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Posts Made By: Bob Chester

January 14, 2006 06:13 PM Forum: Eyepieces

Longest FL and Widest FOV in a 1.25" ep?

Posted By Bob Chester

A 32mm plössl with a 50º afov will give the widest fov in a 1-1/4" ep.
A 24mm Panoptic at 68º afov gives the same fov.
A 20mm 80º afov ep would give very nearly the same fov but I don't know if such an ep exists in a 1-1/4" format.
Hope this helps,

January 17, 2006 10:07 PM Forum: Takahashi

Takahashi Micro focuser

Posted By Bob Chester


I am sitting in the same boat as you, though the funds have not materialized yet. Before you abandon the Starlight option, maybe we can approach it from another direction. Starlight does make a unit for the Sky 90. The Sky 90 and FS78 share the same tube diam., camera angle adjuster, and focal reducer. I thought they shared the same focuser also but I'm not 100% sure.

Sooo...the question is: (hey Art...we need ya)
Do the Sky 90 and FS78 share the same focuser and is there any reason to think the Starlight option made for the 90 would not work with the 78?


February 3, 2006 05:35 PM Forum: CCD Imaging and Processing/Solar System

Wanna see 10/10 seeing (link fixed)

Posted By Bob Chester

I get a "url not found" message. Is that the correct address?

April 11, 2006 07:28 PM Forum: Telescope Making

2 refractor OTA's side by side with 2 diagonals??

Posted By Bob Chester

Same, as others have stated.
Adjusting the interpupilary distance is the trick.
Here is a site you might enjoy and they are an ASTOMART sponsor.


April 16, 2006 12:43 AM Forum: Beginning Astronomy?

How old are you???

Posted By Bob Chester

I'll add to the peak in John's graph.

I hit 52 last week.

Wanted a scope since the early 60s. Finally finished my first mirror in 89'.

I'm just a recreational user but hope to be an addict when I grow up.


May 3, 2006 09:03 PM Forum: Eyepieces

Barlow before diagonal?

Posted By Bob Chester

Yes, I have done it. Works O.K.. A nuisance in my scope though.

If the scope can be used in straight through mode (no diag.) you should have no problem with focus travel. The scope will focus as if no diag. were there. If you need extensions for straight through viewing it becomes a pain.


fwiw: Here is a link to the barlow/distance/mag. calculation.

May 3, 2006 11:02 PM Forum: Telescope Making

Size of Illuminated Circle

Posted By Bob Chester

The freeware program 'NEWT' will calculate that for you under -view-performance specs.

Hope it helps,

May 10, 2006 06:22 PM Forum: Telescope Making

Linking two diagonals- path shortening?

Posted By Bob Chester

Not sure if this is what you mean but here is a link to the EMS units used by Binoscope Co. in their units. Looks to me like 2 diags connected together.

The link can also be reached through the Binoscope Companys' web site.

May 17, 2006 06:32 PM Forum: Refractors

What I'm seeing thru a 100mm ed

Posted By Bob Chester

I've read through most of the replies to your post and don't recall anyone suggesting to stop down the aperture. If the problem is not the EPs then you could have a bad edge or SA. Try masking the objective down to 80mm or so and see if the problem persists. Here are a couple helpful star test links.

Does the turned down edge image (1st link) depict what you are seeing?


May 20, 2006 02:09 PM Forum: Eyepieces

Collecting eyepiece data

Posted By Bob Chester

Here are a couple of links to get you started. The first is the Tele-Vue eyepiece spec sheet. I wish all makers would publish this data. It will give you an idea or the sort of data you may want.
The second is the Tele-Vue eyepiece calculator and calculates the performace for every current Tele-Vue eyepiece for your instrument. I have print-outs of the calculator results for each of my scopes.

Hope it helps,