SCT image shift/focus

[Lester]

Hi all,

I have just begun to use my Meade SCT 14" with 2x barlow and Neximage to capture Planets. When focussing the image moves out of FOV from one side to the other as I move the focus back and forth to obtain a good focus. From what I have experienced it is worse in the larger SCT's.

Is there a focuser on the market that will fit straight onto the rear of SCT? I plan to do the course focus with existing focuser and fine adjustments with the add on focuser, so then there would be no mirror shift.

Anyone with ideas will be much appreciated.:thumbsup:

[matt]

There are plenty of options available to you Lester.

JMI, MoonLite and Starlight Instruments all make manual and electronic crayford SCT motor focusers.

There are others.

[Lester]

Thanks Matt,

I will do a bit of searching on the web. :thumbsup:

[Dennis]

Hi Lester

On my Celestron C9.25 I use the JMI NGF-CM motorised focuser. The JMI website is here:
http://www.jimsmobile.com/index.htm

Do a Product search for NGF and look for the SCT models.

I first focus using the Celestron standard focus knob and this does shift the image, although only within the central 2/3 of my field of view, with x2.5 barlow and ToUcam.

Next, I lock the Hutech SCT focus lock which can be seen here:
http://www.sciencecenter.net/hutech/misc/focuslk/index.htm

Then, I use the crayford focuser function of the JMI to get manually better focus. Then, I lock the JMI crayford focuser movement so control is passed from the manual knobs over to the built-in motor. Finally, using the battery operated motor control keys on the hand paddle, I achieve critical focus.

IMO, it is the only was to rapidly, reliably and easily achieve critical focus when imaging at these long focal lengths.

You can purchase quite expensive software controlled focusers that monitor focus through a software program and automatically make adjustments for e.g. temperature fluctuations which can change focus due to key metal parts expanding/contracting.

Cheers

Dennis

[[1ponders]]

Meade also make one Lester. But like Dennis I use the JMI

[Striker]

I just ordered one of these for my Meade 10" sct...dont know why will probably never use it but what the hell.

http://www.optcorp.com/product.aspx?pid=105-175-177-8157

[matt]

I know why Striker. Coz it's shiny... pretty... and nice:lol:

[asimov]

I'll just write that down in my lil' black book....."striker to donate this item to next newbie imaging comp"

Thanks..:thumbsup:

[Lester]

Thanks a heap, just been looking at Crayford focusers looks like Bintel is the cheapest.

You chaps are the best when it comes to finding information. :thumbsup:

[Rodstar]

Lester, I recommend the Williams Optics Manual Crayford Focuser for SCT.

It is available through Frontier Optics. Is the best $310 I ever did spend!

[Lester]

Thanks Rod, I will look into it.

[Rodstar]

Actually, I just looked at Striker's link...that is exactly what I am talking about. You can get it in several colours now. Mine is a beautiful shiney black ,with silver attachments.....Yum.

[Lester]

Hi everyone,

Almost bourght a crayford focuser.

But first I adapted my old 2" rack and pinion from the dismantled 16" newtonian. Glued a thread from a T-mount to its base with araldite. Okay its not electronic or perfect but it cost $14.00 for the glue and when I focus image only moves 1/8 F.O.V.