Questions about high-end focusers and their various benefits.

[pipnina]

Recent discussions about the repeatability and collimation of my scope have suggested that I likely suffer from my focuser not being tough enough to support the weight of my bulky mono imaging train. Seems rather cut and dry that something like a Baader ST (or other, I don't know of any alternatives to that esteemed unit) would be a big boon to my setup.

However I am also curious if mere payload capacity and low/no backlash are the only benefits. I noticed when moving from my 130P-DS to my PHOTON 8" F4, that the compression ring fittings held objects much firmer and truer than the simple bolts driven into the CC/Eyepiece. I am wondering if high end focusers improve on that again, and hold objects not just tightly and without damage, but also very repeatably.

For example, part of my issue with the collimation is that my laser itself is not perfectly collimated, and being the Baader Mk3 I cannot collimate it myself. So I must rotate the collimator or the thing holding it (that seems to be the best option) to work out the center of the circle. But if my focuser isn't QUITE holding it exactly the same every time, I have yet another error bar to contend with! Do these high end focusers help in that regard too?

Also curious how easy/hard people have found it to widen the hole for their focuser barrel when going from 50mm to 55, or even 75mm diameter sizes. Sheet metal like that isn't always easy to cut clean and could release pent up tension.

Also keen to learn if alternative high-end focusers (maybe in the 3" size) are well known like the Baader ST?

Cheers!

[markse68]

I would steer well clear of Baader. But then I have a prejudice against them now as they were very unhelpful and quite rude when I was asking them about their v.expensive amici prism. They do make some nice things though and I never felt a ST focuser so can't comment on that. But I did get lucky and now have a Feathertouch focuser and find it hard to imagine there being any nicer focuser ever made- they are quite exquisite, but you pay for things like that very highly indeed. For holding things like eyepieces and lasers in the focuser the Glatter Paralizer (also made by Starlight instruments in America) is a very good device- it doesn't guarantee concentricity but no adapter does, but it does guarantee much better than most parallel optical axis to the focuser.

For sheet metal hole enlargement you could use a fine toothed file or a dremel with a sanding drum?

Mark

Edited July 18, 2022 by markse68

[Adreneline]

I have a BDST fitted to my 6” RC and I can’t fault it; it also has a built in tilt adjustment. The Baader has allowed me to achieve near perfect collimation.

I also had one on my ED80DS before I sold it and it transformed the OTA for imaging purposes.

I also use a Baader Click-Lock which I consider to be one of the best things I’ve ever bought. 

Edited July 18, 2022 by Adreneline

[Clarkey]

I have 2 Baader ST's, one on my 6" f4 Newtonian and one on my RC8. I found them to be excellent for imaging.

With regards to the scope collimation, the f4 is a right PITA to collimate. I share your pain. However it is much better with a good focuser - the original TS one was pretty awful. Maybe avoid the laser if you are struggling with it?

[ONIKKINEN]

I very much like my BDS and it made many things much easier when fitted. Not perfect in how fluid the mechanics are down to -25c but i doubt anything is. The important part is that it doesnt move on its own and the friction knob doesnt cause the drawtube to move when used.

I have an aluminium tube so just used a simple round file to shave off a few millimeters to make it fit. If i had a steel tube i would probably not bother manually filing but use a rotating sandpaper roll-thingy (dont know the name of that) on a drill to do the trick.

[garryblueboy]

Have owned a couple of Steel Tracks and can’t fault them great build quality and quite a bit cheaper than some I could mention 

[Dan_Paris]

On 18/07/2022 at 22:37, pipnina said:

Also keen to learn if alternative high-end focusers (maybe in the 3" size) are well known like the Baader ST?

I am not sure it qualifies as "high end" however I am using this one on my Newtonian and it works very well: no flex, no slippage (of course as it is R&P), extremely low image shift and many threaded connections possible:

https://www.teleskop-express.de/shop/product_info.php/info/p5995_TS-Optics-3-Inch-Rack-and-Pinion-Focuser-for-heavy-equipment---M117-connection-thread.html

You'd need a custom-made adapter plate to mount it on a newt (this is what I did). Recently Teleskop service added  a version with a newt adapter plate but price is much too high

https://www.teleskop-express.de/shop/product_info.php/info/p14733_TS-Optics-3--rack-and-pinion-focuser-for-Newtonian-telescopes---carries-up-to-6-kg.html

 

Whatever you choose, if the focuser allows a threaded connection to the imaging train it is much better.

 

 

Edited July 20, 2022 by Dan_Paris