Crayford vs Double Helical focuser for SCT?

[Dyno05]

Hi,
I was thinking about getting a dual speed Crayford focuser to use on my SCTs so the mirrors won’t have to move much. Especially my 9.25 which exhibits some image shift when I focus. As I was browsing focusers, I came across a double helical focuser with an SCT adaptor and I thought that it may be a good option for a few reasons, it’s much smaller, lighter, can screw a dslr T ring directly to it and the price is considerably cheaper than the Crayford . Is there any reason why a double helical focuser would be a poor decision for this? It would have to be able to to be able to hold A dslr camera. This is a link to what I was looking at.

https://www.ebay.com/itm/193588508611

[Lady Fraktor]

If you can get away with 10mm of focuser travel, helicals can be quite precise for focusing.
Do the measurements work out for you for proper spacing?

[yobbo89]

i actualy don't know what a high quality helix focuser feels like, i assume it rotates your gear as you turn it,unless higher quality ones don't then i would assume this be a bit of a problem when imaging . i use a gso crayford,i love it over my stock mirror focuser. do you plan to install a electric focuser ontop in the future aswell ?

cons, helix focuser dosn't seem to have an option to add and electric focuser addon ,
pro its shorter, should focuse reasonably, it's shorter so you don't need to shift the primary up ''this increasing the magnification''

cons for a crayford , usualy longer overall and need to shift the primary up thus increasing the magnification
pro, fine focusing over a larger distance,can use an electric focuser addon .

there are ways to reduce backlash in a sct setup aswell as flop , you'll need to pull the scope appart and the the mirror focuser.

[Dyno05]

If you can get away with 10mm of focuser travel, helicals can be quite precise for focusing.
Do the measurements work out for you for proper spacing?

You don’t need to worry about proper spacing with an SCT like you do with a refractor because the mirror moves. You can rough focus with original focuser and fine focus with helical. I have a helical focuser on my guide scope and it’s quite smooth.

[Dyno05]

i actualy don't know what a high quality helix focuser feels like, i assume it rotates your gear as you turn it,unless higher quality ones don't then i would assume this be a bit of a problem when imaging . i use a gso crayford,i love it over my stock mirror focuser. do you plan to install a electric focuser ontop in the future aswell ?

cons, helix focuser dosn't seem to have an option to add and electric focuser addon ,
pro its shorter, should focuse reasonably, it's shorter so you don't need to shift the primary up ''this increasing the magnification''

cons for a crayford , usualy longer overall and need to shift the primary up thus increasing the magnification
pro, fine focusing over a larger distance,can use an electric focuser addon .

there are ways to reduce backlash in a sct setup aswell as flop , you'll need to pull the scope appart and the the mirror focuser.

Thank you for your input. High quality helical focusers don’t rotate your camera when adjusting. I have one on my guide scope and it’s quite smooth.
I don’t really see the need for an electronic focuser. Using a sturdy mount I have no trouble achieving a sharp focus, however on an SE mount it shakes like crazy and an electronic focuser would be great. I was thinking about the GSO linear bearing Crayford focuser but it’s 170 dollars vs 40 bucks for the double helical and they seem to both be able to do what I want.
I’m well versed in taking apart my scopes and adjusting things. I have not taken apart the focuser in my 9.25 yet though to see what’s going on. My Meade Mak had EXTREME image shift. I was able to make it much better by shimming the focuser.