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Posts Made By: Mike Gibson

August 16, 2003 01:32 AM Forum: Equipment Talk

Some MV Filter Question (MV+color?)

Posted By Mike Gibson
You can buy a 48mm #21 Orange filter from Anacortes (Optec):

http://www.buytelescopes.com/product.asp?t=&pid=4044&m=

August 16, 2003 05:04 PM Forum: Equipment Talk

R200SS Rear End

Posted By Mike Gibson
Bill - for a fast Newtonian (200mm f/4), the R200SS rear end is not remarkable compared to other rear ends. This photo courtesy of an Amateur in Japan.

August 17, 2003 02:22 AM Forum: Equipment Talk

Noobie needs help Nexstar 114gt

Posted By Mike Gibson
Bruce - at this price point, the Celestron Nexstar 114GT is a good performer with some limitations. From the short tube length, I am guessing that the 114mm f/9 (1000mm) focal length is accomplished with an integrated Barlow lens. This isn't necessarily bad, but must be manufactured and collimated well.

I don't understand why we can't get better quality 114mm Newtonians; they are brighter than 90mm Maks or short tube achro refractors. Even with spherical mirrors, they can give decent views of brighter objects. The 114GT will easily show Mars' polar cap.

So to answer your question directly, if I could go to Costco and buy one for $160 I would certainly do it. I have even seen an AP130 on the 114GT mount for Nextstar goto.

Yes, you will be able to use the accessory kit on other scopes (Plossls, Barlow, and filters).

August 18, 2003 02:01 AM Forum: Equipment Talk

Meade Pictor 201XT Auto-Guider

Posted By Mike Gibson
This is a sore point for many buyers, even loyal Meade customers like me. Compatibility problems have plagued these products for years. My personal experience is a lack of support for simultaneous RA and Dec commands on a Losmandy mount.

Plus the 201XT is not cooled...very noisy when trying to pick out a guide star. Have no experience with the 208, but many find that Meade CCD gets a lot better with 3rd party software like MaximDL.

Try the CCD Forum for more experiences from users.

August 21, 2003 06:13 AM Forum: Equipment Talk

Refiguring versus buying new?

Posted By Mike Gibson
Use of Pyrex aids in the polishing and figuring process timeline because heat has less of an impact on dimensional stability. Plate glass is OK as a substrate, just takes longer to figure waiting for it to cool. Pyrex, quartz, or other exotic substrates offer nice-to-have but not overwelming thermal advantages for a Dob application.

It could be argued that an investment in a high Strehl first surface will be more compromised thermally with plate glass. So your challenge will be thermal.

Will Steve refigure Coulter optics as a regular service?

September 3, 2003 02:31 PM Forum: Equipment Talk

Question about Airy Disk on AR6

Posted By Mike Gibson
No obvious ideas from me...have you eliminated the eyepiece as the cause? Thomas Back has provided an excellent star test procedure at:

http://voltaire.csun.edu/tmb/tmb4.html

As he suggests, use filters to isolate chromatic and sphero-chromatic aberrations. I have seen such aberrations in my Meade AR5 (127mm f/9.3) when CCD imaging Mars, and would expect a more pronounced error in the 150mm f/8 optic.

My old Celestron (Synta) CR150 did not have a "perfect" intra and extra focal pattern, but performance was still excellent for an achro doublet.

September 5, 2003 04:13 PM Forum: Equipment Talk

TV NP-101 the closest thing to the perfect scope?

Posted By Mike Gibson
The NP-101 has better color correction and a wider FOV than the Tak FS102. I have owned both at the same time and camparisons revealed the NP-101 to be a bit better optically.

The Tak still enjoys the advantage of a robust 2.7" focuser for medium format photography and has enough back-focus for a binoviewer without using a Barlow. But it is also heavier to mount.

September 6, 2003 02:47 AM Forum: Equipment Talk

Nexstar 8" and a Tak 4" / 5" refractor

Posted By Mike Gibson
Because the 8" SCT is a jack-of-all-trades and master of none...a good general purpose instrument with comfortable eyepiece position. The 4" and 5" Taks do things the 8" SCT can never do.

The Taks will do fast cooldown without collimation, pinpoint stars, wider field, and better planetary contrast.

...zipping on flame suit now.

September 13, 2003 06:29 AM Forum: Equipment Talk

SAC8?

Posted By Mike Gibson
Does it look like this? If it does, it's an early SAC8...

September 13, 2003 06:48 AM Forum: Equipment Talk

SAC8?

Posted By Mike Gibson
Here is another one from an Astromart Ad....

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