Posts Made By: Kevin Beebe

I used to really like the 16mm T5. I have a pair of them for binoviewing, but lately have been using 24mm Panoptics. I wasn't sure why I preferred the Pans, just did.

Last weekend I tried the Naglers again and found out why. There is a lot of color in the 16mm T5's. I was looking at the moon (3/4 full) with Denkmeier standards, a 2" power switch through a 22" f/5 Newtonian. The color was very noticable in all 3 power switch positions. I also tried UO 12.5mm orthos and the view through them was very good also.

Has anyone else seen this behavior with the 16mm Nagler? I'd never noticed it in mono mode. Is it because of some effect related to the standard binoviewers and not having the Denk II's?

Kevin

I saw the Denkmeier EP ad, too. They sound very similar to the Pentax EP in AFOV, price, and hopefully performance.

I don't think a 30mm 65 degree AFOV EP is possible in the 1.25" format. The 24mm Panoptic (68* field) is a maximum field, so maybe Denk could make a 25mm EP. The 14mm appealed to me. I have a pair of 25mm Pans that I use for "low power", which is about 150x. Using the power switch, I can go up to a little less than 300x. I'm pretty new to binoviewing, and have only used them on the moon, globulars and some of the brighter nebulas (nebulae?). But usually when I look at the moon, I want even more power before too long. I've been trying out some UO orthos. I like them, but the small FOV makes me feel a little restricted. They don't give me that "hovering over the moon" feeling as much as the Pans or Naglers.

Be interesting to hear the reviews of the 20mm EPs soon.

Kevin

I'll second what Jim said.

I have an f/4.9 telescope with a larger aperture than the Orion. To me the coma is noticable if you look for it at the edge of the field with low magnification. BUT when I'm using a max field (low magnificatin) EP, I'm either finding an object or looking at a large galaxy or star cluster, which are not critical uses. When you move to higher magnifications, you are looking at smaller FOV which are relatively coma free.

At f/4.5, I start to want a coma corrector sometimes.

HTH,
Kevin

Congratulations! It looks very nice, but I'd like more pictures and details.
And how well does it work?

Dark skies!
Kevin

Two questions. First when figuring the balance point do you use the center of the alt bearings or the edge? Second the original designer was going to use a 6 pole truss setup but when he designed the clamping mechanisms he blundered. The secondary cage has the clamps properly spaced at 120 degree intervals around the secondary cage ring. The mirror box however is square and the clamps have been mounted with a 90 degree angle and two 135 degree angles. If I do the trig and work out the poll lengths and mark them will this system work?

1. Use the center of the alt bearings. That is the axis of rotation.

2. You can make it work with what you have, but it is more difficult. I finished a similar project last summer, a 16" with 6 poles. The pole attachments are spaced 120 degrees apart on the secondary cage with an odd spacing on the mirror box. You can make it work, but there are a lot more details to work out, especially the pole connections. I used the Moonlight ball and socket connector to simplify this, but I still had to make some modifications. I did the trig to get an approximation for the pole lengths (3 different lengths), but reached the final length by trial and error and shortening the poles a little at a time.

Hope this helps,
Kevin

P.S. here's a picture of the unfinished scope.

Thanks for the review. I've been interested in the DM-6 for awhile. The thing that's been scaring me off, though, is the price. Your review doesn't mention it, and I had a hard time deciphering the DiscMount price sheet. I'm probably just being obstinate in wanting a lower price. :S

Hi Tom,

Just a few comments (for academic discussion) on your idea. First of all, a 45 cut doesn't necessarily end up a lot higher up the mirror box than a curved cut. It depends on the height of the mirror box (the center of gravity, actually).

As for a larger cut weakening the mirrror box, I think it depends on what you do with the cut away section. If it is left open, then yes, the MB is weaker. If you fill it with plywood (or whatever material you are using), then it should be just as strong.

My only other thought about Box #4 is a lot of dobs use the flat piece as a stop. The front of the MB hits the front of the rocker box and keeps the scope from going past vertical. It's not too big of a difficulty to overcome, and maybe not even necessary. Just some thoughts.

Kevin

Joe Morey said:

Has anyone tried the Johnsonian Type V Platform? I would like to hear your overall impressions. I am planning on using it with my Discovery 13.1" dob, and my new Astrosky 10" dob. I look forward to all your comments. Thanks.

Best,

Joe

Hi Joe,

I bought a used Type V on Astromart last summer. I've only used it for visual (not photography). It tracks well, except when the batteries get low. I've used it with magnifications up to about 350x and could see very little drift. This was as good as expected, since I usually align it by setting the platform in the yard in the daytime and aiming towards where I think Polaris should be.

I've had a few problems. Mainly with the hand controller and with the platform "jumping it's track". The hand controller problem may have been because the batteries were low. The track-jumping problem I think can be attributed to a long moment arm on the telescope and not enough weight over the tracks. I have a 16" scope that weighs less than 60 lbs. This happens when I slew too quickly from one place to another. I think I've solved that problem by adding a pivot post to the platform, moving the weight toward the tracking wheels, and replacing the PFA pads with Teflon.

Hope this helps,
Kevin Beebe

Floyd Blue said:

Hello all,
Because of a comment made about the results I posted of Interferograms by Antares about possible manipulation or masking of edges or defective areas. I thought I would post part of a correspondence I had with Antares about these comments.
The following is an excerpt from this letter for you to read and make your own judgment about the validity of their testing and documentation.
"We measure all of our mirrors at 100% aperture. No Mask data manipulation what so ever. We only trim the outside perimeter to 5 points as shown on the interferogram. True a 1/50 wave PV optic is a rare & prized piece of work; It does happen enough, "here", that I can say it is almost a weekly event. .....

Floyd,
I'm not sure what this means. It almost sounds like, "We don't mask the edge, we trim it." I'm not knowledgable enough to know the difference.

I pulled out my documentation on a couple of mirrors I got from Antares and looked at it more closely. I noticed that the images shown are not elliptical, kind of like the "ends" of the mirror were chopped off. This is from a 3.1" diagonal. On the paper for the 1.83" diagonal the Fringe Map and the main plot look elliptical, so the 3.1" definitely looks strange.

Kevin

Good question. I was just thinking about this.

1. To me, the most important is dark skies. This might not be true for everyone, though. One guy in our club does mostly variable star observing, planets, and splitting doubles from a very light polluted driveway.

2. Location. You've heard the maxim, "the best scope for you is one you'll use." Well, the best location is one you can get to. For me, that's my driveway or backyard. I've got mag 6 skies to the south and east and what could be more convenient. Our club has access to a site about 20 minutes away with slightly darker skies, and a good view to the west. I do go to better places occassionally, but I seem to be too busy to do it on a regular basis. Dark skies was a huge motivating factor for moving to where I live now.

3. Altitude. This helps the seeing and the haze. The less atmosphere you have to look through the better. I would like to rate this higher, but I have places available and don't use them, so it must not be as important to me. When I do get to a high altitude spot with dark skies, it's impressive, though. But like someone mentioned in a previous post, a large your change in altitude can affect your ability to take advantage of the pristine skies, or even cause altitude sickness.

Interesting to see what others think.
Kevin