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Posts Made By: Mike Gibson

June 14, 2003 05:15 PM Forum: Equipment Talk

Focusers

Posted By Mike Gibson
Yes, Meade specializes in high profile focusers! wink

But seriously, a low profile focuser is a physically shorter mechanical aid to position the eyepiece at the focal plane. Since the eyepiece will be closer to the secondary mirror, the secondary mirror can be downsized for a smaller central obstruction (CO). For instance, a f/10 planetary Newtonian might use a low profile focuser to minmize CO size.

Many helical focusers are low profile by design, but a Crayford can be short too. Prime focus photography may be possible with a low profile focuser replacement for a "taller" rack and pinion unit.

See Dave Keller's excellent Newt software application for design considerations, including focuser profile:

http://home.att.net/~dale.keller/atm/newtonians/newtsoft/newtsoft.htm

June 20, 2003 03:08 AM Forum: Equipment Talk

Tak FS102 vs TV102

Posted By Mike Gibson
Optically, the scopes are almost identical, with the TV102 a little slower/narrower at f/8.6. Have compared them all the way down to a 3mm Radian with equally impressive results.

Mechanically, the FS102 has a beefier 2.7" focuser and the bulk to go with it (tube size and dew shade). The TV102 is a more portable instrument with direct tube ring compatibility with TV mounts and assys.

Present prices for new may favor the Tak ($1895?), but one should factor in the cost of Tak tube ring(s).

Sweet scopes....would only favor the Tak for 2.7" with medium format photography.

June 20, 2003 02:04 PM Forum: Equipment Talk

20030617 Mars (joint effort)

Posted By Mike Gibson
Eric - fantastic work, as usual. I've always wanted to ask you if your captured AVI frames are processed before stacking? To get 1900 frames stacked, must you do this in stages because of software limits (e.g. Registax).

Congratulations on such excellent results.

June 23, 2003 02:57 AM Forum: Equipment Talk

C9.25 on the LXD55

Posted By Mike Gibson
The stock C9.25 extruded dovetail bar fits fine on the LXD55 saddle. The bar won't lock into the saddle like a Vixen or Synta plate, but my C9.25 hasn't slipped yet.

June 25, 2003 02:01 PM Forum: Equipment Talk

Best filter for Mars..

Posted By Mike Gibson
For Mars, I like a #21 red, especially with 6" and smaller scopes because of higher light transmission. A darker #23 red is useful when more aperture is available. See Fred Price's Planetary Handbook and this excellent filter site:

http://sciastro.net/portia/advice/filters.htm

June 26, 2003 01:47 PM Forum: Equipment Talk

Meade LX200 12

Posted By Mike Gibson
I'm not sure we can correlate problem LX200's with sales numbers on Astromart. Meade's $100 million+ sales dwarf Celestron, so there may be more 12" SCTs on the used market. The NexStar series has not been problem free either.

We used to have a 12" LX200 in a local group and marveled at its size, especially the tripod. Lack of portability and sore backs may have more to do with used sales than instrument quality.

June 26, 2003 07:34 PM Forum: Equipment Talk

Mars filter?

Posted By Mike Gibson
Repost from yesterday:

For Mars, I like a #21 orange, especially with 6" and smaller scopes because of higher light transmission. A darker #23 red is useful when more aperture is available. See Fred Price's Planetary Handbook and this excellent filter site:

http://sciastro.net/portia/advice/filters.htm

June 28, 2003 11:48 PM Forum: Equipment Talk

interface for lxd55 autostar

Posted By Mike Gibson
The Autostar uses a smart data bus (I2C), so we drive the mount with laptops through the Autostar using a serial cable. I use "The Sky v5", but any planetarium program that supports the LX200/Autostar subset protocol will work.

The #505 serial cable will interface a laptop to the Autostar's AUX port (DB9 to RJ11). See this page from Mike Weasner's site, posted by Dick Seymour:

http://www.weasner.com/etx/autostar/as_cable505.html

If you want to drive the mount without Autostar interface through the HBX port, visit one of several robotic scope sites using Autostar components (DS/LXD55/LX90).

July 1, 2003 05:07 PM Forum: Equipment Talk

Need Bino Review of the AP/Baader Model

Posted By Mike Gibson
Todd Gross has a complete binoviewer page, but it is being updated for the newer units like the Siebert and Denk. Company Seven has a complete "review" of the Baader unit. Links:

http://www.weatherman.com

http://www.company7.com/astrophy/options/apbino.html


July 2, 2003 03:55 PM Forum: Equipment Talk

Grinding off enhanced coatings?

Posted By Mike Gibson
Yes, this may be true. If your mirror has a "coating" from electron beam deposition (e.g. sputtering from a cathode in a vacuum chamber), it is very durable and has properties which exclude conventional chemical coating removal.

As an example, the dielectric mirror diagonals from AP and TeleVue have very hard finishes, using the same multi-layer beam technology developed for tank optics which are cleaned often in a desert environment.

Perhaps "grinding" is a bit strong and "polishing" could accomplish the same task more gently.


See this description of sputtering processes used for one of the Keck optics:

http://www-eng.llnl.gov/silver_mirror/pdf/Hawaii_8_2002.pdf

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