Posts Made By: Doug Scobel

Hi, all, I recently purchased a used 19 mm Televue Panoptic eyepiece. I had my first chance to try it in my 13.1” f/4.5 dob last night. And the images were terrible! Only the middle quarter of the FOV was sharp, the rest showed progressively worse and worse coma as you got further out to the edge. Thinking it’s just showing the coma in my fast Newt, I tried it in a friend’s Televue TV60 (60 mm f/6). Even that showed comatic stars near the edge of the field. We then tried his 24 mm Panoptic in my 13”, and the star images at the edge of the field were much better than with the 19 mm, which is not what one would expect if it was simply revealing the coma inherent in the Newtonian design.

There’s definitely something wrong with this eyepiece. I’m wondering if a former owner took it apart and re-assembled it wrong. Are there any online resources where I can find out what the lens layout ought to be? I imagine I could send it back to Televue for repair, I’ll give them a phone call tomorrow to find out what they might be able to do for me. But I don’t expect it to be cheap

Anyone else have experience with this eyepiece, good or bad? In particular, in fast, large dobs? Any other advice? Right now it’s a dog. I could have saved myself a lot of money and bought an Orion Expanse for these kind of images.

Thanks,
Doug

I believe the solution is to start with Radians (60 degree AFOV) for a few months, then Panoptics (68 degrees) for a few more months, then finally Naglers. The gradual progression will strengthen rather then damage the muscles, and you can then handle the 82 degree views with your bulked-up eyes. You should be on a high-protein regimen while you're doing this for best results.

Don't sell you Naglers yet!

Doug

Here's a link to a timely article I wrote for my club's newsletter last spring, on edge-on galaxies. Hope you enjoy it and find it useful.

http://www.umich.edu/~lowbrows/reflections/2004/dscobel.16.html

Doug

Has anyone tried using Gatorboard in telescope construction? Gatorboard is a very light weight material like foamcore board, but is much stronger and has more stiffness. It is commonly used for graphics displays. It comes in various thicknesses, but I would think the most applicable sizes would be 3/16", 1/2", and 3/4". For example, one could make an extremely lightweight yet strong secondary cage for a truss dob using it. Maybe other components as well.

I think the trick would be making it weatherproof.

Just a thought,
Doug

Anyone heading to the Cherry Springs Star Party first weekend in June?

http://www.cherrysprings.org/

I'll be there with some fellow club members. The Cherry Springs State Park site in Potter County, PA (north central) is excellent! Skies down to mag 6.5.

Doug

Here's a pano of Camp Lowbrow before Sunday night's observing. Left to right is Bobby G. (12.5" Portaball), Joni G. (8" Uti), Mark Deprest (12.5" Bruce Rubin), yours truly (13.1" homemade Dob), and Jim Wadsworth (12.5" Discovery Dob).

As you can see, the place looks pretty much deserted. I'd say a good 2/3 to 3/4 of the folks bugged out - I guess a lot of attendees had to go to work on Monday.

Doug

I finally got around to trying a four hole mask like yours on my 13" dob. I thought you might be interested in what I found out.

First, the seeing was pretty bad. Partly because it was bad, but probably just as problematic is that the temperature was dropping fast, about 10 degrees F in an hour and a half. And with all the thermal mass in my 13” (I’ve really gotta rebuild that thing) I know that I had a lot of turbulence inside the scope, despite the fans. Through the eyepiece, I would rate the seeing at around 3/10 at worst, averaging around 5, and sometimes (but very seldom) reaching 6 or maybe even 7 momentarily.

Anyway, I compared a single five inch aperture offset mask, a four hole mask like yours, and no mask at all. I was comparing views of Jupiter at 213x. Jupiter was losing altitude fast, which didn’t help the steadiness any.

The view with the single offset mask was always inferior. Much darker (5” vs. 13” - duh!), and even though the image was cleanest and steadiest, I could still see more detail with the four hole or no mask at all.

The four hole mask was pretty clean, no spikes, but a very noticeable halo surrounding the planet’s disk. What one would expect due to in effect fat spider vanes but curved 360 degrees. The image was pretty bright, although not as bright as without any mask, also what one would expect. But I have to say, I think I was seeing the most detail (which isn’t saying much due to the poor steadiness) with no mask. Yes the spikes were visible, but the brighter image seemed to provide just a little more detail.

Hard to draw conclusions with just one test session. It looks like it may be clear again tonight, so I may give it another try. If I do I’ll follow up.

Best regards,
Doug

I did some solar observatin' Monday afternoon. This is the first of my best images, taken between 2:27 and 2:52 pm EDT. The large group near the eastern (left) limb is Active Region (AR) 0786, the large group at center is AR 0783 which is also naked eye (with protection of course!), and the small spot near the western limb is AR 0782. In all images north is approximately at the top.

All images were taken through my 8-inch f/8 Newtonian reflector, protected with a 7-inch aperture Baader solar filter (effectively making the scope a 7-inch f/9). All were taken afocally with a Nikon Coolpix 800 digital camera. This full disk image was taken with a 32mm symmetrical eyepiece. The others that follow were taken through a 14mm Televue Radian. The images were processed using Paint Shop Pro 8.

The images don't compare with what was visible visually, but they give you a good idea of how active the sun's face is right now. If you get a chance take a look yourself if you have a solar filter for your scope of course. Be safe!

Doug

There are currently some very nice sunspots crossing the sun's face. These are two of my best shots from yesterday, taken around 11:45 EDT. The large complex near the center of the disk is active region (AR) 792, with AR 795 and AR 794 at top and bottom, respectively, on the eastern limb. In both pictures north is at the top.

I took the images afocally, using my Nikon Coolpix 800 digital camera, through my 8-inch f/8 Newtonian reflector with a 7-inch aperture Baader solar filter. They were taken with the camera mounted to a 14mm TeleVue Radian eyepiece, and then digitally processed using Paint Shop Pro.

Enjoy!

Doug

I took this picture while waiting for clouds to clear while trying to get the Moon, Venus, and Mercury together (see next post). The Moon was about two and a half days old.

13" f/4.5 reflector, Nikon Coolpix 800 mounted to a 14mm Televue Radian eyepiece. Three images stitched together using Panorama Maker, further processed using Paint Shop Pro.

Doug