and drive to a dark site