Posts Made By: Brad Bassett

September 27, 2006 02:50 AM Forum: Equipment Talk

Diagonal with no reflective surface?

Posted By Brad Bassett

I purchased a used Celestron eyepiece turret a couple of months ago. I noticed that it produces a searchlight beam of scatter in two opposite directions. So I took it apart to see if I could tell anything. I noticed a smear or smudge that was not on either exposed surface of the prism, looking like it was on the reflective surface, which mystified me. I thought maybe it was a defect in the aluminizing. So I took it apart further and to my utter surprise found that the reflective surface of the prism was completely clear. There is no metal on it at all. There is only a piece of black paper behind it held in place by a plastic wedge. I cleaned the surface anyway to see if it made any difference. It did reduce the scatter slightly, but not enough to really be to my liking. So I'm really surprised that this works as well as it does, it's better than my old Celestron mirror diagonal for scatter and it's equal in light throughput. I can see the pattern in the paper slightly when looking through the diagonal at a certain angle. Could this be the cause of the scatter beams? Would a darker black backing help? Should I try using charcoal on the paper, or would this getting on the prism be a problem? Wouldn't it be much better with some aluminizing or silver on the reflecting surface? Any other thoughts?

Thanks,
Brad

November 18, 2006 03:55 AM Forum: Telescope Making

I need a threaded fitting

Posted By Brad Bassett

Hi,

I'm trying to cobble together a super wide angle finderscope. I have an old B&L movie camera lens (maybe). It is about 93mm focal length and f/2.1. With a 25mm Plossl it should give me about a 14 deg fov. I'm hoping that it will show just a few more stars than my naked eye. It appears that it does in my tests. I'm looking for some fitting that will mate with the male threads on the back of it. Does anyone know of any telescope or camera parts that will mate to this? One thought is the larger SCT fitting? The C8 SCT fitting is smaller. Any sort of cap, coupling, or retaining ring could do the job. I can shorten or fasten in crude ways, no lathe or milling machine though. Who would I go to if I really wanted something machined (probably not in the budget though)?

Spec's as close as I can measure them: Major diameter = 2 1/8"; Root diameter = 2 1/16" (maybe a little smaller); 16 threads per inch.

Thanks,
Brad

February 15, 2007 03:07 AM Forum: Star Parties

Mt St Helens?

Posted By Brad Bassett

I think I saw a reference to a star party at Mt St Helens (in WA state). Does anyone have info on this? Would it be associated with a local club?

Thanks,
Brad

September 25, 2007 02:47 AM Forum: Reflectors

spherical primary and collimation

Posted By Brad Bassett

Would a spherical primary mirror in a reflector have less issues with collimation than a paraboloid. Would it even be possible to make an off-axis scope without introducing more abberations than are already inherent in that design?

Brad

May 19, 2008 04:22 AM Forum: Home Observatories

Pod not just for astronomy

Posted By Brad Bassett

I ran across this solar power news bulletin and was surprised to see the use of a SkyShed Pod for something other than it's intended use.

http://www.solarbuzz.com/news/NewsNATE52.htm

I'm in the solar power biz and suggest you not get too excited about this supposed breakthrough in solar power. Announcements like this are a dime a dozen and rarely pan out. This one particularly, even though it is IBM, does not look especially good. IBM must need some visibility in the hot "green market".

Brad

June 4, 2008 03:00 AM Forum: Equipment Talk

light scatter

Posted By Brad Bassett

I have not seen much talk about the causes of light scatter in telescopes. I find it one of the most distracting aspects of viewing brighter objects. Am I correct that the smoothness of the polish of the optics is the main factor in reducing scatter? So this would mean that higher quality, more expensive telescopes would likely be better in this regard?

Does anyone have the experience to say if there is any noticeable difference in various vintages of C8 SCT's in the visible light scatter? Is there a difference between the old uncoated, the Starbright and the XLT coated C8's?

Any other comments?

Thanks,
Brad

July 12, 2008 05:35 PM Forum: Solar System Observing

Jupiter moon or star?

Posted By Brad Bassett

Last night observing Jupiter, I noticed a dim moon or star just on the west side of the planet. By midnight 7:00 UT it was no longer visible. This through a 4"ED scope. Is their a site that would show more than the 4 moons like the Sky and Telescope site does? I don't have any planetarium programs, would they show what this was? Anyone know?

Thanks,
Brad

December 31, 2008 02:06 AM Forum: Eyepieces

Vixen LVW 30mm ?

Posted By Brad Bassett

I'd be interested in hearing if anyone has tried this eyepiece, what they think of it. If anyone has measured the field stop, I'd like to know what it is. I calculate it should be about 34mm. Any side by side comparison to the Hyperion 31, or other eyepieces?

Thanks,
Brad

April 15, 2009 02:41 AM Forum: Refractors

Less CA with quality in Achro?

Posted By Brad Bassett

Would a high quality achromat objective produce less chromatic aberration than a poor quality objective? I have a Hardin 90mm f/11 with a fairly poor lens, my 60mm old Jason is much sharper, and am wondering if a "Vixen spec" lens will give less CA than I see in the Hardin, or only sharper images? My understanding is that CA is related to other aberrations, so I expect so, but would like some idea of just how much difference it might make.

Thanks,
Brad

July 8, 2009 03:03 AM Forum: Equipment Talk

GSO focuser visual back

Posted By Brad Bassett

Is the visual back/eyepiece holder on the GSO/Antares focusers threaded on to the draw tube or are they one piece?

Thanks,
Brad