From: Ray Byrne <ray@in4media.co.uk>

Date: April 4, 2012 4:25:47 AM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Re: Mars APril 2 2012 (sort of)

Hi Milton,

Thanks for the info. A question - does the barlow element increase its magnification by being further from the focal plane of the telescope or further from the camera chip?

TIA

Ray

On 3 Apr 2012, at 21:51, Milton Aupperle wrote:

Hi Ray;

On 3-Apr-12, at 11:05 AM, Ray Byrne wrote:

>
>
> Hi Milton,
>
> Tell me about it it's raining here with possible snow forecast, last
> week I was sun bathing in my shorts! (not underpants I hasten to add
> I don't know what you call them).
>
> I need a 3x barlow/amplifier with SCT threads on both sides
> Takahashi only do the 2x one.

I had never heard of an SCT threaded barlow before. You learn
something new every day.

I wonder if SiebertOptics :

http://www.siebertoptics.com/SiebertOptics-barlows.html

has anything like that as they do a lot of oddball reducer / barlow
products.

> I used to use a manual filter wheel but was cheap and caused a lot
> of flexure and I used to get lost on what filter I was on with it.
> The Trutek filter wheel is powered and my imaging system is solid as
> a rock I just need to work out a way to get a bigger image scale,
> perhaps extension tubes would work?

That might work.

With a normal barlow, the further back you are the greater the
magnification. I have an 2x conventional barlow, which when used with
some extension tubes was delivering 3.5x.

With the Televue PowerMates, that makes far less difference and in
some cases no difference. My Televue 2.5X makes very little
magification difference in what the spacing is - other than to change
focus point.

HTH..

Milton Aupperle