What focuser for 10" LX200R

Striker (Tony) · #1 04-10-2006, 06:18 PM

OK Guys I need guidance.

I want to put atleast a 2.7" or even 3" focuser on the back of the 10" LX200R...I need to get rid of that small visual back of 1.5".

Does feathertouch make a larger focuser for a SCT.....I cant find one on their website or even an email I can ask the question.

JMI have a 3" that screws directly into the SCT.

Your help is really appreciated.

[1ponders] (Paul) · #2 04-10-2006, 07:10 PM

The only place to look Tony

http://www.observatory.org/index.htm

beren · #3 04-10-2006, 08:09 PM

Tony I have the moonlite SCT focuser with the large 3 inch meade thread

http://www.focuser.com/cgi-bin/dman....cgi&category=3

Striker (Tony) · #4 04-10-2006, 08:14 PM

Thanks Stuart,

I like the moonlite but it looks only to come in 2" size.

Paul there is heaps of focuser's on that site that look more like robots then focuser.

[1ponders] (Paul) · #5 04-10-2006, 09:18 PM

Yep and lots of them are bigger than 3" too.

beren · #6 04-10-2006, 10:10 PM

Sorry Tony misread your question ....maybe Ron Newman from moonlite could help you with something custom , that Van Slyke gear is priccy

Striker (Tony) · #7 05-10-2006, 06:31 AM

Thanks Stuart,

It may come down to 2" focuser anyway due to the baffles in the sct.

Either way I need to open up the visual back and as you said the moonlite does this.

Merlin66 (Ken) · #8 05-10-2006, 09:51 AM

The internal baffles I think will realistically limit you to a 2" focusser.
I've got the #1906 Zero shift crayford on mine and have adapted the controls to allow the electric drive of the standard knob for rough focus and then switch to the zero shift for fine.

gbeal · #9 05-10-2006, 10:50 AM

Feather Touch. I have two of them, nothing short of amazing.

jase (Jason) · #10 06-10-2006, 02:53 PM

Hi Tony,
Interesting point of view. Firstly, I would recommend measuring the rear cell opening. A 3" focuser could possibly reduce vignetting, but also maybe over kill if the internal baffle opening is only 2" or 2.5" in diameter. I use an eyeopener 2" visual back and a JMI 2" focuser modified with a Robofocus stepper motor. Manual or computer controlled - it works a treat. Simply unless you intend to use a medium format film (6x4) I doubt you'd need something over 2". Even the SBIG STL11k large format CCD camera that has an equivalent frame size of a 35mm camera only uses a 2" nose peice.
Perhaps more importantly, is not the diameter, but the length of the focuser. SCT's have generous back focus, but not all telescopes do. If you imaging train i.e focal reducers, focuser, color filter wheel, camera is too long, i.e move far from the native (most optimal) position you may hit other issues. Just some food for thought.

Striker (Tony) · #11 06-10-2006, 03:27 PM

Thanks Jase for your comments.

I am leaning towards the 2" Feathertouch SCT model with the new Motorised feathertouch system.
http://www.starlightinstruments.com/

I do think there will be some benifit to a larger focuser but the downfall is cost plus parts to suit and most importanatly weight..there very heavy...The STL11000 is already going to add some weight to my system.

jase (Jason) · #12 06-10-2006, 03:37 PM

Weight can always be a problem, especially on a GEM. If you've got a dovetail plate on top of the OTA you can install some weights to get better balance.
If you're really serious about imaging, I would make sure the focuser can be computer controlled (for obvious reasons). In relation to the motor, ensure it is a stepper. Servos and low voltage motors don't provide enough accuracy. When I order the JMI with their motofocus, I quickly guttered it and order a Robofocus. Now I get 0.0005" steps which is nice and tight. Not to mention the Robofocus has temperature compensation. Nice feature. I wouldn't rush the decision as a good focuser can save you a lot of time. More time to gather photons.

jase (Jason) · #13 06-10-2006, 03:44 PM

Sorry, just read the link you provide. Looks like you'll be set with the stepper/computer controlled/and bonus temp compensated. Go for it. Certainly a cheaper alternative in doing what I did. The Robo focus cost me $560 to land in AU alone. I can't remember what the JMI focus cost wasn't too cheap, but ok.
There is a lot of noise regarding TCF by Optinc - http://www.optecinc.com/optec.htm You may also want to check them out.

beren · #14 07-10-2006, 03:38 PM

looks interesting http://www.clementfocuser.com/

Striker (Tony) · #15 07-10-2006, 05:00 PM

There one ugly focuser arn't they Stuart,

I had a look at this focuser a few days ago and yes it's an option.

At the moment I am leaning towards the Feathertouch but only in 2" as they dont do a 3".

Still deciding

Thanks.

beren · #16 07-10-2006, 05:18 PM

Looks count Tony

ausastronomer (John Bambury) · #17 09-10-2006, 12:02 AM

Quote:

Originally Posted by beren

that Van Slyke gear is priccy

Beren,

Use one once and you will know why it's pricey. They are an absolute engineering masterpiece and clearly the best focusers money can buy.

CS-John B