Looking at possibly adding one of these to my rig. Do they achieve better focus when doing astrophotography or do they just make the process easier? I'm referring to mid range kits such as this http://www.robofocus.com/products.htm.
Around US$500 seems an awful lot of money when you can buy the Oz$99 SkyWatcher device that does the same thing.
I fitted one to my TSA120 and it has worked perfectly for some six months now. Very smooth movement but a little slow when racking inwards with a heavy eyepeice but that's no bad thing really. It is battery powered but they have lasted the six month so far.
Try it, it's only a hundred, before you commit to 5/6 times the price.
Mamba
I have one on the ED80 for solar Ha / viewing imaging, one with a belt drive (easy to fit) on the TS102 for solar white light/ PST mod and another belt drive one on the Spectroheliograph.
Makes shakeless, tight, focusing much, much easier.
Likewise, the SWEL motorfocus has worked well for me.
The robofocus can talk to a computer to autofocus. The SW at 1/4 the price is just a remote controlled motorized focuser with variable speed.
I can run my Vixen R&P focuser all the way out and back in again in what seems to be about a minute or so. I haven't timed it. Most of my eyepieces are pretty close to parfocal so I don't have to change the focus by a long distance.
I can also set it to very slow and fine focus using magnified (16x) live view. It's designed for the Skywatcher focusers but comes with a few attachment bits that allow adaption to various focusers such as M Vixen VC200L focuser.
Battery is a 9V transistor. I use the motor focus a lot and I get long battery life. But I always keep a spare battery in my eyepiece case.
If you want a camera control program like Maxim to focus for you and refocus during the imaging run, then the robofocus might be the way to go. Otherwise, the SWEL works well.
The robofocus can talk to a computer to autofocus. The SW at 1/4 the price is just a remote controlled motorized focuser with variable speed.
If you want a camera control program like Maxim to focus for you and refocus during the imaging run, then the robofocus might be the way to go. Otherwise, the SWEL works well.
This is exactly what I'm working towards once I get a grip for things. Maybe for now I might just try something like the SW to simplify things. What I would really like to know is whether these focusers help achieve better focus for astrophotography. I don't mind using the digits for visual observing.
Last edited by LostInSp_ce; 16-03-2017 at 12:43 AM.
The SW focuser (or any electric focuser) just makes life so much easier, you can look at the laptop screen with a zoomed in star and get the best FHWM figure. You could never achieve this turning the focuser knob manually unless you had your laptop right next to the scope.
Plus the critical focus zone for astro-photography is determined by the formula
CFZ = pix size (microns) x Focal ratio ( e.g 5 micron pixels and F5 scope is 25 microns), your fingers would never get that accuracy turning the knob.
P.S. I ditched the 9V battery in mine and run it off a 12V power pack.
The SW focuser (or any electric focuser) just makes life so much easier, you can look at the laptop screen with a zoomed in star and get the best FHWM figure.
That's what I've been doing now manually, but of course with this approach you get vibrations and movement as you make adjustments. This can of course make it tricky to get the best possible FHWM value. The best that I'm able to achieve is between 5-7 FHWM (but will usually average between 9-12) when zoomed in at 10x using APT's focus tool. At actual pixels It's about 2-3 FHWM. Which seems to look OK to me when I take pics.
This is exactly what I'm working towards once I get a grip for things. Maybe for now I might just try something like the SW to simplify things. What I would really like to know is whether these focusers help achieve better focus for astrophotography. I don't mind using the digits for visual observing.
As Ken pointed out with the addition of the Shoestring usb focus controller your astronomy camera control programs can run the Sky Watcher Electric focuser through the ASCOM.
If you are new to this, ASCOM is an astronomy equipment communications protocol. programs and hardware that are ascom compliant can interface with each other. You need to be running a windows PC to do this.
Any time you are doing straight visual observing, just plug in the Sky Watcher hand box and leave the computer behind.
I honestly don't think I could focus accurately enough (well I know I can't!) by hand to obtain best solar imaging....and being able to achieve it from a distance certainly makes things easier.
I put the SW on one of my scopes and to answer the specific question:
Yes these things help you achieve better focus for astrophotography
Not necessarily precise focusing as they do seem to use stepper motors so if precise lies at 1/3 step you wont reach it, thats not to say you'll be out of focus and you'll be far far better focused than you can get by hand on most scopes, especially if they have only their standard focuser.
The SW unit is dead easy to install and i only used it with its handset and was happy with that. Biggest problem is seeing. I would get focus and the seeing would change ,chase focus again and it changes again. Took me a while to just get focus and leave it knowing the seeing will probably come back. Fiddling on the fly only ruined my capture sets
Sil,
I think the SW motor is just a DC motor...the accuracy (in my case) comes from the short DC pulses issued by the shoestring controller (FCusb) and their free FocusPal software. http://www.store.shoestringastronomy...roducts_fc.htm
Either way you go it beats focusing the old fashioned way and you'll kick yourself for bothering to ask. tbh i'm not sure if mine is the sw or a clone, it was a cheapie anyway. the hand controller may be why I was thinking its using a stepper motor, could just be the way the controller signals. but like I said it gets you 99.99% perfect focus. My handset box connectgs to the focuser with a spiral phone cord and you can safely unclip it from the focuseronce youve focused if you want one less cable to trouble you in the dark or get tangled on the tripod in a long session.
You dont need to grab the shoestring too right away, get the focuser, attached and working, it will do the job well then look into the shoestring and software side and add it later on when you're comfortable. I dont know if the combo offers practical benefits over the original product you were looking at besides price. Its not like the difference between cheap optics and expensive.
