Image of the day

Captured by
Michael Scherman

Jupiter Saturn 2023

My Account

New to Astromart?

Register an account...

Need Help?

Posts Made By: Roland Christen

March 22, 2004 05:21 PM Forum: Astro-Physics

Side by side testing of 2 130 scopes

Posted By Roland Christen

Hi all,

If two scopes of equal sides were tested side by side, one on a driven equatorial mount, and the other on an undriven Alt-az mount, which one would you expect to show more detail on Jupiter? Can you really draw a definite conclusion then on which scope is better?

Roland Christen

April 9, 2004 04:13 PM Forum: Astro-Physics

Re: Pentax orthos for AP130 f6

Posted By Roland Christen

>>I have a couple of Pentax orthos, 7mm & 9mm, that are just stunning in my f8, 4 inch Tak. How do these ep's do in a faster scope like the AP?>>

I have looked through these two eyepieces with an F6, and they do indeed work extremely well - very sharp eyepieces. They are not really short enough for good planetery views (you need about 200X for planetary detail) but they could be barlowed. In that case, they would be working at F12.

Roland Christen

April 14, 2004 04:21 PM Forum: Astro-Physics

Re: First light for a new AP 130 f6; TV 102

Posted By Roland Christen

>>The AP had more false color on Mars, worst near the edge of the field where a violet streak was seen (but not on stars, anywhere). >>

Lateral color (off-axis color) is always caused by the eyepiece. It is not caused by the objective lens. Eyepieces will always show more aberrations off-axis the faster the scope. At F6, the aberrations are 2 times worse than at F8, and 4 times worse than at F10. You will see lateral color even in a Newtonian.

Roland Christen

May 6, 2004 09:18 PM Forum: Astro-Physics

Re: gripping an SPL

Posted By Roland Christen

The bottom of the edge is where the focal point is, the top is where the lens ends. As the focal length of the lens gets shorter, the distance gets shorter also. Longer focus eyepieces have longer top barrels. Unfortunately, this is the result of making all eyepieces parfocal. If we extended the upper barrels and made then longer, we would lose some in-focus. This becomes a problem with binoviewers where little or no in-focus is left. The only other solution is to make them non-parfocal, in which case all the upper barrels can be the same length. I suppose we could add some grooves, but for the really short ones there would be no room left for the lettering. Any other ideas?

Roland Christen

May 28, 2004 01:50 AM Forum: Astro-Physics

Comet Neat image

Posted By Roland Christen

I just posted an image in the CCD astrophoto section of comet Neat if anyone is interested.

It is an image of the core of the comet taken last night with the first quarter Moon unfortunately washing out the background sky. The image was taken with my 10" F14.6 mak-Cass operating at F10 with SBIG ST10XE camera and color filter wheel. I was trying to capture any jet detail coming out of the core. You can see a sunward jet which then turns to the right and gets swept toward the back. Also, there is a distinct bow shock visible.

Roland Christen

June 9, 2004 02:03 PM Forum: Astro-Physics

Re: Focuser Removal

Posted By Roland Christen

There were several versions. Do you have a picture?

Roland Christen

July 1, 2004 12:59 AM Forum: CCD Imaging and Processing/Solar System

Pelican Nebula with ST10E

Posted By Roland Christen

Pelican Nebula taken with a cooled CCD camera (ST10E) and AP 105 Traveler telescope
(Consumer cameras have a ways to go yet)


July 13, 2004 08:29 PM Forum: CCD Imaging and Processing/Solar System

Trifid from Vicuna, Chile

Posted By Roland Christen

Hi all,

This image was taken by Stefan Seip from his trip last year to Chile, where he was guest of Daniel Verschatse at his new amateur Astronomy Inn. Stefan sent me the raw files taken with his ST2000 camera and 155EDF refractor to have me do some image processing for him. I finally got around to finishing it, and here is the result.


Data for the picture:
Object: M 20
Name: Trifid Nebula in Sagittarius
Date + Time: Sep 2, 2003 / 2:00 - 6:10 UT
Location: Vicuña, Chile
Optics: Astro-Physics 155mm f/7
Camera: SBIG ST-2000XM with CFW-8A
Exposure Time(s): L: 5x 15 minutes (1x1 binning), RGB: 9x 5 minutes (2x2
binning) each color
Mount: Astro-Physics 900 GTO
Guiding: Self-guiding
Made by: Stefan Seip

July 29, 2004 06:47 PM Forum: Astro-Physics

SPL eyepieces now in production

Posted By Roland Christen

Hi All,

Sorry to take you away from your 10" Mak soap opera, but I wanted everyone to know that The first production run of SPL eyepieces is in production. I have just finished assembling the 12mm versions and now working on the 10mm (working my way down).

After finishing the first batch, I could not resist doing the infamous "sidewalk test". I compared the contrast and back scatter of the 12mm SPL against my pristine 16mm Zeiss Abbe Ortho, a 17mm premium Plossl and a 19mm premium Widefield ocular (see attached image).

For those who don't know this test, it is a way to compare the relative contrast of two or more eyepieces. The test was first suggested to me by the owner of our coating lab to gauge the effectiveness of anti-reflection coatings on an eyepiece. The idea is to place the test eyepiece on the ground on a blue-sky day so that the light from the sky illuminates the optics from the eye end. Any light that bounces around inside and comes back up out of the eye end is an indication of the internal reflections and scatter at the various surfaces. The brighter the eye end of the eyepiece looks, the more reflection and scatter it has.

I'm happy to say that the new SPL oculars are as contrasty and free of scattered light as my pristine Zeiss Abbe Orthos. Note also the size of the eye lens, which is an indication of the eye relief (typically the bigger the lens the longer the eye relief is). Note that the 12mm SPL has almost the same size eye lens as the 16 Ortho, and nearly that of the 17 Plossl. The eye relief of the 12mm is very nearly the same as these oculars.

Roland Christen

August 24, 2004 07:37 PM Forum: Astro-Physics


Posted By Roland Christen

Thanks for your thoughts and suggestions.

Roland Christen