Re: [APML] 9mm or 12mm guiding eyepiece

[Matt BenDaniel <matt@starmatt.com>]

Woolies Woolies wrote:

> Dear Matt,
>
> Thank you for all your information.
> My telescope is an 8" f/5 F1000mm Newtonian.

I don't image with a Newtonian. I think the way that primary/secondary/focusers
are configured, some do not have enough back focus for an OAG. You should
determine your back focus before you make a decision. I am still partial to the
guide scope option. With a diagonal for the guide scope and an adjustable height
chair, you should be in business manually guiding.

> It has a steady EQ mount with
> dual axis motor drive with Hand Controller.
> I have read "Astrophotography for the Amateur" by Covington, I have the
> book.
> How am I suppose to do much piggy back when I do not have a guiding
> eyepiece....yet!

Even without a guide scope you can accurately drift align. This should allow for
piggybacking up to 200mm. (But I don't want to be hypocritical, since I
autoguide my wide field shots.)

> If I get a guidescope I will mount it on the top of my telescope with
> guidescope rings. My both tube rings have the ability to add a guidescope.

As with anything astrographic, you should make sure that the guide scope
mounting has no flexure.

> My question here is for the guiding eyepiece. Should I go for the 9mm with
> double crossline and two concentric circles or the 12mm with double
> crossline and without the concentric circles. What are the
> concentric circles for? When do you use them?

I prefer a plain crosshair. When I drift align, I get the RA line to bisect the
star. For manual guiding you can get the cross hair to bisect the star on both
axes.
--
Matt BenDaniel
http://starmatt.com



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