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Focuser advice

  • albertw
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Focuser advice was created by albertw

Hi folks,

I'm wondering if someone can give me a little focuser advice.

I've a CPC9.25 which I currently get rough focus with the focus knob and then finetune with a borg helical focuser. That gives me some problems though with vibration with a planetary camera and vignetting when used with the DSLR & focal reducer.

So I'd like to get a better focuser. Ideally motorised to avoid touching anything and in future I could manage it through software. Also a focuser on the rear cell rather than changing the focus knob as at some point mirror shift may be a problem in future (it's not a problem with my current level of expertise!)

Money as usual is quite a big consideration here :) The main products seem to be from JMI, Moonlite and feathertouch. From reading up on cloudynights it seems that there isn't a lot in them; moonlite and feathertouch seem to edge it slightly but those with JMI focusers seem very happy with them. I've a JMI motor on my SN10 rack and pinion focuser for years and it's worked well and never gave any trouble, and JMI are a little more economical.

So looking at the JMI range of crayford focusers for SCT rear cells:

* EV-3 motorised is $359.00. That ticks the motorised box but does not have dual speed.
* The EV-1, which is dual speed, non-motorised version of the EV-1 comes in at $349. (The motorised ev-1 is really out of budget!)

So what I'd appreciate advice on is whether I'd be better going with the dual speed option and manually focusing with the finer ratio, or whether having the single speed motorised would be sufficient/equivalent to get a fine focus?

If there are any other options out there that you think would be worth looking at I'd also be interested in hearing about them.

Thanks
Albert White MSc FRAS
Chairperson, International Dark Sky Association - Irish Section
www.darksky.ie/
Last edit: 8 years 11 months ago by albertw. Reason: proofreading...
8 years 11 months ago #97848

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Replied by albertw on topic Re: Focuser advice

So to somewhat answer my own question... :)

The motors on the JMI focusers attach to all units the same. i.e. they do not attach to the fine focus on the ev1.

You'd get the ev1 if you wanted fine manual focus and the additional lifting capability (~3kg).
The ev2 is if you don't want manual fine focus but want the additional lifting capacity.
the ev3 is if you don't want manual fine focus and don't have more than 1.5kg of gear hanging off of it.
All can be motorised and that works the same way for all units.
Albert White MSc FRAS
Chairperson, International Dark Sky Association - Irish Section
www.darksky.ie/
8 years 11 months ago #97867

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Replied by dave_lillis on topic Re: Focuser advice

Hi Al,
I have an EV1 on my 20" dob, it's the dual speed type with no motor.
Having a motor in my situation is not an advantage as I don't do deep sky imaging with it.
It can handle (weight wise) any eyepiece I throw at it, but I do find that most of the time I do not use the finer ratio on the focuser, except when using the highest powers the scope can do.

I would only bother with the motorized focuser if I had a pc and was using it to automatically focus for imaging, I have found in the past that it can be very difficult to use a motorised focuser to manually focus (meade micro focuser) as it doesn't have the same feel feedback as you would get by turning a dial. It might be easier if you used a motorised focuser with a bahtinov mask though.
Dave L. on facebook , See my images in flickr
Chairman. Shannonside Astronomy Club (Limerick)

Carrying around my 20" obsession is going to kill me,
but what a way to go. :)
+ 12"LX200, MK67, Meade2045, 4"refractor
Last edit: 8 years 11 months ago by dave_lillis.
8 years 11 months ago #97868

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  • michaeloconnell
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Replied by michaeloconnell on topic Re: Focuser advice

Al,
When I had the LX90, I ended up buying the Borg non-rotating helical focuser (1.25").
It's very good.
Part nos. 7315 (focuser) + 7316 (1.25" adaptor).
Are you still on for meeting up the weekend of Solarfest - gotta pay you for those binomites!
I can bring along the Borg unit. You can take it home and try it out for a while if you want.
Michael.
8 years 11 months ago #97869

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Replied by albertw on topic Re: Focuser advice

Al,
When I had the LX90, I ended up buying the Borg non-rotating helical focuser (1.25").
It's very good.
Part nos. 7315 (focuser) + 7316 (1.25" adaptor).
Are you still on for meeting up the weekend of Solarfest - gotta pay you for those binomites!
I can bring along the Borg unit. You can take it home and try it out for a while if you want.
Michael.


Not going to be able to make Solarfest due to work commitments Michael. I'll work something out with you though.

I have that Borg combination that I got on your advice before. It's great but for trying f20 and above on planets even the slight movement from turning the focuser makes getting accurate focus hard, perhaps I just don't have a delicate enough touch!; and with the dslr when using the focal reducer the camera ends up a little too far from the reducer. Visually and with the dslr without the reducer it is great though.

Automatic focusing is out of budget for me Dave, unless there is a fairly straightforward way to hack together a setup for it . I'd be using this in conjunction with a laptop though, so probably have the motor control mounted on the desk and judge focus from a mask or fwhm.

Thanks
Albert White MSc FRAS
Chairperson, International Dark Sky Association - Irish Section
www.darksky.ie/
8 years 11 months ago #97873

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Replied by dave_lillis on topic Re: Focuser advice

yea, that would work.
One more thing to note is that minimal force is needed for manually turning the focus dial, this really helps when trying to prevent vibration when focusing.
Also,the focus lock is A1, no way is it going to slide, even if you manage to turn the focus dial.
Dave L. on facebook , See my images in flickr
Chairman. Shannonside Astronomy Club (Limerick)

Carrying around my 20" obsession is going to kill me,
but what a way to go. :)
+ 12"LX200, MK67, Meade2045, 4"refractor
8 years 11 months ago #97875

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