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Posts Made By: Judson Mitchell

March 3, 2006 03:03 AM Forum: Equipment Talk

GSO 12" Mirror Test

Posted By Judson Mitchell
A friend tested my 12" GSO mirror tonight and indicated that it was approximately 1/7th wave with a strehl ratio of .86. He indicated that the turned edge kept the ratio from being higher. He noted some crescent shaped surface roughness primarily extending from the edge inward which he indicated was from incomplete polishing. Star tests show even concentric rings with no apparent astigmatism, however I have not had decent skies to get a better star test.

March 4, 2006 03:24 PM Forum: Reflectors

Mirror Test 12" GSO

Posted By Judson Mitchell
For those of you who may be interested and missed post 421887, I described a mirror test for a GSO 12" in the Equipment Forum. Due to the activity of the forum, the post quickly got buried and became more difficult to find.

March 11, 2006 11:14 PM Forum: Eyepieces

Actual Barlow Magnifications

Posted By Judson Mitchell
A while back I did some preliminary tests using the moon and concluded that my barlows were indicating a power greater than marked. To evaluate barlow magnification, I affixed a steel tape to a board and placed it at a distance of about 400 feet. Using 11 EPs and two barlows (1.5X & 2.0X) I measured the FOV of each combination. Included in the group were a Stratus 8mm and Hyperion 13mm which could be used either as 1.25" or 2.0" EPs. When used as 2" EP the Stratus gave 1.55 and 2.09 for the two barlows and the Hyperion gave 1.43 and 2.05 respectively. However, with the 2.0/1.25" adaptor I got an average of 1.7X and 2.32X respectively. These values were also the approximate average I got for all EPs, 10 of which were 1.25". The adapter raises the EPs approximately 3/8" above the edge of the barlow, thus increasing the effective power of the barlow. However, the 2" EP, a 42 mm GSO Superwide yielded valaues of 1.75 and 2.39. Lesson learned is that it may not be the barlow that causes the apparent increase in magnification, rather the amount your adapter raises the EP above the flush point of the Barlow. More to come after some additional testing.

March 13, 2006 01:02 AM Forum: Solar System Observing

Seeing the Encke Gap

Posted By Judson Mitchell
Under what conditions is the Encke Gap visible. Was viewing at about 400X and had fleeting moments of clarity when it seemed the Gap was visible, but never a "Yeah! That's It!". Observing with a GSO 12" dob 8mm Stratus and 2X UO 2" Barlow. Am I expecting too much. Pickering around 4. Average seeing.

May 5, 2006 01:53 AM Forum: AstroMart FAQ

How do I read my Send Messages

Posted By Judson Mitchell
Is there any way to read your sent messages? Right now, the only way I can see mine is if someone responds. Is there another way?

May 12, 2006 12:00 PM Forum: Eyepieces

Re: What are your 3 most used eyepieces?

Posted By Judson Mitchell
OK, wanna hear from someone who aint got no stinking Naglers, Panoptics, Radians, Pentaxes, or whatever! Actually I have only been back a year into astro after a 30 year Hyatius, and if I could start over I would have picked up a 6 & 13 Nagler and 24 Pan. But to answer the question the most used are

24 TV Widefield, 13 Hyperion, 8 Stratus and 1.5 Proxima 2" barlow. Now keep in mind you can throw in a 1.25 to 2" adapter and get two more magnifications out of the Hyperion and Stratus. By the way, my 17 Hyperion is kinda neat also. In a week or two I will have a 9.9 Siebert Star Splitter and it could creep into the mix.

May 13, 2006 02:04 AM Forum: Deep Sky Observing

Moon-M4 Occultation.

Posted By Judson Mitchell
Was playing with my charts and apparently the moon will occult M4 at about 3:30 pm Jun 10 in SC. This has to be a spectacular phenomena somewhere in the world. Hopefully someone will get a shot of this like the comet and M57, however, the occultation of M4 will be on the edge of the full moon. Correct me if I am wrong on this one. I could not manage my software to predict where this would occur but I would suspect eastern Europe, India or thereabouts.

June 9, 2006 03:27 PM Forum: Equipment Talk

Have You Tried Nite Specs?

Posted By Judson Mitchell
I was just reading about Nite Specs and was wondering if anyone can respond with some personal experience. The claims are interesting and smack of a substitute for Tele Vue's Dioptrix. I have noted a slight improvement with naked eye viewing when using my +0.75 normal vision glasses (not reading prescription). Typically there are tails on most bright stars that virtually disappear when my glasses are used. Have not used them when viewing, but will check them out now that I have read this. In rereading the Nite Specs it indicates that -.5 diopter is removed from the normal lenses. So it appears that the +.75 would be wrong.

June 13, 2006 12:43 PM Forum: Eyepieces

Eyepieces for Fast Dobs

Posted By Judson Mitchell
I am wondering if it would be uesful to have a Forum entitled Eyepieces for Fast Dobs? Particularly for a newbie or a novice like me, it is sometimes very tough to wade through the myriad of comments that mix scope types and focal lengths. It is doubly confusing when the type of scope is never mentioned. As a result it undoubtedly becomes difficult for the less informed to make reasonable decisions. Only by extensively following numerous threads, have I even begun to understand how to select eyepieces. It appears that there is a large enough contingent of observers using fast dobs who could benefit from a more focussed forum. If we can have a Forum with only 29 hits, certainly a Forum on Eyepieces for Fast Dobs can be justified. Yeah, I know, confusion brings more equipment to the classifieds so we all benefit. But, I can cite many parallel examples of that kind of marketing that we all have complained about.

June 26, 2006 08:29 PM Forum: Equipment Talk

Collimation problem with Secondary

Posted By Judson Mitchell
It appears that most of my collimation issues are with the secondary. Commonly I will just use my Catseye to readjust the secondary which will bring my scope back into collimation. A check with the sitetube/crosshairs then shows it dead on. If I use the laser, it seems I then have to adjust the primary. Is it possible that I need to change the Spider? And if so, to what? HOC 12" dob.

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