Posts Made By: david roberts

I just purchased a 13.1 inch dobsonian and have a 32 mm plossel with a 2x barlow. I want to purchase another eyepiece of smaller aperture with a wide angle field. My intent is to view some of the Messier galaxies. I'm sure price does equate to quality, but $200 plus for a nice Nagler is out of my price range. But I don't want to buy a collection of eyepieces I will be unhappy with on the second night of use. What is considered a good size field of view for a small aperture eyepiece? Any suggestions? Thanks

I wish to understand the meaning and use of 'Field of View" (FOV) in regards to oculars. What does it mean to have a 50 or 60 or more FOV. I'm trying to understand in regards to viewing galaxies, nebulas, etc. Is wider better? What is the difference between 'apparent' vs. 'actual'? Should I just stick with a standard plossl FOV?

Also is there a calculation to determine the number of degrees viewed in an eyepiece given its aperture and the focal length of the scope? Is the FOV used in the calculation? Questions ????????? Your comments please. Thanks.

The other day I requested some information regarding ultrawide eps and the meaning of FOV, AFOV. Thanks for all responses. On Astromart under 'cool sites' is a webpage by David Green offering free software. A calculator is provided that will give all kinds of info including FOV and AFOV for any ep. You can run a comparison on several eps at once. It is brainless to use and only takes your scopes aperture, focal length, and ep aperture. He also provides downloads for observation notes and messier viewing. Wouldn't you know Astromart would carry such a great page. Thanks Mr. Green!!!!

Now I can say that a 9mm ep with a 67 degree AFOV will yield 0.5 degree view of the sky. The 82 degree nagler only offers 0.6, not much more, which I found interesting. However, I know of Nagler's reputation and the clarity is probably better.

Now my question is....has anyone tried and have an opinion about the new Orion Expanse eps. I did read the review on www.coudynight.com as recommended (sorry, I don't remember who recommended by thanks much).

The deal was buy 2 and get one free. The 15 and 20mm arived in 3 days from date of order. The 9mm was on backorder. I called the next day to ask when the 9mm would come in. They said it was already in and shipped at no extra charge. Not meaning to plug here, but I'm quite happy with the transaction with Adorama.

Under last nights sky in the Houston area, the FOV on the 15 and 20 were very nice. The focus on Jupiter was a bit soft, but for a F4.5 13.1 inch scope, I expected that. Clounds set in quickly before any serious seeing and dew covered the observing site so I gave up. But my initial impression is, for the money, I'm satisified.

I would like to know how to calculate the degree field seen through a 6x50 finder, or similar finder. I'm trying to starhop and if I place a known star on one side of the finder and move the finder to place the star on the other side of the finder, how many degrees have I moved. I have a dob, so I don't have setting circles. Also how many degrees does the three circles of the terad bulleye represent. Thanks

I just received a Sky Atlas 2000 by Trione (sp?). The constallations were not outlined. I thought what a better way to learn the outlines than to draw them in myself. I used some internet resources, mostly SEDs, for outline examples. Drawing in my own outlines really gel the configuration of the constallations, much more so than just a glance. But I started to realize, there are as many outlines as there are books, or for that matter constallations! I believe there is a convention, as displayed by SEDS, but I'm not sure.

I would recommend this method of learning constallation outlines to anyone. Its fun to boot. While spread out on the kitchen table, my wife said "that not work to you, it it." I said not in any way is this like work!

I have an f4.5 13.1 inch old coulter dob I recently purchased. The other night I used a 9mm ultrawide Pan-Optic ep for observing. I noticed that as I went beyond focused in one direction on a star, the star seemed to draw a white line sideways (horizontal). The more out of focus in one direction, the longer the line got. Then when I focused the other way (sorry I don't know the term for being out of focus on either side of focused), the star drew a line vertically. Also focusing in general with the 9mm seems to be a chore. I saw a diagram of this in a book, but at the time didn't know I have this problem. Now I don't remember where I saw the explanation. Is this just a simple collimation problem? If someone knows what causes this and how to correct it, I would appreciate some help. Thanks

I've been using a 13.1 inch, f4.5 newtonian recently and found coma abberation, which I understand is not uncommon for fast newtonians. I've collimated the scope but still see those light cones when slightly out of focus. I've heard of a 'coma corrector' and assume it is some sort of lense, but have no idea of the size, cost, where it attaches or where to get one. My focuser is a 1 1/4 inch. Any advise, suggestions??????

Living in the Houston area, I've learned to be patient for clear skies. You wait, and wait and wait..... This weekend my chance for dark skies came in the form of a cub scout campout in a national forest about 60 miles north of Houston. The problem was, I didn't bring my scope! It was either my scope or my family, and I opted for the latter.

The sky was overcast until about 11:00pm. I had just about given up hope. A fellow camper brought his son's Bushnell reflector, I think a 3 inch or so, but he packed it up and went to bed just before the sky cleared. I drank to much coffee and the temperature hovered around 35 degrees F, so any sleep for me was out of the question. I had brought a planisphere and the Star Atlas 2000. By midnight the sky became crystal clear and I was enthralled by the magnificant sights. The constellations popped out and burned holes in the sky. I found a few acres of cleared ground nearby, set up my chair, and just marveled, unaided, at the view until dawn. To see all the stars of Ursa Major, the visible cluster in Coma Berenices, Hercules, Lyra, Scorpius, Ophiuchus, Virgo, Leo, and many others. Scorpius rising up was a beautiful sight to behold. And a new moon to boot.

I have a new appreciation for dark crystal skies. They have become a rare commodity. My neck is sore for looking up all night. It was worth every minute.

I'm sure this type of post has appeared 100s of times on this forum. I know everyone has their own bias, personal interest, experience, etc. I have an old coulter 13.1 dob I recently purchased without eps. So I bought the three eps listed at Adamora, the wide angle plossel eps, 9mm, 15mm and 20mm; the buy 2 and get a thrid free deal. Honestly, I'm not happy with any of them. I try to attribute the poor performance to bad seeing conditions, collimation, inexperience, but I believe its the eps. They are hard to focus, seem blurry, and display alot of coma. The 9mm is worthless, again in my opinion. BTW I picked up a $40 no name 32mm plossel and 2x barlow from Telescope World which perform much better, in my opinion. This is not to knock Adoroma, they gave great custormer service. I am satified my mirror is satisfactory and the scope is in collimation.

I want to see the Messier objects, plain and simple, and maybe some other NGC objects. I want to see the dust lanes, hints of spiral arms, individual stars in the globs....the typical stuff with a scope of this size.

I have decided to purchase one quality 1-1/4" ep for Messier viewing. I also want to purchase one filter for nebula viewing. The question is, which ones. And I would like to keep the price under $200 for the ep, but would consider going to $300 if really convinced.

Currently I'm considering a 16mm or so ep, preferable in the 60 to 70 degree FOV range. With a 2x barlow, I can get to 8mm, which seems appropriate for the highest mag I would need. I could be wrong. I know the Tele Vue eps rule the market for top quality, but is there a reasonable choice, am I on track here? Should I just go for a Tele Vue, and if so which one? I don't want to collect eps.

In the vast knowledge base of this forum, what do you think is a good (very good) all around ep and filter system for viewing Messier objects? I need your advice. Thanks